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NAME |
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AnyEvent - the DBI of event loop programming |
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|
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EV, Event, Glib, Tk, Perl, Event::Lib, Irssi, rxvt-unicode, IO::Async, |
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Qt and POE are various supported event loops/environments. |
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SYNOPSIS |
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use AnyEvent; |
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|
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# file descriptor readable |
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my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... }); |
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|
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# one-shot or repeating timers |
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my $w = AnyEvent->timer (after => $seconds, cb => sub { ... }); |
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my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ... |
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print AnyEvent->now; # prints current event loop time |
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print AnyEvent->time; # think Time::HiRes::time or simply CORE::time. |
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# POSIX signal |
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my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... }); |
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|
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# child process exit |
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my $w = AnyEvent->child (pid => $pid, cb => sub { |
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my ($pid, $status) = @_; |
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... |
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}); |
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# called when event loop idle (if applicable) |
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my $w = AnyEvent->idle (cb => sub { ... }); |
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my $w = AnyEvent->condvar; # stores whether a condition was flagged |
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$w->send; # wake up current and all future recv's |
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$w->recv; # enters "main loop" till $condvar gets ->send |
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# use a condvar in callback mode: |
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$w->cb (sub { $_[0]->recv }); |
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|
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INTRODUCTION/TUTORIAL |
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This manpage is mainly a reference manual. If you are interested in a |
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tutorial or some gentle introduction, have a look at the AnyEvent::Intro |
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manpage. |
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SUPPORT |
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There is a mailinglist for discussing all things AnyEvent, and an IRC |
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channel, too. |
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See the AnyEvent project page at the Schmorpforge Ta-Sa Software |
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Repository, at <http://anyevent.schmorp.de>, for more info. |
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|
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WHY YOU SHOULD USE THIS MODULE (OR NOT) |
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Glib, POE, IO::Async, Event... CPAN offers event models by the dozen |
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nowadays. So what is different about AnyEvent? |
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Executive Summary: AnyEvent is *compatible*, AnyEvent is *free of |
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policy* and AnyEvent is *small and efficient*. |
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First and foremost, *AnyEvent is not an event model* itself, it only |
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interfaces to whatever event model the main program happens to use, in a |
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pragmatic way. For event models and certain classes of immortals alike, |
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the statement "there can only be one" is a bitter reality: In general, |
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only one event loop can be active at the same time in a process. |
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AnyEvent cannot change this, but it can hide the differences between |
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those event loops. |
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The goal of AnyEvent is to offer module authors the ability to do event |
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programming (waiting for I/O or timer events) without subscribing to a |
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religion, a way of living, and most importantly: without forcing your |
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module users into the same thing by forcing them to use the same event |
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model you use. |
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For modules like POE or IO::Async (which is a total misnomer as it is |
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actually doing all I/O *synchronously*...), using them in your module is |
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like joining a cult: After you joined, you are dependent on them and you |
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cannot use anything else, as they are simply incompatible to everything |
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that isn't them. What's worse, all the potential users of your module |
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are *also* forced to use the same event loop you use. |
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AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works |
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fine. AnyEvent + Tk works fine etc. etc. but none of these work together |
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with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if your |
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module uses one of those, every user of your module has to use it, too. |
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But if your module uses AnyEvent, it works transparently with all event |
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models it supports (including stuff like IO::Async, as long as those use |
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one of the supported event loops. It is trivial to add new event loops |
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to AnyEvent, too, so it is future-proof). |
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|
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In addition to being free of having to use *the one and only true event |
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model*, AnyEvent also is free of bloat and policy: with POE or similar |
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modules, you get an enormous amount of code and strict rules you have to |
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follow. AnyEvent, on the other hand, is lean and up to the point, by |
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only offering the functionality that is necessary, in as thin as a |
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wrapper as technically possible. |
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|
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Of course, AnyEvent comes with a big (and fully optional!) toolbox of |
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useful functionality, such as an asynchronous DNS resolver, 100% |
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non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms |
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such as Windows) and lots of real-world knowledge and workarounds for |
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platform bugs and differences. |
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Now, if you *do want* lots of policy (this can arguably be somewhat |
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useful) and you want to force your users to use the one and only event |
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model, you should *not* use this module. |
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DESCRIPTION |
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AnyEvent provides an identical interface to multiple event loops. This |
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allows module authors to utilise an event loop without forcing module |
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users to use the same event loop (as only a single event loop can |
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coexist peacefully at any one time). |
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The interface itself is vaguely similar, but not identical to the Event |
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module. |
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During the first call of any watcher-creation method, the module tries |
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to detect the currently loaded event loop by probing whether one of the |
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following modules is already loaded: EV, Event, Glib, |
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AnyEvent::Impl::Perl, Tk, Event::Lib, Qt, POE. The first one found is |
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used. If none are found, the module tries to load these modules |
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(excluding Tk, Event::Lib, Qt and POE as the pure perl adaptor should |
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always succeed) in the order given. The first one that can be |
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successfully loaded will be used. If, after this, still none could be |
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found, AnyEvent will fall back to a pure-perl event loop, which is not |
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very efficient, but should work everywhere. |
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Because AnyEvent first checks for modules that are already loaded, |
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loading an event model explicitly before first using AnyEvent will |
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likely make that model the default. For example: |
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use Tk; |
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use AnyEvent; |
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# .. AnyEvent will likely default to Tk |
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The *likely* means that, if any module loads another event model and |
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starts using it, all bets are off. Maybe you should tell their authors |
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to use AnyEvent so their modules work together with others seamlessly... |
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The pure-perl implementation of AnyEvent is called |
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"AnyEvent::Impl::Perl". Like other event modules you can load it |
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explicitly and enjoy the high availability of that event loop :) |
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|
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WATCHERS |
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AnyEvent has the central concept of a *watcher*, which is an object that |
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stores relevant data for each kind of event you are waiting for, such as |
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the callback to call, the file handle to watch, etc. |
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|
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These watchers are normal Perl objects with normal Perl lifetime. After |
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creating a watcher it will immediately "watch" for events and invoke the |
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callback when the event occurs (of course, only when the event model is |
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in control). |
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Note that callbacks must not permanently change global variables |
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potentially in use by the event loop (such as $_ or $[) and that |
