discourse/lib/presence_channel.rb

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DEV: Introduce PresenceChannel API for core and plugin use PresenceChannel aims to be a generic system for allow the server, and end-users, to track the number and identity of users performing a specific task on the site. For example, it might be used to track who is currently 'replying' to a specific topic, editing a specific wiki post, etc. A few key pieces of information about the system: - PresenceChannels are identified by a name of the format `/prefix/blah`, where `prefix` has been configured by some core/plugin implementation, and `blah` can be any string the implementation wants to use. - Presence is a boolean thing - each user is either present, or not present. If a user has multiple clients 'present' in a channel, they will be deduplicated so that the user is only counted once - Developers can configure the existence and configuration of channels 'just in time' using a callback. The result of this is cached for 2 minutes. - Configuration of a channel can specify permissions in a similar way to MessageBus (public boolean, a list of allowed_user_ids, and a list of allowed_group_ids). A channel can also be placed in 'count_only' mode, where the identity of present users is not revealed to end-users. - The backend implementation uses redis lua scripts, and is designed to scale well. In the future, hard limits may be introduced on the maximum number of users that can be present in a channel. - Clients can enter/leave at will. If a client has not marked itself 'present' in the last 60 seconds, they will automatically 'leave' the channel. The JS implementation takes care of this regular check-in. - On the client-side, PresenceChannel instances can be fetched from the `presence` ember service. Each PresenceChannel can be used entered/left/subscribed/unsubscribed, and the service will automatically deduplicate information before interacting with the server. - When a client joins a PresenceChannel, the JS implementation will automatically make a GET request for the current channel state. To avoid this, the channel state can be serialized into one of your existing endpoints, and then passed to the `subscribe` method on the channel. - The PresenceChannel JS object is an ember object. The `users` and `count` property can be used directly in ember templates, and in computed properties. - It is important to make sure that you `unsubscribe()` and `leave()` any PresenceChannel objects after use An example implementation may look something like this. On the server: ```ruby register_presence_channel_prefix("site") do |channel| next nil unless channel == "/site/online" PresenceChannel::Config.new(public: true) end ``` And on the client, a component could be implemented like this: ```javascript import Component from "@ember/component"; import { inject as service } from "@ember/service"; export default Component.extend({ presence: service(), init() { this._super(...arguments); this.set("presenceChannel", this.presence.getChannel("/site/online")); }, didInsertElement() { this.presenceChannel.enter(); this.presenceChannel.subscribe(); }, willDestroyElement() { this.presenceChannel.leave(); this.presenceChannel.unsubscribe(); }, }); ``` With this template: ```handlebars Online: {{presenceChannel.count}} <ul> {{#each presenceChannel.users as |user|}} <li>{{avatar user imageSize="tiny"}} {{user.username}}</li> {{/each}} </ul> ```
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# frozen_string_literal: true
# The server-side implementation of PresenceChannels. See also {PresenceController}
# and +app/assets/javascripts/discourse/app/services/presence.js+
class PresenceChannel
class NotFound < StandardError
end
class InvalidAccess < StandardError
end
class ConfigNotLoaded < StandardError
end
class InvalidConfig < StandardError
end
class State
include ActiveModel::Serialization
attr_reader :message_bus_last_id
attr_reader :user_ids
attr_reader :count
def initialize(message_bus_last_id:, user_ids: nil, count: nil)
raise "user_ids or count required" if user_ids.nil? && count.nil?
@message_bus_last_id = message_bus_last_id
@user_ids = user_ids
@count = count || user_ids.count
end
def users
return nil if user_ids.nil?
User.where(id: user_ids)
end
end
# Class for managing config of PresenceChannel
# Three parameters can be provided on initialization:
# public: boolean value. If true, channel information is visible to all users (default false)
# allowed_user_ids: array of user_ids that can view, and become present in, the channel (default [])
# allowed_group_ids: array of group_ids that can view, and become present in, the channel (default [])
# count_only: boolean. If true, user identities are never revealed to clients. (default [])
class Config
NOT_FOUND ||= "notfound"
attr_accessor :public, :allowed_user_ids, :allowed_group_ids, :count_only, :timeout
def initialize(
public: false,
allowed_user_ids: nil,
allowed_group_ids: nil,
count_only: false,
timeout: nil
)
DEV: Introduce PresenceChannel API for core and plugin use PresenceChannel aims to be a generic system for allow the server, and end-users, to track the number and identity of users performing a specific task on the site. For example, it might be used to track who is currently 'replying' to a specific topic, editing a specific wiki post, etc. A few key pieces of information about the system: - PresenceChannels are identified by a name of the format `/prefix/blah`, where `prefix` has been configured by some core/plugin implementation, and `blah` can be any string the implementation wants to use. - Presence is a boolean thing - each user is either present, or not present. If a user has multiple clients 'present' in a channel, they will be deduplicated so that the user is only counted once - Developers can configure the existence and configuration of channels 'just in time' using a callback. The result of this is cached for 2 minutes. - Configuration of a channel can specify permissions in a similar way to MessageBus (public boolean, a list of allowed_user_ids, and a list of allowed_group_ids). A channel can also be placed in 'count_only' mode, where the identity of present users is not revealed to end-users. - The backend implementation uses redis lua scripts, and is designed to scale well. In the future, hard limits may be introduced on the maximum number of users that can be present in a channel. - Clients can enter/leave at will. If a client has not marked itself 'present' in the last 60 seconds, they will automatically 'leave' the channel. The JS implementation takes care of this regular check-in. - On the client-side, PresenceChannel instances can be fetched from the `presence` ember service. Each PresenceChannel can be used entered/left/subscribed/unsubscribed, and the service will automatically deduplicate information before interacting with the server. - When a client joins a PresenceChannel, the JS implementation will automatically make a GET request for the current channel state. To avoid this, the channel state can be serialized into one of your existing endpoints, and then passed to the `subscribe` method on the channel. - The PresenceChannel JS object is an ember object. The `users` and `count` property can be used directly in ember templates, and in computed properties. - It is important to make sure that you `unsubscribe()` and `leave()` any PresenceChannel objects after use An example implementation may look something like this. On the server: ```ruby register_presence_channel_prefix("site") do |channel| next nil unless channel == "/site/online" PresenceChannel::Config.new(public: true) end ``` And on the client, a component could be implemented like this: ```javascript import Component from "@ember/component"; import { inject as service } from "@ember/service"; export default Component.extend({ presence: service(), init() { this._super(...arguments); this.set("presenceChannel", this.presence.getChannel("/site/online")); }, didInsertElement() { this.presenceChannel.enter(); this.presenceChannel.subscribe(); }, willDestroyElement() { this.presenceChannel.leave(); this.presenceChannel.unsubscribe(); }, }); ``` With this template: ```handlebars Online: {{presenceChannel.count}} <ul> {{#each presenceChannel.users as |user|}} <li>{{avatar user imageSize="tiny"}} {{user.username}}</li> {{/each}} </ul> ```
2021-08-27 09:43:39 -04:00
@public = public
@allowed_user_ids = allowed_user_ids
@allowed_group_ids = allowed_group_ids
@count_only = count_only
@timeout = timeout
DEV: Introduce PresenceChannel API for core and plugin use PresenceChannel aims to be a generic system for allow the server, and end-users, to track the number and identity of users performing a specific task on the site. For example, it might be used to track who is currently 'replying' to a specific topic, editing a specific wiki post, etc. A few key pieces of information about the system: - PresenceChannels are identified by a name of the format `/prefix/blah`, where `prefix` has been configured by some core/plugin implementation, and `blah` can be any string the implementation wants to use. - Presence is a boolean thing - each user is either present, or not present. If a user has multiple clients 'present' in a channel, they will be deduplicated so that the user is only counted once - Developers can configure the existence and configuration of channels 'just in time' using a callback. The result of this is cached for 2 minutes. - Configuration of a channel can specify permissions in a similar way to MessageBus (public boolean, a list of allowed_user_ids, and a list of allowed_group_ids). A channel can also be placed in 'count_only' mode, where the identity of present users is not revealed to end-users. - The backend implementation uses redis lua scripts, and is designed to scale well. In the future, hard limits may be introduced on the maximum number of users that can be present in a channel. - Clients can enter/leave at will. If a client has not marked itself 'present' in the last 60 seconds, they will automatically 'leave' the channel. The JS implementation takes care of this regular check-in. - On the client-side, PresenceChannel instances can be fetched from the `presence` ember service. Each PresenceChannel can be used entered/left/subscribed/unsubscribed, and the service will automatically deduplicate information before interacting with the server. - When a client joins a PresenceChannel, the JS implementation will automatically make a GET request for the current channel state. To avoid this, the channel state can be serialized into one of your existing endpoints, and then passed to the `subscribe` method on the channel. - The PresenceChannel JS object is an ember object. The `users` and `count` property can be used directly in ember templates, and in computed properties. - It is important to make sure that you `unsubscribe()` and `leave()` any PresenceChannel objects after use An example implementation may look something like this. On the server: ```ruby register_presence_channel_prefix("site") do |channel| next nil unless channel == "/site/online" PresenceChannel::Config.new(public: true) end ``` And on the client, a component could be implemented like this: ```javascript import Component from "@ember/component"; import { inject as service } from "@ember/service"; export default Component.extend({ presence: service(), init() { this._super(...arguments); this.set("presenceChannel", this.presence.getChannel("/site/online")); }, didInsertElement() { this.presenceChannel.enter(); this.presenceChannel.subscribe(); }, willDestroyElement() { this.presenceChannel.leave(); this.presenceChannel.unsubscribe(); }, }); ``` With this template: ```handlebars Online: {{presenceChannel.count}} <ul> {{#each presenceChannel.users as |user|}} <li>{{avatar user imageSize="tiny"}} {{user.username}}</li> {{/each}} </ul> ```
2021-08-27 09:43:39 -04:00
end
def self.from_json(json)
data = JSON.parse(json, symbolize_names: true)
data = {} if !data.is_a? Hash
new(**data.slice(:public, :allowed_user_ids, :allowed_group_ids, :count_only, :timeout))
DEV: Introduce PresenceChannel API for core and plugin use PresenceChannel aims to be a generic system for allow the server, and end-users, to track the number and identity of users performing a specific task on the site. For example, it might be used to track who is currently 'replying' to a specific topic, editing a specific wiki post, etc. A few key pieces of information about the system: - PresenceChannels are identified by a name of the format `/prefix/blah`, where `prefix` has been configured by some core/plugin implementation, and `blah` can be any string the implementation wants to use. - Presence is a boolean thing - each user is either present, or not present. If a user has multiple clients 'present' in a channel, they will be deduplicated so that the user is only counted once - Developers can configure the existence and configuration of channels 'just in time' using a callback. The result of this is cached for 2 minutes. - Configuration of a channel can specify permissions in a similar way to MessageBus (public boolean, a list of allowed_user_ids, and a list of allowed_group_ids). A channel can also be placed in 'count_only' mode, where the identity of present users is not revealed to end-users. - The backend implementation uses redis lua scripts, and is designed to scale well. In the future, hard limits may be introduced on the maximum number of users that can be present in a channel. - Clients can enter/leave at will. If a client has not marked itself 'present' in the last 60 seconds, they will automatically 'leave' the channel. The JS implementation takes care of this regular check-in. - On the client-side, PresenceChannel instances can be fetched from the `presence` ember service. Each PresenceChannel can be used entered/left/subscribed/unsubscribed, and the service will automatically deduplicate information before interacting with the server. - When a client joins a PresenceChannel, the JS implementation will automatically make a GET request for the current channel state. To avoid this, the channel state can be serialized into one of your existing endpoints, and then passed to the `subscribe` method on the channel. - The PresenceChannel JS object is an ember object. The `users` and `count` property can be used directly in ember templates, and in computed properties. - It is important to make sure that you `unsubscribe()` and `leave()` any PresenceChannel objects after use An example implementation may look something like this. On the server: ```ruby register_presence_channel_prefix("site") do |channel| next nil unless channel == "/site/online" PresenceChannel::Config.new(public: true) end ``` And on the client, a component could be implemented like this: ```javascript import Component from "@ember/component"; import { inject as service } from "@ember/service"; export default Component.extend({ presence: service(), init() { this._super(...arguments); this.set("presenceChannel", this.presence.getChannel("/site/online")); }, didInsertElement() { this.presenceChannel.enter(); this.presenceChannel.subscribe(); }, willDestroyElement() { this.presenceChannel.leave(); this.presenceChannel.unsubscribe(); }, }); ``` With this template: ```handlebars Online: {{presenceChannel.count}} <ul> {{#each presenceChannel.users as |user|}} <li>{{avatar user imageSize="tiny"}} {{user.username}}</li> {{/each}} </ul> ```
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end
def to_json
data = { public: public }
data[:allowed_user_ids] = allowed_user_ids if allowed_user_ids
data[:allowed_group_ids] = allowed_group_ids if allowed_group_ids
data[:count_only] = count_only if count_only
data[:timeout] = timeout if timeout
