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CagriYonca merged 2 commits into from
Oct 8, 2026
+218 −38
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test: adapt FastAPI tests for native OTel spans #912

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685990b
test: adapt FastAPI tests for 0.115.0 extra OTel spans
CagriYonca Oct 8, 2026
69e7eb5
test(sqlalchemy): remove unused parent_span variable
CagriYonca Oct 8, 2026
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2 changes: 1 addition & 1 deletion tests/clients/test_sqlalchemy.py
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Original file line number Diff line number Diff line change
Expand Up @@ -305,7 +305,7 @@ def test_context_restored_after_query(self) -> None:
find the correct parent. This validates the fix for the bug where
after_cursor_execute used get_current_span() instead of conn.span, which
could corrupt the context stack and cause child spans to be dropped."""
with self.tracer.start_as_current_span("test") as parent_span:
with self.tracer.start_as_current_span("test"):
with engine.begin() as connection:
connection.execute(text("select 1"))

Expand Down
176 changes: 149 additions & 27 deletions tests/frameworks/test_fastapi.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2,17 +2,72 @@
# (c) Copyright Instana Inc. 2020


import sys
from typing import Generator

from fastapi.testclient import TestClient
import pytest
from instana.singletons import agent, get_tracer
from fastapi.testclient import TestClient

from instana.singletons import agent, get_tracer
from instana.util.ids import hex_id
from tests.apps.fastapi_app.app import fastapi_server
from tests.helpers import get_first_span_by_filter


from tests.helpers import get_first_span_by_filter, get_spans_by_filter


def assert_fastapi_otel_spans(
spans: list,
http_route: str,
*,
Comment thread
pvital marked this conversation as resolved.
expect_serialization: bool = True,
http_status_code: int = 200,
) -> None:
"""Assert the OTel spans emitted by FastAPI >= 0.115.0.

FastAPI registers itself against the global OTel TracerProvider (which
Instana provides), so every request produces extra sdk spans that land in
Instana's recorder.

Per request FastAPI emits:
- fastapi.dependencies (always)
- fastapi.endpoint (always)
- fastapi.serialization (only on non-exception responses)
- GET /path (always, but orphan: p == 0)

Args:
spans: full list returned by recorder.queued_spans()
http_route: the OTel http.route value, e.g. "/" or "/users/{user_id}"
expect_serialization: False for exception responses (4xx/5xx via HTTPException
or Response() objects that bypass JSON serialization)
http_status_code: expected http.response.status_code on the HTTP entry span
"""
otel_sdk_spans = get_spans_by_filter(
spans,
lambda s: s.n == "sdk" and s.data["sdk"]["name"].startswith("fastapi."),
)
otel_names = {s.data["sdk"]["name"] for s in otel_sdk_spans}
assert "fastapi.dependencies" in otel_names
assert "fastapi.endpoint" in otel_names
if expect_serialization:
assert "fastapi.serialization" in otel_names
else:
assert "fastapi.serialization" not in otel_names

http_entry_span = get_first_span_by_filter(
spans,
lambda s: s.n == "sdk" and s.data["sdk"]["name"] == f"GET {http_route}",
)
assert http_entry_span, f"FastAPI HTTP entry span 'GET {http_route}' not found"
assert http_entry_span.p == 0, "FastAPI HTTP entry span must be orphan (p == 0)"
tags = http_entry_span.data["sdk"]["custom"]["tags"]
assert tags["http.request.method"] == "GET"
assert tags["http.route"] == http_route
assert tags["http.response.status_code"] == http_status_code


