1 | =head1 NAME |
1 | =head1 NAME |
2 | |
2 | |
3 | AnyEvent::ProcessPool - manage pools of perl worker processes, exec'ed or fork'ed |
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::ProcessPool; |
7 | use AnyEvent::Fork; |
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8 | |
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9 | ################################################################## |
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10 | # create a single new process, tell it to run your worker function |
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11 | |
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12 | AnyEvent::Fork |
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13 | ->new |
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14 | ->require ("MyModule") |
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15 | ->run ("MyModule::worker, sub { |
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16 | my ($master_filehandle) = @_; |
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17 | |
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18 | # now $master_filehandle is connected to the |
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19 | # $slave_filehandle in the new process. |
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20 | }); |
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21 | |
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22 | # MyModule::worker might look like this |
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23 | sub MyModule::worker { |
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24 | my ($slave_filehandle) = @_; |
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25 | |
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26 | # now $slave_filehandle is connected to the $master_filehandle |
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27 | # in the original prorcess. have fun! |
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28 | } |
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29 | |
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30 | ################################################################## |
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31 | # create a pool of server processes all accepting on the same socket |
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32 | |
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33 | # create listener socket |
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34 | my $listener = ...; |
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35 | |
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36 | # create a pool template, initialise it and give it the socket |
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37 | my $pool = AnyEvent::Fork |
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38 | ->new |
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39 | ->require ("Some::Stuff", "My::Server") |
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40 | ->send_fh ($listener); |
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41 | |
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42 | # now create 10 identical workers |
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43 | for my $id (1..10) { |
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44 | $pool |
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45 | ->fork |
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46 | ->send_arg ($id) |
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47 | ->run ("My::Server::run"); |
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48 | } |
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49 | |
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50 | # now do other things - maybe use the filehandle provided by run |
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51 | # to wait for the processes to die. or whatever. |
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52 | |
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53 | # My::Server::run might look like this |
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54 | sub My::Server::run { |
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55 | my ($slave, $listener, $id) = @_; |
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56 | |
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57 | close $slave; # we do not use the socket, so close it to save resources |
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58 | |
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59 | # we could go ballistic and use e.g. AnyEvent here, or IO::AIO, |
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60 | # or anything we usually couldn't do in a process forked normally. |
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61 | while (my $socket = $listener->accept) { |
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62 | # do sth. with new socket |
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63 | } |
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64 | } |
8 | |
65 | |
9 | =head1 DESCRIPTION |
66 | =head1 DESCRIPTION |
10 | |
67 | |
11 | This module allows you to create single worker processes but also worker |
68 | This module allows you to create new processes, without actually forking |
12 | pool that share memory, by forking from the main program, or exec'ing new |
69 | them from your current process (avoiding the problems of forking), but |
13 | perl interpreters from a module. |
70 | preserving most of the advantages of fork. |
14 | |
71 | |
15 | You create a new processes in a pool by specifying a function to call |
72 | It can be used to create new worker processes or new independent |
16 | with any combination of string values and file handles. |
73 | subprocesses for short- and long-running jobs, process pools (e.g. for use |
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74 | in pre-forked servers) but also to spawn new external processes (such as |
