SpringCloud @RefreshScope刷新机制深入探究

目录

• 梳理过程如下
• @RefreshScope
• ScopedProxyMode
• RefreshAutoConfiguration
• NacosConfigService
• ClientWorker
• CacheData
• AbstractSharedListener
• NacosContextRefresher
• RefreshEventListener
• ContextRefresher
• EventPublishingRunListener
• RestartListener
• Java连接nacos后会定时心跳连接
• 总结

在学习 nacos 的配置修改发现用到了 @RefreshScope 注解，将 spring boot 的日志调整如下

logging:
  level:
    com:
      alibaba:
        cloud: debug
    org:
      springframework:
        context: debug
        cloud: debug

调用 nacos 的配置修改，看到如下信息

2023-03-10 15:48:15.332 INFO [com.alibaba.nacos.client.Worker.longPolling.fixed-node1.hahaou.cn_8848] com.alibaba.nacos.client.config.impl.ClientWorker Caller+0     at com.alibaba.nacos.client.config.impl.ClientWorker.parseUpdateDataIdResponse(ClientWorker.java:486)
 - [fixed-node1.hahaou.cn_8848] [polling-resp] config changed. dataId=soft-jraft-apache-derby-config-test.yaml, group=DEFAULT_GROUP
2023-03-10 15:48:15.333 INFO [com.alibaba.nacos.client.Worker.longPolling.fixed-node1.hahaou.cn_8848] com.alibaba.nacos.client.config.impl.ClientWorker Caller+0     at com.alibaba.nacos.client.config.impl.ClientWorker$LongPollingRunnable.run(ClientWorker.java:598)
 - get changedGroupKeys:[soft-jraft-apache-derby-config-test.yaml+DEFAULT_GROUP]
2023-03-10 15:48:15.400 INFO [com.alibaba.nacos.client.Worker.longPolling.fixed-node1.hahaou.cn_8848] com.alibaba.nacos.client.config.impl.ClientWorker Caller+0     at com.alibaba.nacos.client.config.impl.ClientWorker$LongPollingRunnable.run(ClientWorker.java:616)
 - [fixed-node1.hahaou.cn_8848] [data-received] dataId=soft-jraft-apache-derby-config-test.yaml, group=DEFAULT_GROUP, tenant=null, md5=5f214678315ac83144e77f4c4b3b3416, content=spring:
  youxia:
    config:
      name: test, type=
2023-03-10 15:48:15.400 INFO [com.alibaba.nacos.client.Worker.longPolling.fixed-node1.hahaou.cn_8848] com.alibaba.nacos.client.config.impl.CacheData Caller+0     at com.alibaba.nacos.client.config.impl.CacheData$1.run(CacheData.java:199)
 - [fixed-node1.hahaou.cn_8848] [notify-context] dataId=soft-jraft-apache-derby-config-test.yaml, group=DEFAULT_GROUP, md5=5f214678315ac83144e77f4c4b3b3416
2023-03-10 15:48:15.401 DEBUG [com.alibaba.nacos.client.Worker.longPolling.fixed-node1.hahaou.cn_8848] o.s.cloud.endpoint.event.RefreshEventListener Caller+0     at org.springframework.cloud.endpoint.event.RefreshEventListener.handle(RefreshEventListener.java:71)
 - Event received Refresh Nacos config
2023-03-10 15:48:17.002 DEBUG [com.alibaba.nacos.client.Worker.longPolling.fixed-node1.hahaou.cn_8848] o.s.c.a.AnnotationConfigApplicationContext Caller+0     at org.springframework.context.support.AbstractApplicationContext.prepareRefresh(AbstractApplicationContext.java:596)
 - Refreshing org.springframework.context.annotation.AnnotationConfigApplicationContext@653cd99a
