Fargate tasks running and hanging with no logs

Question

We are launching multiple Fargate tasks using run_task. The container runs a python script as its ENTRYPOINT.

Most of them run, log and complete successfully. But a subset of them start running, produce no logs and just hang for hours.

The entire function is wrapped in a try/catch block so any error should be caught and logged but there is nothing and with nothing logged, I'm having a hard time figuring out what's going wrong.

re:Post Agent · Answer

This issue with Fargate tasks hanging without producing logs can be challenging to troubleshoot. Here are a few potential causes and suggestions to investigate:

1. Resource constraints: Ensure that your task has sufficient CPU and memory allocated. If the task is resource-starved, it might appear to hang without producing logs.

2. Networking issues: Check if there are any networking problems preventing the task from communicating or accessing required resources. Verify that your VPC, subnets, and security groups are correctly configured.

3. Container image issues: Make sure your container image is up-to-date and doesn't have any known bugs or compatibility issues with the Fargate platform version you're using.

4. Python script problems: Review your Python script for any potential infinite loops, deadlocks, or blocking operations that might cause it to hang without producing output.

5. Logging configuration: Verify that your logging driver is correctly configured and that the AWS CloudWatch Logs agent is working properly within the task.

6. Task definition parameters: Some task definition parameters behave differently for Fargate tasks. Review your task definition to ensure all parameters are compatible with Fargate.

7. Capacity issues: In rare cases, Fargate might not have the capacity to properly launch tasks, which could result in unexpected behavior. If you suspect this, you can try running the task in a different availability zone or retry after some time.

To further diagnose the issue:

1. Use AWS CloudWatch Logs Insights to analyze your logs and look for patterns or anomalies.

2. Consider implementing more comprehensive error handling and logging in your Python script to catch and report any issues that might be occurring before the main try/catch block.

3. Use AWS X-Ray or other tracing tools to get more visibility into your task's execution.

4. Monitor your task's resource utilization using CloudWatch metrics to identify any potential resource constraints.

If the problem persists, you may need to contact AWS support for more in-depth troubleshooting assistance.

**Sources**  
[Troubleshoot unavailable capacity for Fargate tasks | AWS re:Post](https://repost.aws/knowledge-center/ecs-fargate-runtask-capacity)  
[AWS Fargate for Amazon ECS - Amazon Elastic Container Service](https://docs.aws.amazon.com/AmazonECS/latest/developerguide/AWS_Fargate.html)  
[Community | Leveraging AWS Fargate for Containerized Workloads](https://community.aws/content/2aJT9iG8tQgfFaotQx59AeRGGbx/leveraging-aws-fargate-for-containerized-workloads)

Fargate tasks running and hanging with no logs

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