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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. |
38 | |
38 | |
39 | If you need some form of RPC, you can either implement it yourself |
39 | If you need some form of RPC, you could use the L<AnyEvent::Fork::RPC> |
40 | in whatever way you like, use some message-passing module such |
40 | companion module, which adds simple RPC/job queueing to a process created |
41 | as L<AnyEvent::MP>, some pipe such as L<AnyEvent::ZeroMQ>, use |
41 | by this module. |
42 | L<AnyEvent::Handle> on both sides to send e.g. JSON or Storable messages, |
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43 | and so on. |
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44 | |
42 | |
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43 | Or you can implement it yourself in whatever way you like, use some |
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44 | message-passing module such as L<AnyEvent::MP>, some pipe such as |
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45 | L<AnyEvent::ZeroMQ>, use L<AnyEvent::Handle> on both sides to send |
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46 | e.g. JSON or Storable messages, and so on. |
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47 | |
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48 | =head2 COMPARISON TO OTHER MODULES |
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49 | |
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50 | There is an abundance of modules on CPAN that do "something fork", such as |
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51 | L<Parallel::ForkManager>, L<AnyEvent::ForkManager>, L<AnyEvent::Worker> |
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52 | or L<AnyEvent::Subprocess>. There are modules that implement their own |
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53 | process management, such as L<AnyEvent::DBI>. |
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54 | |
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55 | The problems that all these modules try to solve are real, however, none |
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56 | of them (from what I have seen) tackle the very real problems of unwanted |
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57 | memory sharing, efficiency, not being able to use event processing or |
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58 | similar modules in the processes they create. |
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59 | |
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60 | This module doesn't try to replace any of them - instead it tries to solve |
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61 | the problem of creating processes with a minimum of fuss and overhead (and |
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62 | also luxury). Ideally, most of these would use AnyEvent::Fork internally, |
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63 | except they were written before AnyEvent:Fork was available, so obviously |
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64 | had to roll their own. |
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65 | |
45 | =head1 PROBLEM STATEMENT |
66 | =head2 PROBLEM STATEMENT |
46 | |
67 | |
47 | There are two traditional ways to implement parallel processing on UNIX |
68 | There are two traditional ways to implement parallel processing on UNIX |
48 | like operating systems - fork and process, and fork+exec and process. They |
69 | like operating systems - fork and process, and fork+exec and process. They |
49 | have different advantages and disadvantages that I describe below, |
70 | have different advantages and disadvantages that I describe below, |
50 | together with how this module tries to mitigate the disadvantages. |
71 | together with how this module tries to mitigate the disadvantages. |
… | |
… | |
203 | } |
224 | } |
204 | } |
225 | } |
205 | |
226 | |
206 | =head2 use AnyEvent::Fork as a faster fork+exec |
227 | =head2 use AnyEvent::Fork as a faster fork+exec |
207 | |
228 | |
208 | This runs C</bin/echo hi>, with stdandard output redirected to /tmp/log |
229 | This runs C</bin/echo hi>, with standard output redirected to F</tmp/log> |
209 | and standard error redirected to the communications socket. It is usually |
230 | and standard error redirected to the communications socket. It is usually |
210 | faster than fork+exec, but still lets you prepare the environment. |
231 | faster than fork+exec, but still lets you prepare the environment. |
