Re: Standby pg_dump Conflict with Recovery

On Oct 15, 2015, at 6:16 PM, Adrian Klaver <adrian.klaver@aklaver.com> wrote:

On 10/15/2015 03:03 PM, Louis Battuello wrote:

Hello All,

I’ve got a confusing issue with dumping data from a standby PostgreSQL
9.4.5 database.

At night, on a nearly completely idle server, I run a pg_dump of a
database that contains numerous small tables and one 3GB table. The
dump consistently fails when reaching the 3GB table with this message:

pg_dump: Dumping the contents of table “<table>" failed: PQgetResult()
failed.
pg_dump: Error message from server: ERROR:  canceling statement due to
conflict with recovery
DETAIL:  User query might have needed to see row versions that must be
removed.
pg_dump: The command was: COPY <table> (...) TO stdout;

I have replication slots enabled on the primary (“repmgr_slot_3" for the
standby pg_dump source), and I’m using hot_standby_feedback. After
getting the failure a couple times, I temporarily set
max_standby_archive_delay and max_standby_streaming_delay to -1 to allow
infinite delay on the standby,  just to see if I could get the dump to
complete. I still encountered the above error.

How did you set and temporarily enable the settings

postgres=# select * from pg_replication_slots ;
   slot_name   | plugin | slot_type | datoid | database | active
|  xmin   | catalog_xmin | restart_lsn
---------------+--------+-----------+--------+----------+--------+---------+--------------+-------------
 repmgr_slot_2 |        | physical  |        |          | t      |
    |              | A/C6502880
 repmgr_slot_3 |        | physical  |        |          | t      |
1356283 |              | A/C6502880
(2 rows)

Is there some other configuration setting I’m forgetting?

Thanks,
Louis

-- 
Adrian Klaver
adrian.klaver@aklaver.com


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