… | |
… | |
3 | AnyEvent::Fork - everything you wanted to use fork() for, but couldn't |
3 | AnyEvent::Fork - everything you wanted to use fork() for, but couldn't |
4 | |
4 | |
5 | =head1 SYNOPSIS |
5 | =head1 SYNOPSIS |
6 | |
6 | |
7 | use AnyEvent::Fork; |
7 | use AnyEvent::Fork; |
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8 | |
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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; |
8 | |
15 | |
9 | =head1 DESCRIPTION |
16 | =head1 DESCRIPTION |
10 | |
17 | |
11 | This module allows you to create new processes, without actually forking |
18 | This module allows you to create new processes, without actually forking |
12 | them from your current process (avoiding the problems of forking), but |
19 | them from your current process (avoiding the problems of forking), but |
13 | preserving most of the advantages of fork. |
20 | preserving most of the advantages of fork. |
14 | |
21 | |
15 | It can be used to create new worker processes or new independent |
22 | It can be used to create new worker processes or new independent |
16 | subprocesses for short- and long-running jobs, process pools (e.g. for use |
23 | subprocesses for short- and long-running jobs, process pools (e.g. for use |
17 | in pre-forked servers) but also to spawn new external processes (such as |
24 | in pre-forked servers) but also to spawn new external processes (such as |
18 | CGI scripts from a webserver), which can be faster (and more well behaved) |
25 | CGI scripts from a web server), which can be faster (and more well behaved) |
19 | than using fork+exec in big processes. |
26 | than using fork+exec in big processes. |
20 | |
27 | |
21 | Special care has been taken to make this module useful from other modules, |
28 | Special care has been taken to make this module useful from other modules, |
22 | while still supporting specialised environments such as L<App::Staticperl> |
29 | while still supporting specialised environments such as L<App::Staticperl> |
23 | or L<PAR::Packer>. |
30 | or L<PAR::Packer>. |
24 | |
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 | |
25 | =head1 PROBLEM STATEMENT |
63 | =head2 PROBLEM STATEMENT |
26 | |
64 | |
27 | There are two ways to implement parallel processing on UNIX like operating |
65 | There are two traditional ways to implement parallel processing on UNIX |
28 | systems - fork and process, and fork+exec and process. They have different |
66 | like operating systems - fork and process, and fork+exec and process. They |
29 | advantages and disadvantages that I describe below, together with how this |
67 | have different advantages and disadvantages that I describe below, |
30 | module tries to mitigate the disadvantages. |
68 | together with how this module tries to mitigate the disadvantages. |
31 | |
69 | |
32 | =over 4 |
70 | =over 4 |
33 | |
71 | |
34 | =item Forking from a big process can be very slow (a 5GB process needs |
72 | =item Forking from a big process can be very slow. |
35 | 0.05s to fork on my 3.6GHz amd64 GNU/Linux box for example). This overhead |
73 | |
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74 | A 5GB process needs 0.05s to fork on my 3.6GHz amd64 GNU/Linux box. This |
36 | is often shared with exec (because you have to fork first), but in some |
75 | overhead is often shared with exec (because you have to fork first), but |
37 | circumstances (e.g. when vfork is used), fork+exec can be much faster. |
76 | in some circumstances (e.g. when vfork is used), fork+exec can be much |
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77 | faster. |
38 | |
78 | |
39 | This module can help here by telling a small(er) helper process to fork, |
79 | This module can help here by telling a small(er) helper process to fork, |
40 | or fork+exec instead. |
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. |
41 | |
82 | |
42 | =item Forking usually creates a copy-on-write copy of the parent |
83 | =item Forking usually creates a copy-on-write copy of the parent |
43 | process. Memory (for example, modules or data files that have been |
84 | process. |
44 | will not take additional memory). When exec'ing a new process, modules |
85 | |
45 | and data files might need to be loaded again, at extra cpu and memory |
86 | For example, modules or data files that are loaded will not use additional |
46 | cost. Likewise when forking, all data structures are copied as well - if |
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 |
47 | the program frees them and replaces them by new data, the child processes |
90 | them and replaces them by new data, the child processes will retain the |
48 | will retain the memory even if it isn't used. |
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. |
49 | |
96 | |
50 | This module allows the main program to do a controlled fork, and allows |
97 | This module allows the main program to do a controlled fork, and allows |
51 | modules to exec processes safely at any time. When creating a custom |
98 | modules to exec processes safely at any time. When creating a custom |
52 | process pool you can take advantage of data sharing via fork without |
99 | process pool you can take advantage of data sharing via fork without |
53 | risking to share large dynamic data structures that will blow up child |
100 | risking to share large dynamic data structures that will blow up child |
54 | memory usage. |
101 | memory usage. |
55 | |
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 | |
56 | =item Exec'ing a new perl process might be difficult and slow. For |
106 | =item Exec'ing a new perl process might be difficult. |
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107 | |
57 | example, it is not easy to find the correct path to the perl interpreter, |
108 | For example, it is not easy to find the correct path to the perl |
58 | and all modules have to be loaded from disk again. Long running processes |
109 | interpreter - C<$^X> might not be a perl interpreter at all. |
59 | might run into problems when perl is upgraded for example. |
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60 | |
110 | |
61 | This module supports creating pre-initialised perl processes to be used |
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62 | as template, and also tries hard to identify the correct path to the perl |
111 | This module tries hard to identify the correct path to the perl |
63 | interpreter. With a cooperative main program, exec'ing the interpreter |
112 | interpreter. With a cooperative main program, exec'ing the interpreter |
64 | might not even be necessary. |
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. |
