apollo-biz/src/main/java/com/ctrip/framework/apollo/biz/message/ReleaseMessageScanner.java/ReleaseMessageScanner/scanMissingMessages
class ReleaseMessageScanner:  private void scanMissingMessages() {
    Set<Long> missingReleaseMessageIds = missingReleaseMessages.keySet();
    Iterable<ReleaseMessage> releaseMessages = releaseMessageRepository
        .findAllById(missingReleaseMessageIds);
    fireMessageScanned(releaseMessages);
    releaseMessages.forEach(releaseMessage -> {
      missingReleaseMessageIds.remove(releaseMessage.getId());
    });
    growAndCleanMissingMessages();
  }