Dubbo源码学习--Redis注册中心（三）

基于 Redis 1 实现的注册中心 2。

使用 Redis 的 Key/Map 结构存储数据结构：

• 主 Key 为服务名和类型
• Map 中的 Key 为 URL 地址
• Map 中的 Value 为过期时间，用于判断脏数据，脏数据由监控中心删除 3

使用 Redis 的 Publish/Subscribe 事件通知数据变更：

• 通过事件的值区分事件类型：register, unregister, subscribe, unsubscribe
• 普通消费者直接订阅指定服务提供者的 Key，只会收到指定服务的 register, unregister 事件
• 监控中心通过 psubscribe 功能订阅 /dubbo/*，会收到所有服务的所有变更事件

调用过程：

1. 服务提供方启动时，向 Key:/dubbo/com.foo.BarService/providers 下，添加当前提供者的地址
2. 并向 Channel:/dubbo/com.foo.BarService/providers 发送 register 事件
3. 服务消费方启动时，从 Channel:/dubbo/com.foo.BarService/providers 订阅 register 和 unregister 事件
4. 并向 Key:/dubbo/com.foo.BarService/providers 下，添加当前消费者的地址
5. 服务消费方收到 register 和 unregister 事件后，从 Key:/dubbo/com.foo.BarService/providers 下获取提供者地址列表
6. 服务监控中心启动时，从 Channel:/dubbo/* 订阅 register 和 unregister，以及 subscribe和unsubsribe事件
7. 服务监控中心收到 register 和 unregister 事件后，从 Key:/dubbo/com.foo.BarService/providers下获取提供者地址列表
8. 服务监控中心收到 subscribe 和 unsubsribe 事件后，从 Key:/dubbo/com.foo.BarService/consumers 下获取消费者地址列表

配置

<dubbo:registry address="redis://10.20.153.10:6379" />

或

<dubbo:registry address="redis://10.20.153.10:6379?backup=10.20.153.11:6379,10.20.153.12:6379" />

或

<dubbo:registry protocol="redis" address="10.20.153.10:6379" />

或

<dubbo:registry protocol="redis" address="10.20.153.10:6379,10.20.153.11:6379,10.20.153.12:6379" />

选项

• 可通过  设置 redis 中 key 的前缀，缺省为 dubbo。
• 可通过  设置 redis 集群策略，缺省为 failover：
  • failover: 只写入和读取任意一台，失败时重试另一台，需要服务器端自行配置数据同步
  • replicate: 在客户端同时写入所有服务器，只读取单台，服务器端不需要同步，注册中心集群增大，性能压力也会更大

可靠性声明

阿里内部并没有采用 Redis 做为注册中心，而是使用自己实现的基于数据库的注册中心，即：Redis 注册中心并没有在阿里内部长时间运行的可靠性保障，此 Redis 桥接实现只为开源版本提供，其可靠性依赖于 Redis 本身的可靠性。

Redis注册中心实现了RedisRegistryFactory工厂，用来生成Registry的实现类RedisRegistry。

public class RedisRegistryFactory extends AbstractRegistryFactory {

    @Override
    protected Registry createRegistry(URL url) {
        return new RedisRegistry(url);
    }
}

RedisRegistry中主要实现了如下接口：
（1）doRegister(URL url);//向注册中心注册服务
（2）doUnregister(URL url);//取消服务注册
（3）doSubscribe(URL url, NotifyListener listener);//向注册中心监听服务

（4）doUnsubscribe(URL url, NotifyListener listener);//取消监听注册中心服务

public class RedisRegistry extends FailbackRegistry {

    private static final Logger logger = LoggerFactory.getLogger(RedisRegistry.class);

    private static final int DEFAULT_REDIS_PORT = 6379;

    private final static String DEFAULT_ROOT = "dubbo";

    private final ScheduledExecutorService expireExecutor = Executors.newScheduledThreadPool(1, new NamedThreadFactory("DubboRegistryExpireTimer", true));

    private final ScheduledFuture expireFuture;

    private final String root;

    private final Map jedisPools = new ConcurrentHashMap();

    private final ConcurrentMap notifiers = new ConcurrentHashMap();

    private final int reconnectPeriod;

    private final int expirePeriod;

    private volatile boolean admin = false;

    private boolean replicate;

