A recent customer call highlighted some misunderstandings about the two
weighers in the nova tree. Firstly, the basis for the metrics used by
the 'IoOpsWeigher' was not well explained and required some spelunking
through the code to understand. Secondly, the 'BuildFailureWeigher'
multiplier, configured by '[scheduler] build_failure_weight_multiplier',
defaults to a very large value for reasons that are not apparent unless
you read the commit logs for that weigher (hint: it's because we wanted
to preserve the behavior of the older filter-based approach to handling
nodes with build failures). Expand the documentation to fill both gaps.
In the process, we also correct some small nits with this doc, mostly
centered around whitespace.
Change-Id: If2d329b86808bdc70619fbe057dd25a938eb79da
Signed-off-by: Stephen Finucane <stephenfin@redhat.com>
Stephen Finucane
0564006a0a