@Override
      public void beforeGoingToCompact() {
        LocalRegion.ISSUE_CALLBACKS_TO_CACHE_OBSERVER = false;
        try {
          th.start();
          Thread.sleep(3000);
        } catch (Exception e) {
          logWriter.error("Exception occurred", e);
          throw new AssertionError("Exception occurred when it was not supposed to occur", e);
        }
      }
Check if the roller thread cant skip rolling the entry & if a get is done on that entry , it is
possible for the get operation to get the Oplog which is not yet destroyed but by the time a
basicGet is done,the oplog gets destroyed & the get operation sees the file length zero or it
may encounter null pointer exception while retrieving the oplog.
geode-core/src/integrationTest/java/org/apache/geode/internal/cache/ConcurrentRollingAndRegionOperationsJUnitTest.java