	//构造函数中主要完成了redis连接相关的操作
    public RedisRegistry(URL url) {
        super(url);
        if (url.isAnyHost()) {
            throw new IllegalStateException("registry address == null");
        }
        GenericObjectPoolConfig config = new GenericObjectPoolConfig();
        config.setTestOnBorrow(url.getParameter("test.on.borrow", true));
        config.setTestOnReturn(url.getParameter("test.on.return", false));
        config.setTestWhileIdle(url.getParameter("test.while.idle", false));
        if (url.getParameter("max.idle", 0) > 0)
            config.setMaxIdle(url.getParameter("max.idle", 0));
        if (url.getParameter("min.idle", 0) > 0)
            config.setMinIdle(url.getParameter("min.idle", 0));
        if (url.getParameter("max.active", 0) > 0)
            config.setMaxTotal(url.getParameter("max.active", 0));
        if (url.getParameter("max.total", 0) > 0)
            config.setMaxTotal(url.getParameter("max.total", 0));
        if (url.getParameter("max.wait", url.getParameter("timeout", 0)) > 0)
            config.setMaxWaitMillis(url.getParameter("max.wait", url.getParameter("timeout", 0)));
        if (url.getParameter("num.tests.per.eviction.run", 0) > 0)
            config.setNumTestsPerEvictionRun(url.getParameter("num.tests.per.eviction.run", 0));
        if (url.getParameter("time.between.eviction.runs.millis", 0) > 0)
            config.setTimeBetweenEvictionRunsMillis(url.getParameter("time.between.eviction.runs.millis", 0));
        if (url.getParameter("min.evictable.idle.time.millis", 0) > 0)
            config.setMinEvictableIdleTimeMillis(url.getParameter("min.evictable.idle.time.millis", 0));

        String cluster = url.getParameter("cluster", "failover");
        if (!"failover".equals(cluster) && !"replicate".equals(cluster)) {
            throw new IllegalArgumentException("Unsupported redis cluster: " + cluster + ". The redis cluster only supported failover or replicate.");
        }
        replicate = "replicate".equals(cluster);

        List addresses = new ArrayList();
        addresses.add(url.getAddress());
        String[] backups = url.getParameter(Constants.BACKUP_KEY, new String[0]);
        if (backups != null && backups.length > 0) {
            addresses.addAll(Arrays.asList(backups));
        }

        String password = url.getPassword();
        for (String address : addresses) {
            int i = address.indexOf(':');
            String host;
            int port;
            if (i > 0) {
                host = address.substring(0, i);
                port = Integer.parseInt(address.substring(i + 1));
            } else {
                host = address;
                port = DEFAULT_REDIS_PORT;
            }
            if (StringUtils.isEmpty(password)) {
                this.jedisPools.put(address, new JedisPool(config, host, port,
                        url.getParameter(Constants.TIMEOUT_KEY, Constants.DEFAULT_TIMEOUT)));
            } else {
                this.jedisPools.put(address, new JedisPool(config, host, port,
                        url.getParameter(Constants.TIMEOUT_KEY, Constants.DEFAULT_TIMEOUT), password));
            }
        }

        this.reconnectPeriod = url.getParameter(Constants.REGISTRY_RECONNECT_PERIOD_KEY, Constants.DEFAULT_REGISTRY_RECONNECT_PERIOD);
        String group = url.getParameter(Constants.GROUP_KEY, DEFAULT_ROOT);
        if (!group.startsWith(Constants.PATH_SEPARATOR)) {
            group = Constants.PATH_SEPARATOR + group;
        }
        if (!group.endsWith(Constants.PATH_SEPARATOR)) {
            group = group + Constants.PATH_SEPARATOR;
        }
        this.root = group;

