… | |
… | |
4 | |
4 | |
5 | =head1 SYNOPSIS |
5 | =head1 SYNOPSIS |
6 | |
6 | |
7 | use AnyEvent::Fork; |
7 | use AnyEvent::Fork; |
8 | |
8 | |
9 | ################################################################## |
9 | AnyEvent::Fork |
|
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10 | ->new |
|
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11 | ->require ("MyModule") |
|
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12 | ->run ("MyModule::server", my $cv = AE::cv); |
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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 |
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|
19 | them from your current process (avoiding the problems of forking), but |
|
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20 | preserving most of the advantages of fork. |
|
|
21 | |
|
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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 | |
|
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32 | =head2 WHAT THIS MODULE IS NOT |
|
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33 | |
|
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34 | This module only creates processes and lets you pass file handles and |
|
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35 | strings to it, and run perl code. It does not implement any kind of RPC - |
|
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36 | there is no back channel from the process back to you, and there is no RPC |
|
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37 | or message passing going on. |
|
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38 | |
|
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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 | |
|
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45 | =head2 COMPARISON TO OTHER MODULES |
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46 | |
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47 | There is an abundance of modules on CPAN that do "something fork", such as |
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48 | L<Parallel::ForkManager>, L<AnyEvent::ForkManager>, L<AnyEvent::Worker> |
|
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49 | or L<AnyEvent::Subprocess>. There are modules that implement their own |
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50 | process management, such as L<AnyEvent::DBI>. |
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51 | |
|
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52 | The problems that all these modules try to solve are real, however, none |
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53 | of them (from what I have seen) tackle the very real problems of unwanted |
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54 | memory sharing, efficiency, not being able to use event processing or |
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55 | similar modules in the processes they create. |
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56 | |
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57 | This module doesn't try to replace any of them - instead it tries to solve |
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58 | the problem of creating processes with a minimum of fuss and overhead (and |
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59 | also luxury). Ideally, most of these would use AnyEvent::Fork internally, |
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60 | except they were written before AnyEvent:Fork was available, so obviously |
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61 | had to roll their own. |
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62 | |
|
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63 | =head2 PROBLEM STATEMENT |
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64 | |
|
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65 | There are two traditional ways to implement parallel processing on UNIX |
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66 | like operating systems - fork and process, and fork+exec and process. They |
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67 | have different advantages and disadvantages that I describe below, |
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68 | together with how this module tries to mitigate the disadvantages. |
|
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69 | |
|
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70 | =over 4 |
|
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71 | |
|
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72 | =item Forking from a big process can be very slow. |
|
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73 | |
|
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74 | A 5GB process needs 0.05s to fork on my 3.6GHz amd64 GNU/Linux box. This |
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75 | overhead is often shared with exec (because you have to fork first), but |
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76 | in some circumstances (e.g. when vfork is used), fork+exec can be much |
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77 | faster. |
|
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78 | |
|
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79 | This module can help here by telling a small(er) helper process to fork, |
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80 | which is faster then forking the main process, and also uses vfork where |
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81 | possible. This gives the speed of vfork, with the flexibility of fork. |
|
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82 | |
|
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83 | =item Forking usually creates a copy-on-write copy of the parent |
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84 | process. |
|
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85 | |
|
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86 | For example, modules or data files that are loaded will not use additional |
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87 | memory after a fork. When exec'ing a new process, modules and data files |
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88 | might need to be loaded again, at extra CPU and memory cost. But when |
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89 | forking, literally all data structures are copied - if the program frees |
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90 | them and replaces them by new data, the child processes will retain the |
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91 | old version even if it isn't used, which can suddenly and unexpectedly |
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92 | increase memory usage when freeing memory. |
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93 | |
|
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94 | The trade-off is between more sharing with fork (which can be good or |
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95 | bad), and no sharing with exec. |
|
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96 | |
|
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97 | This module allows the main program to do a controlled fork, and allows |
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98 | modules to exec processes safely at any time. When creating a custom |
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99 | process pool you can take advantage of data sharing via fork without |
|
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100 | risking to share large dynamic data structures that will blow up child |
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101 | memory usage. |
|
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102 | |
|
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103 | In other words, this module puts you into control over what is being |
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104 | shared and what isn't, at all times. |
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105 | |
|
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106 | =item Exec'ing a new perl process might be difficult. |
|
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107 | |
|
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108 | For example, it is not easy to find the correct path to the perl |
|
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109 | interpreter - C<$^X> might not be a perl interpreter at all. |
|
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110 | |
|
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111 | This module tries hard to identify the correct path to the perl |
|
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112 | interpreter. With a cooperative main program, exec'ing the interpreter |
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113 | might not even be necessary, but even without help from the main program, |
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114 | it will still work when used from a module. |
|
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115 | |
|
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116 | =item Exec'ing a new perl process might be slow, as all necessary modules |
|
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117 | have to be loaded from disk again, with no guarantees of success. |
|
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118 | |
|
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119 | Long running processes might run into problems when perl is upgraded |
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120 | and modules are no longer loadable because they refer to a different |
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121 | perl version, or parts of a distribution are newer than the ones already |
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122 | loaded. |
|
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123 | |
|
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124 | This module supports creating pre-initialised perl processes to be used as |
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125 | a template for new processes. |
|
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126 | |
|
|
127 | =item Forking might be impossible when a program is running. |
|
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128 | |
|
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129 | For example, POSIX makes it almost impossible to fork from a |
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130 | multi-threaded program while doing anything useful in the child - in |
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131 | fact, if your perl program uses POSIX threads (even indirectly via |
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132 | e.g. L<IO::AIO> or L<threads>), you cannot call fork on the perl level |
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133 | anymore without risking corruption issues on a number of operating |
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134 | systems. |
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135 | |
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136 | This module can safely fork helper processes at any time, by calling |
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137 | fork+exec in C, in a POSIX-compatible way (via L<Proc::FastSpawn>). |
|
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138 | |
|
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139 | =item Parallel processing with fork might be inconvenient or difficult |
|
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140 | to implement. Modules might not work in both parent and child. |
|
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141 | |
|
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142 | For example, when a program uses an event loop and creates watchers it |
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143 | becomes very hard to use the event loop from a child program, as the |
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144 | watchers already exist but are only meaningful in the parent. Worse, a |
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145 | module might want to use such a module, not knowing whether another module |
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146 | or the main program also does, leading to problems. |
|
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147 | |
|
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148 | Apart from event loops, graphical toolkits also commonly fall into the |
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149 | "unsafe module" category, or just about anything that communicates with |
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150 | the external world, such as network libraries and file I/O modules, which |
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151 | usually don't like being copied and then allowed to continue in two |
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152 | processes. |
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153 | |
|
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154 | With this module only the main program is allowed to create new processes |
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155 | by forking (because only the main program can know when it is still safe |
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156 | to do so) - all other processes are created via fork+exec, which makes it |
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157 | possible to use modules such as event loops or window interfaces safely. |
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158 | |
|
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159 | =back |
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160 | |
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161 | =head1 EXAMPLES |
|
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162 | |
10 | # create a single new process, tell it to run your worker function |
163 | =head2 Create a single new process, tell it to run your worker function. |
11 | |
164 | |
12 | AnyEvent::Fork |
165 | AnyEvent::Fork |
13 | ->new |
166 | ->new |
14 | ->require ("MyModule") |
167 | ->require ("MyModule") |
15 | ->run ("MyModule::worker, sub { |
168 | ->run ("MyModule::worker, sub { |
… | |
… | |
17 | |
170 | |
18 | # now $master_filehandle is connected to the |
171 | # now $master_filehandle is connected to the |
19 | # $slave_filehandle in the new process. |
172 | # $slave_filehandle in the new process. |
20 | }); |
173 | }); |
21 | |
174 | |
22 | # MyModule::worker might look like this |
175 | C<MyModule> might look like this: |
|
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176 | |
|
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177 | package MyModule; |
|
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178 | |
23 | sub MyModule::worker { |
179 | sub worker { |
24 | my ($slave_filehandle) = @_; |
180 | my ($slave_filehandle) = @_; |
25 | |
181 | |
26 | # now $slave_filehandle is connected to the $master_filehandle |
182 | # now $slave_filehandle is connected to the $master_filehandle |
27 | # in the original prorcess. have fun! |
183 | # in the original prorcess. have fun! |
28 | } |
184 | } |
29 | |
185 | |
30 | ################################################################## |
|
|
31 | # create a pool of server processes all accepting on the same socket |
186 | =head2 Create a pool of server processes all accepting on the same socket. |
32 | |
187 | |
33 | # create listener socket |
188 | # create listener socket |
34 | my $listener = ...; |
189 | my $listener = ...; |
35 | |
190 | |
36 | # create a pool template, initialise it and give it the socket |
191 | # create a pool template, initialise it and give it the socket |
… | |
… | |
48 | } |
203 | } |
49 | |
204 | |
50 | # now do other things - maybe use the filehandle provided by run |
205 | # now do other things - maybe use the filehandle provided by run |
51 | # to wait for the processes to die. or whatever. |
206 | # to wait for the processes to die. or whatever. |
52 | |
207 | |
53 | # My::Server::run might look like this |
208 | C<My::Server> might look like this: |
54 | sub My::Server::run { |
209 | |
|
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210 | package My::Server; |
|
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211 | |
|
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212 | sub run { |
55 | my ($slave, $listener, $id) = @_; |
213 | my ($slave, $listener, $id) = @_; |
56 | |
214 | |
57 | close $slave; # we do not use the socket, so close it to save resources |
215 | close $slave; # we do not use the socket, so close it to save resources |
58 | |
216 | |
59 | # we could go ballistic and use e.g. AnyEvent here, or IO::AIO, |
217 | # we could go ballistic and use e.g. AnyEvent here, or IO::AIO, |
… | |
… | |
61 | while (my $socket = $listener->accept) { |
219 | while (my $socket = $listener->accept) { |
62 | # do sth. with new socket |
220 | # do sth. with new socket |
63 | } |
221 | } |
64 | } |
222 | } |
65 | |
223 | |
66 | =head1 DESCRIPTION |
224 | =head2 use AnyEvent::Fork as a faster fork+exec |
67 | |
225 | |
68 | This module allows you to create new processes, without actually forking |
226 | 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 |
227 | and standard error redirected to the communications socket. It is usually |
70 | preserving most of the advantages of fork. |
228 | faster than fork+exec, but still lets you prepare the environment. |
71 | |
229 | |
72 | It can be used to create new worker processes or new independent |
230 | 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 webserver), which can be faster (and more well behaved) |
|
|
76 | than using fork+exec in big processes. |
|
|
77 | |
231 | |
78 | Special care has been taken to make this module useful from other modules, |
232 | AnyEvent::Fork |
79 | while still supporting specialised environments such as L<App::Staticperl> |
233 | ->new |
80 | or L<PAR::Packer>. |
234 | ->eval (' |
|
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235 | # compile a helper function for later use |
|
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236 | sub run { |
|
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237 | my ($fh, $output, @cmd) = @_; |
81 | |
238 | |
82 | =head1 WHAT THIS MODULE IS NOT |
239 | # perl will clear close-on-exec on STDOUT/STDERR |
|
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240 | open STDOUT, ">&", $output or die; |
|
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241 | open STDERR, ">&", $fh or die; |
83 | |
242 | |
84 | This module only creates processes and lets you pass file handles and |
243 | exec @cmd; |
85 | strings to it, and run perl code. It does not implement any kind of RPC - |
244 | } |
86 | there is no back channel from the process back to you, and there is no RPC |
245 | ') |
87 | or message passing going on. |
246 | ->send_fh ($output) |
|
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247 | ->send_arg ("/bin/echo", "hi") |
|
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248 | ->run ("run", my $cv = AE::cv); |
88 | |
249 | |
89 | If you need some form of RPC, you can either implement it yourself |
250 | 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 multithreaded 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 caling |
|
|
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 |
|
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153 | only the main program can know when it is still safe to do so) - all other |
|
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154 | pools are created by fork+exec, after which such modules can again be |
|
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155 | loaded. |
|
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156 | |
|
|
157 | =back |
|
|
158 | |
251 | |
159 | =head1 CONCEPTS |
252 | =head1 CONCEPTS |
160 | |
253 | |
161 | This module can create new processes either by executing a new perl |
254 | This module can create new processes either by executing a new perl |
162 | process, or by forking from an existing "template" process. |
255 | process, or by forking from an existing "template" process. |
… | |
… | |
179 | needed the first time. Forking from this process shares the memory used |
272 | needed the first time. Forking from this process shares the memory used |
180 | for the perl interpreter with the new process, but loading modules takes |
273 | for the perl interpreter with the new process, but loading modules takes |
181 | time, and the memory is not shared with anything else. |
274 | time, and the memory is not shared with anything else. |
182 | |
275 | |
183 | This is ideal for when you only need one extra process of a kind, with the |
276 | This is ideal for when you only need one extra process of a kind, with the |
184 | option of starting and stipping it on demand. |
277 | option of starting and stopping it on demand. |
185 | |
278 | |
186 | Example: |
279 | Example: |
187 | |
280 | |
188 | AnyEvent::Fork |
281 | AnyEvent::Fork |
189 | ->new |
282 | ->new |
… | |
… | |
204 | modules you loaded) is shared between the processes, and each new process |
297 | modules you loaded) is shared between the processes, and each new process |
205 | consumes relatively little memory of its own. |
298 | consumes relatively little memory of its own. |
206 | |
299 | |
207 | The disadvantage of this approach is that you need to create a template |
300 | The disadvantage of this approach is that you need to create a template |
208 | process for the sole purpose of forking new processes from it, but if you |
301 | process for the sole purpose of forking new processes from it, but if you |
209 | only need a fixed number of proceses you can create them, and then destroy |
302 | only need a fixed number of processes you can create them, and then destroy |
210 | the template process. |
303 | the template process. |
211 | |
304 | |
212 | Example: |
305 | Example: |
213 | |
306 | |
214 | my $template = AnyEvent::Fork->new->require ("Some::Module"); |
307 | my $template = AnyEvent::Fork->new->require ("Some::Module"); |
… | |
… | |
241 | my ($fork_fh) = @_; |
334 | my ($fork_fh) = @_; |
242 | }); |
335 | }); |
243 | |
336 | |
244 | =back |
337 | =back |
245 | |
338 | |
246 | =head1 FUNCTIONS |
339 | =head1 THE C<AnyEvent::Fork> CLASS |
|
|
340 | |
|
|
341 | This module exports nothing, and only implements a single class - |
|
|
342 | C<AnyEvent::Fork>. |
|
|
343 | |
|
|
344 | There are two class constructors that both create new processes - C<new> |
|
|
345 | and C<new_exec>. The C<fork> method creates a new process by forking an |
|
|
346 | existing one and could be considered a third constructor. |
|
|
347 | |
|
|
348 | Most of the remaining methods deal with preparing the new process, by |
|
|
349 | loading code, evaluating code and sending data to the new process. They |
|
|
350 | usually return the process object, so you can chain method calls. |
|
|
351 | |
|
|
352 | If a process object is destroyed before calling its C<run> method, then |
|
|
353 | the process simply exits. After C<run> is called, all responsibility is |
|
|
354 | passed to the specified function. |
|
|
355 | |
|
|
356 | As long as there is any outstanding work to be done, process objects |
|
|
357 | resist being destroyed, so there is no reason to store them unless you |
|
|
358 | need them later - configure and forget works just fine. |
247 | |
359 | |
248 | =over 4 |
360 | =over 4 |
249 | |
361 | |
250 | =cut |
362 | =cut |
251 | |
363 | |
252 | package AnyEvent::Fork; |
364 | package AnyEvent::Fork; |
253 | |
365 | |
254 | use common::sense; |
366 | use common::sense; |
255 | |
367 | |
256 | use Socket (); |
368 | use Errno (); |
257 | |
369 | |
258 | use AnyEvent; |
370 | use AnyEvent; |
259 | use AnyEvent::Util (); |
371 | use AnyEvent::Util (); |
260 | |
372 | |
261 | use IO::FDPass; |
373 | use IO::FDPass; |
262 | |
374 | |
263 | our $VERSION = 0.2; |
375 | our $VERSION = 0.6; |
264 | |
|
|
265 | 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 | |
376 | |
271 | =over 4 |
377 | =over 4 |
272 | |
378 | |
273 | =back |
379 | =back |
274 | |
380 | |
… | |
… | |
278 | our $EARLY; |
384 | our $EARLY; |
279 | |
385 | |
280 | # the empty template process |
386 | # the empty template process |
281 | our $TEMPLATE; |
387 | our $TEMPLATE; |
282 | |
388 | |
|
|
389 | sub QUEUE() { 0 } |
|
|
390 | sub FH() { 1 } |
|
|
391 | sub WW() { 2 } |
|
|
392 | sub PID() { 3 } |
|
|
393 | sub CB() { 4 } |
|
|
394 | |
|
|
395 | sub _new { |
|
|
396 | my ($self, $fh, $pid) = @_; |
|
|
397 | |
|
|
398 | AnyEvent::Util::fh_nonblocking $fh, 1; |
|
|
399 | |
|
|
400 | $self = bless [ |
|
|
401 | [], # write queue - strings or fd's |
|
|
402 | $fh, |
|
|
403 | undef, # AE watcher |
|
|
404 | $pid, |
|
|
405 | ], $self; |
|
|
406 | |
|
|
407 | $self |
|
|
408 | } |
|
|
409 | |
283 | sub _cmd { |
410 | sub _cmd { |
284 | my $self = shift; |
411 | my $self = shift; |
285 | |
412 | |
286 | #TODO: maybe append the packet to any existing string command already in the queue |
|
|
287 | |
|
|
288 | # ideally, we would want to use "a (w/a)*" as format string, but perl versions |
413 | # ideally, we would want to use "a (w/a)*" as format string, but perl |
289 | # from at least 5.8.9 to 5.16.3 are all buggy and can't unpack it. |
414 | # versions from at least 5.8.9 to 5.16.3 are all buggy and can't unpack |
290 | push @{ $self->[2] }, pack "L/a*", pack "(w/a*)*", @_; |
415 | # it. |
|
|
416 | push @{ $self->[QUEUE] }, pack "a L/a*", $_[0], $_[1]; |
291 | |
417 | |
292 | $self->[3] ||= AE::io $self->[1], 1, sub { |
418 | $self->[WW] ||= AE::io $self->[FH], 1, sub { |
|
|
419 | do { |
293 | # send the next "thing" in the queue - either a reference to an fh, |
420 | # send the next "thing" in the queue - either a reference to an fh, |
294 | # or a plain string. |
421 | # or a plain string. |
295 | |
422 | |
296 | if (ref $self->[2][0]) { |
423 | if (ref $self->[QUEUE][0]) { |
297 | # send fh |
424 | # send fh |
298 | IO::FDPass::send fileno $self->[1], fileno ${ $self->[2][0] } |
425 | unless (IO::FDPass::send fileno $self->[FH], fileno ${ $self->[QUEUE][0] }) { |
|
|
426 | return if $! == Errno::EAGAIN || $! == Errno::EWOULDBLOCK; |
|
|
427 | undef $self->[WW]; |
|
|
428 | die "AnyEvent::Fork: file descriptor send failure: $!"; |
|
|
429 | } |
|
|
430 | |
299 | and shift @{ $self->[2] }; |
431 | shift @{ $self->[QUEUE] }; |
300 | |
432 | |
301 | } else { |
433 | } else { |
302 | # send string |
434 | # send string |
303 | my $len = syswrite $self->[1], $self->[2][0] |
435 | my $len = syswrite $self->[FH], $self->[QUEUE][0]; |
|
|
436 | |
|
|
437 | unless ($len) { |
|
|
438 | return if $! == Errno::EAGAIN || $! == Errno::EWOULDBLOCK; |
|
|
439 | undef $self->[3]; |
304 | or do { undef $self->[3]; die "AnyEvent::Fork: command write failure: $!" }; |
440 | die "AnyEvent::Fork: command write failure: $!"; |
|
|
441 | } |
305 | |
442 | |
306 | substr $self->[2][0], 0, $len, ""; |
443 | substr $self->[QUEUE][0], 0, $len, ""; |
307 | shift @{ $self->[2] } unless length $self->[2][0]; |
444 | shift @{ $self->[QUEUE] } unless length $self->[QUEUE][0]; |
308 | } |
445 | } |
|
|
446 | } while @{ $self->[QUEUE] }; |
309 | |
447 | |
310 | unless (@{ $self->[2] }) { |
448 | # everything written |
311 | undef $self->[3]; |
449 | undef $self->[WW]; |
|
|
450 | |
312 | # invoke run callback |
451 | # invoke run callback, if any |
313 | $self->[0]->($self->[1]) if $self->[0]; |
452 | $self->[CB]->($self->[FH]) if $self->[CB]; |
314 | } |
|
|
315 | }; |
453 | }; |
316 | |
454 | |
317 | () # make sure we don't leak the watcher |
455 | () # make sure we don't leak the watcher |
318 | } |
|
|
319 | |
|
|
320 | sub _new { |
|
|
321 | my ($self, $fh) = @_; |
|
|
322 | |
|
|
323 | AnyEvent::Util::fh_nonblocking $fh, 1; |
|
|
324 | |
|
|
325 | $self = bless [ |
|
|
326 | undef, # run callback |
|
|
327 | $fh, |
|
|
328 | [], # write queue - strings or fd's |
|
|
329 | undef, # AE watcher |
|
|
330 | ], $self; |
|
|
331 | |
|
|
332 | $self |
|
|
333 | } |
456 | } |
334 | |
457 | |
335 | # fork template from current process, used by AnyEvent::Fork::Early/Template |
458 | # fork template from current process, used by AnyEvent::Fork::Early/Template |
336 | sub _new_fork { |
459 | sub _new_fork { |
337 | my ($fh, $slave) = AnyEvent::Util::portable_socketpair; |
460 | my ($fh, $slave) = AnyEvent::Util::portable_socketpair; |
… | |
… | |
342 | if ($pid eq 0) { |
465 | if ($pid eq 0) { |
343 | require AnyEvent::Fork::Serve; |
466 | require AnyEvent::Fork::Serve; |
344 | $AnyEvent::Fork::Serve::OWNER = $parent; |
467 | $AnyEvent::Fork::Serve::OWNER = $parent; |
345 | close $fh; |
468 | close $fh; |
346 | $0 = "$_[1] of $parent"; |
469 | $0 = "$_[1] of $parent"; |
347 | $SIG{CHLD} = 'IGNORE'; |
|
|
348 | AnyEvent::Fork::Serve::serve ($slave); |
470 | AnyEvent::Fork::Serve::serve ($slave); |
349 | exit 0; |
471 | exit 0; |
350 | } elsif (!$pid) { |
472 | } elsif (!$pid) { |
351 | die "AnyEvent::Fork::Early/Template: unable to fork template process: $!"; |
473 | die "AnyEvent::Fork::Early/Template: unable to fork template process: $!"; |
352 | } |
474 | } |
353 | |
475 | |
354 | AnyEvent::Fork->_new ($fh) |
476 | AnyEvent::Fork->_new ($fh, $pid) |
355 | } |
477 | } |
356 | |
478 | |
357 | =item my $proc = new AnyEvent::Fork |
479 | =item my $proc = new AnyEvent::Fork |
358 | |
480 | |
359 | Create a new "empty" perl interpreter process and returns its process |
481 | Create a new "empty" perl interpreter process and returns its process |
360 | object for further manipulation. |
482 | object for further manipulation. |
361 | |
483 | |
362 | The new process is forked from a template process that is kept around |
484 | The new process is forked from a template process that is kept around |
363 | for this purpose. When it doesn't exist yet, it is created by a call to |
485 | for this purpose. When it doesn't exist yet, it is created by a call to |
364 | C<new_exec> and kept around for future calls. |
486 | C<new_exec> first and then stays around for future calls. |
365 | |
|
|
366 | When the process object is destroyed, it will release the file handle |
|
|
367 | that connects it with the new process. When the new process has not yet |
|
|
368 | called C<run>, then the process will exit. Otherwise, what happens depends |
|
|
369 | entirely on the code that is executed. |
|
|
370 | |
487 | |
371 | =cut |
488 | =cut |
372 | |
489 | |
373 | sub new { |
490 | sub new { |
374 | my $class = shift; |
491 | my $class = shift; |
… | |
… | |
410 | reduces the amount of memory sharing that is possible, and is also slower. |
527 | reduces the amount of memory sharing that is possible, and is also slower. |
411 | |
528 | |
412 | You should use C<new> whenever possible, except when having a template |
529 | You should use C<new> whenever possible, except when having a template |
413 | process around is unacceptable. |
530 | process around is unacceptable. |
414 | |
531 | |
415 | The path to the perl interpreter is divined usign various methods - first |
532 | The path to the perl interpreter is divined using various methods - first |
416 | C<$^X> is investigated to see if the path ends with something that sounds |
533 | C<$^X> is investigated to see if the path ends with something that sounds |
417 | as if it were the perl interpreter. Failing this, the module falls back to |
534 | as if it were the perl interpreter. Failing this, the module falls back to |
418 | using C<$Config::Config{perlpath}>. |
535 | using C<$Config::Config{perlpath}>. |
419 | |
536 | |
420 | =cut |
537 | =cut |
… | |
… | |
452 | # quick. also doesn't work in win32. of course. what did you expect |
569 | # quick. also doesn't work in win32. of course. what did you expect |
453 | #local $ENV{PERL5LIB} = join ":", grep !ref, @INC; |
570 | #local $ENV{PERL5LIB} = join ":", grep !ref, @INC; |
454 | my %env = %ENV; |
571 | my %env = %ENV; |
455 | $env{PERL5LIB} = join +($^O eq "MSWin32" ? ";" : ":"), grep !ref, @INC; |
572 | $env{PERL5LIB} = join +($^O eq "MSWin32" ? ";" : ":"), grep !ref, @INC; |
456 | |
573 | |
457 | Proc::FastSpawn::spawn ( |
574 | my $pid = Proc::FastSpawn::spawn ( |
458 | $perl, |
575 | $perl, |
459 | ["perl", "-MAnyEvent::Fork::Serve", "-e", "AnyEvent::Fork::Serve::me", fileno $slave, $$], |
576 | ["perl", "-MAnyEvent::Fork::Serve", "-e", "AnyEvent::Fork::Serve::me", fileno $slave, $$], |
460 | [map "$_=$env{$_}", keys %env], |
577 | [map "$_=$env{$_}", keys %env], |
461 | ) or die "unable to spawn AnyEvent::Fork server: $!"; |
578 | ) or die "unable to spawn AnyEvent::Fork server: $!"; |
462 | |
579 | |
463 | $self->_new ($fh) |
580 | $self->_new ($fh, $pid) |
|
|
581 | } |
|
|
582 | |
|
|
583 | =item $pid = $proc->pid |
|
|
584 | |
|
|
585 | Returns the process id of the process I<iff it is a direct child of the |
|
|
586 | process running AnyEvent::Fork>, and C<undef> otherwise. |
|
|
587 | |
|
|
588 | Normally, only processes created via C<< AnyEvent::Fork->new_exec >> and |
|
|
589 | L<AnyEvent::Fork::Template> are direct children, and you are responsible |
|
|
590 | to clean up their zombies when they die. |
|
|
591 | |
|
|
592 | All other processes are not direct children, and will be cleaned up by |
|
|
593 | AnyEvent::Fork itself. |
|
|
594 | |
|
|
595 | =cut |
|
|
596 | |
|
|
597 | sub pid { |
|
|
598 | $_[0][PID] |
464 | } |
599 | } |
465 | |
600 | |
466 | =item $proc = $proc->eval ($perlcode, @args) |
601 | =item $proc = $proc->eval ($perlcode, @args) |
467 | |
602 | |
468 | Evaluates the given C<$perlcode> as ... perl code, while setting C<@_> to |
603 | Evaluates the given C<$perlcode> as ... perl code, while setting C<@_> to |
469 | the strings specified by C<@args>. |
604 | the strings specified by C<@args>, in the "main" package. |
470 | |
605 | |
471 | This call is meant to do any custom initialisation that might be required |
606 | This call is meant to do any custom initialisation that might be required |
472 | (for example, the C<require> method uses it). It's not supposed to be used |
607 | (for example, the C<require> method uses it). It's not supposed to be used |
473 | to completely take over the process, use C<run> for that. |
608 | to completely take over the process, use C<run> for that. |
474 | |
609 | |
475 | The code will usually be executed after this call returns, and there is no |
610 | The code will usually be executed after this call returns, and there is no |
476 | way to pass anything back to the calling process. Any evaluation errors |
611 | way to pass anything back to the calling process. Any evaluation errors |
477 | will be reported to stderr and cause the process to exit. |
612 | will be reported to stderr and cause the process to exit. |
478 | |
613 | |
|
|
614 | If you want to execute some code (that isn't in a module) to take over the |
|
|
615 | process, you should compile a function via C<eval> first, and then call |
|
|
616 | it via C<run>. This also gives you access to any arguments passed via the |
|
|
617 | C<send_xxx> methods, such as file handles. See the L<use AnyEvent::Fork as |
|
|
618 | a faster fork+exec> example to see it in action. |
|
|
619 | |
479 | Returns the process object for easy chaining of method calls. |
620 | Returns the process object for easy chaining of method calls. |
480 | |
621 | |
481 | =cut |
622 | =cut |
482 | |
623 | |
483 | sub eval { |
624 | sub eval { |
484 | my ($self, $code, @args) = @_; |
625 | my ($self, $code, @args) = @_; |
485 | |
626 | |
486 | $self->_cmd (e => $code, @args); |
627 | $self->_cmd (e => pack "(w/a*)*", $code, @args); |
487 | |
628 | |
488 | $self |
629 | $self |
489 | } |
630 | } |
490 | |
631 | |
491 | =item $proc = $proc->require ($module, ...) |
632 | =item $proc = $proc->require ($module, ...) |
… | |
… | |
508 | =item $proc = $proc->send_fh ($handle, ...) |
649 | =item $proc = $proc->send_fh ($handle, ...) |
509 | |
650 | |
510 | Send one or more file handles (I<not> file descriptors) to the process, |
651 | Send one or more file handles (I<not> file descriptors) to the process, |
511 | to prepare a call to C<run>. |
652 | to prepare a call to C<run>. |
512 | |
653 | |
513 | The process object keeps a reference to the handles until this is done, |
654 | The process object keeps a reference to the handles until they have |
514 | so you must not explicitly close the handles. This is most easily |
655 | been passed over to the process, so you must not explicitly close the |
515 | accomplished by simply not storing the file handles anywhere after passing |
656 | handles. This is most easily accomplished by simply not storing the file |
516 | them to this method. |
657 | handles anywhere after passing them to this method - when AnyEvent::Fork |
|
|
658 | is finished using them, perl will automatically close them. |
517 | |
659 | |
518 | Returns the process object for easy chaining of method calls. |
660 | Returns the process object for easy chaining of method calls. |
519 | |
661 | |
520 | Example: pass an fh to a process, and release it without closing. it will |
662 | Example: pass a file handle to a process, and release it without |
521 | be closed automatically when it is no longer used. |
663 | closing. It will be closed automatically when it is no longer used. |
522 | |
664 | |
523 | $proc->send_fh ($my_fh); |
665 | $proc->send_fh ($my_fh); |
524 | undef $my_fh; # free the reference if you want, but DO NOT CLOSE IT |
666 | undef $my_fh; # free the reference if you want, but DO NOT CLOSE IT |
525 | |
667 | |
526 | =cut |
668 | =cut |
… | |
… | |
528 | sub send_fh { |
670 | sub send_fh { |
529 | my ($self, @fh) = @_; |
671 | my ($self, @fh) = @_; |
530 | |
672 | |
531 | for my $fh (@fh) { |
673 | for my $fh (@fh) { |
532 | $self->_cmd ("h"); |
674 | $self->_cmd ("h"); |
533 | push @{ $self->[2] }, \$fh; |
675 | push @{ $self->[QUEUE] }, \$fh; |
534 | } |
676 | } |
535 | |
677 | |
536 | $self |
678 | $self |
537 | } |
679 | } |
538 | |
680 | |
539 | =item $proc = $proc->send_arg ($string, ...) |
681 | =item $proc = $proc->send_arg ($string, ...) |
540 | |
682 | |
541 | Send one or more argument strings to the process, to prepare a call to |
683 | Send one or more argument strings to the process, to prepare a call to |
542 | C<run>. The strings can be any octet string. |
684 | C<run>. The strings can be any octet strings. |
543 | |
685 | |
|
|
686 | The protocol is optimised to pass a moderate number of relatively short |
|
|
687 | strings - while you can pass up to 4GB of data in one go, this is more |
|
|
688 | meant to pass some ID information or other startup info, not big chunks of |
|
|
689 | data. |
|
|
690 | |
544 | Returns the process object for easy chaining of emthod calls. |
691 | Returns the process object for easy chaining of method calls. |
545 | |
692 | |
546 | =cut |
693 | =cut |
547 | |
694 | |
548 | sub send_arg { |
695 | sub send_arg { |
549 | my ($self, @arg) = @_; |
696 | my ($self, @arg) = @_; |
550 | |
697 | |
551 | $self->_cmd (a => @arg); |
698 | $self->_cmd (a => pack "(w/a*)*", @arg); |
552 | |
699 | |
553 | $self |
700 | $self |
554 | } |
701 | } |
555 | |
702 | |
556 | =item $proc->run ($func, $cb->($fh)) |
703 | =item $proc->run ($func, $cb->($fh)) |
557 | |
704 | |
558 | Enter the function specified by the fully qualified name in C<$func> in |
705 | Enter the function specified by the function name in C<$func> in the |
559 | the process. The function is called with the communication socket as first |
706 | process. The function is called with the communication socket as first |
560 | argument, followed by all file handles and string arguments sent earlier |
707 | argument, followed by all file handles and string arguments sent earlier |
561 | via C<send_fh> and C<send_arg> methods, in the order they were called. |
708 | via C<send_fh> and C<send_arg> methods, in the order they were called. |
562 | |
709 | |
563 | If the called function returns, the process exits. |
|
|
564 | |
|
|
565 | Preparing the process can take time - when the process is ready, the |
|
|
566 | callback is invoked with the local communications socket as argument. |
|
|
567 | |
|
|
568 | The process object becomes unusable on return from this function. |
710 | The process object becomes unusable on return from this function - any |
|
|
711 | further method calls result in undefined behaviour. |
|
|
712 | |
|
|
713 | The function name should be fully qualified, but if it isn't, it will be |
|
|
714 | looked up in the C<main> package. |
|
|
715 | |
|
|
716 | If the called function returns, doesn't exist, or any error occurs, the |
|
|
717 | process exits. |
|
|
718 | |
|
|
719 | Preparing the process is done in the background - when all commands have |
|
|
720 | been sent, the callback is invoked with the local communications socket |
|
|
721 | as argument. At this point you can start using the socket in any way you |
|
|
722 | like. |
569 | |
723 | |
570 | If the communication socket isn't used, it should be closed on both sides, |
724 | If the communication socket isn't used, it should be closed on both sides, |
571 | to save on kernel memory. |
725 | to save on kernel memory. |
572 | |
726 | |
573 | The socket is non-blocking in the parent, and blocking in the newly |
727 | The socket is non-blocking in the parent, and blocking in the newly |
574 | created process. The close-on-exec flag is set on both. Even if not used |
728 | created process. The close-on-exec flag is set in both. |
|
|
729 | |
575 | otherwise, the socket can be a good indicator for the existance of the |
730 | Even if not used otherwise, the socket can be a good indicator for the |
576 | process - if the other process exits, you get a readable event on it, |
731 | existence of the process - if the other process exits, you get a readable |
577 | because exiting the process closes the socket (if it didn't create any |
732 | event on it, because exiting the process closes the socket (if it didn't |
578 | children using fork). |
733 | create any children using fork). |
579 | |
734 | |
580 | Example: create a template for a process pool, pass a few strings, some |
735 | Example: create a template for a process pool, pass a few strings, some |
581 | file handles, then fork, pass one more string, and run some code. |
736 | file handles, then fork, pass one more string, and run some code. |
582 | |
737 | |
583 | my $pool = AnyEvent::Fork |
738 | my $pool = AnyEvent::Fork |
… | |
… | |
591 | ->send_arg ("str3") |
746 | ->send_arg ("str3") |
592 | ->run ("Some::function", sub { |
747 | ->run ("Some::function", sub { |
593 | my ($fh) = @_; |
748 | my ($fh) = @_; |
594 | |
749 | |
595 | # fh is nonblocking, but we trust that the OS can accept these |
750 | # fh is nonblocking, but we trust that the OS can accept these |
596 | # extra 3 octets anyway. |
751 | # few octets anyway. |
597 | syswrite $fh, "hi #$_\n"; |
752 | syswrite $fh, "hi #$_\n"; |
598 | |
753 | |
599 | # $fh is being closed here, as we don't store it anywhere |
754 | # $fh is being closed here, as we don't store it anywhere |
600 | }); |
755 | }); |
601 | } |
756 | } |
… | |
… | |
603 | # Some::function might look like this - all parameters passed before fork |
758 | # Some::function might look like this - all parameters passed before fork |
604 | # and after will be passed, in order, after the communications socket. |
759 | # and after will be passed, in order, after the communications socket. |
605 | sub Some::function { |
760 | sub Some::function { |
606 | my ($fh, $str1, $str2, $fh1, $fh2, $str3) = @_; |
761 | my ($fh, $str1, $str2, $fh1, $fh2, $str3) = @_; |
607 | |
762 | |
608 | print scalar <$fh>; # prints "hi 1\n" and "hi 2\n" |
763 | print scalar <$fh>; # prints "hi #1\n" and "hi #2\n" in any order |
609 | } |
764 | } |
610 | |
765 | |
611 | =cut |
766 | =cut |
612 | |
767 | |
613 | sub run { |
768 | sub run { |
614 | my ($self, $func, $cb) = @_; |
769 | my ($self, $func, $cb) = @_; |
615 | |
770 | |
616 | $self->[0] = $cb; |
771 | $self->[CB] = $cb; |
617 | $self->_cmd (r => $func); |
772 | $self->_cmd (r => $func); |
618 | } |
773 | } |
619 | |
774 | |
620 | =back |
775 | =back |
621 | |
776 | |
622 | =head1 PERFORMANCE |
777 | =head1 PERFORMANCE |
623 | |
778 | |
624 | Now for some unscientific benchmark numbers (all done on an amd64 |
779 | Now for some unscientific benchmark numbers (all done on an amd64 |
625 | GNU/Linux box). These are intended to give you an idea of the relative |
780 | GNU/Linux box). These are intended to give you an idea of the relative |
626 | performance you can expect. |
781 | performance you can expect, they are not meant to be absolute performance |
|
|
782 | numbers. |
627 | |
783 | |
628 | Ok, so, I ran a simple benchmark that creates a socketpair, forks, calls |
784 | OK, so, I ran a simple benchmark that creates a socket pair, forks, calls |
629 | exit in the child and waits for the socket to close in the parent. I did |
785 | exit in the child and waits for the socket to close in the parent. I did |
630 | load AnyEvent, EV and AnyEvent::Fork, for a total process size of 6312kB. |
786 | load AnyEvent, EV and AnyEvent::Fork, for a total process size of 5100kB. |
631 | |
787 | |
632 | 2079 new processes per second, using socketpair + fork manually |
788 | 2079 new processes per second, using manual socketpair + fork |
633 | |
789 | |
634 | Then I did the same thing, but instead of calling fork, I called |
790 | Then I did the same thing, but instead of calling fork, I called |
635 | AnyEvent::Fork->new->run ("CORE::exit") and then again waited for the |
791 | AnyEvent::Fork->new->run ("CORE::exit") and then again waited for the |
636 | socket form the child to close on exit. This does the same thing as manual |
792 | socket form the child to close on exit. This does the same thing as manual |
637 | socketpair + fork, except that what is forked is the template process |
793 | socket pair + fork, except that what is forked is the template process |
638 | (2440kB), and the socket needs to be passed to the server at the other end |
794 | (2440kB), and the socket needs to be passed to the server at the other end |
639 | of the socket first. |
795 | of the socket first. |
640 | |
796 | |
641 | 2307 new processes per second, using AnyEvent::Fork->new |
797 | 2307 new processes per second, using AnyEvent::Fork->new |
642 | |
798 | |
643 | And finally, using C<new_exec> instead C<new>, using vforks+execs to exec |
799 | And finally, using C<new_exec> instead C<new>, using vforks+execs to exec |
644 | a new perl interpreter and compile the small server each time, I get: |
800 | a new perl interpreter and compile the small server each time, I get: |
645 | |
801 | |
646 | 479 vfork+execs per second, using AnyEvent::Fork->new_exec |
802 | 479 vfork+execs per second, using AnyEvent::Fork->new_exec |
647 | |
803 | |
648 | So how can C<< AnyEvent->new >> be faster than a standard fork, een though |
804 | So how can C<< AnyEvent->new >> be faster than a standard fork, even |
649 | it uses the same operations, but adds a lot of overhead? |
805 | though it uses the same operations, but adds a lot of overhead? |
650 | |
806 | |
651 | The difference is simply the process size: forking the 6MB process takes |
807 | The difference is simply the process size: forking the 5MB process takes |
652 | so much longer than forking the 2.5MB template process that the overhead |
808 | so much longer than forking the 2.5MB template process that the extra |
653 | introduced is canceled out. |
809 | overhead introduced is canceled out. |
654 | |
810 | |
655 | If the benchmark process grows, the normal fork becomes even slower: |
811 | If the benchmark process grows, the normal fork becomes even slower: |
656 | |
812 | |
657 | 1340 new processes, manual fork in a 20MB process |
813 | 1340 new processes, manual fork of a 20MB process |
658 | 731 new processes, manual fork in a 200MB process |
814 | 731 new processes, manual fork of a 200MB process |
659 | 235 new processes, manual fork in a 2000MB process |
815 | 235 new processes, manual fork of a 2000MB process |
660 | |
816 | |
661 | What that means (to me) is that I can use this module without havign a |
817 | What that means (to me) is that I can use this module without having a bad |
662 | very bad conscience because of the extra overhead requried to strat new |
