SpringBoot的配置如何动态刷新（Nacos实现）

Nacos启动加载配置

        通过  META-INF/spring.factories 加载  NacosConfigBootstrapConfiguration

org.springframework.cloud.bootstrap.BootstrapConfiguration=\
com.alibaba.cloud.nacos.NacosConfigBootstrapConfiguration

初始化 NacosConfigProperties 和 NacosPropertySourceLocator

@Configuration
@ConditionalOnProperty(name = "spring.cloud.nacos.config.enabled", matchIfMissing = true)
public class NacosConfigBootstrapConfiguration {

	@Bean
	@ConditionalOnMissingBean
	public NacosConfigProperties nacosConfigProperties() {
		return new NacosConfigProperties();
	}

	@Bean
	public NacosPropertySourceLocator nacosPropertySourceLocator(
			NacosConfigProperties nacosConfigProperties) {
		return new NacosPropertySourceLocator(nacosConfigProperties);
	}

}

通过 com.alibaba.cloud.nacos.client.NacosPropertySourceLocator 加载配置到 org.springframework.core.env.Environment

@Override
	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);

		loadSharedConfiguration(composite);
		loadExtConfiguration(composite);
		loadApplicationConfiguration(composite, dataIdPrefix, nacosConfigProperties, env);

		return composite;
	}

Nacos启动注册 com.alibaba.nacos.api.config.listener.Listener

通过  META-INF/spring.factories 加载  NacosConfigAutoConfiguration

org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
com.alibaba.cloud.nacos.NacosConfigAutoConfiguration,\
com.alibaba.cloud.nacos.endpoint.NacosConfigEndpointAutoConfiguration

初始化 com.alibaba.cloud.nacos.refresh.NacosContextRefresher 实现启动注册 Listener

    @Override
	public void onApplicationEvent(ApplicationReadyEvent event) {
		// many Spring context
		if (this.ready.compareAndSet(false, true)) {
			this.registerNacosListenersForApplications();
		}
	}

    private void registerNacosListenersForApplications() {
		if (refreshProperties.isEnabled()) {
			for (NacosPropertySource nacosPropertySource : NacosPropertySourceRepository
					.getAll()) {

				if (!nacosPropertySource.isRefreshable()) {
					continue;
				}

				String dataId = nacosPropertySource.getDataId();
				registerNacosListener(nacosPropertySource.getGroup(), dataId);
			}
		}
	}

	private void registerNacosListener(final String group, final String dataId) {

		Listener listener = listenerMap.computeIfAbsent(dataId, i -> new Listener() {
			@Override
			public void receiveConfigInfo(String configInfo) {
				refreshCountIncrement();
				String md5 = "";
				if (!StringUtils.isEmpty(configInfo)) {
					try {
						MessageDigest md = MessageDigest.getInstance("MD5");
						md5 = new BigInteger(1, md.digest(configInfo.getBytes("UTF-8")))
								.toString(16);
					}
					catch (NoSuchAlgorithmException | UnsupportedEncodingException e) {
						log.warn("[Nacos] unable to get md5 for dataId: " + dataId, e);
					}
				}
				refreshHistory.add(dataId, md5);
				applicationContext.publishEvent(
						new RefreshEvent(this, null, "Refresh Nacos config"));
				if (log.isDebugEnabled()) {
					log.debug("Refresh Nacos config group " + group + ",dataId" + dataId);
				}
			}

			@Override
			public Executor getExecutor() {
				return null;
			}
		});

		try {
			configService.addListener(dataId, group, listener);
		}
		catch (NacosException e) {
			e.printStackTrace();
		}
	}

 通过 applicationContext.publishEvent(new RefreshEvent(this, null, "Refresh Nacos config")); 发布更新事件， 触发监听器操作 org.springframework.cloud.endpoint.event.RefreshEventListener

org.springframework.cloud.endpoint.event.RefreshEventListener


    @Override
	public boolean supportsEventType(Class<? extends ApplicationEvent> eventType) {
		return ApplicationReadyEvent.class.isAssignableFrom(eventType)
				|| RefreshEvent.class.isAssignableFrom(eventType);
	}

