Microservices and Service Discovery

 

Service Discovery pattern - The service instances in a microservice architecture could dynamically change with auto-scaling, failure, upgrade etc. A service discovery pattern is used for identifying the instances corresponding to a microservice.

Key component of service discovery is a service registry which is a database of network locations of instances for a given service.

Service Discovery is achieved using the following patterns:

1. Self registration - A service instance typically registers itself with a service registry and service registry invokes a health check API periodically on the service instance to make sure the service instance is Up and Running. Service instances may also be required to invoke a heartbeat API of the service registry inorder to avoid its lease from expiring.

2. Client side discovery - The client service queries a service registry to get the list of available instances and do the client side load balancing across them using frameworks such as Ribbon in netflix OSS.

3. Server side discovery - When making a request to the service, client makes the request via a router, typically a loadbalancer that also acts as a service registry. The router then forwards the request to available service instance.The router takes care of service registration, discovery and the request routing with load balancing.

Spring-boot Eureka

For implementing Service Registry in spring-boot, one of the option is to use netflix eureka server.

From start.spring.io, the dependency for eureka server can be added for a service registry server.

Use @EnableEurekaServer annotation for enabling eureka service discovery server.

if you add the dependency for Eureka Discovery Client - for registering to service discovery server, you are all set with a service registry with your microservice registered in it.

HashiCorp Consul - provides a service mesh which takes care of the following:

Consul follows a peer to peer architecture and follows gossip protocal.

1. Service discovery server - service registry which maintains how to connect other services and the health of the service.

2. Configuration Server - for managing any configuration across for different microservices. 

3. Segmentation - managing connection between the microservices - using service graph to decide which service can access which service.

it also provides a side car proxy and maintain TLS certificates which enables mTLS communication between two services.

This will make sure data in transit is also encrypted inside a microservice architecture.