/**
    *
    * 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.hbase.regionserver;
  
  import java.io.FileNotFoundException;
  import java.io.IOException;
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.List;
  import java.util.Map;
  import java.util.UUID;
  
  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.fs.FSDataInputStream;
  import org.apache.hadoop.fs.FSDataOutputStream;
  import org.apache.hadoop.fs.FileStatus;
  import org.apache.hadoop.fs.FileSystem;
  import org.apache.hadoop.fs.FileUtil;
  import org.apache.hadoop.fs.Path;
  import org.apache.hadoop.fs.PathFilter;
  import org.apache.hadoop.fs.permission.FsPermission;
  import org.apache.hadoop.hbase.HColumnDescriptor;
  import org.apache.hadoop.hbase.HConstants;
  import org.apache.hadoop.hbase.HRegionInfo;
  import org.apache.hadoop.hbase.HTableDescriptor;
  import org.apache.hadoop.hbase.KeyValue;
  import org.apache.hadoop.hbase.backup.HFileArchiver;
  import org.apache.hadoop.hbase.fs.HFileSystem;
  import org.apache.hadoop.hbase.io.Reference;
  import org.apache.hadoop.hbase.util.FSUtils;
  import org.apache.hadoop.hbase.util.Bytes;
  import org.apache.hadoop.hbase.util.Threads;
  
  /**
   * View to an on-disk Region.
   * Provides the set of methods necessary to interact with the on-disk region data.
   */
  @InterfaceAudience.Private
  public class HRegionFileSystem {
    public static final Log LOG = LogFactory.getLog(HRegionFileSystem.class);
  
    /** Name of the region info file that resides just under the region directory. */
    public final static String REGION_INFO_FILE = ".regioninfo";
  
    /** Temporary subdirectory of the region directory used for merges. */
    public static final String REGION_MERGES_DIR = ".merges";
  
    /** Temporary subdirectory of the region directory used for splits. */
    public static final String REGION_SPLITS_DIR = ".splits";
  
    /** Temporary subdirectory of the region directory used for compaction output. */
    private static final String REGION_TEMP_DIR = ".tmp";
  
    private final HRegionInfo regionInfo;
    private final Configuration conf;
    private final Path tableDir;
    private final FileSystem fs;
    
    /**
     * In order to handle NN connectivity hiccups, one need to retry non-idempotent operation at the
     * client level.
     */
    private final int hdfsClientRetriesNumber;
    private final int baseSleepBeforeRetries;
    private static final int DEFAULT_HDFS_CLIENT_RETRIES_NUMBER = 10;
    private static final int DEFAULT_BASE_SLEEP_BEFORE_RETRIES = 1000;
  
    /**
     * Create a view to the on-disk region
     * @param conf the {@link Configuration} to use
     * @param fs {@link FileSystem} that contains the region
     * @param tableDir {@link Path} to where the table is being stored
     * @param regionInfo {@link HRegionInfo} for region
     */
    HRegionFileSystem(final Configuration conf, final FileSystem fs, final Path tableDir,
        final HRegionInfo regionInfo) {
      this.fs = fs;
      this.conf = conf;
      this.tableDir = tableDir;
     this.regionInfo = regionInfo;
     this.hdfsClientRetriesNumber = conf.getInt("hdfs.client.retries.number",
       DEFAULT_HDFS_CLIENT_RETRIES_NUMBER);
     this.baseSleepBeforeRetries = conf.getInt("hdfs.client.sleep.before.retries",
       DEFAULT_BASE_SLEEP_BEFORE_RETRIES);
  }
 
   /** @return the underlying {@link FileSystem} */
   public FileSystem getFileSystem() {
     return this.fs;
   }
 
   /** @return the {@link HRegionInfo} that describe this on-disk region view */
   public HRegionInfo getRegionInfo() {
     return this.regionInfo;
   }
 
   /** @return {@link Path} to the region's root directory. */
   public Path getTableDir() {
     return this.tableDir;
   }
 
   /** @return {@link Path} to the region directory. */
   public Path getRegionDir() {
     return new Path(this.tableDir, this.regionInfo.getEncodedName());
   }
 
   // ===========================================================================
   //  Temp Helpers
   // ===========================================================================
   /** @return {@link Path} to the region's temp directory, used for file creations */
   Path getTempDir() {
     return new Path(getRegionDir(), REGION_TEMP_DIR);
   }
 
   /**
    * Clean up any temp detritus that may have been left around from previous operation attempts.
    */
   void cleanupTempDir() throws IOException {
     deleteDir(getTempDir());
   }
 