65 | |
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 | |
66 | =item Forking might be impossible when a program is running. For example, |
127 | =item Forking might be impossible when a program is running. |
67 | POSIX makes it almost impossible to fork from a multithreaded program and |
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68 | do anything useful in the child - strictly speaking, if your perl program |
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69 | uses posix threads (even indirectly via e.g. L<IO::AIO> or L<threads>), |
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70 | you cannot call fork on the perl level anymore, at all. |
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71 | |
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 | |
72 | This module can safely fork helper processes at any time, by caling |
136 | This module can safely fork helper processes at any time, by calling |
73 | fork+exec in C, in a POSIX-compatible way. |
137 | fork+exec in C, in a POSIX-compatible way (via L<Proc::FastSpawn>). |
74 | |
138 | |
75 | =item Parallel processing with fork might be inconvenient or difficult |
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 | |
76 | to implement. For example, when a program uses an event loop and creates |
142 | For example, when a program uses an event loop and creates watchers it |
77 | watchers it becomes very hard to use the event loop from a child |
143 | becomes very hard to use the event loop from a child program, as the |
78 | program, as the watchers already exist but are only meaningful in the |
144 | watchers already exist but are only meaningful in the parent. Worse, a |
79 | parent. Worse, a module might want to use such a system, not knowing |
145 | module might want to use such a module, not knowing whether another module |
80 | whether another module or the main program also does, leading to problems. |
146 | or the main program also does, leading to problems. |
81 | |
147 | |
82 | This module only lets the main program create pools by forking (because |
148 | Apart from event loops, graphical toolkits also commonly fall into the |
83 | only the main program can know when it is still safe to do so) - all other |
149 | "unsafe module" category, or just about anything that communicates with |
84 | pools are created by fork+exec, after which such modules can again be |
150 | the external world, such as network libraries and file I/O modules, which |
85 | loaded. |
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. |
86 | |
158 | |
87 | =back |
159 | =back |
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160 | |
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161 | =head1 EXAMPLES |
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162 | |
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163 | =head2 Create a single new process, tell it to run your worker function. |
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164 | |
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165 | AnyEvent::Fork |
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166 | ->new |
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167 | ->require ("MyModule") |
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168 | ->run ("MyModule::worker, sub { |
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169 | my ($master_filehandle) = @_; |
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170 | |
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171 | # now $master_filehandle is connected to the |
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172 | # $slave_filehandle in the new process. |
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173 | }); |
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174 | |
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175 | C<MyModule> might look like this: |
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176 | |
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177 | package MyModule; |
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178 | |
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179 | sub worker { |
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180 | my ($slave_filehandle) = @_; |
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181 | |
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182 | # now $slave_filehandle is connected to the $master_filehandle |
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183 | # in the original prorcess. have fun! |
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184 | } |
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185 | |
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186 | =head2 Create a pool of server processes all accepting on the same socket. |
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187 | |
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188 | # create listener socket |
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189 | my $listener = ...; |
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190 | |
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191 | # create a pool template, initialise it and give it the socket |
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192 | my $pool = AnyEvent::Fork |
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193 | ->new |
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194 | ->require ("Some::Stuff", "My::Server") |
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195 | ->send_fh ($listener); |
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196 | |
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197 | # now create 10 identical workers |
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198 | for my $id (1..10) { |
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199 | $pool |
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200 | ->fork |
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201 | ->send_arg ($id) |
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202 | ->run ("My::Server::run"); |
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203 | } |
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204 | |
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205 | # now do other things - maybe use the filehandle provided by run |
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206 | # to wait for the processes to die. or whatever. |
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207 | |
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208 | C<My::Server> might look like this: |
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209 | |