2023-03-10 15:48:18.632 DEBUG [com.alibaba.nacos.client.Worker.longPolling.fixed-node1.hahaou.cn_8848] c.a.cloud.nacos.client.NacosPropertySourceBuilder Caller+0     at com.alibaba.cloud.nacos.client.NacosPropertySourceBuilder.loadNacosData(NacosPropertySourceBuilder.java:93)
 - Loading nacos data, dataId: 'soft-jraft-apache-derby-config-test.yaml', group: 'DEFAULT_GROUP', data: spring:
  youxia:
    config:
      name: test
2023-03-10 15:48:18.706 WARN [com.alibaba.nacos.client.Worker.longPolling.fixed-node1.hahaou.cn_8848] c.a.cloud.nacos.client.NacosPropertySourceBuilder Caller+0     at com.alibaba.cloud.nacos.client.NacosPropertySourceBuilder.loadNacosData(NacosPropertySourceBuilder.java:87)
 - Ignore the empty nacos configuration and get it based on dataId[soft-jraft-apache-derby-config] & group[DEFAULT_GROUP]
2023-03-10 15:48:18.789 WARN [com.alibaba.nacos.client.Worker.longPolling.fixed-node1.hahaou.cn_8848] c.a.cloud.nacos.client.NacosPropertySourceBuilder Caller+0     at com.alibaba.cloud.nacos.client.NacosPropertySourceBuilder.loadNacosData(NacosPropertySourceBuilder.java:87)
 - Ignore the empty nacos configuration and get it based on dataId[soft-jraft-apache-derby-config.properties] & group[DEFAULT_GROUP]
2023-03-10 15:48:18.790 INFO [com.alibaba.nacos.client.Worker.longPolling.fixed-node1.hahaou.cn_8848] o.s.c.b.c.PropertySourceBootstrapConfiguration Caller+0     at org.springframework.cloud.bootstrap.config.PropertySourceBootstrapConfiguration.initialize(PropertySourceBootstrapConfiguration.java:112)
 - Located property source: [BootstrapPropertySource@1783236684 {name='bootstrapProperties-soft-jraft-apache-derby-config.properties,DEFAULT_GROUP', properties={}}, BootstrapPropertySource@942001677 {name='bootstrapProperties-soft-jraft-apache-derby-config,DEFAULT_GROUP', properties={}}, BootstrapPropertySource@1637255792 {name='bootstrapProperties-soft-jraft-apache-derby-config-test.yaml,DEFAULT_GROUP', properties={spring.youxia.config.name=test}}]
2023-03-10 15:48:18.800 INFO [com.alibaba.nacos.client.Worker.longPolling.fixed-node1.hahaou.cn_8848] org.springframework.boot.SpringApplication Caller+0     at org.springframework.boot.SpringApplication.logStartupProfileInfo(SpringApplication.java:651)
 - No active profile set, falling back to default profiles: default
2023-03-10 15:48:18.801 DEBUG [com.alibaba.nacos.client.Worker.longPolling.fixed-node1.hahaou.cn_8848] o.s.c.a.AnnotationConfigApplicationContext Caller+0     at org.springframework.context.support.AbstractApplicationContext.prepareRefresh(AbstractApplicationContext.java:596)
 - Refreshing org.springframework.context.annotation.AnnotationConfigApplicationContext@6709b8b
2023-03-10 15:48:18.806 INFO [com.alibaba.nacos.client.Worker.longPolling.fixed-node1.hahaou.cn_8848] org.springframework.boot.SpringApplication Caller+0     at org.springframework.boot.StartupInfoLogger.logStarted(StartupInfoLogger.java:61)
