1 | NAME |
1 | NAME |
2 | AnyEvent - provide framework for multiple event loops |
2 | AnyEvent - provide framework for multiple event loops |
3 | |
3 | |
4 | EV, Event, Coro::EV, Coro::Event, Glib, Tk, Perl, Event::Lib, Qt, POE - |
4 | EV, Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event |
5 | various supported event loops |
5 | loops |
6 | |
6 | |
7 | SYNOPSIS |
7 | SYNOPSIS |
8 | use AnyEvent; |
8 | use AnyEvent; |
9 | |
9 | |
10 | my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub { |
10 | my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub { |
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14 | my $w = AnyEvent->timer (after => $seconds, cb => sub { |
14 | my $w = AnyEvent->timer (after => $seconds, cb => sub { |
15 | ... |
15 | ... |
16 | }); |
16 | }); |
17 | |
17 | |
18 | my $w = AnyEvent->condvar; # stores whether a condition was flagged |
18 | my $w = AnyEvent->condvar; # stores whether a condition was flagged |
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19 | $w->send; # wake up current and all future recv's |
19 | $w->wait; # enters "main loop" till $condvar gets ->broadcast |
20 | $w->recv; # enters "main loop" till $condvar gets ->send |
20 | $w->broadcast; # wake up current and all future wait's |
21 | |
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22 | INTRODUCTION/TUTORIAL |
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23 | This manpage is mainly a reference manual. If you are interested in a |
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24 | tutorial or some gentle introduction, have a look at the AnyEvent::Intro |
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25 | manpage. |
21 | |
26 | |
22 | WHY YOU SHOULD USE THIS MODULE (OR NOT) |
27 | WHY YOU SHOULD USE THIS MODULE (OR NOT) |
23 | Glib, POE, IO::Async, Event... CPAN offers event models by the dozen |
28 | Glib, POE, IO::Async, Event... CPAN offers event models by the dozen |
24 | nowadays. So what is different about AnyEvent? |
29 | nowadays. So what is different about AnyEvent? |
25 | |
30 | |
26 | Executive Summary: AnyEvent is *compatible*, AnyEvent is *free of |
31 | Executive Summary: AnyEvent is *compatible*, AnyEvent is *free of |
27 | policy* and AnyEvent is *small and efficient*. |
32 | policy* and AnyEvent is *small and efficient*. |
28 | |
33 | |
29 | First and foremost, *AnyEvent is not an event model* itself, it only |
34 | 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 |
35 | 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, |
36 | 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, |
37 | 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. |
38 | only one event loop can be active at the same time in a process. |
34 | AnyEvent helps hiding the differences between those event loops. |
39 | AnyEvent cannot change this, but it can hide the differences between |
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40 | those event loops. |
35 | |
41 | |
36 | The goal of AnyEvent is to offer module authors the ability to do event |
42 | 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 |
43 | programming (waiting for I/O or timer events) without subscribing to a |
38 | religion, a way of living, and most importantly: without forcing your |
44 | 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 |
45 | module users into the same thing by forcing them to use the same event |
40 | model you use. |
46 | model you use. |
41 | |
47 | |
42 | For modules like POE or IO::Async (which is a total misnomer as it is |
48 | 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 |
49 | 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 |
50 | 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 |
51 | cannot use anything else, as they are simply incompatible to everything |
46 | that isn't itself. What's worse, all the potential users of your module |
52 | that isn't them. What's worse, all the potential users of your module |
47 | are *also* forced to use the same event loop you use. |
53 | are *also* forced to use the same event loop you use. |
48 | |
54 | |
49 | AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works |
55 | AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works |
50 | fine. AnyEvent + Tk works fine etc. etc. but none of these work together |
56 | 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 |
57 | 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. |
58 | 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 |
59 | 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 |
60 | models it supports (including stuff like IO::Async, as long as those use |
55 | those use one of the supported event loops. It is trivial to add new |
61 | one of the supported event loops. It is trivial to add new event loops |
56 | event loops to AnyEvent, too, so it is future-proof). |
62 | to AnyEvent, too, so it is future-proof). |
57 | |
63 | |
58 | In addition to being free of having to use *the one and only true event |
64 | 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 |
65 | 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 |
66 | modules, you get an enormous amount of code and strict rules you have to |
61 | to follow. AnyEvent, on the other hand, is lean and up to the point, by |
67 | 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 |
68 | only offering the functionality that is necessary, in as thin as a |
63 | wrapper as technically possible. |
69 | wrapper as technically possible. |
64 | |
70 | |
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71 | Of course, AnyEvent comes with a big (and fully optional!) toolbox of |
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72 | useful functionality, such as an asynchronous DNS resolver, 100% |
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73 | non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms |
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74 | such as Windows) and lots of real-world knowledge and workarounds for |
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75 | platform bugs and differences. |
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76 | |
65 | Of course, if you want lots of policy (this can arguably be somewhat |
77 | Now, if you *do 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 |
78 | useful) and you want to force your users to use the one and only event |
67 | model, you should *not* use this module. |
79 | model, you should *not* use this module. |
68 | |
80 | |
69 | DESCRIPTION |
81 | DESCRIPTION |
70 | AnyEvent provides an identical interface to multiple event loops. This |
82 | AnyEvent provides an identical interface to multiple event loops. This |
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75 | The interface itself is vaguely similar, but not identical to the Event |
87 | The interface itself is vaguely similar, but not identical to the Event |
76 | module. |
88 | module. |
77 | |
89 | |
78 | During the first call of any watcher-creation method, the module tries |
90 | During the first call of any watcher-creation method, the module tries |
79 | to detect the currently loaded event loop by probing whether one of the |
91 | to detect the currently loaded event loop by probing whether one of the |
80 | following modules is already loaded: Coro::EV, Coro::Event, EV, Event, |
92 | following modules is already loaded: EV, Event, Glib, |
81 | Glib, AnyEvent::Impl::Perl, Tk, Event::Lib, Qt, POE. The first one found |
93 | AnyEvent::Impl::Perl, Tk, Event::Lib, Qt, POE. The first one found is |
82 | is used. If none are found, the module tries to load these modules |
94 | used. If none are found, the module tries to load these modules |
83 | (excluding Tk, Event::Lib, Qt and POE as the pure perl adaptor should |
95 | (excluding Tk, Event::Lib, Qt and POE as the pure perl adaptor should |
84 | always succeed) in the order given. The first one that can be |
96 | always succeed) in the order given. The first one that can be |
85 | successfully loaded will be used. If, after this, still none could be |
97 | successfully loaded will be used. If, after this, still none could be |
86 | found, AnyEvent will fall back to a pure-perl event loop, which is not |
98 | found, AnyEvent will fall back to a pure-perl event loop, which is not |
87 | very efficient, but should work everywhere. |
99 | very efficient, but should work everywhere. |
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99 | starts using it, all bets are off. Maybe you should tell their authors |
111 | starts using it, all bets are off. Maybe you should tell their authors |
100 | to use AnyEvent so their modules work together with others seamlessly... |
112 | to use AnyEvent so their modules work together with others seamlessly... |
101 | |
113 | |
102 | The pure-perl implementation of AnyEvent is called |
114 | The pure-perl implementation of AnyEvent is called |
103 | "AnyEvent::Impl::Perl". Like other event modules you can load it |
115 | "AnyEvent::Impl::Perl". Like other event modules you can load it |
104 | explicitly. |
116 | explicitly and enjoy the high availability of that event loop :) |
105 | |
117 | |
106 | WATCHERS |
118 | WATCHERS |
107 | AnyEvent has the central concept of a *watcher*, which is an object that |
119 | AnyEvent has the central concept of a *watcher*, which is an object that |
108 | stores relevant data for each kind of event you are waiting for, such as |
120 | stores relevant data for each kind of event you are waiting for, such as |
109 | the callback to call, the filehandle to watch, etc. |
121 | the callback to call, the file handle to watch, etc. |
110 | |
122 | |
111 | These watchers are normal Perl objects with normal Perl lifetime. After |
123 | These watchers are normal Perl objects with normal Perl lifetime. After |
112 | creating a watcher it will immediately "watch" for events and invoke the |
124 | creating a watcher it will immediately "watch" for events and invoke the |
113 | callback when the event occurs (of course, only when the event model is |
125 | callback when the event occurs (of course, only when the event model is |
114 | in control). |
126 | in control). |
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122 | Many watchers either are used with "recursion" (repeating timers for |
134 | Many watchers either are used with "recursion" (repeating timers for |
123 | example), or need to refer to their watcher object in other ways. |
135 | example), or need to refer to their watcher object in other ways. |
124 | |
136 | |
125 | An any way to achieve that is this pattern: |
137 | An any way to achieve that is this pattern: |
126 | |
138 | |
127 | my $w; $w = AnyEvent->type (arg => value ..., cb => sub { |