        this.expirePeriod = url.getParameter(Constants.SESSION_TIMEOUT_KEY, Constants.DEFAULT_SESSION_TIMEOUT);
        this.expireFuture = expireExecutor.scheduleWithFixedDelay(new Runnable() {
            public void run() {
                try {
                    deferExpired(); // Extend the expiration time
                } catch (Throwable t) { // Defensive fault tolerance
                    logger.error("Unexpected exception occur at defer expire time, cause: " + t.getMessage(), t);
                }
            }
        }, expirePeriod / 2, expirePeriod / 2, TimeUnit.MILLISECONDS);
    }

    private void deferExpired() {
        for (Map.Entry entry : jedisPools.entrySet()) {
            JedisPool jedisPool = entry.getValue();
            try {
                Jedis jedis = jedisPool.getResource();
                try {
                    for (URL url : new HashSet(getRegistered())) {
                        if (url.getParameter(Constants.DYNAMIC_KEY, true)) {
                            String key = toCategoryPath(url);
                            if (jedis.hset(key, url.toFullString(), String.valueOf(System.currentTimeMillis() + expirePeriod)) == 1) {
                                jedis.publish(key, Constants.REGISTER);
                            }
                        }
                    }
                    if (admin) {
                        clean(jedis);
                    }
                    if (!replicate) {
                        break;//  If the server side has synchronized data, just write a single machine
                    }
                } finally {
                    jedis.close();
                }
            } catch (Throwable t) {
                logger.warn("Failed to write provider heartbeat to redis registry. registry: " + entry.getKey() + ", cause: " + t.getMessage(), t);
            }
        }
    }

    // The monitoring center is responsible for deleting outdated dirty data
    private void clean(Jedis jedis) {
        Set keys = jedis.keys(root + Constants.ANY_VALUE);
        if (keys != null && !keys.isEmpty()) {
            for (String key : keys) {
                Map values = jedis.hgetAll(key);
                if (values != null && values.size() > 0) {
                    boolean delete = false;
                    long now = System.currentTimeMillis();
                    for (Map.Entry entry : values.entrySet()) {
                        URL url = URL.valueOf(entry.getKey());
                        if (url.getParameter(Constants.DYNAMIC_KEY, true)) {
                            long expire = Long.parseLong(entry.getValue());
                            if (expire < now) {
                                jedis.hdel(key, entry.getKey());
                                delete = true;
                                if (logger.isWarnEnabled()) {
                                    logger.warn("Delete expired key: " + key + " -> value: " + entry.getKey() + ", expire: " + new Date(expire) + ", now: " + new Date(now));
                                }
                            }
                        }
                    }
                    if (delete) {
                        jedis.publish(key, Constants.UNREGISTER);
                    }
                }
            }
        }
    }

    public boolean isAvailable() {
        for (JedisPool jedisPool : jedisPools.values()) {
            try {
                Jedis jedis = jedisPool.getResource();
                try {
                    if (jedis.isConnected()) {
                        return true; // At least one single machine is available.
                    }
                } finally {
                    jedis.close();
                }
            } catch (Throwable t) {
            }
        }
        return false;
    }

    @Override
    public void destroy() {
        super.destroy();
        try {
            expireFuture.cancel(true);
        } catch (Throwable t) {
            logger.warn(t.getMessage(), t);
        }
        try {
            for (Notifier notifier : notifiers.values()) {
                notifier.shutdown();
            }
        } catch (Throwable t) {
            logger.warn(t.getMessage(), t);
        }
        for (Map.Entry entry : jedisPools.entrySet()) {
            JedisPool jedisPool = entry.getValue();
            try {
                jedisPool.destroy();
            } catch (Throwable t) {
                logger.warn("Failed to destroy the redis registry client. registry: " + entry.getKey() + ", cause: " + t.getMessage(), t);
            }
        }
    }

