這篇文章主要給大家介紹了關於Spring Cloud Ribbon踩坑記錄與原理的相關資料,文中通過示例代碼介紹的非常詳細,對大家的學習或者工作具有一定的參考學習價值,需要的朋友們下面隨著小編來一起學習學習吧
簡介
Spring Cloud Ribbon 是一個基於Http和TCP的客服端負載均衡工具,它是基於Netflix Ribbon實現的。它不像服務註冊中心、配置中心、API網關那樣獨立部署,但是它幾乎存在於每個微服務的基礎設施中。包括前面的提供的聲明式服務調用也是基於該Ribbon實現的。理解Ribbon對於我們使用Spring Cloud來講非常的重要,因為負載均衡是對系統的高可用、網絡壓力的緩解和處理能力擴容的重要手段之一。在上節的例子中,我們採用了聲明式的方式來實現負載均衡。實際上,內部調用維護了一個RestTemplate對象,該對象會使用Ribbon的自動化配置,同時通過@LoadBalanced開啟客戶端負載均衡。其實RestTemplate是Spring自己提供的對象,不是新的內容。讀者不知道RestTemplate可以查看相關的文檔。
現象
前兩天碰到一個ribbon相關的問題,覺得值得記錄一下。表象是對外的接口返回內部異常,這個是封裝的統
一錯誤信息,Spring的異常處理器catch到未捕獲異常統一返回的信息。因此到日誌平臺查看實際的異常:
org.springframework.web.client.HttpClientErrorException: 404 null
這裡介紹一下背景,出現問題的開放網關,做點事情說白了就是轉發對應的請求給後端的服務。這裡用到了ribbon去做服務負載均衡、eureka負責服務發現。
這裡出現404,首先看了下請求的url以及對應的參數,都沒有發現問題,對應的後端服務也沒有收到請求。這就比較詭異了,開始懷疑是ribbon或者Eureka的緩存導致請求到了錯誤的ip或端口,但由於日誌中打印的是Eureka的serviceId而不是實際的ip:port,因此先加了個日誌:
@Slf4j
public class CustomHttpRequestInterceptor implements ClientHttpRequestInterceptor {
@Override
public ClientHttpResponse intercept(HttpRequest request, byte[] body, ClientHttpRequestExecution execution) throws IOException {
log.info("Request , url:{},method:{}.", request.getURI(), request.getMethod());
return execution.execute(request, body);
}
}
這裡是通過給RestTemplate添加攔截器的方式,但要注意,ribbon也是通過給RestTemplate添加攔截器實現的解析serviceId到實際的ip:port,因此需要注意下優先級添加到ribbon的 LoadBalancerInterceptor 之後,我這裡是通過Spring的初始化完成事件的回調中添加的,另外也添加了另一條日誌,在catch到這個異常的時候,利用Eureka的 DiscoveryClient#getInstances 獲取到當前的實例信息。
之後在測試環境中復現了這個問題,看了下日誌,eurek中緩存的實例信息是對的,但是實際調用的確實另外一個服務的地址,從而導致了接口404。
源碼解析
從上述的信息中可以知道,問題出在ribbon中,具體的原因後面會說,這裡先講一下Spring Cloud Ribbon的初始化流程。
@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 {
}
注意這個註解 @RibbonClients , 如果想要覆蓋Spring Cloud提供的默認Ribbon配置就可以使用這個註解,最終的解析類是:
public class RibbonClientConfigurationRegistrar implements ImportBeanDefinitionRegistrar {
@Override
public void registerBeanDefinitions(AnnotationMetadata metadata,
BeanDefinitionRegistry registry) {
Map<string> attrs = metadata.getAnnotationAttributes(/<string>
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> client = metadata.getAnnotationAttributes(/<string>
RibbonClient.class.getName(), true);
String name = getClientName(client);
if (name != null) {
registerClientConfiguration(registry, name, client.get("configuration"));
}
}
private String getClientName(Map<string> client) {/<string>
if (client == null) {
return null;
}
String value = (String) client.get("value");
if (!StringUtils.hasText(value)) {
value = (String) client.get("name");
}
if (StringUtils.hasText(value)) {
return value;
}
throw new IllegalStateException(
"Either 'name' or 'value' must be provided in @RibbonClient");
}
private void registerClientConfiguration(BeanDefinitionRegistry registry,
Object name, Object configuration) {
BeanDefinitionBuilder builder = BeanDefinitionBuilder
.genericBeanDefinition(RibbonClientSpecification.class);
builder.addConstructorArgValue(name);
builder.addConstructorArgValue(configuration);
registry.registerBeanDefinition(name + ".RibbonClientSpecification",
builder.getBeanDefinition());
}
}
atrrs包含defaultConfiguration,因此會註冊RibbonClientSpecification類型的bean,注意名稱以 default. 開頭,類型是RibbonAutoConfiguration,注意上面說的RibbonAutoConfiguration被@RibbonClients修飾。
