1 | NAME |
1 | NAME |
2 | AnyEvent - provide framework for multiple event loops |
2 | AnyEvent - provide framework for multiple event loops |
3 | |
3 | |
4 | EV, Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event |
4 | EV, Event, Glib, Tk, Perl, Event::Lib, Qt and POE are various supported |
5 | loops |
5 | event loops. |
6 | |
6 | |
7 | SYNOPSIS |
7 | SYNOPSIS |
8 | use AnyEvent; |
8 | use AnyEvent; |
9 | |
9 | |
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10 | # file descriptor readable |
10 | my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub { ... }); |
11 | my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... }); |
11 | |
12 | |
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13 | # one-shot or repeating timers |
12 | my $w = AnyEvent->timer (after => $seconds, cb => sub { ... }); |
14 | my $w = AnyEvent->timer (after => $seconds, cb => sub { ... }); |
13 | my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ... |
15 | my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ... |
14 | |
16 | |
15 | print AnyEvent->now; # prints current event loop time |
17 | print AnyEvent->now; # prints current event loop time |
16 | print AnyEvent->time; # think Time::HiRes::time or simply CORE::time. |
18 | print AnyEvent->time; # think Time::HiRes::time or simply CORE::time. |
17 | |
19 | |
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20 | # POSIX signal |
18 | my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... }); |
21 | my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... }); |
19 | |
22 | |
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23 | # child process exit |
20 | my $w = AnyEvent->child (pid => $pid, cb => sub { |
24 | my $w = AnyEvent->child (pid => $pid, cb => sub { |
21 | my ($pid, $status) = @_; |
25 | my ($pid, $status) = @_; |
22 | ... |
26 | ... |
23 | }); |
27 | }); |
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28 | |
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29 | # called when event loop idle (if applicable) |
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30 | my $w = AnyEvent->idle (cb => sub { ... }); |
24 | |
31 | |
25 | my $w = AnyEvent->condvar; # stores whether a condition was flagged |
32 | my $w = AnyEvent->condvar; # stores whether a condition was flagged |
26 | $w->send; # wake up current and all future recv's |
33 | $w->send; # wake up current and all future recv's |
27 | $w->recv; # enters "main loop" till $condvar gets ->send |
34 | $w->recv; # enters "main loop" till $condvar gets ->send |
28 | # use a condvar in callback mode: |
35 | # use a condvar in callback mode: |
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132 | These watchers are normal Perl objects with normal Perl lifetime. After |
139 | These watchers are normal Perl objects with normal Perl lifetime. After |
133 | creating a watcher it will immediately "watch" for events and invoke the |
140 | creating a watcher it will immediately "watch" for events and invoke the |
134 | callback when the event occurs (of course, only when the event model is |
141 | callback when the event occurs (of course, only when the event model is |
135 | in control). |
142 | in control). |
136 | |
143 | |
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144 | Note that callbacks must not permanently change global variables |
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145 | potentially in use by the event loop (such as $_ or $[) and that |
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146 | callbacks must not "die". The former is good programming practise in |
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147 | Perl and the latter stems from the fact that exception handling differs |
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148 | widely between event loops. |
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149 | |
137 | To disable the watcher you have to destroy it (e.g. by setting the |
150 | To disable the watcher you have to destroy it (e.g. by setting the |
138 | variable you store it in to "undef" or otherwise deleting all references |
151 | variable you store it in to "undef" or otherwise deleting all references |
139 | to it). |
152 | to it). |
140 | |
153 | |
141 | All watchers are created by calling a method on the "AnyEvent" class. |
154 | All watchers are created by calling a method on the "AnyEvent" class. |
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156 | |
169 | |
157 | I/O WATCHERS |
170 | I/O WATCHERS |
158 | You can create an I/O watcher by calling the "AnyEvent->io" method with |
171 | You can create an I/O watcher by calling the "AnyEvent->io" method with |
159 | the following mandatory key-value pairs as arguments: |
172 | the following mandatory key-value pairs as arguments: |
160 | |
173 | |
161 | "fh" the Perl *file handle* (*not* file descriptor) to watch for events |
174 | "fh" is the Perl *file handle* (*not* file descriptor) to watch for |
162 | (AnyEvent might or might not keep a reference to this file handle). |
175 | events (AnyEvent might or might not keep a reference to this file |
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176 | handle). Note that only file handles pointing to things for which |
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177 | non-blocking operation makes sense are allowed. This includes sockets, |
