task-debugger

Setup

Taskcluster CLI:

taskcluster version  # check if installed
export TASKCLUSTER_ROOT_URL=https://firefox-ci-tc.services.mozilla.com

If not installed: https://github.com/taskcluster/taskcluster/releases/latest/

Commands:

• taskcluster task log <task-id> - Get logs
• taskcluster task def <task-id> - Get definition (optional)

Debug Process

1. Extract task ID from message or URL
2. Fetch logs: taskcluster task log <task-id>
3. Analyze errors (tracebacks, test failures, build errors)
4. If fix is obvious → apply it. Otherwise → reproduce locally:
   • Docker-worker tasks: taskgraph load-task --develop <task-id> (Firefox: ./mach taskgraph, others: check virtualenv or uv run taskgraph)
   • Flags: --interactive, --volume, --root, --image, --keep
   • Non-docker: extract command from task def and run locally
5. For non-obvious issues: add debug statements → iterate → fix
6. Verify fix using same reproduction method
7. Clean up debug artifacts (don't re-verify after cleanup)
8. Report: root cause, fix, verification, files changed