/**
    *
    * 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.master;
  
  import java.io.IOException;
  import java.io.InterruptedIOException;
  import java.util.ArrayList;
  import java.util.HashSet;
  import java.util.List;
  import java.util.Set;
  import java.util.concurrent.locks.Lock;
  import java.util.concurrent.locks.ReentrantLock;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.fs.FileStatus;
  import org.apache.hadoop.fs.FileSystem;
  import org.apache.hadoop.fs.Path;
  import org.apache.hadoop.fs.PathFilter;
  import org.apache.hadoop.fs.permission.FsPermission;
  import org.apache.hadoop.hbase.ClusterId;
  import org.apache.hadoop.hbase.TableName;
  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.InvalidFamilyOperationException;
  import org.apache.hadoop.hbase.RemoteExceptionHandler;
  import org.apache.hadoop.hbase.Server;
  import org.apache.hadoop.hbase.ServerName;
  import org.apache.hadoop.hbase.backup.HFileArchiver;
  import org.apache.hadoop.hbase.exceptions.DeserializationException;
  import org.apache.hadoop.hbase.fs.HFileSystem;
  import org.apache.hadoop.hbase.protobuf.generated.ZooKeeperProtos.SplitLogTask.RecoveryMode;
  import org.apache.hadoop.hbase.regionserver.HRegion;
  import org.apache.hadoop.hbase.wal.DefaultWALProvider;
  import org.apache.hadoop.hbase.wal.WALSplitter;
  import org.apache.hadoop.hbase.util.Bytes;
  import org.apache.hadoop.hbase.util.EnvironmentEdgeManager;
  import org.apache.hadoop.hbase.util.FSTableDescriptors;
  import org.apache.hadoop.hbase.util.FSUtils;
  
  import com.google.common.annotations.VisibleForTesting;
  
  /**
   * This class abstracts a bunch of operations the HMaster needs to interact with
   * the underlying file system, including splitting log files, checking file
   * system status, etc.
   */
  @InterfaceAudience.Private
  public class MasterFileSystem {
    private static final Log LOG = LogFactory.getLog(MasterFileSystem.class.getName());
    // HBase configuration
    Configuration conf;
    // master status
    Server master;
    // metrics for master
    private final MetricsMasterFileSystem metricsMasterFilesystem = new MetricsMasterFileSystem();
    // Persisted unique cluster ID
    private ClusterId clusterId;
    // Keep around for convenience.
    private final FileSystem fs;
    // Is the fileystem ok?
    private volatile boolean fsOk = true;
    // The Path to the old logs dir
    private final Path oldLogDir;
    // root hbase directory on the FS
    private final Path rootdir;
    // hbase temp directory used for table construction and deletion
    private final Path tempdir;
    // create the split log lock
    final Lock splitLogLock = new ReentrantLock();
    final boolean distributedLogReplay;
    final SplitLogManager splitLogManager;
    private final MasterServices services;
  
    final static PathFilter META_FILTER = new PathFilter() {
      @Override
      public boolean accept(Path p) {
        return DefaultWALProvider.isMetaFile(p);
      }
   };
 
   final static PathFilter NON_META_FILTER = new PathFilter() {
     @Override
     public boolean accept(Path p) {
       return !DefaultWALProvider.isMetaFile(p);
     }
   };
 
   public MasterFileSystem(Server master, MasterServices services)
   throws IOException {
     this.conf = master.getConfiguration();
     this.master = master;
     this.services = services;
     // Set filesystem to be that of this.rootdir else we get complaints about
     // mismatched filesystems if hbase.rootdir is hdfs and fs.defaultFS is
     // default localfs.  Presumption is that rootdir is fully-qualified before
     // we get to here with appropriate fs scheme.
     this.rootdir = FSUtils.getRootDir(conf);
     this.tempdir = new Path(this.rootdir, HConstants.HBASE_TEMP_DIRECTORY);
     // Cover both bases, the old way of setting default fs and the new.
     // We're supposed to run on 0.20 and 0.21 anyways.
     this.fs = this.rootdir.getFileSystem(conf);
     FSUtils.setFsDefault(conf, new Path(this.fs.getUri()));
     // make sure the fs has the same conf
     fs.setConf(conf);
     // setup the filesystem variable
     // set up the archived logs path
     this.oldLogDir = createInitialFileSystemLayout();
     HFileSystem.addLocationsOrderInterceptor(conf);
     this.splitLogManager =
         new SplitLogManager(master, master.getConfiguration(), master, services,
             master.getServerName());
     this.distributedLogReplay = this.splitLogManager.isLogReplaying();
   }
 
