在很多情況下，我們為了不丟失資料，一般都會為資料收集端擴充套件斷點續傳，而隨著公司日誌系統的完善，我們在原有的基礎上開發了斷點續傳的功能，以下是思路，大家共同討論：

核心流程圖：

原始碼：

/*
 * 作者：許恕
 * 時間：2016年5月3日
 * 功能：實現tail 某目錄下的所有符合正則條件的檔案
 * Email：[email protected]
 * To detect all files in a folder
 */

package org.apache.flume.source;

import com.google.common.base.Preconditions;
import com.google.common.util.concurrent.ThreadFactoryBuilder;
import org.apache.flume.Context;
import org.apache.flume.Event;
import org.apache.flume.EventDrivenSource;
import org.apache.flume.SystemClock;
import org.apache.flume.channel.ChannelProcessor;
import org.apache.flume.conf.Configurable;
import org.apache.flume.event.EventBuilder;
import org.apache.flume.instrumentation.SourceCounter;
import org.apache.flume.tools.HostUtils;
import org.mortbay.util.ajax.JSON;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.*;
import java.nio.charset.Charset;
import java.util.*;
import java.util.concurrent.*;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 *  step：
 *    1,config one path
 *    2,find all file with RegExp
 *    3,tail one children file
 *    4,batch to channal
 *
 *  demo:
 *    demo.sources.s1.type = org.apache.flume.source.ExecTailSource
 *    demo.sources.s1.filepath=/export/home/tomcat/logs/auth.el.net/
 *    demo.sources.s1.filenameRegExp=(.log{1})$
 *    demo.sources.s1.tailing=true
 *    demo.sources.s1.readinterval=300
 *    demo.sources.s1.startAtBeginning=false
 *    demo.sources.s1.restart=true
 */
public class ExecTailSource extends AbstractSource implements EventDrivenSource,
Configurable {

  private static final Logger logger = LoggerFactory
      .getLogger(ExecTailSource.class);

  private SourceCounter sourceCounter;
  private ExecutorService executor;
  private List<ExecRunnable> listRuners;
  private List<Future<?>> listFuture;
  private long restartThrottle;
  private boolean restart = true;
  private boolean logStderr;
  private Integer bufferCount;
  private long batchTimeout;
  private Charset charset;
  private String filepath;
  private String filenameRegExp;
  private boolean tailing;
  private Integer readinterval;
  private boolean startAtBeginning;
  private boolean contextIsJson;
  private String fileWriteJson;
  private Long flushTime;
  private boolean contextIsFlumeLog;

  @Override
  public void start() {
    logger.info("=start=> flume tail source start begin time:"+new Date().toString());
    logger.info("ExecTail source starting with filepath:{}", filepath);

    List<String> listFiles = getFileList(filepath);
    if(listFiles==null || listFiles.isEmpty()){
      Preconditions.checkState(listFiles != null && !listFiles.isEmpty(),
              "The filepath's file not have fiels with filenameRegExp");
    }

    Properties prop=null;

    try{
      prop = new Properties();//屬性集合物件
      FileInputStream fis = new FileInputStream(fileWriteJson);//屬性檔案流
      prop.load(fis);
    }catch(Exception ex){
      logger.error("==>",ex);
    }



    executor = Executors.newFixedThreadPool(listFiles.size());

    listRuners = new ArrayList<ExecRunnable>();
    listFuture = new ArrayList<Future<?>>();

    logger.info("files size is {} ", listFiles.size());
    // FIXME: Use a callback-like executor / future to signal us upon failure.
    for(String oneFilePath : listFiles){
      ExecRunnable runner = new ExecRunnable(getChannelProcessor(), sourceCounter,
              restart, restartThrottle, logStderr, bufferCount, batchTimeout,
              charset,oneFilePath,tailing,readinterval,startAtBeginning,contextIsJson,
              prop,fileWriteJson,flushTime,contextIsFlumeLog);
      listRuners.add(runner);
      Future<?> runnerFuture = executor.submit(runner);
      listFuture.add(runnerFuture);
      logger.info("{} is begin running",oneFilePath);
    }

    /*
     * NB: This comes at the end rather than the beginning of the method because
     * it sets our state to running. We want to make sure the executor is alive
     * and well first.
     */
    sourceCounter.start();
    super.start();
    logger.info("=start=> flume tail source start end time:"+new Date().toString());
    logger.debug("ExecTail source started");
  }

