dubbo 3.2.0 consumer bean初始化及服务发现简记

consumer bean初始化

以spring 如下配置
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<dubbo:reference id="versionConsumerBean" interface="org.apache.dubbo.samples.version.api.VersionService" version="*"/>
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为例，先使用spring 的初始化，核心代码

 try {
                final RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
                checkMergedBeanDefinition(mbd, beanName, args);

                // Guarantee initialization of beans that the current bean depends on.
                String[] dependsOn = mbd.getDependsOn();
                if (dependsOn != null) {
                    for (String dep : dependsOn) {
                        if (isDependent(beanName, dep)) {
                            throw new BeanCreationException(mbd.getResourceDescription(), beanName,
                                    "Circular depends-on relationship between '" + beanName + "' and '" + dep + "'");
                        }
                        registerDependentBean(dep, beanName);
                        try {
                            getBean(dep);
                        }
                        catch (NoSuchBeanDefinitionException ex) {
                            throw new BeanCreationException(mbd.getResourceDescription(), beanName,
                                    "'" + beanName + "' depends on missing bean '" + dep + "'", ex);
                        }
                    }
                }
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初始化为class org.apache.dubbo.config.spring.ReferenceBean。

然后在类似如下代码

VersionService versionService = (VersionService) context.getBean("versionConsumerBean");
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处进行了二次变化，创建LazyProxy

核心代码在ReferenceBean的getObject，代码如下：
 /**
     * Create bean instance.
     *
     * 

     * Why we need a lazy proxy?
     *
     * 

     * When Spring searches beans by type, if Spring cannot determine the type of a factory bean, it may try to initialize it.
     * The ReferenceBean is also a FactoryBean.
     * 

     * (This has already been resolved by decorating the BeanDefinition: {@link DubboBeanDefinitionParser#configReferenceBean})
     *
     * 

     * In addition, if some ReferenceBeans are dependent on beans that are initialized very early,
     * and dubbo config beans are not ready yet, there will be many unexpected problems if initializing the dubbo reference immediately.
     *
     * 

     * When it is initialized, only a lazy proxy object will be created,
     * and dubbo reference-related resources will not be initialized.
     * 

     * In this way, the influence of Spring is eliminated, and the dubbo configuration initialization is controllable.
     *
     *
     * @see DubboConfigBeanInitializer
     * @see ReferenceBeanManager#initReferenceBean(ReferenceBean)
     * @see DubboBeanDefinitionParser#configReferenceBean
     */
    @Override
    public T getObject() {
        if (lazyProxy == null) {
            createLazyProxy();
        }
        return (T) lazyProxy;
    }
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变换后返回的是一个aop java对象了。

服务发现

dubbo 的服务调用是proxy通invoker实现，因此核心过程就在如下函数中。

@SuppressWarnings({"unchecked"})
private T createProxy(Map<String, String> referenceParameters) {
    urls.clear();

    meshModeHandleUrl(referenceParameters);

    if (StringUtils.isNotEmpty(url)) {
        // user specified URL, could be peer-to-peer address, or register center's address.
        parseUrl(referenceParameters);
    } else {
        // if protocols not in jvm checkRegistry
        aggregateUrlFromRegistry(referenceParameters);
    }
    createInvoker();

    if (logger.isInfoEnabled()) {
        logger.info("Referred dubbo service: [" + referenceParameters.get(INTERFACE_KEY) + "]." +
                (Boolean.parseBoolean(referenceParameters.get(GENERIC_KEY)) ?
                        " it's GenericService reference" : " it's not GenericService reference"));
    }

    URL consumerUrl = new ServiceConfigURL(CONSUMER_PROTOCOL, referenceParameters.get(REGISTER_IP_KEY), 0,
            referenceParameters.get(INTERFACE_KEY), referenceParameters);
    consumerUrl = consumerUrl.setScopeModel(getScopeModel());
    consumerUrl = consumerUrl.setServiceModel(consumerModel);
    MetadataUtils.publishServiceDefinition(consumerUrl, consumerModel.getServiceModel(), getApplicationModel());

    // create service proxy
    return (T) proxyFactory.getProxy(invoker, ProtocolUtils.isGeneric(generic));
}
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在创建proxy的过程中，可以多次看到TargetService和protocolServiceKey的处理，核心是找到两者批量的service

