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30 | This module only creates processes and lets you pass file handles and |
30 | This module only creates processes and lets you pass file handles and |
31 | strings to it, and run perl code. It does not implement any kind of RPC |
31 | strings to it, and run perl code. It does not implement any kind of RPC |
32 | - there is no back channel from the process back to you, and there is no |
32 | - there is no back channel from the process back to you, and there is no |
33 | RPC or message passing going on. |
33 | RPC or message passing going on. |
34 | |
34 | |
35 | If you need some form of RPC, you can either implement it yourself in |
35 | If you need some form of RPC, you could use the AnyEvent::Fork::RPC |
36 | whatever way you like, use some message-passing module such as |
36 | companion module, which adds simple RPC/job queueing to a process |
37 | AnyEvent::MP, some pipe such as AnyEvent::ZeroMQ, use AnyEvent::Handle |
37 | created by this module. |
38 | on both sides to send e.g. JSON or Storable messages, and so on. |
38 | |
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39 | Or you can implement it yourself in whatever way you like, use some |
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40 | message-passing module such as AnyEvent::MP, some pipe such as |
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41 | AnyEvent::ZeroMQ, use AnyEvent::Handle on both sides to send e.g. JSON |
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42 | or Storable messages, and so on. |
39 | |
43 | |
40 | COMPARISON TO OTHER MODULES |
44 | COMPARISON TO OTHER MODULES |
41 | There is an abundance of modules on CPAN that do "something fork", such |
45 | There is an abundance of modules on CPAN that do "something fork", such |
42 | as Parallel::ForkManager, AnyEvent::ForkManager, AnyEvent::Worker or |
46 | as Parallel::ForkManager, AnyEvent::ForkManager, AnyEvent::Worker or |
43 | AnyEvent::Subprocess. There are modules that implement their own process |
47 | AnyEvent::Subprocess. There are modules that implement their own process |
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202 | # do sth. with new socket |
206 | # do sth. with new socket |
203 | } |
207 | } |
204 | } |
208 | } |
205 | |
209 | |
206 | use AnyEvent::Fork as a faster fork+exec |
210 | use AnyEvent::Fork as a faster fork+exec |
207 | This runs "/bin/echo hi", with stdandard output redirected to /tmp/log |
211 | This runs "/bin/echo hi", with standard output redirected to /tmp/log |
208 | and standard error redirected to the communications socket. It is |
212 | and standard error redirected to the communications socket. It is |
209 | usually faster than fork+exec, but still lets you prepare the |
213 | usually faster than fork+exec, but still lets you prepare the |
210 | environment. |
214 | environment. |
211 | |
215 | |
212 | open my $output, ">/tmp/log" or die "$!"; |
216 | open my $output, ">/tmp/log" or die "$!"; |
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232 | my $stderr = $cv->recv; |
236 | my $stderr = $cv->recv; |
233 | |
237 | |
234 | CONCEPTS |
238 | CONCEPTS |
235 | This module can create new processes either by executing a new perl |
239 | This module can create new processes either by executing a new perl |
236 | process, or by forking from an existing "template" process. |
240 | process, or by forking from an existing "template" process. |
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241 | |
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242 | All these processes are called "child processes" (whether they are |
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243 | direct children or not), while the process that manages them is called |
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244 | the "parent process". |
237 | |
245 | |
238 | Each such process comes with its own file handle that can be used to |
246 | Each such process comes with its own file handle that can be used to |
239 | communicate with it (it's actually a socket - one end in the new |
247 | communicate with it (it's actually a socket - one end in the new |
240 | process, one end in the main process), and among the things you can do |
248 | process, one end in the main process), and among the things you can do |
241 | in it are load modules, fork new processes, send file handles to it, and |
249 | in it are load modules, fork new processes, send file handles to it, and |
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329 | |
337 | |
330 | As long as there is any outstanding work to be done, process objects |