   @VisibleForTesting
   SplitLogManager getSplitLogManager() {
     return this.splitLogManager;
   }
 
   /**
    * Create initial layout in filesystem.
    * <ol>
    * <li>Check if the meta region exists and is readable, if not create it.
    * Create hbase.version and the hbase:meta directory if not one.
    * </li>
    * <li>Create a log archive directory for RS to put archived logs</li>
    * </ol>
    * Idempotent.
    */
   private Path createInitialFileSystemLayout() throws IOException {
     // check if the root directory exists
     checkRootDir(this.rootdir, conf, this.fs);
 
     // check if temp directory exists and clean it
     checkTempDir(this.tempdir, conf, this.fs);
 
     Path oldLogDir = new Path(this.rootdir, HConstants.HREGION_OLDLOGDIR_NAME);
 
     // Make sure the region servers can archive their old logs
     if(!this.fs.exists(oldLogDir)) {
       this.fs.mkdirs(oldLogDir);
     }
 
     return oldLogDir;
   }
 
   public FileSystem getFileSystem() {
     return this.fs;
   }
 
   /**
    * Get the directory where old logs go
    * @return the dir
    */
   public Path getOldLogDir() {
     return this.oldLogDir;
   }
 
   /**
    * Checks to see if the file system is still accessible.
    * If not, sets closed
    * @return false if file system is not available
    */
   public boolean checkFileSystem() {
     if (this.fsOk) {
       try {
         FSUtils.checkFileSystemAvailable(this.fs);
         FSUtils.checkDfsSafeMode(this.conf);
       } catch (IOException e) {
         master.abort("Shutting down HBase cluster: file system not available", e);
         this.fsOk = false;
       }
     }
     return this.fsOk;
   }
 
   /**
    * @return HBase root dir.
    */
   public Path getRootDir() {
     return this.rootdir;
   }
 
   /**
    * @return HBase temp dir.
    */
   public Path getTempDir() {
     return this.tempdir;
   }
 
   /**
    * @return The unique identifier generated for this cluster
    */
   public ClusterId getClusterId() {
     return clusterId;
   }
 
   /**
    * Inspect the log directory to find dead servers which need recovery work
    * @return A set of ServerNames which aren't running but still have WAL files left in file system
    */
   Set<ServerName> getFailedServersFromLogFolders() {
     boolean retrySplitting = !conf.getBoolean("hbase.hlog.split.skip.errors",
         WALSplitter.SPLIT_SKIP_ERRORS_DEFAULT);
 
     Set<ServerName> serverNames = new HashSet<ServerName>();
     Path logsDirPath = new Path(this.rootdir, HConstants.HREGION_LOGDIR_NAME);
 
     do {
       if (master.isStopped()) {
         LOG.warn("Master stopped while trying to get failed servers.");
         break;
       }
       try {
         if (!this.fs.exists(logsDirPath)) return serverNames;
         FileStatus[] logFolders = FSUtils.listStatus(this.fs, logsDirPath, null);
         // Get online servers after getting log folders to avoid log folder deletion of newly
         // checked in region servers . see HBASE-5916
         Set<ServerName> onlineServers = ((HMaster) master).getServerManager().getOnlineServers()
             .keySet();
 
         if (logFolders == null || logFolders.length == 0) {
           LOG.debug("No log files to split, proceeding...");
           return serverNames;
         }
         for (FileStatus status : logFolders) {
           FileStatus[] curLogFiles = FSUtils.listStatus(this.fs, status.getPath(), null);
           if (curLogFiles == null || curLogFiles.length == 0) {
             // Empty log folder. No recovery needed
             continue;
           }
           final ServerName serverName = DefaultWALProvider.getServerNameFromWALDirectoryName(
               status.getPath());
           if (null == serverName) {
             LOG.warn("Log folder " + status.getPath() + " doesn't look like its name includes a " +
                 "region server name; leaving in place. If you see later errors about missing " +
                 "write ahead logs they may be saved in this location.");
           } else if (!onlineServers.contains(serverName)) {
             LOG.info("Log folder " + status.getPath() + " doesn't belong "
                 + "to a known region server, splitting");
             serverNames.add(serverName);
           } else {
             LOG.info("Log folder " + status.getPath() + " belongs to an existing region server");
           }
         }
         retrySplitting = false;
       } catch (IOException ioe) {
         LOG.warn("Failed getting failed servers to be recovered.", ioe);
         if (!checkFileSystem()) {
           LOG.warn("Bad Filesystem, exiting");
           Runtime.getRuntime().halt(1);
         }
         try {
           if (retrySplitting) {
             Thread.sleep(conf.getInt("hbase.hlog.split.failure.retry.interval", 30 * 1000));
           }
         } catch (InterruptedException e) {
           LOG.warn("Interrupted, aborting since cannot return w/o splitting");
           Thread.currentThread().interrupt();
           retrySplitting = false;
           Runtime.getRuntime().halt(1);
         }
       }
     } while (retrySplitting);
 
