Lambda function to run a scheduled task in ECS

run_scheduled_task.py

import boto3
import os


def event_handler(event, context):
    """
    Lambda function that will run a task on ECS with the given command on the given
    task definition family. The ECS task will run a wrapper script that handles the
    dynamodb lock and will exit if the task is already running.
    """
    ecs_client = boto3.client('ecs')
    cluster_arn = os.environ['ECS_CLUSTER_ARN']
    task_definition_family = os.environ['ECS_TASK_DEFINITION_FAMILY']
    container_name = os.environ['CONTAINER_NAME']
    task_name = os.environ['SCHEDULED_TASK_NAME']
    command = os.environ['SCHEDULED_TASK_COMMAND']
    function_name = os.environ['AWS_LAMBDA_FUNCTION_NAME']
    task_command = [
        '/usr/local/bin/scheduled_task_runner.py',  # This wrapper scripts handles the locking code
        '--task_name', task_name,
        command,
    ]

    task_definition = get_task_definition(ecs_client, task_definition_family)

    response = ecs_client.run_task(
        cluster=cluster_arn,
        taskDefinition=task_definition,
        startedBy="{}/{}".format(function_name, context.aws_request_id)[0:36],
        overrides={'containerOverrides': [
            {
                'name': container_name,
                'command': task_command,
            }
        ]}
    )

    if response['failures']:
        raise RuntimeError("Failure for task name {}".format(task_name))
    return {"completed": True}


def get_task_definition(client, family):
    task_definition = client.describe_task_definition(taskDefinition=family)
    if not task_definition:
        raise ValueError("Unable to find task definition corresponding to {}".format(family))
    revision = task_definition['taskDefinition']['revision']
    return "{}:{}".format(family, revision)