@Override
    public void prePut(final ObserverContext<? extends RegionCoprocessorEnvironment> e,
      final Put put, final WALEdit edit, final Durability durability) throws IOException {
      Threads.sleep(SLEEP_TIME);
    }
This class is for testing HBaseConnectionManager ServerBusyException. Be careful adding to this
class. It sets a low HBASE_CLIENT_PERSERVER_REQUESTS_THRESHOLD
hbase-server/src/test/java/org/apache/hadoop/hbase/client/TestServerBusyException.java