| … | |
… | |
| 5 | Qt and POE are various supported event loops/environments. |
5 | Qt and POE are various supported event loops/environments. |
| 6 | |
6 | |
| 7 | SYNOPSIS |
7 | SYNOPSIS |
| 8 | use AnyEvent; |
8 | use AnyEvent; |
| 9 | |
9 | |
|
|
10 | # if you prefer function calls, look at the AE manpage for |
|
|
11 | # an alternative API. |
|
|
12 | |
| 10 | # file descriptor readable |
13 | # file handle or descriptor readable |
| 11 | my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... }); |
14 | my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... }); |
| 12 | |
15 | |
| 13 | # one-shot or repeating timers |
16 | # one-shot or repeating timers |
| 14 | my $w = AnyEvent->timer (after => $seconds, cb => sub { ... }); |
17 | my $w = AnyEvent->timer (after => $seconds, cb => sub { ... }); |
| 15 | my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ... |
18 | my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ... |
| … | |
… | |
| 391 | correctly. |
394 | correctly. |
| 392 | |
395 | |
| 393 | Example: exit on SIGINT |
396 | Example: exit on SIGINT |
| 394 | |
397 | |
| 395 | my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 }); |
398 | my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 }); |
|
|
399 | |
|
|
400 | Restart Behaviour |
|
|
401 | While restart behaviour is up to the event loop implementation, most |
|
|
402 | will not restart syscalls (that includes Async::Interrupt and AnyEvent's |
|
|
403 | pure perl implementation). |
|
|
404 | |
|
|
405 | Safe/Unsafe Signals |
|
|
406 | Perl signals can be either "safe" (synchronous to opcode handling) or |
|
|
407 | "unsafe" (asynchronous) - the former might get delayed indefinitely, the |
|
|
408 | latter might corrupt your memory. |
|
|
409 | |
|
|
410 | AnyEvent signal handlers are, in addition, synchronous to the event |
|
|
411 | loop, i.e. they will not interrupt your running perl program but will |
|
|
412 | only be called as part of the normal event handling (just like timer, |
|
|
413 | I/O etc. callbacks, too). |
| 396 | |
414 | |
| 397 | Signal Races, Delays and Workarounds |
415 | Signal Races, Delays and Workarounds |
| 398 | Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching |
416 | Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching |
| 399 | callbacks to signals in a generic way, which is a pity, as you cannot do |
417 | callbacks to signals in a generic way, which is a pity, as you cannot do |
| 400 | race-free signal handling in perl, requiring C libraries for this. |
418 | race-free signal handling in perl, requiring C libraries for this. |
| … | |
… | |
| 471 | $done->recv; |
489 | $done->recv; |
| 472 | |
490 | |
| 473 | IDLE WATCHERS |
491 | IDLE WATCHERS |
| 474 | $w = AnyEvent->idle (cb => <callback>); |
492 | $w = AnyEvent->idle (cb => <callback>); |
| 475 | |
493 | |
| 476 | Sometimes there is a need to do something, but it is not so important to |
494 | Repeatedly invoke the callback after the process becomes idle, until |
| 477 | do it instantly, but only when there is nothing better to do. This |
495 | either the watcher is destroyed or new events have been detected. |
| 478 | "nothing better to do" is usually defined to be "no other events need |
|
|
| 479 | attention by the event loop". |
|
|
| 480 | |
496 | |
| 481 | Idle watchers ideally get invoked when the event loop has nothing better |
497 | Idle watchers are useful when there is a need to do something, but it is |
| 482 | to do, just before it would block the process to wait for new events. |
498 | not so important (or wise) to do it instantly. The callback will be |
| 483 | Instead of blocking, the idle watcher is invoked. |
499 | invoked only when there is "nothing better to do", which is usually |
|
|
500 | defined as "all outstanding events have been handled and no new events |
|
|
501 | have been detected". That means that idle watchers ideally get invoked |
|
|
502 | when the event loop has just polled for new events but none have been |
|
|
