前言
前情回顾
上一篇讲了Ribbon的初始化过程，从LoadBalancerAutoConfiguration 到RibbonAutoConfiguration 再到RibbonClientConfiguration，我们找到了ILoadBalancer默认初始化的对象等。
本讲目录
这一讲我们会进一步往下探究Ribbon和Eureka是如何结合的。
通过上一讲ILoadBalancer 我们已经可以拿到一个服务所有的服务节点信息了，这里面是怎么把服务的名称转化为对应的具体host请求信息的呢？
通过这一讲 我们来一探究竟
目录如下：
- EurekaClientAutoConfiguration.getLoadBalancer()回顾
- 再次梳理Ribbon初始化过程
- ServerList实现类初始化过程
- getUpdatedListOfServers()获取注册表列表分析
- ribbon如何更新自己保存的注册表信息？
说明
原创不易，如若转载 请标明来源！
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源码阅读
EurekaClientAutoConfiguration.getLoadBalancer()回顾
上一讲我们已经深入的讲解过getLoadBalancer() 方法的实现，每个serviceName都对应一个自己的SpringContext上下文信息，然后通过ILoadBalancer.class从上下文信息中获取默认的LoadBalancer：ZoneAwareLoadBalancer， 我们看下这个类的构造函数：
public ZoneAwareLoadBalancer(IClientConfig clientConfig, IRule rule,
IPing ping, ServerList serverList, ServerListFilter filter,
ServerListUpdater serverListUpdater) {
super(clientConfig, rule, ping, serverList, filter, serverListUpdater);
} 继续跟父类DynamicServerListLoadBalancer的初始化方法：
public class DynamicServerListLoadBalancer extends BaseLoadBalancer {
volatile ServerList serverListImpl;
volatile ServerListFilter filter;
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);
}
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());
}
@VisibleForTesting
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);
}
} 构造方法中有个restOfInit()方法，进去后又会有updateListOfServers() 方法，看方法名就知道这个肯定是和server注册表相关的，继续往后看，servers = serverListImpl.getUpdatedListOfServers();，这里直接调用getUpdatedListOfServers()就获取到了所有的注册表信息。
可以看到ServerList有四个实现类，这个到底是该调用哪个实现类的getUpdatedListOfServers()方法呢？接着往下看。
再次梳理Ribbon初始化过程
第二讲我们已经见过Ribbon的初始化过程，并画了图整理，这里针对于之前的图再更新一下：
这里主要是增加了RibbonEurekaAutoConfiguration和EurekaRibbonClientConfiguration两个配置类的初始化。
ServerList实现类初始化过程
上面已经梳理过 Ribbon初始化的过程，其中在EurekaRibbonClientConfiguration 会初始化RibbonServerList，代码如下：
@Configuration
public class EurekaRibbonClientConfiguration {
@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;
}
} 这里实际的ServerList实际就是DiscoveryEnabledNIWSServerList，我们看下这个类：
public class DiscoveryEnabledNIWSServerList extends AbstractServerList{
}
public abstract class AbstractServerList implements ServerList, IClientConfigAware {
} 所以可以看出来ServerList 实际就是在这里进行初始化的，上面那个serverListImpl.getUpdatedListOfServers();即为调用DiscoveryEnabledNIWSServerList.getUpdatedListOfServers() 方法了，继续往下看。
getUpdatedListOfServers()获取注册表分析
直接看DiscoveryEnabledNIWSServerList.getUpdatedListOfServers()源代码：
@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;
} 看到这里代码就已经很明显了，我们来解读下这段代码：
- 通过eurekaClientProvider获取对应EurekaClient
- 通过vipAdress(实际就是serviceName)获取对应注册表集合信息
- 将注册信息组装成
DiscoveryEnabledServer列表
再回到DynamicServerListLoadBalancer.updateListOfServers() 中，这里获取到对应的DiscoveryEnabledServer list后调用updateAllServerList()方法，一路跟踪这里最终会调用BaseLoadBalancer.setServersList()
public class BaseLoadBalancer extends AbstractLoadBalancer implements
PrimeConnections.PrimeConnectionListener, IClientConfigAware {
@Monitor(name = PREFIX + "AllServerList", type = DataSourceType.INFORMATIONAL)
protected volatile List allServerList = Collections
.synchronizedList(new ArrayList());
public void setServersList(List lsrv) {
Lock writeLock = allServerLock.writeLock();
