public inbox for [email protected]
help / color / mirror / Atom feedFrom: Fujii Masao <[email protected]>
To: Anthonin Bonnefoy <[email protected]>
Cc: Chao Li <[email protected]>
Cc: Mircea Cadariu <[email protected]>
Cc: PostgreSQL Hackers <[email protected]>
Cc: Japin Li <[email protected]>
Subject: Re: Propagate XLogFindNextRecord error to callers
Date: Mon, 23 Mar 2026 21:00:00 +0900
Message-ID: <CAHGQGwGxg40aD5Lp3j4EvVzNf8=hpc8Jq_ueUBpzro_A0RSLVA@mail.gmail.com> (raw)
In-Reply-To: <CAO6_XqruVj8UmLMxeK1yN15cbJRs3e_k86N+D6PF=6OsikA1Cw@mail.gmail.com>
References: <CAO6_XqoxJXddcT4wkd9Xd+cD6Sz-fyspRGuV4Bq-wbXG4pVNzA@mail.gmail.com>
<[email protected]>
<CAO6_Xqqd316HhigkBsE-rC8oVsAprc_mVh5Z312D+aUOzW-5Jg@mail.gmail.com>
<MEAPR01MB3031690E672656BB573711B3B665A@MEAPR01MB3031.ausprd01.prod.outlook.com>
<CAO6_Xqqv5F2cdgs5zCVzLJMOuO6zStsC97gcm41dFNSWOh6B8A@mail.gmail.com>
<[email protected]>
<CAO6_XqrUzBT70kE20uHH=FWyfGJaTDMwqv++yNppdusywsG8-w@mail.gmail.com>
<[email protected]>
<CAO6_XqptRqW5b3=BXZ3=OP2YL+7X_CRayCiRwpOySwuHJ2WYtw@mail.gmail.com>
<[email protected]>
<CAO6_Xqqh-tWFMVAuXPnfB8HCGkeBoHK_AgSMZ-qoymb_1NUQjQ@mail.gmail.com>
<CAHGQGwFSLQZQ+GVnpNDje48D2zpEQQ3nxodHw7Obt0-PmzQNFg@mail.gmail.com>
<CAO6_XqruVj8UmLMxeK1yN15cbJRs3e_k86N+D6PF=6OsikA1Cw@mail.gmail.com>
On Mon, Mar 23, 2026 at 5:15 PM Anthonin Bonnefoy
<[email protected]> wrote:
> > +# Wrong WAL version. We copy an existing wal file and set the
> > +# page's magic value to 0000.
> >
> > Would it be better to describe the purpose of this test at the top?
> > For example:
> >
> > # Test that pg_waldump reports a detailed error message when dumping
> > # a WAL file with an invalid magic number (0000).
> > {
> > # The broken WAL file is created by copying a valid WAL file and
> > # overwriting its magic number with 0000.
> > my $broken_wal_dir = PostgreSQL::Test::Utils::tempdir_short();
>
> Sounds good, I've updated the patch.
Thanks for updating the patch!
It looks like the first part of the comment above wasn't included,
so I've added it. I also made a few cosmetic changes and updated
the commit message. Attached is the updated version of the patch.
Unless there are objections, I'll commit this version.
Regards,
--
Fujii Masao
Attachments:
[application/octet-stream] v8-0001-Report-detailed-errors-from-XLogFindNextRecord-fa.patch (9.3K, 2-v8-0001-Report-detailed-errors-from-XLogFindNextRecord-fa.patch)
download | inline diff:
From 7624005ad6d4413e27c133ef250381114a527b78 Mon Sep 17 00:00:00 2001
From: Fujii Masao <[email protected]>
Date: Mon, 23 Mar 2026 18:37:56 +0900
Subject: [PATCH v8] Report detailed errors from XLogFindNextRecord() failures.