@pytest.mark.skipif(
sys.version_info < (3, 10),
reason="FastAPI >= 0.115.0 (required for OTel span assertions) only supports Python 3.10+",
)
class TestFastAPI:
@pytest.fixture(autouse=True)
def _resource(self) -> Generator[None, None, None]:
Expand Down Expand Up @@ -49,8 +104,15 @@ def test_vanilla_get(self) -> None:
# unless told otherwise
spans = self.recorder.queued_spans()

assert len(spans) == 1
assert spans[0].n == "asgi"
# FastAPI >= 0.115.0 emits 4 extra OTel spans per request via the global
# OTel provider that Instana registers: fastapi.dependencies,
# fastapi.endpoint, fastapi.serialization, GET /
assert len(spans) == 5
span_filter = lambda span: span.n == "asgi" # noqa: E731
asgi_span = get_first_span_by_filter(spans, span_filter)
assert asgi_span

assert_fastapi_otel_spans(spans, "/")
Comment thread
CagriYonca marked this conversation as resolved.

def test_basic_get(self) -> None:
result = None
Expand All @@ -73,8 +135,10 @@ def test_basic_get(self) -> None:
assert result.headers["X-INSTANA-L"] == "1"

spans = self.recorder.queued_spans()
# TODO: after support httpx, the expected value will be 3.
assert len(spans) == 2
# FastAPI >= 0.115.0 adds 4 extra OTel spans per request:
# fastapi.dependencies, fastapi.endpoint, fastapi.serialization, GET /
# TODO: after support httpx, the expected value will be 7.
assert len(spans) == 6

span_filter = ( # noqa: E731
lambda span: span.n == "sdk" and span.data["sdk"]["name"] == "test"
Expand Down Expand Up @@ -103,6 +167,8 @@ def test_basic_get(self) -> None:
assert not asgi_span.data["http"]["error"]
assert not asgi_span.data["http"]["params"]

assert_fastapi_otel_spans(spans, "/")

def test_400(self) -> None:
result = None
with self.tracer.start_as_current_span("test") as span:
Expand All @@ -124,8 +190,11 @@ def test_400(self) -> None:
assert result.headers["X-INSTANA-L"] == "1"

spans = self.recorder.queued_spans()
# TODO: after support httpx, the expected value will be 3.
assert len(spans) == 2
# FastAPI >= 0.115.0 adds 3 extra OTel spans per request:
# fastapi.dependencies, fastapi.endpoint, GET /400 (orphan).
# fastapi.serialization is absent on exception responses.
# TODO: after support httpx, the expected value will be 6.
assert len(spans) == 5

span_filter = ( # noqa: E731
lambda span: span.n == "sdk" and span.data["sdk"]["name"] == "test"
Expand Down Expand Up @@ -154,6 +223,10 @@ def test_400(self) -> None:
assert not asgi_span.data["http"]["error"]
assert not asgi_span.data["http"]["params"]

assert_fastapi_otel_spans(
spans, "/400", expect_serialization=False, http_status_code=400
)

def test_500(self) -> None:
result = None
with self.tracer.start_as_current_span("test") as span:
Expand All @@ -175,8 +248,11 @@ def test_500(self) -> None:
assert result.headers["X-INSTANA-L"] == "1"

spans = self.recorder.queued_spans()
# TODO: after support httpx, the expected value will be 3.
assert len(spans) == 2
# FastAPI >= 0.115.0 adds 3 extra OTel spans per request:
# fastapi.dependencies, fastapi.endpoint, GET /500 (orphan).
# fastapi.serialization is absent on exception responses.
# TODO: after support httpx, the expected value will be 6.
assert len(spans) == 5

span_filter = ( # noqa: E731
lambda span: span.n == "sdk" and span.data["sdk"]["name"] == "test"
Expand Down Expand Up @@ -204,6 +280,16 @@ def test_500(self) -> None:
assert asgi_span.data["http"]["error"] == "500 response"
assert not asgi_span.data["http"]["params"]

assert_fastapi_otel_spans(
spans, "/500", expect_serialization=False, http_status_code=500
)
# error.type is set by FastAPI on 5xx responses
http_entry_span = get_first_span_by_filter(
spans,
lambda s: s.n == "sdk" and s.data["sdk"]["name"] == "GET /500",
)
assert "error.type" in http_entry_span.data["sdk"]["custom"]["tags"]