   // ===========================================================================
   //  Store/StoreFile Helpers
   // ===========================================================================
   /**
    * Returns the directory path of the specified family
    * @param familyName Column Family Name
    * @return {@link Path} to the directory of the specified family
    */
   Path getStoreDir(final String familyName) {
     return new Path(this.getRegionDir(), familyName);
   }
 
   /**
    * Create the store directory for the specified family name
    * @param familyName Column Family Name
    * @return {@link Path} to the directory of the specified family
    * @throws IOException if the directory creation fails.
    */
   Path createStoreDir(final String familyName) throws IOException {
     Path storeDir = getStoreDir(familyName);
     if(!fs.exists(storeDir) && !createDir(storeDir))
       throw new IOException("Failed creating "+storeDir);
     return storeDir;
   }
 
   /**
    * Returns the store files available for the family.
    * This methods performs the filtering based on the valid store files.
    * @param familyName Column Family Name
    * @return a set of {@link StoreFileInfo} for the specified family.
    */
   public Collection<StoreFileInfo> getStoreFiles(final byte[] familyName) throws IOException {
     return getStoreFiles(Bytes.toString(familyName));
   }
 
   /**
    * Returns the store files available for the family.
    * This methods performs the filtering based on the valid store files.
    * @param familyName Column Family Name
    * @return a set of {@link StoreFileInfo} for the specified family.
    */
   public Collection<StoreFileInfo> getStoreFiles(final String familyName) throws IOException {
     Path familyDir = getStoreDir(familyName);
     FileStatus[] files = FSUtils.listStatus(this.fs, familyDir);
     if (files == null) return null;
 
     ArrayList<StoreFileInfo> storeFiles = new ArrayList<StoreFileInfo>(files.length);
     for (FileStatus status: files) {
       if (!StoreFileInfo.isValid(status)) continue;
 
       storeFiles.add(new StoreFileInfo(this.conf, this.fs, status));
     }
     return storeFiles;
   }
 
   /**
    * Returns true if the specified family has reference files
    * @param familyName Column Family Name
    * @return true if family contains reference files
    * @throws IOException
    */
   public boolean hasReferences(final String familyName) throws IOException {
     FileStatus[] files = FSUtils.listStatus(fs, getStoreDir(familyName),
       new PathFilter () {
         public boolean accept(Path path) {
           return StoreFileInfo.isReference(path);
         }
       }
     );
     return files != null && files.length > 0;
   }
 
   /**
    * Check whether region has Reference file
    * @param htd table desciptor of the region
    * @return true if region has reference file
    * @throws IOException
    */
   public boolean hasReferences(final HTableDescriptor htd) throws IOException {
     for (HColumnDescriptor family : htd.getFamilies()) {
       if (hasReferences(family.getNameAsString())) {
         return true;
       }
     }
     return false;
   }
 
   /**
    * @return the set of families present on disk
    * @throws IOException
    */
   public Collection<String> getFamilies() throws IOException {
     FileStatus[] fds = FSUtils.listStatus(fs, getRegionDir(), new FSUtils.FamilyDirFilter(fs));
     if (fds == null) return null;
 
     ArrayList<String> families = new ArrayList<String>(fds.length);
     for (FileStatus status: fds) {
       families.add(status.getPath().getName());
     }
 
     return families;
   }
 
   /**
    * Remove the region family from disk, archiving the store files.
    * @param familyName Column Family Name
    * @throws IOException if an error occours during the archiving
    */
   public void deleteFamily(final String familyName) throws IOException {
     // archive family store files
     HFileArchiver.archiveFamily(fs, conf, regionInfo, tableDir, Bytes.toBytes(familyName));
 
     // delete the family folder
     Path familyDir = getStoreDir(familyName);
     if(fs.exists(familyDir) && !deleteDir(familyDir))
       throw new IOException("Could not delete family " + familyName
           + " from FileSystem for region " + regionInfo.getRegionNameAsString() + "("
           + regionInfo.getEncodedName() + ")");
   }
 
   /**
    * Generate a unique file name, used by createTempName() and commitStoreFile()
    * @param suffix extra information to append to the generated name
    * @return Unique file name
    */
   private static String generateUniqueName(final String suffix) {
     String name = UUID.randomUUID().toString().replaceAll("-", "");
     if (suffix != null) name += suffix;
     return name;
   }
 
   /**
    * Generate a unique temporary Path. Used in conjuction with commitStoreFile()
    * to get a safer file creation.
    * <code>
    * Path file = fs.createTempName();
    * ...StoreFile.Writer(file)...
    * fs.commitStoreFile("family", file);
    * </code>
    *
    * @return Unique {@link Path} of the temporary file
    */
   public Path createTempName() {
     return createTempName(null);
   }
 
