--- cvsroot/EV/README 2007/11/01 13:33:12 1.5 +++ cvsroot/EV/README 2008/01/28 12:24:05 1.22 @@ -1,247 +1,827 @@ NAME - EV - perl interface to libevent, monkey.org/~provos/libevent/ + EV - perl interface to libev, a high performance full-featured event + loop SYNOPSIS use EV; - - # TIMER - - my $w = EV::timer 2, 0, sub { + + # TIMERS + + my $w = EV::timer 2, 0, sub { warn "is called after 2s"; }; - - my $w = EV::timer 2, 1, sub { - warn "is called roughly every 2s (repeat = 1)"; - }; - - undef $w; # destroy event watcher again - - my $w = EV::timer_abs 0, 60, sub { + + my $w = EV::timer 2, 2, sub { + warn "is called roughly every 2s (repeat = 2)"; + }; + + undef $w; # destroy event watcher again + + my $w = EV::periodic 0, 60, 0, sub { warn "is called every minute, on the minute, exactly"; }; - - # IO - - my $w = EV::io \*STDIN, EV::READ | EV::PERSIST, sub { - my ($w, $revents) = @_; # all callbacks get the watcher object and event mask - if ($revents & EV::TIMEOUT) { - warn "nothing received on stdin for 10 seconds, retrying"; - } else { - warn "stdin is readable, you entered: ", ; - } - }; - $w->timeout (10); - - my $w = EV::timed_io \*STDIN, EV::READ, 30, sub { - my ($w, $revents) = @_; - if ($revents & EV::TIMEOUT) { - warn "nothing entered within 30 seconds, bye bye.\n"; - $w->stop; - } else { - my $line = ; - warn "you entered something, you again have 30 seconds.\n"; - } - }; - - # SIGNALS - - my $w = EV::signal 'QUIT', sub { + + # IO + + my $w = EV::io *STDIN, EV::READ, sub { + my ($w, $revents) = @_; # all callbacks receive the watcher and event mask + warn "stdin is readable, you entered: ", ; + }; + + # SIGNALS + + my $w = EV::signal 'QUIT', sub { warn "sigquit received\n"; }; - - my $w = EV::signal 3, sub { - warn "sigquit received (this is GNU/Linux, right?)\n"; - }; - - # CHILD/PID STATUS CHANGES - - my $w = EV::child 666, sub { - my ($w, $revents, $status) = @_; - }; - - # MAINLOOP - EV::dispatch; # loop as long as watchers are active - EV::loop; # the same thing - EV::loop EV::LOOP_ONESHOT; # block until some events could be handles - EV::loop EV::LOOP_NONBLOCK; # check and handle some events, but do not wait + + # CHILD/PID STATUS CHANGES + + my $w = EV::child 666, 0, sub { + my ($w, $revents) = @_; + my $status = $w->rstatus; + }; + + # STAT CHANGES + my $w = EV::stat "/etc/passwd", 10, sub { + my ($w, $revents) = @_; + warn $w->path, " has changed somehow.\n"; + }; + + # MAINLOOP + EV::loop; # loop until EV::unloop is called or all watchers stop + EV::loop EV::LOOP_ONESHOT; # block until at least one event could be handled + EV::loop EV::LOOP_NONBLOCK; # try to handle same events, but do not block DESCRIPTION This module provides an interface to libev - (). You probably should - acquaint yourself with its documentation and source code to be able to - use this module fully. + (). While the documentation + below is comprehensive, one might also consult the documentation of + libev itself () for more subtle + details on watcher semantics or some discussion on the available + backends, or how to force a specific backend with "LIBEV_FLAGS", or just + about in any case because it has much more detailed information. + +EVENT LOOPS + EV supports multiple event loops: There is a single "default event loop" + that can handle everything including signals and child watchers, and any + number of "dynamic event loops" that can use different backends (with + various limitations), but no child and signal watchers. + + You do not have to do anything to create the default event loop: When + the module is loaded a suitable backend is selected on the premise of + selecting a working backend (which for example rules out kqueue on most + BSDs). Modules should, unless they have "special needs" always use the + default loop as this is fastest (perl-wise), best supported by other + modules (e.g. AnyEvent or Coro) and most portable event loop. + + For specific programs you can create additional event loops dynamically. + + $loop = new EV::loop [$flags] + Create a new event loop as per the specified flags. Please refer to + the "ev_loop_new ()" function description in the libev documentation + () for more info. + + The loop will automatically be destroyed when it is no longer + referenced by any watcher and the loop object goes out of scope. + + Using "EV::FLAG_FORKCHECK" is recommended, as only the default event + loop is protected by this module. + + $loop->loop_fork + Must be called after a fork in the child, before entering or + continuing the event loop. An alternative is to use + "EV::FLAG_FORKCHECK" which calls this fucntion automatically, at + some performance loss (refer to the libev documentation). -BASIC INTERFACE - $EV::NPRI - How many priority levels are available. + $loop = EV::default_loop [$flags] + Return the default loop (which is a singleton object). +BASIC INTERFACE $EV::DIED Must contain a reference