503 | detected. Instead of blocking to wait for more events, the idle watchers |
|
|
504 | will be invoked. |
| 484 | |
505 | |
| 485 | Most event loops unfortunately do not really support idle watchers (only |
506 | Unfortunately, most event loops do not really support idle watchers |
| 486 | EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent |
507 | (only EV, Event and Glib do it in a usable fashion) - for the rest, |
| 487 | will simply call the callback "from time to time". |
508 | AnyEvent will simply call the callback "from time to time". |
| 488 | |
509 | |
| 489 | Example: read lines from STDIN, but only process them when the program |
510 | Example: read lines from STDIN, but only process them when the program |
| 490 | is otherwise idle: |
511 | is otherwise idle: |
| 491 | |
512 | |
| 492 | my @lines; # read data |
513 | my @lines; # read data |
| … | |
… | |
| 518 | |
539 | |
| 519 | AnyEvent is slightly different: it expects somebody else to run the |
540 | AnyEvent is slightly different: it expects somebody else to run the |
| 520 | event loop and will only block when necessary (usually when told by the |
541 | event loop and will only block when necessary (usually when told by the |
| 521 | user). |
542 | user). |
| 522 | |
543 | |
| 523 | The instrument to do that is called a "condition variable", so called |
544 | The tool to do that is called a "condition variable", so called because |
| 524 | because they represent a condition that must become true. |
545 | they represent a condition that must become true. |
| 525 | |
546 | |
| 526 | Now is probably a good time to look at the examples further below. |
547 | Now is probably a good time to look at the examples further below. |
| 527 | |
548 | |
| 528 | Condition variables can be created by calling the "AnyEvent->condvar" |
549 | Condition variables can be created by calling the "AnyEvent->condvar" |
| 529 | method, usually without arguments. The only argument pair allowed is |
550 | method, usually without arguments. The only argument pair allowed is |
| … | |
… | |
| 534 | After creation, the condition variable is "false" until it becomes |
555 | After creation, the condition variable is "false" until it becomes |
| 535 | "true" by calling the "send" method (or calling the condition variable |
556 | "true" by calling the "send" method (or calling the condition variable |
| 536 | as if it were a callback, read about the caveats in the description for |
557 | as if it were a callback, read about the caveats in the description for |
| 537 | the "->send" method). |
558 | the "->send" method). |
| 538 | |
559 | |
| 539 | Condition variables are similar to callbacks, except that you can |
560 | Since condition variables are the most complex part of the AnyEvent API, |
| 540 | optionally wait for them. They can also be called merge points - points |
561 | here are some different mental models of what they are - pick the ones |
| 541 | in time where multiple outstanding events have been processed. And yet |
562 | you can connect to: |
| 542 | another way to call them is transactions - each condition variable can |
563 | |
| 543 | be used to represent a transaction, which finishes at some point and |
564 | * Condition variables are like callbacks - you can call them (and pass |
| 544 | delivers a result. And yet some people know them as "futures" - a |
565 | them instead of callbacks). Unlike callbacks however, you can also |
| 545 | promise to compute/deliver something that you can wait for. |
566 | wait for them to be called. |
|
|
567 | |
|
|
568 | * Condition variables are signals - one side can emit or send them, |
|
|
569 | the other side can wait for them, or install a handler that is |
|
|
570 | called when the signal fires. |
|
|
571 | |
|
|
572 | * Condition variables are like "Merge Points" - points in your program |
|
|
573 | where you merge multiple independent results/control flows into one. |
|
|
574 | |
|
|
575 | * Condition variables represent a transaction - function that start |
|
|
