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NAME |
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AnyEvent - provide framework for multiple event loops |
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EV, Event, Coro::EV, Coro::Event, Glib, Tk, Perl, Event::Lib, Qt - |
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various supported event loops |
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SYNOPSIS |
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use AnyEvent; |
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my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub { |
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... |
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}); |
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my $w = AnyEvent->timer (after => $seconds, cb => sub { |
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... |
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}); |
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my $w = AnyEvent->condvar; # stores whether a condition was flagged |
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$w->wait; # enters "main loop" till $condvar gets ->broadcast |
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$w->broadcast; # wake up current and all future wait's |
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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 helps hiding the differences between 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 it is simply incompatible to everything |
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that isn't itself. 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 POE and IO::Async, as long as |
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those use one of the supported event loops. It is trivial to add new |
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event loops to AnyEvent, too, so it is future-proof). |
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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 enourmous amount of code and strict rules you have |
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to 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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Of course, if you 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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1.2 |
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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1.2 |
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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1.16 |
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: Coro::EV, Coro::Event, EV, Event, |
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Glib, Tk, Event::Lib, Qt. The first one found is used. If none are |
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found, the module tries to load these modules (excluding Event::Lib and |
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Qt) in the order given. The first one that can be successfully loaded |
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will be used. If, after this, still none could be found, AnyEvent will |
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fall back to a pure-perl event loop, which is not very efficient, but |
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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. |
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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 filehandle to watch, etc. |
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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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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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1.6 |
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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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1.6 |
IO WATCHERS |
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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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1.6 |
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"fh" the Perl *file handle* (*not* file descriptor) to watch for events. |
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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. "cb" |
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is the callback to invoke each time the file handle becomes ready. |
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1.18 |
As long as the I/O watcher exists it will keep the file descriptor or a |
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copy of it alive/open. |
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1.16 |
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It is not allowed to close a file handle as long as any watcher is |
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active on 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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1.6 |
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Example: |
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# wait for readability of STDIN, then read a line and disable the 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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You can create a time watcher by calling the "AnyEvent->timer" method |
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1.6 |
with the following mandatory arguments: |
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1.16 |
"after" specifies after how many seconds (fractional values are |
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supported) should the timer activate. "cb" the callback to invoke in |