Previously, XLogFindNextRecord() did not return detailed error information
when it failed to find a valid WAL record. As a result, callers such as
the WAL summarizer, pg_waldump, and pg_walinspect could only report generic
errors (e.g., "could not find a valid record after ..."), making
troubleshooting difficult.
This commit fix the issue by extending XLogFindNextRecord() to return
detailed error information on failure, and updating its callers to include
those details in their error messages.
For example, when pg_waldump is run on a WAL file with an invalid magic number,
it now reports not only the generic error but also the specific cause
(e.g., "invalid magic number").
Author: Anthonin Bonnefoy <[email protected]>
Reviewed-by: Mircea Cadariu <[email protected]>
Reviewed-by: Japin Li <[email protected]>
Reviewed-by: Chao Li <[email protected]>
Reviewed-by: Fujii Masao <[email protected]>
Discussion: https://postgr.es/m/CAO6_XqoxJXddcT4wkd9Xd+cD6Sz-fyspRGuV4Bq-wbXG4pVNzA@mail.gmail.com
---
contrib/pg_walinspect/pg_walinspect.c | 16 ++++++++++----
src/backend/access/transam/xlogreader.c | 24 ++++++++++++++++++---
src/backend/postmaster/walsummarizer.c | 17 ++++++++++-----
src/bin/pg_waldump/pg_waldump.c | 12 ++++++++---
src/bin/pg_waldump/t/001_basic.pl | 28 +++++++++++++++++++++++++
src/include/access/xlogreader.h | 3 ++-
6 files changed, 84 insertions(+), 16 deletions(-)
diff --git a/contrib/pg_walinspect/pg_walinspect.c b/contrib/pg_walinspect/pg_walinspect.c
index f6f5f0792d2..4cf6e41e2f5 100644
--- a/contrib/pg_walinspect/pg_walinspect.c
+++ b/contrib/pg_walinspect/pg_walinspect.c
@@ -99,6 +99,7 @@ InitXLogReaderState(XLogRecPtr lsn)
XLogReaderState *xlogreader;
ReadLocalXLogPageNoWaitPrivate *private_data;
XLogRecPtr first_valid_record;
+ char *errormsg;
/*
* Reading WAL below the first page of the first segments isn't allowed.
@@ -126,12 +127,19 @@ InitXLogReaderState(XLogRecPtr lsn)
errdetail("Failed while allocating a WAL reading processor.")));
/* first find a valid recptr to start from */
- first_valid_record = XLogFindNextRecord(xlogreader, lsn);
+ first_valid_record = XLogFindNextRecord(xlogreader, lsn, &errormsg);
if (!XLogRecPtrIsValid(first_valid_record))
- ereport(ERROR,
- errmsg("could not find a valid record after %X/%08X",
- LSN_FORMAT_ARGS(lsn)));
+ {
+ if (errormsg)
+ ereport(ERROR,
+ errmsg("could not find a valid record after %X/%08X: %s",
+ LSN_FORMAT_ARGS(lsn), errormsg));
+ else
+ ereport(ERROR,
+ errmsg("could not find a valid record after %X/%08X",
+ LSN_FORMAT_ARGS(lsn)));
+ }
return xlogreader;
}
diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c
index 8cb2110cb99..8849610db00 100644
--- a/src/backend/access/transam/xlogreader.c
+++ b/src/backend/access/transam/xlogreader.c
@@ -1390,14 +1390,21 @@ XLogReaderResetError(XLogReaderState *state)
*
* This positions the reader, like XLogBeginRead(), so that the next call to
* XLogReadRecord() will read the next valid record.
+ *
+ * On failure, InvalidXLogRecPtr is returned, and *errormsg is set to a string
+ * with details of the failure.
+ *
+ * When set, *errormsg points to an internal buffer that's valid until the next
+ * call to XLogReadRecord.
