… | |
… | |
13 | |
13 | |
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 wether a condition was flagged |
18 | my $w = AnyEvent->condvar; # stores whether a condition was flagged |
19 | $w->wait; # enters "main loop" till $condvar gets ->broadcast |
19 | $w->wait; # enters "main loop" till $condvar gets ->broadcast |
20 | $w->broadcast; # wake up current and all future wait's |
20 | $w->broadcast; # wake up current and all future wait's |
21 | |
21 | |
22 | WHY YOU SHOULD USE THIS MODULE (OR NOT) |
22 | WHY YOU SHOULD USE THIS MODULE (OR NOT) |
23 | Glib, POE, IO::Async, Event... CPAN offers event models by the dozen |
23 | Glib, POE, IO::Async, Event... CPAN offers event models by the dozen |
… | |
… | |
27 | policy* and AnyEvent is *small and efficient*. |
27 | policy* and AnyEvent is *small and efficient*. |
28 | |
28 | |
29 | First and foremost, *AnyEvent is not an event model* itself, it only |
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 |
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, |
31 | pragmatic way. For event models and certain classes of immortals alike, |
32 | the statement "there can only be one" is a bitter reality, and AnyEvent |
32 | the statement "there can only be one" is a bitter reality: In general, |
33 | helps hiding the differences. |
33 | only one event loop can be active at the same time in a process. |
|
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34 | AnyEvent helps hiding the differences between those event loops. |
34 | |
35 | |
35 | The goal of AnyEvent is to offer module authors the ability to do event |
36 | The goal of AnyEvent is to offer module authors the ability to do event |
36 | programming (waiting for I/O or timer events) without subscribing to a |
37 | programming (waiting for I/O or timer events) without subscribing to a |
37 | religion, a way of living, and most importantly: without forcing your |
38 | religion, a way of living, and most importantly: without forcing your |
38 | module users into the same thing by forcing them to use the same event |
39 | module users into the same thing by forcing them to use the same event |
39 | model you use. |
40 | model you use. |
40 | |
41 | |
41 | For modules like POE or IO::Async (which is actually doing all I/O |
42 | For modules like POE or IO::Async (which is a total misnomer as it is |
42 | *synchronously*...), using them in your module is like joining a cult: |
43 | actually doing all I/O *synchronously*...), using them in your module is |
43 | After you joined, you are dependent on them and you cannot use anything |
44 | like joining a cult: After you joined, you are dependent on them and you |
44 | else, as it is simply incompatible to everything that isn't itself. |
45 | cannot use anything else, as it is simply incompatible to everything |
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46 | that isn't itself. What's worse, all the potential users of your module |
|
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47 | are *also* forced to use the same event loop you use. |
45 | |
48 | |
46 | AnyEvent + POE works fine. AnyEvent + Glib works fine. AnyEvent + Tk |
49 | AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works |
47 | works fine etc. etc. but none of these work together with the rest: POE |
50 | fine. AnyEvent + Tk works fine etc. etc. but none of these work together |
48 | + IO::Async? no go. Tk + Event? no go. If your module uses one of those, |
51 | with the rest: POE + IO::Async? no go. Tk + Event? no go. Again: if your |
49 | every user of your module has to use it, too. If your module uses |
52 | module uses one of those, every user of your module has to use it, too. |
50 | AnyEvent, it works transparently with all event models it supports |
53 | But if your module uses AnyEvent, it works transparently with all event |
51 | (including stuff like POE and IO::Async). |
54 | models it supports (including stuff like POE and IO::Async, as long as |
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55 | those use one of the supported event loops. It is trivial to add new |
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56 | event loops to AnyEvent, too, so it is future-proof). |
52 | |
57 | |
53 | In addition of being free of having to use *the one and only true event |
58 | In addition to being free of having to use *the one and only true event |
54 | model*, AnyEvent also is free of bloat and policy: with POE or similar |
59 | model*, AnyEvent also is free of bloat and policy: with POE or similar |
55 | modules, you get an enourmous amount of code and strict rules you have |
60 | modules, you get an enourmous amount of code and strict rules you have |
56 | to follow. AnyEvent, on the other hand, is lean and to the point by only |
61 | to follow. AnyEvent, on the other hand, is lean and up to the point, by |
57 | offering the functionality that is useful, in as thin as a wrapper as |
62 | only offering the functionality that is necessary, in as thin as a |
58 | technically possible. |
63 | wrapper as technically possible. |
59 | |
64 | |
60 | Of course, if you want lots of policy (this can arguably be somewhat |
65 | Of course, if you want lots of policy (this can arguably be somewhat |
61 | useful) and you want to force your users to use the one and only event |
