Most OpenStack modules have a global variable LOG defined already, e.g. in Neutron:
from neutron.openstack.common import log
LOG = log.getLogger(__name__)
use prettyprint to format complex data structures
from pprint import pformat
LOG.debug("foo is: %s" % pformat(foo))
You can also use this decorator to see what was passed to a method.
To find out what calls something or where something is defined.
grep -rn tunnel_sync --include \*.py /opt/stack/neutron
To find out how a function was called, add this line to it:
import traceback; LOG.debug(''.join(traceback.format_stack()))
then restart the service, do whatever to invoke the function, and check the logs for the traceback.
Prereq: graphviz
sudo apt-get -y install graphviz
Needs to be run from the parent directory of the Python package:
vagrant@devstack:/opt/stack/neutron$ pyreverse -A -o png -p ml2.png -m y --ignore exceptions.py,cisco,brocade,mech_ofagent.py neutron/plugins/ml2/
This created a classes_ml2.png.png and ignored the cisco and brocade packages, and the exceptions and mech_ofagent modules.
There may be unit tests for classes/methods you are interested in. If you are really lucky the mocked data might be explicit. The naming convention for test methods is to prefix the function name under test with test_ - so grep the source tree for that to find the test module. e.g. to find the tests for a method named tunnel_sync do:
grep -r 'def test_tunnel_sync' --include \*.py /opt/stack/neutron/neutron/tests/unit