   /**
    * Generate a unique temporary Path. Used in conjuction with commitStoreFile()
    * to get a safer file creation.
    * <code>
    * Path file = fs.createTempName();
    * ...StoreFile.Writer(file)...
    * fs.commitStoreFile("family", file);
    * </code>
    *
    * @param suffix extra information to append to the generated name
    * @return Unique {@link Path} of the temporary file
    */
   public Path createTempName(final String suffix) {
     return new Path(getTempDir(), generateUniqueName(suffix));
   }
 
   /**
    * Move the file from a build/temp location to the main family store directory.
    * @param familyName Family that will gain the file
    * @param buildPath {@link Path} to the file to commit.
    * @return The new {@link Path} of the committed file
    * @throws IOException
    */
   public Path commitStoreFile(final String familyName, final Path buildPath) throws IOException {
     return commitStoreFile(familyName, buildPath, -1, false);
   }
 
   /**
    * Move the file from a build/temp location to the main family store directory.
    * @param familyName Family that will gain the file
    * @param buildPath {@link Path} to the file to commit.
    * @param seqNum Sequence Number to append to the file name (less then 0 if no sequence number)
    * @param generateNewName False if you want to keep the buildPath name
    * @return The new {@link Path} of the committed file
    * @throws IOException
    */
   private Path commitStoreFile(final String familyName, final Path buildPath,
       final long seqNum, final boolean generateNewName) throws IOException {
     Path storeDir = getStoreDir(familyName);
     if(!fs.exists(storeDir) && !createDir(storeDir))
       throw new IOException("Failed creating " + storeDir);
     
     String name = buildPath.getName();
     if (generateNewName) {
       name = generateUniqueName((seqNum < 0) ? null : "_SeqId_" + seqNum + "_");
     }
     Path dstPath = new Path(storeDir, name);
     if (!fs.exists(buildPath)) {
       throw new FileNotFoundException(buildPath.toString());
     }
     LOG.debug("Committing store file " + buildPath + " as " + dstPath);
     // buildPath exists, therefore not doing an exists() check.
     if (!rename(buildPath, dstPath)) {
       throw new IOException("Failed rename of " + buildPath + " to " + dstPath);
     }
     return dstPath;
   }
 
 
   /**
    * Moves multiple store files to the relative region's family store directory.
    * @param storeFiles list of store files divided by family
    * @throws IOException
    */
   void commitStoreFiles(final Map<byte[], List<StoreFile>> storeFiles) throws IOException {
     for (Map.Entry<byte[], List<StoreFile>> es: storeFiles.entrySet()) {
       String familyName = Bytes.toString(es.getKey());
       for (StoreFile sf: es.getValue()) {
         commitStoreFile(familyName, sf.getPath());
       }
     }
   }
 
   /**
    * Archives the specified store file from the specified family.
    * @param familyName Family that contains the store files
    * @param filePath {@link Path} to the store file to remove
    * @throws IOException if the archiving fails
    */
   public void removeStoreFile(final String familyName, final Path filePath)
       throws IOException {
     HFileArchiver.archiveStoreFile(this.conf, this.fs, this.regionInfo,
         this.tableDir, Bytes.toBytes(familyName), filePath);
   }
 
   /**
    * Closes and archives the specified store files from the specified family.
    * @param familyName Family that contains the store files
    * @param storeFiles set of store files to remove
    * @throws IOException if the archiving fails
    */
   public void removeStoreFiles(final String familyName, final Collection<StoreFile> storeFiles)
       throws IOException {
     HFileArchiver.archiveStoreFiles(this.conf, this.fs, this.regionInfo,
         this.tableDir, Bytes.toBytes(familyName), storeFiles);
   }
 
   /**
    * Bulk load: Add a specified store file to the specified family.
    * If the source file is on the same different file-system is moved from the
    * source location to the destination location, otherwise is copied over.
    *
    * @param familyName Family that will gain the file
    * @param srcPath {@link Path} to the file to import
    * @param seqNum Bulk Load sequence number
    * @return The destination {@link Path} of the bulk loaded file
    * @throws IOException
    */
   Path bulkLoadStoreFile(final String familyName, Path srcPath, long seqNum)
       throws IOException {
     // Copy the file if it's on another filesystem
     FileSystem srcFs = srcPath.getFileSystem(conf);
     FileSystem desFs = fs instanceof HFileSystem ? ((HFileSystem)fs).getBackingFs() : fs;
 
