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[Bug]: gRPC interceptor swallows exceptions and returns None instead of re-raising #895
Description
Problem Description
The create_span wrapper in instana/instrumentation/grpcio.py catches exceptions
from gRPC stubs, records them on the trace span, and then falls off the end of
the function returning None. gRPC then tries to unpack the return value as a tuple:
response, call = None # inside grpc._interceptor._with_call
which raises:
TypeError: cannot unpack non-iterable NoneType object
The real gRPC status code (e.g. PERMISSION_DENIED) is silently absorbed into the
span and never reaches the caller. This makes the error completely undiagnosable
from the application side.
This only happens inside an active Instana span (i.e. inside a traced API request).
Calling the same gRPC method without Instana active gives the correct RpcError.
Instana version: 3.15.0
pymilvus version: 2.6.13 (gRPC client)
Python: 3.11/3.12
Minimal, Complete, Verifiable, Example
# Reproduce: make a gRPC call via pymilvus inside a traced FastAPI request
# (Instana must be active with a live span)
from pymilvus import utility
utility.has_collection("my_collection", using="my_connection")
# Expected: grpc.RpcError with StatusCode.PERMISSION_DENIED
# Actual: TypeError: cannot unpack non-iterable NoneType object
# Root cause in instana/instrumentation/grpcio.py::create_span:
# The wrapper catches the gRPC exception, records it on the span via
# span.record_exception(exc), but never re-raises — the function returns
# None implicitly.
# gRPC then does: response, call = None -> TypeError
#
# Fix: add `raise` after span.record_exception(exc) in create_spanPython Version
python 3.12
Python Modules
instana==3.15.0
grpcio==1.62.x
pymilvus==2.6.13
wrapt==1.xPython Environment
Running inside a CP4D (Cloud Pak for Data) Kubernetes pod.
Instana is loaded via AUTOWRAPT_BOOTSTRAP=instana environment variable.
Python 3.11 / 3.12 (container image).
Key env vars relevant to this bug:
AUTOWRAPT_BOOTSTRAP=instana
INSTANA_SERVICE_NAME=datasift-api
Activity
CagriYonca commentedon Oct 6, 2026
Hello @Harshad01 , thanks for the clear report and minimal reproduction.
Your analysis is correct.
create_spanwas catching gRPC exceptions and recording them on the span, but never re-raising them. This caused the wrapper to returnNone, leading to the tuple unpackingTypeErrorinside gRPC's interceptor layer and masking the underlyinggrpc.RpcError.We've addressed this in PR #911 by:
with_calland gRPC interceptors.Could you please review the changes and, if possible, pull from the branch and try with your application?