hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSImageFormatProtobuf.java - hadoop - Git at Google

 /**
  * Licensed to the Apache Software Foundation (ASF) under one
  * or more contributor license agreements.  See the NOTICE file
  * distributed with this work for additional information
  * regarding copyright ownership.  The ASF licenses this file
  * to you under the Apache License, Version 2.0 (the
  * "License"); you may not use this file except in compliance
  * with the License.  You may obtain a copy of the License at
  *
  *     http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 package org.apache.hadoop.hdfs.server.namenode;

 import java.io.BufferedInputStream;
 import java.io.BufferedOutputStream;
 import java.io.File;
 import java.io.FileInputStream;
 import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
 import java.io.RandomAccessFile;
 import java.nio.ByteBuffer;
 import java.nio.channels.FileChannel;
 import java.security.DigestOutputStream;
 import java.security.MessageDigest;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.Comparator;
 import java.util.Map;
 import java.util.Map.Entry;
 import java.util.Set;

 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.hdfs.protocol.LayoutVersion;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.CacheDirectiveInfoProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.CachePoolInfoProto;
 import org.apache.hadoop.hdfs.security.token.delegation.DelegationTokenSecretManager;
 import org.apache.hadoop.hdfs.server.namenode.FsImageProto.CacheManagerSection;
 import org.apache.hadoop.hdfs.server.namenode.FsImageProto.FileSummary;
 import org.apache.hadoop.hdfs.server.namenode.FsImageProto.NameSystemSection;
 import org.apache.hadoop.hdfs.server.namenode.FsImageProto.SecretManagerSection;
 import org.apache.hadoop.hdfs.server.namenode.FsImageProto.StringTableSection;
 import org.apache.hadoop.hdfs.server.namenode.snapshot.FSImageFormatPBSnapshot;
 import org.apache.hadoop.hdfs.server.namenode.startupprogress.Phase;
 import org.apache.hadoop.hdfs.server.namenode.startupprogress.StartupProgress;
 import org.apache.hadoop.hdfs.server.namenode.startupprogress.Step;
 import org.apache.hadoop.hdfs.server.namenode.startupprogress.StepType;
 import org.apache.hadoop.hdfs.util.MD5FileUtils;
 import org.apache.hadoop.io.MD5Hash;
 import org.apache.hadoop.io.compress.CompressionCodec;
 import org.apache.hadoop.io.compress.CompressorStream;

 import com.google.common.collect.Lists;
 import com.google.common.collect.Maps;
 import com.google.common.io.LimitInputStream;
 import com.google.protobuf.CodedOutputStream;

 /**
  * Utility class to read / write fsimage in protobuf format.
  */
 @InterfaceAudience.Private
 public final class FSImageFormatProtobuf {
   private static final Log LOG = LogFactory.getLog(FSImageFormatProtobuf.class);

   public static final class Loader implements FSImageFormat.AbstractLoader {
     static final int MINIMUM_FILE_LENGTH = 8;
     private final Configuration conf;
     private final FSNamesystem fsn;

     private String[] stringTable;

     /** The MD5 sum of the loaded file */
     private MD5Hash imgDigest;
     /** The transaction ID of the last edit represented by the loaded file */
     private long imgTxId;

     Loader(Configuration conf, FSNamesystem fsn) {
       this.conf = conf;
       this.fsn = fsn;
     }

     @Override
     public MD5Hash getLoadedImageMd5() {
       return imgDigest;
     }

     @Override
     public long getLoadedImageTxId() {
       return imgTxId;
     }

     public String[] getStringTable() {
       return stringTable;
     }

     void load(File file) throws IOException {
       long start = System.currentTimeMillis();
       imgDigest = MD5FileUtils.computeMd5ForFile(file);
       RandomAccessFile raFile = new RandomAccessFile(file, "r");
       FileInputStream fin = new FileInputStream(file);
       try {
         loadInternal(raFile, fin);
         long end = System.currentTimeMillis();
         LOG.info("Loaded FSImage in " + (end - start) / 1000 + " seconds.");
       } finally {
         fin.close();
         raFile.close();
       }
     }

     private void loadInternal(RandomAccessFile raFile, FileInputStream fin)
         throws IOException {
       if (!FSImageUtil.checkFileFormat(raFile)) {
         throw new IOException("Unrecognized file format");
       }
       FileSummary summary = FSImageUtil.loadSummary(raFile);

       FileChannel channel = fin.getChannel();

       FSImageFormatPBINode.Loader inodeLoader = new FSImageFormatPBINode.Loader(
           fsn, this);
       FSImageFormatPBSnapshot.Loader snapshotLoader = new FSImageFormatPBSnapshot.Loader(
           fsn, this);

       ArrayList<FileSummary.Section> sections = Lists.newArrayList(summary
           .getSectionsList());
       Collections.sort(sections, new Comparator<FileSummary.Section>() {
         @Override
         public int compare(FileSummary.Section s1, FileSummary.Section s2) {
           SectionName n1 = SectionName.fromString(s1.getName());
           SectionName n2 = SectionName.fromString(s2.getName());
           if (n1 == null) {
             return n2 == null ? 0 : -1;
           } else if (n2 == null) {
             return -1;
           } else {
             return n1.ordinal() - n2.ordinal();
           }
         }
       });