然後再回到上面的源碼:
public class RibbonAutoConfiguration {
//上文中會解析被@RibbonClients註解修飾的類,然後註冊類型為RibbonClientSpecification的bean。
//主要有兩個: RibbonAutoConfiguration、RibbonEurekaAutoConfiguration
@Autowired(required = false)
private List<ribbonclientspecification> configurations = new ArrayList<>();/<ribbonclientspecification>
@Bean
public SpringClientFactory springClientFactory() {
//初始化SpringClientFactory,並將上面的配置注入進去,這段很重要。
SpringClientFactory factory = new SpringClientFactory();
factory.setConfigurations(this.configurations);
return factory;
}
//其他的都是提供一些默認的bean配置
@Bean
@ConditionalOnMissingBean(LoadBalancerClient.class)
public LoadBalancerClient loadBalancerClient() {
return new RibbonLoadBalancerClient(springClientFactory());
}
@Bean
@ConditionalOnClass(name = "org.springframework.retry.support.RetryTemplate")
@ConditionalOnMissingBean
public LoadBalancedRetryPolicyFactory loadBalancedRetryPolicyFactory(SpringClientFactory clientFactory) {
return new RibbonLoadBalancedRetryPolicyFactory(clientFactory);
}
@Bean
@ConditionalOnMissingClass(value = "org.springframework.retry.support.RetryTemplate")
@ConditionalOnMissingBean
public LoadBalancedRetryPolicyFactory neverRetryPolicyFactory() {
return new LoadBalancedRetryPolicyFactory.NeverRetryFactory();
}
@Bean
@ConditionalOnClass(name = "org.springframework.retry.support.RetryTemplate")
@ConditionalOnMissingBean
public LoadBalancedBackOffPolicyFactory loadBalancedBackoffPolicyFactory() {
return new LoadBalancedBackOffPolicyFactory.NoBackOffPolicyFactory();
}
@Bean
@ConditionalOnClass(name = "org.springframework.retry.support.RetryTemplate")
@ConditionalOnMissingBean
public LoadBalancedRetryListenerFactory loadBalancedRetryListenerFactory() {
return new LoadBalancedRetryListenerFactory.DefaultRetryListenerFactory();
}
@Bean
@ConditionalOnMissingBean
public PropertiesFactory propertiesFactory() {
return new PropertiesFactory();
}
@Bean
@ConditionalOnProperty(value = "ribbon.eager-load.enabled", matchIfMissing = false)
public RibbonApplicationContextInitializer ribbonApplicationContextInitializer() {
return new RibbonApplicationContextInitializer(springClientFactory(),
ribbonEagerLoadProperties.getClients());
}
@Configuration
@ConditionalOnClass(HttpRequest.class)
@ConditionalOnRibbonRestClient
protected static class RibbonClientConfig {
@Autowired
private SpringClientFactory springClientFactory;
@Bean
public RestTemplateCustomizer restTemplateCustomizer(
final RibbonClientHttpRequestFactory ribbonClientHttpRequestFactory) {
return new RestTemplateCustomizer() {
@Override
public void customize(RestTemplate restTemplate) {
restTemplate.setRequestFactory(ribbonClientHttpRequestFactory);
}
};
}
@Bean
public RibbonClientHttpRequestFactory ribbonClientHttpRequestFactory() {
return new RibbonClientHttpRequestFactory(this.springClientFactory);
}
}
//TODO: support for autoconfiguring restemplate to use apache http client or okhttp
@Target({ ElementType.TYPE, ElementType.METHOD })
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Conditional(OnRibbonRestClientCondition.class)
@interface ConditionalOnRibbonRestClient { }
private static class OnRibbonRestClientCondition extends AnyNestedCondition {
public OnRibbonRestClientCondition() {
