[JAVA-287]: set TCP_KEEPALIVE on the java driver

Author: agirbal

src/main/com/mongodb/DBPort.java

@@ -196,6 +196,7 @@ boolean _open()
                 _socket.connect( _addr , _options.connectTimeout );
 
                 _socket.setTcpNoDelay( ! USE_NAGLE );
+                _socket.setKeepAlive( _options.socketKeepAlive );
                 _socket.setSoTimeout( _options.socketTimeout );
                 _in = new BufferedInputStream( _socket.getInputStream() );
                 _out = _socket.getOutputStream();

src/main/com/mongodb/MongoOptions.java

@@ -35,6 +35,7 @@ public void reset(){
         maxWaitTime = 1000 * 60 * 2;
         connectTimeout = 0;
         socketTimeout = 0;
+        socketKeepAlive = false;
         autoConnectRetry = false;
         slaveOk = false;
         safe = false;
@@ -94,6 +95,14 @@ else if (safe)
      */
     public int socketTimeout;
 
+    /**
+     * This controls whether or not to have socket keep alive
+     * turned on (SO_KEEPALIVE).
+     *
+     * defaults to false
+     */
+    public boolean socketKeepAlive;
+
     /**
      * This controls whether the system retries automatically
      * on connection errors.
@@ -155,6 +164,7 @@ public String toString(){
         buf.append( "maxWaitTime: " ).append( maxWaitTime ).append( " " );
         buf.append( "connectTimeout: " ).append( connectTimeout ).append( " " );
         buf.append( "socketTimeout: " ).append( socketTimeout ).append( " " );
+        buf.append( "socketKeepAlive: " ).append( socketKeepAlive ).append( " " );
         buf.append( "autoConnectRetry: " ).append( autoConnectRetry ).append( " " );
         buf.append( "slaveOk: " ).append( slaveOk ).append( " " );
         buf.append( "safe: " ).append( safe ).append( " " );