 - Started application in 3.403 seconds (JVM running for 54.758)
2023-03-10 15:48:18.807 DEBUG [com.alibaba.nacos.client.Worker.longPolling.fixed-node1.hahaou.cn_8848] o.s.c.a.AnnotationConfigApplicationContext Caller+0     at org.springframework.context.support.AbstractApplicationContext.doClose(AbstractApplicationContext.java:1006)
 - Closing org.springframework.context.annotation.AnnotationConfigApplicationContext@6709b8b, started on Fri Mar 10 15:48:18 CST 2023, parent: org.springframework.context.annotation.AnnotationConfigApplicationContext@653cd99a
2023-03-10 15:48:18.808 DEBUG [com.alibaba.nacos.client.Worker.longPolling.fixed-node1.hahaou.cn_8848] o.s.c.a.AnnotationConfigApplicationContext Caller+0     at org.springframework.context.support.AbstractApplicationContext.doClose(AbstractApplicationContext.java:1006)
 - Closing org.springframework.context.annotation.AnnotationConfigApplicationContext@653cd99a, started on Fri Mar 10 15:48:17 CST 2023
2023-03-10 15:48:18.819 INFO [com.alibaba.nacos.client.Worker.longPolling.fixed-node1.hahaou.cn_8848] o.s.cloud.endpoint.event.RefreshEventListener Caller+0     at org.springframework.cloud.endpoint.event.RefreshEventListener.handle(RefreshEventListener.java:73)
 - Refresh keys changed: [spring.youxia.config.name]
2023-03-10 15:48:18.820 DEBUG [com.alibaba.nacos.client.Worker.longPolling.fixed-node1.hahaou.cn_8848] c.a.cloud.nacos.refresh.NacosContextRefresher Caller+0     at com.alibaba.cloud.nacos.refresh.NacosContextRefresher$1.innerReceive(NacosContextRefresher.java:136)
 - Refresh Nacos config group=DEFAULT_GROUP,dataId=soft-jraft-apache-derby-config-test.yaml,configInfo=spring:
  youxia:
    config:
      name: test
2023-03-10 15:48:18.820 INFO [com.alibaba.nacos.client.Worker.longPolling.fixed-node1.hahaou.cn_8848] com.alibaba.nacos.client.config.impl.CacheData Caller+0     at com.alibaba.nacos.client.config.impl.CacheData$1.run(CacheData.java:222)
 - [fixed-node1.hahaou.cn_8848] [notify-ok] dataId=soft-jraft-apache-derby-config-test.yaml, group=DEFAULT_GROUP, md5=5f214678315ac83144e77f4c4b3b3416, listener=com.alibaba.cloud.nacos.refresh.NacosContextRefresher$1@59af462e 
2023-03-10 15:48:18.820 INFO [com.alibaba.nacos.client.Worker.longPolling.fixed-node1.hahaou.cn_8848] com.alibaba.nacos.client.config.impl.CacheData Caller+0     at com.alibaba.nacos.client.config.impl.CacheData.safeNotifyListener(CacheData.java:248)
 - [fixed-node1.hahaou.cn_8848] [notify-listener] time cost=3420ms in ClientWorker, dataId=soft-jraft-apache-derby-config-test.yaml, group=DEFAULT_GROUP, md5=5f214678315ac83144e77f4c4b3b3416, listener=com.alibaba.cloud.nacos.refresh.NacosContextRefresher$1@59af462e 
使用Spring Cloud Alibaba接入Nacos配置中心，获取配置信息name为：test
使用Spring Cloud Alibaba接入Nacos配置中心，获取配置信息value为：null

