Debugging mod_perl Perl Internals


This document explains how to debug Perl code under mod_perl.

Most of the mod_perl 1.0 debug documentation applies to mod_perl 2.0:

Detecting Hanging Processes

See Hanging Processes: Detection and Diagnostics for the explanation, but under mp2 to use signals to detect where the process is spinning, you can't use $SIG{USR2}, you have to use POSIX signals. i.e. the code becomes:

  use Carp ();
  use POSIX qw(SIGUSR2);
  my $mask      = POSIX::SigSet->new( SIGUSR2 );
  my $action    = POSIX::SigAction->new(\&tell_where_spinning, $mask);
  my $oldaction = POSIX::SigAction->new();
  POSIX::sigaction(SIGUSR2, $action, $oldaction );
  sub tell_where_spinning {
      Carp::confess("caught SIGUSR2!");

and then:

  % kill USR2 <pid_of_the_spinning_process>

and watch for the trace in error_log.


Maintainer is the person(s) you should contact with updates, corrections and patches.

  • Stas Bekman []


  • Stas Bekman []

Only the major authors are listed above. For contributors see the Changes file.