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 - various supported |
4 | EV, Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event |
5 | 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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… | |
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 |
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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 |
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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 |
24 | nowadays. So what is different about AnyEvent? |
24 | nowadays. So what is different about AnyEvent? |
25 | |
25 | |
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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 enormous amount of code and strict rules you have to |
56 | to follow. AnyEvent, on the other hand, is lean and to the point by only |
61 | 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 | |
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65 | Of course, AnyEvent comes with a big (and fully optional!) toolbox of |
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66 | useful functionality, such as an asynchronous DNS resolver, 100% |
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67 | non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms |
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68 | such as Windows) and lots of real-world knowledge and workarounds for |
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69 | platform bugs and differences. |
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70 | |
60 | Of course, if you want lots of policy (this can arguably be somewhat |
71 | Now, if you *do 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 |
72 | useful) and you want to force your users to use the one and only event |
62 | model, you should *not* use this module. |
73 | model, you should *not* use this module. |
63 | |
74 | |
64 | DESCRIPTION |
75 | DESCRIPTION |
65 | AnyEvent provides an identical interface to multiple event loops. This |
76 | AnyEvent provides an identical interface to multiple event loops. This |
66 | allows module authors to utilise an event loop without forcing module |
77 | 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 |
78 | users to use the same event loop (as only a single event loop can |
68 | coexist peacefully at any one time). |
79 | coexist peacefully at any one time). |
69 | |
80 | |
70 | The interface itself is vaguely similar but not identical to the Event |
81 | The interface itself is vaguely similar, but not identical to the Event |
71 | module. |
82 | module. |
72 | |
83 | |
73 | On the first call of any method, the module tries to detect the |
84 | During the first call of any watcher-creation method, the module tries |
74 | currently loaded event loop by probing wether any of the following |
85 | 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 |
86 | following modules is already loaded: EV, Event, Glib, |
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87 | AnyEvent::Impl::Perl, Tk, Event::Lib, Qt, POE. The first one found is |
76 | one found is used. If none are found, the module tries to load these |
88 | used. If none are found, the module tries to load these modules |
77 | modules in the order given. The first one that could be successfully |
89 | (excluding Tk, Event::Lib, Qt and POE as the pure perl adaptor should |
78 | loaded will be used. If still none could be found, AnyEvent will fall |
90 | always succeed) in the order given. The first one that can be |
79 | back to a pure-perl event loop, which is also not very efficient. |
91 | successfully loaded will be used. If, after this, still none could be |
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92 | found, AnyEvent will fall back to a pure-perl event loop, which is not |
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93 | very efficient, but should work everywhere. |
80 | |
94 | |
81 | Because AnyEvent first checks for modules that are already loaded, |
95 | Because AnyEvent first checks for modules that are already loaded, |
82 | loading an Event model explicitly before first using AnyEvent will |
96 | loading an event model explicitly before first using AnyEvent will |
83 | likely make that model the default. For example: |
97 | likely make that model the default. For example: |
84 | |
98 | |
85 | use Tk; |
99 | use Tk; |
86 | use AnyEvent; |
100 | use AnyEvent; |
87 | |
101 | |
88 | # .. AnyEvent will likely default to Tk |
102 | # .. AnyEvent will likely default to Tk |
89 | |
103 | |
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104 | The *likely* means that, if any module loads another event model and |
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105 | starts using it, all bets are off. Maybe you should tell their authors |
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106 | to use AnyEvent so their modules work together with others seamlessly... |
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107 | |
90 | The pure-perl implementation of AnyEvent is called |
108 | The pure-perl implementation of AnyEvent is called |
91 | "AnyEvent::Impl::Perl". Like other event modules you can load it |
109 | "AnyEvent::Impl::Perl". Like other event modules you can load it |
92 | explicitly. |
110 | explicitly and enjoy the high availability of that event loop :) |
93 | |
111 | |
94 | WATCHERS |
112 | WATCHERS |
95 | AnyEvent has the central concept of a *watcher*, which is an object that |
113 | AnyEvent has the central concept of a *watcher*, which is an object that |
96 | stores relevant data for each kind of event you are waiting for, such as |
114 | stores relevant data for each kind of event you are waiting for, such as |
97 | the callback to call, the filehandle to watch, etc. |
115 | the callback to call, the file handle to watch, etc. |
98 | |
116 | |
99 | These watchers are normal Perl objects with normal Perl lifetime. After |
117 | These watchers are normal Perl objects with normal Perl lifetime. After |
100 | creating a watcher it will immediately "watch" for events and invoke the |
118 | creating a watcher it will immediately "watch" for events and invoke the |
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119 | callback when the event occurs (of course, only when the event model is |
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120 | in control). |
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121 | |
101 | callback. To disable the watcher you have to destroy it (e.g. by setting |
122 | 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 |
123 | variable you store it in to "undef" or otherwise deleting all references |
103 | references to it). |
124 | to it). |
104 | |
125 | |
105 | All watchers are created by calling a method on the "AnyEvent" class. |
126 | All watchers are created by calling a method on the "AnyEvent" class. |
106 | |
127 | |
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128 | Many watchers either are used with "recursion" (repeating timers for |
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129 | example), or need to refer to their watcher object in other ways. |
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130 | |
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131 | An any way to achieve that is this pattern: |
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132 | |
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133 | my $w; $w = AnyEvent->type (arg => value ..., cb => sub { |
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134 | # you can use $w here, for example to undef it |
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135 | undef $w; |
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136 | }); |
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137 | |
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138 | Note that "my $w; $w =" combination. This is necessary because in Perl, |
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139 | my variables are only visible after the statement in which they are |
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140 | declared. |
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141 | |
107 | IO WATCHERS |
142 | I/O WATCHERS |
108 | You can create I/O watcher by calling the "AnyEvent->io" method with the |
143 | You can create an I/O watcher by calling the "AnyEvent->io" method with |
109 | following mandatory arguments: |
144 | the following mandatory key-value pairs as arguments: |
110 | |
145 | |
111 | "fh" the Perl *filehandle* (not filedescriptor) to watch for events. |
146 | "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 |
147 | "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 |
148 | watcher waiting for "r"eadable or "w"ritable events, respectively. "cb" |
114 | to invoke everytime the filehandle becomes ready. |
149 | is the callback to invoke each time the file handle becomes ready. |
115 | |
150 | |
116 | Filehandles will be kept alive, so as long as the watcher exists, the |
151 | Although the callback might get passed parameters, their value and |
117 | filehandle exists, too. |
152 | presence is undefined and you cannot rely on them. Portable AnyEvent |
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153 | callbacks cannot use arguments passed to I/O watcher callbacks. |
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154 | |
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155 | The I/O watcher might use the underlying file descriptor or a copy of |
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156 | it. You must not close a file handle as long as any watcher is active on |
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157 | the underlying file descriptor. |
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158 | |
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159 | Some event loops issue spurious readyness notifications, so you should |
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160 | always use non-blocking calls when reading/writing from/to your file |
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161 | handles. |
118 | |
162 | |
119 | Example: |
163 | Example: |
120 | |
164 | |
121 | # wait for readability of STDIN, then read a line and disable the watcher |
165 | # 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 { |
166 | my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { |
