[vivek-raj1]

Description

Fixes #3992

exclude_spans can only be set through instrument_app(...) or OpenTelemetryMiddleware(...), so apps using opentelemetry-instrument cannot drop the internal http send / http receive spans.

OpenTelemetryMiddleware now falls back to OTEL_PYTHON_ASGI_EXCLUDE_SPANS (comma delimited send and/or receive) when exclude_spans is not passed, the same way it already falls back to the OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_* variables. An explicit exclude_spans argument, including [], takes precedence. FastAPI and Starlette pick this up without changes since they build on the ASGI middleware.

OTEL_PYTHON_ASGI_EXCLUDE_SPANS="send,receive" opentelemetry-instrument uvicorn main:app

AI-assisted: I used AI assistance to prepare this change and reviewed and tested it myself.

Type of change

• New feature (non-breaking change which adds functionality)
• This change requires a documentation update

How Has This Been Tested?

• tox -e py312-test-instrumentation-asgi: 107 passed. New tests cover each env value (receive,send, send, receive, empty) and that exclude_spans=[] overrides the env var.
• tox -e py312-test-instrumentation-fastapi-oldest,py312-test-instrumentation-fastapi-latest: 110 passed each. New test covers auto-instrumentation with the env var set.
• tox -e py312-test-instrumentation-starlette-latest: 62 passed.

Checklist:

See contributing.md for styleguide, changelog guidelines, and more.

• I am a human and not a bot
• I have run tox -e precommit
• I have run tox -e typecheck
• I have run the relevant tests and linting tox environments (lint-instrumentation-asgi, lint-instrumentation-fastapi)

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The committers listed above are authorized under a signed CLA.

• ✅ login: vivek-raj1 / name: Vivek Raj (440b564, 8e43fc1)

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Waiting on maintainers · refreshed 2026-11-02 11:19 UTC

Merge when ready.

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[xrmx]

I have approved but since both starlette and fastapi are getting native instrumentation maybe this is not so important anymore?

[vivek-raj1]

@xrmx Thanks for the review. I think this is still useful for two reasons.

This change is in the ASGI middleware, so it also helps apps that use OpenTelemetryMiddleware without FastAPI or Starlette. Native instrumentation in those two frameworks would not cover them.

It also helps until native instrumentation is available. People using opentelemetry-instrument can't pass exclude_spans in code today, so an environment variable is the only way for them to drop the http send and http receive spans.

If you still think it's better to leave this out, I'm happy to close it.