At Tue, 22 Nov 2022 16:04:56 -0600, Justin Pryzby <pry...@telsasoft.com> wrote
in
> On Fri, Nov 18, 2022 at 05:25:37PM +0900, Kyotaro Horiguchi wrote:
> > + while (*p == 0 && p < pe)
> > + p++;
>
> The bug reported by Andres/cfbot/ubsan is here.
>
> Fixed in attached.
Ur..ou..
- while (*p == 0 && p < pe)
+ while (p < pe && *p == 0)
It was an off-by-one error. Thanks!
> I didn't try to patch the test case to output the failing stderr, but
> that might be good.
I have made use of Cluster::wait_for_log(), but still find_in_log() is
there since it is used to check if a message that should not be logged
is not logged.
regards.
--
Kyotaro Horiguchi
NTT Open Source Software Center
>From 37dd82652bf028811002af9e7c0df9e9d2ddb7d7 Mon Sep 17 00:00:00 2001
From: Kyotaro Horiguchi <horikyota....@gmail.com>
Date: Wed, 30 Nov 2022 11:51:46 +0900
Subject: [PATCH v23] Make End-Of-Recovery error less scary
When recovery in any type ends, we see a bit scary error message like
"invalid record length" that suggests something serious is
happening. Actually if recovery meets a record with length = 0, that
usually means it finished applying all available WAL records.
Make this message less scary as "reached end of WAL". Instead, raise
the error level for other kind of WAL failure to WARNING.
---
src/backend/access/transam/xlogreader.c | 137 +++++++++++++++++-----
src/backend/access/transam/xlogrecovery.c | 94 +++++++++++----
src/backend/replication/walreceiver.c | 7 +-
src/bin/pg_waldump/pg_waldump.c | 13 +-
src/include/access/xlogreader.h | 1 +
src/test/recovery/t/011_crash_recovery.pl | 96 +++++++++++++++
6 files changed, 289 insertions(+), 59 deletions(-)
diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c
index 93f667b254..137de96795 100644
--- a/src/backend/access/transam/xlogreader.c
+++ b/src/backend/access/transam/xlogreader.c
@@ -48,6 +48,8 @@ static int ReadPageInternal(XLogReaderState *state, XLogRecPtr pageptr,
int reqLen);
static void XLogReaderInvalReadState(XLogReaderState *state);
static XLogPageReadResult XLogDecodeNextRecord(XLogReaderState *state, bool nonblocking);
+static bool ValidXLogRecordLength(XLogReaderState *state, XLogRecPtr RecPtr,
+ XLogRecord *record);
static bool ValidXLogRecordHeader(XLogReaderState *state, XLogRecPtr RecPtr,
XLogRecPtr PrevRecPtr, XLogRecord *record, bool randAccess);
static bool ValidXLogRecord(XLogReaderState *state, XLogRecord *record,
@@ -149,6 +151,7 @@ XLogReaderAllocate(int wal_segment_size, const char *waldir,
pfree(state);
return NULL;
}
+ state->EndOfWAL = false;
state->errormsg_buf[0] = '\0';
/*
@@ -558,6 +561,7 @@ XLogDecodeNextRecord(XLogReaderState *state, bool nonblocking)
/* reset error state */
state->errormsg_buf[0] = '\0';
decoded = NULL;
+ state->EndOfWAL = false;
state->abortedRecPtr = InvalidXLogRecPtr;
state->missingContrecPtr = InvalidXLogRecPtr;
@@ -640,25 +644,21 @@ restart:
Assert(pageHeaderSize <= readOff);
/*
- * Read the record length.
+ * Validate the record header.
*
- * NB: Even though we use an XLogRecord pointer here, the whole record
- * header might not fit on this page. xl_tot_len is the first field of the
- * struct, so it must be on this page (the records are MAXALIGNed), but we
- * cannot access any other fields until we've verified that we got the
- * whole header.
- */
- record = (XLogRecord *) (state->readBuf + RecPtr % XLOG_BLCKSZ);
- total_len = record->xl_tot_len;
-
- /*
- * If the whole record header is on this page, validate it immediately.
