1 | NAME |
1 | NAME |
2 | AnyEvent - provide framework for multiple event loops |
2 | AnyEvent - provide framework for multiple event loops |
3 | |
3 | |
4 | Event, Coro, Glib, Tk, Perl - various supported event loops |
4 | EV, Event, Coro::EV, Coro::Event, Glib, Tk, Perl, Event::Lib, Qt - |
|
|
5 | various supported event loops |
5 | |
6 | |
6 | SYNOPSIS |
7 | SYNOPSIS |
7 | use AnyEvent; |
8 | use AnyEvent; |
8 | |
9 | |
9 | my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub { |
10 | my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub { |
… | |
… | |
12 | |
13 | |
13 | my $w = AnyEvent->timer (after => $seconds, cb => sub { |
14 | my $w = AnyEvent->timer (after => $seconds, cb => sub { |
14 | ... |
15 | ... |
15 | }); |
16 | }); |
16 | |
17 | |
17 | my $w = AnyEvent->condvar; # stores wether a condition was flagged |
18 | my $w = AnyEvent->condvar; # stores whether a condition was flagged |
18 | $w->wait; # enters "main loop" till $condvar gets ->broadcast |
19 | $w->wait; # enters "main loop" till $condvar gets ->broadcast |
19 | $w->broadcast; # wake up current and all future wait's |
20 | $w->broadcast; # wake up current and all future wait's |
|
|
21 | |
|
|
22 | WHY YOU SHOULD USE THIS MODULE (OR NOT) |
|
|
23 | Glib, POE, IO::Async, Event... CPAN offers event models by the dozen |
|
|
24 | nowadays. So what is different about AnyEvent? |
|
|
25 | |
|
|
26 | Executive Summary: AnyEvent is *compatible*, AnyEvent is *free of |
|
|
27 | policy* and AnyEvent is *small and efficient*. |
|
|
28 | |
|
|
29 | First and foremost, *AnyEvent is not an event model* itself, it only |
|
|
30 | interfaces to whatever event model the main program happens to use in a |
|
|
31 | pragmatic way. For event models and certain classes of immortals alike, |
|
|
32 | the statement "there can only be one" is a bitter reality: In general, |
|
|
33 | only one event loop can be active at the same time in a process. |
|
|
34 | AnyEvent helps hiding the differences between those event loops. |
|
|
35 | |
|
|
36 | The goal of AnyEvent is to offer module authors the ability to do event |
|
|
37 | programming (waiting for I/O or timer events) without subscribing to a |
|
|
38 | religion, a way of living, and most importantly: without forcing your |
|
|
39 | module users into the same thing by forcing them to use the same event |
|
|
40 | model you use. |
|
|
41 | |
|
|
42 | For modules like POE or IO::Async (which is a total misnomer as it is |
|
|
43 | actually doing all I/O *synchronously*...), using them in your module is |
|
|
44 | like joining a cult: After you joined, you are dependent on them and you |
|
|
45 | cannot use anything else, as it is simply incompatible to everything |
|
|
46 | that isn't itself. What's worse, all the potential users of your module |
|
|
47 | are *also* forced to use the same event loop you use. |
|
|
48 | |
|
|
49 | AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works |
|
|
50 | fine. AnyEvent + Tk works fine etc. etc. but none of these work together |
|
|
51 | with the rest: POE + IO::Async? no go. Tk + Event? no go. Again: if your |
|
|
52 | module uses one of those, every user of your module has to use it, too. |
|
|
53 | But if your module uses AnyEvent, it works transparently with all event |
|
|
54 | models it supports (including stuff like POE and IO::Async, as long as |
|
|
55 | those use one of the supported event loops. It is trivial to add new |
|
|
56 | event loops to AnyEvent, too, so it is future-proof). |
|
|
57 | |
|
|
58 | In addition to being free of having to use *the one and only true event |
|
|
59 | model*, AnyEvent also is free of bloat and policy: with POE or similar |
|
|
60 | modules, you get an enourmous amount of code and strict rules you have |
|
|
61 | to follow. AnyEvent, on the other hand, is lean and up to the point, by |
|
|
62 | only offering the functionality that is necessary, in as thin as a |
|
|
63 | wrapper as technically possible. |
|
|
64 | |
|
|
65 | Of course, if you want lots of policy (this can arguably be somewhat |
|
|
66 | useful) and you want to force your users to use the one and only event |
|
|
67 | model, you should *not* use this module. |
20 | |
68 | |
21 | DESCRIPTION |
69 | DESCRIPTION |
22 | AnyEvent provides an identical interface to multiple event loops. This |
70 | AnyEvent provides an identical interface to multiple event loops. This |
23 | allows module authors to utilise an event loop without forcing module |
71 | allows module authors to utilise an event loop without forcing module |
24 | users to use the same event loop (as only a single event loop can |
72 | users to use the same event loop (as only a single event loop can |
25 | coexist peacefully at any one time). |
73 | coexist peacefully at any one time). |
26 | |
74 | |
27 | The interface itself is vaguely similar but not identical to the Event |
75 | The interface itself is vaguely similar, but not identical to the Event |
28 | module. |
76 | module. |
29 | |
77 | |
30 | On the first call of any method, the module tries to detect the |
