View Javadoc

1   /**
2    * Licensed to the Apache Software Foundation (ASF) under one
3    * or more contributor license agreements.  See the NOTICE file
4    * distributed with this work for additional information
5    * regarding copyright ownership.  The ASF licenses this file
6    * to you under the Apache License, Version 2.0 (the
7    * "License"); you may not use this file except in compliance
8    * with the License.  You may obtain a copy of the License at
9    *
10   *     http://www.apache.org/licenses/LICENSE-2.0
11   *
12   * Unless required by applicable law or agreed to in writing, software
13   * distributed under the License is distributed on an "AS IS" BASIS,
14   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15   * See the License for the specific language governing permissions and
16   * limitations under the License.
17   */
18  
19  package org.apache.hadoop.hbase.snapshot;
20  
21  import java.io.BufferedInputStream;
22  import java.io.FileNotFoundException;
23  import java.io.DataInput;
24  import java.io.DataOutput;
25  import java.io.IOException;
26  import java.io.InputStream;
27  import java.util.ArrayList;
28  import java.util.Collections;
29  import java.util.Comparator;
30  import java.util.LinkedList;
31  import java.util.List;
32  import java.util.Random;
33  
34  import org.apache.commons.logging.Log;
35  import org.apache.commons.logging.LogFactory;
36  import org.apache.hadoop.hbase.classification.InterfaceAudience;
37  import org.apache.hadoop.hbase.classification.InterfaceStability;
38  import org.apache.hadoop.conf.Configuration;
39  import org.apache.hadoop.conf.Configured;
40  import org.apache.hadoop.fs.FSDataInputStream;
41  import org.apache.hadoop.fs.FSDataOutputStream;
42  import org.apache.hadoop.fs.FileChecksum;
43  import org.apache.hadoop.fs.FileStatus;
44  import org.apache.hadoop.fs.FileSystem;
45  import org.apache.hadoop.fs.FileUtil;
46  import org.apache.hadoop.fs.Path;
47  import org.apache.hadoop.fs.permission.FsPermission;
48  import org.apache.hadoop.hbase.TableName;
49  import org.apache.hadoop.hbase.HBaseConfiguration;
50  import org.apache.hadoop.hbase.HConstants;
51  import org.apache.hadoop.hbase.HRegionInfo;
52  import org.apache.hadoop.hbase.io.FileLink;
53  import org.apache.hadoop.hbase.io.HFileLink;
54  import org.apache.hadoop.hbase.io.WALLink;
55  import org.apache.hadoop.hbase.mapreduce.TableMapReduceUtil;
56  import org.apache.hadoop.hbase.protobuf.generated.HBaseProtos.SnapshotDescription;
57  import org.apache.hadoop.hbase.protobuf.generated.SnapshotProtos.SnapshotFileInfo;
58  import org.apache.hadoop.hbase.protobuf.generated.SnapshotProtos.SnapshotRegionManifest;
59  import org.apache.hadoop.hbase.util.FSUtils;
60  import org.apache.hadoop.hbase.util.Pair;
61  import org.apache.hadoop.io.BytesWritable;
62  import org.apache.hadoop.io.IOUtils;
63  import org.apache.hadoop.io.NullWritable;
64  import org.apache.hadoop.io.Writable;
65  import org.apache.hadoop.mapreduce.Job;
66  import org.apache.hadoop.mapreduce.JobContext;
67  import org.apache.hadoop.mapreduce.Mapper;
68  import org.apache.hadoop.mapreduce.InputFormat;
69  import org.apache.hadoop.mapreduce.InputSplit;
70  import org.apache.hadoop.mapreduce.RecordReader;
71  import org.apache.hadoop.mapreduce.TaskAttemptContext;
72  import org.apache.hadoop.mapreduce.lib.output.NullOutputFormat;
73  import org.apache.hadoop.mapreduce.security.TokenCache;
74  import org.apache.hadoop.hbase.io.hadoopbackport.ThrottledInputStream;
75  import org.apache.hadoop.util.StringUtils;
76  import org.apache.hadoop.util.Tool;
77  import org.apache.hadoop.util.ToolRunner;
78  
79  /**
80   * Export the specified snapshot to a given FileSystem.
81   *
82   * The .snapshot/name folder is copied to the destination cluster
83   * and then all the hfiles/wals are copied using a Map-Reduce Job in the .archive/ location.
84   * When everything is done, the second cluster can restore the snapshot.