def test_path_templates(self) -> None:
result = None
with self.tracer.start_as_current_span("test") as span:
Expand All @@ -225,8 +311,10 @@ def test_path_templates(self) -> None:
assert result.headers["X-INSTANA-L"] == "1"

spans = self.recorder.queued_spans()
# TODO: after support httpx, the expected value will be 3.
assert len(spans) == 2
# FastAPI >= 0.115.0 adds 4 extra OTel spans per request:
# fastapi.dependencies, fastapi.endpoint, fastapi.serialization, GET /users/{user_id}
# TODO: after support httpx, the expected value will be 7.
assert len(spans) == 6

span_filter = ( # noqa: E731
lambda span: span.n == "sdk" and span.data["sdk"]["name"] == "test"
Expand Down Expand Up @@ -254,6 +342,14 @@ def test_path_templates(self) -> None:
assert not asgi_span.data["http"]["error"]
assert not asgi_span.data["http"]["params"]

assert_fastapi_otel_spans(spans, "/users/{user_id}")
# url.path carries the resolved path (with actual param value)
http_entry_span = get_first_span_by_filter(
spans,
lambda s: s.n == "sdk" and s.data["sdk"]["name"] == "GET /users/{user_id}",
)
assert http_entry_span.data["sdk"]["custom"]["tags"]["url.path"] == "/users/1"

def test_secret_scrubbing(self) -> None:
result = None
with self.tracer.start_as_current_span("test") as span:
Expand All @@ -275,8 +371,10 @@ def test_secret_scrubbing(self) -> None:
assert result.headers["X-INSTANA-L"] == "1"

spans = self.recorder.queued_spans()
# TODO: after support httpx, the expected value will be 3.
assert len(spans) == 2
# FastAPI >= 0.115.0 adds 4 extra OTel spans per request:
# fastapi.dependencies, fastapi.endpoint, fastapi.serialization, GET /
# TODO: after support httpx, the expected value will be 7.
assert len(spans) == 6

span_filter = ( # noqa: E731
lambda span: span.n == "sdk" and span.data["sdk"]["name"] == "test"
Expand Down Expand Up @@ -305,6 +403,8 @@ def test_secret_scrubbing(self) -> None:
assert not asgi_span.data["http"]["error"]
assert asgi_span.data["http"]["params"] == "secret=<redacted>"

assert_fastapi_otel_spans(spans, "/")

def test_synthetic_request(self) -> None:
with self.tracer.start_as_current_span("test") as span:
# As TestClient() is based on httpx, and we don't support it yet,
Expand All @@ -326,8 +426,10 @@ def test_synthetic_request(self) -> None:
assert result.headers["X-INSTANA-L"] == "1"

spans = self.recorder.queued_spans()
# TODO: after support httpx, the expected value will be 3.
assert len(spans) == 2
# FastAPI >= 0.115.0 adds 4 extra OTel spans per request:
# fastapi.dependencies, fastapi.endpoint, fastapi.serialization, GET /
# TODO: after support httpx, the expected value will be 7.
assert len(spans) == 6

span_filter = ( # noqa: E731
lambda span: span.n == "sdk" and span.data["sdk"]["name"] == "test"
Expand Down Expand Up @@ -359,6 +461,8 @@ def test_synthetic_request(self) -> None:
assert asgi_span.sy
assert not test_span.sy

assert_fastapi_otel_spans(spans, "/")

def test_request_header_capture(self) -> None:
with self.tracer.start_as_current_span("test") as span:
# As TestClient() is based on httpx, and we don't support it yet,
Expand All @@ -381,8 +485,10 @@ def test_request_header_capture(self) -> None:
assert result.headers["X-INSTANA-L"] == "1"

