| … | |
… | |
| 27 | |
27 | |
| 28 | Special care has been taken to make this module useful from other modules, |
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> |
29 | while still supporting specialised environments such as L<App::Staticperl> |
| 30 | or L<PAR::Packer>. |
30 | or L<PAR::Packer>. |
| 31 | |
31 | |
| 32 | =head1 WHAT THIS MODULE IS NOT |
32 | =head2 WHAT THIS MODULE IS NOT |
| 33 | |
33 | |
| 34 | This module only creates processes and lets you pass file handles and |
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 - |
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 |
36 | there is no back channel from the process back to you, and there is no RPC |
| 37 | or message passing going on. |
37 | or message passing going on. |
| … | |
… | |
| 40 | in whatever way you like, use some message-passing module such |
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 |
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, |
42 | L<AnyEvent::Handle> on both sides to send e.g. JSON or Storable messages, |
| 43 | and so on. |
43 | and so on. |
| 44 | |
44 | |
|
|
45 | =head2 COMPARISON TO OTHER MODULES |
|
|
46 | |
|
|
47 | There is an abundance of modules on CPAN that do "something fork", such as |
|
|
48 | L<Parallel::ForkManager>, L<AnyEvent::ForkManager>, L<AnyEvent::Worker> |
|
|
49 | or L<AnyEvent::Subprocess>. There are modules that implement their own |
|
|
50 | process management, such as L<AnyEvent::DBI>. |
|
|
51 | |
|
|
52 | The problems that all these modules try to solve are real, however, none |
|
|
53 | of them (from what I have seen) tackle the very real problems of unwanted |
|
|
54 | memory sharing, efficiency, not being able to use event processing or |
|
|
55 | similar modules in the processes they create. |
|
|
56 | |
|
|
57 | This module doesn't try to replace any of them - instead it tries to solve |
|
|
58 | the problem of creating processes with a minimum of fuss and overhead (and |
|
|
59 | also luxury). Ideally, most of these would use AnyEvent::Fork internally, |
|
|
60 | except they were written before AnyEvent:Fork was available, so obviously |
|
|
61 | had to roll their own. |
|
|
62 | |
| 45 | =head1 PROBLEM STATEMENT |
63 | =head2 PROBLEM STATEMENT |
| 46 | |
64 | |
| 47 | There are two traditional ways to implement parallel processing on UNIX |
65 | There are two traditional ways to implement parallel processing on UNIX |
| 48 | like operating systems - fork and process, and fork+exec and process. They |
66 | like operating systems - fork and process, and fork+exec and process. They |
| 49 | have different advantages and disadvantages that I describe below, |
67 | have different advantages and disadvantages that I describe below, |
| 50 | together with how this module tries to mitigate the disadvantages. |
68 | together with how this module tries to mitigate the disadvantages. |
| … | |
… | |
| 152 | |
170 | |
| 153 | # now $master_filehandle is connected to the |
171 | # now $master_filehandle is connected to the |
| 154 | # $slave_filehandle in the new process. |
172 | # $slave_filehandle in the new process. |
| 155 | }); |
173 | }); |
| 156 | |
174 | |
| 157 | # MyModule::worker might look like this |
175 | C<MyModule> might look like this: |
|
|
176 | |
|
|
177 | package MyModule; |
|
|
178 | |
| 158 | sub MyModule::worker { |
179 | sub worker { |
| 159 | my ($slave_filehandle) = @_; |
180 | my ($slave_filehandle) = @_; |
| 160 | |
181 | |
| 161 | # now $slave_filehandle is connected to the $master_filehandle |
182 | # now $slave_filehandle is connected to the $master_filehandle |
| 162 | # in the original prorcess. have fun! |
183 | # in the original prorcess. have fun! |
| 163 | } |
184 | } |
| … | |
… | |
| 182 | } |
203 | } |
| 183 | |
204 | |
| 184 | # now do other things - maybe use the filehandle provided by run |
