[infinispan-dev] Cache Java 8 API proposal - 2nd draft

Tue Jun 16 08:36:51 EDT 2015

Hey Galder

I have finally read the proto8 code, and it looks quite good.

I do have some concerns about how the lambdas will interact with
distribution, because not every node performs conditional updates the
same way (at least not without total order):

1. In non-transactional caches, we will retry an operation if the
cache topology changes, and the second time around we don't want to
fail the operation if the key already has the correct value on the
primary owner.
2. In transactional caches, the conditional commands are only checked
on the originator - all other owners apply the update unconditionally.
This makes the modifications idempotent, which then allows us to retry
the prepare as many times as necessary.

Are you thinking of handling these differences in the lambdas
themselves, or maybe you have something else in mind?

For optimistic caches we also have the write skew check, is that going
to be in the lambda? It's also be performed only on the primary owner
without TO, and on all the owners with TO...

I also have some questions about the MetaParams:

1. Do we really need MetaParam.Id? Couldn't we index the MetaParams by
their class?
2. Do we really want such fine granularity? We could at least pair
Created/Lifespan and LastUsed/MaxIdle...

Cheers
Dan

On Mon, Jun 15, 2015 at 11:19 AM, Galder Zamarreño <galder at redhat.com> wrote:
>
>> On 10 Jun 2015, at 04:08, William Burns <mudokonman at gmail.com> wrote:
>>
>>
>>
>> On Tue, Jun 9, 2015 at 2:12 AM Galder Zamarreño <galder at redhat.com> wrote:
>>
>> > On 8 Jun 2015, at 10:57, Radim Vansa <rvansa at redhat.com> wrote:
>> >
>> > On 06/08/2015 10:41 AM, Dan Berindei wrote:
>> >> On Mon, Jun 8, 2015 at 10:37 AM, Galder Zamarreño <galder at redhat.com> wrote:
>> >>>> On 5 Jun 2015, at 14:15, Radim Vansa <rvansa at redhat.com> wrote:
>> >>>>
>> >>>> Is the marshalling comparison really fair? The lambda-table-based
>> >>>> approach removes the need for serializing the class definition, but in
>> >>>> practice - is the class definition always send around with each RPC?
>> >>> ^ We've extensively added Infinispan Externalizers (which use the Object Table approach shown in MarshallingTests) to reduce the size of our payloads, and indeed for all those, no class definitions are sent around. So, as long as the types of those are known to us, we can use such approach and avoid expensive serialization.
>> >>>
>> >>> NOTE: JBoss Marshalling's Externalizers are more expensive than ObjectTable based approach but I can't remember why, it might be cos when you use those, it might send the externalizer class' class definition around, but not sure.
>>
>> Yeah I believe that is correct.  If we used the Infinispan Externalizers in conjunction with the ObjectTable it should only pass around an Integer instead I thought, so it should be much more favorable.
>>
>> >>
>> >> I think the Simple/DynamicClassTable classes in WildFly take care of
>> >> writing only a class id in the stream, instead of the class name, same
>> >> as our ExternalizerTable but using JBoss Marshalling's Externalizers.
>> >> I don't know if there's any performance difference between the two
>> >> approaches, but I assume they must be pretty similar.
>> >>
>> >>>> If
>> >>>> it is so, it seems like a serious flaw of the current codebase, and not
>> >>>> something occurring only for the functional interface. In case that we
>> >>>> keep the marshallers around, we should marshall second RPC (with the
>> >>>> same lambda and another instance of the same captured class), and look
>> >>>> on the diff rather than on the first serialized instance.
>> >>> ^ Hmmm, not sure what you mean there exactly.
>> >
>> >
>> > I meant that in case that the class definition is not sent with each RPC
>> > but only once/few times, we should not pay attention to the cost of
>> > sending the definition. As the test marshalls single RPC, the definition
>> > is always marshalled and accounted.
>>
>> ^ There are multiple tests in MarshallingTests, some of which marshall the definition and others not, and I printed payload sizes:
>>
>> -> testObjectTableCapturingLambda payload is 43 bytes
>> testSerializableApplyLambda payload is 587 bytes
>> testExternalizerNonCapturingLambda payload is 160 bytes
>> testExternalizerCapturingLambda payload is 192 bytes
>> testNonCapturingLambdaAndSerializable payload is 501 bytes
>> testSerializableNonCapturingLambda payload is 597 byt
>> -> testObjectTableNonCapturingLambda payload is 3 bytes
>>
>> We're not going to go with any of the approaches that are over 100 bytes.
>>
>> I thought you could only have 1 ObjectTable defined per Marshalling Configuration?  Also it seems we would need to introduce a new facility for users to register their own lambdas then, since they wouldn't be able to use our Externalizers?
>
> Yeah, there can only be 1 ObjectTable. I haven't looked at in great detail the integration part, but the examples show you can produce JBoss Marshalling Externalizers for lambdas, so I don't see why we would not able to provide Infinispan Externalizers for those and integrate into the current architecture.
>
> The only requirement would be that we'd need a fully defined class for the lambda (as done in the example) we want to register, as oppose to be able to support on the fly defined lambdas.
