From: Stefano Brivio <sbrivio@redhat.com>
To: David Gibson <david@gibson.dropbear.id.au>
Cc: passt-dev@passt.top, Yalan Zhang <yalzhang@redhat.com>
Subject: Re: [PATCH 3/6] log, passt: Always print to stderr before initialisation is complete
Date: Wed, 19 Jun 2024 10:17:21 +0200 [thread overview]
Message-ID: <20240619101711.2ce52091@elisabeth> (raw)
In-Reply-To: <ZnI-HkaAiIelQuNu@zatzit>
On Wed, 19 Jun 2024 12:10:38 +1000
David Gibson <david@gibson.dropbear.id.au> wrote:
> On Tue, Jun 18, 2024 at 08:01:31AM +0200, Stefano Brivio wrote:
> > On Tue, 18 Jun 2024 10:44:20 +1000
> > David Gibson <david@gibson.dropbear.id.au> wrote:
> >
> > > On Mon, Jun 17, 2024 at 02:03:16PM +0200, Stefano Brivio wrote:
> > > > After commit 15001b39ef1d ("conf: set the log level much earlier"), we
> > > > had a phase during initialisation when messages wouldn't be printed to
> > > > standard error anymore.
> > > >
> > > > Commit f67238aa864d ("passt, log: Call __openlog() earlier, log to
> > > > stderr until we detach") fixed that, but only for the case where no
> > > > log files are given.
> > > >
> > > > If a log file is configured, vlogmsg() will not call passt_vsyslog(),
> > > > but during initialisation, LOG_PERROR is set, so to avoid duplicated
> > > > prints (which would result from passt_vsyslog() printing to stderr),
> > > > we don't call fprintf() from vlogmsg() either.
> > > >
> > > > This is getting a bit too complicated. Instead of abusing LOG_PERROR,
> > > > define an internal logging flag that clearly represents that we're not
> > > > done with the initialisation phase yet.
> > > >
> > > > If this flag is not set, make sure we always print to stderr, if the
> > > > log mask matches. Then, set LOG_PERROR only as we set this internal
> > > > flag, to make sure we don't duplicate messages.
> > > >
> > > > Reported-by: Yalan Zhang <yalzhang@redhat.com>
> > > > Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
> > > > ---
> > > > log.c | 4 +++-
> > > > log.h | 1 +
> > > > passt.1 | 3 ++-
> > > > passt.c | 17 ++++++++++-------
> > > > 4 files changed, 16 insertions(+), 9 deletions(-)
> > > >
> > > > diff --git a/log.c b/log.c
> > > > index 3b5a1c6..939bb93 100644
> > > > --- a/log.c
> > > > +++ b/log.c
> > > > @@ -49,6 +49,7 @@ int log_trace; /* --trace mode enabled */
> > > > void vlogmsg(int pri, const char *format, va_list ap)
> > > > {
> > > > bool debug_print = (log_mask & LOG_MASK(LOG_DEBUG)) && log_file == -1;
> > > > + bool before_daemon = !(log_flags & LOG_FLAG_DAEMON_READY);
> > >
> > > As in 2/6 would just a global bool be simpler than flags.
> > >
> > > > bool early_print = !(log_flags & LOG_FLAG_CONF_PARSED);
> > > > struct timespec tp;
> > > >
> > > > @@ -71,7 +72,8 @@ void vlogmsg(int pri, const char *format, va_list ap)
> > > > va_end(ap2);
> > > > }
> > > >
> > > > - if (debug_print || (early_print && !(log_opt & LOG_PERROR))) {
> > > > + if (debug_print || early_print ||
> > > > + (before_daemon && (log_mask & LOG_MASK(LOG_PRI(pri))))) {
> > > > (void)vfprintf(stderr, format, ap);
> > > > if (format[strlen(format)] != '\n')
> > > > fprintf(stderr, "\n");
> > > > diff --git a/log.h b/log.h
> > > > index 6a3224a..680baab 100644
> > > > --- a/log.h
> > > > +++ b/log.h
> > > > @@ -10,6 +10,7 @@
> > > > #include <syslog.h>
> > > >
> > > > #define LOG_FLAG_CONF_PARSED BIT(0) /* We already parsed logging options */
> > > > +#define LOG_FLAG_DAEMON_READY BIT(1) /* Daemonised, or ready in foreground */
> > > >
> > > > #define LOGFILE_SIZE_DEFAULT (1024 * 1024UL)
> > > > #define LOGFILE_CUT_RATIO 30 /* When full, cut ~30% size */
> > > > diff --git a/passt.1 b/passt.1
> > > > index 3a23a43..31e528e 100644
> > > > --- a/passt.1
> > > > +++ b/passt.1
> > > > @@ -99,7 +99,8 @@ terminal, and to both system logger and standard error otherwise.