  @Override
  public void stop() {

    logger.info("=stop=> flume tail source stop begin time:"+new Date().toString());
    if(listRuners !=null && !listRuners.isEmpty()){
      for(ExecRunnable oneRunner : listRuners){
        if(oneRunner != null) {
          oneRunner.setRestart(false);
          oneRunner.kill();
        }
      }
    }


    if(listFuture !=null && !listFuture.isEmpty()){
      for(Future<?> oneFuture : listFuture){
        if (oneFuture != null) {
          logger.debug("Stopping ExecTail runner");
          oneFuture.cancel(true);
          logger.debug("ExecTail runner stopped");
        }
      }
    }

    executor.shutdown();
    while (!executor.isTerminated()) {
      logger.debug("Waiting for ExecTail executor service to stop");
      try {
        executor.awaitTermination(500, TimeUnit.MILLISECONDS);
      } catch (InterruptedException e) {
        logger.debug("Interrupted while waiting for ExecTail executor service "
            + "to stop. Just exiting.");
        Thread.currentThread().interrupt();
      }
    }




    sourceCounter.stop();
    super.stop();
    logger.info("=stop=> flume tail source stop end time:"+new Date().toString());

  }

  @Override
  public void configure(Context context) {

    filepath = context.getString("filepath");
    Preconditions.checkState(filepath != null,
        "The parameter filepath must be specified");
    logger.info("The parameter filepath is {}" ,filepath);

    filenameRegExp = context.getString("filenameRegExp");
    Preconditions.checkState(filenameRegExp != null,
            "The parameter filenameRegExp must be specified");
    logger.info("The parameter filenameRegExp is {}" ,filenameRegExp);

    contextIsJson= context.getBoolean(ExecSourceConfigurationConstants.CONFIG_CONTEXTISJSON_THROTTLE,
            ExecSourceConfigurationConstants.DEFAULT_CONTEXTISJSON);

    contextIsFlumeLog=context.getBoolean(ExecSourceConfigurationConstants.CONFIG_CONTEXTISFLUMELOG_THROTTLE,
            ExecSourceConfigurationConstants.DEFAULT_CONTEXTISFLUMELOG);

    fileWriteJson= context.getString(ExecSourceConfigurationConstants.CONFIG_FILEWRITEJSON_THROTTLE,
            ExecSourceConfigurationConstants.DEFAULT_FILEWRITEJSON);

    flushTime= context.getLong(ExecSourceConfigurationConstants.CONFIG_FLUSHTIME_THROTTLE,
            ExecSourceConfigurationConstants.DEFAULT_FLUSHTIME);

    restartThrottle = context.getLong(ExecSourceConfigurationConstants.CONFIG_RESTART_THROTTLE,
        ExecSourceConfigurationConstants.DEFAULT_RESTART_THROTTLE);

    tailing = context.getBoolean(ExecSourceConfigurationConstants.CONFIG_TAILING_THROTTLE,
            ExecSourceConfigurationConstants.DEFAULT_ISTAILING_TRUE);

    readinterval=context.getInteger(ExecSourceConfigurationConstants.CONFIG_READINTERVAL_THROTTLE,
            ExecSourceConfigurationConstants.DEFAULT_READINTERVAL);

    startAtBeginning=context.getBoolean(ExecSourceConfigurationConstants.CONFIG_STARTATBEGINNING_THROTTLE,
            ExecSourceConfigurationConstants.DEFAULT_STARTATBEGINNING);

    restart = context.getBoolean(ExecSourceConfigurationConstants.CONFIG_RESTART,
        ExecSourceConfigurationConstants.DEFAULT_RESTART_TRUE);

    logStderr = context.getBoolean(ExecSourceConfigurationConstants.CONFIG_LOG_STDERR,
        ExecSourceConfigurationConstants.DEFAULT_LOG_STDERR);

    bufferCount = context.getInteger(ExecSourceConfigurationConstants.CONFIG_BATCH_SIZE,
        ExecSourceConfigurationConstants.DEFAULT_BATCH_SIZE);

    batchTimeout = context.getLong(ExecSourceConfigurationConstants.CONFIG_BATCH_TIME_OUT,
        ExecSourceConfigurationConstants.DEFAULT_BATCH_TIME_OUT);

    charset = Charset.forName(context.getString(ExecSourceConfigurationConstants.CHARSET,
        ExecSourceConfigurationConstants.DEFAULT_CHARSET));


    if (sourceCounter == null) {
      sourceCounter = new SourceCounter(getName());
    }
  }