66 | useful) and you want to force your users to use the one and only event |
62 | model, you should *not* use this module. |
67 | model, you should *not* use this module. |
63 | |
68 | |
… | |
… | |
65 | AnyEvent provides an identical interface to multiple event loops. This |
70 | AnyEvent provides an identical interface to multiple event loops. This |
66 | allows module authors to utilise an event loop without forcing module |
71 | allows module authors to utilise an event loop without forcing module |
67 | 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 |
68 | coexist peacefully at any one time). |
73 | coexist peacefully at any one time). |
69 | |
74 | |
70 | 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 |
71 | module. |
76 | module. |
72 | |
77 | |
73 | 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 |
74 | 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 |
75 | modules is loaded: Coro::EV, Coro::Event, EV, Event, Glib, Tk. The first |
80 | following modules is already loaded: Coro::EV, Coro::Event, EV, Event, |
76 | one found is used. If none are found, the module tries to load these |
81 | Glib, Tk. The first one found is used. If none are found, the module |
77 | modules in the order given. The first one that could be successfully |
82 | tries to load these modules in the stated order. The first one that can |
78 | loaded will be used. If still none could be found, AnyEvent will fall |
83 | be successfully loaded will be used. If, after this, still none could be |
79 | back to a pure-perl event loop, which is also not very efficient. |
84 | found, AnyEvent will fall back to a pure-perl event loop, which is not |
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85 | very efficient, but should work everywhere. |
80 | |
86 | |
81 | Because AnyEvent first checks for modules that are already loaded, |
87 | Because AnyEvent first checks for modules that are already loaded, |
82 | loading an Event model explicitly before first using AnyEvent will |
88 | loading an event model explicitly before first using AnyEvent will |
83 | likely make that model the default. For example: |
89 | likely make that model the default. For example: |
84 | |
90 | |
85 | use Tk; |
91 | use Tk; |
86 | use AnyEvent; |
92 | use AnyEvent; |
87 | |
93 | |
88 | # .. AnyEvent will likely default to Tk |
94 | # .. AnyEvent will likely default to Tk |
|
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95 | |
|
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96 | The *likely* means that, if any module loads another event model and |
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97 | starts using it, all bets are off. Maybe you should tell their authors |
|
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98 | to use AnyEvent so their modules work together with others seamlessly... |
89 | |
99 | |
90 | The pure-perl implementation of AnyEvent is called |
100 | The pure-perl implementation of AnyEvent is called |
91 | "AnyEvent::Impl::Perl". Like other event modules you can load it |
101 | "AnyEvent::Impl::Perl". Like other event modules you can load it |
92 | explicitly. |
102 | explicitly. |
93 | |
103 | |
… | |
… | |
96 | stores relevant data for each kind of event you are waiting for, such as |
106 | stores relevant data for each kind of event you are waiting for, such as |
97 | the callback to call, the filehandle to watch, etc. |
107 | the callback to call, the filehandle to watch, etc. |
98 | |
108 | |
99 | These watchers are normal Perl objects with normal Perl lifetime. After |
109 | These watchers are normal Perl objects with normal Perl lifetime. After |
100 | creating a watcher it will immediately "watch" for events and invoke the |
110 | creating a watcher it will immediately "watch" for events and invoke the |
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111 | callback when the event occurs (of course, only when the event model is |
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112 | in control). |
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113 | |
101 | callback. To disable the watcher you have to destroy it (e.g. by setting |
114 | To disable the watcher you have to destroy it (e.g. by setting the |
102 | the variable that stores it to "undef" or otherwise deleting all |
115 | variable you store it in to "undef" or otherwise deleting all references |
103 | references to it). |
116 | to it). |
104 | |
117 | |
105 | All watchers are created by calling a method on the "AnyEvent" class. |
118 | All watchers are created by calling a method on the "AnyEvent" class. |
106 | |
119 | |
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120 | Many watchers either are used with "recursion" (repeating timers for |
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121 | example), or need to refer to their watcher object in other ways. |
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122 | |
|
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123 | An any way to achieve that is this pattern: |
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124 | |
|
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125 | my $w; $w = AnyEvent->type (arg => value ..., cb => sub { |
|
