【Flume】flume ng中HDFS sink设置按天滚动，0点滚动文件，修改源码实现

HDFS sink里有个属性hdfs.rollInterval=86400，这个属性你设置了24小时滚动一次，它的确就到了24小时才滚动，但是我们的需求往往是到了0点就滚动文件了，因为离线的job因为都会放在夜里执行。

如果flume是早上9点启动的，那么要到明天早上9点，hdfs的文件才会关闭，难道job要等到9点后才执行，这显然不合适，所以通过修改源码使其能够在0点滚动文件。

首先添加一个属性，可配置为day，hour，min

只需修改一个文件：具体修改内容，请自行比较

/**
 * 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.flume.sink.hdfs;

import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.Date;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.TimeZone;
import java.util.Map.Entry;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicReference;

import com.google.common.annotations.VisibleForTesting;

import org.apache.flume.Channel;
import org.apache.flume.Clock;
import org.apache.flume.Context;
import org.apache.flume.Event;
import org.apache.flume.EventDeliveryException;
import org.apache.flume.SystemClock;
import org.apache.flume.Transaction;
import org.apache.flume.conf.Configurable;
import org.apache.flume.formatter.output.BucketPath;
import org.apache.flume.instrumentation.SinkCounter;
import org.apache.flume.sink.AbstractSink;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.io.SequenceFile.CompressionType;
import org.apache.hadoop.io.compress.CompressionCodec;
import org.apache.hadoop.io.compress.CompressionCodecFactory;
import org.apache.hadoop.security.SecurityUtil;
import org.apache.hadoop.security.UserGroupInformation;
import org.apache.hadoop.security.UserGroupInformation.AuthenticationMethod;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.google.common.base.Preconditions;
import com.google.common.collect.Lists;
import com.google.common.util.concurrent.ThreadFactoryBuilder;

public class HDFSEventSink extends AbstractSink implements Configurable {
	public interface WriterCallback {
		public void run(String filePath);
	}

	private static final Logger LOG = LoggerFactory.getLogger(HDFSEventSink.class);

	private static String DIRECTORY_DELIMITER = System.getProperty("file.separator");

	private static final long defaultRollInterval = 30;
	private static final long defaultRollSize = 1024;
	private static final long defaultRollCount = 10;
	private static final String defaultFileName = "FlumeData";
	private static final String defaultSuffix = "";
	private static final String defaultInUsePrefix = "";
	private static final String defaultInUseSuffix = ".tmp";
	private static final long defaultBatchSize = 100;
	private static final String defaultFileType = HDFSWriterFactory.SequenceFileType;
	private static final int defaultMaxOpenFiles = 5000;
	// Time between close retries, in seconds
	private static final long defaultRetryInterval = 180;
	// Retry forever.
	private static final int defaultTryCount = Integer.MAX_VALUE;

	/**
	 * Default length of time we wait for blocking BucketWriter calls before
	 * timing out the operation. Intended to prevent server hangs.
	 */
	private static final long defaultCallTimeout = 10000;
	/**
	 * Default number of threads available for tasks such as
	 * append/open/close/flush with hdfs. These tasks are done in a separate
	 * thread in the case that they take too long. In which case we create a new
	 * file and move on.
	 */
	private static final int defaultThreadPoolSize = 10;
	private static final int defaultRollTimerPoolSize = 1;

	/**
	 * Singleton credential manager that manages static credentials for the
	 * entire JVM
	 */
	private static final AtomicReference staticLogin = new AtomicReference();

	private final HDFSWriterFactory writerFactory;
	private WriterLinkedHashMap sfWriters;

	private long rollInterval;
	private long rollSize;
	private long rollCount;
	private long batchSize;
	private int threadsPoolSize;
	private int rollTimerPoolSize;
	private CompressionCodec codeC;
	private CompressionType compType;
	private String fileType;
	private String filePath;
	private String fileName;
	private String suffix;
	private String inUsePrefix;
	private String inUseSuffix;
	private TimeZone timeZone;
	private int maxOpenFiles;
	private ExecutorService callTimeoutPool;
	private ScheduledExecutorService timedRollerPool;

	private String kerbConfPrincipal;
	private String kerbKeytab;
	private String proxyUserName;
	private UserGroupInformation proxyTicket;

	private boolean needRounding = false;
	private int roundUnit = Calendar.SECOND;
	private int roundValue = 1;
	private boolean useLocalTime = false;

