Thanks for the suggestion about registering the class and for the additional info. I have to say that I had already read the link you sent me, but I didn't really get what was the meaning of "you have to register the classes first". In fact, I gave up with my tries at the time and sticked to Java Serializer for my testing purposes.   Maybe I'll need to get back to this in the future, and I'll do it with additional knowledge now. Thanks a lot.   Also, I have to say that now, after reading all this, I find it a bit strange that Cloudera sets Kryo as default serializer. Anyway. ... View more