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callbacks must not "die". The former is good programming practise in |
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Perl and the latter stems from the fact that exception handling differs |
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widely between event loops. |
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To disable the watcher you have to destroy it (e.g. by setting the |
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variable you store it in to "undef" or otherwise deleting all references |
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to it). |
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All watchers are created by calling a method on the "AnyEvent" class. |
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Many watchers either are used with "recursion" (repeating timers for |
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example), or need to refer to their watcher object in other ways. |
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An any way to achieve that is this pattern: |
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my $w; $w = AnyEvent->type (arg => value ..., cb => sub { |
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# you can use $w here, for example to undef it |
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undef $w; |
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}); |
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Note that "my $w; $w =" combination. This is necessary because in Perl, |
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my variables are only visible after the statement in which they are |
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declared. |
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I/O WATCHERS |
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$w = AnyEvent->io ( |
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fh => <filehandle_or_fileno>, |
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poll => <"r" or "w">, |
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cb => <callback>, |
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); |
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You can create an I/O watcher by calling the "AnyEvent->io" method with |
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the following mandatory key-value pairs as arguments: |
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"fh" is the Perl *file handle* (or a naked file descriptor) to watch for |
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events (AnyEvent might or might not keep a reference to this file |
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handle). Note that only file handles pointing to things for which |
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non-blocking operation makes sense are allowed. This includes sockets, |
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most character devices, pipes, fifos and so on, but not for example |
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files or block devices. |
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"poll" must be a string that is either "r" or "w", which creates a |
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watcher waiting for "r"eadable or "w"ritable events, respectively. |
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"cb" is the callback to invoke each time the file handle becomes ready. |
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|
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Although the callback might get passed parameters, their value and |
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presence is undefined and you cannot rely on them. Portable AnyEvent |
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callbacks cannot use arguments passed to I/O watcher callbacks. |
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The I/O watcher might use the underlying file descriptor or a copy of |
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it. You must not close a file handle as long as any watcher is active on |
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the underlying file descriptor. |
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Some event loops issue spurious readyness notifications, so you should |
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always use non-blocking calls when reading/writing from/to your file |
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handles. |
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Example: wait for readability of STDIN, then read a line and disable the |
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watcher. |
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my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { |
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chomp (my $input = <STDIN>); |
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warn "read: $input\n"; |
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undef $w; |
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}); |
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1.8 |
TIME WATCHERS |
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$w = AnyEvent->timer (after => <seconds>, cb => <callback>); |
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$w = AnyEvent->timer ( |
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after => <fractional_seconds>, |
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interval => <fractional_seconds>, |
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cb => <callback>, |
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); |
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You can create a time watcher by calling the "AnyEvent->timer" method |
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with the following mandatory arguments: |
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"after" specifies after how many seconds (fractional values are |
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supported) the callback should be invoked. "cb" is the callback to |
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invoke in that case. |
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Although the callback might get passed parameters, their value and |
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presence is undefined and you cannot rely on them. Portable AnyEvent |
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callbacks cannot use arguments passed to time watcher callbacks. |
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The callback will normally be invoked once only. If you specify another |
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parameter, "interval", as a strictly positive number (> 0), then the |
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callback will be invoked regularly at that interval (in fractional |
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seconds) after the first invocation. If "interval" is specified with a |
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false value, then it is treated as if it were missing. |
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The callback will be rescheduled before invoking the callback, but no |
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attempt is done to avoid timer drift in most backends, so the interval |
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is only approximate. |
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Example: 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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# to cancel the timer: |
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undef $w; |
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Example 2: fire an event after 0.5 seconds, then roughly every second. |
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my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub { |
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warn "timeout\n"; |
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}; |
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TIMING ISSUES |
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There are two ways to handle timers: based on real time (relative, "fire |
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in 10 seconds") and based on wallclock time (absolute, "fire at 12 |
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o'clock"). |
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While most event loops expect timers to specified in a relative way, |
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they use absolute time internally. This makes a difference when your |
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clock "jumps", for example, when ntp decides to set your clock backwards |
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from the wrong date of 2014-01-01 to 2008-01-01, a watcher that is |
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supposed to fire "after" a second might actually take six years to |
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finally fire. |
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AnyEvent cannot compensate for this. The only event loop that is |
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conscious about these issues is EV, which offers both relative |
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(ev_timer, based on true relative time) and absolute (ev_periodic, based |
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on wallclock time) timers. |
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AnyEvent always prefers relative timers, if available, matching the |
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AnyEvent API. |
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AnyEvent has two additional methods that return the "current time": |
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AnyEvent->time |
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This returns the "current wallclock time" as a fractional number of |
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seconds since the Epoch (the same thing as "time" or |
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"Time::HiRes::time" return, and the result is guaranteed to be |
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compatible with those). |
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It progresses independently of any event loop processing, i.e. each |
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call will check the system clock, which usually gets updated |
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frequently. |
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AnyEvent->now |
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This also returns the "current wallclock time", but unlike "time", |
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above, this value might change only once per event loop iteration, |
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depending on the event loop (most return the same time as "time", |
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above). This is the time that AnyEvent's timers get scheduled |
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against. |
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*In almost all cases (in all cases if you don't care), this is the |
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function to call when you want to know the current time.* |
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This function is also often faster then "AnyEvent->time", and thus |
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the preferred method if you want some timestamp (for example, |
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AnyEvent::Handle uses this to update it's activity timeouts). |
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The rest of this section is only of relevance if you try to be very |
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exact with your timing, you can skip it without bad conscience. |
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For a practical example of when these times differ, consider |
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Event::Lib and EV and the following set-up: |
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The event loop is running and has just invoked one of your callback |
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at time=500 (assume no other callbacks delay processing). In your |
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callback, you wait a second by executing "sleep 1" (blocking the |
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process for a second) and then (at time=501) you create a relative |
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timer that fires after three seconds. |
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With Event::Lib, "AnyEvent->time" and "AnyEvent->now" will both |
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return 501, because that is the current time, and the timer will be |
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scheduled to fire at time=504 (501 + 3). |
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With EV, "AnyEvent->time" returns 501 (as that is the current time), |
