… | |
… | |
4 | |
4 | |
5 | =head1 SYNOPSIS |
5 | =head1 SYNOPSIS |
6 | |
6 | |
7 | use AnyEvent::Fork; |
7 | use AnyEvent::Fork; |
8 | |
8 | |
9 | ################################################################## |
9 | AnyEvent::Fork |
|
|
10 | ->new |
|
|
11 | ->require ("MyModule") |
|
|
12 | ->run ("MyModule::server", my $cv = AE::cv); |
|
|
13 | |
|
|
14 | my $fh = $cv->recv; |
|
|
15 | |
|
|
16 | =head1 DESCRIPTION |
|
|
17 | |
|
|
18 | This module allows you to create new processes, without actually forking |
|
|
19 | them from your current process (avoiding the problems of forking), but |
|
|
20 | preserving most of the advantages of fork. |
|
|
21 | |
|
|
22 | It can be used to create new worker processes or new independent |
|
|
23 | subprocesses for short- and long-running jobs, process pools (e.g. for use |
|
|
24 | in pre-forked servers) but also to spawn new external processes (such as |
|
|
25 | CGI scripts from a web server), which can be faster (and more well behaved) |
|
|
26 | than using fork+exec in big processes. |
|
|
27 | |
|
|
28 | Special care has been taken to make this module useful from other modules, |
|
|
29 | while still supporting specialised environments such as L<App::Staticperl> |
|
|
30 | or L<PAR::Packer>. |
|
|
31 | |
|
|
32 | =head1 WHAT THIS MODULE IS NOT |
|
|
33 | |
|
|
34 | This module only creates processes and lets you pass file handles and |
|
|
35 | strings to it, and run perl code. It does not implement any kind of RPC - |
|
|
36 | there is no back channel from the process back to you, and there is no RPC |
|
|
37 | or message passing going on. |
|
|
38 | |
|
|
39 | If you need some form of RPC, you can either implement it yourself |
|
|
40 | in whatever way you like, use some message-passing module such |
|
|
41 | as L<AnyEvent::MP>, some pipe such as L<AnyEvent::ZeroMQ>, use |
|
|
42 | L<AnyEvent::Handle> on both sides to send e.g. JSON or Storable messages, |
|
|
43 | and so on. |
|
|
44 | |
|
|
45 | =head1 PROBLEM STATEMENT |
|
|
46 | |
|
|
47 | There are two traditional ways to implement parallel processing on UNIX |
|
|
48 | like operating systems - fork and process, and fork+exec and process. They |
|
|
49 | have different advantages and disadvantages that I describe below, |
|
|
50 | together with how this module tries to mitigate the disadvantages. |
|
|
51 | |
|
|
52 | =over 4 |
|
|
53 | |
|
|
54 | =item Forking from a big process can be very slow. |
|
|
55 | |
|
|
56 | A 5GB process needs 0.05s to fork on my 3.6GHz amd64 GNU/Linux box. This |
|
|
57 | overhead is often shared with exec (because you have to fork first), but |
|
|
58 | in some circumstances (e.g. when vfork is used), fork+exec can be much |
|
|
59 | faster. |
|
|
60 | |
|
|
61 | This module can help here by telling a small(er) helper process to fork, |
|
|
62 | which is faster then forking the main process, and also uses vfork where |
|
|
63 | possible. This gives the speed of vfork, with the flexibility of fork. |
|
|
64 | |
|
|
65 | =item Forking usually creates a copy-on-write copy of the parent |
|
|
66 | process. |
|
|
67 | |
|
|
68 | For example, modules or data files that are loaded will not use additional |
|
|
69 | memory after a fork. When exec'ing a new process, modules and data files |
|
|
70 | might need to be loaded again, at extra CPU and memory cost. But when |
|
|
71 | forking, literally all data structures are copied - if the program frees |
|
|
72 | them and replaces them by new data, the child processes will retain the |
|
|
73 | old version even if it isn't used, which can suddenly and unexpectedly |
|
|
74 | increase memory usage when freeing memory. |
|
|
75 | |
|
|
76 | The trade-off is between more sharing with fork (which can be good or |
|
|
77 | bad), and no sharing with exec. |
|
|
78 | |
|
|
79 | This module allows the main program to do a controlled fork, and allows |
|
|
80 | modules to exec processes safely at any time. When creating a custom |
|
|
81 | process pool you can take advantage of data sharing via fork without |
|
|
82 | risking to share large dynamic data structures that will blow up child |
|
|
83 | memory usage. |
|
|
84 | |
|
|
85 | In other words, this module puts you into control over what is being |
|
|
86 | shared and what isn't, at all times. |
|
|
87 | |
|
|
88 | =item Exec'ing a new perl process might be difficult. |
|
|
89 | |
|
|
90 | For example, it is not easy to find the correct path to the perl |
|
|
91 | interpreter - C<$^X> might not be a perl interpreter at all. |
|
|
92 | |
|
|
93 | This module tries hard to identify the correct path to the perl |
|
|
94 | interpreter. With a cooperative main program, exec'ing the interpreter |
|
|
95 | might not even be necessary, but even without help from the main program, |
|
|
96 | it will still work when used from a module. |
|
|
97 | |
|
|
98 | =item Exec'ing a new perl process might be slow, as all necessary modules |
