--- AnyEvent/README 2009/08/01 09:14:54 1.50 +++ AnyEvent/README 2017/07/01 15:48:51 1.78 @@ -1,18 +1,22 @@ NAME AnyEvent - the DBI of event loop programming - EV, Event, Glib, Tk, Perl, Event::Lib, Irssi, rxvt-unicode, IO::Async, - Qt and POE are various supported event loops/environments. + EV, Event, Glib, Tk, UV, Perl, Event::Lib, Irssi, rxvt-unicode, + IO::Async, Qt, FLTK and POE are various supported event + loops/environments. SYNOPSIS use AnyEvent; - # file descriptor readable + # if you prefer function calls, look at the AE manpage for + # an alternative API. + + # file handle or descriptor readable my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... }); # one-shot or repeating timers my $w = AnyEvent->timer (after => $seconds, cb => sub { ... }); - my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ... + 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. @@ -41,8 +45,10 @@ manpage. SUPPORT - There is a mailinglist for discussing all things AnyEvent, and an IRC - channel, too. + An FAQ document is available as AnyEvent::FAQ. + + There also is a mailinglist for discussing all things AnyEvent, and an + IRC channel, too. See the AnyEvent project page at the Schmorpforge Ta-Sa Software Repository, at , for more info. @@ -70,26 +76,26 @@ For modules like POE or IO::Async (which is a total misnomer as it is actually doing all I/O *synchronously*...), using them in your module is - like joining a cult: After you joined, you are dependent on them and you + like joining a cult: After you join, you are dependent on them and you cannot use anything else, as they are simply incompatible to everything that isn't them. What's worse, all the potential users of your module are *also* forced to use the same event loop you use. AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works fine. AnyEvent + Tk works fine etc. etc. but none of these work together - with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if your - module uses one of those, every user of your module has to use it, too. - But if your module uses AnyEvent, it works transparently with all event - models it supports (including stuff like IO::Async, as long as those use - one of the supported event loops. It is trivial to add new event loops - to AnyEvent, too, so it is future-proof). + with the rest: POE + EV? No go. Tk + Event? No go. Again: if your module + uses one of those, every user of your module has to use it, too. But if + your module uses AnyEvent, it works transparently with all event models + it supports (including stuff like IO::Async, as long as those use one of + the supported event loops. It is easy to add new event loops to + AnyEvent, too, so it is future-proof). In addition to being free of having to use *the one and only true event model*, AnyEvent also is free of bloat and policy: with POE or similar modules, you get an enormous amount of code and strict rules you have to - follow. AnyEvent, on the other hand, is lean and up to the point, by - only offering the functionality that is necessary, in as thin as a - wrapper as technically possible. + follow. AnyEvent, on the other hand, is lean and to the point, by only + offering the functionality that is necessary, in as thin as a wrapper as + technically possible. Of course, AnyEvent comes with a big (and fully optional!) toolbox of useful functionality, such as an asynchronous DNS resolver, 100% @@ -102,24 +108,22 @@ model, you should *not* use this module. DESCRIPTION - AnyEvent provides an identical interface to multiple event loops. This - allows module authors to utilise an event loop without forcing module - users to use the same event loop (as only a single event loop can - coexist peacefully at any one time). + AnyEvent provides a uniform interface to various event loops. This + allows module authors to use event loop functionality without forcing + module users to use a specific event loop implementation (since more + than one event loop cannot coexist peacefully). The interface itself is vaguely similar, but not identical to the Event module. During the first call of any watcher-creation method, the module tries to detect the currently loaded event loop by probing whether one of the - following modules is already loaded: EV, Event, Glib, - AnyEvent::Impl::Perl, Tk, Event::Lib, Qt, POE. The first one found is - used. If none are found, the module tries to load these modules - (excluding Tk, Event::Lib, Qt and POE as the pure perl adaptor should - always succeed) in the order given. The first one that can be - successfully loaded will be used. If, after this, still none could be - found, AnyEvent will fall back to a pure-perl event loop, which is not - very efficient, but should work everywhere. + following modules is already loaded: EV, AnyEvent::Loop, Event, Glib, + Tk, Event::Lib, Qt, POE. The first one found is used. If none are + detected, the module tries to load the first four modules in the order + given; but note that if EV is not available, the pure-perl + AnyEvent::Loop should always work, so the other two are not normally + tried. Because AnyEvent first checks for modules that are already loaded, loading an event model explicitly before first using AnyEvent will @@ -131,12 +135,13 @@ # .. AnyEvent will likely default to Tk The *likely* means that, if any module loads another event model and - starts using it, all bets are off. Maybe you should tell their authors - to use AnyEvent so their modules work together with others seamlessly... - - The pure-perl implementation of AnyEvent is called - "AnyEvent::Impl::Perl". Like other event modules you can load it - explicitly and enjoy the high availability of that event loop :) + starts using it, all bets are off - this case should be very rare + though, as very few modules hardcode event loops without announcing this + very loudly. + + The pure-perl implementation of AnyEvent is called "AnyEvent::Loop". + Like other event modules you can load it explicitly and enjoy the high + availability of that event loop :) WATCHERS AnyEvent has the central concept of a *watcher*, which is an object that @@ -150,11 +155,11 @@ Note that callbacks must not permanently change global variables potentially in use by the event loop (such as $_ or $[) and that - callbacks must not "die". The former is good programming practise in + callbacks must not "die". The former is good programming practice 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 + To disable a watcher you have to destroy it (e.g. by setting the variable you store it in to "undef" or otherwise deleting all references to it). @@ -163,7 +168,7 @@ Many watchers either are used with "recursion" (repeating timers for example), or need to refer to their watcher object in other ways. - An any way to achieve that is this pattern: + One way to achieve that is this pattern: my $w; $w = AnyEvent->type (arg => value ..., cb => sub { # you can use $w here, for example to undef it @@ -204,7 +209,7 @@ it. You must not close a file handle as long as any watcher is active on the underlying file descriptor. - Some event loops issue spurious readyness notifications, so you should + Some event loops issue spurious readiness notifications, so you should always use non-blocking calls when reading/writing from/to your file handles. @@ -237,14 +242,14 @@ presence is undefined and you cannot rely on them. Portable AnyEvent callbacks cannot use arguments passed to time watcher callbacks. - The callback will normally be invoked once only. If you specify another + The callback will normally