[ViewVC] Diff of: cvs/AnyEvent/lib/AnyEvent.pm

Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.123 by root, Fri May 23 20:41:25 2008 UTC vs.
Revision 1.165 by root, Tue Jul 8 23:07:26 2008 UTC

    });
    my $w = AnyEvent->condvar; # stores whether a condition was flagged
    $w->send; # wake up current and all future recv's
    $w->recv; # enters "main loop" till $condvar gets ->send
+=head1 INTRODUCTION/TUTORIAL
+This manpage is mainly a reference manual. If you are interested
+in a tutorial or some gentle introduction, have a look at the
+L<AnyEvent::Intro> manpage.
 =head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
 Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
 nowadays. So what is different about AnyEvent?
 isn't itself. What's worse, all the potential users of your module are
 I<also> forced to use the same event loop you use.
 AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
 fine. AnyEvent + Tk works fine etc. etc. but none of these work together
-with the rest: POE + IO::Async? no go. Tk + Event? no go. Again: if
+with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if
 your module uses one of those, every user of your module has to use it,
 too. But if your module uses AnyEvent, it works transparently with all
 event models it supports (including stuff like POE and IO::Async, as long
 as those use one of the supported event loops. It is trivial to add new
 event loops to AnyEvent, too, so it is future-proof).
 In addition to being free of having to use I<the one and only true event
 model>, AnyEvent also is free of bloat and policy: with POE or similar
-modules, you get an enourmous amount of code and strict rules you have to
+modules, you get an enormous amount of code and strict rules you have to
 follow. AnyEvent, on the other hand, is lean and up to the point, by only
 offering the functionality that is necessary, in as thin as a wrapper as
 technically possible.
+Of course, AnyEvent comes with a big (and fully optional!) toolbox
+of useful functionality, such as an asynchronous DNS resolver, 100%
+non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
+such as Windows) and lots of real-world knowledge and workarounds for
+platform bugs and differences.
-Of course, if you want lots of policy (this can arguably be somewhat
+Now, if you I<do want> lots of policy (this can arguably be somewhat
 useful) and you want to force your users to use the one and only event
 model, you should I<not> use this module.
 =head1 DESCRIPTION
 starts using it, all bets are off. Maybe you should tell their authors to
 use AnyEvent so their modules work together with others seamlessly...
 The pure-perl implementation of AnyEvent is called
 C<AnyEvent::Impl::Perl>. Like other event modules you can load it
-explicitly.
+explicitly and enjoy the high availability of that event loop :)
 =head1 WATCHERS
 AnyEvent has the central concept of a I<watcher>, which is an object that
 stores relevant data for each kind of event you are waiting for, such as
-the callback to call, the filehandle to watch, etc.
+the callback to call, the file handle to watch, etc.
 These watchers are normal Perl objects with normal Perl lifetime. After
 creating a watcher it will immediately "watch" for events and invoke the
 callback when the event occurs (of course, only when the event model
 is in control).
 Many watchers either are used with "recursion" (repeating timers for
 example), or need to refer to their watcher object in other ways.
 An any way to achieve that is this pattern:
-  my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
+   my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
-     # you can use $w here, for example to undef it
+      # you can use $w here, for example to undef it
-     undef $w;
+      undef $w;
-  });
+   });
 Note that C<my $w; $w => combination. This is necessary because in Perl,
 my variables are only visible after the statement in which they are
 declared.
 Some event loops issue spurious readyness notifications, so you should
 always use non-blocking calls when reading/writing from/to your file
 handles.
-Example:
-   # wait for readability of STDIN, then read a line and disable the watcher
+Example: wait for readability of STDIN, then read a line and disable the
+watcher.
    my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
       chomp (my $input = <STDIN>);
       warn "read: $input\n";
       undef $w;
    });
 Although the callback might get passed parameters, their value and
 presence is undefined and you cannot rely on them. Portable AnyEvent
 callbacks cannot use arguments passed to time watcher callbacks.
