@Override
    public void preGetOp(final ObserverContext<? extends RegionCoprocessorEnvironment> e,
      final Get get, final List<Cell> results) throws IOException {
      // After first sleep, all requests are timeout except the last retry. If we handle
      // all the following requests, finally the last request is also timeout. If we drop all
      // timeout requests, we can handle the last request immediately and it will not timeout.
      if (ct.incrementAndGet() <= 1) {
        Threads.sleep(SLEEP_TIME * RPC_RETRY * 2);
      } else {
        Threads.sleep(SLEEP_TIME);
      }
    }
Coprocessor that sleeps a while the first time you do a Get
hbase-server/src/test/java/org/apache/hadoop/hbase/client/TestDropTimeoutRequest.java