… | |
… | |
56 | or L<AnyEvent::Subprocess>. There are modules that implement their own |
56 | or L<AnyEvent::Subprocess>. There are modules that implement their own |
57 | process management, such as L<AnyEvent::DBI>. |
57 | process management, such as L<AnyEvent::DBI>. |
58 | |
58 | |
59 | The problems that all these modules try to solve are real, however, none |
59 | The problems that all these modules try to solve are real, however, none |
60 | of them (from what I have seen) tackle the very real problems of unwanted |
60 | of them (from what I have seen) tackle the very real problems of unwanted |
61 | memory sharing, efficiency, not being able to use event processing or |
61 | memory sharing, efficiency or not being able to use event processing, GUI |
62 | similar modules in the processes they create. |
62 | toolkits or similar modules in the processes they create. |
63 | |
63 | |
64 | This module doesn't try to replace any of them - instead it tries to solve |
64 | This module doesn't try to replace any of them - instead it tries to solve |
65 | the problem of creating processes with a minimum of fuss and overhead (and |
65 | the problem of creating processes with a minimum of fuss and overhead (and |
66 | also luxury). Ideally, most of these would use AnyEvent::Fork internally, |
66 | also luxury). Ideally, most of these would use AnyEvent::Fork internally, |
67 | except they were written before AnyEvent:Fork was available, so obviously |
67 | except they were written before AnyEvent:Fork was available, so obviously |
… | |
… | |
89 | |
89 | |
90 | =item Forking usually creates a copy-on-write copy of the parent |
90 | =item Forking usually creates a copy-on-write copy of the parent |
91 | process. |
91 | process. |
92 | |
92 | |
93 | For example, modules or data files that are loaded will not use additional |
93 | For example, modules or data files that are loaded will not use additional |
94 | memory after a fork. When exec'ing a new process, modules and data files |
94 | memory after a fork. Exec'ing a new process, in contrast, means modules |
95 | might need to be loaded again, at extra CPU and memory cost. But when |
95 | and data files might need to be loaded again, at extra CPU and memory |
96 | forking, literally all data structures are copied - if the program frees |
96 | cost. |
|
|
97 | |
|
|
98 | But when forking, you still create a copy of your data structures - if |
97 | them and replaces them by new data, the child processes will retain the |
99 | the program frees them and replaces them by new data, the child processes |
98 | old version even if it isn't used, which can suddenly and unexpectedly |
100 | will retain the old version even if it isn't used, which can suddenly and |
99 | increase memory usage when freeing memory. |
101 | unexpectedly increase memory usage when freeing memory. |
100 | |
102 | |
|
|
103 | For example, L<Gtk2::CV> is an image viewer optimised for large |
|
|
104 | directories (millions of pictures). It also forks subprocesses for |
|
|
105 | thumbnail generation, which inherit the data structure that stores all |
|
|
106 | file information. If the user changes the directory, it gets freed in |
|
|
107 | the main process, leaving a copy in the thumbnailer processes. This can |
|
|
108 | lead to many times the memory usage that would actually be required. The |
|
|
109 | solution is to fork early (and being unable to dynamically generate more |
|
|
110 | subprocesses or do this from a module)... or to use L<AnyEvent:Fork>. |
|
|
111 | |
101 | The trade-off is between more sharing with fork (which can be good or |
112 | There is a trade-off between more sharing with fork (which can be good or |
102 | bad), and no sharing with exec. |
113 | bad), and no sharing with exec. |
103 | |
114 | |
104 | This module allows the main program to do a controlled fork, and allows |
115 | This module allows the main program to do a controlled fork, and allows |
105 | modules to exec processes safely at any time. When creating a custom |
