[infinispan-dev] Integration between HotRod and OGM

Tue Jan 21 11:08:57 EST 2014

Hi Mircea,
could you explain how Grouping is different than AtomicMaps ?
I understand you're all suggesting to move to AtomicMaps as "the
implementation is better" but is that an implementation detail, or how
is it inherently different so that we can build something more
reliable on it?

>From the limited knowledge I have in this area, I have been assuming -
since they have very similar properties - that this was essentially a
different syntax to get to the same semantics but obviously I'm wrong.

It would be especially helpfull to have a clear comparison on the
different semantics in terms of transactions, atomicity and visibility
of state across the three kinds: AtomicMaps, FineGrainedAtomicMaps,
Grouping.

Let's also keep in mind that Hibernate OGM uses a carefully selected
combination of *both* AtomicMap and FGAM instances - depending on the
desired semantics we want to achieve, so since those two where clearly
different and we actually build on those differences - I'm not seeing
how we could migrate two different things to the same construct
without having to move "fishy locking details" out of Infinispan but
in OGM, and I wouldn't be too happy with that as such logic would
belong in Infinispan to provide.

- Sanne

On 21 January 2014 15:07, Mircea Markus <mmarkus at redhat.com> wrote:
> Hi Emmanuel,
>
> Just had a good chat with Davide on this and one solution to overcome the shortcoming you mentioned in the above email would be to enhance the hotrod client to support grouping:
>
> RemoteClient.put(G g, K k, V v); //first param is the group
> RemoteClinet.getGroup(G g) : Map<K,V>;
>
> It requires an enhancement on our local grouping API: EmbeddedCache.getGroup(G). This is something useful for us in a broader context, as it is the step needed to be able to deprecated AtomicMaps and get suggest them being replaced with Grouping.
>
> This approach still has some limitations compared to the current embedded integration:
> - performance caused by the lack of transactions: this means increased TCP chattiness between the Hot Rod client and the server.
> - you'd have to handle atomicity, potentially by retrying an operation
>
> What do you think?
>
>
> On Dec 3, 2013, at 3:10 AM, Mircea Markus <mmarkus at redhat.com> wrote:
>
>>
>> On Nov 19, 2013, at 10:22 AM, Emmanuel Bernard <emmanuel at hibernate.org> wrote:
>>
>>> It's an interesting approach that would work fine-ish for entities
>>> assuming the Hot Rod client is multi threaded and assuming the client
>>> uses Future to parallelize the calls.
>>
>> The Java Hotrod client is both multithreaded and exposes an Async API.
>>
>>>
>>> But it won't work for associations as we have them designed today.
>>> Each association - or more precisely the query results to go from an
>>> entity A1 to the list of entities B associated to it - is represented by
>>> an AtomicMap.
>>> Each entry in this map does correspond to an entry in the association.
>>>
>>> While we can "guess" the column names and build from the metadata the
>>> list of composed keys for entities, we cannot do the same for
>>> associations as the key is literally the (composite) id of the
>>> association and we cannot guess that most of the time (we can in very
>>> pathological cases).
>>> We could imagine that we list the association row keys in a special
>>> entry to work around that but this approach is just as problematic and
>>> is conceptually the same.
>>> The only solution would be to lock the whole association for each
>>> operation and I guess impose some versioning / optimistic lock.
>>>
>>> That is not a pattern that scales sufficiently from my experience.
>>
>> I think so too :-)
>>
>>> That's the problem with interconnected data :)
>>>
>>> Emmanuel
>>>
>>> On Mon 2013-11-18 23:05, Mircea Markus wrote:
>>>> Neither the grouping API nor the AtomicMap work over hotrod.
>>>> Between the grouping API and AtomicMap, I think the one that would make more sense migrating is the grouping API.
>>>> One way or the other, I think the hotrod protocol would require an enhancement - mind raising a JIRA for that?
>>>> For now I guess you can sacrifice performance and always sending the entire object across on every update instead of only the deltas?
>>>>
>>>> On Nov 18, 2013, at 9:56 AM, Emmanuel Bernard <emmanuel at hibernate.org> wrote:
>>>>
>>>>> Someone mentioned the grouping API as some sort of alternative to
>>>>> AtomicMap. Maybe we should use that?
>>>>> Note that if we don't have a fine-grained approach we will need to
>>>>> make sure we *copy* the complex data structure upon reads to mimic
>>>>> proper transaction isolation.
>>>>>
>>>>> On Tue 2013-11-12 15:14, Sanne Grinovero wrote:
>>>>>> On 12 November 2013 14:54, Emmanuel Bernard <emmanuel at hibernate.org> wrote:
>>>>>>> On the transaction side, we can start without them.
>>>>>>
>>>>>> +1 on omitting transactions for now.
>>>>>>
>>>>>> And on the missing AtomicMaps, I hope the Infinispan will want to implement it?
>>>>>> Would be good to eventually converge on similar featuresets on remote
>>>>>> vs embedded APIs.
>>>>>>
>>>>>> I know the embedded version relies on batching/transactions, but I
>>>>>> guess we could obtain a similar effect with some ad-hoc commands in
>>>>>> Hot Rod?
>>>>>>
>>>>>> Sanne
>>>>>>
>>>>>>>
>>>>>>> On Tue 2013-11-12 14:34, Davide D'Alto wrote:
>>>>>>>> Hi,
>>>>>>>> I'm working on the integration between HotRod and OGM.
>>>>>>>>
>>>>>>>> We already have a dialect for Inifinispan and I'm trying to follow the same
>>>>>>>> logic.
>>>>>>>> At the moment I'm having two problems:
>>>>>>>>
>>>>>>>> 1) In the Infinispan dialect we are using the AtomicMap and the
>>>>>>>> AtomicMapLookup but this classes don't work with the RemoteCache. Is there
>>>>>>>> an equivalent for HotRod?
>>>>>>>>
>>>>>>>> 2) As far as I know HotRod does not support transactions. I've found a link
>>>>>>>> to a branch on Mircea repository:
>>>>>>>> https://github.com/mmarkus/ops_over_hotrod/wiki/Usage-guide
>>>>>>>> Is this something I could/should use?
>>>>>>>>
>>>>>>>> Any help is appreciated.
>>>>>>>>
>>>>>>>> Thanks,
>>>>>>>> Davide
>>>>>>>
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>>>>
>>>> Cheers,
>>>> --
>>>> Mircea Markus
>>>> Infinispan lead (www.infinispan.org)
>>>>
>>>>
>>>>
>>>>
>>>>
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>>
>> Cheers,
>> --
>> Mircea Markus
>> Infinispan lead (www.infinispan.org)
>>
>>
>>
>>
>
> Cheers,
> --
> Mircea Markus
> Infinispan lead (www.infinispan.org)
>
>
>
>
>
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