       StartupProgress prog = NameNode.getStartupProgress();
       /**
        * beginStep() and the endStep() calls do not match the boundary of the
        * sections. This is because that the current implementation only allows
        * a particular step to be started for once.
        */
       Step currentStep = null;

       for (FileSummary.Section s : sections) {
         channel.position(s.getOffset());
         InputStream in = new BufferedInputStream(new LimitInputStream(fin,
             s.getLength()));

         in = FSImageUtil.wrapInputStreamForCompression(conf,
             summary.getCodec(), in);

         String n = s.getName();

         switch (SectionName.fromString(n)) {
         case NS_INFO:
           loadNameSystemSection(in);
           break;
         case STRING_TABLE:
           loadStringTableSection(in);
           break;
         case INODE: {
           currentStep = new Step(StepType.INODES);
           prog.beginStep(Phase.LOADING_FSIMAGE, currentStep);
           inodeLoader.loadINodeSection(in);
         }
           break;
         case INODE_DIR:
           inodeLoader.loadINodeDirectorySection(in);
           break;
         case FILES_UNDERCONSTRUCTION:
           inodeLoader.loadFilesUnderConstructionSection(in);
           break;
         case SNAPSHOT:
           snapshotLoader.loadSnapshotSection(in);
           break;
         case SNAPSHOT_DIFF:
           snapshotLoader.loadSnapshotDiffSection(in);
           break;
         case SECRET_MANAGER: {
           prog.endStep(Phase.LOADING_FSIMAGE, currentStep);
           Step step = new Step(StepType.DELEGATION_TOKENS);
           prog.beginStep(Phase.LOADING_FSIMAGE, step);
           loadSecretManagerSection(in);
           prog.endStep(Phase.LOADING_FSIMAGE, step);
         }
           break;
         case CACHE_MANAGER: {
           Step step = new Step(StepType.CACHE_POOLS);
           prog.beginStep(Phase.LOADING_FSIMAGE, step);
           loadCacheManagerSection(in);
           prog.endStep(Phase.LOADING_FSIMAGE, step);
         }
           break;
         default:
           LOG.warn("Unregconized section " + n);
           break;
         }
       }
     }

     private void loadNameSystemSection(InputStream in) throws IOException {
       NameSystemSection s = NameSystemSection.parseDelimitedFrom(in);
       fsn.setGenerationStampV1(s.getGenstampV1());
       fsn.setGenerationStampV2(s.getGenstampV2());
       fsn.setGenerationStampV1Limit(s.getGenstampV1Limit());
       fsn.setLastAllocatedBlockId(s.getLastAllocatedBlockId());
       imgTxId = s.getTransactionId();
     }

     private void loadStringTableSection(InputStream in) throws IOException {
       StringTableSection s = StringTableSection.parseDelimitedFrom(in);
       stringTable = new String[s.getNumEntry() + 1];
       for (int i = 0; i < s.getNumEntry(); ++i) {
         StringTableSection.Entry e = StringTableSection.Entry
             .parseDelimitedFrom(in);
         stringTable[e.getId()] = e.getStr();
       }
     }

     private void loadSecretManagerSection(InputStream in) throws IOException {
       SecretManagerSection s = SecretManagerSection.parseDelimitedFrom(in);
       int numKeys = s.getNumKeys(), numTokens = s.getNumTokens();
       ArrayList<SecretManagerSection.DelegationKey> keys = Lists
           .newArrayListWithCapacity(numKeys);
       ArrayList<SecretManagerSection.PersistToken> tokens = Lists
           .newArrayListWithCapacity(numTokens);

       for (int i = 0; i < numKeys; ++i)
         keys.add(SecretManagerSection.DelegationKey.parseDelimitedFrom(in));

       for (int i = 0; i < numTokens; ++i)
         tokens.add(SecretManagerSection.PersistToken.parseDelimitedFrom(in));

       fsn.loadSecretManagerState(s, keys, tokens);
     }

     private void loadCacheManagerSection(InputStream in) throws IOException {
       CacheManagerSection s = CacheManagerSection.parseDelimitedFrom(in);
       ArrayList<CachePoolInfoProto> pools = Lists.newArrayListWithCapacity(s
           .getNumPools());
       ArrayList<CacheDirectiveInfoProto> directives = Lists
           .newArrayListWithCapacity(s.getNumDirectives());
       for (int i = 0; i < s.getNumPools(); ++i)
         pools.add(CachePoolInfoProto.parseDelimitedFrom(in));
       for (int i = 0; i < s.getNumDirectives(); ++i)
         directives.add(CacheDirectiveInfoProto.parseDelimitedFrom(in));
       fsn.getCacheManager().loadState(
           new CacheManager.PersistState(s, pools, directives));
     }

