1 | NAME |
1 | NAME |
2 | AnyEvent - the DBI of event loop programming |
2 | AnyEvent - the DBI of event loop programming |
3 | |
3 | |
4 | EV, Event, Glib, Tk, Perl, Event::Lib, Irssi, rxvt-unicode, IO::Async, |
4 | EV, Event, Glib, Tk, UV, Perl, Event::Lib, Irssi, rxvt-unicode, |
5 | Qt, FLTK and POE are various supported event loops/environments. |
5 | IO::Async, Qt, FLTK and POE are various supported event |
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6 | loops/environments. |
6 | |
7 | |
7 | SYNOPSIS |
8 | SYNOPSIS |
8 | use AnyEvent; |
9 | use AnyEvent; |
9 | |
10 | |
10 | # if you prefer function calls, look at the AE manpage for |
11 | # if you prefer function calls, look at the AE manpage for |
… | |
… | |
262 | |
263 | |
263 | Example 2: fire an event after 0.5 seconds, then roughly every second. |
264 | Example 2: fire an event after 0.5 seconds, then roughly every second. |
264 | |
265 | |
265 | my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub { |
266 | my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub { |
266 | warn "timeout\n"; |
267 | warn "timeout\n"; |
267 | }; |
268 | }); |
268 | |
269 | |
269 | TIMING ISSUES |
270 | TIMING ISSUES |
270 | There are two ways to handle timers: based on real time (relative, "fire |
271 | There are two ways to handle timers: based on real time (relative, "fire |
271 | in 10 seconds") and based on wallclock time (absolute, "fire at 12 |
272 | in 10 seconds") and based on wallclock time (absolute, "fire at 12 |
272 | o'clock"). |
273 | o'clock"). |
… | |
… | |
469 | |
470 | |
470 | Example: fork a process and wait for it |
471 | Example: fork a process and wait for it |
471 | |
472 | |
472 | my $done = AnyEvent->condvar; |
473 | my $done = AnyEvent->condvar; |
473 | |
474 | |
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475 | # this forks and immediately calls exit in the child. this |
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476 | # normally has all sorts of bad consequences for your parent, |
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477 | # so take this as an example only. always fork and exec, |
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478 | # or call POSIX::_exit, in real code. |
474 | my $pid = fork or exit 5; |
479 | my $pid = fork or exit 5; |
475 | |
480 | |
476 | my $w = AnyEvent->child ( |
481 | my $w = AnyEvent->child ( |
477 | pid => $pid, |
482 | pid => $pid, |
478 | cb => sub { |
483 | cb => sub { |
… | |
… | |
718 | This works because for every event source (EOF on file handle), |
723 | This works because for every event source (EOF on file handle), |
719 | there is one call to "begin", so the condvar waits for all calls to |
724 | there is one call to "begin", so the condvar waits for all calls to |
720 | "end" before sending. |
725 | "end" before sending. |
721 | |
726 | |
722 | The ping example mentioned above is slightly more complicated, as |
727 | The ping example mentioned above is slightly more complicated, as |
723 | the there are results to be passwd back, and the number of tasks |
728 | the there are results to be passed back, and the number of tasks |
724 | that are begun can potentially be zero: |
729 | that are begun can potentially be zero: |
725 | |
730 | |
726 | my $cv = AnyEvent->condvar; |
731 | my $cv = AnyEvent->condvar; |
727 | |
732 | |
728 | my %result; |
733 | my %result; |
… | |
… | |
736 | }; |
741 | }; |
737 | } |
742 | } |
738 | |
743 | |
739 | $cv->end; |
744 | $cv->end; |
740 | |
745 | |
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746 | ... |
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747 | |
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748 | my $results = $cv->recv; |
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749 | |
741 | This code fragment supposedly pings a number of hosts and calls |
750 | This code fragment supposedly pings a number of hosts and calls |
742 | "send" after results for all then have have been gathered - in any |
751 | "send" after results for all then have have been gathered - in any |
743 | order. To achieve this, the code issues a call to "begin" when it |
752 | order. To achieve this, the code issues a call to "begin" when it |
