一、报错情况：
Caused by: java.lang.AbstractMethodError: org.springframework.cloud.netflix.ribbon.RibbonLoadBalancerClient.choose(Ljava/lang/String;Lorg/springframework/cloud/client/loadbalancer/Request;)Lorg/springframework/cloud/client/ServiceInstance;
二、报错原因：
当前我的springboot版本 2.4.3 ，springcloud版本 2020.0.2
出现这个问题是没有loadbalancer，但是nacos中ribbon会造成loadbalancer包失效,所以在包中移除ribbion依赖，并加入loadbalancer依赖；
三、解决方案：
网上有方案建议降低springboot和springcloud版本，我个人不太喜欢这种方案，咱们总不能阻止版本进步吧。
按照上面说的在nacos"包中移除ribbion依赖，并加入loadbalancer依赖"
org.springframework.cloud spring-cloud-starter-alibaba-nacos-discoveryorg.springframework.cloud spring-cloud-starter-netflix-ribbonorg.springframework.cloud spring-cloud-loadbalancer
四、修复后显示如下：
启动提供者服务时：
2021-05-21 16:34:23 |WARN |main |LoadBalancerCacheAutoConfiguration.java:82 |org.springframework.cloud.loadbalancer.config.LoadBalancerCacheAutoConfiguration$LoadBalancerCaffeineWarnLogger |Spring Cloud LoadBalancer is currently working with the default cache. You can switch to using Caffeine cache, by adding it and org.springframework.cache.caffeine.CaffeineCacheManager to the classpath.
启动消费者服务时：
2021-05-21 16:34:23 |WARN |main |LoadBalancerCacheAutoConfiguration.java:82 |org.springframework.cloud.loadbalancer.config.LoadBalancerCacheAutoConfiguration$LoadBalancerCaffeineWarnLogger |Spring Cloud LoadBalancer is currently working with the default cache. You can switch to using Caffeine cache, by adding it and org.springframework.cache.caffeine.CaffeineCacheManager to the classpath.
--调用服务时：---
2021-05-21 16:36:40 |WARN |http-nio-8001-exec-9 |ServiceInstanceListSupplierBuilder.java:229 |org.springframework.cloud.loadbalancer.core.ServiceInstanceListSupplierBuilder |LoadBalancerCacheManager not available, returning delegate without caching.