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but "AnyEvent->now" returns 500, as that is the time the last event |
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processing phase started. With EV, your timer gets scheduled to run |
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at time=503 (500 + 3). |
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In one sense, Event::Lib is more exact, as it uses the current time |
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regardless of any delays introduced by event processing. However, |
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most callbacks do not expect large delays in processing, so this |
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causes a higher drift (and a lot more system calls to get the |
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current time). |
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In another sense, EV is more exact, as your timer will be scheduled |
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at the same time, regardless of how long event processing actually |
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took. |
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In either case, if you care (and in most cases, you don't), then you |
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can get whatever behaviour you want with any event loop, by taking |
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|
|
the difference between "AnyEvent->time" and "AnyEvent->now" into |
345 |
|
|
account. |
346 |
|
|
|
347 |
root |
1.37 |
AnyEvent->now_update |
348 |
|
|
Some event loops (such as EV or AnyEvent::Impl::Perl) cache the |
349 |
|
|
current time for each loop iteration (see the discussion of |
350 |
|
|
AnyEvent->now, above). |
351 |
|
|
|
352 |
|
|
When a callback runs for a long time (or when the process sleeps), |
353 |
|
|
then this "current" time will differ substantially from the real |
354 |
|
|
time, which might affect timers and time-outs. |
355 |
|
|
|
356 |
|
|
When this is the case, you can call this method, which will update |
357 |
|
|
the event loop's idea of "current time". |
358 |
|
|
|
359 |
|
|
Note that updating the time *might* cause some events to be handled. |
360 |
|
|
|
361 |
root |
1.16 |
SIGNAL WATCHERS |
362 |
root |
1.50 |
$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>); |
363 |
|
|
|
364 |
root |
1.16 |
You can watch for signals using a signal watcher, "signal" is the signal |
365 |
root |
1.28 |
*name* in uppercase and without any "SIG" prefix, "cb" is the Perl |
366 |
|
|
callback to be invoked whenever a signal occurs. |
367 |
root |
1.16 |
|
368 |
root |
1.19 |
Although the callback might get passed parameters, their value and |
369 |
|
|
presence is undefined and you cannot rely on them. Portable AnyEvent |
370 |
|
|
callbacks cannot use arguments passed to signal watcher callbacks. |
371 |
|
|
|
372 |
root |
1.22 |
Multiple signal occurrences can be clumped together into one callback |
373 |
|
|
invocation, and callback invocation will be synchronous. Synchronous |
374 |
root |
1.16 |
means that it might take a while until the signal gets handled by the |
375 |
root |
1.22 |
process, but it is guaranteed not to interrupt any other callbacks. |
376 |
root |
1.16 |
|
377 |
|
|
The main advantage of using these watchers is that you can share a |
378 |
root |
1.46 |
signal between multiple watchers, and AnyEvent will ensure that signals |
379 |
|
|
will not interrupt your program at bad times. |
380 |
root |
1.16 |
|
381 |
root |
1.46 |
This watcher might use %SIG (depending on the event loop used), so |
382 |
|
|
programs overwriting those signals directly will likely not work |
383 |
|
|
correctly. |
384 |
|
|
|
385 |
root |
1.47 |
Example: exit on SIGINT |
386 |
|
|
|
387 |
|
|
my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 }); |
388 |
|
|
|
389 |
|
|
Signal Races, Delays and Workarounds |
390 |
|
|
Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching |
391 |
|
|
callbacks to signals in a generic way, which is a pity, as you cannot do |
392 |
root |
1.50 |
race-free signal handling in perl, requiring C libraries for this. |
393 |
|
|
AnyEvent will try to do it's best, which means in some cases, signals |
394 |
|
|
will be delayed. The maximum time a signal might be delayed is specified |
395 |
|
|
in $AnyEvent::MAX_SIGNAL_LATENCY (default: 10 seconds). This variable |
396 |
|
|
can be changed only before the first signal watcher is created, and |
397 |
|
|
should be left alone otherwise. This variable determines how often |
398 |
|
|
AnyEvent polls for signals (in case a wake-up was missed). Higher values |
399 |
root |
1.46 |
will cause fewer spurious wake-ups, which is better for power and CPU |
400 |
root |
1.50 |
saving. |
401 |
|
|
|
402 |
|
|
All these problems can be avoided by installing the optional |
403 |
|
|
Async::Interrupt module, which works with most event loops. It will not |
404 |
|
|
work with inherently broken event loops such as Event or Event::Lib (and |
405 |
|
|
not with POE currently, as POE does it's own workaround with one-second |
406 |
|
|
latency). For those, you just have to suffer the delays. |
407 |
root |
1.16 |
|
408 |
|
|
CHILD PROCESS WATCHERS |
409 |
root |
1.50 |
$w = AnyEvent->child (pid => <process id>, cb => <callback>); |
410 |
|
|
|
411 |
root |
1.16 |
You can also watch on a child process exit and catch its exit status. |
412 |
|
|
|
413 |
root |
1.48 |
The child process is specified by the "pid" argument (one some backends, |
414 |
|
|
using 0 watches for any child process exit, on others this will croak). |
415 |
|
|
The watcher will be triggered only when the child process has finished |
416 |
|
|
and an exit status is available, not on any trace events |
417 |
|
|
(stopped/continued). |
418 |
root |
1.30 |
|
419 |
|
|
The callback will be called with the pid and exit status (as returned by |
420 |
|
|
waitpid), so unlike other watcher types, you *can* rely on child watcher |
421 |
|
|
callback arguments. |
422 |
|
|
|
423 |
|
|
This watcher type works by installing a signal handler for "SIGCHLD", |
424 |
|
|
and since it cannot be shared, nothing else should use SIGCHLD or reap |
425 |
|
|
random child processes (waiting for specific child processes, e.g. |
426 |
|
|
inside "system", is just fine). |
427 |
root |
1.19 |
|
428 |
|
|
There is a slight catch to child watchers, however: you usually start |
429 |
|
|
them *after* the child process was created, and this means the process |
430 |
|
|
could have exited already (and no SIGCHLD will be sent anymore). |
431 |
|
|
|
432 |
root |
1.41 |
Not all event models handle this correctly (neither POE nor IO::Async |
433 |
|
|
do, see their AnyEvent::Impl manpages for details), but even for event |
434 |
|
|
models that *do* handle this correctly, they usually need to be loaded |
435 |
|
|
before the process exits (i.e. before you fork in the first place). |
436 |
|
|
AnyEvent's pure perl event loop handles all cases correctly regardless |
437 |
|
|
of when you start the watcher. |
438 |
root |
1.19 |
|
439 |
|
|
This means you cannot create a child watcher as the very first thing in |
440 |
|
|
an AnyEvent program, you *have* to create at least one watcher before |
441 |
|
|
you "fork" the child (alternatively, you can call "AnyEvent::detect"). |
442 |
|
|
|
443 |
root |
1.46 |
As most event loops do not support waiting for child events, they will |
444 |
|
|
be emulated by AnyEvent in most cases, in which the latency and race |
445 |
|
|
problems mentioned in the description of signal watchers apply. |
446 |
|
|
|
447 |
root |
1.19 |
Example: fork a process and wait for it |
448 |
|
|
|
449 |
root |
1.25 |
my $done = AnyEvent->condvar; |
450 |
root |
1.40 |
|
451 |
|
|
my $pid = fork or exit 5; |
452 |
|
|
|
453 |
|
|
my $w = AnyEvent->child ( |
454 |
root |
1.25 |
pid => $pid, |
455 |
|
|
cb => sub { |
456 |
|
|
my ($pid, $status) = @_; |
457 |
|
|
warn "pid $pid exited with status $status"; |
458 |
|
|
$done->send; |
459 |
|
|
}, |
460 |
|
|
); |
461 |
root |
1.40 |
|
462 |
|
|
# do something else, then wait for process exit |
463 |
root |
1.25 |
$done->recv; |
464 |
root |
1.19 |
|
465 |
root |
1.38 |
IDLE WATCHERS |
466 |
root |
1.50 |
$w = AnyEvent->idle (cb => <callback>); |
467 |
|
|
|
468 |
root |
1.38 |
Sometimes there is a need to do something, but it is not so important to |
469 |
|
|
do it instantly, but only when there is nothing better to do. This |
470 |
|
|
"nothing better to do" is usually defined to be "no other events need |
471 |
|
|
attention by the event loop". |
472 |
|
|
|
473 |
|
|
Idle watchers ideally get invoked when the event loop has nothing better |
474 |
|
|
to do, just before it would block the process to wait for new events. |
475 |
|
|
Instead of blocking, the idle watcher is invoked. |
476 |
|
|
|
477 |
|
|
Most event loops unfortunately do not really support idle watchers (only |
478 |
|
|
EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent |
479 |
|
|
will simply call the callback "from time to time". |
480 |
|
|
|
481 |
|
|
Example: read lines from STDIN, but only process them when the program |
482 |
|
|
is otherwise idle: |
483 |
|
|
|
484 |
|
|
my @lines; # read data |
485 |
|
|
my $idle_w; |
486 |
|
|
my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { |
487 |
|
|
push @lines, scalar <STDIN>; |
488 |
|
|
|
489 |
|
|
# start an idle watcher, if not already done |
490 |
|
|
$idle_w ||= AnyEvent->idle (cb => sub { |
491 |
|
|
# handle only one line, when there are lines left |
492 |
|
|
if (my $line = shift @lines) { |
493 |
|
|
print "handled when idle: $line"; |
494 |
|
|
} else { |
495 |
|
|
# otherwise disable the idle watcher again |
496 |
|
|
undef $idle_w; |
497 |
|
|
} |
498 |
|
|
}); |
499 |
|
|
}); |
500 |
|
|
|
501 |
root |
1.16 |
CONDITION VARIABLES |
502 |
root |
1.50 |
$cv = AnyEvent->condvar; |
503 |
|
|
|
504 |
|
|
$cv->send (<list>); |
505 |
|
|
my @res = $cv->recv; |
506 |
|
|
|
507 |
root |
1.20 |
If you are familiar with some event loops you will know that all of them |
508 |
|
|
require you to run some blocking "loop", "run" or similar function that |
509 |
|
|
will actively watch for new events and call your callbacks. |
510 |
|
|
|
511 |
root |
1.45 |
AnyEvent is slightly different: it expects somebody else to run the |
512 |
|
|
event loop and will only block when necessary (usually when told by the |
513 |
|
|
user). |
514 |
root |
1.6 |
|
515 |
root |
1.20 |
The instrument to do that is called a "condition variable", so called |
516 |
|
|
because they represent a condition that must become true. |
517 |
root |
1.6 |
|
518 |
root |
1.45 |
Now is probably a good time to look at the examples further below. |
519 |
|
|
|
520 |
root |
1.20 |
Condition variables can be created by calling the "AnyEvent->condvar" |
521 |
|
|
method, usually without arguments. The only argument pair allowed is |
522 |
|
|
"cb", which specifies a callback to be called when the condition |
523 |
root |
1.29 |
variable becomes true, with the condition variable as the first argument |
524 |
|
|
(but not the results). |
525 |
root |
1.20 |
|
526 |
root |
1.22 |
After creation, the condition variable is "false" until it becomes |
527 |
|
|
"true" by calling the "send" method (or calling the condition variable |
528 |
root |
1.23 |
as if it were a callback, read about the caveats in the description for |
529 |
|
|
the "->send" method). |
530 |
root |
1.20 |
|
531 |
|
|
Condition variables are similar to callbacks, except that you can |
532 |
|
|
optionally wait for them. They can also be called merge points - points |
533 |
root |
1.22 |
in time where multiple outstanding events have been processed. And yet |
534 |
|
|
another way to call them is transactions - each condition variable can |
535 |
|
|
be used to represent a transaction, which finishes at some point and |
536 |
root |
1.47 |
delivers a result. And yet some people know them as "futures" - a |
537 |
|
|
promise to compute/deliver something that you can wait for. |
538 |
root |
1.20 |
|
539 |
|
|
Condition variables are very useful to signal that something has |
540 |
|
|
finished, for example, if you write a module that does asynchronous http |
541 |
|
|
requests, then a condition variable would be the ideal candidate to |
542 |
|
|
signal the availability of results. The user can either act when the |
543 |
|
|
callback is called or can synchronously "->recv" for the results. |
544 |
|
|
|
545 |
|
|
You can also use them to simulate traditional event loops - for example, |
546 |
|
|
you can block your main program until an event occurs - for example, you |
547 |
|
|
could "->recv" in your main program until the user clicks the Quit |
548 |
|
|
button of your app, which would "->send" the "quit" event. |
549 |
root |
1.16 |
|
550 |
|
|
Note that condition variables recurse into the event loop - if you have |
551 |
root |
1.22 |
two pieces of code that call "->recv" in a round-robin fashion, you |
552 |
root |
1.16 |
lose. Therefore, condition variables are good to export to your caller, |
553 |
|
|
but you should avoid making a blocking wait yourself, at least in |
554 |
|
|
callbacks, as this asks for trouble. |
555 |
root |
1.14 |
|
556 |
root |
1.20 |
Condition variables are represented by hash refs in perl, and the keys |
557 |
|
|
used by AnyEvent itself are all named "_ae_XXX" to make subclassing easy |
558 |
|
|
(it is often useful to build your own transaction class on top of |
559 |
|
|
AnyEvent). To subclass, use "AnyEvent::CondVar" as base class and call |
560 |
|
