[hibernate-dev] [Search] Native Java serialization support

[Hardy Ferentschik]

Hi,

I would like to summarize a discussion we had on IRC to get some more feedback and come to 
a decision on how to move forward. 

I am currently in the need of extending our serialization support for the distributed Search
deployment scenarios. Basically we are serializing our different LuceneWork instances from slave
to master in this case. This includes things like Lucene's Document instances, which are part 
of add/update operations. Historically, this needs arose with Lucene dropping all serialization 
support for their classes, so we were forced to implement our custom serialization. To do so we
defined an SPI (org.hibernate.search.indexes.serialization.spi.*) and provided two implementations,
one based on native Java serialization and one based on Avro [1]. The two implementations are provided
as separate artifacts (the serialization/java and serialization/avro modules in our build) and
theoretically it should be possible to switch between them by exchanging jar files. 

I am saying theoretically, since I found out during my recent work, that the Java serialization module
is broken at several places. In its current state it would not work (I guess we never noticed since 
the default is Avro and we do not even document the possibility to change implementation. However, it also
shows that no one has even tried).

The question is, what do we do now? Do we want two implementations and should the Java serialization 
be fixed and then extended with the new functionality (btw, I need to serialize DocValues now) or is
it time to drop this module, reducing the amount of code we have to maintain and making it a bit 
easier to implement new serialization requirements. With dropping the module I mean to
remove the serialization/java module leaving everything else in place. So you still can write
your own serialization implementation, however, we provide no alternative to our preferred choice 
of Avro (which is afaik considerably faster than native Java serialization which was one of the 
driving factors of using it).

I think on IRC we already "kind of" agreed that we should drop native Java serialization. I
just wanted to put it out once more for everyone to comment/vote.

--Hardy

[1] http://avro.apache.org/ 
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