be invoked only once. If you specify another parameter, "interval", as a strictly positive number (> 0), then the callback will be invoked regularly at that interval (in fractional seconds) after the first invocation. If "interval" is specified with a - false value, then it is treated as if it were missing. + false value, then it is treated as if it were not specified at all. The callback will be rescheduled before invoking the callback, but no - attempt is done to avoid timer drift in most backends, so the interval + attempt is made to avoid timer drift in most backends, so the interval is only approximate. Example: fire an event after 7.7 seconds. @@ -260,7 +265,7 @@ my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub { warn "timeout\n"; - }; + }); TIMING ISSUES There are two ways to handle timers: based on real time (relative, "fire @@ -271,13 +276,13 @@ they use absolute time internally. This makes a difference when your clock "jumps", for example, when ntp decides to set your clock backwards from the wrong date of 2014-01-01 to 2008-01-01, a watcher that is - supposed to fire "after" a second might actually take six years to + supposed to fire "after a second" might actually take six years to finally fire. AnyEvent cannot compensate for this. The only event loop that is - conscious about these issues is EV, which offers both relative - (ev_timer, based on true relative time) and absolute (ev_periodic, based - on wallclock time) timers. + conscious of these issues is EV, which offers both relative (ev_timer, + based on true relative time) and absolute (ev_periodic, based on + wallclock time) timers. AnyEvent always prefers relative timers, if available, matching the AnyEvent API. @@ -306,15 +311,15 @@ This function is also often faster then "AnyEvent->time", and thus the preferred method if you want some timestamp (for example, - AnyEvent::Handle uses this to update it's activity timeouts). + AnyEvent::Handle uses this to update its activity timeouts). The rest of this section is only of relevance if you try to be very - exact with your timing, you can skip it without bad conscience. + exact with your timing; you can skip it without a bad conscience. For a practical example of when these times differ, consider Event::Lib and EV and the following set-up: - The event loop is running and has just invoked one of your callback + The event loop is running and has just invoked one of your callbacks at time=500 (assume no other callbacks delay processing). In your callback, you wait a second by executing "sleep 1" (blocking the process for a second) and then (at time=501) you create a relative @@ -345,9 +350,9 @@ account. AnyEvent->now_update - Some event loops (such as EV or AnyEvent::Impl::Perl) cache the - current time for each loop iteration (see the discussion of - AnyEvent->now, above). + Some event loops (such as EV or AnyEvent::Loop) cache the current + time for each loop iteration (see the discussion of 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 @@ -356,6 +361,14 @@ When this is the case, you can call this method, which will update the event loop's idea of "current time". + A typical example would be a script in a web server (e.g. + "mod_perl") - when mod_perl executes the script, then the event loop + will have the wrong idea about the "current time" (being potentially + far in the past, when the script ran the last time). In that case + you should arrange a call to "AnyEvent->now_update" each time the + web server process wakes up again (e.g. at the start of your script, + or in a handler). + Note that updating the time *might* cause some events to be handled. SIGNAL WATCHERS @@ -386,31 +399,42 @@ my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 }); + Restart Behaviour + While restart behaviour is up to the event loop implementation, most + will not restart syscalls (that includes Async::Interrupt and AnyEvent's + pure perl implementation). + + Safe/Unsafe Signals + Perl signals can be either "safe" (synchronous to opcode handling) or + "unsafe" (asynchronous) - the former might delay signal delivery + indefinitely, the latter might corrupt your memory. + + AnyEvent signal handlers are, in addition, synchronous to the event + loop, i.e. they will not interrupt your running perl program but will + only be called as part of the normal event handling (just like timer, + I/O etc. callbacks, too). + 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, requiring C libraries for this. - AnyEvent will try to do it's best, which means in some cases, signals - will be delayed. The maximum time a signal might be delayed is specified - in $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. This variable determines how often - AnyEvent polls for signals (in case a wake-up was missed). Higher values - will cause fewer spurious wake-ups, which is better for power and CPU - saving. + AnyEvent will try to do its best, which means in some cases, signals + will be delayed. The maximum time a signal might be delayed is 10 + seconds by default, but can be overriden via + $ENV{PERL_ANYEVENT_MAX_SIGNAL_LATENCY} or $AnyEvent::MAX_SIGNAL_LATENCY + - see the "ENVIRONMENT VARIABLES" section for details. All these problems can be avoided by installing the optional Async::Interrupt module, which works with most event loops. It will not work with inherently broken event loops such as Event or Event::Lib (and - not with POE currently, as POE does it's own workaround with one-second - latency). For those, you just have to suffer the delays. + not with POE currently). For those, you just have to suffer the delays. CHILD PROCESS WATCHERS $w = AnyEvent->child (pid => , cb => ); - You can also watch on a child process exit and catch its exit status. + You can also watch for a child process exit and catch its exit status. - The child process is specified by the "pid" argument (one some backends, + The child process is specified by the "pid" argument (on some backends, using 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 @@ -441,13 +465,17 @@ you "fork" the child (alternatively, you can call "AnyEvent::detect"). 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. + be emulated by AnyEvent in most cases, in which case the latency and + race problems mentioned in the description of signal watchers apply. Example: fork a process and wait for it my $done = AnyEvent->condvar; + # this forks and immediately calls exit in the child. this + # normally has all sorts of bad consequences for your parent, + # so take this as an example only. always fork and exec, + # or call POSIX::_exit, in real code. my $pid = fork or exit 5; my $w = AnyEvent->child ( @@ -465,18 +493,21 @@ IDLE WATCHERS $w = AnyEvent->idle (cb => ); - 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". + This will repeatedly invoke the callback after the process becomes idle, + until either the watcher is destroyed or new events have been detected. + + Idle watchers are useful when there is a need to do something, but it is + not so important (or wise) to do it instantly. The callback will be + invoked only when there is "nothing better to do", which is usually + defined as "all outstanding events have been handled and no new events + have been detected". That means that idle watchers ideally get invoked + when the event loop has just polled for new events but none have been + detected. Instead of blocking to wait for more events, the idle watchers + will be invoked. + + Unfortunately, most event loops 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: @@ -512,8 +543,8 @@ 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. + The tool 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. @@ -528,13 +559,27 @@ as if it were a callback, read about the caveats in the description for the "->send" method). - Condition variables are similar to callbacks, except that you can - optionally wait for them. They can also be called merge points - points - 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. And yet some people know them as "futures" - a - promise to compute/deliver something that you can wait for. + Since condition variables are the most complex part of the AnyEvent API, + here are some different mental models of what they are - pick the ones + you can connect to: + + * Condition variables are like callbacks - you can call them (and pass + them instead of callbacks). Unlike callbacks however, you can also + wait for them to be called. + + * Condition variables are signals - one side can emit or send them, + the other side can wait for them, or install a handler that is + called when the signal fires. + + * Condition variables are like "Merge Points" - points in your program + where you merge multiple independent results/control flows into one. + + * Condition variables represent a transaction - functions that start + some kind of transaction can return them, leaving the caller the + choice between waiting in a blocking fashion, or setting a callback. + + * Condition variables represent future values, or promises to deliver + some result, long before the result is available. Condition variables are very useful to signal that something has finished, for example, if you write a module that does asynchronous http @@ -557,7 +602,7 @@ used by AnyEvent itself are all named "_ae_XXX" to make subclassing easy (it is often useful to build your own transaction class on top of AnyEvent). To subclass, use "AnyEvent::CondVar" as base class and call - it's "new" method in your own "new" method. + its "new" method in your own "new" method. There are two "sides" to a condition variable - the "producer side" which eventually calls "-> send", and the "consumer side", which waits @@ -565,21 +610,21 @@ Example: wait for a timer. - # wait till the result is ready - my $result_ready = AnyEvent->condvar; + # condition: "wait till the timer is fired" + my $timer_fired = AnyEvent->condvar; - # do something such as adding a timer - # or socket watcher the calls $result_ready->send - # when the "result" is ready. + # create the timer - we could wait for, say + # a handle becomign ready, or even an + # AnyEvent::HTTP request to finish, but # in this case, we simply use a timer: my $w = AnyEvent->timer ( after => 1, - cb => sub { $result_ready->send }, + cb => sub { $timer_fired->send }, ); # this "blocks" (while handling events) till the callback - # calls -recv; + # calls ->send + $timer_fired->recv; Example: wait for a timer, but take advantage of the fact that condition variables are also callable directly. @@ -627,14 +672,14 @@ calling "send". $cv->croak ($error) - Similar to send, but causes all call's to "->recv" to invoke + Similar to send, but causes all calls to "->recv" to invoke "Carp::croak" with the given error message/object/scalar. This can be used to signal any errors to the condition variable user/consumer. Doing it this way instead of calling "croak" directly - delays the error detetcion, but has the overwhelmign advantage that + delays the error detection, but has the overwhelming 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 + and not deep in some event callback with no connection to the actual code causing the problem. $cv->begin ([group callback]) @@ -645,9 +690,10 @@ Every call to "->begin" will increment a counter, and every call to "->end" will decrement it. If the counter reaches 0 in "->end", the - (last) callback passed to "begin" will be executed. That callback is - *supposed* to call "->send", but that is not required. If no - callback was set, "send" will be called without any arguments. + (last) callback passed to "begin" will be executed, passing the + condvar as first argument. That callback is *supposed* to call + "->send", but that is not required. If no group callback was set, + "send" will be called without any arguments. You can think of "$cv->send" giving you an OR condition (one call sends), while "$cv->begin" and "$cv->end" giving you an AND @@ -679,13 +725,13 @@ "end" 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: + the there are results to be passed back, and the number of tasks + that are begun can potentially be zero: my $cv = AnyEvent->condvar; my %result; - $cv->begin (sub { $cv->send (\%result) }); + $cv->begin (sub { shift->send (\%result) }); for my $host (@list_of_hosts) { $cv->begin; @@ -697,6 +743,10 @@ $cv->end; + ... + + my $results = $cv->recv; + This code fragment supposedly pings a number of hosts and calls "send" after results for all then have have been gathered - in any order. To achieve this, the code issues a call to "begin" when it @@ -711,7 +761,7 @@ (the loop doesn't execute once). This is the general pattern when you "fan out" into multiple (but - potentially none) subrequests: use an outer "begin"/"end" pair to + potentially zero) subrequests: use an outer "begin"/"end" pair to set the callback and ensure "end" is called at least once, and then, for each subrequest you start, call "begin" and for each subrequest you finish, call "end". @@ -722,7 +772,7 @@ $cv->recv Wait (blocking if necessary) until the "->send" or "->croak" methods - have been called on c<$cv>, while servicing other watchers normally. + have been called on $cv, while servicing other watchers normally. You can only wait once on a condition - additional calls are valid but will return immediately. @@ -735,10 +785,15 @@ Note that doing a blocking wait in a callback is not supported by any event loop, that is, recursive invocation of a blocking "->recv" - is not allowed, and the "recv" call will "croak" if such a condition - is detected. This condition can be slightly loosened by using - Coro::AnyEvent, which allows you to do a blocking "->recv" from any - thread that doesn't run the event loop itself. + is not allowed and the "recv" call will "croak" if such a condition + is detected. This requirement can be dropped by relying on + Coro::AnyEvent , which allows you to do a blocking "->recv" from any + thread that doesn't run the event loop itself. Coro::AnyEvent is + loaded automatically when Coro is used with AnyEvent, so code does + not need to do anything special to take advantage of that: any code + that would normally block your program because it calls "recv", be + executed in an "async" thread instead without blocking other + threads. Not all event models support a blocking wait - some die in that case (programs might want to do that to stay interactive), so *if you are @@ -749,7 +804,7 @@ the result will not block, while still supporting blocking waits if the caller so desires). - You can ensure that "-recv" never blocks by setting a callback and + You can ensure that "->recv" never blocks by setting a callback and only calling "->recv" from within that callback (or at a later time). This will work even when the event loop does not support blocking waits otherwise. @@ -759,41 +814,49 @@ "croak" have been called. $cb = $cv->cb ($cb->($cv)) - This is a mutator function that returns the callback set and - optionally replaces it before doing so. + This is a mutator function that returns the callback set (or "undef" + if not) and optionally replaces it before doing so. - The callback will be called when the condition becomes (or already - was) "true", i.e. when "send" or "croak" are called (or were - called), with the only argument being the condition variable itself. - Calling "recv" inside the callback or at any later time is - guaranteed not to block. + The callback will be called when the condition becomes "true", i.e. + when "send" or "croak" are called, with the only argument being the + condition variable itself. If the condition is already true, the + callback is called immediately when it is set. Calling "recv" inside + the callback or at any later time is guaranteed not to block. + + Additionally, when the callback is invoked, it is also removed from + the condvar (reset to "undef"), so the condvar does not keep a + reference to the callback after invocation. SUPPORTED EVENT LOOPS/BACKENDS The available backend classes are (every class has its own manpage): Backends that are autoprobed when no other event loop can be found. 