spans = self.recorder.queued_spans()
# TODO: after support httpx, the expected value will be 3.
assert len(spans) == 2
# FastAPI >= 0.115.0 adds 4 extra OTel spans per request:
# fastapi.dependencies, fastapi.endpoint, fastapi.serialization, GET /
# TODO: after support httpx, the expected value will be 7.
assert len(spans) == 6

span_filter = ( # noqa: E731
lambda span: span.n == "sdk" and span.data["sdk"]["name"] == "test"
Expand Down Expand Up @@ -416,6 +522,8 @@ def test_request_header_capture(self) -> None:
assert "X-Capture-That" in asgi_span.data["http"]["header"]
assert asgi_span.data["http"]["header"]["X-Capture-That"] == "that"

assert_fastapi_otel_spans(spans, "/")

def test_response_header_capture(self) -> None:
# The background FastAPI server is pre-configured with custom headers
# to capture.
Expand All @@ -439,8 +547,11 @@ def test_response_header_capture(self) -> None:
assert result.headers["X-INSTANA-L"] == "1"

spans = self.recorder.queued_spans()
# TODO: after support httpx, the expected value will be 3.
assert len(spans) == 2
# FastAPI >= 0.115.0 adds 3 extra OTel spans per request:
# fastapi.dependencies, fastapi.endpoint, GET /response_headers (orphan).
# fastapi.serialization is absent — Response() objects bypass JSON serialization.
# TODO: after support httpx, the expected value will be 6.
assert len(spans) == 5

span_filter = ( # noqa: E731
lambda span: span.n == "sdk" and span.data["sdk"]["name"] == "test"
Expand Down Expand Up @@ -474,6 +585,11 @@ def test_response_header_capture(self) -> None:
assert "X-Capture-That-Too" in asgi_span.data["http"]["header"]
assert asgi_span.data["http"]["header"]["X-Capture-That-Too"] == "that too"

# Response() objects bypass FastAPI's JSON serialization pipeline
assert_fastapi_otel_spans(
spans, "/response_headers", expect_serialization=False
)

def test_non_async_simple(self) -> None:
with self.tracer.start_as_current_span("test") as span:
# As TestClient() is based on httpx, and we don't support it yet,
Expand All @@ -494,7 +610,9 @@ def test_non_async_simple(self) -> None:
assert result.headers["X-INSTANA-L"] == "1"

spans = self.recorder.queued_spans()
assert len(spans) == 3
# FastAPI >= 0.115.0 adds 4 extra OTel spans per request (8 total for 2 requests):
# fastapi.dependencies, fastapi.endpoint, GET /..., and one internal span each.
assert len(spans) == 11

span_filter = ( # noqa: E731
lambda span: span.n == "sdk" and span.data["sdk"]["name"] == "test"
Expand All @@ -506,7 +624,9 @@ def test_non_async_simple(self) -> None:
asgi_span1 = get_first_span_by_filter(spans, span_filter)
assert asgi_span1

span_filter = lambda span: span.n == "asgi" and span.p == asgi_span1.s # noqa: E731
# asgi_span2 is a child of the fastapi.endpoint span which is itself a
# child of asgi_span1; find it by excluding the first asgi span.
span_filter = lambda span: span.n == "asgi" and span.s != asgi_span1.s # noqa: E731
asgi_span2 = get_first_span_by_filter(spans, span_filter)
assert asgi_span2

Expand Down Expand Up @@ -557,8 +677,10 @@ def test_non_async_threadpool(self) -> None:
assert result.headers["X-INSTANA-L"] == "1"

spans = self.recorder.queued_spans()
# TODO: after support httpx, the expected value will be 3.
assert len(spans) == 2
# FastAPI >= 0.115.0 adds 4 extra OTel spans per request:
# fastapi.dependencies, fastapi.endpoint, GET /non_async_threadpool, and one internal span.
# TODO: after support httpx, the expected value will be 7.
assert len(spans) == 6

span_filter = ( # noqa: E731
lambda span: span.n == "sdk" and span.data["sdk"]["name"] == "test"
Expand Down
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