- * Otherwise do just a basic sanity check on xl_tot_len, and validate the
- * rest of the header after reading it from the next page. The xl_tot_len
+ * Even though we use an XLogRecord pointer here, the whole record header
+ * might not fit on this page. If the whole record header is on this page,
+ * validate it immediately. Even otherwise xl_tot_len must be on this page
+ * (it is the first field of MAXALIGNed records), but we still cannot
+ * access any further fields until we've verified that we got the whole
+ * header, so do just a basic sanity check on record length, and validate
+ * the rest of the header after reading it from the next page. The length
* check is necessary here to ensure that we enter the "Need to reassemble
* record" code path below; otherwise we might fail to apply
* ValidXLogRecordHeader at all.
*/
+ record = (XLogRecord *) (state->readBuf + RecPtr % XLOG_BLCKSZ);
+
if (targetRecOff <= XLOG_BLCKSZ - SizeOfXLogRecord)
{
if (!ValidXLogRecordHeader(state, RecPtr, state->DecodeRecPtr, record,
@@ -668,18 +668,14 @@ restart:
}
else
{
- /* XXX: more validation should be done here */
- if (total_len < SizeOfXLogRecord)
- {
- report_invalid_record(state,
- "invalid record length at %X/%X: wanted %u, got %u",
- LSN_FORMAT_ARGS(RecPtr),
- (uint32) SizeOfXLogRecord, total_len);
+ if (!ValidXLogRecordLength(state, RecPtr, record))
goto err;
- }
+
gotheader = false;
}
+ total_len = record->xl_tot_len;
+
/*
* Find space to decode this record. Don't allow oversized allocation if
* the caller requested nonblocking. Otherwise, we *have* to try to
@@ -1105,6 +1101,60 @@ XLogReaderInvalReadState(XLogReaderState *state)
state->readLen = 0;
}
+/*
+ * Validate record length of an XLOG record header.
+ *
+ * This is substantially a part of ValidXLogRecordHeader. But XLogReadRecord
+ * needs this separate from the function in case of a partial record header.
+ */
+static bool
+ValidXLogRecordLength(XLogReaderState *state, XLogRecPtr RecPtr,
+ XLogRecord *record)
+{
+ if (record->xl_tot_len == 0)
+ {
+ char *p;
+ char *pe;
+
+ /*
+ * We are almost sure reaching the end of WAL, make sure that the
+ * whole page after the record is filled with zeroes.
+ */
+ p = (char *) record;
+ pe = p + XLOG_BLCKSZ - (RecPtr & (XLOG_BLCKSZ - 1));
+
+ while (p < pe && *p == 0)
+ p++;
+
+ if (p == pe)
+ {
+ /*
+ * The page after the record is completely zeroed. That suggests
+ * we don't have a record after this point. We don't bother
+ * checking the pages after since they are not zeroed in the case
+ * of recycled segments.
+ */
+ report_invalid_record(state, "empty record at %X/%X",
+ LSN_FORMAT_ARGS(RecPtr));
+
+ /* notify end-of-wal to callers */
+ state->EndOfWAL = true;
+ return false;
+ }
+ }
+
+ if (record->xl_tot_len < SizeOfXLogRecord)
+ {
+ report_invalid_record(state,
+ "invalid record length at %X/%X: wanted %u, got %u",
+ LSN_FORMAT_ARGS(RecPtr),
+ (uint32) SizeOfXLogRecord, record->xl_tot_len);
+ return false;
+ }
+
+ return true;
+}
+
/*
* Validate an XLOG record header.