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. + use. If EV is not installed, then AnyEvent 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 (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::Perl pure-perl AnyEvent::Loop, fast and portable. 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 + These will be used if they are already 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::Event based on Event, very stable, few glitches. AnyEvent::Impl::Glib based on Glib, slow but very stable. AnyEvent::Impl::Tk based on Tk, very broken. + AnyEvent::Impl::UV based on UV, innovated square wheels. AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse. AnyEvent::Impl::POE based on POE, very slow, some limitations. AnyEvent::Impl::Irssi used when running within irssi. + AnyEvent::Impl::IOAsync based on IO::Async. + AnyEvent::Impl::Cocoa based on Cocoa::EventLoop. + AnyEvent::Impl::FLTK based on FLTK (fltk 2 binding). Backends with special needs. Qt requires the Qt::Application to be instantiated first, but will @@ -803,14 +866,6 @@ 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 - AnyEvent::Impl::Async for the gory details. - - AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed. - Event loops that are indirectly supported via other backends. Some event loops can be supported via other modules: @@ -838,7 +893,7 @@ 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 "AnyEvent::Impl:xxx" modules, but can be any + usually one of the "AnyEvent::Impl::xxx" modules, but can be any other class in the case AnyEvent has been extended at runtime (e.g. in *rxvt-unicode* it will be "urxvt::anyevent"). @@ -846,23 +901,27 @@ Returns $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, and not e.g. while initialising of your module. + possible at runtime, and not e.g. during initialisation of your + module. + + The effect of calling this function is as if a watcher had been + created (specifically, actions that happen "when the first watcher + is created" happen when calling detetc as well). If you need to do some initialisation before AnyEvent watchers are created, use "post_detect". $guard = AnyEvent::post_detect { BLOCK } Arranges for the code block to be executed as soon as the event - model is autodetected (or immediately if this has already happened). + model is autodetected (or immediately if that has already happened). The block will be executed *after* the actual backend has been - detected ($AnyEvent::MODEL is set), but *before* any watchers have - been created, so it is possible to e.g. patch @AnyEvent::ISA or do - other initialisations - see the sources of AnyEvent::Strict or - AnyEvent::AIO to see how this is used. + detected ($AnyEvent::MODEL is set), so it is possible to do some + initialisation only when AnyEvent is actually initialised - see the + sources of AnyEvent::AIO 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, AnyEvent::AIO + forcing event module detection too early. For example, AnyEvent::AIO creates and installs the global IO::AIO watcher in a "post_detect" block to avoid autodetecting the event module at load time. @@ -872,7 +931,7 @@ AnyEvent::AIO for a case where this is useful. Example: Create a watcher for the IO::AIO module and store it in - $WATCHER. Only do so after the event loop is initialised, though. + $WATCHER, but do so only do so after the event loop is initialised. our WATCHER; @@ -888,22 +947,98 @@ $WATCHER ||= $guard; @AnyEvent::post_detect - If there are any code references in this array (you can "push" to it - before or after loading AnyEvent), then they will called directly - after the event loop has been chosen. + This is a lower level interface then "AnyEvent::post_detect" (the + function). 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. + + Here is how it works: If there are any code references in this array + (you can "push" to it before or after loading AnyEvent), then they + will be called directly after the event loop has been chosen. You should check $AnyEvent::MODEL before adding to this array, though: if it is defined then the event loop has already been detected, and the array will be ignored. Best use "AnyEvent::post_detect { BLOCK }" when your application - allows it,as it takes care of these details. + allows it, as it takes care of these details. - 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. + Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used + together, you could put this into Coro (this is the actual code used + by Coro to accomplish this): + + if (defined $AnyEvent::MODEL) { + # AnyEvent already initialised, so load Coro::AnyEvent + require Coro::AnyEvent; + } else { + # AnyEvent not yet initialised, so make sure to load Coro::AnyEvent + # as soon as it is + push @AnyEvent::post_detect, sub { require Coro::AnyEvent }; + } + + AnyEvent::postpone { BLOCK } + Arranges for the block to be executed as soon as possible, but not + before the call itself returns. In practise, the block will be + executed just before the event loop polls for new events, or shortly + afterwards. + + This function never returns anything (to make the "return postpone { + ... }" idiom more useful. + + To understand the usefulness of this function, consider a function + that asynchronously does something for you and returns some + transaction object or guard to let you cancel the operation. For + example, "AnyEvent::Socket::tcp_connect": + + # start a connection attempt unless one is active + $self->{connect_guard} ||= AnyEvent::Socket::tcp_connect "www.example.net", 80, sub { + delete $self->{connect_guard}; + ... + }; + + Imagine that this function could instantly call the callback, for + example, because it detects an obvious error such as a negative port + number. Invoking the callback before the function returns causes + problems however: the callback will be called and will try to delete + the guard object. But since the function hasn't returned yet, there + is nothing to delete. When the function eventually returns it will + assign the guard object to "$self->{connect_guard}", where it will + likely never be deleted, so the program thinks it is still trying to + connect. + + This is where "AnyEvent::postpone" should be used. Instead of + calling the callback directly on error: + + $cb->(undef), return # signal error to callback, BAD! + if $some_error_condition; + + It should use "postpone": + + AnyEvent::postpone { $cb->(undef) }, return # signal error to callback, later + if $some_error_condition; + + AnyEvent::log $level, $msg[, @args] + Log