The Fix
Upgrade to version 0.11.4 or later.
Based on closed Kludex/uvicorn issue #285 · PR/commit linked
Production note: Most teams hit this during upgrades or environment changes. Roll out with a canary and smoke critical endpoints (health, OpenAPI/docs) before 100%.
@@ -1,4 +1,4 @@
from uvicorn.main import main, run
-__version__ = "0.3.29"
+__version__ = "0.3.30"
__all__ = ["main", "run"]
repro.py
$ uvicorn app:App --debug
Traceback (most recent call last):
File "/home/jamie.chang/.local/bin/uvicorn", line 11, in <module>
sys.exit(main())
File "/home/jamie.chang/.local/lib/python3.5/site-packages/click/core.py", line 764, in __call__
return self.main(*args, **kwargs)
File "/home/jamie.chang/.local/lib/python3.5/site-packages/click/core.py", line 717, in main
rv = self.invoke(ctx)
File "/home/jamie.chang/.local/lib/python3.5/site-packages/click/core.py", line 956, in invoke
return ctx.invoke(self.callback, **ctx.params)
File "/home/jamie.chang/.local/lib/python3.5/site-packages/click/core.py", line 555, in invoke
return callback(*args, **kwargs)
File "/home/jamie.chang/.local/lib/python3.5/site-packages/uvicorn/main.py", line 166, in main
logger = get_logger(log_level)
NameError: name 'get_logger' is not defined
verify
Re-run: uvicorn app:App --debug
fix.md
Option A — Upgrade to fixed release\nUpgrade to version 0.11.4 or later.\nWhen NOT to use: This fix should not be applied if the application does not require the 'get_logger' functionality.\n\n
Why This Fix Works in Production
- Trigger: $ uvicorn app:App --debug
- Mechanism: A missing import for 'get_logger' caused a NameError when running Uvicorn in debug mode
- Why the fix works: Fixes a NameError by adding a missing import for 'get_logger'. (first fixed release: 0.11.4).
Production impact:
- If left unfixed, the same config can fail only in production (env differences), causing startup failures or partial feature outages.
Why This Breaks in Prod
- Shows up under Python 3.5 in real deployments (not just unit tests).
- A missing import for 'get_logger' caused a NameError when running Uvicorn in debug mode
- Surfaces as: $ uvicorn app:App --debug
Proof / Evidence
- GitHub issue: #285
- Fix PR: https://github.com/kludex/uvicorn/pull/286
- First fixed release: 0.11.4
- Reproduced locally: No (not executed)
- Last verified: 2026-02-09
- Confidence: 0.85
- Did this fix it?: Yes (upstream fix exists)
- Own content ratio: 0.37
Discussion
High-signal excerpts from the issue thread (symptoms, repros, edge-cases).
“Released as 0.3.30. Planning to work on bumping the test coverage up in order to avoid this kind of breakage in the future.”
Failure Signature (Search String)
- $ uvicorn app:App --debug
Error Message
Stack trace
error.txt
Error Message
-------------
$ uvicorn app:App --debug
Traceback (most recent call last):
File "/home/jamie.chang/.local/bin/uvicorn", line 11, in <module>
sys.exit(main())
File "/home/jamie.chang/.local/lib/python3.5/site-packages/click/core.py", line 764, in __call__
return self.main(*args, **kwargs)
File "/home/jamie.chang/.local/lib/python3.5/site-packages/click/core.py", line 717, in main
rv = self.invoke(ctx)
File "/home/jamie.chang/.local/lib/python3.5/site-packages/click/core.py", line 956, in invoke
return ctx.invoke(self.callback, **ctx.params)
File "/home/jamie.chang/.local/lib/python3.5/site-packages/click/core.py", line 555, in invoke
return callback(*args, **kwargs)
File "/home/jamie.chang/.local/lib/python3.5/site-packages/uvicorn/main.py", line 166, in main
logger = get_logger(log_level)
NameError: name 'get_logger' is not defined
Minimal Reproduction
repro.py
$ uvicorn app:App --debug
Traceback (most recent call last):
File "/home/jamie.chang/.local/bin/uvicorn", line 11, in <module>
sys.exit(main())
File "/home/jamie.chang/.local/lib/python3.5/site-packages/click/core.py", line 764, in __call__
return self.main(*args, **kwargs)
File "/home/jamie.chang/.local/lib/python3.5/site-packages/click/core.py", line 717, in main
rv = self.invoke(ctx)
File "/home/jamie.chang/.local/lib/python3.5/site-packages/click/core.py", line 956, in invoke
return ctx.invoke(self.callback, **ctx.params)
File "/home/jamie.chang/.local/lib/python3.5/site-packages/click/core.py", line 555, in invoke
return callback(*args, **kwargs)
File "/home/jamie.chang/.local/lib/python3.5/site-packages/uvicorn/main.py", line 166, in main
logger = get_logger(log_level)
NameError: name 'get_logger' is not defined
Environment
- Python: 3.5
What Broke
Running Uvicorn in debug mode resulted in a NameError, preventing the application from starting.
Why It Broke
A missing import for 'get_logger' caused a NameError when running Uvicorn in debug mode
Fix Options (Details)
Option A — Upgrade to fixed release Safe default (recommended)
Upgrade to version 0.11.4 or later.
When NOT to use: This fix should not be applied if the application does not require the 'get_logger' functionality.
Use when you can deploy the upstream fix. It is usually lower-risk than long-lived workarounds.
Fix reference: https://github.com/kludex/uvicorn/pull/286
First fixed release: 0.11.4
Last verified: 2026-02-09. Validate in your environment.
When NOT to Use This Fix
- This fix should not be applied if the application does not require the 'get_logger' functionality.
Verify Fix
verify
Re-run: uvicorn app:App --debug
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 |
|---|---|
| 0.11.4 | Fixed |
Related Issues
No related fixes found.
Sources
We don’t republish the full GitHub discussion text. Use the links above for context.