Python "httpx.ConnectError" in CI

httpx.ConnectError: All connection attempts failed is raised when httpx exhausts its connection attempts to the target without success, the async/HTTP/2-aware equivalent of a requests ConnectionError.

What this error means

An httpx call fails with "httpx.ConnectError: All connection attempts failed" against a local or remote service.

python

httpx.ConnectError: All connection attempts failed

Common causes

The target service is not accepting connections

A dependency is down or not yet listening when the request runs.

Wrong base URL or port in the CI environment

The configured endpoint does not match where the service runs on the runner.

How to fix it

Verify the endpoint and add bounded retries

Confirm the base URL and port match the CI service.
Use an httpx transport with retries, or wrap the call in a backoff loop.
In unit tests, use httpx MockTransport instead of real connections.

Python

import httpx
transport = httpx.HTTPTransport(retries=3)
client = httpx.Client(transport=transport, base_url="http://api:8000")

How to prevent it

Latchkey managed runners auto-retry transient connection failures while dependent services start.
Use MockTransport in unit tests for deterministic behavior.
Gate integration calls on a readiness check.