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that case. |
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1.6 |
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The timer callback will be invoked at most once: if you want a repeating |
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timer you have to create a new watcher (this is a limitation by both Tk |
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and Glib). |
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Example: |
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# fire an event after 7.7 seconds |
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my $w = AnyEvent->timer (after => 7.7, cb => sub { |
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warn "timeout\n"; |
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}); |
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# to cancel the timer: |
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1.13 |
undef $w; |
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1.16 |
Example 2: |
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# fire an event after 0.5 seconds, then roughly every second |
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my $w; |
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my $cb = sub { |
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# cancel the old timer while creating a new one |
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$w = AnyEvent->timer (after => 1, cb => $cb); |
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}; |
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# start the "loop" by creating the first watcher |
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$w = AnyEvent->timer (after => 0.5, cb => $cb); |
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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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1.18 |
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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1.16 |
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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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1.18 |
(ev_timer, based on true relative time) and absolute (ev_periodic, based |
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on wallclock time) timers. |
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1.16 |
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AnyEvent always prefers relative timers, if available, matching the |
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AnyEvent API. |
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SIGNAL WATCHERS |
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You can watch for signals using a signal watcher, "signal" is the signal |
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*name* without any "SIG" prefix, "cb" is the Perl callback to be invoked |
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whenever a signal occurs. |
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1.18 |
Multiple signal occurances can be clumped together into one callback |
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1.16 |
invocation, and callback invocation will be synchronous. synchronous |
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means that it might take a while until the signal gets handled by the |
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process, but it is guarenteed not to interrupt any other callbacks. |
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The main advantage of using these watchers is that you can share a |
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signal between multiple watchers. |
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This watcher might use %SIG, so programs overwriting those signals |
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directly will likely not work correctly. |
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Example: exit on SIGINT |
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my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 }); |
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CHILD PROCESS WATCHERS |
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You can also watch on a child process exit and catch its exit status. |
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The child process is specified by the "pid" argument (if set to 0, it |
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watches for any child process exit). The watcher will trigger as often |
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as status change for the child are received. This works by installing a |
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signal handler for "SIGCHLD". The callback will be called with the pid |
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and exit status (as returned by waitpid). |
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Example: wait for pid 1333 |
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my $w = AnyEvent->child ( |
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pid => 1333, |
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cb => sub { |
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my ($pid, $status) = @_; |
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warn "pid $pid exited with status $status"; |
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}, |
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); |
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CONDITION VARIABLES |
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Condition variables can be created by calling the "AnyEvent->condvar" |