to a function that is called when a - callback throws an exception (with $@ containing thr error). The + callback throws an exception (with $@ containing the error). The default prints an informative message and continues. If this callback throws an exception it will be silently ignored. - $time = EV::now - Returns the time in (fractional) seconds since the epoch. + $flags = EV::supported_backends + $flags = EV::recommended_backends + $flags = EV::embeddable_backends + Returns the set (see "EV::BACKEND_*" flags) of backends supported by + this instance of EV, the set of recommended backends (supposed to be + good) for this platform and the set of embeddable backends (see + EMBED WATCHERS). - $version = EV::version - $method = EV::method - Return version string and event polling method used. - - EV::loop $flags # EV::LOOP_ONCE, EV::LOOP_ONESHOT - EV::loopexit $after - Exit any active loop or dispatch after $after seconds or immediately - if $after is missing or zero. + EV::sleep $seconds + Block the process for the given number of (fractional) seconds. - EV::dispatch - Same as "EV::loop 0". + $time = EV::time + Returns the current time in (fractional) seconds since the epoch. - EV::event $callback - Creates a new event watcher waiting for nothing, calling the given - callback. + $time = EV::now + $time = $loop->now + Returns the time the last event loop iteration has been started. + This is the time that (relative) timers are based on, and refering + to it is usually faster then calling EV::time. + + $backend = EV::backend + $backend = $loop->backend + Returns an integer describing the backend used by libev + (EV::METHOD_SELECT or EV::METHOD_EPOLL). + + EV::loop [$flags] + $loop->loop ([$flags]) + Begin checking for events and calling callbacks. It returns when a + callback calls EV::unloop. + + The $flags argument can be one of the following: + + 0 as above + EV::LOOP_ONESHOT block at most once (wait, but do not loop) + EV::LOOP_NONBLOCK do not block at all (fetch/handle events but do not wait) + + EV::unloop [$how] + $loop->unloop ([$how]) + When called with no arguments or an argument of EV::UNLOOP_ONE, + makes the innermost call to EV::loop return. + + When called with an argument of EV::UNLOOP_ALL, all calls to + EV::loop will return as fast as possible. + + $count = EV::loop_count + $count = $loop->loop_count + Return the number of times the event loop has polled for new events. + Sometiems useful as a generation counter. + + EV::once $fh_or_undef, $events, $timeout, $cb->($revents) + $loop->once ($fh_or_undef, $events, $timeout, $cb->($revents)) + This function rolls together an I/O and a timer watcher for a single + one-shot event without the need for managing a watcher object. + + If $fh_or_undef is a filehandle or file descriptor, then $events + must be a bitset containing either "EV::READ", "EV::WRITE" or + "EV::READ | EV::WRITE", indicating the type of I/O event you want to + wait for. If you do not want to wait for some I/O event, specify + "undef" for $fh_or_undef and 0 for $events). + + If timeout is "undef" or negative, then there will be no timeout. + Otherwise a EV::timer with this value will be started. + + When an error occurs or either the timeout or I/O watcher triggers, + then the callback will be called with the received event set (in + general you can expect it to be a combination of "EV::ERROR", + "EV::READ", "EV::WRITE" and "EV::TIMEOUT"). + + EV::once doesn't return anything: the watchers stay active till + either of them triggers, then they will be stopped and freed, and + the callback invoked. + + EV::feed_fd_event ($fd, $revents) + $loop->feed_fd_event ($fd, $revents) + Feed an event on a file descriptor into EV. EV will react to this + call as if the readyness notifications specified by $revents (a + combination of "EV::READ" and "EV::WRITE") happened on the file + descriptor $fd. + + EV::feed_signal_event ($signal) + Feed a signal event into EV. EV will react to this call as if the + signal specified by $signal had occured. + + EV::set_io_collect_interval $time + $loop->set_io_collect_interval ($time) + EV::set_timeout_collect_interval $time + $loop->set_timeout_collect_interval ($time) + These advanced functions set the minimum block interval when polling + for I/O events and the minimum wait interval for timer events. See + the libev documentation at + for a more detailed discussion. + +WATCHER OBJECTS + A watcher is an object that gets created to record your interest in some + event. For instance, if you want to wait for STDIN to become readable, + you would create an EV::io watcher for that: + + my $watcher = EV::io *STDIN, EV::READ, sub { + my ($watcher, $revents) = @_; + warn "yeah, STDIN should now be readable without blocking!