205 | # now do other things - maybe use the filehandle provided by run |
| 185 | # to wait for the processes to die. or whatever. |
206 | # to wait for the processes to die. or whatever. |
| 186 | |
207 | |
| 187 | # My::Server::run might look like this |
208 | C<My::Server> might look like this: |
| 188 | sub My::Server::run { |
209 | |
|
|
210 | package My::Server; |
|
|
211 | |
|
|
212 | sub run { |
| 189 | my ($slave, $listener, $id) = @_; |
213 | my ($slave, $listener, $id) = @_; |
| 190 | |
214 | |
| 191 | close $slave; # we do not use the socket, so close it to save resources |
215 | close $slave; # we do not use the socket, so close it to save resources |
| 192 | |
216 | |
| 193 | # we could go ballistic and use e.g. AnyEvent here, or IO::AIO, |
217 | # we could go ballistic and use e.g. AnyEvent here, or IO::AIO, |
| … | |
… | |
| 197 | } |
221 | } |
| 198 | } |
222 | } |
| 199 | |
223 | |
| 200 | =head2 use AnyEvent::Fork as a faster fork+exec |
224 | =head2 use AnyEvent::Fork as a faster fork+exec |
| 201 | |
225 | |
| 202 | This runs /bin/echo hi, with stdout redirected to /tmp/log and stderr to |
226 | This runs C</bin/echo hi>, with stdandard output redirected to /tmp/log |
| 203 | the communications socket. It is usually faster than fork+exec, but still |
227 | and standard error redirected to the communications socket. It is usually |
| 204 | let's you prepare the environment. |
228 | faster than fork+exec, but still lets you prepare the environment. |
| 205 | |
229 | |
| 206 | open my $output, ">/tmp/log" or die "$!"; |
230 | open my $output, ">/tmp/log" or die "$!"; |
| 207 | |
231 | |
| 208 | AnyEvent::Fork |
232 | AnyEvent::Fork |
| 209 | ->new |
233 | ->new |
| 210 | ->eval (' |
234 | ->eval (' |
|
|
235 | # compile a helper function for later use |
| 211 | sub run { |
236 | sub run { |
| 212 | my ($fh, $output, @cmd) = @_; |
237 | my ($fh, $output, @cmd) = @_; |
| 213 | |
238 | |
| 214 | # perl will clear close-on-exec on STDOUT/STDERR |
239 | # perl will clear close-on-exec on STDOUT/STDERR |
| 215 | open STDOUT, ">&", $output or die; |
240 | open STDOUT, ">&", $output or die; |
| … | |
… | |
| 314 | =head1 THE C<AnyEvent::Fork> CLASS |
339 | =head1 THE C<AnyEvent::Fork> CLASS |
| 315 | |
340 | |
| 316 | This module exports nothing, and only implements a single class - |
341 | This module exports nothing, and only implements a single class - |
| 317 | C<AnyEvent::Fork>. |
342 | C<AnyEvent::Fork>. |
| 318 | |
343 | |
| 319 | There are two constructors that both create new processes - C<new> and |
344 | There are two class constructors that both create new processes - C<new> |
| 320 | C<new_exec>. The C<fork> method creates a new process by forking an |
345 | and C<new_exec>. The C<fork> method creates a new process by forking an |
| 321 | existing one and could be considered a third constructor. |
346 | existing one and could be considered a third constructor. |
| 322 | |
347 | |
| 323 | Most of the remaining methods deal with preparing the new process, by |
348 | Most of the remaining methods deal with preparing the new process, by |
| 324 | loading code, evaluating code and sending data to the new process. They |
349 | loading code, evaluating code and sending data to the new process. They |
| 325 | usually return the process object, so you can chain method calls. |
350 | usually return the process object, so you can chain method calls. |
| 326 | |
351 | |
| 327 | If a process object is destroyed before calling its C<run> method, then |
352 | If a process object is destroyed before calling its C<run> method, then |
| 328 | the process simply exits. After C<run> is called, all responsibility is |
353 | the process simply exits. After C<run> is called, all responsibility is |
| 329 | passed to the specified function. |
354 | passed to the specified function. |
| 330 | |
355 | |
|
|
