小编给大家分享一下Spring Cloud Ribbon负载均衡器的示例分析，相信大部分人都还不怎么了解，因此分享这篇文章给大家参考一下，希望大家阅读完这篇文章后大有收获，下面让我们一起去了解一下吧！
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配置
看一看配置类。
位置：
spring-cloud-netflix-core-1.3.5.RELEASE.jar org.springframework.cloud.netflix.ribbon RibbonClientConfiguration.class
@SuppressWarnings("deprecation")
@Configuration
@EnableConfigurationProperties
//Order is important here, last should be the default, first should be optional
// see https://github.com/spring-cloud/spring-cloud-netflix/issues/2086#issuecomment-316281653
@Import({OkHttpRibbonConfiguration.class, RestClientRibbonConfiguration.class, HttpClientRibbonConfiguration.class})
public class RibbonClientConfiguration {
// 略
@Bean
@ConditionalOnMissingBean
public ILoadBalancer ribbonLoadBalancer(IClientConfig config,
ServerList serverList, ServerListFilter serverListFilter,
IRule rule, IPing ping, ServerListUpdater serverListUpdater) {
if (this.propertiesFactory.isSet(ILoadBalancer.class, name)) {
return this.propertiesFactory.get(ILoadBalancer.class, config, name);
}
return new ZoneAwareLoadBalancer<>(config, rule, ping, serverList,
serverListFilter, serverListUpdater);
}
// 略
} 在实例化ZoneAwareLoadBalancer的时候注入了，config、rule、ping、serverList、serverListFilter、serverListUpdater实例。
config：配置实例。
rule：负载均衡策略实例。
ping：ping实例。
serverList：获取和更新服务的实例。
serverListFilter：服务过滤实例。
serverListUpdater：服务列表信息更新实例。
@SuppressWarnings("deprecation")
@Configuration
@EnableConfigurationProperties
//Order is important here, last should be the default, first should be optional
// see https://github.com/spring-cloud/spring-cloud-netflix/issues/2086#issuecomment-316281653
@Import({OkHttpRibbonConfiguration.class, RestClientRibbonConfiguration.class, HttpClientRibbonConfiguration.class})
public class RibbonClientConfiguration {
// 略
@Bean
@ConditionalOnMissingBean
public IClientConfig ribbonClientConfig() {
DefaultClientConfigImpl config = new DefaultClientConfigImpl();
config.loadProperties(this.name);
return config;
}
@Bean
@ConditionalOnMissingBean
public IRule ribbonRule(IClientConfig config) {
if (this.propertiesFactory.isSet(IRule.class, name)) {
return this.propertiesFactory.get(IRule.class, config, name);
}
ZoneAvoidanceRule rule = new ZoneAvoidanceRule();
rule.initWithNiwsConfig(config);
return rule;
}
@Bean
@ConditionalOnMissingBean
public IPing ribbonPing(IClientConfig config) {
if (this.propertiesFactory.isSet(IPing.class, name)) {
return this.propertiesFactory.get(IPing.class, config, name);
}
return new DummyPing();
}
@Bean
@ConditionalOnMissingBean
@SuppressWarnings("unchecked")
public ServerList ribbonServerList(IClientConfig config) {
if (this.propertiesFactory.isSet(ServerList.class, name)) {
return this.propertiesFactory.get(ServerList.class, config, name);
}
ConfigurationBasedServerList serverList = new ConfigurationBasedServerList();
serverList.initWithNiwsConfig(config);
return serverList;
}
@Bean
@ConditionalOnMissingBean
public ServerListUpdater ribbonServerListUpdater(IClientConfig config) {
return new PollingServerListUpdater(config);
}
@Bean
@ConditionalOnMissingBean
public ILoadBalancer ribbonLoadBalancer(IClientConfig config,
ServerList serverList, ServerListFilter serverListFilter,
IRule rule, IPing ping, ServerListUpdater serverListUpdater) {
if (this.propertiesFactory.isSet(ILoadBalancer.class, name)) {
return this.propertiesFactory.get(ILoadBalancer.class, config, name);
}
return new ZoneAwareLoadBalancer<>(config, rule, ping, serverList,
serverListFilter, serverListUpdater);
}
@Bean
@ConditionalOnMissingBean
@SuppressWarnings("unchecked")
public ServerListFilter ribbonServerListFilter(IClientConfig config) {
if (this.propertiesFactory.isSet(ServerListFilter.class, name)) {
return this.propertiesFactory.get(ServerListFilter.class, config, name);
}
ZonePreferenceServerListFilter filter = new ZonePreferenceServerListFilter();
filter.initWithNiwsConfig(config);
return filter;
}
@Bean
@ConditionalOnMissingBean
public RibbonLoadBalancerContext ribbonLoadBalancerContext(
