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

[Galder Zamarreño]

On Dec 13, 2013, at 3:11 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.

True, that's a limitation of the current approach, but I don't see it crucial as long as we have some static filtering in place. The feature itself is already pretty large, so I'd consider this (dynamic filtering) at a later point.

> 
>> 
>>> 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?
> 
> Radim


--
Galder Zamarreño
galder at redhat.com
twitter.com/galderz

Project Lead, Escalante
http://escalante.io

Engineer, Infinispan
http://infinispan.org