Kafka Msg VS REST Calls

Question

Nowadays in microservice world, i’m seeing alot of design in my workplace that uses kafka messaging when you can achieve similar results using rest api calls between microservic

Answer 1

Microservices architecture advocates indepdent and autonomous services that can operate on their own. Lets understand why we need message queues?

HTTP protocol is sync

There is very wide misconception that HTTP is async. Http is synchronous protocol but your client could deal it async. E.g. when you call any service using http your http client would schedule is on the backend thread (async). However The http call will be waiting until either it's timeout or response is back , during all this time the http call chain is awaiting synchronously. Now if you have hundreds of requests at a time you can image how many http calls are scheduled synchronously and you may run of sockets.

AMQP

In Microservices architecture we prefer AMQP (Advance message queue protocol) . Which means the service drops the message in queue and forgets about it. This is true async transport protocol since your service is done once it drops the message in the queue and interested services will pick those.

This type of protocol is preferred since you can scale without worry even when other services are down as they will eventually get message/event/data.

So it really depends on your particular case. HTTP are easy to implement but you can't scale them well. Message services come with own challenges like order of messages and workers but that make the architecture scaleable and is preferred way. For write operation always prefer queue, for read operation you can use HTTP but make sure you are not doing a long chain where one service is calling another and that calls another.

Hope that helps !