Log::Log4perl::Appender::DBI questions (Was: Re: [log4perl-devel] Setting parameters globally in Log::Log4perl::Appender::DBI)

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

On Mon, Oct 20, 2003 at 01:28:04PM -0700, Kevin Goess wrote:
> >I wonder if there is a way, using Log::Log4perl::Appender::DBI, to set a
> >value for a logger, which will be inserted at all subsequent log
> >statements.
> 
> See 'Mapped Diagnostic Context' in the perldoc 
> http://log4perl.sourceforge.net/releases/Log-Log4perl/docs/html/Log/Log4perl.html#mapped_diagnostic_context_(mdc) 
> 
> 
> >my $logger = Log::Log4perl::get_logger();
> >
> >my $customer = get_cust_id();
> 
> #stash the value in a global location for the logger to find
> Log::Log4perl::MDC->put('customer', $customer);
> 
> >do_something_dangerous() || $logger->error("Big problem !");
> ># ...
> >do_something_uncredibly_dangerous() || $logger->error("Aaargh !");
> 
> And set up your appender to look like something this:
> 
>  log4j.appender.DBAppndr.sql         = \
>        insert into logtable           \
>        (custid, message) \
>        values (?,?)
>     log4j.appender.DBAppndr.params.1 = %X{customer}
> 
> Does that answer your question?

That's great !

Well, I have a couple of more questions :)

1) I'd like to have optional parameters to logging statements. The
documentation says that if it lacks a parameter, it will just be
replaced by the undef value. But I got a different behaviour.

2) I would like to do some preprocessing before the value are inserted
in the database. I can manage to do that on %x's values by overriding
the log() method (and I think I could use this trick to solve the
problem #1). But I don't know how to do it on the values in
%X. I'd like to do that because when a value from %X is not initialized,
the string '[undef]' is inserted, but when the corresponding database
column is of type INTEGER, obviously the SQL statements fails. I'd like
to have a way to put a zero or a NULL value instead of the string
'[undef]'.

Here are pieces of code in order to explain my problems :


################################################################################
package MyAppender;
use base 'Log::Log4perl::Appender::DBI';

sub log {
    # Here I'm subclassing to modify value from the %x's parameters
    my $self = shift;
    my %p = @_;
    # Categories are shown as Perl packages
    $p{log4p_category} =~ s/\./::/g;
    Log::Log4perl::Appender::DBI::log($self, %p);
}

1;

################################################################################

package My::Cute::Package;

my $log_conf = <<END;

log4perl.appender.dbLog=MyAppender
log4perl.appender.dbLog.datasource=dbi:Pg:dbname=test
log4perl.appender.dbLog.username=
log4perl.appender.dbLog.password=
log4perl.appender.dbLog.sql=INSERT INTO log (category, level, customer, message, details) VALUES (?, ?, ?, ?, ?)

log4perl.appender.dbLog.params.1 = %c
log4perl.appender.dbLog.params.2 = %p
log4perl.appender.dbLog.params.3 = %X{customer}

log4perl.appender.dbLog.usePreparedStmt = 1
log4perl.appender.dbLog.layout = Log::Log4perl::Layout::NoopLayout
log4perl.appender.dbLog.warp_message = 0

log4perl.logger=DEBUG, dbLog

END

use Log::Log4perl;
Log::Log4perl->init(\$log_conf);
my $logger = Log::Log4perl::get_logger();

# This one fails with the following message because the database wants an
# integer (or a NULL value).
#
# DBD::Pg::st execute failed: ERROR:  pg_atoi: error in "[undef]": can't parse
# "[undef]" at /usr/local/lib/perl5/site_perl/5.8.0/Log/Log4perl/Appender/DBI.pm

$logger->error(
    "Something wrong.", 
    "A problem has happened because of this and that."
);


# %X{customer} is initialized
Log::Log4perl::MDC->put('customer', 1234);

# This one works

$logger->error(
    "Something wrong.", 
    "A problem has happened because of this and that."
);

# This one fails with the message :
#
#  execute called with 4 bind variables, 5 needed at
#  /usr/local/lib/perl5/site_perl/5.8.0/Log/Log4perl/Appender/DBI.pm line 96.

$logger->error(
    "Some other thing wrong."
);

################################################################################

-- 
Alex Marandon
CLARISYS Informatique
http://clarisys.fr