… | |
… | |
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, |
42 | |
43 | and so on. |
43 | And if you need some automatic process pool management on top of |
|
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44 | L<AnyEvent::Fork::RPC>, you can look at the L<AnyEvent::Fork::Pool> |
|
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45 | companion module. |
|
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46 | |
|
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47 | Or you can implement it yourself in whatever way you like: use some |
|
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48 | message-passing module such as L<AnyEvent::MP>, some pipe such as |
|
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49 | L<AnyEvent::ZeroMQ>, use L<AnyEvent::Handle> on both sides to send |
|
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50 | e.g. JSON or Storable messages, and so on. |
|
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51 | |
|
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52 | =head2 COMPARISON TO OTHER MODULES |
|
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53 | |
|
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54 | There is an abundance of modules on CPAN that do "something fork", such as |
|
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55 | L<Parallel::ForkManager>, L<AnyEvent::ForkManager>, L<AnyEvent::Worker> |
|
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56 | or L<AnyEvent::Subprocess>. There are modules that implement their own |
|
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57 | process management, such as L<AnyEvent::DBI>. |
|
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58 | |
|
|
59 | The problems that all these modules try to solve are real, however, none |
|
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60 | of them (from what I have seen) tackle the very real problems of unwanted |
|
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61 | memory sharing, efficiency, not being able to use event processing or |
|
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62 | similar modules in the processes they create. |
|
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63 | |
|
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64 | This module doesn't try to replace any of them - instead it tries to solve |
|
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65 | the problem of creating processes with a minimum of fuss and overhead (and |
|
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66 | also luxury). Ideally, most of these would use AnyEvent::Fork internally, |
|
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67 | except they were written before AnyEvent:Fork was available, so obviously |
|
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68 | had to roll their own. |
|
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69 | |
|
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70 | =head2 PROBLEM STATEMENT |
|
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71 | |
|
|
72 | There are two traditional ways to implement parallel processing on UNIX |
|
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73 | like operating systems - fork and process, and fork+exec and process. They |
|
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74 | have different advantages and disadvantages that I describe below, |
|
|
75 | together with how this module tries to mitigate the disadvantages. |
|
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76 | |
|
|
77 | =over 4 |
|
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78 | |
|
|
79 | =item Forking from a big process can be very slow. |
|
|
80 | |
|
|
81 | A 5GB process needs 0.05s to fork on my 3.6GHz amd64 GNU/Linux box. This |
|
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82 | overhead is often shared with exec (because you have to fork first), but |
|
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83 | in some circumstances (e.g. when vfork is used), fork+exec can be much |
|
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84 | faster. |
|
|
85 | |
|
|
86 | This module can help here by telling a small(er) helper process to fork, |
|
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87 | which is faster then forking the main process, and also uses vfork where |
|
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88 | possible. This gives the speed of vfork, with the flexibility of fork. |
|
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89 | |
|
|
90 | =item Forking usually creates a copy-on-write copy of the parent |
|
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91 | process. |
|
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92 | |
|
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93 | For example, modules or data files that are loaded will not use additional |
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94 | memory after a fork. When exec'ing a new process, modules and data files |
|
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95 | might need to be loaded again, at extra CPU and memory cost. But when |
|
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96 | forking, literally all data structures are copied - if the program frees |
|
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97 | them and replaces them by new data, the child processes will retain the |
|
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98 | old version even if it isn't used, which can suddenly and unexpectedly |
|
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99 | increase memory usage when freeing memory. |
|
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100 | |
|
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101 | The trade-off is between more sharing with fork (which can be good or |
|
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102 | bad), and no sharing with exec. |
|
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103 | |
|
|
104 | This module allows the main program to do a controlled fork, and allows |
|
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105 | modules to exec processes safely at any time. When creating a custom |
|
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106 | process pool you can take advantage of data sharing via fork without |
|
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107 | risking to share large dynamic data structures that will blow up child |
|
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108 | memory usage. |
|
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109 | |
|
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110 | In other words, this module puts you into control over what is being |
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111 | shared and what isn't, at all times. |
|
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112 | |
|
|
113 | =item Exec'ing a new perl process might be difficult. |
|
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114 | |
|
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115 | For example, it is not easy to find the correct path to the perl |
|
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116 | interpreter - C<$^X> might not be a perl interpreter at all. |