*
@@ -1116,14 +1166,9 @@ ValidXLogRecordHeader(XLogReaderState *state, XLogRecPtr RecPtr,
XLogRecPtr PrevRecPtr, XLogRecord *record,
bool randAccess)
{
- if (record->xl_tot_len < SizeOfXLogRecord)
- {
- report_invalid_record(state,
- "invalid record length at %X/%X: wanted %u, got %u",
- LSN_FORMAT_ARGS(RecPtr),
- (uint32) SizeOfXLogRecord, record->xl_tot_len);
+ if (!ValidXLogRecordLength(state, RecPtr, record))
return false;
- }
+
if (!RmgrIdIsValid(record->xl_rmid))
{
report_invalid_record(state,
@@ -1219,6 +1264,32 @@ XLogReaderValidatePageHeader(XLogReaderState *state, XLogRecPtr recptr,
XLByteToSeg(recptr, segno, state->segcxt.ws_segsize);
offset = XLogSegmentOffset(recptr, state->segcxt.ws_segsize);
+ StaticAssertStmt(XLOG_PAGE_MAGIC != 0, "XLOG_PAGE_MAGIC is zero");
+
+ if (hdr->xlp_magic == 0)
+ {
+ /* Regard an empty page as End-Of-WAL */
+ int i;
+
+ for (i = 0; i < XLOG_BLCKSZ && phdr[i] == 0; i++);
+ if (i == XLOG_BLCKSZ)
+ {
+ char fname[MAXFNAMELEN];
+
+ XLogFileName(fname, state->seg.ws_tli, segno,
+ state->segcxt.ws_segsize);
+
+ report_invalid_record(state,
+ "empty page in log segment %s, offset %u",
+ fname,
+ offset);
+ state->EndOfWAL = true;
+ return false;
+ }
+
+ /* The same condition will be caught as invalid magic number */
+ }
+
if (hdr->xlp_magic != XLOG_PAGE_MAGIC)
{
char fname[MAXFNAMELEN];
@@ -1304,6 +1375,14 @@ XLogReaderValidatePageHeader(XLogReaderState *state, XLogRecPtr recptr,
LSN_FORMAT_ARGS(hdr->xlp_pageaddr),
fname,
offset);
+
+ /*
+ * If the page address is less than expected we assume it is an unused
+ * page in a recycled segment.
+ */
+ if (hdr->xlp_pageaddr < recptr)
+ state->EndOfWAL = true;
+
return false;
}
diff --git a/src/backend/access/transam/xlogrecovery.c b/src/backend/access/transam/xlogrecovery.c
index 41ffc57da9..049b468620 100644
--- a/src/backend/access/transam/xlogrecovery.c
+++ b/src/backend/access/transam/xlogrecovery.c
@@ -1625,7 +1625,7 @@ PerformWalRecovery(void)
/* just have to read next record after CheckPoint */
Assert(xlogreader->ReadRecPtr == CheckPointLoc);
replayTLI = CheckPointTLI;
- record = ReadRecord(xlogprefetcher, LOG, false, replayTLI);
+ record = ReadRecord(xlogprefetcher, WARNING, false, replayTLI);
}
if (record != NULL)
@@ -1734,7 +1734,7 @@ PerformWalRecovery(void)
}
/* Else, try to fetch the next WAL record */
- record = ReadRecord(xlogprefetcher, LOG, false, replayTLI);
+ record = ReadRecord(xlogprefetcher, WARNING, false, replayTLI);
} while (record != NULL);
/*
@@ -1788,11 +1788,18 @@ PerformWalRecovery(void)
InRedo = false;
}
- else
+ else if (xlogreader->EndOfWAL)
{
/* there are no WAL records following the checkpoint */
ereport(LOG,
- (errmsg("redo is not required")));
+ errmsg("redo is not required"));
+ }
+ else
+ {
+ /* broken record found */
+ ereport(WARNING,
+ errmsg("redo is skipped"),
+ errhint("This suggests WAL file corruption. You might need to check the database."));
}
/*
@@ -3020,6 +3027,7 @@ ReadRecord(XLogPrefetcher *xlogprefetcher, int emode,
for (;;)
{
char *errormsg;
+ XLogRecPtr ErrRecPtr = InvalidXLogRecPtr;
record = XLogPrefetcherReadRecord(xlogprefetcher, &errormsg);
if (record == NULL)
@@ -3041,6 +3049,18 @@ ReadRecord(XLogPrefetcher *xlogprefetcher, int emode,
{
abortedRecPtr = xlogreader->abortedRecPtr;
missingContrecPtr = xlogreader->missingContrecPtr;
+ ErrRecPtr = abortedRecPtr;
+ }
+ else
+ {
+ /*
+ * EndRecPtr is the LSN we tried to read but failed. In the
+ * case of decoding error, it is at the end of the failed
+ * record but we don't have a means for now to know EndRecPtr
+ * is pointing to which of the beginning or ending of the
+ * failed record.
