std.experimental.logger: practical observations

[Marco Leise via Digitalmars-d]

Am Sat, 13 Sep 2014 14:34:16 +0000
schrieb "Robert burner Schadek" <rburners at gmail.com>:

> On Friday, 12 September 2014 at 16:08:42 UTC, Marco Leise wrote:
> >
> > Remember that the stdlog is __gshared? Imagine we set the
> > LogLevel to off and while executing writeLogMsg ...
> >
> > * a different thread wants to log a warning to stdlog
> > * a different thread wants to inspect/set the log level
> >
> > It is your design to have loggers shared between threads.
> > You should go all the way to make them thread safe.
> >
> > * catch recursive calls from within the same thread,
> >   while not affecting other threads' logging
> > * make Logger a shared class and work with atomicLoad/Store,
> >   a synchronized class or use the built-in monitor field
> >   through synchronized(this) blocks.
> 
> hm, I don't know of any magic pill for that. I guess this would 
> require some dataflow analysis.

Why so complicated? In general - not specific to std.logger -
I'd wrap those calls in some function that acquires a mutex
and then check a recursion flag to abort the logging if this
thread has already been here.

synchronized(loggingMutex) {
  if (isRecursion) return;
  isRecursion = true;
  scope(exit) isRecursion = false;
  logger.writeLogMsg(...);
}

> > I know when to throw an exception, but I never used logging
> > much. If some function throws, would I also log the same
> > message with error() one line before the throw statement?
> > Or would I log at the place where I catch the exception?
> > What to do about the stack trace when I only have one line per
> > log entry?
> > You see, I am a total newbie when it comes to logging and from
> > the question that arose in my head I figured exceptions and
> > logging don't really mix. Maybe only info() and debug() should
> > be used and actual problems left to exception handling alone.
> 
> that is depended on what your program requires. You can write 
> more than one line, just indent it by a tab or two. again no 
> magic pill as far as I know

Ok, I'll experiment a bit and see what works best.

-- 
Marco