116 | modules to exec processes safely at any time. When creating a custom |
106 | process pool you can take advantage of data sharing via fork without |
117 | process pool you can take advantage of data sharing via fork without |
… | |
… | |
111 | shared and what isn't, at all times. |
122 | shared and what isn't, at all times. |
112 | |
123 | |
113 | =item Exec'ing a new perl process might be difficult. |
124 | =item Exec'ing a new perl process might be difficult. |
114 | |
125 | |
115 | For example, it is not easy to find the correct path to the perl |
126 | For example, it is not easy to find the correct path to the perl |
116 | interpreter - C<$^X> might not be a perl interpreter at all. |
127 | interpreter - C<$^X> might not be a perl interpreter at all. Worse, there |
|
|
128 | might not even be a perl binary installed on the system. |
117 | |
129 | |
118 | This module tries hard to identify the correct path to the perl |
130 | This module tries hard to identify the correct path to the perl |
119 | interpreter. With a cooperative main program, exec'ing the interpreter |
131 | interpreter. With a cooperative main program, exec'ing the interpreter |
120 | might not even be necessary, but even without help from the main program, |
132 | might not even be necessary, but even without help from the main program, |
121 | it will still work when used from a module. |
133 | it will still work when used from a module. |
… | |
… | |
127 | and modules are no longer loadable because they refer to a different |
139 | and modules are no longer loadable because they refer to a different |
128 | perl version, or parts of a distribution are newer than the ones already |
140 | perl version, or parts of a distribution are newer than the ones already |
129 | loaded. |
141 | loaded. |
130 | |
142 | |
131 | This module supports creating pre-initialised perl processes to be used as |
143 | This module supports creating pre-initialised perl processes to be used as |
132 | a template for new processes. |
144 | a template for new processes at a later time, e.g. for use in a process |
|
|
145 | pool. |
133 | |
146 | |
134 | =item Forking might be impossible when a program is running. |
147 | =item Forking might be impossible when a program is running. |
135 | |
148 | |
136 | For example, POSIX makes it almost impossible to fork from a |
149 | For example, POSIX makes it almost impossible to fork from a |
137 | multi-threaded program while doing anything useful in the child - in |
150 | multi-threaded program while doing anything useful in the child - in |
138 | fact, if your perl program uses POSIX threads (even indirectly via |
151 | fact, if your perl program uses POSIX threads (even indirectly via |
139 | e.g. L<IO::AIO> or L<threads>), you cannot call fork on the perl level |
152 | e.g. L<IO::AIO> or L<threads>), you cannot call fork on the perl level |
140 | anymore without risking corruption issues on a number of operating |
153 | anymore without risking memory corruption or worse on a number of |
141 | systems. |
154 | operating systems. |
142 | |
155 | |
143 | This module can safely fork helper processes at any time, by calling |
156 | This module can safely fork helper processes at any time, by calling |
144 | fork+exec in C, in a POSIX-compatible way (via L<Proc::FastSpawn>). |
157 | fork+exec in C, in a POSIX-compatible way (via L<Proc::FastSpawn>). |
145 | |
158 | |
146 | =item Parallel processing with fork might be inconvenient or difficult |
159 | =item Parallel processing with fork might be inconvenient or difficult |
… | |
… | |
165 | |
178 | |
166 | =back |
179 | =back |
167 | |
180 | |
168 | =head1 EXAMPLES |
181 | =head1 EXAMPLES |
169 | |
182 | |
|
|
183 | This is where the wall of text ends and code speaks. |
|
|
184 | |
170 | =head2 Create a single new process, tell it to run your worker function. |
185 | =head2 Create a single new process, tell it to run your worker function. |
171 | |
186 | |
172 | AnyEvent::Fork |
187 | AnyEvent::Fork |