+ */
+ ErrRecPtr = xlogreader->EndRecPtr;
}
if (readFile >= 0)
@@ -3051,13 +3071,15 @@ ReadRecord(XLogPrefetcher *xlogprefetcher, int emode,
/*
* We only end up here without a message when XLogPageRead()
- * failed - in that case we already logged something. In
- * StandbyMode that only happens if we have been triggered, so we
- * shouldn't loop anymore in that case.
+ * failed- in that case we already logged something. In StandbyMode
+ * that only happens if we have been triggered, so we shouldn't
+ * loop anymore in that case. When EndOfWAL is true, we don't emit
+ * the message immediately and instead will show it as a part of a
+ * decent end-of-wal message later.
*/
- if (errormsg)
- ereport(emode_for_corrupt_record(emode, xlogreader->EndRecPtr),
- (errmsg_internal("%s", errormsg) /* already translated */ ));
+ if (!xlogreader->EndOfWAL && errormsg)
+ ereport(emode_for_corrupt_record(emode, ErrRecPtr),
+ errmsg_internal("%s", errormsg) /* already translated */ );
}
/*
@@ -3087,11 +3109,14 @@ ReadRecord(XLogPrefetcher *xlogprefetcher, int emode,
/* Great, got a record */
return record;
}
- else
+
+ Assert(ErrRecPtr != InvalidXLogRecPtr);
+
+ /* No valid record available from this source */
+ lastSourceFailed = true;
+
+ if (!fetching_ckpt)
{
- /* No valid record available from this source */
- lastSourceFailed = true;
-
/*
* If archive recovery was requested, but we were still doing
* crash recovery, switch to archive recovery and retry using the
@@ -3104,11 +3129,16 @@ ReadRecord(XLogPrefetcher *xlogprefetcher, int emode,
* we'd have no idea how far we'd have to replay to reach
* consistency. So err on the safe side and give up.
*/
- if (!InArchiveRecovery && ArchiveRecoveryRequested &&
- !fetching_ckpt)
+ if (!InArchiveRecovery && ArchiveRecoveryRequested)
{
+ /*
+ * We don't report this as LOG, since we don't stop recovery
+ * here
+ */
ereport(DEBUG1,
- (errmsg_internal("reached end of WAL in pg_wal, entering archive recovery")));
+ errmsg_internal("reached end of WAL at %X/%X on timeline %u in pg_wal during crash recovery, entering archive recovery",
+ LSN_FORMAT_ARGS(ErrRecPtr),
+ replayTLI));
InArchiveRecovery = true;
if (StandbyModeRequested)
StandbyMode = true;
@@ -3129,12 +3159,24 @@ ReadRecord(XLogPrefetcher *xlogprefetcher, int emode,
continue;
}
- /* In standby mode, loop back to retry. Otherwise, give up. */
- if (StandbyMode && !CheckForStandbyTrigger())
- continue;
- else
- return NULL;
+ /*
+ * recovery ended.
+ *
+ * Emit a decent message if we met end-of-WAL. Otherwise we should
+ * have already emitted an error message.
