# WSGIScriptAliasMatch

Description: | Maps a URL to a filesystem location and designates the target as a WSGI script.
Syntax: | `WSGIScriptAliasMatch` regex file-path|directory-path `[` options `]`
Context: | server config, virtual host

This directive is similar to the WSGIScriptAlias directive, but makes use of regular expressions, instead of simple prefix matching. The supplied regular expression is matched against the URL-path, and if it matches, the server will substitute any parenthesized matches into the given string and use it as a filename.

For example, to map a URL to scripts contained within a directory where the script files use the `.wsgi` extension, but it is desired that the extension not appear in the URL, use:

    WSGIScriptAliasMatch ^/wsgi-scripts/([^/]+) /web/wsgi-scripts/$1.wsgi

Note that you should only use WSGIScriptAliasMatch if you know what you are doing. In most cases you should be using WSGIScriptAlias instead. If you use WSGIScriptAliasMatch and don’t do things the correct way, then you risk modifying the value of SCRIPT_NAME as passed to the WSGI application and this can stuff things up badly causing URL mapping to not work correctly within the WSGI application or stuff up reconstruction of the full URL when doing redirects. This is because the substitution of the matched sub pattern from the left hand side back into the right hand side is often critical.

If you think you need to use WSGIScriptAliasMatch, you probably don’t really. If you really really think you need it, then check on the mod_wsgi mailing list about how to use it properly.

Options which can be supplied to the `WSGIScriptAlias` directive are:

process-group=name

  Defines which process group the WSGI application will be executed in. All WSGI applications within the same process group will execute within the context of the same group of daemon processes.

  If the name is set to be `%{GLOBAL}` the process group name will be set to the empty string. Any WSGI applications in the global process group will always be executed within the context of the standard Apache child processes. Such WSGI applications will incur the least runtime overhead, however, they will share the same process space with other Apache modules such as PHP, as well as the process being used to serve up static file content. Running WSGI applications within the standard Apache child processes will also mean the application will run as the user that Apache would normally run as.

application-group=name

  Defines which application group a WSGI application or set of WSGI applications belongs to. All WSGI applications within the same application group will execute within the context of the same Python sub interpreter of the process handling the request.

  If the name is set to be `%{GLOBAL}` the application group will be set to the empty string. Any WSGI applications in the global application group will always be executed within the context of the first interpreter created by Python when it is initialised, of the process handling the request. Forcing a WSGI application to run within the first interpreter can be necessary when a third party C extension module for Python has used the simplified threading API for manipulation of the Python GIL and thus will not run correctly within any additional sub interpreters created by Python.

If both `process-group` and `application-group` options are set, and the WSGI script file doesn’t include substiutions values to be supplied from the matched URL pattern, the WSGI script file will be pre-loaded when the process it is to run in is started, rather than being lazily loaded on the first request.