   }

   public static final class Saver {
     private final SaveNamespaceContext context;
     private long currentOffset = FSImageUtil.MAGIC_HEADER.length;
     private MD5Hash savedDigest;
     private StringMap stringMap = new StringMap();

     private FileChannel fileChannel;
     // OutputStream for the section data
     private OutputStream sectionOutputStream;
     private CompressionCodec codec;
     private OutputStream underlyingOutputStream;
     public static final int CHECK_CANCEL_INTERVAL = 4096;

     Saver(SaveNamespaceContext context) {
       this.context = context;
     }

     public MD5Hash getSavedDigest() {
       return savedDigest;
     }

     public SaveNamespaceContext getContext() {
       return context;
     }

     public void commitSection(FileSummary.Builder summary, SectionName name)
         throws IOException {
       long oldOffset = currentOffset;
       flushSectionOutputStream();

       if (codec != null) {
         sectionOutputStream = codec.createOutputStream(underlyingOutputStream);
       } else {
         sectionOutputStream = underlyingOutputStream;
       }
       long length = fileChannel.position() - oldOffset;
       summary.addSections(FileSummary.Section.newBuilder().setName(name.name)
           .setLength(length).setOffset(currentOffset));
       currentOffset += length;
     }

     private void flushSectionOutputStream() throws IOException {
       if (codec != null) {
         ((CompressorStream) sectionOutputStream).finish();
       }
       sectionOutputStream.flush();
     }

     void save(File file, FSImageCompression compression) throws IOException {
       FileOutputStream fout = new FileOutputStream(file);
       fileChannel = fout.getChannel();
       try {
         saveInternal(fout, compression, file.getAbsolutePath().toString());
       } finally {
         fout.close();
       }
     }

     private static void saveFileSummary(OutputStream out, FileSummary summary)
         throws IOException {
       summary.writeDelimitedTo(out);
       int length = getOndiskTrunkSize(summary);
       byte[] lengthBytes = new byte[4];
       ByteBuffer.wrap(lengthBytes).asIntBuffer().put(length);
       out.write(lengthBytes);
     }

     private void saveInodes(FileSummary.Builder summary) throws IOException {
       FSImageFormatPBINode.Saver saver = new FSImageFormatPBINode.Saver(this,
           summary);

       saver.serializeINodeSection(sectionOutputStream);
       saver.serializeINodeDirectorySection(sectionOutputStream);
       saver.serializeFilesUCSection(sectionOutputStream);
     }

     private void saveSnapshots(FileSummary.Builder summary) throws IOException {
       FSImageFormatPBSnapshot.Saver snapshotSaver = new FSImageFormatPBSnapshot.Saver(
           this, summary, context, context.getSourceNamesystem());

       snapshotSaver.serializeSnapshotSection(sectionOutputStream);
       snapshotSaver.serializeSnapshotDiffSection(sectionOutputStream);
     }

     private void saveInternal(FileOutputStream fout,
         FSImageCompression compression, String filePath) throws IOException {
       StartupProgress prog = NameNode.getStartupProgress();
       MessageDigest digester = MD5Hash.getDigester();

       underlyingOutputStream = new DigestOutputStream(new BufferedOutputStream(
           fout), digester);
       underlyingOutputStream.write(FSImageUtil.MAGIC_HEADER);

       fileChannel = fout.getChannel();

       FileSummary.Builder b = FileSummary.newBuilder()
           .setOndiskVersion(FSImageUtil.FILE_VERSION)
           .setLayoutVersion(LayoutVersion.getCurrentLayoutVersion());

       codec = compression.getImageCodec();
       if (codec != null) {
         b.setCodec(codec.getClass().getCanonicalName());
         sectionOutputStream = codec.createOutputStream(underlyingOutputStream);
       } else {
         sectionOutputStream = underlyingOutputStream;
       }

       saveNameSystemSection(b);
       // Check for cancellation right after serializing the name system section.
       // Some unit tests, such as TestSaveNamespace#testCancelSaveNameSpace
       // depends on this behavior.
       context.checkCancelled();

       Step step = new Step(StepType.INODES, filePath);
       prog.beginStep(Phase.SAVING_CHECKPOINT, step);
       saveInodes(b);
       saveSnapshots(b);
       prog.endStep(Phase.SAVING_CHECKPOINT, step);

       step = new Step(StepType.DELEGATION_TOKENS, filePath);
       prog.beginStep(Phase.SAVING_CHECKPOINT, step);
       saveSecretManagerSection(b);
       prog.endStep(Phase.SAVING_CHECKPOINT, step);

       step = new Step(StepType.CACHE_POOLS, filePath);
       prog.beginStep(Phase.SAVING_CHECKPOINT, step);
       saveCacheManagerSection(b);
       prog.endStep(Phase.SAVING_CHECKPOINT, step);

       saveStringTableSection(b);

       // We use the underlyingOutputStream to write the header. Therefore flush
       // the buffered stream (which is potentially compressed) first.
       flushSectionOutputStream();

