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From st...@apache.org
Subject svn commit: r556334 - in /lucene/hadoop/trunk/src/contrib/hbase: ./ src/java/org/apache/hadoop/hbase/ src/test/org/apache/hadoop/hbase/
Date Sat, 14 Jul 2007 20:08:02 GMT
Author: stack
Date: Sat Jul 14 13:08:01 2007
New Revision: 556334

URL: http://svn.apache.org/viewvc?view=rev&rev=556334
Log:
HADOOP-1574 Concurrent creates of a table named 'X' all succeed
M src/contrib/hbase/src/test/org/apache/hadoop/hbase/TestTable.java
    (testTable): Add checking of actual exceptions thrown and
    assertions that we are getting right behavior.  Add a test
    that has ten clients concurrently trying to create same table.
M src/contrib/hbase/src/java/org/apache/hadoop/hbase/HClient.java
    javadoc edit. Fix debug message that could give impression
    table was found when it wasn't.
M src/contrib/hbase/src/java/org/apache/hadoop/hbase/HTableDescriptor.java
    Added comment on table nameing.
M src/contrib/hbase/src/java/org/apache/hadoop/hbase/HMaster.java
    (createTable): Refactored. Bulk moved to a private override.
    Changed how check for existance is done.
M rc/contrib/hbase/src/java/org/apache/hadoop/hbase/HRegionInfo.java
    (getTableNameFromRegionName): Utility method added.
A src/contrib/hbase/src/java/org/apache/hadoop/hbase/TableExistsException.java
    Added.

Modified:
    lucene/hadoop/trunk/src/contrib/hbase/CHANGES.txt
    lucene/hadoop/trunk/src/contrib/hbase/src/java/org/apache/hadoop/hbase/HClient.java
    lucene/hadoop/trunk/src/contrib/hbase/src/java/org/apache/hadoop/hbase/HMaster.java
    lucene/hadoop/trunk/src/contrib/hbase/src/java/org/apache/hadoop/hbase/HRegionInfo.java
    lucene/hadoop/trunk/src/contrib/hbase/src/java/org/apache/hadoop/hbase/HTableDescriptor.java
    lucene/hadoop/trunk/src/contrib/hbase/src/test/org/apache/hadoop/hbase/TestTable.java

Modified: lucene/hadoop/trunk/src/contrib/hbase/CHANGES.txt
URL: http://svn.apache.org/viewvc/lucene/hadoop/trunk/src/contrib/hbase/CHANGES.txt?view=diff&rev=556334&r1=556333&r2=556334
==============================================================================
--- lucene/hadoop/trunk/src/contrib/hbase/CHANGES.txt (original)
+++ lucene/hadoop/trunk/src/contrib/hbase/CHANGES.txt Sat Jul 14 13:08:01 2007
@@ -59,3 +59,4 @@
  35. HADOOP-1375 a simple parser for hbase (Edward Yoon via Stack)
  36. HADOOP-1600 Update license in HBase code
  37. HADOOP-1589 Exception handling in HBase is broken over client server
+ 38. HADOOP-1574 Concurrent creates of a table named 'X' all succeed

