public class KafkaMigrationTool
extends java.lang.Object
This is a kafka 0.7 to 0.8 online migration tool used for migrating data from 0.7 to 0.8 cluster. Internally,
it's composed of a kafka 0.7 consumer and kafka 0.8 producer. The kafka 0.7 consumer consumes data from the
0.7 cluster, and the kafka 0.8 producer produces data to the 0.8 cluster.
The 0.7 consumer is loaded from kafka 0.7 jar using a "parent last, child first" java class loader.
Ordinary class loader is "parent first, child last", and kafka 0.8 and 0.7 both have classes for a lot of
class names like "kafka.consumer.Consumer", etc., so ordinary java URLClassLoader with kafka 0.7 jar will
will still load the 0.8 version class.
As kafka 0.7 and kafka 0.8 used different version of zkClient, the zkClient jar used by kafka 0.7 should
also be used by the class loader.
The user need to provide the configuration file for 0.7 consumer and 0.8 producer. For 0.8 producer,
the "serializer.class" config is set to "kafka.serializer.DefaultEncoder" by the code.