85   */
86  @InterfaceAudience.Public
87  @InterfaceStability.Evolving
88  public class ExportSnapshot extends Configured implements Tool {
89    public static final String NAME = "exportsnapshot";
90    /** Configuration prefix for overrides for the source filesystem */
91    public static final String CONF_SOURCE_PREFIX = NAME + ".from.";
92    /** Configuration prefix for overrides for the destination filesystem */
93    public static final String CONF_DEST_PREFIX = NAME + ".to.";
94  
95    private static final Log LOG = LogFactory.getLog(ExportSnapshot.class);
96  
97    private static final String MR_NUM_MAPS = "mapreduce.job.maps";
98    private static final String CONF_NUM_SPLITS = "snapshot.export.format.splits";
99    private static final String CONF_SNAPSHOT_NAME = "snapshot.export.format.snapshot.name";
100   private static final String CONF_SNAPSHOT_DIR = "snapshot.export.format.snapshot.dir";
101   private static final String CONF_FILES_USER = "snapshot.export.files.attributes.user";
102   private static final String CONF_FILES_GROUP = "snapshot.export.files.attributes.group";
103   private static final String CONF_FILES_MODE = "snapshot.export.files.attributes.mode";
104   private static final String CONF_CHECKSUM_VERIFY = "snapshot.export.checksum.verify";
105   private static final String CONF_OUTPUT_ROOT = "snapshot.export.output.root";
106   private static final String CONF_INPUT_ROOT = "snapshot.export.input.root";
107   private static final String CONF_BUFFER_SIZE = "snapshot.export.buffer.size";
108   private static final String CONF_MAP_GROUP = "snapshot.export.default.map.group";
109   private static final String CONF_BANDWIDTH_MB = "snapshot.export.map.bandwidth.mb";
110   protected static final String CONF_SKIP_TMP = "snapshot.export.skip.tmp";
111 
112   static final String CONF_TEST_FAILURE = "test.snapshot.export.failure";
113   static final String CONF_TEST_RETRY = "test.snapshot.export.failure.retry";
114 
115   private static final String INPUT_FOLDER_PREFIX = "export-files.";
116 
117   // Export Map-Reduce Counters, to keep track of the progress
118   public enum Counter {
119     MISSING_FILES, FILES_COPIED, FILES_SKIPPED, COPY_FAILED,
120     BYTES_EXPECTED, BYTES_SKIPPED, BYTES_COPIED
121   }
122 
123   private static class ExportMapper extends Mapper<BytesWritable, NullWritable,
124                                                    NullWritable, NullWritable> {
125     final static int REPORT_SIZE = 1 * 1024 * 1024;
126     final static int BUFFER_SIZE = 64 * 1024;
127 
128     private boolean testFailures;
129     private Random random;
130 
131     private boolean verifyChecksum;
132     private String filesGroup;
133     private String filesUser;
134     private short filesMode;
135     private int bufferSize;
136 
137     private FileSystem outputFs;
138     private Path outputArchive;
139     private Path outputRoot;
140 
141     private FileSystem inputFs;
142     private Path inputArchive;
143     private Path inputRoot;
144 
145     @Override
146     public void setup(Context context) throws IOException {
147       Configuration conf = context.getConfiguration();
148       Configuration srcConf = HBaseConfiguration.createClusterConf(conf, null, CONF_SOURCE_PREFIX);
149       Configuration destConf = HBaseConfiguration.createClusterConf(conf, null, CONF_DEST_PREFIX);
150 
151       verifyChecksum = conf.getBoolean(CONF_CHECKSUM_VERIFY, true);
152 
153       filesGroup = conf.get(CONF_FILES_GROUP);
154       filesUser = conf.get(CONF_FILES_USER);
155       filesMode = (short)conf.getInt(CONF_FILES_MODE, 0);
156       outputRoot = new Path(conf.get(CONF_OUTPUT_ROOT));
157       inputRoot = new Path(conf.get(CONF_INPUT_ROOT));
158 
159       inputArchive = new Path(inputRoot, HConstants.HFILE_ARCHIVE_DIRECTORY);
160       outputArchive = new Path(outputRoot, HConstants.HFILE_ARCHIVE_DIRECTORY);
161 
162       testFailures = conf.getBoolean(CONF_TEST_FAILURE, false);
163 
164       try {
165         srcConf.setBoolean("fs." + inputRoot.toUri().getScheme() + ".impl.disable.cache", true);
166         inputFs = FileSystem.get(inputRoot.toUri(), srcConf);
167       } catch (IOException e) {
168         throw new IOException("Could not get the input FileSystem with root=" + inputRoot, e);
169       }
170 
171       try {
172         destConf.setBoolean("fs." + outputRoot.toUri().getScheme() + ".impl.disable.cache", true);
173         outputFs = FileSystem.get(outputRoot.toUri(), destConf);
174       } catch (IOException e) {
175         throw new IOException("Could not get the output FileSystem with root="+ outputRoot, e);
176       }
177 
178       // Use the default block size of the outputFs if bigger
179       int defaultBlockSize = Math.max((int) outputFs.getDefaultBlockSize(outputRoot), BUFFER_SIZE);
180       bufferSize = conf.getInt(CONF_BUFFER_SIZE, defaultBlockSize);
181       LOG.info("Using bufferSize=" + StringUtils.humanReadableInt(bufferSize));
182 
183       for (Counter c : Counter.values()) {
184         context.getCounter(c).increment(0);
185       }
186     }
187 
188     @Override
189     protected void cleanup(Context context) {
190       IOUtils.closeStream(inputFs);
191       IOUtils.closeStream(outputFs);
192     }
193 
194     @Override
195     public void map(BytesWritable key, NullWritable value, Context context)
196         throws InterruptedException, IOException {
197       SnapshotFileInfo inputInfo = SnapshotFileInfo.parseFrom(key.copyBytes());
198       Path outputPath = getOutputPath(inputInfo);
199 
200       copyFile(context, inputInfo, outputPath);
201     }
202 
203     /**
204      * Returns the location where the inputPath will be copied.
205      */
206     private Path getOutputPath(final SnapshotFileInfo inputInfo) throws IOException {
207       Path path = null;
208       switch (inputInfo.getType()) {
209         case HFILE:
210           Path inputPath = new Path(inputInfo.getHfile());
211           String family = inputPath.getParent().getName();
212           TableName table =HFileLink.getReferencedTableName(inputPath.getName());
213           String region = HFileLink.getReferencedRegionName(inputPath.getName());
214           String hfile = HFileLink.getReferencedHFileName(inputPath.getName());
215           path = new Path(FSUtils.getTableDir(new Path("./"), table),
216               new Path(region, new Path(family, hfile)));
217           break;
218         case WAL:
219           LOG.warn("snapshot does not keeps WALs: " + inputInfo);
220           break;
221         default:
222           throw new IOException("Invalid File Type: " + inputInfo.getType().toString());
223       }
224       return new Path(outputArchive, path);
225     }
226 
227     /*
228      * Used by TestExportSnapshot to simulate a failure
229      */
230     private void injectTestFailure(final Context context, final SnapshotFileInfo inputInfo)
231         throws IOException {
232       if (testFailures) {
233         if (context.getConfiguration().getBoolean(CONF_TEST_RETRY, false)) {
234           if (random == null) {
235             random = new Random();
236           }
237 
238           // FLAKY-TEST-WARN: lower is better, we can get some runs without the
239           // retry, but at least we reduce the number of test failures due to
240           // this test exception from the same map task.