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178 | most character devices, pipes, fifos and so on, but not for example |
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179 | files or block devices. |
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180 | |
163 | "poll" must be a string that is either "r" or "w", which creates a |
181 | "poll" must be a string that is either "r" or "w", which creates a |
164 | watcher waiting for "r"eadable or "w"ritable events, respectively. "cb" |
182 | watcher waiting for "r"eadable or "w"ritable events, respectively. |
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183 | |
165 | is the callback to invoke each time the file handle becomes ready. |
184 | "cb" is the callback to invoke each time the file handle becomes ready. |
166 | |
185 | |
167 | Although the callback might get passed parameters, their value and |
186 | Although the callback might get passed parameters, their value and |
168 | presence is undefined and you cannot rely on them. Portable AnyEvent |
187 | presence is undefined and you cannot rely on them. Portable AnyEvent |
169 | callbacks cannot use arguments passed to I/O watcher callbacks. |
188 | callbacks cannot use arguments passed to I/O watcher callbacks. |
170 | |
189 | |
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302 | In either case, if you care (and in most cases, you don't), then you |
321 | In either case, if you care (and in most cases, you don't), then you |
303 | can get whatever behaviour you want with any event loop, by taking |
322 | can get whatever behaviour you want with any event loop, by taking |
304 | the difference between "AnyEvent->time" and "AnyEvent->now" into |
323 | the difference between "AnyEvent->time" and "AnyEvent->now" into |
305 | account. |
324 | account. |
306 | |
325 | |
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326 | AnyEvent->now_update |
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327 | Some event loops (such as EV or AnyEvent::Impl::Perl) cache the |
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328 | current time for each loop iteration (see the discussion of |
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329 | AnyEvent->now, above). |
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330 | |
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331 | When a callback runs for a long time (or when the process sleeps), |
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332 | then this "current" time will differ substantially from the real |
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333 | time, which might affect timers and time-outs. |
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334 | |
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335 | When this is the case, you can call this method, which will update |
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336 | the event loop's idea of "current time". |
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337 | |
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338 | Note that updating the time *might* cause some events to be handled. |
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339 | |
307 | SIGNAL WATCHERS |
340 | SIGNAL WATCHERS |
308 | You can watch for signals using a signal watcher, "signal" is the signal |
341 | You can watch for signals using a signal watcher, "signal" is the signal |
309 | *name* in uppercase and without any "SIG" prefix, "cb" is the Perl |
342 | *name* in uppercase and without any "SIG" prefix, "cb" is the Perl |
310 | callback to be invoked whenever a signal occurs. |
343 | callback to be invoked whenever a signal occurs. |
311 | |
344 | |
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347 | |
380 | |
348 | There is a slight catch to child watchers, however: you usually start |
381 | There is a slight catch to child watchers, however: you usually start |
349 | them *after* the child process was created, and this means the process |
382 | them *after* the child process was created, and this means the process |
350 | could have exited already (and no SIGCHLD will be sent anymore). |
383 | could have exited already (and no SIGCHLD will be sent anymore). |
351 | |
384 | |
352 | Not all event models handle this correctly (POE doesn't), but even for |
385 | Not all event models handle this correctly (neither POE nor IO::Async |
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386 | do, see their AnyEvent::Impl manpages for details), but even for event |
353 | event models that *do* handle this correctly, they usually need to be |
387 | models that *do* handle this correctly, they usually need to be loaded |
354 | loaded before the process exits (i.e. before you fork in the first |
388 | before the process exits (i.e. before you fork in the first place). |
355 | place). |
389 | AnyEvent's pure perl event loop handles all cases correctly regardless |
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390 | of when you start the watcher. |
356 | |
391 | |
357 | This means you cannot create a child watcher as the very first thing in |
392 | This means you cannot create a child watcher as the very first thing in |
358 | an AnyEvent program, you *have* to create at least one watcher before |
393 | an AnyEvent program, you *have* to create at least one watcher before |