-The timer callback will be invoked at most once: if you want a repeating
+The callback will normally be invoked once only. If you specify another
-timer you have to create a new watcher (this is a limitation by both Tk
+parameter, C<interval>, as a strictly positive number (> 0), then the
-and Glib).
+callback will be invoked regularly at that interval (in fractional
+seconds) after the first invocation. If C<interval> is specified with a
+false value, then it is treated as if it were missing.
-Example:
+The callback will be rescheduled before invoking the callback, but no
+attempt is done to avoid timer drift in most backends, so the interval is
+only approximate.
-   # fire an event after 7.7 seconds
+Example: fire an event after 7.7 seconds.
    my $w = AnyEvent->timer (after => 7.7, cb => sub {
       warn "timeout\n";
    });
    # to cancel the timer:
    undef $w;
-Example 2:
-   # fire an event after 0.5 seconds, then roughly every second
+Example 2: fire an event after 0.5 seconds, then roughly every second.
-   my $w;
-   my $cb = sub {
-      # cancel the old timer while creating a new one
-      $w = AnyEvent->timer (after => 1, cb => $cb);
+   my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
+      warn "timeout\n";
    };
-   # start the "loop" by creating the first watcher
-   $w = AnyEvent->timer (after => 0.5, cb => $cb);
 =head3 TIMING ISSUES
 There are two ways to handle timers: based on real time (relative, "fire
 in 10 seconds") and based on wallclock time (absolute, "fire at 12
 timers.
 AnyEvent always prefers relative timers, if available, matching the
 AnyEvent API.
+AnyEvent has two additional methods that return the "current time":
+=over 4
+=item AnyEvent->time
+This returns the "current wallclock time" as a fractional number of
+seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
+return, and the result is guaranteed to be compatible with those).
+It progresses independently of any event loop processing, i.e. each call
+will check the system clock, which usually gets updated frequently.
+=item AnyEvent->now
+This also returns the "current wallclock time", but unlike C<time>, above,
+this value might change only once per event loop iteration, depending on
+the event loop (most return the same time as C<time>, above). This is the
+time that AnyEvent's timers get scheduled against.
+I<In almost all cases (in all cases if you don't care), this is the
+function to call when you want to know the current time.>
+This function is also often faster then C<< AnyEvent->time >>, and
+thus the preferred method if you want some timestamp (for example,
+L<AnyEvent::Handle> uses this to update it's activity timeouts).
+The rest of this section is only of relevance if you try to be very exact
+with your timing, you can skip it without bad conscience.
+For a practical example of when these times differ, consider L<Event::Lib>
+and L<EV> and the following set-up:
+The event loop is running and has just invoked one of your callback at
+time=500 (assume no other callbacks delay processing). In your callback,
+you wait a second by executing C<sleep 1> (blocking the process for a
+second) and then (at time=501) you create a relative timer that fires
+after three seconds.
+With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
+both return C<501>, because that is the current time, and the timer will
+be scheduled to fire at time=504 (C<501> + C<3>).
+With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
+time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
+last event processing phase started. With L<EV>, your timer gets scheduled
+to run at time=503 (C<500> + C<3>).
+In one sense, L<Event::Lib> is more exact, as it uses the current time
+regardless of any delays introduced by event processing. However, most
+callbacks do not expect large delays in processing, so this causes a
+higher drift (and a lot more system calls to get the current time).
+In another sense, L<EV> is more exact, as your timer will be scheduled at
+the same time, regardless of how long event processing actually took.
+In either case, if you care (and in most cases, you don't), then you
+can get whatever behaviour you want with any event loop, by taking the
+difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
+account.
+=back
 =head2 SIGNAL WATCHERS
 You can watch for signals using a signal watcher, C<signal> is the signal
 I<name> without any C<SIG> prefix, C<cb> is the Perl callback to
 be invoked whenever a signal occurs.
 Although the callback might get passed parameters, their value and
 presence is undefined and you cannot rely on them. Portable AnyEvent
 callbacks cannot use arguments passed to signal watcher callbacks.
