Sunday, October 04, 2015

Service Discovery Mechanisms in Microservices

In a microservices based architecture, we would not know the number of instances of a server or their IP addresses beforehand. This is because microservices typically run in VMs or Docker containers that are dynamically spawned based on usage load.

So consumers would need some kind of service discovery mechanism to communicate with microservices. There are two options to design this -

a) Server-side Service Discovery - Here the consumers make a request to a load-balancer/service registry and then the request is routed to the actual service end-point. This paradigm is clearly explained on this blog here. Examples of this design pattern is the AWS Elastic Load Balancer.

b) Client-side Service Discovery - Here the consumers use a small library for making service calls. This library makes calls to the service registry and obtains the load-balanced actual service end-point. Netflix uses this approach and its service registry is called Eureka and its client library is called Ribbon.