Compatibility between disparate clients should certainly be supported, but what about a pluggable marshaller mechanism? Let's consider all usage scenarios:

* Only Java clients: in most cases, JBoss marshalling is adequate, no need to involve protobuf or json and since JBoss Marshalling is default, no need to configure anything.

* Mix of Java and C++/C#/Python clients: the Protobuf encoding works wonderfully for that. The client could be configured to use the protostream marshaller, the same for the server.

* Mix of Java, C++/C#/Python and REST clients: protobuf with json [1] encoding is an interesting option. Same as above, a protostream marshaller with json support could
be configured both on client and server.

* Custom marshallers: consider FlatBuffers [2], for example, an interesting new cross-platform serializer that allows to access serialized data without de-serializing the whole payload,

and without generating any transient memory, and it optionally supports JSON. It could be interesting to write a marshaller based on it and plug it on Infinispan.

Although we have a way of configuring the marshaller on client (via RemoteCacheManager) and server (deployable jar), there'd be more work to do in order make them really pluggable:

- Some serialization formats like Protobuf and [2] require interface description to be available on both client and server. This is not supported for all marshallers, just for Protostream
- Remote query requires some metadata regarding which fields to index and how, and this would need to be possible on every language regardless of the marshalling.
Currently, this info can be encoded in the .proto file only, a custom marshaller would not work.
- Currently remote query is settled on protobuf not only for the byte array but for the the HotRod query request and response [3]

Is having a pluggable serializer mechanism too far fetched, given the effort already invested towards protobuf?

Gustavo

[1] https://developers.google.com/protocol-buffers/docs/proto3#json
[2] https://google.github.io/flatbuffers/
[2] https://code.facebook.com/posts/872547912839369/improving-facebook-s-performance-on-android-with-flatbuffers/
[3] https://github.com/infinispan/infinispan/blob/master/remote-query/remote-query-client/src/main/resources/org/infinispan/query/remote/client/query.proto