From ef18cb7da6ab0bde676ad8f7b17452d7cd8f7970 Mon Sep 17 00:00:00 2001 From: Robert Haas Date: Thu, 27 Oct 2016 11:19:51 -0400 Subject: [PATCH] Fix possible pg_basebackup failure on standby with "include WAL". If a restartpoint flushed no dirty buffers, it could fail to update the minimum recovery point, leading to a minimum recovery point prior to the starting REDO location. perform_base_backup() would interpret that as meaning that no WAL files at all needed to be included in the backup, failing an internal sanity check. To fix, have restartpoints always update the minimum recovery point to just after the checkpoint record itself, so that the file (or files) containing the checkpoint record will always be included in the backup. Code by Amit Kapila, per a design suggestion by me, with some additional work on the code comment by me. Test case by Michael Paquier. Report by Kyotaro Horiguchi. --- src/backend/access/transam/xlog.c | 29 ++++++++++++++++++++++++++++- 1 file changed, 28 insertions(+), 1 deletion(-) diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 63154a1675..720edf75d0 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -610,11 +610,14 @@ typedef struct XLogCtlData /* * During recovery, we keep a copy of the latest checkpoint record here. - * Used by the background writer when it wants to create a restartpoint. + * lastCheckPointRecPtr points to start of checkpoint record and + * lastCheckPointEndPtr points to end+1 of checkpoint record. Used by the + * background writer when it wants to create a restartpoint. * * Protected by info_lck. */ XLogRecPtr lastCheckPointRecPtr; + XLogRecPtr lastCheckPointEndPtr; CheckPoint lastCheckPoint; /* @@ -8644,6 +8647,7 @@ RecoveryRestartPoint(const CheckPoint *checkPoint) */ SpinLockAcquire(&XLogCtl->info_lck); XLogCtl->lastCheckPointRecPtr = ReadRecPtr; + XLogCtl->lastCheckPointEndPtr = EndRecPtr; XLogCtl->lastCheckPoint = *checkPoint; SpinLockRelease(&XLogCtl->info_lck); } @@ -8663,6 +8667,7 @@ bool CreateRestartPoint(int flags) { XLogRecPtr lastCheckPointRecPtr; + XLogRecPtr lastCheckPointEndPtr; CheckPoint lastCheckPoint; XLogRecPtr PriorRedoPtr; TimestampTz xtime; @@ -8676,6 +8681,7 @@ CreateRestartPoint(int flags) /* Get a local copy of the last safe checkpoint record. */ SpinLockAcquire(&XLogCtl->info_lck); lastCheckPointRecPtr = XLogCtl->lastCheckPointRecPtr; + lastCheckPointEndPtr = XLogCtl->lastCheckPointEndPtr; lastCheckPoint = XLogCtl->lastCheckPoint; SpinLockRelease(&XLogCtl->info_lck); @@ -8779,6 +8785,27 @@ CreateRestartPoint(int flags) ControlFile->checkPoint = lastCheckPointRecPtr; ControlFile->checkPointCopy = lastCheckPoint; ControlFile->time = (pg_time_t) time(NULL); + + /* + * Ensure minRecoveryPoint is past the checkpoint record. Normally, + * this will have happened already while writing out dirty buffers, + * but not necessarily - e.g. because no buffers were dirtied. We do + * this because a non-exclusive base backup uses minRecoveryPoint to + * determine which WAL files must be included in the backup, and the + * file (or files) containing the checkpoint record must be included, + * at a minimum. Note that for an ordinary restart of recovery there's + * no value in having the minimum recovery point any earlier than this + * anyway, because redo will begin just after the checkpoint record. + */ + if (ControlFile->minRecoveryPoint < lastCheckPointEndPtr) + { + ControlFile->minRecoveryPoint = lastCheckPointEndPtr; + ControlFile->minRecoveryPointTLI = lastCheckPoint.ThisTimeLineID; + + /* update local copy */ + minRecoveryPoint = ControlFile->minRecoveryPoint; + minRecoveryPointTLI = ControlFile->minRecoveryPointTLI; + } if (flags & CHECKPOINT_IS_SHUTDOWN) ControlFile->state = DB_SHUTDOWNED_IN_RECOVERY; UpdateControlFile();