|
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117 | |
|
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118 | This module tries hard to identify the correct path to the perl |
|
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119 | interpreter. With a cooperative main program, exec'ing the interpreter |
|
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120 | might not even be necessary, but even without help from the main program, |
|
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121 | it will still work when used from a module. |
|
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122 | |
|
|
123 | =item Exec'ing a new perl process might be slow, as all necessary modules |
|
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124 | have to be loaded from disk again, with no guarantees of success. |
|
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125 | |
|
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126 | Long running processes might run into problems when perl is upgraded |
|
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127 | and modules are no longer loadable because they refer to a different |
|
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128 | perl version, or parts of a distribution are newer than the ones already |
|
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129 | loaded. |
|
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130 | |
|
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131 | This module supports creating pre-initialised perl processes to be used as |
|
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132 | a template for new processes. |
|
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133 | |
|
|
134 | =item Forking might be impossible when a program is running. |
|
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135 | |
|
|
136 | For example, POSIX makes it almost impossible to fork from a |
|
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137 | multi-threaded program while doing anything useful in the child - in |
|
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138 | fact, if your perl program uses POSIX threads (even indirectly via |
|
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139 | e.g. L<IO::AIO> or L<threads>), you cannot call fork on the perl level |
|
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140 | anymore without risking corruption issues on a number of operating |
|
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141 | systems. |
|
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142 | |
|
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143 | This module can safely fork helper processes at any time, by calling |
|
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144 | fork+exec in C, in a POSIX-compatible way (via L<Proc::FastSpawn>). |
|
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145 | |
|
|
146 | =item Parallel processing with fork might be inconvenient or difficult |
|
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147 | to implement. Modules might not work in both parent and child. |
|
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148 | |
|
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149 | For example, when a program uses an event loop and creates watchers it |
|
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150 | becomes very hard to use the event loop from a child program, as the |
|
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151 | watchers already exist but are only meaningful in the parent. Worse, a |
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152 | module might want to use such a module, not knowing whether another module |
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153 | or the main program also does, leading to problems. |
|
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154 | |
|
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155 | Apart from event loops, graphical toolkits also commonly fall into the |
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156 | "unsafe module" category, or just about anything that communicates with |
|
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157 | the external world, such as network libraries and file I/O modules, which |
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158 | usually don't like being copied and then allowed to continue in two |
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159 | processes. |
|
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160 | |
|
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161 | With this module only the main program is allowed to create new processes |
|
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162 | by forking (because only the main program can know when it is still safe |
|
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163 | to do so) - all other processes are created via fork+exec, which makes it |
|
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164 | possible to use modules such as event loops or window interfaces safely. |
|
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165 | |
|
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166 | =back |
44 | |
167 | |
45 | =head1 EXAMPLES |
168 | =head1 EXAMPLES |
46 | |
169 | |
47 | =head2 Create a single new process, tell it to run your worker function. |
170 | =head2 Create a single new process, tell it to run your worker function. |
48 | |
171 | |
… | |
… | |
54 | |
177 | |
55 | # now $master_filehandle is connected to the |
178 | # now $master_filehandle is connected to the |
56 | # $slave_filehandle in the new process. |
179 | # $slave_filehandle in the new process. |
57 | }); |
180 | }); |
58 | |
181 | |
59 | # MyModule::worker might look like this |
182 | C<MyModule> might look like this: |
|
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183 | |
|
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184 | package MyModule; |
|
|
185 | |
60 | sub MyModule::worker { |
186 | sub worker { |
61 | my ($slave_filehandle) = @_; |
187 | my ($slave_filehandle) = @_; |
62 | |
188 | |
63 | # now $slave_filehandle is connected to the $master_filehandle |
189 | # now $slave_filehandle is connected to the $master_filehandle |
64 | # in the original prorcess. have fun! |
190 | # in the original prorcess. have fun! |
65 | } |
191 | } |
… | |
… | |
84 | } |
210 | } |
85 | |
211 | |
86 | # now do other things - maybe use the filehandle provided by run |
212 | # now do other things - maybe use the filehandle provided by run |
87 | # to wait for the processes to die. or whatever. |
213 | # to wait for the processes to die. or whatever. |
88 | |
214 | |
89 | # My::Server::run might look like this |
215 | C<My::Server> might look like this: |
90 | sub My::Server::run { |
216 | |
|
|
217 | package My::Server; |
|
|
218 | |
|
|
219 | sub run { |
91 | my ($slave, $listener, $id) = @_; |
220 | my ($slave, $listener, $id) = @_; |
92 | |
221 | |
93 | close $slave; # we do not use the socket, so close it to save resources |
222 | close $slave; # we do not use the socket, so close it to save resources |
94 | |
223 | |
95 | # we could go ballistic and use e.g. AnyEvent here, or IO::AIO, |
