Cinder API WSGI application under Apache/Nginx

Cinder API uses eventlet as a webserver and WSGI application managing.
This spec describes new option to deploy Cinder API with Apache/Nginx

Related blueprint: non-eventlet-wsgi-app

Change-Id: Ie17dbca185d33c75c98175dceda024f8713149a6

specs/liberty/non-eventlet-wsgi-app.rst

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+..
+ This work is licensed under a Creative Commons Attribution 3.0 Unported
+ License.
+
+ http://creativecommons.org/licenses/by/3.0/legalcode
+
+==============================================
+Cinder API WSGI application under Apache/Nginx
+==============================================
+
+https://blueprints.launchpad.net/cinder/+spec/non-eventlet-wsgi-app.
+
+Cinder API uses eventelt as a webserver and WSGI application managing. Eventlet
+provides own WSGI application to provide web server functionality.
+
+
+Problem description
+===================
+
+* Cinder API is deployed in other way as a common web application. Apache/Nginx
+  is generally used web servers for REST API application.
+
+* Cinder API is runned as a separate service. It means that cloud operator need
+  to configure some software to monitor that Cinder API is running.
+
+* Apache/Nginx works better under the real heavy load then eventlet.
+
+
+
+Use Cases
+=========
+
+* Deploy Cinder API with Apache/Nginx like an any other web applicaction.
+
+* Deploy Cinder API with Apache/Nginx to have load balancing and web applicaion
+   monitoring out of the box. E.g. Nginx/uWSGI can restart backend service if
+   it stopped by any case.
+
+
+Proposed change
+===============
+
+Provide WSGI application based on used web-framework instead of eventlet. Leave
+eventlet-based WSGI application as a default option and make it configurable.
+
+Alternatives
+------------
+
+Leave as is and use eventlet for REST API web serving. Use something like
+haproxy for API requests load balancing and some watchdog to restart Cinder API
+service after shutdown.
+
+Data model impact
+-----------------
+
+None.
+
+REST API impact
+---------------
+
+None.
+
+Security impact
+---------------
+
+None
+
+Notifications impact
+--------------------
+
+None
+
+Other end user impact
+---------------------
+
+None
+
+Performance Impact
+------------------
+
+Potential performance impact could be present if we will have a lot of requests
+to Cinder API. Performance impact will be tested with Rally.
+
+Other deployer impact
+---------------------
+
+Deployers should configure Apache/Nginx/etc and WSGI module to handle requests
+to Cinder API. By default, Cinder API will use eventlet and no deployer impact
+will be.
+
+No new configuration options for Cinder will be introduced.
+
+New deployment mode should be supported by Chef cookbooks and Puppet manifests.
+
+Developer impact
+----------------
+
+None
+
+
+Implementation
+==============
+
+Assignee(s)
+-----------
+
+Primary assignee:
+  Ivan Kolodyazhny <e0ne>
+
+Other contributors:
+  Anton Arefiev <aarefiev>
+
+Work Items
+----------
+
+* Implement WSGI application based on webob framework.
+
+* Test performance impact with Rally.
+
+* Write documentation how to run Cinder API with Apache/Nginx.
+
+* Implement configuration option in Devstack to support new deployment mode.
+
+* Make sure usage of eventlet doesn't break WSGI in Nginx/Apache.
+
+* Start cross-project initiative to implement this in oslo.
+
+
+Dependencies
+============
+
+None
+
+
+Testing
+=======
+
+Functional tests for new deployment mode will be implemented. We need to test
+this feature on every commit on infra with CI.
+
+
+Documentation Impact
+====================
+
+Administrators Guide will be updated.
+
+
+References
+==========
+
+
+* https://review.openstack.org/#/c/154642/
+
+* https://review.openstack.org/#/c/164035/
+
+* https://review.openstack.org/#/c/196088/
+
+* http://lists.openstack.org/pipermail/openstack-dev/2015-February/057359.html