Installing the API via WSGI

This document provides two WSGI deployments as examples: uwsgi and mod_wsgi.

See also

https://governance.openstack.org/tc/goals/pike/deploy-api-in-wsgi.html#uwsgi-vs-mod-wsgi

Installing the API behind mod_wsgi

Zun comes with a few example files for configuring the API service to run behind Apache with mod_wsgi.

app.wsgi

The file zun/api/app.wsgi sets up the V2 API WSGI application. The file is installed with the rest of the zun application code, and should not need to be modified.

etc/apache2/zun.conf

The etc/apache2/zun.conf file contains example settings that work with a copy of zun installed via devstack.

# 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
# zun 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 %PUBLICPORT%
LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-agent}i\" %D(us)" zun_combined

<VirtualHost *:%PUBLICPORT%>
    WSGIDaemonProcess zun-api user=%USER% processes=5 threads=1 display-name=%{GROUP}
    WSGIScriptAlias / %PUBLICWSGI%
    WSGIProcessGroup zun-api
    ErrorLogFormat "%M"
    ErrorLog /var/log/%APACHE_NAME%/zun_api.log
    LogLevel info
    CustomLog /var/log/%APACHE_NAME%/zun_access.log zun_combined

    <Directory /opt/stack/zun/zun/api>
        WSGIProcessGroup zun-api
        WSGIApplicationGroup %{GLOBAL}
        AllowOverride All
        Require all granted
    </Directory>
</VirtualHost>

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 an appropriate user on your server. In many installations zun will be correct. Modify the WSGIScriptAlias directive to set the path of the wsgi script. If you are using devstack, the value should be /opt/stack/zun/zun/api/app.wsgi. In the ErrorLog and CustomLog directives, replace %APACHE_NAME% with apache2.

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

   $ a2ensite zun
   $ service apache2 reload
   

   On rpm-based systems:

   $ service httpd reload
   

Installing the API with uwsgi

Create zun-uwsgi.ini file:

[uwsgi]
http = 0.0.0.0:9517
wsgi-file = <path_to_zun>/zun/api/app.wsgi
plugins = python
# This is running standalone
master = true
# Set die-on-term & exit-on-reload so that uwsgi shuts down
exit-on-reload = true
die-on-term = true
# uwsgi recommends this to prevent thundering herd on accept.
thunder-lock = true
# Override the default size for headers from the 4k default. (mainly for keystone token)
buffer-size = 65535
enable-threads = true
# Set the number of threads usually with the returns of command nproc
threads = 8
# Make sure the client doesn't try to re-use the connection.
add-header = Connection: close
# Set uid and gip to a appropriate user on your server. In many
# installations ``zun`` will be correct.
uid = zun
gid = zun

Then start the uwsgi server:

uwsgi ./zun-uwsgi.ini

Or start in background with:

uwsgi -d ./zun-uwsgi.ini