Summary of distributed related interview questions

One 、 What is distributed transaction ？ What are the solutions ?

In distributed systems , One business process may require multiple applications to implement , For example, the user sends an order request , It involves creating orders in the order system , Inventory system minus inventory , And for a single order , Order creation and inventory reduction should be successful or ineffective at the same time , But in a distributed system , If you don't do it , It is very likely that the order will be created successfully , But inventory reduction failed , So solve this kind of problem , You need distributed transactions , Common solutions are as follows ：

Two 、 The usage scenarios of distributed lock ？ What are the implementation schemes ？

3、 ... and 、 The usage scenarios of distributed lock ？ What are the implementation schemes ？

Four 、 What is? RPC？

5、 ... and 、 What is? CAP theory ？

Uniformity （C：Consistency）： Consistency is the ability of data to be consistent across multiple copies . For example, a data is updated after a partition node , The data read from other partition nodes is also the updated data ;

Usability （A：Availability）： Availability means that the services provided by the system must always be available , For each operation request of the user, the result can always be returned in a limited time . Here's the point " In a limited time " and " Return results ";

Partition tolerance （P：Partition tolerance）： Distributed systems encounter any network partition failure , There is still a need to be able to ensure that external services meet the requirements of consistency and availability .

Distributed environment （ The data distribution ） It's impossible to guarantee data consistency at any time , Only compromise can be adopted to ensure the final consistency of data . This is famous CAP Theorem .

choice	explain
CA	Give up partition fault tolerance , Enhance consistency and availability , In fact, it is the choice of traditional stand-alone database
AP	Give up consistency （ This means strong consistency ）, Pursue availability and partition fault tolerance , for example hdfs, Distributed database
CP	Discard availability , Pursue consistency and partition fault tolerance , Basically not choosing , Because the network will make the system unavailable

One thing that needs to be clear is , For a distributed system , Partition fault tolerance is a basic requirement . because Since it's a distributed system , Then the components in the distributed system must be deployed to different nodes , Otherwise, it doesn't matter what the distributed system is , So there must be subnetworks . And for distributed systems , network The problem of collaterals is another inevitable abnormal situation , So partition fault tolerance has become a problem that a distributed system must face and solve . So system architects often need to focus on how to base their efforts on the business Features in C（ Uniformity ） and A（ Usability ） Find a balance between .

6、 ... and 、 What is? BASE theory ？

It's right CAP in AP An extension of . For our business system , We consider sacrificing consistency for system availability and partition fault tolerance .BASE yes Basically Available、Soft state and Eventually consistent Abbreviations of three phrases .

Basically Available（ Basic available ）： It is realized by supporting local fault rather than global fault of the system . If you partition users in 5 Database server , The failure of a user database only affects the specific host 20% Users of , Other users are not affected ;

Soft State（ Soft state ）： The state can be out of sync for a while ;

Eventually Consistent（ Final agreement ）： Finally, the data is consistent , Instead of being consistent all the time .

7、 ... and 、 What is? ZAB agreement ？

8、 ... and 、 Why? ZooKeeper Can be used as a registry ？

Nine 、 What is the service avalanche ？ What is service limiting ？

Ten 、 What is service fusing ？ What is service degradation ？ What's the difference ？

11、 ... and 、SpringCloud and Dubbo What are the differences ？