       FileSummary summary = b.build();
       saveFileSummary(underlyingOutputStream, summary);
       underlyingOutputStream.close();
       savedDigest = new MD5Hash(digester.digest());
     }

     private void saveSecretManagerSection(FileSummary.Builder summary)
         throws IOException {
       final FSNamesystem fsn = context.getSourceNamesystem();
       DelegationTokenSecretManager.SecretManagerState state = fsn
           .saveSecretManagerState();
       state.section.writeDelimitedTo(sectionOutputStream);
       for (SecretManagerSection.DelegationKey k : state.keys)
         k.writeDelimitedTo(sectionOutputStream);

       for (SecretManagerSection.PersistToken t : state.tokens)
         t.writeDelimitedTo(sectionOutputStream);

       commitSection(summary, SectionName.SECRET_MANAGER);
     }

     private void saveCacheManagerSection(FileSummary.Builder summary)
         throws IOException {
       final FSNamesystem fsn = context.getSourceNamesystem();
       CacheManager.PersistState state = fsn.getCacheManager().saveState();
       state.section.writeDelimitedTo(sectionOutputStream);

       for (CachePoolInfoProto p : state.pools)
         p.writeDelimitedTo(sectionOutputStream);

       for (CacheDirectiveInfoProto p : state.directives)
         p.writeDelimitedTo(sectionOutputStream);

       commitSection(summary, SectionName.CACHE_MANAGER);
     }

     private void saveNameSystemSection(FileSummary.Builder summary)
         throws IOException {
       final FSNamesystem fsn = context.getSourceNamesystem();
       OutputStream out = sectionOutputStream;
       NameSystemSection.Builder b = NameSystemSection.newBuilder()
           .setGenstampV1(fsn.getGenerationStampV1())
           .setGenstampV1Limit(fsn.getGenerationStampV1Limit())
           .setGenstampV2(fsn.getGenerationStampV2())
           .setLastAllocatedBlockId(fsn.getLastAllocatedBlockId())
           .setTransactionId(context.getTxId());

       // We use the non-locked version of getNamespaceInfo here since
       // the coordinating thread of saveNamespace already has read-locked
       // the namespace for us. If we attempt to take another readlock
       // from the actual saver thread, there's a potential of a
       // fairness-related deadlock. See the comments on HDFS-2223.
       b.setNamespaceId(fsn.unprotectedGetNamespaceInfo().getNamespaceID());
       NameSystemSection s = b.build();
       s.writeDelimitedTo(out);

       commitSection(summary, SectionName.NS_INFO);
     }

     private void saveStringTableSection(FileSummary.Builder summary)
         throws IOException {
       OutputStream out = sectionOutputStream;
       StringTableSection.Builder b = StringTableSection.newBuilder()
           .setNumEntry(stringMap.size());
       b.build().writeDelimitedTo(out);
       for (Entry<String, Integer> e : stringMap.entrySet()) {
         StringTableSection.Entry.Builder eb = StringTableSection.Entry
             .newBuilder().setId(e.getValue()).setStr(e.getKey());
         eb.build().writeDelimitedTo(out);
       }
       commitSection(summary, SectionName.STRING_TABLE);
     }

     public StringMap getStringMap() {
       return stringMap;
     }
   }

   public static class StringMap {
     private final Map<String, Integer> stringMap;

     public StringMap() {
       stringMap = Maps.newHashMap();
     }

     int getStringId(String str) {
       if (str == null) {
         return 0;
       }
       Integer v = stringMap.get(str);
       if (v == null) {
         int nv = stringMap.size() + 1;
         stringMap.put(str, nv);
         return nv;
       }
       return v;
     }

     int size() {
       return stringMap.size();
     }

     Set<Entry<String, Integer>> entrySet() {
       return stringMap.entrySet();
     }
   }

   /**
    * Supported section name. The order of the enum determines the order of
    * loading.
    */
   public enum SectionName {
     NS_INFO("NS_INFO"),
     STRING_TABLE("STRING_TABLE"),
     INODE("INODE"),
     SNAPSHOT("SNAPSHOT"),
     INODE_DIR("INODE_DIR"),
     FILES_UNDERCONSTRUCTION("FILES_UNDERCONSTRUCTION"),
     SNAPSHOT_DIFF("SNAPSHOT_DIFF"),
     SECRET_MANAGER("SECRET_MANAGER"),
     CACHE_MANAGER("CACHE_MANAGER");

     private static final SectionName[] values = SectionName.values();

     public static SectionName fromString(String name) {
       for (SectionName n : values) {
         if (n.name.equals(name))
           return n;
       }
       return null;
     }

     private final String name;

     private SectionName(String name) {
       this.name = name;
     }
   }

   private static int getOndiskTrunkSize(com.google.protobuf.GeneratedMessage s) {
     return CodedOutputStream.computeRawVarint32Size(s.getSerializedSize())
         + s.getSerializedSize();
   }

