Eureka service registration and discovery

One 、 The registry of microservices

The registry can be said to be in the microservice architecture “ Mail list ”, It records the mapping relationship between service and service address . In a distributed architecture , The service will register here , When a service needs to call other services , You will find the service address here , To call .

1.1 The main role of the registry

Service registry （ Hereinafter referred to as the registry ） Is a very important component of microservice architecture , It mainly plays the role of coordinator in the microservice architecture . The registry generally includes the following functions ：
1、 Service discovery ：

• Service registration / Anti registration ： Save information about service providers and service callers
• Service subscription / Unsubscribe ： The service caller subscribes to the service provider's information , It's better to have the function of real-time push
• Service routing （ Optional ）： Have the ability to screen integrated service providers

2、 Service configuration ：

• Configure subscription ： Service providers and service callers subscribe to microservice related configurations
• Configure distribution ： Actively push configuration to service providers and service callers

3、 Service health testing

• Check the health status of the service provider

1.2 Common registries

Zookeeper
Zookeeper Is a distributed services framework , yes Apache Hadoop A subproject of , It is mainly used to solve some data management problems often encountered in distributed applications , Such as ： Unified naming service 、 State synchronization service 、 Cluster management 、 Management of distributed application configuration items . Simply speaking Zookeeper = file system + Monitoring notification mechanism .

Eureka
Eureka Is in Java Language , be based on RESTful API Developed service registration and discovery components ,SpringCloud Netflix Important components in .

Consul
Consul By HashiCorp be based on Go Service publishing and registration software supporting distributed and highly available services in multiple data centers developed by language , use Raft Algorithm guarantees service consistency , And support health examination

Nacos
Nacos It is a dynamic service discovery that is easier to build cloud native applications 、 Configuration management and service management platform . Simply speaking Nacos It's the registry + A combination of configuration centers , Provide an easy to use feature set , Help us to solve the problems of service registration and discovery that microservice development must involve , Service configuration , Service management, etc .Nacos still SpringCloud Alibaba One of the components , Responsible for service registration and discovery .

Component name	Language	CAP	Consistency algorithm	Service health check	Exposed interface
Eureka	Java	AP	nothing	With support	HTTP
Consul	Go	CP	Raft	Support	HTTP/DNS
Zookeeper	Java	CP	Paxos	Support	client
Nacos	Java	AP	Raft	Support	HTTP

Two 、Eureka Overview

2.1 Eureka Basic knowledge of

Eureka yes Netflix Developed service discovery framework ,SpringCloud Integrate it into your own subproject spring-cloud-netflix in , Realization SpringCloud Service discovery capabilities for .

The picture above briefly describes Eureka Basic architecture , from 3 The characters make up ：
1、Eureka Server

• Provide service registration and discovery

2、Service Provider

• service provider
• Register your services with Eureka, So that service consumers can find

3、Service Consumer

• Service consumer
• from Eureka Get the list of registered services , To be able to consume Services

2.2 Eureka Interaction process and principle of

Figure is from Eureka Official architecture , It gives a general description Eureka Working process of cluster . There are many components in the diagram , Explain it. ：

• Application Service Equivalent to a service provider ,Application Client Equivalent to serving consumers
• Make Remote Call, It can be simply understood as calling RESTful API
• us-east-1c、us-east-1d Are all zone, They all belong to us-east-1 This region

About zone and region You can see this article for an introduction to ：eureka In depth explanation of zoning

It can be seen from the picture that ,Eureka There are two components ：Eureka Server and Eureka Client, Their functions are as follows ：

• Eureka Client It's a Java client , Used to simplify and Eureka Server Interaction ;
• Eureka Server The ability to provide service discovery , When each microservice starts , Will pass Eureka Client towards Eureka Server Register your own information （ For example, network information ）,Eureka Server Will store information about the service
• After the micro service is started , Periodically Eureka Server Send a heartbeat （ Default period 30 second ） To renew your information . If Eureka Server The heartbeat of a microservice node is not received within a certain period of time ,Eureka Server The microservice node will be unregistered （ Default 90 second ）
• Every Eureka Server It's also Eureka Client, Multiple Eureka Server Complete the synchronization of service registry through replication
• Eureka Client Will cache Eureka Server Information in . Even if all Eureka Server All nodes are down , Service consumers can still find service providers using cached information .

Sum up ,Eureka By heartbeat detection 、 Mechanisms such as health checks and client caching , Improved system flexibility 、 Scalability and availability .