139 | my $w; $w = AnyEvent->type (arg => value ..., cb => sub { |
128 | # you can use $w here, for example to undef it |
140 | # you can use $w here, for example to undef it |
129 | undef $w; |
141 | undef $w; |
130 | }); |
142 | }); |
131 | |
143 | |
132 | Note that "my $w; $w =" combination. This is necessary because in Perl, |
144 | Note that "my $w; $w =" combination. This is necessary because in Perl, |
133 | my variables are only visible after the statement in which they are |
145 | my variables are only visible after the statement in which they are |
134 | declared. |
146 | declared. |
135 | |
147 | |
136 | I/O WATCHERS |
148 | I/O WATCHERS |
137 | You can create an I/O watcher by calling the "AnyEvent->io" method with |
149 | You can create an I/O watcher by calling the "AnyEvent->io" method with |
138 | the following mandatory key-value pairs as arguments: |
150 | the following mandatory key-value pairs as arguments: |
139 | |
151 | |
140 | "fh" the Perl *file handle* (*not* file descriptor) to watch for events. |
152 | "fh" the Perl *file handle* (*not* file descriptor) to watch for events |
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153 | (AnyEvent might or might not keep a reference to this file handle). |
141 | "poll" must be a string that is either "r" or "w", which creates a |
154 | "poll" must be a string that is either "r" or "w", which creates a |
142 | watcher waiting for "r"eadable or "w"ritable events, respectively. "cb" |
155 | watcher waiting for "r"eadable or "w"ritable events, respectively. "cb" |
143 | is the callback to invoke each time the file handle becomes ready. |
156 | is the callback to invoke each time the file handle becomes ready. |
144 | |
157 | |
145 | Although the callback might get passed parameters, their value and |
158 | Although the callback might get passed parameters, their value and |
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152 | |
165 | |
153 | Some event loops issue spurious readyness notifications, so you should |
166 | Some event loops issue spurious readyness notifications, so you should |
154 | always use non-blocking calls when reading/writing from/to your file |
167 | always use non-blocking calls when reading/writing from/to your file |
155 | handles. |
168 | handles. |
156 | |
169 | |
157 | Example: |
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158 | |
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159 | # wait for readability of STDIN, then read a line and disable the watcher |
170 | Example: wait for readability of STDIN, then read a line and disable the |
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171 | watcher. |
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172 | |
160 | my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { |
173 | my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { |
161 | chomp (my $input = <STDIN>); |
174 | chomp (my $input = <STDIN>); |
162 | warn "read: $input\n"; |
175 | warn "read: $input\n"; |
163 | undef $w; |
176 | undef $w; |
164 | }); |
177 | }); |
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173 | |
186 | |
174 | Although the callback might get passed parameters, their value and |
187 | Although the callback might get passed parameters, their value and |
175 | presence is undefined and you cannot rely on them. Portable AnyEvent |
188 | presence is undefined and you cannot rely on them. Portable AnyEvent |
176 | callbacks cannot use arguments passed to time watcher callbacks. |
189 | callbacks cannot use arguments passed to time watcher callbacks. |
177 | |
190 | |
178 | The timer callback will be invoked at most once: if you want a repeating |
191 | The callback will normally be invoked once only. If you specify another |
179 | timer you have to create a new watcher (this is a limitation by both Tk |
192 | parameter, "interval", as a strictly positive number (> 0), then the |
180 | and Glib). |
193 | callback will be invoked regularly at that interval (in fractional |
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194 | seconds) after the first invocation. If "interval" is specified with a |
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195 | false value, then it is treated as if it were missing. |
181 | |
196 | |
182 | Example: |
197 | The callback will be rescheduled before invoking the callback, but no |
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198 | attempt is done to avoid timer drift in most backends, so the interval |
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199 | is only approximate. |
183 | |
200 | |
184 | # fire an event after 7.7 seconds |
201 | Example: fire an event after 7.7 seconds. |
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202 | |
185 | my $w = AnyEvent->timer (after => 7.7, cb => sub { |
203 | my $w = AnyEvent->timer (after => 7.7, cb => sub { |
186 | warn "timeout\n"; |
204 | warn "timeout\n"; |
187 | }); |
205 | }); |
188 | |
206 | |
189 | # to cancel the timer: |
207 | # to cancel the timer: |
190 | undef $w; |
208 | undef $w; |
191 | |
209 | |
192 | Example 2: |
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193 | |
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194 | # fire an event after 0.5 seconds, then roughly every second |
210 | Example 2: fire an event after 0.5 seconds, then roughly every second. |
195 | my $w; |
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196 | |
211 | |
197 | my $cb = sub { |
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198 | # cancel the old timer while creating a new one |
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199 | $w = AnyEvent->timer (after => 1, cb => $cb); |
212 | my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub { |
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213 | warn "timeout\n"; |
200 | }; |
214 | }; |
201 | |
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202 | # start the "loop" by creating the first watcher |
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203 | $w = AnyEvent->timer (after => 0.5, cb => $cb); |
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204 | |
215 | |
205 | TIMING ISSUES |
216 | TIMING ISSUES |
206 | There are two ways to handle timers: based on real time (relative, "fire |
217 | There are two ways to handle timers: based on real time (relative, "fire |
207 | in 10 seconds") and based on wallclock time (absolute, "fire at 12 |
218 | in 10 seconds") and based on wallclock time (absolute, "fire at 12 |
208 | o'clock"). |
219 | o'clock"). |
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220 | on wallclock time) timers. |
231 | on wallclock time) timers. |
221 | |
232 | |
222 | AnyEvent always prefers relative timers, if available, matching the |
233 | AnyEvent always prefers relative timers, if available, matching the |
223 | AnyEvent API. |
234 | AnyEvent API. |
224 | |
235 | |
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236 | AnyEvent has two additional methods that return the "current time": |
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237 | |
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238 | AnyEvent->time |
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239 | This returns the "current wallclock time" as a fractional number of |
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240 | seconds since the Epoch (the same thing as "time" or |
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241 | "Time::HiRes::time" return, and the result is guaranteed to be |
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242 | compatible with those). |
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243 | |
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244 | It progresses independently of any event loop processing, i.e. each |
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245 | call will check the system clock, which usually gets updated |
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246 | frequently. |
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247 | |
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248 | AnyEvent->now |
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249 | This also returns the "current wallclock time", but unlike "time", |
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250 | above, this value might change only once per event loop iteration, |
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251 | depending on the event loop (most return the same time as "time", |
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252 | above). This is the time that AnyEvent's timers get scheduled |
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253 | against. |
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254 | |
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255 | *In almost all cases (in all cases if you don't care), this is the |
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256 | function to call when you want to know the current time.* |
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257 | |
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258 | This function is also often faster then "AnyEvent->time", and thus |
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259 | the preferred method if you want some timestamp (for example, |
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260 | AnyEvent::Handle uses this to update it's activity timeouts). |
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261 | |
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262 | The rest of this section is only of relevance if you try to be very |
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263 | exact with your timing, you can skip it without bad conscience. |
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264 | |
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265 | For a practical example of when these times differ, consider |
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266 | Event::Lib and EV and the following set-up: |
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267 | |
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268 | The event loop is running and has just invoked one of your callback |
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269 | at time=500 (assume no other callbacks delay processing). In your |
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270 | callback, you wait a second by executing "sleep 1" (blocking the |
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271 | process for a second) and then (at time=501) you create a relative |
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272 | timer that fires after three seconds. |