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75 | CGI scripts from a web server), which can be faster (and more well behaved) |
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76 | than using fork+exec in big processes. |
17 | |
77 | |
18 | A pool can have initialisation code which is executed before forking. The |
78 | Special care has been taken to make this module useful from other modules, |
19 | initialisation code is only executed once and the resulting process is |
79 | while still supporting specialised environments such as L<App::Staticperl> |
20 | cached, to be used as a template. |
80 | or L<PAR::Packer>. |
21 | |
81 | |
22 | Pools without such initialisation code don't cache an extra process. |
82 | =head1 WHAT THIS MODULE IS NOT |
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83 | |
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84 | This module only creates processes and lets you pass file handles and |
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85 | strings to it, and run perl code. It does not implement any kind of RPC - |
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86 | there is no back channel from the process back to you, and there is no RPC |
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87 | or message passing going on. |
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88 | |
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89 | If you need some form of RPC, you can either implement it yourself |
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90 | in whatever way you like, use some message-passing module such |
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91 | as L<AnyEvent::MP>, some pipe such as L<AnyEvent::ZeroMQ>, use |
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92 | L<AnyEvent::Handle> on both sides to send e.g. JSON or Storable messages, |
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93 | and so on. |
23 | |
94 | |
24 | =head1 PROBLEM STATEMENT |
95 | =head1 PROBLEM STATEMENT |
25 | |
96 | |
26 | There are two ways to implement parallel processing on UNIX like operating |
97 | There are two ways to implement parallel processing on UNIX like operating |
27 | systems - fork and process, and fork+exec and process. They have different |
98 | systems - fork and process, and fork+exec and process. They have different |
… | |
… | |
39 | or fork+exec instead. |
110 | or fork+exec instead. |
40 | |
111 | |
41 | =item Forking usually creates a copy-on-write copy of the parent |
112 | =item Forking usually creates a copy-on-write copy of the parent |
42 | process. Memory (for example, modules or data files that have been |
113 | process. Memory (for example, modules or data files that have been |
43 | will not take additional memory). When exec'ing a new process, modules |
114 | will not take additional memory). When exec'ing a new process, modules |
44 | and data files might need to be loaded again, at extra cpu and memory |
115 | and data files might need to be loaded again, at extra CPU and memory |
45 | cost. Likewise when forking, all data structures are copied as well - if |
116 | cost. Likewise when forking, all data structures are copied as well - if |
46 | the program frees them and replaces them by new data, the child processes |
117 | the program frees them and replaces them by new data, the child processes |
47 | will retain the memory even if it isn't used. |
118 | will retain the memory even if it isn't used. |
48 | |
119 | |
49 | This module allows the main program to do a controlled fork, and allows |
120 | This module allows the main program to do a controlled fork, and allows |
… | |
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61 | as template, and also tries hard to identify the correct path to the perl |
132 | as template, and also tries hard to identify the correct path to the perl |
62 | interpreter. With a cooperative main program, exec'ing the interpreter |
133 | interpreter. With a cooperative main program, exec'ing the interpreter |
63 | might not even be necessary. |
134 | might not even be necessary. |
64 | |
135 | |
65 | =item Forking might be impossible when a program is running. For example, |
136 | =item Forking might be impossible when a program is running. For example, |
66 | POSIX makes it almost impossible to fork from a multithreaded program and |
137 | POSIX makes it almost impossible to fork from a multi-threaded program and |
67 | do anything useful in the child - strictly speaking, if your perl program |
138 | do anything useful in the child - strictly speaking, if your perl program |
68 | uses posix threads (even indirectly via e.g. L<IO::AIO> or L<threads>), |
139 | uses posix threads (even indirectly via e.g. L<IO::AIO> or L<threads>), |
69 | you cannot call fork on the perl level anymore, at all. |
140 | you cannot call fork on the perl level anymore, at all. |
70 | |
141 | |
71 | This module can safely fork helper processes at any time, by caling |
142 | This module can safely fork helper processes at any time, by calling |
72 | fork+exec in C, in a POSIX-compatible way. |
143 | fork+exec in C, in a POSIX-compatible way. |
73 | |
144 | |
74 | =item Parallel processing with fork might be inconvenient or difficult |
145 | =item Parallel processing with fork might be inconvenient or difficult |
75 | to implement. For example, when a program uses an event loop and creates |
146 | to implement. For example, when a program uses an event loop and creates |
76 | watchers it becomes very hard to use the event loop from a child |
147 | watchers it becomes very hard to use the event loop from a child |
… | |
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83 | pools are created by fork+exec, after which such modules can again be |
154 | pools are created by fork+exec, after which such modules can again be |
84 | loaded. |
155 | loaded. |
85 | |
156 | |
86 | =back |
