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

[Galder Zamarreño]

On Dec 19, 2013, at 1:15 PM, Emmanuel Bernard <emmanuel at hibernate.org> wrote:

> On Thu 2013-12-19  9:46, Galder Zamarreño wrote:
>>> == Example of continuous query atop remote listeners
>>> 
>>> Thinking about how to implement continuous query atop this
>>> infrastructure I am missing a few things.
>>> 
>>> The primary problem is that I don't want to enlist a filter id per
>>> continuous query I want to run. Not only that but I'd love to be able to
>>> add a continuous query on the fly and disable it on the fly as well per
>>> client. For that filters and converters are not flexible enough.
>>> 
>>> What is missing is the ability to pass parameters from the client to
>>> the remote filter and remote converter. Parameters should be provided
>>> *per client*. Say Client 1 register the continuous query listener with
>>> "where age > 19" and client 2 registers the CQ listener with "where name
>>> = emmanuel". The filter knowing for which client it filters, it will be able to only
>>> return the keys that match the query.
>> 
>> This all sounds a bit like remote code exectution to me? You're asking for the client to pass some kind of executable thing that acts as a filter. That's a separate feature IMO, which I believe @Tristan is looking into. Once that's in place, I'm happy to enhance stuff in the remote event side to support it.
> 
> I don't think you are correct.
> This is not remote execution in the sense of arbitrary code driven by
> the client. Remote execution will likely be triggered, render a
> result and stop. It will not send matching events in a continuous fashion.
> Plus remote execution will likely involve dynamic languages and I'm not
> sure we want to go that route for things like continuous query.

Well, it's remote execution of a condition, which is a type of code :)

>From Hot Rod perspective, until remote code execution is in place, we could add a list of N byte[] that are treated as parameters for the filter, and the filter deciphers what those mean. So, in your case, there would be only 1 parameter, a byte[], and it would be unmarshalled by the filter into "where age > 19". If multiple clients add the same parameter, we could use the same filter instance, that's assuming equality can be calculated based on the contents of the byte[] by Hot Rod.

WRT your suggestion to activate/deactivate the continous query on the fly, can't we achieve that with registration/deregistration of listeners? Or are you trying to avoid all the set up involved in sending the listener registration stuff around? Adding activate/deactivate would require two new operations.

Cheers,

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

Project Lead, Escalante
http://escalante.io

Engineer, Infinispan
http://infinispan.org