Hi folks!
I spent some time thinking about bringing profile matching back in, so
I'd like to get your comments on the following near-future plan.
First, the scope of the problem. What we do is essentially kind of
capability discovery. We'll help nova scheduler with doing the right
thing by assigning a capability like "suits for compute", "suits for
controller", etc. The most obvious path is to use inspector to assign
capabilities like "profile=1" and then filter nodes by it.
A special care, however, is needed when some of the nodes match 2 or
more profiles. E.g. if we have all 4 nodes matching "compute" and then
only 1 matching "controller", nova can select this one node for
"compute" flavor, and then complain that it does not have enough hosts
for "controller".
We also want to conduct some sanity check before even calling to
heat/nova to avoid cryptic "no valid host found" errors.
(1) Inspector part
During the liberty cycle we've landed a whole bunch of API's to
inspector that allow us to define rules on introspection data. The plan
is to have rules saying, for example:
rule 1: if memory_mb >= 8192, add capability "compute_profile=1"
rule 2: if local_gb >= 100, add capability "controller_profile=1"
Note that these rules are defined via inspector API using a JSON-based
DSL [1].
As you see, one node can receive 0, 1 or many such capabilities. So we
need the next step to make a final decision, based on how many nodes we
need of every profile.
(2) Modifications of `overcloud deploy` command: assigning profiles
New argument --assign-profiles will be added. If it's provided,
tripleoclient will fetch all ironic nodes, and try to ensure that we
have enough nodes with all profiles.
Nodes with existing "profile:xxx" capability are left as they are. For
nodes without a profile it will look at "xxx_profile" capabilities
discovered on the previous step. One of the possible profiles will be
chosen and assigned to "profile" capability. The assignment stops as
soon as we have enough nodes of a flavor as requested by a user.
(3) Modifications of `overcloud deploy` command: validation
To avoid 'no valid host found' errors from nova, the deploy command will
fetch all flavors involved and look at the "profile" capabilities. If
they are set for any flavors, it will check if we have enough ironic
nodes with a given "profile:xxx" capability. This check will happen
after profiles assigning, if --assign-profiles is used.
Please let me know what you think.
[1] https://github.com/openstack/ironic-inspector#introspection-rules
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