Re: Re: logical replication and PANIC during shutdown checkpoint in publisher

On 16/04/17 08:12, Noah Misch wrote:
> On Wed, Apr 12, 2017 at 10:55:08PM +0900, Fujii Masao wrote:
>> When I shut down the publisher while I repeated creating and dropping
>> the subscription in the subscriber, the publisher emitted the following
>> PANIC error during shutdown checkpoint.
>>
>> PANIC:  concurrent transaction log activity while database system is
>> shutting down
>>
>> The cause of this problem is that walsender for logical replication can
>> generate WAL records even during shutdown checkpoint.
>>
>> Firstly walsender keeps running until shutdown checkpoint finishes
>> so that all the WAL including shutdown checkpoint record can be
>> replicated to the standby. This was safe because previously walsender
>> could not generate WAL records. However this assumption became
>> invalid because of logical replication. That is, currenty walsender for
>> logical replication can generate WAL records, for example, by executing
>> CREATE_REPLICATION_SLOT command. This is an oversight in
>> logical replication patch, I think.
>>
>> To fix this issue, we should terminate walsender for logical replication
>> before shutdown checkpoint starts. Of course walsender for physical
>> replication still needs to keep running until shutdown checkpoint ends,
>> though.
> 
> [Action required within three days.  This is a generic notification.]
> 
> The above-described topic is currently a PostgreSQL 10 open item.  Peter,
> 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.
> 

Just FYI this is not new in 10, the issue exists since the 9.4
introduction of logical replication slots.

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