	private long callTimeout;
	private Context context;
	private SinkCounter sinkCounter;

	private volatile int idleTimeout;
	private Clock clock;
	private FileSystem mockFs;
	private HDFSWriter mockWriter;
	private final Object sfWritersLock = new Object();
	private long retryInterval;
	private int tryCount;

	private String timeRollerFlag;

	private static Date fileOpenTime = new Date();
	private Calendar calendar = Calendar.getInstance();
	private int lastDayOfYear;
	private int lastYear;
	private int lastHour;
	private int lastMin;
	private int nowDayOfYear;
	private int nowYear;
	private int nowHour;
	private int nowMin;

	private int sfWritersMapSize = 0;
	
	/*
	 * Extended Java LinkedHashMap for open file handle LRU queue. We want to
	 * clear the oldest file handle if there are too many open ones.
	 */
	private static class WriterLinkedHashMap extends LinkedHashMap {

		private final int maxOpenFiles;

		public WriterLinkedHashMap(int maxOpenFiles) {
			super(16, 0.75f, true); // stock initial capacity/load, access
									// ordering
			this.maxOpenFiles = maxOpenFiles;
		}

		@Override
		protected boolean removeEldestEntry(Entry eldest) {
			if (size() > maxOpenFiles) {
				// If we have more that max open files, then close the last one
				// and
				// return true
				try {
					eldest.getValue().close();
				} catch (IOException e) {
					LOG.warn(eldest.getKey().toString(), e);
				} catch (InterruptedException e) {
					LOG.warn(eldest.getKey().toString(), e);
					Thread.currentThread().interrupt();
				}
				return true;
			} else {
				return false;
			}
		}
	}

	public HDFSEventSink() {
		this(new HDFSWriterFactory());
	}

	public HDFSEventSink(HDFSWriterFactory writerFactory) {
		this.writerFactory = writerFactory;
	}

	@VisibleForTesting
	Map getSfWriters() {
		return sfWriters;
	}

	// read configuration and setup thresholds
	@Override
	public void configure(Context context) {
		this.context = context;

		filePath = Preconditions.checkNotNull(context.getString("hdfs.path"),
				"hdfs.path is required");
		fileName = context.getString("hdfs.filePrefix", defaultFileName);
		this.suffix = context.getString("hdfs.fileSuffix", defaultSuffix);
		inUsePrefix = context.getString("hdfs.inUsePrefix", defaultInUsePrefix);
		inUseSuffix = context.getString("hdfs.inUseSuffix", defaultInUseSuffix);
		String tzName = context.getString("hdfs.timeZone");
		timeZone = tzName == null ? null : TimeZone.getTimeZone(tzName);
		rollInterval = context.getLong("hdfs.rollInterval", defaultRollInterval);
		rollSize = context.getLong("hdfs.rollSize", defaultRollSize);
		rollCount = context.getLong("hdfs.rollCount", defaultRollCount);
		batchSize = context.getLong("hdfs.batchSize", defaultBatchSize);
		idleTimeout = context.getInteger("hdfs.idleTimeout", 0);
		String codecName = context.getString("hdfs.codeC");
		fileType = context.getString("hdfs.fileType", defaultFileType);
		maxOpenFiles = context.getInteger("hdfs.maxOpenFiles", defaultMaxOpenFiles);
		callTimeout = context.getLong("hdfs.callTimeout", defaultCallTimeout);
		threadsPoolSize = context.getInteger("hdfs.threadsPoolSize", defaultThreadPoolSize);
		rollTimerPoolSize = context.getInteger("hdfs.rollTimerPoolSize", defaultRollTimerPoolSize);
		kerbConfPrincipal = context.getString("hdfs.kerberosPrincipal", "");
		kerbKeytab = context.getString("hdfs.kerberosKeytab", "");
		proxyUserName = context.getString("hdfs.proxyUser", "");
		tryCount = context.getInteger("hdfs.closeTries", defaultTryCount);
		timeRollerFlag = context.getString("hdfs.timeroller.flag",
				Constants.defaultTimeRollerFlagDay);
		if (tryCount <= 0) {
			LOG.warn("Retry count value : " + tryCount + " is not "
					+ "valid. The sink will try to close the file until the file "
					+ "is eventually closed.");
			tryCount = defaultTryCount;
		}
		retryInterval = context.getLong("hdfs.retryInterval", defaultRetryInterval);
		if (retryInterval <= 0) {
			LOG.warn("Retry Interval value: " + retryInterval + " is not "
					+ "valid. If the first close of a file fails, "
					+ "it may remain open and will not be renamed.");
			tryCount = 1;
		}

