mirror of
https://github.com/discourse/discourse.git
synced 2024-12-16 16:43:44 +08:00
30990006a9
This reduces chances of errors where consumers of strings mutate inputs and reduces memory usage of the app. Test suite passes now, but there may be some stuff left, so we will run a few sites on a branch prior to merging
73 lines
1.5 KiB
Ruby
73 lines
1.5 KiB
Ruby
# frozen_string_literal: true
|
|
|
|
class DistributedMemoizer
|
|
|
|
# never wait for longer that 1 second for a cross process lock
|
|
MAX_WAIT = 2
|
|
LOCK = Mutex.new
|
|
|
|
# memoize a key across processes and machines
|
|
def self.memoize(key, duration = 60 * 60 * 24, redis = nil)
|
|
redis ||= $redis
|
|
|
|
redis_key = self.redis_key(key)
|
|
|
|
unless result = redis.get(redis_key)
|
|
redis_lock_key = self.redis_lock_key(key)
|
|
|
|
start = Time.new
|
|
got_lock = false
|
|
|
|
begin
|
|
while Time.new < start + MAX_WAIT && !got_lock
|
|
LOCK.synchronize do
|
|
got_lock = get_lock(redis, redis_lock_key)
|
|
end
|
|
sleep 0.001
|
|
end
|
|
|
|
unless result = redis.get(redis_key)
|
|
result = yield
|
|
redis.setex(redis_key, duration, result)
|
|
end
|
|
|
|
ensure
|
|
# NOTE: delete regardless so next one in does not need to wait MAX_WAIT again
|
|
redis.del(redis_lock_key)
|
|
end
|
|
end
|
|
|
|
result
|
|
end
|
|
|
|
def self.redis_lock_key(key)
|
|
+"memoize_lock_" << key
|
|
end
|
|
|
|
def self.redis_key(key)
|
|
+"memoize_" << key
|
|
end
|
|
|
|
# Used for testing
|
|
def self.flush!
|
|
$redis.scan_each(match: "memoize_*").each { |key| $redis.del(key) }
|
|
end
|
|
|
|
protected
|
|
|
|
def self.get_lock(redis, redis_lock_key)
|
|
redis.watch(redis_lock_key)
|
|
current = redis.get(redis_lock_key)
|
|
return false if current
|
|
|
|
unique = SecureRandom.hex
|
|
|
|
result = redis.multi do
|
|
redis.setex(redis_lock_key, MAX_WAIT, unique)
|
|
end
|
|
|
|
redis.unwatch
|
|
result == ["OK"]
|
|
end
|
|
end
|