--- AnyEvent/lib/AnyEvent.pm 2008/07/09 11:53:40 1.170 +++ AnyEvent/lib/AnyEvent.pm 2009/07/24 23:45:54 1.255 @@ -1,24 +1,41 @@ =head1 NAME -AnyEvent - provide framework for multiple event loops +AnyEvent - events independent of event loop implementation -EV, Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops +EV, Event, Glib, Tk, Perl, Event::Lib, Irssi, IO::Async, Qt and POE are +various supported event loops/environments. =head1 SYNOPSIS use AnyEvent; - my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub { - ... - }); + # file descriptor readable + my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... }); - my $w = AnyEvent->timer (after => $seconds, cb => sub { + # one-shot or repeating timers + my $w = AnyEvent->timer (after => $seconds, cb => sub { ... }); + my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ... + + print AnyEvent->now; # prints current event loop time + print AnyEvent->time; # think Time::HiRes::time or simply CORE::time. + + # POSIX signal + my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... }); + + # child process exit + my $w = AnyEvent->child (pid => $pid, cb => sub { + my ($pid, $status) = @_; ... }); + # called when event loop idle (if applicable) + my $w = AnyEvent->idle (cb => sub { ... }); + my $w = AnyEvent->condvar; # stores whether a condition was flagged $w->send; # wake up current and all future recv's $w->recv; # enters "main loop" till $condvar gets ->send + # use a condvar in callback mode: + $w->cb (sub { $_[0]->recv }); =head1 INTRODUCTION/TUTORIAL @@ -26,6 +43,14 @@ in a tutorial or some gentle introduction, have a look at the L manpage. +=head1 SUPPORT + +There is a mailinglist for discussing all things AnyEvent, and an IRC +channel, too. + +See the AnyEvent project page at the B, at L, for more info. + =head1 WHY YOU SHOULD USE THIS MODULE (OR NOT) Glib, POE, IO::Async, Event... CPAN offers event models by the dozen @@ -130,6 +155,12 @@ callback when the event occurs (of course, only when the event model is in control). +Note that B +potentially in use by the event loop (such as C<$_> or C<$[>) and that B<< +callbacks must not C >>. The former is good programming practise in +Perl and the latter stems from the fact that exception handling differs +widely between event loops. + To disable the watcher you have to destroy it (e.g. by setting the variable you store it in to C or otherwise deleting all references to it). @@ -155,11 +186,17 @@ You can create an I/O watcher by calling the C<< AnyEvent->io >> method with the following mandatory key-value pairs as arguments: -C the Perl I (I file descriptor) to watch for events -(AnyEvent might or might not keep a reference to this file handle). C -must be a string that is either C or C, which creates a watcher -waiting for "r"eadable or "w"ritable events, respectively. C is the -callback to invoke each time the file handle becomes ready. +C is the Perl I (or a naked file descriptor) to watch +for events (AnyEvent might or might not keep a reference to this file +handle). Note that only file handles pointing to things for which +non-blocking operation makes sense are allowed. This includes sockets, +most character devices, pipes, fifos and so on, but not for example files +or block devices. + +C must be a string that is either C or C, which creates a +watcher waiting for "r"eadable or "w"ritable events, respectively. + +C is the callback to invoke each time the file handle becomes ready. Although the callback might get passed parameters, their value and presence is undefined and you cannot rely on them. Portable AnyEvent @@ -301,6 +338,21 @@ difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into account. +=item AnyEvent->now_update + +Some event loops (such as L or L) cache +the current time for each loop iteration (see the discussion of L<< +AnyEvent->now >>, above). + +When a callback runs for a long time (or when the process sleeps), then +this "current" time will differ substantially from the real time, which +might affect timers and time-outs. + +When this is the case, you can call this method, which will update the +event loop's idea of "current time". + +Note that updating the time I cause some events to be handled. + =back =head2 SIGNAL WATCHERS @@ -319,37 +371,71 @@ but it is guaranteed not to interrupt any other callbacks. The main advantage of using these watchers is that you can share a signal -between multiple watchers. +between multiple watchers, and AnyEvent will ensure that signals will not +interrupt your program at bad times. -This watcher might use C<%SIG>, so programs overwriting those signals -directly will likely not work correctly. +This watcher might use C<%SIG> (depending on the event loop used), +so programs overwriting those signals directly will likely not work +correctly. Example: exit on SIGINT my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 }); +=head3 Signal Races, Delays and Workarounds + +Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching +callbacks to signals in a generic way, which is a pity, as you cannot do +race-free signal handling in perl. AnyEvent will try to do it's best, but +in some cases, signals will be delayed. The maximum time a signal might +be delayed is specified in C<$AnyEvent::MAX_SIGNAL_LATENCY> (default: 10 +seconds). This variable can be changed only before the first signal +watcher is created, and should be left alone otherwise. Higher values +will cause fewer spurious wake-ups, which is better for power and CPU +saving. All these problems can be avoided by installing the optional +L module. This will not work with inherently broken +event loops such as L or L (and not with L +currently, as POE does it's own workaround with one-second latency). With +those, you just have to suffer the delays. + =head2 CHILD PROCESS WATCHERS You can also watch on a child process exit and catch its exit status. -The child process is specified by the C argument (if set to C<0>, it -watches for any child process exit). The watcher will trigger as often -as status change for the child are received. This works by installing a -signal handler for C. The callback will be called with the pid -and exit status (as returned by waitpid), so unlike other watcher types, -you I rely on child watcher callback arguments. +The child process is specified by the C argument (one some backends, +using C<0> watches for any child process exit, on others this will +croak). The watcher will be triggered only when the child process has +finished and an exit status is available, not on any trace events +(stopped/continued). + +The callback will be called with the pid and exit status (as returned by +waitpid), so unlike other watcher types, you I rely on child watcher +callback arguments. + +This watcher type works by installing a signal handler for C, +and since it cannot be shared, nothing else should use SIGCHLD or reap +random child processes (waiting for specific child processes, e.g. inside +C, is just fine). There is a slight catch to child watchers, however: you usually start them I the child process was created, and this means the process could have exited already (and no SIGCHLD will be sent anymore). -Not