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
/**
     * Default value for the times of retry: 3
     */
    public static final int DEFAULT_REGISTRY_RETRY_TIMES = 3;
    /**
     * Reconnection period in milliseconds for register center
     */
    public static final String REGISTRY_RECONNECT_PERIOD_KEY = "reconnect.period";
    public static final int DEFAULT_REGISTRY_RECONNECT_PERIOD = 3 * 1000;
    public static final String SESSION_TIMEOUT_KEY = "session";
    public static final int DEFAULT_SESSION_TIMEOUT = 60 * 1000;
    /**
     * The key name for export URL in register center
     */
    public static final String EXPORT_KEY = "export";
    /**
     * The key name for reference URL in register center
     */
    public static final String REFER_KEY = "refer";
    /**
     * callback inst id
     */
    public static final String CALLBACK_SERVICE_KEY = "callback.service.instid";
    /**
     * The limit of callback service instances for one interface on every client
     */
    public static final String CALLBACK_INSTANCES_LIMIT_KEY = "callbacks";
    /**
     * The default limit number for callback service instances
     *