359 | you "fork" the child (alternatively, you can call "AnyEvent::detect"). |
394 | you "fork" the child (alternatively, you can call "AnyEvent::detect"). |
360 | |
395 | |
361 | Example: fork a process and wait for it |
396 | Example: fork a process and wait for it |
362 | |
397 | |
363 | my $done = AnyEvent->condvar; |
398 | my $done = AnyEvent->condvar; |
364 | |
399 | |
365 | my $pid = fork or exit 5; |
400 | my $pid = fork or exit 5; |
366 | |
401 | |
367 | my $w = AnyEvent->child ( |
402 | my $w = AnyEvent->child ( |
368 | pid => $pid, |
403 | pid => $pid, |
369 | cb => sub { |
404 | cb => sub { |
370 | my ($pid, $status) = @_; |
405 | my ($pid, $status) = @_; |
371 | warn "pid $pid exited with status $status"; |
406 | warn "pid $pid exited with status $status"; |
372 | $done->send; |
407 | $done->send; |
373 | }, |
408 | }, |
374 | ); |
409 | ); |
375 | |
410 | |
376 | # do something else, then wait for process exit |
411 | # do something else, then wait for process exit |
377 | $done->recv; |
412 | $done->recv; |
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413 | |
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414 | IDLE WATCHERS |
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415 | Sometimes there is a need to do something, but it is not so important to |
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416 | do it instantly, but only when there is nothing better to do. This |
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417 | "nothing better to do" is usually defined to be "no other events need |
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418 | attention by the event loop". |
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419 | |
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420 | Idle watchers ideally get invoked when the event loop has nothing better |
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421 | to do, just before it would block the process to wait for new events. |
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422 | Instead of blocking, the idle watcher is invoked. |
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423 | |
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424 | Most event loops unfortunately do not really support idle watchers (only |
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425 | EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent |
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426 | will simply call the callback "from time to time". |
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427 | |
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428 | Example: read lines from STDIN, but only process them when the program |
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429 | is otherwise idle: |
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430 | |
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431 | my @lines; # read data |
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432 | my $idle_w; |
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433 | my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { |
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434 | push @lines, scalar <STDIN>; |
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435 | |
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436 | # start an idle watcher, if not already done |
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437 | $idle_w ||= AnyEvent->idle (cb => sub { |
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438 | # handle only one line, when there are lines left |
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439 | if (my $line = shift @lines) { |
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440 | print "handled when idle: $line"; |
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441 | } else { |
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442 | # otherwise disable the idle watcher again |
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443 | undef $idle_w; |
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444 | } |
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445 | }); |
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446 | }); |
378 | |
447 | |
379 | CONDITION VARIABLES |
448 | CONDITION VARIABLES |
380 | If you are familiar with some event loops you will know that all of them |
449 | If you are familiar with some event loops you will know that all of them |
381 | require you to run some blocking "loop", "run" or similar function that |
450 | require you to run some blocking "loop", "run" or similar function that |
382 | will actively watch for new events and call your callbacks. |
451 | will actively watch for new events and call your callbacks. |
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508 | This can be used to signal any errors to the condition variable |
577 | This can be used to signal any errors to the condition variable |
509 | user/consumer. |
578 | user/consumer. |
510 | |
579 | |
511 | $cv->begin ([group callback]) |
580 | $cv->begin ([group callback]) |
512 | $cv->end |
581 | $cv->end |
513 | These two methods are EXPERIMENTAL and MIGHT CHANGE. |
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514 | |
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515 | These two methods can be used to combine many transactions/events |
