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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.dubbo.registry;

import org.apache.dubbo.common.URL;
import org.apache.dubbo.common.logger.ErrorTypeAwareLogger;
import org.apache.dubbo.common.logger.LoggerFactory;
import org.apache.dubbo.common.threadpool.manager.FrameworkExecutorRepository;

import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicInteger;

import static org.apache.dubbo.common.constants.CommonConstants.DEFAULT_DELAY_EXECUTE_TIMES;
import static org.apache.dubbo.common.constants.LoggerCodeConstants.COMMON_FAILED_NOTIFY_EVENT;
import static org.apache.dubbo.common.constants.LoggerCodeConstants.REGISTRY_FAILED_NOTIFY_EVENT;

public abstract class RegistryNotifier {

    private static final ErrorTypeAwareLogger logger = LoggerFactory.getErrorTypeAwareLogger(RegistryNotifier.class);
    private volatile long lastExecuteTime;
    private volatile long lastEventTime;
    private final URL url;
    private Object rawAddresses;
    private long delayTime;

    // should delay notify or not
    private final AtomicBoolean shouldDelay = new AtomicBoolean(false);
    // for the first 10 notification will be notified immediately
    private final AtomicInteger executeTime = new AtomicInteger(0);

    private ScheduledExecutorService scheduler;

    public RegistryNotifier(URL registryUrl, long delayTime) {
        this(registryUrl, delayTime, null);
    }

    public RegistryNotifier(URL registryUrl, long delayTime, ScheduledExecutorService scheduler) {
        this.url = registryUrl;
        this.delayTime = delayTime;
        if (scheduler == null) {
            this.scheduler = registryUrl
                    .getOrDefaultFrameworkModel()
                    .getBeanFactory()
                    .getBean(FrameworkExecutorRepository.class)
                    .getRegistryNotificationExecutor();
        } else {
            this.scheduler = scheduler;
        }
    }

    public synchronized void notify(Object rawAddresses) {
        this.rawAddresses = rawAddresses;
        long notifyTime = System.currentTimeMillis();
        this.lastEventTime = notifyTime;

        long delta = (System.currentTimeMillis() - lastExecuteTime) - delayTime;

        // more than 10 calls && next execute time is in the future
        boolean delay = shouldDelay.get() && delta < 0;
        // when the scheduler is shutdown, no notification is sent
        if (scheduler.isShutdown()) {
            if (logger.isWarnEnabled()) {
                logger.warn(
                        COMMON_FAILED_NOTIFY_EVENT,
                        "",
                        "",
                        "Notification scheduler is off, no notifications are sent. Registry URL:  " + url);
            }
            return;
        } else if (delay) {
            scheduler.schedule(new NotificationTask(this, notifyTime), -delta, TimeUnit.MILLISECONDS);
        } else {
            // check if more than 10 calls
            if (!shouldDelay.get() && executeTime.incrementAndGet() > DEFAULT_DELAY_EXECUTE_TIMES) {
                shouldDelay.set(true);
            }
            scheduler.submit(new NotificationTask(this, notifyTime));
        }
        try {
            while (this.lastEventTime == System.currentTimeMillis()) {
                // wait to let event time refresh
                Thread.sleep(1);
            }
        } catch (InterruptedException e) {
            Thread.currentThread().interrupt();
        }
    }

    public long getDelayTime() {
        return delayTime;
    }

    /**
     * notification of instance addresses (aka providers).
     *
     * @param rawAddresses data.
     */
    protected abstract void doNotify(Object rawAddresses);

    public static class NotificationTask implements Runnable {
        private final RegistryNotifier listener;
        private final long time;

        public NotificationTask(RegistryNotifier listener, long time) {
            this.listener = listener;
            this.time = time;
        }

        @Override
        public void run() {
            try {
                if (this.time == listener.lastEventTime) {
                    listener.doNotify(listener.rawAddresses);
                    listener.lastExecuteTime = System.currentTimeMillis();
                    synchronized (listener) {
                        if (this.time == listener.lastEventTime) {
                            listener.rawAddresses = null;
                        }
                    }
                }
            } catch (Throwable t) {
                logger.error(REGISTRY_FAILED_NOTIFY_EVENT, "", "", "Error occurred when notify directory. ", t);
            }
        }
    }
}