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1.6 |
method without any arguments. |
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1.16 |
A condition variable waits for a condition - precisely that the |
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1.6 |
"->broadcast" method has been called. |
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1.16 |
They are very useful to signal that a condition has been fulfilled, for |
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example, if you write a module that does asynchronous http requests, |
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then a condition variable would be the ideal candidate to signal the |
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availability of results. |
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You can also use condition variables to block your main program until an |
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event occurs - for example, you could "->wait" in your main program |
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until the user clicks the Quit button in your app, which would |
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"->broadcast" the "quit" event. |
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Note that condition variables recurse into the event loop - if you have |
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two pirces of code that call "->wait" in a round-robbin fashion, you |
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lose. Therefore, condition variables are good to export to your caller, |
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but you should avoid making a blocking wait yourself, at least in |
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callbacks, as this asks for trouble. |
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1.14 |
|
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1.16 |
This object has two methods: |
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1.6 |
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$cv->wait |
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Wait (blocking if necessary) until the "->broadcast" method has been |
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called on c<$cv>, while servicing other watchers normally. |
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You can only wait once on a condition - additional calls will return |
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immediately. |
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1.15 |
Not all event models support a blocking wait - some die in that case |
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1.16 |
(programs might want to do that to stay interactive), so *if you are |
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using this from a module, never require a blocking wait*, but let |
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the caller decide whether the call will block or not (for example, |
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by coupling condition variables with some kind of request results |
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and supporting callbacks so the caller knows that getting the result |
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will not block, while still suppporting blocking waits if the caller |
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so desires). |
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1.15 |
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Another reason *never* to "->wait" in a module is that you cannot |
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sensibly have two "->wait"'s in parallel, as that would require |
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multiple interpreters or coroutines/threads, none of which |
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1.16 |
"AnyEvent" can supply (the coroutine-aware backends |
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AnyEvent::Impl::CoroEV and AnyEvent::Impl::CoroEvent explicitly |
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support concurrent "->wait"'s from different coroutines, however). |
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1.15 |
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1.6 |
$cv->broadcast |
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Flag the condition as ready - a running "->wait" and all further |
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1.16 |
calls to "wait" will (eventually) return after this method has been |
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called. If nobody is waiting the broadcast will be remembered.. |
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1.6 |
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1.16 |
Example: |
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1.8 |
|
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1.16 |
# wait till the result is ready |
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my $result_ready = AnyEvent->condvar; |
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1.8 |
|
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1.16 |
# do something such as adding a timer |
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# or socket watcher the calls $result_ready->broadcast |
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# when the "result" is ready. |
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# in this case, we simply use a timer: |
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my $w = AnyEvent->timer ( |
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after => 1, |
