Implement WSGI middleware integration. (#84)

ext/opentelemetry-ext-wsgi/README.rst

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+OpenTelemetry WSGI Middleware
+=============================
+
+This library provides a WSGI middleware that can be used on any WSGI framework
+(such as Django / Flask) to track requests timing through OpenTelemetry.
+
+
+Usage (Flask)
+-------------
+
+.. code-block:: python
+
+    from flask import Flask
+    from opentelemetry.ext.wsgi import OpenTelemetryMiddleware
+
+    app = Flask(__name__)
+    app.wsgi_app = OpenTelemetryMiddleware(app.wsgi_app)
+
+    @app.route("/")
+    def hello():
+        return "Hello!"
+
+    if __name__ == "__main__":
+        app.run(debug=True)
+
+
+Usage (Django)
+--------------
+
+Modify the application's ``wsgi.py`` file as shown below.
+
+.. code-block:: python
+
+    import os
+    from opentelemetry.ext.wsgi import OpenTelemetryMiddleware
+    from django.core.wsgi import get_wsgi_application
+
+    os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'application.settings')
+
+    application = get_wsgi_application()
+    application = OpenTelemetryMiddleware(application)
+
+References
+----------
+
+* `OpenTelemetry Project <https://opentelemetry.io/>`_
+* `WSGI <https://www.python.org/dev/peps/pep-3333>`_

ext/opentelemetry-ext-wsgi/setup.cfg

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+# 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.
+#
+[metadata]
+name = opentelemetry-ext-wsgi
+description = WSGI Middleware for OpenTelemetry
+long_description = file: README.rst
+long_description_content_type = text/x-rst
+author = OpenTelemetry Authors
+author_email = cncf-opentelemetry-contributors@lists.cncf.io
+url = https://github.com/open-telemetry/opentelemetry-python/ext/opentelemetry-ext-wsgi
+platforms = any
+license = Apache-2.0
+classifiers =
+    Development Status :: 3 - Alpha
+    Intended Audience :: Developers
+    License :: OSI Approved :: Apache Software License
+    Programming Language :: Python
+    Programming Language :: Python :: 3
+    Programming Language :: Python :: 3.4
+    Programming Language :: Python :: 3.5
+    Programming Language :: Python :: 3.6
+    Programming Language :: Python :: 3.7
+
+[options]
+python_requires = >=3.4
+package_dir=
+    =src
+packages=find:
+install_requires =
+    opentelemetry-api
+
+[options.packages.find]
+where = src

ext/opentelemetry-ext-wsgi/setup.py

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+# 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.
+import os
+import setuptools
+
+BASE_DIR = os.path.dirname(__file__)
+VERSION_FILENAME = os.path.join(
+    BASE_DIR,
+    "src",
+    "opentelemetry",
+    "ext",
+    "wsgi",
+    "version.py",
+)
+PACKAGE_INFO = {}
+with open(VERSION_FILENAME) as f:
+    exec(f.read(), PACKAGE_INFO)
+
+setuptools.setup(version=PACKAGE_INFO["__version__"])

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

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+# 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.
+
+"""
+The opentelemetry-ext-wsgi package provides a WSGI middleware that can be used
+on any WSGI framework (such as Django / Flask) to track requests timing through
+OpenTelemetry.
+"""
+
+import functools
+import wsgiref.util as wsgiref_util
+
+from opentelemetry import trace
+from opentelemetry.ext.wsgi.version import __version__  # noqa
+
+
+class OpenTelemetryMiddleware:
+    """The WSGI application middleware.
+
+    This class is used to create and annotate spans for requests to a WSGI
+    application.
+
+    Args:
+        wsgi: The WSGI application callable.
+    """
+
+    def __init__(
+            self,
+            wsgi,
+            propagators=None,
+    ):
+        self.wsgi = wsgi
+
+        # TODO: implement context propagation
+        self.propagators = propagators
+
+    @staticmethod
+    def _add_request_attributes(span, environ):
+        span.set_attribute("component", "http")
+        span.set_attribute("http.method", environ["REQUEST_METHOD"])
+
+        host = environ.get("HTTP_HOST") or environ["SERVER_NAME"]
+        span.set_attribute("http.host", host)
+
+        url = (
+            environ.get("REQUEST_URI") or
+            environ.get("RAW_URI") or
+            wsgiref_util.request_uri(environ, include_query=False)
+        )
+        span.set_attribute("http.url", url)
+
+    @staticmethod
+    def _add_response_attributes(span, status):
+        status_code, status_text = status.split(" ", 1)
+        span.set_attribute("http.status_text", status_text)
+
+        try:
+            status_code = int(status_code)
+        except ValueError:
+            pass
+        else:
+            span.set_attribute("http.status_code", status_code)
+
+    @classmethod
+    def _create_start_response(cls, span, start_response):
+        @functools.wraps(start_response)
+        def _start_response(status, response_headers, *args, **kwargs):
+            cls._add_response_attributes(span, status)
+            return start_response(status, response_headers, *args, **kwargs)
+
+        return _start_response
+
+    def __call__(self, environ, start_response):
+        """The WSGI application
+
+        Args:
+            environ: A WSGI environment.
+            start_response: The WSGI start_response callable.
+        """
+
+        tracer = trace.tracer()
+        path_info = environ["PATH_INFO"] or "/"
+
+        with tracer.start_span(path_info) as span:
+            self._add_request_attributes(span, environ)
+            start_response = self._create_start_response(span, start_response)
+
+            iterable = self.wsgi(environ, start_response)
+            try:
+                for yielded in iterable:
+                    yield yielded
+            finally:
+                if hasattr(iterable, 'close'):
+                    iterable.close()

ext/opentelemetry-ext-wsgi/src/opentelemetry/ext/wsgi/version.py

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+# 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.
+
+__version__ = "0.1.dev0"