Re: [xmlblaster] two xmlblaster servers with one floating IP address?

[Marcel Ruff <mr at marcelruff.info>]

Dominique Petitpierre wrote:
> Hello,
>
> is there a way to have redundancy at the level of the xmlblaster
> servers that is transparent for the clients (i.e. the clients do not
> need to be programmed specially)?
>
> More specifically, I would like to use two server machines with a
> floating service address managed by heartbeat
> (http://www.linux-ha.org/heartbeat/ ). A client would see only one
> xmlblaster server; the currently serving server would communicate with
> the standby server in order to maintain exactly the same state on both
> machines (i.e. a message is considered written to or read from a queue
> only when both servers have completed the necessary operations).  If
> the serving server fails, then heartbeat initiates a failover, the
> floating address is taken over by the standby server which becomes the
> serving server and the client continues with that server
> (not noticing anything if no operation was currently going on, or
> possibly restarting the current failed operation).
> When the failed server is available again, it catches up on
> the states of the queues and becomes a usable standby server.

Sorry, mirroring is not yet implemented.
We almost started on it last winter but due to
lack of resources we had to defer it.

Our requirements where exactly as yours (your compendium
is a nice overview).
Our current cluster approach is a good base to extend it to
support such a mirroring, but coding testsuite, specifying details
coding the implementation and make a documentation takes its time ...

> I'd like to use this in a PtX framework where multiple
> clients read the same message sent by one publisher.
> Load balancing is not a concern (yet :-)).
>
> I read the cluster requirement page on
> http://www.xmlblaster.com/xmlBlaster/doc/requirements/cluster.html
> but could not determine if that approach was possible. In particular
> the note mentionned under "Multiple masters for same domain"
> is puzzling:
>
> | If multiple nodes acquire the master mode for a certain domain there
> | are two approaches.
> | Messages which are published are sent to all masters.
>
> it seems strange that the client should handle many message
> submissions (with all the synchronisation problems that it entails in
> case of failure). I'd prefer the clients to think there is
> only one server with which it has to sometimes restart
> an operation that did not complete successfully. 

Yes, what you say is ment there, the server to which the client
talks is responsible to forward it to other masters.

For the time being you can extend the cluster support
in xmlBlaster yourself or hire somebody (e.g. the xmlBlaster maintainers)
to do it for you.
As far as i know no xmlBlaster contributer is currently working on mirroring.

regards

Marcel

> Thanks in advances for sharing you experience and knowledge!
>
> Best regards,
> Dominique
> --
> Mr. Dominique Petitpierre      Email: User at Domain
> Division Informatique                 User=Dominique.Petitpierre
> University of Geneva                  Domain=adm.unige.ch
> (Switzerland)                  WWW  : http://www.unige.ch/dinf/


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