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273 | |
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274 | With Event::Lib, "AnyEvent->time" and "AnyEvent->now" will both |
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275 | return 501, because that is the current time, and the timer will be |
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276 | scheduled to fire at time=504 (501 + 3). |
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277 | |
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278 | With EV, "AnyEvent->time" returns 501 (as that is the current time), |
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279 | but "AnyEvent->now" returns 500, as that is the time the last event |
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280 | processing phase started. With EV, your timer gets scheduled to run |
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281 | at time=503 (500 + 3). |
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282 | |
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283 | In one sense, Event::Lib is more exact, as it uses the current time |
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284 | regardless of any delays introduced by event processing. However, |
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285 | most callbacks do not expect large delays in processing, so this |
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286 | causes a higher drift (and a lot more system calls to get the |
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287 | current time). |
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288 | |
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289 | In another sense, EV is more exact, as your timer will be scheduled |
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290 | at the same time, regardless of how long event processing actually |
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291 | took. |
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292 | |
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293 | In either case, if you care (and in most cases, you don't), then you |
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294 | can get whatever behaviour you want with any event loop, by taking |
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295 | the difference between "AnyEvent->time" and "AnyEvent->now" into |
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296 | account. |
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297 | |
225 | SIGNAL WATCHERS |
298 | SIGNAL WATCHERS |
226 | You can watch for signals using a signal watcher, "signal" is the signal |
299 | You can watch for signals using a signal watcher, "signal" is the signal |
227 | *name* without any "SIG" prefix, "cb" is the Perl callback to be invoked |
300 | *name* in uppercase and without any "SIG" prefix, "cb" is the Perl |
228 | whenever a signal occurs. |
301 | callback to be invoked whenever a signal occurs. |
229 | |
302 | |
230 | Although the callback might get passed parameters, their value and |
303 | Although the callback might get passed parameters, their value and |
231 | presence is undefined and you cannot rely on them. Portable AnyEvent |
304 | presence is undefined and you cannot rely on them. Portable AnyEvent |
232 | callbacks cannot use arguments passed to signal watcher callbacks. |
305 | callbacks cannot use arguments passed to signal watcher callbacks. |
233 | |
306 | |
234 | Multiple signal occurances can be clumped together into one callback |
307 | Multiple signal occurrences can be clumped together into one callback |
235 | invocation, and callback invocation will be synchronous. synchronous |
308 | invocation, and callback invocation will be synchronous. Synchronous |
236 | means that it might take a while until the signal gets handled by the |
309 | means that it might take a while until the signal gets handled by the |
237 | process, but it is guarenteed not to interrupt any other callbacks. |
310 | process, but it is guaranteed not to interrupt any other callbacks. |
238 | |
311 | |
239 | The main advantage of using these watchers is that you can share a |
312 | The main advantage of using these watchers is that you can share a |
240 | signal between multiple watchers. |
313 | signal between multiple watchers. |
241 | |
314 | |
242 | This watcher might use %SIG, so programs overwriting those signals |
315 | This watcher might use %SIG, so programs overwriting those signals |
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269 | an AnyEvent program, you *have* to create at least one watcher before |
342 | an AnyEvent program, you *have* to create at least one watcher before |
270 | you "fork" the child (alternatively, you can call "AnyEvent::detect"). |
343 | you "fork" the child (alternatively, you can call "AnyEvent::detect"). |
271 | |
344 | |
272 | Example: fork a process and wait for it |
345 | Example: fork a process and wait for it |
273 | |
346 | |
274 | my $done = AnyEvent->condvar; |
347 | my $done = AnyEvent->condvar; |
275 | |
348 | |
276 | AnyEvent::detect; # force event module to be initialised |
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277 | |
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278 | my $pid = fork or exit 5; |
349 | my $pid = fork or exit 5; |
279 | |
350 | |
280 | my $w = AnyEvent->child ( |
351 | my $w = AnyEvent->child ( |
281 | pid => $pid, |
352 | pid => $pid, |
282 | cb => sub { |
353 | cb => sub { |
283 | my ($pid, $status) = @_; |
354 | my ($pid, $status) = @_; |
284 | warn "pid $pid exited with status $status"; |
355 | warn "pid $pid exited with status $status"; |
285 | $done->broadcast; |
356 | $done->send; |
286 | }, |
357 | }, |
287 | ); |
358 | ); |
288 | |
359 | |
289 | # do something else, then wait for process exit |
360 | # do something else, then wait for process exit |
290 | $done->wait; |
361 | $done->recv; |
291 | |
362 | |
292 | CONDITION VARIABLES |
363 | CONDITION VARIABLES |
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364 | If you are familiar with some event loops you will know that all of them |
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365 | require you to run some blocking "loop", "run" or similar function that |
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366 | will actively watch for new events and call your callbacks. |
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367 | |
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368 | AnyEvent is different, it expects somebody else to run the event loop |
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369 | and will only block when necessary (usually when told by the user). |
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370 | |
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371 | The instrument to do that is called a "condition variable", so called |
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372 | because they represent a condition that must become true. |
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373 | |
293 | Condition variables can be created by calling the "AnyEvent->condvar" |
374 | Condition variables can be created by calling the "AnyEvent->condvar" |
294 | method without any arguments. |
375 | method, usually without arguments. The only argument pair allowed is |
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376 | "cb", which specifies a callback to be called when the condition |
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377 | variable becomes true. |
295 | |
378 | |
296 | A condition variable waits for a condition - precisely that the |
379 | After creation, the condition variable is "false" until it becomes |
297 | "->broadcast" method has been called. |
380 | "true" by calling the "send" method (or calling the condition variable |
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381 | as if it were a callback, read about the caveats in the description for |
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382 | the "->send" method). |
298 | |
383 | |
299 | They are very useful to signal that a condition has been fulfilled, for |
384 | Condition variables are similar to callbacks, except that you can |
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385 | optionally wait for them. They can also be called merge points - points |
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386 | in time where multiple outstanding events have been processed. And yet |
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387 | another way to call them is transactions - each condition variable can |
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388 | be used to represent a transaction, which finishes at some point and |
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389 | delivers a result. |
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390 | |
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391 | Condition variables are very useful to signal that something has |
300 | example, if you write a module that does asynchronous http requests, |
392 | finished, for example, if you write a module that does asynchronous http |
301 | then a condition variable would be the ideal candidate to signal the |
393 | requests, then a condition variable would be the ideal candidate to |
302 | availability of results. |
394 | signal the availability of results. The user can either act when the |
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395 | callback is called or can synchronously "->recv" for the results. |
303 | |
396 | |
304 | You can also use condition variables to block your main program until an |
397 | You can also use them to simulate traditional event loops - for example, |
305 | event occurs - for example, you could "->wait" in your main program |
398 | you can block your main program until an event occurs - for example, you |
306 | until the user clicks the Quit button in your app, which would |
399 | could "->recv" in your main program until the user clicks the Quit |
307 | "->broadcast" the "quit" event. |
400 | button of your app, which would "->send" the "quit" event. |
308 | |
401 | |
309 | Note that condition variables recurse into the event loop - if you have |
402 | Note that condition variables recurse into the event loop - if you have |
310 | two pirces of code that call "->wait" in a round-robbin fashion, you |
403 | two pieces of code that call "->recv" in a round-robin fashion, you |
311 | lose. Therefore, condition variables are good to export to your caller, |
404 | lose. Therefore, condition variables are good to export to your caller, |