核心比较代码如下

public static boolean isMatch(URL consumerUrl, URL providerUrl) {
    String consumerInterface = consumerUrl.getServiceInterface();
    String providerInterface = providerUrl.getServiceInterface();
    if (!"*".equals(consumerInterface) && !"*".equals(providerInterface) && !StringUtils.isEquals(consumerInterface, providerInterface)) {
        return false;
    } else if (!isMatchCategory(providerUrl.getCategory("providers"), consumerUrl.getCategory("providers"))) {
        return false;
    } else if (!providerUrl.getParameter("enabled", true) && !"*".equals(consumerUrl.getParameter("enabled"))) {
        return false;
    } else {
        String consumerGroup = consumerUrl.getGroup();
        String consumerVersion = consumerUrl.getVersion();
        String consumerClassifier = consumerUrl.getParameter("classifier", "*");
        String providerGroup = providerUrl.getGroup();
        String providerVersion = providerUrl.getVersion();
        String providerClassifier = providerUrl.getParameter("classifier", "*");
        boolean groupMatches = "*".equals(consumerGroup) || StringUtils.isEquals(consumerGroup, providerGroup) || StringUtils.isContains(consumerGroup, providerGroup);
        boolean versionMatches = "*".equals(consumerVersion) || StringUtils.isEquals(consumerVersion, providerVersion);
        boolean classifierMatches = consumerClassifier == null || "*".equals(consumerClassifier) || StringUtils.isEquals(consumerClassifier, providerClassifier);
        return groupMatches && versionMatches && classifierMatches;
    }
}
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注意看最后几段boolean的match，即

1. group
2. version
3. class（interface）

要匹配

invoker 是在服务发现后依次进行router-cluster-failover 判定后进行调用，可以参考下图

而服务发现（以zk为例），核心用到以下类

zk 数据结构

dubbo root

[zk: localhost:2181(CONNECTED) 23] ls /dubbo
[config, mapping, metadata, org.apache.dubbo.metadata.MetadataService, org.apache.dubbo.mock.api.MockService, org.apache.dubbo.samples.version.api.VersionService]
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provider创建时候负责写入zk的providers

[zk: localhost:2181(CONNECTED) 24] ls /dubbo/org.apache.dubbo.samples.version.api.VersionService
[configurators, providers]
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providers可以有多版本

[zk: localhost:2181(CONNECTED) 25] ls /dubbo/org.apache.dubbo.samples.version.api.VersionService/providers
[dubbo%3A%2F%2F192.168.3.28%3A20880%2Forg.apache.dubbo.samples.version.api.VersionService%3Fanyhost%3Dtrue%26application%3Dversion-provider%26background%3Dfalse%26deprecated%3Dfalse%26dubbo%3D2.0.2%26dynamic%3Dtrue%26executor-management-mode%3Disolation%26file-cache%3Dtrue%26generic%3Dfalse%26interface%3Dorg.apache.dubbo.samples.version.api.VersionService%26methods%3DsayHello%26pid%3D8804%26prefer.serialization%3Dfastjson2%2Chessian2%26release%3D3.2.0%26revision%3D1.0.0%26service-name-mapping%3Dtrue%26side%3Dprovider%26timestamp%3D1685160190088%26token%3Db4d3e756-3a85-40ab-b3fd-c4b1352879ce%26version%3D1.0.0, dubbo%3A%2F%2F192.168.3.28%3A20880%2Forg.apache.dubbo.samples.version.api.VersionService%3Fanyhost%3Dtrue%26application%3Dversion-provider%26background%3Dfalse%26deprecated%3Dfalse%26dubbo%3D2.0.2%26dynamic%3Dtrue%26executor-management-mode%3Disolation%26file-cache%3Dtrue%26generic%3Dfalse%26interface%3Dorg.apache.dubbo.samples.version.api.VersionService%26methods%3DsayHello%26pid%3D8804%26prefer.serialization%3Dfastjson2%2Chessian2%26release%3D3.2.0%26revision%3D2.0.0%26service-name-mapping%3Dtrue%26side%3Dprovider%26timestamp%3D1685160186753%26token%3Dbc2534d5-f980-4a41-ab90-e4e9ae688ad9%26version%3D2.0.0]
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完整的service下目录

[zk: localhost:2181(CONNECTED) 7] ls -s /dubbo/org.apache.dubbo.samples.version.api.VersionService
[configurators, consumers, providers, routers]
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