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127 | |
171 | |
128 | TIME WATCHERS |
172 | TIME WATCHERS |
129 | You can create a time watcher by calling the "AnyEvent->timer" method |
173 | You can create a time watcher by calling the "AnyEvent->timer" method |
130 | with the following mandatory arguments: |
174 | with the following mandatory arguments: |
131 | |
175 | |
132 | "after" after how many seconds (fractions are supported) should the |
176 | "after" specifies after how many seconds (fractional values are |
133 | timer activate. "cb" the callback to invoke. |
177 | supported) the callback should be invoked. "cb" is the callback to |
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178 | invoke in that case. |
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179 | |
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180 | Although the callback might get passed parameters, their value and |
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181 | presence is undefined and you cannot rely on them. Portable AnyEvent |
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182 | callbacks cannot use arguments passed to time watcher callbacks. |
134 | |
183 | |
135 | The timer callback will be invoked at most once: if you want a repeating |
184 | 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 |
185 | timer you have to create a new watcher (this is a limitation by both Tk |
137 | and Glib). |
186 | and Glib). |
138 | |
187 | |
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144 | }); |
193 | }); |
145 | |
194 | |
146 | # to cancel the timer: |
195 | # to cancel the timer: |
147 | undef $w; |
196 | undef $w; |
148 | |
197 | |
149 | CONDITION WATCHERS |
198 | Example 2: |
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199 | |
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200 | # fire an event after 0.5 seconds, then roughly every second |
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201 | my $w; |
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202 | |
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203 | my $cb = sub { |
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204 | # cancel the old timer while creating a new one |
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205 | $w = AnyEvent->timer (after => 1, cb => $cb); |
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206 | }; |
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207 | |
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208 | # start the "loop" by creating the first watcher |
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209 | $w = AnyEvent->timer (after => 0.5, cb => $cb); |
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210 | |
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211 | TIMING ISSUES |
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212 | There are two ways to handle timers: based on real time (relative, "fire |
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213 | in 10 seconds") and based on wallclock time (absolute, "fire at 12 |
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214 | o'clock"). |
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215 | |
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216 | While most event loops expect timers to specified in a relative way, |
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217 | they use absolute time internally. This makes a difference when your |
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218 | clock "jumps", for example, when ntp decides to set your clock backwards |
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219 | from the wrong date of 2014-01-01 to 2008-01-01, a watcher that is |
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220 | supposed to fire "after" a second might actually take six years to |
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221 | finally fire. |
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222 | |
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223 | AnyEvent cannot compensate for this. The only event loop that is |
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224 | conscious about these issues is EV, which offers both relative |
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225 | (ev_timer, based on true relative time) and absolute (ev_periodic, based |
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226 | on wallclock time) timers. |
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227 | |
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228 | AnyEvent always prefers relative timers, if available, matching the |
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229 | AnyEvent API. |
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230 | |
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231 | AnyEvent has two additional methods that return the "current time": |
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232 | |
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233 | AnyEvent->time |
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234 | This returns the "current wallclock time" as a fractional number of |
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235 | seconds since the Epoch (the same thing as "time" or |
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236 | "Time::HiRes::time" return, and the result is guaranteed to be |
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237 | compatible with those). |
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238 | |
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239 | It progresses independently of any event loop processing, i.e. each |
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240 | call will check the system clock, which usually gets updated |
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241 | frequently. |
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242 | |
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243 | AnyEvent->now |
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244 | This also returns the "current wallclock time", but unlike "time", |
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245 | above, this value might change only once per event loop iteration, |
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246 | depending on the event loop (most return the same time as "time", |
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247 | above). This is the time that AnyEvent's timers get scheduled |
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248 | against. |
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249 | |
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250 | *In almost all cases (in all cases if you don't care), this is the |
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251 | function to call when you want to know the current time.* |
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252 | |
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253 | This function is also often faster then "AnyEvent->time", and thus |
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254 | the preferred method if you want some timestamp (for example, |
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255 | AnyEvent::Handle uses this to update it's activity timeouts). |
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256 | |
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257 | The rest of this section is only of relevance if you try to be very |
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258 | exact with your timing, you can skip it without bad conscience. |
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259 | |
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260 | For a practical example of when these times differ, consider |
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261 | Event::Lib and EV and the following set-up: |
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262 | |
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263 | The event loop is running and has just invoked one of your callback |
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264 | at time=500 (assume no other callbacks delay processing). In your |
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265 | callback, you wait a second by executing "sleep 1" (blocking the |
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266 | process for a second) and then (at time=501) you create a relative |
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267 | timer that fires after three seconds. |
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268 | |
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269 | With Event::Lib, "AnyEvent->time" and "AnyEvent->now" will both |
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270 | return 501, because that is the current time, and the timer will be |
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271 | scheduled to fire at time=504 (501 + 3). |
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272 | |
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273 | With EV, "AnyEvent->time" returns 501 (as that is the current time), |
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274 | but "AnyEvent->now" returns 500, as that is the time the last event |
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275 | processing phase started. With EV, your timer gets scheduled to run |
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276 | at time=503 (500 + 3). |
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277 | |
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278 | In one sense, Event::Lib is more exact, as it uses the current time |
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279 | regardless of any delays introduced by event processing. However, |
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280 | most callbacks do not expect large delays in processing, so this |
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281 | causes a higher drift (and a lot more system calls to get the |
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282 | current time). |
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283 | |
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284 | In another sense, EV is more exact, as your timer will be scheduled |
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285 | at the same time, regardless of how long event processing actually |
