First customer pain point pull request - default-hook

[Nate Finch]

Anyone who has ever written a switch statement should be used to putting in
a default clause for "something I don't expect"... I don't think it should
be a big deal.


On Wed, Aug 20, 2014 at 4:46 AM, Matthew Williams <
matthew.williams at canonical.com> wrote:

> I'm not attempting to cause trouble here - I just want to make sure I
> understand the feature - and what effects it might have.
>
> It sounds like any implementation of the default-hook would need to start
> with something like: (pseudo-bash)
>
> if JUJU_HOOK_NAME == "start"
>  //run start
> else if JUJU_HOOK_NAME == "config-changed"
>  //run config-changed
> else if JUJU_HOOK_NAME == "stop"
>  //run stop
> else
>   //unknown hook
>   exit 1
> fi
>
> Any default-hook that deviated from this pattern could find itself being
> run multiple times in succession - I wonder if that might be confusing/
> unexpected to a charm author?
> Gustavo's observation about hooks that the charm might no know about yet
> means that the else clause is absolutely required, I wonder if that's
> obvious to someone who's new to charming?
>
> Just some thoughts - in principle I love the feature
>
> Matt
>
>
>
>
>
> On Tue, Aug 19, 2014 at 11:10 PM, Gustavo Niemeyer <gustavo at niemeyer.net>
> wrote:
>
>> On Tue, Aug 19, 2014 at 6:58 PM, Matthew Williams
>> <matthew.williams at canonical.com> wrote:
>> > Something to be mindful of is that we will shortly be implementing a new
>> > hook for metering (likely called collect-metrics). This hook differs
>> > slightly to the others in that it will be called periodically (e.g. once
>> > every hour) with the intention of sending metrics for that unit to the
>> state
>> > server.
>> >
>> > I'm not sure it changes any of the details in this feature or the pr -
>> but I
>> > thought you should be aware of it
>>
>> Yeah, that's a good point. I'm wonder how reliable the use of
>> default-hook will be, as it's supposed to run whenever any given hook
>> doesn't exist, so charms using that feature should expect _any_ hook
>> to be called there, even those they don't know about, or that don't
>> even exist yet. The charms that symlink into a single hook seem to be
>> symlinking a few things, not everything. It may well turn out that
>> default-hook will lead to brittle charms.
>>
>>
>> gustavo @ http://niemeyer.net
>>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.ubuntu.com/archives/juju-dev/attachments/20140820/5420c3da/attachment.html>