744 | starts each ping request and calls "end" when it has received some |
753 | starts each ping request and calls "end" when it has received some |
745 | result for it. Since "begin" and "end" only maintain a counter, the |
754 | result for it. Since "begin" and "end" only maintain a counter, the |
… | |
… | |
774 | In list context, all parameters passed to "send" will be returned, |
783 | In list context, all parameters passed to "send" will be returned, |
775 | in scalar context only the first one will be returned. |
784 | in scalar context only the first one will be returned. |
776 | |
785 | |
777 | Note that doing a blocking wait in a callback is not supported by |
786 | Note that doing a blocking wait in a callback is not supported by |
778 | any event loop, that is, recursive invocation of a blocking "->recv" |
787 | any event loop, that is, recursive invocation of a blocking "->recv" |
779 | is not allowed, and the "recv" call will "croak" if such a condition |
788 | is not allowed and the "recv" call will "croak" if such a condition |
780 | is detected. This condition can be slightly loosened by using |
789 | is detected. This requirement can be dropped by relying on |
781 | Coro::AnyEvent, which allows you to do a blocking "->recv" from any |
790 | Coro::AnyEvent , which allows you to do a blocking "->recv" from any |
782 | thread that doesn't run the event loop itself. |
791 | thread that doesn't run the event loop itself. Coro::AnyEvent is |
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792 | loaded automatically when Coro is used with AnyEvent, so code does |
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793 | not need to do anything special to take advantage of that: any code |
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794 | that would normally block your program because it calls "recv", be |
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795 | executed in an "async" thread instead without blocking other |
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796 | threads. |
783 | |
797 | |
784 | Not all event models support a blocking wait - some die in that case |
798 | Not all event models support a blocking wait - some die in that case |
785 | (programs might want to do that to stay interactive), so *if you are |
799 | (programs might want to do that to stay interactive), so *if you are |
786 | using this from a module, never require a blocking wait*. Instead, |
800 | using this from a module, never require a blocking wait*. Instead, |
787 | let the caller decide whether the call will block or not (for |
801 | let the caller decide whether the call will block or not (for |
… | |
… | |
798 | $bool = $cv->ready |
812 | $bool = $cv->ready |
799 | Returns true when the condition is "true", i.e. whether "send" or |
813 | Returns true when the condition is "true", i.e. whether "send" or |
800 | "croak" have been called. |
814 | "croak" have been called. |
801 | |
815 | |
802 | $cb = $cv->cb ($cb->($cv)) |
816 | $cb = $cv->cb ($cb->($cv)) |
803 | This is a mutator function that returns the callback set and |
817 | This is a mutator function that returns the callback set (or "undef" |
804 | optionally replaces it before doing so. |
818 | if not) and optionally replaces it before doing so. |
805 | |
819 | |
806 | The callback will be called when the condition becomes "true", i.e. |
820 | The callback will be called when the condition becomes "true", i.e. |
807 | when "send" or "croak" are called, with the only argument being the |
821 | when "send" or "croak" are called, with the only argument being the |
808 | condition variable itself. If the condition is already true, the |
822 | condition variable itself. If the condition is already true, the |
809 | callback is called immediately when it is set. Calling "recv" inside |
823 | callback is called immediately when it is set. Calling "recv" inside |
810 | the callback or at any later time is guaranteed not to block. |
824 | the callback or at any later time is guaranteed not to block. |
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825 | |
