apollo-configservice/src/main/java/com/ctrip/framework/apollo/configservice/service/AccessKeyServiceWithCache.java/AccessKeyServiceWithCache/initialize
class AccessKeyServiceWithCache:  private void initialize() {
    scheduledExecutorService = new ScheduledThreadPoolExecutor(1,
        ApolloThreadFactory.create("AccessKeyServiceWithCache", true));
    lastTimeScanned = new Date(0L);

    ListMultimap<String, AccessKey> multimap = ListMultimapBuilder.treeKeys(String.CASE_INSENSITIVE_ORDER)
        .arrayListValues().build();
    accessKeyCache = Multimaps.synchronizedListMultimap(multimap);
    accessKeyIdCache = Maps.newConcurrentMap();
  }