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.

# Copyright (c) 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.

# This is an example Apache2 configuration file for using the
# ceilometer API through mod_wsgi.

# Note: If you are using a Debian-based system then the paths
# "/var/log/httpd" and "/var/run/httpd" will use "apache2" instead
# of "httpd".
#
# The number of processes and threads is an example only and should
# be adjusted according to local requirements.

Listen 8777

<VirtualHost *:8777>
    WSGIDaemonProcess ceilometer-api processes=2 threads=10 user=SOMEUSER display-name=%{GROUP}
    WSGIProcessGroup ceilometer-api
    WSGIScriptAlias / /var/www/ceilometer/app
    WSGIApplicationGroup %{GLOBAL}
    <IfVersion >= 2.4>
        ErrorLogFormat "%{cu}t %M"
    </IfVersion>
    ErrorLog /var/log/httpd/ceilometer_error.log
    CustomLog /var/log/httpd/ceilometer_access.log combined
</VirtualHost>

WSGISocketPrefix /var/run/httpd

1. On deb-based systems copy or symlink the file to /etc/apache2/sites-available. For rpm-based systems the file will go in /etc/httpd/conf.d.

2. Modify the WSGIDaemonProcess directive to set the user and group values to a appropriate user on your server. In many installations ceilometer will be correct.

3. Enable the ceilometer site. On deb-based systems:

   $ a2ensite ceilometer
   $ service apache2 reload
   

   On rpm-based systems:

   $ service httpd 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. To allow multiple processes the DebugMiddleware may be turned off by setting pecan_debug to False in the api section of ceilometer.conf.

For other WSGI setup you can refer to the pecan deployment documentation. .. pecan deployment: http://pecan.readthedocs.org/en/latest/deployment.html