@Override
  protected RpcHandler getHandler(final String name, final double handlerFailureThreshhold,
    final int handlerCount, final BlockingQueue<CallRunner> q,
    final AtomicInteger activeHandlerCount, final AtomicInteger failedHandlerCount,
    final Abortable abortable) {
    return new FastPathRpcHandler(name, handlerFailureThreshhold, handlerCount, q,
      activeHandlerCount, failedHandlerCount, abortable, fastPathHandlerStack);
  }
Balanced queue executor with a fastpath. Because this is FIFO, it has no respect for ordering so
a fast path skipping the queuing of Calls if an Handler is available, is possible. Just pass the
Call direct to waiting Handler thread. Try to keep the hot Handlers bubbling rather than let them
go cold and lose context. Idea taken from Apace Kudu (incubating). See
https://gerrit.cloudera.org/#/c/2938/7/src/kudu/rpc/service_queue.h
hbase-server/src/main/java/org/apache/hadoop/hbase/ipc/FastPathBalancedQueueRpcExecutor.java