@julienledem , if it implements Configurable, will Hadoop make sure that it is given a configuration object on both the client and the mappers and reducers? When?

@isnotinvain , the issue is that the Configuration object is used during deserialization. It's true that cluster-side the getRecordReader has access to the conf object, but this is called _after_ the InsputSplit is deserialized. Does that make sense? I could, I suppose, partically deserialize it. I could deserialize the part that needs the conf into a bytearray and then wait until initialize is called and deserialize with the conf?

I would prefer Julien's approach if it works... looking at Hadoop's code, such as https://github.com/apache/hadoop-mapreduce/blob/HDFS-641/src/java/org/apache/hadoop/mapreduce/lib/input/TaggedInputSplit.java, it looks like that is indeed the approach.