     // We can't compare FileSystem instances as equals() includes UGI instance
     // as part of the comparison and won't work when doing SecureBulkLoad
     // TODO deal with viewFS
     if (!srcFs.getUri().equals(desFs.getUri())) {
       LOG.info("Bulk-load file " + srcPath + " is on different filesystem than " +
           "the destination store. Copying file over to destination filesystem.");
       Path tmpPath = createTempName();
       FileUtil.copy(srcFs, srcPath, fs, tmpPath, false, conf);
       LOG.info("Copied " + srcPath + " to temporary path on destination filesystem: " + tmpPath);
       srcPath = tmpPath;
     }
 
     return commitStoreFile(familyName, srcPath, seqNum, true);
   }
 
   // ===========================================================================
   //  Splits Helpers
   // ===========================================================================
   /** @return {@link Path} to the temp directory used during split operations */
   Path getSplitsDir() {
     return new Path(getRegionDir(), REGION_SPLITS_DIR);
   }
 
   Path getSplitsDir(final HRegionInfo hri) {
     return new Path(getSplitsDir(), hri.getEncodedName());
   }
 
   /**
    * Clean up any split detritus that may have been left around from previous split attempts.
    */
   void cleanupSplitsDir() throws IOException {
     deleteDir(getSplitsDir());
   }
 
   /**
    * Clean up any split detritus that may have been left around from previous
    * split attempts.
    * Call this method on initial region deploy.
    * @throws IOException
    */
   void cleanupAnySplitDetritus() throws IOException {
     Path splitdir = this.getSplitsDir();
     if (!fs.exists(splitdir)) return;
     // Look at the splitdir.  It could have the encoded names of the daughter
     // regions we tried to make.  See if the daughter regions actually got made
     // out under the tabledir.  If here under splitdir still, then the split did
     // not complete.  Try and do cleanup.  This code WILL NOT catch the case
     // where we successfully created daughter a but regionserver crashed during
     // the creation of region b.  In this case, there'll be an orphan daughter
     // dir in the filesystem.  TOOD: Fix.
     FileStatus[] daughters = FSUtils.listStatus(fs, splitdir, new FSUtils.DirFilter(fs));
     if (daughters != null) {
       for (FileStatus daughter: daughters) {
         Path daughterDir = new Path(getTableDir(), daughter.getPath().getName());
         if (fs.exists(daughterDir) && !deleteDir(daughterDir)) {
           throw new IOException("Failed delete of " + daughterDir);
         }
       }
     }
     cleanupSplitsDir();
     LOG.info("Cleaned up old failed split transaction detritus: " + splitdir);
   }
 
   /**
    * Remove daughter region
    * @param regionInfo daughter {@link HRegionInfo}
    * @throws IOException
    */
   void cleanupDaughterRegion(final HRegionInfo regionInfo) throws IOException {
     Path regionDir = new Path(this.tableDir, regionInfo.getEncodedName());
     if (this.fs.exists(regionDir) && !deleteDir(regionDir)) {
       throw new IOException("Failed delete of " + regionDir);
     }
   }
 
   /**
    * Commit a daughter region, moving it from the split temporary directory
    * to the proper location in the filesystem.
    * @param regionInfo daughter {@link HRegionInfo}
    * @throws IOException
    */
   Path commitDaughterRegion(final HRegionInfo regionInfo) throws IOException {
     Path regionDir = new Path(this.tableDir, regionInfo.getEncodedName());
     Path daughterTmpDir = this.getSplitsDir(regionInfo);
     if (fs.exists(daughterTmpDir) && !rename(daughterTmpDir, regionDir)) {
       throw new IOException("Unable to rename " + daughterTmpDir + " to " + regionDir);
     }
     return regionDir;
   }
 
   /**
    * Create the region splits directory.
    */
   void createSplitsDir() throws IOException {
     Path splitdir = getSplitsDir();
     if (fs.exists(splitdir)) {
       LOG.info("The " + splitdir + " directory exists.  Hence deleting it to recreate it");
       if (!deleteDir(splitdir)) {
         throw new IOException("Failed deletion of " + splitdir
             + " before creating them again.");
       }
     }
     // splitDir doesn't exists now. No need to do an exists() call for it.
     if (!createDir(splitdir)) {
       throw new IOException("Failed create of " + splitdir);
     }
   }
 
   /**
    * Write out a split reference. Package local so it doesnt leak out of
    * regionserver.
    * @param hri {@link HRegionInfo} of the destination
    * @param familyName Column Family Name
    * @param f File to split.
    * @param splitRow Split Row
    * @param top True if we are referring to the top half of the hfile.
    * @return Path to created reference.
    * @throws IOException
    */
   Path splitStoreFile(final HRegionInfo hri, final String familyName,
       final StoreFile f, final byte[] splitRow, final boolean top) throws IOException {
     