DEV: Introduce PresenceChannel API for core and plugin use PresenceChannel aims to be a generic system for allow the server, and end-users, to track the number and identity of users performing a specific task on the site. For example, it might be used to track who is currently 'replying' to a specific topic, editing a specific wiki post, etc. A few key pieces of information about the system: - PresenceChannels are identified by a name of the format `/prefix/blah`, where `prefix` has been configured by some core/plugin implementation, and `blah` can be any string the implementation wants to use. - Presence is a boolean thing - each user is either present, or not present. If a user has multiple clients 'present' in a channel, they will be deduplicated so that the user is only counted once - Developers can configure the existence and configuration of channels 'just in time' using a callback. The result of this is cached for 2 minutes. - Configuration of a channel can specify permissions in a similar way to MessageBus (public boolean, a list of allowed_user_ids, and a list of allowed_group_ids). A channel can also be placed in 'count_only' mode, where the identity of present users is not revealed to end-users. - The backend implementation uses redis lua scripts, and is designed to scale well. In the future, hard limits may be introduced on the maximum number of users that can be present in a channel. - Clients can enter/leave at will. If a client has not marked itself 'present' in the last 60 seconds, they will automatically 'leave' the channel. The JS implementation takes care of this regular check-in. - On the client-side, PresenceChannel instances can be fetched from the `presence` ember service. Each PresenceChannel can be used entered/left/subscribed/unsubscribed, and the service will automatically deduplicate information before interacting with the server. - When a client joins a PresenceChannel, the JS implementation will automatically make a GET request for the current channel state. To avoid this, the channel state can be serialized into one of your existing endpoints, and then passed to the `subscribe` method on the channel. - The PresenceChannel JS object is an ember object. The `users` and `count` property can be used directly in ember templates, and in computed properties. - It is important to make sure that you `unsubscribe()` and `leave()` any PresenceChannel objects after use An example implementation may look something like this. On the server: ```ruby register_presence_channel_prefix("site") do |channel| next nil unless channel == "/site/online" PresenceChannel::Config.new(public: true) end ``` And on the client, a component could be implemented like this: ```javascript import Component from "@ember/component"; import { inject as service } from "@ember/service"; export default Component.extend({ presence: service(), init() { this._super(...arguments); this.set("presenceChannel", this.presence.getChannel("/site/online")); }, didInsertElement() { this.presenceChannel.enter(); this.presenceChannel.subscribe(); }, willDestroyElement() { this.presenceChannel.leave(); this.presenceChannel.unsubscribe(); }, }); ``` With this template: ```handlebars Online: {{presenceChannel.count}} <ul> {{#each presenceChannel.users as |user|}} <li>{{avatar user imageSize="tiny"}} {{user.username}}</li> {{/each}} </ul> ```
2021-08-27 09:43:39 -04:00
data.to_json
end
end
DEFAULT_TIMEOUT ||= 60
CONFIG_CACHE_SECONDS ||= 10
DEV: Introduce PresenceChannel API for core and plugin use PresenceChannel aims to be a generic system for allow the server, and end-users, to track the number and identity of users performing a specific task on the site. For example, it might be used to track who is currently 'replying' to a specific topic, editing a specific wiki post, etc. A few key pieces of information about the system: - PresenceChannels are identified by a name of the format `/prefix/blah`, where `prefix` has been configured by some core/plugin implementation, and `blah` can be any string the implementation wants to use. - Presence is a boolean thing - each user is either present, or not present. If a user has multiple clients 'present' in a channel, they will be deduplicated so that the user is only counted once - Developers can configure the existence and configuration of channels 'just in time' using a callback. The result of this is cached for 2 minutes. - Configuration of a channel can specify permissions in a similar way to MessageBus (public boolean, a list of allowed_user_ids, and a list of allowed_group_ids). A channel can also be placed in 'count_only' mode, where the identity of present users is not revealed to end-users. - The backend implementation uses redis lua scripts, and is designed to scale well. In the future, hard limits may be introduced on the maximum number of users that can be present in a channel. - Clients can enter/leave at will. If a client has not marked itself 'present' in the last 60 seconds, they will automatically 'leave' the channel. The JS implementation takes care of this regular check-in. - On the client-side, PresenceChannel instances can be fetched from the `presence` ember service. Each PresenceChannel can be used entered/left/subscribed/unsubscribed, and the service will automatically deduplicate information before interacting with the server. - When a client joins a PresenceChannel, the JS implementation will automatically make a GET request for the current channel state. To avoid this, the channel state can be serialized into one of your existing endpoints, and then passed to the `subscribe` method on the channel. - The PresenceChannel JS object is an ember object. The `users` and `count` property can be used directly in ember templates, and in computed properties. - It is important to make sure that you `unsubscribe()` and `leave()` any PresenceChannel objects after use An example implementation may look something like this. On the server: ```ruby register_presence_channel_prefix("site") do |channel| next nil unless channel == "/site/online" PresenceChannel::Config.new(public: true) end ``` And on the client, a component could be implemented like this: ```javascript import Component from "@ember/component"; import { inject as service } from "@ember/service"; export default Component.extend({ presence: service(), init() { this._super(...arguments); this.set("presenceChannel", this.presence.getChannel("/site/online")); }, didInsertElement() { this.presenceChannel.enter(); this.presenceChannel.subscribe(); }, willDestroyElement() { this.presenceChannel.leave(); this.presenceChannel.unsubscribe(); }, }); ``` With this template: ```handlebars Online: {{presenceChannel.count}} <ul> {{#each presenceChannel.users as |user|}} <li>{{avatar user imageSize="tiny"}} {{user.username}}</li> {{/each}} </ul> ```
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GC_SECONDS ||= 24.hours.to_i
MUTEX_TIMEOUT_SECONDS ||= 10
MUTEX_LOCKED_ERROR ||= "PresenceChannel mutex is locked"
@@configuration_blocks ||= {}
attr_reader :name, :timeout, :message_bus_channel_name, :config
def initialize(name, raise_not_found: true, use_cache: true)
DEV: Introduce PresenceChannel API for core and plugin use PresenceChannel aims to be a generic system for allow the server, and end-users, to track the number and identity of users performing a specific task on the site. For example, it might be used to track who is currently 'replying' to a specific topic, editing a specific wiki post, etc. A few key pieces of information about the system: - PresenceChannels are identified by a name of the format `/prefix/blah`, where `prefix` has been configured by some core/plugin implementation, and `blah` can be any string the implementation wants to use. - Presence is a boolean thing - each user is either present, or not present. If a user has multiple clients 'present' in a channel, they will be deduplicated so that the user is only counted once - Developers can configure the existence and configuration of channels 'just in time' using a callback. The result of this is cached for 2 minutes. - Configuration of a channel can specify permissions in a similar way to MessageBus (public boolean, a list of allowed_user_ids, and a list of allowed_group_ids). A channel can also be placed in 'count_only' mode, where the identity of present users is not revealed to end-users. - The backend implementation uses redis lua scripts, and is designed to scale well. In the future, hard limits may be introduced on the maximum number of users that can be present in a channel. - Clients can enter/leave at will. If a client has not marked itself 'present' in the last 60 seconds, they will automatically 'leave' the channel. The JS implementation takes care of this regular check-in. - On the client-side, PresenceChannel instances can be fetched from the `presence` ember service. Each PresenceChannel can be used entered/left/subscribed/unsubscribed, and the service will automatically deduplicate information before interacting with the server. - When a client joins a PresenceChannel, the JS implementation will automatically make a GET request for the current channel state. To avoid this, the channel state can be serialized into one of your existing endpoints, and then passed to the `subscribe` method on the channel. - The PresenceChannel JS object is an ember object. The `users` and `count` property can be used directly in ember templates, and in computed properties. - It is important to make sure that you `unsubscribe()` and `leave()` any PresenceChannel objects after use An example implementation may look something like this. On the server: ```ruby register_presence_channel_prefix("site") do |channel| next nil unless channel == "/site/online" PresenceChannel::Config.new(public: true) end ``` And on the client, a component could be implemented like this: ```javascript import Component from "@ember/component"; import { inject as service } from "@ember/service"; export default Component.extend({ presence: service(), init() { this._super(...arguments); this.set("presenceChannel", this.presence.getChannel("/site/online")); }, didInsertElement() { this.presenceChannel.enter(); this.presenceChannel.subscribe(); }, willDestroyElement() { this.presenceChannel.leave(); this.presenceChannel.unsubscribe(); }, }); ``` With this template: ```handlebars Online: {{presenceChannel.count}} <ul> {{#each presenceChannel.users as |user|}} <li>{{avatar user imageSize="tiny"}} {{user.username}}</li> {{/each}} </ul> ```
2021-08-27 09:43:39 -04:00
@name = name
@message_bus_channel_name = "/presence#{name}"
begin
@config = fetch_config(use_cache: use_cache)
DEV: Introduce PresenceChannel API for core and plugin use PresenceChannel aims to be a generic system for allow the server, and end-users, to track the number and identity of users performing a specific task on the site. For example, it might be used to track who is currently 'replying' to a specific topic, editing a specific wiki post, etc. A few key pieces of information about the system: - PresenceChannels are identified by a name of the format `/prefix/blah`, where `prefix` has been configured by some core/plugin implementation, and `blah` can be any string the implementation wants to use. - Presence is a boolean thing - each user is either present, or not present. If a user has multiple clients 'present' in a channel, they will be deduplicated so that the user is only counted once - Developers can configure the existence and configuration of channels 'just in time' using a callback. The result of this is cached for 2 minutes. - Configuration of a channel can specify permissions in a similar way to MessageBus (public boolean, a list of allowed_user_ids, and a list of allowed_group_ids). A channel can also be placed in 'count_only' mode, where the identity of present users is not revealed to end-users. - The backend implementation uses redis lua scripts, and is designed to scale well. In the future, hard limits may be introduced on the maximum number of users that can be present in a channel. - Clients can enter/leave at will. If a client has not marked itself 'present' in the last 60 seconds, they will automatically 'leave' the channel. The JS implementation takes care of this regular check-in. - On the client-side, PresenceChannel instances can be fetched from the `presence` ember service. Each PresenceChannel can be used entered/left/subscribed/unsubscribed, and the service will automatically deduplicate information before interacting with the server. - When a client joins a PresenceChannel, the JS implementation will automatically make a GET request for the current channel state. To avoid this, the channel state can be serialized into one of your existing endpoints, and then passed to the `subscribe` method on the channel. - The PresenceChannel JS object is an ember object. The `users` and `count` property can be used directly in ember templates, and in computed properties. - It is important to make sure that you `unsubscribe()` and `leave()` any PresenceChannel objects after use An example implementation may look something like this. On the server: ```ruby register_presence_channel_prefix("site") do |channel| next nil unless channel == "/site/online" PresenceChannel::Config.new(public: true) end ``` And on the client, a component could be implemented like this: ```javascript import Component from "@ember/component"; import { inject as service } from "@ember/service"; export default Component.extend({ presence: service(), init() { this._super(...arguments); this.set("presenceChannel", this.presence.getChannel("/site/online")); }, didInsertElement() { this.presenceChannel.enter(); this.presenceChannel.subscribe(); }, willDestroyElement() { this.presenceChannel.leave(); this.presenceChannel.unsubscribe(); }, }); ``` With this template: ```handlebars Online: {{presenceChannel.count}} <ul> {{#each presenceChannel.users as |user|}} <li>{{avatar user imageSize="tiny"}} {{user.username}}</li> {{/each}} </ul> ```
2021-08-27 09:43:39 -04:00
rescue PresenceChannel::NotFound
raise if raise_not_found
@config = Config.new
end
@timeout = config.timeout || DEFAULT_TIMEOUT
DEV: Introduce PresenceChannel API for core and plugin use PresenceChannel aims to be a generic system for allow the server, and end-users, to track the number and identity of users performing a specific task on the site. For example, it might be used to track who is currently 'replying' to a specific topic, editing a specific wiki post, etc. A few key pieces of information about the system: - PresenceChannels are identified by a name of the format `/prefix/blah`, where `prefix` has been configured by some core/plugin implementation, and `blah` can be any string the implementation wants to use. - Presence is a boolean thing - each user is either present, or not present. If a user has multiple clients 'present' in a channel, they will be deduplicated so that the user is only counted once - Developers can configure the existence and configuration of channels 'just in time' using a callback. The result of this is cached for 2 minutes. - Configuration of a channel can specify permissions in a similar way to MessageBus (public boolean, a list of allowed_user_ids, and a list of allowed_group_ids). A channel can also be placed in 'count_only' mode, where the identity of present users is not revealed to end-users. - The backend implementation uses redis lua scripts, and is designed to scale well. In the future, hard limits may be introduced on the maximum number of users that can be present in a channel. - Clients can enter/leave at will. If a client has not marked itself 'present' in the last 60 seconds, they will automatically 'leave' the channel. The JS implementation takes care of this regular check-in. - On the client-side, PresenceChannel instances can be fetched from the `presence` ember service. Each PresenceChannel can be used entered/left/subscribed/unsubscribed, and the service will automatically deduplicate information before interacting with the server. - When a client joins a PresenceChannel, the JS implementation will automatically make a GET request for the current channel state. To avoid this, the channel state can be serialized into one of your existing endpoints, and then passed to the `subscribe` method on the channel. - The PresenceChannel JS object is an ember object. The `users` and `count` property can be used directly in ember templates, and in computed properties. - It is important to make sure that you `unsubscribe()` and `leave()` any PresenceChannel objects after use An example implementation may look something like this. On the server: ```ruby register_presence_channel_prefix("site") do |channel| next nil unless channel == "/site/online" PresenceChannel::Config.new(public: true) end ``` And on the client, a component could be implemented like this: ```javascript import Component from "@ember/component"; import { inject as service } from "@ember/service"; export default Component.extend({ presence: service(), init() { this._super(...arguments); this.set("presenceChannel", this.presence.getChannel("/site/online")); }, didInsertElement() { this.presenceChannel.enter(); this.presenceChannel.subscribe(); }, willDestroyElement() { this.presenceChannel.leave(); this.presenceChannel.unsubscribe(); }, }); ``` With this template: ```handlebars Online: {{presenceChannel.count}} <ul> {{#each presenceChannel.users as |user|}} <li>{{avatar user imageSize="tiny"}} {{user.username}}</li> {{/each}} </ul> ```
