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Revision 1.9 by root, Thu Apr 25 00:27:22 2013 UTC vs.
Revision 1.17 by root, Thu Oct 27 07:27:56 2022 UTC

1=head1 NAME 1=head1 NAME
2 2
3AnyEvent::Fork::Pool - simple process pool manager on top of AnyEvent::Fork 3AnyEvent::Fork::Pool - simple process pool manager on top of AnyEvent::Fork
4 4
5THE API IS NOT FINISHED, CONSIDER THIS AN ALPHA RELEASE
6
7=head1 SYNOPSIS 5=head1 SYNOPSIS
8 6
9 use AnyEvent; 7 use AnyEvent;
8 use AnyEvent::Fork;
10 use AnyEvent::Fork::Pool; 9 use AnyEvent::Fork::Pool;
11 # use AnyEvent::Fork is not needed
12 10
13 # all possible parameters shown, with default values 11 # all possible parameters shown, with default values
14 my $pool = AnyEvent::Fork 12 my $pool = AnyEvent::Fork
15 ->new 13 ->new
16 ->require ("MyWorker") 14 ->require ("MyWorker")
43 41
44 $finish->recv; 42 $finish->recv;
45 43
46=head1 DESCRIPTION 44=head1 DESCRIPTION
47 45
48This module uses processes created via L<AnyEvent::Fork> and the RPC 46This module uses processes created via L<AnyEvent::Fork> (or
49protocol implement in L<AnyEvent::Fork::RPC> to create a load-balanced 47L<AnyEvent::Fork::Remote>) and the RPC protocol implement in
50pool of processes that handles jobs. 48L<AnyEvent::Fork::RPC> to create a load-balanced pool of processes that
49handles jobs.
51 50
52Understanding of L<AnyEvent::Fork> is helpful but not critical to be able 51Understanding L<AnyEvent::Fork> is helpful but not required to use this
53to use this module, but a thorough understanding of L<AnyEvent::Fork::RPC> 52module, but a thorough understanding of L<AnyEvent::Fork::RPC> is, as
54is, as it defines the actual API that needs to be implemented in the 53it defines the actual API that needs to be implemented in the worker
55worker processes. 54processes.
56
57=head1 EXAMPLES
58 55
59=head1 PARENT USAGE 56=head1 PARENT USAGE
60 57
61To create a pool, you first have to create a L<AnyEvent::Fork> object - 58To create a pool, you first have to create a L<AnyEvent::Fork> object -
62this object becomes your template process. Whenever a new worker process 59this object becomes your template process. Whenever a new worker process
89 86
90use Guard (); 87use Guard ();
91use Array::Heap (); 88use Array::Heap ();
92 89
93use AnyEvent; 90use AnyEvent;
94# explicit version on next line, as some cpan-testers test with the 0.1 version,
95# ignoring dependencies, and this line will at least give a clear indication of that.
96use AnyEvent::Fork 0.6; # we don't actually depend on it, this is for convenience
97use AnyEvent::Fork::RPC; 91use AnyEvent::Fork::RPC;
98 92
99# these are used for the first and last argument of events 93# these are used for the first and last argument of events
100# in the hope of not colliding. yes, I don't like it either, 94# in the hope of not colliding. yes, I don't like it either,
101# but didn't come up with an obviously better alternative. 95# but didn't come up with an obviously better alternative.
102my $magic0 = ':t6Z@HK1N%Dx@_7?=~-7NQgWDdAs6a,jFN=wLO0*jD*1%P'; 96my $magic0 = ':t6Z@HK1N%Dx@_7?=~-7NQgWDdAs6a,jFN=wLO0*jD*1%P';
103my $magic1 = '<~53rexz.U`!]X[A235^"fyEoiTF\T~oH1l/N6+Djep9b~bI9`\1x%B~vWO1q*'; 97my $magic1 = '<~53rexz.U`!]X[A235^"fyEoiTF\T~oH1l/N6+Djep9b~bI9`\1x%B~vWO1q*';
104 98
105our $VERSION = 0.1; 99our $VERSION = 1.3;
106 100
107=item my $pool = AnyEvent::Fork::Pool::run $fork, $function, [key => value...] 101=item my $pool = AnyEvent::Fork::Pool::run $fork, $function, [key => value...]