		Preconditions.checkArgument(batchSize > 0, "batchSize must be greater than 0");
		if (codecName == null) {
			codeC = null;
			compType = CompressionType.NONE;
		} else {
			codeC = getCodec(codecName);
			// TODO : set proper compression type
			compType = CompressionType.BLOCK;
		}

		// Do not allow user to set fileType DataStream with codeC together
		// To prevent output file with compress extension (like .snappy)
		if (fileType.equalsIgnoreCase(HDFSWriterFactory.DataStreamType) && codecName != null) {
			throw new IllegalArgumentException("fileType: " + fileType
					+ " which does NOT support compressed output. Please don't set codeC"
					+ " or change the fileType if compressed output is desired.");
		}

		if (fileType.equalsIgnoreCase(HDFSWriterFactory.CompStreamType)) {
			Preconditions.checkNotNull(codeC, "It's essential to set compress codec"
					+ " when fileType is: " + fileType);
		}

		if (!authenticate()) {
			LOG.error("Failed to authenticate!");
		}
		needRounding = context.getBoolean("hdfs.round", false);

		if (needRounding) {
			String unit = context.getString("hdfs.roundUnit", "second");
			if (unit.equalsIgnoreCase("hour")) {
				this.roundUnit = Calendar.HOUR_OF_DAY;
			} else if (unit.equalsIgnoreCase("minute")) {
				this.roundUnit = Calendar.MINUTE;
			} else if (unit.equalsIgnoreCase("second")) {
				this.roundUnit = Calendar.SECOND;
			} else {
				LOG.warn("Rounding unit is not valid, please set one of"
						+ "minute, hour, or second. Rounding will be disabled");
				needRounding = false;
			}
			this.roundValue = context.getInteger("hdfs.roundValue", 1);
			if (roundUnit == Calendar.SECOND || roundUnit == Calendar.MINUTE) {
				Preconditions.checkArgument(roundValue > 0 && roundValue <= 60, "Round value"
						+ "must be > 0 and <= 60");
			} else if (roundUnit == Calendar.HOUR_OF_DAY) {
				Preconditions.checkArgument(roundValue > 0 && roundValue <= 24, "Round value"
						+ "must be > 0 and <= 24");
			}
		}

		this.useLocalTime = context.getBoolean("hdfs.useLocalTimeStamp", false);
		if (useLocalTime) {
			clock = new SystemClock();
		}

		if (sinkCounter == null) {
			sinkCounter = new SinkCounter(getName());
		}
	}

	private static boolean codecMatches(Class cls, String codecName) {
		String simpleName = cls.getSimpleName();
		if (cls.getName().equals(codecName) || simpleName.equalsIgnoreCase(codecName)) {
			return true;
		}
		if (simpleName.endsWith("Codec")) {
			String prefix = simpleName.substring(0, simpleName.length() - "Codec".length());
			if (prefix.equalsIgnoreCase(codecName)) {
				return true;
			}
		}
		return false;
	}

	@VisibleForTesting
	static CompressionCodec getCodec(String codecName) {
		Configuration conf = new Configuration();
		List> codecs = CompressionCodecFactory
				.getCodecClasses(conf);
		// Wish we could base this on DefaultCodec but appears not all codec's
		// extend DefaultCodec(Lzo)
		CompressionCodec codec = null;
		ArrayList codecStrs = new ArrayList();
		codecStrs.add("None");
		for (Class cls : codecs) {
			codecStrs.add(cls.getSimpleName());
			if (codecMatches(cls, codecName)) {
				try {
					codec = cls.newInstance();
				} catch (InstantiationException e) {
					LOG.error("Unable to instantiate " + cls + " class");
				} catch (IllegalAccessException e) {
					LOG.error("Unable to access " + cls + " class");
				}
			}
		}

		if (codec == null) {
			if (!codecName.equalsIgnoreCase("None")) {
				throw new IllegalArgumentException("Unsupported compression codec " + codecName
						+ ".  Please choose from: " + codecStrs);
			}
		} else if (codec instanceof org.apache.hadoop.conf.Configurable) {
			// Must check instanceof codec as BZip2Codec doesn't inherit
			// Configurable
			// Must set the configuration for Configurable objects that may or
			// do use
			// native libs
			((org.apache.hadoop.conf.Configurable) codec).setConf(conf);
		}
		return codec;
	}