     return serverNames;
   }
 
   public void splitLog(final ServerName serverName) throws IOException {
     Set<ServerName> serverNames = new HashSet<ServerName>();
     serverNames.add(serverName);
     splitLog(serverNames);
   }
 
   /**
    * Specialized method to handle the splitting for meta WAL
    * @param serverName
    * @throws IOException
    */
   public void splitMetaLog(final ServerName serverName) throws IOException {
     Set<ServerName> serverNames = new HashSet<ServerName>();
     serverNames.add(serverName);
     splitMetaLog(serverNames);
   }
 
   /**
    * Specialized method to handle the splitting for meta WAL
    * @param serverNames
    * @throws IOException
    */
   public void splitMetaLog(final Set<ServerName> serverNames) throws IOException {
     splitLog(serverNames, META_FILTER);
   }
 
   @edu.umd.cs.findbugs.annotations.SuppressWarnings(value="UL_UNRELEASED_LOCK", justification=
       "We only release this lock when we set it. Updates to code that uses it should verify use " +
       "of the guard boolean.")
   private List<Path> getLogDirs(final Set<ServerName> serverNames) throws IOException {
     List<Path> logDirs = new ArrayList<Path>();
     boolean needReleaseLock = false;
     if (!this.services.isInitialized()) {
       // during master initialization, we could have multiple places splitting a same wal
       this.splitLogLock.lock();
       needReleaseLock = true;
     }
     try {
       for (ServerName serverName : serverNames) {
         Path logDir = new Path(this.rootdir,
             DefaultWALProvider.getWALDirectoryName(serverName.toString()));
         Path splitDir = logDir.suffix(DefaultWALProvider.SPLITTING_EXT);
         // Rename the directory so a rogue RS doesn't create more WALs
         if (fs.exists(logDir)) {
           if (!this.fs.rename(logDir, splitDir)) {
             throw new IOException("Failed fs.rename for log split: " + logDir);
           }
           logDir = splitDir;
           LOG.debug("Renamed region directory: " + splitDir);
         } else if (!fs.exists(splitDir)) {
           LOG.info("Log dir for server " + serverName + " does not exist");
           continue;
         }
         logDirs.add(splitDir);
       }
     } catch (IOException ioe) {
       if (!checkFileSystem()) {
         this.services.abort("Aborting due to filesystem unavailable", ioe);
         throw ioe;
       }
     } finally {
       if (needReleaseLock) {
         this.splitLogLock.unlock();
       }
     }
     return logDirs;
   }
 
   /**
    * Mark regions in recovering state when distributedLogReplay are set true
    * @param serverName Failed region server whose wals to be replayed
    * @param regions Set of regions to be recovered
    * @throws IOException
    */
   public void prepareLogReplay(ServerName serverName, Set<HRegionInfo> regions) throws IOException {
     if (!this.distributedLogReplay) {
       return;
     }
     // mark regions in recovering state
     if (regions == null || regions.isEmpty()) {
       return;
     }
     this.splitLogManager.markRegionsRecovering(serverName, regions);
   }
 
   public void splitLog(final Set<ServerName> serverNames) throws IOException {
     splitLog(serverNames, NON_META_FILTER);
   }
 
   /**
    * Wrapper function on {@link SplitLogManager#removeStaleRecoveringRegions(Set)}
    * @param failedServers
    * @throws IOException
    */
   void removeStaleRecoveringRegionsFromZK(final Set<ServerName> failedServers)
       throws IOException, InterruptedIOException {
     this.splitLogManager.removeStaleRecoveringRegions(failedServers);
   }
 
