}
return response;
}, new LoadBalancedRecoveryCallback
//This is a special case, where both parameters to LoadBalancedRecoveryCallback are
//the same. In most cases they would be different.
@Override
protected ClientHttpResponse createResponse(ClientHttpResponse response, URI uri) {
return response;
}
});
}
doExecute方法：
protected
RecoveryCallback recoveryCallback, RetryState state)
throws E, ExhaustedRetryException {
//省略部分代码
/*
We allow the whole loop to be skipped if the policy or context already forbid the first try. This is used in the case of external retry to allow a recovery in handleRetryExhausted without the callback processing (which would throw an exception).
*/
//执行逻辑的关键方法
while (canRetry(retryPolicy, context) && !context.isExhaustedOnly()) {
}
继续跟踪canRetry方法
@Override
public boolean canRetry(RetryContext context) {
LoadBalancedRetryContext lbContext = (LoadBalancedRetryContext)context;
if(lbContext.getRetryCount() == 0 && lbContext.getServiceInstance() == null) {
//We haven’t even tried to make the request yet so return true so we do
//设置选中的服务提供者
lbContext.setServiceInstance(serviceInstanceChooser.choose(serviceName));
return true;
}
return policy.canRetryNextServer(lbContext);
}
我们跟踪serviceInstanceChooser.choose(serviceName)看看怎么通过serviceName选服务提供者的。
@Override
public ServiceInstance choose(String serviceId) {
//选择server
Server server = getServer(serviceId);
if (server == null) {
return null;
}
return new RibbonServer(serviceId, server, isSecure(server, serviceId),
serverIntrospector(serviceId).getMetadata(server));
}
跟踪getServer方法
protected Server getServer(ILoadBalancer loadBalancer) {
if (loadBalancer == null) {
return null;
}
//可以看出是loadBalancer在选择
return loadBalancer.chooseServer(“default”); // TODO: better handling of key
}
继续深入
public Server chooseServer(Object key) {
if (counter == null) {
counter = createCounter();
}
//有一个调用次数在+1
counter.increment();
if (rule == null) {
return null;
} else {
try {
//委托给了IRule，所以Irule是负载均衡的关键，最后来总结
return rule.choose(key);
} catch (Exception e) {
logger.warn(“LoadBalancer [{}]: Error choosing server for key {}”, name, key, e);
return null;
}
}
}
查看Irule的实现
public Server choose(Object key) {
ILoadBalancer lb = getLoadBalancer();
//lb.getAllServers里面是所有的服务提供者列表
Optional server = getPredicate().chooseRoundRobinAfterFiltering(lb.getAllServers(), key);
if (server.isPresent()) {
return server.get();
} else {
return null;
}
}
跟踪chooseRoundRobinAfterFiltering方法
public Optional chooseRoundRobinAfterFiltering(List servers, Object loadBalancerKey) {
//拿到筛选后的servers
List eligible = getEligibleServers(servers, loadBalancerKey);
if (eligible.size() == 0) {
return Optional.absent();
}
//incrementAndGetModulo方法拿到下标，然后根据list.get取到一个服务
return Optional.of(eligible.get(incrementAndGetModulo(eligible.size())));
}
至此就拿到了具体的服务提供者。
但是到这里还有个问题？
怎么根据服务名拿到server的？ 有一个ServerList接口是用于拿到服务列表的。我们使用的loadBalancer(ZoneAwareLoadBalancer)的父类DynamicServerListLoadBalancer类的构造方法里，有一个restOfinit方法
public DynamicServerListLoadBalancer(IClientConfig clientConfig, IRule rule, IPing ping,
ServerList serverList, ServerListFilter filter,
ServerListUpdater serverListUpdater) {
super(clientConfig, rule, ping);
this.serverListImpl = serverList;
this.filter = filter;
this.serverListUpdater = serverListUpdater;
if (filter instanceof AbstractServerListFilter) {
((AbstractServerListFilter) filter).setLoadBalancerStats(getLoadBalancerStats());
