HBASE-2531 32-bit encoding of regionnames waaaaaaayyyyy too susceptible to hash clashes

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@949919 13f79535-47bb-0310-9956-ffa450edef68

CHANGES.txt

@@ -1032,6 +1032,8 @@ Release 0.20.0 - Tue Sep  8 12:53:05 PDT 2009
    HBASE-2352  Small values for hbase.client.retries.number and
                ipc.client.connect.max.retries breaks long ops in hbase shell
                (Alexey Kovyrin via Stack)
+   HBASE-2531  32-bit encoding of regionnames waaaaaaayyyyy too susceptible to
+               hash clashes (Kannan Muthukkaruppan via Stack)
 
   IMPROVEMENTS
    HBASE-1089  Add count of regions on filesystem to master UI; add percentage

bin/add_table.rb

@@ -19,14 +19,15 @@
 #
 # Script adds a table back to a running hbase.
 # Currently only works on if table data is in place.
-# 
+#
-# To see usage for this script, run: 
+# To see usage for this script, run:
 #
 #  ${HBASE_HOME}/bin/hbase org.jruby.Main addtable.rb
 #
 include Java
 import org.apache.hadoop.hbase.util.Bytes
 import org.apache.hadoop.hbase.HConstants
+import org.apache.hadoop.hbase.regionserver.HRegion
 import org.apache.hadoop.hbase.HRegionInfo
 import org.apache.hadoop.hbase.client.HTable
 import org.apache.hadoop.hbase.client.Delete
@@ -84,7 +85,7 @@ elsif
 end
 HTableDescriptor.isLegalTableName(tableName.to_java_bytes)
 
-# Figure locations under hbase.rootdir 
+# Figure locations under hbase.rootdir
 # Move directories into place; be careful not to overwrite.
 rootdir = FSUtils.getRootDir(c)
 tableDir = fs.makeQualified(Path.new(rootdir, tableName))
@@ -129,15 +130,15 @@ statuses = fs.listStatus(srcdir)
 for status in statuses
   next unless status.isDir()
   next if status.getPath().getName() == "compaction.dir"
-  regioninfofile =  Path.new(status.getPath(), ".regioninfo")
+  regioninfofile =  Path.new(status.getPath(), HRegion::REGIONINFO_FILE)
   unless fs.exists(regioninfofile)
     LOG.warn("Missing .regioninfo: " + regioninfofile.toString())
     next
   end
-  is = fs.open(regioninfofile) 
+  is = fs.open(regioninfofile)
   hri = HRegionInfo.new()
   hri.readFields(is)
-  is.close() 
+  is.close()
   # TODO: Need to redo table descriptor with passed table name and then recalculate the region encoded names.
   p = Put.new(hri.getRegionName())
   p.add(HConstants::CATALOG_FAMILY, HConstants::REGIONINFO_QUALIFIER, Writables.getBytes(hri))

src/main/java/org/apache/hadoop/hbase/HRegionInfo.java

@@ -24,9 +24,12 @@ import java.io.DataOutput;
 import java.io.IOException;
 import java.util.Arrays;
 
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
 import org.apache.hadoop.hbase.KeyValue.KVComparator;
 import org.apache.hadoop.hbase.util.Bytes;
 import org.apache.hadoop.hbase.util.JenkinsHash;
+import org.apache.hadoop.hbase.util.MD5Hash;
 import org.apache.hadoop.io.VersionedWritable;
 import org.apache.hadoop.io.WritableComparable;
 
@@ -37,13 +40,74 @@ import org.apache.hadoop.io.WritableComparable;
  */
 public class HRegionInfo extends VersionedWritable implements WritableComparable<HRegionInfo>{
   private static final byte VERSION = 0;
+  private static final Log LOG = LogFactory.getLog(HRegionInfo.class);
 