356 | As long as there is any outstanding work to be done, process objects |
|
|
357 | resist being destroyed, so there is no reason to store them unless you |
|
|
358 | need them later - configure and forget works just fine. |
|
|
359 | |
| 331 | =over 4 |
360 | =over 4 |
| 332 | |
361 | |
| 333 | =cut |
362 | =cut |
| 334 | |
363 | |
| 335 | package AnyEvent::Fork; |
364 | package AnyEvent::Fork; |
| … | |
… | |
| 341 | use AnyEvent; |
370 | use AnyEvent; |
| 342 | use AnyEvent::Util (); |
371 | use AnyEvent::Util (); |
| 343 | |
372 | |
| 344 | use IO::FDPass; |
373 | use IO::FDPass; |
| 345 | |
374 | |
| 346 | our $VERSION = 0.5; |
375 | our $VERSION = 0.6; |
| 347 | |
|
|
| 348 | our $PERL; # the path to the perl interpreter, deduces with various forms of magic |
|
|
| 349 | |
|
|
| 350 | =item my $pool = new AnyEvent::Fork key => value... |
|
|
| 351 | |
|
|
| 352 | Create a new process pool. The following named parameters are supported: |
|
|
| 353 | |
376 | |
| 354 | =over 4 |
377 | =over 4 |
| 355 | |
378 | |
| 356 | =back |
379 | =back |
| 357 | |
380 | |
| … | |
… | |
| 360 | # the early fork template process |
383 | # the early fork template process |
| 361 | our $EARLY; |
384 | our $EARLY; |
| 362 | |
385 | |
| 363 | # the empty template process |
386 | # the empty template process |
| 364 | our $TEMPLATE; |
387 | our $TEMPLATE; |
|
|
388 | |
|
|
389 | sub QUEUE() { 0 } |
|
|
390 | sub FH() { 1 } |
|
|
391 | sub WW() { 2 } |
|
|
392 | sub PID() { 3 } |
|
|
393 | sub CB() { 4 } |
|
|
394 | |
|
|
395 | sub _new { |
|
|
396 | my ($self, $fh, $pid) = @_; |
|
|
397 | |
|
|
398 | AnyEvent::Util::fh_nonblocking $fh, 1; |
|
|
399 | |
|
|
400 | $self = bless [ |
|
|
401 | [], # write queue - strings or fd's |
|
|
402 | $fh, |
|
|
403 | undef, # AE watcher |
|
|
404 | $pid, |
|
|
405 | ], $self; |
|
|
406 | |
|
|
407 | $self |
|
|
408 | } |
| 365 | |
409 | |
| 366 | sub _cmd { |
410 | sub _cmd { |
| 367 | my $self = shift; |
411 | my $self = shift; |
| 368 | |
412 | |
| 369 | # ideally, we would want to use "a (w/a)*" as format string, but perl |
413 | # ideally, we would want to use "a (w/a)*" as format string, but perl |
| 370 | # versions from at least 5.8.9 to 5.16.3 are all buggy and can't unpack |
414 | # versions from at least 5.8.9 to 5.16.3 are all buggy and can't unpack |
| 371 | # it. |
415 | # it. |
| 372 | push @{ $self->[2] }, pack "a L/a*", $_[0], $_[1]; |
416 | push @{ $self->[QUEUE] }, pack "a L/a*", $_[0], $_[1]; |
| 373 | |
417 | |
| 374 | $self->[3] ||= AE::io $self->[1], 1, sub { |
418 | $self->[WW] ||= AE::io $self->[FH], 1, sub { |
| 375 | do { |
419 | do { |
| 376 | # send the next "thing" in the queue - either a reference to an fh, |
420 | # send the next "thing" in the queue - either a reference to an fh, |
| 377 | # or a plain string. |
421 | # or a plain string. |
| 378 | |
422 | |
| 379 | if (ref $self->[2][0]) { |
423 | if (ref $self->[QUEUE][0]) { |
| 380 | # send fh |
424 | # send fh |
| 381 | unless (IO::FDPass::send fileno $self->[1], fileno ${ $self->[2][0] }) { |
425 | unless (IO::FDPass::send fileno $self->[FH], fileno ${ $self->[QUEUE][0] }) { |
| 382 | return if $! == Errno::EAGAIN || $! == Errno::EWOULDBLOCK; |
426 | return if $! == Errno::EAGAIN || $! == Errno::EWOULDBLOCK; |
| 383 | undef $self->[3]; |
427 | undef $self->[WW]; |
| 384 | die "AnyEvent::Fork: file descriptor send failure: $!"; |
428 | die "AnyEvent::Fork: file descriptor send failure: $!"; |
| 385 | } |
429 | } |
| 386 | |
430 | |
| 387 | shift @{ $self->[2] }; |
431 | shift @{ $self->[QUEUE] }; |
| 388 | |
432 | |
| 389 | } else { |
433 | } else { |
| 390 | # send string |
434 | # send string |
| 391 | my $len = syswrite $self->[1], $self->[2][0]; |
435 | my $len = syswrite $self->[FH], $self->[QUEUE][0]; |
| 392 | |
436 | |
| 393 | unless ($len) { |
437 | unless ($len) { |