157 | =back |
87 | |
158 | |
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159 | =head1 CONCEPTS |
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160 | |
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161 | This module can create new processes either by executing a new perl |
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162 | process, or by forking from an existing "template" process. |
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163 | |
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164 | Each such process comes with its own file handle that can be used to |
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165 | communicate with it (it's actually a socket - one end in the new process, |
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166 | one end in the main process), and among the things you can do in it are |
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167 | load modules, fork new processes, send file handles to it, and execute |
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168 | functions. |
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169 | |
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170 | There are multiple ways to create additional processes to execute some |
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171 | jobs: |
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172 | |
88 | =over 4 |
173 | =over 4 |
89 | |
174 | |
90 | =cut |
175 | =item fork a new process from the "default" template process, load code, |
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176 | run it |
91 | |
177 | |
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178 | This module has a "default" template process which it executes when it is |
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179 | needed the first time. Forking from this process shares the memory used |
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180 | for the perl interpreter with the new process, but loading modules takes |
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181 | time, and the memory is not shared with anything else. |
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182 | |
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183 | This is ideal for when you only need one extra process of a kind, with the |
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184 | option of starting and stopping it on demand. |
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185 | |
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186 | Example: |
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187 | |
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188 | AnyEvent::Fork |
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189 | ->new |
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190 | ->require ("Some::Module") |
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191 | ->run ("Some::Module::run", sub { |
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192 | my ($fork_fh) = @_; |
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193 | }); |
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194 | |
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195 | =item fork a new template process, load code, then fork processes off of |
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196 | it and run the code |
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197 | |
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198 | When you need to have a bunch of processes that all execute the same (or |
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199 | very similar) tasks, then a good way is to create a new template process |
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200 | for them, loading all the modules you need, and then create your worker |
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201 | processes from this new template process. |
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202 | |
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203 | This way, all code (and data structures) that can be shared (e.g. the |
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204 | modules you loaded) is shared between the processes, and each new process |
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205 | consumes relatively little memory of its own. |
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206 | |
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207 | The disadvantage of this approach is that you need to create a template |
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208 | process for the sole purpose of forking new processes from it, but if you |
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209 | only need a fixed number of processes you can create them, and then destroy |
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210 | the template process. |
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211 | |
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212 | Example: |
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213 | |
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214 | my $template = AnyEvent::Fork->new->require ("Some::Module"); |
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215 | |
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216 | for (1..10) { |
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217 | $template->fork->run ("Some::Module::run", sub { |
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218 | my ($fork_fh) = @_; |
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219 | }); |
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220 | } |
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221 | |
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222 | # at this point, you can keep $template around to fork new processes |
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223 | # later, or you can destroy it, which causes it to vanish. |
