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[Bug] ECS observer leaves runs PENDING when capacity provider can't place task - #22417
desertaxle merged 7 commits into
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When a capacity provider cannot place an ECS task, the task transitions to STOPPED with stopCode TaskFailedToStart and an empty containers array. Previously, mark_runs_as_crashed only proposed Crashed when a container exited non-zero, so runs whose tasks never placed remained PENDING forever. Now the handler checks for TaskFailedToStart with empty containers and proposes Crashed with the stop reason included in the crash message. The diagnostic (infra level) was already handled by diagnose_ecs_task; this fix closes the state transition gap. Closes PrefectHQ#22410
- Apply ruff formatting to ecs.py and test_ecs_observer_crash.py - Remove unused imports (uuid, mark_runs_as_crashed, StateType, Crashed) - Remove unused variable assignment in test helper
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Thanks for the PR @goingforstudying-ctrl! The changes look good, but I want to make sure the your changes are covered with tests before merging.
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These new tests never appear to call mark_runs_as_crashed, so I don't think your code changes are covered by tests. Could you refactor these tests to invoke the actual handler and make assertions about the Crashed proposal?
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Thanks for the review. I refactored the tests to call mark_runs_as_crashed directly with mocked prefect.get_client and propose_state, matching the pattern used in the existing TestMarkRunsAsCrashed class. The new tests verify that TaskFailedToStart produces a Crashed proposal and that edge cases (normal exit, wrong stopCode, final flow run, missing flow run) are handled correctly.
…ed proposal Replace inline detection logic with real handler calls using the same mock pattern as the rest of TestMarkRunsAsCrashed. New tests verify that TaskFailedToStart proposes Crashed, normal exits do not, empty containers without the right stopCode do not, and edge cases like final flow runs and missing flow runs are handled correctly.
Remove extra blank line between third-party and first-party imports to satisfy ruff's isort rules.
…_args The test test_task_failed_to_start_crash_message_includes_reason was checking for a 'message' key in propose_state's kwargs, but the actual call passes the message inside a Crashed state object via state=Crashed(message=...). Fix extracts the state from kwargs first, then reads .message from it.
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LGTM! Thanks @goingforstudying-ctrl!
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…lace task (PrefectHQ#22417) Co-authored-by: goingforstudying-ctrl <goingforstudying-ctrl@users.noreply.github.com>
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Noticed this while debugging a stuck pipeline on an ECS work pool — when a capacity provider can't get an instance (GPU shortage, ASG at ceiling, etc.), ECS leaves the task in PROVISIONING for ~30 minutes and then stops it with
stopCode: TaskFailedToStartand an emptycontainersarray.The observer's
mark_runs_as_crashedhandler runs on STOPPED events, but only proposesCrashedwhen a container exited non-zero. With an empty containers array,containers_with_non_zero_exit_codesis empty,any()returns False, and the crash proposal is skipped. The only thing the handler does is log a diagnostic — but the flow run just sits inPENDINGforever.The fix
Added a check for
stopCode == "TaskFailedToStart"with empty containers, and proposeCrashedwith thestoppedReasonin the message so operators can see WHY it failed (e.g.TaskFailedToStart: RESOURCE:GPU).The diagnostic (infra-level logging via
diagnose_ecs_task) already handled this case — the gap was only in the state transition.Files changed
src/integrations/prefect-aws/prefect_aws/observers/ecs.py— the core fixsrc/integrations/prefect-aws/tests/observers/test_ecs_observer_crash.py— unit tests for the TaskFailedToStart detection logicCloses #22410