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I'm having troubles with the communication between microservices. I have many spring boot applications, and many requests HTTP and AMQP (RabbitMQ) between them. Locally (in dev) I use Eureka (Netflix Oss) without Docker Images.

The question is: in the Amazon ECS Infraestructure how i can work with the same behavior? Which is the common pratice for the communication between microservices using Docker? I can still use Eureka for Service Discovery? Besides that, how this comunication will works between container instances?

alltej
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jpcolling
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2 Answers2

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I'd suggest reading up on ECS Service Load Balancing, in particular two points:

  1. Your ECS service configuration may say that you let ECS or the EC2 instance essentially pick what port number the service runs on externally. (ie for Spring Boot applications inside the Docker container your application thinks it's running on port 8080, but in reality to anything outside the Docker container it may be running on port 1234 2 ECS clusters will check the health endpoint you defined in the load balancer, and kill / respawn instances of your service that have died
  2. A load balancer gives you different ways to specify which application in the cluster you are talking to. This can be route based or DNS name based (and maybe some others). Thus http://myservice.example.com/api could point to a different ECS service than http://myservice.exaple.com/app... or http://app.myservice.example.com vs http://api.myservice.example.com.

You can configure ECS without a load balancer, I'm unsure how well that will work in this situation.

Now, you're talking service discovery. You can still use Eureka for service discovery, having Spring Boot take care of that. You may need to be clever about how you tell Eureka where your service lives (as the hostname inside the Docker container may be useless, and the port number inside the container totally will be too.) You may need to do something clever here to correctly derive that number, like introspecting using AWS APIs. I think this SO answer describes it correctly, or at least close enough to get started.

Additionally apparently ECS has service discovery built in now. This is either new since I last used ECS, or we didn't use it because we had other solutions. If you aren't completely tied to Eureka for other reasons.

RyanWilcox
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Thanks for you reply. For now I'm using Eureka because I'm using Feign too for comunication between microservices.

My case is this: I have microservices (Example A,B,C). A communicates with B and C by way of Feign (Rest). Microservices Example

Example of Code on Microservice A:

@FeignClient("b-service")
public interface BFeign {
}

@FeignClient("c-service")
public interface CFeign {
}

Using ECS and ALB it's possible still using Feign? If yes or not, how you suggest I do this?

juanlumn
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jpcolling
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