Thanks for clarifying this Galder.
Yes, the network layer is indeed the culprit and the purpose of this experiment.

What is the approach you envision regarding the IDL? Should we strive for a pure IDL definition of the service? That could be an interesting approach that would make it possible for a third party to generate their own infinispan grpc client in any new language that we do not already offer support, just based on the IDL. And maybe using a different grpc implementation if they do not find suitable the one from google.

I was not suggesting we should do type transformation or anything on the client side that would require an extra layer of code on top of what grpc generates for the client, so maybe a pure IDL based service definition would indeed be possible, without extra helpers. No type transformation, just type information. Exposing the type info that comes from the server would be enough, a lot better than dumbing everything down to a byte[].

Adrian

On 05/30/2018 12:16 PM, Galder Zamarreno wrote:
On Tue, May 29, 2018 at 8:57 PM Adrian Nistor <anis...@redhat.com <mailto:anis...@redhat.com>> wrote:

    Vittorio, a few remarks regarding your statement "...The
    alternative to this is to develop a protostream equivalent for
    each supported language and it doesn't seem really feasible to me."

    No way! That's a big misunderstanding. We do not need to
    re-implement the protostream library in C/C++/C# or any new
    supported language.
    Protostream is just for Java and it is compatible with Google's
    protobuf lib we already use in the other clients. We can continue
    using Google's protobuf lib for these clients, with or without gRPC.
    Protostream does not handle protobuf services as gRPC does, but we
    can add support for that with little effort.

    The real problem here is if we want to replace our hot rod
    invocation protocol with gRPC to save on the effort of
    implementing and maintaining hot rod in all those clients. I
    wonder why the obvious question is being avoided in this thread.


^ It is not being avoided. I stated it quite clearly when I replied but maybe not with enough detail. So, I said:

> The biggest problem I see in our client/server architecture is the ability to quickly deliver features/APIs across multiple language clients. Both Vittorio and I have seen how long it takes to implement all the different features available in Java client and port them to Node.js, C/C++/C#...etc. This effort lead by Vittorio is trying to improve on that by having some of that work done for us. Granted, not all of it will be done, but it should give us some good foundations on which to build.

To expand on it a bit further: the reason it takes us longer to get different features in is because each client implements its own network layer, parses the protocol and does type transformations (between byte[] and whatever the client expects).

IMO, the most costly things there are getting the network layer right (from experience with Node.js, it has taken a while to do so) and parsing work (not only parsing itself, but doing it in a efficient way). Network layer also includes load balancing, failover, cluster failover...etc.

From past experience, transforming from byte[] to what the client expects has never really been very problematic for me. What's been difficult here is coming up with encoding architecture that Gustavo lead, whose aim was to improve on the initial compatibility mode. But, with that now clear, understood and proven to solve our issues, the rest in this area should be fairly straightforward IMO.

Type transformation, once done, is a constant. As we add more Hot Rod operations, it's mostly the parsing that starts to become more work. Network can also become more work if instead of RPC commands you start supporting streams based commands.

gRPC solves the network (FYI: with key as HTTP header and SubchannelPicker you can do hash-aware routing) and parsing for us. I don't see the need for it to solve our type transformations for us. If it does it, great, but does it support our compatibility requirements? (I had already told Vittorio to check Gustavo on this). Type transformation is a lower prio for me, network and parsing are more important.

Hope this clarifies better my POV.

Cheers



    Adrian


    On 05/29/2018 03:45 PM, Vittorio Rigamonti wrote:
    Thanks Adrian,

    of course there's a marshalling work under the cover and that is
    reflected into the generated code (specially the accessor methods
    generated from the oneof clause).

    My opinion is that on the client side this could be accepted, as
    long as the API are well defined and documented: application
    developer can build an adhoc decorator on the top if needed. The
    alternative to this is to develop a protostream equivalent for
    each supported language and it doesn't seem really feasible to me.

    On the server side (java only) the situation is different:
    protobuf is optimized for streaming not for storing so probably a
    Protostream layer is needed.

    On Mon, May 28, 2018 at 4:47 PM, Adrian Nistor
    <anis...@redhat.com <mailto:anis...@redhat.com>> wrote:

        Hi Vittorio,
        thanks for exploring gRPC. It seems like a very elegant
        solution for exposing services. I'll have a look at your PoC
        soon.

        I feel there are some remarks that need to be made regarding
        gRPC. gRPC is just some nice cheesy topping on top of
        protobuf. Google's implementation of protobuf, to be more
        precise.
        It does not need handwritten marshallers, but the 'No need
        for marshaller' does not accurately describe it. Marshallers
        are needed and are generated under the cover by the library
        and so are the data objects and you are unfortunately forced
        to use them. That's both the good news and the bad news:) The
        whole thing looks very promising and friendly for many uses
        cases, especially for demos and PoCs :))). Nobody wants to
        write those marshallers. But it starts to become a nuisance
        if you want to use your own data objects.
        There is also the ugliness and excessive memory footprint of
        the generated code, which is the reason Infinispan did not
        adopt the protobuf-java library although it did adopt
        protobuf as an encoding format.
        The Protostream library was created as an alternative
        implementation to solve the aforementioned problems with the
        generated code. It solves this by letting the user provide
        their own data objects. And for the marshallers it gives you
        two options: a) write the marshaller yourself (hated), b)
        annotated your data objects and the marshaller gets generated
        (loved). Protostream does not currently support service
        definitions right now but this is something I started to
        investigate recently after Galder asked me if I think it's
        doable. I think I'll only find out after I do it:)

        Adrian


        On 05/28/2018 04:15 PM, Vittorio Rigamonti wrote:
        Hi Infinispan developers,

        I'm working on a solution for developers who need to access
        Infinispan services  through different programming languages.

        The focus is not on developing a full featured client, but
        rather discover the value and the limits of this approach.

        - is it possible to automatically generate useful clients in
        different languages?
        - can that clients interoperate on the same cache with the
        same data types?

        I came out with a small prototype that I would like to
        submit to you and on which I would like to gather your
        impressions.

         You can found the project here [1]: is a gRPC-based
        client/server architecture for Infinispan based on and
        EmbeddedCache, with very few features exposed atm.

        Currently the project is nothing more than a poc with the
        following interesting features:

        - client can be generated in all the grpc supported
        language: java, go, c++ examples are provided;
        - the interface is full typed. No need for marshaller and
        clients build in different language can cooperate on the
        same cache;

        The second item is my preferred one beacuse it frees the
        developer from data marshalling.

        What do you think about?
        Sounds interesting?
        Can you see any flaw?

        There's also a list of issues for the future [2], basically
        I would like to investigate these questions:
        How far this architecture can go?
        Topology, events, queries... how many of the Infinispan
        features can be fit in a grpc architecture?

        Thank you
        Vittorio

        [1] https://github.com/rigazilla/ispn-grpc
        [2] https://github.com/rigazilla/ispn-grpc/issues

--
        Vittorio Rigamonti

        Senior Software Engineer

        Red Hat

        <https://www.redhat.com>

        Milan, Italy

        vriga...@redhat.com <mailto:vriga...@redhat.com>

        irc: rigazilla

        <https://red.ht/sig>


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--
    Vittorio Rigamonti

    Senior Software Engineer

    Red Hat

    <https://www.redhat.com>

    Milan, Italy

    vriga...@redhat.com <mailto:vriga...@redhat.com>

    irc: rigazilla

    <https://red.ht/sig>


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