582 | These two methods can be used to combine many transactions/events |
516 | into one. For example, a function that pings many hosts in parallel |
583 | into one. For example, a function that pings many hosts in parallel |
517 | might want to use a condition variable for the whole process. |
584 | might want to use a condition variable for the whole process. |
518 | |
585 | |
519 | Every call to "->begin" will increment a counter, and every call to |
586 | Every call to "->begin" will increment a counter, and every call to |
520 | "->end" will decrement it. If the counter reaches 0 in "->end", the |
587 | "->end" will decrement it. If the counter reaches 0 in "->end", the |
521 | (last) callback passed to "begin" will be executed. That callback is |
588 | (last) callback passed to "begin" will be executed. That callback is |
522 | *supposed* to call "->send", but that is not required. If no |
589 | *supposed* to call "->send", but that is not required. If no |
523 | callback was set, "send" will be called without any arguments. |
590 | callback was set, "send" will be called without any arguments. |
524 | |
591 | |
525 | Let's clarify this with the ping example: |
592 | You can think of "$cv->send" giving you an OR condition (one call |
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593 | sends), while "$cv->begin" and "$cv->end" giving you an AND |
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594 | condition (all "begin" calls must be "end"'ed before the condvar |
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595 | sends). |
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596 | |
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597 | Let's start with a simple example: you have two I/O watchers (for |
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598 | example, STDOUT and STDERR for a program), and you want to wait for |
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599 | both streams to close before activating a condvar: |
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600 | |
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601 | my $cv = AnyEvent->condvar; |
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602 | |
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603 | $cv->begin; # first watcher |
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604 | my $w1 = AnyEvent->io (fh => $fh1, cb => sub { |
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605 | defined sysread $fh1, my $buf, 4096 |
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606 | or $cv->end; |
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607 | }); |
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608 | |
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609 | $cv->begin; # second watcher |
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610 | my $w2 = AnyEvent->io (fh => $fh2, cb => sub { |
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611 | defined sysread $fh2, my $buf, 4096 |
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612 | or $cv->end; |
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613 | }); |
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614 | |
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615 | $cv->recv; |
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616 | |
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617 | This works because for every event source (EOF on file handle), |
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618 | there is one call to "begin", so the condvar waits for all calls to |
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619 | "end" before sending. |
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620 | |
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621 | The ping example mentioned above is slightly more complicated, as |
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622 | the there are results to be passwd back, and the number of tasks |
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623 | that are begung can potentially be zero: |
526 | |
624 | |
527 | my $cv = AnyEvent->condvar; |
625 | my $cv = AnyEvent->condvar; |
528 | |
626 | |
529 | my %result; |
627 | my %result; |
530 | $cv->begin (sub { $cv->send (\%result) }); |
628 | $cv->begin (sub { $cv->send (\%result) }); |
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550 | the loop, which serves two important purposes: first, it sets the |
648 | the loop, which serves two important purposes: first, it sets the |
551 | callback to be called once the counter reaches 0, and second, it |
649 | callback to be called once the counter reaches 0, and second, it |
552 | ensures that "send" is called even when "no" hosts are being pinged |
650 | ensures that "send" is called even when "no" hosts are being pinged |
553 | (the loop doesn't execute once). |
651 | (the loop doesn't execute once). |
554 | |
652 | |
555 | This is the general pattern when you "fan out" into multiple |
653 | This is the general pattern when you "fan out" into multiple (but |
556 | subrequests: use an outer "begin"/"end" pair to set the callback and |
654 | potentially none) subrequests: use an outer "begin"/"end" pair to |
557 | ensure "end" is called at least once, and then, for each subrequest |
