Programming Jabber

Host Filter

For the host filter, we have an empty tag:

<host/>

specified, which signifies that this xdb component instance will answer data storage and retrieval requests for all hosts. This, in turn, means that all data to be stored server-side will be stored using the same data storage mechanism, in this case xdb_file, which is a simple lowest common denominator storage system based upon directories containing files with XML content; these files are at a ratio of one per JID, plus “global” files where storage of data not tied to a JID is required. An example of this would be JUD’s usage of xdb (and implicitly xdb_file in our configuration); a file called global.xml is used to store the user directory information that JUD manages.

If you want to use separate data storage mechanisms for your different virtual servers, you can define more than one xdb instance in your jabber.xml configuration and have the first use one storage system—say, xdb_file—and the second use another—say, a Relational Database Management System (RDBMS)-based system.^[5]

You may also want to store data from different virtual hosts in different places on your system; by specifying more than one xdb instance, even if all of them use the same storage mechanism, you can specify a different spool directory in the configuration for each one.

As well as a host filter, there is another filter possible for xdb components. This is the namespace filter, represented by the <ns/> tag.

Every xdb storage and retrieval ...