得知保存配置后进行了 jvm 重启。

梳理过程如下

@RefreshScope

package org.springframework.cloud.context.config.annotation;
import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import org.springframework.context.annotation.Scope;
import org.springframework.context.annotation.ScopedProxyMode;
/**
 * Convenience annotation to put a <code>@Bean</code> definition in
 * {@link org.springframework.cloud.context.scope.refresh.RefreshScope refresh scope}.
 * Beans annotated this way can be refreshed at runtime and any components that are using
 * them will get a new instance on the next method call, fully initialized and injected
 * with all dependencies.
 *
 * @author Dave Syer
 *
 */
@Target({ ElementType.TYPE, ElementType.METHOD })
@Retention(RetentionPolicy.RUNTIME)
@Scope("refresh")
@Documented
public @interface RefreshScope {
    /**
     * @see Scope#proxyMode()
     * @return proxy mode
     */
    ScopedProxyMode proxyMode() default ScopedProxyMode.TARGET_CLASS;
}

可以得知，@RefreshScope 是一个 scopeName 为 refresh 的 @Scope。

ScopedProxyMode

package org.springframework.context.annotation;
/**
 * Enumerates the various scoped-proxy options.
 *
 * <p>For a more complete discussion of exactly what a scoped proxy is, see the
 * section of the Spring reference documentation entitled '<em>Scoped beans as
 * dependencies</em>'.
 *
 * @author Mark Fisher
 * @since 2.5
 * @see ScopeMetadata
 */
public enum ScopedProxyMode {
    /**
     * Default typically equals {@link #NO}, unless a different default
     * has been configured at the component-scan instruction level.
     */
    DEFAULT,
    /**
     * Do not create a scoped proxy.
     * <p>This proxy-mode is not typically useful when used with a
     * non-singleton scoped instance, which should favor the use of the
     * {@link #INTERFACES} or {@link #TARGET_CLASS} proxy-modes instead if it
     * is to be used as a dependency.
     */
    NO,
    /**
     * Create a JDK dynamic proxy implementing <i>all</i> interfaces exposed by
     * the class of the target object.
     */
    INTERFACES,
    /**
     * Create a class-based proxy (uses CGLIB).
     */
    TARGET_CLASS
}

由枚举 ScopedProxyMode 得知，ScopedProxyMode.TARGET_CLASS 通过 cglib 生成一个代理类进行字节码增强

RefreshAutoConfiguration

部分源码如下

package org.springframework.cloud.autoconfigure;
import java.util.HashSet;
import java.util.Set;
import javax.annotation.PostConstruct;
import org.springframework.aop.scope.ScopedProxyUtils;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.ListableBeanFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.beans.factory.config.BeanDefinitionHolder;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.beans.factory.support.BeanDefinitionRegistryPostProcessor;
import org.springframework.boot.autoconfigure.AutoConfigureBefore;
import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
import org.springframework.boot.autoconfigure.orm.jpa.HibernateJpaAutoConfiguration;
import org.springframework.boot.context.properties.bind.Bindable;
import org.springframework.boot.context.properties.bind.Binder;
import org.springframework.cloud.context.refresh.ContextRefresher;
import org.springframework.cloud.context.scope.refresh.RefreshScope;
import org.springframework.cloud.endpoint.event.RefreshEventListener;
import org.springframework.cloud.logging.LoggingRebinder;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.EnvironmentAware;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.weaving.LoadTimeWeaverAware;
import org.springframework.core.env.Environment;
import org.springframework.core.env.StandardEnvironment;
import org.springframework.instrument.classloading.LoadTimeWeaver;
import org.springframework.stereotype.Component;
import org.springframework.util.StringUtils;
/**
 * Autoconfiguration for the refresh scope and associated features to do with changes in
 * the Environment (e.g. rebinding logger levels).
 *
 * @author Dave Syer
 * @author Venil Noronha
 */
@Configuration(proxyBeanMethods = false)
@ConditionalOnClass(RefreshScope.class)
@ConditionalOnProperty(name = RefreshAutoConfiguration.REFRESH_SCOPE_ENABLED,
        matchIfMissing = true)
@AutoConfigureBefore(HibernateJpaAutoConfiguration.class)
public class RefreshAutoConfiguration {
    /**
     * Name of the refresh scope name.
     */
    public static final String REFRESH_SCOPE_NAME = "refresh";
    /**
     * Name of the prefix for refresh scope.
     */
    public static final String REFRESH_SCOPE_PREFIX = "spring.cloud.refresh";
    /**
     * Name of the enabled prefix for refresh scope.
     */
    public static final String REFRESH_SCOPE_ENABLED = REFRESH_SCOPE_PREFIX + ".enabled";
    @Bean
    @ConditionalOnMissingBean(RefreshScope.class)
    public static RefreshScope refreshScope() {
        return new RefreshScope();
    }
    @Bean
    @ConditionalOnMissingBean
    public static LoggingRebinder loggingRebinder() {
        return new LoggingRebinder();
    }
    @Bean
    @ConditionalOnMissingBean
    public ContextRefresher contextRefresher(ConfigurableApplicationContext context,
            RefreshScope scope) {
        return new ContextRefresher(context, scope);
    }
    @Bean
    public RefreshEventListener refreshEventListener(ContextRefresher contextRefresher) {
        return new RefreshEventListener(contextRefresher);
    }
}