the given $msg at the given $level. + + If AnyEvent::Log is not loaded then this function makes a simple + test to see whether the message will be logged. If the test succeeds + it will load AnyEvent::Log and call "AnyEvent::Log::log" - + consequently, look at the AnyEvent::Log documentation for details. + + If the test fails it will simply return. Right now this happens when + a numerical loglevel is used and it is larger than the level + specified via $ENV{PERL_ANYEVENT_VERBOSE}. + + If you want to sprinkle loads of logging calls around your code, + consider creating a logger callback with the "AnyEvent::Log::logger" + function, which can reduce typing, codesize and can reduce the + logging overhead enourmously. + + AnyEvent::fh_block $filehandle + AnyEvent::fh_unblock $filehandle + Sets blocking or non-blocking behaviour for the given filehandle. WHAT TO DO IN A MODULE As a module author, you should "use AnyEvent" and call AnyEvent methods @@ -921,17 +1056,18 @@ It is fine, however, to call "->recv" when the user of your module requests it (i.e. if you create a http request object ad have a method - called "results" that returns the results, it should call "->recv" - freely, as the user of your module knows what she is doing. always). + called "results" that returns the results, it may call "->recv" freely, + as the user of your module knows what she is doing. Always). WHAT TO DO IN THE MAIN PROGRAM There will always be a single main program - the only place that should dictate which event model to use. - If it doesn't care, it can just "use AnyEvent" and use it itself, or not - do anything special (it does not need to be event-based) and let - AnyEvent decide which implementation to chose if some module relies on - it. + If the program is not event-based, it need not do anything special, even + when it depends on a module that uses an AnyEvent. If the program itself + uses AnyEvent, but does not care which event loop is used, all it needs + to do is "use AnyEvent". In either case, AnyEvent will choose the best + available loop implementation. If the main program relies on a specific event model - for example, in Gtk2 programs you have to rely on the Glib module - you should load the @@ -939,12 +1075,12 @@ generally speaking, you should load it as early as possible. The reason is that modules might create watchers when they are loaded, and AnyEvent will decide on the event model to use as soon as it creates watchers, - and it might chose the wrong one unless you load the correct one + and it might choose the wrong one unless you load the correct one yourself. You can chose to use a pure-perl implementation by loading the - "AnyEvent::Impl::Perl" module, which gives you similar behaviour - everywhere, but letting AnyEvent chose the model is generally better. + "AnyEvent::Loop" module, which gives you similar behaviour everywhere, + but letting AnyEvent chose the model is generally better. MAINLOOP EMULATION Sometimes (often for short test scripts, or even standalone programs who @@ -966,74 +1102,95 @@ The following is a non-exhaustive list of additional modules that use 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. + modules come as part of AnyEvent, the others are available via CPAN (see + for a longer + non-exhaustive list), and the list is heavily biased towards modules of + the AnyEvent author himself :) + + AnyEvent::Util (part of the AnyEvent distribution) + Contains various utility functions that replace often-used blocking + functions such as "inet_aton" with event/callback-based versions. - AnyEvent::Util - Contains various utility functions that replace often-used but - blocking functions such as "inet_aton" by event-/callback-based - versions. - - AnyEvent::Socket + AnyEvent::Socket (part of the AnyEvent distribution) Provides various utility functions for (internet protocol) sockets, addresses and name resolution. Also functions to create non-blocking tcp connections or tcp servers, with IPv6 and SRV record support and more. - AnyEvent::Handle + AnyEvent::Handle (part of the AnyEvent distribution) 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 (via AnyEvent::TLS. + transparent and non-blocking SSL/TLS (via AnyEvent::TLS). - AnyEvent::DNS + AnyEvent::DNS (part of the AnyEvent distribution) Provides rich asynchronous DNS resolver capabilities. - AnyEvent::HTTP - A simple-to-use HTTP library that is capable of making a lot of - concurrent HTTP requests. + AnyEvent::HTTP, AnyEvent::IRC, AnyEvent::XMPP, AnyEvent::GPSD, + AnyEvent::IGS, AnyEvent::FCP + Implement event-based interfaces to the protocols of the same name + (for the curious, IGS is the International Go Server and FCP is the + Freenet Client Protocol). + + AnyEvent::AIO (part of the AnyEvent distribution) + Truly asynchronous (as opposed to non-blocking) I/O, should be in + the toolbox of every event programmer. AnyEvent::AIO transparently + fuses IO::AIO and AnyEvent together, giving AnyEvent access to + event-based file I/O, and much more. + + AnyEvent::Fork, AnyEvent::Fork::RPC, AnyEvent::Fork::Pool, + AnyEvent::Fork::Remote + These let you safely fork new subprocesses, either locally or + remotely (e.g.v ia ssh), using some RPC protocol or not, without the + limitations normally imposed by fork (AnyEvent works fine for + example). Dynamically-resized worker pools are obviously included as + well. + + And they are quite tiny and fast as well - "abusing" AnyEvent::Fork + just to exec external programs can easily beat using "fork" and + "exec" (or even "system") in most programs. + + AnyEvent::Filesys::Notify + AnyEvent is good for non-blocking stuff, but it can't detect file or + path changes (e.g. "watch this directory for new files", "watch this + file for changes"). The AnyEvent::Filesys::Notify module promises to + do just that in a portbale fashion, supporting inotify on GNU/Linux + and some weird, without doubt broken, stuff on OS X to monitor + files. It can fall back to blocking scans at regular intervals + transparently on other platforms, so it's about as portable as it + gets. + + (I haven't used it myself, but it seems the biggest problem with it + is it quite bad performance). - AnyEvent::HTTPD - Provides a simple web application server framework. + AnyEvent::DBI + Executes DBI requests asynchronously in a proxy process for you, + notifying you in an event-based way when the operation is finished. AnyEvent::FastPing The fastest ping in the west. - AnyEvent::DBI - Executes DBI requests asynchronously in a proxy process. + Coro + Has special support for AnyEvent via Coro::AnyEvent, which allows + you to simply invert the flow control - don't call us, we will call + you: + + async { + Coro::AnyEvent::sleep 5; # creates a 5s timer and waits for it + print "5 seconds later!