Implement system reboot via juju hooks

[Stuart Bishop]

On 11 August 2014 18:20, William Reade <william.reade at canonical.com> wrote:

> I'd like to explore your use cases a bit more to see if we can find a clean
> solution to your problems that doesn't go too far down the (2) road that I'm
> nervous about. (The try-again-later mechanism is much smaller and cleaner
> and I think we can accommodate that one pretty easily, fwiw -- but what are
> the other problems you want to solve?)

Memory related settings in PostgreSQL will only take effect when the
database is bounced. I need to avoid bouncing the primary database:
 1) when backups are in progress.
 2) when a hot standby unit is being rebuilt from the primary.

Being able to have a hook abort and be retried later would let me
avoid blocking.

A locking service would be useful too for units to signal certain
operations (with locks automatically released when the hooks that took
them exit). The in-progress update to the Cassandra charm has
convoluted logic in its peer relation hooks to do rolling restarts of
all the nodes, and I imagine MongoDB, Swift and many others have the
same issue to solve.

-- 
Stuart Bishop <stuart.bishop at canonical.com>