224 | # we could go ballistic and use e.g. AnyEvent here, or IO::AIO, |
… | |
… | |
99 | } |
228 | } |
100 | } |
229 | } |
101 | |
230 | |
102 | =head2 use AnyEvent::Fork as a faster fork+exec |
231 | =head2 use AnyEvent::Fork as a faster fork+exec |
103 | |
232 | |
104 | This runs /bin/echo hi, with stdout redirected to /tmp/log and stderr to |
233 | This runs C</bin/echo hi>, with standard output redirected to F</tmp/log> |
105 | the communications socket. It is usually faster than fork+exec, but still |
234 | and standard error redirected to the communications socket. It is usually |
106 | let's you prepare the environment. |
235 | faster than fork+exec, but still lets you prepare the environment. |
107 | |
236 | |
108 | open my $output, ">/tmp/log" or die "$!"; |
237 | open my $output, ">/tmp/log" or die "$!"; |
109 | |
238 | |
110 | AnyEvent::Fork |
239 | AnyEvent::Fork |
111 | ->new |
240 | ->new |
112 | ->eval (' |
241 | ->eval (' |
|
|
242 | # compile a helper function for later use |
113 | sub run { |
243 | sub run { |
114 | my ($fh, $output, @cmd) = @_; |
244 | my ($fh, $output, @cmd) = @_; |
115 | |
245 | |
116 | # perl will clear close-on-exec on STDOUT/STDERR |
246 | # perl will clear close-on-exec on STDOUT/STDERR |
117 | open STDOUT, ">&", $output or die; |
247 | open STDOUT, ">&", $output or die; |
… | |
… | |
124 | ->send_arg ("/bin/echo", "hi") |
254 | ->send_arg ("/bin/echo", "hi") |
125 | ->run ("run", my $cv = AE::cv); |
255 | ->run ("run", my $cv = AE::cv); |
126 | |
256 | |
127 | my $stderr = $cv->recv; |
257 | my $stderr = $cv->recv; |
128 | |
258 | |
129 | =head1 PROBLEM STATEMENT |
259 | =head2 For stingy users: put the worker code into a C<DATA> section. |
130 | |
260 | |
131 | There are two ways to implement parallel processing on UNIX like operating |
261 | When you want to be stingy with files, you cna put your code into the |
132 | systems - fork and process, and fork+exec and process. They have different |
262 | C<DATA> section of your module (or program): |
133 | advantages and disadvantages that I describe below, together with how this |
|
|
134 | module tries to mitigate the disadvantages. |
|
|
135 | |
263 | |
136 | =over 4 |
264 | use AnyEvent::Fork; |
137 | |
265 | |
138 | =item Forking from a big process can be very slow (a 5GB process needs |
266 | AnyEvent::Fork |
139 | 0.05s to fork on my 3.6GHz amd64 GNU/Linux box for example). This overhead |
267 | ->new |
140 | is often shared with exec (because you have to fork first), but in some |
268 | ->eval (do { local $/; <DATA> }) |
141 | circumstances (e.g. when vfork is used), fork+exec can be much faster. |
269 | ->run ("doit", sub { ... }); |
142 | |
270 | |
143 | This module can help here by telling a small(er) helper process to fork, |
271 | __DATA__ |
144 | or fork+exec instead. |
|
|
145 | |
272 | |
146 | =item Forking usually creates a copy-on-write copy of the parent |
273 | sub doit { |
147 | process. Memory (for example, modules or data files that have been |
274 | ... do something! |
148 | will not take additional memory). When exec'ing a new process, modules |
275 | } |
149 | and data files might need to be loaded again, at extra CPU and memory |
|
|
150 | cost. Likewise when forking, all data structures are copied as well - if |
|
|
151 | the program frees them and replaces them by new data, the child processes |
|
|
152 | will retain the memory even if it isn't used. |
|
|
153 | |
276 | |
154 | This module allows the main program to do a controlled fork, and allows |
277 | =head2 For stingy standalone programs: do not rely on external files at |
155 | modules to exec processes safely at any time. When creating a custom |
278 | all. |
156 | process pool you can take advantage of data sharing via fork without |
|
|
157 | risking to share large dynamic data structures that will blow up child |
|
|
158 | memory usage. |
|
|
159 | |
279 | |
160 | =item Exec'ing a new perl process might be difficult and slow. For |
280 | For single-file scripts it can be inconvenient to rely on external |
161 | example, it is not easy to find the correct path to the perl interpreter, |
281 | files - even when using < C<DATA> section, you still need to C<exec> |
162 | and all modules have to be loaded from disk again. Long running processes |
282 | an external perl interpreter, which might not be available when using |
163 | might run into problems when perl is upgraded for example. |
283 | L<App::Staticperl>, L<Urlader> or L<PAR::Packer> for example. |
164 | |
284 | |
165 | This module supports creating pre-initialised perl processes to be used |
285 | Two modules help here - L<AnyEvent::Fork::Early> forks a template process |
166 | as template, and also tries hard to identify the correct path to the perl |
286 | for all further calls to C<new_exec>, and L<AnyEvent::Fork::Template> |
167 | interpreter. With a cooperative main program, exec'ing the interpreter |
287 | forks the main program as a template process. |
168 | might not even be necessary. |
|
|
169 | |
288 | |
170 | =item Forking might be impossible when a program is running. For example, |
289 | Here is how your main program should look like: |
171 | POSIX makes it almost impossible to fork from a multi-threaded program and |
|
|
172 | do anything useful in the child - strictly speaking, if your perl program |
|
|
173 | uses posix threads (even indirectly via e.g. L<IO::AIO> or L<threads>), |
|
|
174 | you cannot call fork on the perl level anymore, at all. |
|
|
175 | |
290 | |
176 | This module can safely fork helper processes at any time, by calling |
291 | #! perl |
177 | fork+exec in C, in a POSIX-compatible way. |
|
|
178 | |
292 | |
179 | =item Parallel processing with fork might be inconvenient or difficult |
293 | # optional, as the very first thing. |
180 | to implement. For example, when a program uses an event loop and creates |
294 | # in case modules want to create their own processes. |
181 | watchers it becomes very hard to use the event loop from a child |
295 | use AnyEvent::Fork::Early; |
182 | program, as the watchers already exist but are only meaningful in the |
|
|
183 | parent. Worse, a module might want to use such a system, not knowing |
|
|
184 | whether another module or the main program also does, leading to problems. |
|
|
185 | |
296 | |
186 | This module only lets the main program create pools by forking (because |
297 | # next, load all modules you need in your template process |
187 | only the main program can know when it is still safe to do so) - all other |
298 | use Example::My::Module |
188 | pools are created by fork+exec, after which such modules can again be |
299 | use Example::Whatever; |
189 | loaded. |
|
|
190 | |
300 | |
191 | =back |
301 | # next, put your run function definition and anything else you |
|
|
302 | # need, but do not use code outside of BEGIN blocks. |
|
|
303 | sub worker_run { |
|
|
304 | my ($fh, @args) = @_; |
|
|
305 | ... |
|
|
306 | } |
|
|
307 | |
|
|
308 | # now preserve everything so far as AnyEvent::Fork object |
|
|
309 | # in §TEMPLATE. |
|
|
310 | use AnyEvent::Fork::Template; |
|
|
311 | |
|
|
312 | # do not put code outside of BEGIN blocks until here |
|
|
313 | |
|
|
314 | # now use the $TEMPLATE process in any way you like |
|
|
315 | |
|
|
316 | # for example: create 10 worker processes |
