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From Andrey Kornev <andrewkor...@hotmail.com>
Subject RE: OSGi migration may require a special marshaller
Date Tue, 03 Nov 2015 21:42:11 GMT
Romain/Dmitriy,

I prefer Romain's approach, but just curious, in the API you guys are proposing why use a
byte[] rather than OutputStream/InputStream? With a byte[], one would inevitably end up wrapping
it into a byte stream class. Also, the stream-based interface would be more in line with the
Marshaller API.

Also for symmetry with the readClass() method, I suggest the writeClass() take a Class<?>
rather than an object.

Regards
Andrey

> From: romain.gilles@gmail.com
> Date: Tue, 3 Nov 2015 21:24:01 +0000
> Subject: Re: OSGi migration may require a special marshaller
> To: dev@ignite.apache.org
> 
> Hi Dmitriy,
> I think your solution is good. Maybe I will change it a little bit... :P
> I think you should delegate the Class resolution to the resolver. Because
> for example with your current solution the marshaller may before (or after)
> store the fqn of the class (maybe only the first time it encounter it) but
> in order to save the classloader context resolution the implementation of
> the resolver may have to save the package name of the given object and some
> extra info therefore the content package name will be serialized two times.
> Ok, it's not a big deal.
> But now if the resolver identify that it can reuse the same class loader
> for a couple of classes. It will be interesting for it to have a
> serialization context in order to save, let say, classloader/id mapping in
> order to save the id instead of a more longer representation.
> So I propose something like that:
> *public interface ClassResolver {*
> *    // This method is invoked on the sender side to *
> *    // marshal the information about the class.*
> *    // where the context is a map style object that is reset/new for each
> object graph serialization.*
> *    public byte[] writeClass(Object o, Context context) throws
> IgniteException;*
> 
> *    // This method is invoked on the receiving side to*
> *    // retrieve the class based on provided information.*
> *    // where the context is a map style object that is reset/new for each
> object graph serialization.*
> *    public Class<?> readClass(byte[], Context context) throws
> IgniteException;*
> *}*
> 
> I think your proposal will solve our issue and maybe also open a door for
> the osgi development.
> Let me know what do you think about me proposal? :)
> 
> Thanks,
> 
> Romain
> 
> Le mar. 3 nov. 2015 à 20:05, Dmitriy Setrakyan <dsetrakyan@apache.org> a
> écrit :
> 
> > Romain,
> >
> > Can you comment on the ClassLoaderResolver suggestion that I proposed
> > earlier? Will it solve your problem?
> >
> > D.
> >
> > On Tue, Nov 3, 2015 at 2:38 AM, Romain Gilles <romain.gilles@gmail.com>
> > wrote:
> >
> > > Hi Raul,
> > >  - Do you plan to use the TCCL when marshalling in OSGi env? If yes how?
> > >  - I like the point 2. Maybe for a graph of object that come from
> > different
> > > packages / bundles you may have to recursively capture the package
> > version
> > > of the individual element of your graph.
> > >  - For the point 3 I wonder if it will not over-complexify the solution.
> > As
> > > a developer you will have to think about it. And it is not obvious in the
> > > code where things are serialized or not. You may use lambda in your
> > > application code therefore the current package become what you call a DTO
> > > package. The current state of ignite does not enforce you to specify it
> > for
> > > "classical" classloading application. If you introduce this extra step
> > for
> > > OSGi ready application you will maybe discourage people to use OSGi.
> > >
> > > To comeback to our solution. We start we a strong assumption: our cluster
> > > is homogeneous in term of code so, of course, it simplify our life :).
> > >
> > > BTW if you can introduce an extension point in the class resolution
> > > mechanism it can be interesting for end user in order to allow them to
> > > optimize it based on there specific use cases.
> > >
> > > Romain.
> > >
> > > Le mar. 3 nov. 2015 à 00:21, Raul Kripalani <raul@evosent.com> a écrit
:
> > >
> > > > Hi Andrey,
> > > >
> > > > Thanks for the participation in this topic.
> > > >
> > > > I don't like the solution to incorporate the bundle symbolic name in
> > the
> > > > serialised form. Nothing guarantees that the classdef will be located
> > > under
> > > > the same bundle in both source and target machines. We also have to
> > take
> > > > into account that OSGi allows for multiple versions of the same
> > > > bundle/packages to co-exist in the same  container. So it becomes more
> > > > complex.
> > > >
> > > > Using the TCCL should work when serialising, but it'll probably be of
> > no
> > > > use when deserialising on the other end.
> > > >
> > > > I need to enhance Ignite to:
> > > >
> > > > 1. Use the TCCL when marshalling on one end.
> > > > 2. Incorporate the package version of the class in the serialised form
> > if
> > > > Ignite is running in an OSGi environment.
> > > > 3. On the receiver end, discover cache entities / DTOs in all bundles
> > > > through a custom OSGi manifest header or the like, as I explained
> > before.
> > > > Package version must be taken into account.
> > > >
> > > > What do you think?
> > > >
> > > > Raúl.
> > > > On 2 Nov 2015 17:25, "Andrey Kornev" <andrewkornev@hotmail.com>
wrote:
> > > >
> > > > > Raul,
> > > > >
> > > > > The fundamental hurdle we need to jump over to make Ignite