     // Check whether the split row lies in the range of the store file
     // If it is outside the range, return directly.
     if (top) {
       //check if larger than last key.
       KeyValue splitKey = KeyValue.createFirstOnRow(splitRow);
       byte[] lastKey = f.createReader().getLastKey();      
       if (f.getReader().getComparator().compare(splitKey.getBuffer(), 
           splitKey.getKeyOffset(), splitKey.getKeyLength(), lastKey, 0, lastKey.length) > 0) {
         return null;
       }
     } else {
       //check if smaller than first key
       KeyValue splitKey = KeyValue.createLastOnRow(splitRow);
       byte[] firstKey = f.createReader().getFirstKey();
       if (f.getReader().getComparator().compare(splitKey.getBuffer(), 
           splitKey.getKeyOffset(), splitKey.getKeyLength(), firstKey, 0, firstKey.length) < 0) {
         return null;
       }      
     }
  
     f.getReader().close(true);
     
     Path splitDir = new Path(getSplitsDir(hri), familyName);
     // A reference to the bottom half of the hsf store file.
     Reference r =
       top ? Reference.createTopReference(splitRow): Reference.createBottomReference(splitRow);
     // Add the referred-to regions name as a dot separated suffix.
     // See REF_NAME_REGEX regex above.  The referred-to regions name is
     // up in the path of the passed in <code>f</code> -- parentdir is family,
     // then the directory above is the region name.
     String parentRegionName = regionInfo.getEncodedName();
     // Write reference with same file id only with the other region name as
     // suffix and into the new region location (under same family).
     Path p = new Path(splitDir, f.getPath().getName() + "." + parentRegionName);
     return r.write(fs, p);
   }
 
   // ===========================================================================
   //  Merge Helpers
   // ===========================================================================
   /** @return {@link Path} to the temp directory used during merge operations */
   Path getMergesDir() {
     return new Path(getRegionDir(), REGION_MERGES_DIR);
   }
 
   Path getMergesDir(final HRegionInfo hri) {
     return new Path(getMergesDir(), hri.getEncodedName());
   }
 
   /**
    * Clean up any merge detritus that may have been left around from previous merge attempts.
    */
   void cleanupMergesDir() throws IOException {
     deleteDir(getMergesDir());
   }
 
   /**
    * Remove merged region
    * @param mergedRegion {@link HRegionInfo}
    * @throws IOException
    */
   void cleanupMergedRegion(final HRegionInfo mergedRegion) throws IOException {
     Path regionDir = new Path(this.tableDir, mergedRegion.getEncodedName());
     if (this.fs.exists(regionDir) && !this.fs.delete(regionDir, true)) {
       throw new IOException("Failed delete of " + regionDir);
     }
   }
 
   /**
    * Create the region merges directory.
    * @throws IOException If merges dir already exists or we fail to create it.
    * @see HRegionFileSystem#cleanupMergesDir()
    */
   void createMergesDir() throws IOException {
     Path mergesdir = getMergesDir();
     if (fs.exists(mergesdir)) {
       LOG.info("The " + mergesdir
           + " directory exists.  Hence deleting it to recreate it");
       if (!fs.delete(mergesdir, true)) {
         throw new IOException("Failed deletion of " + mergesdir
             + " before creating them again.");
       }
     }
     if (!fs.mkdirs(mergesdir))
       throw new IOException("Failed create of " + mergesdir);
   }
 
   /**
    * Write out a merge reference under the given merges directory. Package local
    * so it doesnt leak out of regionserver.
    * @param mergedRegion {@link HRegionInfo} of the merged region
    * @param familyName Column Family Name
    * @param f File to create reference.
    * @param mergedDir
    * @return Path to created reference.
    * @throws IOException
    */
   Path mergeStoreFile(final HRegionInfo mergedRegion, final String familyName,
       final StoreFile f, final Path mergedDir)
       throws IOException {
     Path referenceDir = new Path(new Path(mergedDir,
         mergedRegion.getEncodedName()), familyName);
     // A whole reference to the store file.
     Reference r = Reference.createTopReference(regionInfo.getStartKey());
     // Add the referred-to regions name as a dot separated suffix.
     // See REF_NAME_REGEX regex above. The referred-to regions name is
     // up in the path of the passed in <code>f</code> -- parentdir is family,
     // then the directory above is the region name.
     String mergingRegionName = regionInfo.getEncodedName();
     // Write reference with same file id only with the other region name as
     // suffix and into the new region location (under same family).
     Path p = new Path(referenceDir, f.getPath().getName() + "."
         + mergingRegionName);
     return r.write(fs, p);
   }
 
   /**
    * Commit a merged region, moving it from the merges temporary directory to
    * the proper location in the filesystem.
    * @param mergedRegionInfo merged region {@link HRegionInfo}
    * @throws IOException 
    */
   void commitMergedRegion(final HRegionInfo mergedRegionInfo) throws IOException {
     Path regionDir = new Path(this.tableDir, mergedRegionInfo.getEncodedName());
     Path mergedRegionTmpDir = this.getMergesDir(mergedRegionInfo);
     // Move the tmp dir in the expected location
     if (mergedRegionTmpDir != null && fs.exists(mergedRegionTmpDir)) {
       if (!fs.rename(mergedRegionTmpDir, regionDir)) {
         throw new IOException("Unable to rename " + mergedRegionTmpDir + " to "
             + regionDir);
       }
     }
   }
 
