【Nacos】Nacos配置中心客户端启动源码分析

SpringCloud项目启动过程中会解析bootstrop.properties、bootstrap.yaml配置文件，启动父容器，在子容器启动过程中会加入PropertySourceBootstrapConfiguration来读取配置中心的配置。

PropertySourceBootstrapConfiguration#initialize

PropertySourceBootstrapConfiguration是SpringCloud的配置类，实现了ApplicationContextInitializer，会在容器创建前调用其initialize()方法。
org.springframework.cloud.bootstrap.config.PropertySourceBootstrapConfiguration#initialize

public void initialize(ConfigurableApplicationContext applicationContext) {List<PropertySource<?>> composite = new ArrayList<>();AnnotationAwareOrderComparator.sort(this.propertySourceLocators);boolean empty = true;ConfigurableEnvironment environment = applicationContext.getEnvironment();for (PropertySourceLocator locator : this.propertySourceLocators) {// 调用PropertySourceLocator.locateCollection()来读取配置Collection<PropertySource<?>> source = locator.locateCollection(environment);if (source == null || source.size() == 0) {continue;}List<PropertySource<?>> sourceList = new ArrayList<>();for (PropertySource<?> p : source) {if (p instanceof EnumerablePropertySource) {EnumerablePropertySource<?> enumerable = (EnumerablePropertySource<?>) p;sourceList.add(new BootstrapPropertySource<>(enumerable));}else {sourceList.add(new SimpleBootstrapPropertySource(p));}}logger.info("Located property source: " + sourceList);composite.addAll(sourceList);empty = false;}if (!empty) {MutablePropertySources propertySources = environment.getPropertySources();String logConfig = environment.resolvePlaceholders("${logging.config:}");LogFile logFile = LogFile.get(environment);for (PropertySource<?> p : environment.getPropertySources()) {if (p.getName().startsWith(BOOTSTRAP_PROPERTY_SOURCE_NAME)) {propertySources.remove(p.getName());}}insertPropertySources(propertySources, composite);reinitializeLoggingSystem(environment, logConfig, logFile);setLogLevels(applicationContext, environment);handleIncludedProfiles(environment);}
}

在PropertySourceBootstrapConfiguration这个单例对象初始化的时候会将Spring容器中所有的PropertySourceLocator实现注入进来。然后在initialize()方法中循环所有的PropertySourceLocator进行配置的获取，从这儿可以看出SpringCloud应用是支持我们引入多个配置中心实现的，获取到配置后调用insertPropertySources方法将所有的PropertySource（封装的一个个配置文件）添加到Spring的环境变量environment中。

org.springframework.cloud.bootstrap.config.PropertySourceLocator#locateCollection(org.springframework.core.env.Environment)

default Collection<PropertySource<?>> locateCollection(Environment environment) {return locateCollection(this, environment);
}static Collection<PropertySource<?>> locateCollection(PropertySourceLocator locator,Environment environment) {// 最终会调用PropertySourceLocator.locate()PropertySource<?> propertySource = locator.locate(environment);if (propertySource == null) {return Collections.emptyList();}if (CompositePropertySource.class.isInstance(propertySource)) {Collection<PropertySource<?>> sources = ((CompositePropertySource) propertySource).getPropertySources();List<PropertySource<?>> filteredSources = new ArrayList<>();for (PropertySource<?> p : sources) {if (p != null) {filteredSources.add(p);}}return filteredSources;}else {return Arrays.asList(propertySource);}
}

