Re: log spam with postgres_fdw

[Jeff Janes]

On Sun, Sep 15, 2019 at 11:14 AM Tom Lane  wrote:

> Jeff Janes  writes:
> > When closing the local session which had used postgres_fdw over an ssl
> > connection, I get log spam on the foreign server saying:
> > LOG:  could not receive data from client: Connection reset by peer
> > It is easy to reproduce, but you must be using ssl to do so.
> > On searching, I see that a lot of people have run into this issue, with
> > considerable confusion, but as far as I can see it has never been
> diagnosed.
>
> In
>
> https://www.postgresql.org/message-id/flat/3DPLMQIC.YU6IFMLY.3PLOWL6W%40FQT5M7HS.IFBAANAE.A7GUPCPM
>
>
Thanks, I had not spotted that one, I guess because the log message itself
was not in the subject so it ranked lower.


> we'd concluded that the issue is probably that postgres_fdw has no
> logic to shut down its external connections when the session closes.
> It's not very clear why the SSL dependency, but we speculated that
> adding an on_proc_exit callback to close the connection(s) would help.
>
>
It is easy to reproduce the ssl dependency without any FDW, just by doing a
kill -9 on psql. Apparently the backend process for unencrypted connections
are happy to be ghosted, while ssl ones are not; which seems like an odd
distinction to make.  So should this be addressed on both sides (the server
not whining, and the client doing the on_proc_exit anyway?).  I can take a
stab at the client side one, but I'm over my head on the ssl connection
handling logic on the server side.

Cheers,

Jeff

Re: log spam with postgres_fdw

[Tom Lane]

Jeff Janes  writes:
> When closing the local session which had used postgres_fdw over an ssl
> connection, I get log spam on the foreign server saying:
> LOG:  could not receive data from client: Connection reset by peer
> It is easy to reproduce, but you must be using ssl to do so.
> On searching, I see that a lot of people have run into this issue, with
> considerable confusion, but as far as I can see it has never been diagnosed.

In
https://www.postgresql.org/message-id/flat/3DPLMQIC.YU6IFMLY.3PLOWL6W%40FQT5M7HS.IFBAANAE.A7GUPCPM

we'd concluded that the issue is probably that postgres_fdw has no
logic to shut down its external connections when the session closes.
It's not very clear why the SSL dependency, but we speculated that
adding an on_proc_exit callback to close the connection(s) would help.

I imagine dblink has a similar issue.

regards, tom lane

log spam with postgres_fdw

[Jeff Janes]

I'm sending this to hackers, because it is not exactly a bug, and it can't
be addressed from userland.  I think it is a coding issue, although I
haven't identified the exact code.

When closing the local session which had used postgres_fdw over an ssl
connection, I get log spam on the foreign server saying:

LOG:  could not receive data from client: Connection reset by peer

It is easy to reproduce, but you must be using ssl to do so.

On searching, I see that a lot of people have run into this issue, with
considerable confusion, but as far as I can see it has never been diagnosed.

Is there anything that can be done about this, other than just learning to
ignore it?

Cheers,

Jeff
-- set up ssl, I won't walk through those steps.
\! pgbench -i
create extension postgres_fdw ;
create server ssl foreign data wrapper postgres_fdw OPTIONS ( host '127.0.0.1');
create schema fgn;
create user MAPPING FOR CURRENT_USER SERVER ssl;
import  foreign schema public from server ssl into fgn;
select count(*) from fgn.pgbench_history;
\q