apollo-biz/src/main/java/com/ctrip/framework/apollo/biz/message/ReleaseMessageScanner.java/ReleaseMessageScanner/growAndCleanMissingMessages
class ReleaseMessageScanner:  private void growAndCleanMissingMessages() {
    Iterator<Entry<Long, Integer>> iterator = missingReleaseMessages.entrySet()
        .iterator();
    while (iterator.hasNext()) {
      Entry<Long, Integer> entry = iterator.next();
      if (entry.getValue() > missingReleaseMessageMaxAge) {
        iterator.remove();
      } else {
        entry.setValue(entry.getValue() + 1);
      }
    }
  }