上面会将CompositePropertySource拆分为多个PropertySource。

NacosPropertySourceLocator#locate

Nacos也实现了SpringCloud配置中心规范，其实现类为NacosPropertySourceLocator。

com.alibaba.cloud.nacos.client.NacosPropertySourceLocator#locate

public PropertySource<?> locate(Environment env) {nacosConfigProperties.setEnvironment(env);ConfigService configService = nacosConfigManager.getConfigService();if (null == configService) {log.warn("no instance of config service found, can't load config from nacos");return null;}long timeout = nacosConfigProperties.getTimeout();nacosPropertySourceBuilder = new NacosPropertySourceBuilder(configService,timeout);String name = nacosConfigProperties.getName();String dataIdPrefix = nacosConfigProperties.getPrefix();if (StringUtils.isEmpty(dataIdPrefix)) {dataIdPrefix = name;}if (StringUtils.isEmpty(dataIdPrefix)) {dataIdPrefix = env.getProperty("spring.application.name");}CompositePropertySource composite = new CompositePropertySource(NACOS_PROPERTY_SOURCE_NAME);// 读取共享配置loadSharedConfiguration(composite);// 读取扩展配置loadExtConfiguration(composite);// 读取应用配置loadApplicationConfiguration(composite, dataIdPrefix, nacosConfigProperties, env);return composite;
}

Nacos启动会加载以下三种配置文件，也就是我们在bootstrap.yml文件里配置的扩展配置extension-configs、共享配置 shared-configs以及应用自己的配置，加载到配置文件后会封装成NacosPropertySource返回，最后只会返回一个CompositePropertySource。

NacosPropertySourceLocator#loadApplicationConfiguration

实际开发过程中我们主要使用的就是应用配置，所以这里重点关注应用配置的加载过程。

com.alibaba.cloud.nacos.client.NacosPropertySourceLocator#loadApplicationConfiguration

private void loadApplicationConfiguration(CompositePropertySource compositePropertySource, String dataIdPrefix,NacosConfigProperties properties, Environment environment) {String fileExtension = properties.getFileExtension();String nacosGroup = properties.getGroup();// load directly once by defaultloadNacosDataIfPresent(compositePropertySource, dataIdPrefix, nacosGroup,fileExtension, true);// load with suffix, which have a higher priority than the defaultloadNacosDataIfPresent(compositePropertySource,dataIdPrefix + DOT + fileExtension, nacosGroup, fileExtension, true);// Loaded with profile, which have a higher priority than the suffixfor (String profile : environment.getActiveProfiles()) {String dataId = dataIdPrefix + SEP1 + profile + DOT + fileExtension;loadNacosDataIfPresent(compositePropertySource, dataId, nacosGroup,fileExtension, true);}}

加载应用配置时，同时会加载以下三种配置，配置的优先级从低到高，分别是：

1. 不带扩展名后缀，application
2. 带扩展名后缀，application.yml、application.propertie
3. 带环境，带扩展名后缀，application-prod.yml

com.alibaba.cloud.nacos.client.NacosPropertySourceLocator#loadNacosDataIfPresent

private void loadNacosDataIfPresent(final CompositePropertySource composite,final String dataId, final String group, String fileExtension,boolean isRefreshable) {if (null == dataId || dataId.trim().length() < 1) {return;}if (null == group || group.trim().length() < 1) {return;}NacosPropertySource propertySource = this.loadNacosPropertySource(dataId, group,fileExtension, isRefreshable);this.addFirstPropertySource(composite, propertySource, false);
}

com.alibaba.cloud.nacos.client.NacosPropertySourceLocator#loadNacosPropertySource

private NacosPropertySource loadNacosPropertySource(final String dataId,final String group, String fileExtension, boolean isRefreshable) {if (NacosContextRefresher.getRefreshCount() != 0) {if (!isRefreshable) {// 从缓冲中获取return NacosPropertySourceRepository.getNacosPropertySource(dataId,group);}}return nacosPropertySourceBuilder.build(dataId, group, fileExtension,isRefreshable);
}