78 | During the first call of any watcher-creation method, the module tries |
31 | currently loaded event loop by probing wether any of the following |
79 | to detect the currently loaded event loop by probing whether one of the |
32 | modules is loaded: Coro::Event, Event, Glib, Tk. The first one found is |
80 | following modules is already loaded: Coro::EV, Coro::Event, EV, Event, |
33 | used. If none is found, the module tries to load these modules in the |
81 | Glib, Tk, Event::Lib, Qt. The first one found is used. If none are |
|
|
82 | found, the module tries to load these modules (excluding Event::Lib and |
34 | order given. The first one that could be successfully loaded will be |
83 | Qt) in the order given. The first one that can be successfully loaded |
35 | used. If still none could be found, AnyEvent will fall back to a |
84 | will be used. If, after this, still none could be found, AnyEvent will |
36 | pure-perl event loop, which is also not very efficient. |
85 | fall back to a pure-perl event loop, which is not very efficient, but |
|
|
86 | should work everywhere. |
37 | |
87 | |
38 | Because AnyEvent first checks for modules that are already loaded, |
88 | Because AnyEvent first checks for modules that are already loaded, |
39 | loading an Event model explicitly before first using AnyEvent will |
89 | loading an event model explicitly before first using AnyEvent will |
40 | likely make that model the default. For example: |
90 | likely make that model the default. For example: |
41 | |
91 | |
42 | use Tk; |
92 | use Tk; |
43 | use AnyEvent; |
93 | use AnyEvent; |
44 | |
94 | |
45 | # .. AnyEvent will likely default to Tk |
95 | # .. AnyEvent will likely default to Tk |
|
|
96 | |
|
|
97 | The *likely* means that, if any module loads another event model and |
|
|
98 | starts using it, all bets are off. Maybe you should tell their authors |
|
|
99 | to use AnyEvent so their modules work together with others seamlessly... |
46 | |
100 | |
47 | The pure-perl implementation of AnyEvent is called |
101 | The pure-perl implementation of AnyEvent is called |
48 | "AnyEvent::Impl::Perl". Like other event modules you can load it |
102 | "AnyEvent::Impl::Perl". Like other event modules you can load it |
49 | explicitly. |
103 | explicitly. |
50 | |
104 | |
… | |
… | |
53 | stores relevant data for each kind of event you are waiting for, such as |
107 | stores relevant data for each kind of event you are waiting for, such as |
54 | the callback to call, the filehandle to watch, etc. |
108 | the callback to call, the filehandle to watch, etc. |
55 | |
109 | |
56 | These watchers are normal Perl objects with normal Perl lifetime. After |
110 | These watchers are normal Perl objects with normal Perl lifetime. After |
57 | creating a watcher it will immediately "watch" for events and invoke the |
111 | creating a watcher it will immediately "watch" for events and invoke the |
|
|
112 | callback when the event occurs (of course, only when the event model is |
|
|
113 | in control). |
|
|
114 | |
58 | callback. To disable the watcher you have to destroy it (e.g. by setting |
115 | To disable the watcher you have to destroy it (e.g. by setting the |
59 | the variable that stores it to "undef" or otherwise deleting all |
116 | variable you store it in to "undef" or otherwise deleting all references |
60 | references to it). |
117 | to it). |
61 | |
118 | |
62 | All watchers are created by calling a method on the "AnyEvent" class. |
119 | All watchers are created by calling a method on the "AnyEvent" class. |
63 | |
120 | |
|
|
121 | Many watchers either are used with "recursion" (repeating timers for |
|
|
122 | example), or need to refer to their watcher object in other ways. |
|
|
123 | |
|
|
124 | An any way to achieve that is this pattern: |
|
|
125 | |
|
|
126 | my $w; $w = AnyEvent->type (arg => value ..., cb => sub { |
|
|
127 | # you can use $w here, for example to undef it |
|
|
128 | undef $w; |
|
|
129 | }); |
|
|
130 | |
|
|
131 | Note that "my $w; $w =" combination. This is necessary because in Perl, |
|
|
132 | my variables are only visible after the statement in which they are |
|
|
133 | declared. |
|
|
134 | |
64 | IO WATCHERS |
135 | IO WATCHERS |
65 | You can create I/O watcher by calling the "AnyEvent->io" method with the |
136 | You can create an I/O watcher by calling the "AnyEvent->io" method with |
66 | following mandatory arguments: |
137 | the following mandatory key-value pairs as arguments: |
67 | |
138 | |
68 | "fh" the Perl *filehandle* (not filedescriptor) to watch for events. |
139 | "fh" the Perl *file handle* (*not* file descriptor) to watch for events. |
69 | "poll" must be a string that is either "r" or "w", that creates a |
140 | "poll" must be a string that is either "r" or "w", which creates a |
70 | watcher waiting for "r"eadable or "w"ritable events. "cb" teh callback |
141 | watcher waiting for "r"eadable or "w"ritable events, respectively. "cb" |
71 | to invoke everytime the filehandle becomes ready. |
