[jdev] mirroring many presence servers
Jonathan Dickinson
chayce.za at gmail.com
Thu Aug 16 09:07:36 CDT 2007
Hey Koder,
First take a look at <http://www.xmpp.org/extensions/xep-0163.html>.
"There is no need for multiple publishers to a PEP service, since by
definition the service generates information associated with only one
entity. The owner-publisher for every node is the bare JID of the
account owner."
From that it is safe to assume that a server can not subscribe via
PubSub. Edit: According to Section 10 it can, but servers/clients may
still break, best not to try.
Your server will have a hard time keeping track of all of the
information, but I will outline how it could be possible. Two
corporations/servers: benvolio (your client), juliet (your client's
contact), montague.net (your client's server, a.k.a. your server),
capulet.com (juliet's server). By the end of this you will see that it
is, unfortunately, not possible.
Firstly, as per the XEP, the Juliet creates the node. That is of no
interest to your users, unless the subscription has initial data (in
which case their server should forward it anyway).
Second, Juliet updates that data. Benvolio will receive a presence
notification via montague.net. It is at this point that montague.net
should interpret the data and store it.
<message from='juliet at capulet.com'
to='benvolio at montague.net'
type='headline'
id='foo'>
<event xmlns='http://jabber.org/protocol/pubsub#event'>
<items node='http://jabber.org/protocol/tune'>
<item>
[...]
</item>
</items>
</event>
</message>
Montague.net can now use this opportunity to store the subscription
information about juliet at capulet.com. There will be many 'items'
elements and many 'item' elements per 'items' element, you will have to
decide how to store that in your database (you could piggy-back off the
exact same table that your clients use).
Third, Benvolio logs off and on again. First thing his client does is to
send his presence.
<presence from='benvolio at montague.net'>
<c xmlns='http://jabber.org/protocol/caps'
node='http://www.chatopus.com/ec'
ver='2.1'
ext='foobar pres+'/>
</presence>
Montague will now forward that to all his subscriptions (which is
important, you CAN'T stop this message, otherwise Juliet will not know
about his new log-in, he will appear offline).
<presence from='benvolio at montague.net' to='juliet at capulet.com'>
<c xmlns='http://jabber.org/protocol/caps'
node='http://www.chatopus.com/ec'
ver='2.1'
ext='foobar pres+'/>
</presence>
Capulet.com now sees this message and realises that it must send
Juliet's last subscription notice.
<message from='juliet at capulet.com'
to='benvolio at montague.net'
type='headline'
id='foo'>
<event xmlns='http://jabber.org/protocol/pubsub#event'>
<items node='http://jabber.org/protocol/tune'>
<item>
[...]
</item>
</items>
</event>
<x xmlns='jabber:x:delay' stamp='20031213T23:58:37'/>
</message>
You can't avoid it. Sorry. Nor would I know why you would want to, maybe
if you could explain your situation?
Cheers,
Jonathan Dickinson
cherami at gmx.de wrote:
> Hi Peter,
>
> could you please elaborate on this subject?
>
> Thank you in advance.
> Koder
>
> -------- Original-Nachricht --------
> Datum: Thu, 16 Aug 2007 09:51:33 +0200
> Von: Jonathan Dickinson <chayce.za at gmail.com>
> An: cherami at gmx.de
> Betreff: Re: [jdev] mirroring many presence servers
>
> Hey,
>
> Sorry, I don't know of any JEP that would help. You will probably have
> to write it yourself. As I said:
>
> * Client sends presence notification
> * Your server "notices" the notification
> * Your server stores this in the database
> * Your server forwardes the original notification
>
> You can also subscribing your sever. As far as I know, that should work,
> but some other clients/servers might break if you try that. Maybe
> someone else could elaborate (Peter)? I have noticed that websites (such
> as the Jabber world map) need a contact in your contact list to
> subscribe, I'm not sure if has occurred to anyone to just subscribe the
> server.
>
> Cheers,
> Jonathan Dickinson
>
> cherami at gmx.de wrote:
> > Hi Jonathan,
> >
> > I understand that a client must/can subscribe to an other client to
> > get notifications of his status.
> >
> > But can a presence server do something like that?
> > Can a presence server subscribe to other clients?
> >
> > The Idea is, that I have in my organisation Clients, that only needs
> > the presence information of other clients in other organisations. So I
> > want to cache/mirror in my server the presence information ot the
> > clients ot the other organisation, so that I do need to connect the
> > server ot the partners for each request from the clients of my
> > organisation.
> >
> > Thanks
> > Koder
> >
> >> -------- Original-Nachricht --------
> >> Datum: Wed, 15 Aug 2007 10:34:35 +0200
> >> Von: Jonathan Chayce Dickinson <chayce.za at gmail.com>
> >> An: Jabber software development list <jdev at jabber.org>
> >> Betreff: Re: [jdev] mirroring many presence servers
> >>
> >> Hey,
> >>
> >> If you know the language that your server is written in you could catch
> >> all the presence notifications before sending them on and store them
> >> locally (in your database etc.).
> >>
> >> However, what you are asking kinda doesn't make sense. If you never get
> >> a presence notification from a contact, they *are* offline (if you
> >> notice, while your client is connecting to a Jabber server all your
> >> contacts briefly show as offline), unless you are not subscribed to
> >> them, in which case you would never know anyway.
> >>
> >> Hope this helps.
> >>
> >> Cheers,
> >> Jonathan Dickinson
> >>
> >> On Wed, 2007-08-15 at 10:19 +0200, cherami at gmx.de wrote:
> >> > Hi,
> >> >
> >> > I have the following scenario in my student project. Which solution
> >> > would you propose?
> >> >
> >> > I have many business partners "B", "C" and "D", each of them has his
> >> > own presence server "PB", "PC" and "PD".
> >> >
> >> > I need in my organisation "A" a presence service "PA", who "mirros"
> >> > the actual status of all the users on PB, PC and PD, to whom I
> >> > subscribed.
> >> >
> >> > I know, that I could implement my presence service PA as a client,
> who
> >> > subscribes to all the users on PB, PC and PD. What I am asking for:
> is
> >> > there an other solution?
> >> >
> >> > 1. Can I be on the one hand a client of the servers PB, PC, PD, and
> on
> >> > the other hand a "server" for other applications/clients/servers.
> >> >
> >> > 2. Can I say to the other servers PB, PC and PD "hey, I am a presence
> >> > server (and not a client), would you please send me each change of
> the
> >> > status of my users, to whom I subscribed".
> >> >
> >> > 3. Can I make benefit of the s2s protocol in my scenario?
> >> >
> >> > You can say: What I want to have, is a local presence service in my
> >> > organisation, who localy mirros many others presence servers of other
> >> > partners. How would be your solution?
> >> >
> >> > Thank you for your help and your patience.
> >> > Koder
> >> >
> >> >
> >> >
> >> > --
> >> > Psssst! Schon vom neuen GMX MultiMessenger gehört?
> >> > Der kanns mit allen: http://www.gmx.net/de/go/multimessenger
> >> --
> >> Jonathan Dickinson
> >> Developer [Xeer Technology]
> >>
> >> email: chayce.za at gmail.com
> >> jabber: chayce.za at jabber.org
> >> twitter: Moitoius
> >>
> >> Principle will kick us all in the butt one day. If you have principle,
> >> you have all you will ever need.
> >
> >
> >
> > --
> > Psssst! Schon vom neuen GMX MultiMessenger gehört?
> > Der kanns mit allen: http://www.gmx.net/de/go/multimessenger
>
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