|
it's "new" method in your own "new" method. |
561 |
|
|
|
562 |
|
|
There are two "sides" to a condition variable - the "producer side" |
563 |
|
|
which eventually calls "-> send", and the "consumer side", which waits |
564 |
|
|
for the send to occur. |
565 |
root |
1.6 |
|
566 |
root |
1.22 |
Example: wait for a timer. |
567 |
root |
1.6 |
|
568 |
root |
1.20 |
# wait till the result is ready |
569 |
|
|
my $result_ready = AnyEvent->condvar; |
570 |
|
|
|
571 |
|
|
# do something such as adding a timer |
572 |
|
|
# or socket watcher the calls $result_ready->send |
573 |
|
|
# when the "result" is ready. |
574 |
|
|
# in this case, we simply use a timer: |
575 |
|
|
my $w = AnyEvent->timer ( |
576 |
|
|
after => 1, |
577 |
|
|
cb => sub { $result_ready->send }, |
578 |
|
|
); |
579 |
|
|
|
580 |
|
|
# this "blocks" (while handling events) till the callback |
581 |
root |
1.53 |
# calls ->send |
582 |
root |
1.20 |
$result_ready->recv; |
583 |
|
|
|
584 |
root |
1.22 |
Example: wait for a timer, but take advantage of the fact that condition |
585 |
root |
1.45 |
variables are also callable directly. |
586 |
root |
1.22 |
|
587 |
|
|
my $done = AnyEvent->condvar; |
588 |
|
|
my $delay = AnyEvent->timer (after => 5, cb => $done); |
589 |
|
|
$done->recv; |
590 |
|
|
|
591 |
root |
1.29 |
Example: Imagine an API that returns a condvar and doesn't support |
592 |
|
|
callbacks. This is how you make a synchronous call, for example from the |
593 |
|
|
main program: |
594 |
|
|
|
595 |
|
|
use AnyEvent::CouchDB; |
596 |
|
|
|
597 |
|
|
... |
598 |
|
|
|
599 |
|
|
my @info = $couchdb->info->recv; |
600 |
|
|
|
601 |
root |
1.45 |
And this is how you would just set a callback to be called whenever the |
602 |
root |
1.29 |
results are available: |
603 |
|
|
|
604 |
|
|
$couchdb->info->cb (sub { |
605 |
|
|
my @info = $_[0]->recv; |
606 |
|
|
}); |
607 |
|
|
|
608 |
root |
1.20 |
METHODS FOR PRODUCERS |
609 |
|
|
These methods should only be used by the producing side, i.e. the |
610 |
|
|
code/module that eventually sends the signal. Note that it is also the |
611 |
|
|
producer side which creates the condvar in most cases, but it isn't |
612 |
|
|
uncommon for the consumer to create it as well. |
613 |
|
|
|
614 |
|
|
$cv->send (...) |
615 |
|
|
Flag the condition as ready - a running "->recv" and all further |
616 |
|
|
calls to "recv" will (eventually) return after this method has been |
617 |
|
|
called. If nobody is waiting the send will be remembered. |
618 |
|
|
|
619 |
|
|
If a callback has been set on the condition variable, it is called |
620 |
|
|
immediately from within send. |
621 |
|
|
|
622 |
|
|
Any arguments passed to the "send" call will be returned by all |
623 |
|
|
future "->recv" calls. |
624 |
|
|
|
625 |
root |
1.22 |
Condition variables are overloaded so one can call them directly (as |
626 |
root |
1.45 |
if they were a code reference). Calling them directly is the same as |
627 |
|
|
calling "send". |
628 |
root |
1.22 |
|
629 |
root |
1.20 |
$cv->croak ($error) |
630 |
|
|
Similar to send, but causes all call's to "->recv" to invoke |
631 |
|
|
"Carp::croak" with the given error message/object/scalar. |
632 |
|
|
|
633 |
|
|
This can be used to signal any errors to the condition variable |
634 |
root |
1.45 |
user/consumer. Doing it this way instead of calling "croak" directly |
635 |
|
|
delays the error detetcion, but has the overwhelmign advantage that |
636 |
|
|
it diagnoses the error at the place where the result is expected, |
637 |
|
|
and not deep in some event clalback without connection to the actual |
638 |
|
|
code causing the problem. |
639 |
root |
1.20 |
|
640 |
|
|
$cv->begin ([group callback]) |
641 |
|
|
$cv->end |
642 |
|
|
These two methods can be used to combine many transactions/events |
643 |
|
|
into one. For example, a function that pings many hosts in parallel |
644 |
|
|
might want to use a condition variable for the whole process. |
645 |
|
|
|
646 |
|
|
Every call to "->begin" will increment a counter, and every call to |
647 |
|
|
"->end" will decrement it. If the counter reaches 0 in "->end", the |
648 |
root |
1.52 |
(last) callback passed to "begin" will be executed, passing the |
649 |
|
|
condvar as first argument. That callback is *supposed* to call |
650 |
|
|
"->send", but that is not required. If no group callback was set, |
651 |
|
|
"send" will be called without any arguments. |
652 |
root |
1.20 |
|
653 |
root |
1.42 |
You can think of "$cv->send" giving you an OR condition (one call |
654 |
|
|
sends), while "$cv->begin" and "$cv->end" giving you an AND |
655 |
|
|
condition (all "begin" calls must be "end"'ed before the condvar |
656 |
|
|
sends). |
657 |
|
|
|
658 |
|
|
Let's start with a simple example: you have two I/O watchers (for |
659 |
|
|
example, STDOUT and STDERR for a program), and you want to wait for |
660 |
|
|
both streams to close before activating a condvar: |
661 |
|
|
|
662 |
|
|
my $cv = AnyEvent->condvar; |
663 |
|
|
|
664 |
|
|
$cv->begin; # first watcher |
665 |
|
|
my $w1 = AnyEvent->io (fh => $fh1, cb => sub { |
666 |
|
|
defined sysread $fh1, my $buf, 4096 |
667 |
|
|
or $cv->end; |
668 |
|
|
}); |
669 |
|
|
|
670 |
|
|
$cv->begin; # second watcher |
671 |
|
|
my $w2 = AnyEvent->io (fh => $fh2, cb => sub { |
672 |
|
|
defined sysread $fh2, my $buf, 4096 |
673 |
|
|
or $cv->end; |
674 |
|
|
}); |
675 |
|
|
|
676 |
|
|
$cv->recv; |
677 |
|
|
|
678 |
|
|
This works because for every event source (EOF on file handle), |
679 |
|
|
there is one call to "begin", so the condvar waits for all calls to |
680 |
|
|
"end" before sending. |
681 |
|
|
|
682 |
|
|
The ping example mentioned above is slightly more complicated, as |
683 |
|
|
the there are results to be passwd back, and the number of tasks |
684 |
|
|
that are begung can potentially be zero: |
685 |
root |
1.20 |
|
686 |
|
|
my $cv = AnyEvent->condvar; |
687 |
|
|
|
688 |
|
|
my %result; |
689 |
root |
1.52 |
$cv->begin (sub { shift->send (\%result) }); |
690 |
root |
1.20 |
|
691 |
|
|
for my $host (@list_of_hosts) { |
692 |
|
|
$cv->begin; |
693 |
|
|
ping_host_then_call_callback $host, sub { |
694 |
|
|
$result{$host} = ...; |
695 |
|
|
$cv->end; |
696 |
|
|
}; |
697 |
|
|
} |
698 |
|
|
|
699 |
|
|
$cv->end; |
700 |
|
|
|
701 |
|
|
This code fragment supposedly pings a number of hosts and calls |
702 |
|
|
"send" after results for all then have have been gathered - in any |
703 |
|
|
order. To achieve this, the code issues a call to "begin" when it |
704 |
|
|
starts each ping request and calls "end" when it has received some |
705 |
|
|
result for it. Since "begin" and "end" only maintain a counter, the |
706 |
|
|
order in which results arrive is not relevant. |
707 |
|
|
|
708 |
|
|
There is an additional bracketing call to "begin" and "end" outside |
709 |
|
|
the loop, which serves two important purposes: first, it sets the |
710 |
|
|
callback to be called once the counter reaches 0, and second, it |
711 |
|
|
ensures that "send" is called even when "no" hosts are being pinged |
712 |
|
|
(the loop doesn't execute once). |
713 |
|
|
|
714 |
root |
1.42 |
This is the general pattern when you "fan out" into multiple (but |
715 |
|
|
potentially none) subrequests: use an outer "begin"/"end" pair to |
716 |
|
|
set the callback and ensure "end" is called at least once, and then, |
717 |
|
|
for each subrequest you start, call "begin" and for each subrequest |
718 |
|
|
you finish, call "end". |
719 |
root |
1.20 |
|
720 |
|
|
METHODS FOR CONSUMERS |
721 |
|
|
These methods should only be used by the consuming side, i.e. the code |
722 |
|
|
awaits the condition. |
723 |
|
|
|
724 |
|
|
$cv->recv |
725 |
|
|
Wait (blocking if necessary) until the "->send" or "->croak" methods |
726 |
|
|
have been called on c<$cv>, while servicing other watchers normally. |
727 |
|
|
|
728 |
|
|
You can only wait once on a condition - additional calls are valid |
729 |
|
|
but will return immediately. |
730 |
|
|
|
731 |
|
|
If an error condition has been set by calling "->croak", then this |
732 |
|
|
function will call "croak". |
733 |
|
|
|
734 |
|
|
In list context, all parameters passed to "send" will be returned, |
735 |
|
|
in scalar context only the first one will be returned. |
736 |
root |
1.6 |
|
737 |
root |
1.45 |
Note that doing a blocking wait in a callback is not supported by |
738 |
|
|
any event loop, that is, recursive invocation of a blocking "->recv" |
739 |
|
|
is not allowed, and the "recv" call will "croak" if such a condition |
740 |
|
|
is detected. This condition can be slightly loosened by using |
741 |
|
|
Coro::AnyEvent, which allows you to do a blocking "->recv" from any |
742 |
|
|
thread that doesn't run the event loop itself. |
743 |
|
|
|
744 |
root |
1.15 |
Not all event models support a blocking wait - some die in that case |
745 |
root |
1.16 |
(programs might want to do that to stay interactive), so *if you are |
746 |
root |
1.45 |
using this from a module, never require a blocking wait*. Instead, |
747 |
|
|
let the caller decide whether the call will block or not (for |
748 |
|
|
example, by coupling condition variables with some kind of request |
749 |
|
|
results and supporting callbacks so the caller knows that getting |
750 |
|
|
the result will not block, while still supporting blocking waits if |
751 |
|
|
the caller so desires). |
752 |
root |
1.20 |
|
753 |
|
|
You can ensure that "-recv" never blocks by setting a callback and |
754 |
|
|
only calling "->recv" from within that callback (or at a later |
755 |
|
|
time). This will work even when the event loop does not support |
756 |
|
|
blocking waits otherwise. |
757 |
|
|
|
758 |
|
|
$bool = $cv->ready |
759 |
|
|
Returns true when the condition is "true", i.e. whether "send" or |
760 |
|
|
"croak" have been called. |
761 |
|
|
|
762 |
root |
1.29 |
$cb = $cv->cb ($cb->($cv)) |
763 |
root |
1.20 |
This is a mutator function that returns the callback set and |
764 |
|
|
optionally replaces it before doing so. |
765 |
|
|
|
766 |
root |
1.50 |
The callback will be called when the condition becomes (or already |
767 |
|
|
was) "true", i.e. when "send" or "croak" are called (or were |
768 |
|
|
called), with the only argument being the condition variable itself. |
769 |
|
|
Calling "recv" inside the callback or at any later time is |
770 |
|
|
guaranteed not to block. |
771 |
root |
1.8 |
|
772 |
root |
1.43 |
SUPPORTED EVENT LOOPS/BACKENDS |
773 |
|
|
The available backend classes are (every class has its own manpage): |
774 |
root |
1.7 |
|
775 |
root |
1.43 |
Backends that are autoprobed when no other event loop can be found. |
776 |
|
|
EV is the preferred backend when no other event loop seems to be in |
777 |
root |
1.51 |
use. If EV is not installed, then AnyEvent will fall back to its own |
778 |
|
|
pure-perl implementation, which is available everywhere as it comes |
779 |
|
|
with AnyEvent itself. |
780 |
root |
1.7 |
|
781 |
root |
1.43 |
AnyEvent::Impl::EV based on EV (interface to libev, best choice). |
782 |
root |
1.20 |
AnyEvent::Impl::Perl pure-perl implementation, fast and portable. |
783 |
root |
1.43 |
|
784 |
|
|
Backends that are transparently being picked up when they are used. |
785 |
|
|
These will be used when they are currently loaded when the first |
786 |
|
|
watcher is created, in which case it is assumed that the application |
787 |
|
|
is using them. This means that AnyEvent will automatically pick the |
788 |
|
|
right backend when the main program loads an event module before |
789 |
|
|
anything starts to create watchers. Nothing special needs to be done |
790 |
|
|
by the main program. |
791 |
|
|
|
792 |
root |
1.51 |
AnyEvent::Impl::Event based on Event, very stable, few glitches. |
793 |
root |
1.43 |
AnyEvent::Impl::Glib based on Glib, slow but very stable. |
794 |
|
|
AnyEvent::Impl::Tk based on Tk, very broken. |
795 |
root |
1.18 |
AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse. |
796 |
root |
1.43 |
AnyEvent::Impl::POE based on POE, very slow, some limitations. |
797 |
root |
1.48 |
AnyEvent::Impl::Irssi used when running within irssi. |
798 |
root |
1.43 |
|
799 |
|
|
Backends with special needs. |
800 |
|
|
Qt requires the Qt::Application to be instantiated first, but will |
801 |
|
|
otherwise be picked up automatically. As long as the main program |
802 |
|
|
instantiates the application before any AnyEvent watchers are |
803 |
|
|
created, everything should just work. |
804 |
|
|
|
805 |
|
|
AnyEvent::Impl::Qt based on Qt. |
806 |
|
|
|
807 |
|
|
Support for IO::Async can only be partial, as it is too broken and |
808 |
|
|
architecturally limited to even support the AnyEvent API. It also is |
809 |
|
|
the only event loop that needs the loop to be set explicitly, so it |
810 |
|
|
can only be used by a main program knowing about AnyEvent. See |
811 |
|
|
AnyEvent::Impl::Async for the gory details. |
812 |
|
|
|
813 |
|
|
AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed. |
814 |
root |
1.19 |
|
815 |
root |
1.43 |
Event loops that are indirectly supported via other backends. |
816 |
|
|
Some event loops can be supported via other modules: |
817 |
root |
1.19 |
|
818 |
root |
1.43 |
There is no direct support for WxWidgets (Wx) or Prima. |
819 |
|
|
|
820 |
|
|
WxWidgets has no support for watching file handles. However, you can |
821 |
|
|
use WxWidgets through the POE adaptor, as POE has a Wx backend that |
822 |
|
|
simply polls 20 times per second, which was considered to be too |
823 |
|
|
horrible to even consider for AnyEvent. |
824 |
|
|
|
825 |