Modified: lucene/hadoop/trunk/src/contrib/hbase/src/java/org/apache/hadoop/hbase/HClient.java
URL: http://svn.apache.org/viewvc/lucene/hadoop/trunk/src/contrib/hbase/src/java/org/apache/hadoop/hbase/HClient.java?view=diff&rev=556334&r1=556333&r2=556334
==============================================================================
--- lucene/hadoop/trunk/src/contrib/hbase/src/java/org/apache/hadoop/hbase/HClient.java (original)
+++ lucene/hadoop/trunk/src/contrib/hbase/src/java/org/apache/hadoop/hbase/HClient.java Sat
Jul 14 13:08:01 2007
@@ -220,9 +220,14 @@
    * 
    * @param desc table descriptor for table
    * 
+   * @throws RemoteException if exception occurred on remote side of
+   * connection.
    * @throws IllegalArgumentException if the table name is reserved
    * @throws MasterNotRunningException if master is not running
    * @throws NoServerForRegionException if root region is not being served
+   * @throws TableExistsException if table already exists (If concurrent
+   * threads, the table may have been created between test-for-existence
+   * and attempt-at-creation).
    * @throws IOException
    */
   public synchronized void createTable(HTableDescriptor desc)
@@ -247,13 +252,18 @@
    * 
    * @param desc table descriptor for table
    * 
+   * @throws RemoteException if exception occurred on remote side of
+   * connection.
    * @throws IllegalArgumentException if the table name is reserved
    * @throws MasterNotRunningException if master is not running
    * @throws NoServerForRegionException if root region is not being served
+   * @throws TableExistsException if table already exists (If concurrent
+   * threads, the table may have been created between test-for-existence
+   * and attempt-at-creation).
    * @throws IOException
    */
   public synchronized void createTableAsync(HTableDescriptor desc)
-      throws IOException {
+  throws IOException {
     checkReservedTableName(desc.getName());
     checkMaster();
     try {
@@ -266,7 +276,7 @@
   /**
    * Deletes a table
    * 
-   * @param tableName           - name of table to delete
+   * @param tableName name of table to delete
    * @throws IOException
    */
   public synchronized void deleteTable(Text tableName) throws IOException {
@@ -338,8 +348,8 @@
   /**
    * Add a column to an existing table
    * 
-   * @param tableName   - name of the table to add column to
-   * @param column      - column descriptor of column to be added
+   * @param tableName name of the table to add column to
+   * @param column column descriptor of column to be added
    * @throws IOException
    */
   public synchronized void addColumn(Text tableName, HColumnDescriptor column)
@@ -357,8 +367,8 @@
   /**
    * Delete a column from a table
    * 
-   * @param tableName           - name of table
-   * @param columnName          - name of column to be deleted
+   * @param tableName name of table
+   * @param columnName name of column to be deleted
    * @throws IOException
    */
   public synchronized void deleteColumn(Text tableName, Text columnName)
@@ -376,7 +386,7 @@
   /**
    * Brings a table on-line (enables it)
    * 
-   * @param tableName   - name of the table
+   * @param tableName name of the table
    * @throws IOException
    */
   public synchronized void enableTable(Text tableName) throws IOException {
@@ -467,7 +477,7 @@
    * Disables a table (takes it off-line) If it is being served, the master
    * will tell the servers to stop serving it.
    * 
-   * @param tableName           - name of table
+   * @param tableName name of table
    * @throws IOException
    */
   public synchronized void disableTable(Text tableName) throws IOException {
@@ -591,8 +601,8 @@
   /**
    * Loads information so that a table can be manipulated.
    * 
-   * @param tableName - the table to be located
-   * @throws IOException - if the table can not be located after retrying
+   * @param tableName the table to be located
+   * @throws IOException if the table can not be located after retrying
    */
   public synchronized void openTable(Text tableName) throws IOException {
     if(tableName == null || tableName.getLength() == 0) {
@@ -851,7 +861,8 @@
           if(!regionInfo.tableDesc.getName().equals(tableName)) {
             // We're done
             if (LOG.isDebugEnabled()) {
-              LOG.debug("Found " + tableName);
+              LOG.debug("Found " + servers.size() + " servers for table " +
+                tableName);
             }
             break;
           }
@@ -1352,11 +1363,12 @@
   }
   
   /** 
-   * Change a value for the specified column
+   * Change a value for the specified column.
+   * Runs {@link #abort(long)} if exception thrown.
    *
-   * @param lockid              - lock id returned from startUpdate
-   * @param column              - column whose value is being set
-   * @param val                 - new value for column
+   * @param lockid lock id returned from startUpdate
+   * @param column column whose value is being set
+   * @param val new value for column
    * @throws IOException
    */
   public void put(long lockid, Text column, byte val[]) throws IOException {

