ECS Tasks Stuck in "Deprovisioning" - Execution Time Increased from 1.5 min to 4 min

The increased time in the "Deprovisioning" phase of your ECS Fargate tasks could be due to several factors. Here are some insights and recommendations to help you address this issue:

1. Network Interface Cleanup: The "Deprovisioning" state is when Amazon ECS performs additional steps after the task has stopped but before it transitions to the "STOPPED" state. For tasks using the awsvpc network mode (which is the case for Fargate), this includes detaching and deleting the elastic network interface (ENI). If there are issues or delays in this process, it can lead to longer deprovisioning times.

2. VPC and Subnet Configuration: Since you mentioned that tasks are randomly assigned to different subnets and availability zones, there might be network-related issues in certain subnets or AZs. Check if the increased deprovisioning time is consistent across all subnets or if it's more pronounced in specific ones.

3. AWS-side Issues: While it's possible that there could be an AWS-side issue with ECS Fargate networking, it's not common. However, you can check the AWS Service Health Dashboard or contact AWS Support if you suspect this is the case.

To optimize ECS task deprovisioning and potentially restore the previous execution time:

1. Monitor ENI Deletion: Use CloudWatch metrics or custom logging to track the time taken for ENI deletion. This can help identify if the delay is specifically in this step.

2. Review VPC Flow Logs: Analyze VPC flow logs to identify any network-related issues that might be causing delays in the deprovisioning process.

3. Adjust Task Placement: If you find that certain subnets or AZs consistently have longer deprovisioning times, consider adjusting your task placement strategy to favor faster-performing locations.

4. Optimize Task Definition: Although you mentioned no recent changes, review your task definition to ensure it's optimized for quick startup and shutdown. Minimize the number of volumes and network interfaces if possible.

5. Increase Resources: While this may not directly address the deprovisioning issue, increasing CPU and memory resources might help speed up the overall process.

6. Check for Resource Contention: Ensure that there isn't resource contention in your VPC or at the AWS account level that could be affecting the deprovisioning process.

7. AWS Support: If the issue persists and you can't identify the root cause, consider reaching out to AWS Support for a more in-depth investigation.

Remember that the deprovisioning process involves several steps and can be affected by various factors. Systematic investigation and potentially working with AWS Support may be necessary to fully resolve the issue and restore your previous execution times.

Sources
Amazon ECS task lifecycle - Amazon Elastic Container Service
ECS TASK PROVISIONING STATE | AWS re:Post