108 102
109The traditional way to call the pool creation function. But it is way 103The traditional way to call the pool creation function. But it is way
110cooler to call it in the following way: 104cooler to call it in the following way:
403 397
404 last; 398 last;
405 } 399 }
406 } 400 }
407 } elsif ($shutdown) { 401 } elsif ($shutdown) {
408 @pool = (); 402 undef $_->[2]
403 for @pool;
404
409 undef $start_w; 405 undef $start_w;
410 undef $start_worker; # frees $destroy_guard reference 406 undef $start_worker; # frees $destroy_guard reference
411 407
412 $stop_worker->($pool[0]) 408 $stop_worker->($pool[0])
413 while $nidle; 409 while $nidle;
452 448
453=item $cpus = AnyEvent::Fork::Pool::ncpu [$default_cpus] 449=item $cpus = AnyEvent::Fork::Pool::ncpu [$default_cpus]
454 450
455=item ($cpus, $eus) = AnyEvent::Fork::Pool::ncpu [$default_cpus] 451=item ($cpus, $eus) = AnyEvent::Fork::Pool::ncpu [$default_cpus]
456 452
457Tries to detect the number of CPUs (C<$cpus> often called cpu cores 453Tries to detect the number of CPUs (C<$cpus> often called CPU cores
458nowadays) and execution units (C<$eus>) which include e.g. extra 454nowadays) and execution units (C<$eus>) which include e.g. extra
459hyperthreaded units). When C<$cpus> cannot be determined reliably, 455hyperthreaded units). When C<$cpus> cannot be determined reliably,
460C<$default_cpus> is returned for both values, or C<1> if it is missing. 456C<$default_cpus> is returned for both values, or C<1> if it is missing.
461 457
462For normal CPU bound uses, it is wise to have as many worker processes 458For normal CPU bound uses, it is wise to have as many worker processes
464hyperthreading is usually detrimental to performance, but in those rare 460hyperthreading is usually detrimental to performance, but in those rare
465cases where that really helps it might be beneficial to use more workers 461cases where that really helps it might be beneficial to use more workers
466(C<$eus>). 462(C<$eus>).
467 463
468Currently, F</proc/cpuinfo> is parsed on GNU/Linux systems for both 464Currently, F</proc/cpuinfo> is parsed on GNU/Linux systems for both
469C<$cpus> and C<$eu>, and on {Free,Net,Open}BSD, F<sysctl -n hw.ncpu> is 465C<$cpus> and C<$eus>, and on {Free,Net,Open}BSD, F<sysctl -n hw.ncpu> is
470used for C<$cpus>. 466used for C<$cpus>.
471 467
472Example: create a worker pool with as many workers as cpu cores, or C<2>, 468Example: create a worker pool with as many workers as CPU cores, or C<2>,
473if the actual number could not be determined. 469if the actual number could not be determined.
474 470
475 $fork->AnyEvent::Fork::Pool::run ("myworker::function", 471 $fork->AnyEvent::Fork::Pool::run ("myworker::function",
476 max => (scalar AnyEvent::Fork::Pool::ncpu 2), 472 max => (scalar AnyEvent::Fork::Pool::ncpu 2),
477 ); 473 );
524 520
525=item AnyEvent::Fork::Pool::retire () 521=item AnyEvent::Fork::Pool::retire ()
526 522
527This function sends an event to the parent process to request retirement: 523This function sends an event to the parent process to request retirement:
528the worker is removed from the pool and no new jobs will be sent to it, 524the worker is removed from the pool and no new jobs will be sent to it,
529but it has to handle the jobs that are already queued. 525but it still has to handle the jobs that are already queued.
