Distributed Locks

One reason why Redis has custom locking, instead of using operating system–level locks, language-level locks, and so forth, is a matter of scope. Clients want to have exclusive access to data stored on Redis, so clients need to have access to a lock defined in a scope that all clients can see—Redis.

Redis does have a basic sort of lock already available as part of the command set (SETNX), which we use, but it’s not full-featured and doesn’t offer advanced functionality that users would expect of a distributed lock.

In fact there are two patterns which have emerged for locking in Redis.

1. Locking with SETNX
   • it’s not full-featured and doesn’t offer advanced functionality
2. Redlock
   • the distributed locking algorithm.

 

References:

• http://redis.io/topics/distlock
• http://martin.kleppmann.com/2016/02/08/how-to-do-distributed-locking.html
• http://antirez.com/news/101
• http://redis.io/commands/setnx