One 、 Common distributed locks

Based on database

be based on redis Realization （ The highest performance ）

be based on zookeeper Realization （ Highest reliability ）

Two 、 be based on redis Realize distributed locking

1、 command

1、 Set lock   command ：setnx key_name value

setnx users 10

 Then perform  setnx user 20  return 0  operation failed   Because it's locked 

2、 Release the lock   command ：del key_name
del users

3、 Expiration settings   command ：expire key_name value
expire users 20

 That is, lock and set the expiration time to make the operation called atomic operation 

set users 10 nx ex 12

2、java Code

3、 ... and 、uuid Prevent accidental deletion of lock operation

Problem analysis

solve

Set up different uuid, When releasing the lock, judge the current uuid And the lock to be released uuid Whether or not the same

The above code is modified

Set up uuid

Compare release

Four 、lua Ensure atomicity of deletion