576 | some kind of transaction can return them, leaving the caller the |
|
|
577 | choice between waiting in a blocking fashion, or setting a callback. |
|
|
578 | |
|
|
579 | * Condition variables represent future values, or promises to deliver |
|
|
580 | some result, long before the result is available. |
| 546 | |
581 | |
| 547 | Condition variables are very useful to signal that something has |
582 | Condition variables are very useful to signal that something has |
| 548 | finished, for example, if you write a module that does asynchronous http |
583 | finished, for example, if you write a module that does asynchronous http |
| 549 | requests, then a condition variable would be the ideal candidate to |
584 | requests, then a condition variable would be the ideal candidate to |
| 550 | signal the availability of results. The user can either act when the |
585 | signal the availability of results. The user can either act when the |
| … | |
… | |
| 571 | which eventually calls "-> send", and the "consumer side", which waits |
606 | which eventually calls "-> send", and the "consumer side", which waits |
| 572 | for the send to occur. |
607 | for the send to occur. |
| 573 | |
608 | |
| 574 | Example: wait for a timer. |
609 | Example: wait for a timer. |
| 575 | |
610 | |
| 576 | # wait till the result is ready |
611 | # condition: "wait till the timer is fired" |
| 577 | my $result_ready = AnyEvent->condvar; |
612 | my $timer_fired = AnyEvent->condvar; |
| 578 | |
613 | |
| 579 | # do something such as adding a timer |
614 | # create the timer - we could wait for, say |
| 580 | # or socket watcher the calls $result_ready->send |
615 | # a handle becomign ready, or even an |
| 581 | # when the "result" is ready. |
616 | # AnyEvent::HTTP request to finish, but |
| 582 | # in this case, we simply use a timer: |
617 | # in this case, we simply use a timer: |
| 583 | my $w = AnyEvent->timer ( |
618 | my $w = AnyEvent->timer ( |
| 584 | after => 1, |
619 | after => 1, |
| 585 | cb => sub { $result_ready->send }, |
620 | cb => sub { $timer_fired->send }, |
| 586 | ); |
621 | ); |
| 587 | |
622 | |
| 588 | # this "blocks" (while handling events) till the callback |
623 | # this "blocks" (while handling events) till the callback |
| 589 | # calls ->send |
624 | # calls ->send |
| 590 | $result_ready->recv; |
625 | $timer_fired->recv; |
| 591 | |
626 | |
| 592 | Example: wait for a timer, but take advantage of the fact that condition |
627 | Example: wait for a timer, but take advantage of the fact that condition |
| 593 | variables are also callable directly. |
628 | variables are also callable directly. |
| 594 | |
629 | |
| 595 | my $done = AnyEvent->condvar; |
630 | my $done = AnyEvent->condvar; |
| … | |
… | |
| 904 | You should check $AnyEvent::MODEL before adding to this array, |
939 | You should check $AnyEvent::MODEL before adding to this array, |
| 905 | though: if it is defined then the event loop has already been |
940 | though: if it is defined then the event loop has already been |
| 906 | detected, and the array will be ignored. |
941 | detected, and the array will be ignored. |
| 907 | |
942 | |
| 908 | Best use "AnyEvent::post_detect { BLOCK }" when your application |
943 | Best use "AnyEvent::post_detect { BLOCK }" when your application |
| 909 | allows it,as it takes care of these details. |
944 | allows it, as it takes care of these details. |
| 910 | |
945 | |
| 911 | This variable is mainly useful for modules that can do something |
946 | This variable is mainly useful for modules that can do something |
| 912 | useful when AnyEvent is used and thus want to know when it is |
947 | useful when AnyEvent is used and thus want to know when it is |
| 913 | initialised, but do not need to even load it by default. This array |
948 | initialised, but do not need to even load it by default. This array |
| 914 | provides the means to hook into AnyEvent passively, without loading |
949 | provides the means to hook into AnyEvent passively, without loading |
