Asynchronous programming with AnyEvent

Asynchronous Event programming with AnyEvent Tatsuhiko Miyagawa YAPC::Asia 2009

Questions: Are you familiar with Event loops?

Questions: Have you used POE?

Intro Basics Examples Tips

AnyEvent Intro

“DBI of event loops”

(Used in Remedie!)

Event loops on CPAN

POE IO::Async Danga::Socket IO::Lambda Event Event::Lib EV Glib Qt Tk ...

Incompatible APIs

Different Styles

#!/usr/bin/perl use POE; POE::Session->create( inline_states => { _start => sub { $_[HEAP]->{count} = 0; $_[KERNEL]->yield(‘incr’); }, incr => sub { warn $_[HEAP]->{count}++; $_[KERNEL]->yield(‘incr’); }, } ); POE::Kernel->run

use IO::Async::Loop; use IO::Async::Stream; use Socket qw( SOCK_STREAM ); my $loop = IO::Async::Loop->new; $loop->connect( host => “example.com”, service => 80, socktype => SOCK_STREAM, on_connected => sub { my $socket = shift; ... } ); $loop->loop_forever;

More important:

CPAN Modules

POE::Components on CPAN

POE::Component::* don’t work with IO::Async etc.

AnyEvent::Impl::*

AnyEvent code can work under “Any Event” loops

#!/usr/bin/perl use POE; use AnyEvent; POE::Session->create( inline_states => { ... } ); my $w = AnyEvent->timer( after => 0, cb => sub { ... } ); POE::Kernel->run; # Just works

AnyEvent modules: 35

CPAN authors: Stop writing PoCos :)

#!/usr/bin/perl use AnyEvent; my $i; my $cv = AnyEvent->condvar; my $w = AnyEvent->timer( after => 0, interval => 1, cb => sub { warn “checking “, $i++; $cv->send() if $i > 10; } ); $cv->recv;

Timer Watcher condvar I/O subprocess modules

my $t1 = AnyEvent->timer( after => 0, cb => sub { # ... } ); my $t2 = AnyEvent->timer( after => 0, interval => 3, cb => sub { # ... } );

my $cv = AnyEvent->condvar; my $w = AnyEvent->timer( after => 5, cb => sub { $cv->send(“DONE”); }, ); my $r = $cv->recv; # $r = ‘DONE’

my $io = AnyEvent->io( fh => *STDIN, poll => ‘r’, cb => sub { # $fh is ready to read my $line = <$fh>; # scalar! } );

use AnyEvent::Handle; my $hd; $hd = AnyEvent::Handle->new( fh => $fh, ); $hd->push_read(line => sub { my($hd, $line) = @_; }); $hd->push_read(chunk => 8, sub { my($hd, $bytes) = @_; }); $hd->push_read(json => sub { my($hd, $obj) = @_; });

use AnyEvent::Socket; tcp_connect $host, $port, sub { my $fh = shift or die “FAIL”; my $hd = AnyEvent::Handle->new( fh => $fh, ); $hd->push_read(json => sub { my($hd2, $obj) = @_; }); };

use AnyEvent::HTTP; http_get “http://google.com/”, sub { my($body, $header) = @_; # $header->{Status}; # $header->{‘content-type’}; };

AnyEvent::Twitter::Stream

Twitter Streaming API aka Firehose

use AnyEvent::Twitter::Stream; my $cv = AnyEvent->condvar; my $s = AnyEvent::Twitter::Stream->new( username => $user, password => $pass, method => ‘filter’, track => ‘#yapc,#yapcasia2009’, on_tweet => sub { my $tweet = shift; printf “%s:%sn”, $tweet->{user}{screen_name}, $tweet->{text}; }, on_eof => $cv, ); $cv->recv;

AnyEvent::ReverseHTTP

client becomes server server becomes client

Polling HTTP GET with AnyEvent::HTTP

use AnyEvent::ReverseHTTP; my $guard = reverse_http $hostname, $token, sub { my $req = shift; return “Hello World”; }; AnyEvent->condvar->recv;

Condvars

Transactions (multi signals)

Parallel downloads with AnyEvent::HTTP

use AnyEvent::HTTP; my $cv = AnyEvent->condvar; for my $i (1..3) { $cv->begin; http_get "http://search.cpan.org/ search?q=$i", sub { my $body = shift; warn length $body; $cv->end; }; } $cv->recv;

Scope of watchers

for (1..10) { my $w = AnyEvent->timer( after => 1, cb => sub { ... } ); } AnyEvent->condvar->recv;

for (1..10) { my $w = AnyEvent->timer( after => 1, cb => sub { ... } ); # $w goes out of scope! } AnyEvent->condvar->recv;

for (1..10) { my $w; $w = AnyEvent->timer( after => 1, cb => sub { ... undef $w; } ); } AnyEvent->condvar->recv;

multiple condvars waiting

You can’t call ->recv on multiple $cv

USe $cv->cb() instead

for (1..10) { my $cv = AnyEvent->condvar; my $w; $w = AnyEvent->timer( after => 1, cb => sub { $w; $cv->send }, ); $cv->recv; # blocks }

for (1..10) { my $cv = AnyEvent->condvar; my $w; $w = AnyEvent->timer( after => 1, cb => sub { $w; $cv->send($v) }, ); $cv->cb(sub { my $v = $cv->recv; ... }); }

Or: use Coro::AnyEvent

CPAN authors:

Write a simple callback API

use AnyEvent::mDNS; my $cv = AnyEvent->condvar; # $cv can be called as a callbak my $g = AnyEvent::mDNS::discover ‘_daap._tcp’, $cv; my @itunes = $cv->recv;

Use guard { } to cleanup

use AnyEvent::ReverseHTTP; { my $guard = reverse_http $h, $t, sub { my $req = shift; }; # ... }

Beware of circular references (Scalar::Util::weaken)

API to pass/return condvar for better control by users

use AnyEvent::ReverseHTTP; my $guard = reverse_http $h, $t, sub { my $req = shift; my $cv = AnyEvent->condvar; my $t; $t = AnyEvent->timer( after => 5, cb => sub { my $res = HTTP::Response->new; undef $t; $cv->send($res); } }; return $cv; };

New AE API

use AnyEvent; my $t = AE::timer 0, 1, $cb; my $w = AE::io $fh, $write, $cb; my $cv = AE::cv;

Summary

AnyEvent Very useful Nice utilities No bloated POE stuff

Questions?

Thank you.

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Asynchronous programming with AnyEvent

by Tatsuhiko Miyagawa

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