  /**
   * 獲取指定路徑下的所有檔案列表
   *
   * @param dir 要查詢的目錄
   * @return
   */
  public  List<String> getFileList(String dir) {
    List<String> listFile = new ArrayList<String>();
    File dirFile = new File(dir);
    //如果不是目錄檔案，則直接返回
    if (dirFile.isDirectory()) {
      //獲得資料夾下的檔案列表，然後根據檔案型別分別處理
      File[] files = dirFile.listFiles();
      if (null != files && files.length > 0) {
        //根據時間排序
        Arrays.sort(files, new Comparator<File>() {
          public int compare(File f1, File f2) {
            return (int) (f1.lastModified() - f2.lastModified());
          }

          public boolean equals(Object obj) {
            return true;
          }
        });
        for (File file : files) {
          //如果不是目錄，直接新增
          if (!file.isDirectory()) {
            String oneFileName = file.getName();
            if(match(filenameRegExp,oneFileName)){
              listFile.add(file.getAbsolutePath());
              logger.info("filename:{} is pass",oneFileName);
            }
          } else {
            //對於目錄檔案，遞迴呼叫
            listFile.addAll(getFileList(file.getAbsolutePath()));
          }
        }
      }
    }else{
      logger.info("FilePath:{} is not Directory",dir);
    }
    return listFile;
  }

  /**
   * @param regex
   * 正則表示式字串
   * @param str
   * 要匹配的字串
   * @return 如果str 符合 regex的正則表示式格式,返回true, 否則返回 false;
   */
  private boolean match(String regex, String str) {
    Pattern pattern = Pattern.compile(regex);
    Matcher matcher = pattern.matcher(str);
   return matcher.find();
  }


  private static class ExecRunnable implements Runnable {

    public ExecRunnable( ChannelProcessor channelProcessor,
        SourceCounter sourceCounter, boolean restart, long restartThrottle,
        boolean logStderr, int bufferCount, long batchTimeout,
                         Charset charset, String filepath,
                         boolean tailing,Integer readinterval,
                         boolean startAtBeginning,boolean contextIsJson,
                         Properties prop,String fileWriteJson,Long flushTime,
                         boolean contextIsFlumeLog) {

      this.channelProcessor = channelProcessor;
      this.sourceCounter = sourceCounter;
      this.restartThrottle = restartThrottle;
      this.bufferCount = bufferCount;
      this.batchTimeout = batchTimeout;
      this.restart = restart;
      this.logStderr = logStderr;
      this.charset = charset;
      this.filepath=filepath;
      this.logfile=new File(filepath);
      this.tailing=tailing;
      this.readinterval=readinterval;
      this.startAtBeginning=startAtBeginning;
      this.contextIsJson=contextIsJson;
      this.prop = prop;
      this.fileWriteJson=fileWriteJson;
      this.flushTime=flushTime;
      this.contextIsFlumeLog=contextIsFlumeLog;
    }



    private final ChannelProcessor channelProcessor;
    private final SourceCounter sourceCounter;
    private volatile boolean restart;
    private final long restartThrottle;
    private final int bufferCount;
    private long batchTimeout;
    private final boolean logStderr;
    private final Charset charset;
    private SystemClock systemClock = new SystemClock();
    private Long lastPushToChannel = systemClock.currentTimeMillis();
    ScheduledExecutorService timedFlushService;
    ScheduledFuture<?> future;
    private String filepath;
    private boolean contextIsJson;
    private Properties prop;
    private long timepoint;
    private String fileWriteJson;
    private Long flushTime;

    /**
     * 當讀到檔案結尾後暫停的時間間隔
     */
    private long readinterval = 500;

    /**
     * 設定日誌檔案
     */
    private File logfile;

    /**
     * 設定是否從頭開始讀
     */
    private boolean startAtBeginning = false;

    /**
     * 設定tail執行標記
     */
    private boolean tailing = false;

    private boolean contextIsFlumeLog=false;

    private static String getDomain(String filePath){
      String[] strs = filePath.split("/");
      String domain ;
      domain=strs[strs.length-2];
      if(domain==null || domain.isEmpty()){
        domain=filePath;
      }
      return domain;
    }