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210 | package My::Server; |
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211 | |
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212 | sub run { |
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213 | my ($slave, $listener, $id) = @_; |
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214 | |
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215 | close $slave; # we do not use the socket, so close it to save resources |
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216 | |
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217 | # we could go ballistic and use e.g. AnyEvent here, or IO::AIO, |
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218 | # or anything we usually couldn't do in a process forked normally. |
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219 | while (my $socket = $listener->accept) { |
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220 | # do sth. with new socket |
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221 | } |
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222 | } |
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223 | |
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224 | =head2 use AnyEvent::Fork as a faster fork+exec |
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225 | |
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226 | This runs C</bin/echo hi>, with stdandard output redirected to /tmp/log |
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227 | and standard error redirected to the communications socket. It is usually |
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228 | faster than fork+exec, but still lets you prepare the environment. |
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229 | |
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230 | open my $output, ">/tmp/log" or die "$!"; |
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231 | |
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232 | AnyEvent::Fork |
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233 | ->new |
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234 | ->eval (' |
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235 | sub run { |
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236 | my ($fh, $output, @cmd) = @_; |
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237 | |
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238 | # perl will clear close-on-exec on STDOUT/STDERR |
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239 | open STDOUT, ">&", $output or die; |
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240 | open STDERR, ">&", $fh or die; |
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241 | |
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242 | exec @cmd; |
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243 | } |
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244 | ') |
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245 | ->send_fh ($output) |
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246 | ->send_arg ("/bin/echo", "hi") |
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247 | ->run ("run", my $cv = AE::cv); |
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248 | |
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249 | my $stderr = $cv->recv; |
88 | |
250 | |
89 | =head1 CONCEPTS |
251 | =head1 CONCEPTS |
90 | |
252 | |
91 | This module can create new processes either by executing a new perl |
253 | This module can create new processes either by executing a new perl |
92 | process, or by forking from an existing "template" process. |
254 | process, or by forking from an existing "template" process. |
… | |
… | |
109 | needed the first time. Forking from this process shares the memory used |
271 | needed the first time. Forking from this process shares the memory used |
110 | for the perl interpreter with the new process, but loading modules takes |
272 | for the perl interpreter with the new process, but loading modules takes |
111 | time, and the memory is not shared with anything else. |
273 | time, and the memory is not shared with anything else. |
112 | |
274 | |
113 | This is ideal for when you only need one extra process of a kind, with the |
275 | This is ideal for when you only need one extra process of a kind, with the |
114 | option of starting and stipping it on demand. |
276 | option of starting and stopping it on demand. |
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277 | |
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278 | Example: |
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279 | |
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280 | AnyEvent::Fork |
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281 | ->new |
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282 | ->require ("Some::Module") |
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283 | ->run ("Some::Module::run", sub { |
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284 | my ($fork_fh) = @_; |
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285 | }); |
115 | |
286 | |
116 | =item fork a new template process, load code, then fork processes off of |
287 | =item fork a new template process, load code, then fork processes off of |
117 | it and run the code |
288 | it and run the code |
118 | |
289 | |
119 | When you need to have a bunch of processes that all execute the same (or |
290 | When you need to have a bunch of processes that all execute the same (or |
… | |
… | |
125 | modules you loaded) is shared between the processes, and each new process |
296 | modules you loaded) is shared between the processes, and each new process |
126 | consumes relatively little memory of its own. |
297 | consumes relatively little memory of its own. |
127 | |
298 | |
128 | The disadvantage of this approach is that you need to create a template |
299 | The disadvantage of this approach is that you need to create a template |
129 | process for the sole purpose of forking new processes from it, but if you |
300 | process for the sole purpose of forking new processes from it, but if you |
130 | only need a fixed number of proceses you can create them, and then destroy |
301 | only need a fixed number of processes you can create them, and then destroy |
131 | the template process. |
302 | the template process. |
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303 | |
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304 | Example: |
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305 | |
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306 | my $template = AnyEvent::Fork->new->require ("Some::Module"); |
