SpringCloud @RefreshScope刷新机制深入探究

 更新时间:2023年03月12日 11:00:37   作者:zlpzlpzyd  
RefeshScope这个注解想必大家都用过,在微服务配置中心的场景下经常出现,他可以用来刷新Bean中的属性配置,那大家对他的实现原理了解吗?它为什么可以做到动态刷新呢

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

到此这篇关于SpringCloud @RefreshScope刷新机制深入探究的文章就介绍到这了,更多相关SpringCloud @RefreshScope内容请搜索脚本之家以前的文章或继续浏览下面的相关文章希望大家以后多多支持脚本之家!

相关文章

  • java设计模式—静态代理模式(聚合与继承方式对比)

    java设计模式—静态代理模式(聚合与继承方式对比)

    下面小编就为大家带来一篇java设计模式—静态代理模式(聚合与继承方式对比)。小编觉得挺不错的,现在就分享给大家,也给大家做个参考。一起跟随小编过来看看吧
    2017-05-05
  • Maven打包jar(lib目录分离和不分离)的两种方式

    Maven打包jar(lib目录分离和不分离)的两种方式

    打包jar的方式有很多种,本文主要介绍了Maven打包jar的两种方式,包含lib目录分离和不分离,具有一定的参考价值,感兴趣的可以了解一下
    2024-07-07
  • 完整B树算法Java实现代码

    完整B树算法Java实现代码

    这篇文章主要为大家详细介绍了完整的B树算法Java实现代码,具有一定的参考价值,感兴趣的小伙伴们可以参考一下
    2016-09-09
  • Spring cloud如何实现FeignClient指定Zone调用

    Spring cloud如何实现FeignClient指定Zone调用

    这篇文章主要介绍了Spring cloud如何实现FeignClient指定Zone调用方式,具有很好的参考价值,希望对大家有所帮助。如有错误或未考虑完全的地方,望不吝赐教
    2022-03-03
  • 手把手教你SpringBoot轻松整合Minio

    手把手教你SpringBoot轻松整合Minio

    这篇文章主要介绍了手把手教你SpringBoot轻松整合Minio的方法,帮助大家更好的理解和使用springboot框架,感兴趣的朋友可以了解下
    2021-01-01
  • web中拖拽排序和java后台交互实现方法示例

    web中拖拽排序和java后台交互实现方法示例

    这篇文章主要给大家介绍了关于web中拖拽排序和java后台交互实现的相关资料,文中通过示例代码介绍的非常详细,对大家的学习或者工作具有一定的参考学习价值,需要的朋友们下面随着小编来一起学习学习吧
    2018-12-12
  • Java报错:UnsupportedOperationException in Collections的解决方案

    Java报错:UnsupportedOperationException in Collection

    在Java编程中,UnsupportedOperationException是一种常见的运行时异常,通常在试图对不支持的操作执行修改时发生,它表示当前操作不被支持,本文将深入探讨UnsupportedOperationException的产生原因,并提供具体的解决方案和最佳实践,需要的朋友可以参考下
    2024-06-06
  • Java string不可变原理实例解析

    Java string不可变原理实例解析

    这篇文章主要介绍了Java string不可变原理实例解析,文中通过示例代码介绍的非常详细,对大家的学习或者工作具有一定的参考学习价值,需要的朋友可以参考下
    2020-04-04
  • 解决@SpringBootTest 单元测试遇到的坑

    解决@SpringBootTest 单元测试遇到的坑

    这篇文章主要介绍了解决@SpringBootTest 单元测试遇到的坑,具有很好的参考价值,希望对大家有所帮助。如有错误或未考虑完全的地方,望不吝赐教
    2021-10-10
  • Spring Security密码解析器PasswordEncoder自定义登录逻辑

    Spring Security密码解析器PasswordEncoder自定义登录逻辑

    这篇文章主要为大家介绍了Spring Security密码解析器PasswordEncoder自定义登录逻辑示例详解,有需要的朋友可以借鉴参考下,希望能够有所帮助,祝大家多多进步,早日升职加薪
    2022-08-08

最新评论