|
|
Prima is not supported as nobody seems to be using it, but it has a |
826 |
|
|
POE backend, so it can be supported through POE. |
827 |
|
|
|
828 |
|
|
AnyEvent knows about both Prima and Wx, however, and will try to |
829 |
|
|
load POE when detecting them, in the hope that POE will pick them |
830 |
|
|
up, in which case everything will be automatic. |
831 |
|
|
|
832 |
|
|
GLOBAL VARIABLES AND FUNCTIONS |
833 |
|
|
These are not normally required to use AnyEvent, but can be useful to |
834 |
|
|
write AnyEvent extension modules. |
835 |
|
|
|
836 |
|
|
$AnyEvent::MODEL |
837 |
|
|
Contains "undef" until the first watcher is being created, before |
838 |
|
|
the backend has been autodetected. |
839 |
|
|
|
840 |
|
|
Afterwards it contains the event model that is being used, which is |
841 |
|
|
the name of the Perl class implementing the model. This class is |
842 |
|
|
usually one of the "AnyEvent::Impl:xxx" modules, but can be any |
843 |
|
|
other class in the case AnyEvent has been extended at runtime (e.g. |
844 |
|
|
in *rxvt-unicode* it will be "urxvt::anyevent"). |
845 |
root |
1.7 |
|
846 |
root |
1.8 |
AnyEvent::detect |
847 |
|
|
Returns $AnyEvent::MODEL, forcing autodetection of the event model |
848 |
|
|
if necessary. You should only call this function right before you |
849 |
root |
1.16 |
would have created an AnyEvent watcher anyway, that is, as late as |
850 |
root |
1.43 |
possible at runtime, and not e.g. while initialising of your module. |
851 |
|
|
|
852 |
|
|
If you need to do some initialisation before AnyEvent watchers are |
853 |
|
|
created, use "post_detect". |
854 |
root |
1.8 |
|
855 |
root |
1.20 |
$guard = AnyEvent::post_detect { BLOCK } |
856 |
|
|
Arranges for the code block to be executed as soon as the event |
857 |
|
|
model is autodetected (or immediately if this has already happened). |
858 |
|
|
|
859 |
root |
1.43 |
The block will be executed *after* the actual backend has been |
860 |
|
|
detected ($AnyEvent::MODEL is set), but *before* any watchers have |
861 |
|
|
been created, so it is possible to e.g. patch @AnyEvent::ISA or do |
862 |
|
|
other initialisations - see the sources of AnyEvent::Strict or |
863 |
|
|
AnyEvent::AIO to see how this is used. |
864 |
|
|
|
865 |
|
|
The most common usage is to create some global watchers, without |
866 |
|
|
forcing event module detection too early, for example, AnyEvent::AIO |
867 |
|
|
creates and installs the global IO::AIO watcher in a "post_detect" |
868 |
|
|
block to avoid autodetecting the event module at load time. |
869 |
|
|
|
870 |
root |
1.20 |
If called in scalar or list context, then it creates and returns an |
871 |
|
|
object that automatically removes the callback again when it is |
872 |
root |
1.48 |
destroyed (or "undef" when the hook was immediately executed). See |
873 |
|
|
AnyEvent::AIO for a case where this is useful. |
874 |
|
|
|
875 |
|
|
Example: Create a watcher for the IO::AIO module and store it in |
876 |
|
|
$WATCHER. Only do so after the event loop is initialised, though. |
877 |
|
|
|
878 |
|
|
our WATCHER; |
879 |
|
|
|
880 |
|
|
my $guard = AnyEvent::post_detect { |
881 |
|
|
$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb); |
882 |
|
|
}; |
883 |
|
|
|
884 |
|
|
# the ||= is important in case post_detect immediately runs the block, |
885 |
|
|
# as to not clobber the newly-created watcher. assigning both watcher and |
886 |
|
|
# post_detect guard to the same variable has the advantage of users being |
887 |
|
|
# able to just C<undef $WATCHER> if the watcher causes them grief. |
888 |
|
|
|
889 |
|
|
$WATCHER ||= $guard; |
890 |
root |
1.20 |
|
891 |
|
|
@AnyEvent::post_detect |
892 |
|
|
If there are any code references in this array (you can "push" to it |
893 |
|
|
before or after loading AnyEvent), then they will called directly |
894 |
|
|
after the event loop has been chosen. |
895 |
|
|
|
896 |
|
|
You should check $AnyEvent::MODEL before adding to this array, |
897 |
root |
1.43 |
though: if it is defined then the event loop has already been |
898 |
|
|
detected, and the array will be ignored. |
899 |
|
|
|
900 |
|
|
Best use "AnyEvent::post_detect { BLOCK }" when your application |
901 |
|
|
allows it,as it takes care of these details. |
902 |
root |
1.20 |
|
903 |
root |
1.43 |
This variable is mainly useful for modules that can do something |
904 |
|
|
useful when AnyEvent is used and thus want to know when it is |
905 |
|
|
initialised, but do not need to even load it by default. This array |
906 |
|
|
provides the means to hook into AnyEvent passively, without loading |
907 |
|
|
it. |
908 |
root |
1.20 |
|
909 |
root |
1.6 |
WHAT TO DO IN A MODULE |
910 |
|
|
As a module author, you should "use AnyEvent" and call AnyEvent methods |
911 |
|
|
freely, but you should not load a specific event module or rely on it. |
912 |
|
|
|
913 |
root |
1.16 |
Be careful when you create watchers in the module body - AnyEvent will |
914 |
root |
1.6 |
decide which event module to use as soon as the first method is called, |
915 |
|
|
so by calling AnyEvent in your module body you force the user of your |
916 |
|
|
module to load the event module first. |
917 |
|
|
|
918 |
root |
1.20 |
Never call "->recv" on a condition variable unless you *know* that the |
919 |
|
|
"->send" method has been called on it already. This is because it will |
920 |
|
|
stall the whole program, and the whole point of using events is to stay |
921 |
|
|
interactive. |
922 |
root |
1.16 |
|
923 |
root |
1.20 |
It is fine, however, to call "->recv" when the user of your module |
924 |
root |
1.16 |
requests it (i.e. if you create a http request object ad have a method |
925 |
root |
1.20 |
called "results" that returns the results, it should call "->recv" |
926 |
root |
1.16 |
freely, as the user of your module knows what she is doing. always). |
927 |
|
|
|
928 |
root |
1.6 |
WHAT TO DO IN THE MAIN PROGRAM |
929 |
|
|
There will always be a single main program - the only place that should |
930 |
|
|
dictate which event model to use. |
931 |
|
|
|
932 |
|
|
If it doesn't care, it can just "use AnyEvent" and use it itself, or not |
933 |
root |
1.16 |
do anything special (it does not need to be event-based) and let |
934 |
|
|
AnyEvent decide which implementation to chose if some module relies on |
935 |
|
|
it. |
936 |
|
|
|
937 |
root |
1.23 |
If the main program relies on a specific event model - for example, in |
938 |
|
|
Gtk2 programs you have to rely on the Glib module - you should load the |
939 |
root |
1.16 |
event module before loading AnyEvent or any module that uses it: |
940 |
|
|
generally speaking, you should load it as early as possible. The reason |
941 |
|
|
is that modules might create watchers when they are loaded, and AnyEvent |
942 |
|
|
will decide on the event model to use as soon as it creates watchers, |
943 |
|
|
and it might chose the wrong one unless you load the correct one |
944 |
|
|
yourself. |
945 |
root |
1.6 |
|
946 |
root |
1.23 |
You can chose to use a pure-perl implementation by loading the |
947 |
|
|
"AnyEvent::Impl::Perl" module, which gives you similar behaviour |
948 |
|
|
everywhere, but letting AnyEvent chose the model is generally better. |
949 |
|
|
|
950 |
|
|
MAINLOOP EMULATION |
951 |
|
|
Sometimes (often for short test scripts, or even standalone programs who |
952 |
|
|
only want to use AnyEvent), you do not want to run a specific event |
953 |
|
|
loop. |
954 |
|
|
|
955 |
|
|
In that case, you can use a condition variable like this: |
956 |
|
|
|
957 |
|
|
AnyEvent->condvar->recv; |
958 |
|
|
|
959 |
|
|
This has the effect of entering the event loop and looping forever. |
960 |
|
|
|
961 |
|
|
Note that usually your program has some exit condition, in which case it |
962 |
|
|
is better to use the "traditional" approach of storing a condition |
963 |
|
|
variable somewhere, waiting for it, and sending it when the program |
964 |
|
|
should exit cleanly. |
965 |
root |
1.2 |
|
966 |
root |
1.19 |
OTHER MODULES |
967 |
|
|
The following is a non-exhaustive list of additional modules that use |
968 |
root |
1.43 |
AnyEvent as a client and can therefore be mixed easily with other |
969 |
|
|
AnyEvent modules and other event loops in the same program. Some of the |
970 |
|
|
modules come with AnyEvent, most are available via CPAN. |
971 |
root |
1.19 |
|
972 |
|
|
AnyEvent::Util |
973 |
|
|
Contains various utility functions that replace often-used but |
974 |
|
|
blocking functions such as "inet_aton" by event-/callback-based |
975 |
|
|
versions. |
976 |
|
|
|
977 |
root |
1.22 |
AnyEvent::Socket |
978 |
|
|
Provides various utility functions for (internet protocol) sockets, |
979 |
|
|
addresses and name resolution. Also functions to create non-blocking |
980 |
|
|
tcp connections or tcp servers, with IPv6 and SRV record support and |
981 |
|
|
more. |
982 |
|
|
|
983 |
root |
1.28 |
AnyEvent::Handle |
984 |
|
|
Provide read and write buffers, manages watchers for reads and |
985 |
|
|
writes, supports raw and formatted I/O, I/O queued and fully |
986 |
root |
1.43 |
transparent and non-blocking SSL/TLS (via AnyEvent::TLS. |
987 |
root |
1.28 |
|
988 |
root |
1.23 |
AnyEvent::DNS |
989 |
|
|
Provides rich asynchronous DNS resolver capabilities. |
990 |
|
|
|
991 |
root |
1.26 |
AnyEvent::HTTP |
992 |
|
|
A simple-to-use HTTP library that is capable of making a lot of |
993 |
|
|
concurrent HTTP requests. |
994 |
|
|
|
995 |
root |
1.19 |
AnyEvent::HTTPD |
996 |
|
|
Provides a simple web application server framework. |
997 |
|
|
|
998 |
|
|
AnyEvent::FastPing |
999 |
|
|
The fastest ping in the west. |
1000 |
|
|
|
1001 |
root |
1.27 |
AnyEvent::DBI |
1002 |
|
|
Executes DBI requests asynchronously in a proxy process. |
1003 |
|
|
|
1004 |
root |
1.28 |
AnyEvent::AIO |
1005 |
|
|
Truly asynchronous I/O, should be in the toolbox of every event |
1006 |
|
|
programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent |
1007 |
|
|
together. |
1008 |
|
|
|
1009 |
|
|
AnyEvent::BDB |
1010 |
|
|
Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently |
1011 |
|
|
fuses BDB and AnyEvent together. |
1012 |
|
|
|
1013 |
|
|
AnyEvent::GPSD |
1014 |
|
|
A non-blocking interface to gpsd, a daemon delivering GPS |
1015 |
|
|
information. |
1016 |
|
|
|
1017 |
root |
1.31 |
AnyEvent::IRC |
1018 |
|
|
AnyEvent based IRC client module family (replacing the older |
1019 |
|
|
Net::IRC3). |
1020 |
root |
1.19 |
|
1021 |
root |
1.43 |
AnyEvent::XMPP |
1022 |
|
|
AnyEvent based XMPP (Jabber protocol) module family (replacing the |
1023 |
|
|
older Net::XMPP2>. |
1024 |
|
|
|
1025 |
|
|
AnyEvent::IGS |
1026 |
|
|
A non-blocking interface to the Internet Go Server protocol (used by |
1027 |
|
|
App::IGS). |
1028 |
root |
1.19 |
|
1029 |
|
|
Net::FCP |
1030 |
|
|
AnyEvent-based implementation of the Freenet Client Protocol, |
1031 |
|
|
birthplace of AnyEvent. |
1032 |
|
|
|
1033 |
|
|
Event::ExecFlow |
1034 |
|
|
High level API for event-based execution flow control. |
1035 |
|
|
|
1036 |
|
|
Coro |
1037 |
root |
1.20 |
Has special support for AnyEvent via Coro::AnyEvent. |
1038 |
|
|
|
1039 |
root |
1.51 |
SIMPLIFIED AE API |
1040 |
|
|
Starting with version 5.0, AnyEvent officially supports a second, much |
1041 |
|
|
simpler, API that is designed to reduce the calling, typing and memory |
1042 |
|
|
overhead. |
1043 |
|
|
|
1044 |
|
|
See the AE manpage for details. |
1045 |
|
|
|
1046 |
root |
1.30 |
ERROR AND EXCEPTION HANDLING |
1047 |
|
|
In general, AnyEvent does not do any error handling - it relies on the |
1048 |
|
|
caller to do that if required. The AnyEvent::Strict module (see also the |
1049 |
|
|
"PERL_ANYEVENT_STRICT" environment variable, below) provides strict |
1050 |
|
|
checking of all AnyEvent methods, however, which is highly useful during |
1051 |
|
|
development. |
1052 |
|
|
|
1053 |
|
|
As for exception handling (i.e. runtime errors and exceptions thrown |
1054 |
|
|
while executing a callback), this is not only highly event-loop |
1055 |
|
|
specific, but also not in any way wrapped by this module, as this is the |
1056 |
|
|
job of the main program. |
1057 |
|
|
|
1058 |
|
|
The pure perl event loop simply re-throws the exception (usually within |
1059 |
|
|
"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()", |
1060 |
|
|
Glib uses "install_exception_handler" and so on. |
1061 |
root |
1.6 |
|
1062 |
root |
1.4 |
ENVIRONMENT VARIABLES |
1063 |
root |
1.30 |
The following environment variables are used by this module or its |
1064 |
root |
1.40 |
submodules. |
1065 |
|
|
|
1066 |
|
|
Note that AnyEvent will remove *all* environment variables starting with |
1067 |
|
|
"PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is |
1068 |
|
|
enabled. |
1069 |
root |
1.4 |
|
1070 |
root |
1.18 |
"PERL_ANYEVENT_VERBOSE" |
1071 |
root |
1.19 |
By default, AnyEvent will be completely silent except in fatal |
1072 |
|
|
conditions. You can set this environment variable to make AnyEvent |
1073 |
|
|
more talkative. |
1074 |
|
|
|
1075 |
|
|
When set to 1 or higher, causes AnyEvent to warn about unexpected |
1076 |
|
|
conditions, such as not being able to load the event model specified |
1077 |
|
|
by "PERL_ANYEVENT_MODEL". |
1078 |
|
|
|
1079 |
root |
1.18 |
When set to 2 or higher, cause AnyEvent to report to STDERR which |
1080 |
|
|
event model it chooses. |
1081 |
|
|
|
1082 |
root |
1.46 |
When set to 8 or higher, then AnyEvent will report extra information |
1083 |
|
|
on which optional modules it loads and how it implements certain |
1084 |
|
|
features. |
1085 |