\n" + }; - my $w = EV::io $fileno_or_fh, $eventmask, $callback - my $w = EV::io_ns $fileno_or_fh, $eventmask, $callback - As long as the returned watcher object is alive, call the $callback - when the events specified in $eventmask happen. Initially, the - timeout is disabled. + All watchers can be active (waiting for events) or inactive (paused). + Only active watchers will have their callbacks invoked. All callbacks + will be called with at least two arguments: the watcher and a bitmask of + received events. + + Each watcher type has its associated bit in revents, so you can use the + same callback for multiple watchers. The event mask is named after the + type, i..e. EV::child sets EV::CHILD, EV::prepare sets EV::PREPARE, + EV::periodic sets EV::PERIODIC and so on, with the exception of I/O + events (which can set both EV::READ and EV::WRITE bits), and EV::timer + (which uses EV::TIMEOUT). + + In the rare case where one wants to create a watcher but not start it at + the same time, each constructor has a variant with a trailing "_ns" in + its name, e.g. EV::io has a non-starting variant EV::io_ns and so on. + + Please note that a watcher will automatically be stopped when the + watcher object is destroyed, so you *need* to keep the watcher objects + returned by the constructors. + + Also, all methods changing some aspect of a watcher (->set, ->priority, + ->fh and so on) automatically stop and start it again if it is active, + which means pending events get lost. - You can additionall set a timeout to occur on the watcher, but note - that this timeout will not be reset when you get an I/O event in the - EV::PERSIST case, and reaching a timeout will always stop the - watcher even in the EV::PERSIST case. + COMMON WATCHER METHODS + This section lists methods common to all watchers. - If you want a timeout to occur only after a specific time of - inactivity, set a repeating timeout and do NOT use EV::PERSIST. + $w->start + Starts a watcher if it isn't active already. Does nothing to an + already active watcher. By default, all watchers start out in the + active state (see the description of the "_ns" variants if you need + stopped watchers). - Eventmask can be one or more of these constants ORed together: + $w->stop + Stop a watcher if it is active. Also clear any pending events + (events that have been received but that didn't yet result in a + callback invocation), regardless of whether the watcher was active + or not. + + $bool = $w->is_active + Returns true if the watcher is active, false otherwise. + + $current_data = $w->data + $old_data = $w->data ($new_data) + Queries a freely usable data scalar on the watcher and optionally + changes it. This is a way to associate custom data with a watcher: + + my $w = EV::timer 60, 0, sub { + warn $_[0]->data; + }; + $w->data ("print me!"); + + $current_cb = $w->cb + $old_cb = $w->cb ($new_cb) + Queries the callback on the watcher and optionally changes it. You + can do this at any time without the watcher restarting. + + $current_priority = $w->priority + $old_priority = $w->priority ($new_priority) + Queries the priority on the watcher and optionally changes it. + Pending watchers with higher priority will be invoked first. The + valid range of priorities lies between EV::MAXPRI (default 2) and + EV::MINPRI (default -2). If the priority is outside this range it + will automatically be normalised to the nearest valid priority. + + The default priority of any newly-created watcher is 0. + + Note that the priority semantics have not yet been fleshed out and + are subject to almost certain change. + + $w->invoke ($revents) + Call the callback *now* with the given event mask. + + $w->feed_event ($revents) + Feed some events on this watcher into EV. EV will react to this call + as if the watcher had received the given $revents mask. + + $revents = $w->clear_pending + If the watcher is pending, this function clears its pending status + and returns its $revents bitset (as if its callback was invoked). If + the watcher isn't pending it does nothing and returns 0. + + $previous_state = $w->keepalive ($bool) + Normally, "EV::loop" will return when there are no active watchers + (which is a "deadlock" because no progress can be made anymore). + This is convinient because it allows you to start your watchers (and + your jobs), call "EV::loop" once and when it returns you know that + all your jobs are finished (or they forgot to register some watchers + for their task :). + + Sometimes, however, this gets in your way, for example when the + module that calls "EV::loop" (usually the main program) is not the + same module as a long-living watcher (for example a DNS client + module written by somebody else even). Then you might want any + outstanding requests to be handled, but you would not want to keep + "EV::loop" from returning just because you happen to have this + long-running UDP port watcher. + + In this case you can clear the keepalive status, which means that + even though your watcher is active, it won't keep "EV::loop" from + returning. + + The initial value for keepalive is true (enabled), and you cna + change it any time. + + Example: Register an I/O watcher for some UDP socket but do not keep + the event loop from running just because of that watcher. + + my $udp_socket = ... + my $udp_watcher = EV::io $udp_socket, EV::READ, sub { ... }; + $1000udp_watcher->keepalive (0); + + $loop = $w->loop + Return the loop that this watcher is attached to. + +WATCHER TYPES + Each of the following subsections describes a single watcher type. + + I/O WATCHERS - is this file descriptor readable or writable? + $w = EV::io $fileno_or_fh, $eventmask, $callback + $w = EV::io_ns $fileno_or_fh, $eventmask, $callback + $w = $loop->io ($fileno_or_fh, $eventmask, $callback) + $w = $loop->io_ns ($fileno_or_fh, $eventmask, $callback) + As long as the returned watcher object is alive, call the $callback + when at least one of events specified in $eventmask occurs. + + The $eventmask can be one or more of these constants ORed together: EV::READ wait until read() wouldn't block anymore EV::WRITE wait until write() wouldn't block anymore - EV::PERSIST stay active after a (non-timeout) event occured - The "io_ns" variant doesn't add/start the newly created watcher. + The "io_ns" variant doesn't start (activate) the newly created + watcher. - my $w = EV::timed_io $fileno_or_fh, $eventmask, $timeout, $callback - my $w = EV::timed_io_ns $fileno_or_fh, $eventmask, $timeout, $callback - Same as "io" and "io_ns", but also specifies a timeout (as if there - was a call to "$w->timeout ($timout, 1)". The persist flag is not - allowed and will automatically be cleared. The watcher will be - restarted after each event. + $w->set ($fileno_or_fh, $eventmask) + Reconfigures the watcher, see the constructor above for details. Can + be called at any time. - If the timeout is zero or undef, no timeout will be set, and a - normal watcher (with the persist flag set!) will be created. + $current_fh = $w->fh + $old_fh = $w->fh ($new_fh) + Returns the previously set filehandle and optionally set a new one. - This has the effect of timing out after the specified period of - inactivity has happened. + $current_eventmask = $w->events + $old_eventmask = $w->events ($new_eventmask) + Returns the previously set event mask and optionally set a new one. - Due to the design of libevent, this is also relatively inefficient, - having one or two io watchers and a separate timeout watcher that - you reset on activity (by calling its "start" method) is usually - more efficient. + TIMER WATCHERS - relative and optionally repeating timeouts + $w = EV::timer $after, $repeat, $callback + $w = EV::timer_ns $after, $repeat, $callback + $w = $loop->timer ($after, $repeat, $callback) + $w = $loop->timer_ns ($after, $repeat, $callback) + Calls the callback after $after seconds (which may be fractional). + If $repeat is non-zero, the timer will be restarted (with the + $repeat value as $after) after the callback returns. + + This means that the callback would be called roughly after $after + seconds, and then every $repeat seconds. The timer does his best not + to drift, but it will not invoke the timer more often then once per + event loop iteration, and might drift in other cases. If that isn't + acceptable, look at EV::periodic, which can provide long-term stable + timers. + + The timer is based on a monotonic clock, that is, if somebody is + sitting in front of the machine while the timer is running and + changes the system clock, the timer will nevertheless run (roughly) + the same time. - my $w = EV::timer $after, $repeat, $callback - my $w = EV::timer_ns $after, $repeat, $callback - Calls the callback after $after seconds. If $repeat is true, the - timer will be restarted after the callback returns. This means that - the callback would be called roughly every $after seconds, prolonged - by the time the callback takes. + The "timer_ns" variant doesn't start (activate) the newly created + watcher. - The "timer_ns" variant doesn't add/start the newly created watcher. + $w->set ($after, $repeat) + Reconfigures the watcher, see the constructor above for details. Can + be called at any time. + + $w->again + Similar to the "start" method, but has special semantics for + repeating timers: + + If the timer is active and non-repeating, it will be stopped. + + If the timer is active and repeating, reset the timeout to occur + $repeat seconds after now. + + If the timer is inactive and repeating, start it using the repeat + value. + + Otherwise do nothing. + + This behaviour is useful when you have a timeout for some IO + operation. You create a timer object with the same value for $after + and $repeat, and then, in the read/write watcher, run the "again" + method on the timeout. + + PERIODIC WATCHERS - to cron or not to cron? + $w = EV::periodic $at, $interval, $reschedule_cb, $callback + $w = EV::periodic_ns $at, $interval, $reschedule_cb, $callback + $w = $loop->periodic ($at, $interval, $reschedule_cb, $callback) + $w = $loop->periodic_ns ($at, $interval, $reschedule_cb, $callback) + Similar to EV::timer, but is not based on relative timeouts but on + absolute times. Apart from creating "simple" timers that trigger + "at" the specified time, it can also be used for non-drifting + absolute timers and more complex, cron-like, setups that are not + adversely affected by time jumps (i.e. when the system clock is + changed by explicit date -s or other means such as ntpd). It is also + the most complex watcher type in EV. + + It has three distinct "modes": + + * absolute timer ($interval = $reschedule_cb = 0) + + This time simply fires at the wallclock time $at and doesn't + repeat. It will not adjust when a time jump occurs, that is, if + it is to be run at January 1st 2011 then it will run when the + system time reaches or surpasses this time. + + * non-repeating interval timer ($interval > 0, $reschedule_cb = 0) + + In this mode the watcher will always be scheduled to time out at + the next "$at + N * $interval" time (for some integer N) and + then repeat, regardless of any time jumps. + + This can be used to create timers that do not drift with respect + to system time: + + my $hourly = EV::periodic 0, 3600, 0, sub { print "once/hour\n" }; + + That doesn't mean there will always be 3600 seconds in between + triggers, but only that the the clalback will be called when the + system time shows a full hour (UTC). + + Another way to think about it (for the mathematically inclined) + is that EV::periodic will try to run the callback in this mode + at the next possible time where "$time = $at (mod $interval)", + regardless of any time jumps. + + * manual reschedule mode ($reschedule_cb = coderef) + + In this mode $interval and $at are both being ignored. Instead, + each time the periodic watcher gets scheduled, the reschedule + callback ($reschedule_cb) will be called with the watcher as + first, and the current time as second argument. + + *This callback MUST NOT stop or destroy this or any other + periodic watcher, ever*. If you need to stop it, return 1e30 and + stop it afterwards. + + It must return the next time to trigger, based on the passed + time value (that is, the lowest time value larger than to the + second argument). It will usually be called just before the + callback will be triggered, but might be called at other times, + too. + + This can be used to create very complex timers, such as a timer + that triggers on each midnight, local time (actually 24 hours + after the last midnight, to keep the example simple. If you know + a way to do it correctly in about the same space (without + requiring elaborate modules), drop me a note :): + + my $daily = EV::periodic 0, 0, sub { + my ($w, $now) = @_; + + use Time::Local (); + my (undef, undef, undef, $d, $m, $y) = localtime $now; + 86400 + Time::Local::timelocal 0, 0, 0, $d, $m, $y + }, sub { + print "it's midnight or likely shortly after, now\n"; + }; - my $w = EV::timer_abs $at, $interval, $callback - my $w = EV::timer_abs_ns $at, $interval, $callback - Similar to EV::timer, but the time is given as an absolute point in - time ($at), plus an optional $interval. + The "periodic_ns" variant doesn't start (activate) the newly created + watcher. - If the $interval is zero, then the callback will be called at the - time $at if that is in the future, or as soon as possible if its in - the past. It will not automatically repeat. + $w->set ($at, $interval, $reschedule_cb) + Reconfigures the watcher, see the constructor above for details. Can + be called at any time. + + $w->again + Simply stops and starts the watcher again. + + $time = $w->at + Return the time that the watcher is expected to trigger next. + + SIGNAL WATCHERS - signal me when a signal gets signalled! + $w = EV::signal $signal, $callback + $w = EV::signal_ns $signal, $callback + Call the callback when $signal is received (the signal can be + specified by number or by name, just as with "kill" or %SIG). - If the $interval is nonzero, then the watcher will always be - scheduled to time out at the next "$at + integer * $interval" time. + EV will grab the signal for the process (the kernel only allows one + component to receive a signal at a time) when you start a signal + watcher, and removes it again when you stop it. Perl does the same + when you add/remove callbacks to %SIG, so watch out. + + You can have as many signal watchers per signal as you want. + + The "signal_ns" variant doesn't start (activate) the newly created + watcher. + + $w->set ($signal) + Reconfigures the watcher, see the constructor above for details. Can + be called at any time. + + $current_signum = $w->signal + $old_signum = $w->signal ($new_signal) + Returns the previously set signal (always as a number not name) and + optionally set a new one. + + CHILD WATCHERS - watch out for process status changes + $w = EV::child $pid, $trace, $callback + $w = EV::child_ns $pid, $trace, $callback + $w = $loop->child ($pid, $trace, $callback) + $w = $loop->child_ns ($pid, $trace, $callback) + Call the callback when a status change for pid $pid (or any pid if + $pid is 0) has been received (a status change happens when the + process terminates or is killed, or, when trace is true, + additionally when it is stopped or continued). More precisely: when + the process receives a "SIGCHLD", EV will fetch the outstanding + exit/wait status for all changed/zombie children and call the + callback. + + It is valid (and fully supported) to install a child watcher after a + child has exited but before the event loop has started its next + iteration (for example, first you "fork", then the new child process + might exit, and only then do you install a child watcher in the + parent for the new pid). - This can be used to schedule a callback to run at very regular - intervals, as long as the processing time is less then the interval - (otherwise obviously events will be skipped). + You can access both exit (or tracing) status and pid by using the + "rstatus" and "rpid" methods on the watcher object. - Another way to think about it (for the mathematically inclined) is - that "timer_abs" will try to tun the callback at the next possible - time where "$time = $at (mod $interval)", regardless of any time - jumps. + You can have as many pid watchers per pid as you want, they will all + be called. - The "timer_abs_ns" variant doesn't add/start the newly created + The "child_ns" variant doesn't start (activate) the newly created watcher. - my $w = EV::signal $signal, $callback - my $w = EV::signal_ns $signal, $callback - Call the callback when $signal is received (the signal can be - specified by number or by name, just as with kill or %SIG). Signal - watchers are persistent no natter what. + $w->set ($pid, $trace) + Reconfigures the watcher, see the constructor above for details. Can + be called at any time. + + $current_pid = $w->pid + Returns the previously set process id and optionally set a new one. + + $exit_status = $w->rstatus + Return the exit/wait status (as returned by waitpid, see the waitpid + entry in perlfunc). + + $pid = $w->rpid + Return the pid of the awaited child (useful when you have installed + a watcher for all pids). + + STAT WATCHERS - did the file attributes just change? + $w = EV::stat $path, $interval, $callback + $w = EV::stat_ns $path, $interval, $callback + $w = $loop->stat ($path, $interval, $callback) + $w = $loop->stat_ns ($path, $interval, $callback) + Call the callback when a file status change has been detected on + $path. The $path does not need to exist, changing from "path exists" + to "path does not exist" is a status change like any other. + + The $interval is a recommended polling interval for systems where + OS-supported change notifications don't exist or are not supported. + If you use 0 then an unspecified default is used (which is highly + recommended!), which is to be expected to be around five seconds + usually. + + This watcher type is not meant for massive numbers of stat watchers, + as even with OS-supported change notifications, this can be + resource-intensive. - EV will grab the signal for the process (the kernel only allows one - component to receive signals) when you start a signal watcher, and - removes it again when you stop it. Pelr does the same when you - add/remove callbacks to %SIG, so watch out. - - Unfortunately, only one handler can be registered per signal. Screw - libevent. - - The "signal_ns" variant doesn't add/start the newly created watcher. - -THE EV::Event CLASS - All EV functions creating an event watcher (designated by "my $w =" - above) support the following methods on the returned watcher object: - - $w->add ($timeout) - Stops and (re-)starts the event watcher, setting the optional - timeout to the given value, or clearing the timeout if none is - given. + The "stat_ns" variant doesn't start (activate) the newly created + watcher. - $w->start - Stops and (re-)starts the event watcher without touching the - timeout. + ... = $w->stat + This call is very similar to the perl "stat" built-in: It stats + (using "lstat") the path specified in the watcher and sets perls + stat cache (as well as EV's idea of the current stat values) to the + values found. + + In scalar context, a boolean is return indicating success or failure + of the stat. In list context, the same 13-value list as with stat is + returned (except that the blksize and blocks fields are not + reliable). + + In the case of an error, errno is set to "ENOENT" (regardless of the + actual error value) and the "nlink" value is forced to zero (if the + stat was successful then nlink is guaranteed to be non-zero). + + See also