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cb => sub { $result_ready->broadcast }, |
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); |
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# this "blocks" (while handling events) till the watcher |
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# calls broadcast |
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$result_ready->wait; |
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1.8 |
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1.16 |
GLOBAL VARIABLES AND FUNCTIONS |
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1.7 |
$AnyEvent::MODEL |
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Contains "undef" until the first watcher is being created. Then it |
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contains the event model that is being used, which is the name of |
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the Perl class implementing the model. This class is usually one of |
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the "AnyEvent::Impl:xxx" modules, but can be any other class in the |
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case AnyEvent has been extended at runtime (e.g. in *rxvt-unicode*). |
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The known classes so far are: |
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1.12 |
AnyEvent::Impl::CoroEV based on Coro::EV, best choice. |
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1.15 |
AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice. |
340 |
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1.18 |
AnyEvent::Impl::EV based on EV (an interface to libev, best choice). |
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AnyEvent::Impl::Event based on Event, second best choice. |
342 |
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1.15 |
AnyEvent::Impl::Glib based on Glib, third-best choice. |
343 |
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1.7 |
AnyEvent::Impl::Tk based on Tk, very bad choice. |
344 |
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1.15 |
AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable. |
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1.18 |
AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs). |
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AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse. |
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1.7 |
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1.8 |
AnyEvent::detect |
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Returns $AnyEvent::MODEL, forcing autodetection of the event model |
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if necessary. You should only call this function right before you |
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root |
1.16 |
would have created an AnyEvent watcher anyway, that is, as late as |
352 |
|
|
possible at runtime. |
353 |
root |
1.8 |
|
354 |
root |
1.6 |
WHAT TO DO IN A MODULE |
355 |
|
|
As a module author, you should "use AnyEvent" and call AnyEvent methods |
356 |
|
|
freely, but you should not load a specific event module or rely on it. |
357 |
|
|
|
358 |
root |
1.16 |
Be careful when you create watchers in the module body - AnyEvent will |
359 |
root |
1.6 |
decide which event module to use as soon as the first method is called, |
360 |
|
|
so by calling AnyEvent in your module body you force the user of your |
361 |
|
|
module to load the event module first. |
362 |
|
|
|
363 |
root |
1.16 |
Never call "->wait" on a condition variable unless you *know* that the |
364 |
|
|
"->broadcast" method has been called on it already. This is because it |
365 |
|
|
will stall the whole program, and the whole point of using events is to |
366 |
|
|
stay interactive. |
367 |
|
|
|
368 |
|
|
It is fine, however, to call "->wait" when the user of your module |
369 |
|
|
requests it (i.e. if you create a http request object ad have a method |
370 |
|
|
called "results" that returns the results, it should call "->wait" |
371 |
|
|
freely, as the user of your module knows what she is doing. always). |
372 |
|
|
|
373 |
root |
1.6 |
WHAT TO DO IN THE MAIN PROGRAM |
374 |
|
|
There will always be a single main program - the only place that should |
375 |
|
|
dictate which event model to use. |
376 |
|
|
|
377 |
|
|
If it doesn't care, it can just "use AnyEvent" and use it itself, or not |
378 |
root |
1.16 |
do anything special (it does not need to be event-based) and let |
379 |
|
|
AnyEvent decide which implementation to chose if some module relies on |
380 |
|
|
it. |
381 |
|
|
|
382 |
|
|
If the main program relies on a specific event model. For example, in |
383 |
|
|
Gtk2 programs you have to rely on the Glib module. You should load the |
384 |
|
|
event module before loading AnyEvent or any module that uses it: |
385 |
|
|
generally speaking, you should load it as early as possible. The reason |
386 |
|
|
is that modules might create watchers when they are loaded, and AnyEvent |
387 |
|
|
will decide on the event model to use as soon as it creates watchers, |
388 |
|
|
and it might chose the wrong one unless you load the correct one |
389 |
|
|
yourself. |
390 |
root |
1.6 |
|
391 |
|
|
You can chose to use a rather inefficient pure-perl implementation by |
392 |
root |
1.16 |
loading the "AnyEvent::Impl::Perl" module, which gives you similar |
393 |
|
|
behaviour everywhere, but letting AnyEvent chose is generally better. |
394 |
root |
1.2 |
|
395 |
root |
1.5 |
SUPPLYING YOUR OWN EVENT MODEL INTERFACE |
396 |
root |
1.16 |
This is an advanced topic that you do not normally need to use AnyEvent |
397 |
|
|
in a module. This section is only of use to event loop authors who want |
398 |
|
|
to provide AnyEvent compatibility. |