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307 | |
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308 | for (1..10) { |
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309 | $template->fork->run ("Some::Module::run", sub { |
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310 | my ($fork_fh) = @_; |
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311 | }); |
|
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312 | } |
|
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313 | |
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314 | # at this point, you can keep $template around to fork new processes |
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315 | # later, or you can destroy it, which causes it to vanish. |
132 | |
316 | |
133 | =item execute a new perl interpreter, load some code, run it |
317 | =item execute a new perl interpreter, load some code, run it |
134 | |
318 | |
135 | This is relatively slow, and doesn't allow you to share memory between |
319 | This is relatively slow, and doesn't allow you to share memory between |
136 | multiple processes. |
320 | multiple processes. |
… | |
… | |
138 | The only advantage is that you don't have to have a template process |
322 | The only advantage is that you don't have to have a template process |
139 | hanging around all the time to fork off some new processes, which might be |
323 | hanging around all the time to fork off some new processes, which might be |
140 | an advantage when there are long time spans where no extra processes are |
324 | an advantage when there are long time spans where no extra processes are |
141 | needed. |
325 | needed. |
142 | |
326 | |
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327 | Example: |
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328 | |
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329 | AnyEvent::Fork |
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330 | ->new_exec |
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331 | ->require ("Some::Module") |
|
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332 | ->run ("Some::Module::run", sub { |
|
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333 | my ($fork_fh) = @_; |
|
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334 | }); |
|
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335 | |
143 | =back |
336 | =back |
144 | |
337 | |
145 | =head1 FUNCTIONS |
338 | =head1 THE C<AnyEvent::Fork> CLASS |
|
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339 | |
|
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340 | This module exports nothing, and only implements a single class - |
|
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341 | C<AnyEvent::Fork>. |
|
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342 | |
|
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343 | There are two class constructors that both create new processes - C<new> |
|
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344 | and C<new_exec>. The C<fork> method creates a new process by forking an |
|
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345 | existing one and could be considered a third constructor. |
|
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346 | |
|
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347 | Most of the remaining methods deal with preparing the new process, by |
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348 | loading code, evaluating code and sending data to the new process. They |
|
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349 | usually return the process object, so you can chain method calls. |
|
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350 | |
|
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351 | If a process object is destroyed before calling its C<run> method, then |
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352 | the process simply exits. After C<run> is called, all responsibility is |
|
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353 | passed to the specified function. |
|
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354 | |
|
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355 | As long as there is any outstanding work to be done, process objects |
|
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356 | resist being destroyed, so there is no reason to store them unless you |
|
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357 | need them later - configure and forget works just fine. |
146 | |
358 | |
147 | =over 4 |
359 | =over 4 |
148 | |
360 | |
149 | =cut |
361 | =cut |
150 | |
362 | |
151 | package AnyEvent::Fork; |
363 | package AnyEvent::Fork; |
152 | |
364 | |
153 | use common::sense; |
365 | use common::sense; |
154 | |
366 | |
155 | use Socket (); |
367 | use Errno (); |
156 | |
368 | |
157 | use AnyEvent; |
369 | use AnyEvent; |
158 | use AnyEvent::Fork::Util; |
|
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159 | use AnyEvent::Util (); |
370 | use AnyEvent::Util (); |
160 | |
371 | |
|
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372 | use IO::FDPass; |
|
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373 | |
|
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374 | our $VERSION = 0.5; |
|
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375 | |
161 | our $PERL; # the path to the perl interpreter, deduces with various forms of magic |
376 | our $PERL; # the path to the perl interpreter, deduces with various forms of magic |
162 | |
|
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163 | =item my $pool = new AnyEvent::Fork key => value... |
|
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164 | |
|
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165 | Create a new process pool. The following named parameters are supported: |
|
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166 | |
377 | |
167 | =over 4 |
378 | =over 4 |
168 | |
379 | |
169 | =back |
380 | =back |
170 | |
381 | |
… | |
… | |
177 | our $TEMPLATE; |
388 | our $TEMPLATE; |
178 | |
389 | |
179 | sub _cmd { |
390 | sub _cmd { |
180 | my $self = shift; |
391 | my $self = shift; |
181 | |
392 | |
182 | # ideally, we would want to use "a (w/a)*" as format string, but perl versions |
393 | # ideally, we would want to use "a (w/a)*" as format string, but perl |
183 | # from at least 5.8.9 to 5.16.3 are all buggy and can't unpack it. |
394 | # versions from at least 5.8.9 to 5.16.3 are all buggy and can't unpack |
184 | push @{ $self->[2] }, pack "N/a", pack "(w/a)*", @_; |
395 | # it. |
|
|
396 | push @{ $self->[2] }, pack "a L/a*", $_[0], $_[1]; |
