[ECS] container enforces having port mappings

Describe the bug Should be able to create ECS container with no port mappings. This error occurs when trying to do so:

Error: Container test hasn't defined any ports. Call addPortMappings().

To Reproduce Create an ecs cluster with a Ec2TaskDefinition that has a container with no port mappings specified.

Expected behavior Should be able to have a container with no port mappings.

Version:

OS: Win10 Programming Language: Typescript CDK Version: 0.28.0

#2264

There are cases a container is behind a reverse proxy so it doesn’t need any port mapping.

[upparekh]

Hi @yanyansk , thanks for providing your task definition. When using the service object as target for the Application Load Balancer (ALB) here:

listner.addTargets('target', {
  port: 80,
  targets: [service]
})

it uses the first essential container (in the error case it is the Firelens log router) as the target. cdk synth will throw this error as the LB target is expected to have an exposed port while the Firelens log router doesn’t have one. When the app container is added before the log router, it becomes the default essential container and as it has an exposed port, no errors are thrown on doing cdk synth.

You’ll either need to add the container with exposed ports first or you can also add the ALB target like so:

listner.addTargets('target', {
      port: 80,
      targets: [service.loadBalancerTarget({
        containerName: 'app',
        containerPort: 80,
      })]
    })

The loadBalancerTarget() function can be used to create a target if you want to load balance to a container other than the first essential container (so the containers can be added in any order) or the first mapped port on the container.

[alexbaileyuk]

For future reference, in case anyone else comes across this issue, it was caused by the order that containers are defined in. If you define a container without ports before a container with ports then you get the error. Switch the order in which you call addContainer so the one with ports open is first and it works fine.