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Python asyncio first triage response

A Python first triage note for asyncio: Python asyncio failure caused by nested event loops, un-awaited coroutine, blocking IO inside async code, cancellation handling, or task lifecycle leak. It includes evidence, output examples, branches, and the smallest reliable fix.

lowasyncio8 min read
First command
grep -R "asyncio" ./logs
First evidence

Treat asyncio as a first triage case. First collect evidence for the first observable mismatch before any setting is changed.

Search queries
Python asyncioPython error asyncioPython asyncio first triage response

When this happens

Use this when only the visible message is known. Do not stop at the screen message; validate the first observable mismatch before any setting is changed first.

Symptom checklist

  • asyncio appears repeatedly in the Python UI or logs.
  • venv, pip freeze, stack trace, encoding, path differs between successful and failed requests.
  • The issue appears only after separating code error from environment/package conflict.
  • It often follows deploys, permission changes, configuration edits, or data refreshes.

Likely causes

  • asyncio specifically changes the investigation surface for Python: verify the exact failing object, route, user, and timestamp before applying the broader pattern.
  • A coroutine is created but never awaited.
  • An event loop is nested inside an already running loop.
  • Blocking IO runs in the event loop and starves other tasks.
  • Cancellation is swallowed and leaves resources open.
  • Background tasks are created without ownership or shutdown handling.
  • For the first triage case, the first useful clue is the first observable mismatch before any setting is changed.

First 1-minute checks

  1. Write down the first failure time, latest change, affected user, path, and object ID.
  2. Compare venv, pip freeze, stack trace, encoding, path for success and failure in the same window.
  3. Test the hypothesis: Python asyncio failure caused by nested event loops, un-awaited coroutine, blocking IO inside async code, cancellation handling, or task lifecycle leak.
  4. Classify this as first triage: the first observable mismatch before any setting is changed.
  5. Capture current values before changing configuration.

First evidence

Treat asyncio as a first triage case. First collect evidence for the first observable mismatch before any setting is changed.

Output examples

Normal output

No matching error appears during the affected request window.

Failing output

The same error appears at the exact request time with the affected path, user, or object.

Output-to-action branches

  • Only the visible message is known.
    Collect timestamp, route, request ID, user, and the first backend log line before editing configuration.
  • The working and failing outputs differ.
    Act on the differing layer first: For asyncio, apply the fix only after reproducing the same condition and saving the before/after evidence for this exact code.
  • Command output is normal but users still fail.
    Separate browser cache, cookies, permissions, and network location before declaring it fixed.

Do not do this

  • Do not change DNS, SSL, cache, and permissions at the same time.
  • Do not change multiple layers before identifying the failing layer.
  • Do not delete production data, grant broad permissions, or disable security controls as a first response.

Evidence quality

Auto-generated operator draft: includes issue-specific causes, commands, output branches, and unsafe-action warnings. Official-source links and real incident validation are queued for enrichment.

Commands to run first

grep -R "asyncio" ./logs
python -m pip freeze
python -X dev script.py
python -m traceback
grep -R "asyncio" .
python -X dev script.py
PYTHONASYNCIODEBUG=1 python script.py
grep -R "asyncio\|await\|create_task\|run_until_complete" .
date -u && grep -R "ERROR\|WARN\|failed" ./logs | tail -n 50

Fix order

  1. Record the full asyncio message, failing URL, user, object ID, and latest change.
  2. Collect issue-specific evidence for Python asyncio failure caused by nested event loops, un-awaited coroutine, blocking IO inside async code, cancellation handling, or task lifecycle leak.
  3. Compare the failing case with a successful case before editing settings.
  4. If this is the first triage branch, Collect timestamp, route, request ID, user, and the first backend log line before editing configuration.
  5. Re-check with the same command and URL, then record the normal output.

Actions by cause

  • For asyncio, apply the fix only after reproducing the same condition and saving the before/after evidence for this exact code.
  • Trace coroutine creation and await boundaries before adding sleeps.
  • Use one top-level event loop and avoid nested asyncio.run calls.
  • Move blocking work to a thread or process executor.
  • Propagate cancellation and close resources in finally blocks.
  • Track background tasks and await shutdown during service stop.
  • For the first triage branch, Collect timestamp, route, request ID, user, and the first backend log line before editing configuration.

Verification metadata

  • operator-draft
  • official-reference-linked
  • 2026-07-23

Update queue

  • Review cadence
    weekly-source-review
  • Next enrichment
    Add one official-source check and one real output example for Python asyncio.

Environment-specific checks

  • Shared hosting, proxies, VPNs, or CDN layers can change code error from environment/package conflict results.
  • Do not trust only the Python UI; compare command output.
  • Japanese hosting panels may show completion before DNS or SSL fully propagates.
  • Test from both office and external networks.

Prevent it next time

  • Store normal examples for venv, pip freeze, stack trace, encoding, path.
  • Add venv reproduction, dependency pinning, explicit encoding, type checks to the release checklist.
  • Keep recurring errors in the same note format.
  • Split alerts by error rate, latency, certificates, disk, and permission changes.