docs: private Map<ServiceInstanceToken, InstanceHealthPair> getCacheServiceInstances() {
          if (instanceCache == null) {
              synchronized (this) {
                  if (instanceCache == null) {
                      instanceCache = new ConcurrentHashMap<ServiceInstanceToken, InstanceHealthPair>();
                      initJobTasks();
                  }
              }
          }
          return instanceCache;
      }