312 | but you should avoid making a blocking wait yourself, at least in |
405 | but you should avoid making a blocking wait yourself, at least in |
313 | callbacks, as this asks for trouble. |
406 | callbacks, as this asks for trouble. |
314 | |
407 | |
315 | This object has two methods: |
408 | Condition variables are represented by hash refs in perl, and the keys |
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409 | used by AnyEvent itself are all named "_ae_XXX" to make subclassing easy |
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410 | (it is often useful to build your own transaction class on top of |
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411 | AnyEvent). To subclass, use "AnyEvent::CondVar" as base class and call |
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412 | it's "new" method in your own "new" method. |
316 | |
413 | |
317 | $cv->wait |
414 | There are two "sides" to a condition variable - the "producer side" |
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415 | which eventually calls "-> send", and the "consumer side", which waits |
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416 | for the send to occur. |
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417 | |
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418 | Example: wait for a timer. |
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419 | |
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420 | # wait till the result is ready |
|
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421 | my $result_ready = AnyEvent->condvar; |
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422 | |
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423 | # do something such as adding a timer |
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424 | # or socket watcher the calls $result_ready->send |
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425 | # when the "result" is ready. |
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426 | # in this case, we simply use a timer: |
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427 | my $w = AnyEvent->timer ( |
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428 | after => 1, |
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429 | cb => sub { $result_ready->send }, |
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430 | ); |
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431 | |
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432 | # this "blocks" (while handling events) till the callback |
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433 | # calls send |
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434 | $result_ready->recv; |
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435 | |
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436 | Example: wait for a timer, but take advantage of the fact that condition |
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437 | variables are also code references. |
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438 | |
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439 | my $done = AnyEvent->condvar; |
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440 | my $delay = AnyEvent->timer (after => 5, cb => $done); |
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441 | $done->recv; |
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442 | |
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443 | METHODS FOR PRODUCERS |
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444 | These methods should only be used by the producing side, i.e. the |
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445 | code/module that eventually sends the signal. Note that it is also the |
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446 | producer side which creates the condvar in most cases, but it isn't |
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447 | uncommon for the consumer to create it as well. |
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448 | |
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449 | $cv->send (...) |
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450 | Flag the condition as ready - a running "->recv" and all further |
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451 | calls to "recv" will (eventually) return after this method has been |
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452 | called. If nobody is waiting the send will be remembered. |
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453 | |
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454 | If a callback has been set on the condition variable, it is called |
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455 | immediately from within send. |
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456 | |
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457 | Any arguments passed to the "send" call will be returned by all |
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458 | future "->recv" calls. |
|
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459 | |
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460 | Condition variables are overloaded so one can call them directly (as |
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461 | a code reference). Calling them directly is the same as calling |
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462 | "send". Note, however, that many C-based event loops do not handle |
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463 | overloading, so as tempting as it may be, passing a condition |
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464 | variable instead of a callback does not work. Both the pure perl and |
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465 | EV loops support overloading, however, as well as all functions that |
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466 | use perl to invoke a callback (as in AnyEvent::Socket and |
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467 | AnyEvent::DNS for example). |
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468 | |
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469 | $cv->croak ($error) |
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470 | Similar to send, but causes all call's to "->recv" to invoke |
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471 | "Carp::croak" with the given error message/object/scalar. |
|
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472 | |
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473 | This can be used to signal any errors to the condition variable |
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474 | user/consumer. |
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475 | |
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476 | $cv->begin ([group callback]) |
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477 | $cv->end |
|
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478 | These two methods are EXPERIMENTAL and MIGHT CHANGE. |
|
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479 | |
|
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480 | These two methods can be used to combine many transactions/events |
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481 | into one. For example, a function that pings many hosts in parallel |
|
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482 | might want to use a condition variable for the whole process. |
|
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483 | |
|
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484 | Every call to "->begin" will increment a counter, and every call to |
|
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485 | "->end" will decrement it. If the counter reaches 0 in "->end", the |
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486 | (last) callback passed to "begin" will be executed. That callback is |
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487 | *supposed* to call "->send", but that is not required. If no |
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488 | callback was set, "send" will be called without any arguments. |
|
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489 | |
|
|
490 | Let's clarify this with the ping example: |
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491 | |
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492 | my $cv = AnyEvent->condvar; |
|
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493 | |
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494 | my %result; |
|
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495 | $cv->begin (sub { $cv->send (\%result) }); |
|
|
496 | |
|
|
497 | for my $host (@list_of_hosts) { |
|
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498 | $cv->begin; |
|
|
499 | ping_host_then_call_callback $host, sub { |
|
|
500 | $result{$host} = ...; |
|
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501 | $cv->end; |
|
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502 | }; |
|
|
503 | } |
|
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504 | |
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505 | $cv->end; |
|
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506 | |
|
|
507 | This code fragment supposedly pings a number of hosts and calls |
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508 | "send" after results for all then have have been gathered - in any |
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509 | order. To achieve this, the code issues a call to "begin" when it |
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510 | starts each ping request and calls "end" when it has received some |
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511 | result for it. Since "begin" and "end" only maintain a counter, the |
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512 | order in which results arrive is not relevant. |
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513 | |
|
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514 | There is an additional bracketing call to "begin" and "end" outside |
|
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515 | the loop, which serves two important purposes: first, it sets the |
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516 | callback to be called once the counter reaches 0, and second, it |
|
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517 | ensures that "send" is called even when "no" hosts are being pinged |
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518 | (the loop doesn't execute once). |
|
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519 | |
|
|
