dubbo-cluster/src/main/java/org/apache/dubbo/rpc/cluster/loadbalance/
ConsistentHashLoadBalance.java
![image](https://user-images.githubusercontent.com/30815149/55045041-740f4980-5077-11e9-8b6c-7a2b18b0d58e.png)
我看其他地方都是用Constants进行替换，这里是不是可以使用Constants类里的属性进行替换
*
     * @since 2.7.0
     */
    public static final String SIMPLIFIED_KEY = "simplified";
    /**
     * After simplify the registry, should add some paramter individually for provider.
     *
     * @since 2.7.0
     */
    public static final String EXTRA_KEYS_KEY = "extra-keys";
    /**
     * To decide whether to exclude unavailable invoker from the cluster
     */
    public static final String CLUSTER_AVAILABLE_CHECK_KEY = "cluster.availablecheck";
    /**
     * The default value of cluster.availablecheck
     *
     * @see #CLUSTER_AVAILABLE_CHECK_KEY
     */
    public static final boolean DEFAULT_CLUSTER_AVAILABLE_CHECK = true;
    /**
     * To decide whether to enable sticky strategy for cluster
     */
    public static final String CLUSTER_STICKY_KEY = "sticky";
    /**
     * The default value of sticky
     *
     * @see #CLUSTER_STICKY_KEY
     */
    public static final boolean DEFAULT_CLUSTER_STICKY = false;