818 | conscience because of the extra overhead required to start new processes. |
663 | processes. |
|
|
664 | |
819 | |
665 | =head1 TYPICAL PROBLEMS |
820 | =head1 TYPICAL PROBLEMS |
666 | |
821 | |
667 | This section lists typical problems that remain. I hope by recognising |
822 | This section lists typical problems that remain. I hope by recognising |
668 | them, most can be avoided. |
823 | them, most can be avoided. |
669 | |
824 | |
670 | =over 4 |
825 | =over 4 |
671 | |
826 | |
672 | =item "leaked" file descriptors for exec'ed processes |
827 | =item leaked file descriptors for exec'ed processes |
673 | |
828 | |
674 | POSIX systems inherit file descriptors by default when exec'ing a new |
829 | POSIX systems inherit file descriptors by default when exec'ing a new |
675 | process. While perl itself laudably sets the close-on-exec flags on new |
830 | process. While perl itself laudably sets the close-on-exec flags on new |
676 | file handles, most C libraries don't care, and even if all cared, it's |
831 | file handles, most C libraries don't care, and even if all cared, it's |
677 | often not possible to set the flag in a race-free manner. |
832 | often not possible to set the flag in a race-free manner. |
678 | |
833 | |
679 | That means some file descriptors can leak through. And since it isn't |
834 | That means some file descriptors can leak through. And since it isn't |
680 | possible to know which file descriptors are "good" and "neccessary" (or |
835 | possible to know which file descriptors are "good" and "necessary" (or |
681 | even to know which file descreiptors are open), there is no good way to |
836 | even to know which file descriptors are open), there is no good way to |
682 | close the ones that might harm. |
837 | close the ones that might harm. |
683 | |
838 | |
684 | As an example of what "harm" can be done consider a web server that |
839 | As an example of what "harm" can be done consider a web server that |
685 | accepts connections and afterwards some module uses AnyEvent::Fork for the |
840 | accepts connections and afterwards some module uses AnyEvent::Fork for the |
686 | first time, causing it to fork and exec a new process, which might inherit |
841 | first time, causing it to fork and exec a new process, which might inherit |
… | |
… | |
694 | well before many random file descriptors are open. |
849 | well before many random file descriptors are open. |
695 | |
850 | |
696 | In general, the solution for these kind of problems is to fix the |
851 | In general, the solution for these kind of problems is to fix the |
697 | libraries or the code that leaks those file descriptors. |
852 | libraries or the code that leaks those file descriptors. |
698 | |
853 | |
699 | Fortunately, most of these lekaed descriptors do no harm, other than |
854 | Fortunately, most of these leaked descriptors do no harm, other than |
700 | sitting on some resources. |
855 | sitting on some resources. |
701 | |
856 | |
702 | =item "leaked" file descriptors for fork'ed processes |
857 | =item leaked file descriptors for fork'ed processes |
703 | |
858 | |
704 | Normally, L<AnyEvent::Fork> does start new processes by exec'ing them, |
859 | Normally, L<AnyEvent::Fork> does start new processes by exec'ing them, |
705 | which closes file descriptors not marked for being inherited. |
860 | which closes file descriptors not marked for being inherited. |
706 | |
861 | |
707 | However, L<AnyEvent::Fork::Early> and L<AnyEvent::Fork::Template> offer |
862 | However, L<AnyEvent::Fork::Early> and L<AnyEvent::Fork::Template> offer |
… | |
… | |
716 | |
871 | |
717 | The solution is to either not load these modules before use'ing |
872 | The solution is to either not load these modules before use'ing |
718 | L<AnyEvent::Fork::Early> or L<AnyEvent::Fork::Template>, or to delay |
873 | L<AnyEvent::Fork::Early> or L<AnyEvent::Fork::Template>, or to delay |
719 | initialising them, for example, by calling C<init Gtk2> manually. |
874 | initialising them, for example, by calling C<init Gtk2> manually. |
720 | |
875 | |
|
|
876 | =item exiting calls object destructors |
|
|
877 | |
|
|
878 | This only applies to users of L<AnyEvent::Fork:Early> and |
|
|
879 | L<AnyEvent::Fork::Template>, or when initialiasing code creates objects |
|
|
880 | that reference external resources. |
|
|
881 | |
|
|
882 | When a process created by AnyEvent::Fork exits, it might do so by calling |
|
|
883 | exit, or simply letting perl reach the end of the program. At which point |
|
|
884 | Perl runs all destructors. |
|
|
885 | |
|
|
886 | Not all destructors are fork-safe - for example, an object that represents |
|
|
887 | the connection to an X display might tell the X server to free resources, |
|
|
888 | which is inconvenient when the "real" object in the parent still needs to |
|
|
889 | use them. |
|
|
890 | |
|
|
891 | This is obviously not a problem for L<AnyEvent::Fork::Early>, as you used |
|
|
892 | it as the very first thing, right? |
|
|
893 | |
|
|
894 | It is a problem for L<AnyEvent::Fork::Template> though - and the solution |
|
|
895 | is to not create objects with nontrivial destructors that might have an |
|
|
896 | effect outside of Perl. |
|
|
897 | |
721 | =back |
898 | =back |
722 | |
899 | |
723 | =head1 PORTABILITY NOTES |
900 | =head1 PORTABILITY NOTES |
724 | |
901 | |
725 | Native win32 perls are somewhat supported (AnyEvent::Fork::Early is a nop, |
902 | Native win32 perls are somewhat supported (AnyEvent::Fork::Early is a nop, |
726 | and ::Template is not going to work), and it cost a lot of blood and sweat |
903 | and ::Template is not going to work), and it cost a lot of blood and sweat |
727 | to make it so, mostly due to the bloody broken perl that nobody seems to |
904 | to make it so, mostly due to the bloody broken perl that nobody seems to |
728 | care about. The fork emulation is a bad joke - I have yet to see something |
905 | care about. The fork emulation is a bad joke - I have yet to see something |
729 | useful that you cna do with it without running into memory corruption |
906 | useful that you can do with it without running into memory corruption |
730 | issues or other braindamage. Hrrrr. |
907 | issues or other braindamage. Hrrrr. |
731 | |
908 | |
732 | Cygwin perl is not supported at the moment, as it should implement fd |
909 | Cygwin perl is not supported at the moment due to some hilarious |
733 | passing, but doesn't, and rolling my own is hard, as cygwin doesn't |
910 | shortcomings of its API - see L<IO::FDPoll> for more details. |
734 | support enough functionality to do it. |
|
|
735 | |
911 | |
736 | =head1 SEE ALSO |
912 | =head1 SEE ALSO |
737 | |
913 | |
738 | L<AnyEvent::Fork::Early> (to avoid executing a perl interpreter), |
914 | L<AnyEvent::Fork::Early> (to avoid executing a perl interpreter), |
739 | L<AnyEvent::Fork::Template> (to create a process by forking the main |
915 | L<AnyEvent::Fork::Template> (to create a process by forking the main |