@Override
      public void beforeGoingToCompact() {
        synchronized (this) {
          if (!callOnce) {
            try {
              for (int i = 0; i < 100; i++) {
                region.put(i, "newVal" + i);
              }
            } catch (Exception e) {
              logWriter.error("exception not expected", e);
              failureCause = "FAILED::" + e;
              testFailed = true;
              fail("FAILED::" + e);
            }
          }
          callOnce = true;
        }

      }
OplogRoller should correctly add those entries created in an Oplog , but by the time rolling
has started , the entry exists in the current oplog
geode-core/src/integrationTest/java/org/apache/geode/internal/cache/DiskRegOplogSwtchingAndRollerJUnitTest.java