Re: [PATCH v1] Add and report the new "in_hot_standby" GUC pseudo-variable.

On Tue, Sep 12, 2017 at 6:11 PM, Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com
> wrote:

> On Wed, Sep 13, 2017 at 3:48 AM, Elvis Pranskevichus <elprans(at)gmail(dot)com>
> wrote:
> > I incorporated those bits into your patch and rebased in onto master.
> > Please see attached.
> >
> > FWIW, I think that mixing the standby status and the default
> > transaction writability is suboptimal. They are related, yes, but not
> > the same thing. It is possible to have a master cluster in the
> > read-only mode, and with this patch it would be impossible to
> > distinguish from a hot-standby replica without also polling
> > pg_is_in_recovery(), which defeats the purpose of having to do no
> > database roundtrips.
>
> Hi Elvis,
>
> FYI the recovery test 001_stream_rep.pl fails with this patch applied.
> You can see that if you configure with --enable-tap-tests, build and
> then cd into src/test/recovery and "make check".
>
> The latest patch applies cleanly and builds (I am also seeing the failing
TAP tests), however, I have a concern. With a single server set up, when I
attempt to make a connection with target_session_attrs=read-write, I get
the message
psql: could not make a suitable connection to server "localhost:5432"
Whereas, when I attempt to make a connection with
target_session_attrs=read-only, it is successful.

I might be missing something, but this seems somewhat counter-intuitive. I
would expect to specify read-write as target_session_attrs and successfully
connect to a server on which read and write operations are permitted. I see
this behavior implemented in src/interfaces/libpq/fe-connect.c
Is there a reason to reject a connection to a primary server when I specify
'read-write'? Is this intentional?