Prevent references to invalid relation pages after fresh promotion

Enterprise / PostgreSQL - Michael Paquier [paquier.xyz] - 5 July 2018 01:46 EDT

If a standby crashes after promotion before having completed its first post-recovery checkpoint, then the minimal recovery point which marks the LSN position where the cluster is able to reach consistency may be set to a position older than the first end-of-recovery checkpoint while all the WAL available should be replayed. This leads to the instance thinking that it contains inconsistent pages, causing a PANIC and a hard instance crash even if all the WAL available has not been replayed for certain sets of records replayed. When in crash recovery, minRecoveryPoint is expected to always be set to InvalidXLogRecPtr, which forces the recovery to replay all the WAL available, so this commit makes sure that the local copy of minRecoveryPoint from the control file is initialized properly and stays as it is while crash recovery is performed. Once switching to archive recovery or if crash recovery finishes, then the local copy minRecoveryPoint can be safely updated.

Pavan Deolasee has reported and diagnosed the failure in the first place, and the base fix idea to rely on the local copy of minRecoveryPoint comes from Kyotaro Horiguchi, which has been expanded into a full-fledged patch by me. The test included in this commit has been written by Álvaro Herrera and Pavan Deolasee, which I have modified to make it faster and more reliable with sleep phases.

Backpatch down to all supported versions where the bug appears, aka 9.3 which is where the end-of-recovery checkpoint is not run by the startup process anymore. The test gets easily supported down to 10, still it has been tested on all branches.

3c64dcb1e3 Prevent references to invalid relation pages after fresh promotion
src/backend/access/transam/xlog.c | 101 ++++++++++++++++++++---------
src/test/recovery/t/015_promotion_pages.pl | 87 +++++++++++++++++++++++++
2 files changed, 157 insertions(+), 31 deletions(-)

Upstream: git.postgresql.org


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