   private FSImageFormatProtobuf() {
   }
 }
	/**
	* Licensed to the Apache Software Foundation (ASF) under one
	* or more contributor license agreements. See the NOTICE file
	* distributed with this work for additional information
	* regarding copyright ownership. The ASF licenses this file
	* to you under the Apache License, Version 2.0 (the
	* "License"); you may not use this file except in compliance
	* with the License. You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	package org.apache.hadoop.hdfs.server.namenode;

	import java.io.BufferedInputStream;
	import java.io.BufferedOutputStream;
	import java.io.File;
	import java.io.FileInputStream;
	import java.io.FileOutputStream;
	import java.io.IOException;
	import java.io.InputStream;
	import java.io.OutputStream;
	import java.io.RandomAccessFile;
	import java.nio.ByteBuffer;
	import java.nio.channels.FileChannel;
	import java.security.DigestOutputStream;
	import java.security.MessageDigest;
	import java.util.ArrayList;
	import java.util.Collections;
	import java.util.Comparator;
	import java.util.Map;
	import java.util.Map.Entry;
	import java.util.Set;

	import org.apache.commons.logging.Log;
	import org.apache.commons.logging.LogFactory;
	import org.apache.hadoop.classification.InterfaceAudience;
	import org.apache.hadoop.conf.Configuration;
	import org.apache.hadoop.hdfs.protocol.LayoutVersion;
	import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.CacheDirectiveInfoProto;
	import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.CachePoolInfoProto;
	import org.apache.hadoop.hdfs.security.token.delegation.DelegationTokenSecretManager;
	import org.apache.hadoop.hdfs.server.namenode.FsImageProto.CacheManagerSection;
	import org.apache.hadoop.hdfs.server.namenode.FsImageProto.FileSummary;
	import org.apache.hadoop.hdfs.server.namenode.FsImageProto.NameSystemSection;
	import org.apache.hadoop.hdfs.server.namenode.FsImageProto.SecretManagerSection;
	import org.apache.hadoop.hdfs.server.namenode.FsImageProto.StringTableSection;
	import org.apache.hadoop.hdfs.server.namenode.snapshot.FSImageFormatPBSnapshot;
	import org.apache.hadoop.hdfs.server.namenode.startupprogress.Phase;
	import org.apache.hadoop.hdfs.server.namenode.startupprogress.StartupProgress;
	import org.apache.hadoop.hdfs.server.namenode.startupprogress.Step;
	import org.apache.hadoop.hdfs.server.namenode.startupprogress.StepType;
	import org.apache.hadoop.hdfs.util.MD5FileUtils;
	import org.apache.hadoop.io.MD5Hash;
	import org.apache.hadoop.io.compress.CompressionCodec;
	import org.apache.hadoop.io.compress.CompressorStream;

	import com.google.common.collect.Lists;
	import com.google.common.collect.Maps;
	import com.google.common.io.LimitInputStream;
	import com.google.protobuf.CodedOutputStream;

	/**
	* Utility class to read / write fsimage in protobuf format.
	*/
	@InterfaceAudience.Private
	public final class FSImageFormatProtobuf {
	private static final Log LOG = LogFactory.getLog(FSImageFormatProtobuf.class);

	public static final class Loader implements FSImageFormat.AbstractLoader {
	static final int MINIMUM_FILE_LENGTH = 8;
	private final Configuration conf;
	private final FSNamesystem fsn;

	private String[] stringTable;

	/** The MD5 sum of the loaded file */
	private MD5Hash imgDigest;
	/** The transaction ID of the last edit represented by the loaded file */
	private long imgTxId;

	Loader(Configuration conf, FSNamesystem fsn) {
	this.conf = conf;
	this.fsn = fsn;
	}

	@Override
	public MD5Hash getLoadedImageMd5() {
	return imgDigest;
	}

	@Override
	public long getLoadedImageTxId() {
	return imgTxId;
	}

	public String[] getStringTable() {
	return stringTable;
	}

	void load(File file) throws IOException {
	long start = System.currentTimeMillis();
	imgDigest = MD5FileUtils.computeMd5ForFile(file);
	RandomAccessFile raFile = new RandomAccessFile(file, "r");
	FileInputStream fin = new FileInputStream(file);
	try {
	loadInternal(raFile, fin);
	long end = System.currentTimeMillis();
	LOG.info("Loaded FSImage in " + (end - start) / 1000 + " seconds.");
	} finally {
	fin.close();
	raFile.close();
	}
	}

	private void loadInternal(RandomAccessFile raFile, FileInputStream fin)
	throws IOException {
	if (!FSImageUtil.checkFileFormat(raFile)) {
	throw new IOException("Unrecognized file format");
	}
	FileSummary summary = FSImageUtil.loadSummary(raFile);

	FileChannel channel = fin.getChannel();

	FSImageFormatPBINode.Loader inodeLoader = new FSImageFormatPBINode.Loader(
	fsn, this);
	FSImageFormatPBSnapshot.Loader snapshotLoader = new FSImageFormatPBSnapshot.Loader(
	fsn, this);

