… | |
… | |
3 | AnyEvent::Fork - everything you wanted to use fork() for, but couldn't |
3 | AnyEvent::Fork - everything you wanted to use fork() for, but couldn't |
4 | |
4 | |
5 | =head1 SYNOPSIS |
5 | =head1 SYNOPSIS |
6 | |
6 | |
7 | use AnyEvent::Fork; |
7 | use AnyEvent::Fork; |
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8 | |
|
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9 | ################################################################## |
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10 | # create a single new process, tell it to run your worker function |
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11 | |
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12 | AnyEvent::Fork |
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13 | ->new |
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14 | ->require ("MyModule") |
|
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15 | ->run ("MyModule::worker, sub { |
|
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16 | my ($master_filehandle) = @_; |
|
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17 | |
|
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18 | # now $master_filehandle is connected to the |
|
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19 | # $slave_filehandle in the new process. |
|
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20 | }); |
|
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21 | |
|
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22 | # MyModule::worker might look like this |
|
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23 | sub MyModule::worker { |
|
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24 | my ($slave_filehandle) = @_; |
|
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25 | |
|
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26 | # now $slave_filehandle is connected to the $master_filehandle |
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27 | # in the original prorcess. have fun! |
|
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28 | } |
|
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29 | |
|
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30 | ################################################################## |
|
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31 | # create a pool of server processes all accepting on the same socket |
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32 | |
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33 | # create listener socket |
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34 | my $listener = ...; |
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35 | |
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36 | # create a pool template, initialise it and give it the socket |
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37 | my $pool = AnyEvent::Fork |
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38 | ->new |
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39 | ->require ("Some::Stuff", "My::Server") |
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40 | ->send_fh ($listener); |
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41 | |
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42 | # now create 10 identical workers |
|
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43 | for my $id (1..10) { |
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44 | $pool |
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45 | ->fork |
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46 | ->send_arg ($id) |
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47 | ->run ("My::Server::run"); |
|
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48 | } |
|
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49 | |
|
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50 | # now do other things - maybe use the filehandle provided by run |
|
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51 | # to wait for the processes to die. or whatever. |
|
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52 | |
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53 | # My::Server::run might look like this |
|
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54 | sub My::Server::run { |
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55 | my ($slave, $listener, $id) = @_; |
|
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56 | |
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57 | close $slave; # we do not use the socket, so close it to save resources |
|
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58 | |
|
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59 | # we could go ballistic and use e.g. AnyEvent here, or IO::AIO, |
|
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60 | # or anything we usually couldn't do in a process forked normally. |
|
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61 | while (my $socket = $listener->accept) { |
|
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62 | # do sth. with new socket |
|
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63 | } |
|
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64 | } |
8 | |
65 | |
9 | =head1 DESCRIPTION |
66 | =head1 DESCRIPTION |
10 | |
67 | |
11 | This module allows you to create new processes, without actually forking |
68 | This module allows you to create new processes, without actually forking |