Modified: lucene/hadoop/trunk/src/contrib/hbase/src/java/org/apache/hadoop/hbase/HMaster.java
URL: http://svn.apache.org/viewvc/lucene/hadoop/trunk/src/contrib/hbase/src/java/org/apache/hadoop/hbase/HMaster.java?view=diff&rev=556334&r1=556333&r2=556334
==============================================================================
--- lucene/hadoop/trunk/src/contrib/hbase/src/java/org/apache/hadoop/hbase/HMaster.java (original)
+++ lucene/hadoop/trunk/src/contrib/hbase/src/java/org/apache/hadoop/hbase/HMaster.java Sat
Jul 14 13:08:01 2007
@@ -24,10 +24,12 @@
 import java.io.IOException;
 import java.io.UnsupportedEncodingException;
 import java.util.Collections;
+import java.util.HashSet;
 import java.util.Iterator;
 import java.util.LinkedList;
 import java.util.Map;
 import java.util.Random;
+import java.util.Set;
 import java.util.SortedMap;
 import java.util.SortedSet;
 import java.util.Timer;
@@ -49,6 +51,7 @@
 import org.apache.hadoop.ipc.Server;
 import org.apache.hadoop.util.StringUtils;
 
+
 /**
  * HMaster is the "master server" for a HBase.
  * There is only one HMaster for a single HBase deployment.
@@ -174,7 +177,7 @@
       try {
         regionServer = client.getHRegionConnection(region.server);
         scannerId = regionServer.openScanner(region.regionName, METACOLUMNS,
-            FIRST_ROW, System.currentTimeMillis(), null);
+          FIRST_ROW, System.currentTimeMillis(), null);
 
         while (true) {
           TreeMap<Text, byte[]> results = new TreeMap<Text, byte[]>();
@@ -231,7 +234,6 @@
     
     protected void checkAssigned(final HRegionInfo info,
         final String serverName, final long startCode) {
-
       // Skip region - if ...
       if(info.offLine                                           // offline
           || killedRegions.contains(info.regionName)            // queued for offline
@@ -466,7 +468,6 @@
             try {
               
               // Rescan the known meta regions every so often
-
               synchronized(metaScannerLock) { // Don't interrupt us while we're working
                 Vector<MetaRegion> v = new Vector<MetaRegion>();
                 v.addAll(knownMetaRegions.values());
@@ -637,15 +638,13 @@
     this.maxRegionOpenTime = conf.getLong("hbase.hbasemaster.maxregionopen", 30 * 1000);
     this.msgQueue = new LinkedList<PendingOperation>();
     this.serverLeases = new Leases(
-        conf.getLong("hbase.master.lease.period", 30 * 1000), 
-        conf.getLong("hbase.master.lease.thread.wakefrequency", 15 * 1000));
-    
+      conf.getLong("hbase.master.lease.period", 30 * 1000), 
+      conf.getLong("hbase.master.lease.thread.wakefrequency", 15 * 1000));
     this.server = RPC.getServer(this, address.getBindAddress(),
-        address.getPort(), conf.getInt("hbase.regionserver.handler.count", 10),
-        false, conf);
+      address.getPort(), conf.getInt("hbase.regionserver.handler.count", 10),
+      false, conf);
 
     //  The rpc-server port can be ephemeral... ensure we have the correct info
-    
     this.address = new HServerAddress(server.getListenerAddress());
     conf.set(MASTER_ADDRESS, address.toString());
     
@@ -847,13 +846,7 @@
   synchronized boolean waitForRootRegionOrClose() {
     while (!closed && rootRegionLocation == null) {
       try {
-        if (LOG.isDebugEnabled()) {
-          LOG.debug("Wait for root region (or close)");
-        }
         wait(threadWakeFrequency);
-        if (LOG.isDebugEnabled()) {
-          LOG.debug("Wake from wait for root region (or close)");
-        }
       } catch(InterruptedException e) {
         if (LOG.isDebugEnabled()) {
           LOG.debug("Wake from wait for root region (or close) (IE)");
@@ -1154,12 +1147,10 @@
 