| 394 | return if $! == Errno::EAGAIN || $! == Errno::EWOULDBLOCK; |
438 | return if $! == Errno::EAGAIN || $! == Errno::EWOULDBLOCK; |
| 395 | undef $self->[3]; |
439 | undef $self->[3]; |
| 396 | die "AnyEvent::Fork: command write failure: $!"; |
440 | die "AnyEvent::Fork: command write failure: $!"; |
| 397 | } |
441 | } |
| 398 | |
442 | |
| 399 | substr $self->[2][0], 0, $len, ""; |
443 | substr $self->[QUEUE][0], 0, $len, ""; |
| 400 | shift @{ $self->[2] } unless length $self->[2][0]; |
444 | shift @{ $self->[QUEUE] } unless length $self->[QUEUE][0]; |
| 401 | } |
445 | } |
| 402 | } while @{ $self->[2] }; |
446 | } while @{ $self->[QUEUE] }; |
| 403 | |
447 | |
| 404 | # everything written |
448 | # everything written |
| 405 | undef $self->[3]; |
449 | undef $self->[WW]; |
| 406 | |
450 | |
| 407 | # invoke run callback, if any |
451 | # invoke run callback, if any |
| 408 | $self->[4]->($self->[1]) if $self->[4]; |
452 | $self->[CB]->($self->[FH]) if $self->[CB]; |
| 409 | }; |
453 | }; |
| 410 | |
454 | |
| 411 | () # make sure we don't leak the watcher |
455 | () # make sure we don't leak the watcher |
| 412 | } |
|
|
| 413 | |
|
|
| 414 | sub _new { |
|
|
| 415 | my ($self, $fh, $pid) = @_; |
|
|
| 416 | |
|
|
| 417 | AnyEvent::Util::fh_nonblocking $fh, 1; |
|
|
| 418 | |
|
|
| 419 | $self = bless [ |
|
|
| 420 | $pid, |
|
|
| 421 | $fh, |
|
|
| 422 | [], # write queue - strings or fd's |
|
|
| 423 | undef, # AE watcher |
|
|
| 424 | ], $self; |
|
|
| 425 | |
|
|
| 426 | $self |
|
|
| 427 | } |
456 | } |
| 428 | |
457 | |
| 429 | # fork template from current process, used by AnyEvent::Fork::Early/Template |
458 | # fork template from current process, used by AnyEvent::Fork::Early/Template |
| 430 | sub _new_fork { |
459 | sub _new_fork { |
| 431 | my ($fh, $slave) = AnyEvent::Util::portable_socketpair; |
460 | my ($fh, $slave) = AnyEvent::Util::portable_socketpair; |
| … | |
… | |
| 436 | if ($pid eq 0) { |
465 | if ($pid eq 0) { |
| 437 | require AnyEvent::Fork::Serve; |
466 | require AnyEvent::Fork::Serve; |
| 438 | $AnyEvent::Fork::Serve::OWNER = $parent; |
467 | $AnyEvent::Fork::Serve::OWNER = $parent; |
| 439 | close $fh; |
468 | close $fh; |
| 440 | $0 = "$_[1] of $parent"; |
469 | $0 = "$_[1] of $parent"; |
| 441 | $SIG{CHLD} = 'IGNORE'; |
|
|
| 442 | AnyEvent::Fork::Serve::serve ($slave); |
470 | AnyEvent::Fork::Serve::serve ($slave); |
| 443 | exit 0; |
471 | exit 0; |
| 444 | } elsif (!$pid) { |
472 | } elsif (!$pid) { |
| 445 | die "AnyEvent::Fork::Early/Template: unable to fork template process: $!"; |
473 | die "AnyEvent::Fork::Early/Template: unable to fork template process: $!"; |
| 446 | } |
474 | } |
| … | |
… | |
| 453 | Create a new "empty" perl interpreter process and returns its process |
481 | Create a new "empty" perl interpreter process and returns its process |
| 454 | object for further manipulation. |
482 | object for further manipulation. |
| 455 | |
483 | |
| 456 | The new process is forked from a template process that is kept around |
484 | The new process is forked from a template process that is kept around |
| 457 | for this purpose. When it doesn't exist yet, it is created by a call to |
485 | for this purpose. When it doesn't exist yet, it is created by a call to |
| 458 | C<new_exec> and kept around for future calls. |
486 | C<new_exec> first and then stays around for future calls. |
| 459 | |
|
|
| 460 | When the process object is destroyed, it will release the file handle |
|
|
| 461 | that connects it with the new process. When the new process has not yet |
|
|
| 462 | called C<run>, then the process will exit. Otherwise, what happens depends |
|
|
| 463 | entirely on the code that is executed. |
|
|
| 464 | |
487 | |
| 465 | =cut |
488 | =cut |
| 466 | |
489 | |
| 467 | sub new { |
490 | sub new { |
| 468 | my $class = shift; |
491 | my $class = shift; |
| … | |
… | |