+ */
+ if (xlogreader->EndOfWAL)
+ ereport(LOG,
+ errmsg("reached end of WAL at %X/%X on timeline %u",
+ LSN_FORMAT_ARGS(ErrRecPtr), replayTLI),
+ (errormsg ? errdetail_internal("%s", errormsg) : 0));
}
+
+ /* In standby mode, loop back to retry. Otherwise, give up. */
+ if (StandbyMode && !CheckForStandbyTrigger())
+ continue;
+ else
+ return NULL;
}
}
@@ -3229,11 +3271,16 @@ retry:
case XLREAD_WOULDBLOCK:
return XLREAD_WOULDBLOCK;
case XLREAD_FAIL:
+ Assert(!StandbyMode || CheckForStandbyTrigger());
+
if (readFile >= 0)
close(readFile);
readFile = -1;
readLen = 0;
readSource = XLOG_FROM_ANY;
+
+ /* promotion exit is not end-of-WAL */
+ xlogreader->EndOfWAL = !StandbyMode;
return XLREAD_FAIL;
case XLREAD_SUCCESS:
break;
@@ -3899,7 +3946,8 @@ emode_for_corrupt_record(int emode, XLogRecPtr RecPtr)
{
static XLogRecPtr lastComplaint = 0;
- if (readSource == XLOG_FROM_PG_WAL && emode == LOG)
+ /* use currentSource as readSource is reset at failure */
+ if (currentSource == XLOG_FROM_PG_WAL && emode <= WARNING)
{
if (RecPtr == lastComplaint)
emode = DEBUG1;
diff --git a/src/backend/replication/walreceiver.c b/src/backend/replication/walreceiver.c
index ad383dbcaa..054a4cb127 100644
--- a/src/backend/replication/walreceiver.c
+++ b/src/backend/replication/walreceiver.c
@@ -498,10 +498,9 @@ WalReceiverMain(void)
else if (len < 0)
{
ereport(LOG,
- (errmsg("replication terminated by primary server"),
- errdetail("End of WAL reached on timeline %u at %X/%X.",
- startpointTLI,
- LSN_FORMAT_ARGS(LogstreamResult.Write))));
+ errmsg("replication terminated by primary server at %X/%X on timeline %u.",
+ LSN_FORMAT_ARGS(LogstreamResult.Write),
+ startpointTLI));
endofwal = true;
break;
}
diff --git a/src/bin/pg_waldump/pg_waldump.c b/src/bin/pg_waldump/pg_waldump.c
index 9993378ca5..26a4125b30 100644
--- a/src/bin/pg_waldump/pg_waldump.c
+++ b/src/bin/pg_waldump/pg_waldump.c
@@ -1168,9 +1168,16 @@ main(int argc, char **argv)
exit(0);
if (errormsg)
- pg_fatal("error in WAL record at %X/%X: %s",
- LSN_FORMAT_ARGS(xlogreader_state->ReadRecPtr),
- errormsg);
+ {
+ if (xlogreader_state->EndOfWAL)
+ pg_log_info("end of WAL at %X/%X: %s",
+ LSN_FORMAT_ARGS(xlogreader_state->EndRecPtr),
+ errormsg);
+ else
+ pg_fatal("error in WAL record at %X/%X: %s",
+ LSN_FORMAT_ARGS(xlogreader_state->EndRecPtr),
+ errormsg);
+ }
XLogReaderFree(xlogreader_state);
diff --git a/src/include/access/xlogreader.h b/src/include/access/xlogreader.h
index e87f91316a..70d3b25eda 100644
--- a/src/include/access/xlogreader.h
+++ b/src/include/access/xlogreader.h
@@ -205,6 +205,7 @@ struct XLogReaderState
*/
XLogRecPtr ReadRecPtr; /* start of last record read */
XLogRecPtr EndRecPtr; /* end+1 of last record read */
+ bool EndOfWAL; /* was the last attempt EOW? */
/*
* Set at the end of recovery: the start point of a partial record at the
diff --git a/src/test/recovery/t/011_crash_recovery.pl b/src/test/recovery/t/011_crash_recovery.pl
index 1b57d01046..8a379e8988 100644
--- a/src/test/recovery/t/011_crash_recovery.pl
+++ b/src/test/recovery/t/011_crash_recovery.pl
@@ -9,7 +9,9 @@ use warnings;
use PostgreSQL::Test::Cluster;
use PostgreSQL::Test::Utils;
use Test::More;
+use IPC::Run;
+my $reached_eow_pat = "reached end of WAL at ";