   // ===========================================================================
   //  Create/Open/Delete Helpers
   // ===========================================================================
   /**
    * Log the current state of the region
    * @param LOG log to output information
    * @throws IOException if an unexpected exception occurs
    */
   void logFileSystemState(final Log LOG) throws IOException {
     FSUtils.logFileSystemState(fs, this.getRegionDir(), LOG);
   }
 
   /**
    * @param hri
    * @return Content of the file we write out to the filesystem under a region
    * @throws IOException
    */
   private static byte[] getRegionInfoFileContent(final HRegionInfo hri) throws IOException {
     return hri.toDelimitedByteArray();
   }
 
   /**
    * Create a {@link HRegionInfo} from the serialized version on-disk.
    * @param fs {@link FileSystem} that contains the Region Info file
    * @param regionDir {@link Path} to the Region Directory that contains the Info file
    * @return An {@link HRegionInfo} instance gotten from the Region Info file.
    * @throws IOException if an error occurred during file open/read operation.
    */
   public static HRegionInfo loadRegionInfoFileContent(final FileSystem fs, final Path regionDir)
       throws IOException {
     FSDataInputStream in = fs.open(new Path(regionDir, REGION_INFO_FILE));
     try {
       return HRegionInfo.parseFrom(in);
     } finally {
       in.close();
     }
   }
 
   /**
    * Write the .regioninfo file on-disk.
    */
   private static void writeRegionInfoFileContent(final Configuration conf, final FileSystem fs,
       final Path regionInfoFile, final byte[] content) throws IOException {
     // First check to get the permissions
     FsPermission perms = FSUtils.getFilePermissions(fs, conf, HConstants.DATA_FILE_UMASK_KEY);
     // Write the RegionInfo file content
     FSDataOutputStream out = FSUtils.create(fs, regionInfoFile, perms, null);
     try {
       out.write(content);
     } finally {
       out.close();
     }
   }
 
   /**
    * Write out an info file under the stored region directory. Useful recovering mangled regions.
    * If the regionInfo already exists on-disk, then we fast exit.
    */
   void checkRegionInfoOnFilesystem() throws IOException {
     // Compose the content of the file so we can compare to length in filesystem. If not same,
     // rewrite it (it may have been written in the old format using Writables instead of pb). The
     // pb version is much shorter -- we write now w/o the toString version -- so checking length
     // only should be sufficient. I don't want to read the file every time to check if it pb
     // serialized.
     byte[] content = getRegionInfoFileContent(regionInfo);
     try {
       Path regionInfoFile = new Path(getRegionDir(), REGION_INFO_FILE);
 
       FileStatus status = fs.getFileStatus(regionInfoFile);
       if (status != null && status.getLen() == content.length) {
         // Then assume the content good and move on.
         // NOTE: that the length is not sufficient to define the the content matches.
         return;
       }
 
       LOG.info("Rewriting .regioninfo file at: " + regionInfoFile);
       if (!fs.delete(regionInfoFile, false)) {
         throw new IOException("Unable to remove existing " + regionInfoFile);
       }
     } catch (FileNotFoundException e) {
       LOG.warn(REGION_INFO_FILE + " file not found for region: " + regionInfo.getEncodedName());
     }
 
     // Write HRI to a file in case we need to recover .META.
     writeRegionInfoOnFilesystem(content, true);
   }
 
   /**
    * Write out an info file under the region directory. Useful recovering mangled regions.
    * @param useTempDir indicate whether or not using the region .tmp dir for a safer file creation.
    */
   private void writeRegionInfoOnFilesystem(boolean useTempDir) throws IOException {
     byte[] content = getRegionInfoFileContent(regionInfo);
     writeRegionInfoOnFilesystem(content, useTempDir);
   }
 
   /**
    * Write out an info file under the region directory. Useful recovering mangled regions.
    * @param regionInfoContent serialized version of the {@link HRegionInfo}
    * @param useTempDir indicate whether or not using the region .tmp dir for a safer file creation.
    */
   private void writeRegionInfoOnFilesystem(final byte[] regionInfoContent,
       final boolean useTempDir) throws IOException {
     Path regionInfoFile = new Path(getRegionDir(), REGION_INFO_FILE);
     if (useTempDir) {
       // Create in tmpDir and then move into place in case we crash after
       // create but before close. If we don't successfully close the file,
       // subsequent region reopens will fail the below because create is
       // registered in NN.
 
