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From Andrey Gura <ag...@gridgain.com>
Subject Re: Cluster group affinity
Date Tue, 06 Oct 2015 19:30:51 GMT
>
> Just curios, how about providing an override for Ignite.affinity() method
> that ClusterGroup? Is there something fundamentally wrong about calculating
> the affinity for an arbitrary collection of nodes (such as a ClusterGroup
> is)?
>

Andrey,

I think Ignite.affinity() method for ClusterGroup does not make sense in
API because for each cache topology snapshot always consist of cache
affinity nodes. However, I don't see any fundamentally problems in using
affinity fucntion for some collection of nodes. But you should make sure
that your code is aware of changes in this collection.

On Tue, Oct 6, 2015 at 6:46 PM, Andrey Kornev <andrewkornev@hotmail.com>
wrote:

> Thanks, Andrey! This definitely helps.
>
> It's just that implementing such a simple feature in the "user space"
> feels awkward and requires intimate knowledge of  fairly low-level details
> of how things work in the current version.
>
> Just curios, how about providing an override for Ignite.affinity() method
> that ClusterGroup? Is there something fundamentally wrong about calculating
> the affinity for an arbitrary collection of nodes (such as a ClusterGroup
> is)?
>
> Regards
> Andrey
>
> > Date: Tue, 6 Oct 2015 18:12:48 +0300
> > Subject: Re: Cluster group affinity
> > From: agura@gridgain.com
> > To: dev@ignite.apache.org
> >
> > Andrey,
> >
> >
> > > 1) I'm expected to return an instance of the internal class
> > > AffinityTopologyVersion.
> >
> >
> > If you are talking about AffinityContextFunction.currentTopologyVersion
> > method then for now this method is nowhere uses. But it make sense to
> > return non null value in order to avoid problems in the future.
> >
> > 2) the consequences of returning null from
> > > AffinityFunctionContext.previousAssignment and
> > > AffinityFunctionContext.discoveryEvent methods (because I can't
> provide any
> > > meaningful implementation for them) are not clear.
> > >
> >
> > Both methods declared as @Nullable, so affinity function developer should
> > correctly handle this cases. In Ignite only FairAffinityFunction uses
> these
> > methods. FairAffinityFunction tries to obtain left node Id from event of
> > EventType.EVT_NODE_LEFT or EventType.EVT_NODE_FAILED type. It needs to
> > exclude this node assignment from previous assignments. So if your
> cluster
> > group lost node you can return EVT_NODE_LEFT discovery event with Id of
> > lost node from discoveryEvent method and assignments for previous cluster
> > group state from previousAssignment method.
> >
> > RendezvousAffinityFunction uses only currentTopologySnapshot() and
> > backups() methods of AffinityFunctionContext interface.
> >
> >
> > On Tue, Oct 6, 2015 at 5:07 PM, Andrey Kornev <andrewkornev@hotmail.com>
> > wrote:
> >
> > > Andrey, thanks!
> > >
> > > But a "properly formed AffinityFunctionContext" is the problem:
> > > 1) I'm expected to return an instance of the internal class
> > > AffinityTopologyVersion.
> > > 2) the consequences of returning null from
> > > AffinityFunctionContext.previousAssignment and
> > > AffinityFunctionContext.discoveryEvent methods (because I can't
> provide any
> > > meaningful implementation for them) are not clear.
> > >
> > > Please advise.
> > >
> > > Thanks
> > > Andrey
> > >
> > > > Date: Tue, 6 Oct 2015 16:43:10 +0300
> > > > Subject: Re: Cluster group affinity
> > > > From: agura@gridgain.com
> > > > To: dev@ignite.apache.org
> > > >
> > > > Andrey,
> > > >
> > > > See AffinityFunction.assignPartitions method. It returns assignment
> list
> > > as
> > > > List<List<ClusterNode>> where index of element in returned
list
> > > corresponds
> > > > to partition number. Assignment for each partition represented as
> list of
> > > > nodes where primary node is always the first. So you can use existing
> > > > affinity functions for you case just passing properly formed
> > > > AffinityFunctionContext to assignPartitions method.
> > > >
> > > > On Tue, Oct 6, 2015 at 4:25 PM, Andrey Kornev <
> andrewkornev@hotmail.com>
> > > > wrote:
> > > >
> > > > > Dmitriy,
> > > > >
> > > > > The affinity function only maps a key to a partition id and it
> doesn't
> > > > > seem to provide a way to map the partition id to a cluster node.
So
> > > I'm a
> > > > > little bit confused right now.
> > > > >
> > > > > Could you please clarify?
> > > > >
> > > > > Thanks a lot
> > > > > Andrey
> > > > >
> > > > > > From: dsetrakyan@apache.org
> > > > > > Date: Mon, 5 Oct 2015 09:53:25 -0700
> > > > > > Subject: Re: Cluster group affinity
> > > > > > To: dev@ignite.apache.org
> > > > > >
> > > > > > On Mon, Oct 5, 2015 at 2:28 AM, Andrey Kornev <
> > > andrewkornev@hotmail.com>
> > > > > > wrote:
> > > > > >
> > > > > > > Hello,
> > > > > > >
> > > > > > > I have a user-defined cluster group and I'd like to be
able to
> > > > > > > consistently pick the same node in the group for a given
key.
> > > > > Essentially,
> > > > > > > what I want is a cluster group affinity that is not associated
> > > with any
> > > > > > > cache. How can I do it?
> > > > > > >
> > > > > >
> > > > > > Andrey, perhaps you could just take our affinity function and
> use it
> > > > > > directly, no?
> > > > > >
> > > > > >
> > > > > > >
> > > > > > > Thanks
> > > > > > > Andrey
> > > > > > >
> > > > >
> > > > >
> > > >
> > > >
> > > >
> > > > --
> > > > Andrey Gura
> > > > GridGain Systems, Inc.
> > > > www.gridgain.com
> > >
> > >
> >
> >
> >
> > --
> > Andrey Gura
> > GridGain Systems, Inc.
> > www.gridgain.com
>
>



-- 
Andrey Gura
GridGain Systems, Inc.
www.gridgain.com

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