|
|
99 | have to be loaded from disk again, with no guarantees of success. |
|
|
100 | |
|
|
101 | Long running processes might run into problems when perl is upgraded |
|
|
102 | and modules are no longer loadable because they refer to a different |
|
|
103 | perl version, or parts of a distribution are newer than the ones already |
|
|
104 | loaded. |
|
|
105 | |
|
|
106 | This module supports creating pre-initialised perl processes to be used as |
|
|
107 | a template for new processes. |
|
|
108 | |
|
|
109 | =item Forking might be impossible when a program is running. |
|
|
110 | |
|
|
111 | For example, POSIX makes it almost impossible to fork from a |
|
|
112 | multi-threaded program while doing anything useful in the child - in |
|
|
113 | fact, if your perl program uses POSIX threads (even indirectly via |
|
|
114 | e.g. L<IO::AIO> or L<threads>), you cannot call fork on the perl level |
|
|
115 | anymore without risking corruption issues on a number of operating |
|
|
116 | systems. |
|
|
117 | |
|
|
118 | This module can safely fork helper processes at any time, by calling |
|
|
119 | fork+exec in C, in a POSIX-compatible way (via L<Proc::FastSpawn>). |
|
|
120 | |
|
|
121 | =item Parallel processing with fork might be inconvenient or difficult |
|
|
122 | to implement. Modules might not work in both parent and child. |
|
|
123 | |
|
|
124 | For example, when a program uses an event loop and creates watchers it |
|
|
125 | becomes very hard to use the event loop from a child program, as the |
|
|
126 | watchers already exist but are only meaningful in the parent. Worse, a |
|
|
127 | module might want to use such a module, not knowing whether another module |
|
|
128 | or the main program also does, leading to problems. |
|
|
129 | |
|
|
130 | Apart from event loops, graphical toolkits also commonly fall into the |
|
|
131 | "unsafe module" category, or just about anything that communicates with |
|
|
132 | the external world, such as network libraries and file I/O modules, which |
|
|
133 | usually don't like being copied and then allowed to continue in two |
|
|
134 | processes. |
|
|
135 | |
|
|
136 | With this module only the main program is allowed to create new processes |
|
|
137 | by forking (because only the main program can know when it is still safe |
|
|
138 | to do so) - all other processes are created via fork+exec, which makes it |
|
|
139 | possible to use modules such as event loops or window interfaces safely. |
|
|
140 | |
|
|
141 | =back |
|
|
142 | |
|
|
143 | =head1 EXAMPLES |
|
|
144 | |
10 | # create a single new process, tell it to run your worker function |
145 | =head2 Create a single new process, tell it to run your worker function. |
11 | |
146 | |
12 | AnyEvent::Fork |
147 | AnyEvent::Fork |
13 | ->new |
148 | ->new |
14 | ->require ("MyModule") |
149 | ->require ("MyModule") |
15 | ->run ("MyModule::worker, sub { |
150 | ->run ("MyModule::worker, sub { |
… | |
… | |
17 | |
152 | |
18 | # now $master_filehandle is connected to the |
153 | # now $master_filehandle is connected to the |
19 | # $slave_filehandle in the new process. |
154 | # $slave_filehandle in the new process. |
20 | }); |
155 | }); |
21 | |
156 | |
22 | # MyModule::worker might look like this |
157 | C<MyModule> might look like this: |
|
|
158 | |
|
|
159 | package MyModule; |
|
|
160 | |
23 | sub MyModule::worker { |
161 | sub worker { |
24 | my ($slave_filehandle) = @_; |
162 | my ($slave_filehandle) = @_; |
25 | |
163 | |
26 | # now $slave_filehandle is connected to the $master_filehandle |
164 | # now $slave_filehandle is connected to the $master_filehandle |
27 | # in the original prorcess. have fun! |
165 | # in the original prorcess. have fun! |
28 | } |
166 | } |
29 | |
167 | |
30 | ################################################################## |
|
|
31 | # create a pool of server processes all accepting on the same socket |
168 | =head2 Create a pool of server processes all accepting on the same socket. |
32 | |
169 | |
33 | # create listener socket |
170 | # create listener socket |
34 | my $listener = ...; |
171 | my $listener = ...; |
35 | |
172 | |
36 | # create a pool template, initialise it and give it the socket |
173 | # create a pool template, initialise it and give it the socket |
… | |
… | |
48 | } |
185 | } |
49 | |
186 | |
50 | # now do other things - maybe use the filehandle provided by run |
187 | # now do other things - maybe use the filehandle provided by run |
51 | # to wait for the processes to die. or whatever. |
188 | # to wait for the processes to die. or whatever. |
52 | |
189 | |
53 | # My::Server::run might look like this |
190 | C<My::Server> might look like this: |
54 | sub My::Server::run { |
191 | |
|
|
192 | package My::Server; |
|
|
193 | |
|
|
194 | sub run { |
55 | my ($slave, $listener, $id) = @_; |
195 | my ($slave, $listener, $id) = @_; |
56 | |
196 | |
