nacos配置中心源碼分析（1）

nacos版本
 <dependency>
     <groupId>com.alibaba.cloud</groupId>
     <artifactId>spring-cloud-starter-alibaba-nacos-config</artifactId>
     <version>2.0.0.RELEASE</version>
 </dependency>

bootstrap.yaml

spring:
  application:
    name: service1
  profiles:
    active: dev
  cloud:
    nacos:
      config:
        namespace: 14d29622-bf23-4d4a-b86d-cdedc18ff83b
        file-extension: yaml
        server-addr: 127.0.0.1:8848
        ext-config[0]:
          data-id: common-${spring.profiles.active}.yaml
          refresh: true

nacos是Alibaba 開源的微服務(wù)發(fā)現(xiàn)、管理、配置的組件，它提供了server端和客戶端的能力，這里我們將來分析下nacos與spring cloud服務(wù)集成，作為微服務(wù)的配置中心的nacos的底層源碼

nacos讀取配置分析
// springboot服務(wù)的統(tǒng)一入口
public static void main(String[] args) {
        SpringApplication.run(MyApplication.class, args);
}

啟動微服務(wù)，從SpringApplication.run()方法進(jìn)入，到達(dá)SpringApplication#run(java.lang.String...) 進(jìn)行spring容器的啟動的各項工作：
1、準(zhǔn)備上下文


2、應(yīng)用初始化設(shè)定（配置刷新）



3、加載各種初始化配置，其中包括屬性配置初始化



4、PropertySourceBootstrapConfiguration#initialize方法中加載到nacos配置源 
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) {
       // 配置源
      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);
   }
}

5、然后到達(dá)此方法NacosPropertySourceLocator#locate 進(jìn)行bootstrap.yaml配置的nacos相關(guān)配置獲取與加載

public PropertySource<?> locate(Environment env) {

   ConfigService configService = nacosConfigProperties.configServiceInstance();

   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);
    // 加載共享配置 對應(yīng) shared-dataids 配置項
   loadSharedConfiguration(composite);
    // 加載額外配置 對應(yīng) ext-config[n] 配置項
   loadExtConfiguration(composite);
    // 加載微服務(wù)對應(yīng)配置
   loadApplicationConfiguration(composite, dataIdPrefix, nacosConfigProperties, env);

   return composite;
}

6、主要看NacosPropertySourceLocator#loadApplicationConfiguration 加載微服務(wù)配置，另外兩個加載方法雷同。加載順序，按照

${prefix}.${file-extension}  => ${prefix}-${spring.profiles.active}.${file-extension}


7、第一次啟動從遠(yuǎn)程獲取數(shù)據(jù)進(jìn)行加載

8、然后在NacosConfigService#getConfigInner方法進(jìn)行加載配置，首先加載本地配置：nacos從遠(yuǎn)程讀取配置文件成功，會將配置文件快照備份在磁盤上，當(dāng)無法連接服務(wù)端時，使用本地快照的配置。如果存在本地備份，則不會從遠(yuǎn)程獲取配置。那如果配置發(fā)生更新怎么辦？這就涉及到nacos動態(tài)配置功能，將在下一篇進(jìn)行分析。

private String getConfigInner(String tenant, String dataId, String group, long timeoutMs) throws NacosException {
    group = null2defaultGroup(group);
    ParamUtils.checkKeyParam(dataId, group);
    ConfigResponse cr = new ConfigResponse();

    cr.setDataId(dataId);
    cr.setTenant(tenant);
    cr.setGroup(group);

    // 優(yōu)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);
        configFilterChainManager.doFilter(null, cr);
        content = cr.getContent();
        return content;
    }

    try {  // 沒有磁盤快照，從配置中心加載服務(wù)配置
        content = worker.getServerConfig(dataId, group, tenant, timeoutMs);

        cr.setContent(content);

        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);
    configFilterChainManager.doFilter(null, cr);
    content = cr.getContent();
    return content;
}

9、ClientWorker#getServerConfig方法

public String getServerConfig(String dataId, String group, String tenant, long readTimeout)
    throws NacosException {
    if (StringUtils.isBlank(group)) {
        group = Constants.DEFAULT_GROUP;
    }