    @Override
    public void run() {
      do {
        logger.info("=run=> flume tail source run start time:"+new Date().toString());
        timepoint=System.currentTimeMillis();
        Long filePointer = 0l;
        if (this.startAtBeginning) { //判斷是否從頭開始讀檔案
          filePointer = 0l;
        } else {
          if(prop!=null || prop.contains(filepath)){

            try {
              filePointer = Long.valueOf((String) prop.get(filepath));
             logger.info("=ExecRunnable.run=>filePointer get from  Properties");
            }catch (Exception ex){
              logger.error("=ExecRunnable.run=>",ex);
              logger.info("=ExecRunnable.run=> error filePointer get from file size");
            }
          }
          if(filePointer ==null){
            filePointer = this.logfile.length(); //指標標識從檔案的當前長度開始。
            logger.info("=ExecRunnable.run=>filePointer get from file size");
          }

        }

        final List<Event> eventList = new ArrayList<Event>();

        timedFlushService = Executors.newSingleThreadScheduledExecutor(
                new ThreadFactoryBuilder().setNameFormat(
                "timedFlushExecService" +
                Thread.currentThread().getId() + "-%d").build());
        RandomAccessFile randomAccessFile = null;
        try {

          randomAccessFile= new RandomAccessFile(logfile, "r"); //建立隨機讀寫檔案
          future = timedFlushService.scheduleWithFixedDelay(new Runnable() {
                                                              @Override
                                                              public void run() {
                                                                try {
                                                                  synchronized (eventList) {
                                                                    if(!eventList.isEmpty() && timeout()) {
                                                                      flushEventBatch(eventList);
                                                                    }
                                                                  }
                                                                } catch (Exception e) {
                                                                  logger.error("Exception occured when processing event batch", e);
                                                                  if(e instanceof InterruptedException) {
                                                                    Thread.currentThread().interrupt();
                                                                  }
                                                                }
                                                              }
                                                            },
                  batchTimeout, batchTimeout, TimeUnit.MILLISECONDS);

          while (this.tailing) {
            long fileLength = this.logfile.length();
            if (fileLength < filePointer) {
              randomAccessFile = new RandomAccessFile(logfile, "r");
              filePointer = 0l;
            }
            if (fileLength > filePointer) {
              randomAccessFile.seek(filePointer);
              String line = randomAccessFile.readLine();
              while (line != null) {

                //送channal
                synchronized (eventList) {
                  sourceCounter.incrementEventReceivedCount();


                  String bodyjson = "";
                  if (!contextIsJson) {
                    HashMap body = new HashMap();
                    body.put("context", line.toString());
                    body.put("filepath", filepath);
                    body.put("contextType", filepath);
                    body.put("created", System.currentTimeMillis());
                    body.put("localHostIp", HostUtils.getLocalHostIp());
                    body.put("localHostName", HostUtils.getLocalHostName());
                    body.put("domain", getDomain(filepath));
                    String context = line.toString();
                    if(contextIsFlumeLog){
                      body = ParseFlumeLog(context,body);
                    }
                    bodyjson = JSON.toString(body);
                    if(bodyjson.indexOf("{")>0){
                      bodyjson.substring(bodyjson.indexOf("{"),bodyjson.length()-1);
                    }
                  } else {
                    bodyjson = line.toString();
                  }

                  Event oneEvent = EventBuilder.withBody(bodyjson.getBytes(charset));
                  eventList.add(oneEvent);
                  if (eventList.size() >= bufferCount || timeout()) {
                    flushEventBatch(eventList);
                  }
                }

                //讀下一行
                line = randomAccessFile.readLine();
                try {
                  Long nowfilePointer = randomAccessFile.getFilePointer();
                  if (!nowfilePointer.equals(filePointer)) {
                    filePointer = nowfilePointer;
                    if (System.currentTimeMillis() - timepoint > flushTime) {
                      timepoint = System.currentTimeMillis();
                      prop.setProperty(filepath, filePointer.toString());
                      FileOutputStream fos = new FileOutputStream(fileWriteJson);
                      if (fos != null) {
                        prop.store(fos, "Update '" + filepath + "' value");
                      }
                      fos.close();

                    }
                  }
                }catch(Exception ex){
                  ex.printStackTrace();
                }
              }

            }
            Thread.sleep(this.readinterval);
          }

          synchronized (eventList) {
              if(!eventList.isEmpty()) {
                flushEventBatch(eventList);
              }
          }

