Ansible facts can have a large impact on the performance of the Ansible
control host. This patch introduces some control over which facts are
gathered (kolla_ansible_setup_gather_subset) and which facts are stored
(kolla_ansible_setup_filter). By default we do not change the default
values of these arguments to the setup module. The flexibility of these
arguments is limited, but they do provide enough for a large performance
improvement in a typical moderate to large OpenStack cloud.
In particular, the large complex dict fact for each interface has a
large effect, and on an OpenStack controller or hypervisor there may be
many virtual interfaces. We can use the kolla_ansible_setup_filter
variable to help:
kolla_ansible_setup_filter: 'ansible_[!qt]*'
This causes Ansible to collect but not store facts matching that
pattern, which includes the virtual interface facts. Currently we are
not referencing other facts matching the pattern within Kolla Ansible.
Note that including the 'ansible_' prefix causes meta facts module_setup
and gather_subset to be filtered, but this seems to be the only way to
get a good match on the interface facts. To work around this, we use
ansible_facts rather than module_setup to detect whether facts exist in
the cache.
The exact improvement will vary, but has been reported to be as large as
18x on systems with many virtual interfaces.
For reference, here are some other tunings tried:
* Increased the number of forks (great speedup depending of the size of
the deployment)
* Use `strategy = mitogen_linear` (cut processing time in half)
* Ansible caching (little speed up)
* SSH tunning (little speed up)
Co-Authored-By: Mark Goddard <mark@stackhpc.com>
Closes-Bug: #1921538
Change-Id: Iae8ca4aae945892f1dc65e1b10381d2e26e88805
15f2fdcd5d