	//注册地址到redis中主 Key 为服务名和类型
	//Map 中的 Key 为 URL 地址,Map 中的 Value 为过期时间，用于判断脏数据，脏数据由监控中心删除
    @Override
    public void doRegister(URL url) {
        String key = toCategoryPath(url);
        String value = url.toFullString();
        String expire = String.valueOf(System.currentTimeMillis() + expirePeriod);
        boolean success = false;
        RpcException exception = null;
        for (Map.Entry entry : jedisPools.entrySet()) {
            JedisPool jedisPool = entry.getValue();
            try {
                Jedis jedis = jedisPool.getResource();
                try {
                    jedis.hset(key, value, expire);
                    jedis.publish(key, Constants.REGISTER);
                    success = true;
                    if (!replicate) {
                        break; //  If the server side has synchronized data, just write a single machine
                    }
                } finally {
                    jedis.close();
                }
            } catch (Throwable t) {
                exception = new RpcException("Failed to register service to redis registry. registry: " + entry.getKey() + ", service: " + url + ", cause: " + t.getMessage(), t);
            }
        }
        if (exception != null) {
            if (success) {
                logger.warn(exception.getMessage(), exception);
            } else {
                throw exception;
            }
        }
    }

	//取消注册，删除key值并发送通知
    @Override
    public void doUnregister(URL url) {
        String key = toCategoryPath(url);
        String value = url.toFullString();
        RpcException exception = null;
        boolean success = false;
        for (Map.Entry entry : jedisPools.entrySet()) {
            JedisPool jedisPool = entry.getValue();
            try {
                Jedis jedis = jedisPool.getResource();
                try {
                    jedis.hdel(key, value);
                    jedis.publish(key, Constants.UNREGISTER);
                    success = true;
                    if (!replicate) {
                        break; //  If the server side has synchronized data, just write a single machine
                    }
                } finally {
                    jedis.close();
                }
            } catch (Throwable t) {
                exception = new RpcException("Failed to unregister service to redis registry. registry: " + entry.getKey() + ", service: " + url + ", cause: " + t.getMessage(), t);
            }
        }
        if (exception != null) {
            if (success) {
                logger.warn(exception.getMessage(), exception);
            } else {
                throw exception;
            }
        }
    }

	//订阅
    @Override
    public void doSubscribe(final URL url, final NotifyListener listener) {
        String service = toServicePath(url);
        Notifier notifier = notifiers.get(service);
        if (notifier == null) {
			//开启线程来订阅通知数据
            Notifier newNotifier = new Notifier(service);
            notifiers.putIfAbsent(service, newNotifier);
            notifier = notifiers.get(service);
            if (notifier == newNotifier) {
                notifier.start();
            }
        }
        boolean success = false;
        RpcException exception = null;
        for (Map.Entry entry : jedisPools.entrySet()) {
            JedisPool jedisPool = entry.getValue();
            try {
                Jedis jedis = jedisPool.getResource();
                try {
                    if (service.endsWith(Constants.ANY_VALUE)) {
                        admin = true;
                        Set keys = jedis.keys(service);
                        if (keys != null && !keys.isEmpty()) {
                            Map> serviceKeys = new HashMap>();
                            for (String key : keys) {
                                String serviceKey = toServicePath(key);
                                Set sk = serviceKeys.get(serviceKey);
                                if (sk == null) {
                                    sk = new HashSet();
                                    serviceKeys.put(serviceKey, sk);
                                }
                                sk.add(key);
                            }
                            for (Set sk : serviceKeys.values()) {
                                doNotify(jedis, sk, url, Arrays.asList(listener));
                            }
                        }
                    } else {
                        doNotify(jedis, jedis.keys(service + Constants.PATH_SEPARATOR + Constants.ANY_VALUE), url, Arrays.asList(listener));
                    }
                    success = true;
                    break; // Just read one server's data
                } finally {
                    jedis.close();
                }
            } catch (Throwable t) { // Try the next server
                exception = new RpcException("Failed to subscribe service from redis registry. registry: " + entry.getKey() + ", service: " + url + ", cause: " + t.getMessage(), t);
            }
        }
        if (exception != null) {
            if (success) {
                logger.warn(exception.getMessage(), exception);
            } else {
                throw exception;
            }
        }
    }