-Multiple signal occurances can be clumped together into one callback
+Multiple signal occurrences can be clumped together into one callback
-invocation, and callback invocation will be synchronous. synchronous means
+invocation, and callback invocation will be synchronous. Synchronous means
 that it might take a while until the signal gets handled by the process,
-but it is guarenteed not to interrupt any other callbacks.
+but it is guaranteed not to interrupt any other callbacks.
 The main advantage of using these watchers is that you can share a signal
 between multiple watchers.
 This watcher might use C<%SIG>, so programs overwriting those signals
 AnyEvent program, you I<have> to create at least one watcher before you
 C<fork> the child (alternatively, you can call C<AnyEvent::detect>).
 Example: fork a process and wait for it
-  my $done = AnyEvent->condvar;
+   my $done = AnyEvent->condvar;
-  my $pid = fork or exit 5;
+   my $pid = fork or exit 5;
-  my $w = AnyEvent->child (
+   my $w = AnyEvent->child (
-     pid => $pid,
+      pid => $pid,
-     cb  => sub {
+      cb  => sub {
-        my ($pid, $status) = @_;
+         my ($pid, $status) = @_;
-        warn "pid $pid exited with status $status";
+         warn "pid $pid exited with status $status";
-        $done->send;
+         $done->send;
-     },
+      },
-  );
+   );
-  # do something else, then wait for process exit
+   # do something else, then wait for process exit
-  $done->recv;
+   $done->recv;
 =head2 CONDITION VARIABLES
 If you are familiar with some event loops you will know that all of them
 require you to run some blocking "loop", "run" or similar function that
 Condition variables can be created by calling the C<< AnyEvent->condvar
 >> method, usually without arguments. The only argument pair allowed is
 C<cb>, which specifies a callback to be called when the condition variable
 becomes true.
-After creation, the conditon variable is "false" until it becomes "true"
+After creation, the condition variable is "false" until it becomes "true"
-by calling the C<send> method.
+by calling the C<send> method (or calling the condition variable as if it
+were a callback, read about the caveats in the description for the C<<
+->send >> method).
 Condition variables are similar to callbacks, except that you can
 optionally wait for them. They can also be called merge points - points
-in time where multiple outstandign events have been processed. And yet
+in time where multiple outstanding events have been processed. And yet
-another way to call them is transations - each condition variable can be
+another way to call them is transactions - each condition variable can be
 used to represent a transaction, which finishes at some point and delivers
 a result.
 Condition variables are very useful to signal that something has finished,
 for example, if you write a module that does asynchronous http requests,
 you can block your main program until an event occurs - for example, you
 could C<< ->recv >> in your main program until the user clicks the Quit
 button of your app, which would C<< ->send >> the "quit" event.
 Note that condition variables recurse into the event loop - if you have
-two pieces of code that call C<< ->recv >> in a round-robbin fashion, you
+two pieces of code that call C<< ->recv >> in a round-robin fashion, you
 lose. Therefore, condition variables are good to export to your caller, but
 you should avoid making a blocking wait yourself, at least in callbacks,
 as this asks for trouble.
 Condition variables are represented by hash refs in perl, and the keys
 There are two "sides" to a condition variable - the "producer side" which
 eventually calls C<< -> send >>, and the "consumer side", which waits
 for the send to occur.
-Example:
+Example: wait for a timer.
    # wait till the result is ready
    my $result_ready = AnyEvent->condvar;
    # do something such as adding a timer
    # this "blocks" (while handling events) till the callback
    # calls send
    $result_ready->recv;
+Example: wait for a timer, but take advantage of the fact that
+condition variables are also code references.
+   my $done = AnyEvent->condvar;
+   my $delay = AnyEvent->timer (after => 5, cb => $done);
+   $done->recv;
 =head3 METHODS FOR PRODUCERS
 These methods should only be used by the producing side, i.e. the
 code/module that eventually sends the signal. Note that it is also
 the producer side which creates the condvar in most cases, but it isn't
 If a callback has been set on the condition variable, it is called
 immediately from within send.
 Any arguments passed to the C<send> call will be returned by all
 future C<< ->recv >> calls.