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286 | took. |
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287 | |
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288 | In either case, if you care (and in most cases, you don't), then you |
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289 | can get whatever behaviour you want with any event loop, by taking |
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290 | the difference between "AnyEvent->time" and "AnyEvent->now" into |
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291 | account. |
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292 | |
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293 | SIGNAL WATCHERS |
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294 | You can watch for signals using a signal watcher, "signal" is the signal |
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295 | *name* without any "SIG" prefix, "cb" is the Perl callback to be invoked |
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296 | whenever a signal occurs. |
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297 | |
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298 | Although the callback might get passed parameters, their value and |
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299 | presence is undefined and you cannot rely on them. Portable AnyEvent |
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300 | callbacks cannot use arguments passed to signal watcher callbacks. |
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301 | |
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302 | Multiple signal occurrences can be clumped together into one callback |
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303 | invocation, and callback invocation will be synchronous. Synchronous |
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304 | means that it might take a while until the signal gets handled by the |
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305 | process, but it is guaranteed not to interrupt any other callbacks. |
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306 | |
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307 | The main advantage of using these watchers is that you can share a |
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308 | signal between multiple watchers. |
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309 | |
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310 | This watcher might use %SIG, so programs overwriting those signals |
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311 | directly will likely not work correctly. |
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312 | |
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313 | Example: exit on SIGINT |
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314 | |
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315 | my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 }); |
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316 | |
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317 | CHILD PROCESS WATCHERS |
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318 | You can also watch on a child process exit and catch its exit status. |
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319 | |
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320 | The child process is specified by the "pid" argument (if set to 0, it |
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321 | watches for any child process exit). The watcher will trigger as often |
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322 | as status change for the child are received. This works by installing a |
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323 | signal handler for "SIGCHLD". The callback will be called with the pid |
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324 | and exit status (as returned by waitpid), so unlike other watcher types, |
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325 | you *can* rely on child watcher callback arguments. |
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326 | |
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327 | There is a slight catch to child watchers, however: you usually start |
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328 | them *after* the child process was created, and this means the process |
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329 | could have exited already (and no SIGCHLD will be sent anymore). |
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330 | |
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331 | Not all event models handle this correctly (POE doesn't), but even for |
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332 | event models that *do* handle this correctly, they usually need to be |
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333 | loaded before the process exits (i.e. before you fork in the first |
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334 | place). |
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335 | |
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336 | This means you cannot create a child watcher as the very first thing in |
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337 | an AnyEvent program, you *have* to create at least one watcher before |
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338 | you "fork" the child (alternatively, you can call "AnyEvent::detect"). |
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339 | |
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340 | Example: fork a process and wait for it |
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341 | |
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342 | my $done = AnyEvent->condvar; |
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343 | |
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344 | my $pid = fork or exit 5; |
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345 | |
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346 | my $w = AnyEvent->child ( |
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347 | pid => $pid, |
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348 | cb => sub { |
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349 | my ($pid, $status) = @_; |
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350 | warn "pid $pid exited with status $status"; |
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351 | $done->send; |
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352 | }, |
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353 | ); |
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354 | |
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355 | # do something else, then wait for process exit |
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356 | $done->recv; |
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357 | |
|
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358 | CONDITION VARIABLES |
|
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359 | If you are familiar with some event loops you will know that all of them |
|
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360 | require you to run some blocking "loop", "run" or similar function that |
|
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361 | will actively watch for new events and call your callbacks. |
|
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362 | |
|
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363 | AnyEvent is different, it expects somebody else to run the event loop |
|
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364 | and will only block when necessary (usually when told by the user). |
|
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365 | |
|
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366 | The instrument to do that is called a "condition variable", so called |
|
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367 | because they represent a condition that must become true. |
|
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368 | |
150 | Condition watchers can be created by calling the "AnyEvent->condvar" |
369 | Condition variables can be created by calling the "AnyEvent->condvar" |
151 | method without any arguments. |
370 | method, usually without arguments. The only argument pair allowed is |
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371 | "cb", which specifies a callback to be called when the condition |
|
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372 | variable becomes true. |
152 | |
373 | |
153 | A condition watcher watches for a condition - precisely that the |
374 | After creation, the condition variable is "false" until it becomes |
154 | "->broadcast" method has been called. |
375 | "true" by calling the "send" method (or calling the condition variable |
|
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376 | as if it were a callback, read about the caveats in the description for |
|
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377 | the "->send" method). |
155 | |
378 | |
|
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379 | Condition variables are similar to callbacks, except that you can |
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380 | optionally wait for them. They can also be called merge points - points |
|
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381 | in time where multiple outstanding events have been processed. And yet |
|
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382 | another way to call them is transactions - each condition variable can |
|
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383 | be used to represent a transaction, which finishes at some point and |
|
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384 | delivers a result. |
|
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385 | |
|
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386 | Condition variables are very useful to signal that something has |
|
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387 | finished, for example, if you write a module that does asynchronous http |
|
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388 | requests, then a condition variable would be the ideal candidate to |
|
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389 | signal the availability of results. The user can either act when the |
