| 1 |
=head1 NAME |
| 2 |
|
| 3 |
AnyEvent - provide framework for multiple event loops |
| 4 |
|
| 5 |
Event, Coro, Glib, Tk, Perl - various supported event loops |
| 6 |
|
| 7 |
=head1 SYNOPSIS |
| 8 |
|
| 9 |
use AnyEvent; |
| 10 |
|
| 11 |
my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub { |
| 12 |
... |
| 13 |
}); |
| 14 |
|
| 15 |
my $w = AnyEvent->timer (after => $seconds, cb => sub { |
| 16 |
... |
| 17 |
}); |
| 18 |
|
| 19 |
my $w = AnyEvent->condvar; # stores wether a condition was flagged |
| 20 |
$w->wait; # enters "main loop" till $condvar gets ->broadcast |
| 21 |
$w->broadcast; # wake up current and all future wait's |
| 22 |
|
| 23 |
=head1 DESCRIPTION |
| 24 |
|
| 25 |
L<AnyEvent> provides an identical interface to multiple event loops. This |
| 26 |
allows module authors to utilise an event loop without forcing module |
| 27 |
users to use the same event loop (as only a single event loop can coexist |
| 28 |
peacefully at any one time). |
| 29 |
|
| 30 |
The interface itself is vaguely similar but not identical to the Event |
| 31 |
module. |
| 32 |
|
| 33 |
On the first call of any method, the module tries to detect the currently |
| 34 |
loaded event loop by probing wether any of the following modules is |
| 35 |
loaded: L<Coro::Event>, L<Event>, L<Glib>, L<Tk>. The first one found is |
| 36 |
used. If none is found, the module tries to load these modules in the |
| 37 |
order given. The first one that could be successfully loaded will be |
| 38 |
used. If still none could be found, AnyEvent will fall back to a pure-perl |
| 39 |
event loop, which is also not very efficient. |
| 40 |
|
| 41 |
Because AnyEvent first checks for modules that are already loaded, loading |
| 42 |
an Event model explicitly before first using AnyEvent will likely make |
| 43 |
that model the default. For example: |
| 44 |
|
| 45 |
use Tk; |
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use AnyEvent; |
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|
| 48 |
# .. AnyEvent will likely default to Tk |
| 49 |
|
| 50 |
The pure-perl implementation of AnyEvent is called |
| 51 |
C<AnyEvent::Impl::Perl>. Like other event modules you can load it |
| 52 |
explicitly. |
| 53 |
|
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=head1 WATCHERS |
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|
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AnyEvent has the central concept of a I<watcher>, which is an object that |
| 57 |
stores relevant data for each kind of event you are waiting for, such as |
| 58 |
the callback to call, the filehandle to watch, etc. |
| 59 |
|
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These watchers are normal Perl objects with normal Perl lifetime. After |
| 61 |
creating a watcher it will immediately "watch" for events and invoke |
| 62 |
the callback. To disable the watcher you have to destroy it (e.g. by |
| 63 |
setting the variable that stores it to C<undef> or otherwise deleting all |
| 64 |
references to it). |
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|
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All watchers are created by calling a method on the C<AnyEvent> class. |
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|
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=head2 IO WATCHERS |
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|
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You can create I/O watcher by calling the C<< AnyEvent->io >> method with |
| 71 |
the following mandatory arguments: |
| 72 |
|
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C<fh> the Perl I<filehandle> (not filedescriptor) to watch for |
| 74 |
events. C<poll> must be a string that is either C<r> or C<w>, that creates |
| 75 |
a watcher waiting for "r"eadable or "w"ritable events. C<cb> teh callback |
| 76 |
to invoke everytime the filehandle becomes ready. |
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|
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Only one io watcher per C<fh> and C<poll> combination is allowed (i.e. on |
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a socket you can have one r + one w, not any more (limitation comes from |
| 80 |
Tk - if you are sure you are not using Tk this limitation is gone). |
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|
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Filehandles will be kept alive, so as long as the watcher exists, the |
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filehandle exists, too. |
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|
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Example: |
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|
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# wait for readability of STDIN, then read a line and disable the watcher |
| 88 |
my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { |
| 89 |
chomp (my $input = <STDIN>); |
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warn "read: $input\n"; |
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undef $w; |
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}); |
| 93 |
|
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=head2 TIMER WATCHERS |
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|
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You can create a timer watcher by calling the C<< AnyEvent->timer >> |
| 97 |
method with the following mandatory arguments: |
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|
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C<after> after how many seconds (fractions are supported) should the timer |
| 100 |
activate. C<cb> the callback to invoke. |
| 101 |
|
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The timer callback will be invoked at most once: if you want a repeating |
| 103 |
timer you have to create a new watcher (this is a limitation by both Tk |
| 104 |
and Glib). |
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|
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Example: |
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|
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# fire an event after 7.7 seconds |
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my $w = AnyEvent->timer (after => 7.7, cb => sub { |
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warn "timeout\n"; |
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}); |
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|
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# to cancel the timer: |
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undef $w |
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|
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=head2 CONDITION WATCHERS |
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|
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Condition watchers can be created by calling the C<< AnyEvent->condvar >> |
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method without any arguments. |
