/*
    * 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.
   */
  
  // Contibutors:  Aaron Greenhouse <aarong@cs.cmu.edu>
  //               Thomas Tuft Muller <ttm@online.no>
  package org.apache.log4j;
  
  import java.text.MessageFormat;
  import java.util.ArrayList;
  import java.util.Enumeration;
  import java.util.HashMap;
  import java.util.Iterator;
  import java.util.List;
  import java.util.Map;
  
  import org.apache.log4j.helpers.AppenderAttachableImpl;
  import org.apache.log4j.spi.AppenderAttachable;
  import org.apache.log4j.spi.LoggingEvent;
  
  
  /**
   * The AsyncAppender lets users log events asynchronously.
   * <p/>
   * <p/>
   * The AsyncAppender will collect the events sent to it and then dispatch them
   * to all the appenders that are attached to it. You can attach multiple
   * appenders to an AsyncAppender.
   * </p>
   * <p/>
   * <p/>
   * The AsyncAppender uses a separate thread to serve the events in its buffer.
   * </p>
   * <p/>
   * <b>Important note:</b> The <code>AsyncAppender</code> can only be script
   * configured using the {@link org.apache.log4j.xml.DOMConfigurator}.
   * </p>
   *
   * @author Ceki G&uuml;lc&uuml;
   * @author Curt Arnold
   * @since 0.9.1
   */
  public class AsyncAppender extends AppenderSkeleton
    implements AppenderAttachable {
    /**
     * The default buffer size is set to 128 events.
     */
    public static final int DEFAULT_BUFFER_SIZE = 128;
  
    /**
     * Event buffer, also used as monitor to protect itself and
     * discardMap from simulatenous modifications.
     */
    private final List buffer = new ArrayList();
  
    /**
     * Map of DiscardSummary objects keyed by logger name.
     */
    private final Map discardMap = new HashMap();
  
    /**
     * Buffer size.
     */
    private int bufferSize = DEFAULT_BUFFER_SIZE;
  
    /** Nested appenders. */
    AppenderAttachableImpl aai;
  
    /**
     * Nested appenders.
     */
    private final AppenderAttachableImpl appenders;
  
    /**
     * Dispatcher.
     */
    private final Thread dispatcher;
  
    /**
     * Should location info be included in dispatched messages.
     */
    private boolean locationInfo = false;
  
    /**
     * Does appender block when buffer is full.
     */
   private boolean blocking = true;
 
   /**
    * Create new instance.
    */
   public AsyncAppender() {
     appenders = new AppenderAttachableImpl();
 
     //
     //   only set for compatibility
     aai = appenders;
 
     dispatcher =
       new Thread(new Dispatcher(this, buffer, discardMap, appenders));
 
     // It is the user's responsibility to close appenders before
     // exiting.
     dispatcher.setDaemon(true);
 
     // set the dispatcher priority to lowest possible value
     //        dispatcher.setPriority(Thread.MIN_PRIORITY);
     dispatcher.setName("AsyncAppender-Dispatcher-" + dispatcher.getName());
     dispatcher.start();
   }
 
   /**
    * Add appender.
    *
    * @param newAppender appender to add, may not be null.
    */
   public void addAppender(final Appender newAppender) {
     synchronized (appenders) {
       appenders.addAppender(newAppender);
     }
   }
 
   /**
    * {@inheritDoc}
    */
   public void append(final LoggingEvent event) {
     //
     //   if dispatcher thread has died then
     //      append subsequent events synchronously
     //   See bug 23021
     if ((dispatcher == null) || !dispatcher.isAlive() || (bufferSize <= 0)) {
       synchronized (appenders) {
         appenders.appendLoopOnAppenders(event);
       }
 
       return;
     }
 
     // Set the NDC and thread name for the calling thread as these
     // LoggingEvent fields were not set at event creation time.
     event.getNDC();
     event.getThreadName();
     // Get a copy of this thread's MDC.
     event.getMDCCopy();
     if (locationInfo) {
       event.getLocationInformation();
     }
     event.getRenderedMessage();
     event.getThrowableStrRep();
 
     synchronized (buffer) {
       while (true) {
         int previousSize = buffer.size();
 
         if (previousSize < bufferSize) {
           buffer.add(event);
 
           //
           //   if buffer had been empty
           //       signal all threads waiting on buffer
           //       to check their conditions.
           //
           if (previousSize == 0) {
             buffer.notifyAll();
           }
 
           break;
         }
 
         //
         //   Following code is only reachable if buffer is full
         //
         //
         //   if blocking and thread is not already interrupted
         //      and not the dispatcher then
         //      wait for a buffer notification
         boolean discard = true;
         if (blocking
                 && !Thread.interrupted()
                 && Thread.currentThread() != dispatcher) {
           try {
             buffer.wait();
             discard = false;
           } catch (InterruptedException e) {
             //
             //  reset interrupt status so
             //    calling code can see interrupt on
             //    their next wait or sleep.
             Thread.currentThread().interrupt();
           }
         }
 
