[issue 307] in terms of implementation principle, why is Nacos so strong?

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Nacos framework

• Provider APP： Service providers

• Consumer APP： Serving consumers

• Name Server： adopt VIP（Virtual IP） or DNS The way to achieve Nacos High availability cluster service routing

• Nacos Server：Nacos Service providers , It contains Open API Is the function access portal ,Conig Service、Naming Service yes Nacos Configuration services provided 、 Name the service module .Consitency Protocol It's a consistency agreement , Used to implement Nacos Data synchronization of cluster nodes , What we use here is Raft Algorithm （Etcd、Redis Sentinel election ）

• Nacos Console： Console

How the registry works

• The service instance is registered to the service registry at startup , And log off on shutdown

• The service consumer queries the service registry , Get available instances

• The service registry needs to call the health check of the service instance API To verify that it can handle requests

SpringCloud Time to complete registration

stay Spring-Cloud-Common There is a class in the package org.springframework.cloud. client.serviceregistry .ServiceRegistry , It is Spring Cloud Standards for registration of services provided . Integrated into the Spring Cloud Components that implement service registration in , Will implement the interface .

The interface has an implementation class that is NacoServiceRegistry.

SpringCloud Integrate Nacos Implementation process ：

stay spring-clou-commons Bag META-INF/spring.factories The configuration information of automatic assembly is as follows ：

among AutoServiceRegistrationAutoConfiguration This is the configuration class related to service registration ：

stay AutoServiceRegistrationAutoConfiguration Configuration class , You can see the injection of a AutoServiceRegistration example , The relationship diagram of this class is as follows .

It can be seen that , AbstractAutoServiceRegistration The abstract class implements the interface , And most importantly NacosAutoServiceRegistration Inherited AbstractAutoServiceRegistration.

notice EventListener We should know ,Nacos It's through Spring The event mechanism of inherits to SpringCloud Middle going .

AbstractAutoServiceRegistration Realized onApplicationEvent Abstract method , And monitor WebServerInitializedEvent event ( When Webserver After initialization ) , call this.bind ( event ) Method .

Will eventually call NacosServiceREgistry.register() Method to register the service .

NacosServiceRegistry The implementation of the

stay NacosServiceRegistry.registry In the method , Called Nacos Client SDK Medium namingService.registerInstance Complete service registration .

track NacosNamingService Of registerInstance() Method ：

• adopt beatReactor.addBeatInfo() Create heartbeat information for health detection , Nacos Server You must ensure that the registered service instance is healthy , And heartbeat detection is the means to serve health testing .

• serverProxy.registerService() Implement service registration

heartbeat ：

From the above code , The so-called heartbeat mechanism is that the client passes schedule Send a packet to the server regularly , Then start - A thread constantly detects the server's response , If no response is received from the server within the set time , The server fails .Nacos The server will update the service status according to the heartbeat packet of the client .

Registration principle ：

Nacos Provides SDK and Open API There are two forms to implement service registration .

Open API：

SDK：

Both forms are essentially the same , The bottom is all based on HTTP The agreement completes the requested . So the registration service is to send a HTTP request ：

about nacos Server side , The external service interface request address is nacos/v1/ns/instance, Implementation code nacos-naming Under the module of InstanceController Class ：

• Get... From the request parameter summary serviceName（ service name ） and namespaceId（ Namespace Id）

• call registerInstance Registration instance

• Create a control service （ stay Nacos Console “ List of services ” Service information displayed in ）, It's actually initializing a serviceMap, It's a ConcurrentHashMap aggregate

• getService, from serviceMap According to the namespaceId and serviceName Get a service object

• in addition , official account Java selected , About springcloud Interview questions , reply java interview , Obtain interview question information .

• call addInstance Add service instance

• according to namespaceId、serviceName From the cache Service example

• If Service Instance is empty , Then create and save to the cache

• adopt putService() Method to cache the service into memory

• service.init() Set up a heartbeat mechanism

• consistencyService.listen Achieve data consistency monitoring

service.init ( ) The method is shown in the figure below , It continuously detects the time when all instances in the current service last send heartbeat packets through scheduled tasks . If the timeout , Is set healthy by false Indicates that the service is unhealthy , And send service change events .

Here, please think about one question , Who triggered the last heartbeat packet update time of the service instance ? In fact, I mentioned earlier , Nacos While the client registers the service, it also establishes a heartbeat mechanism .

putService Method , Its function is to Service Save to serviceMap in ：

Continue to call addInstance Method to save the currently registered service instance to Service in ：

summary ：

• Nacos Client pass Open API Send a service registration request in the form of

• Nacos After the server receives the request , Do the following three things ：

  • Construct a Service Object to save to ConcurrentHashMap Collection

  • Use a scheduled task to establish a heartbeat detection mechanism for all instances under the current service

  • Service data is synchronized based on data consistency protocol

Service provider address query

Open API：

SDK：

InstanceController Medium list Method ：

• Parse request parameters

• adopt doSrvIPXT Return service list data

• according to namespaceId、serviceName get Service example

• from Service The example is based on srvIPs Get all service provider instances

• Traversal assembly JSON String and return

Nacos Dynamic sensing principle of service address

Can pass subscribe Method to implement listening , among serviceName Indicates the service name 、EventListener Indicates the monitored event ：

The specific calling method is as follows ：

Or call selectInstance Method , If you will subscribe Property is set to true, Will automatically register to listen ：

Nacos There is one in the client HostReactor class , Its function is to realize the dynamic update of services , The basic principle is ：

• After the client initiates the subscription , stay HostReactor There is one of them. UpdateTask Threads , Every time 10s Send it once Pull request , Get the latest address list of the server

• For the server , Heartbeat detection is maintained between it and the instance of the service provider , Once the service provider has an exception , Will send a Push A message to Nacos client , That is, service end consumers

• After the service consumer receives the request , Use HostReactor Provided in processServiceJSON Parsing message , And update the local service address list

author ： Wu Shengzi night song

https://blog.csdn.net/cold___play/article/details/108032204

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