	private void closeNowFile() {
		for (Entry entry : sfWriters.entrySet()) {
			String file = entry.getKey();
			LOG.info("Closing {}", file);

			try {
				entry.getValue().close();
				sfWriters.remove(file);
			} catch (Exception ex) {
				LOG.warn("Exception while closing " + entry.getKey() + ". " + "Exception follows.",
						ex);
				if (ex instanceof InterruptedException) {
					Thread.currentThread().interrupt();
				}
			}
		}
	}

	/**
	 * Pull events out of channel and send it to HDFS. Take at most batchSize
	 * events per Transaction. Find the corresponding bucket for the event.
	 * Ensure the file is open. Serialize the data and write it to the file on
	 * HDFS. 

	 * This method is not thread safe.
	 */
	public Status process() throws EventDeliveryException {
		sfWritersMapSize = sfWriters.size();
		if(sfWritersMapSize>0) {
			if(LOG.isDebugEnabled()) {
				LOG.debug("##############HDFS sink process() method");
				LOG.debug("The sfWriters Map size is {},need to judge whether to roll or not",sfWritersMapSize);
			}
			calendar.setTime(fileOpenTime);
			lastDayOfYear = calendar.get(Calendar.DAY_OF_YEAR);
			lastYear = calendar.get(Calendar.YEAR);
			lastHour = calendar.get(Calendar.HOUR_OF_DAY);
			lastMin = calendar.get(Calendar.MINUTE);
			Date now = new Date();
			calendar.setTime(now);
			nowDayOfYear = calendar.get(Calendar.DAY_OF_YEAR);
			nowYear = calendar.get(Calendar.YEAR);
			nowHour = calendar.get(Calendar.HOUR_OF_DAY);
			nowMin = calendar.get(Calendar.MINUTE);
			LOG.debug("fileOpenTime = {},nowTime = {}", JodaTimeUtil.parseToString(fileOpenTime,
					JodaTimeUtil.FORMAT_FULL_DATE_TIME_WITH_SYMBOL), JodaTimeUtil.parseToString(now,
					JodaTimeUtil.FORMAT_FULL_DATE_TIME_WITH_SYMBOL));

			// 年份相同，日期+1，年份+1，now日期=1
			boolean condition1 = (lastYear == nowYear && (nowDayOfYear == (lastDayOfYear + 1)))
					|| (nowYear == (lastYear + 1) && nowDayOfYear == 1);
			// day相同，小时+1，或者day不同，小时=0
			boolean condition2 = (lastDayOfYear == nowDayOfYear && nowHour == (lastHour + 1))
					|| (lastDayOfYear != nowDayOfYear && nowHour == 0);
			// hour相同，分钟+1，或者hour不同，分钟=0
			boolean condition3 = (lastHour == nowHour && nowMin == (lastMin + 1))
					|| (lastHour != nowHour && nowMin == 0);
			// 判断滚动标识
			if (timeRollerFlag.equals(Constants.defaultTimeRollerFlagDay)) {
				if (condition1) {
					LOG.info("rollflag = {},rolling", Constants.defaultTimeRollerFlagDay);
					closeNowFile();
				}
			} else if (timeRollerFlag.equals(Constants.timeRollerFlagHour)) {
				if (condition2) {
					LOG.info("rollflag = {},rolling", Constants.timeRollerFlagHour);
					closeNowFile();
				}
			} else if (timeRollerFlag.equals(Constants.timeRollerFlagMin)) {
				if (condition3) {
					LOG.info("rollflag = {},rolling", Constants.timeRollerFlagMin);
					closeNowFile();
				}
			}
		}

		Channel channel = getChannel();
		Transaction transaction = channel.getTransaction();
		List writers = Lists.newArrayList();
		transaction.begin();
		try {
			int txnEventCount = 0;
			for (txnEventCount = 0; txnEventCount < batchSize; txnEventCount++) {
				Event event = channel.take();
				if (event == null) {
					break;
				}

				// reconstruct the path name by substituting place holders
				String realPath = BucketPath.escapeString(filePath, event.getHeaders(), timeZone,
						needRounding, roundUnit, roundValue, useLocalTime);
				String realName = BucketPath.escapeString(fileName, event.getHeaders(), timeZone,
						needRounding, roundUnit, roundValue, useLocalTime);