}
restOfInit(clientConfig);
}
跟踪restOfInit方法
void restOfInit(IClientConfig clientConfig) {
boolean primeConnection = this.isEnablePrimingConnections();
// turn this off to avoid duplicated asynchronous priming done in BaseLoadBalancer.setServerList()
this.setEnablePrimingConnections(false);
enableAndInitLearnNewServersFeature();
//用于获取所有的serverList
updateListOfServers();
if (primeConnection && this.getPrimeConnections() != null) {
this.getPrimeConnections()
.primeConnections(getReachableServers());
}
this.setEnablePrimingConnections(primeConnection);
LOGGER.info(“DynamicServerListLoadBalancer for client {} initialized: {}”, clientConfig.getClientName(), this.toString());
}
继续跟踪updateListOfServers方法
public void updateListOfServers() {
List servers = new ArrayList();
if (serverListImpl != null) {
//查询serverList
servers = serverListImpl.getUpdatedListOfServers();
LOGGER.debug(“List of Servers for {} obtained from Discovery client: {}”,
getIdentifier(), servers);
if (filter != null) {
servers = filter.getFilteredListOfServers(servers);
LOGGER.debug(“Filtered List of Servers for {} obtained from Discovery client: {}”,
getIdentifier(), servers);
}
}
updateAllServerList(servers);
}
继续跟踪源码到obtainServersViaDiscovery方法，
private List obtainServersViaDiscovery() {
List serverList = new ArrayList();
//eurekaClientProvider.get()会去获取EurekaClient
if (eurekaClientProvider == null || eurekaClientProvider.get() == null) {
logger.warn(“EurekaClient has not been initialized yet, returning an empty list”);
return new ArrayList();
}
EurekaClient eurekaClient = eurekaClientProvider.get();
//vipAddresses就是serviceName
if (vipAddresses!=null){
for (String vipAddress : vipAddresses.split(“,”)) {
// if targetRegion is null, it will be interpreted as the same region of client
//此处获取到服务的信息
List listOfInstanceInfo = eurekaClient.getInstancesByVipAddress(vipAddress, isSecure, targetRegion);
for (InstanceInfo ii : listOfInstanceInfo) {
if (ii.getStatus().equals(InstanceStatus.UP)) {
if(shouldUseOverridePort){
if(logger.isDebugEnabled()){
logger.debug("Overriding port on client name: " + clientName + " to " + overridePort);
}
// copy is necessary since the InstanceInfo builder just uses the original reference,
// and we don’t want to corrupt the global eureka copy of the object which may be
// used by other clients in our system
InstanceInfo copy = new InstanceInfo(ii);
if(isSecure){
ii = new InstanceInfo.Builder(copy).setSecurePort(overridePort).build();
}else{
ii = new InstanceInfo.Builder(copy).setPort(overridePort).build();
自我介绍一下，小编13年上海交大毕业，曾经在小公司待过，也去过华为、OPPO等大厂，18年进入阿里一直到现在。
深知大多数同学面临毕业设计项目选题时，很多人都会感到无从下手，尤其是对于计算机专业的学生来说，选择一个合适的题目尤为重要。因为毕业设计不仅是我们在大学四年学习的一个总结，更是展示自己能力的重要机会。
因此收集整理了一份《2024年计算机毕业设计项目大全》，初衷也很简单，就是希望能够帮助提高效率，同时减轻大家的负担。
既有Java、Web、PHP、也有C、小程序、Python等项目供你选择，真正体系化！
由于项目比较多，这里只是将部分目录截图出来，每个节点里面都包含素材文档、项目源码、讲解视频
如果你觉得这些内容对你有帮助，可以添加VX：vip1024c （备注项目大全获取）
目选题时，很多人都会感到无从下手，尤其是对于计算机专业的学生来说，选择一个合适的题目尤为重要。因为毕业设计不仅是我们在大学四年学习的一个总结，更是展示自己能力的重要机会。**
因此收集整理了一份《2024年计算机毕业设计项目大全》，初衷也很简单，就是希望能够帮助提高效率，同时减轻大家的负担。 [外链图片转存中…(img-P2zagjBz-1712554598055)] [外链图片转存中…(img-YyInNasF-1712554598056)] [外链图片转存中…(img-yWVSEsrk-1712554598056)]
既有Java、Web、PHP、也有C、小程序、Python等项目供你选择，真正体系化！
由于项目比较多，这里只是将部分目录截图出来，每个节点里面都包含素材文档、项目源码、讲解视频
如果你觉得这些内容对你有帮助，可以添加VX：vip1024c （备注项目大全获取） [外链图片转存中…(img-dHctzu4c-1712554598056)]
参考文章
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