Re: PATCH: Make pg_stop_backup() archive wait optional

On 2/27/17 7:50 PM, Michael Paquier wrote:
> On Tue, Feb 28, 2017 at 9:42 AM, David Steele <david(at)pgmasters(dot)net> wrote:
>> On 2/27/17 7:38 PM, Michael Paquier wrote:
>>> On Tue, Feb 28, 2017 at 9:25 AM, David Steele <david(at)pgmasters(dot)net> wrote:
>>>> I also marked the pg_stop_* functions as parallel restricted, the same
>>>> as pg_start_backup(). Previously they were parallel safe which I don't
>>>> believe is accurate for the non-exclusive version at the very least,
>>>> since it is tied to a particular backend.
>>>
>>> Yeah, those should really be parallel restricted. For the exclusive
>>> version, having the function run in parallel would also lead to errors
>>> per the presence/lack of backup_label file.
>>
>> I'm not sure that's the case. It seems like it should lock just as
>> multiple backends would now. One process would succeed and the others
>> would error. Maybe I'm missing something?
>
> Hm, any errors happening in the workers would be reported to the
> leader, meaning that even if one worker succeeded to run
> pg_start_backup() it would be reported as an error at the end to the
> client, no? By marking the exclusive function restricted we get sure
> that it is just the leader that fails or succeeds.

Good point, and it strengthens the argument beyond, "it just seems right."

--
-David
david(at)pgmasters(dot)net