241           if (random.nextFloat() < 0.03) {
242             throw new IOException("TEST RETRY FAILURE: Unable to copy input=" + inputInfo
243                                   + " time=" + System.currentTimeMillis());
244           }
245         } else {
246           context.getCounter(Counter.COPY_FAILED).increment(1);
247           throw new IOException("TEST FAILURE: Unable to copy input=" + inputInfo);
248         }
249       }
250     }
251 
252     private void copyFile(final Context context, final SnapshotFileInfo inputInfo,
253         final Path outputPath) throws IOException {
254       injectTestFailure(context, inputInfo);
255 
256       // Get the file information
257       FileStatus inputStat = getSourceFileStatus(context, inputInfo);
258 
259       // Verify if the output file exists and is the same that we want to copy
260       if (outputFs.exists(outputPath)) {
261         FileStatus outputStat = outputFs.getFileStatus(outputPath);
262         if (outputStat != null && sameFile(inputStat, outputStat)) {
263           LOG.info("Skip copy " + inputStat.getPath() + " to " + outputPath + ", same file.");
264           context.getCounter(Counter.FILES_SKIPPED).increment(1);
265           context.getCounter(Counter.BYTES_SKIPPED).increment(inputStat.getLen());
266           return;
267         }
268       }
269 
270       InputStream in = openSourceFile(context, inputInfo);
271       int bandwidthMB = context.getConfiguration().getInt(CONF_BANDWIDTH_MB, 100);
272       if (Integer.MAX_VALUE != bandwidthMB) {
273         in = new ThrottledInputStream(new BufferedInputStream(in), bandwidthMB * 1024L * 1024L);
274       }
275 
276       try {
277         context.getCounter(Counter.BYTES_EXPECTED).increment(inputStat.getLen());
278 
279         // Ensure that the output folder is there and copy the file
280         createOutputPath(outputPath.getParent());
281         FSDataOutputStream out = outputFs.create(outputPath, true);
282         try {
283           copyData(context, inputStat.getPath(), in, outputPath, out, inputStat.getLen());
284         } finally {
285           out.close();
286         }
287 
288         // Try to Preserve attributes
289         if (!preserveAttributes(outputPath, inputStat)) {
290           LOG.warn("You may have to run manually chown on: " + outputPath);
291         }
292       } finally {
293         in.close();
294       }
295     }
296 
297     /**
298      * Create the output folder and optionally set ownership.
299      */
300     private void createOutputPath(final Path path) throws IOException {
301       if (filesUser == null && filesGroup == null) {
302         outputFs.mkdirs(path);
303       } else {
304         Path parent = path.getParent();
305         if (!outputFs.exists(parent) && !parent.isRoot()) {
306           createOutputPath(parent);
307         }
308         outputFs.mkdirs(path);
309         if (filesUser != null || filesGroup != null) {
310           // override the owner when non-null user/group is specified
311           outputFs.setOwner(path, filesUser, filesGroup);
312         }
313         if (filesMode > 0) {
314           outputFs.setPermission(path, new FsPermission(filesMode));
315         }
316       }
317     }
318 
319     /**
320      * Try to Preserve the files attribute selected by the user copying them from the source file
321      * This is only required when you are exporting as a different user than "hbase" or on a system
322      * that doesn't have the "hbase" user.
323      *
324      * This is not considered a blocking failure since the user can force a chmod with the user
325      * that knows is available on the system.
326      */
327     private boolean preserveAttributes(final Path path, final FileStatus refStat) {
328       FileStatus stat;
329       try {
330         stat = outputFs.getFileStatus(path);
331       } catch (IOException e) {
332         LOG.warn("Unable to get the status for file=" + path);
333         return false;
334       }
335 
336       try {
337         if (filesMode > 0 && stat.getPermission().toShort() != filesMode) {
338           outputFs.setPermission(path, new FsPermission(filesMode));
339         } else if (refStat != null && !stat.getPermission().equals(refStat.getPermission())) {
340           outputFs.setPermission(path, refStat.getPermission());
341         }
342       } catch (IOException e) {
343         LOG.warn("Unable to set the permission for file="+ stat.getPath() +": "+ e.getMessage());
344         return false;
345       }
346 
347       boolean hasRefStat = (refStat != null);
348       String user = stringIsNotEmpty(filesUser) || !hasRefStat ? filesUser : refStat.getOwner();
349       String group = stringIsNotEmpty(filesGroup) || !hasRefStat ? filesGroup : refStat.getGroup();
350       if (stringIsNotEmpty(user) || stringIsNotEmpty(group)) {
351         try {
352           if (!(user.equals(stat.getOwner()) && group.equals(stat.getGroup()))) {
353             outputFs.setOwner(path, user, group);
354           }
355         } catch (IOException e) {
356           LOG.warn("Unable to set the owner/group for file="+ stat.getPath() +": "+ e.getMessage());
357           LOG.warn("The user/group may not exist on the destination cluster: user=" +
358                    user + " group=" + group);
359           return false;
360         }
361       }
362 
363       return true;
364     }
365 
366     private boolean stringIsNotEmpty(final String str) {
367       return str != null && str.length() > 0;
368     }
369 
370     private void copyData(final Context context,
371         final Path inputPath, final InputStream in,
372         final Path outputPath, final FSDataOutputStream out,
373         final long inputFileSize)
374         throws IOException {
375       final String statusMessage = "copied %s/" + StringUtils.humanReadableInt(inputFileSize) +
376                                    " (%.1f%%)";
377 
378       try {
379         byte[] buffer = new byte[bufferSize];
380         long totalBytesWritten = 0;
381         int reportBytes = 0;
382         int bytesRead;
383 
384         long stime = System.currentTimeMillis();
385         while ((bytesRead = in.read(buffer)) > 0) {
386           out.write(buffer, 0, bytesRead);
387           totalBytesWritten += bytesRead;
388           reportBytes += bytesRead;
389 
390           if (reportBytes >= REPORT_SIZE) {
391             context.getCounter(Counter.BYTES_COPIED).increment(reportBytes);
392             context.setStatus(String.format(statusMessage,
393                               StringUtils.humanReadableInt(totalBytesWritten),
394                               (totalBytesWritten/(float)inputFileSize) * 100.0f) +
395                               " from " + inputPath + " to " + outputPath);
396             reportBytes = 0;
397           }
398         }
399         long etime = System.currentTimeMillis();
400 
401         context.getCounter(Counter.BYTES_COPIED).increment(reportBytes);
402         context.setStatus(String.format(statusMessage,
403                           StringUtils.humanReadableInt(totalBytesWritten),
404                           (totalBytesWritten/(float)inputFileSize) * 100.0f) +
405                           " from " + inputPath + " to " + outputPath);
406 
407         // Verify that the written size match
408         if (totalBytesWritten != inputFileSize) {
409           String msg = "number of bytes copied not matching copied=" + totalBytesWritten +
410                        " expected=" + inputFileSize + " for file=" + inputPath;
411           throw new IOException(msg);
412         }
413 
414         LOG.info("copy completed for input=" + inputPath + " output=" + outputPath);
415         LOG.info("size=" + totalBytesWritten +
416             " (" + StringUtils.humanReadableInt(totalBytesWritten) + ")" +
417             " time=" + StringUtils.formatTimeDiff(etime, stime) +
418             String.format(" %.3fM/sec", (totalBytesWritten / ((etime - stime)/1000.0))/1048576.0));
419         context.getCounter(Counter.FILES_COPIED).increment(1);
420       } catch (IOException e) {
421         LOG.error("Error copying " + inputPath + " to " + outputPath, e);
422         context.getCounter(Counter.COPY_FAILED).increment(1);
423         throw e;
424       }
425     }
426 
427     /**
428      * Try to open the "source" file.
