[infinispan-dev] Design of Remote Hot Rod events

[Emmanuel Bernard]

Hey there,

Here are a few comments based on a quick reading.
I might have totally misread or misinterpreted what was exposed, feel
free to correct me.

## General

I think you are restricting the design to listeners:

* that only listen to raw entry changes
* whose processing is remote
* with no way to filter out the event from the server

Is that correct? I can see that it does address the remote L1 use case
but I feel like it will close the doors to many more use cases. An
interesting example being continuous query.

In that use case the listener code runs a filtering logic server side
and only send keys that are impacted by the query plus some flag
defining whether it's added to changed or removed from the corpus.
The key is filtering event before sending it to the client.

I wish the design document was showing how we can achieve a general
purpose remote listener approach but have a step 1 that is only
targeting a restricted set of listeners if you feel that it's too much
to chew. I don't want us to be trapped in a situation where backward
compatibility prevent us from adding use cases.

## Specific questions

When the topology changes, it is the responsibility of the client to add
the listener to the new servers that show up. Correct? The API is a
global addRemoteListener but I imagine the client implementation will
have to transparently deal with that.
I wonder if a server approach is not more convinient. At least it does
not put the burden and bugs in several implementations and several
languages.

You never send code at the moment. Only one kind of listener is
available and listeners to all entry change and deletion. Correct?

Why not have the ability to listen to new entry events? That would limit
generic listeners as it is.

Do you have plans to make the ACK optional depending on the listener
requirement? Looks like an expensive process.

"Only the latest event is tracked for ACK for a given key"
It seems it's fine for L1 but would be a problem for many more generic
listeners.

Emmanuel


On Tue 2013-11-12 16:17, Galder Zamarreño wrote:
> Hi all,
> 
> Re: https://github.com/infinispan/infinispan/wiki/Remote-Hot-Rod-Events
> 
> I've just finished writing up the Hot Rod remote events design document. Amongst many other use cases, this will enable near caching use cases with the help of Hot Rod client callbacks.
> 
> Cheers,
> --
> Galder Zamarreño
> galder at redhat.com
> twitter.com/galderz
> 
> Project Lead, Escalante
> http://escalante.io
> 
> Engineer, Infinispan
> http://infinispan.org
> 
> 
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