338 | As long as there is any outstanding work to be done, process objects |
331 | resist being destroyed, so there is no reason to store them unless you |
339 | resist being destroyed, so there is no reason to store them unless you |
332 | need them later - configure and forget works just fine. |
340 | need them later - configure and forget works just fine. |
333 | |
341 | |
334 | my $proc = new AnyEvent::Fork |
342 | my $proc = new AnyEvent::Fork |
335 | |
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336 | Create a new "empty" perl interpreter process and returns its |
343 | Create a new "empty" perl interpreter process and returns its |
337 | process object for further manipulation. |
344 | process object for further manipulation. |
338 | |
345 | |
339 | The new process is forked from a template process that is kept |
346 | The new process is forked from a template process that is kept |
340 | around for this purpose. When it doesn't exist yet, it is created by |
347 | around for this purpose. When it doesn't exist yet, it is created by |
341 | a call to "new_exec" first and then stays around for future calls. |
348 | a call to "new_exec" first and then stays around for future calls. |
342 | |
349 | |
343 | $new_proc = $proc->fork |
350 | $new_proc = $proc->fork |
344 | |
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345 | Forks $proc, creating a new process, and returns the process object |
351 | Forks $proc, creating a new process, and returns the process object |
346 | of the new process. |
352 | of the new process. |
347 | |
353 | |
348 | If any of the "send_" functions have been called before fork, then |
354 | If any of the "send_" functions have been called before fork, then |
349 | they will be cloned in the child. For example, in a pre-forked |
355 | they will be cloned in the child. For example, in a pre-forked |
350 | server, you might "send_fh" the listening socket into the template |
356 | server, you might "send_fh" the listening socket into the template |
351 | process, and then keep calling "fork" and "run". |
357 | process, and then keep calling "fork" and "run". |
352 | |
358 | |
353 | my $proc = new_exec AnyEvent::Fork |
359 | my $proc = new_exec AnyEvent::Fork |
354 | |
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355 | Create a new "empty" perl interpreter process and returns its |
360 | Create a new "empty" perl interpreter process and returns its |
356 | process object for further manipulation. |
361 | process object for further manipulation. |
357 | |
362 | |
358 | Unlike the "new" method, this method *always* spawns a new perl |
363 | Unlike the "new" method, this method *always* spawns a new perl |
359 | process (except in some cases, see AnyEvent::Fork::Early for |
364 | process (except in some cases, see AnyEvent::Fork::Early for |
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366 | The path to the perl interpreter is divined using various methods - |
371 | The path to the perl interpreter is divined using various methods - |
367 | first $^X is investigated to see if the path ends with something |
372 | first $^X is investigated to see if the path ends with something |
368 | that sounds as if it were the perl interpreter. Failing this, the |
373 | that sounds as if it were the perl interpreter. Failing this, the |
369 | module falls back to using $Config::Config{perlpath}. |
374 | module falls back to using $Config::Config{perlpath}. |
370 | |
375 | |
371 | $pid = $proc->pid |
376 | $pid = $proc->pid |
372 | |
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373 | Returns the process id of the process *iff it is a direct child of |
377 | Returns the process id of the process *iff it is a direct child of |
374 | the process running AnyEvent::Fork*, and "undef" otherwise. |
378 | the process running AnyEvent::Fork*, and "undef" otherwise. |
375 | |
379 | |
376 | Normally, only processes created via "AnyEvent::Fork->new_exec" and |
380 | Normally, only processes created via "AnyEvent::Fork->new_exec" and |
377 | AnyEvent::Fork::Template are direct children, and you are |
381 | AnyEvent::Fork::Template are direct children, and you are |
378 | responsible to clean up their zombies when they die. |
382 | responsible to clean up their zombies when they die. |
379 | |
383 | |
380 | All other processes are not direct children, and will be cleaned up |
384 | All other processes are not direct children, and will be cleaned up |
381 | by AnyEvent::Fork itself. |
385 | by AnyEvent::Fork itself. |
382 | |
386 | |
383 | $proc = $proc->eval ($perlcode, @args) |
