Re: [infinispan-dev] ISPN-425 - Issues with waiting for rehash to complete on startup
Actually, doing this seems more complex than I originally thought. Specially when you take
in account that you could have multiple caches checking the coordinator and expecting it
to return the CH address list. For example, if you have nodes A, B and C and assuming B
and C had requests on 'hotRodDistSync', B could assume it's only himself, but
when C comes in, how's A gonna tell that B is part of the CH address list?
Another possibility I'm toying with is for the coordinator to start the given cache if
it does not exist in cache manager.
----- galder(a)redhat.com wrote:
Hi,
Re: https://jira.jboss.org/jira/browse/ISPN-425
We've been discussing solutions to the fundamental problem in this
issue which is the fact that operations are allowed in the cache
before rehashing has finished starting up. I've been playing around
with a solution based around waiting for rehashing to complete but
this is causing issues with Hot Rod distribution tests. In Hot Rod,
this is what happens:
1. Start Hot Rod server 1 which starts a replicated topology cache.
2. Start Hot Rod server 2 which starts a replicated topology cache.
3. Send a request for a distributed cache called 'hotRodDistSync' in
Hot Rod server 2.
4. As a result of this request, 'hotRodDistSync' cache should be
started up but it does not succeed. It stays in a Rehash join loop,
saying:
4595 INFO [org.infinispan.remoting.InboundInvocationHandlerImpl]
(OOB-2,Infinispan-Cluster,eq-52045:) Cache named hotRodDistSync does
not exist on this cache manager!
4595 TRACE [org.infinispan.marshall.VersionAwareMarshaller]
(OOB-2,Infinispan-Cluster,eq-52045:) Wrote version 410
4596 TRACE [org.infinispan.marshall.VersionAwareMarshaller]
(OOB-2,Infinispan-Cluster,eq-64501:) Read version 410
4596 TRACE
[org.infinispan.remoting.transport.jgroups.CommandAwareRpcDispatcher]
(Rehasher-eq-64501:) responses: [sender=eq-52045, retval=null,
received=true, suspected=false]
4597 DEBUG [org.infinispan.distribution.JoinTask]
(Rehasher-eq-64501:) Retrieved old consistent hash address list null
4597 TRACE [org.infinispan.distribution.JoinTask]
(Rehasher-eq-64501:) Sleeping for 1.54 seconds
The problem here is that Hot Rod server 1 has not yet started
'hotRodDistSync' cache since no requests where sent to it. Now, this
is different to the cache not allowing invocations yet cos it's in
middle of the startup. So, I wondered if
InboundInvocationHandlerImpl.handle() could return a custom response
rather than null and for JoinTask to handle it in such a way that if
all the responses received say that the cache does not exist, then
consider rehash completed and finish the process.
Now, the reason I'm saying to return a custom response is because I
can see that JOIN_REQ returning null can also mean that the
coordinator is in the middle of another join
(DMI.requestPermissionToJoin). These two situations are not the same,
hence why I suggest a different treatment.
Cheers,
--
Galder Zamarreño
Sr. Software Engineer
Infinispan, JBoss Cache
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