	@Override
	public void onApplicationEvent(ApplicationEvent event) {
		if (event instanceof ApplicationReadyEvent) {
			handle((ApplicationReadyEvent) event);
		}
		else if (event instanceof RefreshEvent) {
			handle((RefreshEvent) event);
		}
	}

	public void handle(ApplicationReadyEvent event) {
		this.ready.compareAndSet(false, true);
	}

	public void handle(RefreshEvent event) {
		if (this.ready.get()) { // don't handle events before app is ready
			log.debug("Event received " + event.getEventDesc());
			Set<String> keys = this.refresh.refresh();
			log.info("Refresh keys changed: " + keys);
		}
	}

监听器触发调用 org.springframework.cloud.context.refresh.ContextRefresher.refresh()

	public synchronized Set<String> refresh() {
		Set<String> keys = refreshEnvironment();
		this.scope.refreshAll();
		return keys;
	}

	public synchronized Set<String> refreshEnvironment() {
		Map<String, Object> before = extract(
				this.context.getEnvironment().getPropertySources());
		addConfigFilesToEnvironment();
		Set<String> keys = changes(before,
				extract(this.context.getEnvironment().getPropertySources())).keySet();
		this.context.publishEvent(new EnvironmentChangeEvent(this.context, keys));
		return keys;
	}



Set<String> keys = refreshEnvironment();
    1. 实现 Environment 的刷新 
    2. 获取配置发生变化的 key
    3. EnvironmentChangeEvent 事件的发布， 触发监听 
org.springframework.cloud.context.properties.ConfigurationPropertiesRebinder
实现 org.springframework.boot.context.properties.ConfigurationProperties 注解的刷新


this.scope.refreshAll();
    刷新 org.springframework.cloud.context.scope.refresh.RefreshScope 管理的Bean

Nacos实现监听

通过  META-INF/spring.factories 加载  NacosConfigAutoConfiguration

org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
com.alibaba.cloud.nacos.NacosConfigAutoConfiguration,\
com.alibaba.cloud.nacos.endpoint.NacosConfigEndpointAutoConfiguration

根据配置获取 com.alibaba.nacos.api.config.ConfigService

设置  com.alibaba.nacos.client.config.impl.ClientWorker

 1. 获取ConfigService  com.alibaba.cloud.nacos.NacosConfigAutoConfiguration.nacosContextRefresher(NacosConfigProperties, NacosRefreshProperties, NacosRefreshHistory)

     @Bean
	public NacosContextRefresher nacosContextRefresher(
			NacosConfigProperties nacosConfigProperties,
			NacosRefreshProperties nacosRefreshProperties,
			NacosRefreshHistory refreshHistory) {
		return new NacosContextRefresher(nacosRefreshProperties, refreshHistory,
				nacosConfigProperties.configServiceInstance());
	}

2. 获取 ConfigService  
com.alibaba.cloud.nacos.NacosConfigProperties.configServiceInstance()

3. 工厂方法获取 ConfigService
com.alibaba.nacos.api.NacosFactory.createConfigService(Properties)

    public static ConfigService createConfigService(Properties properties) throws NacosException {
        try {
            Class<?> driverImplClass = Class.forName("com.alibaba.nacos.client.config.NacosConfigService");
            Constructor constructor = driverImplClass.getConstructor(Properties.class);
            ConfigService vendorImpl = (ConfigService) constructor.newInstance(properties);
            return vendorImpl;
        } catch (Throwable e) {
            throw new NacosException(NacosException.CLIENT_INVALID_PARAM, e);
        }
    }

4. 反射生成 NacosConfigService
com.alibaba.nacos.client.config.NacosConfigService.NacosConfigService(Properties)

    public NacosConfigService(Properties properties) throws NacosException {
        String encodeTmp = properties.getProperty(PropertyKeyConst.ENCODE);
        if (StringUtils.isBlank(encodeTmp)) {
            encode = Constants.ENCODE;
        } else {
            encode = encodeTmp.trim();
        }
        initNamespace(properties);
        agent = new MetricsHttpAgent(new ServerHttpAgent(properties));
        agent.start();
        worker = new ClientWorker(agent, configFilterChainManager, properties);
    }