399 |
|
|
|
400 |
root |
1.5 |
If you need to support another event library which isn't directly |
401 |
|
|
supported by AnyEvent, you can supply your own interface to it by |
402 |
root |
1.6 |
pushing, before the first watcher gets created, the package name of the |
403 |
root |
1.5 |
event module and the package name of the interface to use onto |
404 |
|
|
@AnyEvent::REGISTRY. You can do that before and even without loading |
405 |
root |
1.16 |
AnyEvent, so it is reasonably cheap. |
406 |
root |
1.5 |
|
407 |
|
|
Example: |
408 |
|
|
|
409 |
|
|
push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::]; |
410 |
|
|
|
411 |
root |
1.6 |
This tells AnyEvent to (literally) use the "urxvt::anyevent::" |
412 |
root |
1.16 |
package/class when it finds the "urxvt" package/module is already |
413 |
|
|
loaded. |
414 |
|
|
|
415 |
|
|
When AnyEvent is loaded and asked to find a suitable event model, it |
416 |
|
|
will first check for the presence of urxvt by trying to "use" the |
417 |
|
|
"urxvt::anyevent" module. |
418 |
|
|
|
419 |
|
|
The class should provide implementations for all watcher types. See |
420 |
|
|
AnyEvent::Impl::EV (source code), AnyEvent::Impl::Glib (Source code) and |
421 |
|
|
so on for actual examples. Use "perldoc -m AnyEvent::Impl::Glib" to see |
422 |
|
|
the sources. |
423 |
|
|
|
424 |
|
|
If you don't provide "signal" and "child" watchers than AnyEvent will |
425 |
|
|
provide suitable (hopefully) replacements. |
426 |
|
|
|
427 |
|
|
The above example isn't fictitious, the *rxvt-unicode* (a.k.a. urxvt) |
428 |
|
|
terminal emulator uses the above line as-is. An interface isn't included |
429 |
|
|
in AnyEvent because it doesn't make sense outside the embedded |
430 |
|
|
interpreter inside *rxvt-unicode*, and it is updated and maintained as |
431 |
|
|
part of the *rxvt-unicode* distribution. |
432 |
root |
1.5 |
|
433 |
root |
1.6 |
*rxvt-unicode* also cheats a bit by not providing blocking access to |
434 |
|
|
condition variables: code blocking while waiting for a condition will |
435 |
|
|
"die". This still works with most modules/usages, and blocking calls |
436 |
root |
1.16 |
must not be done in an interactive application, so it makes sense. |
437 |
root |
1.6 |
|
438 |
root |
1.4 |
ENVIRONMENT VARIABLES |
439 |
|
|
The following environment variables are used by this module: |
440 |
|
|
|
441 |
root |
1.18 |
"PERL_ANYEVENT_VERBOSE" |
442 |
|
|
When set to 2 or higher, cause AnyEvent to report to STDERR which |
443 |
|
|
event model it chooses. |
444 |
|
|
|
445 |
|
|
"PERL_ANYEVENT_MODEL" |
446 |
|
|
This can be used to specify the event model to be used by AnyEvent, |
447 |
|
|
before autodetection and -probing kicks in. It must be a string |
448 |
|
|
consisting entirely of ASCII letters. The string "AnyEvent::Impl::" |
449 |
|
|
gets prepended and the resulting module name is loaded and if the |
450 |
|
|
load was successful, used as event model. If it fails to load |
451 |
|
|
AnyEvent will proceed with autodetection and -probing. |
452 |
|
|
|
453 |
|
|
This functionality might change in future versions. |
454 |
|
|
|
455 |
|
|
For example, to force the pure perl model (AnyEvent::Impl::Perl) you |
456 |
|
|
could start your program like this: |
457 |
|
|
|
458 |
|
|
PERL_ANYEVENT_MODEL=Perl perl ... |
459 |
root |
1.4 |
|
460 |
root |
1.16 |
EXAMPLE PROGRAM |
461 |
|
|
The following program uses an IO watcher to read data from STDIN, a |
462 |
|
|
timer to display a message once per second, and a condition variable to |
463 |
|
|
quit the program when the user enters quit: |
464 |
root |
1.2 |
|
465 |
|
|
use AnyEvent; |
466 |
|
|
|
467 |
|
|
my $cv = AnyEvent->condvar; |
468 |
|
|
|
469 |
root |
1.16 |
my $io_watcher = AnyEvent->io ( |
470 |
|
|
fh => \*STDIN, |
471 |
|
|
poll => 'r', |
472 |
|
|
cb => sub { |
473 |
|
|
warn "io event <$_[0]>\n"; # will always output <r> |
474 |
|
|
chomp (my $input = <STDIN>); # read a line |
475 |
|
|
warn "read: $input\n"; # output what has been read |
476 |
|
|
$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i |
477 |
|
|
}, |
478 |
|
|
); |
479 |
root |
1.2 |
|
480 |
|
|
my $time_watcher; # can only be used once |
481 |
|
|
|
482 |
|
|
sub new_timer { |
483 |
|
|
$timer = AnyEvent->timer (after => 1, cb => sub { |
484 |
|
|
warn "timeout\n"; # print 'timeout' about every second |
485 |
|
|
&new_timer; # and restart the time |
486 |
|
|
}); |
487 |
|
|
} |
488 |
|
|
|
489 |
|
|
new_timer; # create first timer |
490 |
|
|
|
491 |
|
|
$cv->wait; # wait until user enters /^q/i |
492 |
|
|
|
493 |
root |
1.3 |
REAL-WORLD EXAMPLE |
494 |
|
|
Consider the Net::FCP module. It features (among others) the following |
495 |
|
|
API calls, which are to freenet what HTTP GET requests are to http: |
496 |
|
|
|
497 |
|
|
my $data = $fcp->client_get ($url); # blocks |
498 |
|
|
|
499 |
|
|
my $transaction = $fcp->txn_client_get ($url); # does not block |
500 |
|
|
$transaction->cb ( sub { ... } ); # set optional result callback |
501 |
|
|
my $data = $transaction->result; # possibly blocks |
502 |
|
|
|
503 |
|
|
The "client_get" method works like "LWP::Simple::get": it requests the |
504 |
|
|
given URL and waits till the data has arrived. It is defined to be: |
505 |
|
|
|
506 |
|
|
sub client_get { $_[0]->txn_client_get ($_[1])->result } |
507 |
|
|
|
508 |
|
|
And in fact is automatically generated. This is the blocking API of |
509 |
|
|
Net::FCP, and it works as simple as in any other, similar, module. |
510 |
|
|
|
511 |
|
|
More complicated is "txn_client_get": It only creates a transaction |
512 |
|
|
(completion, result, ...) object and initiates the transaction. |
513 |
|
|
|
514 |
|
|
my $txn = bless { }, Net::FCP::Txn::; |
515 |
|
|
|
516 |
|
|
