Ensure option groups don't change during logging

oslo.config allows us to configure groups and options dynamically. This
can cause a race with our logging as we attempt to iterate through
option groups that are changing under our feet. This wouldn't be a huge
issue, since these are just logs are we can always log again, if needed,
but we store groups in a dictionary and Python doesn't like us changing
the size of a dict it's iterating through:

  RuntimeError: dictionary changed size during iteration

Given that we're only reading through this option group and don't need
to worry about a group _disappearing_, the solution is pretty simple:
create a copy of our option group names ahead of time so we don't need
to worry about new ones coming and messing things up.

No tests are included since this is a race and the only way I see to
reproduce this would involve lots of ugly threading.

Change-Id: Id3b28465d645a24f0fcebff2dd68a9bd30e21594
Signed-off-by: Stephen Finucane <sfinucan@redhat.com>
Closes-Bug: #1856312

1 files changed, 1 insertions, 1 deletions

diff --git a/oslo_config/cfg.py b/oslo_config/cfg.py
index ca3ae56..5dcb3f1 100644
--- a/oslo_config/cfg.py
+++ b/oslo_config/cfg.py
@@ -2576,7 +2576,7 @@ class ConfigOpts(Mapping):
             logger.log(lvl, "%-30s = %s", opt_name,
                        _sanitize(opt, getattr(self, opt_name)))
 
-        for group_name in self._groups:
+        for group_name in list(self._groups):
             group_attr = self.GroupAttr(self, self._get_group(group_name))
             for opt_name in sorted(self._groups[group_name]._opts):
                 opt = self._get_opt_info(opt_name, group_name)['opt']