AnyEvent::Debug(3pm)					User Contributed Perl Documentation				      AnyEvent::Debug(3pm)

NAME

       AnyEvent::Debug - debugging utilities for AnyEvent

SYNOPSIS

	  use AnyEvent::Debug;

	  # create an interactive shell into the program
	  my $shell = AnyEvent::Debug::shell "unix/", "/home/schmorp/myshell";
	  # then on the shell: "socat readline /home/schmorp/myshell"

DESCRIPTION

       This module provides functionality hopefully useful for debugging.

       At the moment, "only" an interactive shell is implemented. This shell allows you to interactively "telnet into" your program and execute
       Perl code, e.g. to look at global variables.

FUNCTIONS

       $shell = AnyEvent::Debug::shell $host, $service
	   This function binds on the given host and service port and returns a shell object, which determines the lifetime of the shell. Any
	   number of conenctions are accepted on the port, and they will give you a very primitive shell that simply executes every line you
	   enter.

	   All commands will be executed "blockingly" with the socket "select"ed for output. For a less "blocking" interface see Coro::Debug.

	   The commands will be executed in the "AnyEvent::Debug::shell" package, which currently has "help" and a few other commands, and can be
	   freely modified by all shells. Code is evaluated under "use strict 'subs'".

	   Every shell has a logging context ($LOGGER) that is attached to $AnyEvent::Log::COLLECT), which is especially useful to gether debug
	   and trace messages.

	   As a general programming guide, consider the beneficial aspects of using more global ("our") variables than local ones ("my") in
	   package scope: Earlier all my modules tended to hide internal variables inside "my" variables, so users couldn't accidentally access
	   them. Having interactive access to your programs changed that: having internal variables still in the global scope means you can debug
	   them easier.

	   As no authentication is done, in most cases it is best not to use a TCP port, but a unix domain socket, whcih can be put wherever you
	   can access it, but not others:

	      our $SHELL = AnyEvent::Debug::shell "unix/", "/home/schmorp/shell";

	   Then you can use a tool to connect to the shell, such as the ever versatile "socat", which in addition can give you readline support:

	      socat readline /home/schmorp/shell
	      # or:
	      cd /home/schmorp; socat readline unix:shell

	   Socat can even give you a persistent history:

	      socat readline,history=.anyevent-history unix:shell

	   Binding on 127.0.0.1 (or "::1") might be a less secure but sitll not totally insecure (on single-user machines) alternative to let you
	   use other tools, such as telnet:

	      our $SHELL = AnyEvent::Debug::shell "127.1", "1357";

	   And then:

	      telnet localhost 1357

       AnyEvent::Debug::wrap [$level]
	   Sets the instrumenting/wrapping level of all watchers that are being created after this call. If no $level has been specified, then it
	   toggles between 0 and 1.

	   The default wrap level is 0, or whatever $ENV{PERL_ANYEVENT_DEBUG_WRAP} specifies.

	   A level of 0 disables wrapping, i.e. AnyEvent works normally, and in its most efficient mode.

	   A level of 1 or higher enables wrapping, which replaces all watchers by AnyEvent::Debug::Wrapped objects, stores the location where a
	   watcher was created and wraps the callback to log all invocations at "trace" loglevel if tracing is enabled fore the watcher. The
	   initial state of tracing when creating a watcher is taken from the global variable $AnyEvent:Debug::TRACE. The default value of that
	   variable is 1, but it can make sense to set it to 0 and then do "local $AnyEvent::Debug::TRACE = 1" in a block where you create
	   "interesting" watchers. Tracing can also be enabled and disabled later by calling the watcher's "trace" method.

	   The wrapper will also count how many times the callback was invoked and will record up to ten runtime errors with corresponding
	   backtraces. It will also log runtime errors at "error" loglevel.

	   To see the trace messages, you can invoke your program with "PERL_ANYEVENT_VERBOSE=9", or you can use AnyEvent::Log to divert the trace
	   messages in any way you like (the EXAMPLES section in AnyEvent::Log has some examples).

