On Friday, February 16, 2024 3:43 PM Amit Kapila <amit.kapil...@gmail.com> wrote: > > On Fri, Feb 16, 2024 at 11:43 AM Amit Kapila <amit.kapil...@gmail.com> wrote: > > > > Thanks for noticing this. I have pushed all your debug patches. Let's > > hope if there is a BF failure next time, we can gather enough > > information to know the reason of the same. > > > > There is a new BF failure [1] after adding these LOGs and I think I know what > is > going wrong. First, let's look at standby LOGs: > > 2024-02-16 06:18:18.442 UTC [241414][client backend][2/14:0] DEBUG: > segno: 4 of purposed restart_lsn for the synced slot, oldest_segno: 4 > available > 2024-02-16 06:18:18.443 UTC [241414][client backend][2/14:0] DEBUG: > xmin required by slots: data 0, catalog 741 > 2024-02-16 06:18:18.443 UTC [241414][client backend][2/14:0] LOG:mote could > not sync slot information as reslot precedes local slot: remote slot > "lsub1_slot": > LSN (0/4000168), catalog xmin (739) local slot: LSN (0/4000168), catalog xmin > (741) > > So, from the above LOG, it is clear that the remote slot's catalog xmin (739) > precedes the local catalog xmin (741) which makes the sync on standby to not > complete. > > Next, let's look at the LOG from the primary during the nearby time: > 2024-02-16 06:18:11.354 UTC [238037][autovacuum worker][5/17:0] DEBUG: > analyzing "pg_catalog.pg_depend" > 2024-02-16 06:18:11.360 UTC [238037][autovacuum worker][5/17:0] DEBUG: > "pg_depend": scanned 13 of 13 pages, containing 1709 live rows and 0 dead > rows; 1709 rows in sample, 1709 estimated total rows ... > 2024-02-16 06:18:11.372 UTC [238037][autovacuum worker][5/0:0] DEBUG: > Autovacuum VacuumUpdateCosts(db=1, rel=14050, dobalance=yes, > cost_limit=200, cost_delay=2 active=yes failsafe=no) > 2024-02-16 06:18:11.372 UTC [238037][autovacuum worker][5/19:0] DEBUG: > analyzing "information_schema.sql_features" > 2024-02-16 06:18:11.377 UTC [238037][autovacuum worker][5/19:0] DEBUG: > "sql_features": scanned 8 of 8 pages, containing 756 live rows and 0 dead > rows; > 756 rows in sample, 756 estimated total rows > > It shows us that autovacuum worker has analyzed catalog table and for updating > its statistics in pg_statistic table, it would have acquired a new > transaction id. Now, > after the slot creation, a new transaction id that has updated the catalog is > generated on primary and would have been replication to standby. Due to this > catalog_xmin of primary's slot would precede standby's catalog_xmin and we see > this failure. > > As per this theory, we should disable autovacuum on primary to avoid updates > to > catalog_xmin values. >
Agreed. Here is the patch to disable autovacuum in the test. Best Regards, Hou zj
0001-Disable-autovacuum-on-primary-to-stabilize-the-040_s.patch
Description: 0001-Disable-autovacuum-on-primary-to-stabilize-the-040_s.patch
