Ribbon之ILoadBalancer

Ribbon 负载均衡的连轴方法，它聚合来IPing，IRule, ServerList, ServerListUpdater, ServerListFilter。

• ILoadBalancer
  

public interface ILoadBalancer {   /**    * Initial list of servers.    * This API also serves to add additional ones at a later time    * The same logical server (host:port) could essentially be added multiple times    * (helpful in cases where you want to give more "weightage" perhaps ..)    *     * @param newServers new servers to add    */   public void addServers(List newServers);      /**    * Choose a server from load balancer.    *     * @param key An object that the load balancer may use to determine which server to return. null if     *         the load balancer does not use this parameter.    * @return server chosen    */   public Server chooseServer(Object key);      /**    * To be called by the clients of the load balancer to notify that a Server is down    * else, the LB will think its still Alive until the next Ping cycle - potentially    * (assuming that the LB Impl does a ping)    *     * @param server Server to mark as down    */   public void markServerDown(Server server);      /**    * @deprecated 2016-01-20 This method is deprecated in favor of the    * cleaner {@link #getReachableServers} (equivalent to availableOnly=true)    * and {@link #getAllServers} API (equivalent to availableOnly=false).    *    * Get the current list of servers.    *    * @param availableOnly if true, only live and available servers should be returned    */   @Deprecated   public List getServerList(boolean availableOnly);   /**    * @return Only the servers that are up and reachable.     */    public List getReachableServers();    /**     * @return All known servers, both reachable and unreachable.     */   public List getAllServers();}

• AbstractLoadBalancer
  

public abstract class AbstractLoadBalancer implements ILoadBalancer {        public enum ServerGroup{        ALL,        STATUS_UP,        STATUS_NOT_UP            }            /**     * delegate to {@link #chooseServer(Object)} with parameter null.     */    public Server chooseServer() {       return chooseServer(null);    }        /**     * List of servers that this Loadbalancer knows about     *      * @param serverGroup Servers grouped by status, e.g., {@link ServerGroup#STATUS_UP}     */    public abstract List getServerList(ServerGroup serverGroup);        /**     * Obtain LoadBalancer related Statistics     */    public abstract LoadBalancerStats getLoadBalancerStats();    }

• BaseLoadBalancer
  

基本实现了ILoadBalancer所使用的接口。

• DynamicServerListLoadBalancer
  

在BaseLoadBalancer上，增加额外特性。这里主要是实现动态的服务列表特性。

• ZoneAwareLoadBalancer
  

在DynamicServerListLoadBalancer之上，增加了额外的特性。分zone的形式来配置多个loadBalancer.