+Condition variables are overloaded so one can call them directly
+(as a code reference). Calling them directly is the same as calling
+C<send>. Note, however, that many C-based event loops do not handle
+overloading, so as tempting as it may be, passing a condition variable
+instead of a callback does not work. Both the pure perl and EV loops
+support overloading, however, as well as all functions that use perl to
+invoke a callback (as in L<AnyEvent::Socket> and L<AnyEvent::DNS> for
+example).
 =item $cv->croak ($error)
 Similar to send, but causes all call's to C<< ->recv >> to invoke
 C<Carp::croak> with the given error message/object/scalar.
 doesn't execute once).
 This is the general pattern when you "fan out" into multiple subrequests:
 use an outer C<begin>/C<end> pair to set the callback and ensure C<end>
 is called at least once, and then, for each subrequest you start, call
-C<begin> and for eahc subrequest you finish, call C<end>.
+C<begin> and for each subrequest you finish, call C<end>.
 =back
 =head3 METHODS FOR CONSUMERS
 (programs might want to do that to stay interactive), so I<if you are
 using this from a module, never require a blocking wait>, but let the
 caller decide whether the call will block or not (for example, by coupling
 condition variables with some kind of request results and supporting
 callbacks so the caller knows that getting the result will not block,
-while still suppporting blocking waits if the caller so desires).
+while still supporting blocking waits if the caller so desires).
 Another reason I<never> to C<< ->recv >> in a module is that you cannot
 sensibly have two C<< ->recv >>'s in parallel, as that would require
 multiple interpreters or coroutines/threads, none of which C<AnyEvent>
 can supply.
 This is a mutator function that returns the callback set and optionally
 replaces it before doing so.
 The callback will be called when the condition becomes "true", i.e. when
-C<send> or C<croak> are called. Calling C<recv> inside the callback
+C<send> or C<croak> are called, with the only argument being the condition
-or at any later time is guaranteed not to block.
+variable itself. Calling C<recv> inside the callback or at any later time
+is guaranteed not to block.
 =back
 =head1 GLOBAL VARIABLES AND FUNCTIONS
 If it doesn't care, it can just "use AnyEvent" and use it itself, or not
 do anything special (it does not need to be event-based) and let AnyEvent
 decide which implementation to chose if some module relies on it.
-If the main program relies on a specific event model. For example, in
+If the main program relies on a specific event model - for example, in
-Gtk2 programs you have to rely on the Glib module. You should load the
+Gtk2 programs you have to rely on the Glib module - you should load the
 event module before loading AnyEvent or any module that uses it: generally
 speaking, you should load it as early as possible. The reason is that
 modules might create watchers when they are loaded, and AnyEvent will
 decide on the event model to use as soon as it creates watchers, and it
 might chose the wrong one unless you load the correct one yourself.
-You can chose to use a rather inefficient pure-perl implementation by
+You can chose to use a pure-perl implementation by loading the
-loading the C<AnyEvent::Impl::Perl> module, which gives you similar
+C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
-behaviour everywhere, but letting AnyEvent chose is generally better.
+everywhere, but letting AnyEvent chose the model is generally better.
+=head2 MAINLOOP EMULATION
+Sometimes (often for short test scripts, or even standalone programs who
+only want to use AnyEvent), you do not want to run a specific event loop.
+In that case, you can use a condition variable like this:
+   AnyEvent->condvar->recv;
+This has the effect of entering the event loop and looping forever.
+Note that usually your program has some exit condition, in which case
+it is better to use the "traditional" approach of storing a condition
+variable somewhere, waiting for it, and sending it when the program should
+exit cleanly.
 =head1 OTHER MODULES
 The following is a non-exhaustive list of additional modules that use
 AnyEvent and can therefore be mixed easily with other AnyEvent modules
 =item L<AnyEvent::Util>
 Contains various utility functions that replace often-used but blocking
 functions such as C<inet_aton> by event-/callback-based versions.
+=item L<AnyEvent::Socket>
+Provides various utility functions for (internet protocol) sockets,
+addresses and name resolution. Also functions to create non-blocking tcp
+connections or tcp servers, with IPv6 and SRV record support and more.