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126 | # you can use $w here, for example to undef it |
|
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127 | undef $w; |
|
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128 | }); |
|
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129 | |
|
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130 | Note that "my $w; $w =" combination. This is necessary because in Perl, |
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131 | my variables are only visible after the statement in which they are |
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132 | declared. |
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133 | |
107 | IO WATCHERS |
134 | IO WATCHERS |
108 | You can create I/O watcher by calling the "AnyEvent->io" method with the |
135 | You can create an I/O watcher by calling the "AnyEvent->io" method with |
109 | following mandatory arguments: |
136 | the following mandatory key-value pairs as arguments: |
110 | |
137 | |
111 | "fh" the Perl *filehandle* (not filedescriptor) to watch for events. |
138 | "fh" the Perl *file handle* (*not* file descriptor) to watch for events. |
112 | "poll" must be a string that is either "r" or "w", that creates a |
139 | "poll" must be a string that is either "r" or "w", which creates a |
113 | watcher waiting for "r"eadable or "w"ritable events. "cb" the callback |
140 | watcher waiting for "r"eadable or "w"ritable events, respectively. "cb" |
114 | to invoke everytime the filehandle becomes ready. |
141 | is the callback to invoke each time the file handle becomes ready. |
115 | |
142 | |
116 | Filehandles will be kept alive, so as long as the watcher exists, the |
143 | File handles will be kept alive, so as long as the watcher exists, the |
117 | filehandle exists, too. |
144 | file handle exists, too. |
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145 | |
|
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146 | It is not allowed to close a file handle as long as any watcher is |
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147 | active on the underlying file descriptor. |
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148 | |
|
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149 | Some event loops issue spurious readyness notifications, so you should |
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150 | always use non-blocking calls when reading/writing from/to your file |
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151 | handles. |
118 | |
152 | |
119 | Example: |
153 | Example: |
120 | |
154 | |
121 | # wait for readability of STDIN, then read a line and disable the watcher |
155 | # wait for readability of STDIN, then read a line and disable the watcher |
122 | my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { |
156 | my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { |
… | |
… | |
127 | |
161 | |
128 | TIME WATCHERS |
162 | TIME WATCHERS |
129 | You can create a time watcher by calling the "AnyEvent->timer" method |
163 | You can create a time watcher by calling the "AnyEvent->timer" method |
130 | with the following mandatory arguments: |
164 | with the following mandatory arguments: |
131 | |
165 | |
132 | "after" after how many seconds (fractions are supported) should the |
166 | "after" specifies after how many seconds (fractional values are |
133 | timer activate. "cb" the callback to invoke. |
167 | supported) should the timer activate. "cb" the callback to invoke in |
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168 | that case. |
134 | |
169 | |
135 | The timer callback will be invoked at most once: if you want a repeating |
170 | The timer callback will be invoked at most once: if you want a repeating |
136 | timer you have to create a new watcher (this is a limitation by both Tk |
171 | timer you have to create a new watcher (this is a limitation by both Tk |
137 | and Glib). |
172 | and Glib). |
138 | |
173 | |
… | |
… | |
144 | }); |
179 | }); |
145 | |
180 | |
146 | # to cancel the timer: |
181 | # to cancel the timer: |
147 | undef $w; |
182 | undef $w; |
148 | |
183 | |
149 | CONDITION WATCHERS |
184 | Example 2: |
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185 | |
|
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186 | # fire an event after 0.5 seconds, then roughly every second |
|
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187 | my $w; |
|
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188 | |
|
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189 | my $cb = sub { |
|
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190 | # cancel the old timer while creating a new one |
|
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191 | $w = AnyEvent->timer (after => 1, cb => $cb); |
|
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192 | }; |
|
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193 | |
|
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194 | # start the "loop" by creating the first watcher |
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195 | $w = AnyEvent->timer (after => 0.5, cb => $cb); |
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196 | |
|
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197 | TIMING ISSUES |
|