| 915 | it. |
950 | it. |
|
|
951 | |
|
|
952 | Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used |
|
|
953 | together, you could put this into Coro (this is the actual code used |
|
|
954 | by Coro to accomplish this): |
|
|
955 | |
|
|
956 | if (defined $AnyEvent::MODEL) { |
|
|
957 | # AnyEvent already initialised, so load Coro::AnyEvent |
|
|
958 | require Coro::AnyEvent; |
|
|
959 | } else { |
|
|
960 | # AnyEvent not yet initialised, so make sure to load Coro::AnyEvent |
|
|
961 | # as soon as it is |
|
|
962 | push @AnyEvent::post_detect, sub { require Coro::AnyEvent }; |
|
|
963 | } |
| 916 | |
964 | |
| 917 | WHAT TO DO IN A MODULE |
965 | WHAT TO DO IN A MODULE |
| 918 | As a module author, you should "use AnyEvent" and call AnyEvent methods |
966 | As a module author, you should "use AnyEvent" and call AnyEvent methods |
| 919 | freely, but you should not load a specific event module or rely on it. |
967 | freely, but you should not load a specific event module or rely on it. |
| 920 | |
968 | |
| … | |
… | |
| 973 | |
1021 | |
| 974 | OTHER MODULES |
1022 | OTHER MODULES |
| 975 | The following is a non-exhaustive list of additional modules that use |
1023 | The following is a non-exhaustive list of additional modules that use |
| 976 | AnyEvent as a client and can therefore be mixed easily with other |
1024 | AnyEvent as a client and can therefore be mixed easily with other |
| 977 | AnyEvent modules and other event loops in the same program. Some of the |
1025 | AnyEvent modules and other event loops in the same program. Some of the |
| 978 | modules come with AnyEvent, most are available via CPAN. |
1026 | modules come as part of AnyEvent, the others are available via CPAN. |
| 979 | |
1027 | |
| 980 | AnyEvent::Util |
1028 | AnyEvent::Util |
| 981 | Contains various utility functions that replace often-used but |
1029 | Contains various utility functions that replace often-used but |
| 982 | blocking functions such as "inet_aton" by event-/callback-based |
1030 | blocking functions such as "inet_aton" by event-/callback-based |
| 983 | versions. |
1031 | versions. |
| … | |
… | |
| 994 | transparent and non-blocking SSL/TLS (via AnyEvent::TLS. |
1042 | transparent and non-blocking SSL/TLS (via AnyEvent::TLS. |
| 995 | |
1043 | |
| 996 | AnyEvent::DNS |
1044 | AnyEvent::DNS |
| 997 | Provides rich asynchronous DNS resolver capabilities. |
1045 | Provides rich asynchronous DNS resolver capabilities. |
| 998 | |
1046 | |
|
|
1047 | AnyEvent::HTTP, AnyEvent::IRC, AnyEvent::XMPP, AnyEvent::GPSD, |
|
|
1048 | AnyEvent::IGS, AnyEvent::FCP |
|
|
1049 | Implement event-based interfaces to the protocols of the same name |
|
|
1050 | (for the curious, IGS is the International Go Server and FCP is the |
|
|
1051 | Freenet Client Protocol). |
|
|
1052 | |
|
|
1053 | AnyEvent::Handle::UDP |
|
|
1054 | Here be danger! |
|
|
1055 | |
|
|
1056 | As Pauli would put it, "Not only is it not right, it's not even |
|
|
1057 | wrong!" - there are so many things wrong with AnyEvent::Handle::UDP, |
|
|
1058 | most notably it's use of a stream-based API with a protocol that |
|
|
1059 | isn't streamable, that the only way to improve it is to delete it. |
|
|
1060 | |
|
|
1061 | It features data corruption (but typically only under load) and |
|
|
1062 | general confusion. On top, the author is not only clueless about UDP |
|
|
1063 | but also fact-resistant - some gems of his understanding: "connect |
|
|
1064 | doesn't work with UDP", "UDP packets are not IP packets", "UDP only |
|
|
1065 | has datagrams, not packets", "I don't need to implement proper error |
|
|
1066 | checking as UDP doesn't support error checking" and so on - he |
|
|
1067 | doesn't even understand what's wrong with his module when it is |
|
|
1068 | explained to him. |
|
|
1069 | |
| 999 | AnyEvent::HTTP |
1070 | AnyEvent::DBI |
| 1000 | A simple-to-use HTTP library that is capable of making a lot of |
1071 | Executes DBI requests asynchronously in a proxy process for you, |