@ConditionalOnProperty(name = RefreshAutoConfiguration.REFRESH_SCOPE_ENABLED,
        matchIfMissing = true)

通过上面的注解得知，自动刷新在 spring cloud 中默认启用

nacos中添加配置

NacosConfigService

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

NacosConfigService 构造器创建 ClientWorker 对象

ClientWorker

public ClientWorker(final HttpAgent agent, final ConfigFilterChainManager configFilterChainManager,
        final Properties properties) {
    this.agent = agent;
    this.configFilterChainManager = configFilterChainManager;
    // Initialize the timeout parameter
    init(properties);
    this.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;
        }
    });
    this.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;
                }
            });
    this.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);
}
public void checkConfigInfo() {
    // Dispatch taskes.
    int listenerSize = cacheMap.size();
    // Round up the longingTaskCount.
    int longingTaskCount = (int) Math.ceil(listenerSize / ParamUtil.getPerTaskConfigSize());
    if (longingTaskCount > currentLongingTaskCount) {
        for (int i = (int) currentLongingTaskCount; i < longingTaskCount; i++) {
            // The task list is no order.So it maybe has issues when changing.
            executorService.execute(new LongPollingRunnable(i));
        }
        currentLongingTaskCount = longingTaskCount;
    }
}
class LongPollingRunnable implements Runnable {
    private final int taskId;
    public LongPollingRunnable(int taskId) {
        this.taskId = taskId;
    }
    @Override
    public void run() {
        List<CacheData> cacheDatas = new ArrayList<CacheData>();
        List<String> inInitializingCacheList = new ArrayList<String>();
        try {
            // check failover config
            for (CacheData cacheData : cacheMap.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);
            if (!CollectionUtils.isEmpty(changedGroupKeys)) {
                LOGGER.info("get changedGroupKeys:" + changedGroupKeys);
            }
            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[] ct = getServerConfig(dataId, group, tenant, 3000L);
                    CacheData cache = cacheMap.get(GroupKey.getKeyTenant(dataId, group, tenant));
                    cache.setContent(ct[0]);
                    if (null != ct[1]) {
                        cache.setType(ct[1]);
                    }
                    LOGGER.info("[{}] [data-received] dataId={}, group={}, tenant={}, md5={}, content={}, type={}",
                            agent.getName(), dataId, group, tenant, cache.getMd5(),
                            ContentUtils.truncateContent(ct[0]), ct[1]);
                } 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);
        }
    }
}

ClientWorker checkConfigInfo() 中通过线程池创建 LongPollingRunnable 对象，线程池名称前缀为 com.alibaba.nacos.client.Worker.longPolling

CacheData

void checkListenerMd5() {
    for (ManagerListenerWrap wrap : listeners) {
        if (!md5.equals(wrap.lastCallMd5)) {
            safeNotifyListener(dataId, group, content, type, md5, wrap);
        }
    }
}
private void safeNotifyListener(final String dataId, final String group, final String content, final String type,
        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);
                // compare lastContent and content
                if (listener instanceof AbstractConfigChangeListener) {
                    Map data = ConfigChangeHandler.getInstance()
                            .parseChangeData(listenerWrap.lastContent, content, type);
                    ConfigChangeEvent event = new ConfigChangeEvent(data);
                    ((AbstractConfigChangeListener) listener).receiveConfigChange(event);
                    listenerWrap.lastContent = content;
                }
                listenerWrap.lastCallMd5 = md5;
                LOGGER.info("[{}] [notify-ok] dataId={}, group={}, md5={}, listener={} ", name, dataId, group, md5,
                        listener);
            } catch (NacosException ex) {
                LOGGER.error("[{}] [notify-error] dataId={}, group={}, md5={}, listener={} errCode={} errMsg={}",
                        name, dataId, group, md5, listener, ex.getErrCode(), ex.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);
}