all event models handle this correctly (POE doesn't), but even for -event models that I handle this correctly, they usually need to be -loaded before the process exits (i.e. before you fork in the first place). - -This means you cannot create a child watcher as the very first thing in an -AnyEvent program, you I to create at least one watcher before you -C the child (alternatively, you can call C). +Not all event models handle this correctly (neither POE nor IO::Async do, +see their AnyEvent::Impl manpages for details), but even for event models +that I handle this correctly, they usually need to be loaded before +the process exits (i.e. before you fork in the first place). AnyEvent's +pure perl event loop handles all cases correctly regardless of when you +start the watcher. + +This means you cannot create a child watcher as the very first +thing in an AnyEvent program, you I to create at least one +watcher before you C the child (alternatively, you can call +C). + +As most event loops do not support waiting for child events, they will be +emulated by AnyEvent in most cases, in which the latency and race problems +mentioned in the description of signal watchers apply. Example: fork a process and wait for it @@ -369,22 +455,60 @@ # do something else, then wait for process exit $done->recv; +=head2 IDLE WATCHERS + +Sometimes there is a need to do something, but it is not so important +to do it instantly, but only when there is nothing better to do. This +"nothing better to do" is usually defined to be "no other events need +attention by the event loop". + +Idle watchers ideally get invoked when the event loop has nothing +better to do, just before it would block the process to wait for new +events. Instead of blocking, the idle watcher is invoked. + +Most event loops unfortunately do not really support idle watchers (only +EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent +will simply call the callback "from time to time". + +Example: read lines from STDIN, but only process them when the +program is otherwise idle: + + my @lines; # read data + my $idle_w; + my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { + push @lines, scalar ; + + # start an idle watcher, if not already done + $idle_w ||= AnyEvent->idle (cb => sub { + # handle only one line, when there are lines left + if (my $line = shift @lines) { + print "handled when idle: $line"; + } else { + # otherwise disable the idle watcher again + undef $idle_w; + } + }); + }); + =head2 CONDITION VARIABLES If you are familiar with some event loops you will know that all of them require you to run some blocking "loop", "run" or similar function that will actively watch for new events and call your callbacks. -AnyEvent is different, it expects somebody else to run the event loop and -will only block when necessary (usually when told by the user). +AnyEvent is slightly different: it expects somebody else to run the event +loop and will only block when necessary (usually when told by the user). The instrument to do that is called a "condition variable", so called because they represent a condition that must become true. +Now is probably a good time to look at the examples further below. + Condition variables can be created by calling the C<< AnyEvent->condvar >> method, usually without arguments. The only argument pair allowed is C, which specifies a callback to be called when the condition variable -becomes true. +becomes true, with the condition variable as the first argument (but not +the results). After creation, the condition variable is "false" until it becomes "true" by calling the C method (or calling the condition variable as if it @@ -396,7 +520,8 @@ in time where multiple outstanding events have been processed. And yet another way to call them is transactions - each condition variable can be used to represent a transaction, which finishes at some point and delivers -a result. +a result. And yet some people know them as "futures" - a promise to +compute/deliver something that you can wait for. Condition variables are very useful to signal that something has finished, for example, if you write a module that does asynchronous http requests, @@ -440,16 +565,33 @@ ); # this "blocks" (while handling events) till the callback - # calls send + # calls -recv; -Example: wait for a timer, but take advantage of the fact that -condition variables are also code references. +Example: wait for a timer, but take advantage of the fact that condition +variables are also callable directly. my $done = AnyEvent->condvar; my $delay = AnyEvent->timer (after => 5, cb => $done); $done->recv; +Example: Imagine an API that returns a condvar and doesn't support +callbacks. This is how you make a synchronous call, for example from +the main program: + + use AnyEvent::CouchDB; + + ... + + my @info = $couchdb->info->recv; + +And this is how you would just set a callback to be called whenever the +results are available: + + $couchdb->info->cb (sub { + my @info = $_[0]->recv; + }); + =head3 METHODS FOR PRODUCERS These methods should only be used by the producing side, i.e. the @@ -471,14 +613,9 @@ Any arguments passed to the C call will be returned by all future C<< ->recv >> calls. -Condition variables are overloaded so one can call them directly -(as a code reference). Calling them directly is the same as calling -C. Note, however, that many C-based event loops do not handle -overloading, so as tempting as it may be, passing a condition variable -instead of a callback does not work. Both the pure perl and EV loops -support overloading, however, as well as all functions that use perl to -invoke a callback (as in L and L for -example). +Condition variables are overloaded so one can call them directly (as if +they were a code reference). Calling them directly is the same as calling +C. =item $cv->croak ($error) @@ -486,14 +623,16 @@ C with the given error message/object/scalar. This can be used to signal any errors to the condition variable -user/consumer. +user/consumer. Doing it this way instead of calling C directly +delays the error detetcion, but has the overwhelmign advantage that it +diagnoses the error at the place where the result is expected, and not +deep in some event clalback without connection to the actual code causing +the problem. =item $cv->begin ([group callback]) =item $cv->end -These two methods are EXPERIMENTAL and MIGHT CHANGE. - These two methods can be used to combine many transactions/events into one. For example, a function that pings many hosts in parallel might want to use a condition variable for the whole process. @@ -504,7 +643,37 @@ is I to call C<< ->send >>, but that is not required. If no callback was set, C will be called without any arguments. -Let's clarify this with the ping example: +You can think of C<< $cv->send >> giving you an OR condition (one call +sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND +condition (all C calls must be C'ed before the condvar sends). + +Let's start with a simple example: you have two I/O watchers (for example, +STDOUT and STDERR for a program), and you want to wait for both streams to +close before activating a condvar: + + my $cv = AnyEvent->condvar; + + $cv->begin; # first watcher + my $w1 = AnyEvent->io (fh => $fh1, cb => sub { + defined sysread $fh1, my $buf, 4096 + or $cv->end; + }); + + $cv->begin; # second watcher + my $w2 = AnyEvent->io (fh => $fh2, cb => sub { + defined sysread $fh2, my $buf, 4096 + or $cv->end; + }); + + $cv->recv; + +This works because for every event source (EOF on file handle), there is +one call to C, so the condvar waits for all calls to C before +sending. + +The ping example mentioned above is slightly more complicated, as the +there are results to be passwd back, and the number of tasks that are +begung can potentially be zero: my $cv = AnyEvent->condvar; @@ -534,10 +703,11 @@ C is called even when C hosts are being pinged (the loop doesn't execute once). -This is the general pattern when you "fan out" into multiple subrequests: -use an outer C/C pair to set the callback and ensure C -is called at least once, and then, for each subrequest you start, call -C and for each subrequest you finish, call C. +This is the general pattern when you "fan out" into multiple (but +potentially none) subrequests: use an outer C/C pair to set +the callback and ensure C is called at least once, and then, for each +subrequest you start, call C and for each subrequest you finish, +call C. =back @@ -563,25 +733,21 @@ In list context, all parameters passed to C will be returned, in scalar context only the first one will be returned. +Note that doing a blocking wait in a callback is not supported by any +event loop, that is, recursive invocation of a blocking C<< ->recv +>> is not allowed, and the C call will C if such a +condition is detected. This condition can be slightly loosened by using +L, which allows you to do a blocking C<< ->recv >> from +any thread that doesn't run the event loop itself. + Not all event models support a blocking wait - some die in that case (programs might want to do that to stay interactive), so I, but let the +using this from a module, never require a blocking wait>. Instead, let the caller decide whether the call will block or not (for example, by coupling condition variables with some kind of request results and supporting callbacks so the caller knows that getting the result will not block, while still supporting blocking waits if the caller so desires). -Another reason I to C<< ->recv >> in a module is that you cannot -sensibly have two C<< ->recv >>'s in parallel, as that would require -multiple interpreters or coroutines/threads, none of which C -can supply. - -The L module, however, I and I supply coroutines and, in -fact, L replaces AnyEvent's condvars by coroutine-safe -versions and also integrates coroutines into AnyEvent, making blocking -C<< ->recv >> calls perfectly safe as long as they are done from another -coroutine (one that doesn't run the event loop). - You can ensure that C<< -recv >> never blocks by setting a callback and only calling C<< ->recv >> from within that callback (or at a later time). This will work even when the event loop does not support blocking @@ -592,7 +758,7 @@ Returns true when the condition is "true", i.e. whether C or C have been called. -=item $cb = $cv->cb ([new callback]) +=item $cb = $cv->cb ($cb->($cv)) This is a mutator function that returns the callback set and optionally replaces it before doing so. @@ -604,54 +770,138 @@ =back -=head1 GLOBAL VARIABLES AND FUNCTIONS +=head1 SUPPORTED EVENT LOOPS/BACKENDS -=over 4 +The available backend classes are (every class has its own manpage): -=item $AnyEvent::MODEL +=over 4 -Contains C until the first watcher is being created. Then it -contains the event model that is being used, which is the name of the -Perl class implementing the model. This class is usually one of the -C modules, but can be any other class in the case -AnyEvent has been extended at runtime (e.g. in I). +=item Backends that are autoprobed when no other event loop can be found. -The known classes so far are: +EV is the preferred backend when no other event loop seems to be in +use. If EV is not installed, then AnyEvent will try Event, and, failing +that, will fall back to its own pure-perl implementation, which is +available everywhere as it comes with AnyEvent itself. - AnyEvent::Impl::EV based on EV (an interface to libev, best choice). - AnyEvent::Impl::Event based on Event, second best choice. + AnyEvent::Impl::EV based on EV (interface to libev, best choice). + AnyEvent::Impl::Event based on Event, very stable, few glitches. AnyEvent::Impl::Perl pure-perl implementation, fast and portable. - AnyEvent::Impl::Glib based on Glib, third-best choice. - AnyEvent::Impl::Tk based on Tk, very bad choice. - AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs). + +=item Backends that are transparently being picked up when they are used. + +These will be used when they are currently loaded when the first watcher +is created, in which case it is assumed that the application is using +them. This means that AnyEvent will automatically pick the right backend +when the main program loads an event module before anything starts to +create watchers. Nothing special needs to be done by the main program. + + AnyEvent::Impl::Glib based on Glib, slow but very stable. + AnyEvent::Impl::Tk based on Tk, very broken. AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse. - AnyEvent::Impl::POE based on POE, not generic enough for full support. + AnyEvent::Impl::POE based on POE, very slow, some limitations. + AnyEvent::Impl::Irssi used when running within irssi. + +=item Backends with special needs. + +Qt requires the Qt::Application to be instantiated first, but will +otherwise be picked up automatically. As long as the main program +instantiates the application before any AnyEvent watchers are created, +everything should just work. + + AnyEvent::Impl::Qt based on Qt. + +Support for IO::Async can only be partial, as it is too broken and +architecturally limited to even support the AnyEvent API. It also +is the only event loop that needs the loop to be set explicitly, so +it can only be used by a main program knowing about AnyEvent. See +L for the gory details. + + AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed. -There is no support for WxWidgets, as WxWidgets has no support for -watching file handles. However, you can use WxWidgets through the -POE Adaptor, as POE has a Wx backend that simply polls 20 times per -second, which was considered to be too horrible to even consider for -AnyEvent. Likewise, other POE backends can be used by AnyEvent by using -it's adaptor. +=item Event loops that are indirectly supported via other backends. -AnyEvent knows about L and L and will try to use L when -autodetecting them. +Some event loops can be supported via other modules: + +There is no direct support for WxWidgets (L) or L. + +B has no support for watching file handles. However, you can +use WxWidgets through the POE adaptor, as POE has a Wx backend that simply +polls 20 times per second, which was considered to be too horrible to even +consider for AnyEvent. + +B is not supported as nobody seems to be using it, but it has a POE +backend, so it can be supported through POE. + +AnyEvent knows about both