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224 | |
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225 | =item execute a new perl interpreter, load some code, run it |
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226 | |
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227 | This is relatively slow, and doesn't allow you to share memory between |
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228 | multiple processes. |
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229 | |
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230 | The only advantage is that you don't have to have a template process |
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231 | hanging around all the time to fork off some new processes, which might be |
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232 | an advantage when there are long time spans where no extra processes are |
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233 | needed. |
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234 | |
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235 | Example: |
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236 | |
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237 | AnyEvent::Fork |
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238 | ->new_exec |
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239 | ->require ("Some::Module") |
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240 | ->run ("Some::Module::run", sub { |
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241 | my ($fork_fh) = @_; |
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242 | }); |
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243 | |
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244 | =back |
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245 | |
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246 | =head1 FUNCTIONS |
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247 | |
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248 | =over 4 |
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249 | |
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250 | =cut |
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251 | |
92 | package AnyEvent::ProcessPool; |
252 | package AnyEvent::Fork; |
93 | |
253 | |
94 | use common::sense; |
254 | use common::sense; |
95 | |
255 | |
96 | use Socket (); |
256 | use Socket (); |
97 | |
257 | |
98 | use Proc::FastSpawn; |
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99 | use AnyEvent; |
258 | use AnyEvent; |
100 | use AnyEvent::ProcessPool::Util; |
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101 | use AnyEvent::Util (); |
259 | use AnyEvent::Util (); |
102 | |
260 | |
103 | BEGIN { |
261 | use IO::FDPass; |
104 | # require Exporter; |
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105 | } |
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106 | |
262 | |
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263 | our $VERSION = 0.2; |
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264 | |
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265 | our $PERL; # the path to the perl interpreter, deduces with various forms of magic |
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266 | |
107 | =item my $pool = new AnyEvent::ProcessPool key => value... |
267 | =item my $pool = new AnyEvent::Fork key => value... |
108 | |
268 | |
109 | Create a new process pool. The following named parameters are supported: |
269 | Create a new process pool. The following named parameters are supported: |
110 | |
270 | |
111 | =over 4 |
271 | =over 4 |
112 | |
272 | |
113 | =back |
273 | =back |
114 | |
274 | |
115 | =cut |
275 | =cut |
116 | |
276 | |
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277 | # the early fork template process |
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278 | our $EARLY; |
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279 | |
117 | # the template process |
280 | # the empty template process |
118 | our $template; |
281 | our $TEMPLATE; |
119 | |
282 | |
120 | sub _queue { |
283 | sub _cmd { |
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284 | my $self = shift; |
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285 | |
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286 | #TODO: maybe append the packet to any existing string command already in the queue |
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287 | |
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288 | # ideally, we would want to use "a (w/a)*" as format string, but perl versions |
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289 | # from at least 5.8.9 to 5.16.3 are all buggy and can't unpack it. |
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290 | push @{ $self->[2] }, pack "L/a*", pack "(w/a*)*", @_; |
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291 | |
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292 | $self->[3] ||= AE::io $self->[1], 1, sub { |
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293 | # send the next "thing" in the queue - either a reference to an fh, |
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294 | # or a plain string. |
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295 | |
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296 | if (ref $self->[2][0]) { |
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297 | # send fh |
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298 | IO::FDPass::send fileno $self->[1], fileno ${ $self->[2][0] } |
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299 | and shift @{ $self->[2] }; |
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300 | |
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301 | } else { |
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302 | # send string |
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303 | my $len = syswrite $self->[1], $self->[2][0] |