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|
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A condition watcher watches for a condition - precisely that the C<< |
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->broadcast >> method has been called. |
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|
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The watcher has only two methods: |
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|
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=over 4 |
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|
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=item $cv->wait |
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|
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Wait (blocking if necessary) until the C<< ->broadcast >> method has been |
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called on c<$cv>, while servicing other watchers normally. |
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|
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Not all event models support a blocking wait - some die in that case, so |
| 134 |
if you are using this from a module, never require a blocking wait, but |
| 135 |
let the caller decide wether the call will block or not (for example, |
| 136 |
by coupling condition variables with some kind of request results and |
| 137 |
supporting callbacks so the caller knows that getting the result will not |
| 138 |
block, while still suppporting blockign waits if the caller so desires). |
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|
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You can only wait once on a condition - additional calls will return |
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immediately. |
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|
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=item $cv->broadcast |
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|
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Flag the condition as ready - a running C<< ->wait >> and all further |
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calls to C<wait> will return after this method has been called. If nobody |
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is waiting the broadcast will be remembered.. |
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|
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Example: |
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|
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# wait till the result is ready |
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my $result_ready = AnyEvent->condvar; |
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|
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# do something such as adding a timer |
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# or socket watcher the calls $result_ready->broadcast |
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# when the "result" is ready. |
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|
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$result_ready->wait; |
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|
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=back |
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|
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=head1 WHAT TO DO IN A MODULE |
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|
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As a module author, you should "use AnyEvent" and call AnyEvent methods |
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freely, but you should not load a specific event module or rely on it. |
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|
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Be careful when you create watchers in the module body - Anyevent will |
| 168 |
decide which event module to use as soon as the first method is called, so |
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by calling AnyEvent in your module body you force the user of your module |
| 170 |
to load the event module first. |
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|
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=head1 WHAT TO DO IN THE MAIN PROGRAM |
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|
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There will always be a single main program - the only place that should |
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dictate which event model to use. |
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|
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If it doesn't care, it can just "use AnyEvent" and use it itself, or not |
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do anything special and let AnyEvent decide which implementation to chose. |
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|
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If the main program relies on a specific event model (for example, in Gtk2 |
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programs you have to rely on either Glib or Glib::Event), you should load |
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it before loading AnyEvent or any module that uses it, generally, as early |
| 183 |
as possible. The reason is that modules might create watchers when they |
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are loaded, and AnyEvent will decide on the event model to use as soon as |
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it creates watchers, and it might chose the wrong one unless you load the |
| 186 |
correct one yourself. |
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|
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You can chose to use a rather inefficient pure-perl implementation by |
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loading the C<AnyEvent::Impl::Perl> module, but letting AnyEvent chose is |
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generally better. |
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|
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=cut |
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|
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package AnyEvent; |
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|
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no warnings; |
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use strict 'vars'; |
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use Carp; |
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|
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our $VERSION = '2.0'; |
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our $MODEL; |
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|
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our $AUTOLOAD; |
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our @ISA; |
