Programming Jabber

Delivery trees

The phrase delivery tree is often used in Jabber terminology to signify a component or components that handle certain types of packet. The path a packet makes as it descends the collection of decision branches that guide it to the component or components that will handle it can be described in terms of such a delivery tree. For example, an xdb component type is sometimes referred to as an xdb Delivery Tree. Considering the division of components into different types that handle different packet types is perhaps easier to visualize as a tree, as shown in Figure 4-2.

Figure 4-2. The Jabber delivery tree

The Jabber Delivery Tree shows which component types can handle what sorts of packets in the Jabber world. Furthermore, the log packets are distinguished by their log type (error, notice, or record), the xdb packets are distinguished by namespace, and all the packets are distinguished by hostname. This means, for example, multiple xdb components can be organized, and configured, to handle packets qualified by different namespaces, and intended for different hosts, while different log components can be set up to handle different log packet types. We’ll see examples of this configuration later in this chapter.