Class RedisLocker

A Redis Locker that can be used as both:

• a Read Write Locker that uses a (single) Redis server to store the locks and counts.
• a Resource Locker that uses a (single) Redis server to store the lock. This solution should be process-safe. The only references to locks are string keys derived from identifier paths.

The Read Write algorithm roughly goes as follows:

• Acquire a read lock: allowed as long as there is no write lock. On acquiring the read counter goes up.
• Acquire a write lock: allowed as long as there is no other write lock AND the read counter is 0.
• Release a read lock: decreases the read counter with 1
• Release a write lock: unlocks the write lock

The Resource locking algorithm uses a single mutex/lock.

All operations, such as checking for a write lock AND read count, are executed in a single Lua script. These scripts are used by Redis as a single new command. Redis executes its operations in a single thread, as such, each such operation can be considered atomic.

The operation to (un)lock will always resolve with either 1/OK/true if succeeded or 0/false if not succeeded. Rejection with errors will be happen on actual failures. Retrying the (un)lock operations will be done by making use of the LockUtils' retryFunctionUntil function.

See

• Redis Commands documentation

• Redis Lua scripting documentation

• ioredis Lua scripting API