387 | $proc = $proc->eval ($perlcode, @args) |
384 | |
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385 | Evaluates the given $perlcode as ... perl code, while setting @_ to |
388 | Evaluates the given $perlcode as ... Perl code, while setting @_ to |
386 | the strings specified by @args, in the "main" package. |
389 | the strings specified by @args, in the "main" package. |
387 | |
390 | |
388 | This call is meant to do any custom initialisation that might be |
391 | This call is meant to do any custom initialisation that might be |
389 | required (for example, the "require" method uses it). It's not |
392 | required (for example, the "require" method uses it). It's not |
390 | supposed to be used to completely take over the process, use "run" |
393 | supposed to be used to completely take over the process, use "run" |
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402 | See the "use AnyEvent::Fork as a faster fork+exec" example to see it |
405 | See the "use AnyEvent::Fork as a faster fork+exec" example to see it |
403 | in action. |
406 | in action. |
404 | |
407 | |
405 | Returns the process object for easy chaining of method calls. |
408 | Returns the process object for easy chaining of method calls. |
406 | |
409 | |
407 | $proc = $proc->require ($module, ...) |
410 | $proc = $proc->require ($module, ...) |
408 | |
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409 | Tries to load the given module(s) into the process |
411 | Tries to load the given module(s) into the process |
410 | |
412 | |
411 | Returns the process object for easy chaining of method calls. |
413 | Returns the process object for easy chaining of method calls. |
412 | |
414 | |
413 | $proc = $proc->send_fh ($handle, ...) |
415 | $proc = $proc->send_fh ($handle, ...) |
414 | |
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415 | Send one or more file handles (*not* file descriptors) to the |
416 | Send one or more file handles (*not* file descriptors) to the |
416 | process, to prepare a call to "run". |
417 | process, to prepare a call to "run". |
417 | |
418 | |
418 | The process object keeps a reference to the handles until they have |
419 | The process object keeps a reference to the handles until they have |
419 | been passed over to the process, so you must not explicitly close |
420 | been passed over to the process, so you must not explicitly close |
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428 | closing. It will be closed automatically when it is no longer used. |
429 | closing. It will be closed automatically when it is no longer used. |
429 | |
430 | |
430 | $proc->send_fh ($my_fh); |
431 | $proc->send_fh ($my_fh); |
431 | undef $my_fh; # free the reference if you want, but DO NOT CLOSE IT |
432 | undef $my_fh; # free the reference if you want, but DO NOT CLOSE IT |
432 | |
433 | |
433 | $proc = $proc->send_arg ($string, ...) |
434 | $proc = $proc->send_arg ($string, ...) |
434 | |
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435 | Send one or more argument strings to the process, to prepare a call |
435 | Send one or more argument strings to the process, to prepare a call |
436 | to "run". The strings can be any octet strings. |
436 | to "run". The strings can be any octet strings. |
437 | |
437 | |
438 | The protocol is optimised to pass a moderate number of relatively |
438 | The protocol is optimised to pass a moderate number of relatively |
439 | short strings - while you can pass up to 4GB of data in one go, this |
439 | short strings - while you can pass up to 4GB of data in one go, this |
440 | is more meant to pass some ID information or other startup info, not |
440 | is more meant to pass some ID information or other startup info, not |
441 | big chunks of data. |
441 | big chunks of data. |
442 | |
442 | |
443 | Returns the process object for easy chaining of method calls. |
443 | Returns the process object for easy chaining of method calls. |
444 | |
444 | |
445 | $proc->run ($func, $cb->($fh)) |
445 | $proc->run ($func, $cb->($fh)) |
446 | |
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447 | Enter the function specified by the function name in $func in the |
446 | Enter the function specified by the function name in $func in the |
448 | process. The function is called with the communication socket as |
447 | process. The function is called with the communication socket as |
449 | first argument, followed by all file handles and string arguments |
448 | first argument, followed by all file handles and string arguments |
450 | sent earlier via "send_fh" and "send_arg" methods, in the order they |
