--- cvsroot/EV/README 2007/10/28 06:40:46 1.3 +++ cvsroot/EV/README 2007/11/14 21:25:46 1.10 @@ -1,56 +1,56 @@ 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 { - 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 - - # IO - - my $w = EV::timer_abs 0, 60, sub { - warn "is called every minute, on the minute, exactly"; - }; - - my $w = EV::io \*STDIN, EV::READ | EV::PERSIST, sub { - my ($w, $events) = @_; # all callbacks get the watcher object and event mask - if ($events & EV::TIMEOUT) { - warn "nothign received on stdin for 10 seconds, retrying"; - } else { - warn "stdin is readable, you entered: ", ; - } - }; - $w->timeout (10); - - # MAINLOOP - EV::dispatch; # loop as long as watchers are active - EV::loop; # the same thing - EV::loop EV::LOOP_ONCE; - EV::loop EV::LOOP_ONSHOT; + use EV; + + # TIMERS + + my $w = EV::timer 2, 0, sub { + warn "is called after 2s"; + }; + + 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 $w = EV::io *STDIN, EV::READ, sub { + my ($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"; + }; + + # CHILD/PID STATUS CHANGES + + my $w = EV::child 666, sub { + my ($w, $revents) = @_; + my $status = $w->rstatus; + }; + + # 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 libevent - (). You probably should acquaint - yourself with its documentation and source code to be able to use this - module fully. - - Please note thta this module disables the libevent EPOLL method by - default, see BUGS, below, if you need to enable it. + This module provides an interface to libev + (). BASIC INTERFACE - $EV::NPRI - How many priority levels are available. - $EV::DIED Must contain a reference to a function that is called when a callback throws an exception (with $@ containing thr error). The @@ -58,140 +58,401 @@ If this callback throws an exception it will be silently ignored. + $time = EV::time + Returns the current time in (fractional) seconds since the epoch. + $time = EV::now - Returns the time in (fractional) seconds since the epoch. + 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. + + $method = EV::ev_method + Returns an integer describing the backend used by libev + (EV::METHOD_SELECT or EV::METHOD_EPOLL). + + EV::loop [$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] + 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. + + WATCHER + 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 not be readable without blocking!\n" + }; + + 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 IO + 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. + + WATCHER TYPES + Now lets move to the existing watcher types and asociated methods. + + The following methods are available for all watchers. Then followes a + description of each watcher constructor (EV::io, EV::timer, + EV::periodic, EV::signal, EV::child, EV::idle, EV::prepare and + EV::check), followed by any type-specific methods (if any). - $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::dispatch - Same as "EV::loop 0". - - EV::event $callback - Creates a new event watcher waiting for nothing, calling the given - callback. + $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). - 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. + $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 wether 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. - Youc an 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. + The default priority of any newly-created weatcher is 0. - If you want a timeout to occur only after a specific time of - inactivity, set a repeating timeout and do NOT use EV::PERSIST. + $w->trigger ($revents) + Call the callback *now* with the given event mask. - Eventmask can be one or more of these constants ORed together: + $w = EV::io $fileno_or_fh, $eventmask, $callback + $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. + + 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::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. + $w->set ($fileno_or_fh, $eventmask) + Reconfigures the watcher, see the constructor above for details. Can + be called at any time. - The "timer_ns" variant doesn't add/start the newly created watcher. + $current_fh = $w->fh + $old_fh = $w->fh ($new_fh) + Returns the previously set filehandle and optionally set a new one. - 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. + $current_eventmask = $w->events + $old_eventmask = $w->events ($new_eventmask) + Returns the previously set event mask and optionally set a new one. - 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 = EV::timer $after, $repeat, $callback + $w = EV::timer_ns $after, $repeat, $callback + Calls the callback after $after seconds. 