+  /**
+   * The new format for a region name contains its encodedName at the end.
+   * The encoded name also serves as the directory name for the region
+   * in the filesystem.
+   *
+   * New region name format:
+   *    &lt;tablename>,,&lt;startkey>,&lt;regionIdTimestamp>.&lt;encodedName>.
+   * where,
+   *    &lt;encodedName> is a hex version of the MD5 hash of
+   *    &lt;tablename>,&lt;startkey>,&lt;regionIdTimestamp>
+   * 
+   * The old region name format:
+   *    &lt;tablename>,&lt;startkey>,&lt;regionIdTimestamp>
+   * For region names in the old format, the encoded name is a 32-bit
+   * JenkinsHash integer value (in its decimal notation, string form). 
+   *<p>
+   * **NOTE**
+   *
+   * ROOT, the first META region, and regions created by an older
+   * version of HBase (0.20 or prior) will continue to use the
+   * old region name format.
+   */
+
+  /** Separator used to demarcate the encodedName in a region name
+   * in the new format. See description on new format above. 
+   */ 
+  private static final int ENC_SEPARATOR = '.';
+  public  static final int MD5_HEX_LENGTH   = 32;
+
+  /**
+   * Does region name contain its encoded name?
+   * @param regionName region name
+   * @return boolean indicating if this a new format region
+   *         name which contains its encoded name.
+   */
+  private static boolean hasEncodedName(final byte[] regionName) {
+    // check if region name ends in ENC_SEPARATOR
+    if ((regionName.length >= 1)
+        && (regionName[regionName.length - 1] == ENC_SEPARATOR)) {
+      // region name is new format. it contains the encoded name.
+      return true; 
+    }
+    return false;
+  }
+  
   /**
    * @param regionName
    * @return the encodedName
    */
-  public static int encodeRegionName(final byte [] regionName) {
+  public static String encodeRegionName(final byte [] regionName) {
-    return Math.abs(JenkinsHash.getInstance().hash(regionName, regionName.length, 0));
+    String encodedName;
+    if (hasEncodedName(regionName)) {
+      // region is in new format:
+      // <tableName>,<startKey>,<regionIdTimeStamp>/encodedName/
+      encodedName = Bytes.toString(regionName,
+          regionName.length - MD5_HEX_LENGTH - 1,
+          MD5_HEX_LENGTH);
+    } else {
+      // old format region name. ROOT and first META region also 
+      // use this format.EncodedName is the JenkinsHash value.
+      int hashVal = Math.abs(JenkinsHash.getInstance().hash(regionName,
+                                                            regionName.length,
+                                                            0));
+      encodedName = String.valueOf(hashVal);
+    }
+    return encodedName;
   }
 
   /** delimiter used between portions of a region name */
@@ -67,8 +131,8 @@ public class HRegionInfo extends VersionedWritable implements WritableComparable
   protected HTableDescriptor tableDesc = null;
   private int hashCode = -1;
   //TODO: Move NO_HASH to HStoreFile which is really the only place it is used.
-  public static final int NO_HASH = -1;
+  public static final String NO_HASH = null;
-  private volatile int encodedName = NO_HASH;
+  private volatile String encodedName = NO_HASH;
 
   private void setHashCode() {
     int result = Arrays.hashCode(this.regionName);
@@ -88,7 +152,10 @@ public class HRegionInfo extends VersionedWritable implements WritableComparable
     super();
     this.regionId = regionId;
     this.tableDesc = tableDesc;
-    this.regionName = createRegionName(tableDesc.getName(), null, regionId);
+    
+    // Note: Root & First Meta regions names are still in old format   
+    this.regionName = createRegionName(tableDesc.getName(), null,
+                                       regionId, false);
     this.regionNameStr = Bytes.toStringBinary(this.regionName);
     setHashCode();
   }
@@ -149,7 +216,7 @@ public class HRegionInfo extends VersionedWritable implements WritableComparable
     }
     this.offLine = false;
     this.regionId = regionid;
-    this.regionName = createRegionName(tableDesc.getName(), startKey, regionId);
+    this.regionName = createRegionName(tableDesc.getName(), startKey, regionId, true);
     this.regionNameStr = Bytes.toStringBinary(this.regionName);
     this.split = split;
     this.endKey = endKey == null? HConstants.EMPTY_END_ROW: endKey.clone();
@@ -179,8 +246,8 @@ public class HRegionInfo extends VersionedWritable implements WritableComparable
   }
 
   private static byte [] createRegionName(final byte [] tableName,
-      final byte [] startKey, final long regionid) {
+      final byte [] startKey, final long regionid, boolean newFormat) {
-    return createRegionName(tableName, startKey, Long.toString(regionid));
+    return createRegionName(tableName, startKey, Long.toString(regionid), newFormat);
   }
 