5. 实例化 ClientWorker
com.alibaba.nacos.client.config.impl.ClientWorker.ClientWorker(HttpAgent, ConfigFilterChainManager, Properties)

ClientWorker 实现定时检测 10ms 检测一次

@SuppressWarnings("PMD.ThreadPoolCreationRule")
    public ClientWorker(final HttpAgent agent, final ConfigFilterChainManager configFilterChainManager, final Properties properties) {
        this.agent = agent;
        this.configFilterChainManager = configFilterChainManager;

        // Initialize the timeout parameter

        init(properties);

        executor = Executors.newScheduledThreadPool(1, new ThreadFactory() {
            @Override
            public Thread newThread(Runnable r) {
                Thread t = new Thread(r);
                t.setName("com.alibaba.nacos.client.Worker." + agent.getName());
                t.setDaemon(true);
                return t;
            }
        });

        executorService = Executors.newScheduledThreadPool(Runtime.getRuntime().availableProcessors(), new ThreadFactory() {
            @Override
            public Thread newThread(Runnable r) {
                Thread t = new Thread(r);
                t.setName("com.alibaba.nacos.client.Worker.longPolling." + agent.getName());
                t.setDaemon(true);
                return t;
            }
        });

        executor.scheduleWithFixedDelay(new Runnable() {
            @Override
            public void run() {
                try {
                    checkConfigInfo();
                } catch (Throwable e) {
                    LOGGER.error("[" + agent.getName() + "] [sub-check] rotate check error", e);
                }
            }
        }, 1L, 10L, TimeUnit.MILLISECONDS);
    }



executor 定时运行 com.alibaba.nacos.client.config.impl.ClientWorker.checkConfigInfo()
    单线程 10ms 执行一次
executorService 运行 LongPollingRunnable 

LongPollingRunnable 长轮训实现变化通知

com.alibaba.nacos.client.config.impl.ClientWorker.LongPollingRunnable


        @Override
        public void run() {

            List<CacheData> cacheDatas = new ArrayList<CacheData>();
            List<String> inInitializingCacheList = new ArrayList<String>();
            try {
                // check failover config
                for (CacheData cacheData : cacheMap.get().values()) {
                    if (cacheData.getTaskId() == taskId) {
                        cacheDatas.add(cacheData);
                        try {
                            checkLocalConfig(cacheData);
                            if (cacheData.isUseLocalConfigInfo()) {
                                cacheData.checkListenerMd5();
                            }
                        } catch (Exception e) {
                            LOGGER.error("get local config info error", e);
                        }
                    }
                }

                // check server config
                List<String> changedGroupKeys = checkUpdateDataIds(cacheDatas, inInitializingCacheList);

                for (String groupKey : changedGroupKeys) {
                    String[] key = GroupKey.parseKey(groupKey);
                    String dataId = key[0];
                    String group = key[1];
                    String tenant = null;
                    if (key.length == 3) {
                        tenant = key[2];
                    }
                    try {
                        String content = getServerConfig(dataId, group, tenant, 3000L);
                        CacheData cache = cacheMap.get().get(GroupKey.getKeyTenant(dataId, group, tenant));
                        cache.setContent(content);
                        LOGGER.info("[{}] [data-received] dataId={}, group={}, tenant={}, md5={}, content={}",
                            agent.getName(), dataId, group, tenant, cache.getMd5(),
                            ContentUtils.truncateContent(content));
                    } catch (NacosException ioe) {
                        String message = String.format(
                            "[%s] [get-update] get changed config exception. dataId=%s, group=%s, tenant=%s",
                            agent.getName(), dataId, group, tenant);
                        LOGGER.error(message, ioe);
                    }
                }
                for (CacheData cacheData : cacheDatas) {
                    if (!cacheData.isInitializing() || inInitializingCacheList
                        .contains(GroupKey.getKeyTenant(cacheData.dataId, cacheData.group, cacheData.tenant))) {
                        cacheData.checkListenerMd5();
                        cacheData.setInitializing(false);
                    }
                }
                inInitializingCacheList.clear();

                executorService.execute(this);