429      * Throws an IOException if the communication with the inputFs fail or
430      * if the file is not found.
431      */
432     private FSDataInputStream openSourceFile(Context context, final SnapshotFileInfo fileInfo)
433             throws IOException {
434       try {
435         Configuration conf = context.getConfiguration();
436         FileLink link = null;
437         switch (fileInfo.getType()) {
438           case HFILE:
439             Path inputPath = new Path(fileInfo.getHfile());
440             link = HFileLink.buildFromHFileLinkPattern(conf, inputPath);
441             break;
442           case WAL:
443             String serverName = fileInfo.getWalServer();
444             String logName = fileInfo.getWalName();
445             link = new WALLink(inputRoot, serverName, logName);
446             break;
447           default:
448             throw new IOException("Invalid File Type: " + fileInfo.getType().toString());
449         }
450         return link.open(inputFs);
451       } catch (IOException e) {
452         context.getCounter(Counter.MISSING_FILES).increment(1);
453         LOG.error("Unable to open source file=" + fileInfo.toString(), e);
454         throw e;
455       }
456     }
457 
458     private FileStatus getSourceFileStatus(Context context, final SnapshotFileInfo fileInfo)
459         throws IOException {
460       try {
461         Configuration conf = context.getConfiguration();
462         FileLink link = null;
463         switch (fileInfo.getType()) {
464           case HFILE:
465             Path inputPath = new Path(fileInfo.getHfile());
466             link = HFileLink.buildFromHFileLinkPattern(conf, inputPath);
467             break;
468           case WAL:
469             link = new WALLink(inputRoot, fileInfo.getWalServer(), fileInfo.getWalName());
470             break;
471           default:
472             throw new IOException("Invalid File Type: " + fileInfo.getType().toString());
473         }
474         return link.getFileStatus(inputFs);
475       } catch (FileNotFoundException e) {
476         context.getCounter(Counter.MISSING_FILES).increment(1);
477         LOG.error("Unable to get the status for source file=" + fileInfo.toString(), e);
478         throw e;
479       } catch (IOException e) {
480         LOG.error("Unable to get the status for source file=" + fileInfo.toString(), e);
481         throw e;
482       }
483     }
484 
485     private FileChecksum getFileChecksum(final FileSystem fs, final Path path) {
486       try {
487         return fs.getFileChecksum(path);
488       } catch (IOException e) {
489         LOG.warn("Unable to get checksum for file=" + path, e);
490         return null;
491       }
492     }
493 
494     /**
495      * Check if the two files are equal by looking at the file length,
496      * and at the checksum (if user has specified the verifyChecksum flag).
497      */
498     private boolean sameFile(final FileStatus inputStat, final FileStatus outputStat) {
499       // Not matching length
500       if (inputStat.getLen() != outputStat.getLen()) return false;
501 
502       // Mark files as equals, since user asked for no checksum verification
503       if (!verifyChecksum) return true;
504 
505       // If checksums are not available, files are not the same.
506       FileChecksum inChecksum = getFileChecksum(inputFs, inputStat.getPath());
507       if (inChecksum == null) return false;
508 
509       FileChecksum outChecksum = getFileChecksum(outputFs, outputStat.getPath());
510       if (outChecksum == null) return false;
511 
512       return inChecksum.equals(outChecksum);
513     }
514   }
515 
516   // ==========================================================================
517   //  Input Format
518   // ==========================================================================
519 
520   /**
521    * Extract the list of files (HFiles/WALs) to copy using Map-Reduce.
522    * @return list of files referenced by the snapshot (pair of path and size)
523    */
524   private static List<Pair<SnapshotFileInfo, Long>> getSnapshotFiles(final Configuration conf,
525       final FileSystem fs, final Path snapshotDir) throws IOException {
526     SnapshotDescription snapshotDesc = SnapshotDescriptionUtils.readSnapshotInfo(fs, snapshotDir);
527 
528     final List<Pair<SnapshotFileInfo, Long>> files = new ArrayList<Pair<SnapshotFileInfo, Long>>();
529     final TableName table = TableName.valueOf(snapshotDesc.getTable());
530 
531     // Get snapshot files
532     LOG.info("Loading Snapshot '" + snapshotDesc.getName() + "' hfile list");
533     SnapshotReferenceUtil.visitReferencedFiles(conf, fs, snapshotDir, snapshotDesc,
534       new SnapshotReferenceUtil.SnapshotVisitor() {
535         @Override
536         public void storeFile(final HRegionInfo regionInfo, final String family,
537             final SnapshotRegionManifest.StoreFile storeFile) throws IOException {
538           if (storeFile.hasReference()) {
539             // copied as part of the manifest
540           } else {
541             String region = regionInfo.getEncodedName();
542             String hfile = storeFile.getName();
543             Path path = HFileLink.createPath(table, region, family, hfile);
544 
545             SnapshotFileInfo fileInfo = SnapshotFileInfo.newBuilder()
546               .setType(SnapshotFileInfo.Type.HFILE)
547               .setHfile(path.toString())
548               .build();
549 
550             long size;
551             if (storeFile.hasFileSize()) {
552               size = storeFile.getFileSize();
553             } else {
554               size = HFileLink.buildFromHFileLinkPattern(conf, path).getFileStatus(fs).getLen();
555             }
556             files.add(new Pair<SnapshotFileInfo, Long>(fileInfo, size));
557           }
558         }
559     });
560 
561     return files;
562   }
563 
564   /**
565    * Given a list of file paths and sizes, create around ngroups in as balanced a way as possible.
