Ribbon service invocation and load balancing

Learn from the previous content , Service registration and service discovery have been implemented . When you start a service , Can pass HTTP To register information in the registry , And through SpringCloud Provides a tool to get a list of Registry Services . But there are still many problems in the call between services , How to call microservices more conveniently , How to choose multiple micro service providers , How to load balance and so on .

One 、Ribbon summary

1.1 What is? Ribbon

Ribbon yes Netflix Released a load balancer , It helps to control HTTP and TCP Client behavior . stay SpringCloud in ,Eureka General coordination Ribbon To use ,Ribbon It provides the function of client load balancing ,Ribbon Use from Eureka Service information read in , When calling the service provided by the service node , The load will be reasonable .

stay SpringCloud The registry and Ribbon In combination with ,Ribbon Automatically get the list information of service providers from the registry , And based on the built-in load balancing algorithm , Request service .

1.2 Ribbon Main role of

（1） The service call
be based on Ribbon Implement service calls , It is composed of all service lists pulled （ service name - Request path ） The mapping relationship . With the help of RestTemplate Finally call .

（2） Load balancing
When there are multiple service providers ,Ribbon According to the load balancing algorithm （ Such as simple polling 、 Random connection, etc ） Automatically select the service address to be called .

1.3 Ribbon Load balancing and Nginx The difference between load balancing

LB Load balancing （Load Balance） What is it? ？ To put it simply, users' requests are evenly distributed to multiple services , So as to achieve systematic HA（ High availability ）. Common load balancing software Nginx,LVS, Hardware F5 etc. .

Nginx It's server load balancing , All client requests are delivered to Nginx, Then from Nginx Implement forwarding request , That is, load balancing is performed by , Server implementation .
Ribbon Local load balancing , When the micro interface is called , After obtaining the list of registration information services in the Registration Center , The cache to JVM Local , Thus in Local implementation RPC Remote service call technology .

Centralized LB： I.e. use independent... Between consumers and providers of services LB facilities （ It can be hardware , Such as F5, It can also be software , Such as Nginx）, The facility payload forwards the access request to the service provider through some policy .

In process LB： take LB Logic is integrated into the consumer , The consumer knows from the service registry what addresses are available , Then I choose a suitable server from these addresses .Ribbon It's in the process LB, It's just a class library , Integrated into consumer processes , The consumer uses it to get the address of the service provider .