super(ConfigurationPhase.REGISTER_BEAN);
}
@Deprecated //remove in Edgware"
@ConditionalOnProperty("ribbon.http.client.enabled")
static class ZuulProperty {}
@ConditionalOnProperty("ribbon.restclient.enabled")
static class RibbonProperty {}
}
}
注意這裡的SpringClientFactory, ribbon默認情況下,每個eureka的serviceId(服務),都會分配自己獨立的Spring的上下文,即ApplicationContext, 然後這個上下文中包含了必要的一些bean,比如: ILoadBalancer 、 ServerListFilter 等。而Spring Cloud默認是使用RestTemplate封裝了ribbon的調用,核心是通過一個攔截器:
@Bean
@ConditionalOnMissingBean
public RestTemplateCustomizer restTemplateCustomizer(
final LoadBalancerInterceptor loadBalancerInterceptor) {
return new RestTemplateCustomizer() {
@Override
public void customize(RestTemplate restTemplate) {
List<clienthttprequestinterceptor> list = new ArrayList<>(/<clienthttprequestinterceptor>
restTemplate.getInterceptors());
list.add(loadBalancerInterceptor);
restTemplate.setInterceptors(list);
}
};
}
因此核心是通過這個攔截器實現的負載均衡:
public class LoadBalancerInterceptor implements ClientHttpRequestInterceptor {
private LoadBalancerClient loadBalancer;
private LoadBalancerRequestFactory requestFactory;
@Override
public ClientHttpResponse intercept(final HttpRequest request, final byte[] body,
final ClientHttpRequestExecution execution) throws IOException {
final URI originalUri = request.getURI(); //這裡傳入的url是解析之前的,即http://serviceId/服務地址的形式
String serviceName = originalUri.getHost(); //解析拿到對應的serviceId
Assert.state(serviceName != null, "Request URI does not contain a valid hostname: " + originalUri);
return this.loadBalancer.execute(serviceName, requestFactory.createRequest(request, body, execution));
}
}
然後將請求轉發給LoadBalancerClient:
public class RibbonLoadBalancerClient implements LoadBalancerClient {
@Override
public
ILoadBalancer loadBalancer = getLoadBalancer(serviceId); //獲取對應的LoadBalancer
Server server = getServer(loadBalancer); //獲取服務器,這裡會執行對應的分流策略,比如輪訓
//、隨機等
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);
}
}然後將請求轉發給LoadBalancerClient:
然後將請求轉發給LoadBalancerClient:
public class RibbonLoadBalancerClient implements LoadBalancerClient {
@Override
public
ILoadBalancer loadBalancer = getLoadBalancer(serviceId); //獲取對應的LoadBalancer
Server server = getServer(loadBalancer); //獲取服務器,這裡會執行對應的分流策略,比如輪訓
//、隨機等
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);
}
}
而這裡的LoadBalancer是通過上文中提到的SpringClientFactory獲取到的,這裡會初始化一個新的Spring上下文,然後將Ribbon默認的配置類,比如說: RibbonAutoConfiguration 、 RibbonEurekaAutoConfiguration 等添加進去, 然後將當前spring的上下文設置為parent,再調用refresh方法進行初始化。
public class SpringClientFactory extends NamedContextFactory<ribbonclientspecification> {/<ribbonclientspecification>
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> entry : this.configurations.entrySet()) {/<string>
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> singletonMap(this.propertyName, name)));/<string>
if (this.parent != null) {
// Uses Environment from parent as well as beans
context.setParent(this.parent);
}
context.refresh();
return context;
}
}
最核心的就在這一段,也就是說對於每一個不同的serviceId來說,都擁有一個獨立的spring上下文,並且在第一次調用這個服務的時候,會初始化ribbon相關的所有bean, 如果不存在 才回去父context中去找。
再回到上文中根據分流策略獲取實際的ip:port的代碼段:
public class RibbonLoadBalancerClient implements LoadBalancerClient {
@Override
public
ILoadBalancer loadBalancer = getLoadBalancer(serviceId); //獲取對應的LoadBalancer