2021-08-27 09:43:39 -04:00
end
# Is this user allowed to view this channel?
# Pass `nil` for anonymous viewers
def can_view?(user_id: nil, group_ids: nil)
DEV: Introduce PresenceChannel API for core and plugin use PresenceChannel aims to be a generic system for allow the server, and end-users, to track the number and identity of users performing a specific task on the site. For example, it might be used to track who is currently 'replying' to a specific topic, editing a specific wiki post, etc. A few key pieces of information about the system: - PresenceChannels are identified by a name of the format `/prefix/blah`, where `prefix` has been configured by some core/plugin implementation, and `blah` can be any string the implementation wants to use. - Presence is a boolean thing - each user is either present, or not present. If a user has multiple clients 'present' in a channel, they will be deduplicated so that the user is only counted once - Developers can configure the existence and configuration of channels 'just in time' using a callback. The result of this is cached for 2 minutes. - Configuration of a channel can specify permissions in a similar way to MessageBus (public boolean, a list of allowed_user_ids, and a list of allowed_group_ids). A channel can also be placed in 'count_only' mode, where the identity of present users is not revealed to end-users. - The backend implementation uses redis lua scripts, and is designed to scale well. In the future, hard limits may be introduced on the maximum number of users that can be present in a channel. - Clients can enter/leave at will. If a client has not marked itself 'present' in the last 60 seconds, they will automatically 'leave' the channel. The JS implementation takes care of this regular check-in. - On the client-side, PresenceChannel instances can be fetched from the `presence` ember service. Each PresenceChannel can be used entered/left/subscribed/unsubscribed, and the service will automatically deduplicate information before interacting with the server. - When a client joins a PresenceChannel, the JS implementation will automatically make a GET request for the current channel state. To avoid this, the channel state can be serialized into one of your existing endpoints, and then passed to the `subscribe` method on the channel. - The PresenceChannel JS object is an ember object. The `users` and `count` property can be used directly in ember templates, and in computed properties. - It is important to make sure that you `unsubscribe()` and `leave()` any PresenceChannel objects after use An example implementation may look something like this. On the server: ```ruby register_presence_channel_prefix("site") do |channel| next nil unless channel == "/site/online" PresenceChannel::Config.new(public: true) end ``` And on the client, a component could be implemented like this: ```javascript import Component from "@ember/component"; import { inject as service } from "@ember/service"; export default Component.extend({ presence: service(), init() { this._super(...arguments); this.set("presenceChannel", this.presence.getChannel("/site/online")); }, didInsertElement() { this.presenceChannel.enter(); this.presenceChannel.subscribe(); }, willDestroyElement() { this.presenceChannel.leave(); this.presenceChannel.unsubscribe(); }, }); ``` With this template: ```handlebars Online: {{presenceChannel.count}} <ul> {{#each presenceChannel.users as |user|}} <li>{{avatar user imageSize="tiny"}} {{user.username}}</li> {{/each}} </ul> ```
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return true if config.public
return true if user_id && config.allowed_user_ids&.include?(user_id)
DEV: Introduce PresenceChannel API for core and plugin use PresenceChannel aims to be a generic system for allow the server, and end-users, to track the number and identity of users performing a specific task on the site. For example, it might be used to track who is currently 'replying' to a specific topic, editing a specific wiki post, etc. A few key pieces of information about the system: - PresenceChannels are identified by a name of the format `/prefix/blah`, where `prefix` has been configured by some core/plugin implementation, and `blah` can be any string the implementation wants to use. - Presence is a boolean thing - each user is either present, or not present. If a user has multiple clients 'present' in a channel, they will be deduplicated so that the user is only counted once - Developers can configure the existence and configuration of channels 'just in time' using a callback. The result of this is cached for 2 minutes. - Configuration of a channel can specify permissions in a similar way to MessageBus (public boolean, a list of allowed_user_ids, and a list of allowed_group_ids). A channel can also be placed in 'count_only' mode, where the identity of present users is not revealed to end-users. - The backend implementation uses redis lua scripts, and is designed to scale well. In the future, hard limits may be introduced on the maximum number of users that can be present in a channel. - Clients can enter/leave at will. If a client has not marked itself 'present' in the last 60 seconds, they will automatically 'leave' the channel. The JS implementation takes care of this regular check-in. - On the client-side, PresenceChannel instances can be fetched from the `presence` ember service. Each PresenceChannel can be used entered/left/subscribed/unsubscribed, and the service will automatically deduplicate information before interacting with the server. - When a client joins a PresenceChannel, the JS implementation will automatically make a GET request for the current channel state. To avoid this, the channel state can be serialized into one of your existing endpoints, and then passed to the `subscribe` method on the channel. - The PresenceChannel JS object is an ember object. The `users` and `count` property can be used directly in ember templates, and in computed properties. - It is important to make sure that you `unsubscribe()` and `leave()` any PresenceChannel objects after use An example implementation may look something like this. On the server: ```ruby register_presence_channel_prefix("site") do |channel| next nil unless channel == "/site/online" PresenceChannel::Config.new(public: true) end ``` And on the client, a component could be implemented like this: ```javascript import Component from "@ember/component"; import { inject as service } from "@ember/service"; export default Component.extend({ presence: service(), init() { this._super(...arguments); this.set("presenceChannel", this.presence.getChannel("/site/online")); }, didInsertElement() { this.presenceChannel.enter(); this.presenceChannel.subscribe(); }, willDestroyElement() { this.presenceChannel.leave(); this.presenceChannel.unsubscribe(); }, }); ``` With this template: ```handlebars Online: {{presenceChannel.count}} <ul> {{#each presenceChannel.users as |user|}} <li>{{avatar user imageSize="tiny"}} {{user.username}}</li> {{/each}} </ul> ```
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if user_id && config.allowed_group_ids.present?
group_ids ||= GroupUser.where(user_id: user_id).pluck("group_id")
return true if (group_ids & config.allowed_group_ids).present?
DEV: Introduce PresenceChannel API for core and plugin use PresenceChannel aims to be a generic system for allow the server, and end-users, to track the number and identity of users performing a specific task on the site. For example, it might be used to track who is currently 'replying' to a specific topic, editing a specific wiki post, etc. A few key pieces of information about the system: - PresenceChannels are identified by a name of the format `/prefix/blah`, where `prefix` has been configured by some core/plugin implementation, and `blah` can be any string the implementation wants to use. - Presence is a boolean thing - each user is either present, or not present. If a user has multiple clients 'present' in a channel, they will be deduplicated so that the user is only counted once - Developers can configure the existence and configuration of channels 'just in time' using a callback. The result of this is cached for 2 minutes. - Configuration of a channel can specify permissions in a similar way to MessageBus (public boolean, a list of allowed_user_ids, and a list of allowed_group_ids). A channel can also be placed in 'count_only' mode, where the identity of present users is not revealed to end-users. - The backend implementation uses redis lua scripts, and is designed to scale well. In the future, hard limits may be introduced on the maximum number of users that can be present in a channel. - Clients can enter/leave at will. If a client has not marked itself 'present' in the last 60 seconds, they will automatically 'leave' the channel. The JS implementation takes care of this regular check-in. - On the client-side, PresenceChannel instances can be fetched from the `presence` ember service. Each PresenceChannel can be used entered/left/subscribed/unsubscribed, and the service will automatically deduplicate information before interacting with the server. - When a client joins a PresenceChannel, the JS implementation will automatically make a GET request for the current channel state. To avoid this, the channel state can be serialized into one of your existing endpoints, and then passed to the `subscribe` method on the channel. - The PresenceChannel JS object is an ember object. The `users` and `count` property can be used directly in ember templates, and in computed properties. - It is important to make sure that you `unsubscribe()` and `leave()` any PresenceChannel objects after use An example implementation may look something like this. On the server: ```ruby register_presence_channel_prefix("site") do |channel| next nil unless channel == "/site/online" PresenceChannel::Config.new(public: true) end ``` And on the client, a component could be implemented like this: ```javascript import Component from "@ember/component"; import { inject as service } from "@ember/service"; export default Component.extend({ presence: service(), init() { this._super(...arguments); this.set("presenceChannel", this.presence.getChannel("/site/online")); }, didInsertElement() { this.presenceChannel.enter(); this.presenceChannel.subscribe(); }, willDestroyElement() { this.presenceChannel.leave(); this.presenceChannel.unsubscribe(); }, }); ``` With this template: ```handlebars Online: {{presenceChannel.count}} <ul> {{#each presenceChannel.users as |user|}} <li>{{avatar user imageSize="tiny"}} {{user.username}}</li> {{/each}} </ul> ```
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end
false
end
# Is a user allowed to enter this channel?
# Currently equal to the the can_view? permission
def can_enter?(user_id: nil, group_ids: nil)
DEV: Introduce PresenceChannel API for core and plugin use PresenceChannel aims to be a generic system for allow the server, and end-users, to track the number and identity of users performing a specific task on the site. For example, it might be used to track who is currently 'replying' to a specific topic, editing a specific wiki post, etc. A few key pieces of information about the system: - PresenceChannels are identified by a name of the format `/prefix/blah`, where `prefix` has been configured by some core/plugin implementation, and `blah` can be any string the implementation wants to use. - Presence is a boolean thing - each user is either present, or not present. If a user has multiple clients 'present' in a channel, they will be deduplicated so that the user is only counted once - Developers can configure the existence and configuration of channels 'just in time' using a callback. The result of this is cached for 2 minutes. - Configuration of a channel can specify permissions in a similar way to MessageBus (public boolean, a list of allowed_user_ids, and a list of allowed_group_ids). A channel can also be placed in 'count_only' mode, where the identity of present users is not revealed to end-users. - The backend implementation uses redis lua scripts, and is designed to scale well. In the future, hard limits may be introduced on the maximum number of users that can be present in a channel. - Clients can enter/leave at will. If a client has not marked itself 'present' in the last 60 seconds, they will automatically 'leave' the channel. The JS implementation takes care of this regular check-in. - On the client-side, PresenceChannel instances can be fetched from the `presence` ember service. Each PresenceChannel can be used entered/left/subscribed/unsubscribed, and the service will automatically deduplicate information before interacting with the server. - When a client joins a PresenceChannel, the JS implementation will automatically make a GET request for the current channel state. To avoid this, the channel state can be serialized into one of your existing endpoints, and then passed to the `subscribe` method on the channel. - The PresenceChannel JS object is an ember object. The `users` and `count` property can be used directly in ember templates, and in computed properties. - It is important to make sure that you `unsubscribe()` and `leave()` any PresenceChannel objects after use An example implementation may look something like this. On the server: ```ruby register_presence_channel_prefix("site") do |channel| next nil unless channel == "/site/online" PresenceChannel::Config.new(public: true) end ``` And on the client, a component could be implemented like this: ```javascript import Component from "@ember/component"; import { inject as service } from "@ember/service"; export default Component.extend({ presence: service(), init() { this._super(...arguments); this.set("presenceChannel", this.presence.getChannel("/site/online")); }, didInsertElement() { this.presenceChannel.enter(); this.presenceChannel.subscribe(); }, willDestroyElement() { this.presenceChannel.leave(); this.presenceChannel.unsubscribe(); }, }); ``` With this template: ```handlebars Online: {{presenceChannel.count}} <ul> {{#each presenceChannel.users as |user|}} <li>{{avatar user imageSize="tiny"}} {{user.username}}</li> {{/each}} </ul> ```
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return false if user_id.nil?