|
|
317 | my @worker; |
|
|
318 | my $cv = AE::cv; |
|
|
319 | for (1..10) { |
|
|
320 | $cv->begin; |
|
|
321 | $TEMPLATE->fork->send_arg ($_)->run ("worker_run", sub { |
|
|
322 | push @worker, shift; |
|
|
323 | $cv->end; |
|
|
324 | }); |
|
|
325 | } |
|
|
326 | $cv->recv; |
192 | |
327 | |
193 | =head1 CONCEPTS |
328 | =head1 CONCEPTS |
194 | |
329 | |
195 | This module can create new processes either by executing a new perl |
330 | This module can create new processes either by executing a new perl |
196 | process, or by forking from an existing "template" process. |
331 | process, or by forking from an existing "template" process. |
|
|
332 | |
|
|
333 | All these processes are called "child processes" (whether they are direct |
|
|
334 | children or not), while the process that manages them is called the |
|
|
335 | "parent process". |
197 | |
336 | |
198 | Each such process comes with its own file handle that can be used to |
337 | Each such process comes with its own file handle that can be used to |
199 | communicate with it (it's actually a socket - one end in the new process, |
338 | communicate with it (it's actually a socket - one end in the new process, |
200 | one end in the main process), and among the things you can do in it are |
339 | one end in the main process), and among the things you can do in it are |
201 | load modules, fork new processes, send file handles to it, and execute |
340 | load modules, fork new processes, send file handles to it, and execute |
… | |
… | |
275 | my ($fork_fh) = @_; |
414 | my ($fork_fh) = @_; |
276 | }); |
415 | }); |
277 | |
416 | |
278 | =back |
417 | =back |
279 | |
418 | |
280 | =head1 FUNCTIONS |
419 | =head1 THE C<AnyEvent::Fork> CLASS |
|
|
420 | |
|
|
421 | This module exports nothing, and only implements a single class - |
|
|
422 | C<AnyEvent::Fork>. |
|
|
423 | |
|
|
424 | There are two class constructors that both create new processes - C<new> |
|
|
425 | and C<new_exec>. The C<fork> method creates a new process by forking an |
|
|
426 | existing one and could be considered a third constructor. |
|
|
427 | |
|
|
428 | Most of the remaining methods deal with preparing the new process, by |
|
|
429 | loading code, evaluating code and sending data to the new process. They |
|
|
430 | usually return the process object, so you can chain method calls. |
|
|
431 | |
|
|
432 | If a process object is destroyed before calling its C<run> method, then |
|
|
433 | the process simply exits. After C<run> is called, all responsibility is |
|
|
434 | passed to the specified function. |
|
|
435 | |
|
|
436 | As long as there is any outstanding work to be done, process objects |
|
|
437 | resist being destroyed, so there is no reason to store them unless you |
|
|
438 | need them later - configure and forget works just fine. |
281 | |
439 | |
282 | =over 4 |
440 | =over 4 |
283 | |
441 | |
284 | =cut |
442 | =cut |
285 | |
443 | |
… | |
… | |
292 | use AnyEvent; |
450 | use AnyEvent; |
293 | use AnyEvent::Util (); |
451 | use AnyEvent::Util (); |
294 | |
452 | |
295 | use IO::FDPass; |
453 | use IO::FDPass; |
296 | |
454 | |
297 | our $VERSION = 0.5; |
455 | our $VERSION = 1.1; |
298 | |
|
|
299 | our $PERL; # the path to the perl interpreter, deduces with various forms of magic |
|
|
300 | |
|
|
301 | =item my $pool = new AnyEvent::Fork key => value... |
|
|
302 | |
|
|
303 | Create a new process pool. The following named parameters are supported: |
|
|
304 | |
|
|
305 | =over 4 |
|
|
306 | |
|
|
307 | =back |
|
|
308 | |
|
|
309 | =cut |
|
|
310 | |
456 | |
311 | # the early fork template process |
457 | # the early fork template process |
312 | our $EARLY; |
458 | our $EARLY; |
313 | |
459 | |
314 | # the empty template process |
460 | # the empty template process |
315 | our $TEMPLATE; |
461 | our $TEMPLATE; |
|
|
462 | |
|
|
463 | sub QUEUE() { 0 } |
|
|
464 | sub FH() { 1 } |
|
|
465 | sub WW() { 2 } |
|
|
466 | sub PID() { 3 } |
|
|
467 | sub CB() { 4 } |
|
|
468 | |
|
|
469 | sub _new { |
|
|
470 | my ($self, $fh, $pid) = @_; |
|
|
471 | |
|
|
472 | AnyEvent::Util::fh_nonblocking $fh, 1; |
|
|
473 | |
|
|
474 | $self = bless [ |
|
|
475 | [], # write queue - strings or fd's |
|
|
476 | $fh, |
|
|
477 | undef, # AE watcher |
|
|
478 | $pid, |
|
|
479 | ], $self; |
|
|
480 | |
|
|
481 | $self |
|
|
482 | } |
316 | |
483 | |
317 | sub _cmd { |
484 | sub _cmd { |
318 | my $self = shift; |
485 | my $self = shift; |
319 | |
486 | |
320 | # ideally, we would want to use "a (w/a)*" as format string, but perl |
487 | # ideally, we would want to use "a (w/a)*" as format string, but perl |
321 | # versions from at least 5.8.9 to 5.16.3 are all buggy and can't unpack |
488 | # versions from at least 5.8.9 to 5.16.3 are all buggy and can't unpack |
322 | # it. |
489 | # it. |
323 | push @{ $self->[2] }, pack "a L/a*", $_[0], $_[1]; |
490 | push @{ $self->[QUEUE] }, pack "a L/a*", $_[0], $_[1]; |
324 | |
491 | |
325 | $self->[3] ||= AE::io $self->[1], 1, sub { |
492 | $self->[WW] ||= AE::io $self->[FH], 1, sub { |
326 | do { |
493 | do { |
327 | # send the next "thing" in the queue - either a reference to an fh, |
494 | # send the next "thing" in the queue - either a reference to an fh, |
328 | # or a plain string. |
495 | # or a plain string. |
329 | |
496 | |
330 | if (ref $self->[2][0]) { |
497 | if (ref $self->[QUEUE][0]) { |
331 | # send fh |
498 | # send fh |
332 | unless (IO::FDPass::send fileno $self->[1], fileno ${ $self->[2][0] }) { |
499 | unless (IO::FDPass::send fileno $self->[FH], fileno ${ $self->[QUEUE][0] }) { |
333 | return if $! == Errno::EAGAIN || $! == Errno::EWOULDBLOCK; |
500 | return if $! == Errno::EAGAIN || $! == Errno::EWOULDBLOCK; |
334 | undef $self->[3]; |
501 | undef $self->[WW]; |
335 | die "AnyEvent::Fork: file descriptor send failure: $!"; |
502 | die "AnyEvent::Fork: file descriptor send failure: $!"; |
336 | } |
503 | } |
337 | |
504 | |
338 | shift @{ $self->[2] }; |
505 | shift @{ $self->[QUEUE] }; |
339 | |
506 | |
340 | } else { |
507 | } else { |
341 | # send string |
508 | # send string |
342 | my $len = syswrite $self->[1], $self->[2][0]; |
509 | my $len = syswrite $self->[FH], $self->[QUEUE][0]; |
343 | |
510 | |
344 | unless ($len) { |
511 | unless ($len) { |
345 | return if $! == Errno::EAGAIN || $! == Errno::EWOULDBLOCK; |
512 | return if $! == Errno::EAGAIN || $! == Errno::EWOULDBLOCK; |
346 | undef $self->[3]; |
513 | undef $self->[WW]; |
347 | die "AnyEvent::Fork: command write failure: $!"; |
514 | die "AnyEvent::Fork: command write failure: $!"; |
348 | } |
515 | } |
349 | |
516 | |
350 | substr $self->[2][0], 0, $len, ""; |
517 | substr $self->[QUEUE][0], 0, $len, ""; |
351 | shift @{ $self->[2] } unless length $self->[2][0]; |
518 | shift @{ $self->[QUEUE] } unless length $self->[QUEUE][0]; |
352 | } |
519 | } |
353 | } while @{ $self->[2] }; |
520 | } while @{ $self->[QUEUE] }; |
354 | |
521 | |
355 | # everything written |
522 | # everything written |
356 | undef $self->[3]; |
523 | undef $self->[WW]; |
357 | |
524 | |
358 | # invoke run callback, if any |
525 | # invoke run callback, if any |
359 | $self->[4]->($self->[1]) if $self->[4]; |
526 | if ($self->[CB]) { |
|
|
527 | $self->[CB]->($self->[FH]); |
|
|
528 | @$self = (); |
|
|
529 | } |
360 | }; |
