The AWS ECS container does not exist

Problem

Your CodePipeline ECS deployment is failing with a The AWS ECS container ${container} does not exist message.

Scenario

This problem can occur in a number of situations but let’s just imagine we have a task definition contains a single entry in its container definitions.¹ Now we want to add another container to the task, say a sidecar container like the datadog agent.

First, you add it to your ECS task definition and push a new revision.

[
  ...
  ...
  {
    "name": "${datadog_name}",
    "image": "${datadog_image}",
    "essential": true,
    "logConfiguration": {
      "logDriver": "awslogs",
      "options": {
        "awslogs-group": "/aws/ecs/${cluster_name}/${datadog_name}",
        "awslogs-region": "us-west-2",
        "awslogs-stream-prefix": "${datadog_name}"
      }
    },
    "secrets": [
      { "name": "DD_API_KEY",  "valueFrom": "${DD_API_KEY}" }
    ],
    "environment": [
      { "name": "ECS_FARGATE", "value": "true" }
    ]
  }
]

Second, you add it to your imagedefinitions.json generated in your CodePipeline build stage.

[
	{
		"name": "${your_container_name}",
		"imageUri":"${your_container_image}"
	}
	{
		"name": "${datadog_agent_name}",
		"imageUri":"${datadog_agent_image}"
	}
]

After that, you run a new CodePipeline and run into the following error: The AWS ECS container datadog-agent does not exist.

What the heck?

The ECS service being updated with a new task definition from CodePipeline MUST have the container defined in it. This means that you must add the container definition, create a new task revision, AND force a new service deployment prior to doing an ECS deployment via CodePipeline.