com.alibaba.cloud.nacos.client.NacosPropertySourceBuilder#build

NacosPropertySource build(String dataId, String group, String fileExtension,boolean isRefreshable) {// 加载数据List<PropertySource<?>> propertySources = loadNacosData(dataId, group,fileExtension);NacosPropertySource nacosPropertySource = new NacosPropertySource(propertySources,group, dataId, new Date(), isRefreshable);// 加入缓存NacosPropertySourceRepository.collectNacosPropertySource(nacosPropertySource);return nacosPropertySource;
}

com.alibaba.cloud.nacos.client.NacosPropertySourceBuilder#loadNacosData

private List<PropertySource<?>> loadNacosData(String dataId, String group,String fileExtension) {String data = null;try {// 委托configService获取配置，我们也可以手动使用此类获取配置data = configService.getConfig(dataId, group, timeout);if (StringUtils.isEmpty(data)) {log.warn("Ignore the empty nacos configuration and get it based on dataId[{}] & group[{}]",dataId, group);return Collections.emptyList();}if (log.isDebugEnabled()) {log.debug(String.format("Loading nacos data, dataId: '%s', group: '%s', data: %s", dataId,group, data));}return NacosDataParserHandler.getInstance().parseNacosData(dataId, data,fileExtension);}catch (NacosException e) {log.error("get data from Nacos error,dataId:{} ", dataId, e);}catch (Exception e) {log.error("parse data from Nacos error,dataId:{},data:{}", dataId, data, e);}return Collections.emptyList();
}

loadNacosData()方法中会将实际配置加载请求委托给ConfigService去做，然后解析返回的字符串，解析器实现了PropertySourceLoader接口，支持yml、properties、xml、json这几种格式。

NacosConfigService#getConfig

getConfig()方法会调用到getConfigInner()方法，通过namespace, dataId, group唯一定位一个配置文件。

com.alibaba.nacos.client.config.NacosConfigService#getConfig

public String getConfig(String dataId, String group, long timeoutMs) throws NacosException {return getConfigInner(namespace, dataId, group, timeoutMs);
}

首先获取本地缓存文件的配置内容，如果有直接返回，如果从本地没找到相应配置文件，就从远程服务器拉取，Nacos2.0以上版本使用Grpc协议进行远程通信，1.0及以下使用Http协议进行远程通信，我们这里使用的是1.4.2版本。
com.alibaba.nacos.client.config.NacosConfigService#getConfigInner

private String getConfigInner(String tenant, String dataId, String group, long timeoutMs) throws NacosException {group = blank2defaultGroup(group);ParamUtils.checkKeyParam(dataId, group);ConfigResponse cr = new ConfigResponse();cr.setDataId(dataId);cr.setTenant(tenant);cr.setGroup(group);// 优先使用本地配置String content = LocalConfigInfoProcessor.getFailover(agent.getName(), dataId, group, tenant);if (content != null) {LOGGER.warn("[{}] [get-config] get failover ok, dataId={}, group={}, tenant={}, config={}", agent.getName(),dataId, group, tenant, ContentUtils.truncateContent(content));cr.setContent(content);String encryptedDataKey = LocalEncryptedDataKeyProcessor.getEncryptDataKeyFailover(agent.getName(), dataId, group, tenant);cr.setEncryptedDataKey(encryptedDataKey);configFilterChainManager.doFilter(null, cr);content = cr.getContent();return content;}try {// 从远程服务器拉取ConfigResponse response = worker.getServerConfig(dataId, group, tenant, timeoutMs);cr.setContent(response.getContent());cr.setEncryptedDataKey(response.getEncryptedDataKey());configFilterChainManager.doFilter(null, cr);content = cr.getContent();return content;} catch (NacosException ioe) {if (NacosException.NO_RIGHT == ioe.getErrCode()) {throw ioe;}LOGGER.warn("[{}] [get-config] get from server error, dataId={}, group={}, tenant={}, msg={}",agent.getName(), dataId, group, tenant, ioe.toString());}LOGGER.warn("[{}] [get-config] get snapshot ok, dataId={}, group={}, tenant={}, config={}", agent.getName(),dataId, group, tenant, ContentUtils.truncateContent(content));content = LocalConfigInfoProcessor.getSnapshot(agent.getName(), dataId, group, tenant);cr.setContent(content);String encryptedDataKey = LocalEncryptedDataKeyProcessor.getEncryptDataKeyFailover(agent.getName(), dataId, group, tenant);cr.setEncryptedDataKey(encryptedDataKey);// 这里会对配置进行拦截，可以用于加解密configFilterChainManager.doFilter(null, cr);content = cr.getContent();return content;
}