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826 | Additionally, when the callback is invoked, it is also removed from |
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827 | the condvar (reset to "undef"), so the condvar does not keep a |
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828 | reference to the callback after invocation. |
811 | |
829 | |
812 | SUPPORTED EVENT LOOPS/BACKENDS |
830 | SUPPORTED EVENT LOOPS/BACKENDS |
813 | The available backend classes are (every class has its own manpage): |
831 | The available backend classes are (every class has its own manpage): |
814 | |
832 | |
815 | Backends that are autoprobed when no other event loop can be found. |
833 | Backends that are autoprobed when no other event loop can be found. |
… | |
… | |
830 | by the main program. |
848 | by the main program. |
831 | |
849 | |
832 | AnyEvent::Impl::Event based on Event, very stable, few glitches. |
850 | AnyEvent::Impl::Event based on Event, very stable, few glitches. |
833 | AnyEvent::Impl::Glib based on Glib, slow but very stable. |
851 | AnyEvent::Impl::Glib based on Glib, slow but very stable. |
834 | AnyEvent::Impl::Tk based on Tk, very broken. |
852 | AnyEvent::Impl::Tk based on Tk, very broken. |
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853 | AnyEvent::Impl::UV based on UV, innovated square wheels. |
835 | AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse. |
854 | AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse. |
836 | AnyEvent::Impl::POE based on POE, very slow, some limitations. |
855 | AnyEvent::Impl::POE based on POE, very slow, some limitations. |
837 | AnyEvent::Impl::Irssi used when running within irssi. |
856 | AnyEvent::Impl::Irssi used when running within irssi. |
838 | AnyEvent::Impl::IOAsync based on IO::Async. |
857 | AnyEvent::Impl::IOAsync based on IO::Async. |
839 | AnyEvent::Impl::Cocoa based on Cocoa::EventLoop. |
858 | AnyEvent::Impl::Cocoa based on Cocoa::EventLoop. |
… | |
… | |
895 | $guard = AnyEvent::post_detect { BLOCK } |
914 | $guard = AnyEvent::post_detect { BLOCK } |
896 | Arranges for the code block to be executed as soon as the event |
915 | Arranges for the code block to be executed as soon as the event |
897 | model is autodetected (or immediately if that has already happened). |
916 | model is autodetected (or immediately if that has already happened). |
898 | |
917 | |
899 | The block will be executed *after* the actual backend has been |
918 | The block will be executed *after* the actual backend has been |
900 | detected ($AnyEvent::MODEL is set), but *before* any watchers have |
919 | detected ($AnyEvent::MODEL is set), so it is possible to do some |
901 | been created, so it is possible to e.g. patch @AnyEvent::ISA or do |
920 | initialisation only when AnyEvent is actually initialised - see the |
902 | other initialisations - see the sources of AnyEvent::Strict or |
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903 | AnyEvent::AIO to see how this is used. |
921 | sources of AnyEvent::AIO to see how this is used. |
904 | |
922 | |
905 | The most common usage is to create some global watchers, without |
923 | The most common usage is to create some global watchers, without |
906 | forcing event module detection too early, for example, AnyEvent::AIO |
924 | forcing event module detection too early. For example, AnyEvent::AIO |
907 | creates and installs the global IO::AIO watcher in a "post_detect" |
925 | creates and installs the global IO::AIO watcher in a "post_detect" |
908 | block to avoid autodetecting the event module at load time. |
926 | block to avoid autodetecting the event module at load time. |
909 | |
927 | |
910 | If called in scalar or list context, then it creates and returns an |
928 | If called in scalar or list context, then it creates and returns an |
911 | object that automatically removes the callback again when it is |
929 | object that automatically removes the callback again when it is |
… | |
… | |
927 | # able to just C<undef $WATCHER> if the watcher causes them grief. |
945 | # able to just C<undef $WATCHER> if the watcher causes them grief. |
928 | |
946 | |
929 | $WATCHER ||= $guard; |
947 | $WATCHER ||= $guard; |
930 | |
948 | |