566    * The groups created will have similar amounts of bytes.
567    * <p>
568    * The algorithm used is pretty straightforward; the file list is sorted by size,
569    * and then each group fetch the bigger file available, iterating through groups
570    * alternating the direction.
571    */
572   static List<List<Pair<SnapshotFileInfo, Long>>> getBalancedSplits(
573       final List<Pair<SnapshotFileInfo, Long>> files, final int ngroups) {
574     // Sort files by size, from small to big
575     Collections.sort(files, new Comparator<Pair<SnapshotFileInfo, Long>>() {
576       public int compare(Pair<SnapshotFileInfo, Long> a, Pair<SnapshotFileInfo, Long> b) {
577         long r = a.getSecond() - b.getSecond();
578         return (r < 0) ? -1 : ((r > 0) ? 1 : 0);
579       }
580     });
581 
582     // create balanced groups
583     List<List<Pair<SnapshotFileInfo, Long>>> fileGroups =
584       new LinkedList<List<Pair<SnapshotFileInfo, Long>>>();
585     long[] sizeGroups = new long[ngroups];
586     int hi = files.size() - 1;
587     int lo = 0;
588 
589     List<Pair<SnapshotFileInfo, Long>> group;
590     int dir = 1;
591     int g = 0;
592 
593     while (hi >= lo) {
594       if (g == fileGroups.size()) {
595         group = new LinkedList<Pair<SnapshotFileInfo, Long>>();
596         fileGroups.add(group);
597       } else {
598         group = fileGroups.get(g);
599       }
600 
601       Pair<SnapshotFileInfo, Long> fileInfo = files.get(hi--);
602 
603       // add the hi one
604       sizeGroups[g] += fileInfo.getSecond();
605       group.add(fileInfo);
606 
607       // change direction when at the end or the beginning
608       g += dir;
609       if (g == ngroups) {
610         dir = -1;
611         g = ngroups - 1;
612       } else if (g < 0) {
613         dir = 1;
614         g = 0;
615       }
616     }
617 
618     if (LOG.isDebugEnabled()) {
619       for (int i = 0; i < sizeGroups.length; ++i) {
620         LOG.debug("export split=" + i + " size=" + StringUtils.humanReadableInt(sizeGroups[i]));
621       }
622     }
623 
624     return fileGroups;
625   }
626 
627   private static class ExportSnapshotInputFormat extends InputFormat<BytesWritable, NullWritable> {
628     @Override
629     public RecordReader<BytesWritable, NullWritable> createRecordReader(InputSplit split,
630         TaskAttemptContext tac) throws IOException, InterruptedException {
631       return new ExportSnapshotRecordReader(((ExportSnapshotInputSplit)split).getSplitKeys());
632     }
633 
634     @Override
635     public List<InputSplit> getSplits(JobContext context) throws IOException, InterruptedException {
636       Configuration conf = context.getConfiguration();
637       Path snapshotDir = new Path(conf.get(CONF_SNAPSHOT_DIR));
638       FileSystem fs = FileSystem.get(snapshotDir.toUri(), conf);
639 
640       List<Pair<SnapshotFileInfo, Long>> snapshotFiles = getSnapshotFiles(conf, fs, snapshotDir);
641       int mappers = conf.getInt(CONF_NUM_SPLITS, 0);
642       if (mappers == 0 && snapshotFiles.size() > 0) {
643         mappers = 1 + (snapshotFiles.size() / conf.getInt(CONF_MAP_GROUP, 10));
644         mappers = Math.min(mappers, snapshotFiles.size());
645         conf.setInt(CONF_NUM_SPLITS, mappers);
646         conf.setInt(MR_NUM_MAPS, mappers);
647       }
648 
649       List<List<Pair<SnapshotFileInfo, Long>>> groups = getBalancedSplits(snapshotFiles, mappers);
650       List<InputSplit> splits = new ArrayList(groups.size());
651       for (List<Pair<SnapshotFileInfo, Long>> files: groups) {
652         splits.add(new ExportSnapshotInputSplit(files));
653       }
654       return splits;
655     }
656 
657     private static class ExportSnapshotInputSplit extends InputSplit implements Writable {
658       private List<Pair<BytesWritable, Long>> files;
659       private long length;
660 
661       public ExportSnapshotInputSplit() {
662         this.files = null;
663       }
664 
665       public ExportSnapshotInputSplit(final List<Pair<SnapshotFileInfo, Long>> snapshotFiles) {
666         this.files = new ArrayList(snapshotFiles.size());
667         for (Pair<SnapshotFileInfo, Long> fileInfo: snapshotFiles) {
668           this.files.add(new Pair<BytesWritable, Long>(
669             new BytesWritable(fileInfo.getFirst().toByteArray()), fileInfo.getSecond()));
670           this.length += fileInfo.getSecond();
671         }
672       }
673 
674       private List<Pair<BytesWritable, Long>> getSplitKeys() {
675         return files;
676       }
677 
678       @Override
679       public long getLength() throws IOException, InterruptedException {
680         return length;
681       }
682 
683       @Override
684       public String[] getLocations() throws IOException, InterruptedException {
685         return new String[] {};
686       }
687 
688       @Override
689       public void readFields(DataInput in) throws IOException {
690         int count = in.readInt();
691         files = new ArrayList<Pair<BytesWritable, Long>>(count);
692         length = 0;
693         for (int i = 0; i < count; ++i) {
694           BytesWritable fileInfo = new BytesWritable();
695           fileInfo.readFields(in);
696           long size = in.readLong();
697           files.add(new Pair<BytesWritable, Long>(fileInfo, size));
