Sha256: 077e8385832ea5121c6fdff9d3c505f35db548bda73b4033236c85fbf95c0872
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Size: 1.74 KB
Versions: 10
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Stored size: 1.74 KB
Contents
require "securerandom"
module Redstream
# @api private
#
# As the name suggests, the Redstream::Lock class implements a redis based
# locking mechanism. It atomically (lua script) gets/sets the lock key and
# updates its expire timeout, in case it currently holds the lock. Moreover,
# once it got the lock, it tries to keep it by updating the lock expire
# timeout from within a thread every 3 seconds.
#
# @example
# lock = Redstream::Lock.new(name: "user_stream_lock")
#
# loop do
# got_lock = lock.acquire do
# # ...
# end
#
# sleep(5) unless got_lock
# end
class Lock
def initialize(name:)
@name = name
@id = SecureRandom.hex
end
def acquire(&block)
got_lock = get_lock
keep_lock(&block) if got_lock
got_lock
end
private
def keep_lock(&block)
stop = false
mutex = Mutex.new
Thread.new do
until mutex.synchronize { stop }
Redstream.connection_pool.with { |redis| redis.expire(Redstream.lock_key_name(@name), 5) }
sleep 3
end
end
block.call
ensure
mutex.synchronize do
stop = true
end
end
def get_lock
@get_lock_script = <<~GET_LOCK_SCRIPT
local lock_key_name, id = ARGV[1], ARGV[2]
local cur = redis.call('get', lock_key_name)
if not cur then
redis.call('setex', lock_key_name, 5, id)
return true
elseif cur == id then
redis.call('expire', lock_key_name, 5)
return true
end
return false
GET_LOCK_SCRIPT
Redstream.connection_pool.with { |redis| redis.eval(@get_lock_script, argv: [Redstream.lock_key_name(@name), @id]) }
end
end
end
Version data entries
10 entries across 10 versions & 1 rubygems