931 | @AnyEvent::post_detect |
949 | @AnyEvent::post_detect |
932 | If there are any code references in this array (you can "push" to it |
950 | This is a lower level interface then "AnyEvent::post_detect" (the |
933 | before or after loading AnyEvent), then they will be called directly |
951 | function). This variable is mainly useful for modules that can do |
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952 | something useful when AnyEvent is used and thus want to know when it |
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953 | is initialised, but do not need to even load it by default. This |
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954 | array provides the means to hook into AnyEvent passively, without |
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955 | loading it. |
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956 | |
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957 | Here is how it works: If there are any code references in this array |
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958 | (you can "push" to it before or after loading AnyEvent), then they |
934 | after the event loop has been chosen. |
959 | will be called directly after the event loop has been chosen. |
935 | |
960 | |
936 | You should check $AnyEvent::MODEL before adding to this array, |
961 | You should check $AnyEvent::MODEL before adding to this array, |
937 | though: if it is defined then the event loop has already been |
962 | though: if it is defined then the event loop has already been |
938 | detected, and the array will be ignored. |
963 | detected, and the array will be ignored. |
939 | |
964 | |
940 | Best use "AnyEvent::post_detect { BLOCK }" when your application |
965 | Best use "AnyEvent::post_detect { BLOCK }" when your application |
941 | allows it, as it takes care of these details. |
966 | allows it, as it takes care of these details. |
942 | |
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943 | This variable is mainly useful for modules that can do something |
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944 | useful when AnyEvent is used and thus want to know when it is |
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945 | initialised, but do not need to even load it by default. This array |
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946 | provides the means to hook into AnyEvent passively, without loading |
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947 | it. |
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948 | |
967 | |
949 | Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used |
968 | Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used |
950 | together, you could put this into Coro (this is the actual code used |
969 | together, you could put this into Coro (this is the actual code used |
951 | by Coro to accomplish this): |
970 | by Coro to accomplish this): |
952 | |
971 | |
… | |
… | |
971 | To understand the usefulness of this function, consider a function |
990 | To understand the usefulness of this function, consider a function |
972 | that asynchronously does something for you and returns some |
991 | that asynchronously does something for you and returns some |
973 | transaction object or guard to let you cancel the operation. For |
992 | transaction object or guard to let you cancel the operation. For |
974 | example, "AnyEvent::Socket::tcp_connect": |
993 | example, "AnyEvent::Socket::tcp_connect": |
975 | |
994 | |
976 | # start a conenction attempt unless one is active |
995 | # start a connection attempt unless one is active |
977 | $self->{connect_guard} ||= AnyEvent::Socket::tcp_connect "www.example.net", 80, sub { |
996 | $self->{connect_guard} ||= AnyEvent::Socket::tcp_connect "www.example.net", 80, sub { |
978 | delete $self->{connect_guard}; |
997 | delete $self->{connect_guard}; |
979 | ... |
998 | ... |
980 | }; |
999 | }; |
981 | |
1000 | |
… | |
… | |
1015 | If you want to sprinkle loads of logging calls around your code, |
1034 | If you want to sprinkle loads of logging calls around your code, |
1016 | consider creating a logger callback with the "AnyEvent::Log::logger" |