173 | ->new |
188 | ->new |
174 | ->require ("MyModule") |
189 | ->require ("MyModule") |
… | |
… | |
185 | |
200 | |
186 | sub worker { |
201 | sub worker { |
187 | my ($slave_filehandle) = @_; |
202 | my ($slave_filehandle) = @_; |
188 | |
203 | |
189 | # now $slave_filehandle is connected to the $master_filehandle |
204 | # now $slave_filehandle is connected to the $master_filehandle |
190 | # in the original prorcess. have fun! |
205 | # in the original process. have fun! |
191 | } |
206 | } |
192 | |
207 | |
193 | =head2 Create a pool of server processes all accepting on the same socket. |
208 | =head2 Create a pool of server processes all accepting on the same socket. |
194 | |
209 | |
195 | # create listener socket |
210 | # create listener socket |
… | |
… | |
256 | |
271 | |
257 | my $stderr = $cv->recv; |
272 | my $stderr = $cv->recv; |
258 | |
273 | |
259 | =head2 For stingy users: put the worker code into a C<DATA> section. |
274 | =head2 For stingy users: put the worker code into a C<DATA> section. |
260 | |
275 | |
261 | When you want to be stingy with files, you cna put your code into the |
276 | When you want to be stingy with files, you can put your code into the |
262 | C<DATA> section of your module (or program): |
277 | C<DATA> section of your module (or program): |
263 | |
278 | |
264 | use AnyEvent::Fork; |
279 | use AnyEvent::Fork; |
265 | |
280 | |
266 | AnyEvent::Fork |
281 | AnyEvent::Fork |
… | |
… | |
276 | |
291 | |
277 | =head2 For stingy standalone programs: do not rely on external files at |
292 | =head2 For stingy standalone programs: do not rely on external files at |
278 | all. |
293 | all. |
279 | |
294 | |
280 | For single-file scripts it can be inconvenient to rely on external |
295 | For single-file scripts it can be inconvenient to rely on external |
281 | files - even when using < C<DATA> section, you still need to C<exec> |
296 | files - even when using a C<DATA> section, you still need to C<exec> an |
282 | an external perl interpreter, which might not be available when using |
297 | external perl interpreter, which might not be available when using |
283 | L<App::Staticperl>, L<Urlader> or L<PAR::Packer> for example. |
298 | L<App::Staticperl>, L<Urlader> or L<PAR::Packer> for example. |
284 | |
299 | |
285 | Two modules help here - L<AnyEvent::Fork::Early> forks a template process |
300 | Two modules help here - L<AnyEvent::Fork::Early> forks a template process |
286 | for all further calls to C<new_exec>, and L<AnyEvent::Fork::Template> |
301 | for all further calls to C<new_exec>, and L<AnyEvent::Fork::Template> |
287 | forks the main program as a template process. |
302 | forks the main program as a template process. |
… | |
… | |
304 | my ($fh, @args) = @_; |
319 | my ($fh, @args) = @_; |
305 | ... |
320 | ... |
306 | } |
321 | } |
307 | |
322 | |
308 | # now preserve everything so far as AnyEvent::Fork object |
323 | # now preserve everything so far as AnyEvent::Fork object |
309 | # in ยงTEMPLATE. |
324 | # in $TEMPLATE. |
310 | use AnyEvent::Fork::Template; |
325 | use AnyEvent::Fork::Template; |
311 | |
326 | |
312 | # do not put code outside of BEGIN blocks until here |
327 | # do not put code outside of BEGIN blocks until here |
313 | |
328 | |
314 | # now use the $TEMPLATE process in any way you like |
329 | # now use the $TEMPLATE process in any way you like |
… | |
… | |
450 | use AnyEvent; |
465 | use AnyEvent; |
451 | use AnyEvent::Util (); |
466 | use AnyEvent::Util (); |
452 | |
467 | |
453 | use IO::FDPass; |
468 | use IO::FDPass; |
454 | |
469 | |
455 | our $VERSION = '1.0'; |
470 | our $VERSION = 1.3; |
456 | |
471 | |
457 | # the early fork template process |
472 | # the early fork template process |
458 | our $EARLY; |
473 | our $EARLY; |
459 | |
474 | |
460 | # the empty template process |
475 | # the empty template process |
… | |
… | |
605 | |
620 | |
606 | You should use C<new> whenever possible, except when having a template |
621 | You should use C<new> whenever possible, except when having a template |
