Merge pull request #80 from ziadsawalha/context

feat(middleware): add context middleware

README.md

@@ -44,6 +44,7 @@ Includes sample middleware for use with WSGI apps including bottle.
 
 Middleware included:
 - CORS: handles CORS requests
+- Context: handles setting a threadlocal context and adds a transaction ID.
 
 
 ## <a name="rest"></a>REST API Tooling

simpl/middleware/context.py

@@ -0,0 +1,92 @@
+# Copyright (c) 2011-2015 Rackspace US, Inc.
+# All Rights Reserved.
+#    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.
+
+"""Context WSGI Middleware.
+
+Creates a context for the WSGI call and adds the following to the context:
+- transaction_id: a UUID to identify the call (this can be passed in the
+        context to remote workers)
+- base_url: the URL of the incoming call (overrideable)
+
+The transaction id is returned in responses as an X-Transaction-Id header.
+
+Example usage:
+
+    # Disable all CORS checks:
+    import bottle
+    from simpl.middleware import context
+
+    app = bottle.default_app()
+    chain = context.ContextMiddleware(app, override_url="https://my_app.io")
+    bottle.run(app=chain)
+"""
+
+import logging
+import uuid
+
+from simpl import threadlocal
+
+LOG = logging.getLogger(__name__)
+
+
+class ContextMiddleware(object):  # pylint: disable=R0903
+
+    """Adds a call context to the call environ which holds call data."""
+
+    def __init__(self, app, override_url=None):
+        """Add a call context to the call environ which holds authn+z data."""
+        self.app = app
+        self.override_url = override_url
+
+    def __call__(self, environ, start_response):
+        """Handle WSGI Request."""
+        if self.override_url:
+            url = self.override_url
+        else:
+            # PEP333: wsgi.url_scheme, HTTP_HOST, SERVER_NAME, and SERVER_PORT
+            # can be used to reconstruct a request's complete URL
+
+            # Much of the following is copied from bottle.py
+            http = environ.get('HTTP_X_FORWARDED_PROTO') \
+                or environ.get('wsgi.url_scheme', 'http')
+            host = environ.get('HTTP_X_FORWARDED_HOST') \
+                or environ.get('HTTP_HOST')
+            if not host:
+                # HTTP 1.1 requires a Host-header. This is for HTTP/1.0
+                # clients.
+                host = environ.get('SERVER_NAME', '127.0.0.1')
+                port = environ.get('SERVER_PORT')
+                if port and port != ('80' if http == 'http' else '443'):
+                    host += ':' + port
+            url = "%s://%s" % (http, host)
+
+        # Use a default empty context
+        transaction_id = uuid.uuid4().hex
+        context = threadlocal.default()
+        context['base_url'] = url
+        context['transaction_id'] = transaction_id
+        environ['context'] = context
+        LOG.debug("Context created: base_url=%s, tid=%s", url, transaction_id)
+        return self.app(environ, self.start_response_callback(start_response,
+                                                              transaction_id))
+
+    @staticmethod
+    def start_response_callback(start_response, transaction_id):
+        """Intercept upstream start_response and adds our headers."""
+        def callback(status, headers, exc_info=None):
+            """Add our headers to response using a closure."""
+            headers.append(('X-Transaction-Id', transaction_id))
+            # Call upstream start_response
+            start_response(status, headers, exc_info)
+        return callback

tests/test_middleware_context.py

@@ -0,0 +1,98 @@
+# pylint: disable=C0103,R0904,R0903
+
+# Copyright (c) 2011-2015 Rackspace US, Inc.
+# All Rights Reserved.
+#    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.
+
+"""Tests for Context middleware."""
+
+import unittest
+
+import mock
+from webtest.debugapp import debug_app
+
+from simpl.middleware import context
+
+
+class TestContextMiddleware(unittest.TestCase):
+
+    def setUp(self):
+        self.filter = context.ContextMiddleware(debug_app)
+        self.headers = []
+
+    def start_response(self, status, headers, exc_info=None):
+        """Emulate WSGI start_response."""
+        self.headers += headers
+
+    def test_url_override(self):
+        env = {'REQUEST_METHOD': 'GET',
+               'PATH_INFO': '/'}
+        self.filter.override_url = "http://OVERRIDDEN"
+        self.filter(env, self.start_response)
+        self.assertEqual('http://OVERRIDDEN', env['context']['base_url'])
+
+    def test_no_url_scheme(self):
+        with self.assertRaises(KeyError):
+            self.filter({}, self.start_response)
+
+    def test_http_host(self):
+        env = {'REQUEST_METHOD': 'GET',
+               'PATH_INFO': '/',
+               'wsgi.url_scheme': 'http',
+               'HTTP_HOST': 'MOCK'}
+        self.filter(env, self.start_response)
+        self.assertEqual('http://MOCK', env['context']['base_url'])
+
+    def test_server_name(self):
+        env = {'REQUEST_METHOD': 'GET',
+               'PATH_INFO': '/',
+               'wsgi.url_scheme': 'http',
+               'SERVER_NAME': 'MOCK',
+               'SERVER_PORT': '80'}
+        self.filter(env, self.start_response)
+        self.assertEqual('http://MOCK', env['context']['base_url'])
+
+    def test_https_weird_port(self):
+        env = {'REQUEST_METHOD': 'GET',
+               'PATH_INFO': '/',
+               'wsgi.url_scheme': 'https',
+               'SERVER_NAME': 'MOCK',
+               'SERVER_PORT': '444'}
+        self.filter(env, self.start_response)
+        self.assertEqual('https://MOCK:444', env['context']['base_url'])
+
+    def test_http_weird_port(self):
+        env = {'REQUEST_METHOD': 'GET',
+               'PATH_INFO': '/',
+               'wsgi.url_scheme': 'http',
+               'SERVER_NAME': 'MOCK',
+               'SERVER_PORT': '81'}
+        self.filter(env, self.start_response)
+        self.assertEqual('http://MOCK:81', env['context']['base_url'])
+
+    @mock.patch.object(context.uuid, 'uuid4')
+    def test_transaction_id(self, mock_uuid):
+        mock_uuid.return_value = mock.Mock(hex="12345abc")
+        env = {'REQUEST_METHOD': 'GET',
+               'PATH_INFO': '/',
+               'wsgi.url_scheme': 'http',
+               'SERVER_NAME': 'MOCK',
+               'SERVER_PORT': '80'}
+        self.filter(env, self.start_response)
+        self.assertIn(('X-Transaction-Id', '12345abc'), self.headers)
+        self.assertIn('transaction_id', env['context'])
+        self.assertEqual('12345abc', env['context']['transaction_id'])
+
+
+if __name__ == '__main__':
+    unittest.main()

tests/test_middleware_cors.py

@@ -118,6 +118,5 @@ def test_conditional_import(self):
             with self.assertRaises(RuntimeError):
                 app({}, self.start_response)
 
-
 if __name__ == '__main__':
     unittest.main()