211 | |
232 | |
212 | open my $output, ">/tmp/log" or die "$!"; |
233 | open my $output, ">/tmp/log" or die "$!"; |
213 | |
234 | |
214 | AnyEvent::Fork |
235 | AnyEvent::Fork |
215 | ->new |
236 | ->new |
216 | ->eval (' |
237 | ->eval (' |
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238 | # compile a helper function for later use |
217 | sub run { |
239 | sub run { |
218 | my ($fh, $output, @cmd) = @_; |
240 | my ($fh, $output, @cmd) = @_; |
219 | |
241 | |
220 | # perl will clear close-on-exec on STDOUT/STDERR |
242 | # perl will clear close-on-exec on STDOUT/STDERR |
221 | open STDOUT, ">&", $output or die; |
243 | open STDOUT, ">&", $output or die; |
… | |
… | |
351 | use AnyEvent; |
373 | use AnyEvent; |
352 | use AnyEvent::Util (); |
374 | use AnyEvent::Util (); |
353 | |
375 | |
354 | use IO::FDPass; |
376 | use IO::FDPass; |
355 | |
377 | |
356 | our $VERSION = 0.5; |
378 | our $VERSION = 0.6; |
357 | |
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358 | our $PERL; # the path to the perl interpreter, deduces with various forms of magic |
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359 | |
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360 | =over 4 |
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361 | |
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362 | =back |
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363 | |
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364 | =cut |
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365 | |
379 | |
366 | # the early fork template process |
380 | # the early fork template process |
367 | our $EARLY; |
381 | our $EARLY; |
368 | |
382 | |
369 | # the empty template process |
383 | # the empty template process |
370 | our $TEMPLATE; |
384 | our $TEMPLATE; |
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385 | |
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386 | sub QUEUE() { 0 } |
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387 | sub FH() { 1 } |
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388 | sub WW() { 2 } |
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389 | sub PID() { 3 } |
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390 | sub CB() { 4 } |
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391 | |
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392 | sub _new { |
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393 | my ($self, $fh, $pid) = @_; |
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394 | |
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395 | AnyEvent::Util::fh_nonblocking $fh, 1; |
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396 | |
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397 | $self = bless [ |
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398 | [], # write queue - strings or fd's |
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399 | $fh, |
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400 | undef, # AE watcher |
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401 | $pid, |
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402 | ], $self; |
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403 | |
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404 | $self |
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405 | } |
371 | |
406 | |
372 | sub _cmd { |
407 | sub _cmd { |
373 | my $self = shift; |
408 | my $self = shift; |
374 | |
409 | |
375 | # ideally, we would want to use "a (w/a)*" as format string, but perl |
410 | # ideally, we would want to use "a (w/a)*" as format string, but perl |
376 | # versions from at least 5.8.9 to 5.16.3 are all buggy and can't unpack |
411 | # versions from at least 5.8.9 to 5.16.3 are all buggy and can't unpack |
377 | # it. |
412 | # it. |
378 | push @{ $self->[2] }, pack "a L/a*", $_[0], $_[1]; |
413 | push @{ $self->[QUEUE] }, pack "a L/a*", $_[0], $_[1]; |
379 | |
414 | |
380 | $self->[3] ||= AE::io $self->[1], 1, sub { |
415 | $self->[WW] ||= AE::io $self->[FH], 1, sub { |
381 | do { |
416 | do { |
382 | # send the next "thing" in the queue - either a reference to an fh, |
417 | # send the next "thing" in the queue - either a reference to an fh, |
383 | # or a plain string. |
418 | # or a plain string. |
384 | |
419 | |
385 | if (ref $self->[2][0]) { |
420 | if (ref $self->[QUEUE][0]) { |
386 | # send fh |
421 | # send fh |
387 | unless (IO::FDPass::send fileno $self->[1], fileno ${ $self->[2][0] }) { |
422 | unless (IO::FDPass::send fileno $self->[FH], fileno ${ $self->[QUEUE][0] }) { |
