Re: [infinispan-dev] Distribution, take 2

On 20 Jul 2009, at 09:24, Galder Zamarreno wrote: > > > On 07/17/2009 08:24 PM, Manik Surtani wrote: >> 6.3. Nodes (L - replCount + 1), (L + 1) and (L + replCount) kick off a >> LeaveTask. > > Shouldn't (L - replCount + 1) be (L - 1) ? Well spotted. That was leftover from an earlier version I was working on. It should be (L - 1). > >> 6.3.1. Not everyone in the cluster need be involved in this rehash >> thanks to fixed CH positions. >> >> 7. LeaveTask: This is PUSH based >> 7.1. If an existing LeaveTask is running, the existing task should be >> cancelled first. > > Why should it be cancelled? In a cluster of 3 nodes, A:B:C:D, imagine > A leaves and while B is pushing state for A, C leaves as well. Are you > gonna cancel B's push? So in the case of cluster {A, B, C, D, E, F} Let's take the case of C leaving. B pushes C's state to D. This task being cancelled will only happen if A or D were to leave (others leaving will not trigger a LeaveTask on B) So if D leaves, it should be cancelled and restarted since there is no point in beaming state to D. Even if A leaves, a rehash should only happen once. So a rehash due to A leaving should cover state being pushed to D as well.

While typing this I realised that points 7.4.1 and 8.2. in my original email will prevent this from working since the conditions in those steps do not assume that a task could be cancelled. A potential way for this is to maintain a "leavers list". Every time a LeaveTask completes, the LeaversList is emptied. Every time the LeaveTask starts, it adds the leaver's address to the LeaversList. Conditions 7.4.1 and 8.2 consider all leavers in the LeaversList, not just the current leaver, L. Thoughts?

Cheers Manik -- Manik Surtani manik(a)jboss.org Lead, Infinispan Lead, JBoss Cache http://www.infinispan.org http://www.jbosscache.org