    @Override
    public void doUnsubscribe(URL url, NotifyListener listener) {
    }

    private void doNotify(Jedis jedis, String key) {
        for (Map.Entry> entry : new HashMap>(getSubscribed()).entrySet()) {
            doNotify(jedis, Arrays.asList(key), entry.getKey(), new HashSet(entry.getValue()));
        }
    }

    private void doNotify(Jedis jedis, Collection keys, URL url, Collection listeners) {
        if (keys == null || keys.isEmpty()
                || listeners == null || listeners.isEmpty()) {
            return;
        }
        long now = System.currentTimeMillis();
        List result = new ArrayList();
        List categories = Arrays.asList(url.getParameter(Constants.CATEGORY_KEY, new String[0]));
        String consumerService = url.getServiceInterface();
        for (String key : keys) {
            if (!Constants.ANY_VALUE.equals(consumerService)) {
                String prvoiderService = toServiceName(key);
                if (!prvoiderService.equals(consumerService)) {
                    continue;
                }
            }
            String category = toCategoryName(key);
            if (!categories.contains(Constants.ANY_VALUE) && !categories.contains(category)) {
                continue;
            }
            List urls = new ArrayList();
            Map values = jedis.hgetAll(key);
            if (values != null && values.size() > 0) {
                for (Map.Entry entry : values.entrySet()) {
                    URL u = URL.valueOf(entry.getKey());
                    if (!u.getParameter(Constants.DYNAMIC_KEY, true)
                            || Long.parseLong(entry.getValue()) >= now) {
                        if (UrlUtils.isMatch(url, u)) {
                            urls.add(u);
                        }
                    }
                }
            }
            if (urls.isEmpty()) {
                urls.add(url.setProtocol(Constants.EMPTY_PROTOCOL)
                        .setAddress(Constants.ANYHOST_VALUE)
                        .setPath(toServiceName(key))
                        .addParameter(Constants.CATEGORY_KEY, category));
            }
            result.addAll(urls);
            if (logger.isInfoEnabled()) {
                logger.info("redis notify: " + key + " = " + urls);
            }
        }
        if (result == null || result.isEmpty()) {
            return;
        }
        for (NotifyListener listener : listeners) {
            notify(url, listener, result);
        }
    }

    private String toServiceName(String categoryPath) {
        String servicePath = toServicePath(categoryPath);
        return servicePath.startsWith(root) ? servicePath.substring(root.length()) : servicePath;
    }

    private String toCategoryName(String categoryPath) {
        int i = categoryPath.lastIndexOf(Constants.PATH_SEPARATOR);
        return i > 0 ? categoryPath.substring(i + 1) : categoryPath;
    }

    private String toServicePath(String categoryPath) {
        int i;
        if (categoryPath.startsWith(root)) {
            i = categoryPath.indexOf(Constants.PATH_SEPARATOR, root.length());
        } else {
            i = categoryPath.indexOf(Constants.PATH_SEPARATOR);
        }
        return i > 0 ? categoryPath.substring(0, i) : categoryPath;
    }

    private String toServicePath(URL url) {
        return root + url.getServiceInterface();
    }

    private String toCategoryPath(URL url) {
        return toServicePath(url) + Constants.PATH_SEPARATOR + url.getParameter(Constants.CATEGORY_KEY, Constants.DEFAULT_CATEGORY);
    }

	//创建消息订阅线程，当服务未多个的时候创建的线程也是多个，比较消耗资源
    private class NotifySub extends JedisPubSub {

        private final JedisPool jedisPool;

        public NotifySub(JedisPool jedisPool) {
            this.jedisPool = jedisPool;
        }