655 | set the callback and ensure "end" is called at least once, and then, |
558 | you start, call "begin" and for each subrequest you finish, call |
656 | for each subrequest you start, call "begin" and for each subrequest |
559 | "end". |
657 | you finish, call "end". |
560 | |
658 | |
561 | METHODS FOR CONSUMERS |
659 | METHODS FOR CONSUMERS |
562 | These methods should only be used by the consuming side, i.e. the code |
660 | These methods should only be used by the consuming side, i.e. the code |
563 | awaits the condition. |
661 | awaits the condition. |
564 | |
662 | |
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630 | AnyEvent::Impl::Tk based on Tk, very bad choice. |
728 | AnyEvent::Impl::Tk based on Tk, very bad choice. |
631 | AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs). |
729 | AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs). |
632 | AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse. |
730 | AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse. |
633 | AnyEvent::Impl::POE based on POE, not generic enough for full support. |
731 | AnyEvent::Impl::POE based on POE, not generic enough for full support. |
634 | |
732 | |
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733 | # warning, support for IO::Async is only partial, as it is too broken |
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734 | # and limited toe ven support the AnyEvent API. See AnyEvent::Impl::Async. |
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735 | AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed (see its docs). |
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736 | |
635 | There is no support for WxWidgets, as WxWidgets has no support for |
737 | There is no support for WxWidgets, as WxWidgets has no support for |
636 | watching file handles. However, you can use WxWidgets through the |
738 | watching file handles. However, you can use WxWidgets through the |
637 | POE Adaptor, as POE has a Wx backend that simply polls 20 times per |
739 | POE Adaptor, as POE has a Wx backend that simply polls 20 times per |
638 | second, which was considered to be too horrible to even consider for |
740 | second, which was considered to be too horrible to even consider for |
639 | AnyEvent. Likewise, other POE backends can be used by AnyEvent by |
741 | AnyEvent. Likewise, other POE backends can be used by AnyEvent by |
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777 | |
879 | |
778 | AnyEvent::IGS |
880 | AnyEvent::IGS |
779 | A non-blocking interface to the Internet Go Server protocol (used by |
881 | A non-blocking interface to the Internet Go Server protocol (used by |
780 | App::IGS). |
882 | App::IGS). |
781 | |
883 | |
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884 | AnyEvent::IRC |
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885 | AnyEvent based IRC client module family (replacing the older |
782 | Net::IRC3 |
886 | Net::IRC3). |
783 | AnyEvent based IRC client module family. |
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784 | |
887 | |
785 | Net::XMPP2 |
888 | Net::XMPP2 |
786 | AnyEvent based XMPP (Jabber protocol) module family. |
889 | AnyEvent based XMPP (Jabber protocol) module family. |
787 | |
890 | |
788 | Net::FCP |
891 | Net::FCP |
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815 | "condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()", |
918 | "condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()", |
816 | Glib uses "install_exception_handler" and so on. |
919 | Glib uses "install_exception_handler" and so on. |
817 | |
920 | |
818 | ENVIRONMENT VARIABLES |
921 | ENVIRONMENT VARIABLES |
819 | The following environment variables are used by this module or its |
922 | The following environment variables are used by this module or its |
820 | submodules: |
923 | submodules. |
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924 | |
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925 | Note that AnyEvent will remove *all* environment variables starting with |
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926 | "PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is |
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927 | enabled. |
821 | |
928 | |
822 | "PERL_ANYEVENT_VERBOSE" |
929 | "PERL_ANYEVENT_VERBOSE" |
823 | By default, AnyEvent will be completely silent except in fatal |
930 | By default, AnyEvent will be completely silent except in fatal |
824 | conditions. You can set this environment variable to make AnyEvent |
931 | conditions. You can set this environment variable to make AnyEvent |
825 | more talkative. |
932 | more talkative. |
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834 | "PERL_ANYEVENT_STRICT" |
941 | "PERL_ANYEVENT_STRICT" |
835 | AnyEvent does not do much argument checking by default, as thorough |
942 | AnyEvent does not do much argument checking by default, as thorough |
836 | argument checking is very costly. Setting this variable to a true |
943 | argument checking is very costly. Setting this variable to a true |
837 | value will cause AnyEvent to load "AnyEvent::Strict" and then to |
944 | value will cause AnyEvent to load "AnyEvent::Strict" and then to |
838 | thoroughly check the arguments passed to most method calls. If it |
945 | thoroughly check the arguments passed to most method calls. If it |