| 558 | } |
581 | } |
| 559 | |
582 | |
| 560 | =item $pid = $proc->pid |
583 | =item $pid = $proc->pid |
| 561 | |
584 | |
| 562 | Returns the process id of the process I<iff it is a direct child of the |
585 | Returns the process id of the process I<iff it is a direct child of the |
| 563 | process> running AnyEvent::Fork, and C<undef> otherwise. |
586 | process running AnyEvent::Fork>, and C<undef> otherwise. |
| 564 | |
587 | |
| 565 | Normally, only processes created via C<< AnyEvent::Fork->new_exec >> and |
588 | Normally, only processes created via C<< AnyEvent::Fork->new_exec >> and |
| 566 | L<AnyEvent::Fork::Template> are direct children, and you are responsible |
589 | L<AnyEvent::Fork::Template> are direct children, and you are responsible |
| 567 | to clean up their zombies when they die. |
590 | to clean up their zombies when they die. |
| 568 | |
591 | |
| 569 | All other processes are not direct children, and will be cleaned up by |
592 | All other processes are not direct children, and will be cleaned up by |
| 570 | AnyEvent::Fork. |
593 | AnyEvent::Fork itself. |
| 571 | |
594 | |
| 572 | =cut |
595 | =cut |
| 573 | |
596 | |
| 574 | sub pid { |
597 | sub pid { |
| 575 | $_[0][0] |
598 | $_[0][PID] |
| 576 | } |
599 | } |
| 577 | |
600 | |
| 578 | =item $proc = $proc->eval ($perlcode, @args) |
601 | =item $proc = $proc->eval ($perlcode, @args) |
| 579 | |
602 | |
| 580 | Evaluates the given C<$perlcode> as ... perl code, while setting C<@_> to |
603 | Evaluates the given C<$perlcode> as ... perl code, while setting C<@_> to |
| … | |
… | |
| 586 | |
609 | |
| 587 | The code will usually be executed after this call returns, and there is no |
610 | The code will usually be executed after this call returns, and there is no |
| 588 | way to pass anything back to the calling process. Any evaluation errors |
611 | way to pass anything back to the calling process. Any evaluation errors |
| 589 | will be reported to stderr and cause the process to exit. |
612 | will be reported to stderr and cause the process to exit. |
| 590 | |
613 | |
| 591 | If you want to execute some code to take over the process (see the |
614 | If you want to execute some code (that isn't in a module) to take over the |
| 592 | "fork+exec" example in the SYNOPSIS), you should compile a function via |
615 | process, you should compile a function via C<eval> first, and then call |
| 593 | C<eval> first, and then call it via C<run>. This also gives you access to |
616 | it via C<run>. This also gives you access to any arguments passed via the |
| 594 | any arguments passed via the C<send_xxx> methods, such as file handles. |
617 | C<send_xxx> methods, such as file handles. See the L<use AnyEvent::Fork as |
|
|
618 | a faster fork+exec> example to see it in action. |
| 595 | |
619 | |
| 596 | Returns the process object for easy chaining of method calls. |
620 | Returns the process object for easy chaining of method calls. |
| 597 | |
621 | |
| 598 | =cut |
622 | =cut |
| 599 | |
623 | |
| … | |
… | |
| 625 | =item $proc = $proc->send_fh ($handle, ...) |
649 | =item $proc = $proc->send_fh ($handle, ...) |
| 626 | |
650 | |
| 627 | Send one or more file handles (I<not> file descriptors) to the process, |
651 | Send one or more file handles (I<not> file descriptors) to the process, |
| 628 | to prepare a call to C<run>. |
652 | to prepare a call to C<run>. |
| 629 | |
653 | |
| 630 | The process object keeps a reference to the handles until this is done, |
654 | The process object keeps a reference to the handles until they have |
| 631 | so you must not explicitly close the handles. This is most easily |
655 | been passed over to the process, so you must not explicitly close the |
| 632 | accomplished by simply not storing the file handles anywhere after passing |
656 | handles. This is most easily accomplished by simply not storing the file |