388 | return if $! == Errno::EAGAIN || $! == Errno::EWOULDBLOCK; |
423 | return if $! == Errno::EAGAIN || $! == Errno::EWOULDBLOCK; |
389 | undef $self->[3]; |
424 | undef $self->[WW]; |
390 | die "AnyEvent::Fork: file descriptor send failure: $!"; |
425 | die "AnyEvent::Fork: file descriptor send failure: $!"; |
391 | } |
426 | } |
392 | |
427 | |
393 | shift @{ $self->[2] }; |
428 | shift @{ $self->[QUEUE] }; |
394 | |
429 | |
395 | } else { |
430 | } else { |
396 | # send string |
431 | # send string |
397 | my $len = syswrite $self->[1], $self->[2][0]; |
432 | my $len = syswrite $self->[FH], $self->[QUEUE][0]; |
398 | |
433 | |
399 | unless ($len) { |
434 | unless ($len) { |
400 | return if $! == Errno::EAGAIN || $! == Errno::EWOULDBLOCK; |
435 | return if $! == Errno::EAGAIN || $! == Errno::EWOULDBLOCK; |
401 | undef $self->[3]; |
436 | undef $self->[3]; |
402 | die "AnyEvent::Fork: command write failure: $!"; |
437 | die "AnyEvent::Fork: command write failure: $!"; |
403 | } |
438 | } |
404 | |
439 | |
405 | substr $self->[2][0], 0, $len, ""; |
440 | substr $self->[QUEUE][0], 0, $len, ""; |
406 | shift @{ $self->[2] } unless length $self->[2][0]; |
441 | shift @{ $self->[QUEUE] } unless length $self->[QUEUE][0]; |
407 | } |
442 | } |
408 | } while @{ $self->[2] }; |
443 | } while @{ $self->[QUEUE] }; |
409 | |
444 | |
410 | # everything written |
445 | # everything written |
411 | undef $self->[3]; |
446 | undef $self->[WW]; |
412 | |
447 | |
413 | # invoke run callback, if any |
448 | # invoke run callback, if any |
414 | $self->[4]->($self->[1]) if $self->[4]; |
449 | $self->[CB]->($self->[FH]) if $self->[CB]; |
415 | }; |
450 | }; |
416 | |
451 | |
417 | () # make sure we don't leak the watcher |
452 | () # make sure we don't leak the watcher |
418 | } |
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419 | |
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420 | sub _new { |
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421 | my ($self, $fh, $pid) = @_; |
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422 | |
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423 | AnyEvent::Util::fh_nonblocking $fh, 1; |
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424 | |
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425 | $self = bless [ |
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426 | $pid, |
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427 | $fh, |
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428 | [], # write queue - strings or fd's |
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429 | undef, # AE watcher |
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430 | ], $self; |
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431 | |
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432 | $self |
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433 | } |
453 | } |
434 | |
454 | |
435 | # fork template from current process, used by AnyEvent::Fork::Early/Template |
455 | # fork template from current process, used by AnyEvent::Fork::Early/Template |
436 | sub _new_fork { |
456 | sub _new_fork { |
437 | my ($fh, $slave) = AnyEvent::Util::portable_socketpair; |
457 | my ($fh, $slave) = AnyEvent::Util::portable_socketpair; |
… | |
… | |
442 | if ($pid eq 0) { |
462 | if ($pid eq 0) { |
443 | require AnyEvent::Fork::Serve; |
463 | require AnyEvent::Fork::Serve; |
444 | $AnyEvent::Fork::Serve::OWNER = $parent; |
464 | $AnyEvent::Fork::Serve::OWNER = $parent; |
445 | close $fh; |
465 | close $fh; |
446 | $0 = "$_[1] of $parent"; |
466 | $0 = "$_[1] of $parent"; |
447 | $SIG{CHLD} = 'IGNORE'; |
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448 | AnyEvent::Fork::Serve::serve ($slave); |
467 | AnyEvent::Fork::Serve::serve ($slave); |
449 | exit 0; |
468 | exit 0; |
450 | } elsif (!$pid) { |
469 | } elsif (!$pid) { |
451 | die "AnyEvent::Fork::Early/Template: unable to fork template process: $!"; |
470 | die "AnyEvent::Fork::Early/Template: unable to fork template process: $!"; |
452 | } |
471 | } |
… | |
… | |
571 | AnyEvent::Fork itself. |
590 | AnyEvent::Fork itself. |
572 | |
591 | |
573 | =cut |
592 | =cut |
574 | |
593 | |
575 | sub pid { |
594 | sub pid { |
576 | $_[0][0] |
595 | $_[0][PID] |
577 | } |
596 | } |
578 | |
597 | |
579 | =item $proc = $proc->eval ($perlcode, @args) |
598 | =item $proc = $proc->eval ($perlcode, @args) |
580 | |
599 | |
581 | Evaluates the given C<$perlcode> as ... perl code, while setting C<@_> to |
600 | Evaluates the given C<$perlcode> as ... Perl code, while setting C<@_> to |
582 | the strings specified by C<@args>, in the "main" package. |
