How to use redis to realize things and locks?

---

Hello everyone , I'm cabbage . This article mainly explains Redis And the simple implementation of the lock , If you get something after reading the article , You can support bloggers three times in a row ~, Hee hee .

---

One 、 What is? Redis thing

• Redis Business is a Separate isolation operation ： All commands in the transaction are serialized 、 To execute in order . Transaction is in the process of execution , Will not be interrupted by command requests from other clients .
• effect ： Concatenate multiple commands to prevent other commands from jumping in line .

Two 、Redis Business order

The following table lists them redis Orders related to the transaction ：

Be careful ： The command to join the transaction temporarily enters the task queue , Not immediately , Only execute exec It's the order that begins

3、 ... and 、 Command line Demo

• Demonstrate the beginning of things 、 perform

127.0.0.1:6379> MULTI
OK
127.0.0.1:6379(TX)> set name cabbage
QUEUED
127.0.0.1:6379(TX)> set age 20
QUEUED
127.0.0.1:6379(TX)> EXEC
1) OK
2) OK
127.0.0.1:6379> keys * 
1) "name"
2) "age"

• Demonstrate the beginning and cancellation of things ：

127.0.0.1:6379> MULTI
OK
127.0.0.1:6379(TX)> set name cabbage
QUEUED
127.0.0.1:6379(TX)> set age 20
QUEUED
127.0.0.1:6379(TX)> DISCARD
OK
127.0.0.1:6379> keys *
(empty array)

• Demonstrating things watch：
  

Four 、 Things to note

• Refers to when the command writing format is incorrect , All commands in the overall transaction will not be executed , Including commands with correct syntax
  
• Indicates that the command format is correct , But when it cannot be executed correctly , Commands that run correctly execute , The wrong command will not be executed and the corresponding data will not be rolled back .

5、 ... and 、 Three characteristics of transaction

• Separate isolation operation
  All commands in the transaction are serialized 、 To execute in order . Transaction is in the process of execution , Will not be interrupted by command requests from other clients .
• There is no concept of isolation level
  The commands in the queue are not actually executed until they are submitted , Because no instruction is actually executed before the transaction is committed
• There is no guarantee of atomicity
  If a command fails in a transaction , Subsequent orders will still be executed , No rollback

6、 ... and 、 Distributed lock

• Business analysis ： although redis It's single threaded , But when multiple clients operate on the same data at the same time , How to avoid not being modified at the same time ？

• Solution ： Use expire For lock key Add time limit , Don't release , Then give up the lock

• Command line Demo ：

127.0.0.1:6379> set name cabbage
OK
127.0.0.1:6379> setnx lock_time 1
(integer) 1
127.0.0.1:6379> EXPIRE lock_time 20
(integer) 1
127.0.0.1:6379> get name 
"cabbage"

In this way , Even if a client does not manually release the lock for some reason , It won't cause deadlock . Because the lock is set lock_time The effective time of is 20 second , When 20 Seconds later , Other clients can get the lock 、 Implement business operations 、 Lock released .

---

Thank you for reading , Progress together , Hee hee ~