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304 | or do { undef $self->[3]; die "AnyEvent::Fork: command write failure: $!" }; |
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305 | |
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306 | substr $self->[2][0], 0, $len, ""; |
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307 | shift @{ $self->[2] } unless length $self->[2][0]; |
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308 | } |
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309 | |
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310 | unless (@{ $self->[2] }) { |
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311 | undef $self->[3]; |
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312 | # invoke run callback |
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313 | $self->[0]->($self->[1]) if $self->[0]; |
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314 | } |
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315 | }; |
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316 | |
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317 | () # make sure we don't leak the watcher |
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318 | } |
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319 | |
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320 | sub _new { |
121 | my ($pid, $fh) = @_; |
321 | my ($self, $fh) = @_; |
122 | |
322 | |
123 | [ |
323 | AnyEvent::Util::fh_nonblocking $fh, 1; |
124 | $pid, |
324 | |
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325 | $self = bless [ |
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326 | undef, # run callback |
125 | $fh, |
327 | $fh, |
126 | [], |
328 | [], # write queue - strings or fd's |
127 | undef |
329 | undef, # AE watcher |
128 | ] |
330 | ], $self; |
129 | } |
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130 | |
331 | |
131 | sub queue_cmd { |
332 | $self |
132 | my ($queue, $cmd) = @_; |
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133 | |
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134 | push @{ $queue->[2] }, pack "N/a", $cmd; |
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135 | |
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136 | $queue->[3] ||= AE::io $queue->[1], 1, sub { |
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137 | warn "oopl0 ", scalar @{ $queue->[2] }; |
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138 | if (ref $queue->[2][0]) { |
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139 | warn "oopla2\n";#d# |
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140 | AnyEvent::ProcessPool::Util::fd_send fileno $queue->[1], fileno ${ $queue->[2][0] } |
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141 | and shift @{ $queue->[2] }; |
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142 | } else { |
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143 | warn "write ", length $queue->[2][0];#d# |
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144 | my $len = syswrite $queue->[1], $queue->[2][0] |
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145 | or die "AnyEvent::ProcessPool::queue write failure: $!"; |
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146 | substr $queue->[2][0], 0, $len, ""; |
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147 | shift @{ $queue->[2] } unless length $queue->[2][0]; |
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148 | } |
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149 | |
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150 | undef $queue->[3] unless @{ $queue->[2] }; |
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151 | warn "oopl3 ", scalar @{ $queue->[2] }; |
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152 | warn "oopl4 $queue->[3]\n";#d# |
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153 | }; |
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154 | } |
333 | } |
155 | |
334 | |
156 | sub run_template { |
335 | # fork template from current process, used by AnyEvent::Fork::Early/Template |
157 | return if $template; |
336 | sub _new_fork { |
158 | |
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159 | my ($fh, $slave) = AnyEvent::Util::portable_socketpair; |
337 | my ($fh, $slave) = AnyEvent::Util::portable_socketpair; |
160 | AnyEvent::Util::fh_nonblocking $fh, 1; |
338 | my $parent = $$; |
161 | fd_inherit fileno $slave; |
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162 | |
339 | |
163 | my %env = %ENV; |
340 | my $pid = fork; |
164 | $env{PERL5LIB} = join ":", grep !ref, @INC; |
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165 | |
341 | |
166 | my $pid = spawn |
342 | if ($pid eq 0) { |
167 | $^X, |
343 | require AnyEvent::Fork::Serve; |
168 | ["perl", "-MAnyEvent::ProcessPool::Serve", "-e", "AnyEvent::ProcessPool::Serve::me", fileno $slave], |
344 | $AnyEvent::Fork::Serve::OWNER = $parent; |
169 | [map "$_=$env{$_}", keys %env], |
345 | close $fh; |
170 | or die "unable to spawn AnyEvent::ProcessPool server: $!"; |
346 | $0 = "$_[1] of $parent"; |
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347 | $SIG{CHLD} = 'IGNORE'; |
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348 | AnyEvent::Fork::Serve::serve ($slave); |
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349 | exit 0; |
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350 | } elsif (!$pid) { |
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351 | die "AnyEvent::Fork::Early/Template: unable to fork template process: $!"; |
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352 | } |
171 | |
353 | |
172 | close $slave; |
354 | AnyEvent::Fork->_new ($fh) |
173 | |
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174 | $template = _queue $pid, $fh; |
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175 | |
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176 | my ($a, $b) = AnyEvent::Util::portable_socketpair; |
