[JDEV] server components

[David Waite]

Bill Marcum wrote:

>Can anyone point me towards more in-depth documentation for developing
>server components?  I've looked at all the documentation supplied for JECL
>and Jabberbeans, and read the 'Programming Jabber' book (which was very
>good), but I have yet to find anything that discusses the component -
>component protocol, (i.e., the syntax of the Route message).  
>
Component to component protocol is not standardized, and left to be 
server implementation specific. As you delve deeper into the component 
protocol, you quickly suspect it was not fully designed, but left to 
evolve around features needed for the specific implementation.

As far as what most server implementations have exposed (that I have 
experience with):

Route messages are (currently) used almost exclusively for 
communications between a client connection manager and the session 
manager. The purpose of the route tag is mostly to overload the delivery 
information on an inner packet, since a connection manager proxies 
packets to the session manager independant of where they are actually 
directed to (or if they even have the 'to' and 'from' attributes set). 
Routes also have types, which are used in the connection manager to 
session manager protocol (I believe valid types are auth, session, and 
error)

Xdb messages are nearly impossible to store in anything other than a 
filesystem, does not readily allow for partial updates of data, and most 
of the Xdb storage mechanisms are based around namespaces which share 
the name but do not have the same format as the client-accessable 
namespaces. Xdb has never really been documented because it has never 
really been anyone's favorite solution; it gets the job done until 
something better comes along. It is used heavily by the session manager, 
and not really used that much by most third-party components. It has an 
orthogonal delivery tree; sending an xdb request to a domain name does 
not neccessarily go to the same component as any other type of request.

Log messages are mixed data sent out into the ether. Filtering is done 
based on the severity (type) and originating address.

So other than the handshake tag (which you should be happily not exposed 
to with either of the libraries mentioned above), most components I have 
had experience with:
- ignore route tags, unless they are communicating with something that 
expects route tags
- send out normal messages as if they were clients, except that the 'to' 
and 'from' addresses must always be explicitly set.
- try to use Xdb as little as possible, mostly to retrieve configuration 
information from the server for the particular component. (<xdb 
type='get' to='config at -internal' from='your-component' id='unique' 
ns='namespace:of:configuration:block'/> )

-David Waite