There are two issues with these threads:
- there should have a better name. pool-x-thread-y is the default name given by java.util.concurrent.Executors
- these threads should not survive to a minicluster shutdown
They are created by org.apache.hadoop.ipc.Server$Listener (with version 0.20.205.0; the code was different before), so the first issue is a hadoop common one. It's unclear for the second one, it could be hadoop-common as well.
Constructor for org.apache.hadoop.ipc.Server$Listener:
Server#stop shutdowns the thread pool.