530 | }; |
361 | |
531 | |
362 | () # make sure we don't leak the watcher |
532 | () # make sure we don't leak the watcher |
363 | } |
|
|
364 | |
|
|
365 | sub _new { |
|
|
366 | my ($self, $fh, $pid) = @_; |
|
|
367 | |
|
|
368 | AnyEvent::Util::fh_nonblocking $fh, 1; |
|
|
369 | |
|
|
370 | $self = bless [ |
|
|
371 | $pid, |
|
|
372 | $fh, |
|
|
373 | [], # write queue - strings or fd's |
|
|
374 | undef, # AE watcher |
|
|
375 | ], $self; |
|
|
376 | |
|
|
377 | $self |
|
|
378 | } |
533 | } |
379 | |
534 | |
380 | # fork template from current process, used by AnyEvent::Fork::Early/Template |
535 | # fork template from current process, used by AnyEvent::Fork::Early/Template |
381 | sub _new_fork { |
536 | sub _new_fork { |
382 | my ($fh, $slave) = AnyEvent::Util::portable_socketpair; |
537 | my ($fh, $slave) = AnyEvent::Util::portable_socketpair; |
… | |
… | |
387 | if ($pid eq 0) { |
542 | if ($pid eq 0) { |
388 | require AnyEvent::Fork::Serve; |
543 | require AnyEvent::Fork::Serve; |
389 | $AnyEvent::Fork::Serve::OWNER = $parent; |
544 | $AnyEvent::Fork::Serve::OWNER = $parent; |
390 | close $fh; |
545 | close $fh; |
391 | $0 = "$_[1] of $parent"; |
546 | $0 = "$_[1] of $parent"; |
392 | $SIG{CHLD} = 'IGNORE'; |
|
|
393 | AnyEvent::Fork::Serve::serve ($slave); |
547 | AnyEvent::Fork::Serve::serve ($slave); |
394 | exit 0; |
548 | exit 0; |
395 | } elsif (!$pid) { |
549 | } elsif (!$pid) { |
396 | die "AnyEvent::Fork::Early/Template: unable to fork template process: $!"; |
550 | die "AnyEvent::Fork::Early/Template: unable to fork template process: $!"; |
397 | } |
551 | } |
… | |
… | |
404 | Create a new "empty" perl interpreter process and returns its process |
558 | Create a new "empty" perl interpreter process and returns its process |
405 | object for further manipulation. |
559 | object for further manipulation. |
406 | |
560 | |
407 | The new process is forked from a template process that is kept around |
561 | The new process is forked from a template process that is kept around |
408 | for this purpose. When it doesn't exist yet, it is created by a call to |
562 | for this purpose. When it doesn't exist yet, it is created by a call to |
409 | C<new_exec> and kept around for future calls. |
563 | C<new_exec> first and then stays around for future calls. |
410 | |
|
|
411 | When the process object is destroyed, it will release the file handle |
|
|
412 | that connects it with the new process. When the new process has not yet |
|
|
413 | called C<run>, then the process will exit. Otherwise, what happens depends |
|
|
414 | entirely on the code that is executed. |
|
|
415 | |
564 | |
416 | =cut |
565 | =cut |
417 | |
566 | |
418 | sub new { |
567 | sub new { |
419 | my $class = shift; |
568 | my $class = shift; |
… | |
… | |
456 | |
605 | |
457 | You should use C<new> whenever possible, except when having a template |
606 | You should use C<new> whenever possible, except when having a template |
458 | process around is unacceptable. |
607 | process around is unacceptable. |
459 | |
608 | |
460 | The path to the perl interpreter is divined using various methods - first |
609 | The path to the perl interpreter is divined using various methods - first |
461 | C<$^X> is investigated to see if the path ends with something that sounds |
610 | C<$^X> is investigated to see if the path ends with something that looks |
462 | as if it were the perl interpreter. Failing this, the module falls back to |
611 | as if it were the perl interpreter. Failing this, the module falls back to |
463 | using C<$Config::Config{perlpath}>. |
612 | using C<$Config::Config{perlpath}>. |
464 | |
613 | |
|
|
614 | The path to perl can also be overriden by setting the global variable |
|
|
615 | C<$AnyEvent::Fork::PERL> - it's value will be used for all subsequent |
|
|
616 | invocations. |
|
|
617 | |
465 | =cut |
618 | =cut |
|
|
619 | |
|
|
620 | our $PERL; |
466 | |
621 | |
467 | sub new_exec { |
622 | sub new_exec { |
468 | my ($self) = @_; |
623 | my ($self) = @_; |
469 | |
624 | |
470 | return $EARLY->fork |
625 | return $EARLY->fork |
471 | if $EARLY; |
626 | if $EARLY; |
472 | |
627 | |
|
|
628 | unless (defined $PERL) { |
473 | # first find path of perl |
629 | # first find path of perl |
474 | my $perl = $; |
630 | my $perl = $; |
475 | |
631 | |
476 | # first we try $^X, but the path must be absolute (always on win32), and end in sth. |
632 | # first we try $^X, but the path must be absolute (always on win32), and end in sth. |
477 | # that looks like perl. this obviously only works for posix and win32 |
633 | # that looks like perl. this obviously only works for posix and win32 |
478 | unless ( |
634 | unless ( |
479 | ($^O eq "MSWin32" || $perl =~ m%^/%) |
635 | ($^O eq "MSWin32" || $perl =~ m%^/%) |
480 | && $perl =~ m%[/\\]perl(?:[0-9]+(\.[0-9]+)+)?(\.exe)?$%i |
636 | && $perl =~ m%[/\\]perl(?:[0-9]+(\.[0-9]+)+)?(\.exe)?$%i |
481 | ) { |
637 | ) { |
482 | # if it doesn't look perlish enough, try Config |
638 | # if it doesn't look perlish enough, try Config |
483 | require Config; |
639 | require Config; |
484 | $perl = $Config::Config{perlpath}; |
640 | $perl = $Config::Config{perlpath}; |
485 | $perl =~ s/(?:\Q$Config::Config{_exe}\E)?$/$Config::Config{_exe}/; |
641 | $perl =~ s/(?:\Q$Config::Config{_exe}\E)?$/$Config::Config{_exe}/; |
|
|
642 | } |
|
|
643 | |
|
|
644 | $PERL = $perl; |
486 | } |
645 | } |
487 | |
646 | |
488 | require Proc::FastSpawn; |
647 | require Proc::FastSpawn; |
489 | |
648 | |
490 | my ($fh, $slave) = AnyEvent::Util::portable_socketpair; |
649 | my ($fh, $slave) = AnyEvent::Util::portable_socketpair; |
… | |
… | |
498 | #local $ENV{PERL5LIB} = join ":", grep !ref, @INC; |
657 | #local $ENV{PERL5LIB} = join ":", grep !ref, @INC; |
499 | my %env = %ENV; |
658 | my %env = %ENV; |
500 | $env{PERL5LIB} = join +($^O eq "MSWin32" ? ";" : ":"), grep !ref, @INC; |
659 | $env{PERL5LIB} = join +($^O eq "MSWin32" ? ";" : ":"), grep !ref, @INC; |
501 | |
660 | |
502 | my $pid = Proc::FastSpawn::spawn ( |
661 | my $pid = Proc::FastSpawn::spawn ( |
503 | $perl, |
662 | $PERL, |
504 | ["perl", "-MAnyEvent::Fork::Serve", "-e", "AnyEvent::Fork::Serve::me", fileno $slave, $$], |
663 | ["perl", "-MAnyEvent::Fork::Serve", "-e", "AnyEvent::Fork::Serve::me", fileno $slave, $$], |
505 | [map "$_=$env{$_}", keys %env], |
664 | [map "$_=$env{$_}", keys %env], |
506 | ) or die "unable to spawn AnyEvent::Fork server: $!"; |
665 | ) or die "unable to spawn AnyEvent::Fork server: $!"; |
507 | |
666 | |
508 | $self->_new ($fh, $pid) |
667 | $self->_new ($fh, $pid) |
509 | } |
668 | } |
510 | |
669 | |
511 | =item $pid = $proc->pid |
670 | =item $pid = $proc->pid |
512 | |
671 | |
513 | Returns the process id of the process I<iff it is a direct child of the |
672 | Returns the process id of the process I<iff it is a direct child of the |
514 | process> running AnyEvent::Fork, and C<undef> otherwise. |
673 | process running AnyEvent::Fork>, and C<undef> otherwise. As a general |
|
|
674 | rule (that you cannot rely upon), processes created via C<new_exec>, |
|
|
675 | L<AnyEvent::Fork::Early> or L<AnyEvent::Fork::Template> are direct |
|
|
676 | children, while all other processes are not. |
515 | |
677 | |
516 | Normally, only processes created via C<< AnyEvent::Fork->new_exec >> and |