    HttpResult result = null;
    try {
        List<String> params = null;
        if (StringUtils.isBlank(tenant)) {
            params = Arrays.asList("dataId", dataId, "group", group);
        } else {
            params = Arrays.asList("dataId", dataId, "group", group, "tenant", tenant);
        }
        // get方法獲取配置文件內(nèi)容
        result = agent.httpGet(Constants.CONFIG_CONTROLLER_PATH, null, params, agent.getEncode(), readTimeout);
    } catch (IOException e) {
        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, e);
        throw new NacosException(NacosException.SERVER_ERROR, e);
    }

    switch (result.code) {
        case HttpURLConnection.HTTP_OK:
            // 備份快照至磁盤
            LocalConfigInfoProcessor.saveSnapshot(agent.getName(), dataId, group, tenant, result.content);
            return result.content;
        case HttpURLConnection.HTTP_NOT_FOUND:
            LocalConfigInfoProcessor.saveSnapshot(agent.getName(), dataId, group, tenant, null);
            return null;
        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.code, result.content);
        }
        default: {
            LOGGER.error("[{}] [sub-server-error]  dataId={}, group={}, tenant={}, code={}", agent.getName(), dataId,
                group, tenant, result.code);
            throw new NacosException(result.code,
                "http error, code=" + result.code + ",dataId=" + dataId + ",group=" + group + ",tenant=" + tenant);
        }
    }
}

10、具體http請求方法，請求失敗時，重試3次，從服務(wù)端配置地址獲取下一個服務(wù)地址進(jìn)行新的請求。如果請求成功nacos服務(wù)端返回的字符串內(nèi)容。

public HttpResult httpGet(String path, List<String> headers, List<String> paramValues, String encoding,
                          long readTimeoutMs) throws IOException {
    final long endTime = System.currentTimeMillis() + readTimeoutMs;
    final boolean isSSL = false;

    String currentServerAddr = serverListMgr.getCurrentServerAddr();
    // 默認(rèn) 3
    int maxRetry = this.maxRetry;

    do {
        try {
            List<String> newHeaders = getSpasHeaders(paramValues);
            if (headers != null) {
                newHeaders.addAll(headers);
            }
            HttpResult result = HttpSimpleClient.httpGet(
                getUrl(currentServerAddr, path), newHeaders, paramValues, encoding,
                readTimeoutMs, isSSL);
            if (result.code == HttpURLConnection.HTTP_INTERNAL_ERROR
                || result.code == HttpURLConnection.HTTP_BAD_GATEWAY
                || result.code == HttpURLConnection.HTTP_UNAVAILABLE) {
                LOGGER.error("[NACOS ConnectException] currentServerAddr: {}, httpCode: {}",
                    serverListMgr.getCurrentServerAddr(), result.code);
            } else {
                // Update the currently available server addr
                serverListMgr.updateCurrentServerAddr(currentServerAddr);
                return result;
            }
        } catch (ConnectException ce) {
            LOGGER.error("[NACOS ConnectException httpGet] currentServerAddr:{}, err : {}", serverListMgr.getCurrentServerAddr(), ce.getMessage());
        } catch (SocketTimeoutException stoe) {
            LOGGER.error("[NACOS SocketTimeoutException httpGet] currentServerAddr:{}， err : {}", serverListMgr.getCurrentServerAddr(), stoe.getMessage());
        } catch (IOException ioe) {
            LOGGER.error("[NACOS IOException httpGet] currentServerAddr: " + serverListMgr.getCurrentServerAddr(), ioe);
            throw ioe;
        }

        if (serverListMgr.getIterator().hasNext()) {
            // 下一個nacos服務(wù)地址
            currentServerAddr = serverListMgr.getIterator().next();
        } else {
            maxRetry --;
            if (maxRetry < 0) {
                throw new ConnectException("[NACOS HTTP-GET] The maximum number of tolerable server reconnection errors has been reached");
            }
            serverListMgr.refreshCurrentServerAddr();
        }

    } while (System.currentTimeMillis() <= endTime);

    LOGGER.error("no available server");
    throw new ConnectException("no available server");
}

至此，nacos從配置中心加載配置的源碼就分析完了。

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