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390 | callback is called or can synchronously "->recv" for the results. |
|
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391 | |
|
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392 | You can also use them to simulate traditional event loops - for example, |
|
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393 | you can block your main program until an event occurs - for example, you |
|
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394 | could "->recv" in your main program until the user clicks the Quit |
|
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395 | button of your app, which would "->send" the "quit" event. |
|
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396 | |
156 | Note that condition watchers recurse into the event loop - if you have |
397 | 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. |
398 | two pieces of code that call "->recv" in a round-robin fashion, you |
158 | Therefore, condition watchers are good to export to your caller, but you |
399 | lose. Therefore, condition variables are good to export to your caller, |
159 | should avoid making a blocking wait, at least in callbacks, as this |
400 | but you should avoid making a blocking wait yourself, at least in |
160 | usually asks for trouble. |
401 | callbacks, as this asks for trouble. |
161 | |
402 | |
162 | The watcher has only two methods: |
403 | Condition variables are represented by hash refs in perl, and the keys |
|
|
404 | used by AnyEvent itself are all named "_ae_XXX" to make subclassing easy |
|
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405 | (it is often useful to build your own transaction class on top of |
|
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406 | AnyEvent). To subclass, use "AnyEvent::CondVar" as base class and call |
|
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407 | it's "new" method in your own "new" method. |
163 | |
408 | |
164 | $cv->wait |
409 | There are two "sides" to a condition variable - the "producer side" |
|
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410 | which eventually calls "-> send", and the "consumer side", which waits |
|
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411 | for the send to occur. |
|
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412 | |
|
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413 | Example: wait for a timer. |
|
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414 | |
|
|
415 | # wait till the result is ready |
|
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416 | my $result_ready = AnyEvent->condvar; |
|
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417 | |
|
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418 | # do something such as adding a timer |
|
|
419 | # or socket watcher the calls $result_ready->send |
|
|
420 | # when the "result" is ready. |
|
|
421 | # in this case, we simply use a timer: |
|
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422 | my $w = AnyEvent->timer ( |
|
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423 | after => 1, |
|
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424 | cb => sub { $result_ready->send }, |
|
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425 | ); |
|
|
426 | |
|
|
427 | # this "blocks" (while handling events) till the callback |
|
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428 | # calls send |
|
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429 | $result_ready->recv; |
|
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430 | |
|
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431 | Example: wait for a timer, but take advantage of the fact that condition |
|
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432 | variables are also code references. |
|
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433 | |
|
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434 | my $done = AnyEvent->condvar; |
|
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435 | my $delay = AnyEvent->timer (after => 5, cb => $done); |
|
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436 | $done->recv; |
|
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437 | |
|
|
438 | METHODS FOR PRODUCERS |
|
|
439 | These methods should only be used by the producing side, i.e. the |
|
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440 | code/module that eventually sends the signal. Note that it is also the |
|
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441 | producer side which creates the condvar in most cases, but it isn't |
|
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442 | uncommon for the consumer to create it as well. |
|
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443 | |
|
|
444 | $cv->send (...) |
|
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445 | Flag the condition as ready - a running "->recv" and all further |
|
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446 | calls to "recv" will (eventually) return after this method has been |
|
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447 | called. If nobody is waiting the send will be remembered. |
|
|
448 | |
|
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449 | If a callback has been set on the condition variable, it is called |
|
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450 | immediately from within send. |
|
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451 | |
|
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452 | Any arguments passed to the "send" call will be returned by all |
|
|
453 | future "->recv" calls. |
|
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454 | |
|
|
455 | Condition variables are overloaded so one can call them directly (as |
|
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456 | a code reference). Calling them directly is the same as calling |
|
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457 | "send". Note, however, that many C-based event loops do not handle |
|
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458 | overloading, so as tempting as it may be, passing a condition |
|
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459 | variable instead of a callback does not work. Both the pure perl and |
|
|
460 | EV loops support overloading, however, as well as all functions that |
|
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461 | use perl to invoke a callback (as in AnyEvent::Socket and |
|
|
462 | AnyEvent::DNS for example). |
|
|
463 | |
|
|
464 | $cv->croak ($error) |
|
|
465 | Similar to send, but causes all call's to "->recv" to invoke |
|
|
466 | "Carp::croak" with the given error message/object/scalar. |
|
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467 | |
|
|
468 | This can be used to signal any errors to the condition variable |
|
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469 | user/consumer. |
|
|
470 | |
|
|
471 | $cv->begin ([group callback]) |
|
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472 | $cv->end |
|
|
473 | These two methods are EXPERIMENTAL and MIGHT CHANGE. |
|
|
474 | |
|
|
475 | These two methods can be used to combine many transactions/events |
|
|
476 | into one. For example, a function that pings many hosts in parallel |
|
|
477 | might want to use a condition variable for the whole process. |
|
|
478 | |
|
|
479 | Every call to "->begin" will increment a counter, and every call to |
|
|
480 | "->end" will decrement it. If the counter reaches 0 in "->end", the |
|
|
481 | (last) callback passed to "begin" will be executed. That callback is |
|
|
482 | *supposed* to call "->send", but that is not required. If no |
|
|
483 | callback was set, "send" will be called without any arguments. |
|
|
484 | |
|
|
485 | Let's clarify this with the ping example: |
|
|
486 | |
|
|
487 | my $cv = AnyEvent->condvar; |
|
|
488 | |
|
|
489 | my %result; |
|
|
490 | $cv->begin (sub { $cv->send (\%result) }); |
|
|
491 | |
|
|
492 | for my $host (@list_of_hosts) { |
|
|
493 | $cv->begin; |
|
|
494 | ping_host_then_call_callback $host, sub { |
|
|
495 | $result{$host} = ...; |
|
|
496 | $cv->end; |
|
|
497 | }; |
|
|
498 | } |
|
|
499 | |
|
|
500 | $cv->end; |
|
|
501 | |
|
|
502 | This code fragment supposedly pings a number of hosts and calls |
|
|
503 | "send" after results for all then have have been gathered - in any |
|
|
504 | order. To achieve this, the code issues a call to "begin" when it |
|
|
505 | starts each ping request and calls "end" when it has received some |
|
|
506 | result for it. Since "begin" and "end" only maintain a counter, the |
|
|
507 | order in which results arrive is not relevant. |
|
|
508 | |
|
|
509 | There is an additional bracketing call to "begin" and "end" outside |
|
|
510 | the loop, which serves two important purposes: first, it sets the |
|
|
511 | callback to be called once the counter reaches 0, and second, it |
|
|
512 | ensures that "send" is called even when "no" hosts are being pinged |
|
|
513 | (the loop doesn't execute once). |
|
|
514 | |
|
|
515 | This is the general pattern when you "fan out" into multiple |
|
|
516 | subrequests: use an outer "begin"/"end" pair to set the callback and |
|
|
517 | ensure "end" is called at least once, and then, for each subrequest |
|
|
518 | you start, call "begin" and for each subrequest you finish, call |
|
|
519 | "end". |
|
|
520 | |
|
|
521 | METHODS FOR CONSUMERS |
|
|
522 | These methods should only be used by the consuming side, i.e. the code |
|
|
523 | awaits the condition. |
|
|
524 | |
|
|
525 | $cv->recv |
165 | Wait (blocking if necessary) until the "->broadcast" method has been |
526 | Wait (blocking if necessary) until the "->send" or "->croak" methods |
166 | called on c<$cv>, while servicing other watchers normally. |
527 | have been called on c<$cv>, while servicing other watchers normally. |
167 | |
528 | |
168 | You can only wait once on a condition - additional calls will return |
529 | You can only wait once on a condition - additional calls are valid |
169 | immediately. |
530 | but will return immediately. |
|
|
531 | |
|
|
532 | If an error condition has been set by calling "->croak", then this |
|
|
533 | function will call "croak". |
|
|
534 | |
|
|
535 | In list context, all parameters passed to "send" will be returned, |
|
|
536 | in scalar context only the first one will be returned. |
170 | |
537 | |