*/
XLogRecPtr
-XLogFindNextRecord(XLogReaderState *state, XLogRecPtr RecPtr)
+XLogFindNextRecord(XLogReaderState *state, XLogRecPtr RecPtr, char **errormsg)
{
XLogRecPtr tmpRecPtr;
XLogRecPtr found = InvalidXLogRecPtr;
XLogPageHeader header;
- char *errormsg;
+
+ *errormsg = NULL;
Assert(XLogRecPtrIsValid(RecPtr));
@@ -1482,7 +1489,7 @@ XLogFindNextRecord(XLogReaderState *state, XLogRecPtr RecPtr)
* or we just jumped over the remaining data of a continuation.
*/
XLogBeginRead(state, tmpRecPtr);
- while (XLogReadRecord(state, &errormsg) != NULL)
+ while (XLogReadRecord(state, errormsg) != NULL)
{
/* past the record we've found, break out */
if (RecPtr <= state->ReadRecPtr)
@@ -1497,6 +1504,17 @@ XLogFindNextRecord(XLogReaderState *state, XLogRecPtr RecPtr)
err:
XLogReaderInvalReadState(state);
+ /*
+ * We may have reported errors due to invalid WAL header, propagate the
+ * error message to the caller.
+ */
+ if (state->errormsg_deferred)
+ {
+ if (state->errormsg_buf[0] != '\0')
+ *errormsg = state->errormsg_buf;
+ state->errormsg_deferred = false;
+ }
+
return InvalidXLogRecPtr;
}
diff --git a/src/backend/postmaster/walsummarizer.c b/src/backend/postmaster/walsummarizer.c
index e1aa102f41d..0c0670f7da9 100644
--- a/src/backend/postmaster/walsummarizer.c
+++ b/src/backend/postmaster/walsummarizer.c
@@ -915,6 +915,7 @@ SummarizeWAL(TimeLineID tli, XLogRecPtr start_lsn, bool exact,
WalSummaryIO io;
BlockRefTable *brtab = CreateEmptyBlockRefTable();
bool fast_forward = true;
+ char *errormsg;
/* Initialize private data for xlogreader. */
private_data = palloc0_object(SummarizerReadLocalXLogPrivate);
@@ -966,7 +967,7 @@ SummarizeWAL(TimeLineID tli, XLogRecPtr start_lsn, bool exact,
}
else
{
- summary_start_lsn = XLogFindNextRecord(xlogreader, start_lsn);
+ summary_start_lsn = XLogFindNextRecord(xlogreader, start_lsn, &errormsg);
if (!XLogRecPtrIsValid(summary_start_lsn))
{
/*
@@ -995,9 +996,16 @@ SummarizeWAL(TimeLineID tli, XLogRecPtr start_lsn, bool exact,
switch_lsn = xlogreader->EndRecPtr;
}
else
- ereport(ERROR,
- errmsg("could not find a valid record after %X/%08X",
- LSN_FORMAT_ARGS(start_lsn)));
+ {
+ if (errormsg)
+ ereport(ERROR,
+ errmsg("could not find a valid record after %X/%08X: %s",
+ LSN_FORMAT_ARGS(start_lsn), errormsg));
+ else
+ ereport(ERROR,
+ errmsg("could not find a valid record after %X/%08X",
+ LSN_FORMAT_ARGS(start_lsn)));
+ }
}
/* We shouldn't go backward. */
@@ -1010,7 +1018,6 @@ SummarizeWAL(TimeLineID tli, XLogRecPtr start_lsn, bool exact,
while (1)
{
int block_id;
- char *errormsg;
XLogRecord *record;
uint8 rmid;
diff --git a/src/bin/pg_waldump/pg_waldump.c b/src/bin/pg_waldump/pg_waldump.c
index f82507ef696..630d9859882 100644
--- a/src/bin/pg_waldump/pg_waldump.c
+++ b/src/bin/pg_waldump/pg_waldump.c
@@ -1384,11 +1384,17 @@ main(int argc, char **argv)
pg_fatal("out of memory while allocating a WAL reading processor");
/* first find a valid recptr to start from */
- first_record = XLogFindNextRecord(xlogreader_state, private.startptr);
+ first_record = XLogFindNextRecord(xlogreader_state, private.startptr, &errormsg);
