On Mon, Jun 13, 2016 at 6:59 PM, Alex Malek <magicagent@xxxxxxxxx> wrote:
-- I am experiencing two problems
1) pg_stop_backup hangs until pg_basebackup finishes2) WAL contains references to invalid pages(I suspect when 1. is fixed I won't experience 2. )Full description below:
postgresql: 9.3.13My situation is I create a writable report database every day using pg_start_backup() / rsync / pg_stop_backup()(whole process takes 1-2 hours, the rsync actually copies the data dir of a slave/warm spare DB)
Taking what is called an exclusive backup, which is what pg_start_backup() does, is not supported off a standby node. Only pg_basebackup is supported against a standby node.
Can you reproduce your errors if you make this backup from the master?
Also once a week I create a database for backup/archive purposes using pg_basebackup(whole process takes about 13 hours)These two processes used to be able to coincide until recently.
Recent changes include a major debian upgrade and a minor version of postgres upgrade from 9.3.10.Now when the report sync occurs during the pg_basebackup (w/ --xlog-method=stream option) the pg_stop_backup() hangs untilthe the pg_basebackup has completed (4 hours later).
Do you also have an archive_command, and what is it? Normally, pg_stop_backup() blocks on the archive command - so perhaps you have ended up with a dependency between that one and the base backup command somehow?
A labeled WAL backup file is created when the pg_stop_backup() is first executed and anotheris created when the pg_basebackup completes.While the pg_stop_backup() hangs the following appears in the logs:2016-06-11 07:50:45 EDT: WARNING: pg_stop_backup still waiting for all required WAL segments to be archived (7680 seconds elapsed)
2016-06-11 07:50:45 EDT: HINT: Check that your archive_command is executing properly. pg_stop_backup can be canceled safely, but the database backup will not be usable without all the WAL segments.
until eventually:2016-06-11 12:59:07 EDT:LOG: duration: 26190082.497 ms statement: SELECT pg_stop_backup()The archive command appears to work as WAL files are being archived successfully with timestamps that occur while pg_stop_backup is hanging.
-rw------- 1 postgres postgres 314 Jun 11 12:56 000000030000109200000066.00000028.backup
-rw------- 1 postgres postgres 16M Jun 11 12:56 000000030000109300000029
-rw------- 1 postgres postgres 16M Jun 11 12:54 000000030000109300000028
-rw------- 1 postgres postgres 16M Jun 11 12:52 000000030000109300000027<snip>
-rw------- 1 postgres postgres 16M Jun 11 06:22 0000000300001092000000F1
-rw------- 1 postgres postgres 335 Jun 11 05:42 0000000300001092000000D4.00000028.backup
-rw------- 1 postgres postgres 16M Jun 11 05:42 0000000300001092000000F0Content of 0000000300001092000000D4.00000028.backup:
START WAL LOCATION: 1092/D4000028 (file 0000000300001092000000D4)
STOP WAL LOCATION: 1092/F008EA10 (file 0000000300001092000000F0)
CHECKPOINT LOCATION: 1092/D4004E08
BACKUP METHOD: pg_start_backup
BACKUP FROM: master
START TIME: 2016-06-11 04:51:04 EDT
LABEL: reporting 2016-06-11 04:51:03.892804-04
STOP TIME: 2016-06-11 05:42:37 EDT
This file shows that the backup took about an hour, doesn't it? So it doesn't look like it was waiting?
Or are you saying the wait happens *after* the .backup file has been dropped in the archives?
Should I be be able to use those two styles of backup at the same time?
As a general rule, yes. But you cannot run the start/stop version safely against a standby.
Should I replace the start_backup/stop_backup with separate calls to create a checkpoint and switch transaction log files?
That will be equally insecure. You need to run your rsync off the master to make exclusive base backups.