520 | This is the general pattern when you "fan out" into multiple |
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521 | subrequests: use an outer "begin"/"end" pair to set the callback and |
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522 | ensure "end" is called at least once, and then, for each subrequest |
|
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523 | you start, call "begin" and for each subrequest you finish, call |
|
|
524 | "end". |
|
|
525 | |
|
|
526 | METHODS FOR CONSUMERS |
|
|
527 | These methods should only be used by the consuming side, i.e. the code |
|
|
528 | awaits the condition. |
|
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529 | |
|
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530 | $cv->recv |
318 | Wait (blocking if necessary) until the "->broadcast" method has been |
531 | Wait (blocking if necessary) until the "->send" or "->croak" methods |
319 | called on c<$cv>, while servicing other watchers normally. |
532 | have been called on c<$cv>, while servicing other watchers normally. |
320 | |
533 | |
321 | You can only wait once on a condition - additional calls will return |
534 | You can only wait once on a condition - additional calls are valid |
322 | immediately. |
535 | but will return immediately. |
|
|
536 | |
|
|
537 | If an error condition has been set by calling "->croak", then this |
|
|
538 | function will call "croak". |
|
|
539 | |
|
|
540 | In list context, all parameters passed to "send" will be returned, |
|
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541 | in scalar context only the first one will be returned. |
323 | |
542 | |
324 | Not all event models support a blocking wait - some die in that case |
543 | Not all event models support a blocking wait - some die in that case |
325 | (programs might want to do that to stay interactive), so *if you are |
544 | (programs might want to do that to stay interactive), so *if you are |
326 | using this from a module, never require a blocking wait*, but let |
545 | using this from a module, never require a blocking wait*, but let |
327 | the caller decide whether the call will block or not (for example, |
546 | the caller decide whether the call will block or not (for example, |
328 | by coupling condition variables with some kind of request results |
547 | by coupling condition variables with some kind of request results |
329 | and supporting callbacks so the caller knows that getting the result |
548 | and supporting callbacks so the caller knows that getting the result |
330 | will not block, while still suppporting blocking waits if the caller |
549 | will not block, while still supporting blocking waits if the caller |
331 | so desires). |
550 | so desires). |
332 | |
551 | |
333 | Another reason *never* to "->wait" in a module is that you cannot |
552 | Another reason *never* to "->recv" in a module is that you cannot |
334 | sensibly have two "->wait"'s in parallel, as that would require |
553 | sensibly have two "->recv"'s in parallel, as that would require |
335 | multiple interpreters or coroutines/threads, none of which |
554 | multiple interpreters or coroutines/threads, none of which |
336 | "AnyEvent" can supply (the coroutine-aware backends |
555 | "AnyEvent" can supply. |
337 | AnyEvent::Impl::CoroEV and AnyEvent::Impl::CoroEvent explicitly |
|
|
338 | support concurrent "->wait"'s from different coroutines, however). |
|
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339 | |
556 | |
340 | $cv->broadcast |
557 | The Coro module, however, *can* and *does* supply coroutines and, in |
341 | Flag the condition as ready - a running "->wait" and all further |
558 | fact, Coro::AnyEvent replaces AnyEvent's condvars by coroutine-safe |
342 | calls to "wait" will (eventually) return after this method has been |
559 | versions and also integrates coroutines into AnyEvent, making |
343 | called. If nobody is waiting the broadcast will be remembered.. |
560 | blocking "->recv" calls perfectly safe as long as they are done from |
|
|
561 | another coroutine (one that doesn't run the event loop). |
344 | |
562 | |
345 | Example: |
563 | You can ensure that "-recv" never blocks by setting a callback and |
|
|
564 | only calling "->recv" from within that callback (or at a later |
|
|
565 | time). This will work even when the event loop does not support |
|
|
566 | blocking waits otherwise. |
346 | |
567 | |
347 | # wait till the result is ready |
568 | $bool = $cv->ready |
348 | my $result_ready = AnyEvent->condvar; |
569 | Returns true when the condition is "true", i.e. whether "send" or |
|
|
570 | "croak" have been called. |
349 | |
571 | |
350 | # do something such as adding a timer |
572 | $cb = $cv->cb ([new callback]) |
351 | # or socket watcher the calls $result_ready->broadcast |
573 | This is a mutator function that returns the callback set and |
352 | # when the "result" is ready. |
574 | optionally replaces it before doing so. |
353 | # in this case, we simply use a timer: |
|
|
354 | my $w = AnyEvent->timer ( |
|
|
355 | after => 1, |
|
|
356 | cb => sub { $result_ready->broadcast }, |
|
|
357 | ); |
|
|
358 | |
575 | |
359 | # this "blocks" (while handling events) till the watcher |
576 | The callback will be called when the condition becomes "true", i.e. |
360 | # calls broadcast |
577 | when "send" or "croak" are called, with the only argument being the |
361 | $result_ready->wait; |
578 | condition variable itself. Calling "recv" inside the callback or at |
|
|
579 | any later time is guaranteed not to block. |
362 | |
580 | |
363 | GLOBAL VARIABLES AND FUNCTIONS |
581 | GLOBAL VARIABLES AND FUNCTIONS |
364 | $AnyEvent::MODEL |
582 | $AnyEvent::MODEL |
365 | Contains "undef" until the first watcher is being created. Then it |
583 | Contains "undef" until the first watcher is being created. Then it |
366 | contains the event model that is being used, which is the name of |
584 | contains the event model that is being used, which is the name of |
… | |
… | |
368 | the "AnyEvent::Impl:xxx" modules, but can be any other class in the |
586 | the "AnyEvent::Impl:xxx" modules, but can be any other class in the |
369 | case AnyEvent has been extended at runtime (e.g. in *rxvt-unicode*). |
587 | case AnyEvent has been extended at runtime (e.g. in *rxvt-unicode*). |
370 | |
588 | |
371 | The known classes so far are: |
589 | The known classes so far are: |
372 | |
590 | |
373 | AnyEvent::Impl::CoroEV based on Coro::EV, best choice. |
|
|
374 | AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice. |
|
|
375 | AnyEvent::Impl::EV based on EV (an interface to libev, best choice). |
591 | AnyEvent::Impl::EV based on EV (an interface to libev, best choice). |
376 | AnyEvent::Impl::Event based on Event, second best choice. |
592 | AnyEvent::Impl::Event based on Event, second best choice. |
|
|
593 | AnyEvent::Impl::Perl pure-perl implementation, fast and portable. |
377 | AnyEvent::Impl::Glib based on Glib, third-best choice. |
594 | AnyEvent::Impl::Glib based on Glib, third-best choice. |
378 | AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable. |
|
|
379 | AnyEvent::Impl::Tk based on Tk, very bad choice. |
595 | AnyEvent::Impl::Tk based on Tk, very bad choice. |
380 | AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs). |
596 | AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs). |
381 | AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse. |
597 | AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse. |
382 | AnyEvent::Impl::POE based on POE, not generic enough for full support. |
598 | AnyEvent::Impl::POE based on POE, not generic enough for full support. |
383 | |
599 | |
… | |
… | |
395 | Returns $AnyEvent::MODEL, forcing autodetection of the event model |
611 | Returns $AnyEvent::MODEL, forcing autodetection of the event model |
396 | if necessary. You should only call this function right before you |
612 | if necessary. You should only call this function right before you |
397 | would have created an AnyEvent watcher anyway, that is, as late as |
613 | would have created an AnyEvent watcher anyway, that is, as late as |
398 | possible at runtime. |
614 | possible at runtime. |
399 | |
615 | |
|
|
616 | $guard = AnyEvent::post_detect { BLOCK } |
|
|
617 | Arranges for the code block to be executed as soon as the event |
|
|
618 | model is autodetected (or immediately if this has already happened). |
|
|
619 | |
|
|
620 | If called in scalar or list context, then it creates and returns an |
|
|
621 | object that automatically removes the callback again when it is |
|
|
622 | destroyed. See Coro::BDB for a case where this is useful. |
|
|
623 | |
|
|
624 | @AnyEvent::post_detect |
|
|
625 | If there are any code references in this array (you can "push" to it |
|
|
626 | before or after loading AnyEvent), then they will called directly |
|
|
627 | after the event loop has been chosen. |
|
|
628 | |
|
|
629 | You should check $AnyEvent::MODEL before adding to this array, |
|
|
630 | though: if it contains a true value then the event loop has already |
|
|
631 | been detected, and the array will be ignored. |
|
|
632 | |
|
|
633 | Best use "AnyEvent::post_detect { BLOCK }" instead. |
|
|
634 | |
400 | WHAT TO DO IN A MODULE |
635 | WHAT TO DO IN A MODULE |
401 | As a module author, you should "use AnyEvent" and call AnyEvent methods |
636 | As a module author, you should "use AnyEvent" and call AnyEvent methods |
402 | freely, but you should not load a specific event module or rely on it. |
637 | freely, but you should not load a specific event module or rely on it. |
403 | |
638 | |
404 | Be careful when you create watchers in the module body - AnyEvent will |
639 | Be careful when you create watchers in the module body - AnyEvent will |
405 | decide which event module to use as soon as the first method is called, |
640 | decide which event module to use as soon as the first method is called, |
406 | so by calling AnyEvent in your module body you force the user of your |
641 | so by calling AnyEvent in your module body you force the user of your |
407 | module to load the event module first. |
642 | module to load the event module first. |
408 | |
643 | |
409 | Never call "->wait" on a condition variable unless you *know* that the |
644 | Never call "->recv" on a condition variable unless you *know* that the |
410 | "->broadcast" method has been called on it already. This is because it |
645 | "->send" method has been called on it already. This is because it will |
411 | will stall the whole program, and the whole point of using events is to |
646 | stall the whole program, and the whole point of using events is to stay |
412 | stay interactive. |
