@Override
  public void setDone() throws InterruptedException {
    downstreamConsumer.setDone();
    cvbPool.clear();
  }
Returns the ECB to caller for reuse. Only safe to call if the thread is the only owner
of the ECB in question; or, if ECB is still in pendingData, pendingData must be locked.
llap-server/src/java/org/apache/hadoop/hive/llap/io/decode/EncodedDataConsumer.java