Celery Allow custom hostname for celery

The Fix

pip install celery==5.5.0

Based on closed celery/celery issue #9404 · PR/commit linked

Production note: This usually shows up under retries/timeouts. Treat it as a side-effect risk until you can verify behavior with a canary + real traffic.

Jump to Verify Open PR/Commit

@@ -155,7 +155,7 @@ def _start_worker_thread(app: Celery,
         app=app,
         concurrency=concurrency,
-        hostname=anon_nodename(),
+        hostname=kwargs.pop("hostname", anon_nodename()),
         pool=pool,

repro.py

@pytest.fixture
def patch_pytest_celery_worker_hostname():
    with patch('celery.contrib.testing.worker.anon_nodename', return_value='test_plugin@localhost') as p:
        yield p


@pytest.fixture
def celery_worker(patch_pytest_celery_worker_hostname, celery_worker):
    return celery_worker

verify

Re-run the minimal reproduction on your broken version, then apply the fix and re-run.

fix.md

Option A — Upgrade to fixed release\npip install celery==5.5.0\nWhen NOT to use: This fix should not be used if consistent worker names are not required during testing.\n\n

Why This Fix Works in Production

Trigger: - [X] I have included all related issues and possible duplicate issues in this issue
Mechanism: The celery_worker fixture did not allow for a user-defined hostname during testing
Why the fix works: Introduces the functionality to use a user defined hostname during TestWorkerController initialization, allowing users to mimic the CLI argument for hostname during testing. (first fixed release: 5.5.0).

Production impact:

If left unfixed, retries/timeouts can trigger duplicate external side-effects (double charges, duplicate emails, repeated writes).

Why This Breaks in Prod

The celery_worker fixture did not allow for a user-defined hostname during testing
Production symptom (often without a traceback): - [X] I have included all related issues and possible duplicate issues in this issue

Proof / Evidence

GitHub issue: #9404
Fix PR: https://github.com/celery/celery/pull/9405
First fixed release: 5.5.0
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.85
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.65

Discussion

High-signal excerpts from the issue thread (symptoms, repros, edge-cases).

Jump to Sources Open on GitHub

“Interesting change - please tag me for review if you want to offer a PR. Thanks!”

@Nusnus · 2024-11-09 · source

Failure Signature (Search String)

- [X] I have included all related issues and possible duplicate issues in this issue
or possible duplicates to this issue as requested by the checklist above.

Copy-friendly signature

signature.txt

Failure Signature
-----------------
- [X] I have included all related issues and possible duplicate issues in this issue
or possible duplicates to this issue as requested by the checklist above.

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
- [X] I have included all related issues and possible duplicate issues in this issue
or possible duplicates to this issue as requested by the checklist above.

Minimal Reproduction

repro.py

@pytest.fixture
def patch_pytest_celery_worker_hostname():
    with patch('celery.contrib.testing.worker.anon_nodename', return_value='test_plugin@localhost') as p:
        yield p


@pytest.fixture
def celery_worker(patch_pytest_celery_worker_hostname, celery_worker):
    return celery_worker

What Broke

Testing did not mimic production behavior due to fixed worker names.

Why It Broke

The celery_worker fixture did not allow for a user-defined hostname during testing

Fix Options (Details)

Option A — Upgrade to fixed release Safe default (recommended)

pip install celery==5.5.0

When NOT to use: This fix should not be used if consistent worker names are not required during testing.

Use when you can deploy the upstream fix. It is usually lower-risk than long-lived workarounds.

Fix reference: https://github.com/celery/celery/pull/9405

First fixed release: 5.5.0

Last verified: 2026-02-09. Validate in your environment.

When NOT to Use This Fix

This fix should not be used if consistent worker names are not required during testing.

Verify Fix

verify

Re-run the minimal reproduction on your broken version, then apply the fix and re-run.

Did This Fix Work in Your Case?

Quick signal helps us prioritize which fixes to verify and improve.

Prevention

Capture the exact failing error string in logs and tests so you can reproduce via a minimal script.
Pin production dependencies and upgrade only with a reproducible test that hits the failing path.

Version Compatibility Table

Version	Status
5.5.0	Fixed

Related Issues

No related fixes found.

Cluster: celery:duplicates Celery hub Celery best practices All hubs All clusters

Related clusters: Configuration error Data consistency Duplicate processing

Sources

We don’t republish the full GitHub discussion text. Use the links above for context.

Celery Allow custom hostname for celery_worker in celery.contrib.pytest / (Fix)