If SyncRepWaitForLSN() fails, would the postgres backend do a roll-back?
Hi,
I'm researching the synchronous replication. I see the backend of the
Primary Server calls SyncRepWaitForLSN() to wait for the Standby Server to
write the WAL records.
If some thing happens, such as network failure or disk failure, causes the
Standby Server fail to receive WAL records or fail to write WAL records,
would the backend of the Primary Server catch and handle this failure?
Would the backend roll-back the transactions? Would the backend continue to
work?
If the transactions at the Primary Server need rollback, I think
SyncRepWaitForLSN() should return some information to the backend.
Thank you,
Rui Hai
Hi,
I'm researching the synchronous replication. I see the backend of the
Primary Server calls SyncRepWaitForLSN() to wait for the Standby Server to
write the WAL records.If some thing happens, such as network failure or disk failure, causes the
Standby Server fail to receive WAL records or fail to write WAL records,
would the backend of the Primary Server catch and handle this failure?
Would the backend roll-back the transactions? Would the backend continue to
work?
I don't think the backend would roll back the transaction because when
SyncRepWaitForLSN() is called, the transaction has been already
committed. There's no way to roll back a transaction which has been
committed.
Best regards,
--
Tatsuo Ishii
SRA OSS, Inc. Japan
English: http://www.sraoss.co.jp/index_en.php
Japanese:http://www.sraoss.co.jp
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On Wed, Jun 8, 2016 at 7:43 PM, Tatsuo Ishii <ishii@postgresql.org> wrote:
Hi,
I'm researching the synchronous replication. I see the backend of the
Primary Server calls SyncRepWaitForLSN() to wait for the Standby Server to
write the WAL records.If some thing happens, such as network failure or disk failure, causes the
Standby Server fail to receive WAL records or fail to write WAL records,
would the backend of the Primary Server catch and handle this failure?
Would the backend roll-back the transactions? Would the backend continue to
work?I don't think the backend would roll back the transaction because when
SyncRepWaitForLSN() is called, the transaction has been already
committed. There's no way to roll back a transaction which has been
committed.
Confirmed. The transaction is not rolled back and is considered
committed locally. Don't count of course on statement_timeout to stop
the transaction from being stuck.
--
Michael
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