ILoadBalancer loadBalancer, IClientConfig config, RetryHandler retryHandler) {
return new RibbonLoadBalancerContext(loadBalancer, config, retryHandler);
}
// 略
} 在这里配置相关的实例
config：DefaultClientConfigImpl。
rule：ZoneAvoidanceRule。
ping：DummyPing。
serverList：ConfigurationBasedServerList，基于配置的服务列表实例。
serverListFilter：ZonePreferenceServerListFilter。
serverListUpdater：PollingServerListUpdater。
要注意的是，在这里serverList的实例是ConfigurationBasedServerList，这是在未使用Eureka时获取服务信息的实例，是从配置文件中获取。
那么在和Eureka配合使用时，需要从 Eureka Server获取服务信息，那该是哪个实例来做这件事情呢。
在启用Eureka服务发现时，会首先会采用EurekaRibbonClientConfiguration配置类。
位置：
spring-cloud-netflix-eureka-client-1.3.5.RELEASE.jar org.springframework.cloud.netflix.ribbon.eureka EurekaRibbonClientConfiguration.class
@Configuration
@CommonsLog
public class EurekaRibbonClientConfiguration {
// 略
@Bean
@ConditionalOnMissingBean
public IPing ribbonPing(IClientConfig config) {
if (this.propertiesFactory.isSet(IPing.class, serviceId)) {
return this.propertiesFactory.get(IPing.class, config, serviceId);
}
NIWSDiscoveryPing ping = new NIWSDiscoveryPing();
ping.initWithNiwsConfig(config);
return ping;
}
@Bean
@ConditionalOnMissingBean
public ServerList ribbonServerList(IClientConfig config, Provider eurekaClientProvider) {
if (this.propertiesFactory.isSet(ServerList.class, serviceId)) {
return this.propertiesFactory.get(ServerList.class, config, serviceId);
}
DiscoveryEnabledNIWSServerList discoveryServerList = new DiscoveryEnabledNIWSServerList(
config, eurekaClientProvider);
DomainExtractingServerList serverList = new DomainExtractingServerList(
discoveryServerList, config, this.approximateZoneFromHostname);
return serverList;
}
// 略
} 在首先采用了EurekaRibbonClientConfiguration配置后，实际上各实例变成了
config：DefaultClientConfigImpl。
rule：ZoneAvoidanceRule。
ping：NIWSDiscoveryPing。
serverList：DomainExtractingServerList，内部是DiscoveryEnabledNIWSServerList，实际上是通过服务发现获取服务信息列表。
serverListFilter：ZonePreferenceServerListFilter。
serverListUpdater：PollingServerListUpdater。
获取服务
在找到获取服务信息入口前，先把负载均衡器的类继承关系撸一下。
在ZoneAwareLoadBalancer的构造中调用了父类DynamicServerListLoadBalancer构造。
位置：
ribbon-loadbalancer-2.2.2.jar
com.netflix.loadbalancer
ZoneAwareLoadBalancer.class
在DynamicServerListLoadBalancer的构造中，调用了restOfInit函数。
ribbon-loadbalancer-2.2.2.jar
com.netflix.loadbalancer
DynamicServerListLoadBalancer.class
void restOfInit(IClientConfig clientConfig) {
boolean primeConnection = this.isEnablePrimingConnections();
// turn this off to avoid duplicated asynchronous priming done in BaseLoadBalancer.setServerList()
this.setEnablePrimingConnections(false);
enableAndInitLearnNewServersFeature();
updateListOfServers();
if (primeConnection && this.getPrimeConnections() != null) {
this.getPrimeConnections()
.primeConnections(getReachableServers());
}
this.setEnablePrimingConnections(primeConnection);
LOGGER.info("DynamicServerListLoadBalancer for client {} initialized: {}", clientConfig.getClientName(), this.toString());
}先是通过调用enableAndInitLearnNewServersFeature方法启动定时更新服务列表，然后立即调用updateListOfServers函数马上获取并更新服务列表信息。
先看下enableAndInitLearnNewServersFeature方法，实际上是调用了服务列表信息更新实例的start方法启动定时更新功能。
/**
* Feature that lets us add new instances (from AMIs) to the list of
* existing servers that the LB will use Call this method if you want this
* feature enabled
*/
public void enableAndInitLearnNewServersFeature() {
LOGGER.info("Using serverListUpdater {}", serverListUpdater.getClass().getSimpleName());
serverListUpdater.start(updateAction);
}这里的服务列表信息更新实例就是配置阶段配置的PollingServerListUpdater实例，看一下这个类的构造和start方法。
public class PollingServerListUpdater implements ServerListUpdater {
// 略
private static long LISTOFSERVERS_CACHE_UPDATE_DELAY = 1000; // msecs;
private static int LISTOFSERVERS_CACHE_REPEAT_INTERVAL = 30 * 1000; // msecs;
// 略
private final AtomicBoolean isActive = new AtomicBoolean(false);
private volatile long lastUpdated = System.currentTimeMillis();
private final long initialDelayMs;
private final long refreshIntervalMs;
// 略
public PollingServerListUpdater(IClientConfig clientConfig) {