            } catch (Throwable e) {

                // If the rotation training task is abnormal, the next execution time of the task will be punished
                LOGGER.error("longPolling error : ", e);
                executorService.schedule(this, taskPenaltyTime, TimeUnit.MILLISECONDS);
            }
        }
    }

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

1. 循环遍历 CacheData
2. 检测本地配置
    com.alibaba.nacos.client.config.impl.ClientWorker.checkLocalConfig(CacheData)
3. 如果是 本地配置，执行md5对比
    if (cacheData.isUseLocalConfigInfo()) { cacheData.checkListenerMd5(); }


## com.alibaba.nacos.client.config.impl.CacheData
1. 执行 md5 对比
    com.alibaba.nacos.client.config.impl.CacheData.checkListenerMd5()
2. 如果 md5 发生变化， 执行回调
    com.alibaba.nacos.client.config.impl.CacheData.safeNotifyListener(String, String, String, String, ManagerListenerWrap)
3. 执行 listener 回调 ： 存在线程池， 线程池执行， 不存在直接运行




private void safeNotifyListener(final String dataId, final String group, final String content,
                                    final String md5, final ManagerListenerWrap listenerWrap) {
        final Listener listener = listenerWrap.listener;

        Runnable job = new Runnable() {
            @Override
            public void run() {
                ClassLoader myClassLoader = Thread.currentThread().getContextClassLoader();
                ClassLoader appClassLoader = listener.getClass().getClassLoader();
                try {
                    if (listener instanceof AbstractSharedListener) {
                        AbstractSharedListener adapter = (AbstractSharedListener) listener;
                        adapter.fillContext(dataId, group);
                        LOGGER.info("[{}] [notify-context] dataId={}, group={}, md5={}", name, dataId, group, md5);
                    }
                    // 执行回调之前先将线程classloader设置为具体webapp的classloader，以免回调方法中调用spi接口是出现异常或错用（多应用部署才会有该问题）。
                    Thread.currentThread().setContextClassLoader(appClassLoader);

                    ConfigResponse cr = new ConfigResponse();
                    cr.setDataId(dataId);
                    cr.setGroup(group);
                    cr.setContent(content);
                    configFilterChainManager.doFilter(null, cr);
                    String contentTmp = cr.getContent();
                    listener.receiveConfigInfo(contentTmp);
                    listenerWrap.lastCallMd5 = md5;
                    LOGGER.info("[{}] [notify-ok] dataId={}, group={}, md5={}, listener={} ", name, dataId, group, md5,
                        listener);
                } catch (NacosException de) {
                    LOGGER.error("[{}] [notify-error] dataId={}, group={}, md5={}, listener={} errCode={} errMsg={}", name,
                        dataId, group, md5, listener, de.getErrCode(), de.getErrMsg());
                } catch (Throwable t) {
                    LOGGER.error("[{}] [notify-error] dataId={}, group={}, md5={}, listener={} tx={}", name, dataId, group,
                        md5, listener, t.getCause());
                } finally {
                    Thread.currentThread().setContextClassLoader(myClassLoader);
                }
            }
        };

        final long startNotify = System.currentTimeMillis();
        try {
            if (null != listener.getExecutor()) {
                listener.getExecutor().execute(job);
            } else {
                job.run();
            }
        } catch (Throwable t) {
            LOGGER.error("[{}] [notify-error] dataId={}, group={}, md5={}, listener={} throwable={}", name, dataId, group,
                md5, listener, t.getCause());
        }
        final long finishNotify = System.currentTimeMillis();
        LOGGER.info("[{}] [notify-listener] time cost={}ms in ClientWorker, dataId={}, group={}, md5={}, listener={} ",
            name, (finishNotify - startNotify), dataId, group, md5, listener);
    }

com.alibaba.nacos.api.config.listener.Listener 触发 receiveConfigInfo 即可发布刷新事件，完成RefreshEvent 的触发