Revert Flask changes

Author: ocelotl

docs/examples/opentelemetry-example-app/src/opentelemetry_example_app/flask_example.py

@@ -33,8 +33,8 @@
     SimpleExportSpanProcessor(ConsoleSpanExporter())
 )
 
-Flask = FlaskInstrumentor().instrument(flask_class=flask.Flask)
-app = Flask(__name__)
+FlaskInstrumentor().instrument()
+app = flask.Flask(__name__)
 opentelemetry.ext.http_requests.enable(trace.get_tracer_provider())
 
 

docs/getting-started.rst

@@ -184,6 +184,9 @@ And let's write a small Flask application that sends an HTTP request, activating
 .. code-block:: python
 
     # flask_example.py
+    from opentelemetry.ext.flask import FlaskInstrumentor
+    FlaskInstrumentor().instrument()  # This needs to be executed before importing Flask
+
     import flask
     import requests
 
@@ -192,16 +195,13 @@ And let's write a small Flask application that sends an HTTP request, activating
     from opentelemetry.sdk.trace import TracerProvider
     from opentelemetry.sdk.trace.export import ConsoleSpanExporter
     from opentelemetry.sdk.trace.export import SimpleExportSpanProcessor
-    from opentelemetry.ext.flask import FlaskInstrumentor
-
-    Flask = FlaskInstrumentor().instrument(flask_class=flask.Flask)
 
     trace.set_tracer_provider(TracerProvider())
     trace.get_tracer_provider().add_span_processor(
         SimpleExportSpanProcessor(ConsoleSpanExporter())
     )
 
-    app = Flask(__name__)
+    app = flask.Flask(__name__)
     opentelemetry.ext.http_requests.enable(trace.get_tracer_provider())
 
     @app.route("/")

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

@@ -29,10 +29,9 @@
 
 .. code-block:: python
 
-    from flask import Flask
     from opentelemetry.ext.flask import FlaskInstrumentor
-
-    Flask = FlaskInstrumentor().instrument(flask_class=Flask)
+    FlaskInstrumentor().instrument()  # This needs to be executed before importing Flask
+    from flask import Flask
 
     app = Flask(__name__)
 
@@ -159,20 +158,11 @@ class FlaskInstrumentor(BaseInstrumentor):
 
     def __init__(self):
         super().__init__()
-        self._original_flask_class = None
+        self._original_flask = None
 
-    def _instrument(
-        self, flask_class=None
-    ):  # pylint: disable=arguments-differ
-        if flask_class is not None:
-            self._original_flask_class = flask_class
-            return _InstrumentedFlask
-
-        self._original_flask_class = flask.Flask
+    def _instrument(self):
+        self._original_flask = flask.Flask
         flask.Flask = _InstrumentedFlask
 
-        return None
-
-    def _uninstrument(self):  # pylint: disable=arguments-differ
-        flask.Flask = self._original_flask_class
-        return self._original_flask_class
+    def _uninstrument(self):
+        flask.Flask = self._original_flask

ext/opentelemetry-ext-flask/tests/conftest.py

@@ -0,0 +1,25 @@
+# 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.
+
+from opentelemetry.ext.flask import FlaskInstrumentor
+
+_FLASK_INSTRUMENTOR = FlaskInstrumentor()
+
+
+def pytest_sessionstart(session):  # pylint: disable=unused-argument
+    _FLASK_INSTRUMENTOR.instrument()
+
+
+def pytest_sessionfinish(session):  # pylint: disable=unused-argument
+    _FLASK_INSTRUMENTOR.uninstrument()

ext/opentelemetry-ext-flask/tests/test_flask_integration.py

@@ -19,11 +19,8 @@
 from werkzeug.wrappers import BaseResponse
 
 from opentelemetry import trace as trace_api
-from opentelemetry.ext.flask import FlaskInstrumentor
 from opentelemetry.test.wsgitestutil import WsgiTestBase
 
-Flask = FlaskInstrumentor().instrument(flask_class=Flask)
-
 
 def expected_attributes(override_attributes):
     default_attributes = {