       int counter = 0;
       long now = System.currentTimeMillis();
-
-      for(Text curRegionName: unassignedRegions.keySet()) {
+      for (Text curRegionName: unassignedRegions.keySet()) {
         HRegionInfo regionInfo = unassignedRegions.get(curRegionName);
         long assignedTime = assignAttempts.get(curRegionName);
-
-        if(now - assignedTime > maxRegionOpenTime) {
+        if (now - assignedTime > maxRegionOpenTime) {
           if(LOG.isDebugEnabled()) {
             LOG.debug("assigning region " + regionInfo.regionName + " to server "
                 + info.getServerAddress().toString());
@@ -1757,7 +1748,8 @@
   /**
    * {@inheritDoc}
    */
-  public void createTable(HTableDescriptor desc) throws IOException {
+  public void createTable(HTableDescriptor desc)
+  throws IOException {
     if (!isMasterRunning()) {
       throw new MasterNotRunningException();
     }
@@ -1765,61 +1757,13 @@
 
     for(int tries = 0; tries < numRetries; tries++) {
       try {
-        // We can not access any meta region if they have not already been assigned
-        // and scanned.
-
-        if(metaScanner.waitForMetaScanOrClose()) {
-          return;                       // We're shutting down. Forget it.
-        }
-
-        // 1. Check to see if table already exists
-        MetaRegion m = (knownMetaRegions.containsKey(newRegion.regionName))?
-          knownMetaRegions.get(newRegion.regionName):
-          knownMetaRegions.get(
-              knownMetaRegions.headMap(newRegion.regionName).lastKey());
-        Text metaRegionName = m.regionName;
-        HRegionInterface server = client.getHRegionConnection(m.server);
-        byte [] infoBytes =
-          server.get(metaRegionName, desc.getName(), COL_REGIONINFO);
-        if (infoBytes != null && infoBytes.length != 0) {
-          DataInputBuffer inbuf = new DataInputBuffer();
-          inbuf.reset(infoBytes, infoBytes.length);
-          HRegionInfo info = new HRegionInfo();
-          info.readFields(inbuf);
-          if (info.tableDesc.getName().compareTo(desc.getName()) == 0) {
-            throw new IOException("table already exists");
-          }
+        // We can not access meta regions if they have not already been
+        // assigned and scanned.  If we timeout waiting, just shutdown.
+        if (metaScanner.waitForMetaScanOrClose()) {
+          return;
         }
-
-        // 2. Create the HRegion
-        HRegion r = HRegion.createHRegion(newRegion.regionId, desc, this.dir,
-          this.conf);
-
-        // 3. Insert into meta
-
-        HRegionInfo info = r.getRegionInfo();
-        Text regionName = r.getRegionName();
-        ByteArrayOutputStream byteValue = new ByteArrayOutputStream();
-        DataOutputStream s = new DataOutputStream(byteValue);
-        info.write(s);
-
-        long clientId = rand.nextLong();
-        long lockid = server.startUpdate(metaRegionName, clientId, regionName);
-        server.put(metaRegionName, clientId, lockid, COL_REGIONINFO,
-          byteValue.toByteArray());
-        server.commit(metaRegionName, clientId, lockid,
-            System.currentTimeMillis());
-
-        // 4. Close the new region to flush it to disk
-
-        r.close();
-
-        // 5. Get it assigned to a server
-
-        unassignedRegions.put(regionName, info);
-        assignAttempts.put(regionName, Long.valueOf(0L));
+         createTable(newRegion);