|
|
|
1086 |
root |
1.28 |
"PERL_ANYEVENT_STRICT" |
1087 |
|
|
AnyEvent does not do much argument checking by default, as thorough |
1088 |
|
|
argument checking is very costly. Setting this variable to a true |
1089 |
|
|
value will cause AnyEvent to load "AnyEvent::Strict" and then to |
1090 |
|
|
thoroughly check the arguments passed to most method calls. If it |
1091 |
root |
1.41 |
finds any problems, it will croak. |
1092 |
root |
1.28 |
|
1093 |
|
|
In other words, enables "strict" mode. |
1094 |
|
|
|
1095 |
root |
1.46 |
Unlike "use strict" (or it's modern cousin, "use common::sense", it |
1096 |
|
|
is definitely recommended to keep it off in production. Keeping |
1097 |
|
|
"PERL_ANYEVENT_STRICT=1" in your environment while developing |
1098 |
|
|
programs can be very useful, however. |
1099 |
root |
1.28 |
|
1100 |
root |
1.18 |
"PERL_ANYEVENT_MODEL" |
1101 |
|
|
This can be used to specify the event model to be used by AnyEvent, |
1102 |
root |
1.22 |
before auto detection and -probing kicks in. It must be a string |
1103 |
root |
1.18 |
consisting entirely of ASCII letters. The string "AnyEvent::Impl::" |
1104 |
|
|
gets prepended and the resulting module name is loaded and if the |
1105 |
|
|
load was successful, used as event model. If it fails to load |
1106 |
root |
1.22 |
AnyEvent will proceed with auto detection and -probing. |
1107 |
root |
1.18 |
|
1108 |
|
|
This functionality might change in future versions. |
1109 |
|
|
|
1110 |
|
|
For example, to force the pure perl model (AnyEvent::Impl::Perl) you |
1111 |
|
|
could start your program like this: |
1112 |
|
|
|
1113 |
root |
1.25 |
PERL_ANYEVENT_MODEL=Perl perl ... |
1114 |
root |
1.4 |
|
1115 |
root |
1.22 |
"PERL_ANYEVENT_PROTOCOLS" |
1116 |
|
|
Used by both AnyEvent::DNS and AnyEvent::Socket to determine |
1117 |
|
|
preferences for IPv4 or IPv6. The default is unspecified (and might |
1118 |
|
|
change, or be the result of auto probing). |
1119 |
|
|
|
1120 |
|
|
Must be set to a comma-separated list of protocols or address |
1121 |
|
|
families, current supported: "ipv4" and "ipv6". Only protocols |
1122 |
|
|
mentioned will be used, and preference will be given to protocols |
1123 |
|
|
mentioned earlier in the list. |
1124 |
|
|
|
1125 |
|
|
This variable can effectively be used for denial-of-service attacks |
1126 |
|
|
against local programs (e.g. when setuid), although the impact is |
1127 |
root |
1.35 |
likely small, as the program has to handle conenction and other |
1128 |
|
|
failures anyways. |
1129 |
root |
1.22 |
|
1130 |
|
|
Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over |
1131 |
|
|
IPv6, but support both and try to use both. |
1132 |
|
|
"PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to |
1133 |
|
|
resolve or contact IPv6 addresses. |
1134 |
|
|
"PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4" support either IPv4 or IPv6, but |
1135 |
|
|
prefer IPv6 over IPv4. |
1136 |
|
|
|
1137 |
|
|
"PERL_ANYEVENT_EDNS0" |
1138 |
|
|
Used by AnyEvent::DNS to decide whether to use the EDNS0 extension |
1139 |
|
|
for DNS. This extension is generally useful to reduce DNS traffic, |
1140 |
|
|
but some (broken) firewalls drop such DNS packets, which is why it |
1141 |
|
|
is off by default. |
1142 |
|
|
|
1143 |
|
|
Setting this variable to 1 will cause AnyEvent::DNS to announce |
1144 |
|
|
EDNS0 in its DNS requests. |
1145 |
|
|
|
1146 |
root |
1.24 |
"PERL_ANYEVENT_MAX_FORKS" |
1147 |
|
|
The maximum number of child processes that |
1148 |
|
|
"AnyEvent::Util::fork_call" will create in parallel. |
1149 |
|
|
|
1150 |
root |
1.43 |
"PERL_ANYEVENT_MAX_OUTSTANDING_DNS" |
1151 |
|
|
The default value for the "max_outstanding" parameter for the |
1152 |
|
|
default DNS resolver - this is the maximum number of parallel DNS |
1153 |
|
|
requests that are sent to the DNS server. |
1154 |
|
|
|
1155 |
|
|
"PERL_ANYEVENT_RESOLV_CONF" |
1156 |
|
|
The file to use instead of /etc/resolv.conf (or OS-specific |
1157 |
|
|
configuration) in the default resolver. When set to the empty |
1158 |
|
|
string, no default config will be used. |
1159 |
|
|
|
1160 |
|
|
"PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH". |
1161 |
|
|
When neither "ca_file" nor "ca_path" was specified during |
1162 |
|
|
AnyEvent::TLS context creation, and either of these environment |
1163 |
|
|
variables exist, they will be used to specify CA certificate |
1164 |
|
|
locations instead of a system-dependent default. |
1165 |
|
|
|
1166 |
root |
1.46 |
"PERL_ANYEVENT_AVOID_GUARD" and "PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT" |
1167 |
|
|
When these are set to 1, then the respective modules are not loaded. |
1168 |
|
|
Mostly good for testing AnyEvent itself. |
1169 |
|
|
|
1170 |
root |
1.30 |
SUPPLYING YOUR OWN EVENT MODEL INTERFACE |
1171 |
|
|
This is an advanced topic that you do not normally need to use AnyEvent |
1172 |
|
|
in a module. This section is only of use to event loop authors who want |
1173 |
|
|
to provide AnyEvent compatibility. |
1174 |
|
|
|
1175 |
|
|
If you need to support another event library which isn't directly |
1176 |
|
|
supported by AnyEvent, you can supply your own interface to it by |
1177 |
|
|
pushing, before the first watcher gets created, the package name of the |
1178 |
|
|
event module and the package name of the interface to use onto |
1179 |
|
|
@AnyEvent::REGISTRY. You can do that before and even without loading |
1180 |
|
|
AnyEvent, so it is reasonably cheap. |
1181 |
|
|
|
1182 |
|
|
Example: |
1183 |
|
|
|
1184 |
|
|
push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::]; |
1185 |
|
|
|
1186 |
|
|
This tells AnyEvent to (literally) use the "urxvt::anyevent::" |
1187 |
|
|
package/class when it finds the "urxvt" package/module is already |
1188 |
|
|
loaded. |
1189 |
|
|
|
1190 |
|
|
When AnyEvent is loaded and asked to find a suitable event model, it |
1191 |
|
|
will first check for the presence of urxvt by trying to "use" the |
1192 |
|
|
"urxvt::anyevent" module. |
1193 |
|
|
|
1194 |
|
|
The class should provide implementations for all watcher types. See |
1195 |
|
|
AnyEvent::Impl::EV (source code), AnyEvent::Impl::Glib (Source code) and |
1196 |
|
|
so on for actual examples. Use "perldoc -m AnyEvent::Impl::Glib" to see |
1197 |
|
|
the sources. |
1198 |
|
|
|
1199 |
|
|
If you don't provide "signal" and "child" watchers than AnyEvent will |
1200 |
|
|
provide suitable (hopefully) replacements. |
1201 |
|
|
|
1202 |
|
|
The above example isn't fictitious, the *rxvt-unicode* (a.k.a. urxvt) |
1203 |
|
|
terminal emulator uses the above line as-is. An interface isn't included |
1204 |
|
|
in AnyEvent because it doesn't make sense outside the embedded |
1205 |
|
|
interpreter inside *rxvt-unicode*, and it is updated and maintained as |
1206 |
|
|
part of the *rxvt-unicode* distribution. |
1207 |
|
|
|
1208 |
|
|
*rxvt-unicode* also cheats a bit by not providing blocking access to |
1209 |
|
|
condition variables: code blocking while waiting for a condition will |
1210 |
|
|
"die". This still works with most modules/usages, and blocking calls |
1211 |
|
|
must not be done in an interactive application, so it makes sense. |
1212 |
|
|
|
1213 |
root |
1.16 |
EXAMPLE PROGRAM |
1214 |
root |
1.19 |
The following program uses an I/O watcher to read data from STDIN, a |
1215 |
root |
1.16 |
timer to display a message once per second, and a condition variable to |
1216 |
|
|
quit the program when the user enters quit: |
1217 |
root |
1.2 |
|
1218 |
|
|
use AnyEvent; |
1219 |
|
|
|
1220 |
|
|
my $cv = AnyEvent->condvar; |
1221 |
|
|
|
1222 |
root |
1.16 |
my $io_watcher = AnyEvent->io ( |
1223 |
|
|
fh => \*STDIN, |
1224 |
|
|
poll => 'r', |
1225 |
|
|
cb => sub { |
1226 |
|
|
warn "io event <$_[0]>\n"; # will always output <r> |
1227 |
|
|
chomp (my $input = <STDIN>); # read a line |
1228 |
|
|
warn "read: $input\n"; # output what has been read |
1229 |
root |
1.21 |
$cv->send if $input =~ /^q/i; # quit program if /^q/i |
1230 |
root |
1.16 |
}, |
1231 |
|
|
); |
1232 |
root |
1.2 |
|
1233 |
root |
1.54 |
my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub { |
1234 |
|
|
warn "timeout\n"; # print 'timeout' at most every second |
1235 |
|
|
}); |
1236 |
root |
1.2 |
|
1237 |
root |
1.21 |
$cv->recv; # wait until user enters /^q/i |
1238 |
root |
1.2 |
|
1239 |
root |
1.3 |
REAL-WORLD EXAMPLE |
1240 |
|
|
Consider the Net::FCP module. It features (among others) the following |
1241 |
|
|
API calls, which are to freenet what HTTP GET requests are to http: |
1242 |
|
|
|
1243 |
|
|
my $data = $fcp->client_get ($url); # blocks |
1244 |
|
|
|
1245 |
|
|
my $transaction = $fcp->txn_client_get ($url); # does not block |
1246 |
|
|
$transaction->cb ( sub { ... } ); # set optional result callback |
1247 |
|
|
my $data = $transaction->result; # possibly blocks |
1248 |
|
|
|
1249 |
|
|
The "client_get" method works like "LWP::Simple::get": it requests the |
1250 |
|
|
given URL and waits till the data has arrived. It is defined to be: |
1251 |
|
|
|
1252 |
|
|
sub client_get { $_[0]->txn_client_get ($_[1])->result } |
1253 |
|
|
|
1254 |
|
|
And in fact is automatically generated. This is the blocking API of |
1255 |
|
|
Net::FCP, and it works as simple as in any other, similar, module. |
1256 |
|
|
|
1257 |
|
|
More complicated is "txn_client_get": It only creates a transaction |
1258 |
|
|
(completion, result, ...) object and initiates the transaction. |
1259 |
|
|
|
1260 |
|
|
my $txn = bless { }, Net::FCP::Txn::; |
1261 |
|
|
|
1262 |
|
|
It also creates a condition variable that is used to signal the |
1263 |
|
|
completion of the request: |
1264 |
|
|
|
1265 |
|
|
$txn->{finished} = AnyAvent->condvar; |
1266 |
|
|
|
1267 |
|
|
It then creates a socket in non-blocking mode. |
1268 |
|
|
|
1269 |
|
|
socket $txn->{fh}, ...; |
1270 |
|
|
fcntl $txn->{fh}, F_SETFL, O_NONBLOCK; |
1271 |
|
|
connect $txn->{fh}, ... |
1272 |
|
|
and !$!{EWOULDBLOCK} |
1273 |
|
|
and !$!{EINPROGRESS} |
1274 |
|
|
and Carp::croak "unable to connect: $!\n"; |
1275 |
|
|
|
1276 |
root |
1.4 |
Then it creates a write-watcher which gets called whenever an error |
1277 |
root |
1.3 |
occurs or the connection succeeds: |
1278 |
|
|
|
1279 |
|
|
$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'w', cb => sub { $txn->fh_ready_w }); |
1280 |
|
|
|
1281 |
|
|
And returns this transaction object. The "fh_ready_w" callback gets |
1282 |
|
|
called as soon as the event loop detects that the socket is ready for |
1283 |
|
|
writing. |
1284 |
|
|
|
1285 |
|
|
The "fh_ready_w" method makes the socket blocking again, writes the |
1286 |
|
|
request data and replaces the watcher by a read watcher (waiting for |
1287 |
|
|
reply data). The actual code is more complicated, but that doesn't |
1288 |
|
|
matter for this example: |
1289 |
|
|
|
1290 |
|
|
fcntl $txn->{fh}, F_SETFL, 0; |
1291 |
|
|
syswrite $txn->{fh}, $txn->{request} |
1292 |
|
|
or die "connection or write error"; |
1293 |
|
|
$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r }); |
1294 |
|
|
|
1295 |
|
|
Again, "fh_ready_r" waits till all data has arrived, and then stores the |
1296 |
root |
1.22 |
result and signals any possible waiters that the request has finished: |
1297 |
root |
1.3 |
|
1298 |
|
|
sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf}; |
1299 |
|
|
|
1300 |
|
|
if (end-of-file or data complete) { |
1301 |
|
|
$txn->{result} = $txn->{buf}; |
1302 |
root |
1.21 |
$txn->{finished}->send; |
1303 |
root |
1.4 |
$txb->{cb}->($txn) of $txn->{cb}; # also call callback |
1304 |
root |
1.3 |
} |
1305 |
|
|
|
1306 |
|
|
The "result" method, finally, just waits for the finished signal (if the |
1307 |
|
|
request was already finished, it doesn't wait, of course, and returns |
1308 |
|
|
the data: |
1309 |
|
|
|
1310 |
root |
1.21 |
$txn->{finished}->recv; |
1311 |
root |
1.4 |
return $txn->{result}; |
1312 |
root |
1.3 |
|
1313 |
|
|
The actual code goes further and collects all errors ("die"s, |
1314 |
root |
1.22 |
exceptions) that occurred during request processing. The "result" method |
1315 |
root |
1.16 |
detects whether an exception as thrown (it is stored inside the $txn |
1316 |
root |
1.3 |
object) and just throws the exception, which means connection errors and |
1317 |
|
|
other problems get reported tot he code that tries to use the result, |
1318 |
|
|
not in a random callback. |
1319 |
|
|
|
1320 |
|
|
All of this enables the following usage styles: |
1321 |
|
|
|
1322 |
|
|
1. Blocking: |
1323 |
|
|
|
1324 |
|
|
my $data = $fcp->client_get ($url); |
1325 |
|
|
|
1326 |
root |
1.15 |
2. Blocking, but running in parallel: |
1327 |
root |
1.3 |
|
1328 |
|
|
my @datas = map $_->result, |
1329 |
|
|
map $fcp->txn_client_get ($_), |
1330 |
|
|
@urls; |
1331 |
|
|
|
1332 |
|
|
Both blocking examples work without the module user having to know |
1333 |
|
|
anything about events. |
1334 |
|
|
|
1335 |
root |
1.15 |
3a. Event-based in a main program, using any supported event module: |
1336 |
root |
1.3 |
|
1337 |
root |
1.15 |
use EV; |
1338 |
root |
1.3 |
|
1339 |
|
|
$fcp->txn_client_get ($url)->cb (sub { |
1340 |
|
|
my $txn = shift; |
1341 |
|
|
my $data = $txn->result; |
1342 |
|
|
... |
1343 |
|
|
}); |
1344 |
|
|
|
1345 |
root |
1.15 |
EV::loop; |
1346 |
root |
1.3 |
|
1347 |
|
|
3b. The module user could use AnyEvent, too: |
1348 |
|
|
|
1349 |
|
|
use AnyEvent; |
1350 |
|
|
|
1351 |
|
|
my $quit = AnyEvent->condvar; |
1352 |
|
|
|
1353 |
|
|
$fcp->txn_client_get ($url)->cb (sub { |
1354 |
|
|
... |
1355 |
root |
1.21 |
$quit->send; |
1356 |
root |