607 | process around is unacceptable. |
622 | process around is unacceptable. |
608 | |
623 | |
609 | The path to the perl interpreter is divined using various methods - first |
624 | The path to the perl interpreter is divined using various methods - first |
610 | C<$^X> is investigated to see if the path ends with something that sounds |
625 | C<$^X> is investigated to see if the path ends with something that looks |
611 | as if it were the perl interpreter. Failing this, the module falls back to |
626 | as if it were the perl interpreter. Failing this, the module falls back to |
612 | using C<$Config::Config{perlpath}>. |
627 | using C<$Config::Config{perlpath}>. |
613 | |
628 | |
|
|
629 | The path to perl can also be overriden by setting the global variable |
|
|
630 | C<$AnyEvent::Fork::PERL> - it's value will be used for all subsequent |
|
|
631 | invocations. |
|
|
632 | |
614 | =cut |
633 | =cut |
|
|
634 | |
|
|
635 | our $PERL; |
615 | |
636 | |
616 | sub new_exec { |
637 | sub new_exec { |
617 | my ($self) = @_; |
638 | my ($self) = @_; |
618 | |
639 | |
619 | return $EARLY->fork |
640 | return $EARLY->fork |
620 | if $EARLY; |
641 | if $EARLY; |
621 | |
642 | |
|
|
643 | unless (defined $PERL) { |
622 | # first find path of perl |
644 | # first find path of perl |
623 | my $perl = $; |
645 | my $perl = $^X; |
624 | |
646 | |
625 | # first we try $^X, but the path must be absolute (always on win32), and end in sth. |
647 | # first we try $^X, but the path must be absolute (always on win32), and end in sth. |
626 | # that looks like perl. this obviously only works for posix and win32 |
648 | # that looks like perl. this obviously only works for posix and win32 |
627 | unless ( |
649 | unless ( |
628 | ($^O eq "MSWin32" || $perl =~ m%^/%) |
650 | ($^O eq "MSWin32" || $perl =~ m%^/%) |
629 | && $perl =~ m%[/\\]perl(?:[0-9]+(\.[0-9]+)+)?(\.exe)?$%i |
651 | && $perl =~ m%[/\\]perl(?:[0-9]+(\.[0-9]+)+)?(\.exe)?$%i |
630 | ) { |
652 | ) { |
631 | # if it doesn't look perlish enough, try Config |
653 | # if it doesn't look perlish enough, try Config |
632 | require Config; |
654 | require Config; |
633 | $perl = $Config::Config{perlpath}; |
655 | $perl = $Config::Config{perlpath}; |
634 | $perl =~ s/(?:\Q$Config::Config{_exe}\E)?$/$Config::Config{_exe}/; |
656 | $perl =~ s/(?:\Q$Config::Config{_exe}\E)?$/$Config::Config{_exe}/; |
|
|
657 | } |
|
|
658 | |
|
|
659 | $PERL = $perl; |
635 | } |
660 | } |
636 | |
661 | |
637 | require Proc::FastSpawn; |
662 | require Proc::FastSpawn; |
638 | |
663 | |
639 | my ($fh, $slave) = AnyEvent::Util::portable_socketpair; |
664 | my ($fh, $slave) = AnyEvent::Util::portable_socketpair; |
… | |
… | |
647 | #local $ENV{PERL5LIB} = join ":", grep !ref, @INC; |
672 | #local $ENV{PERL5LIB} = join ":", grep !ref, @INC; |
648 | my %env = %ENV; |
673 | my %env = %ENV; |
649 | $env{PERL5LIB} = join +($^O eq "MSWin32" ? ";" : ":"), grep !ref, @INC; |
674 | $env{PERL5LIB} = join +($^O eq "MSWin32" ? ";" : ":"), grep !ref, @INC; |
650 | |
675 | |
651 | my $pid = Proc::FastSpawn::spawn ( |
676 | my $pid = Proc::FastSpawn::spawn ( |
652 | $perl, |
677 | $PERL, |
653 | ["perl", "-MAnyEvent::Fork::Serve", "-e", "AnyEvent::Fork::Serve::me", fileno $slave, $$], |
678 | [$PERL, "-MAnyEvent::Fork::Serve", "-e", "AnyEvent::Fork::Serve::me", fileno $slave, $$], |
654 | [map "$_=$env{$_}", keys %env], |
679 | [map "$_=$env{$_}", keys %env], |
655 | ) or die "unable to spawn AnyEvent::Fork server: $!"; |
680 | ) or die "unable to spawn AnyEvent::Fork server: $!"; |
656 | |
681 | |
657 | $self->_new ($fh, $pid) |
682 | $self->_new ($fh, $pid) |
658 | } |
683 | } |
659 | |
684 | |
660 | =item $pid = $proc->pid |
685 | =item $pid = $proc->pid |
661 | |
686 | |
662 | Returns the process id of the process I<iff it is a direct child of the |
687 | Returns the process id of the process I<iff it is a direct child of the |
663 | process running AnyEvent::Fork>, and C<undef> otherwise. |
688 | process running AnyEvent::Fork>, and C<undef> otherwise. As a general |