 =item L<AnyEvent::Handle>
-Provide read and write buffers and manages watchers for reads and writes.
+Provide read and write buffers, manages watchers for reads and writes,
+supports raw and formatted I/O, I/O queued and fully transparent and
+non-blocking SSL/TLS.
+=item L<AnyEvent::DNS>
+Provides rich asynchronous DNS resolver capabilities.
+=item L<AnyEvent::HTTP>
+A simple-to-use HTTP library that is capable of making a lot of concurrent
+HTTP requests.
 =item L<AnyEvent::HTTPD>
 Provides a simple web application server framework.
-=item L<AnyEvent::DNS>
-Provides asynchronous DNS resolver capabilities, beyond what
-L<AnyEvent::Util> offers.
 =item L<AnyEvent::FastPing>
 The fastest ping in the west.
+=item L<AnyEvent::DBI>
+Executes L<DBI> requests asynchronously in a proxy process.
+=item L<AnyEvent::AIO>
+Truly asynchronous I/O, should be in the toolbox of every event
+programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
+together.
+=item L<AnyEvent::BDB>
+Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
+L<BDB> and AnyEvent together.
+=item L<AnyEvent::GPSD>
+A non-blocking interface to gpsd, a daemon delivering GPS information.
+=item L<AnyEvent::IGS>
+A non-blocking interface to the Internet Go Server protocol (used by
+L<App::IGS>).
 =item L<Net::IRC3>
 AnyEvent based IRC client module family.
 =item L<Coro>
 Has special support for AnyEvent via L<Coro::AnyEvent>.
-=item L<AnyEvent::AIO>, L<IO::AIO>
-Truly asynchronous I/O, should be in the toolbox of every event
-programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
-together.
-=item L<AnyEvent::BDB>, L<BDB>
-Truly asynchronous Berkeley DB access. AnyEvent::AIO transparently fuses
-IO::AIO and AnyEvent together.
 =item L<IO::Lambda>
 The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
 =back
 no warnings;
 use strict;
 use Carp;
-our $VERSION = '3.6';
+our $VERSION = 4.2;
 our $MODEL;
 our $AUTOLOAD;
 our @ISA;
+our @REGISTRY;
+our $WIN32;
+BEGIN {
+   my $win32 = ! ! ($^O =~ /mswin32/i);
+   eval "sub WIN32(){ $win32 }";
+}
 our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
-our @REGISTRY;
+our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
+{
+   my $idx;
+   $PROTOCOL{$_} = ++$idx
+      for reverse split /\s*,\s*/,
+             $ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
+}
 my @models = (
    [EV::                   => AnyEvent::Impl::EV::],
    [Event::                => AnyEvent::Impl::Event::],
-   [Tk::                   => AnyEvent::Impl::Tk::],
-   [Wx::                   => AnyEvent::Impl::POE::],
-   [Prima::                => AnyEvent::Impl::POE::],
    [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
-   # everything below here will not be autoprobed as the pureperl backend should work everywhere
+   # everything below here will not be autoprobed
-   [Glib::                 => AnyEvent::Impl::Glib::],
+   # as the pureperl backend should work everywhere
+   # and is usually faster
+   [Tk::                   => AnyEvent::Impl::Tk::],       # crashes with many handles
+   [Glib::                 => AnyEvent::Impl::Glib::],     # becomes extremely slow with many watchers
    [Event::Lib::           => AnyEvent::Impl::EventLib::], # too buggy
    [Qt::                   => AnyEvent::Impl::Qt::],       # requires special main program
    [POE::Kernel::          => AnyEvent::Impl::POE::],      # lasciate ogni speranza
+   [Wx::                   => AnyEvent::Impl::POE::],
+   [Prima::                => AnyEvent::Impl::POE::],
 );
-our %method = map +($_ => 1), qw(io timer signal child condvar one_event DESTROY);
+our %method = map +($_ => 1), qw(io timer time now signal child condvar one_event DESTROY);
 our @post_detect;
 sub post_detect(&) {
    my ($cb) = @_;
 }
 sub detect() {
    unless ($MODEL) {
       no strict 'refs';
+      local $SIG{__DIE__};
       if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
          my $model = "AnyEvent::Impl::$1";
          if (eval "require $model") {
             $MODEL = $model;
    $class->$func (@_);
 }
 package AnyEvent::Base;
+# default implementation for now and time
+use Time::HiRes ();
+sub time { Time::HiRes::time }
+sub now  { Time::HiRes::time }
 # default implementation for ->condvar
 sub condvar {
-   bless {}, AnyEvent::CondVar::
+   bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, AnyEvent::CondVar::
 }
 # default implementation for ->signal
 our %SIG_CB;