| 1001 | concurrent HTTP requests. |
1072 | notifying you in an event-bnased way when the operation is finished. |
|
|
1073 | |
|
|
1074 | AnyEvent::AIO |
|
|
1075 | Truly asynchronous (as opposed to non-blocking) I/O, should be in |
|
|
1076 | the toolbox of every event programmer. AnyEvent::AIO transparently |
|
|
1077 | fuses IO::AIO and AnyEvent together, giving AnyEvent access to |
|
|
1078 | event-based file I/O, and much more. |
| 1002 | |
1079 | |
| 1003 | AnyEvent::HTTPD |
1080 | AnyEvent::HTTPD |
| 1004 | Provides a simple web application server framework. |
1081 | A simple embedded webserver. |
| 1005 | |
1082 | |
| 1006 | AnyEvent::FastPing |
1083 | AnyEvent::FastPing |
| 1007 | The fastest ping in the west. |
1084 | The fastest ping in the west. |
| 1008 | |
|
|
| 1009 | AnyEvent::DBI |
|
|
| 1010 | Executes DBI requests asynchronously in a proxy process. |
|
|
| 1011 | |
|
|
| 1012 | AnyEvent::AIO |
|
|
| 1013 | Truly asynchronous I/O, should be in the toolbox of every event |
|
|
| 1014 | programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent |
|
|
| 1015 | together. |
|
|
| 1016 | |
|
|
| 1017 | AnyEvent::BDB |
|
|
| 1018 | Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently |
|
|
| 1019 | fuses BDB and AnyEvent together. |
|
|
| 1020 | |
|
|
| 1021 | AnyEvent::GPSD |
|
|
| 1022 | A non-blocking interface to gpsd, a daemon delivering GPS |
|
|
| 1023 | information. |
|
|
| 1024 | |
|
|
| 1025 | AnyEvent::IRC |
|
|
| 1026 | AnyEvent based IRC client module family (replacing the older |
|
|
| 1027 | Net::IRC3). |
|
|
| 1028 | |
|
|
| 1029 | AnyEvent::XMPP |
|
|
| 1030 | AnyEvent based XMPP (Jabber protocol) module family (replacing the |
|
|
| 1031 | older Net::XMPP2>. |
|
|
| 1032 | |
|
|
| 1033 | AnyEvent::IGS |
|
|
| 1034 | A non-blocking interface to the Internet Go Server protocol (used by |
|
|
| 1035 | App::IGS). |
|
|
| 1036 | |
|
|
| 1037 | Net::FCP |
|
|
| 1038 | AnyEvent-based implementation of the Freenet Client Protocol, |
|
|
| 1039 | birthplace of AnyEvent. |
|
|
| 1040 | |
|
|
| 1041 | Event::ExecFlow |
|
|
| 1042 | High level API for event-based execution flow control. |
|
|
| 1043 | |
1085 | |
| 1044 | Coro |
1086 | Coro |
| 1045 | Has special support for AnyEvent via Coro::AnyEvent. |
1087 | Has special support for AnyEvent via Coro::AnyEvent. |
| 1046 | |
1088 | |
| 1047 | SIMPLIFIED AE API |
1089 | SIMPLIFIED AE API |
| 1048 | Starting with version 5.0, AnyEvent officially supports a second, much |
1090 | Starting with version 5.0, AnyEvent officially supports a second, much |
| 1049 | simpler, API that is designed to reduce the calling, typing and memory |
1091 | simpler, API that is designed to reduce the calling, typing and memory |
| 1050 | overhead. |
1092 | overhead by using function call syntax and a fixed number of parameters. |
| 1051 | |
1093 | |
| 1052 | See the AE manpage for details. |
1094 | See the AE manpage for details. |
| 1053 | |
1095 | |
| 1054 | ERROR AND EXCEPTION HANDLING |
1096 | ERROR AND EXCEPTION HANDLING |
| 1055 | In general, AnyEvent does not do any error handling - it relies on the |
1097 | In general, AnyEvent does not do any error handling - it relies on the |
| … | |
… | |
| 1320 | |
1362 | |
| 1321 | The actual code goes further and collects all errors ("die"s, |
1363 | The actual code goes further and collects all errors ("die"s, |
| 1322 | exceptions) that occurred during request processing. The "result" method |
1364 | exceptions) that occurred during request processing. The "result" method |
| 1323 | detects whether an exception as thrown (it is stored inside the $txn |
1365 | detects whether an exception as thrown (it is stored inside the $txn |
| 1324 | object) and just throws the exception, which means connection errors and |
1366 | object) and just throws the exception, which means connection errors and |
| 1325 | other problems get reported tot he code that tries to use the result, |
1367 | other problems get reported to the code that tries to use the result, |
