@Override
      public void afterWritingBytes() {
        if (!alreadyComeHere) {
          try {

            region.destroy("Key");
          } catch (Exception e1) {
            logWriter.error("Exception occurred", e1);
            fail("encounter exception when not expected " + e1);
          }
        }
        alreadyComeHere = true;
      }
A region close is done after flush is over. The close is done in a separate thread and a 3000
ms wait is put to ensure that the separate thread has closed the region
geode-core/src/integrationTest/java/org/apache/geode/internal/cache/ConcurrentFlushingAndRegionOperationsJUnitTest.java