647 | interactive. |
413 | |
648 | |
414 | It is fine, however, to call "->wait" when the user of your module |
649 | It is fine, however, to call "->recv" when the user of your module |
415 | requests it (i.e. if you create a http request object ad have a method |
650 | requests it (i.e. if you create a http request object ad have a method |
416 | called "results" that returns the results, it should call "->wait" |
651 | called "results" that returns the results, it should call "->recv" |
417 | freely, as the user of your module knows what she is doing. always). |
652 | freely, as the user of your module knows what she is doing. always). |
418 | |
653 | |
419 | WHAT TO DO IN THE MAIN PROGRAM |
654 | WHAT TO DO IN THE MAIN PROGRAM |
420 | There will always be a single main program - the only place that should |
655 | There will always be a single main program - the only place that should |
421 | dictate which event model to use. |
656 | dictate which event model to use. |
… | |
… | |
423 | If it doesn't care, it can just "use AnyEvent" and use it itself, or not |
658 | If it doesn't care, it can just "use AnyEvent" and use it itself, or not |
424 | do anything special (it does not need to be event-based) and let |
659 | do anything special (it does not need to be event-based) and let |
425 | AnyEvent decide which implementation to chose if some module relies on |
660 | AnyEvent decide which implementation to chose if some module relies on |
426 | it. |
661 | it. |
427 | |
662 | |
428 | If the main program relies on a specific event model. For example, in |
663 | If the main program relies on a specific event model - for example, in |
429 | Gtk2 programs you have to rely on the Glib module. You should load the |
664 | Gtk2 programs you have to rely on the Glib module - you should load the |
430 | event module before loading AnyEvent or any module that uses it: |
665 | event module before loading AnyEvent or any module that uses it: |
431 | generally speaking, you should load it as early as possible. The reason |
666 | generally speaking, you should load it as early as possible. The reason |
432 | is that modules might create watchers when they are loaded, and AnyEvent |
667 | is that modules might create watchers when they are loaded, and AnyEvent |
433 | will decide on the event model to use as soon as it creates watchers, |
668 | will decide on the event model to use as soon as it creates watchers, |
434 | and it might chose the wrong one unless you load the correct one |
669 | and it might chose the wrong one unless you load the correct one |
435 | yourself. |
670 | yourself. |
436 | |
671 | |
437 | You can chose to use a rather inefficient pure-perl implementation by |
672 | You can chose to use a pure-perl implementation by loading the |
438 | loading the "AnyEvent::Impl::Perl" module, which gives you similar |
673 | "AnyEvent::Impl::Perl" module, which gives you similar behaviour |
439 | behaviour everywhere, but letting AnyEvent chose is generally better. |
674 | everywhere, but letting AnyEvent chose the model is generally better. |
|
|
675 | |
|
|
676 | MAINLOOP EMULATION |
|
|
677 | Sometimes (often for short test scripts, or even standalone programs who |
|
|
678 | only want to use AnyEvent), you do not want to run a specific event |
|
|
679 | loop. |
|
|
680 | |
|
|
681 | In that case, you can use a condition variable like this: |
|
|
682 | |
|
|
683 | AnyEvent->condvar->recv; |
|
|
684 | |
|
|
685 | This has the effect of entering the event loop and looping forever. |
|
|
686 | |
|
|
687 | Note that usually your program has some exit condition, in which case it |
|
|
688 | is better to use the "traditional" approach of storing a condition |
|
|
689 | variable somewhere, waiting for it, and sending it when the program |
|
|
690 | should exit cleanly. |
440 | |
691 | |
441 | OTHER MODULES |
692 | OTHER MODULES |
442 | The following is a non-exhaustive list of additional modules that use |
693 | The following is a non-exhaustive list of additional modules that use |
443 | AnyEvent and can therefore be mixed easily with other AnyEvent modules |
694 | AnyEvent and can therefore be mixed easily with other AnyEvent modules |
444 | in the same program. Some of the modules come with AnyEvent, some are |
695 | in the same program. Some of the modules come with AnyEvent, some are |
… | |
… | |
447 | AnyEvent::Util |
698 | AnyEvent::Util |
448 | Contains various utility functions that replace often-used but |
699 | Contains various utility functions that replace often-used but |
449 | blocking functions such as "inet_aton" by event-/callback-based |
700 | blocking functions such as "inet_aton" by event-/callback-based |
450 | versions. |
701 | versions. |
451 | |
702 | |
|
|
703 | AnyEvent::Socket |
|
|
704 | Provides various utility functions for (internet protocol) sockets, |
|
|
705 | addresses and name resolution. Also functions to create non-blocking |
|
|
706 | tcp connections or tcp servers, with IPv6 and SRV record support and |
|
|
707 | more. |
|
|
708 | |
452 | AnyEvent::Handle |
709 | AnyEvent::Handle |
453 | Provide read and write buffers and manages watchers for reads and |
710 | Provide read and write buffers, manages watchers for reads and |
454 | writes. |
711 | writes, supports raw and formatted I/O, I/O queued and fully |
|
|
712 | transparent and non-blocking SSL/TLS. |
455 | |
713 | |
456 | AnyEvent::Socket |
714 | AnyEvent::DNS |
457 | Provides a means to do non-blocking connects, accepts etc. |
715 | Provides rich asynchronous DNS resolver capabilities. |
|
|
716 | |
|
|
717 | AnyEvent::HTTP |
|
|
718 | A simple-to-use HTTP library that is capable of making a lot of |
|
|
719 | concurrent HTTP requests. |
458 | |
720 | |
459 | AnyEvent::HTTPD |
721 | AnyEvent::HTTPD |
460 | Provides a simple web application server framework. |
722 | Provides a simple web application server framework. |
461 | |
723 | |
462 | AnyEvent::DNS |
|
|
463 | Provides asynchronous DNS resolver capabilities, beyond what |
|
|
464 | AnyEvent::Util offers. |
|
|
465 | |
|
|
466 | AnyEvent::FastPing |
724 | AnyEvent::FastPing |
467 | The fastest ping in the west. |
725 | The fastest ping in the west. |
|
|
726 | |
|
|
727 | AnyEvent::DBI |
|
|
728 | Executes DBI requests asynchronously in a proxy process. |
|
|
729 | |
|
|
730 | AnyEvent::AIO |
|
|
731 | Truly asynchronous I/O, should be in the toolbox of every event |
|
|
732 | programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent |
|
|
733 | together. |
|
|
734 | |
|
|
735 | AnyEvent::BDB |
|
|
736 | Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently |
|
|
737 | fuses BDB and AnyEvent together. |
|
|
738 | |
|
|
739 | AnyEvent::GPSD |
|
|
740 | A non-blocking interface to gpsd, a daemon delivering GPS |
|
|
741 | information. |
|
|
742 | |
|
|
743 | AnyEvent::IGS |
|
|
744 | A non-blocking interface to the Internet Go Server protocol (used by |
|
|
745 | App::IGS). |
468 | |
746 | |
469 | Net::IRC3 |
747 | Net::IRC3 |
470 | AnyEvent based IRC client module family. |
748 | AnyEvent based IRC client module family. |
471 | |
749 | |
472 | Net::XMPP2 |
750 | Net::XMPP2 |
… | |
… | |
478 | |
756 | |
479 | Event::ExecFlow |
757 | Event::ExecFlow |
480 | High level API for event-based execution flow control. |
758 | High level API for event-based execution flow control. |
481 | |
759 | |
482 | Coro |
760 | Coro |
483 | Has special support for AnyEvent. |
761 | Has special support for AnyEvent via Coro::AnyEvent. |
484 | |
762 | |
485 | IO::Lambda |
763 | IO::Lambda |
486 | The lambda approach to I/O - don't ask, look there. Can use |
764 | The lambda approach to I/O - don't ask, look there. Can use |
487 | AnyEvent. |
|
|
488 | |
|
|
489 | IO::AIO |
|
|
490 | Truly asynchronous I/O, should be in the toolbox of every event |
|
|
491 | programmer. Can be trivially made to use AnyEvent. |
|
|
492 | |
|
|
493 | BDB Truly asynchronous Berkeley DB access. Can be trivially made to use |
|
|
494 | AnyEvent. |
765 | AnyEvent. |
495 | |
766 | |
496 | SUPPLYING YOUR OWN EVENT MODEL INTERFACE |
767 | SUPPLYING YOUR OWN EVENT MODEL INTERFACE |
497 | This is an advanced topic that you do not normally need to use AnyEvent |
768 | This is an advanced topic that you do not normally need to use AnyEvent |
498 | in a module. This section is only of use to event loop authors who want |
769 | in a module. This section is only of use to event loop authors who want |
… | |
… | |
549 | by "PERL_ANYEVENT_MODEL". |
820 | by "PERL_ANYEVENT_MODEL". |
550 | |
821 | |
551 | When set to 2 or higher, cause AnyEvent to report to STDERR which |
822 | When set to 2 or higher, cause AnyEvent to report to STDERR which |
552 | event model it chooses. |
823 | event model it chooses. |
553 | |
824 | |
|
|
825 | "PERL_ANYEVENT_STRICT" |
|
|
826 | AnyEvent does not do much argument checking by default, as thorough |
|
|
827 | argument checking is very costly. Setting this variable to a true |
|
|
828 | value will cause AnyEvent to load "AnyEvent::Strict" and then to |
|
|
829 | thoroughly check the arguments passed to most method calls. If it |
|
|
830 | finds any problems it will croak. |
|
|
831 | |
|
|
832 | In other words, enables "strict" mode. |
|
|
833 | |
|
|
834 | Unlike "use strict" it is definitely recommended ot keep it off in |
|
|
835 | production. |
|
|
836 | |
554 | "PERL_ANYEVENT_MODEL" |
837 | "PERL_ANYEVENT_MODEL" |
555 | This can be used to specify the event model to be used by AnyEvent, |
838 | This can be used to specify the event model to be used by AnyEvent, |
556 | before autodetection and -probing kicks in. It must be a string |
839 | before auto detection and -probing kicks in. It must be a string |
557 | consisting entirely of ASCII letters. The string "AnyEvent::Impl::" |
840 | consisting entirely of ASCII letters. The string "AnyEvent::Impl::" |
558 | gets prepended and the resulting module name is loaded and if the |
841 | gets prepended and the resulting module name is loaded and if the |
559 | load was successful, used as event model. If it fails to load |
842 | load was successful, used as event model. If it fails to load |
560 | AnyEvent will proceed with autodetection and -probing. |
843 | AnyEvent will proceed with auto detection and -probing. |
561 | |
844 | |
562 | This functionality might change in future versions. |
845 | This functionality might change in future versions. |
563 | |
846 | |
564 | For example, to force the pure perl model (AnyEvent::Impl::Perl) you |
847 | For example, to force the pure perl model (AnyEvent::Impl::Perl) you |
565 | could start your program like this: |
848 | could start your program like this: |
566 | |
849 | |
