Re: Built-in connection pooler

From: Konstantin Knizhnik <k(dot)knizhnik(at)postgrespro(dot)ru>
To: Jaime Casanova <jaime(dot)casanova(at)2ndquadrant(dot)com>
Cc: Li Japin <japinli(at)hotmail(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Built-in connection pooler
Date: 2020-07-05 13:46:09
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Thank your for your help.

On 05.07.2020 07:17, Jaime Casanova wrote:
> You should also allow cursors without the WITH HOLD option or there is
> something i'm missing?

Yes, good point.
> a few questions about tainted backends:
> - why the use of check_primary_key() and check_foreign_key() in
> contrib/spi/refint.c make the backend tainted?

I think this is because without it contrib test is not passed with
connection pooler.
This extension uses static variables which are assumed to be session
specific  but in case f connection pooler are shared by all backends.

> - the comment in src/backend/commands/sequence.c needs some fixes, it
> seems just quickly typed

Sorry, done.

> some usability problem:
> - i compiled this on a debian machine with "--enable-debug
> --enable-cassert --with-pgport=54313", so nothing fancy
> - then make, make install, and initdb: so far so good
> configuration:
> listen_addresses = '*'
> connection_proxies = 20
> and i got this:
> """
> jcasanov(at)DangerBox:/opt/var/pgdg/14dev$ /opt/var/pgdg/14dev/bin/psql
> -h -p 6543 postgres
> psql: error: could not connect to server: no se pudo conectar con el
> servidor: No existe el fichero o el directorio
> ¿Está el servidor en ejecución localmente y aceptando
> conexiones en el socket de dominio Unix «/var/run/postgresql/.s.PGSQL.54313»?
> """
> but connect at the postgres port works well
> """
> jcasanov(at)DangerBox:/opt/var/pgdg/14dev$ /opt/var/pgdg/14dev/bin/psql
> -h -p 54313 postgres
> psql (14devel)
> Type "help" for help.
> postgres=# \q
> jcasanov(at)DangerBox:/opt/var/pgdg/14dev$ /opt/var/pgdg/14dev/bin/psql
> -p 54313 postgres
> psql (14devel)
> Type "help" for help.
> postgres=#
> """
> PS: unix_socket_directories is setted at /tmp and because i'm not
> doing this with postgres user i can use /var/run/postgresql
Looks like for some reasons your Postgres was not configured to accept
TCP connection.
It accepts only local connections through Unix sockets.
But pooler is not listening unix sockets because there is absolutely no
sense in pooling local connections.

I have done the same steps as you and have no problem to access pooler:

knizhnik(at)xps:~/postgresql.vanilla$ psql postgres -h -p 6543
psql (14devel)
Type "help" for help.

postgres=# \q

Please notice that if I specify some unexisted port, then I get error
message which is different with yours:

knizhnik(at)xps:~/postgresql.vanilla$ psql postgres -h -p 65433
psql: error: could not connect to server: could not connect to server:
Connection refused
    Is the server running on host "" and accepting
    TCP/IP connections on port 65433?

So Postgres is not mentioning unix socket path in this case. It makes me
think that your server is not accepting TCP connections at all (despite to

listen_addresses = '*'


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