On 28/05/15 10:54, Richard Raseley wrote:
Zane Bitter wrote:
Steve is working on a patch to allow package-based updates of overcloud
nodes[1] using the distro's package manager (yum in the case of RDO, but
conceivable apt in others). Note we're talking exclusively about minor
updates, not version-to-version upgrades here.
Dan mentioned at the summit that this approach fails to take into
account the complex ballet of service restarts required to update
OpenStack services. (/me shakes fist at OpenStack services.) And
furthermore, that the Puppet manifests already encode the necessary
relationships to do this properly. (Thanks Puppeteers!) Indeed we'd be
doing the Wrong Thing by Puppet if we changed this stuff from under it.
The problem of course is that neither Puppet nor yum/apt has a view of
the entire system. Yum doesn't know about the relationships between
services and Puppet doesn't know about all of the _other_ packages that
they depend on.
One solution proposed was to do a yum update first but specifically
exclude any packages that Puppet knows about (the --excludes flag
appears sufficient for this); then follow that up with another Puppet
run using ensure -> latest.
My only concern with this approach is how do we collect and maintain the
excludes list. Other than that it sounds reasonable.
A problem with that approach is that it still fails to restart services
which have had libraries updated but have not themselves been updated.
That's no worse than the pure yum approach though. We might need an
additional way to just manually trigger a restart of services.
Maybe this could be handled at the packaging stage by reving the package
version when there is a known fix in a low-level library, thus
triggering a service restart in the puppet phase.
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