Re: Question: Multiple pg clusters on one server can be reached with the standard port.

16. Juni 2023 21:54, "Francisco Olarte" <folarte(at)peoplecall(dot)com> schrieb:

> Michael:
>
> On Fri, 16. Juni 2023 at 13:53, brainmue <brainmue(at)weiller(dot)eu> wrote:
>
>> Because with iptables or netfilter I can't forward TCP packets based on the DNS alias name. Or is
>> that possible?
>
> The dns alias name does not reach the listening tcp socket, it is
> mapped to the target record, then finally to the A record and this is
> what is used to start the tcp connection.
>
>> I have the same problem with nginx.
>
> In nginx you cannot use the dns alias, but if you are using http the
> "normal" clients send it as host when they open an url. But there is
> no "host" parameter in the pg protocol. There is a dbaname, which can
> be used with the adequate software, like pgbouncer, but you said you
> do not like it.
>
> You may try to write a small program which parses the startup message
> and redirects the connection based on the info there. I'm not sure why
> pgbouncer has not this option, but it may be because it has a lot more
> option. It does not seem to be that difficult, receive the packet,
> parse it, connect to remote, send it the packet and from there on just
> forward traffic blindly. Parsing startup seems quite simple,
> maintaining a socket pool and forwarding is simple, you could probably
> prototype that in an afternoon ( if no guru replies me "but this won't
> work because .... ).
>
>> I just looked in the documentation again but I can't find a way to distinguish which cluster to
>> forward to based on the DNS alias.
>
> As I asaid above, DNS alias is not avalilable to the listener. On any
> protocol. Things like http work because the clients send the dns alias
> on some place on the default usage, but you can write an http client
> which sends Host: from the uri given but connects to a different IP
> address.
>
> Francisco Olarte.

Thank you for the detailed explanations.
I could not have explained it but it also seemed strange to me that it should go that way.
pgbouncer I will definitely look again carefully.
Maybe I already have my solution with it.

Regards
Michael