apollo-configservice/src/main/java/com/ctrip/framework/apollo/configservice/service/AppNamespaceServiceWithCache.java/AppNamespaceServiceWithCache/initialize
class AppNamespaceServiceWithCache:  private void initialize() {
    maxIdScanned = 0;
    publicAppNamespaceCache = new CaseInsensitiveMapWrapper<>(Maps.newConcurrentMap());
    appNamespaceCache = new CaseInsensitiveMapWrapper<>(Maps.newConcurrentMap());
    appNamespaceIdCache = Maps.newConcurrentMap();
    scheduledExecutorService = Executors.newScheduledThreadPool(1, ApolloThreadFactory
        .create("AppNamespaceServiceWithCache", true));
  }