| 633 | them to this method. |
657 | handles anywhere after passing them to this method - when AnyEvent::Fork |
|
|
658 | is finished using them, perl will automatically close them. |
| 634 | |
659 | |
| 635 | Returns the process object for easy chaining of method calls. |
660 | Returns the process object for easy chaining of method calls. |
| 636 | |
661 | |
| 637 | Example: pass a file handle to a process, and release it without |
662 | Example: pass a file handle to a process, and release it without |
| 638 | closing. It will be closed automatically when it is no longer used. |
663 | closing. It will be closed automatically when it is no longer used. |
| … | |
… | |
| 645 | sub send_fh { |
670 | sub send_fh { |
| 646 | my ($self, @fh) = @_; |
671 | my ($self, @fh) = @_; |
| 647 | |
672 | |
| 648 | for my $fh (@fh) { |
673 | for my $fh (@fh) { |
| 649 | $self->_cmd ("h"); |
674 | $self->_cmd ("h"); |
| 650 | push @{ $self->[2] }, \$fh; |
675 | push @{ $self->[QUEUE] }, \$fh; |
| 651 | } |
676 | } |
| 652 | |
677 | |
| 653 | $self |
678 | $self |
| 654 | } |
679 | } |
| 655 | |
680 | |
| 656 | =item $proc = $proc->send_arg ($string, ...) |
681 | =item $proc = $proc->send_arg ($string, ...) |
| 657 | |
682 | |
| 658 | Send one or more argument strings to the process, to prepare a call to |
683 | Send one or more argument strings to the process, to prepare a call to |
| 659 | C<run>. The strings can be any octet string. |
684 | C<run>. The strings can be any octet strings. |
| 660 | |
685 | |
| 661 | The protocol is optimised to pass a moderate number of relatively short |
686 | The protocol is optimised to pass a moderate number of relatively short |
| 662 | strings - while you can pass up to 4GB of data in one go, this is more |
687 | strings - while you can pass up to 4GB of data in one go, this is more |
| 663 | meant to pass some ID information or other startup info, not big chunks of |
688 | meant to pass some ID information or other startup info, not big chunks of |
| 664 | data. |
689 | data. |
| … | |
… | |
| 680 | Enter the function specified by the function name in C<$func> in the |
705 | Enter the function specified by the function name in C<$func> in the |
| 681 | process. The function is called with the communication socket as first |
706 | process. The function is called with the communication socket as first |
| 682 | argument, followed by all file handles and string arguments sent earlier |
707 | argument, followed by all file handles and string arguments sent earlier |
| 683 | via C<send_fh> and C<send_arg> methods, in the order they were called. |
708 | via C<send_fh> and C<send_arg> methods, in the order they were called. |
| 684 | |
709 | |
|
|
710 | The process object becomes unusable on return from this function - any |
|
|
711 | further method calls result in undefined behaviour. |
|
|
712 | |
| 685 | The function name should be fully qualified, but if it isn't, it will be |
713 | The function name should be fully qualified, but if it isn't, it will be |
| 686 | looked up in the main package. |
714 | looked up in the C<main> package. |
| 687 | |
715 | |
| 688 | If the called function returns, doesn't exist, or any error occurs, the |
716 | If the called function returns, doesn't exist, or any error occurs, the |
| 689 | process exits. |
717 | process exits. |
| 690 | |
718 | |
| 691 | Preparing the process is done in the background - when all commands have |
719 | Preparing the process is done in the background - when all commands have |
| 692 | been sent, the callback is invoked with the local communications socket |
720 | been sent, the callback is invoked with the local communications socket |
| 693 | as argument. At this point you can start using the socket in any way you |
721 | as argument. At this point you can start using the socket in any way you |