698           length += size;
699         }
700       }
701 
702       @Override
703       public void write(DataOutput out) throws IOException {
704         out.writeInt(files.size());
705         for (final Pair<BytesWritable, Long> fileInfo: files) {
706           fileInfo.getFirst().write(out);
707           out.writeLong(fileInfo.getSecond());
708         }
709       }
710     }
711 
712     private static class ExportSnapshotRecordReader
713         extends RecordReader<BytesWritable, NullWritable> {
714       private final List<Pair<BytesWritable, Long>> files;
715       private long totalSize = 0;
716       private long procSize = 0;
717       private int index = -1;
718 
719       ExportSnapshotRecordReader(final List<Pair<BytesWritable, Long>> files) {
720         this.files = files;
721         for (Pair<BytesWritable, Long> fileInfo: files) {
722           totalSize += fileInfo.getSecond();
723         }
724       }
725 
726       @Override
727       public void close() { }
728 
729       @Override
730       public BytesWritable getCurrentKey() { return files.get(index).getFirst(); }
731 
732       @Override
733       public NullWritable getCurrentValue() { return NullWritable.get(); }
734 
735       @Override
736       public float getProgress() { return (float)procSize / totalSize; }
737 
738       @Override
739       public void initialize(InputSplit split, TaskAttemptContext tac) { }
740 
741       @Override
742       public boolean nextKeyValue() {
743         if (index >= 0) {
744           procSize += files.get(index).getSecond();
745         }
746         return(++index < files.size());
747       }
748     }
749   }
750 
751   // ==========================================================================
752   //  Tool
753   // ==========================================================================
754 
755   /**
756    * Run Map-Reduce Job to perform the files copy.
757    */
758   private void runCopyJob(final Path inputRoot, final Path outputRoot,
759       final String snapshotName, final Path snapshotDir, final boolean verifyChecksum,
760       final String filesUser, final String filesGroup, final int filesMode,
761       final int mappers, final int bandwidthMB)
762           throws IOException, InterruptedException, ClassNotFoundException {
763     Configuration conf = getConf();
764     if (filesGroup != null) conf.set(CONF_FILES_GROUP, filesGroup);
765     if (filesUser != null) conf.set(CONF_FILES_USER, filesUser);
766     if (mappers > 0) {
767       conf.setInt(CONF_NUM_SPLITS, mappers);
768       conf.setInt(MR_NUM_MAPS, mappers);
769     }
770     conf.setInt(CONF_FILES_MODE, filesMode);
771     conf.setBoolean(CONF_CHECKSUM_VERIFY, verifyChecksum);
772     conf.set(CONF_OUTPUT_ROOT, outputRoot.toString());
773     conf.set(CONF_INPUT_ROOT, inputRoot.toString());
774     conf.setInt(CONF_BANDWIDTH_MB, bandwidthMB);
775     conf.set(CONF_SNAPSHOT_NAME, snapshotName);
776     conf.set(CONF_SNAPSHOT_DIR, snapshotDir.toString());
777 
778     Job job = new Job(conf);
779     job.setJobName("ExportSnapshot-" + snapshotName);
780     job.setJarByClass(ExportSnapshot.class);
781     TableMapReduceUtil.addDependencyJars(job);
782     job.setMapperClass(ExportMapper.class);
783     job.setInputFormatClass(ExportSnapshotInputFormat.class);
784     job.setOutputFormatClass(NullOutputFormat.class);
785     job.setMapSpeculativeExecution(false);
786     job.setNumReduceTasks(0);
787 
788     // Acquire the delegation Tokens
789     Configuration srcConf = HBaseConfiguration.createClusterConf(conf, null, CONF_SOURCE_PREFIX);
790     TokenCache.obtainTokensForNamenodes(job.getCredentials(),
791       new Path[] { inputRoot }, srcConf);
792     Configuration destConf = HBaseConfiguration.createClusterConf(conf, null, CONF_DEST_PREFIX);
793     TokenCache.obtainTokensForNamenodes(job.getCredentials(),
794         new Path[] { outputRoot }, destConf);
795 
796     // Run the MR Job
797     if (!job.waitForCompletion(true)) {
798       throw new ExportSnapshotException(job.getStatus().getFailureInfo());
799     }
800   }
801 
802   private void verifySnapshot(final Configuration baseConf,
803       final FileSystem fs, final Path rootDir, final Path snapshotDir) throws IOException {
804     // Update the conf with the current root dir, since may be a different cluster
805     Configuration conf = new Configuration(baseConf);
806     FSUtils.setRootDir(conf, rootDir);
807     FSUtils.setFsDefault(conf, FSUtils.getRootDir(conf));
808     SnapshotDescription snapshotDesc = SnapshotDescriptionUtils.readSnapshotInfo(fs, snapshotDir);
809     SnapshotReferenceUtil.verifySnapshot(conf, fs, snapshotDir, snapshotDesc);
810   }
811 
812   /**
813    * Set path ownership.
814    */
815   private void setOwner(final FileSystem fs, final Path path, final String user,
816       final String group, final boolean recursive) throws IOException {
817     if (user != null || group != null) {
818       if (recursive && fs.isDirectory(path)) {
819         for (FileStatus child : fs.listStatus(path)) {
820           setOwner(fs, child.getPath(), user, group, recursive);
821         }
822       }
823       fs.setOwner(path, user, group);
824     }
825   }
826 
827   /**
828    * Set path permission.
