Add support for automatic instrumentation and injection

Fixes open-telemetry#300

ext/__init__.py

@@ -0,0 +1,27 @@
+# Copyright 2019, 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.
+
+"OpenTelemetry extension specification"
+
+from abc import ABC, abstractmethod
+
+
+class OpenTelemetryExtension(ABC):
+    "OpenTelemetry extension base class"
+
+    @abstractmethod
+    def patch(self, *args, **kwargs):
+        "Monkey patch a OpenTelemetry extension"
+
+        pass

ext/opentelemetry-ext-flask/setup.py

@@ -23,4 +23,13 @@
 with open(VERSION_FILENAME) as f:
     exec(f.read(), PACKAGE_INFO)
 
-setuptools.setup(version=PACKAGE_INFO["__version__"])
+setuptools.setup(
+    version=PACKAGE_INFO["__version__"],
+    entry_points={
+        "opentelemetry_extension": [
+            "opentelemetry_extension_flask = "
+            "opentelemetry-ext-flask.flask:"
+            "OpenTelemetryFlaskExtension"
+        ]
+    }
+)

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

@@ -6,6 +6,7 @@
 from flask import request as flask_request
 
 import opentelemetry.ext.wsgi as otel_wsgi
+from opentelemetry.ext import OpenTelemetryExtension
 from opentelemetry import propagators, trace
 from opentelemetry.util import time_ns
 
@@ -16,6 +17,12 @@
 _ENVIRON_ACTIVATION_KEY = object()
 
 
+class OpenTelemetryExtensionFlask(OpenTelemetryExtension):
+
+    def patch(self):
+
+        pass
+
 def instrument_app(flask):
     """Makes the passed-in Flask object traced by OpenTelemetry.
 

opentelemetry-sdk/setup.py

@@ -56,4 +56,14 @@
         "/tree/master/opentelemetry-sdk"
     ),
     zip_safe=False,
+    entry_points={
+        "console_scripts": [
+            "opentelemetry_python_autoagent = opentelemetry."
+            "scripts.opentelemetry_python_autoagent:run"
+        ],
+        "opentelemetry_extension": [
+            "opentelemetry_extension = opentelemetry.ext:"
+            "OpenTelemetryExtension"
+        ]
+    }
 )

opentelemetry-sdk/src/opentelemetry/sdk/initialize/sitecustomize.py

@@ -0,0 +1,25 @@
+from pkg_resources import iter_entry_points
+from logging import getLogger
+
+_LOGGER = getLogger(__file__)
+
+
+for entry_point in iter_entry_points(
+    group='opentelemetry_extension'
+):
+
+    try:
+
+        entry_point.load()().patch()
+
+    except Exception as error:
+
+        _LOG.warning(
+            (
+                "Unable to patch extension {extension}, this "
+                "error happened while attempting to patch: "
+                "{error}. Execution may continue but no "
+                "automatic instrumentation will be performed on "
+                "{extension}."
+            ).format(extension=entry_point.name, error=error)
+        )

opentelemetry-sdk/src/opentelemetry/sdk/scripts/opentelemetry_python_autoagent.py

@@ -0,0 +1,18 @@
+#!/usr/bin/env python3
+
+from sys import exit, argv
+from os import execl
+import os
+from os.path import dirname, join
+from distutils.spawn import find_executable
+
+
+def run():
+
+    os.environ['PYTHONPATH'] = join(dirname(__file__), 'initialize')
+
+    python3 = find_executable('python3')
+
+    execl(python3, python3, argv[1])
+
+    exit(0)