   /**
@@ -188,23 +255,29 @@ public class HRegionInfo extends VersionedWritable implements WritableComparable
    * @param tableName
    * @param startKey Can be null
    * @param id Region id.
+   * @param newFormat should we create the region name in the new format
+   *                  (such that it contains its encoded name?).
    * @return Region name made of passed tableName, startKey and id
    */
   public static byte [] createRegionName(final byte [] tableName,
-      final byte [] startKey, final String id) {
+      final byte [] startKey, final String id, boolean newFormat) {
-    return createRegionName(tableName, startKey, Bytes.toBytes(id));
+    return createRegionName(tableName, startKey, Bytes.toBytes(id), newFormat);
   }
   /**
    * Make a region name of passed parameters.
    * @param tableName
    * @param startKey Can be null
    * @param id Region id
+   * @param newFormat should we create the region name in the new format
+   *                  (such that it contains its encoded name?).
    * @return Region name made of passed tableName, startKey and id
    */
   public static byte [] createRegionName(final byte [] tableName,
-      final byte [] startKey, final byte [] id) {
+      final byte [] startKey, final byte [] id, boolean newFormat) {
     byte [] b = new byte [tableName.length + 2 + id.length +
-       (startKey == null? 0: startKey.length)];
+       (startKey == null? 0: startKey.length) +
+       (newFormat ? (MD5_HEX_LENGTH + 2) : 0)];
+
     int offset = tableName.length;
     System.arraycopy(tableName, 0, b, 0, offset);
     b[offset++] = DELIMITER;
@@ -214,6 +287,31 @@ public class HRegionInfo extends VersionedWritable implements WritableComparable
     }
     b[offset++] = DELIMITER;
     System.arraycopy(id, 0, b, offset, id.length);
+    offset += id.length;
+
+    if (newFormat) {
+      //
+      // Encoded name should be built into the region name.
+      //
+      // Use the region name thus far (namely, <tablename>,<startKey>,<id>)
+      // to compute a MD5 hash to be used as the encoded name, and append
+      // it to the byte buffer.
+      //
+      String md5Hash = MD5Hash.getMD5AsHex(b, 0, offset);
+      byte [] md5HashBytes = Bytes.toBytes(md5Hash);
+
+      if (md5HashBytes.length != MD5_HEX_LENGTH) {
+        LOG.error("MD5-hash length mismatch: Expected=" + MD5_HEX_LENGTH +
+                  "; Got=" + md5HashBytes.length); 
+      }
+
+      // now append the bytes '.<encodedName>.' to the end
+      b[offset++] = ENC_SEPARATOR;
+      System.arraycopy(md5HashBytes, 0, b, offset, MD5_HEX_LENGTH);
+      offset += MD5_HEX_LENGTH;
+      b[offset++] = ENC_SEPARATOR;
+    }
+    
     return b;
   }
 
@@ -281,11 +379,19 @@ public class HRegionInfo extends VersionedWritable implements WritableComparable
    * @return Region name as a String for use in logging, etc.
    */
   public String getRegionNameAsString() {
-    return this.regionNameStr;
+    if (hasEncodedName(this.regionName)) {
+      // new format region names already have their encoded name.
+      return this.regionNameStr;
+    }
+
+    // old format. regionNameStr doesn't have the region name.
+    //
+    //
+    return this.regionNameStr + "." + this.getEncodedName();
   }
 
   /** @return the encoded region name */
-  public synchronized int getEncodedName() {
+  public synchronized String getEncodedName() {
     if (this.encodedName == NO_HASH) {
       this.encodedName = encodeRegionName(this.regionName);
     }

src/main/java/org/apache/hadoop/hbase/client/HBaseAdmin.java

@@ -915,7 +915,7 @@ public class HBaseAdmin {
   private HRegionLocation getFirstMetaServerForTable(final byte [] tableName)
   throws IOException {
     return connection.locateRegion(HConstants.META_TABLE_NAME,
-      HRegionInfo.createRegionName(tableName, null, HConstants.NINES));
+      HRegionInfo.createRegionName(tableName, null, HConstants.NINES, false));
   }
 
   /**

src/main/java/org/apache/hadoop/hbase/client/HConnectionManager.java

@@ -515,7 +515,7 @@ public class HConnectionManager implements HConstants {
       int rowsScanned = 0;
       int rowsOffline = 0;
       byte[] startKey =
-        HRegionInfo.createRegionName(tableName, null, HConstants.ZEROES);
+        HRegionInfo.createRegionName(tableName, null, HConstants.ZEROES, false);
       byte[] endKey;
       HRegionInfo currentRegion;
       Scan scan = new Scan(startKey);
@@ -663,7 +663,7 @@ public class HConnectionManager implements HConstants {
       // the extra 9's on the end are necessary to allow "exact" matches
       // without knowing the precise region names.
       byte [] metaKey = HRegionInfo.createRegionName(tableName, row,
-        HConstants.NINES);
+        HConstants.NINES, false);
       for (int tries = 0; true; tries++) {
         if (tries >= numRetries) {
           throw new NoServerForRegionException("Unable to find region for "

src/main/java/org/apache/hadoop/hbase/client/MetaScanner.java

@@ -63,7 +63,7 @@ class MetaScanner implements HConstants {
     HConnection connection = HConnectionManager.getConnection(configuration);
     byte [] startRow = tableName == null || tableName.length == 0 ?
         HConstants.EMPTY_START_ROW :
-          HRegionInfo.createRegionName(tableName, null, ZEROES);
+          HRegionInfo.createRegionName(tableName, null, ZEROES, false);
 
