[infinispan-dev] JoinTask.broadcastNewCh

[Bela Ban]

On 2/10/11 1:07 PM, Mircea Markus wrote:
> Hi,
>
> This is something Bela has brought up while working on integrating RELAY in infinispan.
> Right now it's the joiner (JoinTask) that broadcast the new CH to the cluster members. In the case of RELAY, this wouldn't be that good as the joiner might be on a remote site and this means a potentially costly RPC.


On top of that, IMO it would be simpler for every member to compute its 
new CH *itself*, rather than relying on a new joiner to do that.


> Isn't it possible for all the existing members to determine the new CH internally on the @viewChanged call and not wait for new joiner's broadcast?


+1


Let me give a bit of background. In RELAY I can have members A in one 
local cluster and B in a different cluster. RELAY connects both to form 
a virtual view {A,B}.

So, when A has been started and B starts up, what happens is that B will 
get view {B} first, before getting {A,B}.

When B gets {B}, it becomes the coordinator and doesn't start a JoinTask 
because it has the correct view. When B gets the new view {A,B}, it 
handleView() is does *not* broadcast the CH either, because the view is 
not a merge view. This results in the CH on B having a membership of 
{A,B}, but A's CH only has a membership of {A}, thus A will *not* 
distribute its data to B !

I think the simplest solution here would be to simply compute the CH on 
a viewChange(); this way, we don't even have to have communication 
across the cluster to determine the new CH.

-- 
Bela Ban
Lead JGroups / Clustering Team
JBoss