         //
         //   if blocking is false or thread has been interrupted
         //   add event to discard map.
         //
         if (discard) {
           String loggerName = event.getLoggerName();
           DiscardSummary summary = (DiscardSummary) discardMap.get(loggerName);
 
           if (summary == null) {
             summary = new DiscardSummary(event);
             discardMap.put(loggerName, summary);
           } else {
             summary.add(event);
           }
 
           break;
         }
       }
     }
   }
 
   /**
    * Close this <code>AsyncAppender</code> by interrupting the dispatcher
    * thread which will process all pending events before exiting.
    */
   public void close() {
     /**
      * Set closed flag and notify all threads to check their conditions.
      * Should result in dispatcher terminating.
      */
     synchronized (buffer) {
       closed = true;
       buffer.notifyAll();
     }
 
     try {
       dispatcher.join();
     } catch (InterruptedException e) {
       Thread.currentThread().interrupt();
       org.apache.log4j.helpers.LogLog.error(
         "Got an InterruptedException while waiting for the "
         + "dispatcher to finish.", e);
     }
 
     //
     //    close all attached appenders.
     //
     synchronized (appenders) {
       Enumeration iter = appenders.getAllAppenders();
 
       if (iter != null) {
         while (iter.hasMoreElements()) {
           Object next = iter.nextElement();
 
           if (next instanceof Appender) {
             ((Appender) next).close();
           }
         }
       }
     }
   }
 
   /**
    * Get iterator over attached appenders.
    * @return iterator or null if no attached appenders.
    */
   public Enumeration getAllAppenders() {
     synchronized (appenders) {
       return appenders.getAllAppenders();
     }
   }
 
   /**
    * Get appender by name.
    *
    * @param name name, may not be null.
    * @return matching appender or null.
    */
   public Appender getAppender(final String name) {
     synchronized (appenders) {
       return appenders.getAppender(name);
     }
   }
 
   /**
    * Gets whether the location of the logging request call
    * should be captured.
    *
    * @return the current value of the <b>LocationInfo</b> option.
    */
   public boolean getLocationInfo() {
     return locationInfo;
   }
 
   /**
    * Determines if specified appender is attached.
    * @param appender appender.
    * @return true if attached.
    */
   public boolean isAttached(final Appender appender) {
     synchronized (appenders) {
       return appenders.isAttached(appender);
     }
   }
 
   /**
    * {@inheritDoc}
    */
   public boolean requiresLayout() {
     return false;
   }
 
   /**
    * Removes and closes all attached appenders.
    */
   public void removeAllAppenders() {
     synchronized (appenders) {
       appenders.removeAllAppenders();
     }
   }
 
   /**
    * Removes an appender.
    * @param appender appender to remove.
    */
   public void removeAppender(final Appender appender) {
     synchronized (appenders) {
       appenders.removeAppender(appender);
     }
   }
 
   /**
    * Remove appender by name.
    * @param name name.
    */
   public void removeAppender(final String name) {
     synchronized (appenders) {
       appenders.removeAppender(name);
     }
   }
 
   /**
    * The <b>LocationInfo</b> option takes a boolean value. By default, it is
    * set to false which means there will be no effort to extract the location
    * information related to the event. As a result, the event that will be
    * ultimately logged will likely to contain the wrong location information
    * (if present in the log format).
    * <p/>
    * <p/>
    * Location information extraction is comparatively very slow and should be
    * avoided unless performance is not a concern.
    * </p>
    * @param flag true if location information should be extracted.
    */
   public void setLocationInfo(final boolean flag) {
     locationInfo = flag;
   }
 
   /**
    * Sets the number of messages allowed in the event buffer
    * before the calling thread is blocked (if blocking is true)
    * or until messages are summarized and discarded.  Changing
    * the size will not affect messages already in the buffer.
    *
    * @param size buffer size, must be positive.
    */
   public void setBufferSize(final int size) {
     //
     //   log4j 1.2 would throw exception if size was negative
     //      and deadlock if size was zero.
     //
     if (size < 0) {
       throw new java.lang.NegativeArraySizeException("size");
     }
 
     synchronized (buffer) {
       //
       //   don't let size be zero.
       //
       bufferSize = (size < 1) ? 1 : size;
       buffer.notifyAll();
     }
   }
 
