On 06.10.2017 15:29, Petr Jelinek wrote:
On 06/10/17 12:16, Konstantin Knizhnik wrote:
When creating logical replication slots we quite often get the following
error:
ERROR: cannot build an initial slot snapshot when MyPgXact->xmin
already is valid
which cause restart of WAL sender.
The comment to this line doesn't clarify much:
/* so we don't overwrite the existing value */
if (TransactionIdIsValid(MyPgXact->xmin))
elog(ERROR, "cannot build an initial slot snapshot when
MyPgXact->xmin already is valid");
I wonder if it is normal situation or something goes wrong?
Hi,
no it's not normal situation, it seems you are doing something that
assigns xid before you run the CREATE_REPLICATION_SLOT command on that
connection.
I have not doing something in this connection: it is wal sender
executing CREATE_REPLICATION_SLOT replication command.
Please look at the stack in my original e-mail. It shows who and when is
setting MyPgXact->xmin.
It is GetSnapshotData called because of reloading configuration settings.
And configuration setting are reloaded because our application is
updating "synchronous_standby_names".
--
Konstantin Knizhnik
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company
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