It also creates a condition variable that is used to signal the |
517 |
|
|
completion of the request: |
518 |
|
|
|
519 |
|
|
$txn->{finished} = AnyAvent->condvar; |
520 |
|
|
|
521 |
|
|
It then creates a socket in non-blocking mode. |
522 |
|
|
|
523 |
|
|
socket $txn->{fh}, ...; |
524 |
|
|
fcntl $txn->{fh}, F_SETFL, O_NONBLOCK; |
525 |
|
|
connect $txn->{fh}, ... |
526 |
|
|
and !$!{EWOULDBLOCK} |
527 |
|
|
and !$!{EINPROGRESS} |
528 |
|
|
and Carp::croak "unable to connect: $!\n"; |
529 |
|
|
|
530 |
root |
1.4 |
Then it creates a write-watcher which gets called whenever an error |
531 |
root |
1.3 |
occurs or the connection succeeds: |
532 |
|
|
|
533 |
|
|
$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'w', cb => sub { $txn->fh_ready_w }); |
534 |
|
|
|
535 |
|
|
And returns this transaction object. The "fh_ready_w" callback gets |
536 |
|
|
called as soon as the event loop detects that the socket is ready for |
537 |
|
|
writing. |
538 |
|
|
|
539 |
|
|
The "fh_ready_w" method makes the socket blocking again, writes the |
540 |
|
|
request data and replaces the watcher by a read watcher (waiting for |
541 |
|
|
reply data). The actual code is more complicated, but that doesn't |
542 |
|
|
matter for this example: |
543 |
|
|
|
544 |
|
|
fcntl $txn->{fh}, F_SETFL, 0; |
545 |
|
|
syswrite $txn->{fh}, $txn->{request} |
546 |
|
|
or die "connection or write error"; |
547 |
|
|
$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r }); |
548 |
|
|
|
549 |
|
|
Again, "fh_ready_r" waits till all data has arrived, and then stores the |
550 |
|
|
result and signals any possible waiters that the request ahs finished: |
551 |
|
|
|
552 |
|
|
sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf}; |
553 |
|
|
|
554 |
|
|
if (end-of-file or data complete) { |
555 |
|
|
$txn->{result} = $txn->{buf}; |
556 |
|
|
$txn->{finished}->broadcast; |
557 |
root |
1.4 |
$txb->{cb}->($txn) of $txn->{cb}; # also call callback |
558 |
root |
1.3 |
} |
559 |
|
|
|
560 |
|
|
The "result" method, finally, just waits for the finished signal (if the |
561 |
|
|
request was already finished, it doesn't wait, of course, and returns |
562 |
|
|
the data: |
563 |
|
|
|
564 |
|
|
$txn->{finished}->wait; |
565 |
root |
1.4 |
return $txn->{result}; |
566 |
root |
1.3 |
|
567 |
|
|
The actual code goes further and collects all errors ("die"s, |
568 |
|
|
exceptions) that occured during request processing. The "result" method |
569 |
root |
1.16 |
detects whether an exception as thrown (it is stored inside the $txn |
570 |
root |
1.3 |
object) and just throws the exception, which means connection errors and |
571 |
|
|
other problems get reported tot he code that tries to use the result, |
572 |
|
|
not in a random callback. |
573 |
|
|
|
574 |
|
|
All of this enables the following usage styles: |
575 |
|
|
|
576 |
|
|
1. Blocking: |
577 |
|
|
|
578 |
|
|
my $data = $fcp->client_get ($url); |
579 |
|
|
|
580 |
root |
1.15 |
2. Blocking, but running in parallel: |
581 |
root |
1.3 |
|
582 |
|
|
my @datas = map $_->result, |
583 |
|
|
map $fcp->txn_client_get ($_), |
584 |
|
|
@urls; |
585 |
|
|
|
586 |
|
|
Both blocking examples work without the module user having to know |
587 |
|
|
anything about events. |
588 |
|
|
|
589 |
root |
1.15 |
3a. Event-based in a main program, using any supported event module: |
590 |
root |
1.3 |
|
591 |
root |
1.15 |
use EV; |
592 |
root |
1.3 |
|
593 |
|
|
$fcp->txn_client_get ($url)->cb (sub { |
594 |
|
|
my $txn = shift; |
595 |
|
|
my $data = $txn->result; |
596 |
|
|
... |
597 |
|
|
}); |
598 |
|
|
|
599 |
root |
1.15 |
EV::loop; |
600 |
root |
1.3 |
|
601 |
|
|
3b. The module user could use AnyEvent, too: |
602 |
|
|
|
603 |
|
|
use AnyEvent; |
604 |
|
|
|
605 |
|
|
my $quit = AnyEvent->condvar; |
606 |
|
|
|
607 |
|
|
$fcp->txn_client_get ($url)->cb (sub { |
608 |
|
|
... |
609 |
|
|
$quit->broadcast; |
610 |
|
|
}); |
611 |
|
|
|
612 |
|
|
$quit->wait; |
613 |
|
|
|
614 |
root |
1.18 |
FORK |
615 |
|
|
Most event libraries are not fork-safe. The ones who are usually are |
616 |
|
|
because they are so inefficient. Only EV is fully fork-aware. |
617 |
|
|
|
618 |
|
|
If you have to fork, you must either do so *before* creating your first |
619 |
|
|
watcher OR you must not use AnyEvent at all in the child. |
620 |
|
|
|
621 |
|
|
SECURITY CONSIDERATIONS |
622 |
|
|
AnyEvent can be forced to load any event model via |
623 |
|
|
$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used |
624 |
|
|
to execute arbitrary code or directly gain access, it can easily be used |
625 |
|
|
to make the program hang or malfunction in subtle ways, as AnyEvent |
626 |
|
|
watchers will not be active when the program uses a different event |
627 |
|
|
model than specified in the variable. |
628 |
|
|
|
629 |
|
|
You can make AnyEvent completely ignore this variable by deleting it |
630 |
|
|
before the first watcher gets created, e.g. with a "BEGIN" block: |
631 |
|
|
|
632 |
|
|
BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } |
633 |
|
|
|
634 |
|
|
use AnyEvent; |
635 |
|
|
|
636 |
root |
1.2 |
SEE ALSO |
637 |
root |
1.15 |
Event modules: Coro::EV, EV, EV::Glib, Glib::EV, Coro::Event, Event, |
638 |
root |
1.18 |
Glib::Event, Glib, Coro, Tk, Event::Lib, Qt. |
639 |
root |
1.3 |
|
640 |
root |
1.15 |
Implementations: AnyEvent::Impl::CoroEV, AnyEvent::Impl::EV, |
641 |
|
|
AnyEvent::Impl::CoroEvent, AnyEvent::Impl::Event, AnyEvent::Impl::Glib, |
642 |
root |
1.18 |
AnyEvent::Impl::Tk, AnyEvent::Impl::Perl, AnyEvent::Impl::EventLib, |
643 |
|
|
AnyEvent::Impl::Qt. |
644 |
root |
1.3 |
|
645 |
root |
1.15 |
Nontrivial usage examples: Net::FCP, Net::XMPP2. |
646 |
root |
1.2 |
|
647 |
root |
1.17 |
AUTHOR |
648 |
|
|
Marc Lehmann <schmorp@schmorp.de> |
649 |
|
|
http://home.schmorp.de/ |
650 |
root |
1.2 |
|