if (!XLogRecPtrIsValid(first_record))
- pg_fatal("could not find a valid record after %X/%08X",
- LSN_FORMAT_ARGS(private.startptr));
+ {
+ if (errormsg)
+ pg_fatal("could not find a valid record after %X/%08X: %s",
+ LSN_FORMAT_ARGS(private.startptr), errormsg);
+ else
+ pg_fatal("could not find a valid record after %X/%08X",
+ LSN_FORMAT_ARGS(private.startptr));
+ }
/*
* Display a message that we're skipping data if `from` wasn't a pointer
diff --git a/src/bin/pg_waldump/t/001_basic.pl b/src/bin/pg_waldump/t/001_basic.pl
index 11df7e092bf..8bb8fa225f6 100644
--- a/src/bin/pg_waldump/t/001_basic.pl
+++ b/src/bin/pg_waldump/t/001_basic.pl
@@ -4,6 +4,7 @@
use strict;
use warnings FATAL => 'all';
use Cwd;
+use File::Copy;
use PostgreSQL::Test::Cluster;
use PostgreSQL::Test::Utils;
use Test::More;
@@ -246,6 +247,33 @@ command_like(
qr/^$/,
'no output with --quiet option');
+# Test that pg_waldump reports a detailed error message when dumping
+# a WAL file with an invalid magic number (0000).
+#
+# The broken WAL file is created by copying a valid WAL file and
+# overwriting its magic number with 0000.
+my $broken_wal_dir = PostgreSQL::Test::Utils::tempdir_short();
+my $broken_wal = "$broken_wal_dir/$start_walfile";
+copy($node->data_dir . '/pg_wal/' . $start_walfile, $broken_wal)
+ || die "copying $start_walfile $!";
+
+my $fh;
+open($fh, '+<', $broken_wal)
+ or BAIL_OUT("open failed: $!");
+binmode $fh;
+
+sysseek($fh, 0, 0)
+ or BAIL_OUT("sysseek failed: $!");
+syswrite($fh, pack("S", 0))
+ or BAIL_OUT("syswrite failed: $!");
+close($fh)
+ or BAIL_OUT("close failed: $!");
+
+command_fails_like(
+ [ 'pg_waldump', $broken_wal ],
+ qr/invalid magic number 0000/i,
+ 'detailed error message shown for invalid WAL page magic');
+
# Test for: Display a message that we're skipping data if `from`
# wasn't a pointer to the start of a record.
sub test_pg_waldump_skip_bytes
diff --git a/src/include/access/xlogreader.h b/src/include/access/xlogreader.h
index 80f1a548e08..97eae2c1dab 100644
--- a/src/include/access/xlogreader.h
+++ b/src/include/access/xlogreader.h
@@ -342,7 +342,8 @@ extern void XLogReaderSetDecodeBuffer(XLogReaderState *state,
/* Position the XLogReader to given record */
extern void XLogBeginRead(XLogReaderState *state, XLogRecPtr RecPtr);
-extern XLogRecPtr XLogFindNextRecord(XLogReaderState *state, XLogRecPtr RecPtr);
+extern XLogRecPtr XLogFindNextRecord(XLogReaderState *state, XLogRecPtr RecPtr,
+ char **errormsg);
/* Return values from XLogPageReadCB. */
typedef enum XLogPageReadResult
--
2.51.2
view thread (13+ messages) latest in thread
reply
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: [email protected]
Cc: [email protected], [email protected], [email protected], [email protected], [email protected]
Subject: Re: Propagate XLogFindNextRecord error to callers
In-Reply-To: <CAHGQGwGxg40aD5Lp3j4EvVzNf8=hpc8Jq_ueUBpzro_A0RSLVA@mail.gmail.com>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by agora; see mirroring instructions
for how to clone and mirror all data and code used for this inbox