apollo-configservice/src/main/java/com/ctrip/framework/apollo/configservice/service/ReleaseMessageServiceWithCache.java/ReleaseMessageServiceWithCache/initialize
class ReleaseMessageServiceWithCache:  private void initialize() {
    releaseMessageCache = Maps.newConcurrentMap();
    doScan = new AtomicBoolean(true);
    executorService = Executors.newSingleThreadExecutor(ApolloThreadFactory
        .create("ReleaseMessageServiceWithCache", true));
  }