/**
 * 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.hadoop.yarn;

import java.io.File;
import java.io.Flushable;
import java.util.ArrayDeque;
import java.util.Deque;

import org.apache.hadoop.classification.InterfaceAudience.Public;
import org.apache.hadoop.classification.InterfaceStability.Unstable;
import org.apache.log4j.FileAppender;
import org.apache.log4j.spi.LoggingEvent;

/**
 * A simple log4j-appender for container's logs.
 */
@Public
@Unstable
public class ContainerLogAppender extends FileAppender
    implements Flushable {

  private String containerLogDir;
  private String containerLogFile;
  private int maxEvents;
  private Deque<LoggingEvent> eventBuffer;
  private boolean closed = false;

  @Override
  public synchronized void activateOptions() {
    if (maxEvents > 0) {
      this.eventBuffer = new ArrayDeque<>();
    }
    setFile(new File(this.containerLogDir, containerLogFile).toString());
    setAppend(true);
    super.activateOptions();
  }

  @Override
  public synchronized void append(LoggingEvent event) {
    if (closed) {
      return;
    }
    if (eventBuffer != null) {
      if (eventBuffer.size() == maxEvents) {
        eventBuffer.removeFirst();
      }
      eventBuffer.addLast(event);
    } else {
      super.append(event);
    }
  }

  @Override
  public void flush() {
    if (qw != null) {
      qw.flush();
    }
  }

  @Override
  public synchronized void close() {
    if (!closed) {
      closed = true;
      if (eventBuffer != null) {
        for (LoggingEvent event : eventBuffer) {
          super.append(event);
        }
        // let garbage collection do its work
        eventBuffer = null;
      }
      super.close();
    }
  }

  /**
   * Getter/Setter methods for log4j.
   *
   * @return containerLogDir.
   */
  public String getContainerLogDir() {
    return this.containerLogDir;
  }

  public void setContainerLogDir(String containerLogDir) {
    this.containerLogDir = containerLogDir;
  }

  public String getContainerLogFile() {
    return containerLogFile;
  }

  public void setContainerLogFile(String containerLogFile) {
    this.containerLogFile = containerLogFile;
  }

  private static final long EVENT_SIZE = 100;

  public long getTotalLogFileSize() {
    return maxEvents * EVENT_SIZE;
  }

  /**
   *  Setter so that log4j can configure it from the
   *  configuration(log4j.properties).
   *
   * @param logSize log size.
   */
  public void setTotalLogFileSize(long logSize) {
    maxEvents = (int)(logSize / EVENT_SIZE);
  }
}