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177 | |
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178 | queue_cmd $template, "Iabc"; |
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179 | push @{ $template->[2] }, \$b; |
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180 | |
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181 | use Coro::AnyEvent; Coro::AnyEvent::sleep 1; |
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182 | } |
355 | } |
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356 | |
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357 | =item my $proc = new AnyEvent::Fork |
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358 | |
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359 | Create a new "empty" perl interpreter process and returns its process |
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360 | object for further manipulation. |
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361 | |
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362 | The new process is forked from a template process that is kept around |
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363 | for this purpose. When it doesn't exist yet, it is created by a call to |
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364 | C<new_exec> and kept around for future calls. |
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365 | |
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366 | When the process object is destroyed, it will release the file handle |
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367 | that connects it with the new process. When the new process has not yet |
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368 | called C<run>, then the process will exit. Otherwise, what happens depends |
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369 | entirely on the code that is executed. |
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370 | |
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371 | =cut |
183 | |
372 | |
184 | sub new { |
373 | sub new { |
185 | my $class = shift; |
374 | my $class = shift; |
186 | |
375 | |
187 | my $self = bless { |
376 | $TEMPLATE ||= $class->new_exec; |
188 | @_ |
377 | $TEMPLATE->fork |
189 | }, $class; |
378 | } |
190 | |
379 | |
191 | run_template; |
380 | =item $new_proc = $proc->fork |
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381 | |
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382 | Forks C<$proc>, creating a new process, and returns the process object |
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383 | of the new process. |
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384 | |
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385 | If any of the C<send_> functions have been called before fork, then they |
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386 | will be cloned in the child. For example, in a pre-forked server, you |
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387 | might C<send_fh> the listening socket into the template process, and then |
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388 | keep calling C<fork> and C<run>. |
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389 | |
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390 | =cut |
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391 | |
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392 | sub fork { |
|
|
393 | my ($self) = @_; |
|
|
394 | |
|
|
395 | my ($fh, $slave) = AnyEvent::Util::portable_socketpair; |
|
|
396 | |
|
|
397 | $self->send_fh ($slave); |
|
|
398 | $self->_cmd ("f"); |
|
|
399 | |
|
|
400 | AnyEvent::Fork->_new ($fh) |
|
|
401 | } |
|
|
402 | |
|
|
403 | =item my $proc = new_exec AnyEvent::Fork |
|
|
404 | |
|
|
405 | Create a new "empty" perl interpreter process and returns its process |
|
|
406 | object for further manipulation. |
|
|
407 | |
|
|
408 | Unlike the C<new> method, this method I<always> spawns a new perl process |
|
|
409 | (except in some cases, see L<AnyEvent::Fork::Early> for details). This |
|
|
410 | reduces the amount of memory sharing that is possible, and is also slower. |
|
|
411 | |
|
|
412 | You should use C<new> whenever possible, except when having a template |
|
|
413 | process around is unacceptable. |
|
|
414 | |
|
|
415 | 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 |
|
|
417 | as if it were the perl interpreter. Failing this, the module falls back to |
|
|
418 | using C<$Config::Config{perlpath}>. |
|
|
419 | |
|
|
420 | =cut |
|
|
421 | |
|
|
422 | sub new_exec { |
|
|
423 | my ($self) = @_; |
|
|
424 | |
|
|
425 | return $EARLY->fork |
|
|
426 | if $EARLY; |
|
|
427 | |
|
|
428 | # first find path of perl |
|
|
429 | my $perl = $; |
|
|
430 | |
|
|
431 | # first we try $^X, but the path must be absolute (always on win32), and end in sth. |
|
|
432 | # that looks like perl. this obviously only works for posix and win32 |
|
|
433 | unless ( |
|
|
434 | ($^O eq "MSWin32" || $perl =~ m%^/%) |
|
|
435 | && $perl =~ m%[/\\]perl(?:[0-9]+(\.[0-9]+)+)?(\.exe)?$%i |
|
|
436 | ) { |
|
|
437 | # if it doesn't look perlish enough, try Config |
|
|
438 | require Config; |
|
|
439 | $perl = $Config::Config{perlpath}; |
|
|
440 | $perl =~ s/(?:\Q$Config::Config{_exe}\E)?$/$Config::Config{_exe}/; |
|
|
441 | } |
|
|
442 | |
|
|
443 | require Proc::FastSpawn; |
|
|
444 | |
|
|
445 | my ($fh, $slave) = AnyEvent::Util::portable_socketpair; |
|
|
446 | Proc::FastSpawn::fd_inherit (fileno $slave); |
|
|
447 | |
|
|
448 | # new fh's should always be set cloexec (due to $^F), |
|
|
449 | # but hey, not on win32, so we always clear the inherit flag. |
|
|
450 | Proc::FastSpawn::fd_inherit (fileno $fh, 0); |
|
|
451 | |
|
|
452 | # quick. also doesn't work in win32. of course. what did you expect |
|
|
453 | #local $ENV{PERL5LIB} = join ":", grep !ref, @INC; |
|
|
454 | my %env = %ENV; |
|
|
