负载均衡原理分析
@LoadBalanced
@Bean
public RestTemplate restTemplate(RestTemplateBuilder builder) {
return builder
.setConnectTimeout(Duration.ofMillis(100))
.setReadTimeout(Duration.ofMillis(500))
.requestFactory(this::requestFactory)
.build();
}
进入该注解@LoadBalanced
以看到
Annotation to mark a RestTemplate bean to be configured to use a LoadBalancerClient.
打开LoadBalancerClient
的实现类**RibbonLoadBalancerClient
**
//使用LoadBalancer的ServiceInstance对指定的服务执行请求。
T execute(String serviceId, ServiceInstance serviceInstance,
LoadBalancerRequest request) throws IOException;
//RibbonLoadBalancerClient的实现
public <T> T execute(String serviceId, LoadBalancerRequest<T> request, Object hint)
throws IOException {
ILoadBalancer loadBalancer = getLoadBalancer(serviceId);
Server server = getServer(loadBalancer, hint);
if (server == null) {
throw new IllegalStateException("No instances available for " + serviceId);
}
RibbonServer ribbonServer = new RibbonServer(serviceId, server,
isSecure(server, serviceId),
serverIntrospector(serviceId).getMetadata(server));
return execute(serviceId, ribbonServer, request);
}
Server server = getServer(loadBalancer, hint);
进入
protected Server getServer(ILoadBalancer loadBalancer, Object hint) {
if (loadBalancer == null) {
return null;
}
// Use 'default' on a null hint, or just pass it on?
return loadBalancer.chooseServer(hint != null ? hint : "default");
}
可以看到loadBalancer.chooseServer
选择服务器
com.netflix.loadbalancer.BaseLoadBalancer#chooseServer
public Server chooseServer(Object key) {
if (counter == null) {
counter = createCounter();
}
counter.increment();
if (rule == null) {
return null;
} else {
try {
// 通过rule 执行负载均衡策略。 默认轮训
return rule.choose(key);
} catch (Exception e) {
logger.warn("LoadBalancer [{}]: Error choosing server for key {}", name, key, e);
return null;
}
}
}
默认是使用IRule DEFAULT_RULE = new RoundRobinRule();
@Configuration
public class BalanceRule {
@Bean
RandomRule randomRule(){
return new RandomRule(); #内置的负载均衡规则
}
}
然后启动类中加上@RibbonClient(name = “payment”,configuration = BalanceRule.class)
常用负载均衡算法