142 | is the callback to invoke each time the file handle becomes ready. |
72 | |
143 | |
73 | Only one io watcher per "fh" and "poll" combination is allowed (i.e. on |
144 | As long as the I/O watcher exists it will keep the file descriptor or a |
74 | a socket you can have one r + one w, not any more (limitation comes from |
145 | copy of it alive/open. |
75 | Tk - if you are sure you are not using Tk this limitation is gone). |
|
|
76 | |
146 | |
77 | Filehandles will be kept alive, so as long as the watcher exists, the |
147 | It is not allowed to close a file handle as long as any watcher is |
78 | filehandle exists, too. |
148 | active on the underlying file descriptor. |
|
|
149 | |
|
|
150 | Some event loops issue spurious readyness notifications, so you should |
|
|
151 | always use non-blocking calls when reading/writing from/to your file |
|
|
152 | handles. |
79 | |
153 | |
80 | Example: |
154 | Example: |
81 | |
155 | |
82 | # wait for readability of STDIN, then read a line and disable the watcher |
156 | # wait for readability of STDIN, then read a line and disable the watcher |
83 | my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { |
157 | my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { |
… | |
… | |
88 | |
162 | |
89 | TIME WATCHERS |
163 | TIME WATCHERS |
90 | You can create a time watcher by calling the "AnyEvent->timer" method |
164 | You can create a time watcher by calling the "AnyEvent->timer" method |
91 | with the following mandatory arguments: |
165 | with the following mandatory arguments: |
92 | |
166 | |
93 | "after" after how many seconds (fractions are supported) should the |
167 | "after" specifies after how many seconds (fractional values are |
94 | timer activate. "cb" the callback to invoke. |
168 | supported) should the timer activate. "cb" the callback to invoke in |
|
|
169 | that case. |
95 | |
170 | |
96 | The timer callback will be invoked at most once: if you want a repeating |
171 | The timer callback will be invoked at most once: if you want a repeating |
97 | timer you have to create a new watcher (this is a limitation by both Tk |
172 | timer you have to create a new watcher (this is a limitation by both Tk |
98 | and Glib). |
173 | and Glib). |
99 | |
174 | |
… | |
… | |
103 | my $w = AnyEvent->timer (after => 7.7, cb => sub { |
178 | my $w = AnyEvent->timer (after => 7.7, cb => sub { |
104 | warn "timeout\n"; |
179 | warn "timeout\n"; |
105 | }); |
180 | }); |
106 | |
181 | |
107 | # to cancel the timer: |
182 | # to cancel the timer: |
108 | undef $w |
183 | undef $w; |
109 | |
184 | |
110 | CONDITION WATCHERS |
185 | Example 2: |
|
|
186 | |
|
|
187 | # fire an event after 0.5 seconds, then roughly every second |
|
|
188 | my $w; |
|
|
189 | |
|
|
190 | my $cb = sub { |
|
|
191 | # cancel the old timer while creating a new one |
|
|
192 | $w = AnyEvent->timer (after => 1, cb => $cb); |
|
|
193 | }; |
|
|
194 | |
|
|
195 | # start the "loop" by creating the first watcher |
|
|
196 | $w = AnyEvent->timer (after => 0.5, cb => $cb); |
|
|
197 | |
|
|
198 | TIMING ISSUES |
|
|
199 | There are two ways to handle timers: based on real time (relative, "fire |
|
|
200 | in 10 seconds") and based on wallclock time (absolute, "fire at 12 |
|
|
201 | o'clock"). |
|
|
202 | |
|
|
203 | While most event loops expect timers to specified in a relative way, |
|
|
204 | they use absolute time internally. This makes a difference when your |
|
|
205 | clock "jumps", for example, when ntp decides to set your clock backwards |
|
|
206 | from the wrong date of 2014-01-01 to 2008-01-01, a watcher that is |
|
|
207 | supposed to fire "after" a second might actually take six years to |
|
|
208 | finally fire. |
|
|
209 | |
|
|
210 | AnyEvent cannot compensate for this. The only event loop that is |
|
|
211 | conscious about these issues is EV, which offers both relative |
|
|
212 | (ev_timer, based on true relative time) and absolute (ev_periodic, based |
|
|
213 | on wallclock time) timers. |
|
|
214 | |
|
|
215 | AnyEvent always prefers relative timers, if available, matching the |
|
|
216 | AnyEvent API. |
|
|
217 | |
|
|
218 | SIGNAL WATCHERS |
|
|
219 | You can watch for signals using a signal watcher, "signal" is the signal |
|
|
220 | *name* without any "SIG" prefix, "cb" is the Perl callback to be invoked |
|
|
221 | whenever a signal occurs. |
|
|
222 | |
|
|
223 | Multiple signal occurances can be clumped together into one callback |
|
|
224 | invocation, and callback invocation will be synchronous. synchronous |
|
|
225 | means that it might take a while until the signal gets handled by the |
|
|
226 | process, but it is guarenteed not to interrupt any other callbacks. |
|
|
227 | |
|
|
228 | The main advantage of using these watchers is that you can share a |
|
|
229 | signal between multiple watchers. |
|
|
230 | |
|
|
231 | This watcher might use %SIG, so programs overwriting those signals |
|
|
232 | directly will likely not work correctly. |
|
|
233 | |
|
|
234 | Example: exit on SIGINT |
|
|
235 | |
|
|
236 | my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 }); |