		//调用回调函数
        @Override
        public void onMessage(String key, String msg) {
            if (logger.isInfoEnabled()) {
                logger.info("redis event: " + key + " = " + msg);
            }
            if (msg.equals(Constants.REGISTER)
                    || msg.equals(Constants.UNREGISTER)) {
                try {
                    Jedis jedis = jedisPool.getResource();
                    try {
						//更新本地内存中的通知数据
                        doNotify(jedis, key);
                    } finally {
                        jedis.close();
                    }
                } catch (Throwable t) { // TODO Notification failure does not restore mechanism guarantee
                    logger.error(t.getMessage(), t);
                }
            }
        }

        @Override
        public void onPMessage(String pattern, String key, String msg) {
            onMessage(key, msg);
        }

        @Override
        public void onSubscribe(String key, int num) {
        }

        @Override
        public void onPSubscribe(String pattern, int num) {
        }

        @Override
        public void onUnsubscribe(String key, int num) {
        }

        @Override
        public void onPUnsubscribe(String pattern, int num) {
        }

    }
	//接收通知线程
    private class Notifier extends Thread {

        private final String service;
        private final AtomicInteger connectSkip = new AtomicInteger();
        private final AtomicInteger connectSkiped = new AtomicInteger();
        private final Random random = new Random();
        private volatile Jedis jedis;
        private volatile boolean first = true;
        private volatile boolean running = true;
        private volatile int connectRandom;

        public Notifier(String service) {
            super.setDaemon(true);
            super.setName("DubboRedisSubscribe");
            this.service = service;
        }

        private void resetSkip() {
            connectSkip.set(0);
            connectSkiped.set(0);
            connectRandom = 0;
        }

        private boolean isSkip() {
            int skip = connectSkip.get(); // Growth of skipping times
            if (skip >= 10) { // If the number of skipping times increases by more than 10, take the random number
                if (connectRandom == 0) {
                    connectRandom = random.nextInt(10);
                }
                skip = 10 + connectRandom;
            }
            if (connectSkiped.getAndIncrement() < skip) { // Check the number of skipping times
                return true;
            }
            connectSkip.incrementAndGet();
            connectSkiped.set(0);
            connectRandom = 0;
            return false;
        }
		//开启线程监听通知数据
        @Override
        public void run() {
            while (running) {
                try {
                    if (!isSkip()) {
                        try {
                            for (Map.Entry entry : jedisPools.entrySet()) {
                                JedisPool jedisPool = entry.getValue();
                                try {
                                    jedis = jedisPool.getResource();
                                    try {
                                        if (service.endsWith(Constants.ANY_VALUE)) {
                                            if (!first) {
                                                first = false;
                                                Set keys = jedis.keys(service);
                                                if (keys != null && !keys.isEmpty()) {
                                                    for (String s : keys) {
                                                        doNotify(jedis, s);
                                                    }
                                                }
                                                resetSkip();
                                            }
                                            jedis.psubscribe(new NotifySub(jedisPool), service); // blocking
                                        } else {
                                            if (!first) {
                                                first = false;
                                                doNotify(jedis, service);
                                                resetSkip();
                                            }
                                            jedis.psubscribe(new NotifySub(jedisPool), service + Constants.PATH_SEPARATOR + Constants.ANY_VALUE); // blocking
                                        }
                                        break;
                                    } finally {
                                        jedis.close();
                                    }
                                } catch (Throwable t) { // Retry another server
                                    logger.warn("Failed to subscribe service from redis registry. registry: " + entry.getKey() + ", cause: " + t.getMessage(), t);
                                    // If you only have a single redis, you need to take a rest to avoid overtaking a lot of CPU resources
                                    sleep(reconnectPeriod);
                                }
                            }
                        } catch (Throwable t) {
                            logger.error(t.getMessage(), t);
                            sleep(reconnectPeriod);
                        }
                    }
                } catch (Throwable t) {
                    logger.error(t.getMessage(), t);
                }
            }
        }

        public void shutdown() {
            try {
                running = false;
                jedis.disconnect();
            } catch (Throwable t) {
                logger.warn(t.getMessage(), t);
            }
        }

    }

}