| 694 | like. |
722 | like. |
| 695 | |
|
|
| 696 | The process object becomes unusable on return from this function - any |
|
|
| 697 | further method calls result in undefined behaviour. |
|
|
| 698 | |
723 | |
| 699 | If the communication socket isn't used, it should be closed on both sides, |
724 | If the communication socket isn't used, it should be closed on both sides, |
| 700 | to save on kernel memory. |
725 | to save on kernel memory. |
| 701 | |
726 | |
| 702 | The socket is non-blocking in the parent, and blocking in the newly |
727 | The socket is non-blocking in the parent, and blocking in the newly |
| … | |
… | |
| 741 | =cut |
766 | =cut |
| 742 | |
767 | |
| 743 | sub run { |
768 | sub run { |
| 744 | my ($self, $func, $cb) = @_; |
769 | my ($self, $func, $cb) = @_; |
| 745 | |
770 | |
| 746 | $self->[4] = $cb; |
771 | $self->[CB] = $cb; |
| 747 | $self->_cmd (r => $func); |
772 | $self->_cmd (r => $func); |
| 748 | } |
773 | } |
| 749 | |
774 | |
| 750 | =back |
775 | =back |
| 751 | |
776 | |
| … | |
… | |
| 777 | 479 vfork+execs per second, using AnyEvent::Fork->new_exec |
802 | 479 vfork+execs per second, using AnyEvent::Fork->new_exec |
| 778 | |
803 | |
| 779 | So how can C<< AnyEvent->new >> be faster than a standard fork, even |
804 | So how can C<< AnyEvent->new >> be faster than a standard fork, even |
| 780 | though it uses the same operations, but adds a lot of overhead? |
805 | though it uses the same operations, but adds a lot of overhead? |
| 781 | |
806 | |
| 782 | The difference is simply the process size: forking the 6MB process takes |
807 | The difference is simply the process size: forking the 5MB process takes |
| 783 | so much longer than forking the 2.5MB template process that the overhead |
808 | so much longer than forking the 2.5MB template process that the extra |
| 784 | introduced is canceled out. |
809 | overhead introduced is canceled out. |
| 785 | |
810 | |
| 786 | If the benchmark process grows, the normal fork becomes even slower: |
811 | If the benchmark process grows, the normal fork becomes even slower: |
| 787 | |
812 | |
| 788 | 1340 new processes, manual fork in a 20MB process |
813 | 1340 new processes, manual fork of a 20MB process |
| 789 | 731 new processes, manual fork in a 200MB process |
814 | 731 new processes, manual fork of a 200MB process |
| 790 | 235 new processes, manual fork in a 2000MB process |
815 | 235 new processes, manual fork of a 2000MB process |
| 791 | |
816 | |
| 792 | What that means (to me) is that I can use this module without having a |
817 | What that means (to me) is that I can use this module without having a bad |
| 793 | very bad conscience because of the extra overhead required to start new |
818 | conscience because of the extra overhead required to start new processes. |
| 794 | processes. |
|
|
| 795 | |
819 | |
| 796 | =head1 TYPICAL PROBLEMS |
820 | =head1 TYPICAL PROBLEMS |
| 797 | |
821 | |
| 798 | This section lists typical problems that remain. I hope by recognising |
822 | This section lists typical problems that remain. I hope by recognising |
| 799 | them, most can be avoided. |
823 | them, most can be avoided. |
| 800 | |
824 | |
| 801 | =over 4 |
825 | =over 4 |
| 802 | |
826 | |
| 803 | =item "leaked" file descriptors for exec'ed processes |
827 | =item leaked file descriptors for exec'ed processes |
| 804 | |
828 | |
| 805 | POSIX systems inherit file descriptors by default when exec'ing a new |
829 | POSIX systems inherit file descriptors by default when exec'ing a new |
| 806 | process. While perl itself laudably sets the close-on-exec flags on new |
830 | process. While perl itself laudably sets the close-on-exec flags on new |
| 807 | file handles, most C libraries don't care, and even if all cared, it's |
831 | file handles, most C libraries don't care, and even if all cared, it's |