     // Scan over each meta region
     ScannerCallable callable;

src/main/java/org/apache/hadoop/hbase/io/hfile/HFile.java

@@ -800,7 +800,7 @@ public class HFile {
      * See {@link Writer#appendFileInfo(byte[], byte[])}.
      * @throws IOException
      */
-    public Map<byte [], byte []> loadFileInfo() 
+    public Map<byte [], byte []> loadFileInfo()
     throws IOException {
       this.trailer = readTrailer();
 
@@ -895,7 +895,7 @@ public class HFile {
      * @return Block wrapped in a ByteBuffer
      * @throws IOException
      */
-    public ByteBuffer getMetaBlock(String metaBlockName, boolean cacheBlock) 
+    public ByteBuffer getMetaBlock(String metaBlockName, boolean cacheBlock)
     throws IOException {
       if (trailer.metaIndexCount == 0) {
         return null; // there are no meta blocks
@@ -903,7 +903,7 @@ public class HFile {
       if (metaIndex == null) {
         throw new IOException("Meta index not loaded");
       }
-      
+
       byte [] mbname = Bytes.toBytes(metaBlockName);
       int block = metaIndex.blockContainingKey(mbname, 0, mbname.length);
       if (block == -1)
@@ -924,34 +924,34 @@ public class HFile {
         if (cache != null) {
           ByteBuffer cachedBuf = cache.getBlock(name + "meta" + block);
           if (cachedBuf != null) {
-            // Return a distinct 'shallow copy' of the block, 
+            // Return a distinct 'shallow copy' of the block,
             // so pos doesnt get messed by the scanner
             cacheHits++;
             return cachedBuf.duplicate();
           }
           // Cache Miss, please load.
         }
-        
+
         ByteBuffer buf = decompress(metaIndex.blockOffsets[block],
           longToInt(blockSize), metaIndex.blockDataSizes[block], true);
         byte [] magic = new byte[METABLOCKMAGIC.length];
         buf.get(magic, 0, magic.length);
-  
+
         if (! Arrays.equals(magic, METABLOCKMAGIC)) {
           throw new IOException("Meta magic is bad in block " + block);
         }
-        
+
         // Create a new ByteBuffer 'shallow copy' to hide the magic header
         buf = buf.slice();
-  
+
         readTime += System.currentTimeMillis() - now;
         readOps++;
-  
+
         // Cache the block
         if(cacheBlock && cache != null) {
           cache.cacheBlock(name + "meta" + block, buf.duplicate(), inMemory);
         }
-  
+
         return buf;
       }
     }
@@ -983,7 +983,7 @@ public class HFile {
         if (cache != null) {
           ByteBuffer cachedBuf = cache.getBlock(name + block);
           if (cachedBuf != null) {
-            // Return a distinct 'shallow copy' of the block, 
+            // Return a distinct 'shallow copy' of the block,
             // so pos doesnt get messed by the scanner
             cacheHits++;
             return cachedBuf.duplicate();
@@ -1015,10 +1015,10 @@ public class HFile {
         }
 
         // 'shallow copy' to hide the header
-        // NOTE: you WILL GET BIT if you call buf.array() but don't start 
+        // NOTE: you WILL GET BIT if you call buf.array() but don't start
         //       reading at buf.arrayOffset()
         buf = buf.slice();
-        
+
         readTime += System.currentTimeMillis() - now;
         readOps++;
 
@@ -1096,7 +1096,7 @@ public class HFile {
       }
       return this.blockIndex.isEmpty()? null: this.lastkey;
     }
-    
+
     /**
      * @return number of K entries in this HFile's filter.  Returns KV count if no filter.
      */
@@ -1222,7 +1222,7 @@ public class HFile {
         return true;
       }
 