12 | them from your current process (avoiding the problems of forking), but |
69 | them from your current process (avoiding the problems of forking), but |
13 | preserving most of the advantages of fork. |
70 | preserving most of the advantages of fork. |
14 | |
71 | |
15 | It can be used to create new worker processes or new independent |
72 | It can be used to create new worker processes or new independent |
16 | subprocesses for short- and long-running jobs, process pools (e.g. for use |
73 | subprocesses for short- and long-running jobs, process pools (e.g. for use |
17 | in pre-forked servers) but also to spawn new external processes (such as |
74 | in pre-forked servers) but also to spawn new external processes (such as |
18 | CGI scripts from a webserver), which can be faster (and more well behaved) |
75 | CGI scripts from a web server), which can be faster (and more well behaved) |
19 | than using fork+exec in big processes. |
76 | than using fork+exec in big processes. |
20 | |
77 | |
21 | Special care has been taken to make this module useful from other modules, |
78 | Special care has been taken to make this module useful from other modules, |
22 | while still supporting specialised environments such as L<App::Staticperl> |
79 | while still supporting specialised environments such as L<App::Staticperl> |
23 | or L<PAR::Packer>. |
80 | or L<PAR::Packer>. |
|
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81 | |
|
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82 | =head1 WHAT THIS MODULE IS NOT |
|
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83 | |
|
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84 | This module only creates processes and lets you pass file handles and |
|
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85 | strings to it, and run perl code. It does not implement any kind of RPC - |
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86 | there is no back channel from the process back to you, and there is no RPC |
|
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87 | or message passing going on. |
|
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88 | |
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89 | If you need some form of RPC, you can either implement it yourself |
|
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90 | in whatever way you like, use some message-passing module such |
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91 | as L<AnyEvent::MP>, some pipe such as L<AnyEvent::ZeroMQ>, use |
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92 | L<AnyEvent::Handle> on both sides to send e.g. JSON or Storable messages, |
|
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93 | and so on. |
24 | |
94 | |
25 | =head1 PROBLEM STATEMENT |
95 | =head1 PROBLEM STATEMENT |
26 | |
96 | |
27 | There are two ways to implement parallel processing on UNIX like operating |
97 | There are two ways to implement parallel processing on UNIX like operating |
28 | systems - fork and process, and fork+exec and process. They have different |
98 | systems - fork and process, and fork+exec and process. They have different |
… | |
… | |
40 | or fork+exec instead. |
110 | or fork+exec instead. |
41 | |
111 | |
42 | =item Forking usually creates a copy-on-write copy of the parent |
112 | =item Forking usually creates a copy-on-write copy of the parent |
43 | process. Memory (for example, modules or data files that have been |
113 | process. Memory (for example, modules or data files that have been |
44 | will not take additional memory). When exec'ing a new process, modules |
114 | will not take additional memory). When exec'ing a new process, modules |
45 | and data files might need to be loaded again, at extra cpu and memory |
115 | and data files might need to be loaded again, at extra CPU and memory |
46 | cost. Likewise when forking, all data structures are copied as well - if |
116 | cost. Likewise when forking, all data structures are copied as well - if |
47 | the program frees them and replaces them by new data, the child processes |
117 | the program frees them and replaces them by new data, the child processes |
48 | will retain the memory even if it isn't used. |
118 | will retain the memory even if it isn't used. |
49 | |
119 | |
50 | This module allows the main program to do a controlled fork, and allows |
120 | This module allows the main program to do a controlled fork, and allows |
… | |
… | |
62 | as template, and also tries hard to identify the correct path to the perl |
132 | as template, and also tries hard to identify the correct path to the perl |
63 | interpreter. With a cooperative main program, exec'ing the interpreter |
133 | interpreter. With a cooperative main program, exec'ing the interpreter |
64 | might not even be necessary. |
134 | might not even be necessary. |
65 | |
135 | |
66 | =item Forking might be impossible when a program is running. For example, |
136 | =item Forking might be impossible when a program is running. For example, |
67 | POSIX makes it almost impossible to fork from a multithreaded program and |
137 | POSIX makes it almost impossible to fork from a multi-threaded program and |
68 | do anything useful in the child - strictly speaking, if your perl program |
138 | do anything useful in the child - strictly speaking, if your perl program |
69 | uses posix threads (even indirectly via e.g. L<IO::AIO> or L<threads>), |
