Use aws/alb releaser for ecs

[izaaklauer]

Is your feature request related to a problem? Please describe.

Currently, ECS uses it's own releaser, which has ALB manipulation logic very similar to the aws/alb plugin releaser. The alb releaser also has implemented release status, where ecs has not.

It would be nice if ECS could use the ALB releaser. Currently, trying to specify the ALB releaser on an ECS deployment yields the following error at release time:

» Releasing...
! 1 error occurred:
  	* argument cannot be satisfied: type *anypb.Any

It seems this is because the ALB releaser function wants a target group, while the ecs releaser wants a deployment.

[catsby]

I looked into this and @izaaklauer and I discussed it some; the ECS deployment optionally creates a load balancer, security group, and target group and then the ECS releaser simply sets the weight to 100. The ALB releaser expects a target group to already exist and does the work (optional) of creating the security group, load balancer, et. al.

In order to get the ECS platform to not create the load balancer (and target group) users need to specify disable_alb in the use-ecs configuration... which contradicts the follow up use "alb" we would add in the release block of the configuration.

Ultimately 1 or both of these plugins would require some rework to make this work as described.

If the goal is to add a Status() method to ECS, we may want to instead look at reusing ALB's implementation via a shared utility or something.

[izaaklauer]

Is there a reason that the ECS deployment plugin needs to create the load balancer? If the deployment doesn't need the ALB, then it seems like it should be the the releaser's job to create it.

[briancain]

Just writing a note here that fixing this could be potentially backwards incompatible when users upgrade to the version that has this fix. I removed the 0.5.x milestone and placed it in the Next Major project board for this reason.

[izaaklauer]

There is a reason the ECS plugin needs to create the load balancer. As it turns out, ECS refuses to attach a target group to a service if the target group isn't behind a load balancer. It fails with this error:

The target group with targetGroupArn arn:aws:elasticloadbalancing:us-east-1:797645259670:targetgroup/example-nodejs-01FDG2SXAX5PQ9BW7/e007bed47dbebabc does not have an associated load balancer.

It also isn't possible for the ALB plugin to create the target group, as you can't modify target groups on an ECS service once it's been created: aws/containers-roadmap#712

The only option to standardize left then is to modify the ALB plugin to behave like the ECS releaser (i.e. just enable traffic on the target group), then modify the EC2 plugin to also create an ALB. I believe that will feel counterintuitive to EC2 users though.

Closing for now.