   /**
    * This method is the base split method that splits WAL files matching a filter. Callers should
    * pass the appropriate filter for meta and non-meta WALs.
    * @param serverNames logs belonging to these servers will be split; this will rename the log
    *                    directory out from under a soft-failed server
    * @param filter
    * @throws IOException
    */
   public void splitLog(final Set<ServerName> serverNames, PathFilter filter) throws IOException {
     long splitTime = 0, splitLogSize = 0;
     List<Path> logDirs = getLogDirs(serverNames);
 
     splitLogManager.handleDeadWorkers(serverNames);
     splitTime = EnvironmentEdgeManager.currentTime();
     splitLogSize = splitLogManager.splitLogDistributed(serverNames, logDirs, filter);
     splitTime = EnvironmentEdgeManager.currentTime() - splitTime;
 
     if (this.metricsMasterFilesystem != null) {
       if (filter == META_FILTER) {
         this.metricsMasterFilesystem.addMetaWALSplit(splitTime, splitLogSize);
       } else {
         this.metricsMasterFilesystem.addSplit(splitTime, splitLogSize);
       }
     }
   }
 
   /**
    * Get the rootdir.  Make sure its wholesome and exists before returning.
    * @param rd
    * @param c
    * @param fs
    * @return hbase.rootdir (after checks for existence and bootstrapping if
    * needed populating the directory with necessary bootup files).
    * @throws IOException
    */
   @SuppressWarnings("deprecation")
   private Path checkRootDir(final Path rd, final Configuration c,
     final FileSystem fs)
   throws IOException {
     // If FS is in safe mode wait till out of it.
     FSUtils.waitOnSafeMode(c, c.getInt(HConstants.THREAD_WAKE_FREQUENCY, 10 * 1000));
 
     boolean isSecurityEnabled = "kerberos".equalsIgnoreCase(c.get("hbase.security.authentication"));
     FsPermission rootDirPerms = new FsPermission(c.get("hbase.rootdir.perms", "700"));
 
     // Filesystem is good. Go ahead and check for hbase.rootdir.
     try {
       if (!fs.exists(rd)) {
         if (isSecurityEnabled) {
           fs.mkdirs(rd, rootDirPerms);
         } else {
           fs.mkdirs(rd);
         }
         // DFS leaves safe mode with 0 DNs when there are 0 blocks.
         // We used to handle this by checking the current DN count and waiting until
         // it is nonzero. With security, the check for datanode count doesn't work --
         // it is a privileged op. So instead we adopt the strategy of the jobtracker
         // and simply retry file creation during bootstrap indefinitely. As soon as
         // there is one datanode it will succeed. Permission problems should have
         // already been caught by mkdirs above.
         FSUtils.setVersion(fs, rd, c.getInt(HConstants.THREAD_WAKE_FREQUENCY,
           10 * 1000), c.getInt(HConstants.VERSION_FILE_WRITE_ATTEMPTS,
             HConstants.DEFAULT_VERSION_FILE_WRITE_ATTEMPTS));
       } else {
         if (!fs.isDirectory(rd)) {
           throw new IllegalArgumentException(rd.toString() + " is not a directory");
         }
         if (isSecurityEnabled && !rootDirPerms.equals(fs.getFileStatus(rd).getPermission())) {
           // check whether the permission match
           LOG.warn("Found rootdir permissions NOT matching expected \"hbase.rootdir.perms\" for "
               + "rootdir=" + rd.toString() + " permissions=" + fs.getFileStatus(rd).getPermission()
               + " and  \"hbase.rootdir.perms\" configured as "
               + c.get("hbase.rootdir.perms", "700") + ". Automatically setting the permissions. You"
               + " can change the permissions by setting \"hbase.rootdir.perms\" in hbase-site.xml "
               + "and restarting the master");
           fs.setPermission(rd, rootDirPerms);
         }
         // as above
         FSUtils.checkVersion(fs, rd, true, c.getInt(HConstants.THREAD_WAKE_FREQUENCY,
           10 * 1000), c.getInt(HConstants.VERSION_FILE_WRITE_ATTEMPTS,
             HConstants.DEFAULT_VERSION_FILE_WRITE_ATTEMPTS));
       }
     } catch (DeserializationException de) {
       LOG.fatal("Please fix invalid configuration for " + HConstants.HBASE_DIR, de);
       IOException ioe = new IOException();
       ioe.initCause(de);
       throw ioe;
     } catch (IllegalArgumentException iae) {
       LOG.fatal("Please fix invalid configuration for "
         + HConstants.HBASE_DIR + " " + rd.toString(), iae);
       throw iae;
     }
     // Make sure cluster ID exists
     if (!FSUtils.checkClusterIdExists(fs, rd, c.getInt(
         HConstants.THREAD_WAKE_FREQUENCY, 10 * 1000))) {
       FSUtils.setClusterId(fs, rd, new ClusterId(), c.getInt(HConstants.THREAD_WAKE_FREQUENCY, 10 * 1000));
     }
     clusterId = FSUtils.getClusterId(fs, rd);
 