185 | |
397 | |
186 | $self->[3] ||= AE::io $self->[1], 1, sub { |
398 | $self->[3] ||= AE::io $self->[1], 1, sub { |
|
|
399 | do { |
|
|
400 | # send the next "thing" in the queue - either a reference to an fh, |
|
|
401 | # or a plain string. |
|
|
402 | |
187 | if (ref $self->[2][0]) { |
403 | if (ref $self->[2][0]) { |
|
|
404 | # send fh |
188 | AnyEvent::Fork::Util::fd_send fileno $self->[1], fileno ${ $self->[2][0] } |
405 | unless (IO::FDPass::send fileno $self->[1], fileno ${ $self->[2][0] }) { |
|
|
406 | return if $! == Errno::EAGAIN || $! == Errno::EWOULDBLOCK; |
|
|
407 | undef $self->[3]; |
|
|
408 | die "AnyEvent::Fork: file descriptor send failure: $!"; |
|
|
409 | } |
|
|
410 | |
189 | and shift @{ $self->[2] }; |
411 | shift @{ $self->[2] }; |
190 | |
412 | |
191 | } else { |
413 | } else { |
|
|
414 | # send string |
192 | my $len = syswrite $self->[1], $self->[2][0] |
415 | my $len = syswrite $self->[1], $self->[2][0]; |
|
|
416 | |
|
|
417 | unless ($len) { |
|
|
418 | return if $! == Errno::EAGAIN || $! == Errno::EWOULDBLOCK; |
|
|
419 | undef $self->[3]; |
193 | or do { undef $self->[3]; die "AnyEvent::Fork: command write failure: $!" }; |
420 | die "AnyEvent::Fork: command write failure: $!"; |
|
|
421 | } |
194 | |
422 | |
195 | substr $self->[2][0], 0, $len, ""; |
423 | substr $self->[2][0], 0, $len, ""; |
196 | shift @{ $self->[2] } unless length $self->[2][0]; |
424 | shift @{ $self->[2] } unless length $self->[2][0]; |
197 | } |
425 | } |
|
|
426 | } while @{ $self->[2] }; |
198 | |
427 | |
199 | unless (@{ $self->[2] }) { |
428 | # everything written |
200 | undef $self->[3]; |
429 | undef $self->[3]; |
|
|
430 | |
|
|
431 | # invoke run callback, if any |
201 | $self->[0]->($self->[1]) if $self->[0]; |
432 | $self->[4]->($self->[1]) if $self->[4]; |
202 | } |
|
|
203 | }; |
433 | }; |
|
|
434 | |
|
|
435 | () # make sure we don't leak the watcher |
204 | } |
436 | } |
205 | |
437 | |
206 | sub _new { |
438 | sub _new { |
207 | my ($self, $fh) = @_; |
439 | my ($self, $fh, $pid) = @_; |
|
|
440 | |
|
|
441 | AnyEvent::Util::fh_nonblocking $fh, 1; |
208 | |
442 | |
209 | $self = bless [ |
443 | $self = bless [ |
210 | undef, # run callback |
444 | $pid, |
211 | $fh, |
445 | $fh, |
212 | [], # write queue - strings or fd's |
446 | [], # write queue - strings or fd's |
213 | undef, # AE watcher |
447 | undef, # AE watcher |
214 | ], $self; |
448 | ], $self; |
215 | |
449 | |
216 | # my ($a, $b) = AnyEvent::Util::portable_socketpair; |
|
|
217 | |
|
|
218 | # queue_cmd $template, "Iabc"; |
|
|
219 | # push @{ $template->[2] }, \$b; |
|
|
220 | |
|
|
221 | # use Coro::AnyEvent; Coro::AnyEvent::sleep 1; |
|
|
222 | # undef $b; |
|
|
223 | # die "x" . <$a>; |
|
|
224 | |
|
|
225 | $self |
450 | $self |
|
|
451 | } |
|
|
452 | |
|
|
453 | # fork template from current process, used by AnyEvent::Fork::Early/Template |
|
|
454 | sub _new_fork { |
|
|
455 | my ($fh, $slave) = AnyEvent::Util::portable_socketpair; |
|
|
456 | my $parent = $$; |
|
|
457 | |
|
|
458 | my $pid = fork; |
|
|
459 | |
|
|
460 | if ($pid eq 0) { |
|
|
461 | require AnyEvent::Fork::Serve; |
|
|
462 | $AnyEvent::Fork::Serve::OWNER = $parent; |
|
|
463 | close $fh; |
|
|
464 | $0 = "$_[1] of $parent"; |
|
|
465 | $SIG{CHLD} = 'IGNORE'; |
|
|
466 | AnyEvent::Fork::Serve::serve ($slave); |
|
|
467 | exit 0; |
|
|
468 | } elsif (!$pid) { |
|
|
469 | die "AnyEvent::Fork::Early/Template: unable to fork template process: $!"; |
|
|
470 | } |
|
|
471 | |
|
|
472 | AnyEvent::Fork->_new ($fh, $pid) |
226 | } |
473 | } |
227 | |
474 | |
228 | =item my $proc = new AnyEvent::Fork |
475 | =item my $proc = new AnyEvent::Fork |
229 | |
476 | |
230 | Create a new "empty" perl interpreter process and returns its process |
477 | Create a new "empty" perl interpreter process and returns its process |
231 | object for further manipulation. |
478 | object for further manipulation. |
232 | |
479 | |
233 | The new process is forked from a template process that is kept around |
480 | The new process is forked from a template process that is kept around |
234 | for this purpose. When it doesn't exist yet, it is created by a call to |
481 | for this purpose. When it doesn't exist yet, it is created by a call to |
235 | C<new_exec> and kept around for future calls. |
482 | C<new_exec> first and then stays around for future calls. |
236 | |
483 | |
237 | =cut |
484 | =cut |
238 | |
485 | |
239 | sub new { |
486 | sub new { |
240 | my $class = shift; |
487 | my $class = shift; |
… | |
… | |
261 | my ($fh, $slave) = AnyEvent::Util::portable_socketpair; |
508 | my ($fh, $slave) = AnyEvent::Util::portable_socketpair; |
262 | |
509 | |
263 | $self->send_fh ($slave); |
510 | $self->send_fh ($slave); |
264 | $self->_cmd ("f"); |
511 | $self->_cmd ("f"); |
265 | |
512 | |
266 | AnyEvent::Util::fh_nonblocking $fh, 1; |
|
|
267 | |
|
|
268 | AnyEvent::Fork->_new ($fh) |
513 | AnyEvent::Fork->_new ($fh) |
269 | } |
514 | } |
270 | |
515 | |
271 | =item my $proc = new_exec AnyEvent::Fork |
516 | =item my $proc = new_exec AnyEvent::Fork |
272 | |
517 | |
… | |
… | |
278 | reduces the amount of memory sharing that is possible, and is also slower. |
523 | reduces the amount of memory sharing that is possible, and is also slower. |
279 | |
524 | |
280 | You should use C<new> whenever possible, except when having a template |
525 | You should use C<new> whenever possible, except when having a template |
281 | process around is unacceptable. |
526 | process around is unacceptable. |
282 | |
527 | |
283 | The path to the perl interpreter is divined usign various methods - first |
528 | The path to the perl interpreter is divined using various methods - first |
284 | C<$^X> is investigated to see if the path ends with something that sounds |
529 | C<$^X> is investigated to see if the path ends with something that sounds |
285 | as if it were the perl interpreter. Failing this, the module falls back to |
530 | as if it were the perl interpreter. Failing this, the module falls back to |
286 | using C<$Config::Config{perlpath}>. |
531 | using C<$Config::Config{perlpath}>. |
287 | |
532 | |
288 | =cut |
533 | =cut |
… | |
… | |
297 | my $perl = $; |
542 | my $perl = $; |
298 | |
543 | |
299 | # first we try $^X, but the path must be absolute (always on win32), and end in sth. |
544 | # first we try $^X, but the path must be absolute (always on win32), and end in sth. |
300 | # that looks like perl. this obviously only works for posix and win32 |
545 | # that looks like perl. this obviously only works for posix and win32 |
301 | unless ( |
546 | unless ( |
302 | (AnyEvent::Fork::Util::WIN32 || $perl =~ m%^/%) |
547 | ($^O eq "MSWin32" || $perl =~ m%^/%) |
303 | && $perl =~ m%[/\\]perl(?:[0-9]+(\.[0-9]+)+)?(\.exe)?$%i |
548 | && $perl =~ m%[/\\]perl(?:[0-9]+(\.[0-9]+)+)?(\.exe)?$%i |
304 | ) { |
549 | ) { |
305 | # if it doesn't look perlish enough, try Config |
550 | # if it doesn't look perlish enough, try Config |
306 | require Config; |
551 | require Config; |
307 | $perl = $Config::Config{perlpath}; |
552 | $perl = $Config::Config{perlpath}; |
… | |
… | |
309 | } |
554 | } |
310 | |
555 | |
311 | require Proc::FastSpawn; |
556 | require Proc::FastSpawn; |
312 | |
557 | |
313 | my ($fh, $slave) = AnyEvent::Util::portable_socketpair; |
558 | my ($fh, $slave) = AnyEvent::Util::portable_socketpair; |
314 | AnyEvent::Util::fh_nonblocking $fh, 1; |
|
|
315 | Proc::FastSpawn::fd_inherit (fileno $slave); |
559 | Proc::FastSpawn::fd_inherit (fileno $slave); |
|
|
560 | |
|
|
561 | # new fh's should always be set cloexec (due to $^F), |
|
|
562 | # but hey, not on win32, so we always clear the inherit flag. |
|
|
563 | Proc::FastSpawn::fd_inherit (fileno $fh, 0); |
316 | |
564 | |
317 | # quick. also doesn't work in win32. of course. what did you expect |
565 | # quick. also doesn't work in win32. of course. what did you expect |
318 | #local $ENV{PERL5LIB} = join ":", grep !ref, @INC; |
566 | #local $ENV{PERL5LIB} = join ":", grep !ref, @INC; |
319 | my %env = %ENV; |
567 | my %env = %ENV; |
320 | $env{PERL5LIB} = join ":", grep !ref, @INC; |
568 | $env{PERL5LIB} = join +($^O eq "MSWin32" ? ";" : ":"), grep !ref, @INC; |
321 | |
569 | |
322 | Proc::FastSpawn::spawn ( |
570 | my $pid = Proc::FastSpawn::spawn ( |
323 | $perl, |
571 | $perl, |
324 | ["perl", "-MAnyEvent::Fork::Serve", "-e", "AnyEvent::Fork::Serve::me", fileno $slave], |
572 | ["perl", "-MAnyEvent::Fork::Serve", "-e", "AnyEvent::Fork::Serve::me", fileno $slave, $$], |
325 | [map "$_=$env{$_}", keys %env], |
573 | [map "$_=$env{$_}", keys %env], |
326 | ) or die "unable to spawn AnyEvent::Fork server: $!"; |
574 | ) or die "unable to spawn AnyEvent::Fork server: $!"; |
327 | |
575 | |
328 | $self->_new ($fh) |
576 | $self->_new ($fh, $pid) |
|
|
577 | } |
|
|
578 | |
|
|
579 | =item $pid = $proc->pid |
|
|
580 | |
|
|
581 | Returns the process id of the process I<iff it is a direct child of the |
|
|
582 | process running AnyEvent::Fork>, and C<undef> otherwise. |
|
|
583 | |
|
|
584 | Normally, only processes created via C<< AnyEvent::Fork->new_exec >> and |
|
|
585 | L<AnyEvent::Fork::Template> are direct children, and you are responsible |
|
|
586 | to clean up their zombies when they die. |
|
|
587 | |
|
|
588 | All other processes are not direct children, and will be cleaned up by |
|
|
589 | AnyEvent::Fork itself. |
|
|
590 | |
|
|
591 | =cut |
|
|
592 | |
|
|
593 | sub pid { |
|
|
594 | $_[0][0] |
|
|
595 | } |
|
|
596 | |
|
|
597 | =item $proc = $proc->eval ($perlcode, @args) |
|
|
598 | |
|
|
599 | Evaluates the given C<$perlcode> as ... perl code, while setting C<@_> to |
|
|
600 | the strings specified by C<@args>, in the "main" package. |
|
|
601 | |
|
|
602 | This call is meant to do any custom initialisation that might be required |
|
|
603 | (for example, the C<require> method uses it). It's not supposed to be used |
|
|
604 | to completely take over the process, use C<run> for that. |
|
|
605 | |
|
|
606 | The code will usually be executed after this call returns, and there is no |
|
|
607 | way to pass anything back to the calling process. Any evaluation errors |
|
|
608 | will be reported to stderr and cause the process to exit. |
|
|
609 | |
|
|
610 | If you want to execute some code (that isn't in a module) to take over the |
|
|
611 | process, you should compile a function via C<eval> first, and then call |
|
|
612 | it via C<run>. This also gives you access to any arguments passed via the |
|
|
613 | C<send_xxx> methods, such as file handles. See the L<use AnyEvent::Fork as |
|
|
614 | a faster fork+exec> example to see it in action. |
|
|
615 | |
|
|
616 | Returns the process object for easy chaining of method calls. |
|
|
617 | |
|
|
618 | =cut |
|
|
619 | |
|
|
620 | sub eval { |
|
|
621 | my ($self, $code, @args) = @_; |
|
|
622 | |
|
|
623 | $self->_cmd (e => pack "(w/a*)*", $code, @args); |
|
|
624 | |
|
|
625 | $self |
329 | } |
626 | } |
330 | |
627 | |
331 | =item $proc = $proc->require ($module, ...) |
628 | =item $proc = $proc->require ($module, ...) |
332 | |
629 | |
333 | Tries to load the given modules into the process |
630 | Tries to load the given module(s) into the process |
334 | |
631 | |
335 | Returns the process object for easy chaining of method calls. |
632 | Returns the process object for easy chaining of method calls. |
|
|
633 | |
|
|
634 | =cut |
|
|
635 | |
|
|
636 | sub require { |
|
|
637 | my ($self, @modules) = @_; |
|
|
638 | |
|
|
639 | s%::%/%g for @modules; |
|
|
640 | $self->eval ('require "$_.pm" for @_', @modules); |
|
|
641 | |
|
|
642 | $self |
|
|
643 | } |
336 | |
644 | |
337 | =item $proc = $proc->send_fh ($handle, ...) |
645 | =item $proc = $proc->send_fh ($handle, ...) |
338 | |
646 | |
339 | Send one or more file handles (I<not> file descriptors) to the process, |
647 | Send one or more file handles (I<not> file descriptors) to the process, |
340 | to prepare a call to C<run>. |
648 | to prepare a call to C<run>. |
341 | |
649 | |
342 | The process object keeps a reference to the handles until this is done, |
650 | The process object keeps a reference to the handles until they have |
343 | so you must not explicitly close the handles. This is most easily |
651 | been passed over to the process, so you must not explicitly close the |
344 | accomplished by simply not storing the file handles anywhere after passing |
652 | handles. This is most easily accomplished by simply not storing the file |
345 | them to this method. |
653 | handles anywhere after passing them to this method - when AnyEvent::Fork |
|
|
654 | is finished using them, perl will automatically close them. |
346 | |
655 | |
347 | Returns the process object for easy chaining of method calls. |
656 | Returns the process object for easy chaining of method calls. |
|
|
657 | |
|
|
658 | Example: pass a file handle to a process, and release it without |
|
|
659 | closing. It will be closed automatically when it is no longer used. |
|
|
660 | |
|
|
661 | $proc->send_fh ($my_fh); |
|
|
662 | undef $my_fh; # free the reference if you want, but DO NOT CLOSE IT |
348 | |
663 | |
349 | =cut |
664 | =cut |
350 | |
665 | |
351 | sub send_fh { |
666 | sub send_fh { |
352 | my ($self, @fh) = @_; |
667 | my ($self, @fh) = @_; |
… | |
… | |
360 | } |
675 | } |
361 | |
676 | |
362 | =item $proc = $proc->send_arg ($string, ...) |
677 | =item $proc = $proc->send_arg ($string, ...) |
363 | |
678 | |
364 | Send one or more argument strings to the process, to prepare a call to |
679 | Send one or more argument strings to the process, to prepare a call to |
365 | C<run>. The strings can be any octet string. |
680 | C<run>. The strings can be any octet strings. |
366 | |
681 | |
|
|
682 | The protocol is optimised to pass a moderate number of relatively short |
|
|
683 | strings - while you can pass up to 4GB of data in one go, this is more |
|
|
684 | meant to pass some ID information or other startup info, not big chunks of |
|
|
685 | data. |
|
|
686 | |
367 | Returns the process object for easy chaining of emthod calls. |
687 | Returns the process object for easy chaining of method calls. |
368 | |
688 | |
369 | =cut |
689 | =cut |
370 | |
690 | |
371 | sub send_arg { |
691 | sub send_arg { |
372 | my ($self, @arg) = @_; |
692 | my ($self, @arg) = @_; |
373 | |
693 | |
374 | $self->_cmd (a => @arg); |
694 | $self->_cmd (a => pack "(w/a*)*", @arg); |
375 | |
695 | |
376 | $self |
696 | $self |
377 | } |
697 | } |
378 | |
698 | |
379 | =item $proc->run ($func, $cb->($fh)) |
699 | =item $proc->run ($func, $cb->($fh)) |
380 | |
700 | |
381 | Enter the function specified by the fully qualified name in C<$func> in |
701 | Enter the function specified by the function name in C<$func> in the |
382 | the process. The function is called with the communication socket as first |
702 | process. The function is called with the communication socket as first |
383 | argument, followed by all file handles and string arguments sent earlier |
703 | argument, followed by all file handles and string arguments sent earlier |
384 | via C<send_fh> and C<send_arg> methods, in the order they were called. |
704 | via C<send_fh> and C<send_arg> methods, in the order they were called. |
385 | |
705 | |
386 | If the called function returns, the process exits. |
|
|
387 | |
|
|
388 | Preparing the process can take time - when the process is ready, the |
|
|
389 | callback is invoked with the local communications socket as argument. |
|
|
390 | |
|
|
391 | The process object becomes unusable on return from this function. |
706 | The process object becomes unusable on return from this function - any |
|
|
707 | further method calls result in undefined behaviour. |
|
|
708 | |
|
|
709 | The function name should be fully qualified, but if it isn't, it will be |
|
|
710 | looked up in the C<main> package. |
|
|
711 | |
|
|
712 | If the called function returns, doesn't exist, or any error occurs, the |
|
|
713 | process exits. |
|
|
714 | |
|
|
715 | Preparing the process is done in the background - when all commands have |
|
|
716 | been sent, the callback is invoked with the local communications socket |
|
|
717 | as argument. At this point you can start using the socket in any way you |
|
|
718 | like. |
392 | |
719 | |
393 | If the communication socket isn't used, it should be closed on both sides, |
720 | If the communication socket isn't used, it should be closed on both sides, |
394 | to save on kernel memory. |
721 | to save on kernel memory. |
395 | |
722 | |
396 | The socket is non-blocking in the parent, and blocking in the newly |
723 | The socket is non-blocking in the parent, and blocking in the newly |
397 | created process. The close-on-exec flag is set on both. Even if not used |
724 | created process. The close-on-exec flag is set in both. |
|
|
725 | |
398 | otherwise, the socket can be a good indicator for the existance of the |
726 | Even if not used otherwise, the socket can be a good indicator for the |
399 | process - if the othe rprocess exits, you get a readable event on it, |
727 | existence of the process - if the other process exits, you get a readable |
400 | because exiting the process closes the socket (if it didn't create any |
728 | event on it, because exiting the process closes the socket (if it didn't |
401 | children using fork). |
729 | create any children using fork). |
|
|
730 | |
|
|
731 | Example: create a template for a process pool, pass a few strings, some |
|
|
732 | file handles, then fork, pass one more string, and run some code. |
|
|
733 | |
|
|
734 | my $pool = AnyEvent::Fork |
|
|
735 | ->new |
|
|
736 | ->send_arg ("str1", "str2") |
|
|
737 | ->send_fh ($fh1, $fh2); |
|
|
738 | |
|
|
739 | for (1..2) { |
|
|
740 | $pool |
|
|
741 | ->fork |
|
|
742 | ->send_arg ("str3") |
|
|
743 | ->run ("Some::function", sub { |
|
|
744 | my ($fh) = @_; |
|
|
745 | |
|
|
746 | # fh is nonblocking, but we trust that the OS can accept these |
|
|
747 | # few octets anyway. |
|
|
748 | syswrite $fh, "hi #$_\n"; |
|
|
749 | |
|
|
750 | # $fh is being closed here, as we don't store it anywhere |
|
|
751 | }); |
|
|
752 | } |
|
|
753 | |
|
|
754 | # Some::function might look like this - all parameters passed before fork |
|
|
755 | # and after will be passed, in order, after the communications socket. |
|
|
756 | sub Some::function { |
|
|
757 | my ($fh, $str1, $str2, $fh1, $fh2, $str3) = @_; |
|
|
758 | |
|
|
759 | print scalar <$fh>; # prints "hi #1\n" and "hi #2\n" in any order |
|
|
760 | } |
402 | |
761 | |
403 | =cut |
762 | =cut |
404 | |
763 | |
405 | sub run { |
764 | sub run { |
406 | my ($self, $func, $cb) = @_; |
765 | my ($self, $func, $cb) = @_; |
407 | |
766 | |
408 | $self->[0] = $cb; |
767 | $self->[4] = $cb; |
409 | $self->_cmd ("r", $func); |
768 | $self->_cmd (r => $func); |
410 | } |
769 | } |
411 | |
770 | |
412 | =back |
771 | =back |
|
|
772 | |
|
|
773 | =head1 PERFORMANCE |
|
|
774 | |
|
|
775 | Now for some unscientific benchmark numbers (all done on an amd64 |
|
|
776 | GNU/Linux box). These are intended to give you an idea of the relative |
|
|
777 | performance you can expect, they are not meant to be absolute performance |
|
|
778 | numbers. |
|
|
779 | |
|
|
780 | OK, so, I ran a simple benchmark that creates a socket pair, forks, calls |
|
|
781 | exit in the child and waits for the socket to close in the parent. I did |
|
|
782 | load AnyEvent, EV and AnyEvent::Fork, for a total process size of 5100kB. |
|
|
783 | |
|
|
784 | 2079 new processes per second, using manual socketpair + fork |
|
|
785 | |
|
|
786 | Then I did the same thing, but instead of calling fork, I called |
|
|
787 | AnyEvent::Fork->new->run ("CORE::exit") and then again waited for the |
|
|
788 | socket form the child to close on exit. This does the same thing as manual |
|
|
789 | socket pair + fork, except that what is forked is the template process |
|
|
790 | (2440kB), and the socket needs to be passed to the server at the other end |
|
|
791 | of the socket first. |
