Fix issue with Flask instrumentation when a request spawn children threads and copies the request context

CHANGELOG.md

@@ -32,6 +32,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+- Fix Flask instrumentation to only close the span if it was created by the same thread.
+  ([#1654](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/1654))
 - Fix TortoiseORM instrumentation `AttributeError: type object 'Config' has no attribute 'title'`
   ([#1575](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/1575))
 - Fix SQLAlchemy uninstrumentation

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

@@ -238,8 +238,8 @@ def response_hook(span: Span, status: str, response_headers: List):
 API
 ---
 """
-
 from logging import getLogger
+from threading import get_ident
 from time import time_ns
 from timeit import default_timer
 from typing import Collection
@@ -265,6 +265,7 @@ def response_hook(span: Span, status: str, response_headers: List):
 _ENVIRON_STARTTIME_KEY = "opentelemetry-flask.starttime_key"
 _ENVIRON_SPAN_KEY = "opentelemetry-flask.span_key"
 _ENVIRON_ACTIVATION_KEY = "opentelemetry-flask.activation_key"
+_ENVIRON_THREAD_ID_KEY = "opentelemetry-flask.thread_id_key"
 _ENVIRON_TOKEN = "opentelemetry-flask.token"
 
 _excluded_urls_from_env = get_excluded_urls("FLASK")
@@ -398,6 +399,7 @@ def _before_request():
         activation = trace.use_span(span, end_on_exit=True)
         activation.__enter__()  # pylint: disable=E1101
         flask_request_environ[_ENVIRON_ACTIVATION_KEY] = activation
+        flask_request_environ[_ENVIRON_THREAD_ID_KEY] = get_ident()
         flask_request_environ[_ENVIRON_SPAN_KEY] = span
         flask_request_environ[_ENVIRON_TOKEN] = token
 
@@ -437,10 +439,17 @@ def _teardown_request(exc):
             return
 
         activation = flask.request.environ.get(_ENVIRON_ACTIVATION_KEY)
-        if not activation:
+        thread_id = flask.request.environ.get(_ENVIRON_THREAD_ID_KEY)
+        if not activation or thread_id != get_ident():
             # This request didn't start a span, maybe because it was created in
             # a way that doesn't run `before_request`, like when it is created
             # with `app.test_request_context`.
+            #
+            # Similarly, check the thread_id against the current thread to ensure
+            # tear down only happens on the original thread. This situation can
+            # arise if the original thread handling the request spawn children
+            # threads and then uses something like copy_current_request_context
+            # to copy the request context.
             return
         if exc is None:
             activation.__exit__(None, None, None)

instrumentation/opentelemetry-instrumentation-flask/tests/base_test.py

@@ -12,6 +12,9 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from concurrent.futures import ThreadPoolExecutor, as_completed
+from random import randint
+
 import flask
 from werkzeug.test import Client
 from werkzeug.wrappers import Response
@@ -34,6 +37,25 @@ def _sqlcommenter_endpoint():
         )
         return sqlcommenter_flask_values
 
+    @staticmethod
+    def _multithreaded_endpoint(count):
+        def do_random_stuff():
+            @flask.copy_current_request_context
+            def inner():
+                return randint(0, 100)
+
+            return inner
+
+        executor = ThreadPoolExecutor(count)
+        futures = []
+        for _ in range(count):
+            futures.append(executor.submit(do_random_stuff()))
+        numbers = []
+        for future in as_completed(futures):
+            numbers.append(future.result())
+
+        return " ".join([str(i) for i in numbers])
+
     @staticmethod
     def _custom_response_headers():
         resp = flask.Response("test response")
@@ -61,6 +83,7 @@ def excluded2_endpoint():
         # pylint: disable=no-member
         self.app.route("/hello/<int:helloid>")(self._hello_endpoint)
         self.app.route("/sqlcommenter")(self._sqlcommenter_endpoint)
+        self.app.route("/multithreaded")(self._multithreaded_endpoint)
         self.app.route("/excluded/<int:helloid>")(self._hello_endpoint)
         self.app.route("/excluded")(excluded_endpoint)
         self.app.route("/excluded2")(excluded2_endpoint)

instrumentation/opentelemetry-instrumentation-flask/tests/test_multithreading.py

@@ -0,0 +1,52 @@
+# Copyright The OpenTelemetry Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import flask
+from werkzeug.test import Client
+from werkzeug.wrappers import Response
+
+from opentelemetry.instrumentation.flask import FlaskInstrumentor
+from opentelemetry.test.wsgitestutil import WsgiTestBase
+
+# pylint: disable=import-error
+from .base_test import InstrumentationTest
+
+
+class TestMultiThreading(InstrumentationTest, WsgiTestBase):
+    def setUp(self):
+        super().setUp()
+        FlaskInstrumentor().instrument()
+        self.app = flask.Flask(__name__)
+        self._common_initialization()
+
+    def tearDown(self):
+        super().tearDown()
+        with self.disable_logging():
+            FlaskInstrumentor().uninstrument()
+
+    def test_multithreaded(self):
+        """Test that instrumentation tear down does not blow up
+        when the request thread spawn children threads and the request
+        context is copied to the children threads
+        """
+        self.app = flask.Flask(__name__)
+        self.app.route("/multithreaded/<int:count>")(
+            self._multithreaded_endpoint
+        )
+        client = Client(self.app, Response)
+        count = 5
+        resp = client.get(f"/multithreaded/{count}")
+        self.assertEqual(200, resp.status_code)
+        # Should return the specified number of random integers
+        self.assertEqual(count, len(resp.text.split(" ")))