discourse/lib/discourse_redis.rb

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# frozen_string_literal: true
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#
# A wrapper around redis that namespaces keys with the current site id
#
require_dependency 'cache'
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class DiscourseRedis
class FallbackHandler
include Singleton
MASTER_ROLE_STATUS = "role:master".freeze
MASTER_LOADING_STATUS = "loading:1".freeze
MASTER_LOADED_STATUS = "loading:0".freeze
CONNECTION_TYPES = %w{normal pubsub}.each(&:freeze)
def initialize
@master = true
@running = false
@mutex = Mutex.new
@slave_config = DiscourseRedis.slave_config
@message_bus_keepalive_interval = MessageBus.keepalive_interval
end
def verify_master
synchronize { return if @thread && @thread.alive? }
@thread = Thread.new do
loop do
begin
thread = Thread.new { initiate_fallback_to_master }
thread.join
break if synchronize { @master }
sleep 5
ensure
thread.kill
end
end
end
end
def initiate_fallback_to_master
success = false
begin
redis_config = DiscourseRedis.config.dup
redis_config.delete(:connector)
master_client = ::Redis::Client.new(redis_config)
logger.warn "#{log_prefix}: Checking connection to master server..."
info = master_client.call([:info])
if info.include?(MASTER_LOADED_STATUS) && info.include?(MASTER_ROLE_STATUS)
begin
logger.warn "#{log_prefix}: Master server is active, killing all connections to slave..."
self.master = true
slave_client = ::Redis::Client.new(@slave_config)
CONNECTION_TYPES.each do |connection_type|
slave_client.call([:client, [:kill, 'type', connection_type]])
end
MessageBus.keepalive_interval = @message_bus_keepalive_interval
Discourse.clear_readonly!
Discourse.request_refresh!
success = true
ensure
slave_client&.disconnect
end
end
rescue => e
logger.warn "#{log_prefix}: Connection to Master server failed with '#{e.message}'"
ensure
master_client&.disconnect
end
success
end
def master
synchronize { @master }
end
def master=(args)
synchronize do
@master = args
# Disables MessageBus keepalive when Redis is in readonly mode
MessageBus.keepalive_interval = 0 if !@master
end
end
private
def synchronize
@mutex.synchronize { yield }
end
def logger
Rails.logger
end
def log_prefix
"#{self.class}"
end
end
class Connector < Redis::Client::Connector
def initialize(options)
super(options)
@slave_options = DiscourseRedis.slave_config(options)
@fallback_handler = DiscourseRedis::FallbackHandler.instance
end
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def resolve(client = nil)
if !@fallback_handler.master
@fallback_handler.verify_master
return @slave_options
end
begin
options = @options.dup
options.delete(:connector)
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client ||= Redis::Client.new(options)
loading = client.call([:info, :persistence]).include?(
DiscourseRedis::FallbackHandler::MASTER_LOADING_STATUS
)
loading ? @slave_options : @options
rescue Redis::ConnectionError, Redis::CannotConnectError, RuntimeError => ex
raise ex if ex.class == RuntimeError && ex.message != "Name or service not known"
@fallback_handler.master = false
@fallback_handler.verify_master
raise ex
ensure
client.disconnect
end
end
end
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def self.raw_connection(config = nil)
config ||= self.config
Redis.new(config)
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end
def self.config
GlobalSetting.redis_config
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end
def self.slave_config(options = config)
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options.dup.merge!(host: options[:slave_host], port: options[:slave_port])
end
def initialize(config = nil, namespace: true)
@config = config || DiscourseRedis.config
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@redis = DiscourseRedis.raw_connection(@config)
@namespace = namespace
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end
def self.fallback_handler
@fallback_handler ||= DiscourseRedis::FallbackHandler.instance
end
def without_namespace
# Only use this if you want to store and fetch data that's shared between sites
@redis
end
def self.ignore_readonly
yield
rescue Redis::CommandError => ex
if ex.message =~ /READONLY/
unless Discourse.recently_readonly? || Rails.env.test?
