Re: [HACKERS] Issues with logical replication

On Mon, Oct 9, 2017 at 9:19 PM, Stas Kelvich <s(dot)kelvich(at)postgrespro(dot)ru> wrote:
> I investigated this case and it seems that XactLockTableWait() in SnapBuildWaitSnapshot()
> not always work as expected. XactLockTableWait() waits on LockAcquire() for xid to be
> completed and if we finally got this lock but transaction is still in progress then such xid
> assumed to be a subxid. However LockAcquire/LockRelease cycle can happen after transaction
> set xid, but before XactLockTableInsert().
>
> Namely following history happened for xid 5225 and lead to crash:
>
> [backend] LOG: AssignTransactionId: XactTopTransactionId = 5225
> [walsender] LOG: LogCurrentRunningXacts: Wrote RUNNING_XACTS xctn=1, xid[0]=5225
> [walsender] LOG: XactLockTableWait: LockAcquire 5225
> [walsender] LOG: XactLockTableWait: LockRelease 5225
> [backend] LOG: AssignTransactionId: LockAcquire ExclusiveLock 5225
> [walsender] LOG: TransactionIdIsInProgress: SVC->latestCompletedXid=5224 < xid=5225 => true
> [backend] LOG: CommitTransaction: ProcArrayEndTransaction xid=5225, ipw=0
> [backend] LOG: CommitTransaction: ResourceOwnerRelease locks xid=5225

Ouch. This seems like a bug that needs to be fixed, but do you think
it's related to to Petr's proposed fix to set es_output_cid? That fix
looks reasonable, since we shouldn't try to lock tuples without a
valid CommandId.

Now, having said that, I understand how the lack of that fix could cause:

2017-10-02 18:40:26.101 MSK [2954] ERROR: attempted to lock invisible tuple

But I do not understand how it could cause:

#3 0x000000000086ac1d in XactLockTableWait (xid=0, rel=0x0, ctid=0x0,
oper=XLTW_None) at lmgr.c:582

--
Robert Haas
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