678 | Or in other words, you do not normally have to take care of zombies for |
517 | L<AnyEvent::Fork::Template> are direct children, and you are responsible |
679 | processes created via C<new>, but when in doubt, or zombies are a problem, |
518 | to clean up their zombies when they die. |
680 | you need to check whether a process is a diretc child by calling this |
519 | |
681 | method, and possibly creating a child watcher or reap it manually. |
520 | All other processes are not direct children, and will be cleaned up by |
|
|
521 | AnyEvent::Fork. |
|
|
522 | |
682 | |
523 | =cut |
683 | =cut |
524 | |
684 | |
525 | sub pid { |
685 | sub pid { |
526 | $_[0][0] |
686 | $_[0][PID] |
527 | } |
687 | } |
528 | |
688 | |
529 | =item $proc = $proc->eval ($perlcode, @args) |
689 | =item $proc = $proc->eval ($perlcode, @args) |
530 | |
690 | |
531 | Evaluates the given C<$perlcode> as ... perl code, while setting C<@_> to |
691 | Evaluates the given C<$perlcode> as ... Perl code, while setting C<@_> to |
532 | the strings specified by C<@args>, in the "main" package. |
692 | the strings specified by C<@args>, in the "main" package. |
533 | |
693 | |
534 | This call is meant to do any custom initialisation that might be required |
694 | This call is meant to do any custom initialisation that might be required |
535 | (for example, the C<require> method uses it). It's not supposed to be used |
695 | (for example, the C<require> method uses it). It's not supposed to be used |
536 | to completely take over the process, use C<run> for that. |
696 | to completely take over the process, use C<run> for that. |
537 | |
697 | |
538 | The code will usually be executed after this call returns, and there is no |
698 | The code will usually be executed after this call returns, and there is no |
539 | way to pass anything back to the calling process. Any evaluation errors |
699 | way to pass anything back to the calling process. Any evaluation errors |
540 | will be reported to stderr and cause the process to exit. |
700 | will be reported to stderr and cause the process to exit. |
541 | |
701 | |
542 | If you want to execute some code to take over the process (see the |
702 | If you want to execute some code (that isn't in a module) to take over the |
543 | "fork+exec" example in the SYNOPSIS), you should compile a function via |
703 | process, you should compile a function via C<eval> first, and then call |
544 | C<eval> first, and then call it via C<run>. This also gives you access to |
704 | it via C<run>. This also gives you access to any arguments passed via the |
545 | any arguments passed via the C<send_xxx> methods, such as file handles. |
705 | 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. |
546 | |
707 | |
547 | Returns the process object for easy chaining of method calls. |
708 | Returns the process object for easy chaining of method calls. |
548 | |
709 | |
549 | =cut |
710 | =cut |
550 | |
711 | |
… | |
… | |
576 | =item $proc = $proc->send_fh ($handle, ...) |
737 | =item $proc = $proc->send_fh ($handle, ...) |
577 | |
738 | |
578 | Send one or more file handles (I<not> file descriptors) to the process, |
739 | Send one or more file handles (I<not> file descriptors) to the process, |
579 | to prepare a call to C<run>. |
740 | to prepare a call to C<run>. |
580 | |
741 | |
581 | The process object keeps a reference to the handles until this is done, |
742 | The process object keeps a reference to the handles until they have |
582 | so you must not explicitly close the handles. This is most easily |
743 | been passed over to the process, so you must not explicitly close the |
583 | accomplished by simply not storing the file handles anywhere after passing |
744 | handles. This is most easily accomplished by simply not storing the file |
584 | them to this method. |
745 | handles anywhere after passing them to this method - when AnyEvent::Fork |
|
|
746 | is finished using them, perl will automatically close them. |
585 | |
747 | |
586 | Returns the process object for easy chaining of method calls. |
748 | Returns the process object for easy chaining of method calls. |
587 | |
749 | |
588 | Example: pass a file handle to a process, and release it without |
750 | Example: pass a file handle to a process, and release it without |
589 | closing. It will be closed automatically when it is no longer used. |
751 | closing. It will be closed automatically when it is no longer used. |
… | |
… | |
596 | sub send_fh { |
758 | sub send_fh { |
597 | my ($self, @fh) = @_; |
759 | my ($self, @fh) = @_; |
598 | |
760 | |
599 | for my $fh (@fh) { |
761 | for my $fh (@fh) { |
600 | $self->_cmd ("h"); |
762 | $self->_cmd ("h"); |
601 | push @{ $self->[2] }, \$fh; |
763 | push @{ $self->[QUEUE] }, \$fh; |
602 | } |
764 | } |
603 | |
765 | |
604 | $self |
766 | $self |
605 | } |
767 | } |
606 | |
768 | |
607 | =item $proc = $proc->send_arg ($string, ...) |
769 | =item $proc = $proc->send_arg ($string, ...) |
608 | |
770 | |
609 | Send one or more argument strings to the process, to prepare a call to |
771 | Send one or more argument strings to the process, to prepare a call to |
610 | C<run>. The strings can be any octet string. |
772 | C<run>. The strings can be any octet strings. |
611 | |
773 | |
612 | The protocol is optimised to pass a moderate number of relatively short |
774 | The protocol is optimised to pass a moderate number of relatively short |
613 | strings - while you can pass up to 4GB of data in one go, this is more |
775 | strings - while you can pass up to 4GB of data in one go, this is more |
614 | meant to pass some ID information or other startup info, not big chunks of |
776 | meant to pass some ID information or other startup info, not big chunks of |
615 | data. |
777 | data. |
… | |
… | |
631 | Enter the function specified by the function name in C<$func> in the |
793 | Enter the function specified by the function name in C<$func> in the |
632 | process. The function is called with the communication socket as first |
794 | process. The function is called with the communication socket as first |
633 | argument, followed by all file handles and string arguments sent earlier |
795 | argument, followed by all file handles and string arguments sent earlier |
634 | via C<send_fh> and C<send_arg> methods, in the order they were called. |
796 | via C<send_fh> and C<send_arg> methods, in the order they were called. |
635 | |
797 | |
|
|
798 | The process object becomes unusable on return from this function - any |
|
|
799 | further method calls result in undefined behaviour. |
|
|
800 | |
636 | The function name should be fully qualified, but if it isn't, it will be |
801 | The function name should be fully qualified, but if it isn't, it will be |
637 | looked up in the main package. |
802 | looked up in the C<main> package. |
638 | |
803 | |
639 | If the called function returns, doesn't exist, or any error occurs, the |
804 | If the called function returns, doesn't exist, or any error occurs, the |
640 | process exits. |
805 | process exits. |
641 | |
806 | |
642 | Preparing the process is done in the background - when all commands have |
807 | Preparing the process is done in the background - when all commands have |
643 | been sent, the callback is invoked with the local communications socket |
