Redis based distributed read/write locks

RLOCK = "redis.call('HSETNX', KEYS[1], 'mode', 'r'); local ret = redis.call('HGET', KEYS[1], 'mode'); if ret == 'r' then redis.call('EXPIRE', KEYS[1], ARGV[2]); return redis.call('HSETNX', KEYS[1], ARGV[1], 1) end"
WLOCK = "local ret = redis.call('HSETNX', KEYS[1], 'mode', 'w'); if ret == 0 then return ret end; redis.call('EXPIRE', KEYS[1], ARGV[2]); return redis.call('HSETNX', KEYS[1], ARGV[1], 1)"
RELEASE = "local ret = redis.call('HDEL', KEYS[1], ARGV[1]); local sz = redis.call('HLEN', KEYS[1]); if sz == 1 then redis.call('DEL', KEYS[1]) end; return ret"
RENEW = "local ret = redis.call('HEXISTS', KEYS[1], ARGV[1]); if ret > 0 then ret = redis.call('EXPIRE', KEYS[1], ARGV[2]) end; return ret"