530 526
531The parentheses are part of the syntax: the function usually isn't defined 527The parentheses are part of the syntax: the function usually isn't defined
532when you compile your code (because that happens I<before> handing the 528when you compile your code (because that happens I<before> handing the
533template process over to C<AnyEvent::Fork::Pool::run>, so you need the 529template process over to C<AnyEvent::Fork::Pool::run>, so you need the
534empty parentheses to tell Perl that the function is indeed a function. 530empty parentheses to tell Perl that the function is indeed a function.
535 531
536Retiring a worker can be useful to gracefully shut it down when the worker 532Retiring a worker can be useful to gracefully shut it down when the worker
537deems this useful. For example, after executing a job, one could check 533deems this useful. For example, after executing a job, it could check the
538the process size or the number of jobs handled so far, and if either is 534process size or the number of jobs handled so far, and if either is too
539too high, the worker could ask to get retired, to avoid memory leaks to 535high, the worker could request to be retired, to avoid memory leaks to
540accumulate. 536accumulate.
541 537
538Example: retire a worker after it has handled roughly 100 requests. It
539doesn't matter whether you retire at the beginning or end of your request,
540as the worker will continue to handle some outstanding requests. Likewise,
541it's ok to call retire multiple times.
542
543 my $count = 0;
544
545 sub my::worker {
546
547 ++$count == 100
548 and AnyEvent::Fork::Pool::retire ();
549
550 ... normal code goes here
551 }
552
542=back 553=back
543 554
544=head1 POOL PARAMETERS RECIPES 555=head1 POOL PARAMETERS RECIPES
545 556
546This section describes some recipes for pool paramaters. These are mostly 557This section describes some recipes for pool parameters. These are mostly
547meant for the synchronous RPC backend, as the asynchronous RPC backend 558meant for the synchronous RPC backend, as the asynchronous RPC backend
548changes the rules considerably, making workers themselves responsible for 559changes the rules considerably, making workers themselves responsible for
549their scheduling. 560their scheduling.
550 561
551=over 4 562=over 4
580=item high throughput, I/O bound jobs - set load >= 2, max = 1, or very high 591=item high throughput, I/O bound jobs - set load >= 2, max = 1, or very high
581 592
582When your jobs are I/O bound, using more workers usually boils down to 593When your jobs are I/O bound, using more workers usually boils down to
583higher throughput, depending very much on your actual workload - sometimes 594higher throughput, depending very much on your actual workload - sometimes
584having only one worker is best, for example, when you read or write big 595having only one worker is best, for example, when you read or write big
585files at maixmum speed, as a second worker will increase seek times. 596files at maximum speed, as a second worker will increase seek times.
586 597
587=back 598=back
588 599
589=head1 EXCEPTIONS 600=head1 EXCEPTIONS
590 601
591The same "policy" as with L<AnyEvent::Fork::RPC> applies - exceptins will 602The same "policy" as with L<AnyEvent::Fork::RPC> applies - exceptions
592not be caught, and exceptions in both worker and in callbacks causes 603will not be caught, and exceptions in both worker and in callbacks causes
593undesirable or undefined behaviour. 604undesirable or undefined behaviour.
594 605
595=head1 SEE ALSO 606=head1 SEE ALSO
596 607
597L<AnyEvent::Fork>, to create the processes in the first place. 608L<AnyEvent::Fork>, to create the processes in the first place.
609
610L<AnyEvent::Fork::Remote>, likewise, but helpful for remote processes.
598 611
599L<AnyEvent::Fork::RPC>, which implements the RPC protocol and API. 612L<AnyEvent::Fork::RPC>, which implements the RPC protocol and API.
600 613
601=head1 AUTHOR AND CONTACT INFORMATION 614=head1 AUTHOR AND CONTACT INFORMATION
602 615

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