	   A level of 2 does everything that level 1 does, but also stores a full backtrace of the location the watcher was created, which slows
	   down watcher creation considerably.

	   Every wrapped watcher will be linked into %AnyEvent::Debug::Wrapped, with its address as key. The "wl" command in the debug shell can
	   be used to list watchers.

	   Instrumenting can increase the size of each watcher multiple times, and, especially when backtraces are involved, also slows down
	   watcher creation a lot.

	   Also, enabling and disabling instrumentation will not recover the full performance that you had before wrapping (the AE::xxx functions
	   will stay slower, for example).

	   If you are developing your program, also consider using AnyEvent::Strict to check for common mistakes.

       AnyEvent::Debug::path2mod $path
	   Tries to replace a path (e.g. the file name returned by caller) by a module name. Returns the path unchanged if it fails.

	   Example:

	      print AnyEvent::Debug::path2mod "/usr/lib/perl5/AnyEvent/Debug.pm";
	      # might print "AnyEvent::Debug"

       AnyEvent::Debug::cb2str $cb
	   Using various gambits, tries to convert a callback (e.g. a code reference) into a more useful string.

	   Very useful if you debug a program and have some callback, but you want to know where in the program the callback is actually defined.

       AnyEvent::Debug::backtrace [$skip]
	   Creates a backtrace (actually an AnyEvent::Debug::Backtrace object that you can stringify), not unlike the Carp module would. Unlike
	   the Carp module it resolves some references (such as callbacks) to more user-friendly strings, has a more succinct output format and
	   most importantly: doesn't leak memory like hell.

	   The reason it creates an object is to save time, as formatting can be done at a later time. Still, creating a backtrace is a relatively
	   slow operation.

THE AnyEvent::Debug::Wrapped CLASS
       All watchers created while the wrap level is non-zero will be wrapped inside an AnyEvent::Debug::Wrapped object. The address of the wrapped
       watcher will become its ID - every watcher will be stored in $AnyEvent::Debug::Wrapped{$id}.

       These wrapper objects can be stringified and have some methods defined on them.

       For debugging, of course, it can be helpful to look into these objects, which is why this is documented here, but this might change at any
       time in future versions.

       Each object is a relatively standard hash with the following members:

	  type	 => name of the method used ot create the watcher (e.g. C<io>, C<timer>).
	  w	 => the actual watcher
	  rfile  => reference to the filename of the file the watcher was created in
	  line	 => line number where it was created
	  sub	 => function name (or a special string) which created the watcher
	  cur	 => if created inside another watcher callback, this is the string rep of the other watcher
	  now	 => the timestamp (AE::now) when the watcher was created
	  arg	 => the arguments used to create the watcher (sans C<cb>)
	  cb	 => the original callback used to create the watcher
	  called => the number of times the callback was called

       Each object supports the following mehtods (warning: these are only available on wrapped watchers, so are best for interactive use via the
       debug shell).

       $w->id
	   Returns the numerical id of the watcher, as used in the debug shell.

       $w->verbose
	   Returns a multiline textual description of the watcher, including the first ten exceptions caught while executing the callback.

       $w->trace ($on)
	   Enables ($on is true) or disables ($on is false) tracing on this watcher.

	   To get tracing messages, both the global logging settings must have trace messages enabled for the context "AnyEvent::Debug" and
	   tracing must be enabled for the wrapped watcher.

	   To enable trace messages globally, the simplest way is to start the program with "PERL_ANYEVENT_VERBOSE=9" in the environment.

	   Tracing for each individual watcher is enabled by default (unless $AnyEvent::Debug::TRACE has been set to false).

AUTHOR

	Marc Lehmann <schmorp@schmorp.de>
	http://anyevent.schmorp.de

perl v5.14.2							    2012-04-08						      AnyEvent::Debug(3pm)