my $node = PostgreSQL::Test::Cluster->new('primary');
$node->init(allows_streaming => 1);
$node->start;
@@ -47,7 +49,10 @@ is($node->safe_psql('postgres', qq[SELECT pg_xact_status('$xid');]),
# Crash and restart the postmaster
$node->stop('immediate');
+my $logstart = get_log_size($node);
$node->start;
+$node->wait_for_log($reached_eow_pat, $logstart);
+pass("end-of-wal is logged");
# Make sure we really got a new xid
cmp_ok($node->safe_psql('postgres', 'SELECT pg_current_xact_id()'),
@@ -60,4 +65,95 @@ is($node->safe_psql('postgres', qq[SELECT pg_xact_status('$xid');]),
$stdin .= "\\q\n";
$tx->finish; # wait for psql to quit gracefully
+my $segsize = $node->safe_psql('postgres',
+ qq[SELECT setting FROM pg_settings WHERE name = 'wal_segment_size';]);
+
+# make sure no records afterwards go to the next segment
+$node->safe_psql('postgres', qq[
+ SELECT pg_switch_wal();
+ CHECKPOINT;
+ CREATE TABLE t();
+]);
+$node->stop('immediate');
+
+# identify REDO WAL file
+my $cmd = "pg_controldata -D " . $node->data_dir();
+$cmd = ['pg_controldata', '-D', $node->data_dir()];
+$stdout = '';
+$stderr = '';
+IPC::Run::run $cmd, '>', \$stdout, '2>', \$stderr;
+ok($stdout =~ /^Latest checkpoint's REDO WAL file:[ \t] *(.+)$/m,
+ "checkpoint file is identified");
+my $chkptfile = $1;
+
+# identify the last record
+my $walfile = $node->data_dir() . "/pg_wal/$chkptfile";
+$cmd = ['pg_waldump', $walfile];
+$stdout = '';
+$stderr = '';
+my $lastrec;
+IPC::Run::run $cmd, '>', \$stdout, '2>', \$stderr;
+foreach my $l (split(/\r?\n/, $stdout))
+{
+ $lastrec = $l;
+}
+ok(defined $lastrec, "last WAL record is extracted");
+ok($stderr =~ /end of WAL at ([0-9A-F\/]+): .* at \g1/,
+ "pg_waldump emits the correct ending message");
+
+# read the last record LSN excluding leading zeroes
+ok ($lastrec =~ /, lsn: 0\/0*([1-9A-F][0-9A-F]+),/,
+ "LSN of the last record identified");
+my $lastlsn = $1;
+
+# corrupt the last record
+my $offset = hex($lastlsn) % $segsize;
+open(my $segf, '+<', $walfile) or die "failed to open $walfile\n";
+seek($segf, $offset, 0); # halfway corrupt the last record
+print $segf "\0\0\0\0";
+close($segf);
+
+# pg_waldump complains about the corrupted record
+$stdout = '';
+$stderr = '';
+IPC::Run::run $cmd, '>', \$stdout, '2>', \$stderr;
+ok($stderr =~ /error: error in WAL record at 0\/$lastlsn: .* at 0\/$lastlsn/,
+ "pg_waldump emits the correct error message");
+
+# also server complains
+$logstart = get_log_size($node);
+$node->start;
+$node->wait_for_log("WARNING: invalid record length at 0/$lastlsn: wanted [0-9]+, got 0",
+ $logstart);
+pass("header error is logged at $lastlsn");
+
+# no end-of-wal message should be seen this time
+ok(!find_in_log($node, $reached_eow_pat, $logstart),
+ "false log message is not emitted");
+
+$node->stop('immediate');
+
done_testing();
+
+#### helper routines
+# return the size of logfile of $node in bytes
+sub get_log_size
+{
+ my ($node) = @_;
+
+ return (stat $node->logfile)[7];
+}
+
+# find $pat in logfile of $node after $off-th byte
+sub find_in_log
+{
+ my ($node, $pat, $off) = @_;
+
+ $off = 0 unless defined $off;
+ my $log = PostgreSQL::Test::Utils::slurp_file($node->logfile);
+ return 0 if (length($log) <= $off);
+
+ $log = substr($log, $off);
+
+ return $log =~ m/$pat/;
+}
--
2.31.1
