[Gluster-devel] autodelete in snapshots

[Vijay Bellur]

On 04/23/2014 05:50 AM, Vijay Bellur wrote:
> On 04/20/2014 11:42 PM, Lalatendu Mohanty wrote:
>> On 04/16/2014 11:39 AM, Avra Sengupta wrote:
>>> The whole purpose of introducing the soft-limit is, that at any point
>>> of time the number of
>>> snaps should not exceed the hard limit. If we trigger auto-delete on
>>> hitting hard-limit, then
>>> the purpose itself is lost, because at that point we would be taking a
>>> snap, making the limit
>>> hard-limit + 1, and then triggering auto-delete, which violates the
>>> sanctity of the hard-limit.
>>> Also what happens when we are at hard-limit + 1, and another snap is
>>> issued, while auto-delete
>>> is yet to process the first delete. At that point we end up at
>>> hard-limit + 1. Also what happens
>>> if for a particular snap the auto-delete fails.
>>>
>>> We should see the hard-limit, as something set by the admin keeping in
>>> mind the resource consumption
>>> and at no-point should we cross this limit, come what may. If we hit
>>> this limit, the create command
>>> should fail asking the user to delete snaps using the "snapshot
>>> delete" command.
>>>
>>> The two options Raghavendra mentioned are applicable for the
>>> soft-limit only, in which cases on
>>> hitting the soft-limit
>>>
>>> 1. Trigger auto-delete
>>>
>>> or
>>>
>>> 2. Log a warning-message, for the user saying the number of snaps is
>>> exceeding the snap-limit and
>>> display the number of available snaps
>>>
>>> Now which of these should happen also depends on the user, because the
>>> auto-delete option
>>> is configurable.
>>>
>>> So if the auto-delete option is set as true, auto-delete should be
>>> triggered and the above message
>>> should also be logged.
>>>
>>> But if the option is set as false, only the message should be logged.
>>>
>>> This is the behaviour as designed. Adding Rahul, and Seema in the
>>> mail, to reflect upon the
>>> behaviour as well.
>>>
>>> Regards,
>>> Avra
>>
>> This sounds correct. However we need to make sure that the usage or
>> documentation around this should be good enough , so that users
>> understand the each of the limits correctly.
>>
>
> It might be better to avoid the usage of the term "soft-limit".
> soft-limit as used in quota and other places generally has an alerting
> connotation. Something like "auto-deletion-limit" might be better.
>

I still see references to "soft-limit" and auto deletion seems to get 
triggered upon reaching soft-limit.

Why is the ability to auto delete not configurable? It does seem pretty 
nasty to go about deleting snapshots without obtaining explicit consent 
from the user.

Cheers,
Vijay