Re: [v9.3] Extra Daemons (Re: elegant and effective way for running jobs inside a database)

2012/9/11 Alvaro Herrera <alvherre@2ndquadrant.com>:
> Excerpts from Kohei KaiGai's message of mar sep 11 12:46:34 -0300 2012:
>> 2012/9/11 Alvaro Herrera <alvherre@2ndquadrant.com>:
>> > Excerpts from Boszormenyi Zoltan's message of vie jun 29 09:11:23 -0400 2012:
>> >
>> >> We have some use cases for this patch, when can you post
>> >> a new version? I would test and review it.
>> >
>> > What use cases do you have in mind?
>> >
>> I'm motivated with this feature to implement background calculation server
>> to handle accesses to GPU device; to avoid limitation of number of processes
>> that can use GPU device simultaneously.
>
> Hmm, okay, so basically a worker would need a couple of LWLocks, a
> shared memory area, and not much else?  Not a database connection.
>
Right. It needs shared memory area to communicate with each backend
and locking mechanism, but my case does not take database accesses
right now.

>> Probably, other folks have their use cases.
>> For example, Zoltan introduced his use case in the upthread as follows:
>> > - an SQL-driven scheduler, similar to pgAgent, it's generic enough,
>> >   we might port it to this scheme and publish it
>
> Hm, this would benefit from a direct backend connection to get the
> schedule data (SPI interface I guess).
>
I also think SPI interface will be first candidate for the daemons that
needs database access. Probably, lower layer interfaces (such as
heap_open and heap_beginscan) are also available if SPI interface
can be used.

Thanks,
-- 
KaiGai Kohei <kaigai@kaigai.gr.jp>