aodh/doc/source/install/mod_wsgi.rst
Fei Long Wang f2685fc531 Doc enhancement for API service deployment with mod_wsgi
Now Pecan is sharing the same debug configration with Ceilometer,
but DebugMiddleware of Pecan doesn't support multi processes.
That means user can't enable the Ceilometer debug mode if he is
using multi process mode for mod_wsgi config.

Closes-Bug: 1352088

Change-Id: I6e83fbcbee23a519fe26c3036f42cc619848a989
2014-08-05 10:24:47 +12:00

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Copyright 2013 New Dream Network, LLC (DreamHost)
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.
====================================
Installing the API Behind mod_wsgi
====================================
Ceilometer comes with a few example files for configuring the API
service to run behind Apache with ``mod_wsgi``.
app.wsgi
========
The file ``ceilometer/api/app.wsgi`` sets up the V2 API WSGI
application. The file is installed with the rest of the ceilometer
application code, and should not need to be modified.
etc/apache2/ceilometer
======================
The ``etc/apache2/ceilometer`` file contains example settings that
work with a copy of ceilometer installed via devstack.
.. literalinclude:: ../../../etc/apache2/ceilometer
1. Copy or symlink the file to ``/etc/apache2/sites-avilable``.
2. Modify the ``VirtualHost`` directive, setting a hostname or IP for
the service. The default settings assume that the ceilometer API is
the only service running on the local Apache instance, which
conflicts with Horizon's default configuration.
3. Modify the ``WSGIDaemonProcess`` directive to set the
``user`` and ``group`` values to a user available on your server.
4. Modify the ``APACHE_RUN_USER`` and ``APACHE_RUN_GROUP`` values to
the name of a user and group available on your server.
5. Enable the ceilometer site.
::
$ a2ensite ceilometer
$ service apache2 reload
Limitation
==========
As Ceilometer is using Pecan and Pecan's DebugMiddleware doesn't support
multiple processes, there is no way to set debug mode in the multiprocessing
case. So user will run into HTTP 500 error if the mod_wsgi's multiprocessing
is enabled and the Ceilometer debug mode is enabled at the same time. There
is no good way to make both of them work, since Pecan is sharing the debug
mode with Ceilometer, see[1]. If you really need to enable both, a possible
workaround is hacking that line and hardcode the debug configration to False.
[1] https://github.com/openstack/ceilometer/blob/master/ceilometer/api/app.py