void markCleanupStart() {
    CycleLog cycleLog = getCurrentCycleLog();
    if (!cycleLog.getPhase().equals(Phase.COMMIT)) {
      throw new IllegalStateException("Should be in SWITCH phase to transition to CLEANUP phase");
    }
    cycleLog.cleanupStartTime = time.milliseconds();
    flush();
    logger.trace("{}: Marked cleanup as started for {}", file, cycleLog.compactionDetails);
  }
Marks the start of the cleanup phase.
ambry-store/src/main/java/com/github/ambry/store/CompactionLog.java