57 | close $slave; # we do not use the socket, so close it to save resources |
197 | close $slave; # we do not use the socket, so close it to save resources |
58 | |
198 | |
59 | # we could go ballistic and use e.g. AnyEvent here, or IO::AIO, |
199 | # we could go ballistic and use e.g. AnyEvent here, or IO::AIO, |
… | |
… | |
61 | while (my $socket = $listener->accept) { |
201 | while (my $socket = $listener->accept) { |
62 | # do sth. with new socket |
202 | # do sth. with new socket |
63 | } |
203 | } |
64 | } |
204 | } |
65 | |
205 | |
66 | =head1 DESCRIPTION |
206 | =head2 use AnyEvent::Fork as a faster fork+exec |
67 | |
207 | |
68 | This module allows you to create new processes, without actually forking |
208 | This runs C</bin/echo hi>, with stdandard output redirected to /tmp/log |
69 | them from your current process (avoiding the problems of forking), but |
209 | and standard error redirected to the communications socket. It is usually |
70 | preserving most of the advantages of fork. |
210 | faster than fork+exec, but still lets you prepare the environment. |
71 | |
211 | |
72 | It can be used to create new worker processes or new independent |
212 | open my $output, ">/tmp/log" or die "$!"; |
73 | subprocesses for short- and long-running jobs, process pools (e.g. for use |
|
|
74 | in pre-forked servers) but also to spawn new external processes (such as |
|
|
75 | CGI scripts from a web server), which can be faster (and more well behaved) |
|
|
76 | than using fork+exec in big processes. |
|
|
77 | |
213 | |
78 | Special care has been taken to make this module useful from other modules, |
214 | AnyEvent::Fork |
79 | while still supporting specialised environments such as L<App::Staticperl> |
215 | ->new |
80 | or L<PAR::Packer>. |
216 | ->eval (' |
|
|
217 | sub run { |
|
|
218 | my ($fh, $output, @cmd) = @_; |
81 | |
219 | |
82 | =head1 WHAT THIS MODULE IS NOT |
220 | # perl will clear close-on-exec on STDOUT/STDERR |
|
|
221 | open STDOUT, ">&", $output or die; |
|
|
222 | open STDERR, ">&", $fh or die; |
83 | |
223 | |
84 | This module only creates processes and lets you pass file handles and |
224 | exec @cmd; |
85 | strings to it, and run perl code. It does not implement any kind of RPC - |
225 | } |
86 | there is no back channel from the process back to you, and there is no RPC |
226 | ') |
87 | or message passing going on. |
227 | ->send_fh ($output) |
|
|
228 | ->send_arg ("/bin/echo", "hi") |
|
|
229 | ->run ("run", my $cv = AE::cv); |
88 | |
230 | |
89 | If you need some form of RPC, you can either implement it yourself |
231 | my $stderr = $cv->recv; |
90 | in whatever way you like, use some message-passing module such |
|
|
91 | as L<AnyEvent::MP>, some pipe such as L<AnyEvent::ZeroMQ>, use |
|
|
92 | L<AnyEvent::Handle> on both sides to send e.g. JSON or Storable messages, |
|
|
93 | and so on. |
|
|
94 | |
|
|
95 | =head1 PROBLEM STATEMENT |
|
|
96 | |
|
|
97 | There are two ways to implement parallel processing on UNIX like operating |
|
|
98 | systems - fork and process, and fork+exec and process. They have different |
|
|
99 | advantages and disadvantages that I describe below, together with how this |
|
|
100 | module tries to mitigate the disadvantages. |
|
|
101 | |
|
|
102 | =over 4 |
|
|
103 | |
|
|
104 | =item Forking from a big process can be very slow (a 5GB process needs |
|
|
105 | 0.05s to fork on my 3.6GHz amd64 GNU/Linux box for example). This overhead |
|
|
106 | is often shared with exec (because you have to fork first), but in some |
|
|
107 | circumstances (e.g. when vfork is used), fork+exec can be much faster. |
|
|
108 | |
|
|
109 | This module can help here by telling a small(er) helper process to fork, |
|
|
110 | or fork+exec instead. |
|
|
111 | |
|
|
112 | =item Forking usually creates a copy-on-write copy of the parent |
|
|
113 | process. Memory (for example, modules or data files that have been |
|
|
114 | will not take additional memory). When exec'ing a new process, modules |
|
|
115 | and data files might need to be loaded again, at extra CPU and memory |
|
|
116 | cost. Likewise when forking, all data structures are copied as well - if |
|
|
117 | the program frees them and replaces them by new data, the child processes |
|
|
118 | will retain the memory even if it isn't used. |
|
|
119 | |
|
|
120 | This module allows the main program to do a controlled fork, and allows |
|
|
121 | modules to exec processes safely at any time. When creating a custom |
|
|
122 | process pool you can take advantage of data sharing via fork without |
|
|
123 | risking to share large dynamic data structures that will blow up child |
|
|
124 | memory usage. |
|
|
125 | |
|
|
126 | =item Exec'ing a new perl process might be difficult and slow. For |
|
|
127 | example, it is not easy to find the correct path to the perl interpreter, |
|
|
128 | and all modules have to be loaded from disk again. Long running processes |