808 | been sent, the callback is invoked with the local communications socket |
644 | as argument. At this point you can start using the socket in any way you |
809 | as argument. At this point you can start using the socket in any way you |
645 | like. |
810 | like. |
646 | |
811 | |
647 | The process object becomes unusable on return from this function - any |
|
|
648 | further method calls result in undefined behaviour. |
|
|
649 | |
|
|
650 | If the communication socket isn't used, it should be closed on both sides, |
812 | If the communication socket isn't used, it should be closed on both sides, |
651 | to save on kernel memory. |
813 | to save on kernel memory. |
652 | |
814 | |
653 | The socket is non-blocking in the parent, and blocking in the newly |
815 | The socket is non-blocking in the parent, and blocking in the newly |
654 | created process. The close-on-exec flag is set in both. |
816 | created process. The close-on-exec flag is set in both. |
655 | |
817 | |
656 | Even if not used otherwise, the socket can be a good indicator for the |
818 | Even if not used otherwise, the socket can be a good indicator for the |
657 | existence of the process - if the other process exits, you get a readable |
819 | existence of the process - if the other process exits, you get a readable |
658 | event on it, because exiting the process closes the socket (if it didn't |
820 | event on it, because exiting the process closes the socket (if it didn't |
659 | create any children using fork). |
821 | create any children using fork). |
|
|
822 | |
|
|
823 | =over 4 |
|
|
824 | |
|
|
825 | =item Compatibility to L<AnyEvent::Fork::Remote> |
|
|
826 | |
|
|
827 | If you want to write code that works with both this module and |
|
|
828 | L<AnyEvent::Fork::Remote>, you need to write your code so that it assumes |
|
|
829 | there are two file handles for communications, which might not be unix |
|
|
830 | domain sockets. The C<run> function should start like this: |
|
|
831 | |
|
|
832 | sub run { |
|
|
833 | my ($rfh, @args) = @_; # @args is your normal arguments |
|
|
834 | my $wfh = fileno $rfh ? $rfh : *STDOUT; |
|
|
835 | |
|
|
836 | # now use $rfh for reading and $wfh for writing |
|
|
837 | } |
|
|
838 | |
|
|
839 | This checks whether the passed file handle is, in fact, the process |
|
|
840 | C<STDIN> handle. If it is, then the function was invoked visa |
|
|
841 | L<AnyEvent::Fork::Remote>, so STDIN should be used for reading and |
|
|
842 | C<STDOUT> should be used for writing. |
|
|
843 | |
|
|
844 | In all other cases, the function was called via this module, and there is |
|
|
845 | only one file handle that should be sued for reading and writing. |
|
|
846 | |
|
|
847 | =back |
660 | |
848 | |
661 | Example: create a template for a process pool, pass a few strings, some |
849 | Example: create a template for a process pool, pass a few strings, some |
662 | file handles, then fork, pass one more string, and run some code. |
850 | file handles, then fork, pass one more string, and run some code. |
663 | |
851 | |
664 | my $pool = AnyEvent::Fork |
852 | my $pool = AnyEvent::Fork |
… | |
… | |
692 | =cut |
880 | =cut |
693 | |
881 | |
694 | sub run { |
882 | sub run { |
695 | my ($self, $func, $cb) = @_; |
883 | my ($self, $func, $cb) = @_; |
696 | |
884 | |
697 | $self->[4] = $cb; |
885 | $self->[CB] = $cb; |
698 | $self->_cmd (r => $func); |
886 | $self->_cmd (r => $func); |
|
|
887 | } |
|
|
888 | |
|
|
889 | =back |
|
|
890 | |
|
|
891 | =head2 EXPERIMENTAL METHODS |
|
|
892 | |
|
|
893 | These methods might go away completely or change behaviour, at any time. |
|
|
894 | |
|
|
895 | =over 4 |
|
|
896 | |
|
|
897 | =item $proc->to_fh ($cb->($fh)) # EXPERIMENTAL, MIGHT BE REMOVED |
|
|
898 | |
|
|
899 | Flushes all commands out to the process and then calls the callback with |
|
|
900 | the communications socket. |
|
|
901 | |
|
|
902 | The process object becomes unusable on return from this function - any |
|
|
903 | further method calls result in undefined behaviour. |
|
|
904 | |
|
|
905 | The point of this method is to give you a file handle that you can pass |
|
|
906 | to another process. In that other process, you can call C<new_from_fh |
|
|
907 | AnyEvent::Fork $fh> to create a new C<AnyEvent::Fork> object from it, |
|
|
908 | thereby effectively passing a fork object to another process. |
|
|
909 | |
|
|
910 | =cut |
|
|
911 | |
|
|
912 | sub to_fh { |
|
|
913 | my ($self, $cb) = @_; |
|
|
914 | |
|
|
915 | $self->[CB] = $cb; |
|
|
916 | |
|
|
917 | unless ($self->[WW]) { |
|
|
918 | $self->[CB]->($self->[FH]); |
|
|
919 | @$self = (); |
|
|
920 | } |
|
|
921 | } |
|
|
922 | |
|
|
923 | =item new_from_fh AnyEvent::Fork $fh # EXPERIMENTAL, MIGHT BE REMOVED |
|
|
924 | |
|
|
925 | Takes a file handle originally rceeived by the C<to_fh> method and creates |
|
|
926 | a new C<AnyEvent:Fork> object. The child process itself will not change in |
|
|
927 | any way, i.e. it will keep all the modifications done to it before calling |
|
|
928 | C<to_fh>. |
|
|
929 | |
|
|
930 | The new object is very much like the original object, except that the |
|
|
931 | C<pid> method will return C<undef> even if the process is a direct child. |
|
|
932 | |
|
|
933 | =cut |
|
|
934 | |
|
|
935 | sub new_from_fh { |
|
|
936 | my ($class, $fh) = @_; |
|
|
937 | |
|
|
938 | $class->_new ($fh) |
699 | } |
939 | } |
700 | |
940 | |
701 | =back |
941 | =back |
702 | |
942 | |
703 | =head1 PERFORMANCE |
943 | =head1 PERFORMANCE |
… | |
… | |
713 | |
953 | |
714 | 2079 new processes per second, using manual socketpair + fork |
954 | 2079 new processes per second, using manual socketpair + fork |
715 | |
955 | |
716 | Then I did the same thing, but instead of calling fork, I called |
956 | Then I did the same thing, but instead of calling fork, I called |
717 | AnyEvent::Fork->new->run ("CORE::exit") and then again waited for the |
957 | AnyEvent::Fork->new->run ("CORE::exit") and then again waited for the |
718 | socket form the child to close on exit. This does the same thing as manual |
958 | socket from the child to close on exit. This does the same thing as manual |
719 | socket pair + fork, except that what is forked is the template process |
959 | socket pair + fork, except that what is forked is the template process |
720 | (2440kB), and the socket needs to be passed to the server at the other end |
960 | (2440kB), and the socket needs to be passed to the server at the other end |
721 | of the socket first. |
961 | of the socket first. |
722 | |
962 | |
723 | 2307 new processes per second, using AnyEvent::Fork->new |
963 | 2307 new processes per second, using AnyEvent::Fork->new |
… | |
… | |
728 | 479 vfork+execs per second, using AnyEvent::Fork->new_exec |
968 | 479 vfork+execs per second, using AnyEvent::Fork->new_exec |
729 | |
969 | |
730 | So how can C<< AnyEvent->new >> be faster than a standard fork, even |
970 | So how can C<< AnyEvent->new >> be faster than a standard fork, even |
731 | though it uses the same operations, but adds a lot of overhead? |
971 | though it uses the same operations, but adds a lot of overhead? |
732 | |
972 | |
733 | The difference is simply the process size: forking the 6MB process takes |
973 | The difference is simply the process size: forking the 5MB process takes |
