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202 lines
4.9 KiB
Ruby
202 lines
4.9 KiB
Ruby
# frozen_string_literal: true
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module CachedCounting
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extend ActiveSupport::Concern
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LUA_HGET_DEL = DiscourseRedis::EvalHelper.new <<~LUA
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local result = redis.call("HGET", KEYS[1], KEYS[2])
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redis.call("HDEL", KEYS[1], KEYS[2])
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return result
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LUA
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QUEUE = Queue.new
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SLEEP_SECONDS = 1
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FLUSH_DB_ITERATIONS = 60
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MUTEX = Mutex.new
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def self.disable
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@enabled = false
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if @thread && @thread.alive?
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@thread.wakeup
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@thread.join
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end
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end
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def self.enabled?
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@enabled != false
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end
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def self.enable
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@enabled = true
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end
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def self.reset
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@last_ensure_thread = nil
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clear_queue!
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clear_flush_to_db_lock!
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end
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ENSURE_THREAD_COOLDOWN_SECONDS = 5
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def self.ensure_thread!
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return if !enabled?
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MUTEX.synchronize do
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now = Process.clock_gettime(Process::CLOCK_MONOTONIC)
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delta = @last_ensure_thread && (now - @last_ensure_thread)
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if delta && delta < ENSURE_THREAD_COOLDOWN_SECONDS
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# creating threads can be very expensive and bog down a process
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return
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end
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@last_ensure_thread = now
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@thread = nil if !@thread&.alive?
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@thread ||= Thread.new { thread_loop }
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end
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end
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def self.thread_loop
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iterations = 0
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while true
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break if !enabled?
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sleep SLEEP_SECONDS
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flush_in_memory
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if (iterations >= FLUSH_DB_ITERATIONS) || @flush
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iterations = 0
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flush_to_db
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@flush = false
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end
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iterations += 1
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end
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rescue => ex
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if Redis::CommandError === ex && ex.message =~ /READONLY/
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# do not warn for Redis readonly mode
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elsif PG::ReadOnlySqlTransaction === ex
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# do not warn for PG readonly mode
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else
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Discourse.warn_exception(ex, message: "Unexpected error while processing cached counts")
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end
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end
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def self.flush
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if @thread && @thread.alive?
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@flush = true
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@thread.wakeup
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sleep 0.001 while @flush
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else
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flush_in_memory
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flush_to_db
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end
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end
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COUNTER_REDIS_HASH = "CounterCacheHash"
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def self.flush_in_memory
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counts = nil
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while QUEUE.length > 0
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# only 1 consumer, no need to avoid blocking
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key, klass, db, time = QUEUE.deq
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_redis_key = "#{klass},#{db},#{time.strftime("%Y%m%d")},#{key}"
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counts ||= Hash.new(0)
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counts[_redis_key] += 1
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end
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if counts
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counts.each do |redis_key, count|
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Discourse.redis.without_namespace.hincrby(COUNTER_REDIS_HASH, redis_key, count)
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end
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end
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end
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DB_FLUSH_COOLDOWN_SECONDS = 60
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DB_COOLDOWN_KEY = "cached_counting_cooldown"
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def self.flush_to_db
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redis = Discourse.redis.without_namespace
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DistributedMutex.synchronize("flush_counters_to_db", redis: redis, validity: 5.minutes) do
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if allowed_to_flush_to_db?
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redis
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.hkeys(COUNTER_REDIS_HASH)
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.each do |key|
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val = LUA_HGET_DEL.eval(redis, [COUNTER_REDIS_HASH, key]).to_i
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# unlikely (protected by mutex), but protect just in case
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# could be a race condition in test
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if val > 0
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klass_name, db, date, local_key = key.split(",", 4)
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date = Date.strptime(date, "%Y%m%d")
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klass = Module.const_get(klass_name)
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RailsMultisite::ConnectionManagement.with_connection(db) do
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klass.write_cache!(local_key, val, date)
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end
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end
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end
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end
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end
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end
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def self.clear_flush_to_db_lock!
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Discourse.redis.without_namespace.del(DB_COOLDOWN_KEY)
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end
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def self.flush_to_db_lock_ttl
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Discourse.redis.without_namespace.ttl(DB_COOLDOWN_KEY)
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end
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def self.allowed_to_flush_to_db?
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Discourse.redis.without_namespace.set(
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DB_COOLDOWN_KEY,
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"1",
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ex: DB_FLUSH_COOLDOWN_SECONDS,
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nx: true,
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)
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end
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def self.queue(key, klass)
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QUEUE.push([key, klass, RailsMultisite::ConnectionManagement.current_db, Time.now.utc])
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end
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def self.clear_queue!
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QUEUE.clear
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redis = Discourse.redis.without_namespace
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redis.del(COUNTER_REDIS_HASH)
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end
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class_methods do
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if Rails.env.test?
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# perform increment is a risky call in test,
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# it shifts stuff to background threads and leaks
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# data in the DB
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# Require caller is deliberate if they want that
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#
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# Splitting implementation to avoid any perf impact
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# given this is a method that is called a lot
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def perform_increment!(key, async: false)
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if async
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CachedCounting.ensure_thread!
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CachedCounting.queue(key, self)
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else
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CachedCounting.queue(key, self)
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CachedCounting.clear_flush_to_db_lock!
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CachedCounting.flush_in_memory
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CachedCounting.flush_to_db
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end
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end
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else
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def perform_increment!(key)
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CachedCounting.ensure_thread!
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CachedCounting.queue(key, self)
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end
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end
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def write_cache!(key, count, date)
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raise NotImplementedError
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end
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end
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end
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