	ArrayList<FileSummary.Section> sections = Lists.newArrayList(summary
	.getSectionsList());
	Collections.sort(sections, new Comparator<FileSummary.Section>() {
	@Override
	public int compare(FileSummary.Section s1, FileSummary.Section s2) {
	SectionName n1 = SectionName.fromString(s1.getName());
	SectionName n2 = SectionName.fromString(s2.getName());
	if (n1 == null) {
	return n2 == null ? 0 : -1;
	} else if (n2 == null) {
	return -1;
	} else {
	return n1.ordinal() - n2.ordinal();
	}
	}
	});

	StartupProgress prog = NameNode.getStartupProgress();
	/**
	* beginStep() and the endStep() calls do not match the boundary of the
	* sections. This is because that the current implementation only allows
	* a particular step to be started for once.
	*/
	Step currentStep = null;

	for (FileSummary.Section s : sections) {
	channel.position(s.getOffset());
	InputStream in = new BufferedInputStream(new LimitInputStream(fin,
	s.getLength()));

	in = FSImageUtil.wrapInputStreamForCompression(conf,
	summary.getCodec(), in);

	String n = s.getName();

	switch (SectionName.fromString(n)) {
	case NS_INFO:
	loadNameSystemSection(in);
	break;
	case STRING_TABLE:
	loadStringTableSection(in);
	break;
	case INODE: {
	currentStep = new Step(StepType.INODES);
	prog.beginStep(Phase.LOADING_FSIMAGE, currentStep);
	inodeLoader.loadINodeSection(in);
	}
	break;
	case INODE_DIR:
	inodeLoader.loadINodeDirectorySection(in);
	break;
	case FILES_UNDERCONSTRUCTION:
	inodeLoader.loadFilesUnderConstructionSection(in);
	break;
	case SNAPSHOT:
	snapshotLoader.loadSnapshotSection(in);
	break;
	case SNAPSHOT_DIFF:
	snapshotLoader.loadSnapshotDiffSection(in);
	break;
	case SECRET_MANAGER: {
	prog.endStep(Phase.LOADING_FSIMAGE, currentStep);
	Step step = new Step(StepType.DELEGATION_TOKENS);
	prog.beginStep(Phase.LOADING_FSIMAGE, step);
	loadSecretManagerSection(in);
	prog.endStep(Phase.LOADING_FSIMAGE, step);
	}
	break;
	case CACHE_MANAGER: {
	Step step = new Step(StepType.CACHE_POOLS);
	prog.beginStep(Phase.LOADING_FSIMAGE, step);
	loadCacheManagerSection(in);
	prog.endStep(Phase.LOADING_FSIMAGE, step);
	}
	break;
	default:
	LOG.warn("Unregconized section " + n);
	break;
	}
	}
	}

	private void loadNameSystemSection(InputStream in) throws IOException {
	NameSystemSection s = NameSystemSection.parseDelimitedFrom(in);
	fsn.setGenerationStampV1(s.getGenstampV1());
	fsn.setGenerationStampV2(s.getGenstampV2());
	fsn.setGenerationStampV1Limit(s.getGenstampV1Limit());
	fsn.setLastAllocatedBlockId(s.getLastAllocatedBlockId());
	imgTxId = s.getTransactionId();
	}

	private void loadStringTableSection(InputStream in) throws IOException {
	StringTableSection s = StringTableSection.parseDelimitedFrom(in);
	stringTable = new String[s.getNumEntry() + 1];
	for (int i = 0; i < s.getNumEntry(); ++i) {
	StringTableSection.Entry e = StringTableSection.Entry
	.parseDelimitedFrom(in);
	stringTable[e.getId()] = e.getStr();
	}
	}

	private void loadSecretManagerSection(InputStream in) throws IOException {
	SecretManagerSection s = SecretManagerSection.parseDelimitedFrom(in);
	int numKeys = s.getNumKeys(), numTokens = s.getNumTokens();
	ArrayList<SecretManagerSection.DelegationKey> keys = Lists
	.newArrayListWithCapacity(numKeys);
	ArrayList<SecretManagerSection.PersistToken> tokens = Lists
	.newArrayListWithCapacity(numTokens);

	for (int i = 0; i < numKeys; ++i)
	keys.add(SecretManagerSection.DelegationKey.parseDelimitedFrom(in));

	for (int i = 0; i < numTokens; ++i)
	tokens.add(SecretManagerSection.PersistToken.parseDelimitedFrom(in));

	fsn.loadSecretManagerState(s, keys, tokens);
	}

	private void loadCacheManagerSection(InputStream in) throws IOException {
	CacheManagerSection s = CacheManagerSection.parseDelimitedFrom(in);
	ArrayList<CachePoolInfoProto> pools = Lists.newArrayListWithCapacity(s
	.getNumPools());
	ArrayList<CacheDirectiveInfoProto> directives = Lists
	.newArrayListWithCapacity(s.getNumDirectives());
	for (int i = 0; i < s.getNumPools(); ++i)
	pools.add(CachePoolInfoProto.parseDelimitedFrom(in));
	for (int i = 0; i < s.getNumDirectives(); ++i)
	directives.add(CacheDirectiveInfoProto.parseDelimitedFrom(in));
	fsn.getCacheManager().loadState(
	new CacheManager.PersistState(s, pools, directives));
	}

