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WAS 5.0 session persistence (memory replication)

 
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Hi guys.
I'm trying to set up 'session persistence' via 'memory replication' and have the following question:
Most docu-PDFs explain how to set up a peer-to-peer topology, where each cluster member holds all session-data from all other cluster members. I tried it - it worked fine.
Now I'm trying to set up a client-server topology but can't achive session replication as long as the 'serving' appServer is NOT a member of the cluster.
1) Is this a prerequisite - all replication servers (server or client) have to be members of the same cluster?
2) Is it impossible to make an outside-cluster server act as the replication-server to which clients (inside a cluster) connect???
3) Placing the server inside the cluster means, the server starts the application installed on the cluster and is part of the workload management process (webserver plugin) as well - what if I don't want this to happen???
Any help / suggestions are highly welcome... I'm starting to get crazy about this one...
Thanks,
Sebastian K.
 
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I don't have an answer to this as i am trying this myself..I will let u know if i have some success.
I am also trying to understand what is significance of partitioning when using inmemory replication
 
Sebastian Krzyzanowski
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After a few days of hard work (reading and trying... and reading and trying...) I made it!
It is possible to use a "standalone" AppServer outside a cluster for session-inmemory-replication.
The solution: a WAS 5.0 bug!
PQ71038:REPLICATION SERVICE NOT WORKING ON A SERVER CONFIGURED TO RUN IN THE SERVER ONLY MODE FOR STORING SESSIONS
Fixpacks are required - after fixing WAS 5.0 (in my case up to 5.0.2) all finally works fine.
The whole configuration process (replication domain, replication domain entries, replicators, AppServer session-handling...) is quite a "fussy" work though.
If you get stuck, David, drop me a line.
 
david dhavan
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1) can you pls walk me thru' steps needed for a client server in mem replication to work...??
2) I just have WAS 5.0 base and ND..do I need to upgrade to fixpack 1/ fixpack 2.Does the fixpack already has this PTF or we need to apply on top of it.
Thanks in advance
DD
 
Sebastian Krzyzanowski
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You need to update the Deployment Manager (WAS ND) with the ND-fixpack AND the AppServer(s) (WAS base - although not realy "base" anymore since they are managed by the DeploymentManager) with the base-fixpack. The PTF is included in fixpack 1 so fixpack 1 should suffice - but if you're fixing your WAS with fixpack 1 already you should use fixpack 2 as well. IMPORTANT: you first have to update to 5.01 AND then to 5.02 - fixpack 2 only, will not work without fixpack 1.
And now the required steps for in-memory replication:
1) create AppServers, install a application on them and add them to a cluster.
2) create a replication domain (if not already done when creating the cluster). I used the default values although using object-serialisation instead of byte-serialisation might be an option, it needs some extra configuration effort though...
3) create one replication domain entry = replicator (can be done inside configuration of rep. domain) for each AppServer involved in the replication process. IMPORTANT: chose one, unique AppServer and two unique ports for each single entry!
4) Stop AppServers and switch to in-memory replication for each AppServer (Web Container -> Session Management -> Distributed Environment Settings -> Memory to Memory Replication). There choose the appropriate replicator with the correct AppServer asigned in step 3 and set the 'Runtime Mode' to 'client' for most / to 'server' for one dedicated AppServer.
5) For testing only I would recommend switching the replication method to 'medium' (Distributed Environment Settings -> Custom Tuning Parameters) so the session is replicated after each request to a JSP / Servlet.
6) Restart AppServers.
That's all - good luck!
 
david dhavan
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Thanks Sebastian,
I will try this tomorrow and let you know if I run into any issues.
Quick question -
Is it possible to share in memory sessions between 2 completely seperate (alike)clusters.
I am working on a high availability project and want to know if it was possible to bring down one cluster , do some maintenance on it while other is still actively serving web traffic.
DD.
 
Sebastian Krzyzanowski
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Although I'm not 100% sure about this, I think it's possible. The 'replication domain' is the crucial factor - and a 'replication domain' is cell-based so you should be able to use mem-to-mem rep. between clusters if all the clusters are members of the same cell. Furthermore all replicators (replication entries) are bound to a host and an AppServer, not to a cluster. And finally it's possible to achive replication between cluster-members and NOT cluster-members (remember my question ;-) ) so replication between clusters should work too.
 
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