Re: Synchronous commit behavior during network outage

On Tue, 2021-04-20 at 18:49 +0100, Ondřej Žižka wrote:
> tecmint=# select * from a; --> LAN on sync replica is OK
> id
> ----
> 1
> (1 row)
>
> tecmint=# insert into a values (2); ---> LAN on sync replica is DOWN and
> insert is waiting. During this time kill the background process on the
> PostgreSQL server for this session
> WARNING: canceling the wait for synchronous replication and terminating
> connection due to administrator command
> DETAIL: The transaction has already committed locally, but might not
> have been replicated to the standby.
> server closed the connection unexpectedly
> This probably means the server terminated abnormally
> before or while processing the request.
> The connection to the server was lost. Attempting reset: Succeeded.
>
> tecmint=# select * from a;
> id
> ----
> 1
> 2
> (2 rows)

It is well known that synchronous replication is sublect to that problem,
since it doesn't use the two-phase commit protocol.

What surprises me is that this is a warning.
In my opinion it should be an error.

Yours,
Laurenz Albe