|
|
689 | rule (that you cannot rely upon), processes created via C<new_exec>, |
|
|
690 | L<AnyEvent::Fork::Early> or L<AnyEvent::Fork::Template> are direct |
|
|
691 | children, while all other processes are not. |
664 | |
692 | |
665 | Normally, only processes created via C<< AnyEvent::Fork->new_exec >> and |
693 | Or in other words, you do not normally have to take care of zombies for |
666 | L<AnyEvent::Fork::Template> are direct children, and you are responsible |
694 | processes created via C<new>, but when in doubt, or zombies are a problem, |
667 | to clean up their zombies when they die. |
695 | you need to check whether a process is a diretc child by calling this |
668 | |
696 | method, and possibly creating a child watcher or reap it manually. |
669 | All other processes are not direct children, and will be cleaned up by |
|
|
670 | AnyEvent::Fork itself. |
|
|
671 | |
697 | |
672 | =cut |
698 | =cut |
673 | |
699 | |
674 | sub pid { |
700 | sub pid { |
675 | $_[0][PID] |
701 | $_[0][PID] |
… | |
… | |
694 | C<send_xxx> methods, such as file handles. See the L<use AnyEvent::Fork as |
720 | C<send_xxx> methods, such as file handles. See the L<use AnyEvent::Fork as |
695 | a faster fork+exec> example to see it in action. |
721 | a faster fork+exec> example to see it in action. |
696 | |
722 | |
697 | Returns the process object for easy chaining of method calls. |
723 | Returns the process object for easy chaining of method calls. |
698 | |
724 | |
|
|
725 | It's common to want to call an iniitalisation function with some |
|
|
726 | arguments. Make sure you actually pass C<@_> to that function (for example |
|
|
727 | by using C<&name> syntax), and do not just specify a function name: |
|
|
728 | |
|
|
729 | $proc->eval ('&MyModule::init', $string1, $string2); |
|
|
730 | |
699 | =cut |
731 | =cut |
700 | |
732 | |
701 | sub eval { |
733 | sub eval { |
702 | my ($self, $code, @args) = @_; |
734 | my ($self, $code, @args) = @_; |
703 | |
735 | |
… | |
… | |
806 | |
838 | |
807 | Even if not used otherwise, the socket can be a good indicator for the |
839 | Even if not used otherwise, the socket can be a good indicator for the |
808 | existence of the process - if the other process exits, you get a readable |
840 | existence of the process - if the other process exits, you get a readable |
809 | event on it, because exiting the process closes the socket (if it didn't |
841 | event on it, because exiting the process closes the socket (if it didn't |
810 | create any children using fork). |
842 | create any children using fork). |
|
|
843 | |
|
|
844 | =over 4 |
|
|
845 | |
|
|
846 | =item Compatibility to L<AnyEvent::Fork::Remote> |
|
|
847 | |
|
|
848 | If you want to write code that works with both this module and |
|
|
849 | L<AnyEvent::Fork::Remote>, you need to write your code so that it assumes |
|
|
850 | there are two file handles for communications, which might not be unix |
|
|
851 | domain sockets. The C<run> function should start like this: |
|
|
852 | |
|
|
853 | sub run { |
|
|
854 | my ($rfh, @args) = @_; # @args is your normal arguments |
|
|
855 | my $wfh = fileno $rfh ? $rfh : *STDOUT; |
|
|
856 | |
|
|
857 | # now use $rfh for reading and $wfh for writing |
|
|
858 | } |
|
|
859 | |
|
|
860 | This checks whether the passed file handle is, in fact, the process |
|
|
861 | C<STDIN> handle. If it is, then the function was invoked visa |
|
|
862 | L<AnyEvent::Fork::Remote>, so STDIN should be used for reading and |
|
|
863 | C<STDOUT> should be used for writing. |
|
|
864 | |
|
|
865 | In all other cases, the function was called via this module, and there is |
|
|
866 | only one file handle that should be sued for reading and writing. |
|
|
867 | |
|
|
868 | =back |
811 | |
869 | |
812 | Example: create a template for a process pool, pass a few strings, some |
870 | Example: create a template for a process pool, pass a few strings, some |
813 | file handles, then fork, pass one more string, and run some code. |