1035 | consider creating a logger callback with the "AnyEvent::Log::logger" |
1017 | function, which can reduce typing, codesize and can reduce the |
1036 | function, which can reduce typing, codesize and can reduce the |
1018 | logging overhead enourmously. |
1037 | logging overhead enourmously. |
1019 | |
1038 | |
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1039 | AnyEvent::fh_block $filehandle |
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1040 | AnyEvent::fh_unblock $filehandle |
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1041 | Sets blocking or non-blocking behaviour for the given filehandle. |
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1042 | |
1020 | WHAT TO DO IN A MODULE |
1043 | WHAT TO DO IN A MODULE |
1021 | As a module author, you should "use AnyEvent" and call AnyEvent methods |
1044 | As a module author, you should "use AnyEvent" and call AnyEvent methods |
1022 | freely, but you should not load a specific event module or rely on it. |
1045 | freely, but you should not load a specific event module or rely on it. |
1023 | |
1046 | |
1024 | Be careful when you create watchers in the module body - AnyEvent will |
1047 | Be careful when you create watchers in the module body - AnyEvent will |
… | |
… | |
1082 | modules come as part of AnyEvent, the others are available via CPAN (see |
1105 | modules come as part of AnyEvent, the others are available via CPAN (see |
1083 | <http://search.cpan.org/search?m=module&q=anyevent%3A%3A*> for a longer |
1106 | <http://search.cpan.org/search?m=module&q=anyevent%3A%3A*> for a longer |
1084 | non-exhaustive list), and the list is heavily biased towards modules of |
1107 | non-exhaustive list), and the list is heavily biased towards modules of |
1085 | the AnyEvent author himself :) |
1108 | the AnyEvent author himself :) |
1086 | |
1109 | |
1087 | AnyEvent::Util |
1110 | AnyEvent::Util (part of the AnyEvent distribution) |
1088 | Contains various utility functions that replace often-used blocking |
1111 | Contains various utility functions that replace often-used blocking |
1089 | functions such as "inet_aton" with event/callback-based versions. |
1112 | functions such as "inet_aton" with event/callback-based versions. |
1090 | |
1113 | |
1091 | AnyEvent::Socket |
1114 | AnyEvent::Socket (part of the AnyEvent distribution) |
1092 | Provides various utility functions for (internet protocol) sockets, |
1115 | Provides various utility functions for (internet protocol) sockets, |
1093 | addresses and name resolution. Also functions to create non-blocking |
1116 | addresses and name resolution. Also functions to create non-blocking |
1094 | tcp connections or tcp servers, with IPv6 and SRV record support and |
1117 | tcp connections or tcp servers, with IPv6 and SRV record support and |
1095 | more. |
1118 | more. |
1096 | |
1119 | |
1097 | AnyEvent::Handle |
1120 | AnyEvent::Handle (part of the AnyEvent distribution) |
1098 | Provide read and write buffers, manages watchers for reads and |
1121 | Provide read and write buffers, manages watchers for reads and |
1099 | writes, supports raw and formatted I/O, I/O queued and fully |
1122 | writes, supports raw and formatted I/O, I/O queued and fully |
1100 | transparent and non-blocking SSL/TLS (via AnyEvent::TLS). |
1123 | transparent and non-blocking SSL/TLS (via AnyEvent::TLS). |
1101 | |
1124 | |
1102 | AnyEvent::DNS |
1125 | AnyEvent::DNS (part of the AnyEvent distribution) |
1103 | Provides rich asynchronous DNS resolver capabilities. |
1126 | Provides rich asynchronous DNS resolver capabilities. |
1104 | |
1127 | |
1105 | AnyEvent::HTTP, AnyEvent::IRC, AnyEvent::XMPP, AnyEvent::GPSD, |
1128 | AnyEvent::HTTP, AnyEvent::IRC, AnyEvent::XMPP, AnyEvent::GPSD, |
1106 | AnyEvent::IGS, AnyEvent::FCP |
1129 | AnyEvent::IGS, AnyEvent::FCP |
1107 | Implement event-based interfaces to the protocols of the same name |
1130 | Implement event-based interfaces to the protocols of the same name |
1108 | (for the curious, IGS is the International Go Server and FCP is the |
1131 | (for the curious, IGS is the International Go Server and FCP is the |
1109 | Freenet Client Protocol). |
1132 | Freenet Client Protocol). |
