Getting started with message queuing MQ

The soul of the message queue ：

1. What is the message queue ？

2. Can do ？

3. Advantages and disadvantages ？

4. Why message queues ？

activemq Of ,kafka,rabbitmq、

For getting started ：

https://blog.csdn.net/m0_37499059/article/details/79958073

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1. Why message queues ：

The way the interviewer expects to answer ：

  The company's business scenario

  Technical challenges encountered ,

  If not mq What trouble will there be ,

  But with mq What are the benefits ;


1.1  Message queue scenario ：

You can find it in the blog ：  decoupling 、 asynchronous 、 Peak shaving ;

no need mq System coupling scenario

The use of MQ The system serves as   Benefits of scenarios ：

After multi system interaction ==> The cost of changing the code is high

Use MQ Can reduce coupling ;

Interview skills ：   Consider whether there is in your scenario ,  A module corresponds to the use of other systems or modules ;

2. introduce MQ The problems that arise ;

2.1 Reduced system availability ：

Because there are many external access systems

But when MQ After downtime or , Unable to send a message , Traffic can cause data processing problems , There will be great problems in the availability of various systems ;

MQ Hang up , Will cause many systems to crash ;

2.2   System complexity becomes higher

MQ What might happen ：

• Data message lost \

• Ensure that messages are not consumed repeatedly

• How to ensure the transmission order of data messages

2.3 Data consistency issues

A data request is sent to the system A,  after MQ Sending of ,  The original request is the system ABCD  It's all done  , To return results , System ABCD Execution succeeded , however D The system failed to execute , This causes the entire request to return success to the user , The result is that the logic of success in the background is actually a little poor , Not fully implemented

（ in other words MQ The previous return succeeded , But in BCD In the later system, there will be an incomplete implementation , Result in data inconsistency ）

• each MQ Advantages and disadvantages ;

activeMQ,RabbitMQ