139 | uses posix threads (even indirectly via e.g. L<IO::AIO> or L<threads>), |
70 | you cannot call fork on the perl level anymore, at all. |
140 | you cannot call fork on the perl level anymore, at all. |
71 | |
141 | |
72 | This module can safely fork helper processes at any time, by caling |
142 | This module can safely fork helper processes at any time, by calling |
73 | fork+exec in C, in a POSIX-compatible way. |
143 | fork+exec in C, in a POSIX-compatible way. |
74 | |
144 | |
75 | =item Parallel processing with fork might be inconvenient or difficult |
145 | =item Parallel processing with fork might be inconvenient or difficult |
76 | to implement. For example, when a program uses an event loop and creates |
146 | to implement. For example, when a program uses an event loop and creates |
77 | watchers it becomes very hard to use the event loop from a child |
147 | watchers it becomes very hard to use the event loop from a child |
… | |
… | |
109 | needed the first time. Forking from this process shares the memory used |
179 | needed the first time. Forking from this process shares the memory used |
110 | for the perl interpreter with the new process, but loading modules takes |
180 | for the perl interpreter with the new process, but loading modules takes |
111 | time, and the memory is not shared with anything else. |
181 | time, and the memory is not shared with anything else. |
112 | |
182 | |
113 | This is ideal for when you only need one extra process of a kind, with the |
183 | This is ideal for when you only need one extra process of a kind, with the |
114 | option of starting and stipping it on demand. |
184 | option of starting and stopping it on demand. |
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185 | |
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186 | Example: |
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187 | |
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188 | AnyEvent::Fork |
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189 | ->new |
|
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190 | ->require ("Some::Module") |
|
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191 | ->run ("Some::Module::run", sub { |
|
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192 | my ($fork_fh) = @_; |
|
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193 | }); |
115 | |
194 | |
116 | =item fork a new template process, load code, then fork processes off of |
195 | =item fork a new template process, load code, then fork processes off of |
117 | it and run the code |
196 | it and run the code |
118 | |
197 | |
119 | When you need to have a bunch of processes that all execute the same (or |
198 | When you need to have a bunch of processes that all execute the same (or |
… | |
… | |
125 | modules you loaded) is shared between the processes, and each new process |
204 | modules you loaded) is shared between the processes, and each new process |
126 | consumes relatively little memory of its own. |
205 | consumes relatively little memory of its own. |
127 | |
206 | |
128 | The disadvantage of this approach is that you need to create a template |
207 | The disadvantage of this approach is that you need to create a template |
129 | process for the sole purpose of forking new processes from it, but if you |
208 | process for the sole purpose of forking new processes from it, but if you |
130 | only need a fixed number of proceses you can create them, and then destroy |
209 | only need a fixed number of processes you can create them, and then destroy |
131 | the template process. |
210 | the template process. |
|
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211 | |
|
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212 | Example: |
|
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213 | |
|
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214 | my $template = AnyEvent::Fork->new->require ("Some::Module"); |
|
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215 | |
|
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216 | for (1..10) { |
|
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217 | $template->fork->run ("Some::Module::run", sub { |
|
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218 | my ($fork_fh) = @_; |
|
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219 | }); |
|
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220 | } |
|
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221 | |
|
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222 | # at this point, you can keep $template around to fork new processes |
|
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223 | # later, or you can destroy it, which causes it to vanish. |
132 | |
224 | |
133 | =item execute a new perl interpreter, load some code, run it |
225 | =item execute a new perl interpreter, load some code, run it |
134 | |
226 | |
135 | This is relatively slow, and doesn't allow you to share memory between |
227 | This is relatively slow, and doesn't allow you to share memory between |
136 | multiple processes. |
228 | multiple processes. |
… | |
… | |
138 | The only advantage is that you don't have to have a template process |
230 | The only advantage is that you don't have to have a template process |
139 | hanging around all the time to fork off some new processes, which might be |
231 | hanging around all the time to fork off some new processes, which might be |
