Re: [log4perl-devel] Re: MDC and [undef]

[Alex M. <ale...@cl...>]

On Wed, Oct 29, 2003 at 11:07:26PM -0800, Kevin Goess wrote:
> | I see that MDC.pm has an undef value (which was recently '[undef]')
> | but I don't see where it's changed to an empty string. By subclassing the
> | place where undef values are changed to empty string, I could certainly
> | get rid of my problem.
> 
> It's changed in the sprintf() in PatternLayout::render(), since this:
> 
> 	sprintf("%s", undef)
> 
> produces the empty string, not undef.

Thanks I'll have a look at it. I'll inform you of my research :)

> | That's why it would be nice to provide a way for the users to do some
> | kind of preprocessing on MDC values in order to handle problems which
> | are specific to some kind of appenders.
> 
> Tell me if I'm just being dense (which is more than likely), but is it
> not true that you *do* have complete control the MDC values, you can
> init the troublesome one via MDC->put('somenumeric',0) right next to
> where you call Log4perl::init(), or even in a BEGIN{} block somewhere.
> Right?

Let me explain a bit the context. My application sends email. But it
also does other things (like providing the user a web interface). I have
a table where I insert informations about sent mail. When there is a
problem while sending a mail, I log it in a file, but also in an error
table, and I put in the error table the id of the failed mail. So, the
integer column in the error table references primary keys of the
sent mail table. As I said, error could happen when doing something else
than sending a mail, so the integer column of my error table can hold
NULL values.

If I put a default value (0 for example) it could work if :
 - I remove the referecing integrity constraint
 or
 - I create a fake sent-mail which have an id of 0 and put if clauses
   everywhere in my code in order to not display information about this
   fake sent-mail

Both of these solutions could work as quick workaround, but it's
not clean.