     // Make sure the meta region directory exists!
     if (!FSUtils.metaRegionExists(fs, rd)) {
       bootstrap(rd, c);
     } else {
       // Migrate table descriptor files if necessary
       org.apache.hadoop.hbase.util.FSTableDescriptorMigrationToSubdir
         .migrateFSTableDescriptorsIfNecessary(fs, rd);
     }
 
     // Create tableinfo-s for hbase:meta if not already there.
 
     // meta table is a system table, so descriptors are predefined,
     // we should get them from registry.
     FSTableDescriptors fsd = new FSTableDescriptors(c, fs, rd);
     fsd.createTableDescriptor(
       new HTableDescriptor(fsd.get(TableName.META_TABLE_NAME)));
 
     return rd;
   }
 
   /**
    * Make sure the hbase temp directory exists and is empty.
    * NOTE that this method is only executed once just after the master becomes the active one.
    */
   private void checkTempDir(final Path tmpdir, final Configuration c, final FileSystem fs)
       throws IOException {
     // If the temp directory exists, clear the content (left over, from the previous run)
     if (fs.exists(tmpdir)) {
       // Archive table in temp, maybe left over from failed deletion,
       // if not the cleaner will take care of them.
       for (Path tabledir: FSUtils.getTableDirs(fs, tmpdir)) {
         for (Path regiondir: FSUtils.getRegionDirs(fs, tabledir)) {
           HFileArchiver.archiveRegion(fs, this.rootdir, tabledir, regiondir);
         }
       }
       if (!fs.delete(tmpdir, true)) {
         throw new IOException("Unable to clean the temp directory: " + tmpdir);
       }
     }
 
     // Create the temp directory
     if (!fs.mkdirs(tmpdir)) {
       throw new IOException("HBase temp directory '" + tmpdir + "' creation failure.");
     }
   }
 
   private static void bootstrap(final Path rd, final Configuration c)
   throws IOException {
     LOG.info("BOOTSTRAP: creating hbase:meta region");
     try {
       // Bootstrapping, make sure blockcache is off.  Else, one will be
       // created here in bootstrap and it'll need to be cleaned up.  Better to
       // not make it in first place.  Turn off block caching for bootstrap.
       // Enable after.
       HRegionInfo metaHRI = new HRegionInfo(HRegionInfo.FIRST_META_REGIONINFO);
       HTableDescriptor metaDescriptor = new FSTableDescriptors(c).get(TableName.META_TABLE_NAME);
       setInfoFamilyCachingForMeta(metaDescriptor, false);
       HRegion meta = HRegion.createHRegion(metaHRI, rd, c, metaDescriptor, null, true, true);
       setInfoFamilyCachingForMeta(metaDescriptor, true);
       HRegion.closeHRegion(meta);
     } catch (IOException e) {
       e = RemoteExceptionHandler.checkIOException(e);
       LOG.error("bootstrap", e);
       throw e;
     }
   }
 
   /**
    * Enable in memory caching for hbase:meta
    */
   public static void setInfoFamilyCachingForMeta(final HTableDescriptor metaDescriptor,
       final boolean b) {
     for (HColumnDescriptor hcd: metaDescriptor.getColumnFamilies()) {
       if (Bytes.equals(hcd.getName(), HConstants.CATALOG_FAMILY)) {
         hcd.setBlockCacheEnabled(b);
         hcd.setInMemory(b);
       }
     }
   }
 
   public void deleteRegion(HRegionInfo region) throws IOException {
     HFileArchiver.archiveRegion(conf, fs, region);
   }
 
   public void deleteTable(TableName tableName) throws IOException {
     fs.delete(FSUtils.getTableDir(rootdir, tableName), true);
   }
 