this(LISTOFSERVERS_CACHE_UPDATE_DELAY, getRefreshIntervalMs(clientConfig));
}
public PollingServerListUpdater(final long initialDelayMs, final long refreshIntervalMs) {
this.initialDelayMs = initialDelayMs;
this.refreshIntervalMs = refreshIntervalMs;
}
@Override
public synchronized void start(final UpdateAction updateAction) {
if (isActive.compareAndSet(false, true)) {
final Runnable wrapperRunnable = new Runnable() {
@Override
public void run() {
if (!isActive.get()) {
if (scheduledFuture != null) {
scheduledFuture.cancel(true);
}
return;
}
try {
updateAction.doUpdate();
lastUpdated = System.currentTimeMillis();
} catch (Exception e) {
logger.warn("Failed one update cycle", e);
}
}
};
scheduledFuture = getRefreshExecutor().scheduleWithFixedDelay(
wrapperRunnable,
initialDelayMs,
refreshIntervalMs,
TimeUnit.MILLISECONDS
);
} else {
logger.info("Already active, no-op");
}
}
// 略
}从构造和常量定义看出来，延迟一秒执行，默认每隔30秒执行更新，可以通过配置修改间隔更新的时间。
从start方法看，就是开了一个定时执行的schedule，定时执行 updateAction.doUpdate()。
回到start方法调用方DynamicServerListLoadBalancer类中看一下UpdateAction实例的定义。
protected final ServerListUpdater.UpdateAction updateAction = new ServerListUpdater.UpdateAction() {
@Override
public void doUpdate() {
updateListOfServers();
}
};实际上就是调用了DynamicServerListLoadBalancer类的updateListOfServers方法，这跟启动完定时更新后立即更新服务信息列表的路径是一致的。
继续看updateListOfServers方法。
public void updateListOfServers() {
List servers = new ArrayList();
if (serverListImpl != null) {
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);
} 1.通过ServerList实例获取服务信息列表。
2.通过ServerListFilter 实例对获取到的服务信息列表进行过滤。
3.将过滤后的服务信息列表保存到LoadBalancerStats中作为状态保持。
接下分别看一下。
1.通过ServerList实例获取服务信息列表。
ServerList实例就是配置阶段生成的DomainExtractingServerList，获取服务信息都是委托给DiscoveryEnabledNIWSServerList。
public class DiscoveryEnabledNIWSServerList extends AbstractServerList{ // 略 @Override public List getInitialListOfServers(){ return obtainServersViaDiscovery(); } @Override public List getUpdatedListOfServers(){ return obtainServersViaDiscovery(); } private List obtainServersViaDiscovery() { List serverList = new ArrayList (); 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(); if (vipAddresses!=null){ for (String vipAddress : vipAddresses.split(",")) { // if targetRegion is null, it will be interpreted as the same region of client 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(); } } DiscoveryEnabledServer des = new DiscoveryEnabledServer(ii, isSecure, shouldUseIpAddr); des.setZone(DiscoveryClient.getZone(ii)); serverList.add(des); } } if (serverList.size()>0 && prioritizeVipAddressBasedServers){ break; // if the current vipAddress has servers, we dont use subsequent vipAddress based servers } } } return serverList; } // 略 }
可以看到其实就是通过Eureka客户端从Eureka服务端获取所有服务实例信息并把上线的包装成DiscoveryEnabledServer实例，带有zone信息，做到服务列表中。
2.通过ServerListFilter 实例对获取到的服务信息列表进行过滤。
serverListFilte实例就是配置阶段生成的ZonePreferenceServerListFilter，通过调用该实例的getFilteredListOfServers方法进行过滤。
@Data @EqualsAndHashCode(callSuper = false) public class ZonePreferenceServerListFilter extends ZoneAffinityServerListFilter{ private String zone; @Override public void initWithNiwsConfig(IClientConfig niwsClientConfig) { super.initWithNiwsConfig(niwsClientConfig); if (ConfigurationManager.getDeploymentContext() != null) { this.zone = ConfigurationManager.getDeploymentContext().getValue( ContextKey.zone); } } @Override public List getFilteredListOfServers(List servers) { List output = super.getFilteredListOfServers(servers); if (this.zone != null && output.size() == servers.size()) { List local = new ArrayList (); for (Server server : output) { if (this.zone.equalsIgnoreCase(server.getZone())) { local.add(server); } } if (!local.isEmpty()) { return local; } } return output; } }
在getFilteredListOfServers方法里面，一上来是调用父类的同名方法先过滤，其实父类也是把和消费端同区域的服务给过滤出来使用，不仅如此，增加了些智能的判定，保证在故障/负载较高时或者可用实例较少时不进行同区域的过滤。
但是在ZonePreferenceServerListFilter.getFilteredListOfServers这里，就算父类没做过过滤，这里依然要把同zone的服务给滤出来使用，谁叫这里的类是ZonePreference的呢。
这是比较怪异的地方，感觉父类的智能判定没什么作用。
还是看看ZoneAffinityServerListFilter.getFilteredListOfServers做的辛苦工作吧。