829    */
830   private void setPermission(final FileSystem fs, final Path path, final short filesMode,
831       final boolean recursive) throws IOException {
832     if (filesMode > 0) {
833       FsPermission perm = new FsPermission(filesMode);
834       if (recursive && fs.isDirectory(path)) {
835         for (FileStatus child : fs.listStatus(path)) {
836           setPermission(fs, child.getPath(), filesMode, recursive);
837         }
838       }
839       fs.setPermission(path, perm);
840     }
841   }
842 
843   /**
844    * Execute the export snapshot by copying the snapshot metadata, hfiles and wals.
845    * @return 0 on success, and != 0 upon failure.
846    */
847   @Override
848   public int run(String[] args) throws IOException {
849     boolean verifyTarget = true;
850     boolean verifyChecksum = true;
851     String snapshotName = null;
852     String targetName = null;
853     boolean overwrite = false;
854     String filesGroup = null;
855     String filesUser = null;
856     Path outputRoot = null;
857     int bandwidthMB = Integer.MAX_VALUE;
858     int filesMode = 0;
859     int mappers = 0;
860 
861     Configuration conf = getConf();
862     Path inputRoot = FSUtils.getRootDir(conf);
863 
864     // Process command line args
865     for (int i = 0; i < args.length; i++) {
866       String cmd = args[i];
867       if (cmd.equals("-snapshot")) {
868         snapshotName = args[++i];
869       } else if (cmd.equals("-target")) {
870         targetName = args[++i];
871       } else if (cmd.equals("-copy-to")) {
872         outputRoot = new Path(args[++i]);
873       } else if (cmd.equals("-copy-from")) {
874         inputRoot = new Path(args[++i]);
875         FSUtils.setRootDir(conf, inputRoot);
876       } else if (cmd.equals("-no-checksum-verify")) {
877         verifyChecksum = false;
878       } else if (cmd.equals("-no-target-verify")) {
879         verifyTarget = false;
880       } else if (cmd.equals("-mappers")) {
881         mappers = Integer.parseInt(args[++i]);
882       } else if (cmd.equals("-chuser")) {
883         filesUser = args[++i];
884       } else if (cmd.equals("-chgroup")) {
885         filesGroup = args[++i];
886       } else if (cmd.equals("-bandwidth")) {
887         bandwidthMB = Integer.parseInt(args[++i]);
888       } else if (cmd.equals("-chmod")) {
889         filesMode = Integer.parseInt(args[++i], 8);
890       } else if (cmd.equals("-overwrite")) {
891         overwrite = true;
892       } else if (cmd.equals("-h") || cmd.equals("--help")) {
893         printUsageAndExit();
894       } else {
895         System.err.println("UNEXPECTED: " + cmd);
896         printUsageAndExit();
897       }
898     }
899 
900     // Check user options
901     if (snapshotName == null) {
902       System.err.println("Snapshot name not provided.");
903       printUsageAndExit();
904     }
905 
906     if (outputRoot == null) {
907       System.err.println("Destination file-system not provided.");
908       printUsageAndExit();
909     }
910 
911     if (targetName == null) {
912       targetName = snapshotName;
913     }
914 
915     Configuration srcConf = HBaseConfiguration.createClusterConf(conf, null, CONF_SOURCE_PREFIX);
916     srcConf.setBoolean("fs." + inputRoot.toUri().getScheme() + ".impl.disable.cache", true);
917     FileSystem inputFs = FileSystem.get(inputRoot.toUri(), srcConf);
918     LOG.debug("inputFs=" + inputFs.getUri().toString() + " inputRoot=" + inputRoot);
919     Configuration destConf = HBaseConfiguration.createClusterConf(conf, null, CONF_DEST_PREFIX);
920     destConf.setBoolean("fs." + outputRoot.toUri().getScheme() + ".impl.disable.cache", true);
921     FileSystem outputFs = FileSystem.get(outputRoot.toUri(), destConf);
922     LOG.debug("outputFs=" + outputFs.getUri().toString() + " outputRoot=" + outputRoot.toString());
923 
924     boolean skipTmp = conf.getBoolean(CONF_SKIP_TMP, false);
925 
926     Path snapshotDir = SnapshotDescriptionUtils.getCompletedSnapshotDir(snapshotName, inputRoot);
927     Path snapshotTmpDir = SnapshotDescriptionUtils.getWorkingSnapshotDir(targetName, outputRoot);
928     Path outputSnapshotDir = SnapshotDescriptionUtils.getCompletedSnapshotDir(targetName, outputRoot);
929     Path initialOutputSnapshotDir = skipTmp ? outputSnapshotDir : snapshotTmpDir;
930 
931     // Find the necessary directory which need to change owner and group
932     Path needSetOwnerDir = SnapshotDescriptionUtils.getSnapshotRootDir(outputRoot);
933     if (outputFs.exists(needSetOwnerDir)) {
934       if (skipTmp) {
935         needSetOwnerDir = outputSnapshotDir;
936       } else {
937         needSetOwnerDir = SnapshotDescriptionUtils.getWorkingSnapshotDir(outputRoot);
938         if (outputFs.exists(needSetOwnerDir)) {
939           needSetOwnerDir = snapshotTmpDir;
940         }
941       }
942     }
943 
944     // Check if the snapshot already exists
945     if (outputFs.exists(outputSnapshotDir)) {
946       if (overwrite) {
947         if (!outputFs.delete(outputSnapshotDir, true)) {
948           System.err.println("Unable to remove existing snapshot directory: " + outputSnapshotDir);
949           return 1;
950         }
951       } else {
952         System.err.println("The snapshot '" + targetName +
953           "' already exists in the destination: " + outputSnapshotDir);
954         return 1;
955       }
956     }
957 
958     if (!skipTmp) {
959       // Check if the snapshot already in-progress
960       if (outputFs.exists(snapshotTmpDir)) {
961         if (overwrite) {
962           if (!outputFs.delete(snapshotTmpDir, true)) {
963             System.err.println("Unable to remove existing snapshot tmp directory: "+snapshotTmpDir);
964             return 1;
965           }
966         } else {
967           System.err.println("A snapshot with the same name '"+ targetName +"' may be in-progress");
968           System.err.println("Please check "+snapshotTmpDir+". If the snapshot has completed, ");
969           System.err.println("consider removing "+snapshotTmpDir+" by using the -overwrite option");
970           return 1;
971         }
972       }
973     }
974 
975     // Step 1 - Copy fs1:/.snapshot/<snapshot> to  fs2:/.snapshot/.tmp/<snapshot>
976     // The snapshot references must be copied before the hfiles otherwise the cleaner
977     // will remove them because they are unreferenced.
