Add client-info property to get the number of servers currently in the cluster

and which servers that are available. (patch from  Nikolaj Fogh) 

h2/src/docsrc/html/advanced.html

@@ -390,6 +390,15 @@ If the result is <code>''</code> (two single quotes), then the cluster mode is d
 servers is returned, enclosed in single quote. Example: <code>'server1:9191,server2:9191'</code>.
 </p>
 
+<p>It is also possible to get the list of servers by using Connection.getClientInfo().</p>
+
+<p>The property list returned from <code>getClientInfo()</code> contains a <code>numServers</code> property that returns the 
+number of servers that are in the connection list. To get the actual servers, <code>getClientInfo()</code> also has
+properties <code>server0</code>..<code>serverX</code>, where serverX is the number of servers minus 1.
+
+<p>Example: To get the 2nd server in the connection list one uses <code>getClientInfo('server1')<code>. <b>Note:</b> The 
+<code>serverX</code> property only returns IP addresses and ports and not hostnames.</p>
+
 <h3>Clustering Algorithm and Limitations</h3>
 <p>
 Read-only queries are only executed against the first cluster node, but all other statements are

h2/src/docsrc/html/changelog.html

@@ -19,6 +19,8 @@ Change Log
 <h2>Next Version (unreleased)</h2>
 <ul><li>The LIRS cache now re-sizes the internal hash map if needed.
 <ul><li>Optionally persist session history in the H2 console. (patch from Martin Grajcar)
+<ul><li>Add client-info property to get the number of servers currently in the cluster
+and which servers that are available. (patch from  Nikolaj Fogh) 
 </li></ul>
 
 <h2>Version 1.4.179 Beta (2014-06-23)</h2>

h2/src/main/org/h2/engine/Session.java

@@ -127,6 +127,10 @@ public class Session extends SessionWithState {
         this.currentSchemaName = Constants.SCHEMA_MAIN;
     }
 
+    public ArrayList<String> getClusterServers() {
+        return new ArrayList<String>();
+    }
+    
     public boolean setCommitOrRollbackDisabled(boolean x) {
         boolean old = commitOrRollbackDisabled;
         commitOrRollbackDisabled = x;

h2/src/main/org/h2/engine/SessionInterface.java

@@ -6,6 +6,8 @@
 package org.h2.engine;
 
 import java.io.Closeable;
+import java.util.ArrayList;
+
 import org.h2.command.CommandInterface;
 import org.h2.message.Trace;
 import org.h2.store.DataHandler;
@@ -16,6 +18,13 @@ import org.h2.value.Value;
  */
 public interface SessionInterface extends Closeable {
 
+    /**
+     * Get the list of the cluster servers for this session.
+     *
+     * @return A list of "IP:PORT" strings for the cluster servers in this session.
+     */
+    ArrayList<String> getClusterServers();
+    
     /**
      * Parse a command and prepare it for execution.
      *

h2/src/main/org/h2/engine/SessionRemote.java

@@ -95,6 +95,15 @@ public class SessionRemote extends SessionWithState implements DataHandler {
         this.connectionInfo = ci;
     }
 
+    public ArrayList<String> getClusterServers() {
+        ArrayList<String> serverList = new ArrayList<String>();
+        for (int i = 0; i < transferList.size(); i++) {
+            Transfer transfer = transferList.get(i);
+            serverList.add(transfer.getSocket().getInetAddress().getHostAddress().toString() + ":" + String.valueOf(transfer.getSocket().getPort()));
+        }
+        return serverList;
+    }
+    
     private Transfer initTransfer(ConnectionInfo ci, String db, String server)
             throws IOException {
         Socket socket = NetUtils.createSocket(server,

h2/src/main/org/h2/jdbc/JdbcConnection.java

@@ -25,6 +25,7 @@ import java.sql.SQLXML;
 import java.sql.Savepoint;
 import java.sql.Statement;
 import java.sql.Struct;
+import java.util.ArrayList;
 import java.util.Map;
 import java.util.Properties;
 
@@ -1715,35 +1716,44 @@ public class JdbcConnection extends TraceObject implements Connection {
 
