Re: [PATCH 1/6] conf, passt: Don't try to log to stderr after we close it

[David Gibson <david@gibson.dropbear.id.au>]

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On Tue, Jun 18, 2024 at 08:00:14AM +0200, Stefano Brivio wrote:
> On Tue, 18 Jun 2024 10:36:28 +1000
> David Gibson <david@gibson.dropbear.id.au> wrote:
> 
> > On Mon, Jun 17, 2024 at 02:03:14PM +0200, Stefano Brivio wrote:
> > > If we don't run in foreground, we close standard error as we
> > > daemonise, so it makes no sense to check if the controlling terminal
> > > is an interactive terminal or if --force-stderr was given, to decide
> > > if we want to log to standard error.
> > > 
> > > Make --force-stderr depend on --foreground.
> > > 
> > > Signed-off-by: Stefano Brivio <sbrivio@redhat.com>  
> > 
> > Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
> > 
> > > ---
> > >  conf.c  | 3 +++
> > >  passt.c | 2 +-
> > >  2 files changed, 4 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/conf.c b/conf.c
> > > index 94b3ed6..dbdbb62 100644
> > > --- a/conf.c
> > > +++ b/conf.c
> > > @@ -1693,6 +1693,9 @@ void conf(struct ctx *c, int argc, char **argv)
> > >  
> > >  	conf_ugid(runas, &uid, &gid);
> > >  
> > > +	if (!c->foreground && c->force_stderr)
> > > +		die("Can't log to standard error if not running in foreground");
> > > +
> > >  	if (logfile) {
> > >  		logfile_init(c->mode == MODE_PASTA ? "pasta" : "passt",
> > >  			     logfile, logsize);
> > > diff --git a/passt.c b/passt.c
> > > index a5e2c5a..aa9648a 100644
> > > --- a/passt.c
> > > +++ b/passt.c
> > > @@ -302,7 +302,7 @@ int main(int argc, char **argv)
> > >  	if (isolate_prefork(&c))
> > >  		die("Failed to sandbox process, exiting");
> > >  
> > > -	if (!c.force_stderr && !isatty(fileno(stderr)))
> > > +	if (!c.foreground || (!c.force_stderr && !isatty(fileno(stderr))))  
> > 
> > What's the rationale for the isatty() check in any case?
> 
> To implement the behaviour from the man page:
> 
>        -e, --stderr
>               Log  to standard error too.  Default is to log to the sys‐
>               tem logger only, if started from an interactive  terminal,
>               and to both system logger and standard error otherwise.

Hmm.. maybe I'm getting confused reading either the man page or the
code, but isn't that the opposite of what the code is doing?  The code
appears to be opening the log if we're *not* on an interactive terminal.

> which was needed, in turn, because of earlier versions of passt and of
> the KubeVirt integration where passt was running in foreground, but (of
> course) not attached to a terminal, and there was no option to force
> printing to standard error.
> 
> Given that KubeVirt doesn't have a system logger, it was otherwise
> impossible to get messages out of passt.
> 
> It's an abomination that just adds complexity now, and I don't think
> anybody uses it that way anymore. I guess we should drop that, together
> with qrap, in a few months from now.

Right.. but what I'm after is the rationale for this depending on
whether it's an interactive terminal at all.  Seems to me the logical
thing to do is to (by default) always log to stderr before
daemonization (i.e. forever when in foreground mode), then to logfile
and/or syslog after daemonization.  Regardless of whether there's a
tty or not.

-- 
David Gibson (he or they)	| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you, not the other way
				| around.
http://www.ozlabs.org/~dgibson

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