Although the current preferred setup for running Django is Apache with
mod_wsgi
, many people use shared hosting, on
which protocols such as FastCGI, SCGI or AJP are the only viable options. In
some setups, these protocols may provide better performance than mod_wsgi.

Note

This document primarily focuses on FastCGI. Other protocols, such as SCGI
and AJP, are also supported, through the flup Python package. See the
Protocols section below for specifics about SCGI and AJP.

Essentially, FastCGI is an efficient way of letting an external application
serve pages to a Web server. The Web server delegates the incoming Web requests
(via a socket) to FastCGI, which executes the code and passes the response back
to the Web server, which, in turn, passes it back to the client’s Web browser.

Like mod_python, FastCGI allows code to stay in memory, allowing requests to be
served with no startup time. Unlike mod_python (or mod_perl), a FastCGI
process doesn’t run inside the Web server process, but in a separate,
persistent process.

Why run code in a separate process?

The traditional mod_* arrangements in Apache embed various scripting
languages (most notably PHP, Python and Perl) inside the process space of
your Web server. Although this lowers startup time – because code doesn’t
have to be read off disk for every request – it comes at the cost of
memory use. For mod_python, for example, every Apache process gets its own
Python interpreter, which uses up a considerable amount of RAM.

Due to the nature of FastCGI, it’s even possible to have processes that run
under a different user account than the Web server process. That’s a nice
security benefit on shared systems, because it means you can secure your
code from other users.

Prerequisite: flup

Before you can start using FastCGI with Django, you’ll need to install flup, a
Python library for dealing with FastCGI. Version 0.5 or newer should work fine.

Starting your FastCGI server

FastCGI operates on a client-server model, and in most cases you’ll be starting
the FastCGI process on your own. Your Web server (be it Apache, lighttpd, or
otherwise) only contacts your Django-FastCGI process when the server needs a
dynamic page to be loaded. Because the daemon is already running with the code
in memory, it’s able to serve the response very quickly.

Note

If you’re on a shared hosting system, you’ll probably be forced to use
Web server-managed FastCGI processes. See the section below on running
Django with Web server-managed processes for more information.

A Web server can connect to a FastCGI server in one of two ways: It can use
either a Unix domain socket (a “named pipe” on Win32 systems), or it can use a
TCP socket. What you choose is a manner of preference; a TCP socket is usually
easier due to permissions issues.

To start your server, first change into the directory of your project (wherever
your manage.py is), and then run the
runfcgi command:

If you specify help as the only option after runfcgi, it’ll
display a list of all the available options.

You’ll need to specify either a socket, a protocol or both host and
port. Then, when you set up your Web server, you’ll just need to point it at
the host/port or socket you specified when starting the FastCGI server. See the
examples, below.

Protocols

Django supports all the protocols that flup does, namely fastcgi, SCGI and
AJP1.3 (the Apache JServ Protocol, version 1.3). Select your preferred
protocol by using the protocol= option with ./manage.py
runfcgi
— where may be one of: fcgi (the default),
scgi or ajp. For example:

Examples

Running a threaded server on a TCP port:

Running a preforked server on a Unix domain socket:

Run without daemonizing (backgrounding) the process (good for debugging):

Stopping the FastCGI daemon

If you have the process running in the foreground, it’s easy enough to stop it:
Simply hitting Ctrl-C will stop and quit the FastCGI server. However, when
you’re dealing with background processes, you’ll need to resort to the Unix
kill command.

If you specify the pidfile option to runfcgi, you can kill the
running FastCGI daemon like this:

…where $PIDFILE is the pidfile you specified.

To easily restart your FastCGI daemon on Unix, try this small shell script:

Apache setup

To use Django with Apache and FastCGI, you’ll need Apache installed and
configured, with mod_fastcgi installed and enabled. Consult the Apache
documentation for instructions.

Once you’ve got that set up, point Apache at your Django FastCGI instance by
editing the httpd.conf (Apache configuration) file. You’ll need to do two
things:

  • Use the FastCGIExternalServer directive to specify the location of
    your FastCGI server.
  • Use mod_rewrite to point URLs at FastCGI as appropriate.

Specifying the location of the FastCGI server

The FastCGIExternalServer directive tells Apache how to find your FastCGI
server. As the FastCGIExternalServer docs explain, you can specify either a
socket or a host. Here are examples of both:

In either case, the file /home/user/public_html/mysite.fcgi doesn’t
actually have to exist. It’s just a URL used by the Web server internally — a
hook for signifying which requests at a URL should be handled by FastCGI. (More
on this in the next section.)