|
|
237 | |
|
|
238 | CHILD PROCESS WATCHERS |
|
|
239 | You can also watch on a child process exit and catch its exit status. |
|
|
240 | |
|
|
241 | The child process is specified by the "pid" argument (if set to 0, it |
|
|
242 | watches for any child process exit). The watcher will trigger as often |
|
|
243 | as status change for the child are received. This works by installing a |
|
|
244 | signal handler for "SIGCHLD". The callback will be called with the pid |
|
|
245 | and exit status (as returned by waitpid). |
|
|
246 | |
|
|
247 | Example: wait for pid 1333 |
|
|
248 | |
|
|
249 | my $w = AnyEvent->child ( |
|
|
250 | pid => 1333, |
|
|
251 | cb => sub { |
|
|
252 | my ($pid, $status) = @_; |
|
|
253 | warn "pid $pid exited with status $status"; |
|
|
254 | }, |
|
|
255 | ); |
|
|
256 | |
|
|
257 | CONDITION VARIABLES |
111 | Condition watchers can be created by calling the "AnyEvent->condvar" |
258 | Condition variables can be created by calling the "AnyEvent->condvar" |
112 | method without any arguments. |
259 | method without any arguments. |
113 | |
260 | |
114 | A condition watcher watches for a condition - precisely that the |
261 | A condition variable waits for a condition - precisely that the |
115 | "->broadcast" method has been called. |
262 | "->broadcast" method has been called. |
116 | |
263 | |
117 | The watcher has only two methods: |
264 | They are very useful to signal that a condition has been fulfilled, for |
|
|
265 | example, if you write a module that does asynchronous http requests, |
|
|
266 | then a condition variable would be the ideal candidate to signal the |
|
|
267 | availability of results. |
|
|
268 | |
|
|
269 | You can also use condition variables to block your main program until an |
|
|
270 | event occurs - for example, you could "->wait" in your main program |
|
|
271 | until the user clicks the Quit button in your app, which would |
|
|
272 | "->broadcast" the "quit" event. |
|
|
273 | |
|
|
274 | Note that condition variables recurse into the event loop - if you have |
|
|
275 | two pirces of code that call "->wait" in a round-robbin fashion, you |
|
|
276 | lose. Therefore, condition variables are good to export to your caller, |
|
|
277 | but you should avoid making a blocking wait yourself, at least in |
|
|
278 | callbacks, as this asks for trouble. |
|
|
279 | |
|
|
280 | This object has two methods: |
118 | |
281 | |
119 | $cv->wait |
282 | $cv->wait |
120 | Wait (blocking if necessary) until the "->broadcast" method has been |
283 | Wait (blocking if necessary) until the "->broadcast" method has been |
121 | called on c<$cv>, while servicing other watchers normally. |
284 | called on c<$cv>, while servicing other watchers normally. |
122 | |
285 | |
123 | Not all event models support a blocking wait - some die in that |
|
|
124 | case, so if you are using this from a module, never require a |
|
|
125 | blocking wait, but let the caller decide wether the call will block |
|
|
126 | or not (for example, by coupling condition variables with some kind |
|
|
127 | of request results and supporting callbacks so the caller knows that |
|
|
128 | getting the result will not block, while still suppporting blockign |
|
|
129 | waits if the caller so desires). |
|
|
130 | |
|
|
131 | You can only wait once on a condition - additional calls will return |
286 | You can only wait once on a condition - additional calls will return |
132 | immediately. |
287 | immediately. |
133 | |
288 | |
|
|
289 | Not all event models support a blocking wait - some die in that case |
|
|
290 | (programs might want to do that to stay interactive), so *if you are |
|
|
291 | using this from a module, never require a blocking wait*, but let |
|
|
292 | the caller decide whether the call will block or not (for example, |
|
|
293 | by coupling condition variables with some kind of request results |
|
|
294 | and supporting callbacks so the caller knows that getting the result |
|
|
295 | will not block, while still suppporting blocking waits if the caller |
|
|
296 | so desires). |
|
|
297 | |
|
|
298 | Another reason *never* to "->wait" in a module is that you cannot |
|
|
299 | sensibly have two "->wait"'s in parallel, as that would require |
|
|
300 | multiple interpreters or coroutines/threads, none of which |
|
|
301 | "AnyEvent" can supply (the coroutine-aware backends |
|
|
302 | AnyEvent::Impl::CoroEV and AnyEvent::Impl::CoroEvent explicitly |
|
|
303 | support concurrent "->wait"'s from different coroutines, however). |
|
|
304 | |
134 | $cv->broadcast |
305 | $cv->broadcast |
135 | Flag the condition as ready - a running "->wait" and all further |
306 | Flag the condition as ready - a running "->wait" and all further |
136 | calls to "wait" will return after this method has been called. If |
307 | calls to "wait" will (eventually) return after this method has been |
137 | nobody is waiting the broadcast will be remembered.. |
308 | called. If nobody is waiting the broadcast will be remembered.. |
138 | |
309 | |
