| Name |
Space |
Section |
Page |
Version |
Status |
Reviewed |
Author(s) |
| Production Deployment Using Apache, FastCGI and mod_rewrite, alternate version |
Pylons Cookbook |
Deployment |
Production Deployment Using Apache, FastCGI and mod_rewrite, alternate version |
1.0 |
Draft |
False |
 Graham Higgins |
Production Deployment Using Apache, FastCGI and mod_rewrite, an alternate version
Amended to provide walkthoughs for two distinct configurations:
- Apache.2.0.x: Apache version = 2.0.59, Python = 2.4, mod_fastcgi = mod_fastcgi-SNAP-0404142202
- Apache.2.2.x: Apache version = 2.2.4, Python = 2.5, mod_fcgid = 2.1
 | This should be considered a work in progress, feel free to add/extend as necessary. |
Organisation and bindings
Throughout the following, the Pylons app is called myapp, replace with your Pylons project name as appropriate.
This is based on existing, running installations of Apache+mods+Pylons: the Apache.2.0.x config on my CentOS 4.4-based technology lab server Bel-EPA
and the Apache.2.2.x config on an in-house development Ubuntu-based system. I've tried to screen out as much of my own guff as I can whilst still leaving some context for reference.
The assumption is that Pylons apps live in /var/www/pylons/ and that there is legacy dynamic non-Pylons content that is to be served directly via Apache. It is assumed that the legacy content lives in /var/www/htdocs.
In this scheme, requests are routed by default to Pylons via a catch-all RewriteRule. Requests for legacy content are enabled via explicit RewriteCond statements that act as a guard for legacy content requests, preventing them from reaching the catch-all and allowing Apache to serve them "normally".
Procedure
Create a cache directory
Apache.2.0.x
Create and set permissions of cache directory in /tmp so that the webserver has read/write permissions.
1
2 | % bash> sudo mkdir /tmp/fcgi_ipc
% bash> sudo chown webserver:webserver /tmp/fcgi_ipc
|
Apache.2.2.x
Create and set permissions of cache directories in /tmp so that the webserver has read/write permissions. Change"webserver:webserver" to match your server's user and group.
1
2
3 | % bash> sudo mkdir /tmp/fcgid_sock/
% bash> sudo touch /tmp/fcgid_shm
% bash> sudo chown webserver:webserver /tmp/fcgid*
|
Apache preliminaries
Apache.2.0.x
First, you'll need to ensure you have both mod_rewrite and mod_fastcgi enabled. mod_rewrite is part of the standard Apache distro and may be readily available, if not actually enabled (have a look at the LoadModule statements in your Apache's httpd.conf file).
However, mod_fastcgi is not part of the standard Apache distro and will probably need to be downloaded from the fastcgi website, compiled and installed into /etc/httpd/modules. Note: I used the mod_fastcgi-SNAP-0404142202 download.
Apache.2.2.x
You'll need to have mod_fscgid enabled, so you will need to download, compile and install the mod_fcgid module.
If you can meet these starting conditions, you're ready to go ...
Adjust Apache configuration
Apache.2.0.x
Add the following to the LoadModule statements in /etc/httpd/conf/httpd.conf (assuming they're not there already):
1
2 | LoadModule fastcgi_module modules/mod_fastcgi.so
LoadModule rewrite_module modules/mod_rewrite.so
|
 | I'm assuming a standard Apache setup here. If your module load path is different, just change the path as appropriate. |
And add the following Directive to the others in the same file (/etc/httpd/conf/httpd.conf):
1
2
3
4
5
6
7 | # [ Other directives ...]
<IfModule mod_fastcgi.c>
FastCgiIpcDir /tmp/fcgi_ipc/
AddHandler fastcgi-script .fcgi
</IfModule>
FastCgiExternalServer /var/www/pylons/myapp/myapp.fcgi -socket /var/www/pylons/myapp/myapp.socket
|
Set the following as the content of /etc/httpd/vhosts/myvhost.conf (changing or deleting the RewriteCond conditions as appropriate to your instance).
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57 | <VirtualHost MY.IPA.DDR.ESS:80>
ServerName myvhost.com
ServerAdmin admin@myvhost.com
DocumentRoot /var/www/htdocs
# [ More directives ]
RewriteEngine on
RewriteCond %{REQUEST_URI} !^favicon.ico$
RewriteCond %{REQUEST_URI} !^/robots.txt$
RewriteCond %{REQUEST_URI} !^/error/.*
RewriteCond %{REQUEST_URI} !^/icons/.*
RewriteCond %{REQUEST_URI} !^/codebase/.*
RewriteCond %{REQUEST_URI} !^/systems.html$
RewriteCond %{REQUEST_URI} !^/systems/.*
RewriteCond %{REQUEST_URI} !^/graphics/.*
RewriteRule ^(.*)$ /myapp.fcgi$1 [L]