调用 CacheData 的 checkListenerMd5()

AbstractSharedListener

public abstract class AbstractSharedListener implements Listener {
    private volatile String dataId;
    private volatile String group;
    public final void fillContext(String dataId, String group) {
        this.dataId = dataId;
        this.group = group;
    }
    @Override
    public final void receiveConfigInfo(String configInfo) {
        innerReceive(dataId, group, configInfo);
    }
    @Override
    public Executor getExecutor() {
        return null;
    }
    /**
     * receive.
     *
     * @param dataId     data ID
     * @param group      group
     * @param configInfo content
     */
    public abstract void innerReceive(String dataId, String group, String configInfo);
}

调用 AbstractSharedListener 的 receiveConfigInfo()，在 NacosContextRefresher 的 registerNacosListener() 中进行实现

NacosContextRefresher

private void registerNacosListener(final String groupKey, final String dataKey) {
    String key = NacosPropertySourceRepository.getMapKey(dataKey, groupKey);
    Listener listener = listenerMap.computeIfAbsent(key,
            lst -> new AbstractSharedListener() {
                @Override
                public void innerReceive(String dataId, String group,
                        String configInfo) {
                    refreshCountIncrement();
                    nacosRefreshHistory.addRefreshRecord(dataId, group, configInfo);
                    // todo feature: support single refresh for listening
                    applicationContext.publishEvent(
                            new RefreshEvent(this, null, "Refresh Nacos config"));
                    if (log.isDebugEnabled()) {
                        log.debug(String.format(
                                "Refresh Nacos config group=%s,dataId=%s,configInfo=%s",
                                group, dataId, configInfo));
                    }
                }
            });
    try {
        configService.addListener(dataKey, groupKey, listener);
    }
    catch (NacosException e) {
        log.warn(String.format(
                "register fail for nacos listener ,dataId=[%s],group=[%s]", dataKey,
                groupKey), e);
    }
}

最终通过 ApplicationContext 发布事件 RefreshEvent

至此，nacos 逻辑执行完毕。

RefreshEventListener

public class RefreshEventListener implements SmartApplicationListener {
    private static Log log = LogFactory.getLog(RefreshEventListener.class);
    private ContextRefresher refresh;
    private AtomicBoolean ready = new AtomicBoolean(false);
    public RefreshEventListener(ContextRefresher refresh) {
        this.refresh = refresh;
    }
    @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);
        }
    }
}

调用 RefreshEventListener 的 onApplicationEvent()，事件对象为 RefreshEvent。

执行完可以看到打印了日志

Event received Refresh Nacos config

后面调用 ContextRefresher 的 refresh()

