Celery ProxyLogger.write raises TypeError due to rstrip on

The Fix

pip install celery==5.2.1

Based on closed celery/celery issue #7056 · 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

@@ -224,13 +224,13 @@ def write(self, data):
             # Logger is logging back to this file, so stop recursing.
             return 0
-        data = data.rstrip('\n')
         if data and not self.closed:
             self._thread.recurse_protection = True

repro.py

TypeError: a bytes-like object is required, not 'str'
  File "aspiredu/project/celery.py", line 43, in run_command
    sys.stdout.write(line)  # Write all output from the command
  File "celery/utils/log.py", line 227, in write
    data = data.rstrip('\n')

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==5.2.1\nWhen NOT to use: Do not apply this fix if the data is guaranteed to always be a string.\n\n

Why This Fix Works in Production

Trigger: TypeError: a bytes-like object is required, not 'str'
Mechanism: TypeError occurs when rstrip is called on a bytes instance instead of a string
Why the fix works: Fixes a TypeError in ProxyLogger by ensuring data is safely converted to a string before calling rstrip. (first fixed release: 5.2.1).

Production impact:

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

Why This Breaks in Prod

TypeError occurs when rstrip is called on a bytes instance instead of a string
Surfaces as: TypeError: a bytes-like object is required, not 'str'

Proof / Evidence

GitHub issue: #7056
Fix PR: https://github.com/celery/celery/pull/7057
First fixed release: 5.2.1
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.75
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.55

Discussion

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

Jump to Sources Open on GitHub

“Hey @tim-schilling :wave:, Thank you for opening an issue”

@open-collective-bot · 2021-11-08 · source

Failure Signature (Search String)

TypeError: a bytes-like object is required, not 'str'

Error Message

Stack trace

error.txt

Error Message
-------------
TypeError: a bytes-like object is required, not 'str'
  File "aspiredu/project/celery.py", line 43, in run_command
    sys.stdout.write(line)  # Write all output from the command
  File "celery/utils/log.py", line 227, in write
    data = data.rstrip('\n')

Minimal Reproduction

repro.py

TypeError: a bytes-like object is required, not 'str'
  File "aspiredu/project/celery.py", line 43, in run_command
    sys.stdout.write(line)  # Write all output from the command
  File "celery/utils/log.py", line 227, in write
    data = data.rstrip('\n')

What Broke

Application crashes or logs fail to process due to TypeError.

Why It Broke

TypeError occurs when rstrip is called on a bytes instance instead of a string

Fix Options (Details)

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

pip install celery==5.2.1

When NOT to use: Do not apply this fix if the data is guaranteed to always be a string.

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/7057

First fixed release: 5.2.1

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

When NOT to Use This Fix

Do not apply this fix if the data is guaranteed to always be a string.

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
5.2.1	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 ProxyLogger.write raises TypeError due to rstrip on a bytes instance. (Fix)