455 | $env{PERL5LIB} = join +($^O eq "MSWin32" ? ";" : ":"), grep !ref, @INC; |
|
|
456 | |
|
|
457 | Proc::FastSpawn::spawn ( |
|
|
458 | $perl, |
|
|
459 | ["perl", "-MAnyEvent::Fork::Serve", "-e", "AnyEvent::Fork::Serve::me", fileno $slave, $$], |
|
|
460 | [map "$_=$env{$_}", keys %env], |
|
|
461 | ) or die "unable to spawn AnyEvent::Fork server: $!"; |
|
|
462 | |
|
|
463 | $self->_new ($fh) |
|
|
464 | } |
|
|
465 | |
|
|
466 | =item $proc = $proc->eval ($perlcode, @args) |
|
|
467 | |
|
|
468 | Evaluates the given C<$perlcode> as ... perl code, while setting C<@_> to |
|
|
469 | the strings specified by C<@args>. |
|
|
470 | |
|
|
471 | This call is meant to do any custom initialisation that might be required |
|
|
472 | (for example, the C<require> method uses it). It's not supposed to be used |
|
|
473 | to completely take over the process, use C<run> for that. |
|
|
474 | |
|
|
475 | The code will usually be executed after this call returns, and there is no |
|
|
476 | way to pass anything back to the calling process. Any evaluation errors |
|
|
477 | will be reported to stderr and cause the process to exit. |
|
|
478 | |
|
|
479 | Returns the process object for easy chaining of method calls. |
|
|
480 | |
|
|
481 | =cut |
|
|
482 | |
|
|
483 | sub eval { |
|
|
484 | my ($self, $code, @args) = @_; |
|
|
485 | |
|
|
486 | $self->_cmd (e => $code, @args); |
192 | |
487 | |
193 | $self |
488 | $self |
194 | } |
489 | } |
195 | |
490 | |
|
|
491 | =item $proc = $proc->require ($module, ...) |
|
|
492 | |
|
|
493 | Tries to load the given module(s) into the process |
|
|
494 | |
|
|
495 | Returns the process object for easy chaining of method calls. |
|
|
496 | |
|
|
497 | =cut |
|
|
498 | |
|
|
499 | sub require { |
|
|
500 | my ($self, @modules) = @_; |
|
|
501 | |
|
|
502 | s%::%/%g for @modules; |
|
|
503 | $self->eval ('require "$_.pm" for @_', @modules); |
|
|
504 | |
|
|
505 | $self |
|
|
506 | } |
|
|
507 | |
|
|
508 | =item $proc = $proc->send_fh ($handle, ...) |
|
|
509 | |
|
|
510 | Send one or more file handles (I<not> file descriptors) to the process, |
|
|
511 | to prepare a call to C<run>. |
|
|
512 | |
|
|
513 | The process object keeps a reference to the handles until this is done, |
|
|
514 | so you must not explicitly close the handles. This is most easily |
|
|
515 | accomplished by simply not storing the file handles anywhere after passing |
|
|
516 | them to this method. |
|
|
517 | |
|
|
518 | Returns the process object for easy chaining of method calls. |
|
|
519 | |
|
|
520 | Example: pass a file handle to a process, and release it without |
|
|
521 | closing. It will be closed automatically when it is no longer used. |
|
|
522 | |
|
|
523 | $proc->send_fh ($my_fh); |
|
|
524 | undef $my_fh; # free the reference if you want, but DO NOT CLOSE IT |
|
|
525 | |
|
|
526 | =cut |
|
|
527 | |
|
|
528 | sub send_fh { |
|
|
529 | my ($self, @fh) = @_; |
|
|
530 | |
|
|
531 | for my $fh (@fh) { |
|
|
532 | $self->_cmd ("h"); |
|
|
533 | push @{ $self->[2] }, \$fh; |
|
|
534 | } |
|
|
535 | |
|
|
536 | $self |
|
|
537 | } |
|
|
538 | |
|
|
539 | =item $proc = $proc->send_arg ($string, ...) |
|
|
540 | |
|
|
541 | Send one or more argument strings to the process, to prepare a call to |
|
|
542 | C<run>. The strings can be any octet string. |
|
|
543 | |
|
|
544 | Returns the process object for easy chaining of method calls. |
|
|
545 | |
|
|
546 | =cut |
|
|
547 | |
|
|
548 | sub send_arg { |
|
|
549 | my ($self, @arg) = @_; |
|
|
550 | |
|
|
551 | $self->_cmd (a => @arg); |
|
|
552 | |
|
|
553 | $self |
|
|
554 | } |
|
|
555 | |
|
|
556 | =item $proc->run ($func, $cb->($fh)) |
|
|
557 | |
|
|
558 | Enter the function specified by the fully qualified name in C<$func> in |
|
|
559 | the process. The function is called with the communication socket as first |
|
|
560 | 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. |
|
|
562 | |
|
|
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. |
|
|
569 | |
|
|
570 | If the communication socket isn't used, it should be closed on both sides, |
|
|
571 | to save on kernel memory. |
|
|
572 | |
|
|
573 | 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 |
|
|
575 | otherwise, the socket can be a good indicator for the existence of the |
|
|
576 | process - if the other process exits, you get a readable event on it, |
|
|
577 | because exiting the process closes the socket (if it didn't create any |
|
|
578 | children using fork). |
|
|
579 | |
|
|
580 | 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. |
|
|
582 | |
|
|
583 | my $pool = AnyEvent::Fork |
|
|
584 | ->new |
|
|
585 | ->send_arg ("str1", "str2") |
|
|
586 | ->send_fh ($fh1, $fh2); |
|
|
587 | |
|
|
588 | for (1..2) { |
|
|
589 | $pool |
|
|
590 | ->fork |
|
|
591 | ->send_arg ("str3") |
|
|
592 | ->run ("Some::function", sub { |
|
|
593 | my ($fh) = @_; |
|
|
594 | |
|
|
595 | # fh is nonblocking, but we trust that the OS can accept these |
|
|
596 | # extra 3 octets anyway. |
|
|
597 | syswrite $fh, "hi #$_\n"; |
|
|
598 | |
|
|
599 | # $fh is being closed here, as we don't store it anywhere |
|
|
600 | }); |
|
|
601 | } |
|
|
602 | |
|
|
603 | # Some::function might look like this - all parameters passed before fork |
|
|
604 | # and after will be passed, in order, after the communications socket. |
|
|
605 | sub Some::function { |
|
|
606 | my ($fh, $str1, $str2, $fh1, $fh2, $str3) = @_; |
|
|
607 | |
|
|
608 | print scalar <$fh>; # prints "hi 1\n" and "hi 2\n" |
|
|
609 | } |
|
|
610 | |
|
|
611 | =cut |
|
|
612 | |
|
|
613 | sub run { |
|
|
614 | my ($self, $func, $cb) = @_; |
|
|
615 | |
|
|
616 | $self->[0] = $cb; |
|
|
617 | $self->_cmd (r => $func); |
|
|
618 | } |
|
|
619 | |
196 | =back |
620 | =back |
|
|
621 | |
|
|
622 | =head1 PERFORMANCE |
|
|
623 | |
|
|
624 | 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 |
|
|
626 | performance you can expect. |
|
|
627 | |
|
|
628 | 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 |
|