         break;
-
       } catch (IOException e) {
         if(tries == numRetries - 1) {
           if (e instanceof RemoteException) {
@@ -1834,6 +1778,81 @@
       LOG.debug("created table " + desc.getName());
     }
   }
+  
+  /*
+   * Set of tables currently in creation. Access needs to be synchronized.
+   */
+  private Set<Text> tableInCreation = new HashSet<Text>();
+  
+  private void createTable(final HRegionInfo newRegion) throws IOException {
+    Text tableName = newRegion.tableDesc.getName();
+    synchronized (tableInCreation) {
+      if (tableInCreation.contains(tableName)) {
+        throw new TableExistsException("Table " + tableName + " in process "
+            + "of being created");
+      }
+      tableInCreation.add(tableName);
+    }
+    try {
+      // 1. Check to see if table already exists. Get meta region where
+      // table would sit should it exist. Open scanner on it. If a region
+      // for the table we want to create already exists, then table already
+      // created. Throw already-exists exception.
+      MetaRegion m = (knownMetaRegions.containsKey(newRegion.regionName))?
+          knownMetaRegions.get(newRegion.regionName):
+            knownMetaRegions.get(knownMetaRegions.
+              headMap(newRegion.getTableDesc().getName()).lastKey());
+      Text metaRegionName = m.regionName;
+      HRegionInterface connection = client.getHRegionConnection(m.server);
+      long scannerid = connection.openScanner(metaRegionName,
+        new Text[] { COL_REGIONINFO }, tableName, System.currentTimeMillis(),
+        null);
+      try {
+        KeyedData[] data = connection.next(scannerid);
+        // Test data and that the row for the data is for our table. If
+        // table does not exist, scanner will return row after where our table
+        // would be inserted if it exists so look for exact match on table
+        // name.
+        if (data != null && data.length > 0 &&
+          HRegionInfo.getTableNameFromRegionName(data[0].getKey().getRow()).
+            equals(tableName)) {
+          // Then a region for this table already exists. Ergo table exists.
+          throw new TableExistsException(tableName.toString());
+        }
+      } finally {
+        connection.close(scannerid);
+      }
+
+      // 2. Create the HRegion
+      HRegion r = HRegion.createHRegion(newRegion.regionId, newRegion.
+        getTableDesc(), this.dir, this.conf);
+
+      // 3. Insert into meta
+      HRegionInfo info = r.getRegionInfo();
+      Text regionName = r.getRegionName();
+      ByteArrayOutputStream byteValue = new ByteArrayOutputStream();
+      DataOutputStream s = new DataOutputStream(byteValue);
+      info.write(s);
+      long clientId = rand.nextLong();
+      long lockid = connection.
+        startUpdate(metaRegionName, clientId, regionName);
+      connection.put(metaRegionName, clientId, lockid, COL_REGIONINFO,
+        byteValue.toByteArray());
+      connection.commit(metaRegionName, clientId, lockid,
+        System.currentTimeMillis());
+
+      // 4. Close the new region to flush it to disk
+      r.close();
+
+      // 5. Get it assigned to a server
+      unassignedRegions.put(regionName, info);
+      assignAttempts.put(regionName, Long.valueOf(0L));
+    } finally {
+      synchronized (tableInCreation) {
+        tableInCreation.remove(newRegion.getTableDesc().getName());
+      }
+    }
+  }
 
