Module types

Almost all functionality in Roxen exists in different modules. Each module has a distinct task. Several modules can cooperate in the creation of a page that will be sent to the user.

What task a module has is determined by its type. More complex modules can be of several types and thus perform more than one task.

Authentication

modules handles authentication of, and information about, users. The most common type of Authentication modules are modules that import the user database from the operating system Roxen is running on. The information provided by an Authentication module is often used by other modules, such as the User Filesystem module. It is only possible to have one Authentication module per virtual server.

Directory

modules deals with directory listings and index files. If the requested resource is a directory, a directory module either tries to find a suitable index file or to create a page with a directory listing. It is necessary to have a Directory module in order to get index files, such as index.html, to work. It is only possible to have one Directory module per virtual server.

Extension

modules handle virtual files, with a certain extension. Each time a request is made to a URL ending with that extension, the extension module will be called. There are no Extension modules in the Roxen distribution.

File extension

modules deal with files with a particular extension, such as .html or .gif. The file in question must first have been delivered by a Location module. The ISMAP image-maps module is a File extension module.

Filter

modules filter data that is just about ready to be sent to the browser. This can be used, as the name suggests, to filter out parts of the data that should not be sent.

First try

modules are called before all other module types, except for Authentication modules. This is used to catch certain types of requests, for instance, to block access to your server from certain IP addresses or to send a warning message to the administrator if the server is accessed outside working hours.

Last try

modules are called when all other modules have failed to produce anything at all from the request. A Last try module could give an elaborate error message.

Location

modules deal with file systems, fetching files and directories. A Location module could work with a real file system or a purely virtual one. For example, it could fetch files from a database instead of a file system.

Most web applications are also implemented as Location modules. Pike and CGI scripts work much like a Location module.

Each Location module is mounted somewhere on Roxen's virtual filesystem. Several Location modules may be mounted on overlapping mount points. If the module have the same priority, the module with the longest mount point will be called first. Thus a module mounted on /schedule/server/ will be called before a module mounted on /schedule/.

Logging

modules perform some logging of information about the requests. This could be done by writing log files or in some other way. The Logging module decides whether the request has been logged properly or whether the request should also be logged by the built-in log system.

The Main parser

module handles all RXML parsing. The module handles the interface to Parser modules. A Main parser must be installed for any RXML parsing to take place.

The Main parser must somehow get pages to parse. This is usually done by making the module a File extension module as well. Thus all files with a certain extension will be parsed.

There can only be one Main parser module in each virtual server. The RXML 2.0 parser module is the only Main parser module included in the Roxen distribution.

Parser

modules define one or more RXML tag. This is one of the most common user created modules. Making new tags available is an excellent way of making functionality available to the users of the server.

The Parser modules are called upon by a Main parser module. If no Main parser module is installed in the virtual server, no RXML parsing will take place.

Protocol

modules set the protocols the virtual servers can use. It handles a network connection to a port and then sends the request on to Roxen. HTTP, HTTPS and FTP are examples of protocol modules included in the Roxen distribution.

Provider

modules provides other modules with different services and extra functionality. They do not in themselves have anything to do with the normal request handling.

Proxy

Types

module sets the content type of a file, if it hasn't already been done by the preceding modules. This is usually done by looking up the Mime type for a certain file extension in a database. There can only be one Types module in each virtual server. The Content Types is the only Types module in the Roxen distribution.

URL

modules receives one URL and returns another. In other words, the URL modules transform requests into other requests. This is useful when a web page is published under several names, or when a web page has moved.