Unwrap ExceptionInfo and ExceptionWithTraceback

Instead of reporting the `ExceptionInfo` and `ExceptionWithTraceback`
wrappers raised by Celery, report the exceptions that they wrap.

This ensures that the exception in the OpenTelemetry span has a type
and traceback that are meaningful and relevant to the developer.

Author: unflxw

CHANGELOG.md

@@ -7,6 +7,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Unreleased
 
+- `opentelemetry-instrumentation-celery` Unwrap Celery's `ExceptionInfo` errors and report the actual exception that was raised. ([#1863](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/1863))
+
 ### Added
 
 - Make Flask request span attributes available for `start_span`. 

instrumentation/opentelemetry-instrumentation-celery/src/opentelemetry/instrumentation/celery/__init__.py

@@ -64,6 +64,12 @@ def add(x, y):
 from typing import Collection, Iterable
 
 from celery import signals  # pylint: disable=no-name-in-module
+from billiard.einfo import ExceptionInfo
+
+try:
+    from billiard.einfo import ExceptionWithTraceback # pylint: disable=no-name-in-module
+except ImportError:
+    ExceptionWithTraceback = None
 
 from opentelemetry import trace
 from opentelemetry.instrumentation.celery import utils
@@ -271,6 +277,21 @@ def _trace_failure(*args, **kwargs):
             return
 
         if ex is not None:
+            # Unwrap the actual exception wrapped by billiard's
+            # `ExceptionInfo` and `ExceptionWithTraceback`.
+            if (
+                isinstance(ex, ExceptionInfo)
+                and ex.exception is not None
+            ):
+                ex = ex.exception
+
+            if (
+                ExceptionWithTraceback is not None
+                and isinstance(ex, ExceptionWithTraceback)
+                and ex.exc is not None
+            ):
+                ex = ex.exc
+
             status_kwargs["description"] = str(ex)
             span.record_exception(ex)
         span.set_status(Status(**status_kwargs))

tests/opentelemetry-docker-tests/tests/celery/test_celery_functional.py

@@ -279,7 +279,7 @@ def fn_exception():
     assert len(span.events) == 1
     event = span.events[0]
     assert event.name == "exception"
-    assert event.attributes[SpanAttributes.EXCEPTION_TYPE] == "ExceptionInfo"
+    assert event.attributes[SpanAttributes.EXCEPTION_TYPE] == "Exception"
     assert SpanAttributes.EXCEPTION_MESSAGE in event.attributes
     assert (
         span.attributes.get(SpanAttributes.MESSAGING_MESSAGE_ID)