Add Middleware for correlation_id

The middleware generates the 'correlation_id' if it is not already present
in the request header. This 'correlation_id' can be used to enable more
effective debugging of requests that span multiple services.

Implements: blueprint create-a-unified-correlation-id

Change-Id: Ibc06a5b05b628e0b640e9299c79127ecbf9c684e

1 files changed, 29 insertions, 0 deletions

diff --git a/openstack/common/middleware/correlation_id.py b/openstack/common/middleware/correlation_id.py
new file mode 100644
index 0000000..a3efe34
--- /dev/null
+++ b/openstack/common/middleware/correlation_id.py
@@ -0,0 +1,29 @@
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+# Copyright (c) 2013 Rackspace Hosting
+# 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.
+
+"""Middleware that attaches a correlation id to WSGI request"""
+
+from openstack.common import uuidutils
+from openstack.common import wsgi
+
+
+class CorrelationIdMiddleware(wsgi.Middleware):
+
+    def process_request(self, req):
+        correlation_id = (req.headers.get("X_CORRELATION_ID") or
+                          uuidutils.generate_uuid())
+        req.headers['X_CORRELATION_ID'] = correlation_id