       // And then create the file
       Path tmpPath = new Path(getTempDir(), REGION_INFO_FILE);
 
       // If datanode crashes or if the RS goes down just before the close is called while trying to
       // close the created regioninfo file in the .tmp directory then on next
       // creation we will be getting AlreadyCreatedException.
       // Hence delete and create the file if exists.
       if (FSUtils.isExists(fs, tmpPath)) {
         FSUtils.delete(fs, tmpPath, true);
       }
 
       // Write HRI to a file in case we need to recover .META.
       writeRegionInfoFileContent(conf, fs, tmpPath, regionInfoContent);
 
       // Move the created file to the original path
       if (fs.exists(tmpPath) &&  !rename(tmpPath, regionInfoFile)) {
         throw new IOException("Unable to rename " + tmpPath + " to " + regionInfoFile);
       }
     } else {
       // Write HRI to a file in case we need to recover .META.
       writeRegionInfoFileContent(conf, fs, regionInfoFile, regionInfoContent);
     }
   }
 
   /**
    * Create a new Region on file-system.
    * @param conf the {@link Configuration} to use
    * @param fs {@link FileSystem} from which to add the region
    * @param tableDir {@link Path} to where the table is being stored
    * @param regionInfo {@link HRegionInfo} for region to be added
    * @throws IOException if the region creation fails due to a FileSystem exception.
    */
   public static HRegionFileSystem createRegionOnFileSystem(final Configuration conf,
       final FileSystem fs, final Path tableDir, final HRegionInfo regionInfo) throws IOException {
     HRegionFileSystem regionFs = new HRegionFileSystem(conf, fs, tableDir, regionInfo);
     Path regionDir = regionFs.getRegionDir();
 
     if (fs.exists(regionDir)) {
       LOG.warn("Trying to create a region that already exists on disk: " + regionDir);
       throw new IOException("The specified region already exists on disk: " + regionDir);
     }
 
     // Create the region directory
     if (!createDirOnFileSystem(fs, conf, regionDir)) {
       LOG.warn("Unable to create the region directory: " + regionDir);
       throw new IOException("Unable to create region directory: " + regionDir);
     }
 
     // Write HRI to a file in case we need to recover .META.
     regionFs.writeRegionInfoOnFilesystem(false);
     return regionFs;
   }
 
   /**
    * Open Region from file-system.
    * @param conf the {@link Configuration} to use
    * @param fs {@link FileSystem} from which to add the region
    * @param tableDir {@link Path} to where the table is being stored
    * @param regionInfo {@link HRegionInfo} for region to be added
    * @param readOnly True if you don't want to edit the region data
    * @throws IOException if the region creation fails due to a FileSystem exception.
    */
   public static HRegionFileSystem openRegionFromFileSystem(final Configuration conf,
       final FileSystem fs, final Path tableDir, final HRegionInfo regionInfo, boolean readOnly)
       throws IOException {
     HRegionFileSystem regionFs = new HRegionFileSystem(conf, fs, tableDir, regionInfo);
     Path regionDir = regionFs.getRegionDir();
 
     if (!fs.exists(regionDir)) {
       LOG.warn("Trying to open a region that do not exists on disk: " + regionDir);
       throw new IOException("The specified region do not exists on disk: " + regionDir);
     }
 
     if (!readOnly) {
       // Cleanup temporary directories
       regionFs.cleanupTempDir();
       regionFs.cleanupSplitsDir();
       regionFs.cleanupMergesDir();
 
       // if it doesn't exists, Write HRI to a file, in case we need to recover .META.
       regionFs.checkRegionInfoOnFilesystem();
     }
 
     return regionFs;
   }
 
   /**
    * Remove the region from the table directory, archiving the region's hfiles.
    * @param conf the {@link Configuration} to use
    * @param fs {@link FileSystem} from which to remove the region
    * @param tableDir {@link Path} to where the table is being stored
    * @param regionInfo {@link HRegionInfo} for region to be deleted
    * @throws IOException if the request cannot be completed
    */
   public static void deleteRegionFromFileSystem(final Configuration conf,
       final FileSystem fs, final Path tableDir, final HRegionInfo regionInfo) throws IOException {
     HRegionFileSystem regionFs = new HRegionFileSystem(conf, fs, tableDir, regionInfo);
     Path regionDir = regionFs.getRegionDir();
 
     if (!fs.exists(regionDir)) {
       LOG.warn("Trying to delete a region that do not exists on disk: " + regionDir);
       return;
     }
 
     if (LOG.isDebugEnabled()) {
       LOG.debug("DELETING region " + regionDir);
     }
 