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198 | There are two ways to handle timers: based on real time (relative, "fire |
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199 | in 10 seconds") and based on wallclock time (absolute, "fire at 12 |
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200 | o'clock"). |
|
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201 | |
|
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202 | While most event loops expect timers to specified in a relative way, |
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203 | they use absolute time internally. This makes a difference when your |
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204 | clock "jumps", for example, when ntp decides to set your clock backwards |
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205 | from the wrong 2014-01-01 to 2008-01-01, a watcher that you created to |
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206 | fire "after" a second might actually take six years to finally fire. |
|
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207 | |
|
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208 | AnyEvent cannot compensate for this. The only event loop that is |
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209 | conscious about these issues is EV, which offers both relative |
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210 | (ev_timer) and absolute (ev_periodic) timers. |
|
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211 | |
|
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212 | AnyEvent always prefers relative timers, if available, matching the |
|
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213 | AnyEvent API. |
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214 | |
|
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215 | SIGNAL WATCHERS |
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216 | You can watch for signals using a signal watcher, "signal" is the signal |
|
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217 | *name* without any "SIG" prefix, "cb" is the Perl callback to be invoked |
|
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218 | whenever a signal occurs. |
|
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219 | |
|
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220 | Multiple signals occurances can be clumped together into one callback |
|
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221 | invocation, and callback invocation will be synchronous. synchronous |
|
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222 | means that it might take a while until the signal gets handled by the |
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223 | process, but it is guarenteed not to interrupt any other callbacks. |
|
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224 | |
|
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225 | The main advantage of using these watchers is that you can share a |
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226 | signal between multiple watchers. |
|
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227 | |
|
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228 | This watcher might use %SIG, so programs overwriting those signals |
|
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229 | directly will likely not work correctly. |
|
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230 | |
|
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231 | Example: exit on SIGINT |
|
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232 | |
|
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233 | my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 }); |
|
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234 | |
|
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235 | CHILD PROCESS WATCHERS |
|
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236 | You can also watch on a child process exit and catch its exit status. |
|
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237 | |
|
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238 | The child process is specified by the "pid" argument (if set to 0, it |
|
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239 | watches for any child process exit). The watcher will trigger as often |
|
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240 | as status change for the child are received. This works by installing a |
|
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241 | signal handler for "SIGCHLD". The callback will be called with the pid |
|
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242 | and exit status (as returned by waitpid). |
|
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243 | |
|
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244 | Example: wait for pid 1333 |
|
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245 | |
|
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246 | my $w = AnyEvent->child ( |
|
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247 | pid => 1333, |
|
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248 | cb => sub { |
|
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249 | my ($pid, $status) = @_; |
|
