Michele Beltrame wrote:
Hello all!
First post on this list so... hello again. :-)
I use CGI::Application::Dispatch and am wondering if there is a way to
output errors thrown by the application to the standard output. Since I
began using Dispatch, it just ignores CGI::Carp/fatalsToBrowser/ and any
other thing I try, and just prints errors in the web server error log.
Not that big issue, but can error reporting on the browser be enabled?
I'm not looking for logging or so, but even reporting of things such as
*compilation* errors.
Hi Michele, welcome to the list!
I see no-one more knowledgeable than me has replied so far, so I'll
illustrate how I handle this situation. In my Dispatch sub-class I load
an error handler that overrides $SIG{__DIE__} to trap the error and
display it in the browser, optionally sending the nominated admin an
e-mail alert:
#--------------------------------------------------
package MyApp::Dispatch;
BEGIN {
use MyApp::Local::ErrorHandler;
}
#--------------------------------------------------
package MyApp::Local::ErrorHandler;
$|++;
BEGIN {
use POSIX qw(strftime);
use Mail::Sendmail; # or equivalent
$SIG{__DIE__} = \&fatal_error;
}
sub fatal_error {
my $message = shift;
my $incident = unpack "H*", pack "NS", time, $$;
my $time = strftime "%d-%b-%Y %H:%M:%S", localtime;
my %report = (
incident => $incident,
message => $message,
);
# record reason for death in the error log:
warn join "", map {
sprintf "crash %s [%s]: %s\n", $incident, $time, $_;
} split /\n+/, $message;
# alert admin:
send_email(\%report);
# now give the user a place to record their experience
print sub_that_outputs_nice_html(\%report);
exit 0 unless $ENV{MOD_PERL}; # keeps the script from generating
# a 500 error, but kills the CA:Server
}
It's actually based on an article by Randal Schwartz called "Safe CGI
Death" (http://www.stonehenge.com/merlyn/PerlJournal/col05.html).
But be warned, I've had *many* difficulties with this approach in a
persistent environment (the original article probably didn't intend it
to be used in that capacity), and there are several plugins that just
won't play nice with $SIG{__DIE__} handlers, the most recent one I've
had to eliminate is CAP::Redirect. See an earlier thread for some more
examples of grief with custom die handlers.
I think $SIG{__DIE__} handlers in general are tricky to get working
properly (at least in persistent envs - see some of Rons previous
articles), and I've not yet found a way to make it work reliably under
mod_perl (though most of my work so far has been devel under
CA::Server). But it *is* one way to produce nice end-user feedback for
internal errors that otherwise produce the not very user-friendly
"CGI::Application::Dispatch error! Internal Server Error" page.
Would be interested to hear how others have handled this situation though.
--
Richard Jones
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