L and L, however, and will try to +load L when detecting them, in the hope that POE will pick them up, +in which case everything will be automatic. + +=back + +=head1 GLOBAL VARIABLES AND FUNCTIONS + +These are not normally required to use AnyEvent, but can be useful to +write AnyEvent extension modules. + +=over 4 + +=item $AnyEvent::MODEL + +Contains C until the first watcher is being created, before the +backend has been autodetected. + +Afterwards it contains the event model that is being used, which is the +name of the Perl class implementing the model. This class is usually one +of the C modules, but can be any other class in the +case AnyEvent has been extended at runtime (e.g. in I it +will be C). =item AnyEvent::detect Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model if necessary. You should only call this function right before you would have created an AnyEvent watcher anyway, that is, as late as possible at -runtime. +runtime, and not e.g. while initialising of your module. + +If you need to do some initialisation before AnyEvent watchers are +created, use C. =item $guard = AnyEvent::post_detect { BLOCK } Arranges for the code block to be executed as soon as the event model is autodetected (or immediately if this has already happened). +The block will be executed I the actual backend has been detected +(C<$AnyEvent::MODEL> is set), but I any watchers have been +created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do +other initialisations - see the sources of L or +L to see how this is used. + +The most common usage is to create some global watchers, without forcing +event module detection too early, for example, L creates +and installs the global L watcher in a C block to +avoid autodetecting the event module at load time. + If called in scalar or list context, then it creates and returns an object -that automatically removes the callback again when it is destroyed. See -L for a case where this is useful. +that automatically removes the callback again when it is destroyed (or +C when the hook was immediately executed). See L for +a case where this is useful. + +Example: Create a watcher for the IO::AIO module and store it in +C<$WATCHER>. Only do so after the event loop is initialised, though. + + our WATCHER; + + my $guard = AnyEvent::post_detect { + $WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb); + }; + + # the ||= is important in case post_detect immediately runs the block, + # as to not clobber the newly-created watcher. assigning both watcher and + # post_detect guard to the same variable has the advantage of users being + # able to just C if the watcher causes them grief. + + $WATCHER ||= $guard; =item @AnyEvent::post_detect @@ -660,10 +910,16 @@ the event loop has been chosen. You should check C<$AnyEvent::MODEL> before adding to this array, though: -if it contains a true value then the event loop has already been detected, -and the array will be ignored. +if it is defined then the event loop has already been detected, and the +array will be ignored. + +Best use C when your application allows +it,as it takes care of these details. -Best use C instead. +This variable is mainly useful for modules that can do something useful +when AnyEvent is used and thus want to know when it is initialised, but do +not need to even load it by default. This array provides the means to hook +into AnyEvent passively, without loading it. =back @@ -728,9 +984,9 @@ =head1 OTHER MODULES The following is a non-exhaustive list of additional modules that use -AnyEvent and can therefore be mixed easily with other AnyEvent modules -in the same program. Some of the modules come with AnyEvent, some are -available via CPAN. +AnyEvent as a client and can therefore be mixed easily with other AnyEvent +modules and other event loops in the same program. Some of the modules +come with AnyEvent, most are available via CPAN. =over 4 @@ -749,7 +1005,7 @@ Provide read and write buffers, manages watchers for reads and writes, supports raw and formatted I/O, I/O queued and fully transparent and -non-blocking SSL/TLS. +non-blocking SSL/TLS (via L. =item L @@ -787,18 +1043,19 @@ A non-blocking interface to gpsd, a daemon delivering GPS information. -=item L +=item L -A non-blocking interface to the Internet Go Server protocol (used by -L). +AnyEvent based IRC client module family (replacing the older Net::IRC3). -=item L +=item L -AnyEvent based IRC client module family. +AnyEvent based XMPP (Jabber protocol) module family (replacing the older +Net::XMPP2>. -=item L +=item L -AnyEvent based XMPP (Jabber protocol) module family. +A non-blocking interface to the Internet Go Server protocol (used by +L). =item L @@ -813,22 +1070,25 @@ Has special support for AnyEvent via L. -=item L - -The lambda approach to I/O - don't ask, look there. Can use AnyEvent. - =back =cut package AnyEvent; -no warnings; -use strict; +# basically a tuned-down version of common::sense +sub common_sense { + # no warnings + ${^WARNING_BITS} ^= ${^WARNING_BITS}; + # use strict vars subs + $^H |= 0x00000600; +} + +BEGIN { AnyEvent::common_sense } -use Carp; +use Carp (); -our $VERSION = 4.2; +our $VERSION = 4.86; our $MODEL; our $AUTOLOAD; @@ -838,12 +1098,20 @@ our $WIN32; +our $VERBOSE; + BEGIN { - my $win32 = ! ! ($^O =~ /mswin32/i); - eval "sub WIN32(){ $win32 }"; + eval "sub WIN32(){ " . (($^O =~ /mswin32/i)*1) ." }"; + eval "sub TAINT(){ " . (${^TAINT}*1) . " }"; + + delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV} + if ${^TAINT}; + + $VERBOSE = $ENV{PERL_ANYEVENT_VERBOSE}*1; + } -our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1; +our $MAX_SIGNAL_LATENCY = 10; our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred @@ -855,22 +1123,31 @@ } my @models = ( - [EV:: => AnyEvent::Impl::EV::], - [Event:: => AnyEvent::Impl::Event::], - [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::], - # everything below here will not be autoprobed + [EV:: => AnyEvent::Impl::EV:: , 1], + [Event:: => AnyEvent::Impl::Event::, 1], + [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl:: , 1], + # everything below here will not (normally) be autoprobed # as the pureperl backend should work everywhere # and is usually faster - [Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles - [Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers + [Glib:: => AnyEvent::Impl::Glib:: , 1], # becomes extremely slow with many watchers [Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy + [Irssi:: => AnyEvent::Impl::Irssi::], # Irssi has a bogus "Event" package + [Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles [Qt:: => AnyEvent::Impl::Qt::], # requires special main program [POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza [Wx:: => AnyEvent::Impl::POE::], [Prima:: => AnyEvent::Impl::POE::], + # IO::Async is just too broken - we would need workarounds for its + # byzantine signal and broken child handling, among others. + # IO::Async is rather hard to detect, as it doesn't have any + # obvious default class. +# [0, IO::Async:: => AnyEvent::Impl::IOAsync::], # requires special main program +# [0, IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # requires special main program +# [0, IO::Async::Notifier:: => AnyEvent::Impl::IOAsync::], # requires special main program ); -our %method = map +($_ => 1), qw(io timer time now signal child condvar one_event DESTROY); +our %method = map +($_ => 1), + qw(io timer time now now_update signal child idle condvar one_event DESTROY); our @post_detect; @@ -880,32 +1157,31 @@ if ($MODEL) { $cb->(); - 1 + undef } else { push @post_detect, $cb; defined wantarray - ? bless \$cb, "AnyEvent::Util::PostDetect" + ? bless \$cb, "AnyEvent::Util::postdetect" : () } } -sub AnyEvent::Util::PostDetect::DESTROY { +sub AnyEvent::Util::postdetect::DESTROY { @post_detect = grep $_ != ${$_[0]}, @post_detect; } sub detect() { unless ($MODEL) { - no strict 'refs'; local $SIG{__DIE__}; if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) { my $model = "AnyEvent::Impl::$1"; if (eval "require $model") { $MODEL = $model; - warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1; + warn "AnyEvent: loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.