133 lines
2.8 KiB
Ruby
133 lines
2.8 KiB
Ruby
# Like a hash, just does its best to stay in sync across the farm
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# On boot all instances are blank, but they populate as various processes
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# fill it up
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require 'weakref'
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class DistributedCache
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@subscribers = []
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@subscribed = false
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@lock = Mutex.new
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attr_reader :key
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def self.subscribers
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@subscribers
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end
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def self.process_message(message)
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i = @subscribers.length-1
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payload = message.data
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while i >= 0
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begin
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current = @subscribers[i]
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next if payload["origin"] == current.identity
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next if current.key != payload["hash_key"]
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next if payload["discourse_version"] != Discourse.git_version
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hash = current.hash(message.site_id)
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case payload["op"]
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when "set" then hash[payload["key"]] = payload["marshalled"] ? Marshal.load(payload["value"]) : payload["value"]
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when "delete" then hash.delete(payload["key"])
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when "clear" then hash.clear
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end
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rescue WeakRef::RefError
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@subscribers.delete_at(i)
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ensure
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i -= 1
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end
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end
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end
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def self.channel_name
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"/distributed_hash".freeze
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end
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def self.ensure_subscribe!
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return if @subscribed
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@lock.synchronize do
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return if @subscribed
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MessageBus.subscribe(channel_name) do |message|
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@lock.synchronize do
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process_message(message)
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end
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end
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@subscribed = true
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end
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end
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def self.publish(hash, message)
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message[:origin] = hash.identity
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message[:hash_key] = hash.key
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message[:discourse_version] = Discourse.git_version
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MessageBus.publish(channel_name, message, { user_ids: [-1] })
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end
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def self.set(hash, key, value)
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# special support for set
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marshal = Set === value
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value = Marshal.dump(value) if marshal
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publish(hash, { op: :set, key: key, value: value, marshalled: marshal })
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end
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def self.delete(hash, key)
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publish(hash, { op: :delete, key: key })
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end
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def self.clear(hash)
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publish(hash, { op: :clear })
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end
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def self.register(hash)
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@lock.synchronize do
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@subscribers << WeakRef.new(hash)
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end
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end
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def initialize(key)
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DistributedCache.ensure_subscribe!
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DistributedCache.register(self)
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@key = key
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@data = {}
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end
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def identity
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# fork resilient / multi machine identity
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(@seed_id ||= SecureRandom.hex) + "#{Process.pid}"
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end
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def []=(k,v)
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k = k.to_s if Symbol === k
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DistributedCache.set(self, k, v)
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hash[k] = v
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end
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def [](k)
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k = k.to_s if Symbol === k
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hash[k]
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end
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def delete(k)
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k = k.to_s if Symbol === k
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DistributedCache.delete(self, k)
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hash.delete(k)
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end
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def clear
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DistributedCache.clear(self)
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hash.clear
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end
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def hash(db = nil)
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db ||= RailsMultisite::ConnectionManagement.current_db
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@data[db] ||= ThreadSafe::Hash.new
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end
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end
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