14_ Redis_ Optimistic lock

Optimism lock

monitor ：Watch

Pessimistic locking :

• Very pessimistic , I think it's going to go wrong all the time , Whatever you do, you'll lock it !

Optimism lock :

• Very optimistic. , I don't think anything will go wrong at any time , So it won't lock ! When you update the data, judge , Has anyone modified this data in the meantime ,version !
• obtain version
• When updating, compare version

Redis Monitoring tests for

Normal execution succeeded

127.0.0.1:6379> set money 100
OK
127.0.0.1:6379> set out 0
OK
127.0.0.1:6379> watch money // monitor money object , Once the transaction is successfully executed, the monitoring will be cancelled
OK
127.0.0.1:6379> multi // The business ended normally , There was no change during the data period , At this time, the normal execution is successful !
OK
127.0.0.1:6379(TX)> decrby money 20
QUEUED
127.0.0.1:6379(TX)> INCRby out 20
QUEUED
127.0.0.1:6379(TX)> exec
1 ) (integer) 80
2 ) (integer) 20

Testing multithreaded modification values , Use watch Can be regarded as redis Optimistic lock operation of !

Modify the way ： Release the optimistic lock and re acquire the optimistic lock

1. Transaction execution failed , Just unlock it first

Get the latest value , Watch again ,select version