Fix checksum state transition during promotion
When a standby is promoted to primary during checksum enabling when the
state is inprogress-on, the standby shall revert the state to off since
checksums weren't fully enabled at the time of the crash. Consider the
following scenario:
1) primary/standby cluster has checksums off
2) primary starts enabling checksums
3) primary moves to inprogress-on
4) standby receives that and moves to inprogress-on too
5) primary crashes
6) standby gets promoted, and does the StartupXLOG thing
7) standby moves from inprogress-on back to off
Any processes in the standby need to be informed at step 6 to change
state with a procsignalbarrier, else they will stay in inprogress-on
while new backends will see the state as off. StartupXLOG failed to
emit a procsignalbarrier which caused inconsistent state in the node
promoted to primary.
Fixed by emitting a procsignalbarrier during promotion, and adding a
new test for this scenario.
Author: Daniel Gustafsson <daniel@yesql.se>
Reported-by: Tomas Vondra <tomas@vondra.me>
Discussion: https://postgr.es/m/f1281cf3-89a3-4936-9bc5-2a5a6291229f@vondra.me
Branch
------
master
Details
-------
https://git.postgresql.org/pg/commitdiff/5fee7cab1b8746c9e1bc25b20158cb074c7a76da
Modified Files
--------------
src/backend/access/transam/xlog.c | 5 +-
.../test_checksums/t/003_standby_restarts.pl | 58 ++++++++++++++++++++++
2 files changed, 62 insertions(+), 1 deletion(-)