1.3 |
}); |
1357 |
|
|
|
1358 |
root |
1.21 |
$quit->recv; |
1359 |
root |
1.3 |
|
1360 |
root |
1.19 |
BENCHMARKS |
1361 |
|
|
To give you an idea of the performance and overheads that AnyEvent adds |
1362 |
|
|
over the event loops themselves and to give you an impression of the |
1363 |
|
|
speed of various event loops I prepared some benchmarks. |
1364 |
|
|
|
1365 |
|
|
BENCHMARKING ANYEVENT OVERHEAD |
1366 |
|
|
Here is a benchmark of various supported event models used natively and |
1367 |
root |
1.22 |
through AnyEvent. The benchmark creates a lot of timers (with a zero |
1368 |
root |
1.19 |
timeout) and I/O watchers (watching STDOUT, a pty, to become writable, |
1369 |
|
|
which it is), lets them fire exactly once and destroys them again. |
1370 |
|
|
|
1371 |
|
|
Source code for this benchmark is found as eg/bench in the AnyEvent |
1372 |
root |
1.51 |
distribution. It uses the AE interface, which makes a real difference |
1373 |
|
|
for the EV and Perl backends only. |
1374 |
root |
1.19 |
|
1375 |
|
|
Explanation of the columns |
1376 |
|
|
*watcher* is the number of event watchers created/destroyed. Since |
1377 |
|
|
different event models feature vastly different performances, each event |
1378 |
|
|
loop was given a number of watchers so that overall runtime is |
1379 |
|
|
acceptable and similar between tested event loop (and keep them from |
1380 |
|
|
crashing): Glib would probably take thousands of years if asked to |
1381 |
|
|
process the same number of watchers as EV in this benchmark. |
1382 |
|
|
|
1383 |
|
|
*bytes* is the number of bytes (as measured by the resident set size, |
1384 |
|
|
RSS) consumed by each watcher. This method of measuring captures both C |
1385 |
|
|
and Perl-based overheads. |
1386 |
|
|
|
1387 |
|
|
*create* is the time, in microseconds (millionths of seconds), that it |
1388 |
|
|
takes to create a single watcher. The callback is a closure shared |
1389 |
|
|
between all watchers, to avoid adding memory overhead. That means |
1390 |
|
|
closure creation and memory usage is not included in the figures. |
1391 |
|
|
|
1392 |
|
|
*invoke* is the time, in microseconds, used to invoke a simple callback. |
1393 |
|
|
The callback simply counts down a Perl variable and after it was invoked |
1394 |
root |
1.21 |
"watcher" times, it would "->send" a condvar once to signal the end of |
1395 |
|
|
this phase. |
1396 |
root |
1.19 |
|
1397 |
|
|
*destroy* is the time, in microseconds, that it takes to destroy a |
1398 |
|
|
single watcher. |
1399 |
|
|
|
1400 |
|
|
Results |
1401 |
|
|
name watchers bytes create invoke destroy comment |
1402 |
root |
1.51 |
EV/EV 100000 223 0.47 0.43 0.27 EV native interface |
1403 |
|
|
EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers |
1404 |
|
|
Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal |
1405 |
|
|
Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation |
1406 |
|
|
Event/Event 16000 516 31.16 31.84 0.82 Event native interface |
1407 |
|
|
Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers |
1408 |
|
|
IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll |
1409 |
|
|
IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll |
1410 |
|
|
Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour |
1411 |
|
|
Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers |
1412 |
|
|
POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event |
1413 |
|
|
POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select |
1414 |
root |
1.19 |
|
1415 |
|
|
Discussion |
1416 |
|
|
The benchmark does *not* measure scalability of the event loop very |
1417 |
|
|
well. For example, a select-based event loop (such as the pure perl one) |
1418 |
|
|
can never compete with an event loop that uses epoll when the number of |
1419 |
|
|
file descriptors grows high. In this benchmark, all events become ready |
1420 |
|
|
at the same time, so select/poll-based implementations get an unnatural |
1421 |
|
|
speed boost. |
1422 |
|
|
|
1423 |
|
|
Also, note that the number of watchers usually has a nonlinear effect on |
1424 |
|
|
overall speed, that is, creating twice as many watchers doesn't take |
1425 |
|
|
twice the time - usually it takes longer. This puts event loops tested |
1426 |
|
|
with a higher number of watchers at a disadvantage. |
1427 |
|
|
|
1428 |
|
|
To put the range of results into perspective, consider that on the |
1429 |
|
|
benchmark machine, handling an event takes roughly 1600 CPU cycles with |
1430 |
|
|
EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 |
1431 |
|
|
CPU cycles with POE. |
1432 |
|
|
|
1433 |
|
|
"EV" is the sole leader regarding speed and memory use, which are both |
1434 |
root |
1.51 |
maximal/minimal, respectively. When using the AE API there is zero |
1435 |
|
|
overhead (when going through the AnyEvent API create is about 5-6 times |
1436 |
|
|
slower, with other times being equal, so still uses far less memory than |
1437 |
|
|
any other event loop and is still faster than Event natively). |
1438 |
root |
1.19 |
|
1439 |
|
|
The pure perl implementation is hit in a few sweet spots (both the |
1440 |
|
|
constant timeout and the use of a single fd hit optimisations in the |
1441 |
|
|
perl interpreter and the backend itself). Nevertheless this shows that |
1442 |
|
|
it adds very little overhead in itself. Like any select-based backend |
1443 |
|
|
its performance becomes really bad with lots of file descriptors (and |
1444 |
|
|
few of them active), of course, but this was not subject of this |
1445 |
|
|
benchmark. |
1446 |
|
|
|
1447 |
|
|
The "Event" module has a relatively high setup and callback invocation |
1448 |
|
|
cost, but overall scores in on the third place. |
1449 |
|
|
|
1450 |
root |
1.41 |
"IO::Async" performs admirably well, about on par with "Event", even |
1451 |
|
|
when using its pure perl backend. |
1452 |
|
|
|
1453 |
root |
1.19 |
"Glib"'s memory usage is quite a bit higher, but it features a faster |
1454 |
|
|
callback invocation and overall ends up in the same class as "Event". |
1455 |
|
|
However, Glib scales extremely badly, doubling the number of watchers |
1456 |
|
|
increases the processing time by more than a factor of four, making it |
1457 |
|
|
completely unusable when using larger numbers of watchers (note that |
1458 |
|
|
only a single file descriptor was used in the benchmark, so |
1459 |
|
|
inefficiencies of "poll" do not account for this). |
1460 |
|
|
|
1461 |
|
|
The "Tk" adaptor works relatively well. The fact that it crashes with |
1462 |
|
|
more than 2000 watchers is a big setback, however, as correctness takes |
1463 |
|
|
precedence over speed. Nevertheless, its performance is surprising, as |
1464 |
|
|
the file descriptor is dup()ed for each watcher. This shows that the |
1465 |
|
|
dup() employed by some adaptors is not a big performance issue (it does |
1466 |
|
|
incur a hidden memory cost inside the kernel which is not reflected in |
1467 |
|
|
the figures above). |
1468 |
|
|
|
1469 |
|
|
"POE", regardless of underlying event loop (whether using its pure perl |
1470 |
|
|
select-based backend or the Event module, the POE-EV backend couldn't be |
1471 |
|
|
tested because it wasn't working) shows abysmal performance and memory |
1472 |
root |
1.20 |
usage with AnyEvent: Watchers use almost 30 times as much memory as EV |
1473 |
|
|
watchers, and 10 times as much memory as Event (the high memory |
1474 |
|
|
requirements are caused by requiring a session for each watcher). |
1475 |
|
|
Watcher invocation speed is almost 900 times slower than with AnyEvent's |
1476 |
|
|
pure perl implementation. |
1477 |
|
|
|
1478 |
|
|
The design of the POE adaptor class in AnyEvent can not really account |
1479 |
|
|
for the performance issues, though, as session creation overhead is |
1480 |
|
|
small compared to execution of the state machine, which is coded pretty |
1481 |
|
|
optimally within AnyEvent::Impl::POE (and while everybody agrees that |
1482 |
|
|
using multiple sessions is not a good approach, especially regarding |
1483 |
|
|
memory usage, even the author of POE could not come up with a faster |
1484 |
|
|
design). |
1485 |
root |
1.19 |
|
1486 |
|
|
Summary |
1487 |
|
|
* Using EV through AnyEvent is faster than any other event loop (even |
1488 |
|
|
when used without AnyEvent), but most event loops have acceptable |
1489 |
|
|
performance with or without AnyEvent. |
1490 |
|
|
|
1491 |
|
|
* The overhead AnyEvent adds is usually much smaller than the overhead |
1492 |
|
|
of the actual event loop, only with extremely fast event loops such |
1493 |
|
|
as EV adds AnyEvent significant overhead. |
1494 |
|
|
|
1495 |
|
|
* You should avoid POE like the plague if you want performance or |
1496 |
|
|
reasonable memory usage. |
1497 |
|
|
|
1498 |
|
|
BENCHMARKING THE LARGE SERVER CASE |
1499 |
root |
1.22 |
This benchmark actually benchmarks the event loop itself. It works by |
1500 |
|
|
creating a number of "servers": each server consists of a socket pair, a |
1501 |
root |
1.19 |
timeout watcher that gets reset on activity (but never fires), and an |
1502 |
|
|
I/O watcher waiting for input on one side of the socket. Each time the |
1503 |
|
|
socket watcher reads a byte it will write that byte to a random other |
1504 |
|
|
"server". |
1505 |
|
|
|
1506 |
|
|
The effect is that there will be a lot of I/O watchers, only part of |
1507 |
|
|
which are active at any one point (so there is a constant number of |
1508 |
root |
1.22 |
active fds for each loop iteration, but which fds these are is random). |
1509 |
root |
1.19 |
The timeout is reset each time something is read because that reflects |
1510 |
|
|
how most timeouts work (and puts extra pressure on the event loops). |
1511 |
|
|
|
1512 |
root |
1.22 |
In this benchmark, we use 10000 socket pairs (20000 sockets), of which |
1513 |
root |
1.19 |
100 (1%) are active. This mirrors the activity of large servers with |
1514 |
|
|
many connections, most of which are idle at any one point in time. |
1515 |
|
|
|
1516 |
|
|
Source code for this benchmark is found as eg/bench2 in the AnyEvent |
1517 |
root |
1.51 |
distribution. It uses the AE interface, which makes a real difference |
1518 |
|
|
for the EV and Perl backends only. |
1519 |
root |
1.19 |
|
1520 |
|
|
Explanation of the columns |
1521 |
|
|
*sockets* is the number of sockets, and twice the number of "servers" |
1522 |
|
|
(as each server has a read and write socket end). |
1523 |
|
|
|
1524 |
root |
1.22 |
*create* is the time it takes to create a socket pair (which is |
1525 |
root |
1.19 |
nontrivial) and two watchers: an I/O watcher and a timeout watcher. |
1526 |
|
|
|
1527 |
|
|
*request*, the most important value, is the time it takes to handle a |
1528 |
|
|
single "request", that is, reading the token from the pipe and |
1529 |
|
|
forwarding it to another server. This includes deleting the old timeout |
1530 |
|
|
and creating a new one that moves the timeout into the future. |
1531 |
|
|
|
1532 |
|
|
Results |
1533 |
root |
1.41 |
name sockets create request |
1534 |
root |
1.51 |
EV 20000 62.66 7.99 |
1535 |
|
|
Perl 20000 68.32 32.64 |
1536 |
|
|
IOAsync 20000 174.06 101.15 epoll |
1537 |
|
|
IOAsync 20000 174.67 610.84 poll |
1538 |
|
|
Event 20000 202.69 242.91 |
1539 |
|
|
Glib 20000 557.01 1689.52 |
1540 |
|
|
POE 20000 341.54 12086.32 uses POE::Loop::Event |
1541 |
root |
1.19 |
|
1542 |
|
|
Discussion |
1543 |
|
|
This benchmark *does* measure scalability and overall performance of the |
1544 |
|
|
particular event loop. |
1545 |
|
|
|
1546 |
|
|
EV is again fastest. Since it is using epoll on my system, the setup |
1547 |
|
|
time is relatively high, though. |
1548 |
|
|
|
1549 |
|
|
Perl surprisingly comes second. It is much faster than the C-based event |
1550 |
|
|
loops Event and Glib. |
1551 |
|
|
|
1552 |
root |
1.41 |
IO::Async performs very well when using its epoll backend, and still |
1553 |
|
|
quite good compared to Glib when using its pure perl backend. |
1554 |
|
|
|
1555 |
root |
1.19 |
Event suffers from high setup time as well (look at its code and you |
1556 |
|
|
will understand why). Callback invocation also has a high overhead |
1557 |
|
|
compared to the "$_->() for .."-style loop that the Perl event loop |
1558 |
|
|
uses. Event uses select or poll in basically all documented |
1559 |
|
|
configurations. |
1560 |
|
|
|
1561 |
|
|
Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It |
1562 |
|
|
clearly fails to perform with many filehandles or in busy servers. |
1563 |
|
|
|
1564 |
|
|
POE is still completely out of the picture, taking over 1000 times as |
1565 |
|
|
long as EV, and over 100 times as long as the Perl implementation, even |
1566 |
|
|
though it uses a C-based event loop in this case. |
1567 |
|
|
|
1568 |
|
|
Summary |
1569 |
root |
1.20 |
* The pure perl implementation performs extremely well. |
1570 |
root |
1.19 |
|
1571 |
|
|
* Avoid Glib or POE in large projects where performance matters. |
1572 |
|
|
|
1573 |
|
|
BENCHMARKING SMALL SERVERS |
1574 |
|
|
While event loops should scale (and select-based ones do not...) even to |
1575 |
|
|
large servers, most programs we (or I :) actually write have only a few |
1576 |
|
|
I/O watchers. |
1577 |
|
|
|
1578 |
|
|
In this benchmark, I use the same benchmark program as in the large |
1579 |
|
|
server case, but it uses only eight "servers", of which three are active |
1580 |
|
|
at any one time. This should reflect performance for a small server |
1581 |
|
|
relatively well. |
1582 |
|
|
|
1583 |
|
|