the next two entries for more info. + + ... = $w->attr + Just like "$w->stat", but without the initial stat'ing: this returns + the values most recently detected by EV. See the next entry for more + info. + + ... = $w->prev + Just like "$w->stat", but without the initial stat'ing: this returns + the previous set of values, before the change. + + That is, when the watcher callback is invoked, "$w->prev" will be + set to the values found *before* a change was detected, while + "$w->attr" returns the values found leading to the change detection. + The difference (if any) between "prev" and "attr" is what triggered + the callback. + + If you did something to the filesystem object and do not want to + trigger yet another change, you can call "stat" to update EV's idea + of what the current attributes are. + + $w->set ($path, $interval) + Reconfigures the watcher, see the constructor above for details. Can + be called at any time. + + $current_path = $w->path + $old_path = $w->path ($new_path) + Returns the previously set path and optionally set a new one. + + $current_interval = $w->interval + $old_interval = $w->interval ($new_interval) + Returns the previously set interval and optionally set a new one. + Can be used to query the actual interval used. + + IDLE WATCHERS - when you've got nothing better to do... + $w = EV::idle $callback + $w = EV::idle_ns $callback + $w = $loop->idle ($callback) + $w = $loop->idle_ns ($callback) + Call the callback when there are no other pending watchers of the + same or higher priority (excluding check, prepare and other idle + watchers of the same or lower priority, of course). They are called + idle watchers because when the watcher is the highest priority + pending event in the process, the process is considered to be idle + at that priority. + + If you want a watcher that is only ever called when *no* other + events are outstanding you have to set the priority to "EV::MINPRI". + + The process will not block as long as any idle watchers are active, + and they will be called repeatedly until stopped. + + For example, if you have idle watchers at priority 0 and 1, and an + I/O watcher at priority 0, then the idle watcher at priority 1 and + the I/O watcher will always run when ready. Only when the idle + watcher at priority 1 is stopped and the I/O watcher at priority 0 + is not pending with the 0-priority idle watcher be invoked. - $w->del - $w->stop - Stop the event watcher if it was started. + The "idle_ns" variant doesn't start (activate) the newly created + watcher. - $current_callback = $w->cb - $old_callback = $w->cb ($new_callback) - Return the previously set callback and optionally set a new one. + PREPARE WATCHERS - customise your event loop! + $w = EV::prepare $callback + $w = EV::prepare_ns $callback + $w = $loop->prepare ($callback) + $w = $loop->prepare_ns ($callback) + Call the callback just before the process would block. You can still + create/modify any watchers at this point. - $current_fh = $w->fh - $old_fh = $w->fh ($new_fh) - Returns the previously set filehandle and optionally set a new one - (also clears the EV::SIGNAL flag when setting a filehandle). + See the EV::check watcher, below, for explanations and an example. - $current_signal = $w->signal - $old_signal = $w->signal ($new_signal) - Returns the previously set signal number and optionally set a new - one (also sets the EV::SIGNAL flag when setting a signal). + The "prepare_ns" variant doesn't start (activate) the newly created + watcher. - $current_eventmask = $w->events - $old_eventmask = $w->events ($new_eventmask) - Returns the previously set event mask and optionally set a new one. + CHECK WATCHERS - customise your event loop even more! + $w = EV::check $callback + $w = EV::check_ns $callback + $w = $loop->check ($callback) + $w = $loop->check_ns ($callback) + Call the callback just after the process wakes up again (after it + has gathered events), but before any other callbacks have been + invoked. + + This is used to integrate other event-based software into the EV + mainloop: You register a prepare callback and in there, you create + io and timer watchers as required by the other software. Here is a + real-world example of integrating Net::SNMP (with some details left + out): + + our @snmp_watcher; + + our $snmp_prepare = EV::prepare sub { + # do nothing unless active + $dispatcher->{_event_queue_h} + or return; + + # make the dispatcher handle any outstanding stuff + ... not shown + + # create an I/O watcher for each and every socket + @snmp_watcher = ( + (map { EV::io $_, EV::READ, sub { } } + keys %{ $dispatcher->{_descriptors} }), + + EV::timer +($event->[Net::SNMP::Dispatcher::_ACTIVE] + ? $event->[Net::SNMP::Dispatcher::_TIME] - EV::now : 0), + 0, sub { }, + ); + }; + + The callbacks are irrelevant (and are not even being called), the + only purpose of those watchers is to wake up