Using mod_rewrite to point URLs at FastCGI

The second step is telling Apache to use FastCGI for URLs that match a certain
pattern. To do this, use the mod_rewrite module and rewrite URLs to
mysite.fcgi (or whatever you specified in the FastCGIExternalServer
directive, as explained in the previous section).

In this example, we tell Apache to use FastCGI to handle any request that
doesn’t represent a file on the filesystem and doesn’t start with /media/.
This is probably the most common case, if you’re using Django’s admin site:

Django will automatically use the pre-rewrite version of the URL when
constructing URLs with the {% url %} template tag (and similar methods).

lighttpd setup

lighttpd is a lightweight Web server commonly used for serving static files. It
supports FastCGI natively and, thus, is a good choice for serving both static
and dynamic pages, if your site doesn’t have any Apache-specific needs.

Make sure mod_fastcgi is in your modules list, somewhere after
mod_rewrite and mod_access, but not after mod_accesslog. You’ll
probably want mod_alias as well, for serving admin media.

Add the following to your lighttpd config file:

Running multiple Django sites on one lighttpd

lighttpd lets you use “conditional configuration” to allow configuration to be
customized per host. To specify multiple FastCGI sites, just add a conditional
block around your FastCGI config for each site:

You can also run multiple Django installations on the same site simply by
specifying multiple entries in the fastcgi.server directive. Add one
FastCGI host for each.

Cherokee setup

Cherokee is a very fast, flexible and easy to configure Web Server. It
supports the widespread technologies nowadays: FastCGI, SCGI, PHP, CGI, SSI,
TLS and SSL encrypted connections, Virtual hosts, Authentication, on the fly
encoding, Load Balancing, Apache compatible log files, Data Base Balancer,
Reverse HTTP Proxy and much more.

The Cherokee project provides a documentation to setting up Django with Cherokee.

Running Django on a shared-hosting provider with Apache

Many shared-hosting providers don’t allow you to run your own server daemons or
edit the httpd.conf file. In these cases, it’s still possible to run Django
using Web server-spawned processes.

Note

If you’re using Web server-spawned processes, as explained in this section,
there’s no need for you to start the FastCGI server on your own. Apache
will spawn a number of processes, scaling as it needs to.

In your Web root directory, add this to a file named .htaccess:

Then, create a small script that tells Apache how to spawn your FastCGI
program. Create a file mysite.fcgi and place it in your Web directory, and
be sure to make it executable:

Restarting the spawned server

If you change any Python code on your site, you’ll need to tell FastCGI the
code has changed. But there’s no need to restart Apache in this case. Rather,
just reupload mysite.fcgi, or edit the file, so that the timestamp on the
file will change. When Apache sees the file has been updated, it will restart
your Django application for you.

If you have access to a command shell on a Unix system, you can accomplish this
easily by using the touch command:

Serving admin media files

Regardless of the server and configuration you eventually decide to use, you
will also need to give some thought to how to serve the admin media files. The
advice given in the modpython documentation
is also applicable in the setups detailed above.

Forcing the URL prefix to a particular value

Because many of these fastcgi-based solutions require rewriting the URL at
some point inside the webserver, the path information that Django sees may not
resemble the original URL that was passed in. This is a problem if the Django
application is being served from under a particular prefix and you want your
URLs from the {% url %} tag to look like the prefix, rather than the
rewritten version, which might contain, for example, mysite.fcgi.

Django makes a good attempt to work out what the real script name prefix
should be. In particular, if the webserver sets the SCRIPT_URL (specific
to Apache’s mod_rewrite), or REDIRECT_URL (set by a few servers, including
Apache + mod_rewrite in some situations), Django will work out the original
prefix automatically.

In the cases where Django cannot work out the prefix correctly and where you
want the original value to be used in URLs, you can set the
FORCE_SCRIPT_NAME setting in your main settings file. This sets the
script name uniformly for every URL served via that settings file. Thus you’ll
need to use different settings files if you want different sets of URLs to
have different script names in this case, but that is a rare situation.

As an example of how to use it, if your Django configuration is serving all of
the URLs under '/' and you wanted to use this setting, you would set
FORCE_SCRIPT_NAME = '' in your settings file.

Questions/Feedback

Having trouble? We’d like to help!

原帖地址: http://docs.djangoproject.com/en/dev/howto/deployment/fastcgi/

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