Thread: archive_command during database shutdown

I've recently wanted to run a different archive_command during
database shutdown than during normal operations.  In particular, if
the normal archive process fails during normal operations, I want it
to be retried later (as it currently does).  But if it fails during
shutdown, I want it to run a fallback archive_command.

The only way I can see to accomplish this is to have the
archive_command try to connect back to the database and see if it gets
an error.  That seems pretty ugly.  Is there a better way?

Cheers,

Jeff

On Wed, May 25, 2016 at 10:31 AM, Sameer Kumar <sameer.kumar@ashnik.com> wrote:
>
>
> On Thu, 26 May 2016, 1:25 a.m. Jeff Janes, <jeff.janes@gmail.com> wrote:
>>
>> I've recently wanted to run a different archive_command during
>> database shutdown than during normal operations.  In particular, if
>> the normal archive process fails during normal operations, I want it
>> to be retried later (as it currently does).  But if it fails during
>> shutdown, I want it to run a fallback archive_command.
>
>
> What version of PostgreSQL are you using?

9.2, 9.4, 9.5, 9.6beta.

>
>>
>> The only way I can see to accomplish this is to have the
>> archive_command try to connect back to the database and see if it gets
>> an error.  That seems pretty ugly.  Is there a better way?
>
>
> What's your goal here?

I want my database to shut down cleanly when I tell it to.

>
> During a shutdown, if you don't so much care about checkpoint and fsync of
> buffers to disk, you can do an immediate shutdown.

But I do care about the checkpoint.  Otherwise you lose all your
unlogged tables.  And probably other unfortunate things happen, as
well.

Cheers,

Jeff

On 25/05/16 20:57, Jeff Janes wrote:
> On Wed, May 25, 2016 at 10:31 AM, Sameer Kumar <sameer.kumar@ashnik.com> wrote:
>>
>>
>> On Thu, 26 May 2016, 1:25 a.m. Jeff Janes, <jeff.janes@gmail.com> wrote:
>>>
>>> I've recently wanted to run a different archive_command during
>>> database shutdown than during normal operations.  In particular, if
>>> the normal archive process fails during normal operations, I want it
>>> to be retried later (as it currently does).  But if it fails during
>>> shutdown, I want it to run a fallback archive_command.
>>
>>
>> What version of PostgreSQL are you using?
>
> 9.2, 9.4, 9.5, 9.6beta.
>
>>
>>>
>>> The only way I can see to accomplish this is to have the
>>> archive_command try to connect back to the database and see if it gets
>>> an error.  That seems pretty ugly.  Is there a better way?
>>
>>
>> What's your goal here?
>
> I want my database to shut down cleanly when I tell it to.
>
>>
>> During a shutdown, if you don't so much care about checkpoint and fsync of
>> buffers to disk, you can do an immediate shutdown.
>
> But I do care about the checkpoint.  Otherwise you lose all your
> unlogged tables.  And probably other unfortunate things happen, as

Isn't that the point of unlogged tables? Or rather, isn't that the risk
you knowingly take with them - you trade reliability for speed?

Ray

On Wed, May 25, 2016 at 1:36 PM, Raymond O'Donnell <rod@iol.ie> wrote:
> On 25/05/16 20:57, Jeff Janes wrote:
>>
>> On Wed, May 25, 2016 at 10:31 AM, Sameer Kumar <sameer.kumar@ashnik.com>
>> wrote:
>>>
>>>
>>>
>>> On Thu, 26 May 2016, 1:25 a.m. Jeff Janes, <jeff.janes@gmail.com> wrote:
>>>>
>>>>
>>>> I've recently wanted to run a different archive_command during
>>>> database shutdown than during normal operations.  In particular, if
>>>> the normal archive process fails during normal operations, I want it
>>>> to be retried later (as it currently does).  But if it fails during
>>>> shutdown, I want it to run a fallback archive_command.
>>>
>>>
>>>
>>> What version of PostgreSQL are you using?
>>
>>
>> 9.2, 9.4, 9.5, 9.6beta.
>>
>>>
>>>>
>>>> The only way I can see to accomplish this is to have the
>>>> archive_command try to connect back to the database and see if it gets
>>>> an error.  That seems pretty ugly.  Is there a better way?
>>>
>>>
>>>
>>> What's your goal here?
>>
>>
>> I want my database to shut down cleanly when I tell it to.
>>
>>>
>>> During a shutdown, if you don't so much care about checkpoint and fsync
>>> of
>>> buffers to disk, you can do an immediate shutdown.
>>
>>
>> But I do care about the checkpoint.  Otherwise you lose all your
>> unlogged tables.  And probably other unfortunate things happen, as
>
>
> Isn't that the point of unlogged tables? Or rather, isn't that the risk you
> knowingly take with them - you trade reliability for speed?

Sure.  And I have rebuilt them.  But when the firemen pack up and
leave, I've got better things to be doing with my time (and limited IO
capacity on a half crippled system) than rebuilding unlogged tables
for no particular reason. The purpose of the database is to be a tool,
not a moral scold.

But now I think the problem is not when the archive_command fails, but
when it hangs and never returns at all.  That means the solution has
to look somewhat different, but I still don't know exactly what.

Cheers,

Jeff