139 | Example: |
310 | Example: |
140 | |
311 | |
141 | # wait till the result is ready |
312 | # wait till the result is ready |
142 | my $result_ready = AnyEvent->condvar; |
313 | my $result_ready = AnyEvent->condvar; |
143 | |
314 | |
144 | # do something such as adding a timer |
315 | # do something such as adding a timer |
145 | # or socket watcher the calls $result_ready->broadcast |
316 | # or socket watcher the calls $result_ready->broadcast |
146 | # when the "result" is ready. |
317 | # when the "result" is ready. |
|
|
318 | # in this case, we simply use a timer: |
|
|
319 | my $w = AnyEvent->timer ( |
|
|
320 | after => 1, |
|
|
321 | cb => sub { $result_ready->broadcast }, |
|
|
322 | ); |
147 | |
323 | |
|
|
324 | # this "blocks" (while handling events) till the watcher |
|
|
325 | # calls broadcast |
148 | $result_ready->wait; |
326 | $result_ready->wait; |
149 | |
327 | |
150 | SIGNAL WATCHERS |
328 | GLOBAL VARIABLES AND FUNCTIONS |
151 | You can listen for signals using a signal watcher, "signal" is the |
|
|
152 | signal *name* without any "SIG" prefix. Multiple signals events can be |
|
|
153 | clumped together into one callback invocation, and callback invocation |
|
|
154 | might or might not be asynchronous. |
|
|
155 | |
|
|
156 | These watchers might use %SIG, so programs overwriting those signals |
|
|
157 | directly will likely not work correctly. |
|
|
158 | |
|
|
159 | Example: exit on SIGINT |
|
|
160 | |
|
|
161 | my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 }); |
|
|
162 | |
|
|
163 | CHILD PROCESS WATCHERS |
|
|
164 | You can also listen for the status of a child process specified by the |
|
|
165 | "pid" argument (or any child if the pid argument is 0). The watcher will |
|
|
166 | trigger as often as status change for the child are received. This works |
|
|
167 | by installing a signal handler for "SIGCHLD". The callback will be |
|
|
168 | called with the pid and exit status (as returned by waitpid). |
|
|
169 | |
|
|
170 | Example: wait for pid 1333 |
|
|
171 | |
|
|
172 | my $w = AnyEvent->child (pid => 1333, cb => sub { warn "exit status $?" }); |
|
|
173 | |
|
|
174 | GLOBALS |
|
|
175 | $AnyEvent::MODEL |
329 | $AnyEvent::MODEL |
176 | Contains "undef" until the first watcher is being created. Then it |
330 | Contains "undef" until the first watcher is being created. Then it |
177 | contains the event model that is being used, which is the name of |
331 | contains the event model that is being used, which is the name of |
178 | the Perl class implementing the model. This class is usually one of |
332 | the Perl class implementing the model. This class is usually one of |
179 | the "AnyEvent::Impl:xxx" modules, but can be any other class in the |
333 | the "AnyEvent::Impl:xxx" modules, but can be any other class in the |
180 | case AnyEvent has been extended at runtime (e.g. in *rxvt-unicode*). |
334 | case AnyEvent has been extended at runtime (e.g. in *rxvt-unicode*). |
181 | |
335 | |
182 | The known classes so far are: |
336 | The known classes so far are: |
183 | |
337 | |
184 | AnyEvent::Impl::CoroEV based on Coro::EV, best choice. |
338 | AnyEvent::Impl::CoroEV based on Coro::EV, best choice. |
|
|
339 | AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice. |
185 | AnyEvent::Impl::EV based on EV (an interface to libev, also best choice). |
340 | AnyEvent::Impl::EV based on EV (an interface to libev, best choice). |
186 | AnyEvent::Impl::Coro based on Coro::Event, second best choice. |
|
|
187 | AnyEvent::Impl::Event based on Event, also second best choice :) |
341 | AnyEvent::Impl::Event based on Event, second best choice. |
188 | AnyEvent::Impl::Glib based on Glib, second-best choice. |
342 | AnyEvent::Impl::Glib based on Glib, third-best choice. |
189 | AnyEvent::Impl::Tk based on Tk, very bad choice. |
343 | AnyEvent::Impl::Tk based on Tk, very bad choice. |
190 | AnyEvent::Impl::Perl pure-perl implementation, inefficient. |
344 | AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable. |
|
|
345 | AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs). |
|
|
346 | AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse. |
191 | |
347 | |
192 | AnyEvent::detect |
348 | AnyEvent::detect |
193 | Returns $AnyEvent::MODEL, forcing autodetection of the event model |
349 | Returns $AnyEvent::MODEL, forcing autodetection of the event model |
194 | if necessary. You should only call this function right before you |
350 | if necessary. You should only call this function right before you |
195 | would have created an AnyEvent watcher anyway, that is, very late at |
351 | would have created an AnyEvent watcher anyway, that is, as late as |
196 | runtime. |
352 | possible at runtime. |
197 | |
353 | |
198 | WHAT TO DO IN A MODULE |
354 | WHAT TO DO IN A MODULE |
199 | As a module author, you should "use AnyEvent" and call AnyEvent methods |
355 | As a module author, you should "use AnyEvent" and call AnyEvent methods |
200 | freely, but you should not load a specific event module or rely on it. |