ContextRefresher

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;
}
/* For testing. */ ConfigurableApplicationContext addConfigFilesToEnvironment() {
    ConfigurableApplicationContext capture = null;
    try {
        StandardEnvironment environment = copyEnvironment(
                this.context.getEnvironment());
        SpringApplicationBuilder builder = new SpringApplicationBuilder(Empty.class)
                .bannerMode(Mode.OFF).web(WebApplicationType.NONE)
                .environment(environment);
        // Just the listeners that affect the environment (e.g. excluding logging
        // listener because it has side effects)
        builder.application()
                .setListeners(Arrays.asList(new BootstrapApplicationListener(),
                        new ConfigFileApplicationListener()));
        capture = builder.run();
        if (environment.getPropertySources().contains(REFRESH_ARGS_PROPERTY_SOURCE)) {
            environment.getPropertySources().remove(REFRESH_ARGS_PROPERTY_SOURCE);
        }
        MutablePropertySources target = this.context.getEnvironment()
                .getPropertySources();
        String targetName = null;
        for (PropertySource<?> source : environment.getPropertySources()) {
            String name = source.getName();
            if (target.contains(name)) {
                targetName = name;
            }
            if (!this.standardSources.contains(name)) {
                if (target.contains(name)) {
                    target.replace(name, source);
                }
                else {
                    if (targetName != null) {
                        target.addAfter(targetName, source);
                        // update targetName to preserve ordering
                        targetName = name;
                    }
                    else {
                        // targetName was null so we are at the start of the list
                        target.addFirst(source);
                        targetName = name;
                    }
                }
            }
        }
    }
    finally {
        ConfigurableApplicationContext closeable = capture;
        while (closeable != null) {
            try {
                closeable.close();
            }
            catch (Exception e) {
                // Ignore;
            }
            if (closeable.getParent() instanceof ConfigurableApplicationContext) {
                closeable = (ConfigurableApplicationContext) closeable.getParent();
            }
            else {
                break;
            }
        }
    }
    return capture;
}

refreshEnvironment() 中执行如下操作

addConfigFilesToEnvironment() 添加到配置文件到环境中，发布一系列事件 BootstrapApplicationListener、ConfigFileApplicationListener

调用 EventPublishingRunListener 的发布一系列事件进行 jvm 的重启相关操作，其中 EventPublishingRunListener 是默认的监听器，在 spring boot 的 META-INF/spring.factories 中进行了指定

# Run Listeners
org.springframework.boot.SpringApplicationRunListener=\
org.springframework.boot.context.event.EventPublishingRunListener

EventPublishingRunListener

public class EventPublishingRunListener implements SpringApplicationRunListener, Ordered {
    private final SpringApplication application;
    private final String[] args;
    private final SimpleApplicationEventMulticaster initialMulticaster;
    public EventPublishingRunListener(SpringApplication application, String[] args) {
        this.application = application;
        this.args = args;
        this.initialMulticaster = new SimpleApplicationEventMulticaster();
        for (ApplicationListener<?> listener : application.getListeners()) {
            this.initialMulticaster.addApplicationListener(listener);
        }
    }
    @Override
    public int getOrder() {
        return 0;
    }
    @Override
    public void starting() {
        this.initialMulticaster.multicastEvent(new ApplicationStartingEvent(this.application, this.args));
    }
    @Override
    public void environmentPrepared(ConfigurableEnvironment environment) {
        this.initialMulticaster
                .multicastEvent(new ApplicationEnvironmentPreparedEvent(this.application, this.args, environment));
    }
    @Override
    public void contextPrepared(ConfigurableApplicationContext context) {
        this.initialMulticaster
                .multicastEvent(new ApplicationContextInitializedEvent(this.application, this.args, context));
    }
    @Override
    public void contextLoaded(ConfigurableApplicationContext context) {
        for (ApplicationListener<?> listener : this.application.getListeners()) {
            if (listener instanceof ApplicationContextAware) {
                ((ApplicationContextAware) listener).setApplicationContext(context);
            }
            context.addApplicationListener(listener);
        }
        this.initialMulticaster.multicastEvent(new ApplicationPreparedEvent(this.application, this.args, context));
    }
    @Override
    public void started(ConfigurableApplicationContext context) {
        context.publishEvent(new ApplicationStartedEvent(this.application, this.args, context));
    }
    @Override
    public void running(ConfigurableApplicationContext context) {
        context.publishEvent(new ApplicationReadyEvent(this.application, this.args, context));
    }
    @Override
    public void failed(ConfigurableApplicationContext context, Throwable exception) {
        ApplicationFailedEvent event = new ApplicationFailedEvent(this.application, this.args, context, exception);
        if (context != null && context.isActive()) {
            // Listeners have been registered to the application context so we should
            // use it at this point if we can
            context.publishEvent(event);
        }
        else {
            // An inactive context may not have a multicaster so we use our multicaster to
            // call all of the context's listeners instead
            if (context instanceof AbstractApplicationContext) {
                for (ApplicationListener<?> listener : ((AbstractApplicationContext) context)
                        .getApplicationListeners()) {
                    this.initialMulticaster.addApplicationListener(listener);
                }
            }
            this.initialMulticaster.setErrorHandler(new LoggingErrorHandler());
            this.initialMulticaster.multicastEvent(event);
        }
    }
    private static class LoggingErrorHandler implements ErrorHandler {
        private static final Log logger = LogFactory.getLog(EventPublishingRunListener.class);
        @Override
        public void handleError(Throwable throwable) {
            logger.warn("Error calling ApplicationEventListener", throwable);
        }
    }
}

