I've recently revisited an old project that uses Log::Log4perl, and decided it would be good to have it log to both a file and an SQL database. In future, it will also want to send output to sockets, but that's another story. So, I happily poked around the internet and found out how to use the DBI Appender, and all was working fine until I made an actual complex logging statement. Then, I ran into the dread Log4perl: DBI appender error: 'called with 6 bind variables when 5 are needed' Of course! As suggested, I had set the layout to NoopLayout and used bound parameters... which works just fine when using a single fixed string as your logged data, but of course most of my real logging is done using the logger as if it were sprintf.

$log->info("Data directory: %s", $options->{'dir'});
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My naive through was to pass a coderef in as the warp_message parameter, hoping I could just have it do the sprintf conversion to flatten things into a single argument that would become the last bound parameter passed...

my $spr = sub { my $fmt = shift;  return sprintf $fmt, @_; };
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and then...

my $conf = qq!
    log4perl.rootLogger        = TRACE, DBAppndr
    log4perl.appender.DBAppndr = Log::Log4perl::Appender::DBI
    log4perl.appender.DBAppndr.datasource = $dsn
    log4perl.appender.DBAppndr.username   = $db_user
    log4perl.appender.DBAppndr.password   = $db_passwd
    log4perl.appender.DBAppndr.sql        = INSERT INTO log (level, ti
+mestamp, method, line, message) VALUES (?,?,?,?,?)
    log4perl.appender.DBAppndr.params.1   = %p
    log4perl.appender.DBAppndr.params.2   = %d{yyyy-MM-dd HH:mm:ss.SSS
+}
    log4perl.appender.DBAppndr.params.3   = %M
    log4perl.appender.DBAppndr.params.4   = %L
    log4perl.appender.DBAppndr.usePreparedStmt  = 1
    log4perl.appender.DBAppndr.layout           = Log::Log4perl::Layou
+t::NoopLayout
    log4perl.appender.DBAppndr.warp_message     = $spr

!;
    Log::Log4perl::init( \$conf );
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This resulted in the unfortunate Can't use string ("Can't use string ("Data director"...) as a HASH ref while "strict refs" in use at /usr/local/share/perl/5.14.2/Log/Log4perl/Appender.pm line 281. I also have loggers to the screen and file, but the DBI one is the problem child, and while he's having a tantrum, the others don't even get to run. Obviously, things would work fine if I used sprintf myself at the caller level, but that defeats the purpose of having a nice clean logging statement. Any suggestions?