Re: [PATCH] postgres_fdw connection caching - cause remote sessions linger till the local session exit

On Fri, Jan 29, 2021 at 10:42 AM Bharath Rupireddy
<bharath(dot)rupireddyforpostgres(at)gmail(dot)com> wrote:
> > > Also, now that I've looked at pgfdw_inval_callback, it scares
> > > the heck out of me. Actually disconnecting a connection during
> > > a cache inval callback seems quite unsafe --- what if that happens
> > > while we're using the connection?
> >
> > If the connection is still used in the transaction, pgfdw_inval_callback()
> > marks it as invalidated and doesn't close it. So I was not thinking that
> > this is so unsafe.
> >
> > The disconnection code in pgfdw_inval_callback() was added in commit
> > e3ebcca843 to fix connection leak issue, and it's back-patched. If this
> > change is really unsafe, we need to revert it immediately at least from back
> > branches because the next minor release is scheduled soon.
>
> I think we can remove disconnect_pg_server in pgfdw_inval_callback and
> make entries only invalidated. Anyways, those connections can get
> closed at the end of main txn in pgfdw_xact_callback. Thoughts?
>
> If okay, I can make a patch for this.

Attaching a patch for this, which can be back patched.

With Regards,
Bharath Rupireddy.
EnterpriseDB: http://www.enterprisedb.com