567 | PERL_ANYEVENT_MODEL=Perl perl ... |
850 | PERL_ANYEVENT_MODEL=Perl perl ... |
|
|
851 | |
|
|
852 | "PERL_ANYEVENT_PROTOCOLS" |
|
|
853 | Used by both AnyEvent::DNS and AnyEvent::Socket to determine |
|
|
854 | preferences for IPv4 or IPv6. The default is unspecified (and might |
|
|
855 | change, or be the result of auto probing). |
|
|
856 | |
|
|
857 | Must be set to a comma-separated list of protocols or address |
|
|
858 | families, current supported: "ipv4" and "ipv6". Only protocols |
|
|
859 | mentioned will be used, and preference will be given to protocols |
|
|
860 | mentioned earlier in the list. |
|
|
861 | |
|
|
862 | This variable can effectively be used for denial-of-service attacks |
|
|
863 | against local programs (e.g. when setuid), although the impact is |
|
|
864 | likely small, as the program has to handle connection errors |
|
|
865 | already- |
|
|
866 | |
|
|
867 | Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over |
|
|
868 | IPv6, but support both and try to use both. |
|
|
869 | "PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to |
|
|
870 | resolve or contact IPv6 addresses. |
|
|
871 | "PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4" support either IPv4 or IPv6, but |
|
|
872 | prefer IPv6 over IPv4. |
|
|
873 | |
|
|
874 | "PERL_ANYEVENT_EDNS0" |
|
|
875 | Used by AnyEvent::DNS to decide whether to use the EDNS0 extension |
|
|
876 | for DNS. This extension is generally useful to reduce DNS traffic, |
|
|
877 | but some (broken) firewalls drop such DNS packets, which is why it |
|
|
878 | is off by default. |
|
|
879 | |
|
|
880 | Setting this variable to 1 will cause AnyEvent::DNS to announce |
|
|
881 | EDNS0 in its DNS requests. |
|
|
882 | |
|
|
883 | "PERL_ANYEVENT_MAX_FORKS" |
|
|
884 | The maximum number of child processes that |
|
|
885 | "AnyEvent::Util::fork_call" will create in parallel. |
568 | |
886 | |
569 | EXAMPLE PROGRAM |
887 | EXAMPLE PROGRAM |
570 | The following program uses an I/O watcher to read data from STDIN, a |
888 | The following program uses an I/O watcher to read data from STDIN, a |
571 | timer to display a message once per second, and a condition variable to |
889 | timer to display a message once per second, and a condition variable to |
572 | quit the program when the user enters quit: |
890 | quit the program when the user enters quit: |
… | |
… | |
580 | poll => 'r', |
898 | poll => 'r', |
581 | cb => sub { |
899 | cb => sub { |
582 | warn "io event <$_[0]>\n"; # will always output <r> |
900 | warn "io event <$_[0]>\n"; # will always output <r> |
583 | chomp (my $input = <STDIN>); # read a line |
901 | chomp (my $input = <STDIN>); # read a line |
584 | warn "read: $input\n"; # output what has been read |
902 | warn "read: $input\n"; # output what has been read |
585 | $cv->broadcast if $input =~ /^q/i; # quit program if /^q/i |
903 | $cv->send if $input =~ /^q/i; # quit program if /^q/i |
586 | }, |
904 | }, |
587 | ); |
905 | ); |
588 | |
906 | |
589 | my $time_watcher; # can only be used once |
907 | my $time_watcher; # can only be used once |
590 | |
908 | |
… | |
… | |
595 | }); |
913 | }); |
596 | } |
914 | } |
597 | |
915 | |
598 | new_timer; # create first timer |
916 | new_timer; # create first timer |
599 | |
917 | |
600 | $cv->wait; # wait until user enters /^q/i |
918 | $cv->recv; # wait until user enters /^q/i |
601 | |
919 | |
602 | REAL-WORLD EXAMPLE |
920 | REAL-WORLD EXAMPLE |
603 | Consider the Net::FCP module. It features (among others) the following |
921 | Consider the Net::FCP module. It features (among others) the following |
604 | API calls, which are to freenet what HTTP GET requests are to http: |
922 | API calls, which are to freenet what HTTP GET requests are to http: |
605 | |
923 | |
… | |
… | |
654 | syswrite $txn->{fh}, $txn->{request} |
972 | syswrite $txn->{fh}, $txn->{request} |
655 | or die "connection or write error"; |
973 | or die "connection or write error"; |
656 | $txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r }); |
974 | $txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r }); |
657 | |
975 | |
658 | Again, "fh_ready_r" waits till all data has arrived, and then stores the |
976 | Again, "fh_ready_r" waits till all data has arrived, and then stores the |
659 | result and signals any possible waiters that the request ahs finished: |
977 | result and signals any possible waiters that the request has finished: |
660 | |
978 | |
661 | sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf}; |
979 | sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf}; |
662 | |
980 | |
663 | if (end-of-file or data complete) { |
981 | if (end-of-file or data complete) { |
664 | $txn->{result} = $txn->{buf}; |
982 | $txn->{result} = $txn->{buf}; |
665 | $txn->{finished}->broadcast; |
983 | $txn->{finished}->send; |
666 | $txb->{cb}->($txn) of $txn->{cb}; # also call callback |
984 | $txb->{cb}->($txn) of $txn->{cb}; # also call callback |
667 | } |
985 | } |
668 | |
986 | |
669 | The "result" method, finally, just waits for the finished signal (if the |
987 | The "result" method, finally, just waits for the finished signal (if the |
670 | request was already finished, it doesn't wait, of course, and returns |
988 | request was already finished, it doesn't wait, of course, and returns |
671 | the data: |
989 | the data: |
672 | |
990 | |
673 | $txn->{finished}->wait; |
991 | $txn->{finished}->recv; |
674 | return $txn->{result}; |
992 | return $txn->{result}; |
675 | |
993 | |
676 | The actual code goes further and collects all errors ("die"s, |
994 | The actual code goes further and collects all errors ("die"s, |
677 | exceptions) that occured during request processing. The "result" method |
995 | exceptions) that occurred during request processing. The "result" method |
678 | detects whether an exception as thrown (it is stored inside the $txn |
996 | detects whether an exception as thrown (it is stored inside the $txn |
679 | object) and just throws the exception, which means connection errors and |
997 | object) and just throws the exception, which means connection errors and |
680 | other problems get reported tot he code that tries to use the result, |
998 | other problems get reported tot he code that tries to use the result, |
681 | not in a random callback. |
999 | not in a random callback. |
682 | |
1000 | |
… | |
… | |
713 | |
1031 | |
714 | my $quit = AnyEvent->condvar; |
1032 | my $quit = AnyEvent->condvar; |
715 | |
1033 | |
716 | $fcp->txn_client_get ($url)->cb (sub { |
1034 | $fcp->txn_client_get ($url)->cb (sub { |
717 | ... |
1035 | ... |
718 | $quit->broadcast; |
1036 | $quit->send; |
719 | }); |
1037 | }); |
720 | |
1038 | |
721 | $quit->wait; |
1039 | $quit->recv; |
722 | |
1040 | |
723 | BENCHMARKS |
1041 | BENCHMARKS |
724 | To give you an idea of the performance and overheads that AnyEvent adds |
1042 | To give you an idea of the performance and overheads that AnyEvent adds |
725 | over the event loops themselves and to give you an impression of the |
1043 | over the event loops themselves and to give you an impression of the |
726 | speed of various event loops I prepared some benchmarks. |
1044 | speed of various event loops I prepared some benchmarks. |
727 | |
1045 | |
728 | BENCHMARKING ANYEVENT OVERHEAD |
1046 | BENCHMARKING ANYEVENT OVERHEAD |
729 | Here is a benchmark of various supported event models used natively and |
1047 | Here is a benchmark of various supported event models used natively and |
730 | through anyevent. The benchmark creates a lot of timers (with a zero |
1048 | through AnyEvent. The benchmark creates a lot of timers (with a zero |
731 | timeout) and I/O watchers (watching STDOUT, a pty, to become writable, |
1049 | timeout) and I/O watchers (watching STDOUT, a pty, to become writable, |
732 | which it is), lets them fire exactly once and destroys them again. |
1050 | which it is), lets them fire exactly once and destroys them again. |
733 | |
1051 | |
734 | Source code for this benchmark is found as eg/bench in the AnyEvent |
1052 | Source code for this benchmark is found as eg/bench in the AnyEvent |
735 | distribution. |
1053 | distribution. |
… | |
… | |
751 | between all watchers, to avoid adding memory overhead. That means |
1069 | between all watchers, to avoid adding memory overhead. That means |
752 | closure creation and memory usage is not included in the figures. |
1070 | closure creation and memory usage is not included in the figures. |
753 | |
1071 | |
754 | *invoke* is the time, in microseconds, used to invoke a simple callback. |
1072 | *invoke* is the time, in microseconds, used to invoke a simple callback. |
755 | The callback simply counts down a Perl variable and after it was invoked |
1073 | The callback simply counts down a Perl variable and after it was invoked |
756 | "watcher" times, it would "->broadcast" a condvar once to signal the end |
1074 | "watcher" times, it would "->send" a condvar once to signal the end of |
757 | of this phase. |
1075 | this phase. |
758 | |
1076 | |
759 | *destroy* is the time, in microseconds, that it takes to destroy a |
1077 | *destroy* is the time, in microseconds, that it takes to destroy a |
760 | single watcher. |
1078 | single watcher. |
761 | |
1079 | |
762 | Results |
1080 | Results |
… | |
… | |
823 | the figures above). |
1141 | the figures above). |
824 | |
1142 | |
825 | "POE", regardless of underlying event loop (whether using its pure perl |
1143 | "POE", regardless of underlying event loop (whether using its pure perl |
826 | select-based backend or the Event module, the POE-EV backend couldn't be |
1144 | select-based backend or the Event module, the POE-EV backend couldn't be |
827 | tested because it wasn't working) shows abysmal performance and memory |
1145 | tested because it wasn't working) shows abysmal performance and memory |
828 | usage: Watchers use almost 30 times as much memory as EV watchers, and |
1146 | usage with AnyEvent: Watchers use almost 30 times as much memory as EV |
829 | 10 times as much memory as Event (the high memory requirements are |
1147 | watchers, and 10 times as much memory as Event (the high memory |
830 | caused by requiring a session for each watcher). Watcher invocation |
1148 | requirements are caused by requiring a session for each watcher). |
831 | speed is almost 900 times slower than with AnyEvent's pure perl |
1149 | Watcher invocation speed is almost 900 times slower than with AnyEvent's |
|
|
1150 | pure perl implementation. |
|
|
1151 | |
832 | implementation. The design of the POE adaptor class in AnyEvent can not |
1152 | The design of the POE adaptor class in AnyEvent can not really account |
