聊聊spring cloud netflix ribbon的eager load

序

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<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());
    }

    @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<ApplicationReadyEvent> {

    private final SpringClientFactory springClientFactory;

    // List of Ribbon client names
    private final List<String> clientNames;

    public RibbonApplicationContextInitializer(SpringClientFactory springClientFactory,
            List<String> 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<RibbonClientSpecification> {
    //......

    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<C extends NamedContextFactory.Specification>
        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<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);
            // 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

doc

• RibbonClientConfiguration