content: /**
   * 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.activemq.transport.mqtt;
  
  import java.io.IOException;
  import java.util.Timer;
  import java.util.concurrent.RejectedExecutionException;
  import java.util.concurrent.SynchronousQueue;
  import java.util.concurrent.ThreadFactory;
  import java.util.concurrent.ThreadPoolExecutor;
  import java.util.concurrent.TimeUnit;
  import java.util.concurrent.atomic.AtomicBoolean;
  import java.util.concurrent.atomic.AtomicInteger;
  import java.util.concurrent.locks.ReentrantLock;
  
  import org.apache.activemq.thread.SchedulerTimerTask;
  import org.apache.activemq.transport.AbstractInactivityMonitor;
  import org.apache.activemq.transport.InactivityIOException;
  import org.apache.activemq.transport.Transport;
  import org.apache.activemq.transport.TransportFilter;
  import org.apache.activemq.wireformat.WireFormat;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  public class MQTTInactivityMonitor extends TransportFilter {
  
      private static final Logger LOG = LoggerFactory.getLogger(MQTTInactivityMonitor.class);
  
      private static final long DEFAULT_CHECK_TIME_MILLS = 30000;
  
      private static ThreadPoolExecutor ASYNC_TASKS;
      private static int CHECKER_COUNTER;
      private static Timer READ_CHECK_TIMER;
  
      private final AtomicBoolean failed = new AtomicBoolean(false);
      private final AtomicBoolean inReceive = new AtomicBoolean(false);
      private final AtomicInteger lastReceiveCounter = new AtomicInteger(0);
  
      private final ReentrantLock sendLock = new ReentrantLock();
      private SchedulerTimerTask readCheckerTask;
  
      private long readGraceTime = DEFAULT_CHECK_TIME_MILLS;
      private long readKeepAliveTime = DEFAULT_CHECK_TIME_MILLS;
      private MQTTProtocolConverter protocolConverter;
  
      private long connectionTimeout = MQTTWireFormat.DEFAULT_CONNECTION_TIMEOUT;
      private SchedulerTimerTask connectCheckerTask;
      private final Runnable connectChecker = new Runnable() {
  
          private final long startTime = System.currentTimeMillis();
  
          @Override
          public void run() {
  
              long now = System.currentTimeMillis();
  
              if ((now - startTime) >= connectionTimeout && connectCheckerTask != null && !ASYNC_TASKS.isShutdown()) {
                  if (LOG.isDebugEnabled()) {
                      LOG.debug("No CONNECT frame received in time for " + MQTTInactivityMonitor.this.toString() + "! Throwing InactivityIOException.");
                  }
  
                  try {
                      ASYNC_TASKS.execute(new Runnable() {
                          @Override
                          public void run() {
                              onException(new InactivityIOException("CONNECT frame not received with in connectionTimeout (>" + connectionTimeout + "): "
                                  + next.getRemoteAddress()));
                          }
                      });
                  } catch (RejectedExecutionException ex) {
                      if (!ASYNC_TASKS.isShutdown()) {
                          LOG.error("Async connection timeout task was rejected from the executor: ", ex);
                          throw ex;
                      }
                  }
              }
          }
      };
  
      private final Runnable readChecker = new Runnable() {
          long lastReceiveTime = System.currentTimeMillis();
  
          @Override
          public void run() {
  
              long now = System.currentTimeMillis();
              int currentCounter = next.getReceiveCounter();
              int previousCounter = lastReceiveCounter.getAndSet(currentCounter);
  
              // for the PINGREQ/RESP frames, the currentCounter will be different
              // from previousCounter, and that
              // should be sufficient to indicate the connection is still alive.
              // If there were random data, or something
              // outside the scope of the spec, the wire format unrmarshalling
              // would fail, so we don't need to handle
              // PINGREQ/RESP explicitly here
              if (inReceive.get() || currentCounter != previousCounter) {
                  if (LOG.isTraceEnabled()) {
                      LOG.trace("Command received since last read check.");
                  }
                  lastReceiveTime = now;
                  return;
              }
  
              if ((now - lastReceiveTime) >= readKeepAliveTime + readGraceTime && readCheckerTask != null && !ASYNC_TASKS.isShutdown()) {
                  if (LOG.isDebugEnabled()) {
                      LOG.debug("No message received since last read check for " + MQTTInactivityMonitor.this.toString() + "! Throwing InactivityIOException.");
                  }
                  try {
                      ASYNC_TASKS.execute(new Runnable() {
                          @Override
                          public void run() {
                              onException(new InactivityIOException("Channel was inactive for too (>" +
                                          (connectionTimeout) + ") long: " + next.getRemoteAddress()));
                          }
                      });
                  } catch (RejectedExecutionException ex) {
                      if (!ASYNC_TASKS.isShutdown()) {
                          LOG.error("Async connection timeout task was rejected from the executor: ", ex);
                          throw ex;
                      }
                  }
              }
          }
      };
  
      public MQTTInactivityMonitor(Transport next, WireFormat wireFormat) {
          super(next);
      }
  
