Re: [HACKERS] More replication race conditions

On 27/08/17 04:32, Noah Misch wrote:
> On Fri, Aug 25, 2017 at 12:09:00PM +0200, Petr Jelinek wrote:
>> On 24/08/17 19:54, Tom Lane wrote:
>>> sungazer just failed with
>>>
>>> pg_recvlogical exited with code '256', stdout '' and stderr 'pg_recvlogical: could not send replication command
"START_REPLICATIONSLOT "test_slot" LOGICAL 0/0 ("include-xids" '0', "skip-empty-xacts" '1')": ERROR:  replication slot
"test_slot"is active for PID 8913148
 
>>> pg_recvlogical: disconnected
>>> ' at /home/nm/farm/gcc64/HEAD/pgsql.build/src/test/recovery/../../../src/test/perl/PostgresNode.pm line 1657.
>>>
>>> https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=sungazer&dt=2017-08-24%2015%3A16%3A10
>>>
>>> Looks like we're still not there on preventing replication startup
>>> race conditions.
>>
>> Hmm, that looks like "by design" behavior. Slot acquiring will throw
>> error if the slot is already used by somebody else (slots use their own
>> locking mechanism that does not wait). In this case it seems the
>> walsender which was using slot for previous previous step didn't finish
>> releasing the slot by the time we start new command. We can work around
>> this by changing the test to wait perhaps.
> 
> [Action required within three days.  This is a generic notification.]
> 
> The above-described topic is currently a PostgreSQL 10 open item.  Simon,
> since you committed the patch believed to have created it, you own this open
> item.  If some other commit is more relevant or if this does not belong as a
> v10 open item, please let us know.  Otherwise, please observe the policy on
> open item ownership[1] and send a status update within three calendar days of
> this message.  Include a date for your subsequent status update.  Testers may
> discover new open items at any time, and I want to plan to get them all fixed
> well in advance of shipping v10.  Consequently, I will appreciate your efforts
> toward speedy resolution.  Thanks.
> 
> [1] https://www.postgresql.org/message-id/20170404140717.GA2675809%40tornado.leadboat.com
> 

Attached should fix this.

-- 
  Petr Jelinek                  http://www.2ndQuadrant.com/
  PostgreSQL Development, 24x7 Support, Training & Services

-- 
Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-hackers