Web Front End Considerations¶

Swift can be configured to work both using an integral web front-end and using a full-fledged Web Server such as the Apache2 (HTTPD) web server. The integral web front-end is a wsgi mini "Web Server" which opens up its own socket and serves http requests directly. The incoming requests accepted by the integral web front-end are then forwarded to a wsgi application (the core swift) for further handling, possibly via wsgi middleware sub-components.

client<—->’integral web front-end’<—->middleware<—->’core swift’

To gain full advantage of Apache2, Swift can alternatively be configured to work as a request processor of the Apache2 server. This alternative deployment scenario uses mod_wsgi of Apache2 to forward requests to the swift wsgi application and middleware.

client<—->’Apache2 with mod_wsgi’<—–>middleware<—->’core swift’

The integral web front-end offers simplicity and requires minimal configuration. It is also the web front-end most commonly used with Swift. Additionally, the integral web front-end includes support for receiving chunked transfer encoding from a client, presently not supported by Apache2 in the operation mode described here.

The use of Apache2 offers new ways to extend Swift and integrate it with existing authentication, administration and control systems. A single Apache2 server can serve as the web front end of any number of swift servers residing on a swift node. For example when a storage node offers account, container and object services, a single Apache2 server can serve as the web front end of all three services.

The apache variant described here was tested as part of an IBM research work. It was found that following tuning, the Apache2 offer generally equivalent performance to that offered by the integral web front-end. Alternative to Apache2, other web servers may be used, but were never tested.

Apache2 Setup¶

Both Apache2 and mod-wsgi needs to be installed on the system. Ubuntu comes with Apache2 installed. Install mod-wsgi using:

sudo apt-get install libapache2-mod-wsgi

Create a directory for the Apache2 wsgi files:

sudo mkdir /srv/www/swift

Create a working directory for the wsgi processes:

sudo mkdir -m 2770 /var/lib/swift
sudo chown swift:swift /var/lib/swift

Create a file for each service under /srv/www/swift.

For a proxy service create /srv/www/swift/proxy-server.wsgi:

fromswift.common.wsgiimport init_request_processor
application, conf, logger, log_name = \
 init_request_processor('/etc/swift/proxy-server.conf','proxy-server')

For an account service create /srv/www/swift/account-server.wsgi:

fromswift.common.wsgiimport init_request_processor
application, conf, logger, log_name = \
 init_request_processor('/etc/swift/account-server.conf',
 'account-server')

For an container service create /srv/www/swift/container-server.wsgi:

fromswift.common.wsgiimport init_request_processor
application, conf, logger, log_name = \
 init_request_processor('/etc/swift/container-server.conf',
 'container-server')

For an object service create /srv/www/swift/object-server.wsgi:

fromswift.common.wsgiimport init_request_processor
application, conf, logger, log_name = \
 init_request_processor('/etc/swift/object-server.conf',
 'object-server')

Create a /etc/apache2/conf.d/swift_wsgi.conf configuration file that will define a port and Virtual Host per each local service. For example an Apache2 serving as a web front end of a proxy service:

# Proxy
Listen 8080
<VirtualHost *:8080>
 ServerName proxy-server
 LimitRequestBody 5368709122
 LimitRequestFields 200
 WSGIDaemonProcess proxy-server processes=5 threads=1 user=swift group=swift display-name=%{GROUP}
 WSGIProcessGroup proxy-server
 WSGIScriptAlias / /srv/www/swift/proxy-server.wsgi
 LogLevel debug
 CustomLog /var/log/apache2/proxy.log combined
 ErrorLog /var/log/apache2/proxy-server
</VirtualHost>

Notice that when using Apache the limit on the maximal object size should be imposed by Apache using the LimitRequestBody rather by the swift proxy. Note also that the LimitRequestBody should indicate the same value as indicated by max_file_size located in both /etc/swift/swift.conf and in /etc/swift/test.conf. The Swift default value for max_file_size (when not present) is 5368709122. For example an Apache2 serving as a web front end of a storage node:

# Object Service
Listen 6200
<VirtualHost *:6200>
 ServerName object-server
 LimitRequestFields 200
 WSGIDaemonProcess object-server processes=5 threads=1 user=swift group=swift display-name=%{GROUP}
 WSGIProcessGroup object-server
 WSGIScriptAlias / /srv/www/swift/object-server.wsgi
 LogLevel debug
 CustomLog /var/log/apache2/access.log combined
 ErrorLog /var/log/apache2/object-server
</VirtualHost>
# Container Service
Listen 6201
<VirtualHost *:6201>
 ServerName container-server
 LimitRequestFields 200
 WSGIDaemonProcess container-server processes=5 threads=1 user=swift group=swift display-name=%{GROUP}
 WSGIProcessGroup container-server
 WSGIScriptAlias / /srv/www/swift/container-server.wsgi
 LogLevel debug
 CustomLog /var/log/apache2/access.log combined
 ErrorLog /var/log/apache2/container-server
</VirtualHost>
# Account Service
Listen 6202
<VirtualHost *:6202>
 ServerName account-server
 LimitRequestFields 200
 WSGIDaemonProcess account-server processes=5 threads=1 user=swift group=swift display-name=%{GROUP}
 WSGIProcessGroup account-server
 WSGIScriptAlias / /srv/www/swift/account-server.wsgi
 LogLevel debug
 CustomLog /var/log/apache2/access.log combined
 ErrorLog /var/log/apache2/account-server
</VirtualHost>

Enable the newly configured Virtual Hosts:

a2ensite swift_wsgi.conf

Next, stop, test and start Apache2 again:

# stop it
systemctl stop apache2.service
# test the configuration
apache2ctl -t
# start it if the test succeeds
systemctl start apache2.service

Edit the tests config file and add:

web_front_end = apache2
normalized_urls = True

Also check to see that the file includes max_file_size of the same value as used for the LimitRequestBody in the apache config file above.

We are done. You may run functional tests to test - e.g.:

cd ~swift/swift
./.functests