Module: RedisReadWriteLocks::LockScripts

Defined in:

lib/redis_read_write_locks/lock_scripts.rb

Constant Summary

ACQUIRE_READ =

KEYS = writer_key, KEYS = readers_key ARGV = token, ARGV = expiry (unix ts), ARGV = now (unix ts) Returns 1 = acquired, 0 = blocked

<<~LUA.freeze
  local writer_key = KEYS[1]
  local readers_key = KEYS[2]
  local token = ARGV[1]
  local expiry = tonumber(ARGV[2])
  local now = tonumber(ARGV[3])

  redis.call('ZREMRANGEBYSCORE', readers_key, '-inf', now)

  if redis.call('EXISTS', writer_key) == 1 then
    return 0
  end

  redis.call('ZADD', readers_key, expiry, token)

  local current_ttl = redis.call('TTL', readers_key)
  if current_ttl == -1 or (current_ttl > 0 and (now + current_ttl) < expiry) then
    redis.call('EXPIREAT', readers_key, expiry + 1)
  end

  return 1
LUA

RELEASE_READ =

KEYS = readers_key ARGV = token

<<~LUA.freeze
  redis.call('ZREM', KEYS[1], ARGV[1])
  return 1
LUA

ACQUIRE_WRITE =

KEYS = writer_key, KEYS = readers_key ARGV = token, ARGV = ttl (seconds), ARGV = now (unix ts) Returns 1 = acquired, 0 = blocked

<<~LUA.freeze
  local writer_key = KEYS[1]
  local readers_key = KEYS[2]
  local token = ARGV[1]
  local ttl = tonumber(ARGV[2])
  local now = tonumber(ARGV[3])

  redis.call('ZREMRANGEBYSCORE', readers_key, '-inf', now)

  if redis.call('ZCARD', readers_key) > 0 then
    return 0
  end

  if redis.call('EXISTS', writer_key) == 1 then
    return 0
  end

  redis.call('SET', writer_key, token, 'EX', ttl)
  return 1
LUA

RELEASE_WRITE =

KEYS = writer_key ARGV = token Returns 1 = released, 0 = not owner

<<~LUA.freeze
  if redis.call('GET', KEYS[1]) == ARGV[1] then
    redis.call('DEL', KEYS[1])
    return 1
  end
  return 0
LUA