目录
1. Ribbon调试demo
@Bean
@LoadBalanced
public RestTemplate getRestTemplate() {
return new RestTemplate();
}
@RequestMapping(value = "/greeting/{name}", method = RequestMethod.GET)
public String greeting(@PathVariable("name") String name) {
RestTemplate restTemplate = getRestTemplate();
return restTemplate.getForObject("http://ServiceA/sayHello/" + name, String.class);
}2. 源码调试
进入getForObject方法
public <T> T getForObject(String url, Class<T> responseType, Object... uriVariables) throws RestClientException {
RequestCallback requestCallback = acceptHeaderRequestCallback(responseType);
HttpMessageConverterExtractor<T> responseExtractor =
new HttpMessageConverterExtractor<T>(responseType, getMessageConverters(), logger);
return execute(url, HttpMethod.GET, requestCallback, responseExtractor, uriVariables);
}进入execute方法
public <T> T execute(String url, HttpMethod method, RequestCallback requestCallback,
ResponseExtractor<T> responseExtractor, Object... uriVariables) throws RestClientException {
URI expanded = getUriTemplateHandler().expand(url, uriVariables);
return doExecute(expanded, method, requestCallback, responseExtractor);
}进入doExecute方法
protected <T> T doExecute(URI url, HttpMethod method, RequestCallback requestCallback,
ResponseExtractor<T> responseExtractor) throws RestClientException {
Assert.notNull(url, "'url' must not be null");
Assert.notNull(method, "'method' must not be null");
ClientHttpResponse response = null;
try {
ClientHttpRequest request = createRequest(url, method);
if (requestCallback != null) {
requestCallback.doWithRequest(request);
}
response = request.execute();
// 省略......
}
}进入execute方法
public final ClientHttpResponse execute() throws IOException {
assertNotExecuted();
ClientHttpResponse result = executeInternal(this.headers);
this.executed = true;
return result;
}进入AbstractClientHttpRequest的executeInternal方法
protected ClientHttpResponse executeInternal(HttpHeaders headers) throws IOException {
byte[] bytes = this.bufferedOutput.toByteArray();
if (headers.getContentLength() < 0) {
headers.setContentLength(bytes.length);
}
ClientHttpResponse result = executeInternal(headers, bytes);
this.bufferedOutput = null;
return result;
}再进入AbstractBufferingClientHttpRequest的executeInternal方法
protected ClientHttpResponse executeInternal(HttpHeaders headers) throws IOException {
byte[] bytes = this.bufferedOutput.toByteArray();
if (headers.getContentLength() < 0) {
headers.setContentLength(bytes.length);
}
ClientHttpResponse result = executeInternal(headers, bytes);
this.bufferedOutput = null;
return result;
}再进入InterceptingClientHttpRequest的executeInternal方法
protected final ClientHttpResponse executeInternal(HttpHeaders headers, byte[] bufferedOutput) throws IOException {
InterceptingRequestExecution requestExecution = new InterceptingRequestExecution();
return requestExecution.execute(this, bufferedOutput);
}进入InterceptingRequestExecution的execute方法
public ClientHttpResponse execute(HttpRequest request, final byte[] body) throws IOException {
if (this.iterator.hasNext()) {
ClientHttpRequestInterceptor nextInterceptor = this.iterator.next();
return nextInterceptor.intercept(request, body, this);
}
// 省略......
