[kolla] Plan to deprecate and finally drop the chrony container

Radosław Piliszek radoslaw.piliszek at gmail.com
Thu Feb 25 18:02:56 UTC 2021

Hello Fellow OpenStackers interested in Kolla's way.

The topic should be pretty self-explanatory but let me provide the
details and background.

We are currently working on the Wallaby release and, since we are
cycle-trailing, it is the right moment for us to reflect upon the
various cleanup plans we had (and have).
One of those is the drop of the chrony container.
Chrony serves the time synchronization purpose which is required for
healthy operations (I hope I don't need to explain this point further,
time sync is essential for most services nowadays).
It is still deployed by default by Kolla Ansible.
The point is, most default (even minimal ones) host OS installations
come with some form of NTP client, be it chrony, ntpd, timesyncd or
whatever else there is. :-) This applies also to provisioning
solutions like MAAS or Foreman.
And Kolla Ansible actually stands on its head to detect and disable
those to avoid multiple time sync daemons hell as it may disrupt
normal operations (mostly due to having different time sources but
also due to different compensation algorithms [or rather just their
actual configuration] and the fact that each tool assumes to be the
only source of time changes).
We seem to have placed a relatively sane precheck to detect this but
effective disabling may prove tricky, especially since it is very easy
to get it installed at any point.
The NTP client is considered a very basic service these days.
It also seems that several users known to us do not use the chrony
container and instead orchestrate timesync elsewhere.

Hence, our current plan is to:
1) Deprecate the chrony container in the Wallaby cycle.
- in Kolla Ansible this would mean also warning users that they use it
and defaulting to not using it (with docs and a reno); docs would
suggest an Ansible way to coordinate timesync
- in Kolla docs and a reno
2) Drop the chrony container from both the places

I know Kayobe (the "highest-level" member of the Kolla project) is
planning to incorporate timesync handling by external Ansible role
means so their users should be covered.

Please let us know if you have any comments on the plan above.
Or generally any suggestions you would like us to hear.



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