Celery Memory leak after task raise exception (Fix)

The Fix

pip install celery==4.4.2

Based on closed celery/celery issue #6058 · 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

@@ -82,7 +82,8 @@
 
 log_policy_t = namedtuple(
-    'log_policy_t', ('format', 'description', 'severity', 'traceback', 'mail'),
+    'log_policy_t',
+    ('format', 'description', 'severity', 'traceback', 'mail'),

repro.py

from celery import Celery

app = Celery('tasks', broker='pyamqp://guest:guest@localhost:5672') # for rabitmq broker
# app = Celery('tasks', broker='redis://localhost:6379/0') for refis broker

@app.task
def task_example():
    s = 'a' * 256 * (10**6) # Create a string of 256MB
    raise

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==4.4.2\nWhen NOT to use: This fix should not be applied if the application relies on the traceback for debugging.\n\n

Why This Fix Works in Production

Trigger: Memory leak after task raise exception
Mechanism: A memory leak occurs when an exception is raised in a task due to uncleaned traceback references
Why the fix works: Addresses a memory leak issue that occurs when an exception is raised in a task by cleaning up the traceback. (first fixed release: 4.4.2).

Why This Breaks in Prod

A memory leak occurs when an exception is raised in a task due to uncleaned traceback references
Production symptom (often without a traceback): Memory leak after task raise exception

Proof / Evidence

GitHub issue: #6058
Fix PR: https://github.com/celery/celery/pull/6024
First fixed release: 4.4.2
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.85
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.64

Discussion

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

Jump to Sources Open on GitHub

“Thanks @joaojunior , this is a very important finding! Note: this could be fixed in PR https://github.com/celery/celery/pull/6024 , would you try reproducing on latest celery…”

@asfaltboy · 2020-05-09 · confirmation · source

“> Note: this could be fixed in PR #6024 , would you try reproducing on latest celery master branch? closing for now as per this.…”

@auvipy · 2021-02-16 · confirmation · source

“@asfaltboy I saw your comments only now. I will try with the code of the PR and also with the master and I return here…”

@joaojunior · 2020-09-23 · source

“> @asfaltboy I saw your comments only now. I will try with the code of the PR and also with the master and I return…”

@auvipy · 2021-01-27 · source

Failure Signature (Search String)

Memory leak after task raise exception
- [x] I have included all related issues and possible duplicate issues

Copy-friendly signature

signature.txt

Failure Signature
-----------------
Memory leak after task raise exception
- [x] I have included all related issues and possible duplicate issues

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
Memory leak after task raise exception
- [x] I have included all related issues and possible duplicate issues

Minimal Reproduction

repro.py

from celery import Celery

app = Celery('tasks', broker='pyamqp://guest:guest@localhost:5672') # for rabitmq broker
# app = Celery('tasks', broker='redis://localhost:6379/0') for refis broker

@app.task
def task_example():
    s = 'a' * 256 * (10**6) # Create a string of 256MB
    raise

What Broke

The application experiences increased memory usage leading to potential crashes or slowdowns.

Why It Broke

A memory leak occurs when an exception is raised in a task due to uncleaned traceback references

Fix Options (Details)

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

pip install celery==4.4.2

When NOT to use: This fix should not be applied if the application relies on the traceback for debugging.

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/6024

First fixed release: 4.4.2

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

When NOT to Use This Fix

This fix should not be applied if the application relies on the traceback for debugging.

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

Track RSS + object counts after deployments; alert on monotonic growth and GC pressure.
Add a long-running test that repeats the failing call path and asserts stable memory.

Version Compatibility Table

Version	Status
4.4.2	Fixed

Related Issues

No related fixes found.

Cluster: celery:memory-leak Celery hub Celery best practices All hubs All clusters

Related clusters: Configuration error Data consistency Duplicates

Sources

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