调用了 contextLoaded()，在 RestartListener 的 onApplicationEvent() 中进行调用

RestartListener

public class RestartListener implements SmartApplicationListener {
    private ConfigurableApplicationContext context;
    private ApplicationPreparedEvent event;
    @Override
    public int getOrder() {
        return 0;
    }
    @Override
    public boolean supportsEventType(Class<? extends ApplicationEvent> eventType) {
        return ApplicationPreparedEvent.class.isAssignableFrom(eventType)
                || ContextRefreshedEvent.class.isAssignableFrom(eventType)
                || ContextClosedEvent.class.isAssignableFrom(eventType);
    }
    @Override
    public boolean supportsSourceType(Class<?> sourceType) {
        return true;
    }
    @Override
    public void onApplicationEvent(ApplicationEvent input) {
        if (input instanceof ApplicationPreparedEvent) {
            this.event = (ApplicationPreparedEvent) input;
            if (this.context == null) {
                this.context = this.event.getApplicationContext();
            }
        }
        else if (input instanceof ContextRefreshedEvent) {
            if (this.context != null && input.getSource().equals(this.context)
                    && this.event != null) {
                this.context.publishEvent(this.event);
            }
        }
        else {
            if (this.context != null && input.getSource().equals(this.context)) {
                this.context = null;
                this.event = null;
            }
        }
    }
}

RestartListener 的 onApplicationEvent() 传入 ApplicationPreparedEvent，调用 AbstractApplicationContext 的 refresh()，即进行 ioc 容器重启，此时是第一次

调用 EventPublishingRunListener 的 running()，进行新的配置加载

调用 PropertySourceBootstrapConfiguration 的 initialize()，间接调用 NacosPropertySourceLocator 的 locate() 进行文件加载

调用 RestartListener 的 onApplicationEvent()，参数为 ApplicationPreparedEvent，调用 AbstractApplicationContext 的 refresh() 进行 ioc 容器重启，此时是第二次

调用 RestartListener 的 onApplicationEvent()，参数为 ContextRefreshedEvent

至此，ContextRefresher 的 refreshEnvironment() 逻辑执行完毕

接下来调用 RefreshScope 的 refreshAll()，间接调用父类 GenericScope 的 destroy()，发布事件 RefreshScopeRefreshedEvent 到 ApplicationContext 中

Java连接nacos后会定时心跳连接

通过 NacosWatch 开启 ThreadPoolTaskScheduler 进行定时任务发起，事件为 HeartbeatEvent。

总结

nacos 的在页面上的配置信息的更新是通过 jvm 重启实现的。想到了 jvm 启动后，无法做热更新，这么做也是不错的选择。由于做了重启，这个适合在没有访问的情况下执行，如果在操作过程中有事务在执行会不好，但是在生产环境中是否有这样的应用目前还不清楚。

由此可以看到，spring 中大量使用了事件、还有观察者模式、消息队列、消息通知、web 请求响应、窗口点击事件等。

参考链接

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