auto-instrument hypercorn

What problem do you want to solve?

I am using otel's python auto-instrumentation with my Flask app, and my Flask app is getting instrumented as expected (e.g. my app's logs are able to include the current trace and span so they can be correlated).

Like many users, I am using hypercorn to serve my Flask app. Because otel python auto-instrumentation is currently missing support for hypercorn, hypercorn's access logs are not able to pick up the current trace and span.

Describe the solution you'd like

Here is some code that solved the problem for me, in case you can incorporate something like this here:

from opentelemetry import trace
from opentelemetry.propagate import extract
from opentelemetry.trace import SpanKind

# Patch target
import hypercorn.app_wrappers

_OTEL_PATCHED = False


def extract_headers(scope):  # type: ignore
    # ASGI scope headers are a list of (bytes, bytes)
    return {k.decode("latin1").lower(): v.decode("latin1") for k, v in scope.get("headers", [])}


async def otel_asgi_call_wrapper(self, scope, receive, send, sync_spawn, call_soon):  # type: ignore
    if scope.get("type") != "http":
        return await self._original_asgi_call(scope, receive, send, sync_spawn, call_soon)
    tracer = trace.get_tracer("hypercorn.instrumentation")
    headers = extract_headers(scope)  # type: ignore
    from opentelemetry.propagators.textmap import DefaultGetter
    ctx = extract(headers, getter=DefaultGetter())
    span_name = f"{scope.get('method', 'HTTP')} {scope.get('path', '/') }"
    from opentelemetry.context import attach, detach
    token = attach(ctx)
    try:
        with tracer.start_as_current_span(span_name, kind=SpanKind.SERVER) as span:
            span.set_attribute("http.scheme", scope.get("scheme", "http"))
            span.set_attribute("http.host", headers.get("host", ""))
            if "method" in scope:
                span.set_attribute("http.method", scope["method"])
            if "path" in scope:
                span.set_attribute("http.target", scope["path"])
            return await self._original_asgi_call(scope, receive, send, sync_spawn, call_soon)
    finally:
        detach(token)


def patch_hypercorn_asgi() -> None:
    global _OTEL_PATCHED
    if _OTEL_PATCHED:
        return
    cls = hypercorn.app_wrappers.ASGIWrapper
    if not hasattr(cls, "_original_asgi_call"):
        cls._original_asgi_call = cls.__call__  # type: ignore
        cls.__call__ = otel_asgi_call_wrapper  # type: ignore
    _OTEL_PATCHED = True

Describe alternatives you've considered

No response

Additional Context

No response

Would you like to implement a fix?

None

Tip

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The issue targets hypercorn.app_wrappers.ASGIWrapper and proposes wrapping its ASGI call to extract context and create server spans. Start by reviewing the existing Python auto-instrumentation entry points for comparable server integrations, then verify that Hypercorn access logs can correlate traces and spans. Done means Hypercorn is supported by auto-instrumentation with HTTP requests instrumented as described.