Eureka Basics

What is service governance

Spring Cloud Encapsulates the Netflix company-developed Eureka Module to implement service governance .
In traditional rpc In the remote call framework , Managing each service and the relationship between services is complex , Management is more complicated , So we need to use service governance , Manage dependencies between services , Service calls can be implemented 、 Load balancing 、 Fault tolerance, etc. to realize service discovery and registration .

What is service registration and discovery

Eureka Adopted CS Design framework ,Eureka Server A server that serves as a service registration function , It is a service registry . And other microservices in the system , Use Eureka The client connects to Eureka Server And maintain the heartbeat connection . In this way, the maintenance personnel of the system can pass Eureka Server To monitor the normal operation of each micro service in the system .

In service registration and discovery , There's a registry . When the server starts , Will put the current information of their own servers , For example, service address 、 The mailing address is registered in the registration center by alias . The other side （ consumer ｜ Service providers ） Use this alias to get the actual service address from the registry , And then local RPC, call RPC The core design idea of remote call framework ： It's in the registry , Because the registry is used to manage a dependency between each service （ The concept of service governance ）, In any RPC In the remote framework , There will be a registry （ Store service address information （ Address of the interface ））.

Eureka There are two components Eureka Server and Eureka Client

Eureka Server Provide service registration service
After each microservice node is started through configuration , Will be in Eureka Server Register in , such Eureka Server The service registry in will store information about all available service nodes , The information of the service node can be directly seen in the interface .

Eureka Client Access through the registry
It's a JAVA client , For simplification Eureka Server Interaction , The client also has a built-in 、 Use polling （round-robin） Load balancer of load algorithm . After starting the application , To Eureka Server Send a heartbeat （ The default period is 30 second ）. If Eureka Server The heartbeat of a node is not received in multiple heartbeat cycles ,Eureka Server This service node will be removed from the service registry （ Default 90 second ）.