On Wed, 2011-06-01 at 16:46 +0200, Bela Ban wrote: > > On 6/1/11 4:21 PM, Sanne Grinovero wrote: > > Hi Bela, > > > > 2011/6/1 Bela Ban<b...@redhat.com>: > >> We currently use JGroups' partial state transfer to transfer individual > >> caches from one Infinispan instance to another. > >> > >> Since I got rid of partial state transfer in JGroups 3.0, and don't like > >> to add it back, I'd like to know whether this is still needed. > >> > >> I thought that we currently require the same set of caches to be > >> available in all Infinispan instances, and the reason (IIRC) was that > >> distribution wouldn't work if we have caches 1 and 2 available on > >> instances A and B, but not on C, because consistent hashing distributes > >> the data based on views, and we didn't want to have to keep track of > >> individual caches... > > > > Well I really don't like this limitation in Infinispan and was > > actually hoping that we could remove it at some point. > > Imagine the scenario in which you have a running cluster, and at some > > point the new release of your application needs an additional cache: > > there's no way to start a new node having this new cache. > > > Yes, I fully agree. Another example is HTTP web sessions: currently 1 > webapp == 1 cache, so we currently require the same webapps to be > deployed in all JBoss instances *if* we use replication (distribution is > different) !
As of AS7, web sessions for all webapps are stored in a single cache. https://issues.jboss.org/browse/JBCLUSTER-293 > > Also right now when an application starts, it's possible with the > > proper timing that it joins the cluster before having defined and > > started all caches (starting the cachemanager and the caches is not an > > atomic operation), basically failing to start because of this > > limitation. > > > Yep > > > > Maybe it's still possible to build such a thing on top of non-partial > > state transfer? As it doesn't exist, we didn't design it. > > > Yes. Well, Infinispan already uses its own state transfer for > distribution, I wonder why this isn't the case for replication. > > > >> Why are we actually using JGroups' state transfer with replication, but > >> use our own state transfer with distribution ? > > > > I don't know, but guess it's because each node has a different set of > > keys so no node has the same state as another ? > > You could still use JGroups state transfer; getState() would list the > state provider as target node. > > In general, partial state transfer involves transferring (1) the partial > state and (2) the digest, which is a vector of highest seqnos seen for > every member. When we get a partial state, we always overwrite our own > digest with the one received, and update our state accordingly. However, > when this is done a couple of times, for different partial states, I'm > not sure that we won't receive a few messages multiple times, due to the > digest overwriting... > > I think the cleanest solution would be for you guys to reuse the state > transfer you already use for state transfer in distribution mode. > _______________________________________________ infinispan-dev mailing list infinispan-dev@lists.jboss.org https://lists.jboss.org/mailman/listinfo/infinispan-dev