				String lookupPath = realPath + DIRECTORY_DELIMITER + realName;
				BucketWriter bucketWriter;
				HDFSWriter hdfsWriter = null;
				// Callback to remove the reference to the bucket writer from
				// the
				// sfWriters map so that all buffers used by the HDFS file
				// handles are garbage collected.
				WriterCallback closeCallback = new WriterCallback() {
					@Override
					public void run(String bucketPath) {
						LOG.info("Writer callback called.");
						synchronized (sfWritersLock) {
							sfWriters.remove(bucketPath);
						}
					}
				};
				synchronized (sfWritersLock) {
					bucketWriter = sfWriters.get(lookupPath);
					// we haven't seen this file yet, so open it and cache the
					// handle
					if (bucketWriter == null) {
						hdfsWriter = writerFactory.getWriter(fileType);
						bucketWriter = initializeBucketWriter(realPath, realName, lookupPath,
								hdfsWriter, closeCallback);
						// when open the file in hdfs with
						// inUseSuffix,instantiate the
						// fileOpenTime
						fileOpenTime = new Date();
						sfWriters.put(lookupPath, bucketWriter);
					}
				}

				// track the buckets getting written in this transaction
				if (!writers.contains(bucketWriter)) {
					writers.add(bucketWriter);
				}

				// Write the data to HDFS
				try {
					bucketWriter.append(event);
				} catch (BucketClosedException ex) {
					LOG.info("Bucket was closed while trying to append, "
							+ "reinitializing bucket and writing event.");
					hdfsWriter = writerFactory.getWriter(fileType);
					bucketWriter = initializeBucketWriter(realPath, realName, lookupPath,
							hdfsWriter, closeCallback);
					synchronized (sfWritersLock) {
						sfWriters.put(lookupPath, bucketWriter);
					}
					bucketWriter.append(event);
				}
			}

			if (txnEventCount == 0) {
				sinkCounter.incrementBatchEmptyCount();
			} else if (txnEventCount == batchSize) {
				sinkCounter.incrementBatchCompleteCount();
			} else {
				sinkCounter.incrementBatchUnderflowCount();
			}

			// flush all pending buckets before committing the transaction
			for (BucketWriter bucketWriter : writers) {
				bucketWriter.flush();
			}

			transaction.commit();

			if (txnEventCount < 1) {
				return Status.BACKOFF;
			} else {
				sinkCounter.addToEventDrainSuccessCount(txnEventCount);
				return Status.READY;
			}
		} catch (IOException eIO) {
			transaction.rollback();
			LOG.warn("HDFS IO error", eIO);
			return Status.BACKOFF;
		} catch (Throwable th) {
			transaction.rollback();
			LOG.error("process failed", th);
			if (th instanceof Error) {
				throw (Error) th;
			} else {
				throw new EventDeliveryException(th);
			}
		} finally {
			transaction.close();
		}
	}

	private BucketWriter initializeBucketWriter(String realPath, String realName,
			String lookupPath, HDFSWriter hdfsWriter, WriterCallback closeCallback) {
		BucketWriter bucketWriter = new BucketWriter(rollInterval, rollSize, rollCount, batchSize,
				context, realPath, realName, inUsePrefix, inUseSuffix, suffix, codeC, compType,
				hdfsWriter, timedRollerPool, proxyTicket, sinkCounter, idleTimeout, closeCallback,
				lookupPath, callTimeout, callTimeoutPool, retryInterval, tryCount);
		if (mockFs != null) {
			bucketWriter.setFileSystem(mockFs);
			bucketWriter.setMockStream(mockWriter);
		}
		return bucketWriter;
	}

	@Override
	public void stop() {
		// do not constrain close() calls with a timeout
		for (Entry entry : sfWriters.entrySet()) {
			LOG.info("Closing {}", entry.getKey());

			try {
				entry.getValue().close();
			} catch (Exception ex) {
				LOG.warn("Exception while closing " + entry.getKey() + ". " + "Exception follows.",
						ex);
				if (ex instanceof InterruptedException) {
					Thread.currentThread().interrupt();
				}
			}
		}