| 1326 | not in a random callback. |
1368 | not in a random callback. |
| 1327 | |
1369 | |
| 1328 | All of this enables the following usage styles: |
1370 | All of this enables the following usage styles: |
| 1329 | |
1371 | |
| 1330 | 1. Blocking: |
1372 | 1. Blocking: |
| … | |
… | |
| 1709 | it's built-in modules) are required to use it. |
1751 | it's built-in modules) are required to use it. |
| 1710 | |
1752 | |
| 1711 | That does not mean that AnyEvent won't take advantage of some additional |
1753 | That does not mean that AnyEvent won't take advantage of some additional |
| 1712 | modules if they are installed. |
1754 | modules if they are installed. |
| 1713 | |
1755 | |
| 1714 | This section epxlains which additional modules will be used, and how |
1756 | This section explains which additional modules will be used, and how |
| 1715 | they affect AnyEvent's operetion. |
1757 | they affect AnyEvent's operation. |
| 1716 | |
1758 | |
| 1717 | Async::Interrupt |
1759 | Async::Interrupt |
| 1718 | This slightly arcane module is used to implement fast signal |
1760 | This slightly arcane module is used to implement fast signal |
| 1719 | handling: To my knowledge, there is no way to do completely |
1761 | handling: To my knowledge, there is no way to do completely |
| 1720 | race-free and quick signal handling in pure perl. To ensure that |
1762 | race-free and quick signal handling in pure perl. To ensure that |
| … | |
… | |
| 1723 | 10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY). |
1765 | 10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY). |
| 1724 | |
1766 | |
| 1725 | If this module is available, then it will be used to implement |
1767 | If this module is available, then it will be used to implement |
| 1726 | signal catching, which means that signals will not be delayed, and |
1768 | signal catching, which means that signals will not be delayed, and |
| 1727 | the event loop will not be interrupted regularly, which is more |
1769 | the event loop will not be interrupted regularly, which is more |
| 1728 | efficient (And good for battery life on laptops). |
1770 | efficient (and good for battery life on laptops). |
| 1729 | |
1771 | |
| 1730 | This affects not just the pure-perl event loop, but also other event |
1772 | This affects not just the pure-perl event loop, but also other event |
| 1731 | loops that have no signal handling on their own (e.g. Glib, Tk, Qt). |
1773 | loops that have no signal handling on their own (e.g. Glib, Tk, Qt). |
| 1732 | |
1774 | |
| 1733 | Some event loops (POE, Event, Event::Lib) offer signal watchers |
1775 | Some event loops (POE, Event, Event::Lib) offer signal watchers |
| … | |
… | |
| 1743 | clock is available, can take avdantage of advanced kernel interfaces |
1785 | clock is available, can take avdantage of advanced kernel interfaces |
| 1744 | such as "epoll" and "kqueue", and is the fastest backend *by far*. |
1786 | such as "epoll" and "kqueue", and is the fastest backend *by far*. |
| 1745 | You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and |
1787 | You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and |
| 1746 | Glib::EV). |
1788 | Glib::EV). |
| 1747 | |
1789 | |
|
|
1790 | If you only use backends that rely on another event loop (e.g. |
|
|
1791 | "Tk"), then this module will do nothing for you. |
|
|
1792 | |
| 1748 | Guard |
1793 | Guard |
| 1749 | The guard module, when used, will be used to implement |
1794 | The guard module, when used, will be used to implement |
| 1750 | "AnyEvent::Util::guard". This speeds up guards considerably (and |
1795 | "AnyEvent::Util::guard". This speeds up guards considerably (and |
| 1751 | uses a lot less memory), but otherwise doesn't affect guard |
1796 | uses a lot less memory), but otherwise doesn't affect guard |
| 1752 | operation much. It is purely used for performance. |
1797 | operation much. It is purely used for performance. |
| 1753 | |
1798 | |
| 1754 | JSON and JSON::XS |
1799 | JSON and JSON::XS |