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. - If the $interval is nonzero, then the watcher will always be - scheduled to time out at the next "$at + integer * $interval" time. + The "timer_ns" variant doesn't start (activate) the newly created + watcher. + + $w->set ($after, $repeat) + Reconfigures the watcher, see the constructor above for details. Can + be 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. + + $w = EV::periodic $at, $interval, $reschedule_cb, $callback + $w = EV::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"; + }; + + The "periodic_ns" variant doesn't start (activate) the newly created + watcher. - 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). + $w->set ($at, $interval, $reschedule_cb) + Reconfigures the watcher, see the constructor above for details. Can + be at any time. + + $w->again + Simply stops and starts the watcher again. + + $w = EV::signal $signal, $callback + $w = EV::signal_ns $signal, $callback + Call the callback when $signal is received (the signal can be + specified by number or by name, just as with kill or %SIG). + + EV will grab the signal for the process (the kernel only allows one + component to receive a signal at a time) when you start a signal + watcher, and removes it again when you stop it. Perl does the same + when you add/remove callbacks to %SIG, so watch out. - Another way to think about it (for the mathematically inclined) is - that "timer_abs" will try to tun the callback at the next possible - time where "$time = $at (mod $interval)", regardless of any time - jumps. + You can have as many signal watchers per signal as you want. - The "timer_abs_ns" variant doesn't add/start the newly created + The "signal_ns" variant doesn't start (activate) the newly created watcher. - my $w = EV::signal $signum, $callback - my $w = EV::signal_ns $signum, $callback - Call the callback when signal $signum is received. + $w->set ($signal) + Reconfigures the watcher, see the constructor above for details. Can + be 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. + + $w = EV::child $pid, $callback + $w = EV::child_ns $pid, $callback + Call the callback when a status change for pid $pid (or any pid if + $pid is 0) has been received. 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. - The "signal_ns" variant doesn't add/start the newly created watcher. + You can access both status and pid by using the "rstatus" and "rpid" + methods on the watcher object. -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: + You can have as many pid watchers per pid as you want. - $w->add ($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 "child_ns" variant doesn't start (activate) the newly created + watcher. - $w->start - Stops and (re-)starts the event watcher without touching the - timeout. + $w->set ($pid) + Reconfigures the watcher, see the constructor above for details. Can + be at any time. + + $current_pid = $w->pid + $old_pid = $w->pid ($new_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). + + $w = EV::idle $callback + $w = EV::idle_ns $callback + Call the callback when there are no pending io, timer/periodic, + signal or child events, i.e. when the process is idle. - $w->del - $w->stop - Stop the event watcher if it was started. + The process will not block as long as any idle watchers are active, + and they will be called repeatedly until stopped. - $current_callback = $w->cb - $old_callback = $w->cb ($new_callback) - Return the previously set callback and optionally set a new one. + The "idle_ns" variant doesn't start (activate) the newly created + watcher. - $current_fh = $w->fh - $old_fh = $w->fh ($new_fh) - Returns the previously set filehandle and optionally set a new one. + $w = EV::prepare $callback + $w = EV::prepare_ns $callback + Call the callback just before the process would block. You can still + create/modify any watchers at this point. - $current_eventmask = $w->events - $old_eventmask = $w->events ($new_eventmask) - Returns the previously set event mask and optionally set a new one. + See the EV::check watcher, below, for explanations and an example. - $w->timeout ($after, $repeat) - Resets the timeout (see "EV::timer" for details). + The "prepare_ns" variant doesn't start (activate) the newly created + watcher. - $w->timeout_abs ($at, $interval) - Resets the timeout (see "EV::timer_abs" for details). + $w = EV::check $callback + $w = EV::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 + + # create an IO watcher for each and every socket + @snmp_watcher = ( + (map { EV::io $_, EV::READ, sub { } } + keys %{ $dispatcher->{_descriptors} }), + ); + + # if there are any timeouts, also create a timer + push @snmp_watcher, EV::timer $event->[Net::SNMP::Dispatcher::_TIME] - EV::now, 0, sub { } + if $event->[Net::SNMP::Dispatcher::_ACTIVE]; + }; + + The callbacks are irrelevant, 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 + }; + + 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). - $w->priority_set ($priority) - Set the priority of the watcher to $priority (0 <= $priority < - $EV::NPRI). - -BUGS - Lots. Libevent itself isn't well tested and rather buggy, and this - module is quite new at the moment. - - Please note that the epoll method is not, in general, reliable in - programs that use fork (even if no libveent calls are being made in the - forked process). If your program behaves erratically, try setting the - environment variable "EVENT_NOEPOLL" first when running the program. + The "check_ns" variant doesn't start (activate) the newly created + watcher. - In general, if you fork, then you can only use the EV module in one of - the children. +THREADS + Threads are not supported by this in any way. Perl pseudo-threads is + evil stuff and must die. SEE ALSO - L, L, L, L. - L. + L, L. AUTHOR Marc Lehmann