|
|
792 | |
|
|
793 | 2307 new processes per second, using AnyEvent::Fork->new |
|
|
794 | |
|
|
795 | And finally, using C<new_exec> instead C<new>, using vforks+execs to exec |
|
|
796 | a new perl interpreter and compile the small server each time, I get: |
|
|
797 | |
|
|
798 | 479 vfork+execs per second, using AnyEvent::Fork->new_exec |
|
|
799 | |
|
|
800 | So how can C<< AnyEvent->new >> be faster than a standard fork, even |
|
|
801 | though it uses the same operations, but adds a lot of overhead? |
|
|
802 | |
|
|
803 | The difference is simply the process size: forking the 5MB process takes |
|
|
804 | so much longer than forking the 2.5MB template process that the extra |
|
|
805 | overhead introduced is canceled out. |
|
|
806 | |
|
|
807 | If the benchmark process grows, the normal fork becomes even slower: |
|
|
808 | |
|
|
809 | 1340 new processes, manual fork of a 20MB process |
|
|
810 | 731 new processes, manual fork of a 200MB process |
|
|
811 | 235 new processes, manual fork of a 2000MB process |
|
|
812 | |
|
|
813 | What that means (to me) is that I can use this module without having a bad |
|
|
814 | conscience because of the extra overhead required to start new processes. |
|
|
815 | |
|
|
816 | =head1 TYPICAL PROBLEMS |
|
|
817 | |
|
|
818 | This section lists typical problems that remain. I hope by recognising |
|
|
819 | them, most can be avoided. |
|
|
820 | |
|
|
821 | =over 4 |
|
|
822 | |
|
|
823 | =item leaked file descriptors for exec'ed processes |
|
|
824 | |
|
|
825 | POSIX systems inherit file descriptors by default when exec'ing a new |
|
|
826 | process. While perl itself laudably sets the close-on-exec flags on new |
|
|
827 | file handles, most C libraries don't care, and even if all cared, it's |
|
|
828 | often not possible to set the flag in a race-free manner. |
|
|
829 | |
|
|
830 | That means some file descriptors can leak through. And since it isn't |
|
|
831 | possible to know which file descriptors are "good" and "necessary" (or |
|
|
832 | even to know which file descriptors are open), there is no good way to |
|
|
833 | close the ones that might harm. |
|
|
834 | |
|
|
835 | As an example of what "harm" can be done consider a web server that |
|
|
836 | accepts connections and afterwards some module uses AnyEvent::Fork for the |
|
|
837 | first time, causing it to fork and exec a new process, which might inherit |
|
|
838 | the network socket. When the server closes the socket, it is still open |
|
|
839 | in the child (which doesn't even know that) and the client might conclude |
|
|
840 | that the connection is still fine. |
|
|
841 | |
|
|
842 | For the main program, there are multiple remedies available - |
|
|
843 | L<AnyEvent::Fork::Early> is one, creating a process early and not using |
|
|
844 | C<new_exec> is another, as in both cases, the first process can be exec'ed |
|
|
845 | well before many random file descriptors are open. |
|
|
846 | |
|
|
847 | In general, the solution for these kind of problems is to fix the |
|
|
848 | libraries or the code that leaks those file descriptors. |
|
|
849 | |
|
|
850 | Fortunately, most of these leaked descriptors do no harm, other than |
|
|
851 | sitting on some resources. |
|
|
852 | |
|
|
853 | =item leaked file descriptors for fork'ed processes |
|
|
854 | |
|
|
855 | Normally, L<AnyEvent::Fork> does start new processes by exec'ing them, |
|
|
856 | which closes file descriptors not marked for being inherited. |
|
|
857 | |
|
|
858 | However, L<AnyEvent::Fork::Early> and L<AnyEvent::Fork::Template> offer |
|
|
859 | a way to create these processes by forking, and this leaks more file |
|
|
860 | descriptors than exec'ing them, as there is no way to mark descriptors as |
|
|
861 | "close on fork". |
|
|
862 | |
|
|
863 | An example would be modules like L<EV>, L<IO::AIO> or L<Gtk2>. Both create |
|
|
864 | pipes for internal uses, and L<Gtk2> might open a connection to the X |
|
|
865 | server. L<EV> and L<IO::AIO> can deal with fork, but Gtk2 might have |
|
|
866 | trouble with a fork. |
|
|
867 | |
|
|
868 | The solution is to either not load these modules before use'ing |
|
|
869 | L<AnyEvent::Fork::Early> or L<AnyEvent::Fork::Template>, or to delay |
|
|
870 | initialising them, for example, by calling C<init Gtk2> manually. |
|
|
871 | |
|
|
872 | =item exiting calls object destructors |
|
|
873 | |
|
|
874 | This only applies to users of L<AnyEvent::Fork:Early> and |
|
|
875 | L<AnyEvent::Fork::Template>, or when initialiasing code creates objects |
|
|
876 | that reference external resources. |
|
|
877 | |
|
|
878 | When a process created by AnyEvent::Fork exits, it might do so by calling |
|
|
879 | exit, or simply letting perl reach the end of the program. At which point |
|
|
880 | Perl runs all destructors. |
|
|
881 | |
|
|
882 | Not all destructors are fork-safe - for example, an object that represents |
|
|
883 | the connection to an X display might tell the X server to free resources, |
|
|
884 | which is inconvenient when the "real" object in the parent still needs to |
|
|
885 | use them. |
|
|
886 | |
|
|
887 | This is obviously not a problem for L<AnyEvent::Fork::Early>, as you used |
|
|
888 | it as the very first thing, right? |
|
|
889 | |
|
|
890 | It is a problem for L<AnyEvent::Fork::Template> though - and the solution |
|
|
891 | is to not create objects with nontrivial destructors that might have an |
|
|
892 | effect outside of Perl. |
|
|
893 | |
|
|
894 | =back |
|
|
895 | |
|
|
896 | =head1 PORTABILITY NOTES |
|
|
897 | |
|
|
898 | Native win32 perls are somewhat supported (AnyEvent::Fork::Early is a nop, |
|
|
899 | and ::Template is not going to work), and it cost a lot of blood and sweat |
|
|
900 | to make it so, mostly due to the bloody broken perl that nobody seems to |
|
|
901 | care about. The fork emulation is a bad joke - I have yet to see something |
|
|
902 | useful that you can do with it without running into memory corruption |
|
|
903 | issues or other braindamage. Hrrrr. |
|
|
904 | |
|
|
905 | Cygwin perl is not supported at the moment due to some hilarious |
|
|
906 | shortcomings of its API - see L<IO::FDPoll> for more details. |
|
|
907 | |
|
|
908 | =head1 SEE ALSO |
|
|
909 | |
|
|
910 | L<AnyEvent::Fork::Early> (to avoid executing a perl interpreter), |
|
|
911 | L<AnyEvent::Fork::Template> (to create a process by forking the main |
|
|
912 | program at a convenient time). |
413 | |
913 | |
414 | =head1 AUTHOR |
914 | =head1 AUTHOR |
415 | |
915 | |
416 | Marc Lehmann <schmorp@schmorp.de> |
916 | Marc Lehmann <schmorp@schmorp.de> |
417 | http://home.schmorp.de/ |
917 | http://home.schmorp.de/ |