| 808 | often not possible to set the flag in a race-free manner. |
832 | often not possible to set the flag in a race-free manner. |
| … | |
… | |
| 828 | libraries or the code that leaks those file descriptors. |
852 | libraries or the code that leaks those file descriptors. |
| 829 | |
853 | |
| 830 | Fortunately, most of these leaked descriptors do no harm, other than |
854 | Fortunately, most of these leaked descriptors do no harm, other than |
| 831 | sitting on some resources. |
855 | sitting on some resources. |
| 832 | |
856 | |
| 833 | =item "leaked" file descriptors for fork'ed processes |
857 | =item leaked file descriptors for fork'ed processes |
| 834 | |
858 | |
| 835 | Normally, L<AnyEvent::Fork> does start new processes by exec'ing them, |
859 | Normally, L<AnyEvent::Fork> does start new processes by exec'ing them, |
| 836 | which closes file descriptors not marked for being inherited. |
860 | which closes file descriptors not marked for being inherited. |
| 837 | |
861 | |
| 838 | However, L<AnyEvent::Fork::Early> and L<AnyEvent::Fork::Template> offer |
862 | However, L<AnyEvent::Fork::Early> and L<AnyEvent::Fork::Template> offer |
| … | |
… | |
| 847 | |
871 | |
| 848 | The solution is to either not load these modules before use'ing |
872 | The solution is to either not load these modules before use'ing |
| 849 | L<AnyEvent::Fork::Early> or L<AnyEvent::Fork::Template>, or to delay |
873 | L<AnyEvent::Fork::Early> or L<AnyEvent::Fork::Template>, or to delay |
| 850 | initialising them, for example, by calling C<init Gtk2> manually. |
874 | initialising them, for example, by calling C<init Gtk2> manually. |
| 851 | |
875 | |
| 852 | =item exit runs destructors |
876 | =item exiting calls object destructors |
| 853 | |
877 | |
| 854 | This only applies to users of Lc<AnyEvent::Fork:Early> and |
878 | This only applies to users of L<AnyEvent::Fork:Early> and |
| 855 | L<AnyEvent::Fork::Template>. |
879 | L<AnyEvent::Fork::Template>, or when initialiasing code creates objects |
|
|
880 | that reference external resources. |
| 856 | |
881 | |
| 857 | When a process created by AnyEvent::Fork exits, it might do so by calling |
882 | When a process created by AnyEvent::Fork exits, it might do so by calling |
| 858 | exit, or simply letting perl reach the end of the program. At which point |
883 | exit, or simply letting perl reach the end of the program. At which point |
| 859 | Perl runs all destructors. |
884 | Perl runs all destructors. |
| 860 | |
885 | |
| … | |
… | |
| 879 | to make it so, mostly due to the bloody broken perl that nobody seems to |
904 | to make it so, mostly due to the bloody broken perl that nobody seems to |
| 880 | care about. The fork emulation is a bad joke - I have yet to see something |
905 | care about. The fork emulation is a bad joke - I have yet to see something |
| 881 | useful that you can do with it without running into memory corruption |
906 | useful that you can do with it without running into memory corruption |
| 882 | issues or other braindamage. Hrrrr. |
907 | issues or other braindamage. Hrrrr. |
| 883 | |
908 | |
| 884 | Cygwin perl is not supported at the moment, as it should implement fd |
909 | Cygwin perl is not supported at the moment due to some hilarious |
| 885 | passing, but doesn't, and rolling my own is hard, as cygwin doesn't |
910 | shortcomings of its API - see L<IO::FDPoll> for more details. |
| 886 | support enough functionality to do it. |
|
|
| 887 | |
911 | |
| 888 | =head1 SEE ALSO |
912 | =head1 SEE ALSO |
| 889 | |
913 | |
| 890 | L<AnyEvent::Fork::Early> (to avoid executing a perl interpreter), |
914 | L<AnyEvent::Fork::Early> (to avoid executing a perl interpreter), |
| 891 | L<AnyEvent::Fork::Template> (to create a process by forking the main |
915 | L<AnyEvent::Fork::Template> (to create a process by forking the main |