171 | Not all event models support a blocking wait - some die in that case |
538 | 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 |
539 | (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*, |
540 | 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 |
541 | the caller decide whether the call will block or not (for example, |
175 | example, by coupling condition variables with some kind of request |
542 | by coupling condition variables with some kind of request results |
176 | results and supporting callbacks so the caller knows that getting |
543 | and supporting callbacks so the caller knows that getting the result |
177 | the result will not block, while still suppporting blocking waits if |
544 | will not block, while still supporting blocking waits if the caller |
178 | the caller so desires). |
545 | so desires). |
179 | |
546 | |
180 | Another reason *never* to "->wait" in a module is that you cannot |
547 | Another reason *never* to "->recv" in a module is that you cannot |
181 | sensibly have two "->wait"'s in parallel, as that would require |
548 | sensibly have two "->recv"'s in parallel, as that would require |
182 | multiple interpreters or coroutines/threads, none of which |
549 | multiple interpreters or coroutines/threads, none of which |
183 | "AnyEvent" can supply (the coroutine-aware backends "Coro::EV" and |
550 | "AnyEvent" can supply. |
184 | "Coro::Event" explicitly support concurrent "->wait"'s from |
|
|
185 | different coroutines, however). |
|
|
186 | |
551 | |
187 | $cv->broadcast |
552 | The Coro module, however, *can* and *does* supply coroutines and, in |
188 | Flag the condition as ready - a running "->wait" and all further |
553 | fact, Coro::AnyEvent replaces AnyEvent's condvars by coroutine-safe |
189 | calls to "wait" will return after this method has been called. If |
554 | versions and also integrates coroutines into AnyEvent, making |
190 | nobody is waiting the broadcast will be remembered.. |
555 | blocking "->recv" calls perfectly safe as long as they are done from |
|
|
556 | another coroutine (one that doesn't run the event loop). |
191 | |
557 | |
192 | Example: |
558 | You can ensure that "-recv" never blocks by setting a callback and |
|
|
559 | only calling "->recv" from within that callback (or at a later |
|
|
560 | time). This will work even when the event loop does not support |
|
|
561 | blocking waits otherwise. |
193 | |
562 | |
194 | # wait till the result is ready |
563 | $bool = $cv->ready |
195 | my $result_ready = AnyEvent->condvar; |
564 | Returns true when the condition is "true", i.e. whether "send" or |
|
|
565 | "croak" have been called. |
196 | |
566 | |
197 | # do something such as adding a timer |
567 | $cb = $cv->cb ([new callback]) |
198 | # or socket watcher the calls $result_ready->broadcast |
568 | This is a mutator function that returns the callback set and |
199 | # when the "result" is ready. |
569 | optionally replaces it before doing so. |
200 | |
570 | |
201 | $result_ready->wait; |
571 | The callback will be called when the condition becomes "true", i.e. |
|
|
572 | when "send" or "croak" are called. Calling "recv" inside the |
|
|
573 | callback or at any later time is guaranteed not to block. |
202 | |
574 | |
203 | SIGNAL WATCHERS |
575 | 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 |
576 | $AnyEvent::MODEL |
229 | Contains "undef" until the first watcher is being created. Then it |
577 | 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 |
578 | 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 |
579 | 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 |
580 | the "AnyEvent::Impl:xxx" modules, but can be any other class in the |
233 | case AnyEvent has been extended at runtime (e.g. in *rxvt-unicode*). |
581 | case AnyEvent has been extended at runtime (e.g. in *rxvt-unicode*). |
234 | |
582 | |
235 | The known classes so far are: |
583 | The known classes so far are: |
236 | |
584 | |
237 | AnyEvent::Impl::CoroEV based on Coro::EV, best choice. |
|
|
238 | AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice. |
|
|
239 | AnyEvent::Impl::EV based on EV (an interface to libev, also best choice). |
585 | AnyEvent::Impl::EV based on EV (an interface to libev, best choice). |
240 | AnyEvent::Impl::Event based on Event, also second best choice :) |
586 | AnyEvent::Impl::Event based on Event, second best choice. |
|
|
587 | AnyEvent::Impl::Perl pure-perl implementation, fast and portable. |
241 | AnyEvent::Impl::Glib based on Glib, third-best choice. |
588 | AnyEvent::Impl::Glib based on Glib, third-best choice. |
242 | AnyEvent::Impl::Tk based on Tk, very bad choice. |
589 | AnyEvent::Impl::Tk based on Tk, very bad choice. |
243 | AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable. |
590 | AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs). |
|
|
591 | AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse. |
|
|
592 | AnyEvent::Impl::POE based on POE, not generic enough for full support. |
|
|
593 | |
|
|
594 | There is no support for WxWidgets, as WxWidgets has no support for |
|
|
595 | watching file handles. However, you can use WxWidgets through the |
|
|
596 | POE Adaptor, as POE has a Wx backend that simply polls 20 times per |
|
|
597 | second, which was considered to be too horrible to even consider for |
|
|
598 | AnyEvent. Likewise, other POE backends can be used by AnyEvent by |
|
|
599 | using it's adaptor. |
|
|
600 | |
|
|
601 | AnyEvent knows about Prima and Wx and will try to use POE when |
|
|
602 | autodetecting them. |
244 | |
603 | |
245 | AnyEvent::detect |
604 | AnyEvent::detect |
246 | Returns $AnyEvent::MODEL, forcing autodetection of the event model |
605 | Returns $AnyEvent::MODEL, forcing autodetection of the event model |
247 | if necessary. You should only call this function right before you |
606 | if necessary. You should only call this function right before you |
248 | would have created an AnyEvent watcher anyway, that is, very late at |
607 | would have created an AnyEvent watcher anyway, that is, as late as |
249 | runtime. |
608 | possible at runtime. |
|
|
609 | |
|
|
610 | $guard = AnyEvent::post_detect { BLOCK } |
|
|
611 | Arranges for the code block to be executed as soon as the event |
|
|
612 | model is autodetected (or immediately if this has already happened). |
|
|
613 | |
|
|
614 | If called in scalar or list context, then it creates and returns an |
|
|
615 | object that automatically removes the callback again when it is |
|
|
616 | destroyed. See Coro::BDB for a case where this is useful. |
|
|
617 | |
|
|
618 | @AnyEvent::post_detect |
|
|
619 | If there are any code references in this array (you can "push" to it |
|
|
620 | before or after loading AnyEvent), then they will called directly |
|
|
621 | after the event loop has been chosen. |
|
|
622 | |
|
|
623 | You should check $AnyEvent::MODEL before adding to this array, |
|
|
624 | though: if it contains a true value then the event loop has already |
|
|
625 | been detected, and the array will be ignored. |
|
|
626 | |
|
|
627 | Best use "AnyEvent::post_detect { BLOCK }" instead. |
250 | |
628 | |
251 | WHAT TO DO IN A MODULE |
629 | WHAT TO DO IN A MODULE |
252 | As a module author, you should "use AnyEvent" and call AnyEvent methods |
630 | 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. |
631 | freely, but you should not load a specific event module or rely on it. |
254 | |
632 | |
255 | Be careful when you create watchers in the module body - Anyevent will |
633 | 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, |
634 | 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 |
635 | so by calling AnyEvent in your module body you force the user of your |
258 | module to load the event module first. |
636 | module to load the event module first. |
259 | |
637 | |
|
|
638 | Never call "->recv" on a condition variable unless you *know* that the |
|
|
639 | "->send" method has been called on it already. This is because it will |
|
|
640 | stall the whole program, and the whole point of using events is to stay |
|
|
641 | interactive. |
|
|
642 | |
|
|
643 | It is fine, however, to call "->recv" when the user of your module |
|
|
644 | requests it (i.e. if you create a http request object ad have a method |
|
|
645 | called "results" that returns the results, it should call "->recv" |
|
|
646 | freely, as the user of your module knows what she is doing. always). |
|
|
647 | |
260 | WHAT TO DO IN THE MAIN PROGRAM |
648 | WHAT TO DO IN THE MAIN PROGRAM |
261 | There will always be a single main program - the only place that should |
649 | There will always be a single main program - the only place that should |
262 | dictate which event model to use. |
650 | dictate which event model to use. |
263 | |
651 | |
264 | If it doesn't care, it can just "use AnyEvent" and use it itself, or not |
652 | 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 |
653 | do anything special (it does not need to be event-based) and let |
266 | chose. |
654 | AnyEvent decide which implementation to chose if some module relies on |
|
|
655 | it. |
267 | |
656 | |
268 | If the main program relies on a specific event model (for example, in |
657 | 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 |
658 | 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, |
659 | event module before loading AnyEvent or any module that uses it: |
271 | generally, as early as possible. The reason is that modules might create |
660 | 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 |
661 | 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 |
662 | will decide on the event model to use as soon as it creates watchers, |
274 | wrong one unless you load the correct one yourself. |
663 | and it might chose the wrong one unless you load the correct one |
|
|
664 | yourself. |
275 | |
665 | |
276 | You can chose to use a rather inefficient pure-perl implementation by |
666 | You can chose to use a pure-perl implementation by loading the |
277 | loading the "AnyEvent::Impl::Perl" module, but letting AnyEvent chose is |
667 | "AnyEvent::Impl::Perl" module, which gives you similar behaviour |
278 | generally better. |
668 | everywhere, but letting AnyEvent chose the model is generally better. |
|
|
669 | |
|
|
670 | MAINLOOP EMULATION |
|
|
671 | Sometimes (often for short test scripts, or even standalone programs who |
|
|
672 | only want to use AnyEvent), you do not want to run a specific event |
|
|