     /**
      * Get the client properties.
-     * This method always returns null.
      *
-     * @return always null
+     * @return the property list
      */
     @Override
     public Properties getClientInfo() throws SQLException {
         try {
-            debugCode("getClientInfo();");
-            // we don't have any client properties, so return null
-            return null;
+            if (isDebugEnabled()) {
+                debugCode("getClientInfo();");
+						}
+            checkClosed();
+            ArrayList<String> serverList = session.getClusterServers();
+            Properties p = new Properties();
+
+            p.setProperty("numServers", String.valueOf(serverList.size()));
+            for (int i = 0; i < serverList.size(); i++) {
+                p.setProperty("server" + String.valueOf(i), serverList.get(i));
+            }
+            return p;
         } catch (Exception e) {
             throw logAndConvert(e);
         }
     }
 
     /**
-     * Set a client property.
-     * This method always throws a SQLClientInfoException.
+     * Get a client property.
      *
      * @param name the client info name (ignored)
-     * @return this method never returns normally
+     * @return the property value
      */
     @Override
     public String getClientInfo(String name) throws SQLException {
         try {
-            debugCodeCall("getClientInfo", name);
+            if (isDebugEnabled()) {
+                debugCodeCall("getClientInfo", name);
+            }
             checkClosed();
-            // we don't have any client properties, so just throw
-            throw new SQLClientInfoException();
+        	  Properties p = getClientInfo();
+            return p.getProperty(name);
         } catch (Exception e) {
             throw logAndConvert(e);
         }

h2/src/test/org/h2/test/db/TestCluster.java

@@ -10,6 +10,7 @@ import java.sql.PreparedStatement;
 import java.sql.ResultSet;
 import java.sql.SQLException;
 import java.sql.Statement;
+import java.util.Properties;
 
 import org.h2.api.ErrorCode;
 import org.h2.store.fs.FileUtils;
@@ -39,6 +40,7 @@ public class TestCluster extends TestBase {
         testRecover();
         testRollback();
         testCase();
+        testClientInfo();
         testCreateClusterAtRuntime();
         testStartStopCluster();
     }
@@ -250,6 +252,60 @@ public class TestCluster extends TestBase {
         n1.stop();
         deleteFiles();
     }
+    
+    private void testClientInfo() throws SQLException {
+        if (config.memory || config.networked || config.cipher != null) {
+            return;
+        }
+        int port1 = 9191, port2 = 9192;
+        String serverList = "localhost:" + port1 + ",localhost:" + port2;
+        deleteFiles();
+
+        org.h2.Driver.load();
+        String user = getUser(), password = getPassword();
+        Connection conn;
+
+        String url1 = getURL("jdbc:h2:tcp://localhost:" + port1 + "/test", true);
+        String url2 = getURL("jdbc:h2:tcp://localhost:" + port2 + "/test", true);
+        String urlCluster = getURL("jdbc:h2:tcp://" + serverList + "/test", true);
+
+        Server n1 = org.h2.tools.Server.createTcpServer("-tcpPort",
+                "" + port1, "-baseDir", getBaseDir() + "/node1").start();
+        Server n2 = org.h2.tools.Server.createTcpServer("-tcpPort",
+                "" + port2 , "-baseDir", getBaseDir() + "/node2").start();
+
+        CreateCluster.main("-urlSource", url1, "-urlTarget", url2,
+                "-user", user, "-password", password, "-serverList",
+                serverList);
+
+        conn = getConnection(urlCluster, user, password);
+        Properties p = conn.getClientInfo();
+		
+		    assertEquals("2", p.getProperty("numServers"));
+        assertEquals("127.0.0.1:" + port1, p.getProperty("server0"));
+        assertEquals("127.0.0.1:" + port2, p.getProperty("server1"));
+
+		    assertEquals("2", conn.getClientInfo("numServers"));
+        assertEquals("127.0.0.1:" + port1, conn.getClientInfo("server0"));
+        assertEquals("127.0.0.1:" + port2, conn.getClientInfo("server1"));
+        conn.close();
+
+        // stop server 2, and test if only one server is available
+        n2.stop();
+
+        conn = getConnection(urlCluster, user, password);
+        p = conn.getClientInfo();
+        
+        assertEquals("1", p.getProperty("numServers"));
+        assertEquals("127.0.0.1:" + port1, p.getProperty("server0"));
+        assertEquals("1", conn.getClientInfo("numServers"));
+        assertEquals("127.0.0.1:" + port1, conn.getClientInfo("server0"));
+        conn.close();
+
+        n1.stop();
+        deleteFiles();
+    }
+    
     private void testCreateClusterAtRuntime() throws SQLException {
         if (config.memory || config.networked || config.cipher != null) {
             return;