   /**
    * {@inheritDoc}
@@ -1865,19 +1884,19 @@
   public void enableTable(Text tableName) throws IOException {
     new ChangeTableState(tableName, true).process();
   }
-  
+
   /**
    * {@inheritDoc}
    */
-  public HServerAddress findRootRegion() {
-    return rootRegionLocation;
+  public void disableTable(Text tableName) throws IOException {
+    new ChangeTableState(tableName, false).process();
   }
-
+  
   /**
    * {@inheritDoc}
    */
-  public void disableTable(Text tableName) throws IOException {
-    new ChangeTableState(tableName, false).process();
+  public HServerAddress findRootRegion() {
+    return rootRegionLocation;
   }
   
   // Helper classes for HMasterInterface

Modified: lucene/hadoop/trunk/src/contrib/hbase/src/java/org/apache/hadoop/hbase/HRegionInfo.java
URL: http://svn.apache.org/viewvc/lucene/hadoop/trunk/src/contrib/hbase/src/java/org/apache/hadoop/hbase/HRegionInfo.java?view=diff&rev=556334&r1=556333&r2=556334
==============================================================================
--- lucene/hadoop/trunk/src/contrib/hbase/src/java/org/apache/hadoop/hbase/HRegionInfo.java
(original)
+++ lucene/hadoop/trunk/src/contrib/hbase/src/java/org/apache/hadoop/hbase/HRegionInfo.java
Sat Jul 14 13:08:01 2007
@@ -40,6 +40,7 @@
   Text endKey;
   boolean offLine;
   HTableDescriptor tableDesc;
+  public static final char DELIMITER = '_';
   
   /** Default constructor - creates empty object */
   public HRegionInfo() {
@@ -92,8 +93,8 @@
       this.endKey.set(endKey);
     }
     
-    this.regionName = new Text(tableDesc.getName() + "_" +
-      (startKey == null ? "" : startKey.toString()) + "_" +
+    this.regionName = new Text(tableDesc.getName().toString() + DELIMITER +
+      (startKey == null ? "" : startKey.toString()) + DELIMITER +
       regionId);
     
     this.offLine = false;
@@ -163,6 +164,30 @@
    */
   public Text getRegionName(){
     return regionName;
+  }
+  
+  /**
+   * Extracts table name prefix from a region name.
+   * Presumes region names are ASCII characters only.
+   * @param regionName A region name.
+   * @return The table prefix of a region name.
+   */
+  public static Text getTableNameFromRegionName(final Text regionName) {
+    int index = -1;
+    byte [] bytes = regionName.getBytes();
+    for (int i = 0; i < bytes.length; i++) {
+      if (((char) bytes[i]) == DELIMITER) {
+        index = i;
+        break;
+      }
+    }
+    if (index == -1) {
+      throw new IllegalArgumentException(regionName.toString() + " does not " +
+        "contain " + DELIMITER + " character");
+    }
+    byte [] tableName = new byte[index];
+    System.arraycopy(bytes, 0, tableName, 0, index);
+    return new Text(tableName);
   }
 
   /**

Modified: lucene/hadoop/trunk/src/contrib/hbase/src/java/org/apache/hadoop/hbase/HTableDescriptor.java
URL: http://svn.apache.org/viewvc/lucene/hadoop/trunk/src/contrib/hbase/src/java/org/apache/hadoop/hbase/HTableDescriptor.java?view=diff&rev=556334&r1=556333&r2=556334
==============================================================================
--- lucene/hadoop/trunk/src/contrib/hbase/src/java/org/apache/hadoop/hbase/HTableDescriptor.java
(original)
+++ lucene/hadoop/trunk/src/contrib/hbase/src/java/org/apache/hadoop/hbase/HTableDescriptor.java
Sat Jul 14 13:08:01 2007
@@ -39,11 +39,12 @@
   Text name;
   TreeMap<Text, HColumnDescriptor> families;
   
-  /**
+  /*
    * Legal table names can only contain 'word characters':
    * i.e. <code>[a-zA-Z_0-9]</code>.
-   * 
-   * Let's be restrictive until a reason to be otherwise.
+   * Lets be restrictive until a reason to be otherwise. One reason to limit
+   * characters in table name is to ensure table regions as entries in META
+   * regions can be found (See HADOOP-1581 'HBASE: Un-openable tablename bug').
    */
   private static final Pattern LEGAL_TABLE_NAME =
     Pattern.compile("[\\w-]+");

Modified: lucene/hadoop/trunk/src/contrib/hbase/src/test/org/apache/hadoop/hbase/TestTable.java
URL: http://svn.apache.org/viewvc/lucene/hadoop/trunk/src/contrib/hbase/src/test/org/apache/hadoop/hbase/TestTable.java?view=diff&rev=556334&r1=556333&r2=556334
==============================================================================
--- lucene/hadoop/trunk/src/contrib/hbase/src/test/org/apache/hadoop/hbase/TestTable.java
(original)
+++ lucene/hadoop/trunk/src/contrib/hbase/src/test/org/apache/hadoop/hbase/TestTable.java
Sat Jul 14 13:08:01 2007
@@ -20,6 +20,7 @@
 package org.apache.hadoop.hbase;
 
 import java.io.IOException;
+import java.util.concurrent.atomic.AtomicInteger;
 
