One day, a regularly scheduled job in GitHub Actions suddenly started failing. I investigated the cause by utilizing GitHub Actions’ debug logging feature, so I’d like to share that process with you.

Error “The operation was canceled.”

When checking the error logs, the following message was displayed:

##[error]The runner has received a shutdown signal. This can happen when the runner service is stopped, or a manually started runner is canceled.
················ ELIFECYCLE  Command failed.
##[error]The operation was canceled.

While this log tells us that the runner received a shutdown signal, it’s difficult to identify the specific cause of why this happened.

Even looking at the failed job logs, no additional information was available.

Investigating by Enabling Debug Logging

In such situations, GitHub Actions’ debug logging feature becomes very useful. When debug logging is enabled, more detailed information about workflow execution is output, making it easier to obtain clues that lead to identifying the root cause of problems.

The method to enable debug logging is very simple:

1. Navigate to Settings > Secrets and variables > Actions in the target repository.
2. Select the Variables tab and click New repository variable.
3. Set up the variable with the following content:
   • Name: ACTIONS_RUNNER_DEBUG
   • Value: true
4. Click Add variable to save.

The setup is now complete. When you re-run the workflow in this state, detailed logs will be output.

Information Obtained from Debug Logs

When I actually enabled debug logging and re-executed the workflow, the log output increased dramatically.

Job logs with debug logging enabled

Many lines with the prefix ##[debug] were added to the logs, recording internal operations of each step, API calls, and environment variables with masking applied.

················ ELIFECYCLE  Command failed.
Error: The operation was canceled.
##[debug]System.OperationCanceledException: The operation was canceled.
##[debug]   at System.Threading.CancellationToken.ThrowOperationCanceledException()
##[debug]   at GitHub.Runner.Sdk.ProcessInvoker.ExecuteAsync(String workingDirectory, String fileName, String arguments, IDictionary`2 environment, Boolean requireExitCodeZero, Encoding outputEncoding, Boolean killProcessOnCancel, Channel`1 redirectStandardIn, Boolean inheritConsoleHandler, Boolean keepStandardInOpen, Boolean highPriorityProcess, CancellationToken cancellationToken)
##[debug]   at GitHub.Runner.Common.ProcessInvokerWrapper.ExecuteAsync(String workingDirectory, String fileName, String arguments, IDictionary`2 environment, Boolean requireExitCodeZero, Encoding outputEncoding, Boolean killProcessOnCancel, Channel`1 redirectStandardIn, Boolean inheritConsoleHandler, Boolean keepStandardInOpen, Boolean highPriorityProcess, CancellationToken cancellationToken)
##[debug]   at GitHub.Runner.Worker.Handlers.DefaultStepHost.ExecuteAsync(IExecutionContext context, String workingDirectory, String fileName, String arguments, IDictionary`2 environment, Boolean requireExitCodeZero, Encoding outputEncoding, Boolean killProcessOnCancel, Boolean inheritConsoleHandler, String standardInInput, CancellationToken cancellationToken)
##[debug]   at GitHub.Runner.Worker.Handlers.ScriptHandler.RunAsync(ActionRunStage stage)
##[debug]   at GitHub.Runner.Worker.ActionRunner.RunAsync()
##[debug]   at GitHub.Runner.Worker.StepsRunner.RunStepAsync(IStep step, CancellationToken jobCancellationToken)
##[debug]Finishing: Run e2e tests

This enables more detailed tracking of which command at which timing is causing unexpected behavior.

Summary

When encountering errors of unknown cause in GitHub Actions, I recommend first enabling debug logging. Simply setting ACTIONS_RUNNER_DEBUG to true can potentially provide many hints that lead to problem resolution. Please try this method as a first step in troubleshooting.

That’s all from the Gemba.

Reference Information

• Using workflow run logs - GitHub Docs
• Enabling debug logging - GitHub Docs