        } catch (Exception e) {
          logger.error("Failed while running filpath: " + filepath, e);
          if(e instanceof InterruptedException) {
            Thread.currentThread().interrupt();
          }
        } finally {

          if(randomAccessFile!=null){
            try {
              randomAccessFile.close();
            } catch (IOException ex) {
              logger.error("Failed to close reader for ExecTail source", ex);
            }
          }

        }
        logger.info("=run=> flume tail source run restart:"+restart);
        if(restart) {
          logger.info("=run=> flume tail source run restart time:"+new Date().toString());
          logger.info("Restarting in {}ms", restartThrottle);
          try {
            Thread.sleep(restartThrottle);
          } catch (InterruptedException e) {
            Thread.currentThread().interrupt();
          }
        } else {
          logger.info("filepath [" + filepath + "] exited with restart[" + restart+"]");
        }
      } while(restart);
    }

    private void flushEventBatch(List<Event> eventList){
      channelProcessor.processEventBatch(eventList);
      sourceCounter.addToEventAcceptedCount(eventList.size());
      eventList.clear();
      lastPushToChannel = systemClock.currentTimeMillis();
    }

    private HashMap ParseFlumeLog(String log,HashMap logMap){
      String[] strLogs = log.split("\\|");
      logMap.put("className",strLogs[0]);
      logMap.put("methodName",strLogs[1]);
      logMap.put("level",strLogs[2]);
      logMap.put("treeId",strLogs[3]);
      logMap.put("requestId",strLogs[4]);
      logMap.put("transactionId",strLogs[5]);
      return logMap;
    }

    private boolean timeout(){
      return (systemClock.currentTimeMillis() - lastPushToChannel) >= batchTimeout;
    }

    private static String[] formulateShellCommand(String shell, String command) {
      String[] shellArgs = shell.split("\\s+");
      String[] result = new String[shellArgs.length + 1];
      System.arraycopy(shellArgs, 0, result, 0, shellArgs.length);
      result[shellArgs.length] = command;
      return result;
    }

    public int kill() {
      logger.info("=kill=> flume tail source kill start time:"+new Date().toString());
      this.tailing=false;
        synchronized (this.getClass()) {
          try {
            // Stop the Thread that flushes periodically
            if (future != null) {
              future.cancel(true);
            }

            if (timedFlushService != null) {
              timedFlushService.shutdown();
              while (!timedFlushService.isTerminated()) {
                try {
                  timedFlushService.awaitTermination(500, TimeUnit.MILLISECONDS);
                } catch (InterruptedException e) {
                  logger.debug("Interrupted while waiting for ExecTail executor service "
                          + "to stop. Just exiting.");
                  Thread.currentThread().interrupt();
                }
              }
            }
            logger.info("=kill=> flume tail source kill end time:" + new Date().toString());
            return Integer.MIN_VALUE;
          } catch (Exception ex) {
            logger.error("=kill=>", ex);
            Thread.currentThread().interrupt();
          }
        }
      logger.info("=kill=> flume tail source kill end time:"+new Date().toString());
      return Integer.MIN_VALUE / 2;
    }
    public void setRestart(boolean restart) {
      this.restart = restart;
    }
  }
  private static class StderrReader extends Thread {
    private BufferedReader input;
    private boolean logStderr;

    protected StderrReader(BufferedReader input, boolean logStderr) {
      this.input = input;
      this.logStderr = logStderr;
    }



    @Override
    public void run() {
      try {
        int i = 0;
        String line = null;
        while((line = input.readLine()) != null) {
          if(logStderr) {
            // There is no need to read 'line' with a charset
            // as we do not to propagate it.
            // It is in UTF-16 and would be printed in UTF-8 format.
            logger.info("StderrLogger[{}] = '{}'", ++i, line);
          }
        }
      } catch (IOException e) {
        logger.info("StderrLogger exiting", e);
      } finally {
        try {
          if(input != null) {
            input.close();
          }
        } catch (IOException ex) {
          logger.error("Failed to close stderr reader for ExecTail source", ex);
        }
      }
    }
  }
}
 

總結：

        這是初步的實現，通過多執行緒與file i/o 協作，在效率和實時性上，做平衡，實現一版簡單的斷點續傳，以前看似高大上的功能已經被破解一小部分，在討論中，實際還有結果的收集與去重和正確性驗證，加密，等，綜合成本考慮，這版簡單的，暫行，我們又為flume貢獻了一大功能，希望大家一起，將flume做的更完善！