uvicorn Connection aborted after

The Fix

Upgrade to version 0.17.2 or later.

Based on closed Kludex/uvicorn issue #1345 · 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%.

Jump to Verify Open PR/Commit

@@ -1,5 +1,13 @@
 # Change Log
 
+## 0.17.2 - 2022-02-03
+
+### Fixed

repro.py

"Invalid HTTP request received."
Traceback (most recent call last):
  File "/usr/local/lib/python3.10/site-packages/uvicorn/protocols/http/httptools_impl.py", line 132, in data_received
    self.parser.feed_data(data)
  File "httptools/parser/parser.pyx", line 212, in httptools.parser.parser.HttpParser.feed_data
httptools.parser.errors.HttpParserInvalidMethodError: Invalid method encountered

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\nUpgrade to version 0.17.2 or later.\nWhen NOT to use: This fix should not be applied if the application requires the changes introduced in PR #1332.\n\n

Why This Fix Works in Production

Trigger: return request('post', url, data=data, json=json, **kwargs)
Mechanism: The connection issues were caused by changes in the HTTP parser handling large POST requests
Why the fix works: Release 0.17.2 reverts changes that caused connection issues with large POST requests. (first fixed release: 0.17.2).

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 3.10 in real deployments (not just unit tests).
The connection issues were caused by changes in the HTTP parser handling large POST requests
Surfaces as: File "/usr/local/lib/python3.10/site-packages/requests/api.py", line 117, in post

Proof / Evidence

GitHub issue: #1345
Fix PR: https://github.com/encode/uvicorn/pull/1356
First fixed release: 0.17.2
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.85
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.43

Discussion

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

Jump to Sources Open on GitHub

“Now resolved in 0.17.2 - https://github.com/encode/uvicorn/pull/1356”

@lovelydinosaur · 2022-02-03 · confirmation · source

“The solution I propose is to revert both. PRs were created: - https://github.com/encode/uvicorn/pull/1354 - https://github.com/encode/uvicorn/pull/1355 (branch on top of the above) Both memory leak and…”

@Kludex · 2022-02-03 · source

“I had the same issue with PATCH too and it wasn't consecutive PATCH/POST requests only, there were consecutive GET and OPTIONS requests between these invalid…”

@UKnowWhoIm · 2022-01-31 · source

“I can also confirm that this issue occurs for uvicorn=0.17.1. Tried to add the Expect: 100-continue header per @smeinecke's suggestion, but that did not resolve…”

@narolski · 2022-02-02 · source

Failure Signature (Search String)

return request('post', url, data=data, json=json, **kwargs)

Error Message

Stack trace

error.txt

Error Message
-------------
File "/usr/local/lib/python3.10/site-packages/requests/api.py", line 117, in post
    return request('post', url, data=data, json=json, **kwargs)
  File "/usr/local/lib/python3.10/site-packages/requests/api.py", line 61, in request
    return session.request(method=method, url=url, **kwargs)
  File "/usr/local/lib/python3.10/site-packages/requests/sessions.py", line 529, in request
    resp = self.send(prep, **send_kwargs)
  File "/usr/local/lib/python3.10/site-packages/requests/sessions.py", line 645, in send
    r = adapter.send(request, **kwargs)
  File "/usr/local/lib/python3.10/site-packages/requests/adapters.py", line 501, in send
    raise ConnectionError(err, request=request)
requests.exceptions.ConnectionError: ('Connection aborted.', RemoteDisconnected('Remote end closed connection without response'))

Stack trace

error.txt

Error Message
-------------
"Invalid HTTP request received."
Traceback (most recent call last):
  File "/usr/local/lib/python3.10/site-packages/uvicorn/protocols/http/httptools_impl.py", line 132, in data_received
    self.parser.feed_data(data)
  File "httptools/parser/parser.pyx", line 212, in httptools.parser.parser.HttpParser.feed_data
httptools.parser.errors.HttpParserInvalidMethodError: Invalid method encountered

Minimal Reproduction

repro.py

"Invalid HTTP request received."
Traceback (most recent call last):
  File "/usr/local/lib/python3.10/site-packages/uvicorn/protocols/http/httptools_impl.py", line 132, in data_received
    self.parser.feed_data(data)
  File "httptools/parser/parser.pyx", line 212, in httptools.parser.parser.HttpParser.feed_data
httptools.parser.errors.HttpParserInvalidMethodError: Invalid method encountered

Environment

Python: 3.10

What Broke

Consecutive POST requests resulted in connection errors and invalid HTTP method logs.

Why It Broke

The connection issues were caused by changes in the HTTP parser handling large POST requests

Fix Options (Details)

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

Upgrade to version 0.17.2 or later.

When NOT to use: This fix should not be applied if the application requires the changes introduced in PR #1332.

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

Option D — Guard side-effects with OnceOnly Guardrail for side-effects

Mitigate duplicate external side-effects under retries/timeouts/agent loops by gating the operation before calling external systems.

Place OnceOnly between your code/agent and real side-effects (Stripe, emails, CRM, APIs).
Use a stable key per side-effect (e.g., customer_id + action + idempotency_key).
Fail-safe: configure fail-open vs fail-closed based on blast radius and spend risk.

Show example snippet (optional)

onceonly.py

from onceonly import OnceOnly
import os

once = OnceOnly(api_key=os.environ["ONCEONLY_API_KEY"], fail_open=True)

# Stable idempotency key per real side-effect.
# Use a request id / job id / webhook delivery id / Stripe event id, etc.
event_id = "evt_..."  # replace
key = f"stripe:webhook:{event_id}"

res = once.check_lock(key=key, ttl=3600)
if res.duplicate:
    return {"status": "already_processed"}

# Safe to execute the side-effect exactly once.
handle_event(event_id)

See OnceOnly SDK

When NOT to use: Do not use this to hide logic bugs or data corruption. Use it to block duplicate external side-effects and enforce tool permissions/spend caps.

Fix reference: https://github.com/encode/uvicorn/pull/1356

First fixed release: 0.17.2

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

When NOT to Use This Fix

This fix should not be applied if the application requires the changes introduced in PR #1332.
Do not use this to hide logic bugs or data corruption. Use it to block duplicate external side-effects and enforce tool permissions/spend caps.

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
0.17.2	Fixed

Related Issues

No related fixes found.

Cluster: uvicorn:configuration-error All hubs All clusters

Related clusters: Data consistency Race condition SSL handshake

Sources

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

uvicorn Connection aborted after HttpParserInvalidMethodError when making consecutive POST requests (Fix)