839 | finds any problems it will croak. |
946 | finds any problems, it will croak. |
840 | |
947 | |
841 | In other words, enables "strict" mode. |
948 | In other words, enables "strict" mode. |
842 | |
949 | |
843 | Unlike "use strict", it is definitely recommended ot keep it off in |
950 | Unlike "use strict", it is definitely recommended to keep it off in |
844 | production. Keeping "PERL_ANYEVENT_STRICT=1" in your environment |
951 | production. Keeping "PERL_ANYEVENT_STRICT=1" in your environment |
845 | while developing programs can be very useful, however. |
952 | while developing programs can be very useful, however. |
846 | |
953 | |
847 | "PERL_ANYEVENT_MODEL" |
954 | "PERL_ANYEVENT_MODEL" |
848 | This can be used to specify the event model to be used by AnyEvent, |
955 | This can be used to specify the event model to be used by AnyEvent, |
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869 | mentioned will be used, and preference will be given to protocols |
976 | mentioned will be used, and preference will be given to protocols |
870 | mentioned earlier in the list. |
977 | mentioned earlier in the list. |
871 | |
978 | |
872 | This variable can effectively be used for denial-of-service attacks |
979 | This variable can effectively be used for denial-of-service attacks |
873 | against local programs (e.g. when setuid), although the impact is |
980 | against local programs (e.g. when setuid), although the impact is |
874 | likely small, as the program has to handle connection errors |
981 | likely small, as the program has to handle conenction and other |
875 | already- |
982 | failures anyways. |
876 | |
983 | |
877 | Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over |
984 | Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over |
878 | IPv6, but support both and try to use both. |
985 | IPv6, but support both and try to use both. |
879 | "PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to |
986 | "PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to |
880 | resolve or contact IPv6 addresses. |
987 | resolve or contact IPv6 addresses. |
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1130 | *destroy* is the time, in microseconds, that it takes to destroy a |
1237 | *destroy* is the time, in microseconds, that it takes to destroy a |
1131 | single watcher. |
1238 | single watcher. |
1132 | |
1239 | |
1133 | Results |
1240 | Results |
1134 | name watchers bytes create invoke destroy comment |
1241 | name watchers bytes create invoke destroy comment |
1135 | EV/EV 400000 244 0.56 0.46 0.31 EV native interface |
1242 | EV/EV 400000 224 0.47 0.35 0.27 EV native interface |
1136 | EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers |
1243 | EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers |
1137 | CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal |
1244 | CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal |
1138 | Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation |
1245 | Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation |
1139 | Event/Event 16000 516 31.88 31.30 0.85 Event native interface |
1246 | Event/Event 16000 517 32.20 31.80 0.81 Event native interface |
1140 | Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers |
1247 | Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers |
|
|
1248 | IOAsync/Any 16000 989 38.10 32.77 11.13 via IO::Async::Loop::IO_Poll |
|
|
1249 | IOAsync/Any 16000 990 37.59 29.50 10.61 via IO::Async::Loop::Epoll |
1141 | Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour |
1250 | Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour |
1142 | Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers |
1251 | Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers |
1143 | POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event |
1252 | POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event |
1144 | POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select |
1253 | POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select |
1145 | |
1254 | |
1146 | Discussion |
1255 | Discussion |
1147 | The benchmark does *not* measure scalability of the event loop very |
1256 | The benchmark does *not* measure scalability of the event loop very |
1148 | well. For example, a select-based event loop (such as the pure perl one) |
1257 | well. For example, a select-based event loop (such as the pure perl one) |
1149 | can never compete with an event loop that uses epoll when the number of |
1258 | can never compete with an event loop that uses epoll when the number of |
… | |
… | |
1174 | few of them active), of course, but this was not subject of this |
1283 | few of them active), of course, but this was not subject of this |
1175 | benchmark. |
1284 | benchmark. |
1176 | |
1285 | |
1177 | The "Event" module has a relatively high setup and callback invocation |
1286 | The "Event" module has a relatively high setup and callback invocation |
1178 | cost, but overall scores in on the third place. |
1287 | cost, but overall scores in on the third place. |
|
|
1288 | |
|
|
1289 | "IO::Async" performs admirably well, about on par with "Event", even |
|
|
1290 | when using its pure perl backend. |
1179 | |
1291 | |
1180 | "Glib"'s memory usage is quite a bit higher, but it features a faster |
1292 | "Glib"'s memory usage is quite a bit higher, but it features a faster |