can_view?(user_id: user_id, group_ids: group_ids)
DEV: Introduce PresenceChannel API for core and plugin use PresenceChannel aims to be a generic system for allow the server, and end-users, to track the number and identity of users performing a specific task on the site. For example, it might be used to track who is currently 'replying' to a specific topic, editing a specific wiki post, etc. A few key pieces of information about the system: - PresenceChannels are identified by a name of the format `/prefix/blah`, where `prefix` has been configured by some core/plugin implementation, and `blah` can be any string the implementation wants to use. - Presence is a boolean thing - each user is either present, or not present. If a user has multiple clients 'present' in a channel, they will be deduplicated so that the user is only counted once - Developers can configure the existence and configuration of channels 'just in time' using a callback. The result of this is cached for 2 minutes. - Configuration of a channel can specify permissions in a similar way to MessageBus (public boolean, a list of allowed_user_ids, and a list of allowed_group_ids). A channel can also be placed in 'count_only' mode, where the identity of present users is not revealed to end-users. - The backend implementation uses redis lua scripts, and is designed to scale well. In the future, hard limits may be introduced on the maximum number of users that can be present in a channel. - Clients can enter/leave at will. If a client has not marked itself 'present' in the last 60 seconds, they will automatically 'leave' the channel. The JS implementation takes care of this regular check-in. - On the client-side, PresenceChannel instances can be fetched from the `presence` ember service. Each PresenceChannel can be used entered/left/subscribed/unsubscribed, and the service will automatically deduplicate information before interacting with the server. - When a client joins a PresenceChannel, the JS implementation will automatically make a GET request for the current channel state. To avoid this, the channel state can be serialized into one of your existing endpoints, and then passed to the `subscribe` method on the channel. - The PresenceChannel JS object is an ember object. The `users` and `count` property can be used directly in ember templates, and in computed properties. - It is important to make sure that you `unsubscribe()` and `leave()` any PresenceChannel objects after use An example implementation may look something like this. On the server: ```ruby register_presence_channel_prefix("site") do |channel| next nil unless channel == "/site/online" PresenceChannel::Config.new(public: true) end ``` And on the client, a component could be implemented like this: ```javascript import Component from "@ember/component"; import { inject as service } from "@ember/service"; export default Component.extend({ presence: service(), init() { this._super(...arguments); this.set("presenceChannel", this.presence.getChannel("/site/online")); }, didInsertElement() { this.presenceChannel.enter(); this.presenceChannel.subscribe(); }, willDestroyElement() { this.presenceChannel.leave(); this.presenceChannel.unsubscribe(); }, }); ``` With this template: ```handlebars Online: {{presenceChannel.count}} <ul> {{#each presenceChannel.users as |user|}} <li>{{avatar user imageSize="tiny"}} {{user.username}}</li> {{/each}} </ul> ```
2021-08-27 09:43:39 -04:00
end
# Mark a user's client as present in this channel. The client_id should be unique per
# browser tab. This method should be called repeatedly (at least once every DEFAULT_TIMEOUT)
# while the user is present in the channel.
def present(user_id:, client_id:)
raise PresenceChannel::InvalidAccess if !can_enter?(user_id: user_id)
mutex_value = SecureRandom.hex
result =
retry_on_mutex_error do
PresenceChannel.redis_eval(
:present,
redis_keys,
[name, user_id, client_id, (Time.zone.now + timeout).to_i, mutex_value],
)
end
if result == 1
begin
publish_message(entering_user_ids: [user_id])
ensure
release_mutex(mutex_value)
end
end
end
# Immediately mark a user's client as leaving the channel
def leave(user_id:, client_id:)
mutex_value = SecureRandom.hex
result =
retry_on_mutex_error do
PresenceChannel.redis_eval(:leave, redis_keys, [name, user_id, client_id, nil, mutex_value])
end
if result == 1
begin
publish_message(leaving_user_ids: [user_id])
ensure
release_mutex(mutex_value)
end
end
end
# Fetch a {PresenceChannel::State} instance representing the current state of this
#
# @param [Boolean] count_only set true to skip fetching the list of user ids from redis
def state(count_only: config.count_only)
if count_only
last_id, count = retry_on_mutex_error { PresenceChannel.redis_eval(:count, redis_keys) }
else
last_id, ids = retry_on_mutex_error { PresenceChannel.redis_eval(:user_ids, redis_keys) }
end
count ||= ids&.count
last_id = nil if last_id == -1
if Rails.env.test? && MessageBus.backend == :memory
# Doing it this way is not atomic, but we have no other option when
# messagebus is not using the redis backend
last_id = MessageBus.last_id(message_bus_channel_name)
end
State.new(message_bus_last_id: last_id, user_ids: ids, count: count)
end
def user_ids
state.user_ids
end
def count
state(count_only: true).count
end
# Automatically expire all users which have not been 'present' for more than +DEFAULT_TIMEOUT+
def auto_leave
mutex_value = SecureRandom.hex
left_user_ids =
retry_on_mutex_error do
PresenceChannel.redis_eval(:auto_leave, redis_keys, [name, Time.zone.now.to_i, mutex_value])
end
if !left_user_ids.empty?
begin
publish_message(leaving_user_ids: left_user_ids)
ensure
release_mutex(mutex_value)
end
end
end
# Clear all members of the channel. This is intended for debugging/development only
def clear
PresenceChannel.redis.del(redis_key_zlist)
PresenceChannel.redis.del(redis_key_hash)
PresenceChannel.redis.del(redis_key_config)
PresenceChannel.redis.del(redis_key_mutex)
PresenceChannel.redis.zrem(self.class.redis_key_channel_list, name)
end
# Designed to be run periodically. Checks the channel list for channels with expired members,
2022-02-27 21:20:58 -05:00
# and runs auto_leave for each eligible channel
DEV: Introduce PresenceChannel API for core and plugin use PresenceChannel aims to be a generic system for allow the server, and end-users, to track the number and identity of users performing a specific task on the site. For example, it might be used to track who is currently 'replying' to a specific topic, editing a specific wiki post, etc. A few key pieces of information about the system: - PresenceChannels are identified by a name of the format `/prefix/blah`, where `prefix` has been configured by some core/plugin implementation, and `blah` can be any string the implementation wants to use. - Presence is a boolean thing - each user is either present, or not present. If a user has multiple clients 'present' in a channel, they will be deduplicated so that the user is only counted once - Developers can configure the existence and configuration of channels 'just in time' using a callback. The result of this is cached for 2 minutes. - Configuration of a channel can specify permissions in a similar way to MessageBus (public boolean, a list of allowed_user_ids, and a list of allowed_group_ids). A channel can also be placed in 'count_only' mode, where the identity of present users is not revealed to end-users. - The backend implementation uses redis lua scripts, and is designed to scale well. In the future, hard limits may be introduced on the maximum number of users that can be present in a channel. - Clients can enter/leave at will. If a client has not marked itself 'present' in the last 60 seconds, they will automatically 'leave' the channel. The JS implementation takes care of this regular check-in. - On the client-side, PresenceChannel instances can be fetched from the `presence` ember service. Each PresenceChannel can be used entered/left/subscribed/unsubscribed, and the service will automatically deduplicate information before interacting with the server. - When a client joins a PresenceChannel, the JS implementation will automatically make a GET request for the current channel state. To avoid this, the channel state can be serialized into one of your existing endpoints, and then passed to the `subscribe` method on the channel. - The PresenceChannel JS object is an ember object. The `users` and `count` property can be used directly in ember templates, and in computed properties. - It is important to make sure that you `unsubscribe()` and `leave()` any PresenceChannel objects after use An example implementation may look something like this. On the server: ```ruby register_presence_channel_prefix("site") do |channel| next nil unless channel == "/site/online" PresenceChannel::Config.new(public: true) end ``` And on the client, a component could be implemented like this: ```javascript import Component from "@ember/component"; import { inject as service } from "@ember/service"; export default Component.extend({ presence: service(), init() { this._super(...arguments); this.set("presenceChannel", this.presence.getChannel("/site/online")); }, didInsertElement() { this.presenceChannel.enter(); this.presenceChannel.subscribe(); }, willDestroyElement() { this.presenceChannel.leave(); this.presenceChannel.unsubscribe(); }, }); ``` With this template: ```handlebars Online: {{presenceChannel.count}} <ul> {{#each presenceChannel.users as |user|}} <li>{{avatar user imageSize="tiny"}} {{user.username}}</li> {{/each}} </ul> ```
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def self.auto_leave_all
channels_with_expiring_members =
PresenceChannel.redis.zrangebyscore(redis_key_channel_list, "-inf", Time.zone.now.to_i)
channels_with_expiring_members.each { |name| new(name, raise_not_found: false).auto_leave }
end
# Clear all known channels. This is intended for debugging/development only
def self.clear_all!
channels = PresenceChannel.redis.zrangebyscore(redis_key_channel_list, "-inf", "+inf")
channels.each { |name| new(name, raise_not_found: false).clear }
DEV: Introduce PresenceChannel API for core and plugin use PresenceChannel aims to be a generic system for allow the server, and end-users, to track the number and identity of users performing a specific task on the site. For example, it might be used to track who is currently 'replying' to a specific topic, editing a specific wiki post, etc. A few key pieces of information about the system: - PresenceChannels are identified by a name of the format `/prefix/blah`, where `prefix` has been configured by some core/plugin implementation, and `blah` can be any string the implementation wants to use. - Presence is a boolean thing - each user is either present, or not present. If a user has multiple clients 'present' in a channel, they will be deduplicated so that the user is only counted once - Developers can configure the existence and configuration of channels 'just in time' using a callback. The result of this is cached for 2 minutes. - Configuration of a channel can specify permissions in a similar way to MessageBus (public boolean, a list of allowed_user_ids, and a list of allowed_group_ids). A channel can also be placed in 'count_only' mode, where the identity of present users is not revealed to end-users. - The backend implementation uses redis lua scripts, and is designed to scale well. In the future, hard limits may be introduced on the maximum number of users that can be present in a channel. - Clients can enter/leave at will. If a client has not marked itself 'present' in the last 60 seconds, they will automatically 'leave' the channel. The JS implementation takes care of this regular check-in. - On the client-side, PresenceChannel instances can be fetched from the `presence` ember service. Each PresenceChannel can be used entered/left/subscribed/unsubscribed, and the service will automatically deduplicate information before interacting with the server. - When a client joins a PresenceChannel, the JS implementation will automatically make a GET request for the current channel state. To avoid this, the channel state can be serialized into one of your existing endpoints, and then passed to the `subscribe` method on the channel. - The PresenceChannel JS object is an ember object. The `users` and `count` property can be used directly in ember templates, and in computed properties. - It is important to make sure that you `unsubscribe()` and `leave()` any PresenceChannel objects after use An example implementation may look something like this. On the server: ```ruby register_presence_channel_prefix("site") do |channel| next nil unless channel == "/site/online" PresenceChannel::Config.new(public: true) end ``` And on the client, a component could be implemented like this: ```javascript import Component from "@ember/component"; import { inject as service } from "@ember/service"; export default Component.extend({ presence: service(), init() { this._super(...arguments); this.set("presenceChannel", this.presence.getChannel("/site/online")); }, didInsertElement() { this.presenceChannel.enter(); this.presenceChannel.subscribe(); }, willDestroyElement() { this.presenceChannel.leave(); this.presenceChannel.unsubscribe(); }, }); ``` With this template: ```handlebars Online: {{presenceChannel.count}} <ul> {{#each presenceChannel.users as |user|}} <li>{{avatar user imageSize="tiny"}} {{user.username}}</li> {{/each}} </ul> ```
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config_cache_keys =
PresenceChannel
.redis
.scan_each(match: Discourse.redis.namespace_key("_presence_*_config"))
.to_a
PresenceChannel.redis.del(*config_cache_keys) if config_cache_keys.present?
end
# Shortcut to access a redis client for all PresenceChannel activities.
# PresenceChannel must use the same Redis server as MessageBus, so that
# actions can be applied atomically. For the vast majority of Discourse
# installations, this is the same Redis server as `Discourse.redis`.
def self.redis
if MessageBus.backend == :redis
MessageBus.backend_instance.send(:pub_redis) # TODO: avoid a private API?
DEV: Introduce PresenceChannel API for core and plugin use PresenceChannel aims to be a generic system for allow the server, and end-users, to track the number and identity of users performing a specific task on the site. For example, it might be used to track who is currently 'replying' to a specific topic, editing a specific wiki post, etc. A few key pieces of information about the system: - PresenceChannels are identified by a name of the format `/prefix/blah`, where `prefix` has been configured by some core/plugin implementation, and `blah` can be any string the implementation wants to use. - Presence is a boolean thing - each user is either present, or not present. If a user has multiple clients 'present' in a channel, they will be deduplicated so that the user is only counted once - Developers can configure the existence and configuration of channels 'just in time' using a callback. The result of this is cached for 2 minutes. - Configuration of a channel can specify permissions in a similar way to MessageBus (public boolean, a list of allowed_user_ids, and a list of allowed_group_ids). A channel can also be placed in 'count_only' mode, where the identity of present users is not revealed to end-users. - The backend implementation uses redis lua scripts, and is designed to scale well. In the future, hard limits may be introduced on the maximum number of users that can be present in a channel. - Clients can enter/leave at will. If a client has not marked itself 'present' in the last 60 seconds, they will automatically 'leave' the channel. The JS implementation takes care of this regular check-in. - On the client-side, PresenceChannel instances can be fetched from the `presence` ember service. Each PresenceChannel can be used entered/left/subscribed/unsubscribed, and the service will automatically deduplicate information before interacting with the server. - When a client joins a PresenceChannel, the JS implementation will automatically make a GET request for the current channel state. To avoid this, the channel state can be serialized into one of your existing endpoints, and then passed to the `subscribe` method on the channel. - The PresenceChannel JS object is an ember object. The `users` and `count` property can be used directly in ember templates, and in computed properties. - It is important to make sure that you `unsubscribe()` and `leave()` any PresenceChannel objects after use An example implementation may look something like this. On the server: ```ruby register_presence_channel_prefix("site") do |channel| next nil unless channel == "/site/online" PresenceChannel::Config.new(public: true) end ``` And on the client, a component could be implemented like this: ```javascript import Component from "@ember/component"; import { inject as service } from "@ember/service"; export default Component.extend({ presence: service(), init() { this._super(...arguments); this.set("presenceChannel", this.presence.getChannel("/site/online")); }, didInsertElement() { this.presenceChannel.enter(); this.presenceChannel.subscribe(); }, willDestroyElement() { this.presenceChannel.leave(); this.presenceChannel.unsubscribe(); }, }); ``` With this template: ```handlebars Online: {{presenceChannel.count}} <ul> {{#each presenceChannel.users as |user|}} <li>{{avatar user imageSize="tiny"}} {{user.username}}</li> {{/each}} </ul> ```
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elsif Rails.env.test?
