Server-side discovery

All requests made to any of the services are routed via a router or load balancers that run in a location known to client interfaces. The router then queries a maintained registry and forwards the request based on the query response. An AWS Elastic load balancer is a classic example that has the ability to handle load balancing, handle internal or external traffic, and act as a service registry. EC2 instances are registered to ELB either via exposed API calls or either through auto-scaling. Other options include NGINX and NGINX Plus. There are available consul templates that ultimately generate the nginx.conf file from the consul service registry and can configure proxying as required.

Some of the major advantages of using server-side discovery are as follows:

• The client does not need to know the location of different microservices. They just need to know the location of the router and the service discovery logic is completely abstracted from the client so there is zero logic at the client end.
• Some environments provide this component functionality for free.

While these options have great advantages, there are some drawbacks too that need to be handled:

• It has more network hops, that is, one from the client service registry and another from the service registry microservice.
• If the load balancer is not provided by the environment, then it has to be set up and managed. If not properly handled, then it can be a single point of failure.
• The selected router or load balancer must support different communication protocols for modes of communication.