|
|
129 | might run into problems when perl is upgraded for example. |
|
|
130 | |
|
|
131 | This module supports creating pre-initialised perl processes to be used |
|
|
132 | as template, and also tries hard to identify the correct path to the perl |
|
|
133 | interpreter. With a cooperative main program, exec'ing the interpreter |
|
|
134 | might not even be necessary. |
|
|
135 | |
|
|
136 | =item Forking might be impossible when a program is running. For example, |
|
|
137 | POSIX makes it almost impossible to fork from a multi-threaded program and |
|
|
138 | do anything useful in the child - strictly speaking, if your perl program |
|
|
139 | uses posix threads (even indirectly via e.g. L<IO::AIO> or L<threads>), |
|
|
140 | you cannot call fork on the perl level anymore, at all. |
|
|
141 | |
|
|
142 | This module can safely fork helper processes at any time, by calling |
|
|
143 | fork+exec in C, in a POSIX-compatible way. |
|
|
144 | |
|
|
145 | =item Parallel processing with fork might be inconvenient or difficult |
|
|
146 | to implement. For example, when a program uses an event loop and creates |
|
|
147 | watchers it becomes very hard to use the event loop from a child |
|
|
148 | program, as the watchers already exist but are only meaningful in the |
|
|
149 | parent. Worse, a module might want to use such a system, not knowing |
|
|
150 | whether another module or the main program also does, leading to problems. |
|
|
151 | |
|
|
152 | This module only lets the main program create pools by forking (because |
|
|
153 | only the main program can know when it is still safe to do so) - all other |
|
|
154 | pools are created by fork+exec, after which such modules can again be |
|
|
155 | loaded. |
|
|
156 | |
|
|
157 | =back |
|
|
158 | |
232 | |
159 | =head1 CONCEPTS |
233 | =head1 CONCEPTS |
160 | |
234 | |
161 | This module can create new processes either by executing a new perl |
235 | This module can create new processes either by executing a new perl |
162 | process, or by forking from an existing "template" process. |
236 | process, or by forking from an existing "template" process. |
… | |
… | |
241 | my ($fork_fh) = @_; |
315 | my ($fork_fh) = @_; |
242 | }); |
316 | }); |
243 | |
317 | |
244 | =back |
318 | =back |
245 | |
319 | |
246 | =head1 FUNCTIONS |
320 | =head1 THE C<AnyEvent::Fork> CLASS |
|
|
321 | |
|
|
322 | This module exports nothing, and only implements a single class - |
|
|
323 | C<AnyEvent::Fork>. |
|
|
324 | |
|
|
325 | There are two class constructors that both create new processes - C<new> |
|
|
326 | and C<new_exec>. The C<fork> method creates a new process by forking an |
|
|
327 | existing one and could be considered a third constructor. |
|
|
328 | |
|
|
329 | Most of the remaining methods deal with preparing the new process, by |
|
|
330 | loading code, evaluating code and sending data to the new process. They |
|
|
331 | usually return the process object, so you can chain method calls. |
|
|
332 | |
|
|
333 | If a process object is destroyed before calling its C<run> method, then |
|
|
334 | the process simply exits. After C<run> is called, all responsibility is |
|
|
335 | passed to the specified function. |
|
|
336 | |
|
|
337 | As long as there is any outstanding work to be done, process objects |
|
|
338 | resist being destroyed, so there is no reason to store them unless you |
|
|
339 | need them later - configure and forget works just fine. |
247 | |
340 | |
248 | =over 4 |
341 | =over 4 |
249 | |
342 | |
250 | =cut |
343 | =cut |
251 | |
344 | |
252 | package AnyEvent::Fork; |
345 | package AnyEvent::Fork; |
253 | |
346 | |
254 | use common::sense; |
347 | use common::sense; |
255 | |
348 | |
256 | use Socket (); |
349 | use Errno (); |
257 | |
350 | |
258 | use AnyEvent; |
351 | use AnyEvent; |
259 | use AnyEvent::Util (); |
352 | use AnyEvent::Util (); |
260 | |
353 | |
261 | use IO::FDPass; |
354 | use IO::FDPass; |
262 | |
355 | |
263 | our $VERSION = 0.2; |
356 | our $VERSION = 0.5; |
264 | |
357 | |
265 | our $PERL; # the path to the perl interpreter, deduces with various forms of magic |
358 | our $PERL; # the path to the perl interpreter, deduces with various forms of magic |
266 | |
|
|
267 | =item my $pool = new AnyEvent::Fork key => value... |
|
|
268 | |
|
|
269 | Create a new process pool. The following named parameters are supported: |
|
|
270 | |
359 | |
271 | =over 4 |
360 | =over 4 |
272 | |
361 | |
273 | =back |
362 | =back |
274 | |
363 | |
… | |
… | |
281 | our $TEMPLATE; |
370 | our $TEMPLATE; |
282 | |
371 | |
283 | sub _cmd { |
372 | sub _cmd { |
284 | my $self = shift; |
373 | my $self = shift; |
285 | |
374 | |
286 | #TODO: maybe append the packet to any existing string command already in the queue |
|
|
287 | |
|
|
288 | # ideally, we would want to use "a (w/a)*" as format string, but perl versions |
