On 2017-04-15 02:33:59 +0900, Fujii Masao wrote: > On Fri, Apr 14, 2017 at 10:33 PM, Petr Jelinek > <petr.jeli...@2ndquadrant.com> wrote: > > On 12/04/17 15:55, Fujii Masao wrote: > >> Hi, > >> > >> 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. > > > > Hmm, but CREATE_REPLICATION_SLOT should not generate WAL afaik. I agree > > that the issue with walsender still exist (since we now allow normal SQL > > to run there) but I think it's important to identify what exactly causes > > the WAL activity in your case > > At least in my case, the following CREATE_REPLICATION_SLOT command > generated WAL record. > > BEGIN READ ONLY ISOLATION LEVEL REPEATABLE READ; > CREATE_REPLICATION_SLOT testslot TEMPORARY LOGICAL pgoutput USE_SNAPSHOT; > > Here is the pg_waldump output of the WAL record that CREATE_REPLICATION_SLOT > generated. > > rmgr: Standby len (rec/tot): 24/ 50, tx: 0, > lsn: 0/01601438, prev 0/01601400, desc: RUNNING_XACTS nextXid 692 > latestCompletedXid 691 oldestRunningXid 692 > > So I guess that CREATE_REPLICATION_SLOT code calls LogStandbySnapshot() > and which generates WAL record about snapshot of running transactions.
Erroring out in these cases sounds easy enough. Wonder if there's not a bigger problem with WAL records generated e.g. by HOT pruning or such, during decoding. Not super likely, but would probably hit exactly the same, no? - Andres -- Sent via pgsql-hackers mailing list (firstname.lastname@example.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers