… | |
… | |
4 | |
4 | |
5 | =head1 SYNOPSIS |
5 | =head1 SYNOPSIS |
6 | |
6 | |
7 | use AnyEvent::Fork; |
7 | use AnyEvent::Fork; |
8 | |
8 | |
9 | ################################################################## |
9 | AnyEvent::Fork |
|
|
10 | ->new |
|
|
11 | ->require ("MyModule") |
|
|
12 | ->run ("MyModule::server", my $cv = AE::cv); |
|
|
13 | |
|
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14 | my $fh = $cv->recv; |
|
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15 | |
|
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16 | =head1 DESCRIPTION |
|
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17 | |
|
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18 | This module allows you to create new processes, without actually forking |
|
|
19 | them from your current process (avoiding the problems of forking), but |
|
|
20 | preserving most of the advantages of fork. |
|
|
21 | |
|
|
22 | It can be used to create new worker processes or new independent |
|
|
23 | subprocesses for short- and long-running jobs, process pools (e.g. for use |
|
|
24 | in pre-forked servers) but also to spawn new external processes (such as |
|
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25 | CGI scripts from a web server), which can be faster (and more well behaved) |
|
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26 | than using fork+exec in big processes. |
|
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27 | |
|
|
28 | Special care has been taken to make this module useful from other modules, |
|
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29 | while still supporting specialised environments such as L<App::Staticperl> |
|
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30 | or L<PAR::Packer>. |
|
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31 | |
|
|
32 | =head1 WHAT THIS MODULE IS NOT |
|
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33 | |
|
|
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 - |
|
|
36 | there is no back channel from the process back to you, and there is no RPC |
|
|
37 | or message passing going on. |
|
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38 | |
|
|
39 | If you need some form of RPC, you can either implement it yourself |
|
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40 | in whatever way you like, use some message-passing module such |
|
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41 | as L<AnyEvent::MP>, some pipe such as L<AnyEvent::ZeroMQ>, use |
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42 | L<AnyEvent::Handle> on both sides to send e.g. JSON or Storable messages, |
|
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43 | and so on. |
|
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44 | |
|
|
45 | =head1 PROBLEM STATEMENT |
|
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46 | |
|
|
47 | There are two traditional ways to implement parallel processing on UNIX |
|
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48 | like operating systems - fork and process, and fork+exec and process. They |
|
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49 | have different advantages and disadvantages that I describe below, |
|
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50 | together with how this module tries to mitigate the disadvantages. |
|
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51 | |
|
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52 | =over 4 |
|
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53 | |
|
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54 | =item Forking from a big process can be very slow. |
|
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55 | |
|
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56 | A 5GB process needs 0.05s to fork on my 3.6GHz amd64 GNU/Linux box. This |
|
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57 | overhead is often shared with exec (because you have to fork first), but |
|
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58 | in some circumstances (e.g. when vfork is used), fork+exec can be much |
|
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59 | faster. |
|
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60 | |
|
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61 | This module can help here by telling a small(er) helper process to fork, |
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62 | which is faster then forking the main process, and also uses vfork where |
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63 | possible. This gives the speed of vfork, with the flexibility of fork. |
|
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64 | |
|
|
65 | =item Forking usually creates a copy-on-write copy of the parent |
|
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66 | process. |
|
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67 | |
|
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68 | For example, modules or data files that are loaded will not use additional |
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69 | memory after a fork. When exec'ing a new process, modules and data files |
|
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70 | might need to be loaded again, at extra CPU and memory cost. But when |
|
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71 | forking, literally all data structures are copied - if the program frees |
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72 | them and replaces them by new data, the child processes will retain the |
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73 | old version even if it isn't used, which can suddenly and unexpectedly |
|
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74 | increase memory usage when freeing memory. |
|
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75 | |
|
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76 | The trade-off is between more sharing with fork (which can be good or |
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77 | bad), and no sharing with exec. |
|
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78 | |
|
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79 | This module allows the main program to do a controlled fork, and allows |
|
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80 | modules to exec processes safely at any time. When creating a custom |
|
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81 | process pool you can take advantage of data sharing via fork without |
|
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82 | risking to share large dynamic data structures that will blow up child |
|
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83 | memory usage. |
|
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84 | |
|
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85 | In other words, this module puts you into control over what is being |
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86 | shared and what isn't, at all times. |
|
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87 | |
|
|
88 | =item Exec'ing a new perl process might be difficult. |
|
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89 | |
|
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90 | For example, it is not easy to find the correct path to the perl |
|
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91 | interpreter - C<$^X> might not be a perl interpreter at all. |
|
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92 | |
|
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93 | This module tries hard to identify the correct path to the perl |
|
|
94 | interpreter. With a cooperative main program, exec'ing the interpreter |
|
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95 | might not even be necessary, but even without help from the main program, |
|
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96 | it will still work when used from a module. |
|
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97 | |
|
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98 | =item Exec'ing a new perl process might be slow, as all necessary modules |
|
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99 | have to be loaded from disk again, with no guarantees of success. |
|
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100 | |
|
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101 | Long running processes might run into problems when perl is upgraded |
|
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102 | and modules are no longer loadable because they refer to a different |
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103 | perl version, or parts of a distribution are newer than the ones already |
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104 | loaded. |
|
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105 | |
|
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106 | This module supports creating pre-initialised perl processes to be used as |
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107 | a template for new processes. |
|
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108 | |
|
|
109 | =item Forking might be impossible when a program is running. |
|
|
110 | |
|
|
111 | For example, POSIX makes it almost impossible to fork from a |
|
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112 | multi-threaded program while doing anything useful in the child - in |
|
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113 | fact, if your perl program uses POSIX threads (even indirectly via |
|
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114 | e.g. L<IO::AIO> or L<threads>), you cannot call fork on the perl level |
|
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115 | anymore without risking corruption issues on a number of operating |
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116 | systems. |
|
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117 | |
|
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118 | This module can safely fork helper processes at any time, by calling |
|
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119 | fork+exec in C, in a POSIX-compatible way (via L<Proc::FastSpawn>). |
|
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120 | |
|
|
121 | =item Parallel processing with fork might be inconvenient or difficult |
|
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122 | to implement. Modules might not work in both parent and child. |
|
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123 | |
|
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124 | For example, when a program uses an event loop and creates watchers it |
|
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125 | becomes very hard to use the event loop from a child program, as the |
|
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126 | watchers already exist but are only meaningful in the parent. Worse, a |
|
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127 | module might want to use such a module, not knowing whether another module |
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128 | or the main program also does, leading to problems. |
|
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129 | |
|
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130 | Apart from event loops, graphical toolkits also commonly fall into the |
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131 | "unsafe module" category, or just about anything that communicates with |
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132 | the external world, such as network libraries and file I/O modules, which |
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133 | usually don't like being copied and then allowed to continue in two |
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134 | processes. |
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135 | |
|
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136 | With this module only the main program is allowed to create new processes |
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137 | by forking (because only the main program can know when it is still safe |
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138 | to do so) - all other processes are created via fork+exec, which makes it |
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139 | possible to use modules such as event loops or window interfaces safely. |
|
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140 | |
|
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141 | =back |
|
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142 | |
|
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143 | =head1 EXAMPLES |
|
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144 | |
10 | # create a single new process, tell it to run your worker function |
145 | =head2 Create a single new process, tell it to run your worker function. |
11 | |
146 | |
12 | AnyEvent::Fork |
147 | AnyEvent::Fork |
13 | ->new |
148 | ->new |
14 | ->require ("MyModule") |
149 | ->require ("MyModule") |
15 | ->run ("MyModule::worker, sub { |
150 | ->run ("MyModule::worker, sub { |
… | |
… | |
17 | |
152 | |
18 | # now $master_filehandle is connected to the |
153 | # now $master_filehandle is connected to the |
19 | # $slave_filehandle in the new process. |
154 | # $slave_filehandle in the new process. |
20 | }); |
155 | }); |
21 | |
156 | |
22 | # MyModule::worker might look like this |
157 | C<MyModule> might look like this: |
|
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158 | |
|
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159 | package MyModule; |
|
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160 | |
23 | sub MyModule::worker { |
161 | sub worker { |
24 | my ($slave_filehandle) = @_; |
162 | my ($slave_filehandle) = @_; |
25 | |
163 | |
26 | # now $slave_filehandle is connected to the $master_filehandle |
164 | # now $slave_filehandle is connected to the $master_filehandle |
27 | # in the original prorcess. have fun! |
165 | # in the original prorcess. have fun! |
28 | } |
166 | } |
29 | |
167 | |
30 | ################################################################## |
|
|
31 | # create a pool of server processes all accepting on the same socket |
168 | =head2 Create a pool of server processes all accepting on the same socket. |
32 | |
169 | |
33 | # create listener socket |
170 | # create listener socket |
34 | my $listener = ...; |
171 | my $listener = ...; |
35 | |
172 | |
36 | # create a pool template, initialise it and give it the socket |
173 | # create a pool template, initialise it and give it the socket |
… | |
… | |
48 | } |
185 | } |
49 | |
186 | |
50 | # now do other things - maybe use the filehandle provided by run |
187 | # now do other things - maybe use the filehandle provided by run |
51 | # to wait for the processes to die. or whatever. |
188 | # to wait for the processes to die. or whatever. |
52 | |
189 | |
53 | # My::Server::run might look like this |
190 | C<My::Server> might look like this: |
54 | sub My::Server::run { |
191 | |
|
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192 | package My::Server; |
|
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193 | |
|
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194 | sub run { |
55 | my ($slave, $listener, $id) = @_; |
195 | my ($slave, $listener, $id) = @_; |
56 | |
196 | |
57 | close $slave; # we do not use the socket, so close it to save resources |
197 | close $slave; # we do not use the socket, so close it to save resources |
58 | |
198 | |
59 | # we could go ballistic and use e.g. AnyEvent here, or IO::AIO, |
199 | # we could go ballistic and use e.g. AnyEvent here, or IO::AIO, |
… | |
… | |
61 | while (my $socket = $listener->accept) { |
201 | while (my $socket = $listener->accept) { |
62 | # do sth. with new socket |
202 | # do sth. with new socket |
63 | } |
203 | } |
64 | } |
204 | } |
65 | |
205 | |
66 | =head1 DESCRIPTION |
206 | =head2 use AnyEvent::Fork as a faster fork+exec |
67 | |
207 | |
68 | This module allows you to create new processes, without actually forking |
208 | This runs C</bin/echo hi>, with stdandard output redirected to /tmp/log |
69 | them from your current process (avoiding the problems of forking), but |
209 | and standard error redirected to the communications socket. It is usually |
70 | preserving most of the advantages of fork. |
210 | faster than fork+exec, but still lets you prepare the environment. |
71 | |
211 | |
72 | It can be used to create new worker processes or new independent |
212 | open my $output, ">/tmp/log" or die "$!"; |
73 | subprocesses for short- and long-running jobs, process pools (e.g. for use |
|
|
74 | in pre-forked servers) but also to spawn new external processes (such as |
|
|
75 | CGI scripts from a web server), which can be faster (and more well behaved) |
|
|
76 | than using fork+exec in big processes. |
|
|
77 | |
213 | |
78 | Special care has been taken to make this module useful from other modules, |
214 | AnyEvent::Fork |
79 | while still supporting specialised environments such as L<App::Staticperl> |
215 | ->new |
80 | or L<PAR::Packer>. |
216 | ->eval (' |
|
|
217 | sub run { |
|
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218 | my ($fh, $output, @cmd) = @_; |
81 | |
219 | |
82 | =head1 WHAT THIS MODULE IS NOT |
220 | # perl will clear close-on-exec on STDOUT/STDERR |
|
|
221 | open STDOUT, ">&", $output or die; |
|
|
222 | open STDERR, ">&", $fh or die; |
83 | |
223 | |
84 | This module only creates processes and lets you pass file handles and |
224 | exec @cmd; |
85 | strings to it, and run perl code. It does not implement any kind of RPC - |
225 | } |
86 | there is no back channel from the process back to you, and there is no RPC |
226 | ') |
87 | or message passing going on. |
227 | ->send_fh ($output) |
|
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228 | ->send_arg ("/bin/echo", "hi") |
|
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229 | ->run ("run", my $cv = AE::cv); |
88 | |
230 | |
89 | If you need some form of RPC, you can either implement it yourself |
231 | my $stderr = $cv->recv; |
90 | in whatever way you like, use some message-passing module such |
|
|
91 | as L<AnyEvent::MP>, some pipe such as L<AnyEvent::ZeroMQ>, use |
|
|
92 | L<AnyEvent::Handle> on both sides to send e.g. JSON or Storable messages, |
|
|
93 | and so on. |
|
|
94 | |
|
|
95 | =head1 PROBLEM STATEMENT |
|
|
96 | |
|
|
97 | There are two ways to implement parallel processing on UNIX like operating |
|
|
98 | systems - fork and process, and fork+exec and process. They have different |
|
|
99 | advantages and disadvantages that I describe below, together with how this |
|
|
100 | module tries to mitigate the disadvantages. |
|
|
101 | |
|
|
102 | =over 4 |
|
|
103 | |
|
|
104 | =item Forking from a big process can be very slow (a 5GB process needs |
|
|
105 | 0.05s to fork on my 3.6GHz amd64 GNU/Linux box for example). This overhead |
|
|
106 | is often shared with exec (because you have to fork first), but in some |
|
|
107 | circumstances (e.g. when vfork is used), fork+exec can be much faster. |
|
|
108 | |
|
|
109 | This module can help here by telling a small(er) helper process to fork, |
|
|
110 | or fork+exec instead. |
|
|
111 | |
|
|
112 | =item Forking usually creates a copy-on-write copy of the parent |
|
|
113 | process. Memory (for example, modules or data files that have been |
|
|
114 | will not take additional memory). When exec'ing a new process, modules |
|
|
115 | and data files might need to be loaded again, at extra CPU and memory |
|
|
116 | cost. Likewise when forking, all data structures are copied as well - if |
|
|
117 | the program frees them and replaces them by new data, the child processes |
|
|
118 | will retain the memory even if it isn't used. |
|
|
119 | |
|
|
120 | This module allows the main program to do a controlled fork, and allows |
|
|
121 | modules to exec processes safely at any time. When creating a custom |
|
|
122 | process pool you can take advantage of data sharing via fork without |
|
|
123 | risking to share large dynamic data structures that will blow up child |
|
|
124 | memory usage. |
|
|
125 | |
|
|
126 | =item Exec'ing a new perl process might be difficult and slow. For |
|
|
127 | example, it is not easy to find the correct path to the perl interpreter, |
|
|
128 | and all modules have to be loaded from disk again. Long running processes |
|
|
129 | might run into problems when perl is upgraded for example. |
|
|
130 | |
|
|
131 | This module supports creating pre-initialised perl processes to be used |
|
|
132 | as template, and also tries hard to identify the correct path to the perl |
|
|
133 | interpreter. With a cooperative main program, exec'ing the interpreter |
|
|
134 | might not even be necessary. |
|
|
135 | |
|
|
136 | =item Forking might be impossible when a program is running. For example, |
|
|
137 | POSIX makes it almost impossible to fork from a multi-threaded program and |
|
|
138 | do anything useful in the child - strictly speaking, if your perl program |
|
|
139 | uses posix threads (even indirectly via e.g. L<IO::AIO> or L<threads>), |
|
|
140 | you cannot call fork on the perl level anymore, at all. |
|
|
141 | |
|
|
142 | This module can safely fork helper processes at any time, by calling |
|
|
143 | fork+exec in C, in a POSIX-compatible way. |
|
|
144 | |
|
|
145 | =item Parallel processing with fork might be inconvenient or difficult |
|
|
146 | to implement. For example, when a program uses an event loop and creates |
|
|
147 | watchers it becomes very hard to use the event loop from a child |
|
|
148 | program, as the watchers already exist but are only meaningful in the |
|
|
149 | parent. Worse, a module might want to use such a system, not knowing |
|
|
150 | whether another module or the main program also does, leading to problems. |
|
|
151 | |
|
|
152 | This module only lets the main program create pools by forking (because |
|
|
153 | only the main program can know when it is still safe to do so) - all other |
|
|
154 | pools are created by fork+exec, after which such modules can again be |
|
|
155 | loaded. |
|
|
156 | |
|
|
157 | =back |
|
|
158 | |
232 | |
159 | =head1 CONCEPTS |
233 | =head1 CONCEPTS |
160 | |
234 | |
161 | This module can create new processes either by executing a new perl |
235 | This module can create new processes either by executing a new perl |
162 | process, or by forking from an existing "template" process. |
236 | process, or by forking from an existing "template" process. |
… | |
… | |
241 | my ($fork_fh) = @_; |
315 | my ($fork_fh) = @_; |
242 | }); |
316 | }); |
243 | |
317 | |
244 | =back |
318 | =back |
245 | |
319 | |
246 | =head1 FUNCTIONS |
320 | =head1 THE C<AnyEvent::Fork> CLASS |
|
|
321 | |
|
|
322 | This module exports nothing, and only implements a single class - |
|
|
323 | C<AnyEvent::Fork>. |
|
|
324 | |
|
|
325 | There are two class constructors that both create new processes - C<new> |
|
|
326 | and C<new_exec>. The C<fork> method creates a new process by forking an |
|
|
327 | existing one and could be considered a third constructor. |
|
|
328 | |
|
|
329 | Most of the remaining methods deal with preparing the new process, by |
|
|
330 | loading code, evaluating code and sending data to the new process. They |
|
|
331 | usually return the process object, so you can chain method calls. |
|
|
332 | |
|
|
333 | If a process object is destroyed before calling its C<run> method, then |
|
|
334 | the process simply exits. After C<run> is called, all responsibility is |
|
|
335 | passed to the specified function. |
|
|
336 | |
|
|
337 | As long as there is any outstanding work to be done, process objects |
|
|
338 | resist being destroyed, so there is no reason to store them unless you |
|
|
339 | need them later - configure and forget works just fine. |
247 | |
340 | |
248 | =over 4 |
341 | =over 4 |
249 | |
342 | |
250 | =cut |
343 | =cut |
251 | |
344 | |
… | |
… | |
258 | use AnyEvent; |
351 | use AnyEvent; |
259 | use AnyEvent::Util (); |
352 | use AnyEvent::Util (); |
260 | |
353 | |
261 | use IO::FDPass; |
354 | use IO::FDPass; |
262 | |
355 | |
263 | our $VERSION = 0.2; |
356 | our $VERSION = 0.5; |
264 | |
357 | |
265 | our $PERL; # the path to the perl interpreter, deduces with various forms of magic |
358 | our $PERL; # the path to the perl interpreter, deduces with various forms of magic |
266 | |
|
|
267 | =item my $pool = new AnyEvent::Fork key => value... |
|
|
268 | |
|
|
269 | Create a new process pool. The following named parameters are supported: |
|
|
270 | |
359 | |
271 | =over 4 |
360 | =over 4 |
272 | |
361 | |
273 | =back |
362 | =back |
274 | |
363 | |
… | |
… | |
320 | |
409 | |
321 | # everything written |
410 | # everything written |
322 | undef $self->[3]; |
411 | undef $self->[3]; |
323 | |
412 | |
324 | # invoke run callback, if any |
413 | # invoke run callback, if any |
325 | $self->[0]->($self->[1]) if $self->[0]; |
414 | $self->[4]->($self->[1]) if $self->[4]; |
326 | }; |
415 | }; |
327 | |
416 | |
328 | () # make sure we don't leak the watcher |
417 | () # make sure we don't leak the watcher |
329 | } |
418 | } |
330 | |
419 | |
… | |
… | |
332 | my ($self, $fh, $pid) = @_; |
421 | my ($self, $fh, $pid) = @_; |
333 | |
422 | |
334 | AnyEvent::Util::fh_nonblocking $fh, 1; |
423 | AnyEvent::Util::fh_nonblocking $fh, 1; |
335 | |
424 | |
336 | $self = bless [ |
425 | $self = bless [ |
337 | undef, # run callback |
426 | $pid, |
338 | $fh, |
427 | $fh, |
339 | [], # write queue - strings or fd's |
428 | [], # write queue - strings or fd's |
340 | undef, # AE watcher |
429 | undef, # AE watcher |
341 | $pid, |
|
|
342 | ], $self; |
430 | ], $self; |
343 | |
431 | |
344 | $self |
432 | $self |
345 | } |
433 | } |
346 | |
434 | |
… | |
… | |
371 | Create a new "empty" perl interpreter process and returns its process |
459 | Create a new "empty" perl interpreter process and returns its process |
372 | object for further manipulation. |
460 | object for further manipulation. |
373 | |
461 | |
374 | The new process is forked from a template process that is kept around |
462 | The new process is forked from a template process that is kept around |
375 | for this purpose. When it doesn't exist yet, it is created by a call to |
463 | for this purpose. When it doesn't exist yet, it is created by a call to |
376 | C<new_exec> and kept around for future calls. |
464 | C<new_exec> first and then stays around for future calls. |
377 | |
|
|
378 | When the process object is destroyed, it will release the file handle |
|
|
379 | that connects it with the new process. When the new process has not yet |
|
|
380 | called C<run>, then the process will exit. Otherwise, what happens depends |
|
|
381 | entirely on the code that is executed. |
|
|
382 | |
465 | |
383 | =cut |
466 | =cut |
384 | |
467 | |
385 | sub new { |
468 | sub new { |
386 | my $class = shift; |
469 | my $class = shift; |
… | |
… | |
473 | ) or die "unable to spawn AnyEvent::Fork server: $!"; |
556 | ) or die "unable to spawn AnyEvent::Fork server: $!"; |
474 | |
557 | |
475 | $self->_new ($fh, $pid) |
558 | $self->_new ($fh, $pid) |
476 | } |
559 | } |
477 | |
560 | |
|
|
561 | =item $pid = $proc->pid |
|
|
562 | |
|
|
563 | Returns the process id of the process I<iff it is a direct child of the |
|
|
564 | process running AnyEvent::Fork>, and C<undef> otherwise. |
|
|
565 | |
|
|
566 | Normally, only processes created via C<< AnyEvent::Fork->new_exec >> and |
|
|
567 | L<AnyEvent::Fork::Template> are direct children, and you are responsible |
|
|
568 | to clean up their zombies when they die. |
|
|
569 | |
|
|
570 | All other processes are not direct children, and will be cleaned up by |
|
|
571 | AnyEvent::Fork itself. |
|
|
572 | |
|
|
573 | =cut |
|
|
574 | |
|
|
575 | sub pid { |
|
|
576 | $_[0][0] |
|
|
577 | } |
|
|
578 | |
478 | =item $proc = $proc->eval ($perlcode, @args) |
579 | =item $proc = $proc->eval ($perlcode, @args) |
479 | |
580 | |
480 | Evaluates the given C<$perlcode> as ... perl code, while setting C<@_> to |
581 | Evaluates the given C<$perlcode> as ... perl code, while setting C<@_> to |
481 | the strings specified by C<@args>. |
582 | the strings specified by C<@args>, in the "main" package. |
482 | |
583 | |
483 | This call is meant to do any custom initialisation that might be required |
584 | This call is meant to do any custom initialisation that might be required |
484 | (for example, the C<require> method uses it). It's not supposed to be used |
585 | (for example, the C<require> method uses it). It's not supposed to be used |
485 | to completely take over the process, use C<run> for that. |
586 | to completely take over the process, use C<run> for that. |
486 | |
587 | |
487 | The code will usually be executed after this call returns, and there is no |
588 | The code will usually be executed after this call returns, and there is no |
488 | way to pass anything back to the calling process. Any evaluation errors |
589 | way to pass anything back to the calling process. Any evaluation errors |
489 | will be reported to stderr and cause the process to exit. |
590 | will be reported to stderr and cause the process to exit. |
490 | |
591 | |
|
|
592 | If you want to execute some code (that isn't in a module) to take over the |
|
|
593 | process, you should compile a function via C<eval> first, and then call |
|
|
594 | it via C<run>. This also gives you access to any arguments passed via the |
|
|
595 | C<send_xxx> methods, such as file handles. See the L<use AnyEvent::Fork as |
|
|
596 | a faster fork+exec> example to see it in action. |
|
|
597 | |
491 | Returns the process object for easy chaining of method calls. |
598 | Returns the process object for easy chaining of method calls. |
492 | |
599 | |
493 | =cut |
600 | =cut |
494 | |
601 | |
495 | sub eval { |
602 | sub eval { |
… | |
… | |
520 | =item $proc = $proc->send_fh ($handle, ...) |
627 | =item $proc = $proc->send_fh ($handle, ...) |
521 | |
628 | |
522 | Send one or more file handles (I<not> file descriptors) to the process, |
629 | Send one or more file handles (I<not> file descriptors) to the process, |
523 | to prepare a call to C<run>. |
630 | to prepare a call to C<run>. |
524 | |
631 | |
525 | The process object keeps a reference to the handles until this is done, |
632 | The process object keeps a reference to the handles until they have |
526 | so you must not explicitly close the handles. This is most easily |
633 | been passed over to the process, so you must not explicitly close the |
527 | accomplished by simply not storing the file handles anywhere after passing |
634 | handles. This is most easily accomplished by simply not storing the file |
528 | them to this method. |
635 | handles anywhere after passing them to this method - when AnyEvent::Fork |
|
|
636 | is finished using them, perl will automatically close them. |
529 | |
637 | |
530 | Returns the process object for easy chaining of method calls. |
638 | Returns the process object for easy chaining of method calls. |
531 | |
639 | |
532 | Example: pass a file handle to a process, and release it without |
640 | Example: pass a file handle to a process, and release it without |
533 | closing. It will be closed automatically when it is no longer used. |
641 | closing. It will be closed automatically when it is no longer used. |
… | |
… | |
549 | } |
657 | } |
550 | |
658 | |
551 | =item $proc = $proc->send_arg ($string, ...) |
659 | =item $proc = $proc->send_arg ($string, ...) |
552 | |
660 | |
553 | Send one or more argument strings to the process, to prepare a call to |
661 | Send one or more argument strings to the process, to prepare a call to |
554 | C<run>. The strings can be any octet string. |
662 | C<run>. The strings can be any octet strings. |
555 | |
663 | |
556 | The protocol is optimised to pass a moderate number of relatively short |
664 | The protocol is optimised to pass a moderate number of relatively short |
557 | strings - while you can pass up to 4GB of data in one go, this is more |
665 | strings - while you can pass up to 4GB of data in one go, this is more |
558 | meant to pass some ID information or other startup info, not big chunks of |
666 | meant to pass some ID information or other startup info, not big chunks of |
559 | data. |
667 | data. |
… | |
… | |
570 | $self |
678 | $self |
571 | } |
679 | } |
572 | |
680 | |
573 | =item $proc->run ($func, $cb->($fh)) |
681 | =item $proc->run ($func, $cb->($fh)) |
574 | |
682 | |
575 | Enter the function specified by the fully qualified name in C<$func> in |
683 | Enter the function specified by the function name in C<$func> in the |
576 | the process. The function is called with the communication socket as first |
684 | process. The function is called with the communication socket as first |
577 | argument, followed by all file handles and string arguments sent earlier |
685 | argument, followed by all file handles and string arguments sent earlier |
578 | via C<send_fh> and C<send_arg> methods, in the order they were called. |
686 | via C<send_fh> and C<send_arg> methods, in the order they were called. |
579 | |
687 | |
580 | If the called function returns, the process exits. |
|
|
581 | |
|
|
582 | Preparing the process can take time - when the process is ready, the |
|
|
583 | callback is invoked with the local communications socket as argument. |
|
|
584 | |
|
|
585 | The process object becomes unusable on return from this function. |
688 | The process object becomes unusable on return from this function - any |
|
|
689 | further method calls result in undefined behaviour. |
|
|
690 | |
|
|
691 | The function name should be fully qualified, but if it isn't, it will be |
|
|
692 | looked up in the C<main> package. |
|
|
693 | |
|
|
694 | If the called function returns, doesn't exist, or any error occurs, the |
|
|
695 | process exits. |
|
|
696 | |
|
|
697 | Preparing the process is done in the background - when all commands have |
|
|
698 | been sent, the callback is invoked with the local communications socket |
|
|
699 | as argument. At this point you can start using the socket in any way you |
|
|
700 | like. |
586 | |
701 | |
587 | If the communication socket isn't used, it should be closed on both sides, |
702 | If the communication socket isn't used, it should be closed on both sides, |
588 | to save on kernel memory. |
703 | to save on kernel memory. |
589 | |
704 | |
590 | The socket is non-blocking in the parent, and blocking in the newly |
705 | The socket is non-blocking in the parent, and blocking in the newly |
591 | created process. The close-on-exec flag is set on both. Even if not used |
706 | created process. The close-on-exec flag is set in both. |
|
|
707 | |
592 | otherwise, the socket can be a good indicator for the existence of the |
708 | Even if not used otherwise, the socket can be a good indicator for the |
593 | process - if the other process exits, you get a readable event on it, |
709 | existence of the process - if the other process exits, you get a readable |
594 | because exiting the process closes the socket (if it didn't create any |
710 | event on it, because exiting the process closes the socket (if it didn't |
595 | children using fork). |
711 | create any children using fork). |
596 | |
712 | |
597 | Example: create a template for a process pool, pass a few strings, some |
713 | Example: create a template for a process pool, pass a few strings, some |
598 | file handles, then fork, pass one more string, and run some code. |
714 | file handles, then fork, pass one more string, and run some code. |
599 | |
715 | |
600 | my $pool = AnyEvent::Fork |
716 | my $pool = AnyEvent::Fork |
… | |
… | |
608 | ->send_arg ("str3") |
724 | ->send_arg ("str3") |
609 | ->run ("Some::function", sub { |
725 | ->run ("Some::function", sub { |
610 | my ($fh) = @_; |
726 | my ($fh) = @_; |
611 | |
727 | |
612 | # fh is nonblocking, but we trust that the OS can accept these |
728 | # fh is nonblocking, but we trust that the OS can accept these |
613 | # extra 3 octets anyway. |
729 | # few octets anyway. |
614 | syswrite $fh, "hi #$_\n"; |
730 | syswrite $fh, "hi #$_\n"; |
615 | |
731 | |
616 | # $fh is being closed here, as we don't store it anywhere |
732 | # $fh is being closed here, as we don't store it anywhere |
617 | }); |
733 | }); |
618 | } |
734 | } |
… | |
… | |
620 | # Some::function might look like this - all parameters passed before fork |
736 | # Some::function might look like this - all parameters passed before fork |
621 | # and after will be passed, in order, after the communications socket. |
737 | # and after will be passed, in order, after the communications socket. |
622 | sub Some::function { |
738 | sub Some::function { |
623 | my ($fh, $str1, $str2, $fh1, $fh2, $str3) = @_; |
739 | my ($fh, $str1, $str2, $fh1, $fh2, $str3) = @_; |
624 | |
740 | |
625 | print scalar <$fh>; # prints "hi 1\n" and "hi 2\n" |
741 | print scalar <$fh>; # prints "hi #1\n" and "hi #2\n" in any order |
626 | } |
742 | } |
627 | |
743 | |
628 | =cut |
744 | =cut |
629 | |
745 | |
630 | sub run { |
746 | sub run { |
631 | my ($self, $func, $cb) = @_; |
747 | my ($self, $func, $cb) = @_; |
632 | |
748 | |
633 | $self->[0] = $cb; |
749 | $self->[4] = $cb; |
634 | $self->_cmd (r => $func); |
750 | $self->_cmd (r => $func); |
635 | } |
751 | } |
636 | |
752 | |
637 | =back |
753 | =back |
638 | |
754 | |
… | |
… | |
664 | 479 vfork+execs per second, using AnyEvent::Fork->new_exec |
780 | 479 vfork+execs per second, using AnyEvent::Fork->new_exec |
665 | |
781 | |
666 | So how can C<< AnyEvent->new >> be faster than a standard fork, even |
782 | So how can C<< AnyEvent->new >> be faster than a standard fork, even |
667 | though it uses the same operations, but adds a lot of overhead? |
783 | though it uses the same operations, but adds a lot of overhead? |
668 | |
784 | |
669 | The difference is simply the process size: forking the 6MB process takes |
785 | The difference is simply the process size: forking the 5MB process takes |
670 | so much longer than forking the 2.5MB template process that the overhead |
786 | so much longer than forking the 2.5MB template process that the extra |
671 | introduced is canceled out. |
787 | overhead introduced is canceled out. |
672 | |
788 | |
673 | If the benchmark process grows, the normal fork becomes even slower: |
789 | If the benchmark process grows, the normal fork becomes even slower: |
674 | |
790 | |
675 | 1340 new processes, manual fork in a 20MB process |
791 | 1340 new processes, manual fork of a 20MB process |
676 | 731 new processes, manual fork in a 200MB process |
792 | 731 new processes, manual fork of a 200MB process |
677 | 235 new processes, manual fork in a 2000MB process |
793 | 235 new processes, manual fork of a 2000MB process |
678 | |
794 | |
679 | What that means (to me) is that I can use this module without having a |
795 | What that means (to me) is that I can use this module without having a bad |
680 | very bad conscience because of the extra overhead required to start new |
796 | conscience because of the extra overhead required to start new processes. |
681 | processes. |
|
|
682 | |
797 | |
683 | =head1 TYPICAL PROBLEMS |
798 | =head1 TYPICAL PROBLEMS |
684 | |
799 | |
685 | This section lists typical problems that remain. I hope by recognising |
800 | This section lists typical problems that remain. I hope by recognising |
686 | them, most can be avoided. |
801 | them, most can be avoided. |
687 | |
802 | |
688 | =over 4 |
803 | =over 4 |
689 | |
804 | |
690 | =item "leaked" file descriptors for exec'ed processes |
805 | =item leaked file descriptors for exec'ed processes |
691 | |
806 | |
692 | POSIX systems inherit file descriptors by default when exec'ing a new |
807 | POSIX systems inherit file descriptors by default when exec'ing a new |
693 | process. While perl itself laudably sets the close-on-exec flags on new |
808 | process. While perl itself laudably sets the close-on-exec flags on new |
694 | file handles, most C libraries don't care, and even if all cared, it's |
809 | file handles, most C libraries don't care, and even if all cared, it's |
695 | often not possible to set the flag in a race-free manner. |
810 | often not possible to set the flag in a race-free manner. |
… | |
… | |
715 | libraries or the code that leaks those file descriptors. |
830 | libraries or the code that leaks those file descriptors. |
716 | |
831 | |
717 | Fortunately, most of these leaked descriptors do no harm, other than |
832 | Fortunately, most of these leaked descriptors do no harm, other than |
718 | sitting on some resources. |
833 | sitting on some resources. |
719 | |
834 | |
720 | =item "leaked" file descriptors for fork'ed processes |
835 | =item leaked file descriptors for fork'ed processes |
721 | |
836 | |
722 | Normally, L<AnyEvent::Fork> does start new processes by exec'ing them, |
837 | Normally, L<AnyEvent::Fork> does start new processes by exec'ing them, |
723 | which closes file descriptors not marked for being inherited. |
838 | which closes file descriptors not marked for being inherited. |
724 | |
839 | |
725 | However, L<AnyEvent::Fork::Early> and L<AnyEvent::Fork::Template> offer |
840 | However, L<AnyEvent::Fork::Early> and L<AnyEvent::Fork::Template> offer |
… | |
… | |
734 | |
849 | |
735 | The solution is to either not load these modules before use'ing |
850 | The solution is to either not load these modules before use'ing |
736 | L<AnyEvent::Fork::Early> or L<AnyEvent::Fork::Template>, or to delay |
851 | L<AnyEvent::Fork::Early> or L<AnyEvent::Fork::Template>, or to delay |
737 | initialising them, for example, by calling C<init Gtk2> manually. |
852 | initialising them, for example, by calling C<init Gtk2> manually. |
738 | |
853 | |
739 | =item exit runs destructors |
854 | =item exiting calls object destructors |
740 | |
855 | |
741 | This only applies to users of Lc<AnyEvent::Fork:Early> and |
856 | This only applies to users of Lc<AnyEvent::Fork:Early> and |
742 | L<AnyEvent::Fork::Template>. |
857 | L<AnyEvent::Fork::Template>. |
743 | |
858 | |
744 | When a process created by AnyEvent::Fork exits, it might do so by calling |
859 | When a process created by AnyEvent::Fork exits, it might do so by calling |
… | |
… | |
766 | to make it so, mostly due to the bloody broken perl that nobody seems to |
881 | to make it so, mostly due to the bloody broken perl that nobody seems to |
767 | care about. The fork emulation is a bad joke - I have yet to see something |
882 | care about. The fork emulation is a bad joke - I have yet to see something |
768 | useful that you can do with it without running into memory corruption |
883 | useful that you can do with it without running into memory corruption |
769 | issues or other braindamage. Hrrrr. |
884 | issues or other braindamage. Hrrrr. |
770 | |
885 | |
771 | Cygwin perl is not supported at the moment, as it should implement fd |
886 | Cygwin perl is not supported at the moment due to some hilarious |
772 | passing, but doesn't, and rolling my own is hard, as cygwin doesn't |
887 | shortcomings of its API - see L<IO::FDPoll> for more details. |
773 | support enough functionality to do it. |
|
|
774 | |
888 | |
775 | =head1 SEE ALSO |
889 | =head1 SEE ALSO |
776 | |
890 | |
777 | L<AnyEvent::Fork::Early> (to avoid executing a perl interpreter), |
891 | L<AnyEvent::Fork::Early> (to avoid executing a perl interpreter), |
778 | L<AnyEvent::Fork::Template> (to create a process by forking the main |
892 | L<AnyEvent::Fork::Template> (to create a process by forking the main |