|
630 | load AnyEvent, EV and AnyEvent::Fork, for a total process size of 6312kB. |
|
|
631 | |
|
|
632 | 2079 new processes per second, using socketpair + fork manually |
|
|
633 | |
|
|
634 | 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 |
|
|
636 | socket form the child to close on exit. This does the same thing as manual |
|
|
637 | 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 |
|
|
639 | of the socket first. |
|
|
640 | |
|
|
641 | 2307 new processes per second, using AnyEvent::Fork->new |
|
|
642 | |
|
|
643 | 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: |
|
|
645 | |
|
|
646 | 479 vfork+execs per second, using AnyEvent::Fork->new_exec |
|
|
647 | |
|
|
648 | So how can C<< AnyEvent->new >> be faster than a standard fork, even |
|
|
649 | though it uses the same operations, but adds a lot of overhead? |
|
|
650 | |
|
|
651 | The difference is simply the process size: forking the 6MB process takes |
|
|
652 | so much longer than forking the 2.5MB template process that the overhead |
|
|
653 | introduced is canceled out. |
|
|
654 | |
|
|
655 | If the benchmark process grows, the normal fork becomes even slower: |
|
|
656 | |
|
|
657 | 1340 new processes, manual fork in a 20MB process |
|
|
658 | 731 new processes, manual fork in a 200MB process |
|
|
659 | 235 new processes, manual fork in a 2000MB process |
|
|
660 | |
|
|
661 | What that means (to me) is that I can use this module without having a |
|
|
662 | very bad conscience because of the extra overhead required to start new |
|
|
663 | processes. |
|
|
664 | |
|
|
665 | =head1 TYPICAL PROBLEMS |
|
|
666 | |
|
|
667 | This section lists typical problems that remain. I hope by recognising |
|
|
668 | them, most can be avoided. |
|
|
669 | |
|
|
670 | =over 4 |
|
|
671 | |
|
|
672 | =item exit runs destructors |
|
|
673 | |
|
|
674 | =item "leaked" file descriptors for exec'ed processes |
|
|
675 | |
|
|
676 | POSIX systems inherit file descriptors by default when exec'ing a new |
|
|
677 | process. While perl itself laudably sets the close-on-exec flags on new |
|
|
678 | file handles, most C libraries don't care, and even if all cared, it's |
|
|
679 | often not possible to set the flag in a race-free manner. |
|
|
680 | |
|
|
681 | That means some file descriptors can leak through. And since it isn't |
|
|
682 | possible to know which file descriptors are "good" and "necessary" (or |
|
|
683 | even to know which file descriptors are open), there is no good way to |
|
|
684 | close the ones that might harm. |
|
|
685 | |
|
|
686 | As an example of what "harm" can be done consider a web server that |
|
|
687 | accepts connections and afterwards some module uses AnyEvent::Fork for the |
|
|
688 | first time, causing it to fork and exec a new process, which might inherit |
|
|
689 | the network socket. When the server closes the socket, it is still open |
|
|
690 | in the child (which doesn't even know that) and the client might conclude |
|
|
691 | that the connection is still fine. |
|
|
692 | |
|
|
693 | For the main program, there are multiple remedies available - |
|
|
694 | L<AnyEvent::Fork::Early> is one, creating a process early and not using |
|
|
695 | C<new_exec> is another, as in both cases, the first process can be exec'ed |
|
|
696 | well before many random file descriptors are open. |
|
|
697 | |
|
|
698 | In general, the solution for these kind of problems is to fix the |
|
|
699 | libraries or the code that leaks those file descriptors. |
|
|
700 | |
|
|
701 | Fortunately, most of these leaked descriptors do no harm, other than |
|
|
702 | sitting on some resources. |
|
|
703 | |
|
|
704 | =item "leaked" file descriptors for fork'ed processes |
|
|
705 | |
|
|
706 | Normally, L<AnyEvent::Fork> does start new processes by exec'ing them, |
|
|
707 | which closes file descriptors not marked for being inherited. |
|
|
708 | |
|
|
709 | However, L<AnyEvent::Fork::Early> and L<AnyEvent::Fork::Template> offer |
|
|
710 | a way to create these processes by forking, and this leaks more file |
|
|
711 | descriptors than exec'ing them, as there is no way to mark descriptors as |
|
|
712 | "close on fork". |
|
|
713 | |
|
|
714 | An example would be modules like L<EV>, L<IO::AIO> or L<Gtk2>. Both create |
|
|
715 | pipes for internal uses, and L<Gtk2> might open a connection to the X |
|
|
716 | server. L<EV> and L<IO::AIO> can deal with fork, but Gtk2 might have |
|
|
717 | trouble with a fork. |
|
|
718 | |
|
|
719 | The solution is to either not load these modules before use'ing |
|
|
720 | L<AnyEvent::Fork::Early> or L<AnyEvent::Fork::Template>, or to delay |
|
|
721 | initialising them, for example, by calling C<init Gtk2> manually. |
|
|
722 | |
|
|
723 | =back |
|
|
724 | |
|
|
725 | =head1 PORTABILITY NOTES |
|
|
726 | |
|
|
727 | Native win32 perls are somewhat supported (AnyEvent::Fork::Early is a nop, |
|
|
728 | and ::Template is not going to work), and it cost a lot of blood and sweat |
|
|
729 | to make it so, mostly due to the bloody broken perl that nobody seems to |
|
|
730 | care about. The fork emulation is a bad joke - I have yet to see something |
|
|
731 | useful that you can do with it without running into memory corruption |
|
|
732 | issues or other braindamage. Hrrrr. |
|
|
733 | |
|
|
734 | Cygwin perl is not supported at the moment, as it should implement fd |
|
|
735 | passing, but doesn't, and rolling my own is hard, as cygwin doesn't |
|
|
736 | support enough functionality to do it. |
|
|
737 | |
|
|
738 | =head1 SEE ALSO |
|
|
739 | |
|
|
740 | L<AnyEvent::Fork::Early> (to avoid executing a perl interpreter), |
|
|
741 | L<AnyEvent::Fork::Template> (to create a process by forking the main |
|
|
742 | program at a convenient time). |
197 | |
743 | |
198 | =head1 AUTHOR |
744 | =head1 AUTHOR |
199 | |
745 | |
200 | Marc Lehmann <schmorp@schmorp.de> |
746 | Marc Lehmann <schmorp@schmorp.de> |
201 | http://home.schmorp.de/ |
747 | http://home.schmorp.de/ |