1110 | |
1133 | |
1111 | AnyEvent::AIO |
1134 | AnyEvent::AIO (part of the AnyEvent distribution) |
1112 | Truly asynchronous (as opposed to non-blocking) I/O, should be in |
1135 | Truly asynchronous (as opposed to non-blocking) I/O, should be in |
1113 | the toolbox of every event programmer. AnyEvent::AIO transparently |
1136 | the toolbox of every event programmer. AnyEvent::AIO transparently |
1114 | fuses IO::AIO and AnyEvent together, giving AnyEvent access to |
1137 | fuses IO::AIO and AnyEvent together, giving AnyEvent access to |
1115 | event-based file I/O, and much more. |
1138 | event-based file I/O, and much more. |
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1139 | |
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1140 | AnyEvent::Fork, AnyEvent::Fork::RPC, AnyEvent::Fork::Pool, |
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1141 | AnyEvent::Fork::Remote |
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1142 | These let you safely fork new subprocesses, either locally or |
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1143 | remotely (e.g.v ia ssh), using some RPC protocol or not, without the |
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1144 | limitations normally imposed by fork (AnyEvent works fine for |
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1145 | example). Dynamically-resized worker pools are obviously included as |
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1146 | well. |
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1147 | |
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1148 | And they are quite tiny and fast as well - "abusing" AnyEvent::Fork |
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1149 | just to exec external programs can easily beat using "fork" and |
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1150 | "exec" (or even "system") in most programs. |
1116 | |
1151 | |
1117 | AnyEvent::Filesys::Notify |
1152 | AnyEvent::Filesys::Notify |
1118 | AnyEvent is good for non-blocking stuff, but it can't detect file or |
1153 | AnyEvent is good for non-blocking stuff, but it can't detect file or |
1119 | path changes (e.g. "watch this directory for new files", "watch this |
1154 | path changes (e.g. "watch this directory for new files", "watch this |
1120 | file for changes"). The AnyEvent::Filesys::Notify module promises to |
1155 | file for changes"). The AnyEvent::Filesys::Notify module promises to |
… | |
… | |
1122 | and some weird, without doubt broken, stuff on OS X to monitor |
1157 | and some weird, without doubt broken, stuff on OS X to monitor |
1123 | files. It can fall back to blocking scans at regular intervals |
1158 | files. It can fall back to blocking scans at regular intervals |
1124 | transparently on other platforms, so it's about as portable as it |
1159 | transparently on other platforms, so it's about as portable as it |
1125 | gets. |
1160 | gets. |
1126 | |
1161 | |
1127 | (I haven't used it myself, but I haven't heard anybody complaining |
1162 | (I haven't used it myself, but it seems the biggest problem with it |
1128 | about it yet). |
1163 | is it quite bad performance). |
1129 | |
1164 | |
1130 | AnyEvent::DBI |
1165 | AnyEvent::DBI |
1131 | Executes DBI requests asynchronously in a proxy process for you, |
1166 | Executes DBI requests asynchronously in a proxy process for you, |
1132 | notifying you in an event-based way when the operation is finished. |
1167 | notifying you in an event-based way when the operation is finished. |
1133 | |
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1134 | AnyEvent::HTTPD |
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1135 | A simple embedded webserver. |
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1136 | |
1168 | |
1137 | AnyEvent::FastPing |
1169 | AnyEvent::FastPing |
1138 | The fastest ping in the west. |
1170 | The fastest ping in the west. |
1139 | |
1171 | |
1140 | Coro |
1172 | Coro |
… | |
… | |
1336 | mentioned will be used, and preference will be given to protocols |
1368 | mentioned will be used, and preference will be given to protocols |
1337 | mentioned earlier in the list. |