-      public boolean shouldSeek(final byte[] row, 
+      public boolean shouldSeek(final byte[] row,
           final SortedSet<byte[]> columns) {
         return true;
       }
@@ -1773,8 +1773,8 @@ public class HFile {
         byte[][] hri = HRegionInfo.parseRegionName(rn);
         Path rootDir = FSUtils.getRootDir(conf);
         Path tableDir = new Path(rootDir, Bytes.toString(hri[0]));
-        int enc = HRegionInfo.encodeRegionName(rn);
+        String enc = HRegionInfo.encodeRegionName(rn);
-        Path regionDir = new Path(tableDir, Integer.toString(enc));
+        Path regionDir = new Path(tableDir, enc);
         if (verbose) System.out.println("region dir -> " + regionDir);
         List<Path> regionFiles = getStoreFiles(fs, regionDir);
         if (verbose) System.out.println("Number of region files found -> " +

src/main/java/org/apache/hadoop/hbase/regionserver/HRegion.java

@@ -224,12 +224,6 @@ public class HRegion implements HConstants, HeapSize { // , Writable{
    */
   public final static String REGIONINFO_FILE = ".regioninfo";
 
-  /**
-   * REGIONINFO_FILE as byte array.
-   */
-  public final static byte [] REGIONINFO_FILE_BYTES =
-    Bytes.toBytes(REGIONINFO_FILE);
-
   /**
    * Should only be used for testing purposes
    */
@@ -283,12 +277,11 @@ public class HRegion implements HConstants, HeapSize { // , Writable{
     this.regionInfo = regionInfo;
     this.flushListener = flushListener;
     this.threadWakeFrequency = conf.getLong(THREAD_WAKE_FREQUENCY, 10 * 1000);
-    String encodedNameStr = Integer.toString(this.regionInfo.getEncodedName());
+    String encodedNameStr = this.regionInfo.getEncodedName();
     this.regiondir = new Path(basedir, encodedNameStr);
     if (LOG.isDebugEnabled()) {
       // Write out region name as string and its encoded name.
-      LOG.debug("Creating region " + this + ", encoded=" +
+      LOG.debug("Creating region " + this);
-        this.regionInfo.getEncodedName());
     }
     this.regionCompactionDir =
       new Path(getCompactionDir(basedir), encodedNameStr);
@@ -363,8 +356,8 @@ public class HRegion implements HConstants, HeapSize { // , Writable{
     // HRegion is ready to go!
     this.writestate.compacting = false;
     this.lastFlushTime = System.currentTimeMillis();
-    LOG.info("region " + this + "/" + this.regionInfo.getEncodedName() +
+    LOG.info("region " + this +
-      " available; sequence id is " + this.minSequenceId);
+             " available; sequence id is " + this.minSequenceId);
   }
 
   /*
@@ -728,7 +721,7 @@ public class HRegion implements HConstants, HeapSize { // , Writable{
   private Path getSplitDirForDaughter(final Path splits, final HRegionInfo hri)
   throws IOException {
     Path d =
-      new Path(splits, Integer.toString(hri.getEncodedName()));
+      new Path(splits, hri.getEncodedName());
     if (fs.exists(d)) {
       // This should never happen; the splits dir will be newly made when we
       // come in here.  Even if we crashed midway through a split, the reopen
@@ -2322,8 +2315,8 @@ public class HRegion implements HConstants, HeapSize { // , Writable{
    * @param name ENCODED region name
    * @return Path of HRegion directory
    */
-  public static Path getRegionDir(final Path tabledir, final int name) {
+  public static Path getRegionDir(final Path tabledir, final String name) {
-    return new Path(tabledir, Integer.toString(name));
+    return new Path(tabledir, name);
   }
 
   /**
@@ -2336,7 +2329,7 @@ public class HRegion implements HConstants, HeapSize { // , Writable{
   public static Path getRegionDir(final Path rootdir, final HRegionInfo info) {
     return new Path(
       HTableDescriptor.getTableDir(rootdir, info.getTableDesc().getName()),
-      Integer.toString(info.getEncodedName()));
+                                   info.getEncodedName());
   }
 
   /**
@@ -2464,7 +2457,7 @@ public class HRegion implements HConstants, HeapSize { // , Writable{
 