140 | an advantage when there are long time spans where no extra processes are |
232 | an advantage when there are long time spans where no extra processes are |
141 | needed. |
233 | needed. |
142 | |
234 | |
|
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235 | Example: |
|
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236 | |
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237 | AnyEvent::Fork |
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238 | ->new_exec |
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239 | ->require ("Some::Module") |
|
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240 | ->run ("Some::Module::run", sub { |
|
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241 | my ($fork_fh) = @_; |
|
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242 | }); |
|
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243 | |
143 | =back |
244 | =back |
144 | |
245 | |
145 | =head1 FUNCTIONS |
246 | =head1 FUNCTIONS |
146 | |
247 | |
147 | =over 4 |
248 | =over 4 |
… | |
… | |
150 | |
251 | |
151 | package AnyEvent::Fork; |
252 | package AnyEvent::Fork; |
152 | |
253 | |
153 | use common::sense; |
254 | use common::sense; |
154 | |
255 | |
155 | use Socket (); |
256 | use Errno (); |
156 | |
257 | |
157 | use AnyEvent; |
258 | use AnyEvent; |
158 | use AnyEvent::Fork::Util; |
|
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159 | use AnyEvent::Util (); |
259 | use AnyEvent::Util (); |
|
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260 | |
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261 | use IO::FDPass; |
|
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262 | |
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263 | our $VERSION = 0.2; |
160 | |
264 | |
161 | our $PERL; # the path to the perl interpreter, deduces with various forms of magic |
265 | our $PERL; # the path to the perl interpreter, deduces with various forms of magic |
162 | |
266 | |
163 | =item my $pool = new AnyEvent::Fork key => value... |
267 | =item my $pool = new AnyEvent::Fork key => value... |
164 | |
268 | |
… | |
… | |
177 | our $TEMPLATE; |
281 | our $TEMPLATE; |
178 | |
282 | |
179 | sub _cmd { |
283 | sub _cmd { |
180 | my $self = shift; |
284 | my $self = shift; |
181 | |
285 | |
182 | # ideally, we would want to use "a (w/a)*" as format string, but perl versions |
286 | # ideally, we would want to use "a (w/a)*" as format string, but perl |
183 | # from at least 5.8.9 to 5.16.3 are all buggy and can't unpack it. |
287 | # versions from at least 5.8.9 to 5.16.3 are all buggy and can't unpack |
|
|
288 | # it. |
184 | push @{ $self->[2] }, pack "N/a", pack "(w/a)*", @_; |
289 | push @{ $self->[2] }, pack "L/a*", pack "(w/a*)*", @_; |
185 | |
290 | |
186 | $self->[3] ||= AE::io $self->[1], 1, sub { |
291 | unless ($self->[3]) { |
|
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292 | my $wcb = sub { |
|
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293 | do { |
|
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294 | # send the next "thing" in the queue - either a reference to an fh, |
|
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295 | # or a plain string. |
|
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296 | |
187 | if (ref $self->[2][0]) { |
297 | if (ref $self->[2][0]) { |
|
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298 | # send fh |
188 | AnyEvent::Fork::Util::fd_send fileno $self->[1], fileno ${ $self->[2][0] } |
299 | unless (IO::FDPass::send fileno $self->[1], fileno ${ $self->[2][0] }) { |
|
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300 | return if $! == Errno::EAGAIN || $! == Errno::EWOULDBLOCK; |
|
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301 | undef $self->[3]; |
|
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302 | die "AnyEvent::Fork: file descriptor send failure: $!"; |
|
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303 | } |
|
|
304 | |
189 | and shift @{ $self->[2] }; |
305 | shift @{ $self->[2] }; |
190 | |
306 | |
191 | } else { |
307 | } else { |
|
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308 | # send string |
192 | my $len = syswrite $self->[1], $self->[2][0] |
309 | my $len = syswrite $self->[1], $self->[2][0]; |
|
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310 | |
|
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311 | unless ($len) { |
|
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312 | return if $! == Errno::EAGAIN || $! == Errno::EWOULDBLOCK; |
|
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313 | undef $self->[3]; |
193 | or do { undef $self->[3]; die "AnyEvent::Fork: command write failure: $!" }; |
314 | die "AnyEvent::Fork: command write failure: $!"; |
|
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315 | } |
194 | |
316 | |
195 | substr $self->[2][0], 0, $len, ""; |
317 | substr $self->[2][0], 0, $len, ""; |
196 | shift @{ $self->[2] } unless length $self->[2][0]; |
318 | shift @{ $self->[2] } unless length $self->[2][0]; |
197 | } |
319 | } |
|
|
320 | } while @{ $self->[2] }; |
198 | |
321 | |
199 | unless (@{ $self->[2] }) { |
322 | # everything written |
200 | undef $self->[3]; |
323 | undef $self->[3]; |
|
|
324 | # invoke run callback |
201 | $self->[0]->($self->[1]) if $self->[0]; |
325 | $self->[0]->($self->[1]) if $self->[0]; |
202 | } |
326 | }; |
|
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327 | |
|
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328 | $wcb->(); |
