Distributed transaction solution

background

In the microservices architecture , Suppose the following calls exist A->B, stay A call B There were some operations before C, If C success , call B Failure , At this point, you can roll back the transaction , But if you call first B And successful , Then do the operation C failed , So what to do ？

• B Provide an interface for reverse operation （ It doesn't have to be solved ）
• Business compensation
• Transaction message

Implementation scheme

Transaction compensation mechanism

The basic principle

explain

• In system A Start a transaction , In business , First operate the database of the system a, At the same time to the database a Insert a compensation task , Commit transaction ; The task has three states ,

  The three states of the task 1： To be processed , 2： In processing ,3： Processing is complete

• Start a task externally , Used to pull up the transaction compensation task （ Status as 1： To be processed ）, The change status is in process

• Get the corresponding data , The change status is in process , Interface to call the system B, If it doesn't work （ There is an error ） Change the original compensation task status to 1, If successful, it will be changed to processing completion , The processing result of the current scheduled task is 1 For the next scheduling pull up

Transaction message

The basic principle

Use here rocketMQ, The thought is Two-phase commit + Transaction status check

explain

• Send a transactional message , By current JVM launch （ The first stage ）
• broker Feedback to current JVM（ be based on ACK）
• Perform the operation C
• Follow the instructions C To determine whether to commit news , still rollback news （ The second stage ）
• When mq Of broker A sender who has not received a message for a long time （ At present JVM） Sent Commit/Rollback When instructed by , Transaction status needs to be checked back
• At present JVM Check local transaction status （ Transaction status check ）
• According to the transaction status, it is determined to be Commit/Rollback（ The second stage ）

summary

Introduces the background of distributed transaction , And several basic solutions

Several basic solutions

• Transaction compensation mechanism

  This article gives the possible performance problems , It can be optimized in terms of fragmentation

• Transaction message

Several additional frameworks

• rocketMQ
• seata