> > OSGi-enabled
> > > > is
> > > > > the marshalling. More specifically the issue is with deserialization
> > of
> > > > the
> > > > > classes that are provided by the bundles other than the Ignite bundle
> > > > > itself.
> > > > >
> > > > > When the Ignite transport layer receives a message it needs to figure
> > > out
> > > > > how to deserialize the bytes and for that it needs to know the bundle
> > > > that
> > > > > provides the class to be deserailized. At this point TCCL is of no
> > use.
> > > > To
> > > > > make things more complex, the class may contain other classes that
> > come
> > > > > from other bundles, and so on recursively. This means that each
> > object
> > > in
> > > > > the hierarchy must be serialized with its bundle name (or bundle
id),
> > > so
> > > > > that the deserializer will then be able to correctly resolve the
> > class
> > > > > while traversing the object hierarchy during deserialization.
> > > > >
> > > > > Unfortunately, Ignite's OptimizedMarshaller is lacking the ability
to
> > > > plug
> > > > > in a custom class resolver. Romain's solution was to use Kryo that
> > does
> > > > > provide a way to customize class resolution. It has solved the
> > problem
> > > of
> > > > > capturing the bundle info and he was able to successfully run Ignite
> > > as a
> > > > > bundle in an OSGi container (after some repackaging and inclusion
of
> > > the
> > > > > manifest). But Kryo-based marshalling introduced a lot of complexity
> > to
> > > > the
> > > > > code and incorrect use of Kryo's numerous serializers caused some
> > weird
> > > > > hard-to-debug issues in the Ignite core (like duplicate cache entries
> > > due
> > > > > to incorrect marshalling of the GridDhtPArtitonFullMap class -- go
> > > > > figure!). Overall the Kryo-based solution is brittle and hard to
> > > > maintain.
> > > > >
> > > > > I feel the correct solution to OSGi problem would be to
> > > > > 1) enhance the OptimizedMarshaller to allow custom class resolution.
> > > > > 2) provide an OSGi-enabled OptimizedMarshaller (in addition to the
> > > > > original one) to be used in OSGi environment.
> > > > >
> > > > > Regards
> > > > > Andrey
> > > > >
> > > > > > From: raulk@apache.org
> > > > > > Date: Mon, 2 Nov 2015 12:41:47 +0000
> > > > > > Subject: Re: OSGi migration may require a special marshaller
> > > > > > To: dev@ignite.apache.org
> > > > > >
> > > > > > Hi Romain,
> > > > > >
> > > > > > I'm working on the OSGi compatibility of Ignite. I appreciate
your
> > > > input.
> > > > > >
> > > > > > I'm thinking about the situation you describe and I wonder if
> > you're
> > > > > > exporting Ignite as an OSGi service which is then consumed from
> > other
> > > > > > bundles. Under this situation, it would be quite easy to reproduce
> > > the
> > > > > > behaviour you describe if Ignite is not resolving classes via
the
> > > TCCL.
> > > > > > Need to dig deeper into that.
> > > > > >
> > > > > > Off the top of my head, there are two alternatives to solve
it:
> > > > > >
> > > > > > 1. Use the TCCL for marshalling/unmarshalling (if not already
> > used) –
> > > > we
> > > > > > gotta be wary of possible regressions.
> > > > > > 2. Create a special OSGi header Ignite-Export-Package so that
> > bundles
> > > > > > containing DTOs can expose packages to Ignite's marshallers.
> > > > > >
> > > > > > Regards,
> > > > > >
> > > > > > *Raúl Kripalani*
> > > > > > PMC & Committer @ Apache Ignite, Apache Camel | Integration,
Big
> > Data
> > > > and
> > > > > > Messaging Engineer
> > > > > > http://about.me/raulkripalani |
> > > > http://www.linkedin.com/in/raulkripalani
> > > > > > http://blog.raulkr.net | twitter: @raulvk
> > > > > >
> > > > > > On Mon, Nov 2, 2015 at 9:56 AM, Gilles, Romain <
> > > > romain.gilles@misys.com>
> > > > > > wrote:
> > > > > >
> > > > > > > Hi all,
> > > > > > >
> > > > > > > I'm really interested in this issue:
> > > > > > > https://issues.apache.org/jira/browse/IGNITE-1270 . We
some
> > stuff
> > > to
> > > > > make
> > > > > > > it work in our osgi environment. The main issue for us
now is the
> > > > > > > serialization. I think it you will have to rework the
> > > > > OptimizedMarshaller
> > > > > > > or any other marshaller that works with object that come
from
> > > outside
> > > > > your
> > > > > > > class space.
> > > > > > >
> > > > > > > We have try kryo that works. Kryo provide an extension
point in
> > > order
> > > > > to
> > > > > > > resolve the classes:
> > > > > > >
> > > > >
> > > >
> > >
> > https://github.com/EsotericSoftware/kryo/blob/master/src/com/esotericsoftware/kryo/ClassResolver.java
> > > > > > > . With this extension we are able to solve the problem
of
> > external
> > > > > classes.
> > > > > > > The only issue with kryo is that some classes need a certain
care
> > > in
> > > > > the
> > > > > > > serialization process and therefore a specialized serializer.
> > > > > > >
> > > > > > > So I would like to know from the community what do think
of
> > > changing
> > > > > the
> > > > > > > way the optimized marshaller works or introducing the support
of
> > > yet
> > > > > > > another marshaller based on a kryo like technology?
> > > > > > >
> > > > > > >
> > > > > > > Thanks in advance,
> > > > > > >
> > > > > > >
> > > > > > > Best regards,
> > > > > > >
> > > > > > >
> > > > > > > Romain.
> > > > > > >
> > > > > > >
> > > > > > > PS: I'm ready to help in the both cases.
> > > > > > > "Misys" is the trade name of the Misys group of companies.
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