 sub AnyEvent::Base::Signal::DESTROY {
    my ($signal, $cb) = @{$_[0]};
    delete $SIG_CB{$signal}{$cb};
-   $SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };
+   delete $SIG{$signal} unless keys %{ $SIG_CB{$signal} };
 }
 # default implementation for ->child
 our %PID_CB;
       or Carp::croak "required option 'pid' is missing";
    $PID_CB{$pid}{$arg{cb}} = $arg{cb};
    unless ($WNOHANG) {
-      $WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;
+      $WNOHANG = eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
    }
    unless ($CHLD_W) {
       $CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
       # child could be a zombie already, so make at least one round
 our @ISA = AnyEvent::CondVar::Base::;
 package AnyEvent::CondVar::Base;
+use overload
+   '&{}'    => sub { my $self = shift; sub { $self->send (@_) } },
+   fallback => 1;
 sub _send {
    # nop
 }
 sub send {
    $_[0]{_ae_end_cb} = $_[1] if @_ > 1;
 }
 sub end {
    return if --$_[0]{_ae_counter};
-   &{ $_[0]{_ae_end_cb} } if $_[0]{_ae_end_cb};
+   &{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
 }
 # undocumented/compatibility with pre-3.4
 *broadcast = \&send;
 *wait      = \&_wait;
 model it chooses.
 =item C<PERL_ANYEVENT_MODEL>
 This can be used to specify the event model to be used by AnyEvent, before
-autodetection and -probing kicks in. It must be a string consisting
+auto detection and -probing kicks in. It must be a string consisting
 entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
 and the resulting module name is loaded and if the load was successful,
 used as event model. If it fails to load AnyEvent will proceed with
-autodetection and -probing.
+auto detection and -probing.
 This functionality might change in future versions.
 For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
 could start your program like this:
-  PERL_ANYEVENT_MODEL=Perl perl ...
+   PERL_ANYEVENT_MODEL=Perl perl ...
+=item C<PERL_ANYEVENT_PROTOCOLS>
+Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
+for IPv4 or IPv6. The default is unspecified (and might change, or be the result
+of auto probing).
+Must be set to a comma-separated list of protocols or address families,
+current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
+used, and preference will be given to protocols mentioned earlier in the
+list.
+This variable can effectively be used for denial-of-service attacks
+against local programs (e.g. when setuid), although the impact is likely
+small, as the program has to handle connection errors already-
+Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
+but support both and try to use both.  C<PERL_ANYEVENT_PROTOCOLS=ipv4>
+- only support IPv4, never try to resolve or contact IPv6
+addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
+IPv6, but prefer IPv6 over IPv4.
+=item C<PERL_ANYEVENT_EDNS0>
+Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
+for DNS. This extension is generally useful to reduce DNS traffic, but
+some (broken) firewalls drop such DNS packets, which is why it is off by
+default.
+Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
+EDNS0 in its DNS requests.
+=item C<PERL_ANYEVENT_MAX_FORKS>
+The maximum number of child processes that C<AnyEvent::Util::fork_call>
+will create in parallel.
 =back
 =head1 EXAMPLE PROGRAM
    syswrite $txn->{fh}, $txn->{request}
       or die "connection or write error";
    $txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
 Again, C<fh_ready_r> waits till all data has arrived, and then stores the
-result and signals any possible waiters that the request ahs finished:
+result and signals any possible waiters that the request has finished:
    sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
    if (end-of-file or data complete) {
      $txn->{result} = $txn->{buf};
    $txn->{finished}->recv;
    return $txn->{result};
 The actual code goes further and collects all errors (C<die>s, exceptions)
-that occured during request processing. The C<result> method detects
+that occurred during request processing. The C<result> method detects
 whether an exception as thrown (it is stored inside the $txn object)
 and just throws the exception, which means connection errors and other
 problems get reported tot he code that tries to use the result, not in a
 random callback.
 of various event loops I prepared some benchmarks.
