The Fix
pip install urllib3==1.26.20
Based on closed urllib3/urllib3 issue #3323 · PR/commit linked
@@ -67,7 +67,7 @@ jobs:
experimental: false
nox-session: test-pypy3.8
- - python-version: "pypy-3.9-v7.3.13"
+ - python-version: "pypy-3.9"
os: ubuntu-latest
Option A — Upgrade to fixed release\npip install urllib3==1.26.20\nWhen NOT to use: This fix is not applicable if tests are not leaking threads.\n\n
Why This Fix Works in Production
- Trigger: We just released pypy3.10-v7.3.17 with some improvements in performance, including packaging OpenSSL 3.3.1. Is it any faster in your CI?
- Mechanism: Tests were leaking threads, causing slow execution in pypy
- Why the fix works: Fixes tests that leak threads, which was causing slow test execution in pypy. (first fixed release: 1.26.20).
Why This Breaks in Prod
- Tests were leaking threads, causing slow execution in pypy
- Production symptom (often without a traceback): We just released pypy3.10-v7.3.17 with some improvements in performance, including packaging OpenSSL 3.3.1. Is it any faster in your CI?
Proof / Evidence
- GitHub issue: #3323
- Fix PR: https://github.com/urllib3/urllib3/pull/3452
- First fixed release: 1.26.20
- Reproduced locally: No (not executed)
- Last verified: 2026-02-09
- Confidence: 0.85
- Did this fix it?: Yes (upstream fix exists)
- Own content ratio: 0.78
Discussion
High-signal excerpts from the issue thread (symptoms, repros, edge-cases).
“We just released pypy3.10-v7.3.17 with some improvements in performance, including packaging OpenSSL 3.3.1. Is it any faster in your CI?”
“I would like to see if PyPy3.10, v7.3.17, released last week, is any faster”
“The CI uses 7.3.16 , see https://github.com/urllib3/urllib3/pull/3452 As @mattip realized in https://github.com/pypy/pypy/issues/4877#issuecomment-2296066242 , my PR https://github.com/urllib3/urllib3/pull/3358 fixed the slowness in pypy by closing some thread”
Failure Signature (Search String)
- We just released pypy3.10-v7.3.17 with some improvements in performance, including packaging OpenSSL 3.3.1. Is it any faster in your CI?
Copy-friendly signature
Failure Signature
-----------------
We just released pypy3.10-v7.3.17 with some improvements in performance, including packaging OpenSSL 3.3.1. Is it any faster in your CI?
Error Message
Signature-only (no traceback captured)
Error Message
-------------
We just released pypy3.10-v7.3.17 with some improvements in performance, including packaging OpenSSL 3.3.1. Is it any faster in your CI?
What Broke
Test suite execution time exceeded 1h45m, impacting CI performance.
Why It Broke
Tests were leaking threads, causing slow execution in pypy
Fix Options (Details)
Option A — Upgrade to fixed release Safe default (recommended)
pip install urllib3==1.26.20
Use when you can deploy the upstream fix. It is usually lower-risk than long-lived workarounds.
Fix reference: https://github.com/urllib3/urllib3/pull/3452
First fixed release: 1.26.20
Last verified: 2026-02-09. Validate in your environment.
When NOT to Use This Fix
- This fix is not applicable if tests are not leaking threads.
Did This Fix Work in Your Case?
Quick signal helps us prioritize which fixes to verify and improve.
Prevention
- Add a CI check that diffs key outputs after upgrades (OpenAPI schema snapshots, JSON payload shapes, CLI output).
- Upgrade behind a canary and run integration tests against the canary before 100% rollout.
- Add a TLS smoke test that performs a real handshake in CI (include CA bundle validation and hostname checks).
- Alert on handshake failures by error string and endpoint to catch cert/CA changes quickly.
Version Compatibility Table
| Version | Status |
|---|---|
| 1.26.20 | Fixed |
Related Issues
No related fixes found.
Sources
We don’t republish the full GitHub discussion text. Use the links above for context.