The columns are identical to the previous table. |
1584 |
|
|
|
1585 |
|
|
Results |
1586 |
|
|
name sockets create request |
1587 |
|
|
EV 16 20.00 6.54 |
1588 |
|
|
Perl 16 25.75 12.62 |
1589 |
|
|
Event 16 81.27 35.86 |
1590 |
|
|
Glib 16 32.63 15.48 |
1591 |
|
|
POE 16 261.87 276.28 uses POE::Loop::Event |
1592 |
|
|
|
1593 |
|
|
Discussion |
1594 |
|
|
The benchmark tries to test the performance of a typical small server. |
1595 |
|
|
While knowing how various event loops perform is interesting, keep in |
1596 |
|
|
mind that their overhead in this case is usually not as important, due |
1597 |
|
|
to the small absolute number of watchers (that is, you need efficiency |
1598 |
|
|
and speed most when you have lots of watchers, not when you only have a |
1599 |
|
|
few of them). |
1600 |
|
|
|
1601 |
|
|
EV is again fastest. |
1602 |
|
|
|
1603 |
root |
1.22 |
Perl again comes second. It is noticeably faster than the C-based event |
1604 |
root |
1.19 |
loops Event and Glib, although the difference is too small to really |
1605 |
|
|
matter. |
1606 |
|
|
|
1607 |
|
|
POE also performs much better in this case, but is is still far behind |
1608 |
|
|
the others. |
1609 |
|
|
|
1610 |
|
|
Summary |
1611 |
|
|
* C-based event loops perform very well with small number of watchers, |
1612 |
|
|
as the management overhead dominates. |
1613 |
|
|
|
1614 |
root |
1.40 |
THE IO::Lambda BENCHMARK |
1615 |
|
|
Recently I was told about the benchmark in the IO::Lambda manpage, which |
1616 |
|
|
could be misinterpreted to make AnyEvent look bad. In fact, the |
1617 |
|
|
benchmark simply compares IO::Lambda with POE, and IO::Lambda looks |
1618 |
|
|
better (which shouldn't come as a surprise to anybody). As such, the |
1619 |
root |
1.41 |
benchmark is fine, and mostly shows that the AnyEvent backend from |
1620 |
|
|
IO::Lambda isn't very optimal. But how would AnyEvent compare when used |
1621 |
|
|
without the extra baggage? To explore this, I wrote the equivalent |
1622 |
|
|
benchmark for AnyEvent. |
1623 |
root |
1.40 |
|
1624 |
|
|
The benchmark itself creates an echo-server, and then, for 500 times, |
1625 |
|
|
connects to the echo server, sends a line, waits for the reply, and then |
1626 |
|
|
creates the next connection. This is a rather bad benchmark, as it |
1627 |
root |
1.41 |
doesn't test the efficiency of the framework or much non-blocking I/O, |
1628 |
|
|
but it is a benchmark nevertheless. |
1629 |
root |
1.40 |
|
1630 |
|
|
name runtime |
1631 |
|
|
Lambda/select 0.330 sec |
1632 |
|
|
+ optimized 0.122 sec |
1633 |
|
|
Lambda/AnyEvent 0.327 sec |
1634 |
|
|
+ optimized 0.138 sec |
1635 |
|
|
Raw sockets/select 0.077 sec |
1636 |
|
|
POE/select, components 0.662 sec |
1637 |
|
|
POE/select, raw sockets 0.226 sec |
1638 |
|
|
POE/select, optimized 0.404 sec |
1639 |
|
|
|
1640 |
|
|
AnyEvent/select/nb 0.085 sec |
1641 |
|
|
AnyEvent/EV/nb 0.068 sec |
1642 |
|
|
+state machine 0.134 sec |
1643 |
|
|
|
1644 |
root |
1.41 |
The benchmark is also a bit unfair (my fault): the IO::Lambda/POE |
1645 |
root |
1.40 |
benchmarks actually make blocking connects and use 100% blocking I/O, |
1646 |
|
|
defeating the purpose of an event-based solution. All of the newly |
1647 |
|
|
written AnyEvent benchmarks use 100% non-blocking connects (using |
1648 |
|
|
AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS |
1649 |
root |
1.41 |
resolver), so AnyEvent is at a disadvantage here, as non-blocking |
1650 |
root |
1.40 |
connects generally require a lot more bookkeeping and event handling |
1651 |
|
|
than blocking connects (which involve a single syscall only). |
1652 |
|
|
|
1653 |
|
|
The last AnyEvent benchmark additionally uses AnyEvent::Handle, which |
1654 |
root |
1.41 |
offers similar expressive power as POE and IO::Lambda, using |
1655 |
|
|
conventional Perl syntax. This means that both the echo server and the |
1656 |
|
|
client are 100% non-blocking, further placing it at a disadvantage. |
1657 |
|
|
|
1658 |
|
|
As you can see, the AnyEvent + EV combination even beats the |
1659 |
|
|
hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl |
1660 |
|
|
backend easily beats IO::Lambda and POE. |
1661 |
root |
1.40 |
|
1662 |
|
|
And even the 100% non-blocking version written using the high-level (and |
1663 |
root |
1.54 |
slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda |
1664 |
|
|
higher level ("unoptimised") abstractions by a large margin, even though |
1665 |
|
|
it does all of DNS, tcp-connect and socket I/O in a non-blocking way. |
1666 |
root |
1.41 |
|
1667 |
|
|
The two AnyEvent benchmarks programs can be found as eg/ae0.pl and |
1668 |
|
|
eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are |
1669 |
root |
1.54 |
part of the IO::Lambda distribution and were used without any changes. |
1670 |
root |
1.40 |
|
1671 |
root |
1.32 |
SIGNALS |
1672 |
|
|
AnyEvent currently installs handlers for these signals: |
1673 |
|
|
|
1674 |
|
|
SIGCHLD |
1675 |
|
|
A handler for "SIGCHLD" is installed by AnyEvent's child watcher |
1676 |
|
|
emulation for event loops that do not support them natively. Also, |
1677 |
|
|
some event loops install a similar handler. |
1678 |
|
|
|
1679 |
root |
1.44 |
Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, |
1680 |
|
|
then AnyEvent will reset it to default, to avoid losing child exit |
1681 |
|
|
statuses. |
1682 |
root |
1.41 |
|
1683 |
root |
1.32 |
SIGPIPE |
1684 |
|
|
A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is |
1685 |
|
|
"undef" when AnyEvent gets loaded. |
1686 |
|
|
|
1687 |
|
|
The rationale for this is that AnyEvent users usually do not really |
1688 |
|
|
depend on SIGPIPE delivery (which is purely an optimisation for |
1689 |
|
|
shell use, or badly-written programs), but "SIGPIPE" can cause |
1690 |
|
|
spurious and rare program exits as a lot of people do not expect |
1691 |
|
|
"SIGPIPE" when writing to some random socket. |
1692 |
|
|
|
1693 |
|
|
The rationale for installing a no-op handler as opposed to ignoring |
1694 |
|
|
it is that this way, the handler will be restored to defaults on |
1695 |
|
|
exec. |
1696 |
|
|
|
1697 |
|
|
Feel free to install your own handler, or reset it to defaults. |
1698 |
|
|
|
1699 |
root |
1.46 |
RECOMMENDED/OPTIONAL MODULES |
1700 |
|
|
One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and |
1701 |
|
|
it's built-in modules) are required to use it. |
1702 |
|
|
|
1703 |
|
|
That does not mean that AnyEvent won't take advantage of some additional |
1704 |
|
|
modules if they are installed. |
1705 |
|
|
|
1706 |
|
|
This section epxlains which additional modules will be used, and how |
1707 |
|
|
they affect AnyEvent's operetion. |
1708 |
|
|
|
1709 |
|
|
Async::Interrupt |
1710 |
|
|
This slightly arcane module is used to implement fast signal |
1711 |
|
|
handling: To my knowledge, there is no way to do completely |
1712 |
|
|
race-free and quick signal handling in pure perl. To ensure that |
1713 |
|
|
signals still get delivered, AnyEvent will start an interval timer |
1714 |
root |
1.47 |
to wake up perl (and catch the signals) with some delay (default is |
1715 |
root |
1.46 |
10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY). |
1716 |
|
|
|
1717 |
|
|
If this module is available, then it will be used to implement |
1718 |
|
|
signal catching, which means that signals will not be delayed, and |
1719 |
|
|
the event loop will not be interrupted regularly, which is more |
1720 |
|
|
efficient (And good for battery life on laptops). |
1721 |
|
|
|
1722 |
|
|
This affects not just the pure-perl event loop, but also other event |
1723 |
|
|
loops that have no signal handling on their own (e.g. Glib, Tk, Qt). |
1724 |
|
|
|
1725 |
root |
1.47 |
Some event loops (POE, Event, Event::Lib) offer signal watchers |
1726 |
|
|
natively, and either employ their own workarounds (POE) or use |
1727 |
|
|
AnyEvent's workaround (using $AnyEvent::MAX_SIGNAL_LATENCY). |
1728 |
|
|
Installing Async::Interrupt does nothing for those backends. |
1729 |
|
|
|
1730 |
root |
1.46 |
EV This module isn't really "optional", as it is simply one of the |
1731 |
|
|
backend event loops that AnyEvent can use. However, it is simply the |
1732 |
|
|
best event loop available in terms of features, speed and stability: |
1733 |
|
|
It supports the AnyEvent API optimally, implements all the watcher |
1734 |
|
|
types in XS, does automatic timer adjustments even when no monotonic |
1735 |
|
|
clock is available, can take avdantage of advanced kernel interfaces |
1736 |
|
|
such as "epoll" and "kqueue", and is the fastest backend *by far*. |
1737 |
|
|
You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and |
1738 |
|
|
Glib::EV). |
1739 |
|
|
|
1740 |
|
|
Guard |
1741 |
|
|
The guard module, when used, will be used to implement |
1742 |
|
|
"AnyEvent::Util::guard". This speeds up guards considerably (and |
1743 |
|
|
uses a lot less memory), but otherwise doesn't affect guard |
1744 |
|
|
operation much. It is purely used for performance. |
1745 |
|
|
|
1746 |
|
|
JSON and JSON::XS |
1747 |
root |
1.55 |
One of these modules is required when you want to read or write JSON |
1748 |
|
|
data via AnyEvent::Handle. It is also written in pure-perl, but can |
1749 |
|
|
take advantage of the ultra-high-speed JSON::XS module when it is |
1750 |
root |
1.46 |
installed. |
1751 |
|
|
|
1752 |
|
|
In fact, AnyEvent::Handle will use JSON::XS by default if it is |
1753 |
|
|
installed. |
1754 |
|
|
|
1755 |
|
|
Net::SSLeay |
1756 |
|
|
Implementing TLS/SSL in Perl is certainly interesting, but not very |
1757 |
|
|
worthwhile: If this module is installed, then AnyEvent::Handle (with |
1758 |
|
|
the help of AnyEvent::TLS), gains the ability to do TLS/SSL. |
1759 |
|
|
|
1760 |
|
|
Time::HiRes |
1761 |
|
|
This module is part of perl since release 5.008. It will be used |
1762 |
|
|
when the chosen event library does not come with a timing source on |
1763 |
|
|
it's own. The pure-perl event loop (AnyEvent::Impl::Perl) will |
1764 |
|
|
additionally use it to try to use a monotonic clock for timing |
1765 |
|
|
stability. |
1766 |
|
|
|
1767 |
root |
1.18 |
FORK |
1768 |
|
|
Most event libraries are not fork-safe. The ones who are usually are |
1769 |
root |
1.20 |
because they rely on inefficient but fork-safe "select" or "poll" calls. |
1770 |
|
|
Only EV is fully fork-aware. |
1771 |
root |
1.18 |
|
1772 |
|
|
If you have to fork, you must either do so *before* creating your first |
1773 |
root |
1.46 |
watcher OR you must not use AnyEvent at all in the child OR you must do |
1774 |
|
|
something completely out of the scope of AnyEvent. |
1775 |
root |
1.18 |
|
1776 |
|
|
SECURITY CONSIDERATIONS |
1777 |
|
|
AnyEvent can be forced to load any event model via |
1778 |
|
|
$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used |
1779 |
|
|
to execute arbitrary code or directly gain access, it can easily be used |
1780 |
|
|
to make the program hang or malfunction in subtle ways, as AnyEvent |
1781 |
|
|
watchers will not be active when the program uses a different event |
1782 |
|
|
model than specified in the variable. |
1783 |
|
|
|
1784 |
|
|
You can make AnyEvent completely ignore this variable by deleting it |
1785 |
|
|
before the first watcher gets created, e.g. with a "BEGIN" block: |
1786 |
|
|
|
1787 |
root |
1.25 |
BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } |
1788 |
root |
1.40 |
|
1789 |
|
|
use AnyEvent; |
1790 |
root |
1.18 |
|
1791 |
root |
1.20 |
Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can |
1792 |
|
|
be used to probe what backend is used and gain other information (which |
1793 |
root |
1.28 |
is probably even less useful to an attacker than PERL_ANYEVENT_MODEL), |
1794 |
root |
1.40 |
and $ENV{PERL_ANYEVENT_STRICT}. |
1795 |
root |
1.20 |
|
1796 |
root |
1.41 |
Note that AnyEvent will remove *all* environment variables starting with |
1797 |
|
|
"PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is |
1798 |
|
|
enabled. |
1799 |
|
|
|
1800 |
root |
1.26 |
BUGS |
1801 |
|
|
Perl 5.8 has numerous memleaks that sometimes hit this module and are |
1802 |
|
|
hard to work around. If you suffer from memleaks, first upgrade to Perl |
1803 |
|
|
5.10 and check wether the leaks still show up. (Perl 5.10.0 has other |
1804 |
root |
1.36 |
annoying memleaks, such as leaking on "map" and "grep" but it is usually |
1805 |
root |
1.26 |
not as pronounced). |
1806 |
|
|
|
1807 |
root |
1.2 |
SEE ALSO |
1808 |
root |
1.22 |
Utility functions: AnyEvent::Util. |
1809 |
|
|
|
1810 |
root |
1.20 |
Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk, |
1811 |
|
|
Event::Lib, Qt, POE. |
1812 |
|
|
|
1813 |
|
|
Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event, |
1814 |
|
|
AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl, |
1815 |
root |
1.43 |
AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE, |
1816 |
root |
1.48 |
AnyEvent::Impl::IOAsync, Anyevent::Impl::Irssi. |
1817 |
root |
1.3 |
|
1818 |
root |
1.22 |
Non-blocking file handles, sockets, TCP clients and servers: |
1819 |
root |
1.43 |
AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS. |
1820 |
root |
1.22 |
|
1821 |
|
|
Asynchronous DNS: AnyEvent::DNS. |
1822 |
|
|
|
1823 |
root |
1.20 |
Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event, |
1824 |
root |
1.3 |
|
1825 |
root |
1.43 |
Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::XMPP, |
1826 |
|
|
AnyEvent::HTTP. |
1827 |
root |
1.2 |
|
1828 |
root |
1.17 |
AUTHOR |
1829 |
root |
1.25 |
Marc Lehmann <schmorp@schmorp.de> |
1830 |
|
|
http://home.schmorp.de/ |
1831 |
root |
1.2 |
|