|
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329 | |
|
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330 | $self->[3] ||= AE::io $self->[1], 1, $wcb |
|
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331 | if @{ $self->[2] }; |
203 | }; |
332 | } |
|
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333 | |
|
|
334 | () # make sure we don't leak the watcher |
204 | } |
335 | } |
205 | |
336 | |
206 | sub _new { |
337 | sub _new { |
207 | my ($self, $fh) = @_; |
338 | my ($self, $fh) = @_; |
|
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339 | |
|
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340 | AnyEvent::Util::fh_nonblocking $fh, 1; |
208 | |
341 | |
209 | $self = bless [ |
342 | $self = bless [ |
210 | undef, # run callback |
343 | undef, # run callback |
211 | $fh, |
344 | $fh, |
212 | [], # write queue - strings or fd's |
345 | [], # write queue - strings or fd's |
213 | undef, # AE watcher |
346 | undef, # AE watcher |
214 | ], $self; |
347 | ], $self; |
215 | |
348 | |
216 | # my ($a, $b) = AnyEvent::Util::portable_socketpair; |
|
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217 | |
|
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218 | # queue_cmd $template, "Iabc"; |
|
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219 | # push @{ $template->[2] }, \$b; |
|
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220 | |
|
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221 | # use Coro::AnyEvent; Coro::AnyEvent::sleep 1; |
|
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222 | # undef $b; |
|
|
223 | # die "x" . <$a>; |
|
|
224 | |
|
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225 | $self |
349 | $self |
|
|
350 | } |
|
|
351 | |
|
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352 | # fork template from current process, used by AnyEvent::Fork::Early/Template |
|
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353 | sub _new_fork { |
|
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354 | my ($fh, $slave) = AnyEvent::Util::portable_socketpair; |
|
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355 | my $parent = $$; |
|
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356 | |
|
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357 | my $pid = fork; |
|
|
358 | |
|
|
359 | if ($pid eq 0) { |
|
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360 | require AnyEvent::Fork::Serve; |
|
|
361 | $AnyEvent::Fork::Serve::OWNER = $parent; |
|
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362 | close $fh; |
|
|
363 | $0 = "$_[1] of $parent"; |
|
|
364 | $SIG{CHLD} = 'IGNORE'; |
|
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365 | AnyEvent::Fork::Serve::serve ($slave); |
|
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366 | exit 0; |
|
|
367 | } elsif (!$pid) { |
|
|
368 | die "AnyEvent::Fork::Early/Template: unable to fork template process: $!"; |
|
|
369 | } |
|
|
370 | |
|
|
371 | AnyEvent::Fork->_new ($fh) |
226 | } |
372 | } |
227 | |
373 | |
228 | =item my $proc = new AnyEvent::Fork |
374 | =item my $proc = new AnyEvent::Fork |
229 | |
375 | |
230 | Create a new "empty" perl interpreter process and returns its process |
376 | Create a new "empty" perl interpreter process and returns its process |
231 | object for further manipulation. |
377 | object for further manipulation. |
232 | |
378 | |
233 | The new process is forked from a template process that is kept around |
379 | The new process is forked from a template process that is kept around |
234 | for this purpose. When it doesn't exist yet, it is created by a call to |
380 | for this purpose. When it doesn't exist yet, it is created by a call to |
235 | C<new_exec> and kept around for future calls. |
381 | C<new_exec> and kept around for future calls. |
|
|
382 | |
|
|
383 | When the process object is destroyed, it will release the file handle |
|
|
384 | that connects it with the new process. When the new process has not yet |
|
|
385 | called C<run>, then the process will exit. Otherwise, what happens depends |
|
|
386 | entirely on the code that is executed. |
236 | |
387 | |
237 | =cut |
388 | =cut |
238 | |
389 | |
239 | sub new { |
390 | sub new { |
240 | my $class = shift; |
391 | my $class = shift; |
… | |
… | |
261 | my ($fh, $slave) = AnyEvent::Util::portable_socketpair; |
412 | my ($fh, $slave) = AnyEvent::Util::portable_socketpair; |
262 | |
413 | |
263 | $self->send_fh ($slave); |
414 | $self->send_fh ($slave); |
264 | $self->_cmd ("f"); |
415 | $self->_cmd ("f"); |
265 | |
416 | |
266 | AnyEvent::Util::fh_nonblocking $fh, 1; |
|
|
267 | |
|
|
268 | AnyEvent::Fork->_new ($fh) |
417 | AnyEvent::Fork->_new ($fh) |
269 | } |
418 | } |
270 | |
419 | |
271 | =item my $proc = new_exec AnyEvent::Fork |
420 | =item my $proc = new_exec AnyEvent::Fork |
272 | |
421 | |
… | |
… | |
278 | reduces the amount of memory sharing that is possible, and is also slower. |
427 | reduces the amount of memory sharing that is possible, and is also slower. |
279 | |
428 | |
280 | You should use C<new> whenever possible, except when having a template |
429 | You should use C<new> whenever possible, except when having a template |
281 | process around is unacceptable. |
430 | process around is unacceptable. |
282 | |
431 | |
283 | The path to the perl interpreter is divined usign various methods - first |
432 | The path to the perl interpreter is divined using various methods - first |
