swift/doc/source/apache_deployment_guide.rst

Apache Deployment Guide

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. Additionlly, 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

First, change the User and Group IDs of Apache2 to be those used by Swift. For example in /etc/apache2/envvars use:

export APACHE_RUN_USER=swift
export APACHE_RUN_GROUP=swift

Create a directory for the Apache2 wsgi files:

sudo mkdir /var/www/swift

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

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

from swift.common.wsgi import init_request_processor
application, conf, logger, log_name = \
    init_request_processor('/etc/swift/proxy-server.conf','proxy-server')

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

from swift.common.wsgi import init_request_processor
application, conf, logger, log_name = \
    init_request_processor('/etc/swift/account-server.conf',
                           'account-server')

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

from swift.common.wsgi import init_request_processor
application, conf, logger, log_name = \
    init_request_processor('/etc/swift/container-server.conf',
                          'container-server')

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

from swift.common.wsgi import 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
NameVirtualHost *:8080
Listen 8080
<VirtualHost *:8080>
    ServerName proxy-server
    LimitRequestBody 5368709122
    WSGIDaemonProcess proxy-server processes=5 threads=1
    WSGIProcessGroup proxy-server
    WSGIScriptAlias / /var/www/swift/proxy-server.wsgi
    LimitRequestFields 200
    ErrorLog /var/log/apache2/proxy-server
    LogLevel debug
    CustomLog /var/log/apache2/proxy.log combined
</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
NameVirtualHost *:6000
Listen 6000
<VirtualHost *:6000>
    ServerName object-server
    WSGIDaemonProcess object-server processes=5 threads=1
    WSGIProcessGroup object-server
    WSGIScriptAlias / /var/www/swift/object-server.wsgi
    LimitRequestFields 200
    ErrorLog /var/log/apache2/object-server
    LogLevel debug
    CustomLog /var/log/apache2/access.log combined
</VirtualHost>

#Container Service
NameVirtualHost *:6001
Listen 6001
<VirtualHost *:6001>
    ServerName container-server
    WSGIDaemonProcess container-server processes=5 threads=1
    WSGIProcessGroup container-server
    WSGIScriptAlias / /var/www/swift/container-server.wsgi
    LimitRequestFields 200
    ErrorLog /var/log/apache2/container-server
    LogLevel debug
    CustomLog /var/log/apache2/access.log combined
</VirtualHost>

#Account Service
NameVirtualHost *:6002
Listen 6002
<VirtualHost *:6002>
    ServerName account-server
    WSGIDaemonProcess account-server processes=5 threads=1
    WSGIProcessGroup account-server
    WSGIScriptAlias / /var/www/swift/account-server.wsgi
    LimitRequestFields 200
    ErrorLog /var/log/apache2/account-server
    LogLevel debug
    CustomLog /var/log/apache2/access.log combined
</VirtualHost>

Next stop the Apache2 and start it again (apache2ctl restart is not enough):

apache2ctl stop
apache2ctl start

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