@Override
      public void doWork() {
        // then do some fun where we commit before all nodes have prepared
        // "one" commits before anyone else is done
        ref.memberAcquiredBarrier(this.opName, this.cohort[0]);
        ref.memberFinishedBarrier(this.opName, this.cohort[0], new byte[0]);
        // but "two" takes a while
        ref.memberAcquiredBarrier(this.opName, this.cohort[1]);
        // "three"jumps ahead
        ref.memberAcquiredBarrier(this.opName, this.cohort[2]);
        ref.memberFinishedBarrier(this.opName, this.cohort[2], new byte[0]);
        // and "four" takes a while
        ref.memberAcquiredBarrier(this.opName, this.cohort[3]);
      }
Test that if nodes join the barrier early we still correctly handle the progress
hbase-server/src/test/java/org/apache/hadoop/hbase/procedure/TestProcedureCoordinator.java