375 | # ideally, we would want to use "a (w/a)*" as format string, but perl |
289 | # from at least 5.8.9 to 5.16.3 are all buggy and can't unpack it. |
376 | # versions from at least 5.8.9 to 5.16.3 are all buggy and can't unpack |
|
|
377 | # it. |
290 | push @{ $self->[2] }, pack "L/a*", pack "(w/a*)*", @_; |
378 | push @{ $self->[2] }, pack "a L/a*", $_[0], $_[1]; |
291 | |
379 | |
292 | $self->[3] ||= AE::io $self->[1], 1, sub { |
380 | $self->[3] ||= AE::io $self->[1], 1, sub { |
|
|
381 | do { |
293 | # send the next "thing" in the queue - either a reference to an fh, |
382 | # send the next "thing" in the queue - either a reference to an fh, |
294 | # or a plain string. |
383 | # or a plain string. |
295 | |
384 | |
296 | if (ref $self->[2][0]) { |
385 | if (ref $self->[2][0]) { |
297 | # send fh |
386 | # send fh |
298 | IO::FDPass::send fileno $self->[1], fileno ${ $self->[2][0] } |
387 | unless (IO::FDPass::send fileno $self->[1], fileno ${ $self->[2][0] }) { |
|
|
388 | return if $! == Errno::EAGAIN || $! == Errno::EWOULDBLOCK; |
|
|
389 | undef $self->[3]; |
|
|
390 | die "AnyEvent::Fork: file descriptor send failure: $!"; |
|
|
391 | } |
|
|
392 | |
299 | and shift @{ $self->[2] }; |
393 | shift @{ $self->[2] }; |
300 | |
394 | |
301 | } else { |
395 | } else { |
302 | # send string |
396 | # send string |
303 | my $len = syswrite $self->[1], $self->[2][0] |
397 | my $len = syswrite $self->[1], $self->[2][0]; |
|
|
398 | |
|
|
399 | unless ($len) { |
|
|
400 | return if $! == Errno::EAGAIN || $! == Errno::EWOULDBLOCK; |
|
|
401 | undef $self->[3]; |
304 | or do { undef $self->[3]; die "AnyEvent::Fork: command write failure: $!" }; |
402 | die "AnyEvent::Fork: command write failure: $!"; |
|
|
403 | } |
305 | |
404 | |
306 | substr $self->[2][0], 0, $len, ""; |
405 | substr $self->[2][0], 0, $len, ""; |
307 | shift @{ $self->[2] } unless length $self->[2][0]; |
406 | shift @{ $self->[2] } unless length $self->[2][0]; |
308 | } |
407 | } |
|
|
408 | } while @{ $self->[2] }; |
309 | |
409 | |
310 | unless (@{ $self->[2] }) { |
410 | # everything written |
311 | undef $self->[3]; |
411 | undef $self->[3]; |
|
|
412 | |
312 | # invoke run callback |
413 | # invoke run callback, if any |
313 | $self->[0]->($self->[1]) if $self->[0]; |
414 | $self->[4]->($self->[1]) if $self->[4]; |
314 | } |
|
|
315 | }; |
415 | }; |
316 | |
416 | |
317 | () # make sure we don't leak the watcher |
417 | () # make sure we don't leak the watcher |
318 | } |
418 | } |
319 | |
419 | |
320 | sub _new { |
420 | sub _new { |
321 | my ($self, $fh) = @_; |
421 | my ($self, $fh, $pid) = @_; |
322 | |
422 | |
323 | AnyEvent::Util::fh_nonblocking $fh, 1; |
423 | AnyEvent::Util::fh_nonblocking $fh, 1; |
324 | |
424 | |
325 | $self = bless [ |
425 | $self = bless [ |
326 | undef, # run callback |
426 | $pid, |
327 | $fh, |
427 | $fh, |
328 | [], # write queue - strings or fd's |
428 | [], # write queue - strings or fd's |
329 | undef, # AE watcher |
429 | undef, # AE watcher |
330 | ], $self; |
430 | ], $self; |
331 | |
431 | |
… | |
… | |
349 | exit 0; |
449 | exit 0; |
350 | } elsif (!$pid) { |
450 | } elsif (!$pid) { |
351 | die "AnyEvent::Fork::Early/Template: unable to fork template process: $!"; |
451 | die "AnyEvent::Fork::Early/Template: unable to fork template process: $!"; |
352 | } |
452 | } |
353 | |
453 | |
354 | AnyEvent::Fork->_new ($fh) |
454 | AnyEvent::Fork->_new ($fh, $pid) |
355 | } |
455 | } |
356 | |
456 | |
357 | =item my $proc = new AnyEvent::Fork |
457 | =item my $proc = new AnyEvent::Fork |
358 | |
458 | |
359 | Create a new "empty" perl interpreter process and returns its process |
459 | Create a new "empty" perl interpreter process and returns its process |
360 | object for further manipulation. |
460 | object for further manipulation. |
361 | |
461 | |
362 | The new process is forked from a template process that is kept around |
462 | The new process is forked from a template process that is kept around |
363 | for this purpose. When it doesn't exist yet, it is created by a call to |
463 | for this purpose. When it doesn't exist yet, it is created by a call to |
364 | C<new_exec> and kept around for future calls. |
464 | C<new_exec> first and then stays around for future calls. |
365 | |
|
|
366 | When the process object is destroyed, it will release the file handle |
|
|
367 | that connects it with the new process. When the new process has not yet |
|
|
368 | called C<run>, then the process will exit. Otherwise, what happens depends |
|
|
369 | entirely on the code that is executed. |
|
|
370 | |
465 | |
371 | =cut |
466 | =cut |
372 | |
467 | |
373 | sub new { |
468 | sub new { |
374 | my $class = shift; |
469 | my $class = shift; |
… | |
… | |
452 | # quick. also doesn't work in win32. of course. what did you expect |
547 | # quick. also doesn't work in win32. of course. what did you expect |
453 | #local $ENV{PERL5LIB} = join ":", grep !ref, @INC; |