     HRegionInfo newRegionInfo = new HRegionInfo(tabledesc, startKey, endKey);
     LOG.info("Creating new region " + newRegionInfo.toString());
-    int encodedName = newRegionInfo.getEncodedName();
+    String encodedName = newRegionInfo.getEncodedName();
     Path newRegionDir = HRegion.getRegionDir(a.getBaseDir(), encodedName);
     if(fs.exists(newRegionDir)) {
       throw new IOException("Cannot merge; target file collision at " +

src/main/java/org/apache/hadoop/hbase/regionserver/Store.java

@@ -191,7 +191,7 @@ public class Store implements HConstants, HeapSize {
     }
     this.memstore = new MemStore(this.comparator);
     this.regionCompactionDir = new Path(HRegion.getCompactionDir(basedir),
-        Integer.toString(info.getEncodedName()));
+                                        info.getEncodedName());
     this.storeName = this.family.getName();
     this.storeNameStr = Bytes.toString(this.storeName);
 
@@ -252,8 +252,8 @@ public class Store implements HConstants, HeapSize {
    * @return Path to family/Store home directory.
    */
   public static Path getStoreHomedir(final Path tabledir,
-      final int encodedName, final byte [] family) {
+      final String encodedName, final byte [] family) {
-    return new Path(tabledir, new Path(Integer.toString(encodedName),
+    return new Path(tabledir, new Path(encodedName,
       new Path(Bytes.toString(family))));
   }
 
@@ -413,7 +413,7 @@ public class Store implements HConstants, HeapSize {
       }
       StoreFile curfile = null;
       try {
-        curfile = new StoreFile(fs, p, blockcache, this.conf, 
+        curfile = new StoreFile(fs, p, blockcache, this.conf,
             this.family.getBloomFilterType(), this.inMemory);
         curfile.createReader();
       } catch (IOException ioe) {
@@ -582,10 +582,10 @@ public class Store implements HConstants, HeapSize {
    * @param basedir Directory to put writer in.
    * @throws IOException
    */
-  private StoreFile.Writer createWriter(final Path basedir, int maxKeyCount) 
+  private StoreFile.Writer createWriter(final Path basedir, int maxKeyCount)
   throws IOException {
     return StoreFile.createWriter(this.fs, basedir, this.blocksize,
-        this.compression, this.comparator, this.conf, 
+        this.compression, this.comparator, this.conf,
         this.family.getBloomFilterType(), maxKeyCount);
   }
 
@@ -879,9 +879,9 @@ public class Store implements HConstants, HeapSize {
     for (StoreFile file : filesToCompact) {
       StoreFile.Reader r = file.getReader();
       if (r != null) {
-        // NOTE: getFilterEntries could cause under-sized blooms if the user 
+        // NOTE: getFilterEntries could cause under-sized blooms if the user
         //       switches bloom type (e.g. from ROW to ROWCOL)
-        maxKeyCount += (r.getBloomFilterType() == family.getBloomFilterType()) 
+        maxKeyCount += (r.getBloomFilterType() == family.getBloomFilterType())
           ? r.getFilterEntries() : r.getEntries();
       }
     }
@@ -977,7 +977,7 @@ public class Store implements HConstants, HeapSize {
         LOG.error("Failed move of compacted file " + compactedFile.getPath(), e);
         return null;
       }
-      result = new StoreFile(this.fs, p, blockcache, this.conf, 
+      result = new StoreFile(this.fs, p, blockcache, this.conf,
           this.family.getBloomFilterType(), this.inMemory);
       result.createReader();
     }
@@ -1004,7 +1004,7 @@ public class Store implements HConstants, HeapSize {
         // WARN ugly hack here, but necessary sadly.
         // TODO why is this necessary? need a comment here if it's unintuitive!
         ReadWriteConsistencyControl.resetThreadReadPoint(region.getRWCC());
-        
+
         // Tell observers that list of StoreFiles has changed.
         notifyChangedReadersObservers();
         // Finally, delete old store files.
@@ -1475,7 +1475,7 @@ public class Store implements HConstants, HeapSize {
    * This function will always be seen as atomic by other readers
    * because it only puts a single KV to memstore. Thus no
    * read/write control necessary.
-   * 
+   *
    * @param row
    * @param f
    * @param qualifier
@@ -1563,7 +1563,7 @@ public class Store implements HConstants, HeapSize {
       if (storeFile == null) {
         return false;
       }
-      // Add new file to store files.  Clear snapshot too while we have 
+      // Add new file to store files.  Clear snapshot too while we have
       // the Store write lock.
       return Store.this.updateStorefiles(cacheFlushId, storeFile, snapshot);
     }