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250 | warn "pid $pid exited with status $status"; |
|
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251 | }, |
|
|
252 | ); |
|
|
253 | |
|
|
254 | CONDITION VARIABLES |
150 | Condition watchers can be created by calling the "AnyEvent->condvar" |
255 | Condition variables can be created by calling the "AnyEvent->condvar" |
151 | method without any arguments. |
256 | method without any arguments. |
152 | |
257 | |
153 | A condition watcher watches for a condition - precisely that the |
258 | A condition variable waits for a condition - precisely that the |
154 | "->broadcast" method has been called. |
259 | "->broadcast" method has been called. |
155 | |
260 | |
|
|
261 | They are very useful to signal that a condition has been fulfilled, for |
|
|
262 | example, if you write a module that does asynchronous http requests, |
|
|
263 | then a condition variable would be the ideal candidate to signal the |
|
|
264 | availability of results. |
|
|
265 | |
|
|
266 | You can also use condition variables to block your main program until an |
|
|
267 | event occurs - for example, you could "->wait" in your main program |
|
|
268 | until the user clicks the Quit button in your app, which would |
|
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269 | "->broadcast" the "quit" event. |
|
|
270 | |
156 | Note that condition watchers recurse into the event loop - if you have |
271 | Note that condition variables recurse into the event loop - if you have |
157 | two watchers that call "->wait" in a round-robbin fashion, you lose. |
272 | two pirces of code that call "->wait" in a round-robbin fashion, you |
158 | Therefore, condition watchers are good to export to your caller, but you |
273 | lose. Therefore, condition variables are good to export to your caller, |
159 | should avoid making a blocking wait, at least in callbacks, as this |
274 | but you should avoid making a blocking wait yourself, at least in |
160 | usually asks for trouble. |
275 | callbacks, as this asks for trouble. |
161 | |
276 | |
162 | The watcher has only two methods: |
277 | This object has two methods: |
163 | |
278 | |
164 | $cv->wait |
279 | $cv->wait |
165 | Wait (blocking if necessary) until the "->broadcast" method has been |
280 | Wait (blocking if necessary) until the "->broadcast" method has been |
166 | called on c<$cv>, while servicing other watchers normally. |
281 | called on c<$cv>, while servicing other watchers normally. |
167 | |
282 | |
168 | You can only wait once on a condition - additional calls will return |
283 | You can only wait once on a condition - additional calls will return |
169 | immediately. |
284 | immediately. |
170 | |
285 | |
171 | Not all event models support a blocking wait - some die in that case |
286 | Not all event models support a blocking wait - some die in that case |
172 | (programs might want to do that so they stay interactive), so *if |
287 | (programs might want to do that to stay interactive), so *if you are |
173 | you are using this from a module, never require a blocking wait*, |
288 | using this from a module, never require a blocking wait*, but let |
174 | but let the caller decide wether the call will block or not (for |
289 | the caller decide whether the call will block or not (for example, |
175 | example, by coupling condition variables with some kind of request |
290 | by coupling condition variables with some kind of request results |
176 | results and supporting callbacks so the caller knows that getting |
291 | and supporting callbacks so the caller knows that getting the result |
177 | the result will not block, while still suppporting blocking waits if |
292 | will not block, while still suppporting blocking waits if the caller |
178 | the caller so desires). |
293 | so desires). |
179 | |
294 | |
180 | Another reason *never* to "->wait" in a module is that you cannot |
295 | Another reason *never* to "->wait" in a module is that you cannot |
181 | sensibly have two "->wait"'s in parallel, as that would require |
296 | sensibly have two "->wait"'s in parallel, as that would require |
182 | multiple interpreters or coroutines/threads, none of which |
297 | multiple interpreters or coroutines/threads, none of which |
183 | "AnyEvent" can supply (the coroutine-aware backends "Coro::EV" and |
298 | "AnyEvent" can supply (the coroutine-aware backends |
184 | "Coro::Event" explicitly support concurrent "->wait"'s from |
299 | AnyEvent::Impl::CoroEV and AnyEvent::Impl::CoroEvent explicitly |
185 | different coroutines, however). |
300 | support concurrent "->wait"'s from different coroutines, however). |
186 | |
301 | |
187 | $cv->broadcast |
302 | $cv->broadcast |
188 | Flag the condition as ready - a running "->wait" and all further |
303 | Flag the condition as ready - a running "->wait" and all further |
189 | calls to "wait" will return after this method has been called. If |
304 | calls to "wait" will (eventually) return after this method has been |
190 | nobody is waiting the broadcast will be remembered.. |
305 | called. If nobody is waiting the broadcast will be remembered.. |
191 | |
306 | |
192 | Example: |
307 | Example: |
193 | |
308 | |
194 | # wait till the result is ready |
309 | # wait till the result is ready |