<Location />
Options +ExecCGI
AddHandler fastcgi-script .fcgi
AllowOverride All
</Location>
DirectoryIndex myapp.fcgi
# Typical non-Pylons dynamic legacy content
ScriptAlias /mailman/ /usr/lib/mailman/cgi-bin/
<Directory /usr/lib/mailman/cgi-bin/>
AllowOverride None
Options ExecCGI
Order allow,deny
Allow from all
AddHandler python-cgi-script .py
</Directory>
# *NB* This next Directive is specific to my server and
# my use of mod_pyapache, it's included here merely as
# an example and to provide some context.
<Location /systems>
<IfModule mod_pyapache.c>
AddType application/x-httpd-cgi .py
AddHandler application/x-python-httpd-cgi .py
PythonPath /var/www/myapp/scripts
</IfModule>
</Location>
</VirtualHost>
<Directory /var/www/htdocs>
order allow,deny
allow from all
Options Indexes All FollowSymLinks ExecCGI
AllowOverride All
</Directory>
|
| As an example, I've left in an IfModule directive (commented with "*NB*") that on my system enables mod_pyapache to execute Python source files dynamically but you won't need it (mod_pyapache no longer has effective support, it's legacy content, as mentioned earlier). |
Apache.2.2.x
Add the following to the end of the list of LoadModule instructions in /etc/httpd/httpd.conf. (You can explicitly set the socket path and the shm area, otherwise the default is for them to be created automatically in the logs directory.)
1
2
3
4
5
6 | LoadModule fcgid_module modules/mod_fcgid.so
<IfModule mod_fcgid.c>
SocketPath /tmp/fcgid_sock/
AddHandler fcgid-script .fcgi
SharememPath /tmp/fcgid_shm
</IfModule>
|
Insert the following into the content of extra/httpd-vhost.conf (changing or deleting the RewriteCond conditions as appropriate to your instance).
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35 | <VirtualHost *:80>
ServerAdmin webmaster@myvhost.org
DocumentRoot /var/www/pylons/myapp
ServerName www.myvhost.org
# Other directives
# [ ... ]
RewriteEngine On
# RewriteLog logs/rewrite.log
# A few other Apache-handled paths
RewriteCond %{REQUEST_URI} !^/test/.*
RewriteCond %{REQUEST_URI} !^/error/.*
RewriteRule ^(.*)$ /myapp.fcgi$1 [L]
<Location />
Options Indexes FollowSymLinks ExecCGI Includes
Order allow,deny
Allow from all
AddHandler fcgid-script .fcgi
FCGIWrapper "/usr/bin/python2.5 /var/www/pylons/myapp/myapp.fcgi" .fcgi
</Location>
</VirtualHost>
<Directory /var/www/pylons>
order allow,deny
allow from all
Options Indexes All FollowSymLinks ExecCGI Includes
AllowOverride All
<Files ~ "^\.ht">
Order allow,deny
Deny from all
</Files>
</Directory>
|
Create a WSGI fcgi server
Create /var/www/pylons/myapp/myapp.fcgi with the following content:
1
2
3
4
5
6
7
8
9
10 | #!/usr/bin/env python
import logging
# Load the WSGI application from the config file
from paste.deploy import loadapp
wsgi_app = loadapp('config:/var/www/pylons/myapp/production.ini')
# Deploy it using FastCGI
if __name__ == '__main__':
from flup.server.fcgi import WSGIServer
WSGIServer(wsgi_app).run()
|
Mmmmm. Feel that power. Nearly done ...
Change your Pylons app's config to use PasteScript's flup_fcgi_thread
- Make the following change to /var/www/pylons/myapp/production.ini — I've expressed the changes in diff format for clarity:
Apache.2.0.x
1
2
3
4
5
6 | [server:main]
- use = egg:Paste#http
- host = 127.0.0.1
- port = 5000
+ use = egg:PasteScript#flup_fcgi_thread
+ socket = /var/www/pylons/myapp/myapp.socket
|
Apache.2.2.x
1
2
3
4
5 | [server:main]
- use = egg:Paste#http
- host = 127.0.0.1
- port = 5000
+ use = egg:PasteScript#flup_fcgi_thread
|
That's about it.
Tweaking
For Apache.2.0.x,I ended up having to make a softlink from the fcgi script to the document root ...
1 | % bash> sudo ln -s /var/www/pylons/myapp/myapp.fcgi /var/www/htdocs/
|
But this latter may be pure superstition, it took me a lot of faffing about to get this setup working and as soon as it was working, I sighed with relief and left it alone thereafter.
| If you need to start/restart your Pylons app, you must do that by starting / restarting the Apache webserver. |
Round-up
Where I am not trammelled by legacy content, I prefer to use mod_rewrite and ProxyPass / ProxyPassReverse to route all REQs to Pylons.
Feel free to add any comments or drop an email to gjh at bel-epa.com.
