logical replication: could not create file "state.tmp": File exists

Grigory Smolkin <g.smolkin@postgrespro.ru>

From: Grigory Smolkin <g.smolkin@postgrespro.ru>

To: Pg Bugs <pgsql-bugs@postgresql.org>

Date: 2019-11-30T12:09:39Z

Lists: pgsql-bugs

Attachments

replication_bug.sh (application/x-shellscript)
0001-logical_replication_fix.patch (text/x-patch) patch 0001

Hello!

One of my colleagues encountered an out of space condition, which broke 
his logical replication setup.
It`s manifested with the following errors:

ERROR:  could not receive data from WAL stream: ERROR:  could not create 
file "pg_replslot/some_sub/state.tmp": File exists

I`ve digged a bit into this problem, and it`s turned out that in 
SaveSlotToPath() temp file for replication slot is opened with 'O_CREAT 
| O_EXCL' flags, which makes this routine as not very reentrant.

Since an exclusive lock is taken before temp file creation, I think it 
should be safe to replace O_EXCL with O_TRUNC.
Script to reproduce and patch are attached.

-- 
Grigory Smolkin
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company

Commits

Remove state.tmp when failing to save a replication slot
- c878d9808420 13.23 landed
- f57f2760e665 14.20 landed
- 0adf424b490b 15.15 landed
- bfdd1a12d2d9 16.11 landed
- 42348839d8b7 17.7 landed
- 9a6ea00ac8c0 18.1 landed
- 912af1c7e9c9 19 (unreleased) landed