734 | so much longer than forking the 2.5MB template process that the overhead |
974 | so much longer than forking the 2.5MB template process that the extra |
735 | introduced is canceled out. |
975 | overhead is canceled out. |
736 | |
976 | |
737 | If the benchmark process grows, the normal fork becomes even slower: |
977 | If the benchmark process grows, the normal fork becomes even slower: |
738 | |
978 | |
739 | 1340 new processes, manual fork in a 20MB process |
979 | 1340 new processes, manual fork of a 20MB process |
740 | 731 new processes, manual fork in a 200MB process |
980 | 731 new processes, manual fork of a 200MB process |
741 | 235 new processes, manual fork in a 2000MB process |
981 | 235 new processes, manual fork of a 2000MB process |
742 | |
982 | |
743 | What that means (to me) is that I can use this module without having a |
983 | What that means (to me) is that I can use this module without having a bad |
744 | very bad conscience because of the extra overhead required to start new |
984 | conscience because of the extra overhead required to start new processes. |
745 | processes. |
|
|
746 | |
985 | |
747 | =head1 TYPICAL PROBLEMS |
986 | =head1 TYPICAL PROBLEMS |
748 | |
987 | |
749 | This section lists typical problems that remain. I hope by recognising |
988 | This section lists typical problems that remain. I hope by recognising |
750 | them, most can be avoided. |
989 | them, most can be avoided. |
751 | |
990 | |
752 | =over 4 |
991 | =over 4 |
753 | |
992 | |
754 | =item "leaked" file descriptors for exec'ed processes |
993 | =item leaked file descriptors for exec'ed processes |
755 | |
994 | |
756 | POSIX systems inherit file descriptors by default when exec'ing a new |
995 | POSIX systems inherit file descriptors by default when exec'ing a new |
757 | process. While perl itself laudably sets the close-on-exec flags on new |
996 | process. While perl itself laudably sets the close-on-exec flags on new |
758 | file handles, most C libraries don't care, and even if all cared, it's |
997 | file handles, most C libraries don't care, and even if all cared, it's |
759 | often not possible to set the flag in a race-free manner. |
998 | often not possible to set the flag in a race-free manner. |
… | |
… | |
779 | libraries or the code that leaks those file descriptors. |
1018 | libraries or the code that leaks those file descriptors. |
780 | |
1019 | |
781 | Fortunately, most of these leaked descriptors do no harm, other than |
1020 | Fortunately, most of these leaked descriptors do no harm, other than |
782 | sitting on some resources. |
1021 | sitting on some resources. |
783 | |
1022 | |
784 | =item "leaked" file descriptors for fork'ed processes |
1023 | =item leaked file descriptors for fork'ed processes |
785 | |
1024 | |
786 | Normally, L<AnyEvent::Fork> does start new processes by exec'ing them, |
1025 | Normally, L<AnyEvent::Fork> does start new processes by exec'ing them, |
787 | which closes file descriptors not marked for being inherited. |
1026 | which closes file descriptors not marked for being inherited. |
788 | |
1027 | |
789 | However, L<AnyEvent::Fork::Early> and L<AnyEvent::Fork::Template> offer |
1028 | However, L<AnyEvent::Fork::Early> and L<AnyEvent::Fork::Template> offer |
… | |
… | |
798 | |
1037 | |
799 | The solution is to either not load these modules before use'ing |
1038 | The solution is to either not load these modules before use'ing |
800 | L<AnyEvent::Fork::Early> or L<AnyEvent::Fork::Template>, or to delay |
1039 | L<AnyEvent::Fork::Early> or L<AnyEvent::Fork::Template>, or to delay |
801 | initialising them, for example, by calling C<init Gtk2> manually. |
1040 | initialising them, for example, by calling C<init Gtk2> manually. |
802 | |
1041 | |
803 | =item exit runs destructors |
1042 | =item exiting calls object destructors |
804 | |
1043 | |
805 | This only applies to users of Lc<AnyEvent::Fork:Early> and |
1044 | This only applies to users of L<AnyEvent::Fork:Early> and |
806 | L<AnyEvent::Fork::Template>. |
1045 | L<AnyEvent::Fork::Template>, or when initialising code creates objects |
|
|
1046 | that reference external resources. |
807 | |
1047 | |
808 | When a process created by AnyEvent::Fork exits, it might do so by calling |
1048 | When a process created by AnyEvent::Fork exits, it might do so by calling |
809 | exit, or simply letting perl reach the end of the program. At which point |
1049 | exit, or simply letting perl reach the end of the program. At which point |
810 | Perl runs all destructors. |
1050 | Perl runs all destructors. |
811 | |
1051 | |
… | |
… | |
830 | to make it so, mostly due to the bloody broken perl that nobody seems to |
1070 | to make it so, mostly due to the bloody broken perl that nobody seems to |
831 | care about. The fork emulation is a bad joke - I have yet to see something |
1071 | care about. The fork emulation is a bad joke - I have yet to see something |
832 | useful that you can do with it without running into memory corruption |
1072 | useful that you can do with it without running into memory corruption |
833 | issues or other braindamage. Hrrrr. |
1073 | issues or other braindamage. Hrrrr. |
834 | |
1074 | |
835 | Cygwin perl is not supported at the moment, as it should implement fd |
1075 | Since fork is endlessly broken on win32 perls (it doesn't even remotely |
836 | passing, but doesn't, and rolling my own is hard, as cygwin doesn't |
1076 | work within it's documented limits) and quite obviously it's not getting |
837 | support enough functionality to do it. |
1077 | improved any time soon, the best way to proceed on windows would be to |
|
|
1078 | always use C<new_exec> and thus never rely on perl's fork "emulation". |
|
|
1079 | |
|
|
1080 | 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 |
|
|
1082 | use C<send_fh> and always use C<new_exec> to create processes, it should |
|
|
1083 | work though. |
838 | |
1084 | |
839 | =head1 SEE ALSO |
1085 | =head1 SEE ALSO |
840 | |
1086 | |
841 | L<AnyEvent::Fork::Early> (to avoid executing a perl interpreter), |
1087 | L<AnyEvent::Fork::Early>, to avoid executing a perl interpreter at all |
|
|
1088 | (part of this distribution). |
|
|
1089 | |
842 | L<AnyEvent::Fork::Template> (to create a process by forking the main |
1090 | L<AnyEvent::Fork::Template>, to create a process by forking the main |
843 | program at a convenient time). |
1091 | program at a convenient time (part of this distribution). |
844 | |
1092 | |
845 | =head1 AUTHOR |
1093 | L<AnyEvent::Fork::Remote>, for another way to create processes that is |
|
|
1094 | mostly compatible to this module and modules building on top of it, but |
|
|
1095 | works better with remote processes. |
|
|
1096 | |
|
|
1097 | L<AnyEvent::Fork::RPC>, for simple RPC to child processes (on CPAN). |
|
|
1098 | |
|
|
1099 | L<AnyEvent::Fork::Pool>, for simple worker process pool (on CPAN). |
|
|
1100 | |
|
|
1101 | =head1 AUTHOR AND CONTACT INFORMATION |
846 | |
1102 | |
847 | Marc Lehmann <schmorp@schmorp.de> |
1103 | Marc Lehmann <schmorp@schmorp.de> |
848 | http://home.schmorp.de/ |
1104 | http://software.schmorp.de/pkg/AnyEvent-Fork |
849 | |
1105 | |
850 | =cut |
1106 | =cut |
851 | |
1107 | |
852 | 1 |
1108 | 1 |
853 | |
1109 | |