548 | #local $ENV{PERL5LIB} = join ":", grep !ref, @INC; |
454 | my %env = %ENV; |
549 | my %env = %ENV; |
455 | $env{PERL5LIB} = join +($^O eq "MSWin32" ? ";" : ":"), grep !ref, @INC; |
550 | $env{PERL5LIB} = join +($^O eq "MSWin32" ? ";" : ":"), grep !ref, @INC; |
456 | |
551 | |
457 | Proc::FastSpawn::spawn ( |
552 | my $pid = Proc::FastSpawn::spawn ( |
458 | $perl, |
553 | $perl, |
459 | ["perl", "-MAnyEvent::Fork::Serve", "-e", "AnyEvent::Fork::Serve::me", fileno $slave, $$], |
554 | ["perl", "-MAnyEvent::Fork::Serve", "-e", "AnyEvent::Fork::Serve::me", fileno $slave, $$], |
460 | [map "$_=$env{$_}", keys %env], |
555 | [map "$_=$env{$_}", keys %env], |
461 | ) or die "unable to spawn AnyEvent::Fork server: $!"; |
556 | ) or die "unable to spawn AnyEvent::Fork server: $!"; |
462 | |
557 | |
463 | $self->_new ($fh) |
558 | $self->_new ($fh, $pid) |
|
|
559 | } |
|
|
560 | |
|
|
561 | =item $pid = $proc->pid |
|
|
562 | |
|
|
563 | Returns the process id of the process I<iff it is a direct child of the |
|
|
564 | process running AnyEvent::Fork>, and C<undef> otherwise. |
|
|
565 | |
|
|
566 | Normally, only processes created via C<< AnyEvent::Fork->new_exec >> and |
|
|
567 | L<AnyEvent::Fork::Template> are direct children, and you are responsible |
|
|
568 | to clean up their zombies when they die. |
|
|
569 | |
|
|
570 | All other processes are not direct children, and will be cleaned up by |
|
|
571 | AnyEvent::Fork itself. |
|
|
572 | |
|
|
573 | =cut |
|
|
574 | |
|
|
575 | sub pid { |
|
|
576 | $_[0][0] |
464 | } |
577 | } |
465 | |
578 | |
466 | =item $proc = $proc->eval ($perlcode, @args) |
579 | =item $proc = $proc->eval ($perlcode, @args) |
467 | |
580 | |
468 | Evaluates the given C<$perlcode> as ... perl code, while setting C<@_> to |
581 | Evaluates the given C<$perlcode> as ... perl code, while setting C<@_> to |
469 | the strings specified by C<@args>. |
582 | the strings specified by C<@args>, in the "main" package. |
470 | |
583 | |
471 | This call is meant to do any custom initialisation that might be required |
584 | This call is meant to do any custom initialisation that might be required |
472 | (for example, the C<require> method uses it). It's not supposed to be used |
585 | (for example, the C<require> method uses it). It's not supposed to be used |
473 | to completely take over the process, use C<run> for that. |
586 | to completely take over the process, use C<run> for that. |
474 | |
587 | |
475 | The code will usually be executed after this call returns, and there is no |
588 | The code will usually be executed after this call returns, and there is no |
476 | way to pass anything back to the calling process. Any evaluation errors |
589 | way to pass anything back to the calling process. Any evaluation errors |
477 | will be reported to stderr and cause the process to exit. |
590 | will be reported to stderr and cause the process to exit. |
478 | |
591 | |
|
|
592 | If you want to execute some code (that isn't in a module) to take over the |
|
|
593 | process, you should compile a function via C<eval> first, and then call |
|
|
594 | it via C<run>. This also gives you access to any arguments passed via the |
|
|
595 | C<send_xxx> methods, such as file handles. See the L<use AnyEvent::Fork as |
|
|
596 | a faster fork+exec> example. |
|
|
597 | |
479 | Returns the process object for easy chaining of method calls. |
598 | Returns the process object for easy chaining of method calls. |
480 | |
599 | |
481 | =cut |
600 | =cut |
482 | |
601 | |
483 | sub eval { |
602 | sub eval { |
484 | my ($self, $code, @args) = @_; |
603 | my ($self, $code, @args) = @_; |
485 | |
604 | |
486 | $self->_cmd (e => $code, @args); |
605 | $self->_cmd (e => pack "(w/a*)*", $code, @args); |
487 | |
606 | |
488 | $self |
607 | $self |
489 | } |
608 | } |
490 | |
609 | |
491 | =item $proc = $proc->require ($module, ...) |
610 | =item $proc = $proc->require ($module, ...) |
… | |
… | |
539 | =item $proc = $proc->send_arg ($string, ...) |
658 | =item $proc = $proc->send_arg ($string, ...) |
540 | |
659 | |
541 | Send one or more argument strings to the process, to prepare a call to |
660 | Send one or more argument strings to the process, to prepare a call to |
542 | C<run>. The strings can be any octet string. |
661 | C<run>. The strings can be any octet string. |
543 | |
662 | |
|
|
663 | The protocol is optimised to pass a moderate number of relatively short |
|
|
664 | strings - while you can pass up to 4GB of data in one go, this is more |
|
|
665 | meant to pass some ID information or other startup info, not big chunks of |
|
|
666 | data. |
|
|
667 | |
544 | Returns the process object for easy chaining of method calls. |
668 | Returns the process object for easy chaining of method calls. |
545 | |
669 | |
546 | =cut |
670 | =cut |
547 | |
671 | |
548 | sub send_arg { |
672 | sub send_arg { |
549 | my ($self, @arg) = @_; |
