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From: Imseih (AWS), Sami <[email protected]>
To: Kyotaro Horiguchi <[email protected]>
To: [email protected] <[email protected]>
Cc: [email protected] <[email protected]>
Subject: Re: [BUG] Panic due to incorrect missingContrecPtr after promotion
Date: Thu, 26 May 2022 19:57:41 +0000
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
	<[email protected]>
	<[email protected]>
	<[email protected]>
	<[email protected]>
	<[email protected]>

We see another occurrence of this bug with the last patch applied in 13.7.

After a promotion we observe the following in the logs:

2022-05-25 00:35:38 UTC::@:[371]:PANIC: xlog flush request 10/B1FA3D88 is not satisfied --- flushed only to 7/A8000060
2022-05-25 00:35:38 UTC:172.31.26.238(38610):administrator@postgres:[23433]:ERROR: current transaction is aborted, commands ignored until end of transaction block

However, The logs do not show "LOG: successfully skipped missing contrecord",
therefore we know that  VerifyOverwriteContrecord 
is not being called to invalidate the missingContrecPtr.

VerifyOverwriteContrecord(xl_overwrite_contrecord *xlrec, XLogReaderState *state)
{
   if (xlrec->overwritten_lsn != state->overwrittenRecPtr)
       elog(FATAL, "mismatching overwritten LSN %X/%X -> %X/%X",
            (uint32) (xlrec->overwritten_lsn >> 32),
            (uint32) xlrec->overwritten_lsn,
            (uint32) (state->overwrittenRecPtr >> 32),
            (uint32) state->overwrittenRecPtr);

   /* We have safely skipped the aborted record */
   abortedRecPtr = InvalidXLogRecPtr;
   missingContrecPtr = InvalidXLogRecPtr;

   ereport(LOG,
           (errmsg("successfully skipped missing contrecord at %X/%X, overwritten at %s",
                   (uint32) (xlrec->overwritten_lsn >> 32),
                   (uint32) xlrec->overwritten_lsn,
                   timestamptz_to_str(xlrec->overwrite_time))));

We think it's because VerifyOverwriteContrecord was not 
called which is why we see this behavior. 

Are there are  other places where missingContrecPtr 
should be invalidated, such as after a successful promotion?

--
Sami Imseih
Amazon Web Services

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