How to debug failed fargate task initialization

Question

I have a fargate task which I have scheduled to run with CloudWatch Event rules, and output a timestamp to a database on a successful run. It also outputs a logfile to CloudWatch for every time it runs.

However, there was 1 time where the log file was not created, and the database not updated. I suspect the task was never even started, or had failed to start.

In CloudWatch, the event rule shows trigger and invocation at the time I expected the task to run, so I assume the task at least attempted to start.

My question is: is there any way I can debug or log information about the cluster failing to start a task?

Please let me know if I need to provide more information.

Edit: I should specify I'm looking for a way to read this information in a log file somewhere. I know I can see failed task reason in the web console, but that's only for relatively recent tasks.

I have posted the same question here: https://www.reddit.com/r/aws/comments/adtqvt/debugging_failed_fargate_task_initialization/ and StackOverflow: https://forums.aws.amazon.com/thread.jspa?messageID=884638&#884638

Answer 1

1. Go to the cluster and choose the Tasks tab
2. In the lower pane, choose Stopped for the Desired Task Status value
3. Locate the desired Task and click it's GUID
4. Scroll down to the Containers section and expand the relevant containers that are experiencing errors

You'll see some kind of Status reason for the error. In my case it was:

CannotStartContainerError: API error (500): failed to initialize logging driver: Cannot determine region for awslogs driver

Edit: I can't really take credit for figuring this out - found it here:

https://github.com/aws/amazon-ecs-agent/issues/1654#issuecomment-437178282

Answer 2

Try going to "CloudWatch -> Logs -> Insights" and click on "Run Query":