Microservices: TCP vs Redis

[triedal]

In what circumstances would it be preferable to use Redis over TCP for the transport layer? Does Redis allow you to spin up multiple instances of the same microservice and react to events posted in the broker?

Thanks!

[kamilmysliwiec]

Hi @triedal, They're just different, pros & cons depend on the use-case. It's your decision.

Does Redis allow you to spin up multiple instances of the same microservice and react to events posted in the broker?

Redis is based on pub-sub, you should be able to subscribe to messages across multiple instances.

Also, these built-in transports are sometimes not enough, in this case, you can just provide your custom strategy.

[triedal]

Thank you @kamilmysliwiec

[Renader]

@triedal did u managed to get it to work properly?

I'm new to microservice architecture and so on, tried some example code having 2 separate apps. One acts as a gateway receiving the REST calls. The work should be done by microservices to enable horizontal scaling. In a technical breakthrough, everything works fine. But as I launch 2 instances of my microservice, both get the command.

Is this intended behavior @kamilmysliwiec? What am I missing? I'd expect that each task gets only published to one microservice instance and not to all instances at the same time.

Do I have to implement a load balancer mechanism myself?

[kamilmysliwiec]

Redis doesn't have any built-in groups/topics mechanism as far as I know. In your case, you have to build load balancer by yourself OR reuse any existing, available solution (if fits your requirements).

[Renader]

Just if anyone else runs into the same issue: I solved it by using RabbtiMQ which soon will be available for NestJS https://github.com/nestjs/nest/pull/1170

Until the PR is not merged you can use https://github.com/AlariCode/nestjs-rmq

RabbitMQ defaults to distributing only to 1 listener (what could be changed by using fanout). But don't trust my knowledge too much, I'm still a learner. Anyway I got it to work this way!

[triedal]

@Renader I was able to do the load balancing with NATS queue groups. You can read more about it at https://github.com/nestjs/nest/issues/758#issuecomment-428235340. Seems like your solution is basically the same thing, just with RabbitMQ.

[Renader]

@triedal thanks!

[cojack]

Redis is based on pub-sub, you should be able to subscribe to messages across multiple instances.

There is one problem, you won't receive many responses, but only one. No clue why, @kamilmysliwiec can you explain it, this behaviour? Im just curious.

[kamilmysliwiec]

Redis doesn't have a built-in load balancing mechanism.

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