}进入LoadBalancerInterceptor的intercept方法 public ClientHttpResponse intercept(final HttpRequest request, final byte[] body,
final ClientHttpRequestExecution execution) throws IOException {
final URI originalUri = request.getURI();
String serviceName = originalUri.getHost();
Assert.state(serviceName != null, "Request URI does not contain a valid hostname: " + originalUri);
return this.loadBalancer.execute(serviceName, requestFactory.createRequest(request, body, execution));
}ribbon实际实现了springframwork的拦截器类ClientHttpRequestInterceptor，通过拦截器方式调用ribbon的请求实现。
3.Ribbon与Eureka的整合
先来看下spring如何加载ribbon的
可以看到RibbonAutoConfiguration和RibbonClientConfiguration两个类，RibbonAutoConfiguration首先联想到xxxAutoConfiguration，这种类都是通过SpringFactoriesLoader在springboot启动的时候加载的，只要配置spring.factories文件就可以了。
1.RibbonAutoConfiguration解读
@Configuration
@ConditionalOnClass({ IClient.class, RestTemplate.class, AsyncRestTemplate.class, Ribbon.class})
@RibbonClients
@AutoConfigureAfter(name = "org.springframework.cloud.netflix.eureka.EurekaClientAutoConfiguration")
@AutoConfigureBefore({LoadBalancerAutoConfiguration.class, AsyncLoadBalancerAutoConfiguration.class})
@EnableConfigurationProperties({RibbonEagerLoadProperties.class, ServerIntrospectorProperties.class})
public class RibbonAutoConfiguration {
@Autowired(required = false)
private List<RibbonClientSpecification> configurations = new ArrayList<>();
@Autowired
private RibbonEagerLoadProperties ribbonEagerLoadProperties;
@Bean
public HasFeatures ribbonFeature() {
return HasFeatures.namedFeature("Ribbon", Ribbon.class);
}
@Bean
public SpringClientFactory springClientFactory() {
SpringClientFactory factory = new SpringClientFactory();
factory.setConfigurations(this.configurations);
return factory;
}
@Bean
@ConditionalOnMissingBean(LoadBalancerClient.class)
public LoadBalancerClient loadBalancerClient() {
return new RibbonLoadBalancerClient(springClientFactory());
}
// 省略......
}
在这个类中可以很清晰看到LoadBalancerClient注入到spring容器中的。接着看这个类的注解，重点看三个注解@RibbonClients，@AutoConfigureAfter(name = "org.springframework.cloud.netflix.eureka.EurekaClientAutoConfiguration")，@AutoConfigureBefore({LoadBalancerAutoConfiguration.class, AsyncLoadBalancerAutoConfiguration.class})
进入@RibbonClients注解
@Configuration
@Retention(RetentionPolicy.RUNTIME)
@Target({ ElementType.TYPE })
@Documented
@Import(RibbonClientConfigurationRegistrar.class)
public @interface RibbonClients {
RibbonClient[] value() default {};
Class<?>[] defaultConfiguration() default {};
}可以看到@Import(RibbonClientConfigurationRegistrar.class注解，进入RibbonClientConfigurationRegistrar类
@Override
public void registerBeanDefinitions(AnnotationMetadata metadata,
BeanDefinitionRegistry registry) {
Map<String, Object> attrs = metadata.getAnnotationAttributes(
RibbonClients.class.getName(), true);
if (attrs != null && attrs.containsKey("value")) {
AnnotationAttributes[] clients = (AnnotationAttributes[]) attrs.get("value");
for (AnnotationAttributes client : clients) {
registerClientConfiguration(registry, getClientName(client),
client.get("configuration"));
}
}
if (attrs != null && attrs.containsKey("defaultConfiguration")) {
String name;
if (metadata.hasEnclosingClass()) {
name = "default." + metadata.getEnclosingClassName();
} else {
name = "default." + metadata.getClassName();
}
registerClientConfiguration(registry, name,
attrs.get("defaultConfiguration"));
}
Map<String, Object> client = metadata.getAnnotationAttributes(
RibbonClient.class.getName(), true);
String name = getClientName(client);
if (name != null) {
registerClientConfiguration(registry, name, client.get("configuration"));
}
}registerBeanDefinitions方法会获取defaultConfiguration属性，然后注入到spring容器中，EurekaRibbonClientConfiguration就是通过这种方式注入的。registerBeanDefinitions方法是在springboot启动的时候扫描带有@Configuration的类，然后遍历这些类，是否是ImportBeanDefinitionRegistrar类型，然后执行registerBeanDefinitions方法。
继续看RibbonClientConfiguration是如何注入spring容器中的。回到RibbonAutoConfiguration的springClientFactory方法