Discourse.redis.without_namespace
else
raise "PresenceChannel is unable to access MessageBus's Redis instance"
end
end
def self.redis_eval(key, *args)
LUA_SCRIPTS[key].eval(redis, *args)
DEV: Introduce PresenceChannel API for core and plugin use PresenceChannel aims to be a generic system for allow the server, and end-users, to track the number and identity of users performing a specific task on the site. For example, it might be used to track who is currently 'replying' to a specific topic, editing a specific wiki post, etc. A few key pieces of information about the system: - PresenceChannels are identified by a name of the format `/prefix/blah`, where `prefix` has been configured by some core/plugin implementation, and `blah` can be any string the implementation wants to use. - Presence is a boolean thing - each user is either present, or not present. If a user has multiple clients 'present' in a channel, they will be deduplicated so that the user is only counted once - Developers can configure the existence and configuration of channels 'just in time' using a callback. The result of this is cached for 2 minutes. - Configuration of a channel can specify permissions in a similar way to MessageBus (public boolean, a list of allowed_user_ids, and a list of allowed_group_ids). A channel can also be placed in 'count_only' mode, where the identity of present users is not revealed to end-users. - The backend implementation uses redis lua scripts, and is designed to scale well. In the future, hard limits may be introduced on the maximum number of users that can be present in a channel. - Clients can enter/leave at will. If a client has not marked itself 'present' in the last 60 seconds, they will automatically 'leave' the channel. The JS implementation takes care of this regular check-in. - On the client-side, PresenceChannel instances can be fetched from the `presence` ember service. Each PresenceChannel can be used entered/left/subscribed/unsubscribed, and the service will automatically deduplicate information before interacting with the server. - When a client joins a PresenceChannel, the JS implementation will automatically make a GET request for the current channel state. To avoid this, the channel state can be serialized into one of your existing endpoints, and then passed to the `subscribe` method on the channel. - The PresenceChannel JS object is an ember object. The `users` and `count` property can be used directly in ember templates, and in computed properties. - It is important to make sure that you `unsubscribe()` and `leave()` any PresenceChannel objects after use An example implementation may look something like this. On the server: ```ruby register_presence_channel_prefix("site") do |channel| next nil unless channel == "/site/online" PresenceChannel::Config.new(public: true) end ``` And on the client, a component could be implemented like this: ```javascript import Component from "@ember/component"; import { inject as service } from "@ember/service"; export default Component.extend({ presence: service(), init() { this._super(...arguments); this.set("presenceChannel", this.presence.getChannel("/site/online")); }, didInsertElement() { this.presenceChannel.enter(); this.presenceChannel.subscribe(); }, willDestroyElement() { this.presenceChannel.leave(); this.presenceChannel.unsubscribe(); }, }); ``` With this template: ```handlebars Online: {{presenceChannel.count}} <ul> {{#each presenceChannel.users as |user|}} <li>{{avatar user imageSize="tiny"}} {{user.username}}</li> {{/each}} </ul> ```
2021-08-27 09:43:39 -04:00
end
# Register a callback to configure channels with a given prefix
# Prefix must match [a-zA-Z0-9_-]+
#
# For example, this registration will be used for
# all channels starting /topic-reply/...:
#
# register_prefix("topic-reply") do |channel_name|
# PresenceChannel::Config.new(public: true)
# end
#
# At runtime, the block will be passed a full channel name. If the channel
# should not exist, the block should return `nil`. If the channel should exist,
# the block should return a PresenceChannel::Config object.
#
# Return values may be cached for up to 10 seconds.
DEV: Introduce PresenceChannel API for core and plugin use PresenceChannel aims to be a generic system for allow the server, and end-users, to track the number and identity of users performing a specific task on the site. For example, it might be used to track who is currently 'replying' to a specific topic, editing a specific wiki post, etc. A few key pieces of information about the system: - PresenceChannels are identified by a name of the format `/prefix/blah`, where `prefix` has been configured by some core/plugin implementation, and `blah` can be any string the implementation wants to use. - Presence is a boolean thing - each user is either present, or not present. If a user has multiple clients 'present' in a channel, they will be deduplicated so that the user is only counted once - Developers can configure the existence and configuration of channels 'just in time' using a callback. The result of this is cached for 2 minutes. - Configuration of a channel can specify permissions in a similar way to MessageBus (public boolean, a list of allowed_user_ids, and a list of allowed_group_ids). A channel can also be placed in 'count_only' mode, where the identity of present users is not revealed to end-users. - The backend implementation uses redis lua scripts, and is designed to scale well. In the future, hard limits may be introduced on the maximum number of users that can be present in a channel. - Clients can enter/leave at will. If a client has not marked itself 'present' in the last 60 seconds, they will automatically 'leave' the channel. The JS implementation takes care of this regular check-in. - On the client-side, PresenceChannel instances can be fetched from the `presence` ember service. Each PresenceChannel can be used entered/left/subscribed/unsubscribed, and the service will automatically deduplicate information before interacting with the server. - When a client joins a PresenceChannel, the JS implementation will automatically make a GET request for the current channel state. To avoid this, the channel state can be serialized into one of your existing endpoints, and then passed to the `subscribe` method on the channel. - The PresenceChannel JS object is an ember object. The `users` and `count` property can be used directly in ember templates, and in computed properties. - It is important to make sure that you `unsubscribe()` and `leave()` any PresenceChannel objects after use An example implementation may look something like this. On the server: ```ruby register_presence_channel_prefix("site") do |channel| next nil unless channel == "/site/online" PresenceChannel::Config.new(public: true) end ``` And on the client, a component could be implemented like this: ```javascript import Component from "@ember/component"; import { inject as service } from "@ember/service"; export default Component.extend({ presence: service(), init() { this._super(...arguments); this.set("presenceChannel", this.presence.getChannel("/site/online")); }, didInsertElement() { this.presenceChannel.enter(); this.presenceChannel.subscribe(); }, willDestroyElement() { this.presenceChannel.leave(); this.presenceChannel.unsubscribe(); }, }); ``` With this template: ```handlebars Online: {{presenceChannel.count}} <ul> {{#each presenceChannel.users as |user|}} <li>{{avatar user imageSize="tiny"}} {{user.username}}</li> {{/each}} </ul> ```
2021-08-27 09:43:39 -04:00
#
# Plugins should use the {Plugin::Instance.register_presence_channel_prefix} API instead
def self.register_prefix(prefix, &block)
unless prefix.match? /[a-zA-Z0-9_-]+/
raise "PresenceChannel prefix #{prefix} must match [a-zA-Z0-9_-]+"
end
DEV: Introduce PresenceChannel API for core and plugin use PresenceChannel aims to be a generic system for allow the server, and end-users, to track the number and identity of users performing a specific task on the site. For example, it might be used to track who is currently 'replying' to a specific topic, editing a specific wiki post, etc. A few key pieces of information about the system: - PresenceChannels are identified by a name of the format `/prefix/blah`, where `prefix` has been configured by some core/plugin implementation, and `blah` can be any string the implementation wants to use. - Presence is a boolean thing - each user is either present, or not present. If a user has multiple clients 'present' in a channel, they will be deduplicated so that the user is only counted once - Developers can configure the existence and configuration of channels 'just in time' using a callback. The result of this is cached for 2 minutes. - Configuration of a channel can specify permissions in a similar way to MessageBus (public boolean, a list of allowed_user_ids, and a list of allowed_group_ids). A channel can also be placed in 'count_only' mode, where the identity of present users is not revealed to end-users. - The backend implementation uses redis lua scripts, and is designed to scale well. In the future, hard limits may be introduced on the maximum number of users that can be present in a channel. - Clients can enter/leave at will. If a client has not marked itself 'present' in the last 60 seconds, they will automatically 'leave' the channel. The JS implementation takes care of this regular check-in. - On the client-side, PresenceChannel instances can be fetched from the `presence` ember service. Each PresenceChannel can be used entered/left/subscribed/unsubscribed, and the service will automatically deduplicate information before interacting with the server. - When a client joins a PresenceChannel, the JS implementation will automatically make a GET request for the current channel state. To avoid this, the channel state can be serialized into one of your existing endpoints, and then passed to the `subscribe` method on the channel. - The PresenceChannel JS object is an ember object. The `users` and `count` property can be used directly in ember templates, and in computed properties. - It is important to make sure that you `unsubscribe()` and `leave()` any PresenceChannel objects after use An example implementation may look something like this. On the server: ```ruby register_presence_channel_prefix("site") do |channel| next nil unless channel == "/site/online" PresenceChannel::Config.new(public: true) end ``` And on the client, a component could be implemented like this: ```javascript import Component from "@ember/component"; import { inject as service } from "@ember/service"; export default Component.extend({ presence: service(), init() { this._super(...arguments); this.set("presenceChannel", this.presence.getChannel("/site/online")); }, didInsertElement() { this.presenceChannel.enter(); this.presenceChannel.subscribe(); }, willDestroyElement() { this.presenceChannel.leave(); this.presenceChannel.unsubscribe(); }, }); ``` With this template: ```handlebars Online: {{presenceChannel.count}} <ul> {{#each presenceChannel.users as |user|}} <li>{{avatar user imageSize="tiny"}} {{user.username}}</li> {{/each}} </ul> ```
2021-08-27 09:43:39 -04:00
if @@configuration_blocks&.[](prefix)
raise "PresenceChannel prefix #{prefix} already registered"
end
DEV: Introduce PresenceChannel API for core and plugin use PresenceChannel aims to be a generic system for allow the server, and end-users, to track the number and identity of users performing a specific task on the site. For example, it might be used to track who is currently 'replying' to a specific topic, editing a specific wiki post, etc. A few key pieces of information about the system: - PresenceChannels are identified by a name of the format `/prefix/blah`, where `prefix` has been configured by some core/plugin implementation, and `blah` can be any string the implementation wants to use. - Presence is a boolean thing - each user is either present, or not present. If a user has multiple clients 'present' in a channel, they will be deduplicated so that the user is only counted once - Developers can configure the existence and configuration of channels 'just in time' using a callback. The result of this is cached for 2 minutes. - Configuration of a channel can specify permissions in a similar way to MessageBus (public boolean, a list of allowed_user_ids, and a list of allowed_group_ids). A channel can also be placed in 'count_only' mode, where the identity of present users is not revealed to end-users. - The backend implementation uses redis lua scripts, and is designed to scale well. In the future, hard limits may be introduced on the maximum number of users that can be present in a channel. - Clients can enter/leave at will. If a client has not marked itself 'present' in the last 60 seconds, they will automatically 'leave' the channel. The JS implementation takes care of this regular check-in. - On the client-side, PresenceChannel instances can be fetched from the `presence` ember service. Each PresenceChannel can be used entered/left/subscribed/unsubscribed, and the service will automatically deduplicate information before interacting with the server. - When a client joins a PresenceChannel, the JS implementation will automatically make a GET request for the current channel state. To avoid this, the channel state can be serialized into one of your existing endpoints, and then passed to the `subscribe` method on the channel. - The PresenceChannel JS object is an ember object. The `users` and `count` property can be used directly in ember templates, and in computed properties. - It is important to make sure that you `unsubscribe()` and `leave()` any PresenceChannel objects after use An example implementation may look something like this. On the server: ```ruby register_presence_channel_prefix("site") do |channel| next nil unless channel == "/site/online" PresenceChannel::Config.new(public: true) end ``` And on the client, a component could be implemented like this: ```javascript import Component from "@ember/component"; import { inject as service } from "@ember/service"; export default Component.extend({ presence: service(), init() { this._super(...arguments); this.set("presenceChannel", this.presence.getChannel("/site/online")); }, didInsertElement() { this.presenceChannel.enter(); this.presenceChannel.subscribe(); }, willDestroyElement() { this.presenceChannel.leave(); this.presenceChannel.unsubscribe(); }, }); ``` With this template: ```handlebars Online: {{presenceChannel.count}} <ul> {{#each presenceChannel.users as |user|}} <li>{{avatar user imageSize="tiny"}} {{user.username}}</li> {{/each}} </ul> ```
2021-08-27 09:43:39 -04:00
@@configuration_blocks[prefix] = block
end
# For use in a test environment only
def self.unregister_prefix(prefix)
raise "Only allowed in test environment" if !Rails.env.test?