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|
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our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1; |
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|
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our @REGISTRY; |
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|
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my @models = ( |
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[Coro::Event:: => AnyEvent::Impl::Coro::], |
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[Event:: => AnyEvent::Impl::Event::], |
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[Glib:: => AnyEvent::Impl::Glib::], |
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[Tk:: => AnyEvent::Impl::Tk::], |
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[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::], |
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); |
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|
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our %method = map +($_ => 1), qw(io timer condvar broadcast wait DESTROY); |
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|
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sub AUTOLOAD { |
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$AUTOLOAD =~ s/.*://; |
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|
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$method{$AUTOLOAD} |
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or croak "$AUTOLOAD: not a valid method for AnyEvent objects"; |
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|
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unless ($MODEL) { |
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# check for already loaded models |
| 228 |
for (@REGISTRY, @models) { |
| 229 |
my ($package, $model) = @$_; |
| 230 |
if (${"$package\::VERSION"} > 0) { |
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if (eval "require $model") { |
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$MODEL = $model; |
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warn "AnyEvent: found model '$model', using it.\n" if $verbose > 1; |
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last; |
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} |
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} |
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} |
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|
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unless ($MODEL) { |
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# try to load a model |
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|
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for (@REGISTRY, @models) { |
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my ($package, $model) = @$_; |
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if (eval "require $model") { |
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$MODEL = $model; |
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warn "AnyEvent: autoprobed and loaded model '$model', using it.\n" if $verbose > 1; |
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last; |
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} |
| 249 |
} |
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|
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$MODEL |
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or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: Coro, Event, Glib or Tk."; |
| 253 |
} |
| 254 |
} |
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|
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@ISA = $MODEL; |
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|
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my $class = shift; |
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$class->$AUTOLOAD (@_); |
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} |
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|
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=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE |
| 263 |
|
| 264 |
If you need to support another event library which isn't directly |
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supported by AnyEvent, you can supply your own interface to it by |
| 266 |
pushing, before the first watcher gets created, the package name of |
| 267 |
the event module and the package name of the interface to use onto |
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C<@AnyEvent::REGISTRY>. You can do that before and even without loading |
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AnyEvent. |
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|
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Example: |
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|
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push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::]; |
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|
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This tells AnyEvent to (literally) use the C<urxvt::anyevent::> |
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package/class when it finds the C<urxvt> package/module is loaded. When |
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AnyEvent is loaded and asked to find a suitable event model, it will |
| 278 |
first check for the presence of urxvt. |
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|
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The class should prove implementations for all watcher types (see |
| 281 |
L<AnyEvent::Impl::Event> (source code), L<AnyEvent::Impl::Glib> |
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(Source code) and so on for actual examples, use C<perldoc -m |
| 283 |
AnyEvent::Impl::Glib> to see the sources). |
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|
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The above isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt) |
| 286 |
uses the above line as-is. An interface isn't included in AnyEvent |
| 287 |
because it doesn't make sense outside the embedded interpreter inside |
| 288 |
I<rxvt-unicode>, and it is updated and maintained as part of the |
| 289 |
I<rxvt-unicode> distribution. |
| 290 |
|
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I<rxvt-unicode> also cheats a bit by not providing blocking access to |
| 292 |
condition variables: code blocking while waiting for a condition will |
| 293 |
C<die>. This still works with most modules/usages, and blocking calls must |
| 294 |
not be in an interactive appliation, so it makes sense. |
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|
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=head1 ENVIRONMENT VARIABLES |
| 297 |
|
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The following environment variables are used by this module: |
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|
