First customer pain point pull request - default-hook

[John Meinel]

The main problem with having a hook that just fires instead of the others
is that you end up firing a hook a whole bunch of times where it
essentially "does nothing" because it is still waiting for some other hook
for it to actually be ready. The "something-changed" proposal essentially
colapses the 10 calls to various hooks into a single firing.

William has thought much more about it, so I'd like him to fill in any
details I've missed.

John
=:->



On Sun, Aug 17, 2014 at 1:59 PM, Nate Finch <nate.finch at canonical.com>
wrote:

> That's an interesting document, but I feel like it doesn't really explain
> the problem it's trying to solve.
>
> Why does a single entry point cause a lot of boilerplate (I presume he
> means code boilerplate)? Isn't it just a switch on the name of the hook?
>  What does it mean "when a new hook is introduced"?  Doesn't the charm
> define what hooks it has?  And wouldn't the aforementioned switch mean that
> any new hook (whatever that means) would be ignored the same way it would
> if the hook file wasn't there?
>
> Can someone explain to me what exactly the problem is?
>
>
> On Sun, Aug 17, 2014 at 1:30 AM, John Meinel <john at arbash-meinel.com>
> wrote:
>
>> I'd just like to point out that William has thought long and hard about
>> this problem, and what semantics make the most sense (does it get called
>> for any hook, does it always get called, does it only get called when the
>> hook doesn't exist, etc).
>> I feel like had some really good decisions on it:
>> https://docs.google.com/a/canonical.com/document/d/1V5G6v6WgSoNupCYcRmkPrFKvbfTGjd4DCUZkyUIpLcs/edit#
>>
>> default-hook sounds (IMO) like it may run into problems where we do logic
>> based on whether a hook exists or not. There are hooks being designed like
>> leader-election and address-changed that might have side effects, and
>> default-hook should (probably?) not get called for those.
>>
>> I'd just like us to make sure that we actually think about (and document)
>> what hooks will fall into this, and make sure that it always makes sense to
>> rebuild the world on every possible hook (which is how charm writers will
>> be implementing default-hook, IMO).
>>
>> John
>> =:->
>>
>>
>>
>> On Sat, Aug 16, 2014 at 1:02 AM, Aaron Bentley <
>> aaron.bentley at canonical.com> wrote:
>>
>>> -----BEGIN PGP SIGNED MESSAGE-----
>>> Hash: SHA1
>>>
>>> On 14-08-15 04:36 PM, Nate Finch wrote:
>>> > There's new hook in town: default-hook.  If it exists and a hook
>>> > gets called that doesn't have a corresponding hook file,
>>> > default-hook gets called with the name of the original hook as its
>>> > first argument (arg[1]).
>>> >
>>> > That's it.
>>>
>>> Nice!  Thank you.
>>>
>>> Aaron
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