/*
    * 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.chukwa.datacollection.adaptor.filetailer;
  
  import java.io.IOException;
  import java.io.RandomAccessFile;
  import java.io.File;
  import org.apache.hadoop.chukwa.datacollection.adaptor.*;
  
  /**
   * An adaptor that repeatedly tails a specified file, sending the new bytes.
   * This class does not split out records, but just sends everything up to end of
   * file. Subclasses can alter this behavior by overriding extractRecords().
   * 
   */
  public class FileTailingAdaptor extends LWFTAdaptor {
  
  
    public static int MAX_RETRIES = 300;
    static int GRACEFUL_PERIOD = 3 * 60 * 1000; // 3 minutes
  
    private int attempts = 0;
    private long gracefulPeriodExpired = 0l;
    private boolean adaptorInError = false;
  
    protected RandomAccessFile reader = null;
  
    public void start(long bytes) {
      super.start(bytes);
      log.info("chukwaAgent.fileTailingAdaptor.maxReadSize: " + MAX_READ_SIZE);
      this.attempts = 0;
  
      log.info("started file tailer " + adaptorID +  "  on file " + toWatch
          + " with first byte at offset " + offsetOfFirstByte);
    }
   
    
    @Override
    public long shutdown(AdaptorShutdownPolicy shutdownPolicy) {
      
      log.info("Enter Shutdown:" + shutdownPolicy.name() + " - ObjectId:" + this);
      
      switch(shutdownPolicy) {
        case GRACEFULLY : 
        case WAIT_TILL_FINISHED :{
          if (toWatch.exists()) {
            int retry = 0;
            tailer.stopWatchingFile(this);
            TerminatorThread lastTail = new TerminatorThread(this);
            lastTail.setDaemon(true);
            lastTail.start();
            
            if (shutdownPolicy.ordinal() == AdaptorShutdownPolicy.GRACEFULLY.ordinal()) {
              while (lastTail.isAlive() && retry < 60) {
                try {
                  log.info("GRACEFULLY Retry:" + retry);
                  Thread.sleep(1000);
                  retry++;
                } catch (InterruptedException ex) {
                }
              }
            } else {
              while (lastTail.isAlive()) {
                try {
                  if (retry%100 == 0) {
                    log.info("WAIT_TILL_FINISHED Retry:" + retry);
                  }
                  Thread.sleep(1000);
                  retry++;
                } catch (InterruptedException ex) {
                }
              } 
            }          
          }
        }
        break;
        
        case HARD_STOP:
        default:
          tailer.stopWatchingFile(this);
          try {
            if (reader != null) {
              reader.close();
           }
           reader = null;
         } catch(Throwable e) {
          log.warn("Exception while closing reader:",e);
         }
         break;
     }
     log.info("Exit Shutdown:" + shutdownPolicy.name()+ " - ObjectId:" + this);
     return fileReadOffset + offsetOfFirstByte;
   }
   
 
   /**
    * Looks at the tail of the associated file, adds some of it to event queue
    * This method is not thread safe. Returns true if there's more data in the
    * file
    * 
    */
   @Override
   public boolean tailFile()
       throws InterruptedException {
     boolean hasMoreData = false;
 
     try {
       if ((adaptorInError == true)
           && (System.currentTimeMillis() > gracefulPeriodExpired)) {
         if (!toWatch.exists()) {
           log.warn("Adaptor|" + adaptorID + "|attempts=" + attempts
               + "| File does not exist: " + toWatch.getAbsolutePath()
               + ", streaming policy expired.  File removed from streaming.");
         } else if (!toWatch.canRead()) {
           log.warn("Adaptor|" + adaptorID + "|attempts=" + attempts
               + "| File cannot be read: " + toWatch.getAbsolutePath()
               + ", streaming policy expired.  File removed from streaming.");
         } else {
           // Should have never been there
           adaptorInError = false;
           gracefulPeriodExpired = 0L;
           attempts = 0;
           return false;
         }
 
         deregisterAndStop();
         return false;
       } else if (!toWatch.exists() || !toWatch.canRead()) {
         if (adaptorInError == false) {
           long now = System.currentTimeMillis();
           gracefulPeriodExpired = now + GRACEFUL_PERIOD;
           adaptorInError = true;
           attempts = 0;
           log.warn("failed to stream data for: " + toWatch.getAbsolutePath()
               + ", graceful period will Expire at now:" + now + " + "
               + GRACEFUL_PERIOD + " secs, i.e:" + gracefulPeriodExpired);
         } else if (attempts % 10 == 0) {
           log.info("failed to stream data for: " + toWatch.getAbsolutePath()
               + ", attempt: " + attempts);
         }
 
         attempts++;
         return false; // no more data
       }
 
       if (reader == null) {
         reader = new RandomAccessFile(toWatch, "r");
         log.info("Adaptor|" + adaptorID
             + "|Opening the file for the first time|seek|" + fileReadOffset);
       }
 
       long len = 0L;
       try {
         len = reader.length();
         if (lastSlurpTime == 0) {
           lastSlurpTime = System.currentTimeMillis();
         }
         if (offsetOfFirstByte > fileReadOffset) {
           // If the file rotated, the recorded offsetOfFirstByte is greater than
           // file size,reset the first byte position to beginning of the file.
           fileReadOffset = 0;
           offsetOfFirstByte = 0L;
           log.warn("offsetOfFirstByte>fileReadOffset, resetting offset to 0");
         }
         if (len == fileReadOffset) {
           File fixedNameFile = new File(toWatch.getAbsolutePath());
           long fixedNameLastModified = fixedNameFile.lastModified();
           if (fixedNameLastModified > lastSlurpTime) {
             // If len == fileReadOffset,the file stops rolling log or the file
             // has rotated.
             // But fixedNameLastModified > lastSlurpTime , this means after the
             // last slurping,the file has been written ,
             // so the file has been rotated.
             boolean hasLeftData = true;
             while (hasLeftData) {// read the possiblly generated log
               hasLeftData = slurp(len, reader);
             }
             RandomAccessFile newReader = new RandomAccessFile(toWatch, "r");
             if (reader != null) {
               reader.close();
             }
             reader = newReader;
             fileReadOffset = 0L;
             len = reader.length();
             log.debug("Adaptor|" + adaptorID 
                 + "| File size mismatched, rotating: " 
                 + toWatch.getAbsolutePath());
             hasMoreData = slurp(len, reader);
           } 
         } else if (len < fileReadOffset) {
           // file has rotated and no detection
           if (reader != null) {
             reader.close();
           }
           reader = null;
           fileReadOffset = 0L;
           offsetOfFirstByte = 0L;
           hasMoreData = true;
           log.warn("Adaptor|" + adaptorID + "| file: " + toWatch.getPath() 
               + ", has rotated and no detection - reset counters to 0L");
         } else {
           hasMoreData = slurp(len, reader);
         }
       } catch (IOException e) {
         // do nothing, if file doesn't exist.
       }       
     } catch (IOException e) {
       log.warn("failure reading " + toWatch, e);
     }
     attempts = 0;
     adaptorInError = false;
     return hasMoreData;
   }
 
 
 }