284 | C<$^X> is investigated to see if the path ends with something that sounds |
433 | C<$^X> is investigated to see if the path ends with something that sounds |
285 | as if it were the perl interpreter. Failing this, the module falls back to |
434 | as if it were the perl interpreter. Failing this, the module falls back to |
286 | using C<$Config::Config{perlpath}>. |
435 | using C<$Config::Config{perlpath}>. |
287 | |
436 | |
288 | =cut |
437 | =cut |
… | |
… | |
297 | my $perl = $; |
446 | my $perl = $; |
298 | |
447 | |
299 | # first we try $^X, but the path must be absolute (always on win32), and end in sth. |
448 | # first we try $^X, but the path must be absolute (always on win32), and end in sth. |
300 | # that looks like perl. this obviously only works for posix and win32 |
449 | # that looks like perl. this obviously only works for posix and win32 |
301 | unless ( |
450 | unless ( |
302 | (AnyEvent::Fork::Util::WIN32 || $perl =~ m%^/%) |
451 | ($^O eq "MSWin32" || $perl =~ m%^/%) |
303 | && $perl =~ m%[/\\]perl(?:[0-9]+(\.[0-9]+)+)?(\.exe)?$%i |
452 | && $perl =~ m%[/\\]perl(?:[0-9]+(\.[0-9]+)+)?(\.exe)?$%i |
304 | ) { |
453 | ) { |
305 | # if it doesn't look perlish enough, try Config |
454 | # if it doesn't look perlish enough, try Config |
306 | require Config; |
455 | require Config; |
307 | $perl = $Config::Config{perlpath}; |
456 | $perl = $Config::Config{perlpath}; |
… | |
… | |
309 | } |
458 | } |
310 | |
459 | |
311 | require Proc::FastSpawn; |
460 | require Proc::FastSpawn; |
312 | |
461 | |
313 | my ($fh, $slave) = AnyEvent::Util::portable_socketpair; |
462 | my ($fh, $slave) = AnyEvent::Util::portable_socketpair; |
314 | AnyEvent::Util::fh_nonblocking $fh, 1; |
|
|
315 | Proc::FastSpawn::fd_inherit (fileno $slave); |
463 | Proc::FastSpawn::fd_inherit (fileno $slave); |
|
|
464 | |
|
|
465 | # new fh's should always be set cloexec (due to $^F), |
|
|
466 | # but hey, not on win32, so we always clear the inherit flag. |
|
|
467 | Proc::FastSpawn::fd_inherit (fileno $fh, 0); |
316 | |
468 | |
317 | # quick. also doesn't work in win32. of course. what did you expect |
469 | # quick. also doesn't work in win32. of course. what did you expect |
318 | #local $ENV{PERL5LIB} = join ":", grep !ref, @INC; |
470 | #local $ENV{PERL5LIB} = join ":", grep !ref, @INC; |
319 | my %env = %ENV; |
471 | my %env = %ENV; |
320 | $env{PERL5LIB} = join ":", grep !ref, @INC; |
472 | $env{PERL5LIB} = join +($^O eq "MSWin32" ? ";" : ":"), grep !ref, @INC; |
321 | |
473 | |
322 | Proc::FastSpawn::spawn ( |
474 | Proc::FastSpawn::spawn ( |
323 | $perl, |
475 | $perl, |
324 | ["perl", "-MAnyEvent::Fork::Serve", "-e", "AnyEvent::Fork::Serve::me", fileno $slave], |
476 | ["perl", "-MAnyEvent::Fork::Serve", "-e", "AnyEvent::Fork::Serve::me", fileno $slave, $$], |
325 | [map "$_=$env{$_}", keys %env], |
477 | [map "$_=$env{$_}", keys %env], |
326 | ) or die "unable to spawn AnyEvent::Fork server: $!"; |
478 | ) or die "unable to spawn AnyEvent::Fork server: $!"; |
327 | |
479 | |
328 | $self->_new ($fh) |
480 | $self->_new ($fh) |
329 | } |
481 | } |
330 | |
482 | |
|
|
483 | =item $proc = $proc->eval ($perlcode, @args) |
|
|
484 | |
|
|
485 | Evaluates the given C<$perlcode> as ... perl code, while setting C<@_> to |
|
|
486 | the strings specified by C<@args>. |
|
|
487 | |
|
|
488 | This call is meant to do any custom initialisation that might be required |
|
|
489 | (for example, the C<require> method uses it). It's not supposed to be used |
|
|
490 | to completely take over the process, use C<run> for that. |
|
|
491 | |
|
|
492 | The code will usually be executed after this call returns, and there is no |
|
|
493 | way to pass anything back to the calling process. Any evaluation errors |
|
|
494 | will be reported to stderr and cause the process to exit. |
|
|
495 | |
|
|
496 | Returns the process object for easy chaining of method calls. |
|
|
497 | |
|
|
498 | =cut |
|
|
499 | |
|
|
500 | sub eval { |
|
|
501 | my ($self, $code, @args) = @_; |
|
|
502 | |
|
|
503 | $self->_cmd (e => $code, @args); |
|
|
504 | |
|
|
505 | $self |
|
|
506 | } |
|
|
507 | |
331 | =item $proc = $proc->require ($module, ...) |
508 | =item $proc = $proc->require ($module, ...) |
332 | |
509 | |
333 | Tries to load the given modules into the process |
510 | Tries to load the given module(s) into the process |
334 | |
511 | |
335 | Returns the process object for easy chaining of method calls. |
512 | Returns the process object for easy chaining of method calls. |
|
|
513 | |
|
|
514 | =cut |
|
|
515 | |
|
|
516 | sub require { |
|
|
517 | my ($self, @modules) = @_; |
|
|
518 | |
|
|
519 | s%::%/%g for @modules; |
|
|
520 | $self->eval ('require "$_.pm" for @_', @modules); |
|
|
521 | |
|
|
522 | $self |
|
|
523 | } |
336 | |
524 | |
337 | =item $proc = $proc->send_fh ($handle, ...) |
525 | =item $proc = $proc->send_fh ($handle, ...) |
338 | |
526 | |
339 | Send one or more file handles (I<not> file descriptors) to the process, |
527 | Send one or more file handles (I<not> file descriptors) to the process, |
340 | to prepare a call to C<run>. |
528 | to prepare a call to C<run>. |
… | |
… | |
344 | accomplished by simply not storing the file handles anywhere after passing |
532 | accomplished by simply not storing the file handles anywhere after passing |
345 | them to this method. |
533 | them to this method. |
346 | |
534 | |
347 | Returns the process object for easy chaining of method calls. |