1369 | mentioned earlier in the list. |
1338 | |
1370 | |
1339 | This variable can effectively be used for denial-of-service attacks |
1371 | This variable can effectively be used for denial-of-service attacks |
1340 | against local programs (e.g. when setuid), although the impact is |
1372 | against local programs (e.g. when setuid), although the impact is |
1341 | likely small, as the program has to handle conenction and other |
1373 | likely small, as the program has to handle connection and other |
1342 | failures anyways. |
1374 | failures anyways. |
1343 | |
1375 | |
1344 | Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over |
1376 | Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over |
1345 | IPv6, but support both and try to use both. |
1377 | IPv6, but support both and try to use both. |
1346 | "PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to |
1378 | "PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to |
… | |
… | |
1580 | my $txn = shift; |
1612 | my $txn = shift; |
1581 | my $data = $txn->result; |
1613 | my $data = $txn->result; |
1582 | ... |
1614 | ... |
1583 | }); |
1615 | }); |
1584 | |
1616 | |
1585 | EV::loop; |
1617 | EV::run; |
1586 | |
1618 | |
1587 | 3b. The module user could use AnyEvent, too: |
1619 | 3b. The module user could use AnyEvent, too: |
1588 | |
1620 | |
1589 | use AnyEvent; |
1621 | use AnyEvent; |
1590 | |
1622 | |
… | |
… | |
2001 | This module is part of perl since release 5.008. It will be used |
2033 | This module is part of perl since release 5.008. It will be used |
2002 | when the chosen event library does not come with a timing source of |
2034 | when the chosen event library does not come with a timing source of |
2003 | its own. The pure-perl event loop (AnyEvent::Loop) will additionally |
2035 | its own. The pure-perl event loop (AnyEvent::Loop) will additionally |
2004 | load it to try to use a monotonic clock for timing stability. |
2036 | load it to try to use a monotonic clock for timing stability. |
2005 | |
2037 | |
|
|
2038 | AnyEvent::AIO (and IO::AIO) |
|
|
2039 | The default implementation of AnyEvent::IO is to do I/O |
|
|
2040 | synchronously, stopping programs while they access the disk, which |
|
|
2041 | is fine for a lot of programs. |
|
|
2042 | |
|
|
2043 | Installing AnyEvent::AIO (and its IO::AIO dependency) makes it |
|
|
2044 | switch to a true asynchronous implementation, so event processing |
|
|
2045 | can continue even while waiting for disk I/O. |
|
|
2046 | |
2006 | FORK |
2047 | FORK |
2007 | Most event libraries are not fork-safe. The ones who are usually are |
2048 | Most event libraries are not fork-safe. The ones who are usually are |
2008 | because they rely on inefficient but fork-safe "select" or "poll" calls |
2049 | because they rely on inefficient but fork-safe "select" or "poll" calls |
2009 | - higher performance APIs such as BSD's kqueue or the dreaded Linux |
2050 | - higher performance APIs such as BSD's kqueue or the dreaded Linux |
2010 | epoll are usually badly thought-out hacks that are incompatible with |
2051 | epoll are usually badly thought-out hacks that are incompatible with |
… | |
… | |
2017 | usually happens when the first AnyEvent watcher is created, or the |
2058 | usually happens when the first AnyEvent watcher is created, or the |
2018 | library is loaded). |
2059 | library is loaded). |
2019 | |
2060 | |
2020 | If you have to fork, you must either do so *before* creating your first |
2061 | If you have to fork, you must either do so *before* creating your first |
2021 | watcher OR you must not use AnyEvent at all in the child OR you must do |
2062 | watcher OR you must not use AnyEvent at all in the child OR you must do |
2022 | something completely out of the scope of AnyEvent. |
2063 | something completely out of the scope of AnyEvent (see below). |
2023 | |
2064 | |
2024 | The problem of doing event processing in the parent *and* the child is |
2065 | The problem of doing event processing in the parent *and* the child is |
2025 | much more complicated: even for backends that *are* fork-aware or |
2066 | much more complicated: even for backends that *are* fork-aware or |
