nacos-client 监听配置源码分析_listener getexecutor-优快云博客

本文链接：https://blog.youkuaiyun.com/chudaxiakkk/article/details/115624511

本文详细分析了Nacos客户端如何实现配置监听。通过`addListener`方法添加监听器，内部使用`checkConfigInfo`定时任务每10ms检查配置更新。当配置变化时，通过比较MD5值触发回调，更新缓存并通知监听器。监听器收到通知后执行回调方法，更新内容并处理配置变更事件。

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配置监听，是要重点分析，代码稍微复杂一些。

   
    /**
     * Add a listener to the configuration, after the server modified the configuration, the client will use the
     * incoming listener callback. Recommended asynchronous processing, the application can implement the getExecutor
     * method in the ManagerListener, provide a thread pool of execution. If provided, use the main thread callback, May
     * block other configurations or be blocked by other configurations.
     *
     * @param dataId   dataId
     * @param group    group
     * @param listener listener
     * @throws NacosException NacosException
     */
    void addListener(String dataId, String group, Listener listener) throws NacosException;

1.添加监听器到CacheData

 /**
     * Add listeners for tenant.
     *
     * @param dataId    dataId of data
     * @param group     group of data
     * @param listeners listeners
     * @throws NacosException nacos exception
     */
    public void addTenantListeners(String dataId, String group, List<? extends Listener> listeners)
            throws NacosException {
        group = null2defaultGroup(group);
        String tenant = agent.getTenant();
        CacheData cache = addCacheDataIfAbsent(dataId, group, tenant);
        for (Listener listener : listeners) {
            cache.addListener(listener);
        }
    }

监听的配置组装，putifAbsent,cacheData不存在的话，才添加

/**
     * Add cache data if absent.
     *
     * @param dataId data id if data
     * @param group  group of data
     * @param tenant tenant of data
     * @return cache data
     */
    public CacheData addCacheDataIfAbsent(String dataId, String group, String tenant) throws NacosException {
        String key = GroupKey.getKeyTenant(dataId, group, tenant);
        CacheData cacheData = cacheMap.get(key);
        //查看是否有缓存，有的话返回；没有的话，去服务端查找
        if (cacheData != null) {
            return cacheData;
        }

        cacheData = new CacheData(configFilterChainManager, agent.getName(), dataId, group, tenant);
        // multiple listeners on the same dataid+group and race condition
        CacheData lastCacheData = cacheMap.putIfAbsent(key, cacheData);
        //以前没有监听的情况下，去服务