Re: [boost] Logging Library -- Formal Review Request

From: Caleb Epstein (caleb.epstein_at_[hidden])
Date: 2005-04-26 12:56:49

On 4/26/05, Jody Hagins <jody-boost-011304_at_[hidden]> wrote:
> On Tue, 26 Apr 2005 12:16:03 -0400
> Caleb Epstein <caleb.epstein_at_[hidden]> wrote:
> 
> > I think John's approach to having multiple log "levels" is to just use
> > a separate log for each one (e.g. you might have logs called trace,
> > debug, warning, info, and fatal).  Logs are either enabled or
> > disabled; there is no "level" or above-some-threshold-type checking as
> > with some other common implementations.
> 
> Unfortunately, you lose relativity in logs, which is very important in
> diagnosing failures.  Suppose a problem occurs that gets logged to the
> "fatal" log.  Really, to find out all surrounding context, you need to
> merge all logs.  Unless there is a common sequence number or something
> like that, you have no way of really knowing what sequence of events led
> to the problem since they are scattered about in a number of logs.  You
> can make good guesses, but in large that handle multiple requests at the
> same time, it becomes very difficult.

Note that the presence of multiple logs does *not* imply multiple
files.  You can use a single appender for everything:

add_appender ("*", write_to_file ("app.all.txt"));

> I'd prefer a common log, which records levels.

I don't see any harm in this, I'm just trying to communicate my
impression of John's implementation.

Around the time John announced version 1.3 of the Logging lib
(2004-10-28), there was some discussion around structured log
"records" (e.g. an object that could capture information related to a
log message like a severity, timestamp and possibly a thread ID).

See http://thread.gmane.org/gmane.comp.lib.boost.devel/112436 for some
discussion on this topic, specifically posts from Johan Nilsson, John,
and Darryl Green.

> I also think the concept of multiple log variables is important in large
> systems, where different subsystems may have different log levels (e.g,
> turn on all logging for new subsystems, and only critical logging for
> other subsystems).

How about something like this?

enable_logs ("*");
disable_logs ("*.debug");
enable_logs ("*net.debug");

-- 
Caleb Epstein
caleb dot epstein at gmail dot com