673 | my ($self, @arg) = @_; |
550 | |
674 | |
551 | $self->_cmd (a => @arg); |
675 | $self->_cmd (a => pack "(w/a*)*", @arg); |
552 | |
676 | |
553 | $self |
677 | $self |
554 | } |
678 | } |
555 | |
679 | |
556 | =item $proc->run ($func, $cb->($fh)) |
680 | =item $proc->run ($func, $cb->($fh)) |
557 | |
681 | |
558 | Enter the function specified by the fully qualified name in C<$func> in |
682 | Enter the function specified by the function name in C<$func> in the |
559 | the process. The function is called with the communication socket as first |
683 | process. The function is called with the communication socket as first |
560 | argument, followed by all file handles and string arguments sent earlier |
684 | argument, followed by all file handles and string arguments sent earlier |
561 | via C<send_fh> and C<send_arg> methods, in the order they were called. |
685 | via C<send_fh> and C<send_arg> methods, in the order they were called. |
562 | |
686 | |
563 | If the called function returns, the process exits. |
687 | The function name should be fully qualified, but if it isn't, it will be |
|
|
688 | looked up in the main package. |
564 | |
689 | |
565 | Preparing the process can take time - when the process is ready, the |
690 | If the called function returns, doesn't exist, or any error occurs, the |
|
|
691 | process exits. |
|
|
692 | |
|
|
693 | Preparing the process is done in the background - when all commands have |
566 | callback is invoked with the local communications socket as argument. |
694 | been sent, the callback is invoked with the local communications socket |
|
|
695 | as argument. At this point you can start using the socket in any way you |
|
|
696 | like. |
567 | |
697 | |
568 | The process object becomes unusable on return from this function. |
698 | The process object becomes unusable on return from this function - any |
|
|
699 | further method calls result in undefined behaviour. |
569 | |
700 | |
570 | If the communication socket isn't used, it should be closed on both sides, |
701 | If the communication socket isn't used, it should be closed on both sides, |
571 | to save on kernel memory. |
702 | to save on kernel memory. |
572 | |
703 | |
573 | The socket is non-blocking in the parent, and blocking in the newly |
704 | The socket is non-blocking in the parent, and blocking in the newly |
574 | created process. The close-on-exec flag is set on both. Even if not used |
705 | created process. The close-on-exec flag is set in both. |
|
|
706 | |
575 | otherwise, the socket can be a good indicator for the existence of the |
707 | Even if not used otherwise, the socket can be a good indicator for the |
576 | process - if the other process exits, you get a readable event on it, |
708 | existence of the process - if the other process exits, you get a readable |
577 | because exiting the process closes the socket (if it didn't create any |
709 | event on it, because exiting the process closes the socket (if it didn't |
578 | children using fork). |
710 | create any children using fork). |
579 | |
711 | |
580 | Example: create a template for a process pool, pass a few strings, some |
712 | Example: create a template for a process pool, pass a few strings, some |
581 | file handles, then fork, pass one more string, and run some code. |
713 | file handles, then fork, pass one more string, and run some code. |
582 | |
714 | |
583 | my $pool = AnyEvent::Fork |
715 | my $pool = AnyEvent::Fork |
… | |
… | |
591 | ->send_arg ("str3") |
723 | ->send_arg ("str3") |
592 | ->run ("Some::function", sub { |
724 | ->run ("Some::function", sub { |
593 | my ($fh) = @_; |
725 | my ($fh) = @_; |
594 | |
726 | |
595 | # fh is nonblocking, but we trust that the OS can accept these |
727 | # fh is nonblocking, but we trust that the OS can accept these |
596 | # extra 3 octets anyway. |
728 | # few octets anyway. |
597 | syswrite $fh, "hi #$_\n"; |
729 | syswrite $fh, "hi #$_\n"; |
598 | |
730 | |
599 | # $fh is being closed here, as we don't store it anywhere |
731 | # $fh is being closed here, as we don't store it anywhere |
600 | }); |
732 | }); |
601 | } |
733 | } |
… | |
… | |
603 | # Some::function might look like this - all parameters passed before fork |
735 | # Some::function might look like this - all parameters passed before fork |
604 | # and after will be passed, in order, after the communications socket. |
736 | # and after will be passed, in order, after the communications socket. |
605 | sub Some::function { |
737 | sub Some::function { |
606 | my ($fh, $str1, $str2, $fh1, $fh2, $str3) = @_; |
738 | my ($fh, $str1, $str2, $fh1, $fh2, $str3) = @_; |
607 | |
739 | |
608 | print scalar <$fh>; # prints "hi 1\n" and "hi 2\n" |
740 | print scalar <$fh>; # prints "hi #1\n" and "hi #2\n" in any order |
609 | } |
741 | } |
610 | |
742 | |
611 | =cut |
743 | =cut |
612 | |
744 | |
613 | sub run { |
745 | sub run { |
