Apache::DebugInfo - log various bits of per-request data


There are two ways to use this module...

  1) using Apache::DebugInfo to control debugging automatically


      PerlInitHandler Apache::DebugInfo
      PerlSetVar      DebugInfo On

      PerlSetVar      DebugPID On
      PerlSetVar      DebugHeadersIn On
      PerlSetVar      DebugDirConfig On
      PerlSetVar      DebugHeadersOut On
      PerlSetVar      DebugNotes On
      PerlSetVar      DebugPNotes On
      PerlSetVar      DebugGetHandlers On
      PerlSetVar      DebugTimestamp On
      PerlSetVar      DebugMarkPhases On

      PerlSetVar      DebugFile     "/path/to/debug_log"
      PerlSetVar      DebugIPList   " 1.2.4."
      PerlSetVar      DebugTypeList ".html .cgi"

  2) using Apache::DebugInfo on the fly

    in handler or script:

      use Apache::DebugInfo;

      my $r = shift;

      my $debug = Apache::DebugInfo->new($r);

      # set the output file

      # get the ip addresses for which output is enabled
      my $ip_list = $debug->ip;

      # dump $r->headers_in right now

      # log $r->headers_out after the response goes to the client

      # log all the $r->pnotes at Fixup and at Cleanup


Apache::DebugInfo gives the programmer the ability to monitor various bits of per-request data.

You can enable Apache::DebugInfo as a PerlInitHandler, in which case it chooses what request phase to display the appropriate data. The output of data can be controlled by setting various variables to On:

  DebugInfo          - enable Apache::DebugInfo handler

  DebugPID           - dumps apache child pid during request init
  DebugHeadersIn     - dumps request headers_in during request init
  DebugDirConfig     - dumps PerlSetVar and PerlAddVar during request init
  DebugGetHandlers   - dumps enabled request handlers during init

  DebugHeadersOut    - dumps request headers_out during request cleanup
  DebugNotes         - dumps request notes during request cleanup
  DebugPNotes        - dumps request pnotes during request cleanup

  DebugTimestamp     - prints localtime at the start of each request
  DebugMarkPhases    - prints the name of the request phase when the
                       phase is entered, prior to any other handlers

Alternatively, you can control output activity on the fly by calling Apache::DebugInfo methods directly (see METHODS below).

Additionally, the following optional variables hold special arguments:

  DebugFile          - absolute path of file that will store the info
                       don't forget to make the file writable by 
                       whichever user Apache runs as (likely nobody)
                       defaults to STDERR (which is likely error_log)

  DebugIPList        - a space delimited list of IP address for which
                       debugging is enabled
                       this can be a partial IP - 1.2.3 will match
                       if absent, defaults to all remote ip addresses

  DebugTypeList      - a space delimited list of file extensions for
                       which debugging is enabled (.cgi, .html...)
                       if absent, defaults to all types


Apache::DebugInfo provides an object oriented interface to allow you to call the various methods from either a module, handler, or an Apache::Registry script.

Constructor: new($r) - create a new Apache::DebugInfo object requires a valid Apache request object

Methods: The following methods can be called without any arguments, in which case the associated data is output immediately. Optionally, each can be called with a list (either explicitly or as an array) of Perl*Handlers, which will log the data during the appropriate phase:

  headers_in()   - display incoming HTTP headers

  headers_out()  - display outgoing HTTP headers

  notes()        - display strings set by $r->notes

  pnotes()       - display variables set by $r->pnotes

  pid()          - display the apache child process PID

  get_handlers() - display variables set by PerlSetVar and PerlAddVar

  dir_config()   - display the enabled handlers for this request

  timestamp()    - display the current system time

  mark_phases()  - display the phase before executing any other
                   handlers. if given the argument 'All', 
                   mark_phases  will display the entry into all
                   phases after the current phase.  calling with
                   no arguments outputs the current phase 

  There are also the following methods available for manipulating
  the behavior of the above methods:

  file($file)    - get or set the output file
                   accepts an absolute filename as an argument
                   returns the output filehandle
                   defaults to, but overrides DebugFile above

  ip($list)      - get or set the ip list
                   accepts a space delimited list as an argument
                   defaults to, but overrides DebugIPList above

  type($list)    - get or set the file type list
                   accepts a space delimited list as an argument
                   defaults to, but overrides DebugTypeList above


Setting DebugInfo to Off has no effect on the ability to make direct method calls.

Verbose debugging is enabled by setting the variable $Apache::DebugInfo::DEBUG=1 to or greater. To turn off all messages set LogLevel above info.

This is alpha software, and as such has not been tested on multiple platforms or environments. It requires PERL_INIT=1, PERL_CLEANUP=1, PERL_LOG_API=1, PERL_FILE_API=1, PERL_STACKED_HANDLERS=1, and maybe other hooks to function properly.


Once a debug handler is added to a given request phase, it can no longer be controlled by ip() or type(). file(), however, takes affect on invocation. This is because the matching is done when the Perl*Handler is added to the stack, while the output file is used when the Perl*Handler is actually executed.

Calling Apache::DebugInfo methods with 'PerlHandler' as an argument has been disabled - doing so gets your headers and script printed to the browser, so I thought I'd save the unaware from potential pitfalls.

Phase misspellings, like 'PelrInitHandler' pass through without warning, in case you were wondering where your output went...

The get_handlers and mark_phases methods are incomplete, mainly due to oversights in the mod_perl API. Currently (as of mod_perl 1.2401), they cannot function properly on the following callbacks: PerlInitHandler As such, they have been disabled until forthcoming corrections to the API can be implemented. PerlHeaderParserHandlers and PerlPostRequestHandlers function normally.

The output uri is whatever the uri was when new() was called (either on the fly or in Apache::DebugInfo::handler). Thus if the uri has undergone translation since the new() call the original, not the new, uri will be output. This feature can be easily remedied, but having a changing uri in the output may be confusing when debugging. Future behavior will be influenced by user feedback.


perl(1), mod_perl(1), Apache(3)


Geoffrey Young <>


Copyright (c) 2000, Geoffrey Young. All rights reserved.

This module is free software. It may be used, redistributed and/or modified under the same terms as Perl itself.