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This article mainly introduces "how to understand Redis distributed locks". In daily operation, I believe many people have doubts about how to understand Redis distributed locks. The editor consulted all kinds of materials and sorted out simple and easy-to-use operation methods. I hope it will be helpful for you to answer the doubts about "how to understand Redis distributed locks". Next, please follow the editor to study!

The 1 lock uses the setnx (set if not exists) instruction

Use the del instruction to release the lock.

> setnx lock:hello trueOK... Do something critical... > del lock:hello (integer) 1 deadlock

If an exception occurs in the middle of the logic execution, it may cause the del instruction not to be called, which will fall into a deadlock and the lock will never be released.

The solution is to add an expiration time expire to the lock, such as 10s, to ensure that the lock will be automatically released after 10 seconds even if an exception occurs.

> setnx lock:hello trueOK > expire lock:hello 10... Do something critical... > del lock:codehole (integer) 1 Atomic Operation ex/nx

If there is a problem in the execution of the expire instruction server process, resulting in the expire does not execute, it will still cause a deadlock.

The root of this problem is that setnx and expire are two instructions rather than atomic instructions. If these two instructions can be executed together, there will be no problem. The author added an extension parameter to the set instruction in Redis 2.8. the following instruction is an atomic instruction that combines setnx and expire.

Timeout processing

If the execution interval of the program times out, the lock has been released and other threads occupy the lock. If you perform the delete operation directly, the lock created by other threads will be released. You need to set the vlue to a random string.

Lua

Matching value and deleting key is not an atomic operation, and Redis does not provide instructions like delifequals, which needs to be handled by Lua scripts, because Lua scripts can guarantee the atomic execution of multiple instructions in succession.

At this point, the study on "how to understand Redis distributed locks" is over. I hope to be able to solve your doubts. The collocation of theory and practice can better help you learn, go and try it! If you want to continue to learn more related knowledge, please continue to follow the website, the editor will continue to work hard to bring you more practical articles!

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