apollo-configservice/src/main/java/com/ctrip/framework/apollo/configservice/util/InstanceConfigAuditUtil.java/InstanceConfigAuditUtil/InstanceConfigAuditUtil
class InstanceConfigAuditUtil:  public InstanceConfigAuditUtil(final InstanceService instanceService) {
    this.instanceService = instanceService;
    auditExecutorService = Executors.newSingleThreadExecutor(
        ApolloThreadFactory.create("InstanceConfigAuditUtil", true));
    auditStopped = new AtomicBoolean(false);
    instanceCache = CacheBuilder.newBuilder().expireAfterAccess(1, TimeUnit.HOURS)
        .maximumSize(INSTANCE_CACHE_MAX_SIZE).build();
    instanceConfigReleaseKeyCache = CacheBuilder.newBuilder().expireAfterWrite(1, TimeUnit.DAYS)
        .maximumSize(INSTANCE_CONFIG_CACHE_MAX_SIZE).build();
  }