2026 | fork-safe, their behaviour is not usually what you want: fork clones all |
2067 | fork-safe, their behaviour is not usually what you want: fork clones all |
2027 | watchers, that means all timers, I/O watchers etc. are active in both |
2068 | watchers, that means all timers, I/O watchers etc. are active in both |
2028 | parent and child, which is almost never what you want. USing "exec" to |
2069 | parent and child, which is almost never what you want. Using "exec" to |
2029 | start worker children from some kind of manage rprocess is usually |
2070 | start worker children from some kind of manage prrocess is usually |
2030 | preferred, because it is much easier and cleaner, at the expense of |
2071 | preferred, because it is much easier and cleaner, at the expense of |
2031 | having to have another binary. |
2072 | having to have another binary. |
|
|
2073 | |
|
|
2074 | In addition to logical problems with fork, there are also implementation |
|
|
2075 | problems. For example, on POSIX systems, you cannot fork at all in Perl |
|
|
2076 | code if a thread (I am talking of pthreads here) was ever created in the |
|
|
2077 | process, and this is just the tip of the iceberg. In general, using fork |
|
|
2078 | from Perl is difficult, and attempting to use fork without an exec to |
|
|
2079 | implement some kind of parallel processing is almost certainly doomed. |
|
|
2080 | |
|
|
2081 | To safely fork and exec, you should use a module such as Proc::FastSpawn |
|
|
2082 | that let's you safely fork and exec new processes. |
|
|
2083 | |
|
|
2084 | If you want to do multiprocessing using processes, you can look at the |
|
|
2085 | AnyEvent::Fork module (and some related modules such as |
|
|
2086 | AnyEvent::Fork::RPC, AnyEvent::Fork::Pool and AnyEvent::Fork::Remote). |
|
|
2087 | This module allows you to safely create subprocesses without any |
|
|
2088 | limitations - you can use X11 toolkits or AnyEvent in the children |
|
|
2089 | created by AnyEvent::Fork safely and without any special precautions. |
2032 | |
2090 | |
2033 | SECURITY CONSIDERATIONS |
2091 | SECURITY CONSIDERATIONS |
2034 | AnyEvent can be forced to load any event model via |
2092 | AnyEvent can be forced to load any event model via |
2035 | $ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used |
2093 | $ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used |
2036 | to execute arbitrary code or directly gain access, it can easily be used |
2094 | to execute arbitrary code or directly gain access, it can easily be used |
… | |
… | |
2071 | |
2129 | |
2072 | Development/Debugging: AnyEvent::Strict (stricter checking), |
2130 | Development/Debugging: AnyEvent::Strict (stricter checking), |
2073 | AnyEvent::Debug (interactive shell, watcher tracing). |
2131 | AnyEvent::Debug (interactive shell, watcher tracing). |
2074 | |
2132 | |
2075 | Supported event modules: AnyEvent::Loop, EV, EV::Glib, Glib::EV, Event, |
2133 | Supported event modules: AnyEvent::Loop, EV, EV::Glib, Glib::EV, Event, |
2076 | Glib::Event, Glib, Tk, Event::Lib, Qt, POE, FLTK. |
2134 | Glib::Event, Glib, Tk, Event::Lib, Qt, POE, FLTK, Cocoa::EventLoop, UV. |
2077 | |
2135 | |
2078 | Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event, |
2136 | Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event, |
2079 | AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl, |
2137 | AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl, |
2080 | AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE, |
2138 | AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE, |
2081 | AnyEvent::Impl::IOAsync, Anyevent::Impl::Irssi, AnyEvent::Impl::FLTK. |
2139 | AnyEvent::Impl::IOAsync, AnyEvent::Impl::Irssi, AnyEvent::Impl::FLTK, |
|
|
2140 | AnyEvent::Impl::Cocoa, AnyEvent::Impl::UV. |
2082 | |
2141 | |
2083 | Non-blocking handles, pipes, stream sockets, TCP clients and servers: |
2142 | Non-blocking handles, pipes, stream sockets, TCP clients and servers: |
2084 | AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS. |
2143 | AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS. |
2085 | |
2144 | |
2086 | Asynchronous File I/O: AnyEvent::IO. |
2145 | Asynchronous File I/O: AnyEvent::IO. |