 /** Tests table creation restrictions*/
 public class TestTable extends HBaseClusterTestCase {
@@ -27,55 +28,80 @@
     super(true);
   }
 
-  public void testTable() {
-    HClient client = new HClient(conf);
-    
+  public void testTable() throws IOException {
+    final HClient client = new HClient(conf);
+    String msg = null;
     try {
       client.createTable(HGlobals.rootTableDesc);
-      
-    } catch(IllegalArgumentException e) {
-      // Expected - ignore it
-      
-    } catch(Exception e) {
-      System.err.println("Unexpected exception");
-      e.printStackTrace();
-      fail();
+    } catch (IllegalArgumentException e) {
+      msg = e.toString();
     }
+    assertTrue("Unexcepted exception message " + msg, msg != null &&
+      msg.startsWith(IllegalArgumentException.class.getName()) &&
+      msg.contains(HGlobals.rootTableDesc.getName().toString()));
     
+    msg = null;
     try {
       client.createTable(HGlobals.metaTableDesc);
-      
     } catch(IllegalArgumentException e) {
-      // Expected - ignore it
-      
-    } catch(Exception e) {
-      System.err.println("Unexpected exception");
-      e.printStackTrace();
-      fail();
+      msg = e.toString();
     }
-
-    HTableDescriptor desc = new HTableDescriptor("test");
+    assertTrue("Unexcepted exception message " + msg, msg != null &&
+      msg.startsWith(IllegalArgumentException.class.getName()) &&
+      msg.contains(HGlobals.metaTableDesc.getName().toString()));
+    
+    // Try doing a duplicate database create.
+    msg = null;
+    HTableDescriptor desc = new HTableDescriptor(getName());
     desc.addFamily(new HColumnDescriptor(HConstants.COLUMN_FAMILY.toString()));
-
+    client.createTable(desc);
     try {
       client.createTable(desc);
-      
-    } catch(Exception e) {
-      System.err.println("Unexpected exception");
-      e.printStackTrace();
-      fail();
+    } catch (TableExistsException e) {
+      msg = e.getMessage();
     }
-
-    try {
-      client.createTable(desc);
-      
-    } catch(IOException e) {
-      // Expected. Ignore it.
-      
-    } catch(Exception e) {
-      System.err.println("Unexpected exception");
-      e.printStackTrace();
-      fail();
+    assertTrue("Unexpected exception message " + msg, msg != null &&
+      msg.contains(getName()));
+    
+    // Now try and do concurrent creation with a bunch of threads.
+    final HTableDescriptor threadDesc =
+      new HTableDescriptor("threaded-" + getName());
+    threadDesc.addFamily(new HColumnDescriptor(HConstants.
+      COLUMN_FAMILY.toString()));
+    int count = 10;
+    Thread [] threads = new Thread [count];
+    final AtomicInteger successes = new AtomicInteger(0);
+    final AtomicInteger failures = new AtomicInteger(0);
+    for (int i = 0; i < count; i++) {
+      threads[i] = new Thread(Integer.toString(i)) {
+        @Override
+        public void run() {
+          try {
+            client.createTable(threadDesc);
+            successes.incrementAndGet();
+          } catch (TableExistsException e) {
+            failures.incrementAndGet();
+          } catch (IOException e) {
+            // ignore.
+          }
+        }
+      };
+    }
+    for (int i = 0; i < count; i++) {
+      threads[i].start();
+    }
+    for (int i = 0; i < count; i++) {
+      while(threads[i].isAlive()) {
+        try {
+          Thread.sleep(1000);
+        } catch (InterruptedException e) {
+          // continue
+        }
+      }
     }
+    // All threads are now dead.  Count up how many tables were created and
+    // how many failed w/ appropriate exception.
+    assertTrue(successes.get() == 1);
+    assertTrue(failures.get() == (count - 1));
   }
 }



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