ribbon怎么自定义负载均衡策略

在Ribbon中，可以通过自定义IRule来实现自定义负载均衡策略。IRule是Ribbon中用于路由请求的规则，可以根据自定义的负载均衡算法来选择服务实例。

下面是一个自定义负载均衡策略的示例：

创建自定义规则类CustomRule，继承AbstractLoadBalancerRule，并实现choose方法，该方法会在每次请求时被调用，根据自定义的负载均衡算法选择服务实例。

public class CustomRule extends AbstractLoadBalancerRule {

    private AtomicInteger nextServerCyclicCounter;

    public CustomRule() {
        nextServerCyclicCounter = new AtomicInteger(0);
    }

    @Override
    public Server choose(Object key) {
        ILoadBalancer lb = getLoadBalancer();

        if (lb == null) {
            return null;
        }

        Server server = null;
        int count = 0;
        while (server == null && count++ < 10) {
            List<Server> reachableServers = lb.getReachableServers();
            List<Server> allServers = lb.getAllServers();

            int serverCount = allServers.size();
            if (serverCount == 0) {
                return null;
            }

            int nextServerIndex = getNextServerIndex(serverCount);
            server = reachableServers.get(nextServerIndex);

            if (server == null) {
                Thread.yield();
                continue;
            }

            if (server.isAlive() && (server.isReadyToServe())) {
                return (server);
            }

            server = null;
            Thread.yield();
        }

        if (count >= 10) {
            logger.warn("No available alive servers after 10 tries from load balancer: "
                    + lb);
        }
        return server;
    }

    protected int getNextServerIndex(int serverCount) {
        while (true) {
            int current = nextServerCyclicCounter.get();
            int next = (current + 1) % serverCount;
            if (nextServerCyclicCounter.compareAndSet(current, next))
                return next;
        }
    }
}

在Spring Boot配置文件中配置使用自定义规则：

ribbon:
  eureka:
    enabled: true
  NFLoadBalancerRuleClassName: com.example.CustomRule

这样就可以使用自定义的负载均衡算法了。