@@configuration_blocks&.delete(prefix)
end
private
def fetch_config(use_cache: true)
cached_config = (PresenceChannel.redis.get(redis_key_config) if use_cache)
DEV: Introduce PresenceChannel API for core and plugin use PresenceChannel aims to be a generic system for allow the server, and end-users, to track the number and identity of users performing a specific task on the site. For example, it might be used to track who is currently 'replying' to a specific topic, editing a specific wiki post, etc. A few key pieces of information about the system: - PresenceChannels are identified by a name of the format `/prefix/blah`, where `prefix` has been configured by some core/plugin implementation, and `blah` can be any string the implementation wants to use. - Presence is a boolean thing - each user is either present, or not present. If a user has multiple clients 'present' in a channel, they will be deduplicated so that the user is only counted once - Developers can configure the existence and configuration of channels 'just in time' using a callback. The result of this is cached for 2 minutes. - Configuration of a channel can specify permissions in a similar way to MessageBus (public boolean, a list of allowed_user_ids, and a list of allowed_group_ids). A channel can also be placed in 'count_only' mode, where the identity of present users is not revealed to end-users. - The backend implementation uses redis lua scripts, and is designed to scale well. In the future, hard limits may be introduced on the maximum number of users that can be present in a channel. - Clients can enter/leave at will. If a client has not marked itself 'present' in the last 60 seconds, they will automatically 'leave' the channel. The JS implementation takes care of this regular check-in. - On the client-side, PresenceChannel instances can be fetched from the `presence` ember service. Each PresenceChannel can be used entered/left/subscribed/unsubscribed, and the service will automatically deduplicate information before interacting with the server. - When a client joins a PresenceChannel, the JS implementation will automatically make a GET request for the current channel state. To avoid this, the channel state can be serialized into one of your existing endpoints, and then passed to the `subscribe` method on the channel. - The PresenceChannel JS object is an ember object. The `users` and `count` property can be used directly in ember templates, and in computed properties. - It is important to make sure that you `unsubscribe()` and `leave()` any PresenceChannel objects after use An example implementation may look something like this. On the server: ```ruby register_presence_channel_prefix("site") do |channel| next nil unless channel == "/site/online" PresenceChannel::Config.new(public: true) end ``` And on the client, a component could be implemented like this: ```javascript import Component from "@ember/component"; import { inject as service } from "@ember/service"; export default Component.extend({ presence: service(), init() { this._super(...arguments); this.set("presenceChannel", this.presence.getChannel("/site/online")); }, didInsertElement() { this.presenceChannel.enter(); this.presenceChannel.subscribe(); }, willDestroyElement() { this.presenceChannel.leave(); this.presenceChannel.unsubscribe(); }, }); ``` With this template: ```handlebars Online: {{presenceChannel.count}} <ul> {{#each presenceChannel.users as |user|}} <li>{{avatar user imageSize="tiny"}} {{user.username}}</li> {{/each}} </ul> ```
2021-08-27 09:43:39 -04:00
if cached_config == Config::NOT_FOUND
raise PresenceChannel::NotFound
elsif cached_config
Config.from_json(cached_config)
else
prefix = name[%r{/([a-zA-Z0-9_-]+)/.*}, 1]
raise PresenceChannel::NotFound if prefix.nil?
config_block = @@configuration_blocks[prefix]
config_block ||=
DiscoursePluginRegistry.presence_channel_prefixes.find { |t| t[0] == prefix }&.[](1)
raise PresenceChannel::NotFound if config_block.nil?
result = config_block.call(name)
to_cache =
if result.is_a? Config
result.to_json
elsif result.nil?
Config::NOT_FOUND
else
raise InvalidConfig.new "Expected PresenceChannel::Config or nil. Got a #{result.class.name}"
end
PresenceChannel.redis.set(redis_key_config, to_cache, ex: CONFIG_CACHE_SECONDS)
raise PresenceChannel::NotFound if result.nil?
result
end
end
def publish_message(entering_user_ids: nil, leaving_user_ids: nil)
message = {}
if config.count_only
message["count_delta"] = entering_user_ids&.count || 0
message["count_delta"] -= leaving_user_ids&.count || 0
return if message["count_delta"] == 0
else
message["leaving_user_ids"] = leaving_user_ids if leaving_user_ids.present?
if entering_user_ids.present?
users = User.where(id: entering_user_ids)
message["entering_users"] = ActiveModel::ArraySerializer.new(
users,
each_serializer: BasicUserSerializer,
)
end
end
params = {}
if config.public
# no params required
elsif config.allowed_user_ids || config.allowed_group_ids
params[:user_ids] = config.allowed_user_ids
params[:group_ids] = config.allowed_group_ids
else
# nobody is allowed... don't publish anything
return
end
MessageBus.publish(message_bus_channel_name, message.as_json, **params)
end
# Most atomic actions are achieved via lua scripts. However, when a lua action
# will result in publishing a messagebus message, the atomicity is broken.
#
# For example, if one process is handling a 'user enter' event, and another is
# handling a 'user leave' event, we need to make sure the messagebus messages
# are published in the same sequence that the PresenceChannel lua script are run.
#
# The present/leave/auto_leave lua scripts will automatically acquire this mutex
2022-02-27 21:20:58 -05:00
# if needed. If their return value indicates a change has occurred, the mutex
DEV: Introduce PresenceChannel API for core and plugin use PresenceChannel aims to be a generic system for allow the server, and end-users, to track the number and identity of users performing a specific task on the site. For example, it might be used to track who is currently 'replying' to a specific topic, editing a specific wiki post, etc. A few key pieces of information about the system: - PresenceChannels are identified by a name of the format `/prefix/blah`, where `prefix` has been configured by some core/plugin implementation, and `blah` can be any string the implementation wants to use. - Presence is a boolean thing - each user is either present, or not present. If a user has multiple clients 'present' in a channel, they will be deduplicated so that the user is only counted once - Developers can configure the existence and configuration of channels 'just in time' using a callback. The result of this is cached for 2 minutes. - Configuration of a channel can specify permissions in a similar way to MessageBus (public boolean, a list of allowed_user_ids, and a list of allowed_group_ids). A channel can also be placed in 'count_only' mode, where the identity of present users is not revealed to end-users. - The backend implementation uses redis lua scripts, and is designed to scale well. In the future, hard limits may be introduced on the maximum number of users that can be present in a channel. - Clients can enter/leave at will. If a client has not marked itself 'present' in the last 60 seconds, they will automatically 'leave' the channel. The JS implementation takes care of this regular check-in. - On the client-side, PresenceChannel instances can be fetched from the `presence` ember service. Each PresenceChannel can be used entered/left/subscribed/unsubscribed, and the service will automatically deduplicate information before interacting with the server. - When a client joins a PresenceChannel, the JS implementation will automatically make a GET request for the current channel state. To avoid this, the channel state can be serialized into one of your existing endpoints, and then passed to the `subscribe` method on the channel. - The PresenceChannel JS object is an ember object. The `users` and `count` property can be used directly in ember templates, and in computed properties. - It is important to make sure that you `unsubscribe()` and `leave()` any PresenceChannel objects after use An example implementation may look something like this. On the server: ```ruby register_presence_channel_prefix("site") do |channel| next nil unless channel == "/site/online" PresenceChannel::Config.new(public: true) end ``` And on the client, a component could be implemented like this: ```javascript import Component from "@ember/component"; import { inject as service } from "@ember/service"; export default Component.extend({ presence: service(), init() { this._super(...arguments); this.set("presenceChannel", this.presence.getChannel("/site/online")); }, didInsertElement() { this.presenceChannel.enter(); this.presenceChannel.subscribe(); }, willDestroyElement() { this.presenceChannel.leave(); this.presenceChannel.unsubscribe(); }, }); ``` With this template: ```handlebars Online: {{presenceChannel.count}} <ul> {{#each presenceChannel.users as |user|}} <li>{{avatar user imageSize="tiny"}} {{user.username}}</li> {{/each}} </ul> ```
2021-08-27 09:43:39 -04:00
# should be released via #release_mutex after the messagebus message has been sent
#
# If they need a change, and the mutex is not available, they will raise an error
# and should be retried periodically
def redis_key_mutex
Discourse.redis.namespace_key("_presence_#{name}_mutex")
end
def release_mutex(mutex_value)
PresenceChannel.redis_eval(:release_mutex, [redis_key_mutex], [mutex_value])
end
def retry_on_mutex_error
attempts ||= 0
yield
rescue ::Redis::CommandError => e
if e.to_s =~ /#{MUTEX_LOCKED_ERROR}/ && attempts < 1000
attempts += 1
sleep 0.001
retry
else
raise
end
end
# The redis key which MessageBus uses to store the 'last_id' for the channel
# associated with this PresenceChannel.
def message_bus_last_id_key
return "" if Rails.env.test? && MessageBus.backend == :memory
# TODO: Avoid using private MessageBus methods here
encoded_channel_name = MessageBus.send(:encode_channel_name, message_bus_channel_name)
MessageBus.backend_instance.send(:backlog_id_key, encoded_channel_name)
DEV: Introduce PresenceChannel API for core and plugin use PresenceChannel aims to be a generic system for allow the server, and end-users, to track the number and identity of users performing a specific task on the site. For example, it might be used to track who is currently 'replying' to a specific topic, editing a specific wiki post, etc. A few key pieces of information about the system: - PresenceChannels are identified by a name of the format `/prefix/blah`, where `prefix` has been configured by some core/plugin implementation, and `blah` can be any string the implementation wants to use. - Presence is a boolean thing - each user is either present, or not present. If a user has multiple clients 'present' in a channel, they will be deduplicated so that the user is only counted once - Developers can configure the existence and configuration of channels 'just in time' using a callback. The result of this is cached for 2 minutes. - Configuration of a channel can specify permissions in a similar way to MessageBus (public boolean, a list of allowed_user_ids, and a list of allowed_group_ids). A channel can also be placed in 'count_only' mode, where the identity of present users is not revealed to end-users. - The backend implementation uses redis lua scripts, and is designed to scale well. In the future, hard limits may be introduced on the maximum number of users that can be present in a channel. - Clients can enter/leave at will. If a client has not marked itself 'present' in the last 60 seconds, they will automatically 'leave' the channel. The JS implementation takes care of this regular check-in. - On the client-side, PresenceChannel instances can be fetched from the `presence` ember service. Each PresenceChannel can be used entered/left/subscribed/unsubscribed, and the service will automatically deduplicate information before interacting with the server. - When a client joins a PresenceChannel, the JS implementation will automatically make a GET request for the current channel state. To avoid this, the channel state can be serialized into one of your existing endpoints, and then passed to the `subscribe` method on the channel. - The PresenceChannel JS object is an ember object. The `users` and `count` property can be used directly in ember templates, and in computed properties. - It is important to make sure that you `unsubscribe()` and `leave()` any PresenceChannel objects after use An example implementation may look something like this. On the server: ```ruby register_presence_channel_prefix("site") do |channel| next nil unless channel == "/site/online" PresenceChannel::Config.new(public: true) end ``` And on the client, a component could be implemented like this: ```javascript import Component from "@ember/component"; import { inject as service } from "@ember/service"; export default Component.extend({ presence: service(), init() { this._super(...arguments); this.set("presenceChannel", this.presence.getChannel("/site/online")); }, didInsertElement() { this.presenceChannel.enter(); this.presenceChannel.subscribe(); }, willDestroyElement() { this.presenceChannel.leave(); this.presenceChannel.unsubscribe(); }, }); ``` With this template: ```handlebars Online: {{presenceChannel.count}} <ul> {{#each presenceChannel.users as |user|}} <li>{{avatar user imageSize="tiny"}} {{user.username}}</li> {{/each}} </ul> ```
2021-08-27 09:43:39 -04:00
end
def redis_keys
[
redis_key_zlist,
redis_key_hash,
self.class.redis_key_channel_list,
message_bus_last_id_key,
redis_key_mutex,
]
end
# The zlist is a list of client_ids, ranked by their expiration timestamp
# we periodically delete the 'lowest ranked' items in this list based on the `timeout` of the channel
def redis_key_zlist
Discourse.redis.namespace_key("_presence_#{name}_zlist")
end
# The hash contains a map of user_id => session_count
# when the count for a user reaches 0, the key is deleted
# We use this hash to efficiently count the number of present users
def redis_key_hash
Discourse.redis.namespace_key("_presence_#{name}_hash")
end
# The hash contains a map of user_id => session_count
# when the count for a user reaches 0, the key is deleted
# We use this hash to efficiently count the number of present users
def redis_key_config
Discourse.redis.namespace_key("_presence_#{name}_config")
end
# This list contains all active presence channels, ranked with the expiration timestamp of their least-recently-seen client_id
# We periodically check the 'lowest ranked' items in this list based on the `timeout` of the channel
def self.redis_key_channel_list
Discourse.redis.namespace_key("_presence_channels")
end
COMMON_PRESENT_LEAVE_LUA = <<~LUA
local channel = ARGV[1]
local user_id = ARGV[2]
local client_id = ARGV[3]
local expires = ARGV[4]
local mutex_value = ARGV[5]
local zlist_key = KEYS[1]
local hash_key = KEYS[2]
local channels_key = KEYS[3]
local message_bus_id_key = KEYS[4]
local mutex_key = KEYS[5]
local mutex_locked = redis.call('EXISTS', mutex_key) == 1
local zlist_elem = tostring(user_id) .. " " .. tostring(client_id)
LUA
UPDATE_GLOBAL_CHANNELS_LUA = <<~LUA
-- Update the global channels list with the timestamp of the oldest client
local oldest_client = redis.call('ZRANGE', zlist_key, 0, 0, 'WITHSCORES')
if table.getn(oldest_client) > 0 then
local oldest_client_expire_timestamp = oldest_client[2]
redis.call('ZADD', channels_key, tonumber(oldest_client_expire_timestamp), tostring(channel))
else