356 | freely, but you should not load a specific event module or rely on it. |
201 | |
357 | |
202 | Be careful when you create watchers in the module body - Anyevent will |
358 | Be careful when you create watchers in the module body - AnyEvent will |
203 | decide which event module to use as soon as the first method is called, |
359 | decide which event module to use as soon as the first method is called, |
204 | so by calling AnyEvent in your module body you force the user of your |
360 | so by calling AnyEvent in your module body you force the user of your |
205 | module to load the event module first. |
361 | module to load the event module first. |
206 | |
362 | |
|
|
363 | Never call "->wait" on a condition variable unless you *know* that the |
|
|
364 | "->broadcast" method has been called on it already. This is because it |
|
|
365 | will stall the whole program, and the whole point of using events is to |
|
|
366 | stay interactive. |
|
|
367 | |
|
|
368 | It is fine, however, to call "->wait" when the user of your module |
|
|
369 | requests it (i.e. if you create a http request object ad have a method |
|
|
370 | called "results" that returns the results, it should call "->wait" |
|
|
371 | freely, as the user of your module knows what she is doing. always). |
|
|
372 | |
207 | WHAT TO DO IN THE MAIN PROGRAM |
373 | WHAT TO DO IN THE MAIN PROGRAM |
208 | There will always be a single main program - the only place that should |
374 | There will always be a single main program - the only place that should |
209 | dictate which event model to use. |
375 | dictate which event model to use. |
210 | |
376 | |
211 | If it doesn't care, it can just "use AnyEvent" and use it itself, or not |
377 | If it doesn't care, it can just "use AnyEvent" and use it itself, or not |
212 | do anything special and let AnyEvent decide which implementation to |
378 | do anything special (it does not need to be event-based) and let |
213 | chose. |
379 | AnyEvent decide which implementation to chose if some module relies on |
|
|
380 | it. |
214 | |
381 | |
215 | If the main program relies on a specific event model (for example, in |
382 | If the main program relies on a specific event model. For example, in |
216 | Gtk2 programs you have to rely on either Glib or Glib::Event), you |
383 | Gtk2 programs you have to rely on the Glib module. You should load the |
217 | should load it before loading AnyEvent or any module that uses it, |
384 | event module before loading AnyEvent or any module that uses it: |
218 | generally, as early as possible. The reason is that modules might create |
385 | generally speaking, you should load it as early as possible. The reason |
219 | watchers when they are loaded, and AnyEvent will decide on the event |
386 | is that modules might create watchers when they are loaded, and AnyEvent |
220 | model to use as soon as it creates watchers, and it might chose the |
387 | will decide on the event model to use as soon as it creates watchers, |
221 | wrong one unless you load the correct one yourself. |
388 | and it might chose the wrong one unless you load the correct one |
|
|
389 | yourself. |
222 | |
390 | |
223 | You can chose to use a rather inefficient pure-perl implementation by |
391 | You can chose to use a rather inefficient pure-perl implementation by |
224 | loading the "AnyEvent::Impl::Perl" module, but letting AnyEvent chose is |
392 | loading the "AnyEvent::Impl::Perl" module, which gives you similar |
225 | generally better. |
393 | behaviour everywhere, but letting AnyEvent chose is generally better. |
226 | |
394 | |
227 | SUPPLYING YOUR OWN EVENT MODEL INTERFACE |
395 | SUPPLYING YOUR OWN EVENT MODEL INTERFACE |
|
|
396 | This is an advanced topic that you do not normally need to use AnyEvent |
|
|
397 | in a module. This section is only of use to event loop authors who want |
|
|
398 | to provide AnyEvent compatibility. |
|
|
399 | |
228 | If you need to support another event library which isn't directly |
400 | If you need to support another event library which isn't directly |
229 | supported by AnyEvent, you can supply your own interface to it by |
401 | supported by AnyEvent, you can supply your own interface to it by |
230 | pushing, before the first watcher gets created, the package name of the |
402 | pushing, before the first watcher gets created, the package name of the |
231 | event module and the package name of the interface to use onto |
403 | event module and the package name of the interface to use onto |
232 | @AnyEvent::REGISTRY. You can do that before and even without loading |
404 | @AnyEvent::REGISTRY. You can do that before and even without loading |
233 | AnyEvent. |
405 | AnyEvent, so it is reasonably cheap. |
234 | |
406 | |
235 | Example: |
407 | Example: |
236 | |
408 | |
237 | push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::]; |
409 | push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::]; |
238 | |
410 | |
239 | This tells AnyEvent to (literally) use the "urxvt::anyevent::" |
411 | This tells AnyEvent to (literally) use the "urxvt::anyevent::" |