     // Archive region
     Path rootDir = FSUtils.getRootDir(conf);
     HFileArchiver.archiveRegion(fs, rootDir, tableDir, regionDir);
 
     // Delete empty region dir
     if (!fs.delete(regionDir, true)) {
       LOG.warn("Failed delete of " + regionDir);
     }
   }
 
   /**
    * Creates a directory. Assumes the user has already checked for this directory existence.
    * @param dir
    * @return the result of fs.mkdirs(). In case underlying fs throws an IOException, it checks
    *         whether the directory exists or not, and returns true if it exists.
    * @throws IOException
    */
   boolean createDir(Path dir) throws IOException {
     int i = 0;
     IOException lastIOE = null;
     do {
       try {
         return fs.mkdirs(dir);
       } catch (IOException ioe) {
         lastIOE = ioe;
         if (fs.exists(dir)) return true; // directory is present
         sleepBeforeRetry("Create Directory", i+1);
       }
     } while (++i <= hdfsClientRetriesNumber);
     throw new IOException("Exception in createDir", lastIOE);
   }
 
   /**
    * Renames a directory. Assumes the user has already checked for this directory existence.
    * @param srcpath
    * @param dstPath
    * @return true if rename is successful.
    * @throws IOException
    */
   boolean rename(Path srcpath, Path dstPath) throws IOException {
     IOException lastIOE = null;
     int i = 0;
     do {
       try {
         return fs.rename(srcpath, dstPath);
       } catch (IOException ioe) {
         lastIOE = ioe;
         if (!fs.exists(srcpath) && fs.exists(dstPath)) return true; // successful move
         // dir is not there, retry after some time.
         sleepBeforeRetry("Rename Directory", i+1);
       }
     } while (++i <= hdfsClientRetriesNumber);
     throw new IOException("Exception in rename", lastIOE);
   }
 
   /**
    * Deletes a directory. Assumes the user has already checked for this directory existence.
    * @param dir
    * @return true if the directory is deleted.
    * @throws IOException
    */
   boolean deleteDir(Path dir) throws IOException {
     IOException lastIOE = null;
     int i = 0;
     do {
       try {
         return fs.delete(dir, true);
       } catch (IOException ioe) {
         lastIOE = ioe;
         if (!fs.exists(dir)) return true;
         // dir is there, retry deleting after some time.
         sleepBeforeRetry("Delete Directory", i+1);
       }
     } while (++i <= hdfsClientRetriesNumber);
     throw new IOException("Exception in DeleteDir", lastIOE);
   }
 
   /**
    * sleeping logic; handles the interrupt exception.
    */
   private void sleepBeforeRetry(String msg, int sleepMultiplier) {
     sleepBeforeRetry(msg, sleepMultiplier, baseSleepBeforeRetries, hdfsClientRetriesNumber);
   }
 
   /**
    * Creates a directory for a filesystem and configuration object. Assumes the user has already
    * checked for this directory existence.
    * @param fs
    * @param conf
    * @param dir
    * @return the result of fs.mkdirs(). In case underlying fs throws an IOException, it checks
    *         whether the directory exists or not, and returns true if it exists.
    * @throws IOException
    */
   private static boolean createDirOnFileSystem(FileSystem fs, Configuration conf, Path dir)
       throws IOException {
     int i = 0;
     IOException lastIOE = null;
     int hdfsClientRetriesNumber = conf.getInt("hdfs.client.retries.number",
       DEFAULT_HDFS_CLIENT_RETRIES_NUMBER);
     int baseSleepBeforeRetries = conf.getInt("hdfs.client.sleep.before.retries",
       DEFAULT_BASE_SLEEP_BEFORE_RETRIES);
     do {
       try {
         return fs.mkdirs(dir);
       } catch (IOException ioe) {
         lastIOE = ioe;
         if (fs.exists(dir)) return true; // directory is present
         sleepBeforeRetry("Create Directory", i+1, baseSleepBeforeRetries, hdfsClientRetriesNumber);
       }
     } while (++i <= hdfsClientRetriesNumber);
     throw new IOException("Exception in createDir", lastIOE);
   }
 
   /**
    * sleeping logic for static methods; handles the interrupt exception. Keeping a static version
    * for this to avoid re-looking for the integer values.
    */
   private static void sleepBeforeRetry(String msg, int sleepMultiplier, int baseSleepBeforeRetries,
       int hdfsClientRetriesNumber) {
     if (sleepMultiplier > hdfsClientRetriesNumber) {
       LOG.debug(msg + ", retries exhausted");
       return;
     }
     LOG.debug(msg + ", sleeping " + baseSleepBeforeRetries + " times " + sleepMultiplier);
     Threads.sleep(baseSleepBeforeRetries * sleepMultiplier);
   }
 }