-- The channel is now empty, delete from global list
redis.call('ZREM', channels_key, tostring(channel))
end
LUA
LUA_SCRIPTS ||= {}
LUA_SCRIPTS[:present] = DiscourseRedis::EvalHelper.new <<~LUA
DEV: Introduce PresenceChannel API for core and plugin use PresenceChannel aims to be a generic system for allow the server, and end-users, to track the number and identity of users performing a specific task on the site. For example, it might be used to track who is currently 'replying' to a specific topic, editing a specific wiki post, etc. A few key pieces of information about the system: - PresenceChannels are identified by a name of the format `/prefix/blah`, where `prefix` has been configured by some core/plugin implementation, and `blah` can be any string the implementation wants to use. - Presence is a boolean thing - each user is either present, or not present. If a user has multiple clients 'present' in a channel, they will be deduplicated so that the user is only counted once - Developers can configure the existence and configuration of channels 'just in time' using a callback. The result of this is cached for 2 minutes. - Configuration of a channel can specify permissions in a similar way to MessageBus (public boolean, a list of allowed_user_ids, and a list of allowed_group_ids). A channel can also be placed in 'count_only' mode, where the identity of present users is not revealed to end-users. - The backend implementation uses redis lua scripts, and is designed to scale well. In the future, hard limits may be introduced on the maximum number of users that can be present in a channel. - Clients can enter/leave at will. If a client has not marked itself 'present' in the last 60 seconds, they will automatically 'leave' the channel. The JS implementation takes care of this regular check-in. - On the client-side, PresenceChannel instances can be fetched from the `presence` ember service. Each PresenceChannel can be used entered/left/subscribed/unsubscribed, and the service will automatically deduplicate information before interacting with the server. - When a client joins a PresenceChannel, the JS implementation will automatically make a GET request for the current channel state. To avoid this, the channel state can be serialized into one of your existing endpoints, and then passed to the `subscribe` method on the channel. - The PresenceChannel JS object is an ember object. The `users` and `count` property can be used directly in ember templates, and in computed properties. - It is important to make sure that you `unsubscribe()` and `leave()` any PresenceChannel objects after use An example implementation may look something like this. On the server: ```ruby register_presence_channel_prefix("site") do |channel| next nil unless channel == "/site/online" PresenceChannel::Config.new(public: true) end ``` And on the client, a component could be implemented like this: ```javascript import Component from "@ember/component"; import { inject as service } from "@ember/service"; export default Component.extend({ presence: service(), init() { this._super(...arguments); this.set("presenceChannel", this.presence.getChannel("/site/online")); }, didInsertElement() { this.presenceChannel.enter(); this.presenceChannel.subscribe(); }, willDestroyElement() { this.presenceChannel.leave(); this.presenceChannel.unsubscribe(); }, }); ``` With this template: ```handlebars Online: {{presenceChannel.count}} <ul> {{#each presenceChannel.users as |user|}} <li>{{avatar user imageSize="tiny"}} {{user.username}}</li> {{/each}} </ul> ```
2021-08-27 09:43:39 -04:00
#{COMMON_PRESENT_LEAVE_LUA}
if mutex_locked then
local mutex_required = redis.call('HGET', hash_key, tostring(user_id)) == false
if mutex_required then
error("#{MUTEX_LOCKED_ERROR}")
end
end
local added_clients = redis.call('ZADD', zlist_key, expires, zlist_elem)
local added_users = 0
if tonumber(added_clients) > 0 then
local new_count = redis.call('HINCRBY', hash_key, tostring(user_id), 1)
if new_count == 1 then
added_users = 1
redis.call('SET', mutex_key, mutex_value, 'EX', #{MUTEX_TIMEOUT_SECONDS})
end
-- Add the channel to the global channel list. 'NX' means the value will
-- only be set if doesn't already exist
redis.call('ZADD', channels_key, "NX", expires, tostring(channel))
DEV: Introduce PresenceChannel API for core and plugin use PresenceChannel aims to be a generic system for allow the server, and end-users, to track the number and identity of users performing a specific task on the site. For example, it might be used to track who is currently 'replying' to a specific topic, editing a specific wiki post, etc. A few key pieces of information about the system: - PresenceChannels are identified by a name of the format `/prefix/blah`, where `prefix` has been configured by some core/plugin implementation, and `blah` can be any string the implementation wants to use. - Presence is a boolean thing - each user is either present, or not present. If a user has multiple clients 'present' in a channel, they will be deduplicated so that the user is only counted once - Developers can configure the existence and configuration of channels 'just in time' using a callback. The result of this is cached for 2 minutes. - Configuration of a channel can specify permissions in a similar way to MessageBus (public boolean, a list of allowed_user_ids, and a list of allowed_group_ids). A channel can also be placed in 'count_only' mode, where the identity of present users is not revealed to end-users. - The backend implementation uses redis lua scripts, and is designed to scale well. In the future, hard limits may be introduced on the maximum number of users that can be present in a channel. - Clients can enter/leave at will. If a client has not marked itself 'present' in the last 60 seconds, they will automatically 'leave' the channel. The JS implementation takes care of this regular check-in. - On the client-side, PresenceChannel instances can be fetched from the `presence` ember service. Each PresenceChannel can be used entered/left/subscribed/unsubscribed, and the service will automatically deduplicate information before interacting with the server. - When a client joins a PresenceChannel, the JS implementation will automatically make a GET request for the current channel state. To avoid this, the channel state can be serialized into one of your existing endpoints, and then passed to the `subscribe` method on the channel. - The PresenceChannel JS object is an ember object. The `users` and `count` property can be used directly in ember templates, and in computed properties. - It is important to make sure that you `unsubscribe()` and `leave()` any PresenceChannel objects after use An example implementation may look something like this. On the server: ```ruby register_presence_channel_prefix("site") do |channel| next nil unless channel == "/site/online" PresenceChannel::Config.new(public: true) end ``` And on the client, a component could be implemented like this: ```javascript import Component from "@ember/component"; import { inject as service } from "@ember/service"; export default Component.extend({ presence: service(), init() { this._super(...arguments); this.set("presenceChannel", this.presence.getChannel("/site/online")); }, didInsertElement() { this.presenceChannel.enter(); this.presenceChannel.subscribe(); }, willDestroyElement() { this.presenceChannel.leave(); this.presenceChannel.unsubscribe(); }, }); ``` With this template: ```handlebars Online: {{presenceChannel.count}} <ul> {{#each presenceChannel.users as |user|}} <li>{{avatar user imageSize="tiny"}} {{user.username}}</li> {{/each}} </ul> ```
2021-08-27 09:43:39 -04:00
end
redis.call('EXPIREAT', hash_key, expires + #{GC_SECONDS})
redis.call('EXPIREAT', zlist_key, expires + #{GC_SECONDS})
return added_users
LUA
LUA_SCRIPTS[:leave] = DiscourseRedis::EvalHelper.new <<~LUA
DEV: Introduce PresenceChannel API for core and plugin use PresenceChannel aims to be a generic system for allow the server, and end-users, to track the number and identity of users performing a specific task on the site. For example, it might be used to track who is currently 'replying' to a specific topic, editing a specific wiki post, etc. A few key pieces of information about the system: - PresenceChannels are identified by a name of the format `/prefix/blah`, where `prefix` has been configured by some core/plugin implementation, and `blah` can be any string the implementation wants to use. - Presence is a boolean thing - each user is either present, or not present. If a user has multiple clients 'present' in a channel, they will be deduplicated so that the user is only counted once - Developers can configure the existence and configuration of channels 'just in time' using a callback. The result of this is cached for 2 minutes. - Configuration of a channel can specify permissions in a similar way to MessageBus (public boolean, a list of allowed_user_ids, and a list of allowed_group_ids). A channel can also be placed in 'count_only' mode, where the identity of present users is not revealed to end-users. - The backend implementation uses redis lua scripts, and is designed to scale well. In the future, hard limits may be introduced on the maximum number of users that can be present in a channel. - Clients can enter/leave at will. If a client has not marked itself 'present' in the last 60 seconds, they will automatically 'leave' the channel. The JS implementation takes care of this regular check-in. - On the client-side, PresenceChannel instances can be fetched from the `presence` ember service. Each PresenceChannel can be used entered/left/subscribed/unsubscribed, and the service will automatically deduplicate information before interacting with the server. - When a client joins a PresenceChannel, the JS implementation will automatically make a GET request for the current channel state. To avoid this, the channel state can be serialized into one of your existing endpoints, and then passed to the `subscribe` method on the channel. - The PresenceChannel JS object is an ember object. The `users` and `count` property can be used directly in ember templates, and in computed properties. - It is important to make sure that you `unsubscribe()` and `leave()` any PresenceChannel objects after use An example implementation may look something like this. On the server: ```ruby register_presence_channel_prefix("site") do |channel| next nil unless channel == "/site/online" PresenceChannel::Config.new(public: true) end ``` And on the client, a component could be implemented like this: ```javascript import Component from "@ember/component"; import { inject as service } from "@ember/service"; export default Component.extend({ presence: service(), init() { this._super(...arguments); this.set("presenceChannel", this.presence.getChannel("/site/online")); }, didInsertElement() { this.presenceChannel.enter(); this.presenceChannel.subscribe(); }, willDestroyElement() { this.presenceChannel.leave(); this.presenceChannel.unsubscribe(); }, }); ``` With this template: ```handlebars Online: {{presenceChannel.count}} <ul> {{#each presenceChannel.users as |user|}} <li>{{avatar user imageSize="tiny"}} {{user.username}}</li> {{/each}} </ul> ```
2021-08-27 09:43:39 -04:00
#{COMMON_PRESENT_LEAVE_LUA}
if mutex_locked then
local user_session_count = redis.call('HGET', hash_key, tostring(user_id))
local mutex_required = user_session_count == 1 and redis.call('ZRANK', zlist_key, zlist_elem) ~= false
if mutex_required then
error("#{MUTEX_LOCKED_ERROR}")
end
end
-- Remove the user from the channel zlist
local removed_clients = redis.call('ZREM', zlist_key, zlist_elem)
local removed_users = 0
if tonumber(removed_clients) > 0 then
#{UPDATE_GLOBAL_CHANNELS_LUA}
-- Update the user session count in the channel hash
local val = redis.call('HINCRBY', hash_key, user_id, -1)
if val <= 0 then
redis.call('HDEL', hash_key, user_id)
removed_users = 1
redis.call('SET', mutex_key, mutex_value, 'EX', #{MUTEX_TIMEOUT_SECONDS})
end
end
return removed_users
LUA
LUA_SCRIPTS[:release_mutex] = DiscourseRedis::EvalHelper.new <<~LUA
DEV: Introduce PresenceChannel API for core and plugin use PresenceChannel aims to be a generic system for allow the server, and end-users, to track the number and identity of users performing a specific task on the site. For example, it might be used to track who is currently 'replying' to a specific topic, editing a specific wiki post, etc. A few key pieces of information about the system: - PresenceChannels are identified by a name of the format `/prefix/blah`, where `prefix` has been configured by some core/plugin implementation, and `blah` can be any string the implementation wants to use. - Presence is a boolean thing - each user is either present, or not present. If a user has multiple clients 'present' in a channel, they will be deduplicated so that the user is only counted once - Developers can configure the existence and configuration of channels 'just in time' using a callback. The result of this is cached for 2 minutes. - Configuration of a channel can specify permissions in a similar way to MessageBus (public boolean, a list of allowed_user_ids, and a list of allowed_group_ids). A channel can also be placed in 'count_only' mode, where the identity of present users is not revealed to end-users. - The backend implementation uses redis lua scripts, and is designed to scale well. In the future, hard limits may be introduced on the maximum number of users that can be present in a channel. - Clients can enter/leave at will. If a client has not marked itself 'present' in the last 60 seconds, they will automatically 'leave' the channel. The JS implementation takes care of this regular check-in. - On the client-side, PresenceChannel instances can be fetched from the `presence` ember service. Each PresenceChannel can be used entered/left/subscribed/unsubscribed, and the service will automatically deduplicate information before interacting with the server. - When a client joins a PresenceChannel, the JS implementation will automatically make a GET request for the current channel state. To avoid this, the channel state can be serialized into one of your existing endpoints, and then passed to the `subscribe` method on the channel. - The PresenceChannel JS object is an ember object. The `users` and `count` property can be used directly in ember templates, and in computed properties. - It is important to make sure that you `unsubscribe()` and `leave()` any PresenceChannel objects after use An example implementation may look something like this. On the server: ```ruby register_presence_channel_prefix("site") do |channel| next nil unless channel == "/site/online" PresenceChannel::Config.new(public: true) end ``` And on the client, a component could be implemented like this: ```javascript import Component from "@ember/component"; import { inject as service } from "@ember/service"; export default Component.extend({ presence: service(), init() { this._super(...arguments); this.set("presenceChannel", this.presence.getChannel("/site/online")); }, didInsertElement() { this.presenceChannel.enter(); this.presenceChannel.subscribe(); }, willDestroyElement() { this.presenceChannel.leave(); this.presenceChannel.unsubscribe(); }, }); ``` With this template: ```handlebars Online: {{presenceChannel.count}} <ul> {{#each presenceChannel.users as |user|}} <li>{{avatar user imageSize="tiny"}} {{user.username}}</li> {{/each}} </ul> ```
2021-08-27 09:43:39 -04:00
local mutex_key = KEYS[1]
local expected_value = ARGV[1]
if redis.call("GET", mutex_key) == expected_value then
