airflow task failed but logs are empty

TL;DR

Empty logs on a failed task mean the failure happened before logging was set up or the logs were written somewhere the UI cannot read: a worker crash on startup, a logging config pointing at an unreachable location, or a permissions problem on the log volume. Check the worker's own logs first, then verify the remote logging path is writable and readable from both sides.

airflow task failed but logs are empty

Use this when

• A task instance is marked failed but the log view shows nothing.
• Logs work for some tasks but are blank for others.
• You recently changed logging config or moved to remote logging.

Not for this skill when

• Logs exist and show an error. Read the error.
• Logs are slow to appear. That is log latency, not missing logs.

Steps

1. Check the worker or executor logs around the task's start time for crashes before task logging initialized. Note any worker traceback. Verify: pre-logging crashes are found
2. Verify the task log path: local log folder permissions or the remote logging bucket and prefix. Note the path is writable by workers and readable by the webserver. Verify: the log plumbing is confirmed
3. Look for the log file directly on the worker host or in the remote bucket, bypassing the UI. Note whether the file exists at all. Verify: you know if logs were written but not displayed
4. If the worker crashed (OOM, segfault), fix the underlying crash: the empty log is a side effect. Note the next run produces logs. Verify: the root cause is addressed
5. Re-run the task and confirm logs appear in the UI. Note the full log is visible end to end. Verify: logging is verified working

Variant phrasings

airflow empty logs failed task

The symptom phrasing.

airflow task logs not showing

The UI-shaped search.

Compatibility: Airflow 2.x, all executors. Remote logging config lives under [logging] in airflow.cfg; S3, GCS, and Elasticsearch handlers each have their own quirks.

Why it happens

Task logging is configured inside the worker process after the task starts. If the worker dies during startup, before the handler is attached, nothing is ever written. Separately, remote logging splits the write path (worker) from the read path (webserver); a bucket the worker can write but the webserver cannot read produces exactly this symptom. The UI shows a blank page for both, so you have to check the worker side directly.

Edge cases / pitfalls

• Log filenames include the try number. If you are looking at try 1 while the task is on try 3, the page looks empty for the wrong reason.
• Elasticsearch logging with a full or unreachable cluster silently drops logs. Check the ES cluster health, not just Airflow.
• Tasks killed by the OS OOM killer leave no Python traceback anywhere. Check dmesg or the container runtime for the kill.
• A logging config syntax error fails every task's logging at once. If all logs are empty, suspect the config first.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_0Zfbd7IxEysdJRs-D9gHlQ