[infinispan-dev] Design of Remote Hot Rod events - round 2

[Dan Berindei]

On Fri, Dec 13, 2013 at 4:11 PM, Radim Vansa <rvansa at redhat.com> wrote:

> On 12/13/2013 02:44 PM, Galder Zamarreño wrote:
> > On Dec 6, 2013, at 10:45 AM, Radim Vansa <rvansa at redhat.com> wrote:
> >
> >> Hi,
> >>
> >> 1) IMO, filtering for specific key is a very important use case.
> Registering a filterId is a very powerful feature, but as long as you don't
> provide runtime parameter for this filter, you cannot implement one-key
> filtering.
> > What do you mean by runtime parameter exactly? Can you give a concrete
> example of what you want to achieve that is not possible with what I've
> written up?
>
> As I stressed, if the client wants to listen for events on key_123456,
> then you can deploy a filter matching key_{number} (and additional
> constraints) but the 123456 is not known at deployment time.
>
> >
> >> 2) setting ack/no ack in listener, and then configuring server-wise
> whether you should ack each / only last event sounds weird. I'd replace the
> boolean with enum { NO_ACK, ACK_EACH, ACK_LAST }.
> > Makes a lot of sense, +1.
> >
> >> 3) should the client provide source id when registering listener or
> when starting RemoteCacheManager? No API for that.
> > Every operation will require a source ID from now on, so clients must
> provide it from first operation sent to the server. From a Java client
> perspective, you'd have this from the start via the configuration.
> >
> >> 4) clustered events design does not specify any means to replicating
> the clustered event listener - all it does is that you register the
> listener on one node and the other nodes then route events to this node,
> until the node dies/deregisters the listener. No replication. Please
> specify, how should it piggyback on clustered events, and how should the
> listener list be replicated.
> > In clustered listeners, the other nodes you talk about are gonna need to
> know about the clustered listeners so that they route events. Some kind of
> information about these clustered listeners will need to be sent around the
> cluster. The exact details are probably implementation details but we have
> a clustered registry already in place for this kind of things. In any case,
> it'd make a lot of sense that both use cases reuse as much as logic in this
> area.
>
> OK, this is probably the desired behaviour, it just is not covered by
> the Clustered Events design draft. Probably something to add - I'll ping
> Mircea about that. And you're right that it would make a lot of sense to
> have shared structure for the listeners, and two implementations of the
> delivery boy (one to the node where a clustered event has been
> registered and second to local component handling HotRod clients).
>
> >
> >> 5) non-acked events: how exactly do you expect the ack data to be
> replicated, and updated? I see three options:
> >> A) Let non-acked list be a part of the listener record in replicated
> cache, and the primary owner which executes the event should update these
> via delta messages. I guess for proper reliability it should add operation
> record synchronously before confirming the operation to the originator, and
> then it might asynchronously remove it after the ack from client. When a
> node becomes primary owner, it should send events to client for all
> non-acked events.
> >> B) Having the non-acked list attached directly to cache entry (updating
> it together with regular backup), and then asynchronously updating the
> non-ack list after ack comes
> >> C) Separate cache for acks by entry keys, similar to B, consistent hash
> synced with the main entry cache
> > Definitely not B. I don't wanna tie the internal cache entry to the
> ACKs. The two should be independent. Either C or A. For C, you'd wished to
> have a single cache for all listeners+caches, but you'd have to think about
> the keys and to have the same consistent hash, you'd have to have same
> keys. A might be better, but you certainly don't want this ACK info in a
> replicated structure. You'd want ACKs in a distributed cache preferably,
> and clustered listener info in the clustered replicated registry.
> There already is some CH implementation which aims at sharing the same
> distribution for all caches, SyncConsistentHash. Is there some problem
> with C and forcing this for the caches? Dan?
>
>
I'm not sure what the exact requirements would be here.

SyncConsistentHashFactory does ensure that the same key is mapped to the
same owners in all the caches using it, most of the time. However, it
requires both caches to have the same members, and since topologies aren't
applied at exactly the same time there will be periods when the owners in
the two caches won't match.
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