195 | my $result_ready = AnyEvent->condvar; |
310 | my $result_ready = AnyEvent->condvar; |
196 | |
311 | |
197 | # do something such as adding a timer |
312 | # do something such as adding a timer |
198 | # or socket watcher the calls $result_ready->broadcast |
313 | # or socket watcher the calls $result_ready->broadcast |
199 | # when the "result" is ready. |
314 | # when the "result" is ready. |
|
|
315 | # in this case, we simply use a timer: |
|
|
316 | my $w = AnyEvent->timer ( |
|
|
317 | after => 1, |
|
|
318 | cb => sub { $result_ready->broadcast }, |
|
|
319 | ); |
200 | |
320 | |
|
|
321 | # this "blocks" (while handling events) till the watcher |
|
|
322 | # calls broadcast |
201 | $result_ready->wait; |
323 | $result_ready->wait; |
202 | |
324 | |
203 | SIGNAL WATCHERS |
325 | GLOBAL VARIABLES AND FUNCTIONS |
204 | You can listen for signals using a signal watcher, "signal" is the |
|
|
205 | signal *name* without any "SIG" prefix. Multiple signals events can be |
|
|
206 | clumped together into one callback invocation, and callback invocation |
|
|
207 | might or might not be asynchronous. |
|
|
208 | |
|
|
209 | These watchers might use %SIG, so programs overwriting those signals |
|
|
210 | directly will likely not work correctly. |
|
|
211 | |
|
|
212 | Example: exit on SIGINT |
|
|
213 | |
|
|
214 | my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 }); |
|
|
215 | |
|
|
216 | CHILD PROCESS WATCHERS |
|
|
217 | You can also listen for the status of a child process specified by the |
|
|
218 | "pid" argument (or any child if the pid argument is 0). The watcher will |
|
|
219 | trigger as often as status change for the child are received. This works |
|
|
220 | by installing a signal handler for "SIGCHLD". The callback will be |
|
|
221 | called with the pid and exit status (as returned by waitpid). |
|
|
222 | |
|
|
223 | Example: wait for pid 1333 |
|
|
224 | |
|
|
225 | my $w = AnyEvent->child (pid => 1333, cb => sub { warn "exit status $?" }); |
|
|
226 | |
|
|
227 | GLOBALS |
|
|
228 | $AnyEvent::MODEL |
326 | $AnyEvent::MODEL |
229 | Contains "undef" until the first watcher is being created. Then it |
327 | Contains "undef" until the first watcher is being created. Then it |
230 | contains the event model that is being used, which is the name of |
328 | contains the event model that is being used, which is the name of |
231 | the Perl class implementing the model. This class is usually one of |
329 | the Perl class implementing the model. This class is usually one of |
232 | the "AnyEvent::Impl:xxx" modules, but can be any other class in the |
330 | the "AnyEvent::Impl:xxx" modules, but can be any other class in the |
… | |
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243 | AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable. |
341 | AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable. |
244 | |
342 | |
245 | AnyEvent::detect |
343 | AnyEvent::detect |
246 | Returns $AnyEvent::MODEL, forcing autodetection of the event model |
344 | Returns $AnyEvent::MODEL, forcing autodetection of the event model |
247 | if necessary. You should only call this function right before you |
345 | if necessary. You should only call this function right before you |
248 | would have created an AnyEvent watcher anyway, that is, very late at |
346 | would have created an AnyEvent watcher anyway, that is, as late as |
249 | runtime. |
347 | possible at runtime. |
250 | |
348 | |
251 | WHAT TO DO IN A MODULE |
349 | WHAT TO DO IN A MODULE |
252 | As a module author, you should "use AnyEvent" and call AnyEvent methods |
350 | As a module author, you should "use AnyEvent" and call AnyEvent methods |
253 | freely, but you should not load a specific event module or rely on it. |
351 | freely, but you should not load a specific event module or rely on it. |
254 | |
352 | |
255 | Be careful when you create watchers in the module body - Anyevent will |
353 | Be careful when you create watchers in the module body - AnyEvent will |
256 | decide which event module to use as soon as the first method is called, |
354 | decide which event module to use as soon as the first method is called, |
257 | so by calling AnyEvent in your module body you force the user of your |
355 | so by calling AnyEvent in your module body you force the user of your |
258 | module to load the event module first. |
356 | module to load the event module first. |
259 | |
357 | |
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358 | Never call "->wait" on a condition variable unless you *know* that the |
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359 | "->broadcast" method has been called on it already. This is because it |
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360 | will stall the whole program, and the whole point of using events is to |
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361 | stay interactive. |
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362 | |
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363 | It is fine, however, to call "->wait" when the user of your module |
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364 | requests it (i.e. if you create a http request object ad have a method |