Server server = getServer(loadBalancer); //獲取服務器,這裡會執行對應的分流策略,比如輪訓
//、隨機等
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);
}
}
protected Server getServer(ILoadBalancer loadBalancer) {
if (loadBalancer == null) {
return null;
}
// 選擇對應的服務器
return loadBalancer.chooseServer("default"); // TODO: better handling of key
}
public class ZoneAwareLoadBalancer
@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); //默認不配置可用區,走的是這段
}
Server server = null;
try {
LoadBalancerStats lbStats = getLoadBalancerStats();
Map<string> zoneSnapshot = ZoneAvoidanceRule.createSnapshot(lbStats);/<string>
logger.debug("Zone snapshots: {}", zoneSnapshot);
if (triggeringLoad == null) {
triggeringLoad = DynamicPropertyFactory.getInstance().getDoubleProperty(
"ZoneAwareNIWSDiscoveryLoadBalancer." + this.getName() + ".triggeringLoadPerServerThreshold", 0.2d);
}
if (triggeringBlackoutPercentage == null) {
triggeringBlackoutPercentage = DynamicPropertyFactory.getInstance().getDoubleProperty(
"ZoneAwareNIWSDiscoveryLoadBalancer." + this.getName() + ".avoidZoneWithBlackoutPercetage", 0.99999d);
}
Set<string> availableZones = ZoneAvoidanceRule.getAvailableZones(zoneSnapshot, triggeringLoad.get(), triggeringBlackoutPercentage.get());/<string>
logger.debug("Available zones: {}", availableZones);
if (availableZones != null && availableZones.size() < zoneSnapshot.keySet().size()) {
String zone = ZoneAvoidanceRule.randomChooseZone(zoneSnapshot, availableZones);
logger.debug("Zone chosen: {}", zone);
if (zone != null) {
BaseLoadBalancer zoneLoadBalancer = getLoadBalancer(zone);
server = zoneLoadBalancer.chooseServer(key);
}
}
} catch (Exception e) {
logger.error("Error choosing server using zone aware logic for load balancer={}", name, e);
}
if (server != null) {
return server;
} else {
logger.debug("Zone avoidance logic is not invoked.");
return super.chooseServer(key);
}
}
//實際走到的方法
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;
}
}
}
}
也就是說最終會調用 IRule 選擇到一個節點,這裡支持很多策略,比如隨機、輪訓、響應時間權重等:
public interface IRule{
public Server choose(Object key);
public void setLoadBalancer(ILoadBalancer lb);
public ILoadBalancer getLoadBalancer();
}
這裡的LoadBalancer是在BaseLoadBalancer的構造器中設置的,上文說過,對於每一個serviceId服務來說,當第一次調用的時候會初始化對應的spring上下文,而這個上下文中包含了所有ribbon相關的bean,其中就包括ILoadBalancer、IRule。
原因
通過跟蹤堆棧,發現不同的serviceId,IRule是同一個, 而上文說過,每個serviceId都擁有自己獨立的上下文,包括獨立的loadBalancer、IRule,而IRule是同一個,因此懷疑是這個bean是通過parent context獲取到的,換句話說應用自己定義了一個這樣的bean。查看代碼果然如此。
這樣就會導致一個問題,IRule是共享的,而其他bean是隔離開的,因此後面的serviceId初始化的時候,會修改這個IRule的LoadBalancer, 導致之前的服務獲取到的實例信息是錯誤的,從而導致接口404。
public class BaseLoadBalancer extends AbstractLoadBalancer implements
PrimeConnections.PrimeConnectionListener, IClientConfigAware {
public BaseLoadBalancer() {
this.name = DEFAULT_NAME;
this.ping = null;
setRule(DEFAULT_RULE); // 這裡會設置IRule的loadbalancer
setupPingTask();
lbStats = new LoadBalancerStats(DEFAULT_NAME);
}
}
解決方案
解決方法也很簡單,最簡單就將這個自定義的IRule的bean幹掉,另外更標準的做法是使用RibbonClients註解,具體做法可以參考文檔。
總結
核心原因其實還是對於Spring Cloud的理解不夠深刻,用法有錯誤,導致出現了一些比較詭異的問題。對於自己使用的組件、框架、甚至於每一個註解,都要了解其原理,能夠清楚的說清楚這個註解有什麼效果,有什麼影響,而不是隻著眼於解決眼前的問題。
好了,以上就是這篇文章的全部內容了,希望本文的內容對大家的學習或者工作具有一定的參考學習價值,喜歡小編的文章可以關注小編並幫小編轉發哦~~
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