… | |
… | |
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 $master_filehandle |
190 | # in the original prorcess. have fun! |
205 | # in the original process. have fun! |
191 | } |
206 | } |
192 | |
207 | |
193 | =head2 Create a pool of server processes all accepting on the same socket. |
208 | =head2 Create a pool of server processes all accepting on the same socket. |
194 | |
209 | |
195 | # create listener socket |
210 | # create listener socket |
… | |
… | |
304 | my ($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 |
… | |
… | |
625 | return $EARLY->fork |
640 | return $EARLY->fork |
626 | if $EARLY; |
641 | if $EARLY; |
627 | |
642 | |
628 | unless (defined $PERL) { |
643 | unless (defined $PERL) { |
629 | # first find path of perl |
644 | # first find path of perl |
630 | my $perl = $; |
645 | my $perl = $^X; |
631 | |
646 | |
632 | # first we try $^X, but the path must be absolute (always on win32), and end in sth. |
647 | # first we try $^X, but the path must be absolute (always on win32), and end in sth. |
633 | # that looks like perl. this obviously only works for posix and win32 |
648 | # that looks like perl. this obviously only works for posix and win32 |
634 | unless ( |
649 | unless ( |
635 | ($^O eq "MSWin32" || $perl =~ m%^/%) |
650 | ($^O eq "MSWin32" || $perl =~ m%^/%) |
… | |
… | |
658 | my %env = %ENV; |
673 | my %env = %ENV; |
659 | $env{PERL5LIB} = join +($^O eq "MSWin32" ? ";" : ":"), grep !ref, @INC; |
674 | $env{PERL5LIB} = join +($^O eq "MSWin32" ? ";" : ":"), grep !ref, @INC; |
660 | |
675 | |
661 | my $pid = Proc::FastSpawn::spawn ( |
676 | my $pid = Proc::FastSpawn::spawn ( |
662 | $PERL, |
677 | $PERL, |
663 | ["perl", "-MAnyEvent::Fork::Serve", "-e", "AnyEvent::Fork::Serve::me", fileno $slave, $$], |
678 | [$PERL, "-MAnyEvent::Fork::Serve", "-e", "AnyEvent::Fork::Serve::me", fileno $slave, $$], |
664 | [map "$_=$env{$_}", keys %env], |
679 | [map "$_=$env{$_}", keys %env], |
665 | ) or die "unable to spawn AnyEvent::Fork server: $!"; |
680 | ) or die "unable to spawn AnyEvent::Fork server: $!"; |
666 | |
681 | |
667 | $self->_new ($fh, $pid) |
682 | $self->_new ($fh, $pid) |
668 | } |
683 | } |
… | |
… | |
704 | it via C<run>. This also gives you access to any arguments passed via the |
719 | it via C<run>. This also gives you access to any arguments passed via the |
705 | 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 |
706 | a faster fork+exec> example to see it in action. |
721 | a faster fork+exec> example to see it in action. |
707 | |
722 | |
708 | Returns the process object for easy chaining of method calls. |
723 | Returns the process object for easy chaining of method calls. |
|
|
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, $string2); |
709 | |
730 | |
710 | =cut |
731 | =cut |
711 | |
732 | |
712 | sub eval { |
733 | sub eval { |
713 | my ($self, $code, @args) = @_; |
734 | my ($self, $code, @args) = @_; |
… | |
… | |
1080 | 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 |
1081 | 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 |
1082 | 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 |
1083 | work though. |
1104 | work though. |
1084 | |
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 | |
1085 | =head1 SEE ALSO |
1123 | =head1 SEE ALSO |
1086 | |
1124 | |
1087 | 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 |
1088 | (part of this distribution). |
1126 | (part of this distribution). |
1089 | |
1127 | |