\n" if $VERBOSE >= 2; } else { - warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose; + warn "AnyEvent: unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@" if $VERBOSE; } } @@ -916,28 +1192,30 @@ if (${"$package\::VERSION"} > 0) { if (eval "require $model") { $MODEL = $model; - warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1; + warn "AnyEvent: autodetected model '$model', using it.\n" if $VERBOSE >= 2; last; } } } unless ($MODEL) { - # try to load a model - + # try to autoload a model for (@REGISTRY, @models) { - my ($package, $model) = @$_; - if (eval "require $package" - and ${"$package\::VERSION"} > 0 - and eval "require $model") { + my ($package, $model, $autoload) = @$_; + if ( + $autoload + and eval "require $package" + and ${"$package\::VERSION"} > 0 + and eval "require $model" + ) { $MODEL = $model; - warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1; + warn "AnyEvent: autoloaded model '$model', using it.\n" if $VERBOSE >= 2; last; } } $MODEL - or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib."; + or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.\n"; } } @@ -957,7 +1235,7 @@ (my $func = $AUTOLOAD) =~ s/.*://; $method{$func} - or croak "$func: not a valid method for AnyEvent objects"; + or Carp::croak "$func: not a valid method for AnyEvent objects"; detect unless $MODEL; @@ -968,18 +1246,14 @@ # utility function to dup a filehandle. this is used by many backends # to support binding more than one watcher per filehandle (they usually # allow only one watcher per fd, so we dup it to get a different one). -sub _dupfh($$$$) { +sub _dupfh($$;$$) { my ($poll, $fh, $r, $w) = @_; - require Fcntl; - # cygwin requires the fh mode to be matching, unix doesn't - my ($rw, $mode) = $poll eq "r" ? ($r, "<") - : $poll eq "w" ? ($w, ">") - : Carp::croak "AnyEvent->io requires poll set to either 'r' or 'w'"; + my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&"); - open my $fh2, "$mode&" . fileno $fh - or die "cannot dup() filehandle: $!"; + open my $fh2, $mode, $fh + or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,"; # we assume CLOEXEC is already set by perl in all important cases @@ -988,43 +1262,164 @@ package AnyEvent::Base; -# default implementation for now and time +# default implementations for many methods -use Time::HiRes (); +sub _time { + # probe for availability of Time::HiRes + if (eval "use Time::HiRes (); Time::HiRes::time (); 1") { + warn "AnyEvent: using Time::HiRes for sub-second timing accuracy.\n" if $VERBOSE >= 8; + *_time = \&Time::HiRes::time; + # if (eval "use POSIX (); (POSIX::times())... + } else { + warn "AnyEvent: using built-in time(), WARNING, no sub-second resolution!\n" if $VERBOSE; + *_time = sub { time }; # epic fail + } -sub time { Time::HiRes::time } -sub now { Time::HiRes::time } + &_time +} + +sub time { _time } +sub now { _time } +sub now_update { } # default implementation for ->condvar sub condvar { - bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, AnyEvent::CondVar:: + bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar" } # default implementation for ->signal -our %SIG_CB; +our $HAVE_ASYNC_INTERRUPT; +our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO); +our (%SIG_ASY, %SIG_ASY_W); +our ($SIG_COUNT, $SIG_TW); + +sub _signal_exec { + $HAVE_ASYNC_INTERRUPT + ? $SIGPIPE_R->drain + : sysread $SIGPIPE_R, my $dummy, 9; + + while (%SIG_EV) { + for (keys %SIG_EV) { + delete $SIG_EV{$_}; + $_->() for values %{ $SIG_CB{$_} || {} }; + } + } +} -sub signal { +# install a dumym wakeupw atcher to reduce signal catching latency +sub _sig_add() { + unless ($SIG_COUNT++) { + # try to align timer on a full-second boundary, if possible + my $NOW = AnyEvent->now; + + $SIG_TW = AnyEvent->timer ( + after => $MAX_SIGNAL_LATENCY - ($NOW - int $NOW), + interval => $MAX_SIGNAL_LATENCY, + cb => sub { }, # just for the PERL_ASYNC_CHECK + ); + } +} + +sub _sig_del { + undef $SIG_TW + unless --$SIG_COUNT; +} + +sub _signal { my (undef, %arg) = @_; my $signal = uc $arg{signal} or Carp::croak "required option 'signal' is missing"; $SIG_CB{$signal}{$arg{cb}} = $arg{cb}; - $SIG{$signal} ||= sub { - $_->() for values %{ $SIG_CB{$signal} || {} }; - }; - bless [$signal, $arg{cb}], "AnyEvent::Base::Signal" + if ($HAVE_ASYNC_INTERRUPT) { + # async::interrupt + + $SIG_ASY{$signal} ||= do { + my $asy = new Async::Interrupt + cb => sub { undef $SIG_EV{$signal} }, + signal => $signal, + pipe => [$SIGPIPE_R->filenos], + ; + $asy->pipe_autodrain (0); + + $asy + }; + + } else { + # pure perl + + $SIG{$signal} ||= sub { + local $!; + syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV; + undef $SIG_EV{$signal}; + }; + + # can't do signal processing without introducing races in pure perl, + # so limit the signal latency. + _sig_add; + } + + bless [$signal, $arg{cb}], "AnyEvent::Base::signal" +} + +sub signal { + # probe for availability of Async::Interrupt + if (!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT} && eval "use Async::Interrupt 0.6 (); 1") { + warn "AnyEvent: using Async::Interrupt for race-free signal handling.\n" if $VERBOSE >= 8; + + $HAVE_ASYNC_INTERRUPT = 1; + $SIGPIPE_R = new Async::Interrupt::EventPipe; + $SIG_IO = AnyEvent->io (fh => $SIGPIPE_R->fileno, poll => "r", cb => \&_signal_exec); + + } else { + warn "AnyEvent: using emulated perl signal handling with latency timer.