Add kolla-ansible gather-facts command

In some situations it may be helpful to populate the fact cache on
demand. The 'kolla-ansible gather-facts' command may be used to do this.

One specific case where this may be helpful is when running kolla-ansible
with a --limit argument, since in that case hosts that match the limit
will gather facts for hosts that fall outside the limit. In the extreme
case of a limit that matches only one host, it will serially gather
facts for all other hosts. To avoid this issue, run 'kolla-ansible
gather-facts' without a limit to populate the fact cache in parallel
before running the required command with a limit.

Change-Id: I79db9bca23aa1bd45bafa7e7500a90de5a684593

doc/source/user/ansible-tuning.rst

@@ -65,6 +65,25 @@ the `jsonfile cache plugin
 You may also wish to set the expiration timeout for the cache via ``[defaults]
 fact_caching_timeout``.
 
+Populating the cache
+~~~~~~~~~~~~~~~~~~~~
+
+In some situations it may be helpful to populate the fact cache on demand. The
+``kolla-ansible gather-facts`` command may be used to do this.
+
+One specific case where this may be helpful is when running ``kolla-ansible``
+with a ``--limit`` argument, since in that case hosts that match the limit will
+gather facts for hosts that fall outside the limit. In the extreme case of a
+limit that matches only one host, it will serially gather facts for all other
+hosts. To avoid this issue, run ``kolla-ansible gather-facts`` without a limit
+to populate the fact cache in parallel before running the required command with
+a limit. For example:
+
+.. code-block:: console
+
+   kolla-ansible gather-facts
+   kolla-ansible deploy --limit control01
+
 Fact variable injection
 -----------------------
 

doc/source/user/operating-kolla.rst

@@ -207,6 +207,9 @@ times. This can be useful to share configuration between multiple environments.
 Any common configuration can be set in ``INVENTORY1`` and ``INVENTORY2`` can be
 used to set environment specific details.
 
+``kolla-ansible -i INVENTORY gather-facts`` is used to gather Ansible facts,
+for example to populate a fact cache.
+
 .. note::
 
    In order to do smoke tests, requires ``kolla_enable_sanity_checks=yes``.

releasenotes/notes/gather-facts-command-7b62d2c3eb13ec8e.yaml

@@ -0,0 +1,5 @@
+---
+features:
+  - |
+    Adds a ``kolla-ansible gather-facts`` command that may be used to gather
+    Ansible host facts.

tools/kolla-ansible

@@ -161,6 +161,7 @@ Commands:
     deploy-bifrost       Deploy and start bifrost container
     deploy-servers       Enroll and deploy servers with bifrost
     deploy-containers    Only deploy and start containers (no config updates or bootstrapping)
+    gather-facts         Gather Ansible facts
     post-deploy          Do post deploy on deploy node
     pull                 Pull all images for containers (only pulls, no running container changes)
     reconfigure          Reconfigure OpenStack service
@@ -203,6 +204,7 @@ deploy
 deploy-bifrost
 deploy-containers
 deploy-servers
+gather-facts
 post-deploy
 pull
 reconfigure
@@ -429,6 +431,10 @@ EOF
         PLAYBOOK="${BASEDIR}/ansible/bifrost.yml"
         EXTRA_OPTS="$EXTRA_OPTS -e kolla_action=deploy-servers"
         ;;
+(gather-facts)
+        ACTION="Gathering Ansible facts"
+        PLAYBOOK="${BASEDIR}/ansible/gather-facts.yml"
+        ;;
 (post-deploy)
         ACTION="Post-Deploying Playbooks"
         PLAYBOOK="${BASEDIR}/ansible/post-deploy.yml"