1181 | callback invocation and overall ends up in the same class as "Event". |
1293 | callback invocation and overall ends up in the same class as "Event". |
1182 | However, Glib scales extremely badly, doubling the number of watchers |
1294 | However, Glib scales extremely badly, doubling the number of watchers |
1183 | increases the processing time by more than a factor of four, making it |
1295 | increases the processing time by more than a factor of four, making it |
… | |
… | |
1254 | single "request", that is, reading the token from the pipe and |
1366 | single "request", that is, reading the token from the pipe and |
1255 | forwarding it to another server. This includes deleting the old timeout |
1367 | forwarding it to another server. This includes deleting the old timeout |
1256 | and creating a new one that moves the timeout into the future. |
1368 | and creating a new one that moves the timeout into the future. |
1257 | |
1369 | |
1258 | Results |
1370 | Results |
1259 | name sockets create request |
1371 | name sockets create request |
1260 | EV 20000 69.01 11.16 |
1372 | EV 20000 69.01 11.16 |
1261 | Perl 20000 73.32 35.87 |
1373 | Perl 20000 73.32 35.87 |
|
|
1374 | IOAsync 20000 157.00 98.14 epoll |
|
|
1375 | IOAsync 20000 159.31 616.06 poll |
1262 | Event 20000 212.62 257.32 |
1376 | Event 20000 212.62 257.32 |
1263 | Glib 20000 651.16 1896.30 |
1377 | Glib 20000 651.16 1896.30 |
1264 | POE 20000 349.67 12317.24 uses POE::Loop::Event |
1378 | POE 20000 349.67 12317.24 uses POE::Loop::Event |
1265 | |
1379 | |
1266 | Discussion |
1380 | Discussion |
1267 | This benchmark *does* measure scalability and overall performance of the |
1381 | This benchmark *does* measure scalability and overall performance of the |
1268 | particular event loop. |
1382 | particular event loop. |
1269 | |
1383 | |
1270 | EV is again fastest. Since it is using epoll on my system, the setup |
1384 | EV is again fastest. Since it is using epoll on my system, the setup |
1271 | time is relatively high, though. |
1385 | time is relatively high, though. |
1272 | |
1386 | |
1273 | Perl surprisingly comes second. It is much faster than the C-based event |
1387 | Perl surprisingly comes second. It is much faster than the C-based event |
1274 | loops Event and Glib. |
1388 | loops Event and Glib. |
|
|
1389 | |
|
|
1390 | IO::Async performs very well when using its epoll backend, and still |
|
|
1391 | quite good compared to Glib when using its pure perl backend. |
1275 | |
1392 | |
1276 | Event suffers from high setup time as well (look at its code and you |
1393 | Event suffers from high setup time as well (look at its code and you |
1277 | will understand why). Callback invocation also has a high overhead |
1394 | will understand why). Callback invocation also has a high overhead |
1278 | compared to the "$_->() for .."-style loop that the Perl event loop |
1395 | compared to the "$_->() for .."-style loop that the Perl event loop |
1279 | uses. Event uses select or poll in basically all documented |
1396 | uses. Event uses select or poll in basically all documented |
… | |
… | |
1330 | |
1447 | |
1331 | Summary |
1448 | Summary |
1332 | * C-based event loops perform very well with small number of watchers, |
1449 | * C-based event loops perform very well with small number of watchers, |
1333 | as the management overhead dominates. |
1450 | as the management overhead dominates. |
1334 | |
1451 | |
|
|
1452 | THE IO::Lambda BENCHMARK |
|
|
1453 | Recently I was told about the benchmark in the IO::Lambda manpage, which |
|
|
1454 | could be misinterpreted to make AnyEvent look bad. In fact, the |
|
|
1455 | benchmark simply compares IO::Lambda with POE, and IO::Lambda looks |
|
|
1456 | better (which shouldn't come as a surprise to anybody). As such, the |
|
|
1457 | benchmark is fine, and mostly shows that the AnyEvent backend from |
|
|
1458 | IO::Lambda isn't very optimal. But how would AnyEvent compare when used |
|
|
1459 | without the extra baggage? To explore this, I wrote the equivalent |
|
|
1460 | benchmark for AnyEvent. |
|
|
1461 | |
|
|
1462 | The benchmark itself creates an echo-server, and then, for 500 times, |
|
|
1463 | connects to the echo server, sends a line, waits for the reply, and then |
|
|
1464 | creates the next connection. This is a rather bad benchmark, as it |
|
|
1465 | doesn't test the efficiency of the framework or much non-blocking I/O, |
|
|
1466 | but it is a benchmark nevertheless. |
|
|
1467 | |
|
|
1468 | name runtime |
|
|
1469 | Lambda/select 0.330 sec |
|
|
1470 | + optimized 0.122 sec |
|
|
1471 | Lambda/AnyEvent 0.327 sec |
|
|
1472 | + optimized 0.138 sec |
|
|
1473 | Raw sockets/select 0.077 sec |
|
|
1474 | POE/select, components 0.662 sec |
|
|
1475 | POE/select, raw sockets 0.226 sec |
|
|
1476 | POE/select, optimized 0.404 sec |
|
|
1477 | |
|
|
1478 | AnyEvent/select/nb 0.085 sec |
|
|
1479 | AnyEvent/EV/nb 0.068 sec |
|
|
1480 | +state machine 0.134 sec |
|
|
1481 | |
|
|
1482 | The benchmark is also a bit unfair (my fault): the IO::Lambda/POE |
|
|
1483 | benchmarks actually make blocking connects and use 100% blocking I/O, |
|
|
1484 | defeating the purpose of an event-based solution. All of the newly |
|
|
1485 | written AnyEvent benchmarks use 100% non-blocking connects (using |
|
|