535 | Returns the process object for easy chaining of method calls. |
348 | |
536 | |
|
|
537 | Example: pass a file handle to a process, and release it without |
|
|
538 | closing. It will be closed automatically when it is no longer used. |
|
|
539 | |
|
|
540 | $proc->send_fh ($my_fh); |
|
|
541 | undef $my_fh; # free the reference if you want, but DO NOT CLOSE IT |
|
|
542 | |
349 | =cut |
543 | =cut |
350 | |
544 | |
351 | sub send_fh { |
545 | sub send_fh { |
352 | my ($self, @fh) = @_; |
546 | my ($self, @fh) = @_; |
353 | |
547 | |
… | |
… | |
362 | =item $proc = $proc->send_arg ($string, ...) |
556 | =item $proc = $proc->send_arg ($string, ...) |
363 | |
557 | |
364 | Send one or more argument strings to the process, to prepare a call to |
558 | Send one or more argument strings to the process, to prepare a call to |
365 | C<run>. The strings can be any octet string. |
559 | C<run>. The strings can be any octet string. |
366 | |
560 | |
|
|
561 | The protocol is optimised to pass a moderate number of relatively short |
|
|
562 | strings - while you can pass up to 4GB of data in one go, this is more |
|
|
563 | meant to pass some ID information or other startup info, not big chunks of |
|
|
564 | data. |
|
|
565 | |
367 | Returns the process object for easy chaining of emthod calls. |
566 | Returns the process object for easy chaining of method calls. |
368 | |
567 | |
369 | =cut |
568 | =cut |
370 | |
569 | |
371 | sub send_arg { |
570 | sub send_arg { |
372 | my ($self, @arg) = @_; |
571 | my ($self, @arg) = @_; |
… | |
… | |
393 | If the communication socket isn't used, it should be closed on both sides, |
592 | If the communication socket isn't used, it should be closed on both sides, |
394 | to save on kernel memory. |
593 | to save on kernel memory. |
395 | |
594 | |
396 | The socket is non-blocking in the parent, and blocking in the newly |
595 | The socket is non-blocking in the parent, and blocking in the newly |
397 | created process. The close-on-exec flag is set on both. Even if not used |
596 | created process. The close-on-exec flag is set on both. Even if not used |
398 | otherwise, the socket can be a good indicator for the existance of the |
597 | otherwise, the socket can be a good indicator for the existence of the |
399 | process - if the othe rprocess exits, you get a readable event on it, |
598 | process - if the other process exits, you get a readable event on it, |
400 | because exiting the process closes the socket (if it didn't create any |
599 | because exiting the process closes the socket (if it didn't create any |
401 | children using fork). |
600 | children using fork). |
402 | |
601 | |
|
|
602 | Example: create a template for a process pool, pass a few strings, some |
|
|
603 | file handles, then fork, pass one more string, and run some code. |
|
|
604 | |
|
|
605 | my $pool = AnyEvent::Fork |
|
|
606 | ->new |
|
|
607 | ->send_arg ("str1", "str2") |
|
|
608 | ->send_fh ($fh1, $fh2); |
|
|
609 | |
|
|
610 | for (1..2) { |
|
|
611 | $pool |
|
|
612 | ->fork |
|
|
613 | ->send_arg ("str3") |
|
|
614 | ->run ("Some::function", sub { |
|
|
615 | my ($fh) = @_; |
|
|
616 | |
|
|
617 | # fh is nonblocking, but we trust that the OS can accept these |
|
|
618 | # extra 3 octets anyway. |
|
|
619 | syswrite $fh, "hi #$_\n"; |
|
|
620 | |
|
|
621 | # $fh is being closed here, as we don't store it anywhere |
|
|
622 | }); |
|
|
623 | } |
|
|
624 | |
|
|
625 | # Some::function might look like this - all parameters passed before fork |
|
|
626 | # and after will be passed, in order, after the communications socket. |
|
|
627 | sub Some::function { |
|
|
628 | my ($fh, $str1, $str2, $fh1, $fh2, $str3) = @_; |
|
|
629 | |
|
|
630 | print scalar <$fh>; # prints "hi 1\n" and "hi 2\n" |
|
|
631 | } |
|
|
632 | |
403 | =cut |
633 | =cut |
404 | |
634 | |
405 | sub run { |
635 | sub run { |
406 | my ($self, $func, $cb) = @_; |
636 | my ($self, $func, $cb) = @_; |
407 | |
637 | |
408 | $self->[0] = $cb; |
638 | $self->[0] = $cb; |
409 | $self->_cmd ("r", $func); |
639 | $self->_cmd (r => $func); |
410 | } |
640 | } |
411 | |
641 | |
412 | =back |
642 | =back |
|
|
643 | |
|
|
644 | =head1 PERFORMANCE |
|
|
645 | |
|
|
646 | Now for some unscientific benchmark numbers (all done on an amd64 |
|
|
647 | GNU/Linux box). These are intended to give you an idea of the relative |
|
|
648 | performance you can expect, they are not meant to be absolute performance |
|
|
649 | numbers. |
|
|
650 | |
|
|
651 | OK, so, I ran a simple benchmark that creates a socket pair, forks, calls |
|
|
652 | exit in the child and waits for the socket to close in the parent. I did |
|
|
653 | load AnyEvent, EV and AnyEvent::Fork, for a total process size of 5100kB. |
|
|
654 | |
|
|
655 | 2079 new processes per second, using manual socketpair + fork |
|
|
656 | |
|
|
657 | Then I did the same thing, but instead of calling fork, I called |
|
|
658 | AnyEvent::Fork->new->run ("CORE::exit") and then again waited for the |
|
|
659 | socket form the child to close on exit. This does the same thing as manual |
|
|
660 | socket pair + fork, except that what is forked is the template process |
|
|
661 | (2440kB), and the socket needs to be passed to the server at the other end |
|
|
662 | of the socket first. |
|
|
663 | |
|
|
664 | 2307 new processes per second, using AnyEvent::Fork->new |
|
|
665 | |
|
|
666 | And finally, using C<new_exec> instead C<new>, using vforks+execs to exec |