	}

	public static final class Saver {
	private final SaveNamespaceContext context;
	private long currentOffset = FSImageUtil.MAGIC_HEADER.length;
	private MD5Hash savedDigest;
	private StringMap stringMap = new StringMap();

	private FileChannel fileChannel;
	// OutputStream for the section data
	private OutputStream sectionOutputStream;
	private CompressionCodec codec;
	private OutputStream underlyingOutputStream;
	public static final int CHECK_CANCEL_INTERVAL = 4096;

	Saver(SaveNamespaceContext context) {
	this.context = context;
	}

	public MD5Hash getSavedDigest() {
	return savedDigest;
	}

	public SaveNamespaceContext getContext() {
	return context;
	}

	public void commitSection(FileSummary.Builder summary, SectionName name)
	throws IOException {
	long oldOffset = currentOffset;
	flushSectionOutputStream();

	if (codec != null) {
	sectionOutputStream = codec.createOutputStream(underlyingOutputStream);
	} else {
	sectionOutputStream = underlyingOutputStream;
	}
	long length = fileChannel.position() - oldOffset;
	summary.addSections(FileSummary.Section.newBuilder().setName(name.name)
	.setLength(length).setOffset(currentOffset));
	currentOffset += length;
	}

	private void flushSectionOutputStream() throws IOException {
	if (codec != null) {
	((CompressorStream) sectionOutputStream).finish();
	}
	sectionOutputStream.flush();
	}

	void save(File file, FSImageCompression compression) throws IOException {
	FileOutputStream fout = new FileOutputStream(file);
	fileChannel = fout.getChannel();
	try {
	saveInternal(fout, compression, file.getAbsolutePath().toString());
	} finally {
	fout.close();
	}
	}

	private static void saveFileSummary(OutputStream out, FileSummary summary)
	throws IOException {
	summary.writeDelimitedTo(out);
	int length = getOndiskTrunkSize(summary);
	byte[] lengthBytes = new byte[4];
	ByteBuffer.wrap(lengthBytes).asIntBuffer().put(length);
	out.write(lengthBytes);
	}

	private void saveInodes(FileSummary.Builder summary) throws IOException {
	FSImageFormatPBINode.Saver saver = new FSImageFormatPBINode.Saver(this,
	summary);

	saver.serializeINodeSection(sectionOutputStream);
	saver.serializeINodeDirectorySection(sectionOutputStream);
	saver.serializeFilesUCSection(sectionOutputStream);
	}

	private void saveSnapshots(FileSummary.Builder summary) throws IOException {
	FSImageFormatPBSnapshot.Saver snapshotSaver = new FSImageFormatPBSnapshot.Saver(
	this, summary, context, context.getSourceNamesystem());

	snapshotSaver.serializeSnapshotSection(sectionOutputStream);
	snapshotSaver.serializeSnapshotDiffSection(sectionOutputStream);
	}

	private void saveInternal(FileOutputStream fout,
	FSImageCompression compression, String filePath) throws IOException {
	StartupProgress prog = NameNode.getStartupProgress();
	MessageDigest digester = MD5Hash.getDigester();

	underlyingOutputStream = new DigestOutputStream(new BufferedOutputStream(
	fout), digester);
	underlyingOutputStream.write(FSImageUtil.MAGIC_HEADER);

	fileChannel = fout.getChannel();

	FileSummary.Builder b = FileSummary.newBuilder()
	.setOndiskVersion(FSImageUtil.FILE_VERSION)
	.setLayoutVersion(LayoutVersion.getCurrentLayoutVersion());

	codec = compression.getImageCodec();
	if (codec != null) {
	b.setCodec(codec.getClass().getCanonicalName());
	sectionOutputStream = codec.createOutputStream(underlyingOutputStream);
	} else {
	sectionOutputStream = underlyingOutputStream;
	}

	saveNameSystemSection(b);
	// Check for cancellation right after serializing the name system section.
	// Some unit tests, such as TestSaveNamespace#testCancelSaveNameSpace
	// depends on this behavior.
	context.checkCancelled();

	Step step = new Step(StepType.INODES, filePath);
	prog.beginStep(Phase.SAVING_CHECKPOINT, step);
	saveInodes(b);
	saveSnapshots(b);
	prog.endStep(Phase.SAVING_CHECKPOINT, step);

	step = new Step(StepType.DELEGATION_TOKENS, filePath);
	prog.beginStep(Phase.SAVING_CHECKPOINT, step);
	saveSecretManagerSection(b);
	prog.endStep(Phase.SAVING_CHECKPOINT, step);

	step = new Step(StepType.CACHE_POOLS, filePath);
	prog.beginStep(Phase.SAVING_CHECKPOINT, step);
	saveCacheManagerSection(b);
	prog.endStep(Phase.SAVING_CHECKPOINT, step);

	saveStringTableSection(b);

	// We use the underlyingOutputStream to write the header. Therefore flush
	// the buffered stream (which is potentially compressed) first.
	flushSectionOutputStream();