> > > >
> > > > .TP
> > > > .BR \-l ", " \-\-log-file " " \fIPATH\fR
> > > > -Log to file \fIPATH\fR, not to standard error, and not to the system logger.
> > > > +Log to file \fIPATH\fR, not to standard error (once initialisation is complete),
> > > > +and not to the system logger.
> > >
> > > IIUC when -l is set we'll log to the logfile _as well as_ stderr
> > > before we daemonize. The description above doesn't exactly contradict
> > > that, but seems to imply something different.
> >
> > Is that because "(once initialisation is complete)" doesn't clearly
> > refer to "not to standard error"?
>
> Yes, or rather that it's not entirely clear it refers *only* to that
> clause and not to the "Log to file" part at the beginning.
>
> > I could go with something slightly more verbose:
> >
> > Log to file \fIPATH\fR, not to standard error, and not to the system
> > logger.
> >
> > During initialisation phase, that is, before forking to background,
> > or before being ready for communication when running in foreground,
> > messages are always printed to standard error as well.
>
> Hrm... so I want to say:
>
> Log to file PATH instead of to system logger.
>
> Which may not be totally accurate for the current behaviour... but
> seems like it might be a sensible behaviour. That is, we typically
> log to syslog, but -l replaces it with a logfile. Regardless of
> which, under some circumstances we'll also log to stderr.
No, not really: it's not regardless of that. If the log file is given,
we don't want to log to standard error (once we're up and running)
--
Stefano
next prev parent reply other threads:[~2024-06-19 8:18 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-06-17 12:03 [PATCH 0/6] Fixes for early logging/prints and related cleanups Stefano Brivio
2024-06-17 12:03 ` [PATCH 1/6] conf, passt: Don't try to log to stderr after we close it Stefano Brivio
2024-06-18 0:36 ` David Gibson
2024-06-18 6:00 ` Stefano Brivio
2024-06-19 2:06 ` David Gibson
2024-06-19 8:13 ` Stefano Brivio
2024-06-20 0:12 ` David Gibson
2024-06-17 12:03 ` [PATCH 2/6] conf, log: Introduce internal log flags, instead of abusing log levels Stefano Brivio
2024-06-18 0:39 ` David Gibson
2024-06-18 6:01 ` Stefano Brivio
2024-06-17 12:03 ` [PATCH 3/6] log, passt: Always print to stderr before initialisation is complete Stefano Brivio
2024-06-18 0:44 ` David Gibson
2024-06-18 6:01 ` Stefano Brivio
2024-06-19 2:10 ` David Gibson
2024-06-19 8:17 ` Stefano Brivio [this message]
2024-06-20 0:12 ` David Gibson
2024-06-17 12:03 ` [PATCH 4/6] log: Add _perror() logging function variants Stefano Brivio
2024-06-18 0:46 ` David Gibson
2024-06-18 6:02 ` Stefano Brivio
2024-06-19 2:11 ` David Gibson
2024-06-19 8:25 ` Stefano Brivio
2024-06-20 0:13 ` David Gibson
2024-06-17 12:03 ` [PATCH 5/6] treewide: Replace perror() calls with calls to logging functions Stefano Brivio
2024-06-18 0:50 ` David Gibson
2024-06-17 12:03 ` [PATCH 6/6] treewide: Replace strerror() calls Stefano Brivio
2024-06-18 0:51 ` David Gibson
2024-06-18 6:02 ` Stefano Brivio
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