\n" if $VERBOSE >= 8; + + require Fcntl; + + if (AnyEvent::WIN32) { + require AnyEvent::Util; + + ($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe (); + AnyEvent::Util::fh_nonblocking ($SIGPIPE_R) if $SIGPIPE_R; + AnyEvent::Util::fh_nonblocking ($SIGPIPE_W) if $SIGPIPE_W; # just in case + } else { + pipe $SIGPIPE_R, $SIGPIPE_W; + fcntl $SIGPIPE_R, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_R; + fcntl $SIGPIPE_W, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_W; # just in case + + # not strictly required, as $^F is normally 2, but let's make sure... + fcntl $SIGPIPE_R, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC; + fcntl $SIGPIPE_W, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC; + } + + $SIGPIPE_R + or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n"; + + $SIG_IO = AnyEvent->io (fh => $SIGPIPE_R, poll => "r", cb => \&_signal_exec); + } + + *signal = \&_signal; + &signal } -sub AnyEvent::Base::Signal::DESTROY { +sub AnyEvent::Base::signal::DESTROY { my ($signal, $cb) = @{$_[0]}; + _sig_del; + delete $SIG_CB{$signal}{$cb}; - delete $SIG{$signal} unless keys %{ $SIG_CB{$signal} }; + $HAVE_ASYNC_INTERRUPT + ? delete $SIG_ASY{$signal} + : # delete doesn't work with older perls - they then + # print weird messages, or just unconditionally exit + # instead of getting the default action. + undef $SIG{$signal} + unless keys %{ $SIG_CB{$signal} }; } # default implementation for ->child @@ -1032,24 +1427,21 @@ our %PID_CB; our $CHLD_W; our $CHLD_DELAY_W; -our $PID_IDLE; our $WNOHANG; -sub _child_wait { - while (0 < (my $pid = waitpid -1, $WNOHANG)) { - $_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }), - (values %{ $PID_CB{0} || {} }); - } +sub _emit_childstatus($$) { + my (undef, $rpid, $rstatus) = @_; - undef $PID_IDLE; + $_->($rpid, $rstatus) + for values %{ $PID_CB{$rpid} || {} }, + values %{ $PID_CB{0} || {} }; } sub _sigchld { - # make sure we deliver these changes "synchronous" with the event loop. - $CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub { - undef $CHLD_DELAY_W; - &_child_wait; - }); + my $pid; + + AnyEvent->_emit_childstatus ($pid, $?) + while ($pid = waitpid -1, $WNOHANG) > 0; } sub child { @@ -1060,9 +1452,10 @@ $PID_CB{$pid}{$arg{cb}} = $arg{cb}; - unless ($WNOHANG) { - $WNOHANG = eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1; - } + # WNOHANG is almost cetrainly 1 everywhere + $WNOHANG ||= $^O =~ /^(?:openbsd|netbsd|linux|freebsd|cygwin|MSWin32)$/ + ? 1 + : eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1; unless ($CHLD_W) { $CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld); @@ -1070,10 +1463,10 @@ &_sigchld; } - bless [$pid, $arg{cb}], "AnyEvent::Base::Child" + bless [$pid, $arg{cb}], "AnyEvent::Base::child" } -sub AnyEvent::Base::Child::DESTROY { +sub AnyEvent::Base::child::DESTROY { my ($pid, $cb) = @{$_[0]}; delete $PID_CB{$pid}{$cb}; @@ -1082,15 +1475,59 @@ undef $CHLD_W unless keys %PID_CB; } +# idle emulation is done by simply using a timer, regardless +# of whether the process is idle or not, and not letting +# the callback use more than 50% of the time. +sub idle { + my (undef, %arg) = @_; + + my ($cb, $w, $rcb) = $arg{cb}; + + $rcb = sub { + if ($cb) { + $w = _time; + &$cb; + $w = _time - $w; + + # never use more then 50% of the time for the idle watcher, + # within some limits + $w = 0.0001 if $w < 0.0001; + $w = 5 if $w > 5; + + $w = AnyEvent->timer (after => $w, cb => $rcb); + } else { + # clean up... + undef $w; + undef $rcb; + } + }; + + $w = AnyEvent->timer (after => 0.05, cb => $rcb); + + bless \\$cb, "AnyEvent::Base::idle" +} + +sub AnyEvent::Base::idle::DESTROY { + undef $${$_[0]}; +} + package AnyEvent::CondVar; our @ISA = AnyEvent::CondVar::Base::; package AnyEvent::CondVar::Base; -use overload - '&{}' => sub { my $self = shift; sub { $self->send (@_) } }, - fallback => 1; +#use overload +# '&{}' => sub { my $self = shift; sub { $self->send (@_) } }, +# fallback => 1; + +# save 300+ kilobytes by dirtily hardcoding overloading +${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching. +*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod." +*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{} +${'AnyEvent::CondVar::Base::()'} = 1; # fallback + +our $WAITING; sub _send { # nop @@ -1113,6 +1550,11 @@ } sub _wait { + $WAITING + and !$_[0]{_ae_sent} + and Carp::croak "AnyEvent::CondVar: recursive blocking wait detected"; + + local $WAITING = 1; AnyEvent->one_event while !$_[0]{_ae_sent}; } @@ -1142,52 +1584,32 @@ *broadcast = \&send; *wait = \&_wait; -=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE - -This is an advanced topic that you do not normally need to use AnyEvent in -a module. This section is only of use to event loop authors who want to -provide AnyEvent compatibility. - -If you need to support another event library which isn't directly -supported by AnyEvent, you can supply your own interface to it by -pushing, before the first watcher gets created, the package name of -the event module and the package name of the interface to use onto -C<@AnyEvent::REGISTRY>. You can do that before and even without loading -AnyEvent, so it is reasonably cheap. - -Example: - - push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::]; - -This tells AnyEvent to (literally) use the C -package/class when it finds the C package/module is already loaded. - -When AnyEvent is loaded and asked to find a suitable event model, it -will first check for the presence of urxvt by trying to C the -C module. - -The class should provide implementations for all watcher types. See -L (source code), L (Source code) -and so on for actual examples. Use C to -see the sources. - -If you don't provide C and C watchers than AnyEvent will -provide suitable (hopefully) replacements. - -The above example isn't fictitious, the I (a.k.a. urxvt) -terminal emulator uses the above line as-is. An interface isn't included -in AnyEvent because it doesn't make sense outside the embedded interpreter -inside I, and it is updated and maintained as part of the -I distribution. +=head1 ERROR AND EXCEPTION HANDLING -I also cheats a bit by not providing blocking access to -condition variables: code blocking while waiting for a condition will -C. This still works with most modules/usages, and blocking calls must -not be done in an interactive application, so it makes sense. +In general, AnyEvent does not do any error handling - it relies on the +caller to do that if required. The L module (see also +the C environment variable, below) provides strict +checking of all AnyEvent methods, however, which is highly useful during +development. + +As for exception handling (i.e. runtime errors and exceptions thrown while +executing a callback), this is not only highly event-loop specific, but +also not in any way wrapped by this module, as this is the job of the main +program. + +The pure perl event loop simply re-throws the exception (usually +within C<< condvar->recv >>), the L and L modules call C<< +$Event/EV::DIED->() >>, L uses C<< install_exception_handler >> and +so on. =head1 ENVIRONMENT VARIABLES -The following environment variables are used by this module: +The following environment variables are used by this module or its +submodules. + +Note that AnyEvent will remove I environment variables starting with +C from C<%ENV> when it is loaded while taint mode is +enabled. =over 4 @@ -1204,18 +1626,23 @@ When set to C<2> or higher, cause AnyEvent to report to STDERR which event model it chooses. +When set to C<8> or higher, then AnyEvent will report extra information on +which optional modules it loads and how it implements certain features. + =item C AnyEvent does not do much argument checking by default, as thorough argument checking is very costly. Setting this variable to a true value will cause AnyEvent to load C and then to thoroughly -check the arguments passed to most method calls. If it finds any problems +check the arguments passed to