src/main/java/org/apache/hadoop/hbase/util/MD5Hash.java

@@ -0,0 +1,67 @@
+/**
+ * Copyright 2010 The Apache Software Foundation
+ *
+ * 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.util;
+
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+
+import org.apache.commons.codec.binary.Hex;
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+
+/**
+ * Utility class for MD5
+ * MD5 hash produces a 128-bit digest.
+ */
+public class MD5Hash {
+  private static final Log LOG = LogFactory.getLog(MD5Hash.class);
+
+  /**
+   * Given a byte array, returns in MD5 hash as a hex string.
+   * @param key
+   * @return SHA1 hash as a 32 character hex string.
+   */
+  public static String getMD5AsHex(byte[] key) {
+    return getMD5AsHex(key, 0, key.length);
+  }
+  
+  /**
+   * Given a byte array, returns its MD5 hash as a hex string.
+   * Only "length" number of bytes starting at "offset" within the
+   * byte array are used.
+   *
+   * @param key the key to hash (variable length byte array)
+   * @param offset
+   * @param length 
+   * @return MD5 hash as a 32 character hex string.
+   */
+  public static String getMD5AsHex(byte[] key, int offset, int length) {
+    try {
+      MessageDigest md = MessageDigest.getInstance("MD5");
+      md.update(key, offset, length);
+      byte[] digest = md.digest();
+      return new String(Hex.encodeHex(digest));
+    } catch (NoSuchAlgorithmException e) {
+      // this should never happen unless the JDK is messed up.
+      throw new RuntimeException("Error computing MD5 hash", e);
+    }
+  }
+}

src/main/resources/hbase-webapps/master/table.jsp

@@ -18,7 +18,7 @@
   HBaseAdmin hbadmin = new HBaseAdmin(conf);
   String tableName = request.getParameter("name");
   HTable table = new HTable(conf, tableName);
-  String tableHeader = "<h2>Table Regions</h2><table><tr><th>Name</th><th>Region Server</th><th>Encoded Name</th><th>Start Key</th><th>End Key</th></tr>";
+  String tableHeader = "<h2>Table Regions</h2><table><tr><th>Name</th><th>Region Server</th><th>Start Key</th><th>End Key</th></tr>";
   HServerAddress rootLocation = master.getRegionManager().getRootRegionLocation();
   boolean showFragmentation = conf.getBoolean("hbase.master.ui.fragmentation.enabled", false);
   Map<String, Integer> frags = null;
@@ -146,7 +146,7 @@
 <tr>
   <td><%= Bytes.toStringBinary(hriEntry.getKey().getRegionName())%></td>
   <td><a href="<%= urlRegionServer %>"><%= hriEntry.getValue().getHostname().toString() + ":" + infoPort %></a></td>
-  <td><%= hriEntry.getKey().getEncodedName()%></td> <td><%= Bytes.toStringBinary(hriEntry.getKey().getStartKey())%></td>
+  <td><%= Bytes.toStringBinary(hriEntry.getKey().getStartKey())%></td>
   <td><%= Bytes.toStringBinary(hriEntry.getKey().getEndKey())%></td>
 </tr>
 <% } %>

src/main/resources/hbase-webapps/regionserver/regionserver.jsp

@@ -48,11 +48,11 @@
 <h2>Online Regions</h2>
 <% if (onlineRegions != null && onlineRegions.size() > 0) { %>
 <table>
-<tr><th>Region Name</th><th>Encoded Name</th><th>Start Key</th><th>End Key</th><th>Metrics</th></tr>
+<tr><th>Region Name</th><th>Start Key</th><th>End Key</th><th>Metrics</th></tr>
 <%   for (HRegionInfo r: onlineRegions) { 
         HServerLoad.RegionLoad load = regionServer.createRegionLoad(r.getRegionName());
  %>
-<tr><td><%= r.getRegionNameAsString() %></td><td><%= r.getEncodedName() %></td>
+<tr><td><%= r.getRegionNameAsString() %></td>
     <td><%= Bytes.toStringBinary(r.getStartKey()) %></td><td><%= Bytes.toStringBinary(r.getEndKey()) %></td>
     <td><%= load.toString() %></td>
     </tr>

src/test/java/org/apache/hadoop/hbase/TestEmptyMetaInfo.java

@@ -44,7 +44,7 @@ public class TestEmptyMetaInfo extends HBaseClusterTestCase {
     for (int i = 0; i < COUNT; i++) {
       byte [] regionName = HRegionInfo.createRegionName(tableName,
         Bytes.toBytes(i == 0? "": Integer.toString(i)),
-        Long.toString(System.currentTimeMillis()));
+        Long.toString(System.currentTimeMillis()), true);
       Put put = new Put(regionName);
       put.add(HConstants.CATALOG_FAMILY, HConstants.SERVER_QUALIFIER,
           Bytes.toBytes("localhost:1234"));

src/test/java/org/apache/hadoop/hbase/regionserver/TestCompaction.java

@@ -76,7 +76,7 @@ public class TestCompaction extends HBaseTestCase {
     this.r = createNewHRegion(htd, null, null);
     this.compactionDir = HRegion.getCompactionDir(this.r.getBaseDir());
     this.regionCompactionDir = new Path(this.compactionDir,
-        Integer.toString(this.r.getRegionInfo().getEncodedName()));
+                        this.r.getRegionInfo().getEncodedName());
   }
 