		// shut down all our thread pools
		ExecutorService toShutdown[] = { callTimeoutPool, timedRollerPool };
		for (ExecutorService execService : toShutdown) {
			execService.shutdown();
			try {
				while (execService.isTerminated() == false) {
					execService.awaitTermination(Math.max(defaultCallTimeout, callTimeout),
							TimeUnit.MILLISECONDS);
				}
			} catch (InterruptedException ex) {
				LOG.warn("shutdown interrupted on " + execService, ex);
			}
		}

		callTimeoutPool = null;
		timedRollerPool = null;

		sfWriters.clear();
		sfWriters = null;
		sinkCounter.stop();
		super.stop();
	}

	@Override
	public void start() {
		String timeoutName = "hdfs-" + getName() + "-call-runner-%d";
		callTimeoutPool = Executors.newFixedThreadPool(threadsPoolSize, new ThreadFactoryBuilder()
				.setNameFormat(timeoutName).build());

		String rollerName = "hdfs-" + getName() + "-roll-timer-%d";
		timedRollerPool = Executors.newScheduledThreadPool(rollTimerPoolSize,
				new ThreadFactoryBuilder().setNameFormat(rollerName).build());

		this.sfWriters = new WriterLinkedHashMap(maxOpenFiles);
		sinkCounter.start();
		super.start();
	}

	private boolean authenticate() {

		// logic for kerberos login
		boolean useSecurity = UserGroupInformation.isSecurityEnabled();

		LOG.info("Hadoop Security enabled: " + useSecurity);

		if (useSecurity) {

			// sanity checking
			if (kerbConfPrincipal.isEmpty()) {
				LOG.error("Hadoop running in secure mode, but Flume config doesn't "
						+ "specify a principal to use for Kerberos auth.");
				return false;
			}
			if (kerbKeytab.isEmpty()) {
				LOG.error("Hadoop running in secure mode, but Flume config doesn't "
						+ "specify a keytab to use for Kerberos auth.");
				return false;
			} else {
				// If keytab is specified, user should want it take effect.
				// HDFSEventSink will halt when keytab file is non-exist or
				// unreadable
				File kfile = new File(kerbKeytab);
				if (!(kfile.isFile() && kfile.canRead())) {
					throw new IllegalArgumentException("The keyTab file: " + kerbKeytab
							+ " is nonexistent or can't read. "
							+ "Please specify a readable keytab file for Kerberos auth.");
				}
			}

			String principal;
			try {
				// resolves _HOST pattern using standard Hadoop search/replace
				// via DNS lookup when 2nd argument is empty
				principal = SecurityUtil.getServerPrincipal(kerbConfPrincipal, "");
			} catch (IOException e) {
				LOG.error("Host lookup error resolving kerberos principal (" + kerbConfPrincipal
						+ "). Exception follows.", e);
				return false;
			}

			Preconditions.checkNotNull(principal, "Principal must not be null");
			KerberosUser prevUser = staticLogin.get();
			KerberosUser newUser = new KerberosUser(principal, kerbKeytab);

			// be cruel and unusual when user tries to login as multiple
			// principals
			// this isn't really valid with a reconfigure but this should be
			// rare
			// enough to warrant a restart of the agent JVM
			// TODO: find a way to interrogate the entire current config state,
			// since we don't have to be unnecessarily protective if they switch
			// all
			// HDFS sinks to use a different principal all at once.
			Preconditions.checkState(prevUser == null || prevUser.equals(newUser),
					"Cannot use multiple kerberos principals in the same agent. "
							+ " Must restart agent to use new principal or keytab. "
							+ "Previous = %s, New = %s", prevUser, newUser);

			// attempt to use cached credential if the user is the same
			// this is polite and should avoid flooding the KDC with auth
			// requests
			UserGroupInformation curUser = null;
			if (prevUser != null && prevUser.equals(newUser)) {
				try {
					curUser = UserGroupInformation.getLoginUser();
				} catch (IOException e) {
					LOG.warn("User unexpectedly had no active login. Continuing with "
							+ "authentication", e);
				}
			}

			if (curUser == null || !curUser.getUserName().equals(principal)) {
				try {
					// static login
					kerberosLogin(this, principal, kerbKeytab);
				} catch (IOException e) {
					LOG.error("Authentication or file read error while attempting to "
							+ "login as kerberos principal (" + principal + ") using " + "keytab ("
							+ kerbKeytab + "). Exception follows.", e);
					return false;
				}
			} else {
				LOG.debug("{}: Using existing principal login: {}", this, curUser);
			}