833 | really account for this, as session creation overhead is small compared |
1153 | for the performance issues, though, as session creation overhead is |
834 | to execution of the state machine, which is coded pretty optimally |
1154 | small compared to execution of the state machine, which is coded pretty |
835 | within AnyEvent::Impl::POE. POE simply seems to be abysmally slow. |
1155 | optimally within AnyEvent::Impl::POE (and while everybody agrees that |
|
|
1156 | using multiple sessions is not a good approach, especially regarding |
|
|
1157 | memory usage, even the author of POE could not come up with a faster |
|
|
1158 | design). |
836 | |
1159 | |
837 | Summary |
1160 | Summary |
838 | * Using EV through AnyEvent is faster than any other event loop (even |
1161 | * Using EV through AnyEvent is faster than any other event loop (even |
839 | when used without AnyEvent), but most event loops have acceptable |
1162 | when used without AnyEvent), but most event loops have acceptable |
840 | performance with or without AnyEvent. |
1163 | performance with or without AnyEvent. |
… | |
… | |
845 | |
1168 | |
846 | * You should avoid POE like the plague if you want performance or |
1169 | * You should avoid POE like the plague if you want performance or |
847 | reasonable memory usage. |
1170 | reasonable memory usage. |
848 | |
1171 | |
849 | BENCHMARKING THE LARGE SERVER CASE |
1172 | BENCHMARKING THE LARGE SERVER CASE |
850 | This benchmark atcually benchmarks the event loop itself. It works by |
1173 | This benchmark actually benchmarks the event loop itself. It works by |
851 | creating a number of "servers": each server consists of a socketpair, a |
1174 | creating a number of "servers": each server consists of a socket pair, a |
852 | timeout watcher that gets reset on activity (but never fires), and an |
1175 | timeout watcher that gets reset on activity (but never fires), and an |
853 | I/O watcher waiting for input on one side of the socket. Each time the |
1176 | I/O watcher waiting for input on one side of the socket. Each time the |
854 | socket watcher reads a byte it will write that byte to a random other |
1177 | socket watcher reads a byte it will write that byte to a random other |
855 | "server". |
1178 | "server". |
856 | |
1179 | |
857 | The effect is that there will be a lot of I/O watchers, only part of |
1180 | The effect is that there will be a lot of I/O watchers, only part of |
858 | which are active at any one point (so there is a constant number of |
1181 | which are active at any one point (so there is a constant number of |
859 | active fds for each loop iterstaion, but which fds these are is random). |
1182 | active fds for each loop iteration, but which fds these are is random). |
860 | The timeout is reset each time something is read because that reflects |
1183 | The timeout is reset each time something is read because that reflects |
861 | how most timeouts work (and puts extra pressure on the event loops). |
1184 | how most timeouts work (and puts extra pressure on the event loops). |
862 | |
1185 | |
863 | In this benchmark, we use 10000 socketpairs (20000 sockets), of which |
1186 | In this benchmark, we use 10000 socket pairs (20000 sockets), of which |
864 | 100 (1%) are active. This mirrors the activity of large servers with |
1187 | 100 (1%) are active. This mirrors the activity of large servers with |
865 | many connections, most of which are idle at any one point in time. |
1188 | many connections, most of which are idle at any one point in time. |
866 | |
1189 | |
867 | Source code for this benchmark is found as eg/bench2 in the AnyEvent |
1190 | Source code for this benchmark is found as eg/bench2 in the AnyEvent |
868 | distribution. |
1191 | distribution. |
869 | |
1192 | |
870 | Explanation of the columns |
1193 | Explanation of the columns |
871 | *sockets* is the number of sockets, and twice the number of "servers" |
1194 | *sockets* is the number of sockets, and twice the number of "servers" |
872 | (as each server has a read and write socket end). |
1195 | (as each server has a read and write socket end). |
873 | |
1196 | |
874 | *create* is the time it takes to create a socketpair (which is |
1197 | *create* is the time it takes to create a socket pair (which is |
875 | nontrivial) and two watchers: an I/O watcher and a timeout watcher. |
1198 | nontrivial) and two watchers: an I/O watcher and a timeout watcher. |
876 | |
1199 | |
877 | *request*, the most important value, is the time it takes to handle a |
1200 | *request*, the most important value, is the time it takes to handle a |
878 | single "request", that is, reading the token from the pipe and |
1201 | single "request", that is, reading the token from the pipe and |
879 | forwarding it to another server. This includes deleting the old timeout |
1202 | forwarding it to another server. This includes deleting the old timeout |
… | |
… | |
909 | POE is still completely out of the picture, taking over 1000 times as |
1232 | POE is still completely out of the picture, taking over 1000 times as |
910 | long as EV, and over 100 times as long as the Perl implementation, even |
1233 | long as EV, and over 100 times as long as the Perl implementation, even |
911 | though it uses a C-based event loop in this case. |
1234 | though it uses a C-based event loop in this case. |
912 | |
1235 | |
913 | Summary |
1236 | Summary |
914 | * The pure perl implementation performs extremely well, considering |
1237 | * The pure perl implementation performs extremely well. |
915 | that it uses select. |
|
|
916 | |
1238 | |
917 | * Avoid Glib or POE in large projects where performance matters. |
1239 | * Avoid Glib or POE in large projects where performance matters. |
918 | |
1240 | |
919 | BENCHMARKING SMALL SERVERS |
1241 | BENCHMARKING SMALL SERVERS |
920 | While event loops should scale (and select-based ones do not...) even to |
1242 | While event loops should scale (and select-based ones do not...) even to |
… | |
… | |
944 | and speed most when you have lots of watchers, not when you only have a |
1266 | and speed most when you have lots of watchers, not when you only have a |
945 | few of them). |
1267 | few of them). |
946 | |
1268 | |
947 | EV is again fastest. |
1269 | EV is again fastest. |
948 | |
1270 | |
949 | Perl again comes second. It is noticably faster than the C-based event |
1271 | Perl again comes second. It is noticeably faster than the C-based event |
950 | loops Event and Glib, although the difference is too small to really |
1272 | loops Event and Glib, although the difference is too small to really |
951 | matter. |
1273 | matter. |
952 | |
1274 | |
953 | POE also performs much better in this case, but is is still far behind |
1275 | POE also performs much better in this case, but is is still far behind |
954 | the others. |
1276 | the others. |
… | |
… | |
957 | * C-based event loops perform very well with small number of watchers, |
1279 | * C-based event loops perform very well with small number of watchers, |
958 | as the management overhead dominates. |
1280 | as the management overhead dominates. |
959 | |
1281 | |
960 | FORK |
1282 | FORK |
961 | Most event libraries are not fork-safe. The ones who are usually are |
1283 | Most event libraries are not fork-safe. The ones who are usually are |
962 | because they are so inefficient. Only EV is fully fork-aware. |
1284 | because they rely on inefficient but fork-safe "select" or "poll" calls. |
|
|
1285 | Only EV is fully fork-aware. |
963 | |
1286 | |
964 | If you have to fork, you must either do so *before* creating your first |
1287 | If you have to fork, you must either do so *before* creating your first |
965 | watcher OR you must not use AnyEvent at all in the child. |
1288 | watcher OR you must not use AnyEvent at all in the child. |
966 | |
1289 | |
967 | SECURITY CONSIDERATIONS |
1290 | SECURITY CONSIDERATIONS |
… | |
… | |
973 | model than specified in the variable. |
1296 | model than specified in the variable. |
974 | |
1297 | |
975 | You can make AnyEvent completely ignore this variable by deleting it |
1298 | You can make AnyEvent completely ignore this variable by deleting it |
976 | before the first watcher gets created, e.g. with a "BEGIN" block: |
1299 | before the first watcher gets created, e.g. with a "BEGIN" block: |
977 | |
1300 | |
978 | BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } |
1301 | BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } |
979 | |
1302 | |
980 | use AnyEvent; |
1303 | use AnyEvent; |
|
|
1304 | |
|
|
1305 | Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can |
|
|
1306 | be used to probe what backend is used and gain other information (which |
|
|
1307 | is probably even less useful to an attacker than PERL_ANYEVENT_MODEL), |
|
|
1308 | and $ENV{PERL_ANYEGENT_STRICT}. |
|
|
1309 | |
|
|
1310 | BUGS |
|
|
1311 | Perl 5.8 has numerous memleaks that sometimes hit this module and are |
|
|
1312 | hard to work around. If you suffer from memleaks, first upgrade to Perl |
|
|
1313 | 5.10 and check wether the leaks still show up. (Perl 5.10.0 has other |
|
|
1314 | annoying mamleaks, such as leaking on "map" and "grep" but it is usually |
|
|
1315 | not as pronounced). |
981 | |
1316 | |
982 | SEE ALSO |
1317 | SEE ALSO |
983 | Event modules: Coro::EV, EV, EV::Glib, Glib::EV, Coro::Event, Event, |
1318 | Utility functions: AnyEvent::Util. |
984 | Glib::Event, Glib, Coro, Tk, Event::Lib, Qt, POE. |
|
|
985 | |
1319 | |
986 | Implementations: AnyEvent::Impl::CoroEV, AnyEvent::Impl::EV, |
1320 | Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk, |
987 | AnyEvent::Impl::CoroEvent, AnyEvent::Impl::Event, AnyEvent::Impl::Glib, |
1321 | Event::Lib, Qt, POE. |
988 | AnyEvent::Impl::Tk, AnyEvent::Impl::Perl, AnyEvent::Impl::EventLib, |
1322 | |
|
|
1323 | Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event, |
|
|
1324 | AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl, |
989 | AnyEvent::Impl::Qt, AnyEvent::Impl::POE. |
1325 | AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE. |
990 | |
1326 | |
|
|
1327 | Non-blocking file handles, sockets, TCP clients and servers: |
|
|
1328 | AnyEvent::Handle, AnyEvent::Socket. |
|
|
1329 | |
|
|
1330 | Asynchronous DNS: AnyEvent::DNS. |
|
|
1331 | |
|
|
1332 | Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event, |
|
|
1333 | |
991 | Nontrivial usage examples: Net::FCP, Net::XMPP2. |
1334 | Nontrivial usage examples: Net::FCP, Net::XMPP2, AnyEvent::DNS. |
992 | |
1335 | |
993 | AUTHOR |
1336 | AUTHOR |
994 | Marc Lehmann <schmorp@schmorp.de> |
1337 | Marc Lehmann <schmorp@schmorp.de> |
995 | http://home.schmorp.de/ |
1338 | http://home.schmorp.de/ |
996 | |
1339 | |