Re: psycopg2 conn.poll() hangs when used with sshtunnel

On Tue, 30 Oct 2018, 21:06 Daniele Varrazzo <daniele(dot)varrazzo(at)gmail(dot)com
wrote:

> On Tue, Oct 30, 2018 at 1:55 PM Akshay Joshi <
> akshay(dot)joshi(at)enterprisedb(dot)com> wrote:
>
>
>> What changes should I made to fix this? Or it should be fixed in
>> psycopg2 itself.
>>
>
> Actually, I have another observation. I was surprised to see that the
> whole test suite passed running the connection through an ssh tunnel: there
> are definitely failing queries in the test suite. So I made other tests and
> it seems the bad condition only happens using the `sshtunnel` module: If I
> open a tunnel manually with something like:
>
> ssh -L 36421:localhost:5432 -N localhost
>
> and point your script to port 36421 everything works ok.
>
>
> Conversely, I don't seem able to run the test suite through the tunnel
> open by the sshtunnel module. It doesn't hang, but the tunnel breaks in a
> test with the following reported on the sshtunnel side:
>
> 2018-10-30 15:24:25,550| ERROR | Socket exception: Bad file
> descriptor (9)
> 2018-10-30 15:24:25,551| ERROR | Could not establish connection from
> ('127.0.0.1', 33743) to remote side of the tunnel
>
> and the following tests fail to run as the connection is broken.
>
>
> Con-conversely, the patch I had in mind to fix #801, which very brutally
> is:
>
> ```
> @@ -1136,6 +1136,13 @@ pq_get_last_result(connectionObject *conn)
> || status == PGRES_COPY_IN) {
> break;
> }
> + if (PQisBusy(conn->pgconn)) {
> + /* This happens connecting through ssl tunnel
> + * TODO: just kill this function. The loop should happen
> within
> + * the async/green machinery. */
> + Dprintf("pq_get_last_result: we are busy");
> + break;
> + }
> }
>
> return result;
> ```
>
> doesn't work, and failing queries leave the connection in an inconsistent
> state.
>
>
> So, wrapping up, I think there is something you can do on your side,
> checking why the sshtunnel module behaves differently from a normal ssh
> tunnel, and if you use the latter (or configure sshtunnel to behave so) you
> shouldn't hit the problem. On our side I don't think we can fix #801 with a
> quick band aid, and we should rather do #802, but as things stands now I
> don't trust sshtunnel to do the right thing, and have less of an urgency to
> do so.
>
> Please let us know if you understand what is the difference between the
> module and the tunnel via `ssh -L`, thank you!
>

I have send the sample application and created an issue to sshtunnel
git hub. Not sure where is the problem, as poll() function hangs so i
thought its issue in psycopg2.

>
> -- Daniele
>
>>