微服务系列--深入理解RPC底层原理与设计实践（下）

public interface RegistryService {
    /**
     * 注册url
     *
     * 将dubbo服务写入注册中心节点
     * 当出现网络抖动的时候需要进行适当的重试做法
     * 注册服务url的时候需要写入持久化文件中
     *
     * @param url
     */
    void register(URL url);
    /**
     * 服务下线
     *
     * 持久化节点是无法进行服务下线操作的
     * 下线的服务必须保证url是完整匹配的
     * 移除持久化文件中的一些内容信息
     *
     * @param url
     */
    void unRegister(URL url);
    /**
     * 消费方订阅服务
     *
     * @param urlStr
     * @param providerServiceName
     */
    void subscribe(String urlStr,String providerServiceName);
    /**
     * 更新节点属性之后通知这里
     *
     * @param url
     */
    void doSubscribeAfterUpdate(URL url);
    /**
     * 新增节点之后通知这里
     *
     * @param url
     */
    void doSubscribeAfterAdd(URL url);
    /**
     * 执行取消订阅内部的逻辑
     *
     * @param url
     */
    void doUnSubscribe(URL url);
}
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public class WeightLoadBalance implements LoadBalance {
    public static Map<String, URL[]> randomWeightMap = new ConcurrentHashMap<>();
    public static Map<String, Integer> lastIndexVisitMap = new ConcurrentHashMap<>();
    @Override
    public void doSelect(Invocation invocation) {
        URL[] weightArr = randomWeightMap.get(invocation.getServiceName());
        if (weightArr == null) {
            List<URL> urls = invocation.getUrls();
            Integer totalWeight = 0;
            for (URL url : urls) {
                //weight如果设置地过大，容易造成内存占用过高情况发生，所以weight统一限制最大大小应该为100
                Integer weight = Integer.valueOf(url.getParameters().get("weight"));
                totalWeight += weight;
            }
            weightArr = new URL[totalWeight];
            RandomList<URL> randomList = new RandomList(totalWeight);
            for (URL url : urls) {
                int weight = Integer.parseInt(url.getParameters().get("weight"));
                for (int i = 0; i < weight; i++) {
                    randomList.randomAdd(url);
                }
            }
            int len = randomList.getRandomList().size();
            for (int i = 0; i < len; i++) {
                URL url = randomList.getRandomList().get(i);
                weightArr[i] = url;
            }
            randomWeightMap.put(invocation.getServiceName(), weightArr);
        }
        Integer lastIndex = lastIndexVisitMap.get(invocation.getServiceName());
        if (lastIndex == null) {
            lastIndex = 0;
        }
        if (lastIndex >= weightArr.length) {
            lastIndex = 0;
        }
        URL referUrl = weightArr[lastIndex];
        lastIndex++;
        lastIndexVisitMap.put(invocation.getServiceName(), lastIndex);
        invocation.setReferUrl(referUrl);
    }
}
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public class ExtensionLoader {
    /**
     * 存储扩展spi的map，key是spi文件里面写入的key
     */
    private static Map<String, Class<?>> extensionClassMap = new ConcurrentHashMap<>();
    private static final String EXTENSION_LOADER_DIR_PREFIX = "META-INF/ietty/";
    public static  Map<String, Class<?>> getExtensionClassMap(){
        return extensionClassMap;
    }
    public void loadDirectory(Class clazz) throws IOException {
        synchronized (ExtensionLoader.class){
            String fileName = EXTENSION_LOADER_DIR_PREFIX + clazz.getName();
            ClassLoader classLoader = this.getClass().getClassLoader();
            Enumeration<URL> enumeration = classLoader.getResources(fileName);
            while (enumeration.hasMoreElements()) {
                URL url = enumeration.nextElement();
                InputStreamReader inputStreamReader = new InputStreamReader(url.openStream(), "utf-8");
                BufferedReader bufferedReader = new BufferedReader(inputStreamReader);
                String line;
                while ((line = bufferedReader.readLine()) != null) {
                    if(line.startsWith("#")){
                        continue;
                    }
                    String[] keyClassInstance = line.split("=");
                    try {
                        extensionClassMap.put(keyClassInstance[0],Class.forName(keyClassInstance[1],true,classLoader));
                    } catch (ClassNotFoundException e) {
                        e.printStackTrace();
                    }
                }
            }
        }
    }
    public static <T>Object initClassInstance(String className) {
        if(extensionClassMap!=null && extensionClassMap.size()>0){
            try {
                return (T)extensionClassMap.get(className).newInstance();
            } catch (InstantiationException e) {
                e.printStackTrace();
            } catch (IllegalAccessException e) {
                e.printStackTrace();
            }
        }
        return null;
    }
}
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