673 | loop. |
|
|
674 | |
|
|
675 | In that case, you can use a condition variable like this: |
|
|
676 | |
|
|
677 | AnyEvent->condvar->recv; |
|
|
678 | |
|
|
679 | This has the effect of entering the event loop and looping forever. |
|
|
680 | |
|
|
681 | Note that usually your program has some exit condition, in which case it |
|
|
682 | is better to use the "traditional" approach of storing a condition |
|
|
683 | variable somewhere, waiting for it, and sending it when the program |
|
|
684 | should exit cleanly. |
|
|
685 | |
|
|
686 | OTHER MODULES |
|
|
687 | The following is a non-exhaustive list of additional modules that use |
|
|
688 | AnyEvent and can therefore be mixed easily with other AnyEvent modules |
|
|
689 | in the same program. Some of the modules come with AnyEvent, some are |
|
|
690 | available via CPAN. |
|
|
691 | |
|
|
692 | AnyEvent::Util |
|
|
693 | Contains various utility functions that replace often-used but |
|
|
694 | blocking functions such as "inet_aton" by event-/callback-based |
|
|
695 | versions. |
|
|
696 | |
|
|
697 | AnyEvent::Handle |
|
|
698 | Provide read and write buffers and manages watchers for reads and |
|
|
699 | writes. |
|
|
700 | |
|
|
701 | AnyEvent::Socket |
|
|
702 | Provides various utility functions for (internet protocol) sockets, |
|
|
703 | addresses and name resolution. Also functions to create non-blocking |
|
|
704 | tcp connections or tcp servers, with IPv6 and SRV record support and |
|
|
705 | more. |
|
|
706 | |
|
|
707 | AnyEvent::DNS |
|
|
708 | Provides rich asynchronous DNS resolver capabilities. |
|
|
709 | |
|
|
710 | AnyEvent::HTTPD |
|
|
711 | Provides a simple web application server framework. |
|
|
712 | |
|
|
713 | AnyEvent::FastPing |
|
|
714 | The fastest ping in the west. |
|
|
715 | |
|
|
716 | Net::IRC3 |
|
|
717 | AnyEvent based IRC client module family. |
|
|
718 | |
|
|
719 | Net::XMPP2 |
|
|
720 | AnyEvent based XMPP (Jabber protocol) module family. |
|
|
721 | |
|
|
722 | Net::FCP |
|
|
723 | AnyEvent-based implementation of the Freenet Client Protocol, |
|
|
724 | birthplace of AnyEvent. |
|
|
725 | |
|
|
726 | Event::ExecFlow |
|
|
727 | High level API for event-based execution flow control. |
|
|
728 | |
|
|
729 | Coro |
|
|
730 | Has special support for AnyEvent via Coro::AnyEvent. |
|
|
731 | |
|
|
732 | AnyEvent::AIO, IO::AIO |
|
|
733 | Truly asynchronous I/O, should be in the toolbox of every event |
|
|
734 | programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent |
|
|
735 | together. |
|
|
736 | |
|
|
737 | AnyEvent::BDB, BDB |
|
|
738 | Truly asynchronous Berkeley DB access. AnyEvent::AIO transparently |
|
|
739 | fuses IO::AIO and AnyEvent together. |
|
|
740 | |
|
|
741 | IO::Lambda |
|
|
742 | The lambda approach to I/O - don't ask, look there. Can use |
|
|
743 | AnyEvent. |
279 | |
744 | |
280 | SUPPLYING YOUR OWN EVENT MODEL INTERFACE |
745 | SUPPLYING YOUR OWN EVENT MODEL INTERFACE |
|
|
746 | This is an advanced topic that you do not normally need to use AnyEvent |
|
|
747 | in a module. This section is only of use to event loop authors who want |
|
|
748 | to provide AnyEvent compatibility. |
|
|
749 | |
281 | If you need to support another event library which isn't directly |
750 | 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 |
751 | 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 |
752 | 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 |
753 | event module and the package name of the interface to use onto |
285 | @AnyEvent::REGISTRY. You can do that before and even without loading |
754 | @AnyEvent::REGISTRY. You can do that before and even without loading |
286 | AnyEvent. |
755 | AnyEvent, so it is reasonably cheap. |
287 | |
756 | |
288 | Example: |
757 | Example: |
289 | |
758 | |
290 | push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::]; |
759 | push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::]; |
291 | |
760 | |
292 | This tells AnyEvent to (literally) use the "urxvt::anyevent::" |
761 | This tells AnyEvent to (literally) use the "urxvt::anyevent::" |
293 | package/class when it finds the "urxvt" package/module is loaded. When |
762 | package/class when it finds the "urxvt" package/module is already |
|
|
763 | loaded. |
|
|
764 | |
294 | AnyEvent is loaded and asked to find a suitable event model, it will |
765 | When AnyEvent is loaded and asked to find a suitable event model, it |
295 | first check for the presence of urxvt. |
766 | will first check for the presence of urxvt by trying to "use" the |
|
|
767 | "urxvt::anyevent" module. |
296 | |
768 | |
297 | The class should provide implementations for all watcher types (see |
769 | The class should provide implementations for all watcher types. See |
298 | AnyEvent::Impl::Event (source code), AnyEvent::Impl::Glib (Source code) |
770 | 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 |
771 | so on for actual examples. Use "perldoc -m AnyEvent::Impl::Glib" to see |
300 | see the sources). |
772 | the sources. |
301 | |
773 | |
|
|
774 | If you don't provide "signal" and "child" watchers than AnyEvent will |
|
|
775 | provide suitable (hopefully) replacements. |
|
|
776 | |
302 | The above isn't fictitious, the *rxvt-unicode* (a.k.a. urxvt) uses the |
777 | 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 |
778 | terminal emulator uses the above line as-is. An interface isn't included |
304 | doesn't make sense outside the embedded interpreter inside |
779 | in AnyEvent because it doesn't make sense outside the embedded |
305 | *rxvt-unicode*, and it is updated and maintained as part of the |
780 | interpreter inside *rxvt-unicode*, and it is updated and maintained as |
306 | *rxvt-unicode* distribution. |
781 | part of the *rxvt-unicode* distribution. |
307 | |
782 | |
308 | *rxvt-unicode* also cheats a bit by not providing blocking access to |
783 | *rxvt-unicode* also cheats a bit by not providing blocking access to |
309 | condition variables: code blocking while waiting for a condition will |
784 | condition variables: code blocking while waiting for a condition will |
310 | "die". This still works with most modules/usages, and blocking calls |
785 | "die". This still works with most modules/usages, and blocking calls |
311 | must not be in an interactive application, so it makes sense. |
786 | must not be done in an interactive application, so it makes sense. |
312 | |
787 | |
313 | ENVIRONMENT VARIABLES |
788 | ENVIRONMENT VARIABLES |
314 | The following environment variables are used by this module: |
789 | The following environment variables are used by this module: |
315 | |
790 | |
316 | "PERL_ANYEVENT_VERBOSE" when set to 2 or higher, reports which event |
791 | "PERL_ANYEVENT_VERBOSE" |
317 | model gets used. |
792 | By default, AnyEvent will be completely silent except in fatal |
|
|
793 | conditions. You can set this environment variable to make AnyEvent |
|
|
794 | more talkative. |
318 | |
795 | |
319 | EXAMPLE |
796 | When set to 1 or higher, causes AnyEvent to warn about unexpected |
|
|
797 | conditions, such as not being able to load the event model specified |
|
|
798 | by "PERL_ANYEVENT_MODEL". |
|
|
799 | |
|
|
800 | When set to 2 or higher, cause AnyEvent to report to STDERR which |
|
|
801 | event model it chooses. |
|
|
802 | |
|
|
803 | "PERL_ANYEVENT_MODEL" |
|
|
804 | This can be used to specify the event model to be used by AnyEvent, |
|
|
805 | before auto detection and -probing kicks in. It must be a string |
|
|
806 | consisting entirely of ASCII letters. The string "AnyEvent::Impl::" |
|
|
807 | gets prepended and the resulting module name is loaded and if the |
|
|
808 | load was successful, used as event model. If it fails to load |
|
|
809 | AnyEvent will proceed with auto detection and -probing. |
|
|
810 | |
|
|
811 | This functionality might change in future versions. |
|
|
812 | |
|
|
813 | For example, to force the pure perl model (AnyEvent::Impl::Perl) you |
|
|
814 | could start your program like this: |
|
|
815 | |
|
|
816 | PERL_ANYEVENT_MODEL=Perl perl ... |
|
|
817 | |
|
|
818 | "PERL_ANYEVENT_PROTOCOLS" |
|
|
819 | Used by both AnyEvent::DNS and AnyEvent::Socket to determine |
|
|
820 | preferences for IPv4 or IPv6. The default is unspecified (and might |
|
|
821 | change, or be the result of auto probing). |
|
|
822 | |
|
|
823 | Must be set to a comma-separated list of protocols or address |
|
|
824 | families, current supported: "ipv4" and "ipv6". Only protocols |
|
|
825 | mentioned will be used, and preference will be given to protocols |
|
|
826 | mentioned earlier in the list. |
|
|
827 | |
|
|
828 | This variable can effectively be used for denial-of-service attacks |
|
|
829 | against local programs (e.g. when setuid), although the impact is |
|
|
830 | likely small, as the program has to handle connection errors |
|
|
831 | already- |
|
|
832 | |
|
|
833 | Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over |
|
|
834 | IPv6, but support both and try to use both. |
|
|
835 | "PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to |
|
|
836 | resolve or contact IPv6 addresses. |
|
|
837 | "PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4" support either IPv4 or IPv6, but |
|
|
838 | prefer IPv6 over IPv4. |
|
|
839 | |
|
|
840 | "PERL_ANYEVENT_EDNS0" |
|
|
841 | Used by AnyEvent::DNS to decide whether to use the EDNS0 extension |
|
|
842 | for DNS. This extension is generally useful to reduce DNS traffic, |
|
|
843 | but some (broken) firewalls drop such DNS packets, which is why it |
|
|
844 | is off by default. |
|
|
845 | |
|
|
846 | Setting this variable to 1 will cause AnyEvent::DNS to announce |
|
|
847 | EDNS0 in its DNS requests. |
|
|
848 | |
|
|
849 | "PERL_ANYEVENT_MAX_FORKS" |
|
|
850 | The maximum number of child processes that |
|
|
851 | "AnyEvent::Util::fork_call" will create in parallel. |
|
|
852 | |
|
|
853 | EXAMPLE PROGRAM |
320 | The following program uses an io watcher to read data from stdin, a |
854 | The following program uses an I/O watcher to read data from STDIN, a |
321 | timer to display a message once per second, and a condvar to exit the |
855 | timer to display a message once per second, and a condition variable to |
322 | program when the user enters quit: |
856 | quit the program when the user enters quit: |
323 | |
857 | |
324 | use AnyEvent; |
858 | use AnyEvent; |
325 | |
859 | |
326 | my $cv = AnyEvent->condvar; |
860 | my $cv = AnyEvent->condvar; |
327 | |
861 | |
