[infinispan-dev] AdvancedCache.put with Metadata parameter

Sanne Grinovero sanne at infinispan.org
Mon Apr 8 07:46:23 EDT 2013 

I fail to understand the purpose of the feature then. What prevents me
to use the existing code today just storing some extra fields in my
custom values? What do we get by adding this code?

Sanne

On 8 April 2013 12:40, Galder Zamarreño <galder at redhat.com> wrote:
>
> On Apr 8, 2013, at 1:26 PM, Sanne Grinovero <sanne at infinispan.org> wrote:
>
>> On 8 April 2013 12:06, Galder Zamarreño <galder at redhat.com> wrote:
>>>
>>> On Apr 8, 2013, at 12:56 PM, Sanne Grinovero <sanne at infinispan.org> wrote:
>>>
>>>>
>>>>
>>>>
>>>> On 8 April 2013 11:44, Galder Zamarreño <galder at redhat.com> wrote:
>>>>
>>>> On Apr 8, 2013, at 12:35 PM, Galder Zamarreño <galder at redhat.com> wrote:
>>>>
>>>>>
>>>>> On Apr 8, 2013, at 11:17 AM, Manik Surtani <msurtani at redhat.com> wrote:
>>>>>
>>>>>> All sounds very good. One important thing to consider is that the reference to Metadata passed in by the client app will be tied to the ICE for the entire lifespan of the ICE.  You'll need to think about a defensive copy or some other form of making the Metadata immutable (by the user application, at least) the moment it is passed in.
>>>>>
>>>>> ^ Excellent point, it could be a nightmare if users could change the metadata reference by the ICE at will. I'll have a think on how to best achieve this.
>>>>
>>>> ^ The metadata is gonna have to be marshalled somehow to ship to other nodes, so that could be a way to achieve it, by enforcing this somehow. When the cache receives it, it can marshaller/unmarshall it to make a copy
>>>>
>>>> One way would be to make Metadata extend Serializable, but not keen on that. Another would be to somehow force the interface to define the Externalizer to use (i.e. an interface method like getExternalizer()), but that's akward when it comes to unmarshalling… what about forcing the Metadata object to be provided with a @SerializeWith annotation?
>>>>
>>>> Why is getExternalizer() awkward for unmarshalling?
>>>
>>> ^ Because you don't have an instance yet, so what's the Externalizer for it? IOW, there's no much point to doing that, simply register it depending on your desire:
>>> https://docs.jboss.org/author/display/ISPN/Plugging+Infinispan+With+User+Defined+Externalizers
>>
>> That's what I would expect.
>>
>>>
>>>> I would expect you to have the marshaller already known during deserialization.
>>>
>>> You would, as long as you follow the instructions in https://docs.jboss.org/author/display/ISPN/Plugging+Infinispan+With+User+Defined+Externalizers
>>>
>>>> Agreed that extensing Serializable is not a good idea.
>>>>
>>>> Are you thinking about the impact on CacheStore(s) and state transfer?
>>>
>>> ^ What about it in particular?
>>>
>>>> Eviction of no longer used metadata ?
>>>
>>> ^ Since the metadata is part of the entry, it'd initially go when the entry is evicted. We might wanna leave it around in some cases… but it'd be for other use cases.
>>
>> I thought the plan was to have entries refer to the metadata, but that
>> different entries sharing the same metadata would point to the same
>> instance.
>
> ^ Could be, but most likely not.
>
>> So this metadata needs to be stored separately in the CacheStore,
>> preloaded as appropriate, transferred during state transfer,
>> passivated when convenient and cleaned up when no longer referred to.
>
> ^ Well, it's part of the internal cache entry, so it'd be treated just like ICE.
>
>> Am I wrong? Seems you plan to store a copy of the metadata within each ICE.
>
> ^ The idea is to store it alongside right now, but maybe at some point it might make sense to leave it around (i.e. for 2LC use case), but this won't be done yet.
>
>>
>>
>>>
>>> I'm also considering separating the serialization/marshalling concerns from the defensive copying concerns. IOW, add a copy() method to the Metadata interface, or have a separate interface for those externally provided objects that require to be defensive copied. IOW, do something like what Scala Case Classes do with their copy() method, but without the issues of clone… I need to investigate this further to come up with a nice solution.
>>>
>>> One positive side to splitting both concerns is speed. A Metadata implementation might have ways to make a copy of itself which are more efficient than marshalling/unmarshalling.
>>>
>>> Thoughts?
>>>
>>>>
>>>> Sanne
>>>>
>>>>
>>>> Any other ideas?
>>>>
>>>>>
>>>>> Cheers,
>>>>>
>>>>>>
>>>>>> On 8 Apr 2013, at 09:24, Galder Zamarreño <galder at redhat.com> wrote:
>>>>>>
>>>>>>> Hi all,
>>>>>>>
