Re: [jgroups-users] Ability to set the coordinator programaticaly and the ability to maintain a shared state

On 29/04/18 10:45, Questions/problems related to using JGroups wrote:
> Hi all,
> 
> I am new to jGroups but I found this is an elegant library for cluster 
> management. I have 2 main requirements for one of my projects.
> 
> First, is it possible to programmatically change the coordinator of 
> the jGroups cluster?. I am using the jgroups coordinator as the 
> application level master (for some domain-specific application) of the 
> server's cluster. But for a given server to become the application level 
> master there are some application level criteria to be fulfilled. So in 
> case of the jGroups coordinator cannot fulfill those requirements I want 
> to change the coordinator of the jGroups programmatically. I found [1] 
> for this purpose, but I wanted to understand whether this is a reliable 
> method or is there any side effects of doing this. If there is a 
> recommanded approach, please share that with me.

[1] certainly works, but is a kludge. I recommend implementing a 
membership plugin [2], which determines the order of members in a view. 
You can thus control who the coordinator is/becomes. [1] can be used to 
change the coordinator when no view is getting installed, e.g. triggered 
by the application.


> The second question is about the ability to maintain a shared state. Is 
> it possible to maintain a state which is visible across the cluster?. So 
> the changes are synchronized among the available members and visible to 
> all members without explicit message passing about the changes.

Yes, use state transfer, check the manual for details. Note that the 
state is the same across *all* cluster members, which may lead to heap 
exhaustion if you have a large state and/or many members.


[2] http://www.jgroups.org/manual4/index.html#MembershipChangePolicy

> 
> [1] 
> https://github.com/belaban/JGroups/wiki/Changing-the-coordinator-of-a-cluster
> 
> Thanks & Regards!
> Tharindu,
> 
> Tharindu Munasinghe.
> Undergraduate, Department of Computer Science and Engineering
> University of Moratuwa.
> Contact no. +94770460887
> 
> 
> 
> 
> ------------------------------------------------------------------------------
> Check out the vibrant tech community on one of the world's most
> engaging tech sites, Slashdot.org! http://sdm.link/slashdot
> 
> 
> 
> _______________________________________________
> javagroups-users mailing list
> [email protected]
> https://lists.sourceforge.net/lists/listinfo/javagroups-users
> 

-- 
Bela Ban | http://www.jgroups.org


------------------------------------------------------------------------------
Check out the vibrant tech community on one of the world's most
engaging tech sites, Slashdot.org! http://sdm.link/slashdot
_______________________________________________
javagroups-users mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/javagroups-users