>
>>
>>
>> The most efficient one, as you'd expect, is the Object Table approach with a Non-Capturing lambda where the size of the payload is 3 bytes. Clearly here no definition is marshalled at all. Second one is the one where the lambda captures an external element and hence that needs to be shipped every time.
>>
>> > So, if I understand that correctly, for user classes that do not
>> > register externalizers (I guess the registration is not automatic), the
>> > definition is sent around with each RPC, right?
>>
>> In that case yeah, to get that to work, you'd have to extend Serializable and then you pay the penalty.
>>
>> This is the whole point why we came up with Externalizers and the framework around it. If you want get running as quickly as possible, make whatever you want to ship around extend Serializable but for ultimate performance, pre-registration of externalizers is the way to go, and the same approach works just as well with function/predicates...etc.
>>
>> Cheers,
>>
>> >
>> > Radim
>> >
>> >>>
>> >>>> Radim
>> >>>>
>> >>>> On 06/05/2015 11:44 AM, Galder Zamarreño wrote:
>> >>>>> Hi all,
>> >>>>>
>> >>>>> Thanks to all who contributed to the 1st draft revision. We've taken all that input and created a separate Github project where we have prototytped the 2nd draft of the advanced Java 8 based Infinispan API. The starting point for you should be FunctionalMap [1].
>> >>>>>
>> >>>>> Here's a brief summary the major changes since the 1st draft:
>> >>>>>
>> >>>>> 1. FunctionalMap has been separated into 3 sub-interfaces, one for read only operations, one for write only operations, and a final one for read-write operations. This separation makes it clear the purpouse of each operation and adds a nice layer of type safety, e.g. you can't write with a read-only map, or you can't read with a write-only map.
>> >>>>>
>> >>>>> 2. Param has been added, which is equivalent to Infinispan Flag with the added benefit that it can carry values. There's no such example right now but we could have in the future.
>> >>>>>
>> >>>>> 3. MetaParam has been added. This is a much more flexible and extensible option compared to the current Infinispan's Metadata.
>> >>>>>
>> >>>>> 4. For operations returning mutiple returns, or working on multiple elements, we've exposed something called Traversable, which is a subset of Java's Stream. See its javadoc to find out more. Kudos to Will for his work on distributed streams which has helped hugely with the design of Traversable.
>> >>>>>
>> >>>>> 5. Listeners have been added, again separating between read-write and write-only listeners (JCache does not offer read-only listeners, e.g. cache entry visited, and hence I think we'll drop our cache entry visited listener at some point).
>> >>>>>
>> >>>>> 6. Will and I have explored marshalling aspects of lambdas, and there are some interesting ways to reduce their costs by +90%! See MarshallingTest for different options to marshall both capturing and non-capturing lambdas and their cost in terms of payload sizes.
>> >>>>>
>> >>>>> Some final notes:
>> >>>>>
>> >>>>> * Please do read the javadocs, they contain a lot of information on the reasons behind the design.
>> >>>>>
>> >>>>> * To find out how the different functional map variants are used, look at ConcurrentMapDecorator and JCacheDecorator who use them to implement the ConcurrentMap and javax.cache.Cache APIs respectively.
>> >>>>>
>> >>>>> * FunctionalMapTest contains examples on how to use functional map variants for other operations which we deeply care about, e.g. Hot Rod atomic version-based replace function.
>> >>>>>
>> >>>>> Special thanks to Mario Fusco (Java 8 In Action book co-author) for his feedback throughout this 2nd draft design process.
>> >>>>>
>> >>>>> Cheers,
>> >>>>>
>> >>>>> [1] https://github.com/infinispan/proto8/blob/master/src/main/java/org/infinispan/api/v8/FunctionalMap.java
>> >>>>> --
>> >>>>> Galder Zamarreño
>> >>>>> galder at redhat.com
>> >>>>>
>> >>>>>
>> >>>>>
>> >>>>>
>> >>>>>
>> >>>>> _______________________________________________
>> >>>>> infinispan-dev mailing list
>> >>>>> infinispan-dev at lists.jboss.org
>> >>>>> https://lists.jboss.org/mailman/listinfo/infinispan-dev
>> >>>>
>> >>>> --
>> >>>> Radim Vansa <rvansa at redhat.com>
>> >>>> JBoss Performance Team
>> >>>>
>> >>>> _______________________________________________
>> >>>> infinispan-dev mailing list
>> >>>> infinispan-dev at lists.jboss.org
>> >>>> https://lists.jboss.org/mailman/listinfo/infinispan-dev
>> >>>
>> >>> --
>> >>> Galder Zamarreño
>> >>> galder at redhat.com
>> >>>
>> >>>
>> >>>
>> >>>
>> >>>
>> >>> _______________________________________________
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>> >>> https://lists.jboss.org/mailman/listinfo/infinispan-dev
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>> >
>> >
>> > --
>> > Radim Vansa <rvansa at redhat.com>
>> > JBoss Performance Team
>> >
>> > _______________________________________________
>> > infinispan-dev mailing list
>> > infinispan-dev at lists.jboss.org
>> > https://lists.jboss.org/mailman/listinfo/infinispan-dev
>>
>>
>> --
>> Galder Zamarreño
>> galder at redhat.com
>>
>>
>>
>>
>>
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>
>
> --
> Galder Zamarreño
> galder at redhat.com
>
>
>
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