240 | package/class when it finds the "urxvt" package/module is loaded. When |
412 | package/class when it finds the "urxvt" package/module is already |
|
|
413 | loaded. |
|
|
414 | |
241 | AnyEvent is loaded and asked to find a suitable event model, it will |
415 | When AnyEvent is loaded and asked to find a suitable event model, it |
242 | first check for the presence of urxvt. |
416 | will first check for the presence of urxvt by trying to "use" the |
|
|
417 | "urxvt::anyevent" module. |
243 | |
418 | |
244 | The class should provide implementations for all watcher types (see |
419 | The class should provide implementations for all watcher types. See |
245 | AnyEvent::Impl::Event (source code), AnyEvent::Impl::Glib (Source code) |
420 | AnyEvent::Impl::EV (source code), AnyEvent::Impl::Glib (Source code) and |
246 | and so on for actual examples, use "perldoc -m AnyEvent::Impl::Glib" to |
421 | so on for actual examples. Use "perldoc -m AnyEvent::Impl::Glib" to see |
247 | see the sources). |
422 | the sources. |
248 | |
423 | |
|
|
424 | If you don't provide "signal" and "child" watchers than AnyEvent will |
|
|
425 | provide suitable (hopefully) replacements. |
|
|
426 | |
249 | The above isn't fictitious, the *rxvt-unicode* (a.k.a. urxvt) uses the |
427 | The above example isn't fictitious, the *rxvt-unicode* (a.k.a. urxvt) |
250 | above line as-is. An interface isn't included in AnyEvent because it |
428 | terminal emulator uses the above line as-is. An interface isn't included |
251 | doesn't make sense outside the embedded interpreter inside |
429 | in AnyEvent because it doesn't make sense outside the embedded |
252 | *rxvt-unicode*, and it is updated and maintained as part of the |
430 | interpreter inside *rxvt-unicode*, and it is updated and maintained as |
253 | *rxvt-unicode* distribution. |
431 | part of the *rxvt-unicode* distribution. |
254 | |
432 | |
255 | *rxvt-unicode* also cheats a bit by not providing blocking access to |
433 | *rxvt-unicode* also cheats a bit by not providing blocking access to |
256 | condition variables: code blocking while waiting for a condition will |
434 | condition variables: code blocking while waiting for a condition will |
257 | "die". This still works with most modules/usages, and blocking calls |
435 | "die". This still works with most modules/usages, and blocking calls |
258 | must not be in an interactive application, so it makes sense. |
436 | must not be done in an interactive application, so it makes sense. |
259 | |
437 | |
260 | ENVIRONMENT VARIABLES |
438 | ENVIRONMENT VARIABLES |
261 | The following environment variables are used by this module: |
439 | The following environment variables are used by this module: |
262 | |
440 | |
263 | "PERL_ANYEVENT_VERBOSE" when set to 2 or higher, reports which event |
441 | "PERL_ANYEVENT_VERBOSE" |
264 | model gets used. |
442 | When set to 2 or higher, cause AnyEvent to report to STDERR which |
|
|
443 | event model it chooses. |
265 | |
444 | |
266 | EXAMPLE |
445 | "PERL_ANYEVENT_MODEL" |
|
|
446 | This can be used to specify the event model to be used by AnyEvent, |
|
|
447 | before autodetection and -probing kicks in. It must be a string |
|
|
448 | consisting entirely of ASCII letters. The string "AnyEvent::Impl::" |
|
|
449 | gets prepended and the resulting module name is loaded and if the |
|
|
450 | load was successful, used as event model. If it fails to load |
|
|
451 | AnyEvent will proceed with autodetection and -probing. |
|
|
452 | |
|
|
453 | This functionality might change in future versions. |
|
|
454 | |
|
|
455 | For example, to force the pure perl model (AnyEvent::Impl::Perl) you |
|
|
456 | could start your program like this: |
|
|
457 | |
|
|
458 | PERL_ANYEVENT_MODEL=Perl perl ... |
|
|
459 | |
|
|
460 | EXAMPLE PROGRAM |
267 | The following program uses an io watcher to read data from stdin, a |
461 | The following program uses an IO watcher to read data from STDIN, a |
268 | timer to display a message once per second, and a condvar to exit the |
462 | timer to display a message once per second, and a condition variable to |
269 | program when the user enters quit: |
463 | quit the program when the user enters quit: |
270 | |
464 | |
271 | use AnyEvent; |
465 | use AnyEvent; |
272 | |
466 | |
273 | my $cv = AnyEvent->condvar; |
467 | my $cv = AnyEvent->condvar; |
274 | |
468 | |
275 | my $io_watcher = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { |
469 | my $io_watcher = AnyEvent->io ( |
|
|
470 | fh => \*STDIN, |
|
|
471 | poll => 'r', |
|
|
472 | cb => sub { |
276 | warn "io event <$_[0]>\n"; # will always output <r> |
473 | warn "io event <$_[0]>\n"; # will always output <r> |
277 | chomp (my $input = <STDIN>); # read a line |
474 | chomp (my $input = <STDIN>); # read a line |
278 | warn "read: $input\n"; # output what has been read |
475 | warn "read: $input\n"; # output what has been read |
279 | $cv->broadcast if $input =~ /^q/i; # quit program if /^q/i |
476 | $cv->broadcast if $input =~ /^q/i; # quit program if /^q/i |