com.alibaba.nacos.client.config.impl.ClientWorker#getServerConfig

public ConfigResponse getServerConfig(String dataId, String group, String tenant, long readTimeout)throws NacosException {ConfigResponse configResponse = new ConfigResponse();if (StringUtils.isBlank(group)) {group = Constants.DEFAULT_GROUP;}HttpRestResult<String> result = null;try {Map<String, String> params = new HashMap<String, String>(3);if (StringUtils.isBlank(tenant)) {params.put("dataId", dataId);params.put("group", group);} else {params.put("dataId", dataId);params.put("group", group);params.put("tenant", tenant);}// 调用远程Http接口/v1/cs/configs拉取配置result = agent.httpGet(Constants.CONFIG_CONTROLLER_PATH, null, params, agent.getEncode(), readTimeout);} catch (Exception ex) {String message = String.format("[%s] [sub-server] get server config exception, dataId=%s, group=%s, tenant=%s",agent.getName(), dataId, group, tenant);LOGGER.error(message, ex);throw new NacosException(NacosException.SERVER_ERROR, ex);}switch (result.getCode()) {case HttpURLConnection.HTTP_OK:LocalConfigInfoProcessor.saveSnapshot(agent.getName(), dataId, group, tenant, result.getData());configResponse.setContent(result.getData());String configType;if (result.getHeader().getValue(CONFIG_TYPE) != null) {configType = result.getHeader().getValue(CONFIG_TYPE);} else {configType = ConfigType.TEXT.getType();}configResponse.setConfigType(configType);String encryptedDataKey = result.getHeader().getValue(ENCRYPTED_DATA_KEY);LocalEncryptedDataKeyProcessor.saveEncryptDataKeySnapshot(agent.getName(), dataId, group, tenant, encryptedDataKey);configResponse.setEncryptedDataKey(encryptedDataKey);return configResponse;case HttpURLConnection.HTTP_NOT_FOUND:LocalConfigInfoProcessor.saveSnapshot(agent.getName(), dataId, group, tenant, null);LocalEncryptedDataKeyProcessor.saveEncryptDataKeySnapshot(agent.getName(), dataId, group, tenant, null);return configResponse;case HttpURLConnection.HTTP_CONFLICT: {LOGGER.error("[{}] [sub-server-error] get server config being modified concurrently, dataId={}, group={}, "+ "tenant={}", agent.getName(), dataId, group, tenant);throw new NacosException(NacosException.CONFLICT,"data being modified, dataId=" + dataId + ",group=" + group + ",tenant=" + tenant);}case HttpURLConnection.HTTP_FORBIDDEN: {LOGGER.error("[{}] [sub-server-error] no right, dataId={}, group={}, tenant={}", agent.getName(),dataId, group, tenant);throw new NacosException(result.getCode(), result.getMessage());}default: {LOGGER.error("[{}] [sub-server-error]  dataId={}, group={}, tenant={}, code={}", agent.getName(),dataId, group, tenant, result.getCode());throw new NacosException(result.getCode(),"http error, code=" + result.getCode() + ",dataId=" + dataId + ",group=" + group + ",tenant="+ tenant);}}
}

至此，在项目启动的时候（上下文准备阶段）我们就拉到了远程Nacos中的配置，并且封装成NacosPropertySource放到了Spring 的环境变量里，在Bean的实例化过程中就可以使用Environment中的值了。