      @Override
      public void start() throws Exception {
          next.start();
      }
  
      @Override
      public void stop() throws Exception {
          stopReadChecker();
          stopConnectChecker();
          next.stop();
      }
  
      @Override
      public void onCommand(Object command) {
          inReceive.set(true);
          try {
              transportListener.onCommand(command);
          } finally {
              inReceive.set(false);
          }
      }
  
      @Override
      public void oneway(Object o) throws IOException {
          // To prevent the inactivity monitor from sending a message while we
          // are performing a send we take the lock.
          this.sendLock.lock();
          try {
              doOnewaySend(o);
          } finally {
              this.sendLock.unlock();
          }
      }
  
      // Must be called under lock, either read or write on sendLock.
      private void doOnewaySend(Object command) throws IOException {
          if (failed.get()) {
              throw new InactivityIOException("Cannot send, channel has already failed: " + next.getRemoteAddress());
          }
          next.oneway(command);
      }
  
      @Override
      public void onException(IOException error) {
          if (failed.compareAndSet(false, true)) {
              stopConnectChecker();
              stopReadChecker();
              if (protocolConverter != null) {
                  protocolConverter.onTransportError();
              }
              transportListener.onException(error);
          }
      }
  
      public long getReadGraceTime() {
          return readGraceTime;
      }
  
      public void setReadGraceTime(long readGraceTime) {
          this.readGraceTime = readGraceTime;
      }
  
      public long getReadKeepAliveTime() {
          return readKeepAliveTime;
      }
  
      public void setReadKeepAliveTime(long readKeepAliveTime) {
          this.readKeepAliveTime = readKeepAliveTime;
      }
  
      public void setProtocolConverter(MQTTProtocolConverter protocolConverter) {
          this.protocolConverter = protocolConverter;
      }
  
      public MQTTProtocolConverter getProtocolConverter() {
          return protocolConverter;
      }
  
      public synchronized void startConnectChecker(long connectionTimeout) {
          this.connectionTimeout = connectionTimeout;
          if (connectionTimeout > 0 && connectCheckerTask == null) {
              connectCheckerTask = new SchedulerTimerTask(connectChecker);
  
              long connectionCheckInterval = Math.min(connectionTimeout, 1000);
  
              synchronized (AbstractInactivityMonitor.class) {
                  if (CHECKER_COUNTER == 0) {
                      if (ASYNC_TASKS == null || ASYNC_TASKS.isShutdown()) {
                          ASYNC_TASKS = createExecutor();
                      }
                      READ_CHECK_TIMER = new Timer("InactivityMonitor ReadCheck", true);
                  }
                  CHECKER_COUNTER++;
                  READ_CHECK_TIMER.schedule(connectCheckerTask, connectionCheckInterval, connectionCheckInterval);
              }
          }
      }
  
      synchronized void startReadChecker() {
          if (readKeepAliveTime > 0 && readCheckerTask == null) {
              readCheckerTask = new SchedulerTimerTask(readChecker);
  
              synchronized (AbstractInactivityMonitor.class) {
                  if (CHECKER_COUNTER == 0) {
                      if (ASYNC_TASKS == null || ASYNC_TASKS.isShutdown()) {
                          ASYNC_TASKS = createExecutor();
                      }
                      READ_CHECK_TIMER = new Timer("InactivityMonitor ReadCheck", true);
                  }
                  CHECKER_COUNTER++;
                  READ_CHECK_TIMER.schedule(readCheckerTask, readKeepAliveTime, readGraceTime);
              }
          }
      }
  
      synchronized void stopConnectChecker() {
          if (connectCheckerTask != null) {
              connectCheckerTask.cancel();
              connectCheckerTask = null;
  
              synchronized (AbstractInactivityMonitor.class) {
                  READ_CHECK_TIMER.purge();
                  CHECKER_COUNTER--;
                  if (CHECKER_COUNTER == 0) {
                      READ_CHECK_TIMER.cancel();
                      READ_CHECK_TIMER = null;
                  }
              }
          }
      }
  
      synchronized void stopReadChecker() {
          if (readCheckerTask != null) {
              readCheckerTask.cancel();
              readCheckerTask = null;
  
              synchronized (AbstractInactivityMonitor.class) {
                  READ_CHECK_TIMER.purge();
                  CHECKER_COUNTER--;
                  if (CHECKER_COUNTER == 0) {
                      READ_CHECK_TIMER.cancel();
                      READ_CHECK_TIMER = null;
                  }
              }
          }
      }
  
      private final ThreadFactory factory = new ThreadFactory() {
          @Override
          public Thread newThread(Runnable runnable) {
              Thread thread = new Thread(runnable, "MQTTInactivityMonitor Async Task: " + runnable);
              thread.setDaemon(true);
              return thread;
          }
      };
  
      private ThreadPoolExecutor createExecutor() {
          ThreadPoolExecutor exec = new ThreadPoolExecutor(0, Integer.MAX_VALUE, 60, TimeUnit.SECONDS, new SynchronousQueue<Runnable>(), factory);
          exec.allowCoreThreadTimeOut(true);
          return exec;
      }
  }
  