redis.call("DEL", mutex_key)
end
LUA
LUA_SCRIPTS[:user_ids] = DiscourseRedis::EvalHelper.new <<~LUA
DEV: Introduce PresenceChannel API for core and plugin use PresenceChannel aims to be a generic system for allow the server, and end-users, to track the number and identity of users performing a specific task on the site. For example, it might be used to track who is currently 'replying' to a specific topic, editing a specific wiki post, etc. A few key pieces of information about the system: - PresenceChannels are identified by a name of the format `/prefix/blah`, where `prefix` has been configured by some core/plugin implementation, and `blah` can be any string the implementation wants to use. - Presence is a boolean thing - each user is either present, or not present. If a user has multiple clients 'present' in a channel, they will be deduplicated so that the user is only counted once - Developers can configure the existence and configuration of channels 'just in time' using a callback. The result of this is cached for 2 minutes. - Configuration of a channel can specify permissions in a similar way to MessageBus (public boolean, a list of allowed_user_ids, and a list of allowed_group_ids). A channel can also be placed in 'count_only' mode, where the identity of present users is not revealed to end-users. - The backend implementation uses redis lua scripts, and is designed to scale well. In the future, hard limits may be introduced on the maximum number of users that can be present in a channel. - Clients can enter/leave at will. If a client has not marked itself 'present' in the last 60 seconds, they will automatically 'leave' the channel. The JS implementation takes care of this regular check-in. - On the client-side, PresenceChannel instances can be fetched from the `presence` ember service. Each PresenceChannel can be used entered/left/subscribed/unsubscribed, and the service will automatically deduplicate information before interacting with the server. - When a client joins a PresenceChannel, the JS implementation will automatically make a GET request for the current channel state. To avoid this, the channel state can be serialized into one of your existing endpoints, and then passed to the `subscribe` method on the channel. - The PresenceChannel JS object is an ember object. The `users` and `count` property can be used directly in ember templates, and in computed properties. - It is important to make sure that you `unsubscribe()` and `leave()` any PresenceChannel objects after use An example implementation may look something like this. On the server: ```ruby register_presence_channel_prefix("site") do |channel| next nil unless channel == "/site/online" PresenceChannel::Config.new(public: true) end ``` And on the client, a component could be implemented like this: ```javascript import Component from "@ember/component"; import { inject as service } from "@ember/service"; export default Component.extend({ presence: service(), init() { this._super(...arguments); this.set("presenceChannel", this.presence.getChannel("/site/online")); }, didInsertElement() { this.presenceChannel.enter(); this.presenceChannel.subscribe(); }, willDestroyElement() { this.presenceChannel.leave(); this.presenceChannel.unsubscribe(); }, }); ``` With this template: ```handlebars Online: {{presenceChannel.count}} <ul> {{#each presenceChannel.users as |user|}} <li>{{avatar user imageSize="tiny"}} {{user.username}}</li> {{/each}} </ul> ```
2021-08-27 09:43:39 -04:00
local zlist_key = KEYS[1]
local hash_key = KEYS[2]
local message_bus_id_key = KEYS[4]
local mutex_key = KEYS[5]
if redis.call('EXISTS', mutex_key) > 0 then
error('#{MUTEX_LOCKED_ERROR}')
end
local user_ids = redis.call('HKEYS', hash_key)
table.foreach(user_ids, function(k,v) user_ids[k] = tonumber(v) end)
local message_bus_id = tonumber(redis.call('GET', message_bus_id_key))
if message_bus_id == nil then
message_bus_id = -1
end
return { message_bus_id, user_ids }
LUA
LUA_SCRIPTS[:count] = DiscourseRedis::EvalHelper.new <<~LUA
DEV: Introduce PresenceChannel API for core and plugin use PresenceChannel aims to be a generic system for allow the server, and end-users, to track the number and identity of users performing a specific task on the site. For example, it might be used to track who is currently 'replying' to a specific topic, editing a specific wiki post, etc. A few key pieces of information about the system: - PresenceChannels are identified by a name of the format `/prefix/blah`, where `prefix` has been configured by some core/plugin implementation, and `blah` can be any string the implementation wants to use. - Presence is a boolean thing - each user is either present, or not present. If a user has multiple clients 'present' in a channel, they will be deduplicated so that the user is only counted once - Developers can configure the existence and configuration of channels 'just in time' using a callback. The result of this is cached for 2 minutes. - Configuration of a channel can specify permissions in a similar way to MessageBus (public boolean, a list of allowed_user_ids, and a list of allowed_group_ids). A channel can also be placed in 'count_only' mode, where the identity of present users is not revealed to end-users. - The backend implementation uses redis lua scripts, and is designed to scale well. In the future, hard limits may be introduced on the maximum number of users that can be present in a channel. - Clients can enter/leave at will. If a client has not marked itself 'present' in the last 60 seconds, they will automatically 'leave' the channel. The JS implementation takes care of this regular check-in. - On the client-side, PresenceChannel instances can be fetched from the `presence` ember service. Each PresenceChannel can be used entered/left/subscribed/unsubscribed, and the service will automatically deduplicate information before interacting with the server. - When a client joins a PresenceChannel, the JS implementation will automatically make a GET request for the current channel state. To avoid this, the channel state can be serialized into one of your existing endpoints, and then passed to the `subscribe` method on the channel. - The PresenceChannel JS object is an ember object. The `users` and `count` property can be used directly in ember templates, and in computed properties. - It is important to make sure that you `unsubscribe()` and `leave()` any PresenceChannel objects after use An example implementation may look something like this. On the server: ```ruby register_presence_channel_prefix("site") do |channel| next nil unless channel == "/site/online" PresenceChannel::Config.new(public: true) end ``` And on the client, a component could be implemented like this: ```javascript import Component from "@ember/component"; import { inject as service } from "@ember/service"; export default Component.extend({ presence: service(), init() { this._super(...arguments); this.set("presenceChannel", this.presence.getChannel("/site/online")); }, didInsertElement() { this.presenceChannel.enter(); this.presenceChannel.subscribe(); }, willDestroyElement() { this.presenceChannel.leave(); this.presenceChannel.unsubscribe(); }, }); ``` With this template: ```handlebars Online: {{presenceChannel.count}} <ul> {{#each presenceChannel.users as |user|}} <li>{{avatar user imageSize="tiny"}} {{user.username}}</li> {{/each}} </ul> ```
2021-08-27 09:43:39 -04:00
local zlist_key = KEYS[1]
local hash_key = KEYS[2]
local message_bus_id_key = KEYS[4]
local mutex_key = KEYS[5]
if redis.call('EXISTS', mutex_key) > 0 then
error('#{MUTEX_LOCKED_ERROR}')
end
local message_bus_id = tonumber(redis.call('GET', message_bus_id_key))
if message_bus_id == nil then
message_bus_id = -1
end
local count = redis.call('HLEN', hash_key)
return { message_bus_id, count }
LUA
LUA_SCRIPTS[:auto_leave] = DiscourseRedis::EvalHelper.new <<~LUA
DEV: Introduce PresenceChannel API for core and plugin use PresenceChannel aims to be a generic system for allow the server, and end-users, to track the number and identity of users performing a specific task on the site. For example, it might be used to track who is currently 'replying' to a specific topic, editing a specific wiki post, etc. A few key pieces of information about the system: - PresenceChannels are identified by a name of the format `/prefix/blah`, where `prefix` has been configured by some core/plugin implementation, and `blah` can be any string the implementation wants to use. - Presence is a boolean thing - each user is either present, or not present. If a user has multiple clients 'present' in a channel, they will be deduplicated so that the user is only counted once - Developers can configure the existence and configuration of channels 'just in time' using a callback. The result of this is cached for 2 minutes. - Configuration of a channel can specify permissions in a similar way to MessageBus (public boolean, a list of allowed_user_ids, and a list of allowed_group_ids). A channel can also be placed in 'count_only' mode, where the identity of present users is not revealed to end-users. - The backend implementation uses redis lua scripts, and is designed to scale well. In the future, hard limits may be introduced on the maximum number of users that can be present in a channel. - Clients can enter/leave at will. If a client has not marked itself 'present' in the last 60 seconds, they will automatically 'leave' the channel. The JS implementation takes care of this regular check-in. - On the client-side, PresenceChannel instances can be fetched from the `presence` ember service. Each PresenceChannel can be used entered/left/subscribed/unsubscribed, and the service will automatically deduplicate information before interacting with the server. - When a client joins a PresenceChannel, the JS implementation will automatically make a GET request for the current channel state. To avoid this, the channel state can be serialized into one of your existing endpoints, and then passed to the `subscribe` method on the channel. - The PresenceChannel JS object is an ember object. The `users` and `count` property can be used directly in ember templates, and in computed properties. - It is important to make sure that you `unsubscribe()` and `leave()` any PresenceChannel objects after use An example implementation may look something like this. On the server: ```ruby register_presence_channel_prefix("site") do |channel| next nil unless channel == "/site/online" PresenceChannel::Config.new(public: true) end ``` And on the client, a component could be implemented like this: ```javascript import Component from "@ember/component"; import { inject as service } from "@ember/service"; export default Component.extend({ presence: service(), init() { this._super(...arguments); this.set("presenceChannel", this.presence.getChannel("/site/online")); }, didInsertElement() { this.presenceChannel.enter(); this.presenceChannel.subscribe(); }, willDestroyElement() { this.presenceChannel.leave(); this.presenceChannel.unsubscribe(); }, }); ``` With this template: ```handlebars Online: {{presenceChannel.count}} <ul> {{#each presenceChannel.users as |user|}} <li>{{avatar user imageSize="tiny"}} {{user.username}}</li> {{/each}} </ul> ```
2021-08-27 09:43:39 -04:00
local zlist_key = KEYS[1]
local hash_key = KEYS[2]
local channels_key = KEYS[3]
local mutex_key = KEYS[5]
local channel = ARGV[1]
local time = ARGV[2]
local mutex_value = ARGV[3]
local expire = redis.call('ZRANGEBYSCORE', zlist_key, '-inf', time)
DEV: Introduce PresenceChannel API for core and plugin use PresenceChannel aims to be a generic system for allow the server, and end-users, to track the number and identity of users performing a specific task on the site. For example, it might be used to track who is currently 'replying' to a specific topic, editing a specific wiki post, etc. A few key pieces of information about the system: - PresenceChannels are identified by a name of the format `/prefix/blah`, where `prefix` has been configured by some core/plugin implementation, and `blah` can be any string the implementation wants to use. - Presence is a boolean thing - each user is either present, or not present. If a user has multiple clients 'present' in a channel, they will be deduplicated so that the user is only counted once - Developers can configure the existence and configuration of channels 'just in time' using a callback. The result of this is cached for 2 minutes. - Configuration of a channel can specify permissions in a similar way to MessageBus (public boolean, a list of allowed_user_ids, and a list of allowed_group_ids). A channel can also be placed in 'count_only' mode, where the identity of present users is not revealed to end-users. - The backend implementation uses redis lua scripts, and is designed to scale well. In the future, hard limits may be introduced on the maximum number of users that can be present in a channel. - Clients can enter/leave at will. If a client has not marked itself 'present' in the last 60 seconds, they will automatically 'leave' the channel. The JS implementation takes care of this regular check-in. - On the client-side, PresenceChannel instances can be fetched from the `presence` ember service. Each PresenceChannel can be used entered/left/subscribed/unsubscribed, and the service will automatically deduplicate information before interacting with the server. - When a client joins a PresenceChannel, the JS implementation will automatically make a GET request for the current channel state. To avoid this, the channel state can be serialized into one of your existing endpoints, and then passed to the `subscribe` method on the channel. - The PresenceChannel JS object is an ember object. The `users` and `count` property can be used directly in ember templates, and in computed properties. - It is important to make sure that you `unsubscribe()` and `leave()` any PresenceChannel objects after use An example implementation may look something like this. On the server: ```ruby register_presence_channel_prefix("site") do |channel| next nil unless channel == "/site/online" PresenceChannel::Config.new(public: true) end ``` And on the client, a component could be implemented like this: ```javascript import Component from "@ember/component"; import { inject as service } from "@ember/service"; export default Component.extend({ presence: service(), init() { this._super(...arguments); this.set("presenceChannel", this.presence.getChannel("/site/online")); }, didInsertElement() { this.presenceChannel.enter(); this.presenceChannel.subscribe(); }, willDestroyElement() { this.presenceChannel.leave(); this.presenceChannel.unsubscribe(); }, }); ``` With this template: ```handlebars Online: {{presenceChannel.count}} <ul> {{#each presenceChannel.users as |user|}} <li>{{avatar user imageSize="tiny"}} {{user.username}}</li> {{/each}} </ul> ```
2021-08-27 09:43:39 -04:00
local has_mutex = false
local get_mutex = function()
if redis.call('SETNX', mutex_key, mutex_value) == 0 then
error("#{MUTEX_LOCKED_ERROR}")
end
redis.call('EXPIRE', mutex_key, #{MUTEX_TIMEOUT_SECONDS})
has_mutex = true
end
local expired_user_ids = {}
local expireOld = function(k, v)
local user_id = v:match("[^ ]+")
if (not has_mutex) and (tonumber(redis.call('HGET', hash_key, user_id)) == 1) then
get_mutex()
end
local val = redis.call('HINCRBY', hash_key, user_id, -1)
if val <= 0 then
table.insert(expired_user_ids, tonumber(user_id))
redis.call('HDEL', hash_key, user_id)
end
redis.call('ZREM', zlist_key, v)
end
table.foreach(expire, expireOld)
#{UPDATE_GLOBAL_CHANNELS_LUA}
return expired_user_ids
LUA
end