@Bean
public SpringClientFactory springClientFactory() {
SpringClientFactory factory = new SpringClientFactory();
factory.setConfigurations(this.configurations);
return factory;
}进入springClientFactory的构造方法，
public SpringClientFactory() {
super(RibbonClientConfiguration.class, NAMESPACE, "ribbon.client.name");
}进入父级构造方法，
public NamedContextFactory(Class<?> defaultConfigType, String propertySourceName,
String propertyName) {
this.defaultConfigType = defaultConfigType;
this.propertySourceName = propertySourceName;
this.propertyName = propertyName;
}我们继续看RibbonLoadBalancerClient的execute方法，
@Override
public <T> T execute(String serviceId, LoadBalancerRequest<T> request) throws IOException {
ILoadBalancer loadBalancer = getLoadBalancer(serviceId);
Server server = getServer(loadBalancer);
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);
}进入getLoadBalancer方法
protected ILoadBalancer getLoadBalancer(String serviceId) {
return this.clientFactory.getLoadBalancer(serviceId);
}此处的clientFactory就是SpringClientFactory,实际上Ribbon最重要的三个组件就是ILoadBalancer,IRule,IPing,此处就是获取ILoadBalancer,一步步进入就会进入下面的方法
public <T> T getInstance(String name, Class<T> type) {
AnnotationConfigApplicationContext context = getContext(name);
if (BeanFactoryUtils.beanNamesForTypeIncludingAncestors(context,
type).length > 0) {
return context.getBean(type);
}
return null;
}此处name的是服务名，每个服务都有一个spring的上下文，进入createContext方法
protected AnnotationConfigApplicationContext createContext(String name) {
AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();
if (this.configurations.containsKey(name)) {
for (Class<?> configuration : this.configurations.get(name)
.getConfiguration()) {
context.register(configuration);
}
}
for (Map.Entry<String, C> entry : this.configurations.entrySet()) {
if (entry.getKey().startsWith("default.")) {
for (Class<?> configuration : entry.getValue().getConfiguration()) {
context.register(configuration);
}
}
}
context.register(PropertyPlaceholderAutoConfiguration.class,
this.defaultConfigType);
context.getEnvironment().getPropertySources().addFirst(new MapPropertySource(
this.propertySourceName,
Collections.<String, Object> singletonMap(this.propertyName, name)));
if (this.parent != null) {
// Uses Environment from parent as well as beans
context.setParent(this.parent);
}
context.refresh();
return context;
}我们先来看下configurations变量，
可以看到RibbonAutoConfiguration的configuraiton的size为0，RibbonEurekaAutoConfiguration的size为1，而它里边的元素正是EurekaRibbonClientConfiguration,EurekaRibbonClientConfiguraiton包括他@Bean方法就是在这里注入到spring容器的，再来看这行代码
protected AnnotationConfigApplicationContext createContext(String name) {
AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();
// 省略......
context.register(PropertyPlaceholderAutoConfiguration.class,
this.defaultConfigType);
// 省略......
context.refresh();
return context;
}
这里有个defaultConfigType，这个就是RibbonClientConfiguration，RibbonClientConfiguration就这样注入到了spring容器中了。由于EurekaRibbonClientConfiguration比RibbonClientConfiguration先注入到spring容器，所以IPing，ServerList都是EurekaRibbonClientConfiguration类中注入到spring容器中的。
回到RibbonLoadBalancerClient的execute方法
@Override
public <T> T execute(String serviceId, LoadBalancerRequest<T> request) throws IOException {
ILoadBalancer loadBalancer = getLoadBalancer(serviceId);
Server server = getServer(loadBalancer);
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);
}getLoadBalancer(serviceId)实际获取到是ZoneAwareLoadBalancer
@Bean
@ConditionalOnMissingBean
public ILoadBalancer ribbonLoadBalancer(IClientConfig config,
ServerList<Server> serverList, ServerListFilter<Server> 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);
}进入ZoneAwareLoadBalancer的chooseServer方法
@Override
public Server chooseServer(Object key) {
if (!ENABLED.get() || getLoadBalancerStats().getAvailableZones().size() <= 1) {
logger.debug("Zone aware logic disabled or there is only one zone");
return super.chooseServer(key);
}
// 省略......