449 | sent earlier via "send_fh" and "send_arg" methods, in the order they |
451 | were called. |
450 | were called. |
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537 | So how can "AnyEvent->new" be faster than a standard fork, even though |
536 | So how can "AnyEvent->new" be faster than a standard fork, even though |
538 | it uses the same operations, but adds a lot of overhead? |
537 | it uses the same operations, but adds a lot of overhead? |
539 | |
538 | |
540 | The difference is simply the process size: forking the 5MB process takes |
539 | The difference is simply the process size: forking the 5MB process takes |
541 | so much longer than forking the 2.5MB template process that the extra |
540 | so much longer than forking the 2.5MB template process that the extra |
542 | overhead introduced is canceled out. |
541 | overhead is canceled out. |
543 | |
542 | |
544 | If the benchmark process grows, the normal fork becomes even slower: |
543 | If the benchmark process grows, the normal fork becomes even slower: |
545 | |
544 | |
546 | 1340 new processes, manual fork of a 20MB process |
545 | 1340 new processes, manual fork of a 20MB process |
547 | 731 new processes, manual fork of a 200MB process |
546 | 731 new processes, manual fork of a 200MB process |
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603 | AnyEvent::Fork::Early or AnyEvent::Fork::Template, or to delay |
602 | AnyEvent::Fork::Early or AnyEvent::Fork::Template, or to delay |
604 | initialising them, for example, by calling "init Gtk2" manually. |
603 | initialising them, for example, by calling "init Gtk2" manually. |
605 | |
604 | |
606 | exiting calls object destructors |
605 | exiting calls object destructors |
607 | This only applies to users of AnyEvent::Fork:Early and |
606 | This only applies to users of AnyEvent::Fork:Early and |
608 | AnyEvent::Fork::Template, or when initialiasing code creates objects |
607 | AnyEvent::Fork::Template, or when initialising code creates objects |
609 | that reference external resources. |
608 | that reference external resources. |
610 | |
609 | |
611 | When a process created by AnyEvent::Fork exits, it might do so by |
610 | When a process created by AnyEvent::Fork exits, it might do so by |
612 | calling exit, or simply letting perl reach the end of the program. |
611 | calling exit, or simply letting perl reach the end of the program. |
613 | At which point Perl runs all destructors. |
612 | At which point Perl runs all destructors. |
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634 | |
633 | |
635 | Cygwin perl is not supported at the moment due to some hilarious |
634 | Cygwin perl is not supported at the moment due to some hilarious |
636 | shortcomings of its API - see IO::FDPoll for more details. |
635 | shortcomings of its API - see IO::FDPoll for more details. |
637 | |
636 | |
638 | SEE ALSO |
637 | SEE ALSO |
639 | AnyEvent::Fork::Early (to avoid executing a perl interpreter), |
638 | AnyEvent::Fork::Early, to avoid executing a perl interpreter at all |
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639 | (part of this distribution). |
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640 | |
640 | AnyEvent::Fork::Template (to create a process by forking the main |
641 | AnyEvent::Fork::Template, to create a process by forking the main |
641 | program at a convenient time). |
642 | program at a convenient time (part of this distribution). |
642 | |
643 | |
643 | AUTHOR |
644 | AnyEvent::Fork::RPC, for simple RPC to child processes (on CPAN). |
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645 | |
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646 | AUTHOR AND CONTACT INFORMATION |
644 | Marc Lehmann <schmorp@schmorp.de> |
647 | Marc Lehmann <schmorp@schmorp.de> |
645 | http://home.schmorp.de/ |
648 | http://software.schmorp.de/pkg/AnyEvent-Fork |
646 | |
649 | |
647 | POD ERRORS |
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648 | Hey! The above document had some coding errors, which are explained |
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649 | below: |
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650 | |
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651 | Around line 360: |
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652 | You can't have =items (as at line 476) unless the first thing after |
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653 | the =over is an =item |
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654 | |
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