avoiding unnecessarily entering "upgrade mode"

[David Cheney]

SGTM.

On Wed, Aug 6, 2014 at 11:10 AM, Menno Smits <menno.smits at canonical.com> wrote:
> Right now, a Juju machine agent is in "upgrade mode" from the moment it
> starts until the upgrade-steps worker is finished. During this period API
> logins are heavily restricted and most of the agent's workers don't start
> until upgrade mode stops.
>
> This happens even when there is no upgrade to perform. The upgrade-steps
> worker always runs at machine agent startup and upgrade mode is in force
> until it finishes.
>
> Upgrade mode is typically short-lived (say 10 seconds) but if something is
> wrong (e.g. mongo issues) the upgrade-steps worker may take longer or not
> finish resulting in the user seeing lots of "upgrade in progress" messages
> from the client and in the logs.
> This is particularly confusing when a user hasn't even requested an upgrade
> themselves.
>
> I would like to change the machine agent so that upgrade mode is only
> entered if the version in agent.conf is different from the running software
> version. This would mean that upgrade mode is only entered if there is an
> actual upgrade to perform.
>
> The version in agent.conf is only updated after a successful upgrade so it
> is the right thing to use to determine if upgrade mode should be entered.
>
> The current behaviour means that the (idempotent) upgrade steps for the
> current version are always run each time the machine agent starts. If the
> change I'm proposing is implemented this will no longer happen. Does this
> seem like a problem to anyone? For instance, do we rely on the upgrade steps
> for the current version being run after bootstrap?
>
> The ticket for this work is at: https://bugs.launchpad.net/bugs/1350111
>
> Cheers,
> Menno
>
>
>
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