| 1755 | One of these modules is required when you want to read or write JSON |
1800 | One of these modules is required when you want to read or write JSON |
| 1756 | data via AnyEvent::Handle. It is also written in pure-perl, but can |
1801 | data via AnyEvent::Handle. JSON is also written in pure-perl, but |
| 1757 | take advantage of the ultra-high-speed JSON::XS module when it is |
1802 | can take advantage of the ultra-high-speed JSON::XS module when it |
| 1758 | installed. |
1803 | is installed. |
| 1759 | |
|
|
| 1760 | In fact, AnyEvent::Handle will use JSON::XS by default if it is |
|
|
| 1761 | installed. |
|
|
| 1762 | |
1804 | |
| 1763 | Net::SSLeay |
1805 | Net::SSLeay |
| 1764 | Implementing TLS/SSL in Perl is certainly interesting, but not very |
1806 | Implementing TLS/SSL in Perl is certainly interesting, but not very |
| 1765 | worthwhile: If this module is installed, then AnyEvent::Handle (with |
1807 | worthwhile: If this module is installed, then AnyEvent::Handle (with |
| 1766 | the help of AnyEvent::TLS), gains the ability to do TLS/SSL. |
1808 | the help of AnyEvent::TLS), gains the ability to do TLS/SSL. |
| … | |
… | |
| 1772 | additionally use it to try to use a monotonic clock for timing |
1814 | additionally use it to try to use a monotonic clock for timing |
| 1773 | stability. |
1815 | stability. |
| 1774 | |
1816 | |
| 1775 | FORK |
1817 | FORK |
| 1776 | Most event libraries are not fork-safe. The ones who are usually are |
1818 | Most event libraries are not fork-safe. The ones who are usually are |
| 1777 | because they rely on inefficient but fork-safe "select" or "poll" calls. |
1819 | because they rely on inefficient but fork-safe "select" or "poll" calls |
| 1778 | Only EV is fully fork-aware. |
1820 | - higher performance APIs such as BSD's kqueue or the dreaded Linux |
|
|
1821 | epoll are usually badly thought-out hacks that are incompatible with |
|
|
1822 | fork in one way or another. Only EV is fully fork-aware and ensures that |
|
|
1823 | you continue event-processing in both parent and child (or both, if you |
|
|
1824 | know what you are doing). |
|
|
1825 | |
|
|
1826 | This means that, in general, you cannot fork and do event processing in |
|
|
1827 | the child if the event library was initialised before the fork (which |
|
|
1828 | usually happens when the first AnyEvent watcher is created, or the |
|
|
1829 | library is loaded). |
| 1779 | |
1830 | |
| 1780 | If you have to fork, you must either do so *before* creating your first |
1831 | If you have to fork, you must either do so *before* creating your first |
| 1781 | watcher OR you must not use AnyEvent at all in the child OR you must do |
1832 | watcher OR you must not use AnyEvent at all in the child OR you must do |
| 1782 | something completely out of the scope of AnyEvent. |
1833 | something completely out of the scope of AnyEvent. |
|
|
1834 | |
|
|
1835 | The problem of doing event processing in the parent *and* the child is |
|
|
1836 | much more complicated: even for backends that *are* fork-aware or |
|
|
1837 | fork-safe, their behaviour is not usually what you want: fork clones all |
|
|
1838 | watchers, that means all timers, I/O watchers etc. are active in both |
|
|
1839 | parent and child, which is almost never what you want. USing "exec" to |
|
|
1840 | start worker children from some kind of manage rprocess is usually |
|
|
1841 | preferred, because it is much easier and cleaner, at the expense of |
|
|
1842 | having to have another binary. |
| 1783 | |
1843 | |
| 1784 | SECURITY CONSIDERATIONS |
1844 | SECURITY CONSIDERATIONS |
| 1785 | AnyEvent can be forced to load any event model via |
1845 | AnyEvent can be forced to load any event model via |
| 1786 | $ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used |
1846 | $ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used |
| 1787 | to execute arbitrary code or directly gain access, it can easily be used |
1847 | to execute arbitrary code or directly gain access, it can easily be used |
