Running Glance in HTTPD¶
Since the Pike release Glance has packaged a wsgi script entrypoint that enables you to run it with a real web server like Apache HTTPD or nginx. To deploy this there are several patterns. This doc shows two common ways of deploying Glance with Apache HTTPD.
Note
We are experiencing some problems in the gate when the Pike release of Glance is configured to run in devstack following the guidelines recommended in this documentation. You can follow Bug #1703856 to learn more.
uwsgi¶
This is the current recommended way to deploy Glance with a real web server. In this deployment method we use uwsgi as a web server bound to a random local port. Then we configure apache using mod_proxy to forward all incoming requests on the specified endpoint to that local webserver. This has the advantage of letting apache manage all inbound http connections, but letting uwsgi manage running the python code. It also means when we make changes to Glance code or configuration we don’t need to restart all of apache (which may be running other services too) and just need to restart the local uwsgi daemon.
The httpd/ directory contains sample files for configuring HTTPD to run Glance under uwsgi in this configuration. To use the sample configs simply copy httpd/uwsgi-glance-api.conf to the appropriate location for your Apache server. On Debian/Ubuntu systems it is:
/etc/apache2/sites-available/uwsgi-glance-api.conf
On Red Hat based systems it is:
/etc/httpd/conf.d/uwsgi-glance-api.conf
Enable mod_proxy by running sudo a2enmod proxy
Then on Ubuntu/Debian systems enable the site by creating a symlink from the
file in sites-available to sites-enabled. (This is not required on Red
Hat based systems):
ln -s /etc/apache2/sites-available/uwsgi-glance-api.conf /etc/apache2/sites-enabled
Start or restart HTTPD to pick up the new configuration.
Now we need to configure and start the uwsgi service. Copy the httpd/glance-api-uwsgi.ini file to /etc/glance. Update the file to match your system configuration (for example, you’ll want to set the number of processes and threads).
Install uwsgi and start the glance-api server using uwsgi:
sudo pip install uwsgi
uwsgi --ini /etc/glance/glance-api-uwsgi.ini
Note
In the sample configs port 60999 is used, but this doesn’t matter and is just a randomly selected number. This is not a contract on the port used for the local uwsgi daemon.
Note
In the sample apache config proxy-sendcl is set. This is to workaround glance not leveraging uwsgi’s chunked_read() api in the Pike release. Using this option means apache buffers the input chunked data in the configured TEMPDIR (which defaults to /tmp) before giving the data to glance. This can also be quite slow and might require increasing timeouts.
mod_proxy_uwsgi¶
Warning
Running Glance under HTTPD in this configuration will only work on Python 2
if you use Transfer-Encoding: chunked. Also if running with Python 2
apache will be buffering the chunked encoding before passing the request
on to uwsgi. See bug: https://github.com/unbit/uwsgi/issues/1540
Instead of running uwsgi as a webserver listening on a local port and then having Apache HTTP proxy all the incoming requests with mod_proxy. The normally recommended way of deploying uwsgi with Apache HTTPD is to use mod_proxy_uwsgi and set up a local socket file for uwsgi to listen on. Apache will send the requests using the uwsgi protocol over this local socket file. However, there are issues with doing this and using chunked-encoding.
You can work around these issues by configuring your apache proxy to buffer the chunked data and send the full content length to uwsgi. You do this by adding:
SetEnv proxy-sendcl 1
to the apache config file using mod_proxy_uwsgi. For more details on using mod_proxy_uwsgi see the official docs: http://uwsgi-docs.readthedocs.io/en/latest/Apache.html?highlight=mod_uwsgi_proxy#mod-proxy-uwsgi
mod_wsgi¶
This deployment method is not recommended for using Glance. The mod_wsgi
protocol does not support Transfer-Encoding: chunked and therefore makes it
unsuitable for use with Glance. However, you could theoretically deploy Glance
using mod_wsgi but it will fail on any requests that use a chunked transfer
encoding.
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