Re: [HACKERS] Avahi support for Postgresql

From: tomas(at)tuxteam(dot)de
To: Mathias Hasselmann <mathias(at)openismus(dot)com>
Cc: pgsql-patches(at)postgresql(dot)org, pgsql-hackers(at)postgresql(dot)org, Murray Cumming <murrayc(at)openismus(dot)com>
Subject: Re: [HACKERS] Avahi support for Postgresql
Date: 2008-04-01 15:34:33
Message-ID: 20080401153433.GA18822@www.trapp.net
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On Tue, Apr 01, 2008 at 05:07:31PM +0200, Mathias Hasselmann wrote:
[...]
> > Personally, I'be rather scared than delighted ;-)
>
> So in data centers you don't even trust the machines in your broadcast
> domain?

Kind of. Put it another way: never have services running you don't use.

[...]

> > Isn't there a less-intrusive option to linking a lib into each and every
> > possible server, like a config file in which to put what is to be announced?
>
> You could directly talk to the D-Bus interface of Avahi. libavahi-client
> just is a convenience wrapper. Well, but this route will be much more
> cumbersome.

So this goes through the D-Bus. Makes kind of sense. Thanks for the
enlightenment.

> One other route is calling avahi-publish-service on startup and killing
> it on shutdown, but: avahi-publish-service really only exists for
> demonstration purposes and doesn't handle service name collisions for
> instance. I don't believe that a high-profile application like
> Postgresql should rely on low-quality hacks, like invoking educational
> demo programs.

Unelegant as it might seem -- this solution still affords a lot more
when it comes to "separation of concerns". I'm still a bit wary at the
prospect that each and every daemon evolves into a huge fuzzball
linked to all conceivable service-lets with a multitude of funny
side-effects (remember tcpwrappers?).

Of course, "you can always disable this at compile time", but let's face
it: with the predominance of binary distribs, the path of least
resistance will be to put up with whatever strange side-effects.

I would really prefer a more loosely coupled system.

Regards
- -- tomás
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