1486 | AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS |
|
|
1487 | resolver), so AnyEvent is at a disadvantage here, as non-blocking |
|
|
1488 | connects generally require a lot more bookkeeping and event handling |
|
|
1489 | than blocking connects (which involve a single syscall only). |
|
|
1490 | |
|
|
1491 | The last AnyEvent benchmark additionally uses AnyEvent::Handle, which |
|
|
1492 | offers similar expressive power as POE and IO::Lambda, using |
|
|
1493 | conventional Perl syntax. This means that both the echo server and the |
|
|
1494 | client are 100% non-blocking, further placing it at a disadvantage. |
|
|
1495 | |
|
|
1496 | As you can see, the AnyEvent + EV combination even beats the |
|
|
1497 | hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl |
|
|
1498 | backend easily beats IO::Lambda and POE. |
|
|
1499 | |
|
|
1500 | And even the 100% non-blocking version written using the high-level (and |
|
|
1501 | slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda by a |
|
|
1502 | large margin, even though it does all of DNS, tcp-connect and socket I/O |
|
|
1503 | in a non-blocking way. |
|
|
1504 | |
|
|
1505 | The two AnyEvent benchmarks programs can be found as eg/ae0.pl and |
|
|
1506 | eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are |
|
|
1507 | part of the IO::lambda distribution and were used without any changes. |
|
|
1508 | |
|
|
1509 | SIGNALS |
|
|
1510 | AnyEvent currently installs handlers for these signals: |
|
|
1511 | |
|
|
1512 | SIGCHLD |
|
|
1513 | A handler for "SIGCHLD" is installed by AnyEvent's child watcher |
|
|
1514 | emulation for event loops that do not support them natively. Also, |
|
|
1515 | some event loops install a similar handler. |
|
|
1516 | |
|
|
1517 | If, when AnyEvent is loaded, SIGCHLD is set to IGNORE, then AnyEvent |
|
|
1518 | will reset it to default, to avoid losing child exit statuses. |
|
|
1519 | |
|
|
1520 | SIGPIPE |
|
|
1521 | A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is |
|
|
1522 | "undef" when AnyEvent gets loaded. |
|
|
1523 | |
|
|
1524 | The rationale for this is that AnyEvent users usually do not really |
|
|
1525 | depend on SIGPIPE delivery (which is purely an optimisation for |
|
|
1526 | shell use, or badly-written programs), but "SIGPIPE" can cause |
|
|
1527 | spurious and rare program exits as a lot of people do not expect |
|
|
1528 | "SIGPIPE" when writing to some random socket. |
|
|
1529 | |
|
|
1530 | The rationale for installing a no-op handler as opposed to ignoring |
|
|
1531 | it is that this way, the handler will be restored to defaults on |
|
|
1532 | exec. |
|
|
1533 | |
|
|
1534 | Feel free to install your own handler, or reset it to defaults. |
|
|
1535 | |
1335 | FORK |
1536 | FORK |
1336 | Most event libraries are not fork-safe. The ones who are usually are |
1537 | Most event libraries are not fork-safe. The ones who are usually are |
1337 | because they rely on inefficient but fork-safe "select" or "poll" calls. |
1538 | because they rely on inefficient but fork-safe "select" or "poll" calls. |
1338 | Only EV is fully fork-aware. |
1539 | Only EV is fully fork-aware. |
1339 | |
1540 | |
… | |
… | |
1350 | |
1551 | |
1351 | You can make AnyEvent completely ignore this variable by deleting it |
1552 | You can make AnyEvent completely ignore this variable by deleting it |
1352 | before the first watcher gets created, e.g. with a "BEGIN" block: |
1553 | before the first watcher gets created, e.g. with a "BEGIN" block: |
1353 | |
1554 | |
1354 | BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } |
1555 | BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } |
1355 | |
1556 | |
1356 | use AnyEvent; |
1557 | use AnyEvent; |
1357 | |
1558 | |
1358 | Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can |
1559 | Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can |
1359 | be used to probe what backend is used and gain other information (which |
1560 | be used to probe what backend is used and gain other information (which |
1360 | is probably even less useful to an attacker than PERL_ANYEVENT_MODEL), |
1561 | is probably even less useful to an attacker than PERL_ANYEVENT_MODEL), |
1361 | and $ENV{PERL_ANYEGENT_STRICT}. |
1562 | and $ENV{PERL_ANYEVENT_STRICT}. |
|
|
1563 | |
|
|
1564 | Note that AnyEvent will remove *all* environment variables starting with |
|
|
1565 | "PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is |
|
|
1566 | enabled. |
1362 | |
1567 | |
1363 | BUGS |
1568 | BUGS |
1364 | Perl 5.8 has numerous memleaks that sometimes hit this module and are |
1569 | Perl 5.8 has numerous memleaks that sometimes hit this module and are |
1365 | hard to work around. If you suffer from memleaks, first upgrade to Perl |
1570 | hard to work around. If you suffer from memleaks, first upgrade to Perl |
1366 | 5.10 and check wether the leaks still show up. (Perl 5.10.0 has other |
1571 | 5.10 and check wether the leaks still show up. (Perl 5.10.0 has other |
1367 | annoying mamleaks, such as leaking on "map" and "grep" but it is usually |
1572 | annoying memleaks, such as leaking on "map" and "grep" but it is usually |
1368 | not as pronounced). |
1573 | not as pronounced). |
1369 | |
1574 | |
1370 | SEE ALSO |
1575 | SEE ALSO |
1371 | Utility functions: AnyEvent::Util. |
1576 | Utility functions: AnyEvent::Util. |
1372 | |
1577 | |