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365 | called "results" that returns the results, it should call "->wait" |
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366 | freely, as the user of your module knows what she is doing. always). |
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367 | |
260 | WHAT TO DO IN THE MAIN PROGRAM |
368 | WHAT TO DO IN THE MAIN PROGRAM |
261 | There will always be a single main program - the only place that should |
369 | There will always be a single main program - the only place that should |
262 | dictate which event model to use. |
370 | dictate which event model to use. |
263 | |
371 | |
264 | If it doesn't care, it can just "use AnyEvent" and use it itself, or not |
372 | If it doesn't care, it can just "use AnyEvent" and use it itself, or not |
265 | do anything special and let AnyEvent decide which implementation to |
373 | do anything special (it does not need to be event-based) and let |
266 | chose. |
374 | AnyEvent decide which implementation to chose if some module relies on |
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375 | it. |
267 | |
376 | |
268 | If the main program relies on a specific event model (for example, in |
377 | If the main program relies on a specific event model. For example, in |
269 | Gtk2 programs you have to rely on either Glib or Glib::Event), you |
378 | Gtk2 programs you have to rely on the Glib module. You should load the |
270 | should load it before loading AnyEvent or any module that uses it, |
379 | event module before loading AnyEvent or any module that uses it: |
271 | generally, as early as possible. The reason is that modules might create |
380 | generally speaking, you should load it as early as possible. The reason |
272 | watchers when they are loaded, and AnyEvent will decide on the event |
381 | is that modules might create watchers when they are loaded, and AnyEvent |
273 | model to use as soon as it creates watchers, and it might chose the |
382 | will decide on the event model to use as soon as it creates watchers, |
274 | wrong one unless you load the correct one yourself. |
383 | and it might chose the wrong one unless you load the correct one |
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384 | yourself. |
275 | |
385 | |
276 | You can chose to use a rather inefficient pure-perl implementation by |
386 | You can chose to use a rather inefficient pure-perl implementation by |
277 | loading the "AnyEvent::Impl::Perl" module, but letting AnyEvent chose is |
387 | loading the "AnyEvent::Impl::Perl" module, which gives you similar |
278 | generally better. |
388 | behaviour everywhere, but letting AnyEvent chose is generally better. |
279 | |
389 | |
280 | SUPPLYING YOUR OWN EVENT MODEL INTERFACE |
390 | SUPPLYING YOUR OWN EVENT MODEL INTERFACE |
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391 | This is an advanced topic that you do not normally need to use AnyEvent |
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392 | in a module. This section is only of use to event loop authors who want |
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393 | to provide AnyEvent compatibility. |
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394 | |
281 | If you need to support another event library which isn't directly |
395 | If you need to support another event library which isn't directly |
282 | supported by AnyEvent, you can supply your own interface to it by |
396 | supported by AnyEvent, you can supply your own interface to it by |
283 | pushing, before the first watcher gets created, the package name of the |
397 | pushing, before the first watcher gets created, the package name of the |
284 | event module and the package name of the interface to use onto |
398 | event module and the package name of the interface to use onto |
285 | @AnyEvent::REGISTRY. You can do that before and even without loading |
399 | @AnyEvent::REGISTRY. You can do that before and even without loading |
286 | AnyEvent. |
400 | AnyEvent, so it is reasonably cheap. |
287 | |
401 | |
288 | Example: |
402 | Example: |
289 | |
403 | |
290 | push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::]; |
404 | push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::]; |
291 | |
405 | |
292 | This tells AnyEvent to (literally) use the "urxvt::anyevent::" |
406 | This tells AnyEvent to (literally) use the "urxvt::anyevent::" |
293 | package/class when it finds the "urxvt" package/module is loaded. When |
407 | package/class when it finds the "urxvt" package/module is already |
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408 | loaded. |
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409 | |
294 | AnyEvent is loaded and asked to find a suitable event model, it will |
410 | When AnyEvent is loaded and asked to find a suitable event model, it |
295 | first check for the presence of urxvt. |
411 | will first check for the presence of urxvt by trying to "use" the |
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412 | "urxvt::anyevent" module. |
296 | |
413 | |
297 | The class should provide implementations for all watcher types (see |
414 | The class should provide implementations for all watcher types. See |
298 | AnyEvent::Impl::Event (source code), AnyEvent::Impl::Glib (Source code) |
