Re: Add checkpoint and redo LSN to LogCheckpointEnd log message - Mailing list pgsql-hackers

At Fri, 25 Feb 2022 16:06:31 +0900 (JST), Kyotaro Horiguchi <horikyota.ntt@gmail.com> wrote in 
> At Fri, 25 Feb 2022 15:31:12 +0900 (JST), Kyotaro Horiguchi <horikyota.ntt@gmail.com> wrote in 
> > While making patches for v12, I see a test failure of pg_rewind for
> > uncertain reason. I'm investigating that but I post this for
> > discussion.
> 
> Hmm. Too stupid.  Somehow I overly removed the latchet condition for
> minRecoveryPoint.  So the same patch worked for v12.

So, this is the patches for pg12-10.  11 can share the same patch with
12.  10 has differences in two points.

10 has ControlFile->prevCheckPoint.

The DETAILS of the "recovery restart point at" message is not
capitalized.  But I suppose it is so close to EOL so that we don't
want to "fix" it risking existing usecases.

regards.

-- 
Kyotaro Horiguchi
NTT Open Source Software Center
From c89e2b509723b68897f2af49a154af2a69f0747b Mon Sep 17 00:00:00 2001
From: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Date: Fri, 25 Feb 2022 15:04:00 +0900
Subject: [PATCH v3] Correctly update contfol file at the end of archive
 recovery

CreateRestartPoint runs WAL file cleanup basing on the checkpoint just
have finished in the function.  If the database has exited
DB_IN_ARCHIVE_RECOVERY state when the function is going to update
control file, the function refrains from updating the file at all then
proceeds to WAL cleanup having the latest REDO LSN, which is now
inconsistent with the control file.  As the result, the succeeding
cleanup procedure overly removes WAL files against the control file
and leaves unrecoverable database until the next checkpoint finishes.

Along with that fix, we remove a dead code path for the case some
other process ran a simultaneous checkpoint.  It seems like just a
preventive measure but it's no longer useful because we are sure that
checkpoint is performed only by checkpointer except single process
mode.
---
 src/backend/access/transam/xlog.c | 71 +++++++++++++++++++------------
 1 file changed, 44 insertions(+), 27 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 885558f291..2b2568c475 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -9334,7 +9334,7 @@ CreateRestartPoint(int flags)
 
     /* Also update the info_lck-protected copy */
     SpinLockAcquire(&XLogCtl->info_lck);
-    XLogCtl->RedoRecPtr = lastCheckPoint.redo;
+    XLogCtl->RedoRecPtr = RedoRecPtr;
     SpinLockRelease(&XLogCtl->info_lck);
 
     /*
@@ -9350,7 +9350,10 @@ CreateRestartPoint(int flags)
     if (log_checkpoints)
         LogCheckpointStart(flags, true);
 
-    CheckPointGuts(lastCheckPoint.redo, flags);
+    CheckPointGuts(RedoRecPtr, flags);
+
+    /* Update pg_control */
+    LWLockAcquire(ControlFileLock, LW_EXCLUSIVE);
 
     /*
      * Remember the prior checkpoint's redo ptr for
@@ -9358,31 +9361,28 @@ CreateRestartPoint(int flags)
      */
     PriorRedoPtr = ControlFile->checkPointCopy.redo;
 
+    Assert (PriorRedoPtr < RedoRecPtr);
+
+    ControlFile->checkPoint = lastCheckPointRecPtr;
+    ControlFile->checkPointCopy = lastCheckPoint;
+
+    /* Update control file using current time */
+    ControlFile->time = (pg_time_t) time(NULL);
+
     /*
-     * Update pg_control, using current time.  Check that it still shows
-     * IN_ARCHIVE_RECOVERY state and an older checkpoint, else do nothing;
-     * this is a quick hack to make sure nothing really bad happens if somehow
-     * we get here after the end-of-recovery checkpoint.
+     * Ensure minRecoveryPoint is past the checkpoint record while archive
+     * recovery is still ongoing.  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.
      */
-    LWLockAcquire(ControlFileLock, LW_EXCLUSIVE);
-    if (ControlFile->state == DB_IN_ARCHIVE_RECOVERY &&
-        ControlFile->checkPointCopy.redo < lastCheckPoint.redo)
+    if (ControlFile->state == DB_IN_ARCHIVE_RECOVERY)
     {
-        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;
@@ -9393,9 +9393,26 @@ CreateRestartPoint(int flags)
             minRecoveryPointTLI = ControlFile->minRecoveryPointTLI;
         }
         if (flags & CHECKPOINT_IS_SHUTDOWN)
-            ControlFile->state = DB_SHUTDOWNED_IN_RECOVERY;
-        UpdateControlFile();
+        ControlFile->state = DB_SHUTDOWNED_IN_RECOVERY;
     }
+    else
+    {
+        /* recovery mode is not supposed to end during shutdown restartpoint */
+        Assert((flags & CHECKPOINT_IS_SHUTDOWN) == 0);
+
+        /*
+         * Aarchive recovery has ended. Crash recovery ever after should
+         * always recover to the end of WAL
+         */
+        ControlFile->minRecoveryPoint = InvalidXLogRecPtr;
+        ControlFile->minRecoveryPointTLI = 0;
+
+        /* also update local copy */
+        minRecoveryPoint = InvalidXLogRecPtr;
+        minRecoveryPointTLI = 0;
+    }
+
+    UpdateControlFile();
     LWLockRelease(ControlFileLock);
 
