[pacman-dev] [PATCH] Reformatting log timestamp to include time-zone

[Dave Reisner]

On Thu, Mar 07, 2019 at 10:35:32AM +1000, Allan McRae wrote:
> On 5/3/19 7:46 am, Florian Wehner wrote:
> > The time logged is currently given as localtime without any time-zone
> > information. This is confusing in various scenarios.
> > 
> > Examples:
> > * If one is travelling across time-zones and the timestamps in the log
> > appear out of order.
> 
> Stop updating multiple times per hour!  :D
> 
> > * Comparing dates with `datediff` gives an offset by the time-zone
> > 
> > This patch would reformat the time-stamp to a full ISO-8601 version.
> > It includes the 'T' separating date and time. This could be removed.
> > 
> > Old: [2019-03-04 16:15]
> > New: [2019-03-04T16:15-05:00]
> > 
> 
> Can we switch from localtime() to gmtime() and just use UTC?
> 

I wouldn't do this... it's not normal to have local machine logs in
another timezone. It'll make correlation harder if your natural timezone
isn't already UTC. And, if we magically change the timezone with a new
release of pacman and don't include the TZ explicitly in the timestamp,
it's just going to be a source of confusion for people.

I'm +1 on keeping localtime and explicitly adding the timezone
identifier to the logline.

> 
> > Signed-off-by: Florian Wehner <florian at whnr.de>
> > ---
> >  lib/libalpm/log.c | 10 ++++++++--
> >  1 file changed, 8 insertions(+), 2 deletions(-)
> > 
> > diff --git a/lib/libalpm/log.c b/lib/libalpm/log.c
> > index e46ad3c3..cf869a08 100644
> > --- a/lib/libalpm/log.c
> > +++ b/lib/libalpm/log.c
> > @@ -20,6 +20,7 @@
> >  
> >  #include <stdio.h>
> >  #include <stdarg.h>
> > +#include <stdlib.h>
> >  #include <errno.h>
> >  #include <syslog.h>
> >  
> > @@ -37,12 +38,17 @@
> >  static int _alpm_log_leader(FILE *f, const char *prefix)
> >  {
> >  	time_t t = time(NULL);
> > +	int tz_h, tz_m;
> >  	struct tm *tm = localtime(&t);
> >  
> > +	/* Calculate the timezone offset ±hh:mm */
> > +	tz_h = tm->tm_gmtoff/3600;
> > +	tz_m = abs(tm->tm_gmtoff - (tz_h*3600))/60;
> > +
> >  	/* Use ISO-8601 date format */
> > -	return fprintf(f, "[%04d-%02d-%02d %02d:%02d] [%s] ",
> > +	return fprintf(f, "[%04d-%02d-%02dT%02d:%02d%+03d:%02d] [%s] ",
> >  			tm->tm_year + 1900, tm->tm_mon + 1, tm->tm_mday,
> > -			tm->tm_hour, tm->tm_min, prefix);
> > +			tm->tm_hour, tm->tm_min, tz_h, tz_m, prefix);
> >  }
> >  
> >  /** A printf-like function for logging.
> >