 =head2 BENCHMARKING ANYEVENT OVERHEAD
 Here is a benchmark of various supported event models used natively and
-through anyevent. The benchmark creates a lot of timers (with a zero
+through AnyEvent. The benchmark creates a lot of timers (with a zero
 timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
 which it is), lets them fire exactly once and destroys them again.
 Source code for this benchmark is found as F<eg/bench> in the AnyEvent
 distribution.
 =back
 =head2 BENCHMARKING THE LARGE SERVER CASE
-This benchmark atcually benchmarks the event loop itself. It works by
+This benchmark actually benchmarks the event loop itself. It works by
-creating a number of "servers": each server consists of a socketpair, a
+creating a number of "servers": each server consists of a socket pair, a
 timeout watcher that gets reset on activity (but never fires), and an I/O
 watcher waiting for input on one side of the socket. Each time the socket
 watcher reads a byte it will write that byte to a random other "server".
 The effect is that there will be a lot of I/O watchers, only part of which
 are active at any one point (so there is a constant number of active
-fds for each loop iterstaion, but which fds these are is random). The
+fds for each loop iteration, but which fds these are is random). The
 timeout is reset each time something is read because that reflects how
 most timeouts work (and puts extra pressure on the event loops).
-In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100
+In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
 (1%) are active. This mirrors the activity of large servers with many
 connections, most of which are idle at any one point in time.
 Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
 distribution.
 =head3 Explanation of the columns
 I<sockets> is the number of sockets, and twice the number of "servers" (as
 each server has a read and write socket end).
-I<create> is the time it takes to create a socketpair (which is
+I<create> is the time it takes to create a socket pair (which is
 nontrivial) and two watchers: an I/O watcher and a timeout watcher.
 I<request>, the most important value, is the time it takes to handle a
 single "request", that is, reading the token from the pipe and forwarding
 it to another server. This includes deleting the old timeout and creating
 speed most when you have lots of watchers, not when you only have a few of
 them).
 EV is again fastest.
-Perl again comes second. It is noticably faster than the C-based event
+Perl again comes second. It is noticeably faster than the C-based event
 loops Event and Glib, although the difference is too small to really
 matter.
 POE also performs much better in this case, but is is still far behind the
 others.
 specified in the variable.
 You can make AnyEvent completely ignore this variable by deleting it
 before the first watcher gets created, e.g. with a C<BEGIN> block:
-  BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
+   BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
-  use AnyEvent;
+   use AnyEvent;
 Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
 be used to probe what backend is used and gain other information (which is
 probably even less useful to an attacker than PERL_ANYEVENT_MODEL).
+=head1 BUGS
+Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
+to work around. If you suffer from memleaks, first upgrade to Perl 5.10
+and check wether the leaks still show up. (Perl 5.10.0 has other annoying
+mamleaks, such as leaking on C<map> and C<grep> but it is usually not as
+pronounced).
 =head1 SEE ALSO
+Utility functions: L<AnyEvent::Util>.
 Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
 L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
 Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
 L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
 L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
 L<AnyEvent::Impl::POE>.
+Non-blocking file handles, sockets, TCP clients and
+servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>.
 Asynchronous DNS: L<AnyEvent::DNS>.
 Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,
-Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.
+Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>, L<AnyEvent::DNS>.
 =head1 AUTHOR
- Marc Lehmann <schmorp@schmorp.de>
+   Marc Lehmann <schmorp@schmorp.de>
- http://home.schmorp.de/
+   http://home.schmorp.de/
 =cut
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Revision 1.123 by root, Fri May 23 20:41:25 2008 UTC vs.
Revision 1.165 by root, Tue Jul 8 23:07:26 2008 UTC