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C<PERL_ANYEVENT_VERBOSE> when set to C<2> or higher, reports which event |
| 301 |
model gets used. |
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|
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=head1 EXAMPLE |
| 304 |
|
| 305 |
The following program uses an io watcher to read data from stdin, a timer |
| 306 |
to display a message once per second, and a condvar to exit the program |
| 307 |
when the user enters quit: |
| 308 |
|
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use AnyEvent; |
| 310 |
|
| 311 |
my $cv = AnyEvent->condvar; |
| 312 |
|
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my $io_watcher = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { |
| 314 |
warn "io event <$_[0]>\n"; # will always output <r> |
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chomp (my $input = <STDIN>); # read a line |
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warn "read: $input\n"; # output what has been read |
| 317 |
$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i |
| 318 |
}); |
| 319 |
|
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my $time_watcher; # can only be used once |
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|
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sub new_timer { |
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$timer = AnyEvent->timer (after => 1, cb => sub { |
| 324 |
warn "timeout\n"; # print 'timeout' about every second |
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&new_timer; # and restart the time |
| 326 |
}); |
| 327 |
} |
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|
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new_timer; # create first timer |
| 330 |
|
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$cv->wait; # wait until user enters /^q/i |
| 332 |
|
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=head1 REAL-WORLD EXAMPLE |
| 334 |
|
| 335 |
Consider the L<Net::FCP> module. It features (among others) the following |
| 336 |
API calls, which are to freenet what HTTP GET requests are to http: |
| 337 |
|
| 338 |
my $data = $fcp->client_get ($url); # blocks |
| 339 |
|
| 340 |
my $transaction = $fcp->txn_client_get ($url); # does not block |
| 341 |
$transaction->cb ( sub { ... } ); # set optional result callback |
| 342 |
my $data = $transaction->result; # possibly blocks |
| 343 |
|
| 344 |
The C<client_get> method works like C<LWP::Simple::get>: it requests the |
| 345 |
given URL and waits till the data has arrived. It is defined to be: |
| 346 |
|
| 347 |
sub client_get { $_[0]->txn_client_get ($_[1])->result } |
| 348 |
|
| 349 |
And in fact is automatically generated. This is the blocking API of |
| 350 |
L<Net::FCP>, and it works as simple as in any other, similar, module. |
| 351 |
|
| 352 |
More complicated is C<txn_client_get>: It only creates a transaction |
| 353 |
(completion, result, ...) object and initiates the transaction. |
| 354 |
|
| 355 |
my $txn = bless { }, Net::FCP::Txn::; |
| 356 |
|
| 357 |
It also creates a condition variable that is used to signal the completion |
| 358 |
of the request: |
| 359 |
|
| 360 |
$txn->{finished} = AnyAvent->condvar; |
| 361 |
|
| 362 |
It then creates a socket in non-blocking mode. |
| 363 |
|
| 364 |
socket $txn->{fh}, ...; |
| 365 |
fcntl $txn->{fh}, F_SETFL, O_NONBLOCK; |
| 366 |
connect $txn->{fh}, ... |
| 367 |
and !$!{EWOULDBLOCK} |
| 368 |
and !$!{EINPROGRESS} |
| 369 |
and Carp::croak "unable to connect: $!\n"; |
| 370 |
|
| 371 |
Then it creates a write-watcher which gets called whenever an error occurs |
| 372 |
or the connection succeeds: |
| 373 |
|
| 374 |
$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'w', cb => sub { $txn->fh_ready_w }); |
| 375 |
|
| 376 |
And returns this transaction object. The C<fh_ready_w> callback gets |
| 377 |
called as soon as the event loop detects that the socket is ready for |
| 378 |
writing. |
| 379 |
|
| 380 |
The C<fh_ready_w> method makes the socket blocking again, writes the |
| 381 |
request data and replaces the watcher by a read watcher (waiting for reply |
| 382 |
data). The actual code is more complicated, but that doesn't matter for |
| 383 |
this example: |
| 384 |
|
| 385 |
fcntl $txn->{fh}, F_SETFL, 0; |
| 386 |
syswrite $txn->{fh}, $txn->{request} |
| 387 |
or die "connection or write error"; |
| 388 |
$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r }); |
| 389 |
|
| 390 |
Again, C<fh_ready_r> waits till all data has arrived, and then stores the |
| 391 |
result and signals any possible waiters that the request ahs finished: |
| 392 |
|
| 393 |
sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf}; |
| 394 |
|
| 395 |
if (end-of-file or data complete) { |
| 396 |
$txn->{result} = $txn->{buf}; |
| 397 |
$txn->{finished}->broadcast; |
| 398 |
$txb->{cb}->($txn) of $txn->{cb}; # also call callback |
| 399 |
} |
| 400 |
|
| 401 |
The C<result> method, finally, just waits for the finished signal (if the |
| 402 |
request was already finished, it doesn't wait, of course, and returns the |
| 403 |
data: |
| 404 |
|
| 405 |
$txn->{finished}->wait; |
| 406 |
return $txn->{result}; |
| 407 |
|
| 408 |
The actual code goes further and collects all errors (C<die>s, exceptions) |
| 409 |
that occured during request processing. The C<result> method detects |
| 410 |
wether an exception as thrown (it is stored inside the $txn object) |
| 411 |
and just throws the exception, which means connection errors and other |
| 412 |
problems get reported tot he code that tries to use the result, not in a |
| 413 |
random callback. |
| 414 |
|
| 415 |
All of this enables the following usage styles: |
| 416 |
|
| 417 |
1. Blocking: |
| 418 |
|
| 419 |
my $data = $fcp->client_get ($url); |
| 420 |
|
| 421 |
2. Blocking, but parallelizing: |
| 422 |
|
| 423 |
my @datas = map $_->result, |
| 424 |
map $fcp->txn_client_get ($_), |
| 425 |
@urls; |
| 426 |
|
| 427 |
Both blocking examples work without the module user having to know |
| 428 |
anything about events. |
| 429 |
|
| 430 |
3a. Event-based in a main program, using any support Event module: |
| 431 |
|
| 432 |
use Event; |
| 433 |
|
| 434 |
$fcp->txn_client_get ($url)->cb (sub { |
| 435 |
my $txn = shift; |
| 436 |
my $data = $txn->result; |
| 437 |
... |
| 438 |
}); |
| 439 |
|
| 440 |
Event::loop; |
| 441 |
|
| 442 |
3b. The module user could use AnyEvent, too: |
| 443 |
|
| 444 |
use AnyEvent; |
| 445 |
|
| 446 |
my $quit = AnyEvent->condvar; |
| 447 |
|
| 448 |
$fcp->txn_client_get ($url)->cb (sub { |
| 449 |
... |
| 450 |
$quit->broadcast; |
| 451 |
}); |
| 452 |
|
| 453 |
$quit->wait; |
| 454 |
|
| 455 |
=head1 SEE ALSO |
| 456 |
|
| 457 |
Event modules: L<Coro::Event>, L<Coro>, L<Event>, L<Glib::Event>, L<Glib>. |
| 458 |
|
| 459 |
Implementations: L<AnyEvent::Impl::Coro>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>. |
| 460 |
|
| 461 |
Nontrivial usage example: L<Net::FCP>. |
| 462 |
|
| 463 |
=head1 |
| 464 |
|
| 465 |
=cut |
| 466 |
|
| 467 |
1 |
| 468 |
|
