Server discovery: The client sends a request to the service through the load balancer. The load balancer queries the service registry and routes each request to an available service instance. Like the client discovery mechanism, service instances also need to register and deregister with the service registry.
Client discovery: When the service instance starts, its network address is registered with the service registration center. When the instance is terminated, the address is removed from the service registry. The registration of service instances is usually refreshed periodically using the heartbeat mechanism. The client will get a list of services that can be provided and decide which one to visit.
The role of kubedns: Parse the IP address of the service, so that other services can access the back-end service of the service.