328 | my $io_watcher = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { |
862 | my $io_watcher = AnyEvent->io ( |
|
|
863 | fh => \*STDIN, |
|
|
864 | poll => 'r', |
|
|
865 | cb => sub { |
329 | warn "io event <$_[0]>\n"; # will always output <r> |
866 | warn "io event <$_[0]>\n"; # will always output <r> |
330 | chomp (my $input = <STDIN>); # read a line |
867 | chomp (my $input = <STDIN>); # read a line |
331 | warn "read: $input\n"; # output what has been read |
868 | warn "read: $input\n"; # output what has been read |
332 | $cv->broadcast if $input =~ /^q/i; # quit program if /^q/i |
869 | $cv->send if $input =~ /^q/i; # quit program if /^q/i |
|
|
870 | }, |
333 | }); |
871 | ); |
334 | |
872 | |
335 | my $time_watcher; # can only be used once |
873 | my $time_watcher; # can only be used once |
336 | |
874 | |
337 | sub new_timer { |
875 | sub new_timer { |
338 | $timer = AnyEvent->timer (after => 1, cb => sub { |
876 | $timer = AnyEvent->timer (after => 1, cb => sub { |
… | |
… | |
341 | }); |
879 | }); |
342 | } |
880 | } |
343 | |
881 | |
344 | new_timer; # create first timer |
882 | new_timer; # create first timer |
345 | |
883 | |
346 | $cv->wait; # wait until user enters /^q/i |
884 | $cv->recv; # wait until user enters /^q/i |
347 | |
885 | |
348 | REAL-WORLD EXAMPLE |
886 | REAL-WORLD EXAMPLE |
349 | Consider the Net::FCP module. It features (among others) the following |
887 | Consider the Net::FCP module. It features (among others) the following |
350 | API calls, which are to freenet what HTTP GET requests are to http: |
888 | API calls, which are to freenet what HTTP GET requests are to http: |
351 | |
889 | |
… | |
… | |
400 | syswrite $txn->{fh}, $txn->{request} |
938 | syswrite $txn->{fh}, $txn->{request} |
401 | or die "connection or write error"; |
939 | or die "connection or write error"; |
402 | $txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r }); |
940 | $txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r }); |
403 | |
941 | |
404 | Again, "fh_ready_r" waits till all data has arrived, and then stores the |
942 | Again, "fh_ready_r" waits till all data has arrived, and then stores the |
405 | result and signals any possible waiters that the request ahs finished: |
943 | result and signals any possible waiters that the request has finished: |
406 | |
944 | |
407 | sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf}; |
945 | sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf}; |
408 | |
946 | |
409 | if (end-of-file or data complete) { |
947 | if (end-of-file or data complete) { |
410 | $txn->{result} = $txn->{buf}; |
948 | $txn->{result} = $txn->{buf}; |
411 | $txn->{finished}->broadcast; |
949 | $txn->{finished}->send; |
412 | $txb->{cb}->($txn) of $txn->{cb}; # also call callback |
950 | $txb->{cb}->($txn) of $txn->{cb}; # also call callback |
413 | } |
951 | } |
414 | |
952 | |
415 | The "result" method, finally, just waits for the finished signal (if the |
953 | The "result" method, finally, just waits for the finished signal (if the |
416 | request was already finished, it doesn't wait, of course, and returns |
954 | request was already finished, it doesn't wait, of course, and returns |
417 | the data: |
955 | the data: |
418 | |
956 | |
419 | $txn->{finished}->wait; |
957 | $txn->{finished}->recv; |
420 | return $txn->{result}; |
958 | return $txn->{result}; |
421 | |
959 | |
422 | The actual code goes further and collects all errors ("die"s, |
960 | The actual code goes further and collects all errors ("die"s, |
423 | exceptions) that occured during request processing. The "result" method |
961 | exceptions) that occurred during request processing. The "result" method |
424 | detects wether an exception as thrown (it is stored inside the $txn |
962 | detects whether an exception as thrown (it is stored inside the $txn |
425 | object) and just throws the exception, which means connection errors and |
963 | 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, |
964 | other problems get reported tot he code that tries to use the result, |
427 | not in a random callback. |
965 | not in a random callback. |
428 | |
966 | |
429 | All of this enables the following usage styles: |
967 | All of this enables the following usage styles: |
… | |
… | |
459 | |
997 | |
460 | my $quit = AnyEvent->condvar; |
998 | my $quit = AnyEvent->condvar; |
461 | |
999 | |
462 | $fcp->txn_client_get ($url)->cb (sub { |
1000 | $fcp->txn_client_get ($url)->cb (sub { |
463 | ... |
1001 | ... |
464 | $quit->broadcast; |
1002 | $quit->send; |
465 | }); |
1003 | }); |
466 | |
1004 | |
467 | $quit->wait; |
1005 | $quit->recv; |
|
|
1006 | |
|
|
1007 | BENCHMARKS |
|
|
1008 | To give you an idea of the performance and overheads that AnyEvent adds |
|
|
1009 | over the event loops themselves and to give you an impression of the |
|
|
1010 | speed of various event loops I prepared some benchmarks. |
|
|
1011 | |
|
|
1012 | BENCHMARKING ANYEVENT OVERHEAD |
|
|
1013 | Here is a benchmark of various supported event models used natively and |
|
|
1014 | through AnyEvent. The benchmark creates a lot of timers (with a zero |
|
|
1015 | timeout) and I/O watchers (watching STDOUT, a pty, to become writable, |
|
|
1016 | which it is), lets them fire exactly once and destroys them again. |
|
|
1017 | |
|
|
1018 | Source code for this benchmark is found as eg/bench in the AnyEvent |
|
|
1019 | distribution. |
|
|
1020 | |
|
|
1021 | Explanation of the columns |
|
|
1022 | *watcher* is the number of event watchers created/destroyed. Since |
|
|
1023 | different event models feature vastly different performances, each event |
|
|
1024 | loop was given a number of watchers so that overall runtime is |
|
|
1025 | acceptable and similar between tested event loop (and keep them from |
|
|
1026 | crashing): Glib would probably take thousands of years if asked to |
|
|
1027 | process the same number of watchers as EV in this benchmark. |
|
|
1028 | |
|
|
1029 | *bytes* is the number of bytes (as measured by the resident set size, |
|
|
1030 | RSS) consumed by each watcher. This method of measuring captures both C |
|
|
1031 | and Perl-based overheads. |
|
|
1032 | |
|
|
1033 | *create* is the time, in microseconds (millionths of seconds), that it |
|
|
1034 | takes to create a single watcher. The callback is a closure shared |
|
|
1035 | between all watchers, to avoid adding memory overhead. That means |
|
|
1036 | closure creation and memory usage is not included in the figures. |
|
|
1037 | |
|
|
1038 | *invoke* is the time, in microseconds, used to invoke a simple callback. |
|
|
1039 | The callback simply counts down a Perl variable and after it was invoked |
|
|
1040 | "watcher" times, it would "->send" a condvar once to signal the end of |
|
|
1041 | this phase. |
|
|
1042 | |
|
|
1043 | *destroy* is the time, in microseconds, that it takes to destroy a |
|
|
1044 | single watcher. |
|
|
1045 | |
|
|
1046 | Results |
|
|
1047 | name watchers bytes create invoke destroy comment |
|
|
1048 | EV/EV 400000 244 0.56 0.46 0.31 EV native interface |
|
|
1049 | EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers |
|
|
1050 | CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal |
|
|
1051 | Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation |
|
|
1052 | Event/Event 16000 516 31.88 31.30 0.85 Event native interface |
|
|
1053 | Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers |
|
|
1054 | Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour |
|
|
1055 | Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers |
|
|
1056 | POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event |
|
|
1057 | POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select |
|
|
1058 | |
|
|
1059 | Discussion |
|
|
1060 | The benchmark does *not* measure scalability of the event loop very |
|
|
1061 | well. For example, a select-based event loop (such as the pure perl one) |
|
|
1062 | can never compete with an event loop that uses epoll when the number of |
|
|
1063 | file descriptors grows high. In this benchmark, all events become ready |
|
|
1064 | at the same time, so select/poll-based implementations get an unnatural |
|
|
1065 | speed boost. |
|
|
1066 | |
|
|
1067 | Also, note that the number of watchers usually has a nonlinear effect on |
|
|
1068 | overall speed, that is, creating twice as many watchers doesn't take |
|
|
1069 | twice the time - usually it takes longer. This puts event loops tested |
|
|
1070 | with a higher number of watchers at a disadvantage. |
|
|
1071 | |
|
|
1072 | To put the range of results into perspective, consider that on the |
|
|
1073 | benchmark machine, handling an event takes roughly 1600 CPU cycles with |
|
|
1074 | EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 |
|
|
1075 | CPU cycles with POE. |
|
|
1076 | |
|
|
1077 | "EV" is the sole leader regarding speed and memory use, which are both |
|
|
1078 | maximal/minimal, respectively. Even when going through AnyEvent, it uses |
|
|
1079 | far less memory than any other event loop and is still faster than Event |
|
|
1080 | natively. |
|
|
1081 | |
|
|
1082 | The pure perl implementation is hit in a few sweet spots (both the |
|
|
1083 | constant timeout and the use of a single fd hit optimisations in the |
|
|
1084 | perl interpreter and the backend itself). Nevertheless this shows that |
|
|
1085 | it adds very little overhead in itself. Like any select-based backend |
|
|
1086 | its performance becomes really bad with lots of file descriptors (and |
|
|
1087 | few of them active), of course, but this was not subject of this |
|
|
1088 | benchmark. |
|
|
1089 | |
|
|
1090 | The "Event" module has a relatively high setup and callback invocation |
|
|
1091 | cost, but overall scores in on the third place. |
|
|
1092 | |
|
|
1093 | "Glib"'s memory usage is quite a bit higher, but it features a faster |
|
|
1094 | callback invocation and overall ends up in the same class as "Event". |
|
|
1095 | However, Glib scales extremely badly, doubling the number of watchers |
|
|
1096 | increases the processing time by more than a factor of four, making it |
|
|
1097 | completely unusable when using larger numbers of watchers (note that |
|
|
1098 | only a single file descriptor was used in the benchmark, so |
|
|
1099 | inefficiencies of "poll" do not account for this). |
|
|
1100 | |
|
|
1101 | The "Tk" adaptor works relatively well. The fact that it crashes with |
|
|
1102 | more than 2000 watchers is a big setback, however, as correctness takes |