   /**
    * Move the specified table to the hbase temp directory
    * @param tableName Table name to move
    * @return The temp location of the table moved
    * @throws IOException in case of file-system failure
    */
   public Path moveTableToTemp(TableName tableName) throws IOException {
     Path srcPath = FSUtils.getTableDir(rootdir, tableName);
     Path tempPath = FSUtils.getTableDir(this.tempdir, tableName);
 
     // Ensure temp exists
     if (!fs.exists(tempPath.getParent()) && !fs.mkdirs(tempPath.getParent())) {
       throw new IOException("HBase temp directory '" + tempPath.getParent() + "' creation failure.");
     }
 
     if (!fs.rename(srcPath, tempPath)) {
       throw new IOException("Unable to move '" + srcPath + "' to temp '" + tempPath + "'");
     }
 
     return tempPath;
   }
 
   public void updateRegionInfo(HRegionInfo region) {
     // TODO implement this.  i think this is currently broken in trunk i don't
     //      see this getting updated.
     //      @see HRegion.checkRegioninfoOnFilesystem()
   }
 
   public void deleteFamilyFromFS(HRegionInfo region, byte[] familyName)
       throws IOException {
     // archive family store files
     Path tableDir = FSUtils.getTableDir(rootdir, region.getTable());
     HFileArchiver.archiveFamily(fs, conf, region, tableDir, familyName);
 
     // delete the family folder
     Path familyDir = new Path(tableDir,
       new Path(region.getEncodedName(), Bytes.toString(familyName)));
     if (fs.delete(familyDir, true) == false) {
       if (fs.exists(familyDir)) {
         throw new IOException("Could not delete family "
             + Bytes.toString(familyName) + " from FileSystem for region "
             + region.getRegionNameAsString() + "(" + region.getEncodedName()
             + ")");
       }
     }
   }
 
   public void stop() {
     if (splitLogManager != null) {
       this.splitLogManager.stop();
     }
   }
 
   /**
    * Delete column of a table
    * @param tableName
    * @param familyName
    * @return Modified HTableDescriptor with requested column deleted.
    * @throws IOException
    */
   public HTableDescriptor deleteColumn(TableName tableName, byte[] familyName)
       throws IOException {
     LOG.info("DeleteColumn. Table = " + tableName
         + " family = " + Bytes.toString(familyName));
     HTableDescriptor htd = this.services.getTableDescriptors().get(tableName);
     htd.removeFamily(familyName);
     this.services.getTableDescriptors().add(htd);
     return htd;
   }
 
   /**
    * Modify Column of a table
    * @param tableName
    * @param hcd HColumnDesciptor
    * @return Modified HTableDescriptor with the column modified.
    * @throws IOException
    */
   public HTableDescriptor modifyColumn(TableName tableName, HColumnDescriptor hcd)
       throws IOException {
     LOG.info("AddModifyColumn. Table = " + tableName
         + " HCD = " + hcd.toString());
 
     HTableDescriptor htd = this.services.getTableDescriptors().get(tableName);
     byte [] familyName = hcd.getName();
     if(!htd.hasFamily(familyName)) {
       throw new InvalidFamilyOperationException("Family '" +
         Bytes.toString(familyName) + "' doesn't exists so cannot be modified");
     }
     htd.modifyFamily(hcd);
     this.services.getTableDescriptors().add(htd);
     return htd;
   }
 
   /**
    * Add column to a table
    * @param tableName
    * @param hcd
    * @return Modified HTableDescriptor with new column added.
    * @throws IOException
    */
   public HTableDescriptor addColumn(TableName tableName, HColumnDescriptor hcd)
       throws IOException {
     LOG.info("AddColumn. Table = " + tableName + " HCD = " +
       hcd.toString());
     HTableDescriptor htd = this.services.getTableDescriptors().get(tableName);
     if (htd == null) {
       throw new InvalidFamilyOperationException("Family '" +
         hcd.getNameAsString() + "' cannot be modified as HTD is null");
     }
     htd.addFamily(hcd);
     this.services.getTableDescriptors().add(htd);
     return htd;
   }
 
   /**
    * The function is used in SSH to set recovery mode based on configuration after all outstanding
    * log split tasks drained.
    * @throws IOException
    */
   public void setLogRecoveryMode() throws IOException {
       this.splitLogManager.setRecoveryMode(false);
   }
 
   public RecoveryMode getLogRecoveryMode() {
     return this.splitLogManager.getRecoveryMode();
   }
 
   public void logFileSystemState(Log log) throws IOException {
     FSUtils.logFileSystemState(fs, rootdir, log);
   }
 }