Feature Request: -about-to-depart hook

[Andrew Wilkins]

On Tue, Nov 24, 2015 at 12:55 PM Cheryl Jennings <
cheryl.jennings at canonical.com> wrote:

> I'll be tracking these kind of feature requests here:
> https://github.com/juju/juju/wiki/Feature-Requests
>
> There's not much there yet, but we'll be filling it out as we go through
> the other various requests we've gotten.
>

Comment from the sidelines: we have something similar in storage now, with
"storage-detaching" hook. This runs before storage is detached, so that
charms can stop using the storage before it's ripped out beneath them.

With that in mind, can we please call this "-relation-departing"?

Cheers,
Andrew


> Thanks!
> -Cheryl
>
> On Mon, Nov 23, 2015 at 6:13 PM, Rick Harding <rick.harding at canonical.com>
> wrote:
>
>> Thank you Cheryl!
>>
>> On Mon, Nov 23, 2015, 6:33 PM Cheryl Jennings <
>> cheryl.jennings at canonical.com> wrote:
>>
>>> This is already on my list.  I'm still figuring out a good way to
>>> organize / record these in a publicly viewable place.
>>>
>>> I'll send out a link once I get something together.  (Hopefully tonight!)
>>>
>>> Thanks!
>>>
>>>
>>> -Cheryl
>>> On Nov 23, 2015 5:20 PM, "Rick Harding" <rick.harding at canonical.com>
>>> wrote:
>>>
>>>> Thanks for the feedback. I think this is something we should try to
>>>> make some time for. I've copied Alexis and we'll see what can be done with
>>>> the team.
>>>>
>>>> Alexis, can you put this on the list of things to investigate for
>>>> future roadmap?
>>>>
>>>> Thanks
>>>>
>>>> On Tue, Nov 10, 2015 at 8:22 AM Mario Splivalo <
>>>> mario.splivalo at canonical.com> wrote:
>>>>
>>>>> On 02/12/2015 07:41 PM, Jorge Niedbalski wrote:
>>>>> >> While typing up https://bugs.launchpad.net/juju-core/+bug/1417874 I
>>>>> >> realized that your proposed solution of a pre-departure hook is the
>>>>> >> only one that can work. Once -departed hooks start firing both the
>>>>> >> doomed unit and the leader have already lost the access needed to
>>>>> >> decommission the departing node.
>>>>> >
>>>>> > I have been struggling the last hours with the same exact issue
>>>>> trying
>>>>> > to add replication to memcached.
>>>>> >
>>>>> > The problem is that there is no a point on which i can identify
>>>>> > what's the exact departing unit?
>>>>> >
>>>>> > And this leads to manual operator intervention, which is _highly_ non
>>>>> > desirable for a juju deployed environment.
>>>>> >
>>>>> > +1 for having this feature implemented.
>>>>>
>>>>> Hola!
>>>>>
>>>>> I'm bumping this thread to get some chatter going on - we hit a similar
>>>>> issue with percona-cluster charm, which is reported in this bug:
>>>>>
>>>>> https://bugs.launchpad.net/charms/+source/percona-cluster/+bug/1514472
>>>>>
>>>>> The issue is somewhat similar as to those with mongodb - when unit is
>>>>> leaving relation (issued by 'juju remove-unit'), charm should first
>>>>> shut
>>>>> down percona server on the departing unit. Failing to do results in
>>>>> 'lost quorum' situation where remaining node thinks that network has
>>>>> partitioned. Unfortunately there is now way for a relation's -departed
>>>>> hook to know if it's executing on departing unit or on the other one so
>>>>> it can't know weather or not to stop percona server. Implementing a
>>>>> -about-to-depart hook would solve this issue.
>>>>>
>>>>>         Mario
>>>>>
>>>>>
>>>>> --
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>>>>> Juju-dev at lists.ubuntu.com
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>>>>>
>>>>
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