|
|
667 | a new perl interpreter and compile the small server each time, I get: |
|
|
668 | |
|
|
669 | 479 vfork+execs per second, using AnyEvent::Fork->new_exec |
|
|
670 | |
|
|
671 | So how can C<< AnyEvent->new >> be faster than a standard fork, even |
|
|
672 | though it uses the same operations, but adds a lot of overhead? |
|
|
673 | |
|
|
674 | The difference is simply the process size: forking the 6MB process takes |
|
|
675 | so much longer than forking the 2.5MB template process that the overhead |
|
|
676 | introduced is canceled out. |
|
|
677 | |
|
|
678 | If the benchmark process grows, the normal fork becomes even slower: |
|
|
679 | |
|
|
680 | 1340 new processes, manual fork in a 20MB process |
|
|
681 | 731 new processes, manual fork in a 200MB process |
|
|
682 | 235 new processes, manual fork in a 2000MB process |
|
|
683 | |
|
|
684 | What that means (to me) is that I can use this module without having a |
|
|
685 | very bad conscience because of the extra overhead required to start new |
|
|
686 | processes. |
|
|
687 | |
|
|
688 | =head1 TYPICAL PROBLEMS |
|
|
689 | |
|
|
690 | This section lists typical problems that remain. I hope by recognising |
|
|
691 | them, most can be avoided. |
|
|
692 | |
|
|
693 | =over 4 |
|
|
694 | |
|
|
695 | =item exit runs destructors |
|
|
696 | |
|
|
697 | =item "leaked" file descriptors for exec'ed processes |
|
|
698 | |
|
|
699 | POSIX systems inherit file descriptors by default when exec'ing a new |
|
|
700 | process. While perl itself laudably sets the close-on-exec flags on new |
|
|
701 | file handles, most C libraries don't care, and even if all cared, it's |
|
|
702 | often not possible to set the flag in a race-free manner. |
|
|
703 | |
|
|
704 | That means some file descriptors can leak through. And since it isn't |
|
|
705 | possible to know which file descriptors are "good" and "necessary" (or |
|
|
706 | even to know which file descriptors are open), there is no good way to |
|
|
707 | close the ones that might harm. |
|
|
708 | |
|
|
709 | As an example of what "harm" can be done consider a web server that |
|
|
710 | accepts connections and afterwards some module uses AnyEvent::Fork for the |
|
|
711 | first time, causing it to fork and exec a new process, which might inherit |
|
|
712 | the network socket. When the server closes the socket, it is still open |
|
|
713 | in the child (which doesn't even know that) and the client might conclude |
|
|
714 | that the connection is still fine. |
|
|
715 | |
|
|
716 | For the main program, there are multiple remedies available - |
|
|
717 | L<AnyEvent::Fork::Early> is one, creating a process early and not using |
|
|
718 | C<new_exec> is another, as in both cases, the first process can be exec'ed |
|
|
719 | well before many random file descriptors are open. |
|
|
720 | |
|
|
721 | In general, the solution for these kind of problems is to fix the |
|
|
722 | libraries or the code that leaks those file descriptors. |
|
|
723 | |
|
|
724 | Fortunately, most of these leaked descriptors do no harm, other than |
|
|
725 | sitting on some resources. |
|
|
726 | |
|
|
727 | =item "leaked" file descriptors for fork'ed processes |
|
|
728 | |
|
|
729 | Normally, L<AnyEvent::Fork> does start new processes by exec'ing them, |
|
|
730 | which closes file descriptors not marked for being inherited. |
|
|
731 | |
|
|
732 | However, L<AnyEvent::Fork::Early> and L<AnyEvent::Fork::Template> offer |
|
|
733 | a way to create these processes by forking, and this leaks more file |
|
|
734 | descriptors than exec'ing them, as there is no way to mark descriptors as |
|
|
735 | "close on fork". |
|
|
736 | |
|
|
737 | An example would be modules like L<EV>, L<IO::AIO> or L<Gtk2>. Both create |
|
|
738 | pipes for internal uses, and L<Gtk2> might open a connection to the X |
|
|
739 | server. L<EV> and L<IO::AIO> can deal with fork, but Gtk2 might have |
|
|
740 | trouble with a fork. |
|
|
741 | |
|
|
742 | The solution is to either not load these modules before use'ing |
|
|
743 | L<AnyEvent::Fork::Early> or L<AnyEvent::Fork::Template>, or to delay |
|
|
744 | initialising them, for example, by calling C<init Gtk2> manually. |
|
|
745 | |
|
|
746 | =back |
|
|
747 | |
|
|
748 | =head1 PORTABILITY NOTES |
|
|
749 | |
|
|
750 | Native win32 perls are somewhat supported (AnyEvent::Fork::Early is a nop, |
|
|
751 | and ::Template is not going to work), and it cost a lot of blood and sweat |
|
|
752 | to make it so, mostly due to the bloody broken perl that nobody seems to |
|
|
753 | care about. The fork emulation is a bad joke - I have yet to see something |
|
|
754 | useful that you can do with it without running into memory corruption |
|
|
755 | issues or other braindamage. Hrrrr. |
|
|
756 | |
|
|
757 | Cygwin perl is not supported at the moment, as it should implement fd |
|
|
758 | passing, but doesn't, and rolling my own is hard, as cygwin doesn't |
|
|
759 | support enough functionality to do it. |
|
|
760 | |
|
|
761 | =head1 SEE ALSO |
|
|
762 | |
|
|
763 | L<AnyEvent::Fork::Early> (to avoid executing a perl interpreter), |
|
|
764 | L<AnyEvent::Fork::Template> (to create a process by forking the main |
|
|
765 | program at a convenient time). |
413 | |
766 | |
414 | =head1 AUTHOR |
767 | =head1 AUTHOR |
415 | |
768 | |
416 | Marc Lehmann <schmorp@schmorp.de> |
769 | Marc Lehmann <schmorp@schmorp.de> |
417 | http://home.schmorp.de/ |
770 | http://home.schmorp.de/ |