|
|
477 | }, |
280 | }); |
478 | ); |
281 | |
479 | |
282 | my $time_watcher; # can only be used once |
480 | my $time_watcher; # can only be used once |
283 | |
481 | |
284 | sub new_timer { |
482 | sub new_timer { |
285 | $timer = AnyEvent->timer (after => 1, cb => sub { |
483 | $timer = AnyEvent->timer (after => 1, cb => sub { |
… | |
… | |
366 | $txn->{finished}->wait; |
564 | $txn->{finished}->wait; |
367 | return $txn->{result}; |
565 | return $txn->{result}; |
368 | |
566 | |
369 | The actual code goes further and collects all errors ("die"s, |
567 | The actual code goes further and collects all errors ("die"s, |
370 | exceptions) that occured during request processing. The "result" method |
568 | exceptions) that occured during request processing. The "result" method |
371 | detects wether an exception as thrown (it is stored inside the $txn |
569 | detects whether an exception as thrown (it is stored inside the $txn |
372 | object) and just throws the exception, which means connection errors and |
570 | object) and just throws the exception, which means connection errors and |
373 | other problems get reported tot he code that tries to use the result, |
571 | other problems get reported tot he code that tries to use the result, |
374 | not in a random callback. |
572 | not in a random callback. |
375 | |
573 | |
376 | All of this enables the following usage styles: |
574 | All of this enables the following usage styles: |
377 | |
575 | |
378 | 1. Blocking: |
576 | 1. Blocking: |
379 | |
577 | |
380 | my $data = $fcp->client_get ($url); |
578 | my $data = $fcp->client_get ($url); |
381 | |
579 | |
382 | 2. Blocking, but parallelizing: |
580 | 2. Blocking, but running in parallel: |
383 | |
581 | |
384 | my @datas = map $_->result, |
582 | my @datas = map $_->result, |
385 | map $fcp->txn_client_get ($_), |
583 | map $fcp->txn_client_get ($_), |
386 | @urls; |
584 | @urls; |
387 | |
585 | |
388 | Both blocking examples work without the module user having to know |
586 | Both blocking examples work without the module user having to know |
389 | anything about events. |
587 | anything about events. |
390 | |
588 | |
391 | 3a. Event-based in a main program, using any support Event module: |
589 | 3a. Event-based in a main program, using any supported event module: |
392 | |
590 | |
393 | use Event; |
591 | use EV; |
394 | |
592 | |
395 | $fcp->txn_client_get ($url)->cb (sub { |
593 | $fcp->txn_client_get ($url)->cb (sub { |
396 | my $txn = shift; |
594 | my $txn = shift; |
397 | my $data = $txn->result; |
595 | my $data = $txn->result; |
398 | ... |
596 | ... |
399 | }); |
597 | }); |
400 | |
598 | |
401 | Event::loop; |
599 | EV::loop; |
402 | |
600 | |
403 | 3b. The module user could use AnyEvent, too: |
601 | 3b. The module user could use AnyEvent, too: |
404 | |
602 | |
405 | use AnyEvent; |
603 | use AnyEvent; |
406 | |
604 | |
… | |
… | |
411 | $quit->broadcast; |
609 | $quit->broadcast; |
412 | }); |
610 | }); |
413 | |
611 | |
414 | $quit->wait; |
612 | $quit->wait; |
415 | |
613 | |
|
|
614 | FORK |
|
|
615 | Most event libraries are not fork-safe. The ones who are usually are |
|
|
616 | because they are so inefficient. Only EV is fully fork-aware. |
|
|
617 | |
|
|
618 | If you have to fork, you must either do so *before* creating your first |
|
|
619 | watcher OR you must not use AnyEvent at all in the child. |
|
|
620 | |
|
|
621 | SECURITY CONSIDERATIONS |
|
|
622 | AnyEvent can be forced to load any event model via |
|
|
623 | $ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used |
|
|
624 | to execute arbitrary code or directly gain access, it can easily be used |
|
|
625 | to make the program hang or malfunction in subtle ways, as AnyEvent |
|
|
626 | watchers will not be active when the program uses a different event |
|
|
627 | model than specified in the variable. |
|
|
628 | |
|
|
629 | You can make AnyEvent completely ignore this variable by deleting it |
|
|
630 | before the first watcher gets created, e.g. with a "BEGIN" block: |
|
|
631 | |
|
|
632 | BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } |
|
|
633 | |
|
|
634 | use AnyEvent; |
|
|
635 | |
416 | SEE ALSO |
636 | SEE ALSO |
417 | Event modules: Coro::Event, Coro, Event, Glib::Event, Glib. |
637 | Event modules: Coro::EV, EV, EV::Glib, Glib::EV, Coro::Event, Event, |
|
|
638 | Glib::Event, Glib, Coro, Tk, Event::Lib, Qt. |
418 | |
639 | |
419 | Implementations: AnyEvent::Impl::Coro, AnyEvent::Impl::Event, |
640 | Implementations: AnyEvent::Impl::CoroEV, AnyEvent::Impl::EV, |
420 | AnyEvent::Impl::Glib, AnyEvent::Impl::Tk. |
641 | AnyEvent::Impl::CoroEvent, AnyEvent::Impl::Event, AnyEvent::Impl::Glib, |
|
|
642 | AnyEvent::Impl::Tk, AnyEvent::Impl::Perl, AnyEvent::Impl::EventLib, |
|
|
643 | AnyEvent::Impl::Qt. |
421 | |
644 | |
422 | Nontrivial usage example: Net::FCP. |
645 | Nontrivial usage examples: Net::FCP, Net::XMPP2. |
423 | |
646 | |
|
|
647 | AUTHOR |
|
|
648 | Marc Lehmann <schmorp@schmorp.de> |
|
|
649 | http://home.schmorp.de/ |
424 | |
650 | |