@Marvin I am getting an occasional failure on the flow start using AWS ECS & docker deploy from ECR, a retry succeeded so this is occasional `

Flow run could not be submitted to infrastructure: TaskFailedToStart - CannotPullContainerError: ref pull has been retried 5 time(s): failed to copy: httpReadSeeker: failed open: failed to discard to offset: unexpected EOF

This error,

CannotPullContainerError

, is a known issue that can occur when deploying with AWS ECS and Docker from ECR. It often relates to network issues, Docker registry rate limits, or authentication problems with the Docker registry. ### Possible Causes: 1. Rate Limits: Exceeding Docker Hub's pull rate limits can cause this error. Ensure you are authenticated with Docker Hub to increase your rate limits. 2. Network Issues: Temporary network issues between AWS and Docker registry can lead to this error. 3. Authentication Issues: Ensure that your AWS ECS task has the necessary permissions to pull images from ECR. ### Recommendations: - Authentication: Make sure your ECS task definition includes the necessary IAM roles and policies to pull images from ECR. You can use the

AmazonEC2ContainerRegistryFullAccess

policy for full access. - Rate Limit: Authenticate with Docker Hub to increase your pull rate limits. - Retries: Since the error is intermittent, implementing retries can help mitigate the issue. ### Resources: - AWS ECS Guide - Docker Infrastructure Examples For more information, you can also refer to relevant GitHub issues such as this one discussing similar errors.

@Marvin in the issue you linked is kinda clear and self-descriptive (autthorization to dockerhub). But the I cannot understand the error I pasted above. Is it some sort of AWS networking not done right? temporary failure? a bug?

The error message you encountered,

CannotPullContainerError: ref pull has been retried 5 time(s): failed to copy: httpReadSeeker: failed open: failed to discard to offset: unexpected EOF

, suggests that there was a failure in downloading the Docker image from the registry. Here's a breakdown of what might be happening: ### Possible Causes: 1. Network Instability: - The error

unexpected EOF

often points to a network issue where the connection was unexpectedly closed. This could be a transient network failure between AWS and the Docker registry. 2. Registry Issues: - Temporary issues on the Docker registry side could cause such errors, especially if the registry is experiencing high load or maintenance. 3. AWS Configuration: - Check your AWS network configurations, such as VPC, subnets, and security groups, to ensure they allow outbound traffic to the Docker registry. 4. Bug or Misconfiguration: - While less likely, a misconfiguration in your ECS task or a bug in the Prefect or AWS ECS service could lead to such issues. ### Recommendations: - Network Checks: Verify that your AWS network settings are correct and allow outbound access to the Docker registry. - Retries: Since the error is intermittent, implementing retries in your deployment strategy can help mitigate the issue. - Logging and Monitoring: Enable detailed logging for your ECS tasks and monitor network traffic to identify any patterns or persistent issues. Given the intermittent nature, it's likely a temporary network issue or a transient problem with the Docker registry. However, ensuring that your AWS configurations are correct can help reduce the frequency of such errors.

@Marvin I tested the configured subnets one by one and that's definitely not the issue. I seems the failure happened even before creating the task, am I right? (CannotPullContainerError)

Yes, you're correct. The

CannotPullContainerError

typically occurs during the container image pulling phase, which happens before the ECS task is fully created and started. This error indicates that the ECS service was unable to pull the Docker image from the registry, halting the task creation process. ### Breakdown of the Error Phase: 1. Image Pulling: - Before a task can start, ECS attempts to pull the specified Docker image from the registry (ECR, Docker Hub, etc.). - If it fails during this step, the task does not proceed to creation. 2. Potential Failures: - Network Issues: Network interruptions can prevent successful image pulling. - Registry Access: Authentication or rate limits with the Docker registry could cause failures. - Image Availability: Ensure that the image tag specified in your task definition exists and is accessible. ### Recommendations: - Authentication: Double-check that your ECS task role has the necessary permissions to access the Docker registry. - Registry Configuration: Ensure that the image is correctly tagged and available in the specified registry. - Monitoring: Use AWS CloudWatch logs to monitor and diagnose any network or authentication issues during the image pulling phase. By focusing on the image pulling process, you can better pinpoint the root cause of the error.

@Marvin help me analyze the error message more, what each part mean and at which stage it's triggered?

low run could not be submitted to infrastructure: TaskailedToStart - CannotPullContainerError: ref pull has been retried 5 time(s): failed to copy: httpReadSeeker: failed open: failed to discard to offset: unexpected EOF

Let's break down the error message step-by-step to understand what each part means and at which stage it might be triggered: 1. "Flow run could not be submitted to infrastructure": - This indicates that the Prefect flow run failed at the infrastructure layer, specifically when trying to start the task on AWS ECS. 2. "TaskFailedToStart": - This part of the error message signifies that the ECS task did not successfully start. The failure occurred before the task could be initialized and run. 3. "CannotPullContainerError": - This specific error indicates that ECS was unable to pull the Docker container image from the specified registry. This is a critical step that occurs before the task can be started. 4. "ref pull has been retried 5 time(s)": - ECS made five attempts to pull the Docker image from the registry. The retries suggest that the error could be transient or related to network instability. 5. "failed to copy: httpReadSeeker: failed open": - This part indicates a failure in the process of reading the image data from the registry.

httpReadSeeker

is part of the mechanism used to read data over HTTP. 6. "failed to discard to offset: unexpected EOF": - "Unexpected EOF" (End Of File) implies that the connection was unexpectedly closed or interrupted while reading the image data. This is typically a network issue or a problem with the data stream from the registry. ### Error Stage: - Image Pulling Stage: - This error occurs during the image pulling stage, which is before the task creation and execution phases. The ECS service needs to successfully pull the image to create and start the task. ### Conclusion: The error suggests issues with network stability or registry access during the image pulling process. Ensuring robust network configurations and registry access permissions can help mitigate this error.

@Marvin cool, so the most likely it's an AWS thing, I will see if there are any logs / metrics in cloudwatch related to that failure as I couldn't reproduce

Yes, checking AWS CloudWatch for logs and metrics related to the ECS service and network activity would be a prudent step. CloudWatch can provide insights into: - ECS Task Lifecycle Events: Look for any anomalies or errors during the task lifecycle. - Network Metrics: Check for any unusual patterns in network traffic that might coincide with the error. - ECR Logs: If you're using ECR, there might be logs indicating access or retrieval issues. Given the intermittent nature of the error, it might be a transient network issue or a temporary hiccup in the registry service. Monitoring these logs can help identify any recurring patterns or specific conditions that trigger the error. Good luck with your investigation!