Soren, Thank you for your reply. I have still more questions and explanations. Please let me know if it does not make sense. 1. Your comment at nova-manage >> + ret = rpc.call(ctxt, >> + FLAGS.scheduler_topic, >> + {"method": "live_migration", >> + "args": {"instance_id": instance_id, >> + "dest": dest, >> + "topic": FLAGS.compute_topic}}) > > I don't understand why you pass the compute_topic in the rpc call rather than letting the scheduler worry about that? Altough I agree with you, scheduler requires 4 argument. If I remove the argument "topic", I got following error. > Traceback (most recent call last): > File "bin/nova-manage", line 680, in > main() > File "bin/nova-manage", line 672, in main > fn(*argv) > File "bin/nova-manage", line 488, in live_migration > "dest": dest}}) > File "/opt/nova.20110112/nova/rpc.py", line 340, in call > raise wait_msg.result > nova.rpc.RemoteError: TypeError _schedule() takes at least 4 non-keyword arguments (3 given) > [u'Traceback (most recent call last):\n', u' File "/opt/nova.20110112/nova/rpc.py", line 191, in receive > rval = node_func(context=ctxt, **node_args)\n', u'TypeError: _schedule() takes at lea I think _schedule() is common method, and I should be very careful to change it. That's why I add the argument "topic". But your comment is true - I suggest I wrote this explanation briefly as a comment. What do you think? 2. comment at nova.scheduler.driver.schedule_live_migration >> + try: >> + instance_ref = db.instance_get(context, instance_id) >> + ec2_id = instance_ref['hostname'] >> + internal_id = instance_ref['internal_id'] >> + except exception.NotFound, e: >> + msg = _('Unexpected error: instance is not found') >> + e.args += ('\n' + msg, ) >> + raise e > > Same comment as above wrt to exception mangling. I now see your comment above, but I don't understand how it helps to just not show the id at all? This method (schedule_live_migration) is called when users execute nova-manage. And user inputs like i-xxxx. But in this case, users get nova.db.sqlalchemy.model.Instance.id from upcoming exception. Users may minunderstand when an id is 10, users get i-a. ( I made an mistake - what I wanted to do is: "Unexpected error: instance(%s) is not found" % ec2_id.) Regards, Kei Masumoto -----Original Message----- From: