A ThreadFactory for constructing new HiveServer2 threads that lets you plug in custom cleanup code to be called before this thread is GC-ed. Currently cleans up the following: 1. ThreadLocal RawStore object: In case of an embedded metastore, HiveServer2 threads (foreground and background) end up caching a ThreadLocal RawStore object. The ThreadLocal RawStore object has an instance of PersistenceManagerFactory and PersistenceManager. The PersistenceManagerFactory keeps a cache of PersistenceManager objects, which are only removed when PersistenceManager#close method is called. HiveServer2 uses ExecutorService for managing thread pools for foreground and background threads. ExecutorService unfortunately does not provide any hooks to be called, when a thread from the pool is terminated. As a solution, we're using this ThreadFactory to keep a cache of RawStore objects per thread. And we are doing clean shutdown in the finalizer for each thread.