Using PG 8.2, I have a database in recovery mode using pg_standby to
handle the WAL restores.
Is it allowable to have a backup database in recovery mode, then stop
recovery (in this case, by putting the trigger file in place to stop
pg_standby), check out that the backup db appears up to date, stop the
now active backup db, and then restart it in recover mode again to have
it resume its backup role?
I have had some success doing this, with the restart in recovery showing:
LOG: starting archive recovery
LOG: restore_command = "~/postgresql/bin/pg_standby -l -d -s 2 -k 20 -t
~/postgresql/restoreWALs/STOP_RESTORE ~/postgresql/restoreWALs %f %p 2>>
~/pg_standby.log"
LOG: restored log file "000000010000000500000018" from archive
*LOG: invalid xl_info in primary checkpoint record*
LOG: using previous checkpoint record at 5/18000020
LOG: redo record is at 5/18000020; undo record is at 0/0; shutdown FALSE
LOG: next transaction ID: 0/1535389; next OID: 53990
LOG: next MultiXactId: 1; next MultiXactOffset: 0
*LOG: automatic recovery in progress*
LOG: redo starts at 5/18000068
But there are times when I do this that it cannot. Is this because the
steps are an issue (after all, I did stop recovery and go active
briefly, though I didn't update the db during that time, just did \d and
select queries to see that DDL and row data were updated on the backup),
or is it related to not keeping enough WAL files around (pg_standby -k
20 was chosen, but it's not clear how to select this value, and it
sounds like 8.3 gets rid of that issue entirely) to find the 'secondary
checkpoint record'.
Here's the sort of error I get when it doesn't allow me to restart:
LOG: database system was shut down at 2008-01-11 11:40:05 PST
LOG: starting archive recovery
LOG: restore_command = "~/postgresql/bin/pg_standby -l -d -s 2 -k 20 -t
~/postgresql/restoreWALs/STOP_RESTORE ~/postgresql/restoreWALs %f %p 2>>
~/pg_standby.log"
*LOG: restored log file "00000001000000050000001D" from archive
LOG: invalid record length at 5/1D000068
LOG: invalid primary checkpoint record
LOG: restored log file "00000001000000050000001D" from archive
LOG: invalid resource manager ID in secondary checkpoint record
PANIC: could not locate a valid checkpoint record*
LOG: startup process (PID 9219) was terminated by signal 6
LOG: aborting startup due to startup process failure
LOG: logger shutting down
Thanks,
David