			// we supposedly got through this unscathed... so store the static
			// user
			staticLogin.set(newUser);
		}

		// hadoop impersonation works with or without kerberos security
		proxyTicket = null;
		if (!proxyUserName.isEmpty()) {
			try {
				proxyTicket = UserGroupInformation.createProxyUser(proxyUserName,
						UserGroupInformation.getLoginUser());
			} catch (IOException e) {
				LOG.error("Unable to login as proxy user. Exception follows.", e);
				return false;
			}
		}

		UserGroupInformation ugi = null;
		if (proxyTicket != null) {
			ugi = proxyTicket;
		} else if (useSecurity) {
			try {
				ugi = UserGroupInformation.getLoginUser();
			} catch (IOException e) {
				LOG.error("Unexpected error: Unable to get authenticated user after "
						+ "apparent successful login! Exception follows.", e);
				return false;
			}
		}

		if (ugi != null) {
			// dump login information
			AuthenticationMethod authMethod = ugi.getAuthenticationMethod();
			LOG.info("Auth method: {}", authMethod);
			LOG.info(" User name: {}", ugi.getUserName());
			LOG.info(" Using keytab: {}", ugi.isFromKeytab());
			if (authMethod == AuthenticationMethod.PROXY) {
				UserGroupInformation superUser;
				try {
					superUser = UserGroupInformation.getLoginUser();
					LOG.info(" Superuser auth: {}", superUser.getAuthenticationMethod());
					LOG.info(" Superuser name: {}", superUser.getUserName());
					LOG.info(" Superuser using keytab: {}", superUser.isFromKeytab());
				} catch (IOException e) {
					LOG.error("Unexpected error: unknown superuser impersonating proxy.", e);
					return false;
				}
			}

			LOG.info("Logged in as user {}", ugi.getUserName());

			return true;
		}

		return true;
	}

	/**
	 * Static synchronized method for static Kerberos login. 

	 * Static synchronized due to a thundering herd problem when multiple Sinks
	 * attempt to log in using the same principal at the same time with the
	 * intention of impersonating different users (or even the same user). If
	 * this is not controlled, MIT Kerberos v5 believes it is seeing a replay
	 * attach and it returns: 
Request is a replay (34) -
	 * PROCESS_TGS
 In addition, since the underlying Hadoop APIs we
	 * are using for impersonation are static, we define this method as static
	 * as well.
	 *
	 * @param principal
	 *            Fully-qualified principal to use for authentication.
	 * @param keytab
	 *            Location of keytab file containing credentials for principal.
	 * @return Logged-in user
	 * @throws IOException
	 *             if login fails.
	 */
	private static synchronized UserGroupInformation kerberosLogin(HDFSEventSink sink,
			String principal, String keytab) throws IOException {

		// if we are the 2nd user thru the lock, the login should already be
		// available statically if login was successful
		UserGroupInformation curUser = null;
		try {
			curUser = UserGroupInformation.getLoginUser();
		} catch (IOException e) {
			// not a big deal but this shouldn't typically happen because it
			// will
			// generally fall back to the UNIX user
			LOG.debug("Unable to get login user before Kerberos auth attempt.", e);
		}

		// we already have logged in successfully
		if (curUser != null && curUser.getUserName().equals(principal)) {
			LOG.debug("{}: Using existing principal ({}): {}", new Object[] { sink, principal,
					curUser });

			// no principal found
		} else {

			LOG.info("{}: Attempting kerberos login as principal ({}) from keytab " + "file ({})",
					new Object[] { sink, principal, keytab });

			// attempt static kerberos login
			UserGroupInformation.loginUserFromKeytab(principal, keytab);
			curUser = UserGroupInformation.getLoginUser();
		}

		return curUser;
	}

	@Override
	public String toString() {
		return "{ Sink type:" + getClass().getSimpleName() + ", name:" + getName() + " }";
	}

	@VisibleForTesting
	void setBucketClock(Clock clock) {
		BucketPath.setClock(clock);
	}

	@VisibleForTesting
	void setMockFs(FileSystem mockFs) {
		this.mockFs = mockFs;
	}

	@VisibleForTesting
	void setMockWriter(HDFSWriter writer) {
		this.mockWriter = writer;
	}

	@VisibleForTesting
	int getTryCount() {
		return tryCount;
	}
}

望各位不吝指教！！