ansible/ansible-modules-core — pull request #532 by quentinsf (2014-12-17 13:54:25+00:00)
Title: Add warning to docs about parallel use of add_host

add_host can behave unpredictably (at least from a user's point of view) when run on multiple machines simultaneously - not all instances will succeed in making a change that persists into the future.

After spending many hours yesterday discovering this the hard way, I thought adding a warning note to the documentation was worthwhile, to the effect that 'serial:1' is a good idea.