Web Service state migration/preservation possibly in combination with WSRF

[Bertrand Baesjou <ba...@tid.es>]

Hi all,

I have a question regarding the preservation of the state of a WS. Lets 
say I have two nodes which both run the same service and one of those 
nodes is sort of the primary node (clients only connect to the primary 
node). Now I want that the second node "knows" the state of the first 
node so that in a case of a failure (shutdown or something) of the first 
node, the second knows in which state the sessions of the clients in the 
primary node were and via some sort of negotiation, the second node 
resumes the session with the clients.

What are my possibilities here or stuff I certainly have to look into? 
The WS in question currently uses WSRF to preserve its state internally, 
is that re-usable? I also read something about WS-Context, but that is 
still just a document and not a framework yet, also not sure in which 
extent it is actually useful.

By the way, I am not searching for a solution where an edge node 
preserves  the session (dispatcher like) and the other nodes just 
process jobs. I really want to exchange state information between the 
nodes. This exchange may be done by WS, but might also be done by other 
means (syncing of databases with information using rsync or something). 
Since I am quite new to this, I might not have read everything, thus 
feel free to provide me links to sites or documents that might be 
interesting.

I hope I made myself a bit clear, if not I'll elaborate some more.

Best regards and thank you in advance,
    Bertrand

P.S. I am quite new in the Web Services world, so there is a lot to 
learn for me and maybe more questions will follow.
P.P.S. This question is due to a general model (not only for WS) I am 
developing for my Masters thesis about migrating service interfaces. 
Eventually this thesis will be freely available along with any relevant 
information for WS within the thesis subject.

RE: Web Service state migration/preservation possibly in combination with WSRF

["Richard Mixon (Qwest)" <rn...@qwest.net>]

As you asked on the Tomcat forum, I'm assuming your wish a solution that
runs on Tomcat.

I have seen a number of web services frameworks discussed on this forum -
all that run under Tomcat (Axis is one I believe). I would think they must
all be built using the Servlet API as a foundation - but I do not have
experience using them.

In that event you should be able to configure "session replication" between
the two Tomcats (use the latest version 5.5.x). If your state is preserved
in the session, both Tomcats will have the exact same information available.
You then need a way of switching to the secondary Tomcat should the first
become unavaible.

Hope this helps - Richard

-----Original Message-----
From: baesjou@tid.es [mailto:baesjou@tid.es] 
Sent: Wednesday, November 08, 2006 9:10 AM
To: users@tomcat.apache.org
Subject: Web Service state migration/preservation possibly in combination
with WSRF

Hi all,

I have a question regarding the preservation of the state of a WS. Lets say
I have two nodes which both run the same service and one of those nodes is
sort of the primary node (clients only connect to the primary node). Now I
want that the second node "knows" the state of the first node so that in a
case of a failure (shutdown or something) of the first node, the second
knows in which state the sessions of the clients in the primary node were
and via some sort of negotiation, the second node resumes the session with
the clients.

What are my possibilities here or stuff I certainly have to look into? 
The WS in question currently uses WSRF to preserve its state internally, is
that re-usable? I also read something about WS-Context, but that is still
just a document and not a framework yet, also not sure in which extent it is
actually useful.

By the way, I am not searching for a solution where an edge node preserves
the session (dispatcher like) and the other nodes just process jobs. I
really want to exchange state information between the nodes. This exchange
may be done by WS, but might also be done by other means (syncing of
databases with information using rsync or something). 
Since I am quite new to this, I might not have read everything, thus feel
free to provide me links to sites or documents that might be interesting.

I hope I made myself a bit clear, if not I'll elaborate some more.

Best regards and thank you in advance,
    Bertrand

P.S. I am quite new in the Web Services world, so there is a lot to learn
for me and maybe more questions will follow.
P.P.S. This question is due to a general model (not only for WS) I am
developing for my Masters thesis about migrating service interfaces. 
Eventually this thesis will be freely available along with any relevant
information for WS within the thesis subject.



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