>>>>>>> As mentioned in http://lists.jboss.org/pipermail/infinispan-dev/2013-March/012348.html, in paralell to the switch to Equivalent* collections, I was also working on being able to pass metadata into Infinispan caches. This is done to better support the ability to store custom metadata in Infinispan without the need of extra wrappers. So, the idea is that InternalCacheEntry instances will have a a reference to this Metadata.
>>>>>>>
>>>>>>> One of that metadata is version, which I've been using as test bed to see if clients could pass succesfully version information via metadata. As you already know, Hot Rod requires to store version information. Before, this was stored in a class called CacheValue alongside the value itself, but the work I've done in [1], this is passed via the new API I've added in [2].
>>>>>>>
>>>>>>> So, I'd like to get some thoughts on this new API. I hope that with these new put/replace versions, we can get rid of the nightmare which is all the other put/replace calls taking lifespan and/or maxIdle information. In the end, I think there should be two basic puts:
>>>>>>>
>>>>>>> - put(K, V)
>>>>>>> - put(K, V, Metadata)
>>>>>>>
>>>>>>> And their equivalents.
>>>>>>>
>>>>>>> IMPORTANT NOTE 1: The implementation details are bound to change, because the entire Metadata needs to be stored in InternalCacheEntry, not just version, lifespan..etc. I'll further develop the implementation once I get into adding more metadata, i.e. when working on interoperability with REST. So, don't pay too much attention to the implementation itself, focus on the AdvancedCache API itself and let's refine that.
>>>>>>>
>>>>>>> IMPORTANT NOTE 2: The interoperability work in commit in [1] is WIP, so please let's avoid discussing it in this email thread. Once I have a more final version I'll send an email about it.
>>>>>>>
>>>>>>> Apart from working on enhancements to the API, I'm now carry on tackling the interoperability work with aim to have an initial version of the Embedded <-> Hot Rod interoperability as first step. Once that's in, it can be released to get early feedback while the rest of interoperability modes are developed.
>>>>>>>
>>>>>>> Cheers,
>>>>>>>
>>>>>>> [1] https://github.com/galderz/infinispan/commit/a35956fe291d2b2dc3b7fa7bf44d8965ffb1a54d
>>>>>>> [2] https://github.com/galderz/infinispan/commit/a35956fe291d2b2dc3b7fa7bf44d8965ffb1a54d#L10R313
>>>>>>> --
>>>>>>> Galder Zamarreño
>>>>>>> galder at redhat.com
>>>>>>> twitter.com/galderz
>>>>>>>
>>>>>>> Project Lead, Escalante
>>>>>>> http://escalante.io
>>>>>>>
>>>>>>> Engineer, Infinispan
>>>>>>> http://infinispan.org
>>>>>>>
>>>>>>>
>>>>>>> _______________________________________________
>>>>>>> infinispan-dev mailing list
>>>>>>> infinispan-dev at lists.jboss.org
>>>>>>> https://lists.jboss.org/mailman/listinfo/infinispan-dev
>>>>>>
>>>>>> --
>>>>>> Manik Surtani
>>>>>> manik at jboss.org
>>>>>> twitter.com/maniksurtani
>>>>>>
>>>>>> Platform Architect, JBoss Data Grid
>>>>>> http://red.ht/data-grid
>>>>>>
>>>>>>
>>>>>> _______________________________________________
>>>>>> infinispan-dev mailing list
>>>>>> infinispan-dev at lists.jboss.org
>>>>>> https://lists.jboss.org/mailman/listinfo/infinispan-dev
>>>>>
>>>>>
>>>>> --
>>>>> Galder Zamarreño
>>>>> galder at redhat.com
>>>>> twitter.com/galderz
>>>>>
>>>>> Project Lead, Escalante
>>>>> http://escalante.io
>>>>>
>>>>> Engineer, Infinispan
>>>>> http://infinispan.org
>>>>>
>>>>
>>>>
>>>> --
>>>> Galder Zamarreño
>>>> galder at redhat.com
>>>> twitter.com/galderz
>>>>
>>>> Project Lead, Escalante
>>>> http://escalante.io
>>>>
>>>> Engineer, Infinispan
>>>> http://infinispan.org
>>>>
>>>>
>>>> _______________________________________________
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>>>> infinispan-dev at lists.jboss.org
>>>> https://lists.jboss.org/mailman/listinfo/infinispan-dev
>>>>
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>>>> infinispan-dev mailing list
>>>> infinispan-dev at lists.jboss.org
>>>> https://lists.jboss.org/mailman/listinfo/infinispan-dev
>>>
>>>
>>> --
>>> Galder Zamarreño
>>> galder at redhat.com
>>> twitter.com/galderz
>>>
>>> Project Lead, Escalante
>>> http://escalante.io
>>>
>>> Engineer, Infinispan
>>> http://infinispan.org
>>>
>>>
>>> _______________________________________________
>>> infinispan-dev mailing list
>>> infinispan-dev at lists.jboss.org
>>> https://lists.jboss.org/mailman/listinfo/infinispan-dev
>>
>> _______________________________________________
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>> infinispan-dev at lists.jboss.org
>> https://lists.jboss.org/mailman/listinfo/infinispan-dev
>
>
> --
> Galder Zamarreño
> galder at redhat.com
> twitter.com/galderz
>
> Project Lead, Escalante
> http://escalante.io
>
> Engineer, Infinispan
> http://infinispan.org
>
>
> _______________________________________________
> infinispan-dev mailing list
> infinispan-dev at lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/infinispan-dev

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