}因为就一个Zone，直接进入super.chooseServer(key)
public Server chooseServer(Object key) {
if (counter == null) {
counter = createCounter();
}
counter.increment();
if (rule == null) {
return null;
} else {
try {
return rule.choose(key);
} catch (Exception e) {
logger.warn("LoadBalancer [{}]: Error choosing server for key {}", name, key, e);
return null;
}
}
}默认的IRule是ZoneAvoidanceRule
@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;
}进入choose方法
@Override
public Server choose(Object key) {
ILoadBalancer lb = getLoadBalancer();
Optional<Server> server = getPredicate().chooseRoundRobinAfterFiltering(lb.getAllServers(), key);
if (server.isPresent()) {
return server.get();
} else {
return null;
}
}进入chooseRoundRobinAfterFiltering方法
public Optional<Server> chooseRoundRobinAfterFiltering(List<Server> servers, Object loadBalancerKey) {
List<Server> eligible = getEligibleServers(servers, loadBalancerKey);
if (eligible.size() == 0) {
return Optional.absent();
}
return Optional.of(eligible.get(incrementAndGetModulo(eligible.size())));
}进入incrementAndGetModulo方法，此处就是一个所有服务的取模。
private int incrementAndGetModulo(int modulo) {
for (;;) {
int current = nextIndex.get();
int next = (current + 1) % modulo;
if (nextIndex.compareAndSet(current, next) && current < modulo)
return current;
}
}再回到RibbonLoadBalancerClient的execute方法
@Override
public <T> T execute(String serviceId, LoadBalancerRequest<T> request) throws IOException {
ILoadBalancer loadBalancer = getLoadBalancer(serviceId);
Server server = getServer(loadBalancer);
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)这行代码下边就不在剖析，下边主要分析ribbon更新服务，还有ping服务。
进入RibbonClientConfiguration
@Bean
@ConditionalOnMissingBean
public ILoadBalancer ribbonLoadBalancer(IClientConfig config,
ServerList<Server> serverList, ServerListFilter<Server> 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);
}从这里可以看到Ribbon默认的ILoadBlancer是ZoneAwareLoadBalancer，进入ZoneAwareLoadBalancer的构造方法，它调用的是父级构造方法，进入父级构造方法
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);
}进入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();
updateListOfServers();
if (primeConnection && this.getPrimeConnections() != null) {
this.getPrimeConnections()
.primeConnections(getReachableServers());
}
this.setEnablePrimingConnections(primeConnection);
LOGGER.info("DynamicServerListLoadBalancer for client {} initialized: {}", clientConfig.getClientName(), this.toString());
}继续看updateListOfServers方法
@VisibleForTesting
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);
}可以看到serverListImpl.getUpdatedListOfServers()，serverListImpl是在构造方法初始化的，也就是DomainExtractingServerList,它是在EurekaRibbonClientConfiguration中注入到spring容器中的。
@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;
}进入getUpdatedListOfServers()方法
@Override
public List<DiscoveryEnabledServer> getUpdatedListOfServers() {
List<DiscoveryEnabledServer> servers = setZones(this.list
.getUpdatedListOfServers());
return servers;
}可以看到list .getUpdatedListOfServers())，而list就是DiscoveryEnabledNIWSServerList，进入getUpdatedListOfServers()方法
@Override
public List<DiscoveryEnabledServer> getUpdatedListOfServers(){
return obtainServersViaDiscovery();
}进入obtainServersViaDiscovery()方法
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>();
}
// 获取Eureka实例
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);
}
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;
}可以清楚的看到一直从Eureka客户端拉取服务。
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