978     try {
979       LOG.info("Copy Snapshot Manifest");
980       FileUtil.copy(inputFs, snapshotDir, outputFs, initialOutputSnapshotDir, false, false, conf);
981     } catch (IOException e) {
982       throw new ExportSnapshotException("Failed to copy the snapshot directory: from=" +
983         snapshotDir + " to=" + initialOutputSnapshotDir, e);
984     } finally {
985       if (filesUser != null || filesGroup != null) {
986         LOG.warn((filesUser == null ? "" : "Change the owner of " + needSetOwnerDir + " to "
987             + filesUser)
988             + (filesGroup == null ? "" : ", Change the group of " + needSetOwnerDir + " to "
989             + filesGroup));
990         setOwner(outputFs, needSetOwnerDir, filesUser, filesGroup, true);
991       }
992       if (filesMode > 0) {
993         LOG.warn("Change the permission of " + needSetOwnerDir + " to " + filesMode);
994         setPermission(outputFs, needSetOwnerDir, (short)filesMode, true);
995       }
996     }
997 
998     // Write a new .snapshotinfo if the target name is different from the source name
999     if (!targetName.equals(snapshotName)) {
1000       SnapshotDescription snapshotDesc =
1001         SnapshotDescriptionUtils.readSnapshotInfo(inputFs, snapshotDir)
1002           .toBuilder()
1003           .setName(targetName)
1004           .build();
1005       SnapshotDescriptionUtils.writeSnapshotInfo(snapshotDesc, snapshotTmpDir, outputFs);
1006     }
1007 
1008     // Step 2 - Start MR Job to copy files
1009     // The snapshot references must be copied before the files otherwise the files gets removed
1010     // by the HFileArchiver, since they have no references.
1011     try {
1012       runCopyJob(inputRoot, outputRoot, snapshotName, snapshotDir, verifyChecksum,
1013                  filesUser, filesGroup, filesMode, mappers, bandwidthMB);
1014 
1015       LOG.info("Finalize the Snapshot Export");
1016       if (!skipTmp) {
1017         // Step 3 - Rename fs2:/.snapshot/.tmp/<snapshot> fs2:/.snapshot/<snapshot>
1018         if (!outputFs.rename(snapshotTmpDir, outputSnapshotDir)) {
1019           throw new ExportSnapshotException("Unable to rename snapshot directory from=" +
1020             snapshotTmpDir + " to=" + outputSnapshotDir);
1021         }
1022       }
1023 
1024       // Step 4 - Verify snapshot integrity
1025       if (verifyTarget) {
1026         LOG.info("Verify snapshot integrity");
1027         verifySnapshot(destConf, outputFs, outputRoot, outputSnapshotDir);
1028       }
1029 
1030       LOG.info("Export Completed: " + targetName);
1031       return 0;
1032     } catch (Exception e) {
1033       LOG.error("Snapshot export failed", e);
1034       if (!skipTmp) {
1035         outputFs.delete(snapshotTmpDir, true);
1036       }
1037       outputFs.delete(outputSnapshotDir, true);
1038       return 1;
1039     } finally {
1040       IOUtils.closeStream(inputFs);
1041       IOUtils.closeStream(outputFs);
1042     }
1043   }
1044 
1045   // ExportSnapshot
1046   private void printUsageAndExit() {
1047     System.err.printf("Usage: bin/hbase %s [options]%n", getClass().getName());
1048     System.err.println(" where [options] are:");
1049     System.err.println("  -h|-help                Show this help and exit.");
1050     System.err.println("  -snapshot NAME          Snapshot to restore.");
1051     System.err.println("  -copy-to NAME           Remote destination hdfs://");
1052     System.err.println("  -copy-from NAME         Input folder hdfs:// (default hbase.rootdir)");
1053     System.err.println("  -no-checksum-verify     Do not verify checksum, use name+length only.");
1054     System.err.println("  -no-target-verify       Do not verify the integrity of the \\" +
1055         "exported snapshot.");
1056     System.err.println("  -overwrite              Rewrite the snapshot manifest if already exists");
1057     System.err.println("  -chuser USERNAME        Change the owner of the files " +
1058         "to the specified one.");
1059     System.err.println("  -chgroup GROUP          Change the group of the files to " +
1060         "the specified one.");
1061     System.err.println("  -chmod MODE             Change the permission of the files " +
1062         "to the specified one.");
1063     System.err.println("  -mappers                Number of mappers to use during the " +
1064         "copy (mapreduce.job.maps).");
1065     System.err.println("  -bandwidth              Limit bandwidth to this value in MB/second.");
1066     System.err.println();
1067     System.err.println("Examples:");
1068     System.err.println("  hbase snapshot export \\");
1069     System.err.println("    -snapshot MySnapshot -copy-to hdfs://srv2:8082/hbase \\");
1070     System.err.println("    -chuser MyUser -chgroup MyGroup -chmod 700 -mappers 16");
1071     System.err.println();
1072     System.err.println("  hbase snapshot export \\");
1073     System.err.println("    -snapshot MySnapshot -copy-from hdfs://srv2:8082/hbase \\");
1074     System.err.println("    -copy-to hdfs://srv1:50070/hbase \\");
1075     System.exit(1);
1076   }
1077 
1078   /**
1079    * The guts of the {@link #main} method.
1080    * Call this method to avoid the {@link #main(String[])} System.exit.
1081    * @param args
1082    * @return errCode
1083    * @throws Exception
1084    */
1085   static int innerMain(final Configuration conf, final String [] args) throws Exception {
1086     return ToolRunner.run(conf, new ExportSnapshot(), args);
1087   }
1088 
1089   public static void main(String[] args) throws Exception {
1090     System.exit(innerMain(HBaseConfiguration.create(), args));
1091   }
1092 }