	FileSummary summary = b.build();
	saveFileSummary(underlyingOutputStream, summary);
	underlyingOutputStream.close();
	savedDigest = new MD5Hash(digester.digest());
	}

	private void saveSecretManagerSection(FileSummary.Builder summary)
	throws IOException {
	final FSNamesystem fsn = context.getSourceNamesystem();
	DelegationTokenSecretManager.SecretManagerState state = fsn
	.saveSecretManagerState();
	state.section.writeDelimitedTo(sectionOutputStream);
	for (SecretManagerSection.DelegationKey k : state.keys)
	k.writeDelimitedTo(sectionOutputStream);

	for (SecretManagerSection.PersistToken t : state.tokens)
	t.writeDelimitedTo(sectionOutputStream);

	commitSection(summary, SectionName.SECRET_MANAGER);
	}

	private void saveCacheManagerSection(FileSummary.Builder summary)
	throws IOException {
	final FSNamesystem fsn = context.getSourceNamesystem();
	CacheManager.PersistState state = fsn.getCacheManager().saveState();
	state.section.writeDelimitedTo(sectionOutputStream);

	for (CachePoolInfoProto p : state.pools)
	p.writeDelimitedTo(sectionOutputStream);

	for (CacheDirectiveInfoProto p : state.directives)
	p.writeDelimitedTo(sectionOutputStream);

	commitSection(summary, SectionName.CACHE_MANAGER);
	}

	private void saveNameSystemSection(FileSummary.Builder summary)
	throws IOException {
	final FSNamesystem fsn = context.getSourceNamesystem();
	OutputStream out = sectionOutputStream;
	NameSystemSection.Builder b = NameSystemSection.newBuilder()
	.setGenstampV1(fsn.getGenerationStampV1())
	.setGenstampV1Limit(fsn.getGenerationStampV1Limit())
	.setGenstampV2(fsn.getGenerationStampV2())
	.setLastAllocatedBlockId(fsn.getLastAllocatedBlockId())
	.setTransactionId(context.getTxId());

	// We use the non-locked version of getNamespaceInfo here since
	// the coordinating thread of saveNamespace already has read-locked
	// the namespace for us. If we attempt to take another readlock
	// from the actual saver thread, there's a potential of a
	// fairness-related deadlock. See the comments on HDFS-2223.
	b.setNamespaceId(fsn.unprotectedGetNamespaceInfo().getNamespaceID());
	NameSystemSection s = b.build();
	s.writeDelimitedTo(out);

	commitSection(summary, SectionName.NS_INFO);
	}

	private void saveStringTableSection(FileSummary.Builder summary)
	throws IOException {
	OutputStream out = sectionOutputStream;
	StringTableSection.Builder b = StringTableSection.newBuilder()
	.setNumEntry(stringMap.size());
	b.build().writeDelimitedTo(out);
	for (Entry<String, Integer> e : stringMap.entrySet()) {
	StringTableSection.Entry.Builder eb = StringTableSection.Entry
	.newBuilder().setId(e.getValue()).setStr(e.getKey());
	eb.build().writeDelimitedTo(out);
	}
	commitSection(summary, SectionName.STRING_TABLE);
	}

	public StringMap getStringMap() {
	return stringMap;
	}
	}

	public static class StringMap {
	private final Map<String, Integer> stringMap;

	public StringMap() {
	stringMap = Maps.newHashMap();
	}

	int getStringId(String str) {
	if (str == null) {
	return 0;
	}
	Integer v = stringMap.get(str);
	if (v == null) {
	int nv = stringMap.size() + 1;
	stringMap.put(str, nv);
	return nv;
	}
	return v;
	}

	int size() {
	return stringMap.size();
	}

	Set<Entry<String, Integer>> entrySet() {
	return stringMap.entrySet();
	}
	}

	/**
	* Supported section name. The order of the enum determines the order of
	* loading.
	*/
	public enum SectionName {
	NS_INFO("NS_INFO"),
	STRING_TABLE("STRING_TABLE"),
	INODE("INODE"),
	SNAPSHOT("SNAPSHOT"),
	INODE_DIR("INODE_DIR"),
	FILES_UNDERCONSTRUCTION("FILES_UNDERCONSTRUCTION"),
	SNAPSHOT_DIFF("SNAPSHOT_DIFF"),
	SECRET_MANAGER("SECRET_MANAGER"),
	CACHE_MANAGER("CACHE_MANAGER");

	private static final SectionName[] values = SectionName.values();

	public static SectionName fromString(String name) {
	for (SectionName n : values) {
	if (n.name.equals(name))
	return n;
	}
	return null;
	}

	private final String name;

	private SectionName(String name) {
	this.name = name;
	}
	}

	private static int getOndiskTrunkSize(com.google.protobuf.GeneratedMessage s) {
	return CodedOutputStream.computeRawVarint32Size(s.getSerializedSize())
	+ s.getSerializedSize();
	}

	private FSImageFormatProtobuf() {
	}
	}