nathanpeck/multiple-ports-per-ecs-service.md

## multiple-ports-per-ecs-service.md

      
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              multiple-ports-per-ecs-service.md
            
          
    The information below was written in Oct 2017. In August 2019 AWS launched official support for multiple target groups per AWS ECS service. Please use that feature instead!


Unfortunately as of writing this (Oct 18, 2017) there is no built in integration for multiple
target groups per AWS ECS service. Here are a few things you can try:


If your application just serves port 80 (HTTP) & port 443 (HTTPS) then you should consider
using the application load balancer and terminating SSL at the load balancer. This will allow
your application to function using just port 80.


If your application serves different ports that are backed by different components, perhaps
speaking different protocols then you should consider splitting the application into multiple
ECS services. This has the benefit of allowing the different components to independently scale
in addition to allowing each of them to have their own ports.


You can still use the Classic load balancer with ECS. This load balancer functions at the
instance level, and can have multiple listener ports per instance, so when a service is put on
an instance ECS will register the instance in the classic load balancer, and the classic load
balancer will have multiple listeners directing traffic to multiple ports. This has the downside
of not supporting dynamic ports though, only static port numbers. This means you will only be
able to run a single task per instance, because only one task will be able to bind to the static
port.


You can build your own target group functionality for your application's ancillary ports using
the CloudWatch Event Stream for your service's task state change events. You can subscribe to
the task state change events for your service, and link the subscription to a Lambda function.
When the event for a task start happens you can register your tasks ancillary ports in any
ancillary target groups, and when the task stop event happens you can deregister these ancillary
ports. Obviouslly this is a very complex, and difficult solution to implement however, so I'd
only use it as a method of last resort.


You can use Weaveworks, or LinkerD to implement a mesh network that runs alongside ECS.
This can allow you to build a "gateway" that sends traffic to your ECS services on multiple ports
without using the built in target group functionality.