Re: [bug fix] Stats collector is not restarted on the standby

On Wed, Oct 26, 2016 at 8:41 AM, Kuntal Ghosh
<kuntalghosh(dot)2007(at)gmail(dot)com> wrote:
> On Wed, Oct 26, 2016 at 4:47 PM, Michael Paquier
> <michael(dot)paquier(at)gmail(dot)com> wrote:
>>
>> If you test on a master node that would be the same: there is a delay
>> until the stats process restart. I have not looked at the code closely
>> enough in this area (reaper()?) to determine if there are ways to
>> improve the responsiveness of this process restart that is a
>> non-auxiliary proces btw, still improving this behavior is something I
>> feel would be invasive, and something that would be dedicated to HEAD.
>> The patch proposed here by Tsunakawa-san makes at least sure that a
>> node in PM_HOT_STANDBY state restarts it.
> Yes, you are right. Master also has some delay for restarting the
> process. Otherwise, the patch solves the problem.

The delay is intentional. Per pgstat_start():

/*
* Do nothing if too soon since last collector start. This is a safety
* valve to protect against continuous respawn attempts if the collector
* is dying immediately at launch. Note that since we will be re-called
* from the postmaster main loop, we will get another chance later.
*/
curtime = time(NULL);
if ((unsigned int) (curtime - last_pgstat_start_time) <
(unsigned int) PGSTAT_RESTART_INTERVAL)
return 0;
last_pgstat_start_time = curtime;

Committed and back-patched all the way.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company