ECS Container and Docker

Question

Hey Guys

I have been stuck on this for the longest now:
I am deploying the Python code as a dockerized container.

I am doing all this in Python CDK.

Here is now I am creating the cluster

```
        vpc_test = _ec2.Vpc.from_lookup(self, "VPC",
                          vpc_id= "vpc-64c37b02"
                    )
        #Setting up the container to run the job
        cluster = _ecs.Cluster(self, "ClusterToGetFile",
                               vpc=vpc_test
                               )
        task_definition = _ecs.FargateTaskDefinition(self, "TaskDefinition",
                                                     cpu=2048,
                                                     memory_limit_mib=4096
                                                     )
        task_definition.add_container("getFileTask",

image = _ecs.ContainerImage.from_asset(directory="assets", file="Dockerfile-ecs-file-download"))

```

Here is the - Dockerfile-ecs-file-download

```
FROM python:3.9
WORKDIR /usr/app/src
COPY marketo-ecs-get-file/get_ecs_file_marketo.py ./
COPY marketo-ecs-get-file/requirements.txt ./
COPY common_functions ./
RUN  pip3 install -r requirements.txt  --no-cache
CMD ["python" , "./get_ecs_file_marketo.py"]
```

All i am trying to do, to begin with, is to run the task(Deploy) it manually.

All I have in the get_ecs_file_marketo.py.py file is

```
import logging
logging.info("ECS Container has stareted. ")
```
However, when I deploy the task, I get this error:

```
Stopped reason
Essential container in task exited
```

I am not able to figure out what am I doing incorrectly.

Appreciate any help or directions here.

Regards
Tanmay

Answer

I realized that the container was runnign, however the logs were not being send to cloudwatch as a default. I had to add the logging option in add_container to send the logs to cloudwatch.

Answer

At the risk of not strictly answering the question, given that I don't like CDK too much and prefer Troposphere. In case the problem comes from the way you defined the ECS Service/Task definitions, see if you can get somewhere with AWS Copilot / ECS Compose-X.
Also I would highly recommend you improve your Dockerfile for security reasons not to use the root user etc.

`Essential container in task exited` will have a return code if the container started at all (different than 0) and failed.
Now, if you intend to run the task once (and exit 0 is expected) you probably don't want to use a ECS service but create a scheduled task (will start the containers based on triggers (time, events etc.) which is not expected to stay alive all the time the same way a service is. Now note that, for future work, if you have only 1 container in the task definition, that container is "essential" which means it's got to be up and running / healthy. If you have more than 1 container in the task definition, some can be expected to run and exit (SUCCESS expects return 0, otherwise any return code will do), others to be healthy, and some others just to be RUNNING.

ECS Container and Docker

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