415 | AnyEvent::Impl::EV (source code), AnyEvent::Impl::Glib (Source code) and |
299 | and so on for actual examples, use "perldoc -m AnyEvent::Impl::Glib" to |
416 | so on for actual examples. Use "perldoc -m AnyEvent::Impl::Glib" to see |
300 | see the sources). |
417 | the sources. |
301 | |
418 | |
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419 | If you don't provide "signal" and "child" watchers than AnyEvent will |
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420 | provide suitable (hopefully) replacements. |
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421 | |
302 | The above isn't fictitious, the *rxvt-unicode* (a.k.a. urxvt) uses the |
422 | The above example isn't fictitious, the *rxvt-unicode* (a.k.a. urxvt) |
303 | above line as-is. An interface isn't included in AnyEvent because it |
423 | terminal emulator uses the above line as-is. An interface isn't included |
304 | doesn't make sense outside the embedded interpreter inside |
424 | in AnyEvent because it doesn't make sense outside the embedded |
305 | *rxvt-unicode*, and it is updated and maintained as part of the |
425 | interpreter inside *rxvt-unicode*, and it is updated and maintained as |
306 | *rxvt-unicode* distribution. |
426 | part of the *rxvt-unicode* distribution. |
307 | |
427 | |
308 | *rxvt-unicode* also cheats a bit by not providing blocking access to |
428 | *rxvt-unicode* also cheats a bit by not providing blocking access to |
309 | condition variables: code blocking while waiting for a condition will |
429 | condition variables: code blocking while waiting for a condition will |
310 | "die". This still works with most modules/usages, and blocking calls |
430 | "die". This still works with most modules/usages, and blocking calls |
311 | must not be in an interactive application, so it makes sense. |
431 | must not be done in an interactive application, so it makes sense. |
312 | |
432 | |
313 | ENVIRONMENT VARIABLES |
433 | ENVIRONMENT VARIABLES |
314 | The following environment variables are used by this module: |
434 | The following environment variables are used by this module: |
315 | |
435 | |
316 | "PERL_ANYEVENT_VERBOSE" when set to 2 or higher, reports which event |
436 | "PERL_ANYEVENT_VERBOSE" when set to 2 or higher, cause AnyEvent to |
317 | model gets used. |
437 | report to STDERR which event model it chooses. |
318 | |
438 | |
319 | EXAMPLE |
439 | EXAMPLE PROGRAM |
320 | The following program uses an io watcher to read data from stdin, a |
440 | The following program uses an IO watcher to read data from STDIN, a |
321 | timer to display a message once per second, and a condvar to exit the |
441 | timer to display a message once per second, and a condition variable to |
322 | program when the user enters quit: |
442 | quit the program when the user enters quit: |
323 | |
443 | |
324 | use AnyEvent; |
444 | use AnyEvent; |
325 | |
445 | |
326 | my $cv = AnyEvent->condvar; |
446 | my $cv = AnyEvent->condvar; |
327 | |
447 | |
328 | my $io_watcher = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { |
448 | my $io_watcher = AnyEvent->io ( |
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449 | fh => \*STDIN, |
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450 | poll => 'r', |
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451 | cb => sub { |
329 | warn "io event <$_[0]>\n"; # will always output <r> |
452 | warn "io event <$_[0]>\n"; # will always output <r> |
330 | chomp (my $input = <STDIN>); # read a line |
453 | chomp (my $input = <STDIN>); # read a line |
331 | warn "read: $input\n"; # output what has been read |
454 | warn "read: $input\n"; # output what has been read |
332 | $cv->broadcast if $input =~ /^q/i; # quit program if /^q/i |
455 | $cv->broadcast if $input =~ /^q/i; # quit program if /^q/i |
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456 | }, |
333 | }); |
457 | ); |
334 | |
458 | |
335 | my $time_watcher; # can only be used once |
459 | my $time_watcher; # can only be used once |
336 | |
460 | |
337 | sub new_timer { |
461 | sub new_timer { |
338 | $timer = AnyEvent->timer (after => 1, cb => sub { |
462 | $timer = AnyEvent->timer (after => 1, cb => sub { |
… | |
… | |
419 | $txn->{finished}->wait; |
543 | $txn->{finished}->wait; |
420 | return $txn->{result}; |
544 | return $txn->{result}; |
421 | |
545 | |
422 | The actual code goes further and collects all errors ("die"s, |
546 | The actual code goes further and collects all errors ("die"s, |
423 | exceptions) that occured during request processing. The "result" method |
547 | exceptions) that occured during request processing. The "result" method |
424 | detects wether an exception as thrown (it is stored inside the $txn |
548 | detects whether an exception as thrown (it is stored inside the $txn |
425 | object) and just throws the exception, which means connection errors and |
549 | object) and just throws the exception, which means connection errors and |
426 | other problems get reported tot he code that tries to use the result, |
550 | other problems get reported tot he code that tries to use the result, |
427 | not in a random callback. |
551 | not in a random callback. |
428 | |
552 | |
429 | All of this enables the following usage styles: |
553 | All of this enables the following usage styles: |