uccwiki

Contents

  1. Why Use mod_python
  2. Basic configuring
    1. Install mod_python
    2. Set up a wiki instance
    3. Edit `wikiconfig.py`
    4. Changes to Apache `httpd.conf`
  3. Solving problems for non-root-mounted wikis
  4. Configuring root wiki
  5. Older mod_python versions
    1. Use a wrapper script
    2. Fix mod_python
  6. Troubleshooting

Why Use mod_python

mod_python embeds the python interpreter into the apache server. This saves initialization time and the need of forking cgi scripts. It doesn't have the ability to run as different users. It will always run as the main apache user and group. Be sure that your wiki data files are accessible and writable by your apache server.

<!> The basic configuration is suitable for mod_python 3.1.3 and later. If you use older version, see the section "Older mod_python versions"

<!> mod_python will cause your apache processes to increase their memory requirements considerably - especially as apache runs many separate processes which will each need to have their own copy of the python code and data in the process memory space. You may find that FastCGI, as detailed in HelpOnInstalling/FastCgi is rather more efficient in this respect.

Basic configuring

  1. Install mod_python
  2. Set up a wiki instance

  3. Edit wikiconfig.py

  4. Changes to Apache httpd.conf

  5. Restart Apache

The sample configurations below are for a wiki instance called mywiki installed in a directory /var/www/moin/mywiki with the main MoinMoin installation installed in python's default site library path. The wiki appears as URL /mywiki under the server - ie http://my.ser.ver/mywiki. You will need to change these to reflect your installation.

Install mod_python

Most people will just add a mod_python package to their current operating system installation. If you are building from source then you should consult the mod_python documentation.

The mod_python installation should have added some lines to the Apache configuration file - either in the file itself or in an included configuration file (for example on Red Hat or Fedora linux the mod_python configuration is in /etc/httpd/conf.d/python.conf).

Make sure you have this line in httpd.conf or mod_python will not work: 

LoadModule python_module modules/mod_python.so

After this restart Apache and make sure that it starts successfully, and that the error log has a line similar to this:- 

[Sat Jan 01 15:40:49 2005] [notice] mod_python: Creating 4 session mutexes based on 150 max processes and 0 max threads.

You may need to change some environment variables on (eg) FreeBSD - this is detailed in the port installation message.

Set up a wiki instance

This is done as shown in WikiInstanceCreation. Its recommended to first configure the wiki with cgi and check that it works, then change the configuratin to use mod_python. This allows you be sure that any problems are in the mod_python transition rather than the basic MoinMoin installation.

  1. Copy moin.cgi into your wiki directory

  2. Configure httpd.conf as cgi first (the shown Alias is for moin version 1.6.0): 

    • Alias /moin_static160/ "/usr/share/moin/htdocs/"
ScriptAlias /mywiki "/var/www/moin/mywiki/moin.cgi"

Restart Apache and make test that your wiki works.

Edit `wikiconfig.py`

Make sure you use only absolute paths - relative paths will not work! 

data_dir = '/var/www/moin/mywiki/data/'
data_underlay_dir = '/var/www/moin/mywiki/underlay/'

If you do not want to use absolute paths, you can use Python's os module to construct the relative paths: {{{import os data_dir = os.path.join(os.path.dirname(file), 'data/') data_underlay_dir = os.path.join(os.path.dirname(file), 'underlay/') }}}

Test that the wiki works after this change.

Changes to Apache `httpd.conf`

After your wiki is running as cgi script, convert it to run with mod_python.

If you run your wiki as cgi as we recommended before, remove or comment the ScriptAlias directive: 

#ScriptAlias /mywiki "/var/www/moin/mywiki/moin.cgi"

Add a Location directive: 

<Location /mywiki>
    SetHandler python-program
    # Add the path of your wiki directory
    PythonPath "['/var/www/moin/mywiki'] + sys.path"
    PythonHandler MoinMoin.request.request_modpython::Request.run
</Location>

If you have multiple MoinMoin instances then add one location directive for each one (changing the paths as appropriate) and add a line with the directive PythonInterpreter mywiki to each Location section. With this directive different subinterpreters with completely separate namespaces will be used for each wiki (see here for details).

