Alibaba microservice component Nacos registry

One 、 What is? Nacos

A service discovery that is easy to build cloud native applications （Nacos Discovery）、 Service configuration （Nacos config） And service management platform

Registry Center + Configuration center + Service management

Nacos Key features of ：
1、 Service discovery and service health detection
2、 Dynamic configuration services
3、 dynamic DNS service
4、 Services and metadata management

Two 、Nacos Registry Center

Core functions ：

1、 Service registration

Nacos Client By sending REST The way of request to Nacos Server Register your services , Provide its own metadata , such as ip Address , Port information, etc ,Nacos Server After receiving the registration request , These metadata information will be stored in a double layer Map in .

2、 Service heartbeat

After service registration ,Nacos Client Will maintain a timed heartbeat to continuously notify Nacos Server , Indicates that the service is always available , To prevent being removed , Default 5s Send a heartbeat .

3、 Service synchronization

Nacos Server Service instances will be synchronized between clusters , To ensure the consistency of service information .

4、 Service discovery

Serving consumers （Nacos Client） When invoking the service provided by the service , Will send a REST Request to Nacos Server, Get the list of services registered above , And exist slowly Nacos Client Local , At the same time Nacos Client Start a scheduled task locally to pull the latest registry messages from the server and update them to the local cache .

5、 Service health check

Nacos Server A scheduled task will be started to check the health of the registered service instance , For more than 15s An instance that does not receive a heartbeat from the client will send it healthy Property is set to false（ Client service discovery does not discover ）, If an instance exceeds 30s No heartbeat received , Reject the instance directly （ If the rejected instance resumes sending heartbeat, it will be re registered ）.

Mainstream registries

CAP, C – Uniformity ,A – Usability ,P – Partition tolerance