How to Create AWS Task Definition JSON from Existing task definition? - amazon-web-services

Question

I have a an existing task definition 'my-task-definition' that I can get the data for using 'aws ecs describe-task-definition --task-definition my-task-definition' (I put the output of that into my_file.json'). But my understanding is that the output from 'aws ecs describe-task-definition --task-definition my-task-definition' is not valid input for 'aws ecs register-task-definition --cli-input-json file://<path_to_json_file>/my_file.json'. What additional piece(s) of data do I have to add to that file (or remove from it). The file (with the arns changed) is below:
{
"taskDefinition": {
"taskDefinitionArn": "arn:aws:ecs:us-west-1:112233445566:task-definition/my-task-definition:64",
"containerDefinitions": [
{
"name": "my-container",
"image": "123456789023.dkr.ecr.us-west-1.amazonaws.com/monolith-repo:latest",
"cpu": 0,
"memory": 1600,
"portMappings": [
{
"containerPort": 8080,
"hostPort": 0,
"protocol": "tcp"
}
],
"essential": true,
"environment": [
{
"name": "SERVER_FLAVOR",
"value": "JOB"
}
],
"mountPoints": [],
"volumesFrom": [],
"linuxParameters": {
"initProcessEnabled": true
},
"logConfiguration": {
"logDriver": "awslogs",
"options": {
"awslogs-group": "/ecs/my-task-definition",
"awslogs-region": "us-west-1",
"awslogs-stream-prefix": "ecs"
}
}
}
],
"family": "my-task-definition",
"taskRoleArn": "arn:aws:iam::111222333444:role/my_role",
"networkMode": "bridge",
"revision": 64,
"volumes": [],
"status": "ACTIVE",
"requiresAttributes": [
{
"name": "com.amazonaws.ecs.capability.logging-driver.awslogs"
},
{
"name": "com.amazonaws.ecs.capability.ecr-auth"
},
{
"name": "com.amazonaws.ecs.capability.docker-remote-api.1.19"
},
{
"name": "com.amazonaws.ecs.capability.task-iam-role"
},
{
"name": "com.amazonaws.ecs.capability.docker-remote-api.1.25"
}
],
"placementConstraints": [],
"compatibilities": [
"EXTERNAL",
"EC2"
],
"requiresCompatibilities": [
"EC2"
]
}
}

Answer 1

You are getting an error because the output from the aws ecs describe-task-definition command has additional fields that are not recognized by the aws ecs register-task-definition command.
There is no built in solution to be able to easily update a running Task Definition using the AWS CLI. However, it is possible to script a solution using a tool like jq.
One possible solution is something like this:
TASK_DEFINITION=$(aws ecs describe-task-definition --task-definition "$TASK_FAMILY" --region "us-east-1")
NEW_TASK_DEFINTIION=$(echo $TASK_DEFINITION | jq --arg IMAGE "$NEW_IMAGE" '.taskDefinition | .containerDefinitions[0].image = $IMAGE | del(.taskDefinitionArn) | del(.revision) | del(.status) | del(.requiresAttributes) | del(.compatibilities)')
aws ecs register-task-definition --region "us-east-1" --cli-input-json "$NEW_TASK_DEFINITION"
These commands update the docker image in an existing task definition and delete the extra fields so that you can register a new task definition.
There is an open Github Issue that is tracking this issue. https://github.com/aws/aws-cli/issues/3064