\n"; + + Coro::AnyEvent::readable *STDIN; # uses an I/O watcher + my $line = ; # works for ttys - AnyEvent::AIO - Truly asynchronous I/O, should be in the toolbox of every event - programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent - together. - - AnyEvent::BDB - Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently - fuses BDB and AnyEvent together. - - AnyEvent::GPSD - A non-blocking interface to gpsd, a daemon delivering GPS - information. - - AnyEvent::IRC - AnyEvent based IRC client module family (replacing the older - Net::IRC3). - - AnyEvent::XMPP - AnyEvent based XMPP (Jabber protocol) module family (replacing the - older Net::XMPP2>. - - AnyEvent::IGS - A non-blocking interface to the Internet Go Server protocol (used by - App::IGS). - - Net::FCP - AnyEvent-based implementation of the Freenet Client Protocol, - birthplace of AnyEvent. + AnyEvent::HTTP::http_get "url", Coro::rouse_cb; + my ($body, $hdr) = Coro::rouse_wait; + }; - Event::ExecFlow - High level API for event-based execution flow control. +SIMPLIFIED AE API + Starting with version 5.0, AnyEvent officially supports a second, much + simpler, API that is designed to reduce the calling, typing and memory + overhead by using function call syntax and a fixed number of parameters. - Coro - Has special support for AnyEvent via Coro::AnyEvent. + See the AE manpage for details. ERROR AND EXCEPTION HANDLING In general, AnyEvent does not do any error handling - it relies on the @@ -1052,28 +1209,86 @@ Glib uses "install_exception_handler" and so on. ENVIRONMENT VARIABLES - The following environment variables are used by this module or its - submodules. + AnyEvent supports a number of environment variables that tune the + runtime behaviour. They are usually evaluated when AnyEvent is loaded, + initialised, or a submodule that uses them is loaded. Many of them also + cause AnyEvent to load additional modules - for example, + "PERL_ANYEVENT_DEBUG_WRAP" causes the AnyEvent::Debug module to be + loaded. - Note that AnyEvent will remove *all* environment variables starting with - "PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is - enabled. + All the environment variables documented here start with + "PERL_ANYEVENT_", which is what AnyEvent considers its own namespace. + Other modules are encouraged (but by no means required) to use + "PERL_ANYEVENT_SUBMODULE" if they have registered the + AnyEvent::Submodule namespace on CPAN, for any submodule. For example, + AnyEvent::HTTP could be expected to use "PERL_ANYEVENT_HTTP_PROXY" (it + should not access env variables starting with "AE_", see below). + + All variables can also be set via the "AE_" prefix, that is, instead of + setting "PERL_ANYEVENT_VERBOSE" you can also set "AE_VERBOSE". In case + there is a clash btween anyevent and another program that uses + "AE_something" you can set the corresponding "PERL_ANYEVENT_something" + variable to the empty string, as those variables take precedence. + + When AnyEvent is first loaded, it copies all "AE_xxx" env variables to + their "PERL_ANYEVENT_xxx" counterpart unless that variable already + exists. If taint mode is on, then AnyEvent will remove *all* environment + variables starting with "PERL_ANYEVENT_" from %ENV (or replace them with + "undef" or the empty string, if the corresaponding "AE_" variable is + set). + + The exact algorithm is currently: + + 1. if taint mode enabled, delete all PERL_ANYEVENT_xyz variables from %ENV + 2. copy over AE_xyz to PERL_ANYEVENT_xyz unless the latter alraedy exists + 3. if taint mode enabled, set all PERL_ANYEVENT_xyz variables to undef. + + This ensures that child processes will not see the "AE_" variables. + + The following environment variables are currently known to AnyEvent: "PERL_ANYEVENT_VERBOSE" - By default, AnyEvent will be completely silent except in fatal - conditions. You can set this environment variable to make AnyEvent - more talkative. + By default, AnyEvent will log messages with loglevel 4 ("error") or + higher (see AnyEvent::Log). You can set this environment variable to + a numerical loglevel to make AnyEvent more (or less) talkative. + + If you want to do more than just set the global logging level you + should have a look at "PERL_ANYEVENT_LOG", which allows much more + complex specifications. + + When set to 0 ("off"), then no messages whatsoever will be logged + with everything else at defaults. - When set to 1 or higher, causes AnyEvent to warn about unexpected + When set to 5 or higher ("warn"), AnyEvent warns about unexpected conditions, such as not being able to load the event model specified - by "PERL_ANYEVENT_MODEL". + by "PERL_ANYEVENT_MODEL", or a guard callback throwing an exception + - this is the minimum recommended level for use during development. - When set to 2 or higher, cause AnyEvent to report to STDERR which - event model it chooses. + When set to 7 or higher (info), AnyEvent reports which event model + it chooses. - When set to 8 or higher, then AnyEvent will report extra information - on which optional modules it loads and how it implements certain - features. + When set to 8 or higher (debug), then AnyEvent will report extra + information on which optional modules it loads and how it implements + certain features. + + "PERL_ANYEVENT_LOG" + Accepts rather complex logging specifications. For example, you + could log all "debug" messages of some module to stderr, warnings + and above to stderr, and errors and above to syslog, with: + + PERL_ANYEVENT_LOG=Some::Module=debug,+log:filter=warn,+%syslog:%syslog=error,syslog + + For the rather extensive details, see AnyEvent::Log. + + This variable is evaluated when AnyEvent (or AnyEvent::Log) is + loaded, so will take effect even before AnyEvent has initialised + itself. + + Note that specifying this environment variable causes the + AnyEvent::Log module to be loaded, while "PERL_ANYEVENT_VERBOSE" + does not, so only using the latter saves a few hundred kB of memory + unless a module explicitly needs the extra features of + AnyEvent::Log. "PERL_ANYEVENT_STRICT" AnyEvent does not do much argument checking by default, as thorough @@ -1084,26 +1299,65 @@ In other words, enables "strict" mode. - Unlike "use strict" (or it's modern cousin, "use common::sense", it + Unlike "use strict" (or its modern cousin, "use common::sense", it is definitely recommended to keep it off in production. Keeping "PERL_ANYEVENT_STRICT=1" in your environment while developing programs can be very useful, however. + "PERL_ANYEVENT_DEBUG_SHELL" + If this env variable is nonempty, then its contents will be + interpreted by "AnyEvent::Socket::parse_hostport" and + "AnyEvent::Debug::shell" (after replacing every occurance of $$ by + the process pid). The shell object is saved in + $AnyEvent::Debug::SHELL. + + This happens when the first watcher is created. + + For example, to bind a debug shell on a unix domain socket in + /tmp/debug.sock, you could use this: + + PERL_ANYEVENT_DEBUG_SHELL=/tmp/debug\$\$.sock perlprog + # connect with e.g.: socat readline /tmp/debug123.sock + + Or to bind to tcp port 4545 on localhost: + + PERL_ANYEVENT_DEBUG_SHELL=127.0.0.1:4545 perlprog + # connect with e.g.: telnet localhost 4545 + + Note that creating sockets in /tmp or on localhost is very unsafe on + multiuser systems. + + "PERL_ANYEVENT_DEBUG_WRAP" + Can be set to 0, 1 or 2 and enables wrapping of all watchers for + debugging purposes. See "AnyEvent::Debug::wrap" for details. + "PERL_ANYEVENT_MODEL" This can be used to specify the event model to be used by AnyEvent, - before auto detection and -probing kicks in. It must be a string - consisting entirely of ASCII letters. The string "AnyEvent::Impl::" - gets prepended and the resulting module name is loaded and if the - load was successful, used as event model. If it fails to load - AnyEvent will proceed with auto detection and -probing. + before auto detection and -probing kicks in. - This functionality might change in future versions. + It normally is a string consisting entirely of ASCII letters (e.g. + "EV" or "IOAsync"). The string "AnyEvent::Impl::" gets prepended and + the resulting module name is loaded and - if the load was successful + - used as event model backend. If it fails to load then AnyEvent + will proceed with auto detection and -probing. + + If the string ends with "::" instead (e.g. "AnyEvent::Impl::EV::") + then nothing gets prepended and the module name is used as-is (hint: + "::" at the end of a string designates a module name and quotes it + appropriately). - For example, to force the pure perl model (AnyEvent::Impl::Perl) you + For example, to force the pure perl model (AnyEvent::Loop::Perl) you could start your program like this: PERL_ANYEVENT_MODEL=Perl perl ... + "PERL_ANYEVENT_IO_MODEL" + The current file I/O model - see AnyEvent::IO for more info. + + At the moment, only "Perl" (small, pure-perl, synchronous) and + "IOAIO" (truly asynchronous) are supported. The default is "IOAIO" + if AnyEvent::AIO can be loaded, otherwise it is "Perl". + "PERL_ANYEVENT_PROTOCOLS" Used by both AnyEvent::DNS and AnyEvent::Socket to determine preferences for IPv4 or IPv6. The default is unspecified (and might @@ -1116,7 +1370,7 @@ 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 conenction and other + likely small, as the program has to handle connection and other failures anyways. Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over @@ -1126,11 +1380,16 @@ "PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4" support either IPv4 or IPv6, but prefer IPv6 over IPv4. + "PERL_ANYEVENT_HOSTS" + This variable, if specified, overrides the /etc/hosts file used by + AnyEvent::Socket"::resolve_sockaddr", i.e. hosts aliases will be + read from that file instead. + "PERL_ANYEVENT_EDNS0" Used by AnyEvent::DNS to decide whether to use the EDNS0 extension for DNS. This extension is generally useful to reduce DNS traffic, - but some (broken) firewalls drop such DNS packets, which is why it - is off by default. + especially when DNSSEC is involved, but some (broken) firewalls drop + such DNS packets, which is why it is off by default. Setting this variable to 1 will cause AnyEvent::DNS to announce EDNS0 in its DNS requests. @@ -1144,15 +1403,36 @@ default DNS resolver - this is the maximum number of parallel DNS requests that are sent to the DNS server. + "PERL_ANYEVENT_MAX_SIGNAL_LATENCY" + Perl has inherently racy signal handling (you can basically choose + between losing signals and memory corruption) - pure perl event + loops (including "AnyEvent::Loop", when "Async::Interrupt" isn't + available) therefore have to poll regularly to avoid losing signals. + + Some event loops are racy, but don't poll regularly, and some event + loops are written in C but are still racy. For those event loops, + AnyEvent installs a timer that regularly wakes up the event loop. + + By default, the interval for this timer is 10 seconds, but you can + override this delay with this environment variable (or by setting + the $AnyEvent::MAX_SIGNAL_LATENCY variable before creating signal + watchers). + + Lower values increase CPU (and energy) usage, higher values can + introduce long delays when reaping children or waiting for signals. + + The AnyEvent::Async module, if available, will be used to avoid this + polling (with most event loops). + "PERL_ANYEVENT_RESOLV_CONF" - The file to use instead of /etc/resolv.conf (or OS-specific - configuration) in the default resolver. When set to the empty - string, no default config will be used. + The absolute path to a resolv.conf-style file to use instead of + /etc/resolv.conf (or the OS-specific configuration) in the default + resolver, or the empty string to select the default configuration. "PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH". When neither "ca_file" nor "ca_path" was specified during AnyEvent::TLS context creation, and either of these environment - variables exist, they will be used to specify CA certificate + variables are nonempty, they will be used to specify CA certificate locations instead of a system-dependent default. "PERL_ANYEVENT_AVOID_GUARD" and "PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT" @@ -1222,16 +1502,9 @@ }, ); - my $time_watcher; # can only be used once - - sub new_timer { - $timer = AnyEvent->timer (after => 1, cb => sub { - warn "timeout\n"; # print 'timeout' about every second - &new_timer; # and restart the time - }); - } - - new_timer; # create first timer + my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub { + warn "timeout\n"; # print 'timeout' at most every second + }); $cv->recv; # wait until user enters /^q/i @@ -1313,7 +1586,7 @@ exceptions) that occurred during request processing. The "result" method detects whether an exception as thrown (it is stored inside the $txn object) and just throws the exception, which means connection errors and - other problems get reported tot he code that tries to use the result, + other problems get reported to the code that tries to use the result, not in a random callback. All of this enables the following usage styles: @@ -1341,7 +1614,7 @@ ... }); - EV::loop; + EV::run; 3b. The module user could use AnyEvent, too: @@ -1368,7 +1641,8 @@ which it is), lets them fire exactly once and destroys them again. Source code for this benchmark is found as eg/bench in the AnyEvent - distribution. + distribution. It uses the AE interface, which makes a real difference + for the EV and Perl backends only. Explanation of the columns *watcher* is the number of event watchers created/destroyed. Since @@ -1397,18 +1671,18 @@ Results name watchers bytes create invoke destroy comment - 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 + EV/EV 100000 223 0.47 0.43 0.27 EV native interface + EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers + Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal + Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation + Event/Event 16000 516 31.16 31.84 0.82 Event native interface + Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers + IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll + IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll + Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour + Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers + POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event + POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select Discussion The benchmark does *not* measure scalability of the event loop very @@ -1429,9 +1703,10 @@ CPU cycles with POE. "EV" is the sole leader regarding speed and memory use, which are both - maximal/minimal, respectively. Even when going through AnyEvent, it uses - far less memory than any other event loop and is still faster than Event - natively. + maximal/minimal, respectively. When using the AE API there is zero + overhead (when going through the AnyEvent API create is about 5-6 times + slower, with other times being equal, so still uses far less memory than + any other event loop and is still faster than Event natively). The pure perl implementation is hit in a few sweet spots (both the constant timeout and the use of a single fd hit optimisations in the @@ -1487,7 +1762,7 @@ * The overhead AnyEvent adds is usually much smaller than the overhead of the actual event loop, only with extremely fast event loops such - as EV adds AnyEvent significant overhead. + as EV does AnyEvent add significant overhead. * You should avoid POE like the plague if you want performance or reasonable memory usage. @@ -1511,7 +1786,8 @@ many connections, most of which are idle at any one point in time. Source code for this benchmark is found as eg/bench2 in the AnyEvent - distribution. + distribution. It uses the AE interface, which makes a real difference + for the EV and Perl backends only. Explanation of the columns *sockets* is the number of sockets, and twice