spring cloud netflix ribbon的eager load有什么作用

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本文主要研究一下spring cloud netflix ribbon的eager load

RibbonAutoConfiguration

spring-cloud-netflix-ribbon-2.1.1.RELEASE-sources.jar!/org/springframework/cloud/netflix/ribbon/RibbonAutoConfiguration.java

@Configuration@Conditional(RibbonAutoConfiguration.RibbonClassesConditions.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 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());        }        @Bean        @ConditionalOnClass(name = "org.springframework.retry.support.RetryTemplate")        @ConditionalOnMissingBean        public LoadBalancedRetryFactory loadBalancedRetryPolicyFactory(                        final SpringClientFactory clientFactory) {                return new RibbonLoadBalancedRetryFactory(clientFactory);        }        @Bean        @ConditionalOnMissingBean        public PropertiesFactory propertiesFactory() {                return new PropertiesFactory();        }        @Bean        @ConditionalOnProperty("ribbon.eager-load.enabled")        public RibbonApplicationContextInitializer ribbonApplicationContextInitializer() {                return new RibbonApplicationContextInitializer(springClientFactory(),                                ribbonEagerLoadProperties.getClients());        }        @Configuration        @ConditionalOnClass(HttpRequest.class)        @ConditionalOnRibbonRestClient        protected static class RibbonClientHttpRequestFactoryConfiguration {                @Autowired                private SpringClientFactory springClientFactory;                @Bean                public RestTemplateCustomizer restTemplateCustomizer(                                final RibbonClientHttpRequestFactory ribbonClientHttpRequestFactory) {                        return 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 {                OnRibbonRestClientCondition() {                        super(ConfigurationPhase.REGISTER_BEAN);                }                @Deprecated // remove in Edgware"                @ConditionalOnProperty("ribbon.http.client.enabled")                static class ZuulProperty {                }                @ConditionalOnProperty("ribbon.restclient.enabled")                static class RibbonProperty {                }        }        /**         * {@link AllNestedConditions} that checks that either multiple classes are present.         */        static class RibbonClassesConditions extends AllNestedConditions {                RibbonClassesConditions() {                        super(ConfigurationPhase.PARSE_CONFIGURATION);                }                @ConditionalOnClass(IClient.class)                static class IClientPresent {                }                @ConditionalOnClass(RestTemplate.class)                static class RestTemplatePresent {                }                @ConditionalOnClass(AsyncRestTemplate.class)                static class AsyncRestTemplatePresent {                }                @ConditionalOnClass(Ribbon.class)                static class RibbonPresent {                }        }}

• RibbonAutoConfiguration启用了RibbonEagerLoadProperties、ServerIntrospectorProperties两个配置，这里主要是注册了SpringClientFactory，创建LoadBalancerClient、LoadBalancedRetryFactory、RibbonApplicationContextInitializer、RestTemplateCustomizer及RibbonClientHttpRequestFactory

RibbonApplicationContextInitializer

spring-cloud-netflix-ribbon-2.1.1.RELEASE-sources.jar!/org/springframework/cloud/netflix/ribbon/RibbonApplicationContextInitializer.java

public class RibbonApplicationContextInitializer                implements ApplicationListener {        private final SpringClientFactory springClientFactory;        // List of Ribbon client names        private final List clientNames;        public RibbonApplicationContextInitializer(SpringClientFactory springClientFactory,                        List clientNames) {                this.springClientFactory = springClientFactory;                this.clientNames = clientNames;        }        protected void initialize() {                if (clientNames != null) {                        for (String clientName : clientNames) {                                this.springClientFactory.getContext(clientName);                        }                }        }        @Override        public void onApplicationEvent(ApplicationReadyEvent event) {                initialize();        }}

• RibbonApplicationContextInitializer实现了ApplicationListener接口，其响应ApplicationReadyEvent事件执行initialize操作，这里主要是挨个对配置的clientNames执行springClientFactory.getContext(clientName)操作

SpringClientFactory

spring-cloud-netflix-ribbon-2.1.1.RELEASE-sources.jar!/org/springframework/cloud/netflix/ribbon/SpringClientFactory.java

public class SpringClientFactory extends NamedContextFactory {        //......        protected AnnotationConfigApplicationContext getContext(String name) {                return super.getContext(name);        }        //......}

• SpringClientFactory的getContext方法调用了父类NamedContextFactory的getContext

NamedContextFactory

spring-cloud-context-2.2.0.M1-sources.jar!/org/springframework/cloud/context/named/NamedContextFactory.java

public abstract class NamedContextFactory                implements DisposableBean, ApplicationContextAware {        //......        protected AnnotationConfigApplicationContext getContext(String name) {                if (!this.contexts.containsKey(name)) {                        synchronized (this.contexts) {                                if (!this.contexts.containsKey(name)) {                                        this.contexts.put(name, createContext(name));                                }                        }                }                return this.contexts.get(name);        }        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 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.singletonMap(this.propertyName, name)));                if (this.parent != null) {                        // Uses Environment from parent as well as beans                        context.setParent(this.parent);                        // jdk11 issue                        // https://github.com/spring-cloud/spring-cloud-netflix/issues/3101                        context.setClassLoader(this.parent.getClassLoader());                }                context.setDisplayName(generateDisplayName(name));                context.refresh();                return context;        }        //......}               

• NamedContextFactory的getContext主要是返回或者创建AnnotationConfigApplicationContext

小结

• RibbonAutoConfiguration启用了RibbonEagerLoadProperties、ServerIntrospectorProperties两个配置，这里主要是注册了SpringClientFactory，创建LoadBalancerClient、LoadBalancedRetryFactory、RibbonApplicationContextInitializer、RestTemplateCustomizer及RibbonClientHttpRequestFactory

• RibbonApplicationContextInitializer实现了ApplicationListener接口，其响应ApplicationReadyEvent事件执行initialize操作，这里主要是挨个对配置的clientNames执行springClientFactory.getContext(clientName)操作

• SpringClientFactory的getContext方法调用了父类NamedContextFactory的getContext；NamedContextFactory的getContext主要是返回或者创建AnnotationConfigApplicationContext

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