     /*
@@ -9470,7 +9487,7 @@ CreateRestartPoint(int flags)
     xtime = GetLatestXTime();
     ereport((log_checkpoints ? LOG : DEBUG2),
             (errmsg("recovery restart point at %X/%X",
-                    (uint32) (lastCheckPoint.redo >> 32), (uint32) lastCheckPoint.redo),
+                    (uint32) (RedoRecPtr >> 32), (uint32) RedoRecPtr),
              xtime ? errdetail("Last completed transaction was at log time %s.",
                                timestamptz_to_str(xtime)) : 0));
 
-- 
2.27.0

From 7dd174d165b3639b573bfc47c2e8b2fba61395c5 Mon Sep 17 00:00:00 2001
From: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Date: Fri, 25 Feb 2022 16:35:16 +0900
Subject: [PATCH v3] Correctly update contfol file at the end of archive
 recovery

CreateRestartPoint runs WAL file cleanup basing on the checkpoint just
have finished in the function.  If the database has exited
DB_IN_ARCHIVE_RECOVERY state when the function is going to update
control file, the function refrains from updating the file at all then
proceeds to WAL cleanup having the latest REDO LSN, which is now
inconsistent with the control file.  As the result, the succeeding
cleanup procedure overly removes WAL files against the control file
and leaves unrecoverable database until the next checkpoint finishes.

Along with that fix, we remove a dead code path for the case some
other process ran a simultaneous checkpoint.  It seems like just a
preventive measure but it's no longer useful because we are sure that
checkpoint is performed only by checkpointer except single process
mode.
---
 src/backend/access/transam/xlog.c | 73 +++++++++++++++++++------------
 1 file changed, 45 insertions(+), 28 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index c64febdb53..9fb66ad7d5 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -9434,7 +9434,7 @@ CreateRestartPoint(int flags)
 
     /* Also update the info_lck-protected copy */
     SpinLockAcquire(&XLogCtl->info_lck);
-    XLogCtl->RedoRecPtr = lastCheckPoint.redo;
+    XLogCtl->RedoRecPtr = RedoRecPtr;
     SpinLockRelease(&XLogCtl->info_lck);
 
     /*
@@ -9450,7 +9450,10 @@ CreateRestartPoint(int flags)
     if (log_checkpoints)
         LogCheckpointStart(flags, true);
 
-    CheckPointGuts(lastCheckPoint.redo, flags);
+    CheckPointGuts(RedoRecPtr, flags);
+
+    /* Update pg_control */
+    LWLockAcquire(ControlFileLock, LW_EXCLUSIVE);
 
     /*
      * Remember the prior checkpoint's redo pointer, used later to determine
@@ -9458,32 +9461,29 @@ CreateRestartPoint(int flags)
      */
     PriorRedoPtr = ControlFile->checkPointCopy.redo;
 
+    Assert (PriorRedoPtr < RedoRecPtr);
+
+    ControlFile->prevCheckPoint = ControlFile->checkPoint;
+    ControlFile->checkPoint = lastCheckPointRecPtr;
+    ControlFile->checkPointCopy = lastCheckPoint;
+
+    /* Update control file using current time */
+    ControlFile->time = (pg_time_t) time(NULL);
+
     /*
-     * Update pg_control, using current time.  Check that it still shows
-     * IN_ARCHIVE_RECOVERY state and an older checkpoint, else do nothing;
-     * this is a quick hack to make sure nothing really bad happens if somehow
-     * we get here after the end-of-recovery checkpoint.
+     * Ensure minRecoveryPoint is past the checkpoint record while archive
+     * recovery is still running.  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.
      */
-    LWLockAcquire(ControlFileLock, LW_EXCLUSIVE);
-    if (ControlFile->state == DB_IN_ARCHIVE_RECOVERY &&
-        ControlFile->checkPointCopy.redo < lastCheckPoint.redo)
+    if (ControlFile->state == DB_IN_ARCHIVE_RECOVERY)
     {
-        ControlFile->prevCheckPoint = ControlFile->checkPoint;
-        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;
@@ -9494,9 +9494,26 @@ CreateRestartPoint(int flags)
             minRecoveryPointTLI = ControlFile->minRecoveryPointTLI;
         }
         if (flags & CHECKPOINT_IS_SHUTDOWN)
-            ControlFile->state = DB_SHUTDOWNED_IN_RECOVERY;
-        UpdateControlFile();
+        ControlFile->state = DB_SHUTDOWNED_IN_RECOVERY;
     }
+    else
+    {
+        /* recovery mode is not supposed to end during shutdown restartpoint */
+        Assert((flags & CHECKPOINT_IS_SHUTDOWN) == 0);
+
+        /*
+         * Aarchive recovery has ended. Crash recovery ever after should
+         * always recover to the end of WAL
+         */
+        ControlFile->minRecoveryPoint = InvalidXLogRecPtr;
+        ControlFile->minRecoveryPointTLI = 0;
+
+        /* also update local copy */
+        minRecoveryPoint = InvalidXLogRecPtr;
+        minRecoveryPointTLI = 0;
+    }
+
+    UpdateControlFile();
     LWLockRelease(ControlFileLock);
 
     /*
@@ -9579,7 +9596,7 @@ CreateRestartPoint(int flags)
     xtime = GetLatestXTime();
     ereport((log_checkpoints ? LOG : DEBUG2),
             (errmsg("recovery restart point at %X/%X",
-                    (uint32) (lastCheckPoint.redo >> 32), (uint32) lastCheckPoint.redo),
+                    (uint32) (RedoRecPtr >> 32), (uint32) RedoRecPtr),
              xtime ? errdetail("last completed transaction was at log time %s",
                                timestamptz_to_str(xtime)) : 0));
 
-- 
2.27.0