614 | my ($self, $func, $cb) = @_; |
746 | my ($self, $func, $cb) = @_; |
615 | |
747 | |
616 | $self->[0] = $cb; |
748 | $self->[4] = $cb; |
617 | $self->_cmd (r => $func); |
749 | $self->_cmd (r => $func); |
618 | } |
750 | } |
619 | |
751 | |
620 | =back |
752 | =back |
621 | |
753 | |
622 | =head1 PERFORMANCE |
754 | =head1 PERFORMANCE |
623 | |
755 | |
624 | Now for some unscientific benchmark numbers (all done on an amd64 |
756 | Now for some unscientific benchmark numbers (all done on an amd64 |
625 | GNU/Linux box). These are intended to give you an idea of the relative |
757 | GNU/Linux box). These are intended to give you an idea of the relative |
626 | performance you can expect. |
758 | performance you can expect, they are not meant to be absolute performance |
|
|
759 | numbers. |
627 | |
760 | |
628 | OK, so, I ran a simple benchmark that creates a socket pair, forks, calls |
761 | OK, so, I ran a simple benchmark that creates a socket pair, forks, calls |
629 | exit in the child and waits for the socket to close in the parent. I did |
762 | exit in the child and waits for the socket to close in the parent. I did |
630 | load AnyEvent, EV and AnyEvent::Fork, for a total process size of 6312kB. |
763 | load AnyEvent, EV and AnyEvent::Fork, for a total process size of 5100kB. |
631 | |
764 | |
632 | 2079 new processes per second, using socketpair + fork manually |
765 | 2079 new processes per second, using manual socketpair + fork |
633 | |
766 | |
634 | Then I did the same thing, but instead of calling fork, I called |
767 | Then I did the same thing, but instead of calling fork, I called |
635 | AnyEvent::Fork->new->run ("CORE::exit") and then again waited for the |
768 | AnyEvent::Fork->new->run ("CORE::exit") and then again waited for the |
636 | socket form the child to close on exit. This does the same thing as manual |
769 | socket form the child to close on exit. This does the same thing as manual |
637 | socket pair + fork, except that what is forked is the template process |
770 | socket pair + fork, except that what is forked is the template process |
… | |
… | |
667 | This section lists typical problems that remain. I hope by recognising |
800 | This section lists typical problems that remain. I hope by recognising |
668 | them, most can be avoided. |
801 | them, most can be avoided. |
669 | |
802 | |
670 | =over 4 |
803 | =over 4 |
671 | |
804 | |
672 | =item exit runs destructors |
|
|
673 | |
|
|
674 | =item "leaked" file descriptors for exec'ed processes |
805 | =item "leaked" file descriptors for exec'ed processes |
675 | |
806 | |
676 | POSIX systems inherit file descriptors by default when exec'ing a new |
807 | POSIX systems inherit file descriptors by default when exec'ing a new |
677 | process. While perl itself laudably sets the close-on-exec flags on new |
808 | process. While perl itself laudably sets the close-on-exec flags on new |
678 | file handles, most C libraries don't care, and even if all cared, it's |
809 | file handles, most C libraries don't care, and even if all cared, it's |
… | |
… | |
718 | |
849 | |
719 | The solution is to either not load these modules before use'ing |
850 | The solution is to either not load these modules before use'ing |
720 | L<AnyEvent::Fork::Early> or L<AnyEvent::Fork::Template>, or to delay |
851 | L<AnyEvent::Fork::Early> or L<AnyEvent::Fork::Template>, or to delay |
721 | initialising them, for example, by calling C<init Gtk2> manually. |
852 | initialising them, for example, by calling C<init Gtk2> manually. |
722 | |
853 | |
|
|
854 | =item exit runs destructors |
|
|
855 | |
|
|
856 | This only applies to users of Lc<AnyEvent::Fork:Early> and |
|
|
857 | L<AnyEvent::Fork::Template>. |
|
|
858 | |
|
|
859 | When a process created by AnyEvent::Fork exits, it might do so by calling |
|
|
860 | exit, or simply letting perl reach the end of the program. At which point |
|
|
861 | Perl runs all destructors. |
|
|
862 | |
|
|
863 | Not all destructors are fork-safe - for example, an object that represents |
|
|
864 | the connection to an X display might tell the X server to free resources, |
|
|
865 | which is inconvenient when the "real" object in the parent still needs to |
|
|
866 | use them. |
|
|
867 | |
|
|
868 | This is obviously not a problem for L<AnyEvent::Fork::Early>, as you used |
|
|
869 | it as the very first thing, right? |
|
|
870 | |
|
|
871 | It is a problem for L<AnyEvent::Fork::Template> though - and the solution |
|
|
872 | is to not create objects with nontrivial destructors that might have an |
|
|
873 | effect outside of Perl. |
|
|
874 | |
723 | =back |
875 | =back |
724 | |
876 | |
725 | =head1 PORTABILITY NOTES |
877 | =head1 PORTABILITY NOTES |
726 | |
878 | |
727 | Native win32 perls are somewhat supported (AnyEvent::Fork::Early is a nop, |
879 | Native win32 perls are somewhat supported (AnyEvent::Fork::Early is a nop, |