STDERR.puts "WARN: Redis is in a readonly state. Performed a noop"
end
fallback_handler.verify_master if !fallback_handler.master
Discourse.received_redis_readonly!
nil
else
raise ex
end
end
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# prefix the key with the namespace
def method_missing(meth, *args, &block)
if @redis.respond_to?(meth)
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DiscourseRedis.ignore_readonly { @redis.public_send(meth, *args, &block) }
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else
super
end
end
# Proxy key methods through, but prefix the keys with the namespace
[:append, :blpop, :brpop, :brpoplpush, :decr, :decrby, :exists, :expire, :expireat, :get, :getbit, :getrange, :getset,
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:hdel, :hexists, :hget, :hgetall, :hincrby, :hincrbyfloat, :hkeys, :hlen, :hmget, :hmset, :hset, :hsetnx, :hvals, :incr,
:incrby, :incrbyfloat, :lindex, :linsert, :llen, :lpop, :lpush, :lpushx, :lrange, :lrem, :lset, :ltrim,
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:mapped_hmset, :mapped_hmget, :mapped_mget, :mapped_mset, :mapped_msetnx, :move, :mset,
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:msetnx, :persist, :pexpire, :pexpireat, :psetex, :pttl, :rename, :renamenx, :rpop, :rpoplpush, :rpush, :rpushx, :sadd, :scard,
:sdiff, :set, :setbit, :setex, :setnx, :setrange, :sinter, :sismember, :smembers, :sort, :spop, :srandmember, :srem, :strlen,
:sunion, :ttl, :type, :watch, :zadd, :zcard, :zcount, :zincrby, :zrange, :zrangebyscore, :zrank, :zrem, :zremrangebyrank,
:zremrangebyscore, :zrevrange, :zrevrangebyscore, :zrevrank, :zrangebyscore ].each do |m|
define_method m do |*args|
args[0] = "#{namespace}:#{args[0]}" if @namespace
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DiscourseRedis.ignore_readonly { @redis.public_send(m, *args) }
end
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end
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def mget(*args)
args.map! { |a| "#{namespace}:#{a}" } if @namespace
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DiscourseRedis.ignore_readonly { @redis.mget(*args) }
end
def del(k)
DiscourseRedis.ignore_readonly do
k = "#{namespace}:#{k}" if @namespace
@redis.del k
end
end
def scan_each(options = {}, &block)
DiscourseRedis.ignore_readonly do
match = options[:match].presence || '*'
options[:match] =
if @namespace
"#{namespace}:#{match}"
else
match
end
if block
@redis.scan_each(options) do |key|
key = remove_namespace(key) if @namespace
block.call(key)
end
else
@redis.scan_each(options).map do |key|
key = remove_namespace(key) if @namespace
key
end
end
end
end
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def keys(pattern = nil)
DiscourseRedis.ignore_readonly do
pattern = pattern || '*'
pattern = "#{namespace}:#{pattern}" if @namespace
keys = @redis.keys(pattern)
if @namespace
len = namespace.length + 1
keys.map! { |k| k[len..-1] }
end
keys
end
end
def delete_prefixed(prefix)
DiscourseRedis.ignore_readonly do
keys("#{prefix}*").each { |k| $redis.del(k) }
end
end
def flushdb
DiscourseRedis.ignore_readonly do
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keys.each { |k| del(k) }
end
end
def reconnect
@redis._client.reconnect
end
def namespace_key(key)
if @namespace
"#{namespace}:#{key}"
else
key
end
end
def namespace
RailsMultisite::ConnectionManagement.current_db
end
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def self.namespace
Rails.logger.warn("DiscourseRedis.namespace is going to be deprecated, do not use it!")
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RailsMultisite::ConnectionManagement.current_db
end
def self.new_redis_store
Cache.new
end
private
def remove_namespace(key)
key[(namespace.length + 1)..-1]
end
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end