871 | file handles, then fork, pass one more string, and run some code. |
814 | |
872 | |
815 | my $pool = AnyEvent::Fork |
873 | my $pool = AnyEvent::Fork |
… | |
… | |
863 | the communications socket. |
921 | the communications socket. |
864 | |
922 | |
865 | The process object becomes unusable on return from this function - any |
923 | The process object becomes unusable on return from this function - any |
866 | further method calls result in undefined behaviour. |
924 | further method calls result in undefined behaviour. |
867 | |
925 | |
868 | The point of this method is to give you a file handle thta you cna pass |
926 | The point of this method is to give you a file handle that you can pass |
869 | to another process. In that other process, you can call C<new_from_fh |
927 | to another process. In that other process, you can call C<new_from_fh |
870 | AnyEvent::Fork> to create a new C<AnyEvent::Fork> object from it, thereby |
928 | AnyEvent::Fork $fh> to create a new C<AnyEvent::Fork> object from it, |
871 | effectively passing a fork object to another process. |
929 | thereby effectively passing a fork object to another process. |
872 | |
930 | |
873 | =cut |
931 | =cut |
874 | |
932 | |
875 | sub to_fh { |
933 | sub to_fh { |
876 | my ($self, $cb) = @_; |
934 | my ($self, $cb) = @_; |
… | |
… | |
1043 | Cygwin perl is not supported at the moment due to some hilarious |
1101 | Cygwin perl is not supported at the moment due to some hilarious |
1044 | shortcomings of its API - see L<IO::FDPoll> for more details. If you never |
1102 | shortcomings of its API - see L<IO::FDPoll> for more details. If you never |
1045 | use C<send_fh> and always use C<new_exec> to create processes, it should |
1103 | use C<send_fh> and always use C<new_exec> to create processes, it should |
1046 | work though. |
1104 | work though. |
1047 | |
1105 | |
|
|
1106 | =head1 USING AnyEvent::Fork IN SUBPROCESSES |
|
|
1107 | |
|
|
1108 | AnyEvent::Fork itself cannot generally be used in subprocesses. As long as |
|
|
1109 | only one process ever forks new processes, sharing the template processes |
|
|
1110 | is possible (you could use a pipe as a lock by writing a byte into it to |
|
|
1111 | unlock, and reading the byte to lock for example) |
|
|
1112 | |
|
|
1113 | To make concurrent calls possible after fork, you should get rid of the |
|
|
1114 | template and early fork processes. AnyEvent::Fork will create a new |
|
|
1115 | template process as needed. |
|
|
1116 | |
|
|
1117 | undef $AnyEvent::Fork::EARLY; |
|
|
1118 | undef $AnyEvent::Fork::TEMPLATE; |
|
|
1119 | |
|
|
1120 | It doesn't matter whether you get rid of them in the parent or child after |
|
|
1121 | a fork. |
|
|
1122 | |
1048 | =head1 SEE ALSO |
1123 | =head1 SEE ALSO |
1049 | |
1124 | |
1050 | L<AnyEvent::Fork::Early>, to avoid executing a perl interpreter at all |
1125 | L<AnyEvent::Fork::Early>, to avoid executing a perl interpreter at all |
1051 | (part of this distribution). |
1126 | (part of this distribution). |
1052 | |
1127 | |
1053 | L<AnyEvent::Fork::Template>, to create a process by forking the main |
1128 | L<AnyEvent::Fork::Template>, to create a process by forking the main |
1054 | program at a convenient time (part of this distribution). |
1129 | program at a convenient time (part of this distribution). |
1055 | |
1130 | |
|
|
1131 | L<AnyEvent::Fork::Remote>, for another way to create processes that is |
|
|
1132 | mostly compatible to this module and modules building on top of it, but |
|
|
1133 | works better with remote processes. |
|
|
1134 | |
1056 | L<AnyEvent::Fork::RPC>, for simple RPC to child processes (on CPAN). |
1135 | L<AnyEvent::Fork::RPC>, for simple RPC to child processes (on CPAN). |
1057 | |
1136 | |
1058 | L<AnyEvent::Fork::Pool>, for simple worker process pool (on CPAN). |
1137 | L<AnyEvent::Fork::Pool>, for simple worker process pool (on CPAN). |
1059 | |
1138 | |
1060 | =head1 AUTHOR AND CONTACT INFORMATION |
1139 | =head1 AUTHOR AND CONTACT INFORMATION |