the number of "servers" @@ -1527,13 +1803,13 @@ Results 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 + EV 20000 62.66 7.99 + Perl 20000 68.32 32.64 + IOAsync 20000 174.06 101.15 epoll + IOAsync 20000 174.67 610.84 poll + Event 20000 202.69 242.91 + Glib 20000 557.01 1689.52 + POE 20000 341.54 12086.32 uses POE::Loop::Event Discussion This benchmark *does* measure scalability and overall performance of the @@ -1656,13 +1932,13 @@ backend easily beats IO::Lambda and POE. And even the 100% non-blocking version written using the high-level (and - slow :) AnyEvent::Handle 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. + slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda + higher level ("unoptimised") abstractions 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 eg/ae0.pl and eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are - part of the IO::lambda distribution and were used without any changes. + part of the IO::Lambda distribution and were used without any changes. SIGNALS AnyEvent currently installs handlers for these signals: @@ -1694,13 +1970,13 @@ 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. + its 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. + This section explains which additional modules will be used, and how + they affect AnyEvent's operation. Async::Interrupt This slightly arcane module is used to implement fast signal @@ -1713,7 +1989,7 @@ 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). + 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). @@ -1733,6 +2009,9 @@ You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and Glib::EV). + If you only use backends that rely on another event loop (e.g. + "Tk"), then this module will do nothing for you. + Guard The guard module, when used, will be used to implement "AnyEvent::Util::guard". This speeds up guards considerably (and @@ -1740,13 +2019,10 @@ operation much. It is purely used for performance. JSON and JSON::XS - This module is required when you want to read or write JSON data via - AnyEvent::Handle. It is also written in pure-perl, but can take - advantage of the ultra-high-speed JSON::XS module when it is - installed. - - In fact, AnyEvent::Handle will use JSON::XS by default if it is - installed. + One of these modules is required when you want to read or write JSON + data via AnyEvent::Handle. JSON is also written in pure-perl, but + can take advantage of the ultra-high-speed JSON::XS module when it + is installed. Net::SSLeay Implementing TLS/SSL in Perl is certainly interesting, but not very @@ -1755,19 +2031,62 @@ Time::HiRes 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 (AnyEvent::Impl::Perl) will - additionally use it to try to use a monotonic clock for timing - stability. + when the chosen event library does not come with a timing source of + its own. The pure-perl event loop (AnyEvent::Loop) will additionally + load it to try to use a monotonic clock for timing stability. + + AnyEvent::AIO (and IO::AIO) + The default implementation of AnyEvent::IO is to do I/O + synchronously, stopping programs while they access the disk, which + is fine for a lot of programs. + + Installing AnyEvent::AIO (and its IO::AIO dependency) makes it + switch to a true asynchronous implementation, so event processing + can continue even while waiting for disk I/O. FORK Most event libraries are not fork-safe. The ones who are usually are - because they rely on inefficient but fork-safe "select" or "poll" calls. - Only EV is fully fork-aware. + because they rely on inefficient but fork-safe "select" or "poll" calls + - higher performance APIs such as BSD's kqueue or the dreaded Linux + epoll are usually badly thought-out hacks that are incompatible with + fork in one way or another. Only EV is fully fork-aware and ensures that + you continue event-processing in both parent and child (or both, if you + know what you are doing). + + This means that, in general, you cannot fork and do event processing in + the child if the event library was initialised before the fork (which + usually happens when the first AnyEvent watcher is created, or the + library is loaded). If you have to fork, you must either do so *before* creating your first watcher OR you must not use AnyEvent at all in the child OR you must do - something completely out of the scope of AnyEvent. + something completely out of the scope of AnyEvent (see below). + + The problem of doing event processing in the parent *and* the child is + much more complicated: even for backends that *are* fork-aware or + fork-safe, their behaviour is not usually what you want: fork clones all + watchers, that means all timers, I/O watchers etc. are active in both + parent and child, which is almost never what you want. Using "exec" to + start worker children from some kind of manage prrocess is usually + preferred, because it is much easier and cleaner, at the expense of + having to have another binary. + + In addition to logical problems with fork, there are also implementation + problems. For example, on POSIX systems, you cannot fork at all in Perl + code if a thread (I am talking of pthreads here) was ever created in the + process, and this is just the tip of the iceberg. In general, using fork + from Perl is difficult, and attempting to use fork without an exec to + implement some kind of parallel processing is almost certainly doomed. + + To safely fork and exec, you should use a module such as Proc::FastSpawn + that let's you safely fork and exec new processes. + + If you want to do multiprocessing using processes, you can look at the + AnyEvent::Fork module (and some related modules such as + AnyEvent::Fork::RPC, AnyEvent::Fork::Pool and AnyEvent::Fork::Remote). + This module allows you to safely create subprocesses without any + limitations - you can use X11 toolkits or AnyEvent in the children + created by AnyEvent::Fork safely and without any special precautions. SECURITY CONSIDERATIONS AnyEvent can be forced to load any event model via @@ -1801,27 +2120,38 @@ not as pronounced). SEE ALSO - Utility functions: AnyEvent::Util. + Tutorial/Introduction: AnyEvent::Intro. + + FAQ: AnyEvent::FAQ. - Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk, - Event::Lib, Qt, POE. + Utility functions: AnyEvent::Util (misc. grab-bag), AnyEvent::Log + (simply logging). + + Development/Debugging: AnyEvent::Strict (stricter checking), + AnyEvent::Debug (interactive shell, watcher tracing). + + Supported event modules: AnyEvent::Loop, EV, EV::Glib, Glib::EV, Event, + Glib::Event, Glib, Tk, Event::Lib, Qt, POE, FLTK, Cocoa::EventLoop, UV. Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event, AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl, AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE, - AnyEvent::Impl::IOAsync, Anyevent::Impl::Irssi. + AnyEvent::Impl::IOAsync, AnyEvent::Impl::Irssi, AnyEvent::Impl::FLTK, + AnyEvent::Impl::Cocoa, AnyEvent::Impl::UV. - Non-blocking file handles, sockets, TCP clients and servers: + Non-blocking handles, pipes, stream sockets, TCP clients and servers: AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS. + Asynchronous File I/O: AnyEvent::IO. + Asynchronous DNS: AnyEvent::DNS. - Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event, + Thread support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event. - Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::XMPP, + Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::IRC, AnyEvent::HTTP. AUTHOR Marc Lehmann - http://home.schmorp.de/ + http://anyevent.schmorp.de