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help / color / mirror / Atom feedFrom: Anastasia Lubennikova <[email protected]>
To: Paul Guo <[email protected]>
To: Thomas Munro <[email protected]>
Cc: Kyotaro HORIGUCHI <[email protected]>
Cc: PostgreSQL mailing lists <[email protected]>
Subject: Re: standby recovery fails (tablespace related) (tentative patch and discussion)
Date: Thu, 22 Aug 2019 19:13:05 +0300
Message-ID: <[email protected]> (raw)
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22.08.2019 16:13, Paul Guo wrote:
> Thanks. I updated the patch to v5. It passes install-check testing and
> recovery testing.
Hi,
Thank you for working on this fix.
The overall design of the latest version looks good to me.
But during the review, I found a bug in the current implementation.
New behavior must apply to crash-recovery only, now it applies to
archiveRecovery too.
That can cause a silent loss of a tablespace during regular standby
operation
since it never calls CheckRecoveryConsistency().
Steps to reproduce:
1) run master and replica
2) create dir for tablespace:
mkdir /tmp/tblspc1
3) create tablespace and database on the master:
create tablespace tblspc1 location '/tmp/tblspc1';
create database db1 tablespace tblspc1 ;
4) wait for replica to receive this changes and pause replication:
select pg_wal_replay_pause();
5) move replica's tablespace symlink to some empty directory, i.e.
/tmp/tblspc2
mkdir /tmp/tblspc2
ln -sfn /tmp/tblspc2 postgresql_data_replica/pg_tblspc/16384
6) create another database in tblspc1 on master:
create database db2 tablespace tblspc1 ;
7) resume replication on standby:
select pg_wal_replay_resume();
8) try to connect to db2 on standby
It's expected that dbase_redo() will fail because the directory on
standby is not found.
While with the patch it suppresses the error until we attempt to connect
db2 on the standby:
2019-08-22 18:34:39.178 MSK [21066] HINT: Execute
pg_wal_replay_resume() to continue.
2019-08-22 18:42:41.656 MSK [21066] WARNING: Skip creating database
directory "pg_tblspc/16384/PG_13_201908012". The dest tablespace may
have been removed before abnormal shutdown. If the removal is illegal
after later checking we will panic.
2019-08-22 18:42:41.656 MSK [21066] CONTEXT: WAL redo at 0/3027738 for
Database/CREATE: copy dir base/1 to pg_tblspc/16384/PG_13_201908012/16390
2019-08-22 18:42:46.096 MSK [21688] FATAL:
"pg_tblspc/16384/PG_13_201908012/16390" is not a valid data directory
2019-08-22 18:42:46.096 MSK [21688] DETAIL: File
"pg_tblspc/16384/PG_13_201908012/16390/PG_VERSION" is missing.
Also some nitpicking about code style:
1) Please, add comment to forget_missing_directory().
2) + elog(LOG, "Directory \"%s\" was missing during
directory copying "
I think we'd better update this message elevel to WARNING.
3) Shouldn't we also move FlushDatabaseBuffers(xlrec->src_db_id); call under
if (do_copydir) clause?
I don't see a reason to flush pages that we won't use later.
--
Anastasia Lubennikova
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company
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