Re: logical replication and PANIC during shutdown checkpoint in publisher

On 20/04/17 05:57, Michael Paquier wrote:
> On Thu, Apr 20, 2017 at 12:40 PM, Michael Paquier
> <michael(dot)paquier(at)gmail(dot)com> wrote:
>> On Thu, Apr 20, 2017 at 4:57 AM, Peter Eisentraut
>> <peter(dot)eisentraut(at)2ndquadrant(dot)com> wrote:
>>> I think the problem with a signal-based solution is that there is no
>>> feedback. Ideally, you would wait for all walsenders to acknowledge the
>>> receipt of SIGUSR2 (or similar) and only then proceed with the shutdown
>>> checkpoint.
>>
>> Are you sure that it is necessary to go to such extent? Why wouldn't
>> it be enough to prevent any replication commands generating WAL to run
>> when the WAL sender knows that the postmaster is in shutdown mode?
>
> 2nd thoughts here... Ah now I see your point. True that there is no
> way to ensure that an unwanted command is not running when SIGUSR2 is
> received as the shutdown checkpoint may have already begun. Here is an
> idea: add a new state in WalSndState, say WALSNDSTATE_STOPPING, and
> the shutdown checkpoint does not run as long as all WAL senders still
> running do not reach such a state.
>

+1 to this solution

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