Locking is a special case in which the handle_error event is not called because the ML Server will (when possible) detect that locking has occured and retry, based on the same values you specified for deadlocks when using the -r and -rd switches on the ML Server start line.
Your solution for an SP with an exception handler is one way to handle this from the database, but it will execute a number of times, since the ML Server will retry. Another alternative to capture information using the MobiLink Server would be to implement a Java log listener looking for the -10021 error that the MobiLink Server posts to the log after all attempts to retry have been exhausted. Within the Java code for the log listener, make another connection to the database, and then execute and capture the output from the sa_locks() call. The java code for your very simple log listener might look something like :
import com.sap.ml.script.*;
import java.sql.*;
import java.util.*;
public class Example {
Connection _log_connection;
class MyLogListener implements LogListener {
public void messageLogged( ServerContext sc, LogMessage msg )
{
String user;
if( msg.getText().indexOf("[-10021]") != -1 ) {
try {
PreparedStatement ps_log = _log_connection.prepareStatement( "insert into track_locks select ?,CURRENT TIMESTAMP,* from sa_locks()" );
user = msg.getUser();
if( user == null ) {
user = "UserIsNULL";
}
ps_log.setString( 1, user );
ps_log.executeUpdate();
ps_log.close();
_log_connection.commit();
} catch( Exception e ) {
// print some error output to the Mobilink log
e.printStackTrace();
}
}
}
}
public Example( ServerContext sc ) throws SQLException {
_log_connection = sc.makeConnection();
sc.addErrorListener( new MyLogListener() );
}
}
Next, you just need to add -sl java to the ML Server start line.
-sl java(-DMLStartClasses=Example -cp c:\\path\\to\\dir\\where\\Example\\dot\\class\\exists)"
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