[openstack-dev] [nova] remote debugging hangs nova-compute

Steve Noyes steve.noyes at oracle.com
Thu Dec 8 14:49:26 UTC 2016

Hi, I've been trying to get nova-compute (devstack, Newton, all-in-one) 
to work with the remote debugger in eclipse/pydev. (I've also tried 
pyCharm with the same results.) Following instructions here: 

I see the message in the nova code about results being unpredictable 
when you do this, so I'd like to know if this is expected or if I'm 
doing something wrong.

I am starting nova-compute in devstack with these switches: 
--remote_debug-host --remote_debug-port 5678

Nova-compute starts up ok and then as expected hits its embedded 
settrace() breakpoint:

LOG.warning(_LW('WARNING: Using the remote debug option changes how '
                     'Nova uses the eventlet library to support async 
IO. This '
                     'could result in failures that do not occur under 
normal '
                     'operation. Use at your own risk.'))

which so far is all good. I see the breakpoint and I can see all the 
variables in the debugger.

But when I resume execution, several more log messages are outputted, 
and then nova-compute hangs. The last line in the log is:

... Connecting to libvirt: qemu:///system from (pid=556) 
_get_new_connection /opt/stack/nova/nova/virt/libvirt/host.py:367

At this point I can't ^c the process and the only way to get going again 
is to kill nova-compute from the command line.

I am guessing that this hang is due to some debugger/eventlet conflict 
as mentioned in that log message. Or am I missing some configuration 
step? If this isn't going to work, what do other people recommend for 
debugging nova-compute? Thanks,


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