logger.debug("LoadBalancer [{}]: clearing server list (SET op)", name);
ArrayList newServers = new ArrayList();
writeLock.lock();
try {
ArrayList allServers = new ArrayList();
for (Object server : lsrv) {
if (server == null) {
continue;
}
if (server instanceof String) {
server = new Server((String) server);
}
if (server instanceof Server) {
logger.debug("LoadBalancer [{}]: addServer [{}]", name, ((Server) server).getId());
allServers.add((Server) server);
} else {
throw new IllegalArgumentException(
"Type String or Server expected, instead found:"
+ server.getClass());
}
}
boolean listChanged = false;
if (!allServerList.equals(allServers)) {
listChanged = true;
if (changeListeners != null && changeListeners.size() > 0) {
List oldList = ImmutableList.copyOf(allServerList);
List newList = ImmutableList.copyOf(allServers);
for (ServerListChangeListener l: changeListeners) {
try {
l.serverListChanged(oldList, newList);
} catch (Exception e) {
logger.error("LoadBalancer [{}]: Error invoking server list change listener", name, e);
}
}
}
}
if (isEnablePrimingConnections()) {
for (Server server : allServers) {
if (!allServerList.contains(server)) {
server.setReadyToServe(false);
newServers.add((Server) server);
}
}
if (primeConnections != null) {
primeConnections.primeConnectionsAsync(newServers, this);
}
}
// This will reset readyToServe flag to true on all servers
// regardless whether
// previous priming connections are success or not
allServerList = allServers;
if (canSkipPing()) {
for (Server s : allServerList) {
s.setAlive(true);
}
upServerList = allServerList;
} else if (listChanged) {
forceQuickPing();
}
} finally {
writeLock.unlock();
}
}
} 这个过程最后用一张图总结为：
ribbon如何更新自己保存的注册表信息？
上面已经讲了 Ribbon是如何通过serviceName拉取到注册表的，我们知道EurekaClient默认是30s拉取一次注册表信息的，因为Ribbon要关联注册表信息，那么Ribbon该如何更新自己存储的注册表信息呢？
继续回到DynamicSeverListLoadBalancer.restOfInit()方法中：
public class DynamicServerListLoadBalancer extends BaseLoadBalancer {
protected volatile ServerListUpdater serverListUpdater;
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 enableAndInitLearnNewServersFeature() {
LOGGER.info("Using serverListUpdater {}", serverListUpdater.getClass().getSimpleName());
serverListUpdater.start(updateAction);
}
} 重点查看enableAndInitLearnNewServersFeature()方法，从名字我们就可以看出来这意思为激活和初始化学习新服务的功能，这里实际上就启动serverListUpdater中的一个线程。
在最上面Ribbon初始化的过程中我们知道，在RibbonClientConfiguration中默认初始化的ServerListUpdater为 PollingServreListUpdater，我们继续跟这个类的start方法：
@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");
}
}这里只要是执行updateAction.doUpdate();,然后后面启动了一个调度任务，默认30s执行一次。
继续往后跟doUpdate()方法：
public class DynamicServerListLoadBalancer extends BaseLoadBalancer {
protected final ServerListUpdater.UpdateAction updateAction = new ServerListUpdater.UpdateAction() {
@Override
public void doUpdate() {
updateListOfServers();
}
};
} 这里又调用了之前通过serviceName获取对应注册服务列表的方法了。
总结到一张图如下：
总结
本文主要是重新梳理了Ribbon的初始化过程，主要是几个Configure初始化的过程，然后是Ribbon与Eureka的整合，这里也涉及到了注册表的更新逻辑。
看到这里真是被Spring的各种AutoConfigure绕晕了，哈哈，但是最后分析完 还是觉得挺清晰的，对于复杂的业务画张流程图还挺容易理解的。
申明
本文章首发自本人博客：https://www.cnblogs.com/wang-meng 和公众号：壹枝花算不算浪漫，如若转载请标明来源!
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