   /**
    * Gets the current buffer size.
    * @return the current value of the <b>BufferSize</b> option.
    */
   public int getBufferSize() {
     return bufferSize;
   }
 
   /**
    * Sets whether appender should wait if there is no
    * space available in the event buffer or immediately return.
    *
    * @since 1.2.14
    * @param value true if appender should wait until available space in buffer.
    */
   public void setBlocking(final boolean value) {
     synchronized (buffer) {
       blocking = value;
       buffer.notifyAll();
     }
   }
 
   /**
    * Gets whether appender should block calling thread when buffer is full.
    * If false, messages will be counted by logger and a summary
    * message appended after the contents of the buffer have been appended.
    *
    * @since 1.2.14
    * @return true if calling thread will be blocked when buffer is full.
    */
   public boolean getBlocking() {
     return blocking;
   }
 
   /**
    * Summary of discarded logging events for a logger.
    */
   private static final class DiscardSummary {
     /**
      * First event of the highest severity.
      */
     private LoggingEvent maxEvent;
 
     /**
      * Total count of messages discarded.
      */
     private int count;
 
     /**
      * Create new instance.
      *
      * @param event event, may not be null.
      */
     public DiscardSummary(final LoggingEvent event) {
       maxEvent = event;
       count = 1;
     }
 
     /**
      * Add discarded event to summary.
      *
      * @param event event, may not be null.
      */
     public void add(final LoggingEvent event) {
       if (event.getLevel().toInt() > maxEvent.getLevel().toInt()) {
         maxEvent = event;
       }
 
       count++;
     }
 
     /**
      * Create event with summary information.
      *
      * @return new event.
      */
     public LoggingEvent createEvent() {
       String msg =
         MessageFormat.format(
           "Discarded {0} messages due to full event buffer including: {1}",
           new Object[] { new Integer(count), maxEvent.getMessage() });
 
       return new LoggingEvent(
               "org.apache.log4j.AsyncAppender.DONT_REPORT_LOCATION",
               Logger.getLogger(maxEvent.getLoggerName()),
               maxEvent.getLevel(),
               msg,
               null);
     }
   }
 
   /**
    * Event dispatcher.
    */
   private static class Dispatcher implements Runnable {
     /**
      * Parent AsyncAppender.
      */
     private final AsyncAppender parent;
 
     /**
      * Event buffer.
      */
     private final List buffer;
 
     /**
      * Map of DiscardSummary keyed by logger name.
      */
     private final Map discardMap;
 
     /**
      * Wrapped appenders.
      */
     private final AppenderAttachableImpl appenders;
 
     /**
      * Create new instance of dispatcher.
      *
      * @param parent     parent AsyncAppender, may not be null.
      * @param buffer     event buffer, may not be null.
      * @param discardMap discard map, may not be null.
      * @param appenders  appenders, may not be null.
      */
     public Dispatcher(
       final AsyncAppender parent, final List buffer, final Map discardMap,
       final AppenderAttachableImpl appenders) {
 
       this.parent = parent;
       this.buffer = buffer;
       this.appenders = appenders;
       this.discardMap = discardMap;
     }
 
     /**
      * {@inheritDoc}
      */
     public void run() {
       boolean isActive = true;
 
       //
       //   if interrupted (unlikely), end thread
       //
       try {
         //
         //   loop until the AsyncAppender is closed.
         //
         while (isActive) {
           LoggingEvent[] events = null;
 
           //
           //   extract pending events while synchronized
           //       on buffer
           //
           synchronized (buffer) {
             int bufferSize = buffer.size();
             isActive = !parent.closed;
 
             while ((bufferSize == 0) && isActive) {
               buffer.wait();
               bufferSize = buffer.size();
               isActive = !parent.closed;
             }
 
             if (bufferSize > 0) {
               events = new LoggingEvent[bufferSize + discardMap.size()];
               buffer.toArray(events);
 
               //
               //   add events due to buffer overflow
               //
               int index = bufferSize;
 
               for (
                 Iterator iter = discardMap.values().iterator();
                   iter.hasNext();) {
                 events[index++] = ((DiscardSummary) iter.next()).createEvent();
               }
 
               //
               //    clear buffer and discard map
               //
               buffer.clear();
               discardMap.clear();
 
               //
               //    allow blocked appends to continue
               buffer.notifyAll();
             }
           }
 
           //
           //   process events after lock on buffer is released.
           //
           if (events != null) {
             for (int i = 0; i < events.length; i++) {
               synchronized (appenders) {
                 appenders.appendLoopOnAppenders(events[i]);
               }
             }
           }
         }
       } catch (InterruptedException ex) {
         Thread.currentThread().interrupt();
       }
     }
   }
 }