|
|
1103 | precedence over speed. Nevertheless, its performance is surprising, as |
|
|
1104 | the file descriptor is dup()ed for each watcher. This shows that the |
|
|
1105 | dup() employed by some adaptors is not a big performance issue (it does |
|
|
1106 | incur a hidden memory cost inside the kernel which is not reflected in |
|
|
1107 | the figures above). |
|
|
1108 | |
|
|
1109 | "POE", regardless of underlying event loop (whether using its pure perl |
|
|
1110 | select-based backend or the Event module, the POE-EV backend couldn't be |
|
|
1111 | tested because it wasn't working) shows abysmal performance and memory |
|
|
1112 | usage with AnyEvent: Watchers use almost 30 times as much memory as EV |
|
|
1113 | watchers, and 10 times as much memory as Event (the high memory |
|
|
1114 | requirements are caused by requiring a session for each watcher). |
|
|
1115 | Watcher invocation speed is almost 900 times slower than with AnyEvent's |
|
|
1116 | pure perl implementation. |
|
|
1117 | |
|
|
1118 | The design of the POE adaptor class in AnyEvent can not really account |
|
|
1119 | for the performance issues, though, as session creation overhead is |
|
|
1120 | small compared to execution of the state machine, which is coded pretty |
|
|
1121 | optimally within AnyEvent::Impl::POE (and while everybody agrees that |
|
|
1122 | using multiple sessions is not a good approach, especially regarding |
|
|
1123 | memory usage, even the author of POE could not come up with a faster |
|
|
1124 | design). |
|
|
1125 | |
|
|
1126 | Summary |
|
|
1127 | * Using EV through AnyEvent is faster than any other event loop (even |
|
|
1128 | when used without AnyEvent), but most event loops have acceptable |
|
|
1129 | performance with or without AnyEvent. |
|
|
1130 | |
|
|
1131 | * The overhead AnyEvent adds is usually much smaller than the overhead |
|
|
1132 | of the actual event loop, only with extremely fast event loops such |
|
|
1133 | as EV adds AnyEvent significant overhead. |
|
|
1134 | |
|
|
1135 | * You should avoid POE like the plague if you want performance or |
|
|
1136 | reasonable memory usage. |
|
|
1137 | |
|
|
1138 | BENCHMARKING THE LARGE SERVER CASE |
|
|
1139 | This benchmark actually benchmarks the event loop itself. It works by |
|
|
1140 | creating a number of "servers": each server consists of a socket pair, a |
|
|
1141 | timeout watcher that gets reset on activity (but never fires), and an |
|
|
1142 | I/O watcher waiting for input on one side of the socket. Each time the |
|
|
1143 | socket watcher reads a byte it will write that byte to a random other |
|
|
1144 | "server". |
|
|
1145 | |
|
|
1146 | The effect is that there will be a lot of I/O watchers, only part of |
|
|
1147 | which are active at any one point (so there is a constant number of |
|
|
1148 | active fds for each loop iteration, but which fds these are is random). |
|
|
1149 | The timeout is reset each time something is read because that reflects |
|
|
1150 | how most timeouts work (and puts extra pressure on the event loops). |
|
|
1151 | |
|
|
1152 | In this benchmark, we use 10000 socket pairs (20000 sockets), of which |
|
|
1153 | 100 (1%) are active. This mirrors the activity of large servers with |
|
|
1154 | many connections, most of which are idle at any one point in time. |
|
|
1155 | |
|
|
1156 | Source code for this benchmark is found as eg/bench2 in the AnyEvent |
|
|
1157 | distribution. |
|
|
1158 | |
|
|
1159 | Explanation of the columns |
|
|
1160 | *sockets* is the number of sockets, and twice the number of "servers" |
|
|
1161 | (as each server has a read and write socket end). |
|
|
1162 | |
|
|
1163 | *create* is the time it takes to create a socket pair (which is |
|
|
1164 | nontrivial) and two watchers: an I/O watcher and a timeout watcher. |
|
|
1165 | |
|
|
1166 | *request*, the most important value, is the time it takes to handle a |
|
|
1167 | single "request", that is, reading the token from the pipe and |
|
|
1168 | forwarding it to another server. This includes deleting the old timeout |
|
|
1169 | and creating a new one that moves the timeout into the future. |
|
|
1170 | |
|
|
1171 | Results |
|
|
1172 | name sockets create request |
|
|
1173 | EV 20000 69.01 11.16 |
|
|
1174 | Perl 20000 73.32 35.87 |
|
|
1175 | Event 20000 212.62 257.32 |
|
|
1176 | Glib 20000 651.16 1896.30 |
|
|
1177 | POE 20000 349.67 12317.24 uses POE::Loop::Event |
|
|
1178 | |
|
|
1179 | Discussion |
|
|
1180 | This benchmark *does* measure scalability and overall performance of the |
|
|
1181 | particular event loop. |
|
|
1182 | |
|
|
1183 | EV is again fastest. Since it is using epoll on my system, the setup |
|
|
1184 | time is relatively high, though. |
|
|
1185 | |
|
|
1186 | Perl surprisingly comes second. It is much faster than the C-based event |
|
|
1187 | loops Event and Glib. |
|
|
1188 | |
|
|
1189 | Event suffers from high setup time as well (look at its code and you |
|
|
1190 | will understand why). Callback invocation also has a high overhead |
|
|
1191 | compared to the "$_->() for .."-style loop that the Perl event loop |
|
|
1192 | uses. Event uses select or poll in basically all documented |
|
|
1193 | configurations. |
|
|
1194 | |
|
|
1195 | Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It |
|
|
1196 | clearly fails to perform with many filehandles or in busy servers. |
|
|
1197 | |
|
|
1198 | POE is still completely out of the picture, taking over 1000 times as |
|
|
1199 | long as EV, and over 100 times as long as the Perl implementation, even |
|
|
1200 | though it uses a C-based event loop in this case. |
|
|
1201 | |
|
|
1202 | Summary |
|
|
1203 | * The pure perl implementation performs extremely well. |
|
|
1204 | |
|
|
1205 | * Avoid Glib or POE in large projects where performance matters. |
|
|
1206 | |
|
|
1207 | BENCHMARKING SMALL SERVERS |
|
|
1208 | While event loops should scale (and select-based ones do not...) even to |
|
|
1209 | large servers, most programs we (or I :) actually write have only a few |
|
|
1210 | I/O watchers. |
|
|
1211 | |
|
|
1212 | In this benchmark, I use the same benchmark program as in the large |
|
|
1213 | server case, but it uses only eight "servers", of which three are active |
|
|
1214 | at any one time. This should reflect performance for a small server |
|
|
1215 | relatively well. |
|
|
1216 | |
|
|
1217 | The columns are identical to the previous table. |
|
|
1218 | |
|
|
1219 | Results |
|
|
1220 | name sockets create request |
|
|
1221 | EV 16 20.00 6.54 |
|
|
1222 | Perl 16 25.75 12.62 |
|
|
1223 | Event 16 81.27 35.86 |
|
|
1224 | Glib 16 32.63 15.48 |
|
|
1225 | POE 16 261.87 276.28 uses POE::Loop::Event |
|
|
1226 | |
|
|
1227 | Discussion |
|
|
1228 | The benchmark tries to test the performance of a typical small server. |
|
|
1229 | While knowing how various event loops perform is interesting, keep in |
|
|
1230 | mind that their overhead in this case is usually not as important, due |
|
|
1231 | to the small absolute number of watchers (that is, you need efficiency |
|
|
1232 | and speed most when you have lots of watchers, not when you only have a |
|
|
1233 | few of them). |
|
|
1234 | |
|
|
1235 | EV is again fastest. |
|
|
1236 | |
|
|
1237 | Perl again comes second. It is noticeably faster than the C-based event |
|
|
1238 | loops Event and Glib, although the difference is too small to really |
|
|
1239 | matter. |
|
|
1240 | |
|
|
1241 | POE also performs much better in this case, but is is still far behind |
|
|
1242 | the others. |
|
|
1243 | |
|
|
1244 | Summary |
|
|
1245 | * C-based event loops perform very well with small number of watchers, |
|
|
1246 | as the management overhead dominates. |
|
|
1247 | |
|
|
1248 | FORK |
|
|
1249 | Most event libraries are not fork-safe. The ones who are usually are |
|
|
1250 | because they rely on inefficient but fork-safe "select" or "poll" calls. |
|
|
1251 | Only EV is fully fork-aware. |
|
|
1252 | |
|
|
1253 | If you have to fork, you must either do so *before* creating your first |
|
|
1254 | watcher OR you must not use AnyEvent at all in the child. |
|
|
1255 | |
|
|
1256 | SECURITY CONSIDERATIONS |
|
|
1257 | AnyEvent can be forced to load any event model via |
|
|
1258 | $ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used |
|
|
1259 | to execute arbitrary code or directly gain access, it can easily be used |
|
|
1260 | to make the program hang or malfunction in subtle ways, as AnyEvent |
|
|
1261 | watchers will not be active when the program uses a different event |
|
|
1262 | model than specified in the variable. |
|
|
1263 | |
|
|
1264 | You can make AnyEvent completely ignore this variable by deleting it |
|
|
1265 | before the first watcher gets created, e.g. with a "BEGIN" block: |
|
|
1266 | |
|
|
1267 | BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } |
|
|
1268 | |
|
|
1269 | use AnyEvent; |
|
|
1270 | |
|
|
1271 | Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can |
|
|
1272 | be used to probe what backend is used and gain other information (which |
|
|
1273 | is probably even less useful to an attacker than PERL_ANYEVENT_MODEL). |
468 | |
1274 | |
469 | SEE ALSO |
1275 | SEE ALSO |
470 | Event modules: Coro::EV, EV, EV::Glib, Glib::EV, Coro::Event, Event, |
1276 | Utility functions: AnyEvent::Util. |
471 | Glib::Event, Glib, Coro, Tk. |
|
|
472 | |
1277 | |
473 | Implementations: AnyEvent::Impl::CoroEV, AnyEvent::Impl::EV, |
1278 | Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk, |
474 | AnyEvent::Impl::CoroEvent, AnyEvent::Impl::Event, AnyEvent::Impl::Glib, |
1279 | Event::Lib, Qt, POE. |
|
|
1280 | |
|
|
1281 | Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event, |
475 | AnyEvent::Impl::Tk, AnyEvent::Impl::Perl. |
1282 | AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl, |
|
|
1283 | AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE. |
476 | |
1284 | |
|
|
1285 | Non-blocking file handles, sockets, TCP clients and servers: |
|
|
1286 | AnyEvent::Handle, AnyEvent::Socket. |
|
|
1287 | |
|
|
1288 | Asynchronous DNS: AnyEvent::DNS. |
|
|
1289 | |
|
|
1290 | Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event, |
|
|
1291 | |
477 | Nontrivial usage examples: Net::FCP, Net::XMPP2. |
1292 | Nontrivial usage examples: Net::FCP, Net::XMPP2, AnyEvent::DNS. |
478 | |
1293 | |
|
|
1294 | AUTHOR |
|
|
1295 | Marc Lehmann <schmorp@schmorp.de> |
|
|
1296 | http://home.schmorp.de/ |
479 | |
1297 | |