If you did not install MoinMoin in the default location, you will have to add the path to MoinMoin to the system path: 

    PythonPath "['/var/www/moin/mywiki', '/prefix/lib/python2.x/site-packages'] + sys.path"

Restart Apache - everything should now work correctly.

Solving problems for non-root-mounted wikis

On some installations, mod_python hands MoinMoin incorrect script_name and path_info. It usually happens when using the Apache Location directive, with a wiki in an arbitary path: 

<Location /farm/mywiki>
    ...
</Location>

This will not work, because its not clear what is the script name, since with location setup, there is no real script.

To solve this problem, use a PythonOption directive: 

<Location /farm/mywiki>
    # Location value must match the Apache Location value!
    PythonOption Location /farm/mywiki
    ...
</Location>

Configuring root wiki

You may wish to have your wiki appearing at the root of your webserver - for example so that http://wiki.example.com/ will map to your wiki rather than having to use http://wiki.example.com/mywiki/. This requires a slightly different form of configuration using mod_rewrite - this is a standard module of recent Apache distributions, and is often enabled by default.

You need to set up your wiki instance as described above, and also copy moinmodpy.py from the Moin installation directory to the wiki instance directory (/var/www/moin/mywiki in these examples).

The Apache configuration needs mod_rewrite enabled - so the line 

LoadModule rewrite_module modules/mod_rewrite.so

should appear in the first part of the httpd.conf configuration file.

The wiki and virtual host configuration should look like this (Alias is for moin version 1.6.0):- 

<VirtualHost *:80>
  ServerAdmin [email protected]
  DocumentRoot /var/www/html
  ServerName wiki.example.com
  Alias /moin_static160/ "/usr/share/moin/htdocs/"

  # Rewrite urls
  RewriteEngine On
  RewriteLogLevel 0
  # map /wiki static files to Moin htdocs
  RewriteRule ^/moin_static160/(.*)$ /usr/share/moin/htdocs/$1 [last]
  RewriteRule ^/robots.txt$ /usr/share/moin/htdocs/robots.txt [last]
  RewriteRule ^/favicon.ico$ /usr/share/moin/htdocs/favicon.ico [last]
  # map everything else to server script
  RewriteRule ^(.*)$ /var/www/moin/mywiki/moinmodpy.py$1

  <Directory "/var/www/moin/testwiki">
    # Modpy stuff
    AddHandler python-program .py
    # Add the path to the wiki directory, where
    # moinmodpy.py and wikiconfig.py are located.
    PythonPath "['/var/www/moin/mywiki'] + sys.path"
    PythonHandler MoinMoin.request.request_modpython::Request.run
  </Directory>
</VirtualHost>

Apache should be restarted, and the FrontPage of mywiki should now appear at http://wiki.example.com/.

Other ways of handling root level wikis with Apache are detailed in the appropriately named HelpOnConfiguration/ApacheVoodoo.

Older mod_python versions

mod_python versions 2.7.10, 3.0.4 and 3.1.2b have a bug in apache.resolve_object. This bug was reported to the mod_python maintainers and has been fixed in the 3.1.3 release. The best fix for this is to update to the current release. However if you are unable to do this there are 2 possible solutions:

Use a wrapper script

MoinMoin come with a moinmodpy.py wrapper script, and this could be used by changing the PythonPath and PythonHandler directives as shown in the moinmodpy.htaccess file.

Fix mod_python

mod_python has a small resolver bug in versions 2.7.10, 3.0.4 and 3.1.2b. The method resolve_object in mod_python/apache.py checks the wrong object, and so the lookup for RequestModPy.run fails.

To fix it you need to change the method resolve_object (around line 551 for mod_python 3.1.2b) from 

        if silent and not hasattr(module, obj_str):
            return None

to 

        if silent and not hasattr(obj, obj_str):
            return None

Troubleshooting

Page access gives apache error::