most method calls. If it finds any problems, it will croak. In other words, enables "strict" mode. -Unlike C it is definitely recommended ot keep it off in -production. +Unlike C (or it's modern cousin, C<< use L +>>, it is definitely recommended to keep it off in production. Keeping +C in your environment while developing programs +can be very useful, however. =item C @@ -1246,7 +1673,7 @@ This variable can effectively be used for denial-of-service attacks against local programs (e.g. when setuid), although the impact is likely -small, as the program has to handle connection errors already- +small, as the program has to handle conenction and other failures anyways. Examples: C - prefer IPv4 over IPv6, but support both and try to use both. C @@ -1269,8 +1696,75 @@ The maximum number of child processes that C will create in parallel. +=item C + +The default value for the C parameter for the default DNS +resolver - this is the maximum number of parallel DNS requests that are +sent to the DNS server. + +=item C + +The file to use instead of F (or OS-specific +configuration) in the default resolver. When set to the empty string, no +default config will be used. + +=item C, C. + +When neither C nor C was specified during +L context creation, and either of these environment +variables exist, they will be used to specify CA certificate locations +instead of a system-dependent default. + +=item C and C + +When these are set to C<1>, then the respective modules are not +loaded. Mostly good for testing AnyEvent itself. + =back +=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE + +This is an advanced topic that you do not normally need to use AnyEvent in +a module. This section is only of use to event loop authors who want to +provide AnyEvent compatibility. + +If you need to support another event library which isn't directly +supported by AnyEvent, you can supply your own interface to it by +pushing, before the first watcher gets created, the package name of +the event module and the package name of the interface to use onto +C<@AnyEvent::REGISTRY>. You can do that before and even without loading +AnyEvent, so it is reasonably cheap. + +Example: + + push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::]; + +This tells AnyEvent to (literally) use the C +package/class when it finds the C package/module is already loaded. + +When AnyEvent is loaded and asked to find a suitable event model, it +will first check for the presence of urxvt by trying to C the +C module. + +The class should provide implementations for all watcher types. See +L (source code), L (Source code) +and so on for actual examples. Use C to +see the sources. + +If you don't provide C and C watchers than AnyEvent will +provide suitable (hopefully) replacements. + +The above example isn't fictitious, the I (a.k.a. urxvt) +terminal emulator uses the above line as-is. An interface isn't included +in AnyEvent because it doesn't make sense outside the embedded interpreter +inside I, and it is updated and maintained as part of the +I distribution. + +I also cheats a bit by not providing blocking access to +condition variables: code blocking while waiting for a condition will +C. This still works with most modules/usages, and blocking calls must +not be done in an interactive application, so it makes sense. + =head1 EXAMPLE PROGRAM The following program uses an I/O watcher to read data from STDIN, a timer @@ -1473,16 +1967,18 @@ =head3 Results name watchers bytes create invoke destroy comment - EV/EV 400000 244 0.56 0.46 0.31 EV native interface - EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers - CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal - Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation - Event/Event 16000 516 31.88 31.30 0.85 Event native interface - Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers - Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour - Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers - POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event - POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select + EV/EV 400000 224 0.47 0.35 0.27 EV native interface + EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers + CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal + Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation + Event/Event 16000 517 32.20 31.80 0.81 Event native interface + Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers + IOAsync/Any 16000 989 38.10 32.77 11.13 via IO::Async::Loop::IO_Poll + IOAsync/Any 16000 990 37.59 29.50 10.61 via IO::Async::Loop::Epoll + Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour + Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers + POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event + POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select =head3 Discussion @@ -1518,6 +2014,9 @@ The C module has a relatively high setup and callback invocation cost, but overall scores in on the third place. +C performs admirably well, about on par with C, even +when using its pure perl backend. + C's memory usage is quite a bit higher, but it features a faster callback invocation and overall ends up in the same class as C. However, Glib scales extremely badly, doubling the number of @@ -1604,12 +2103,14 @@ =head3 Results - name sockets create request - EV 20000 69.01 11.16 - Perl 20000 73.32 35.87 - Event 20000 212.62 257.32 - Glib 20000 651.16 1896.30 - POE 20000 349.67 12317.24 uses POE::Loop::Event + name sockets create request + EV 20000 69.01 11.16 + Perl 20000 73.32 35.87 + IOAsync 20000 157.00 98.14 epoll + IOAsync 20000 159.31 616.06 poll + Event 20000 212.62 257.32 + Glib 20000 651.16 1896.30 + POE 20000 349.67 12317.24 uses POE::Loop::Event =head3 Discussion @@ -1622,6 +2123,9 @@ Perl surprisingly comes second. It is much faster than the C-based event loops Event and Glib. +IO::Async performs very well when using its epoll backend, and still quite +good compared to Glib when using its pure perl backend. + Event suffers from high setup time as well (look at its code and you will understand why). Callback invocation also has a high overhead compared to the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event @@ -1693,6 +2197,182 @@ =back +=head2 THE IO::Lambda BENCHMARK + +Recently I was told about the benchmark in the IO::Lambda manpage, which +could be misinterpreted to make AnyEvent look bad. In fact, the benchmark +simply compares IO::Lambda with POE, and IO::Lambda looks better (which +shouldn't come as a surprise to anybody). As such, the benchmark is +fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't +very optimal. But how would AnyEvent compare when used without the extra +baggage? To explore this, I wrote the equivalent benchmark for AnyEvent. + +The benchmark itself creates an echo-server, and then, for 500 times, +connects to the echo server, sends a line, waits for the reply, and then +creates the next connection. This is a rather bad benchmark, as it doesn't +test the efficiency of the framework or much non-blocking I/O, but it is a +benchmark nevertheless. + + name runtime + Lambda/select 0.330 sec + + optimized 0.122 sec + Lambda/AnyEvent 0.327 sec + + optimized 0.138 sec + Raw sockets/select 0.077 sec + POE/select, components 0.662 sec + POE/select, raw sockets 0.226 sec + POE/select, optimized 0.404 sec + + AnyEvent/select/nb 0.085 sec + AnyEvent/EV/nb 0.068 sec + +state machine 0.134 sec + +The benchmark is also a bit unfair (my fault): the IO::Lambda/POE +benchmarks actually make blocking connects and use 100% blocking I/O, +defeating the purpose of an event-based solution. All of the newly +written AnyEvent benchmarks use 100% non-blocking connects (using +AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS +resolver), so AnyEvent is at a disadvantage here, as non-blocking connects +generally require a lot more bookkeeping and event handling than blocking +connects (which involve a single syscall only). + +The last AnyEvent benchmark additionally uses L, which +offers similar expressive power as POE and IO::Lambda, using conventional +Perl syntax. This means that both the echo server and the client are 100% +non-blocking, further placing it at a disadvantage. + +As you can see, the AnyEvent + EV combination even beats the +hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl +backend easily beats IO::Lambda and POE. + +And even the 100% non-blocking version written using the high-level (and +slow :) L abstraction beats both POE and IO::Lambda by a +large margin, even though it does all of DNS, tcp-connect and socket I/O +in a non-blocking way. + +The two AnyEvent benchmarks programs can be found as F and +F in the AnyEvent distribution, the remaining benchmarks are +part of the IO::lambda distribution and were used without any changes. + + +=head1 SIGNALS + +AnyEvent currently installs handlers for these signals: + +=over 4 + +=item SIGCHLD + +A handler for C is installed by AnyEvent's child watcher +emulation for event loops that do not support them natively. Also, some +event loops install a similar handler. + +Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then +AnyEvent will reset it to default, to avoid losing child exit statuses. + +=item SIGPIPE + +A no-op handler is installed for C when C<$SIG{PIPE}> is C +when AnyEvent gets loaded. + +The rationale for this is that AnyEvent users usually do not really depend +on SIGPIPE delivery (which is purely an optimisation for shell use, or +badly-written programs), but C can cause spurious and rare +program exits as a lot of people do not expect C when writing to +some random socket. + +The rationale for installing a no-op handler as opposed to ignoring it is +that this way, the handler will be restored to defaults on exec. + +Feel free to install your own handler, or reset it to defaults. + +=back + +=cut + +undef $SIG{CHLD} + if $SIG{CHLD} eq 'IGNORE'; + +$SIG{PIPE} = sub { } + unless defined $SIG{PIPE}; + +=head1 RECOMMENDED/OPTIONAL MODULES + +One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and +it's built-in modules) are required to use it. + +That does not mean that AnyEvent won't take advantage of some additional +modules if they are installed. + +This section epxlains which additional modules will be used, and how they +affect AnyEvent's operetion. + +=over 4 + +=item L + +This slightly arcane module is used to implement fast signal handling: To +my knowledge, there is no way to do completely race-free and quick +signal handling in pure perl. To ensure that signals still get +delivered, AnyEvent will start an interval timer to wake up perl (and +catch the signals) with some delay (default is 10 seconds, look for +C<$AnyEvent::MAX_SIGNAL_LATENCY>). + +If this module is available, then it will be used to implement signal +catching, which means that signals will not be delayed, and the event loop +will not be interrupted regularly, which is more efficient (And good for +battery life on laptops). + +This affects not just the pure-perl event loop, but also other event loops +that have no signal handling on their own (e.g. Glib, Tk, Qt). + +Some event loops (POE, Event, Event::Lib) offer signal watchers natively, +and either employ their own workarounds (POE) or use AnyEvent's workaround +(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L +does nothing for those backends. + +=item L + +This module isn't really "optional", as it is simply one of the backend +event loops that AnyEvent can use. However, it is simply the best event +loop available in terms of features, speed and stability: It supports +the AnyEvent API optimally, implements all the watcher types in XS, does +automatic timer adjustments even when no monotonic clock is available, +can take avdantage of advanced kernel interfaces such as C and +C, and is the fastest backend I. You can even embed +L/L in it (or vice versa, see L and L). + +=item L + +The guard module, when used, will be used to implement +C. This speeds up guards considerably (and uses a +lot less memory), but otherwise doesn't affect guard operation much. It is +purely used for performance. + +=item L and L + +This module is required when you want to read or write JSON data via +L. It is also written in pure-perl, but can take +advantage of the ultra-high-speed L module when it is installed. + +In fact, L will use L by default if it is +installed. + +=item L + +Implementing TLS/SSL in Perl is certainly interesting, but not very +worthwhile: If this module is installed, then L (with +the help of L), gains the ability to do TLS/SSL. + +=item L + +This module is part of perl since release 5.008. It will be used when the +chosen event library does not come with a timing source on it's own. The +pure-perl event loop (L) will additionally use it to +try to use a monotonic clock for timing stability. + +=back + =head1 FORK @@ -1701,7 +2381,8 @@ calls. Only L is fully fork-aware. If you have to fork, you must either do so I creating your first -watcher OR you must not use AnyEvent at all in the child. +watcher OR you must not use AnyEvent at all in the child OR you must do +something completely out of the scope of AnyEvent. =head1 SECURITY CONSIDERATIONS @@ -1723,7 +2404,11 @@ Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can be used to probe what backend is used and gain other information (which is probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and -$ENV{PERL_ANYEGENT_STRICT}. +$ENV{PERL_ANYEVENT_STRICT}. + +Note that AnyEvent will remove I environment variables starting with +C from C<%ENV> when it is loaded while taint mode is +enabled. =head1 BUGS @@ -1731,7 +2416,7 @@ Perl 5.8 has numerous memleaks that sometimes hit this module and are hard to work around. If you suffer from memleaks, first upgrade to Perl 5.10 and check wether the leaks still show up. (Perl 5.10.0 has other annoying -mamleaks, such as leaking on C and C but it is usually not as +memleaks, such as leaking on C and C but it is usually not as pronounced). @@ -1745,16 +2430,18 @@ Implementations: L, L, L, L, L, L, L, -L. +L, L, L. Non-blocking file handles, sockets, TCP clients and -servers: L, L. +servers: L, L, L. Asynchronous DNS: L. -Coroutine support: L, L, L, L, +Coroutine support: L, L, L, +L, -Nontrivial usage examples: L, L, L. +Nontrivial usage examples: L, L, +L. =head1 AUTHOR