   @Override

src/test/java/org/apache/hadoop/hbase/regionserver/TestGetClosestAtOrBefore.java

@@ -111,7 +111,7 @@ public class TestGetClosestAtOrBefore extends HBaseTestCase implements HConstant
     findRow(mr, 'C', 43, 42);
     // Now delete 'C' and make sure I don't get entries from 'B'.
     byte [] firstRowInC = HRegionInfo.createRegionName(Bytes.toBytes("" + 'C'),
-      HConstants.EMPTY_BYTE_ARRAY, HConstants.ZEROES);
+      HConstants.EMPTY_BYTE_ARRAY, HConstants.ZEROES, false);
     Scan scan = new Scan(firstRowInC);
     s = mr.getScanner(scan);
     try {
@@ -150,7 +150,7 @@ public class TestGetClosestAtOrBefore extends HBaseTestCase implements HConstant
     // Find the row.
     byte [] tofindBytes = Bytes.toBytes((short)rowToFind);
     byte [] metaKey = HRegionInfo.createRegionName(tableb, tofindBytes,
-      HConstants.NINES);
+      HConstants.NINES, false);
     LOG.info("find=" + new String(metaKey));
     Result r = mr.getClosestRowBefore(metaKey);
     if (answer == -1) {

src/test/java/org/apache/hadoop/hbase/regionserver/TestHRegionInfo.java

@@ -22,6 +22,7 @@ package org.apache.hadoop.hbase.regionserver;
 import org.apache.hadoop.hbase.HBaseTestCase;
 import org.apache.hadoop.hbase.HRegionInfo;
 import org.apache.hadoop.hbase.util.Bytes;
+import org.apache.hadoop.hbase.util.MD5Hash;
 
 public class TestHRegionInfo extends HBaseTestCase {
   public void testCreateHRegionInfoName() throws Exception {
@@ -30,8 +31,20 @@ public class TestHRegionInfo extends HBaseTestCase {
     String startKey = "startkey";
     final byte [] sk = Bytes.toBytes(startKey);
     String id = "id";
-    byte [] name = HRegionInfo.createRegionName(tn, sk, id);
+
+    // old format region name
+    byte [] name = HRegionInfo.createRegionName(tn, sk, id, false);
     String nameStr = Bytes.toString(name);
-    assertEquals(nameStr, tableName + "," + startKey + "," + id);
+    assertEquals(tableName + "," + startKey + "," + id, nameStr);
+
+
+    // new format region name.
+    String md5HashInHex = MD5Hash.getMD5AsHex(name);
+    assertEquals(HRegionInfo.MD5_HEX_LENGTH, md5HashInHex.length());
+    name = HRegionInfo.createRegionName(tn, sk, id, true);
+    nameStr = Bytes.toString(name);
+    assertEquals(tableName + "," + startKey + ","
+                 + id + "." + md5HashInHex + ".",
+                 nameStr);
   }
 }

src/test/java/org/apache/hadoop/hbase/regionserver/TestStoreFile.java

@@ -149,14 +149,14 @@ public class TestStoreFile extends HBaseTestCase {
     KeyValue midKV = KeyValue.createKeyValueFromKey(midkey);
     byte [] midRow = midKV.getRow();
     // Create top split.
-    Path topDir = Store.getStoreHomedir(this.testDir, 1,
+    Path topDir = Store.getStoreHomedir(this.testDir, "1",
       Bytes.toBytes(f.getPath().getParent().getName()));
     if (this.fs.exists(topDir)) {
       this.fs.delete(topDir, true);
     }
     Path topPath = StoreFile.split(this.fs, topDir, f, midRow, Range.top);
     // Create bottom split.
-    Path bottomDir = Store.getStoreHomedir(this.testDir, 2,
+    Path bottomDir = Store.getStoreHomedir(this.testDir, "2",
       Bytes.toBytes(f.getPath().getParent().getName()));
     if (this.fs.exists(bottomDir)) {
       this.fs.delete(bottomDir, true);