SpringCloud之Ribbon源码解析(三)--ILoadBalancer
当使用Ribbon作为负载均衡客户端的时候,实际干活的是接口ILoadBalancer及其实现类。本文就介绍一下ILoadBalancer及其实现类
运行时使用的是DynamicServerListLoadBalancer
public class DynamicServerListLoadBalancer<T extends Server> extends BaseLoadBalancer { private static final Logger LOGGER = LoggerFactory.getLogger(DynamicServerListLoadBalancer.class); boolean isSecure = false; boolean useTunnel = false; // to keep track of modification of server lists protected AtomicBoolean serverListUpdateInProgress = new AtomicBoolean(false); volatile ServerList<T> serverListImpl;
注意成员变量 ServerList<T> serverListImpl; Ribbon使用的是DomainExtractingServerList 作为它的实现类,但是注意DomainExtractingServerList 有成员变量DiscoveryEnabledNIWSServerList,实际干活的还是DiscoveryEnabledNIWSServerList
EurekaRibbonClientConfiguration
@Bean @ConditionalOnMissingBean public ServerList<?> ribbonServerList(IClientConfig config, Provider<EurekaClient> 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; }
在DiscoveryEnabledNIWSServerList里有一个很重要的方法,obtainServersViaDiscovery()
private List<DiscoveryEnabledServer> obtainServersViaDiscovery() { List<DiscoveryEnabledServer> serverList = new ArrayList<DiscoveryEnabledServer>(); if (eurekaClientProvider == null || eurekaClientProvider.get() == null) { logger.warn("EurekaClient has not been initialized yet, returning an empty list"); return new ArrayList<DiscoveryEnabledServer>(); } 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<InstanceInfo> 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 = createServer(ii, isSecure, shouldUseIpAddr); serverList.add(des); } } if (serverList.size()>0 && prioritizeVipAddressBasedServers){ break; // if the current vipAddress has servers, we dont use subsequent vipAddress based servers } } } return serverList; }
首先依靠EurekaClient从服务注册中心获取到具体的服务实例InstanceInfo列表,然后对这个列表进行遍历,将状态为UP的实例转换成DiscoveryEnabledServer对象并放到一个集合中,最后将这个集合返回。
getUpdatedListOfServers也是通过obtainServersViaDiscovery实现的
public List<DiscoveryEnabledServer> getUpdatedListOfServers(){ return obtainServersViaDiscovery(); }
下面看一下调用过程
public DynamicServerListLoadBalancer(IClientConfig clientConfig, IRule rule, IPing ping, ServerList<T> serverList, ServerListFilter<T> 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); }
从上面可以看出来,实例化DynamicServerListLoadBalancer的时候就进行了服务的拉取
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()); }
public void updateListOfServers() { List<T> servers = new ArrayList<T>(); 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); }