the process as soon as + one of those events occurs (socket readable, or timer timed out). + The corresponding EV::check watcher will then clean up: + + our $snmp_check = EV::check sub { + # destroy all watchers + @snmp_watcher = (); + + # make the dispatcher handle any new stuff + ... not shown + }; + + The callbacks of the created watchers will not be called as the + watchers are destroyed before this cna happen (remember EV::check + gets called first). + + The "check_ns" variant doesn't start (activate) the newly created + watcher. - $w->timeout ($after, $repeat) - Resets the timeout (see "EV::timer" for details). + FORK WATCHERS - the audacity to resume the event loop after a fork + Fork watchers are called when a "fork ()" was detected. The invocation + is done before the event loop blocks next and before "check" watchers + are being called, and only in the child after the fork. + + $w = EV::fork $callback + $w = EV::fork_ns $callback + $w = $loop->fork ($callback) + $w = $loop->fork_ns ($callback) + Call the callback before the event loop is resumed in the child + process after a fork. - $w->timeout_abs ($at, $interval) - Resets the timeout (see "EV::timer_abs" for details). + The "fork_ns" variant doesn't start (activate) the newly created + watcher. + + EMBED WATCHERS - when one backend isn't enough... + This is a rather advanced watcher type that lets you embed one event + loop into another (currently only IO events are supported in the + embedded loop, other types of watchers might be handled in a delayed or + incorrect fashion and must not be used). + + See the libev documentation at + for more details. + + In short, this watcher is most useful on BSD systems without working + kqueue to still be able to handle a large number of sockets: + + my $socket_loop; + + # check wether we use SELECT or POLL _and_ KQUEUE is supported + if ( + (EV::backend & (EV::BACKEND_POLL | EV::BACKEND_SELECT)) + && (EV::supported_backends & EV::embeddable_backends & EV::BACKEND_KQUEUE) + ) { + # use kqueue for sockets + $socket_loop = new EV::Loop EV::BACKEND_KQUEUE | EV::FLAG_NOENV; + } + + # use the default loop otherwise + $socket_loop ||= EV::default_loop; + + $w = EV::embed $otherloop, $callback + $w = EV::embed_ns $otherloop, $callback + $w = $loop->embed ($otherloop, $callback) + $w = $loop->embed_ns ($otherloop, $callback) + Call the callback when the embedded event loop ($otherloop) has any + I/O activity. The $callback should alwas be specified as "undef" in + this version of EV, which means the embedded event loop will be + managed automatically. + + The "embed_ns" variant doesn't start (activate) the newly created + watcher. - $w->priority_set ($priority) - Set the priority of the watcher to $priority (0 <= $priority < - $EV::NPRI). +PERL SIGNALS + While Perl signal handling (%SIG) is not affected by EV, the behaviour + with EV is as the same as any other C library: Perl-signals will only be + handled when Perl runs, which means your signal handler might be invoked + only the next time an event callback is invoked. + + The solution is to use EV signal watchers (see "EV::signal"), which will + ensure proper operations with regards to other event watchers. + + If you cannot do this for whatever reason, you can also force a watcher + to be called on every event loop iteration by installing a "EV::check" + watcher: + + my $async_check = EV::check sub { }; + + This ensures that perl gets into control for a short time to handle any + pending signals, and also ensures (slightly) slower overall operation. THREADS - Threads are not supported by this in any way. Perl pseudo-threads is - evil and must die. + Threads are not supported by this module in any way. Perl pseudo-threads + is evil stuff and must die. As soon as Perl gains real threads I will + work on thread support for it. + +FORK + Most of the "improved" event delivering mechanisms of modern operating + systems have quite a few problems with fork(2) (to put it bluntly: it is + not supported and usually destructive). Libev makes it possible to work + around this by having a function that recreates the kernel state after + fork in the child. + + On non-win32 platforms, this module requires the pthread_atfork + functionality to do this automatically for you. This function is quite + buggy on most BSDs, though, so YMMV. The overhead for this is quite + negligible, because everything the function currently does is set a flag + that is checked only when the event loop gets used the next time, so + when you do fork but not use EV, the overhead is minimal. + + On win32, there is no notion of fork so all this doesn't apply, of + course. SEE ALSO - L, L, L, L. - L. + EV::ADNS (asynchronous DNS), Glib::EV (makes Glib/Gtk2 use EV as event + loop), EV::Glib (embed Glib into EV), Coro::EV (efficient coroutines + with EV), Net::SNMP::EV (asynchronous SNMP). AUTHOR Marc Lehmann