601 | the strings specified by C<@args>, in the "main" package. |
583 | |
602 | |
584 | This call is meant to do any custom initialisation that might be required |
603 | This call is meant to do any custom initialisation that might be required |
585 | (for example, the C<require> method uses it). It's not supposed to be used |
604 | (for example, the C<require> method uses it). It's not supposed to be used |
586 | to completely take over the process, use C<run> for that. |
605 | to completely take over the process, use C<run> for that. |
… | |
… | |
648 | sub send_fh { |
667 | sub send_fh { |
649 | my ($self, @fh) = @_; |
668 | my ($self, @fh) = @_; |
650 | |
669 | |
651 | for my $fh (@fh) { |
670 | for my $fh (@fh) { |
652 | $self->_cmd ("h"); |
671 | $self->_cmd ("h"); |
653 | push @{ $self->[2] }, \$fh; |
672 | push @{ $self->[QUEUE] }, \$fh; |
654 | } |
673 | } |
655 | |
674 | |
656 | $self |
675 | $self |
657 | } |
676 | } |
658 | |
677 | |
… | |
… | |
744 | =cut |
763 | =cut |
745 | |
764 | |
746 | sub run { |
765 | sub run { |
747 | my ($self, $func, $cb) = @_; |
766 | my ($self, $func, $cb) = @_; |
748 | |
767 | |
749 | $self->[4] = $cb; |
768 | $self->[CB] = $cb; |
750 | $self->_cmd (r => $func); |
769 | $self->_cmd (r => $func); |
751 | } |
770 | } |
752 | |
771 | |
753 | =back |
772 | =back |
754 | |
773 | |
… | |
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782 | So how can C<< AnyEvent->new >> be faster than a standard fork, even |
801 | So how can C<< AnyEvent->new >> be faster than a standard fork, even |
783 | though it uses the same operations, but adds a lot of overhead? |
802 | though it uses the same operations, but adds a lot of overhead? |
784 | |
803 | |
785 | The difference is simply the process size: forking the 5MB process takes |
804 | The difference is simply the process size: forking the 5MB process takes |
786 | so much longer than forking the 2.5MB template process that the extra |
805 | so much longer than forking the 2.5MB template process that the extra |
787 | overhead introduced is canceled out. |
806 | overhead is canceled out. |
788 | |
807 | |
789 | If the benchmark process grows, the normal fork becomes even slower: |
808 | If the benchmark process grows, the normal fork becomes even slower: |
790 | |
809 | |
791 | 1340 new processes, manual fork of a 20MB process |
810 | 1340 new processes, manual fork of a 20MB process |
792 | 731 new processes, manual fork of a 200MB process |
811 | 731 new processes, manual fork of a 200MB process |
… | |
… | |
851 | L<AnyEvent::Fork::Early> or L<AnyEvent::Fork::Template>, or to delay |
870 | L<AnyEvent::Fork::Early> or L<AnyEvent::Fork::Template>, or to delay |
852 | initialising them, for example, by calling C<init Gtk2> manually. |
871 | initialising them, for example, by calling C<init Gtk2> manually. |
853 | |
872 | |
854 | =item exiting calls object destructors |
873 | =item exiting calls object destructors |
855 | |
874 | |
856 | This only applies to users of Lc<AnyEvent::Fork:Early> and |
875 | This only applies to users of L<AnyEvent::Fork:Early> and |
857 | L<AnyEvent::Fork::Template>. |
876 | L<AnyEvent::Fork::Template>, or when initialising code creates objects |
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877 | that reference external resources. |
858 | |
878 | |
859 | When a process created by AnyEvent::Fork exits, it might do so by calling |
879 | 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 |
880 | exit, or simply letting perl reach the end of the program. At which point |
861 | Perl runs all destructors. |
881 | Perl runs all destructors. |
862 | |
882 | |
… | |
… | |
888 | |
908 | |
889 | =head1 SEE ALSO |
909 | =head1 SEE ALSO |
890 | |
910 | |
891 | L<AnyEvent::Fork::Early> (to avoid executing a perl interpreter), |
911 | L<AnyEvent::Fork::Early> (to avoid executing a perl interpreter), |
892 | L<AnyEvent::Fork::Template> (to create a process by forking the main |
912 | L<AnyEvent::Fork::Template> (to create a process by forking the main |
893 | program at a convenient time). |
913 | program at a convenient time), L<AnyEvent::Fork::RPC> (for simple RPC to |
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914 | child processes). |
894 | |
915 | |
895 | =head1 AUTHOR |
916 | =head1 AUTHOR AND CONTACT INFORMATION |
896 | |
917 | |
897 | Marc Lehmann <schmorp@schmorp.de> |
918 | Marc Lehmann <schmorp@schmorp.de> |
898 | http://home.schmorp.de/ |
919 | http://software.schmorp.de/pkg/AnyEvent-Fork |
899 | |
920 | |
900 | =cut |
921 | =cut |
901 | |
922 | |
902 | 1 |
923 | 1 |
903 | |
924 | |