… | |
… | |
27 | |
27 | |
28 | Special care has been taken to make this module useful from other modules, |
28 | Special care has been taken to make this module useful from other modules, |
29 | while still supporting specialised environments such as L<App::Staticperl> |
29 | while still supporting specialised environments such as L<App::Staticperl> |
30 | or L<PAR::Packer>. |
30 | or L<PAR::Packer>. |
31 | |
31 | |
32 | =head1 WHAT THIS MODULE IS NOT |
32 | =head2 WHAT THIS MODULE IS NOT |
33 | |
33 | |
34 | This module only creates processes and lets you pass file handles and |
34 | This module only creates processes and lets you pass file handles and |
35 | strings to it, and run perl code. It does not implement any kind of RPC - |
35 | strings to it, and run perl code. It does not implement any kind of RPC - |
36 | there is no back channel from the process back to you, and there is no RPC |
36 | there is no back channel from the process back to you, and there is no RPC |
37 | or message passing going on. |
37 | or message passing going on. |
38 | |
38 | |
39 | If you need some form of RPC, you can either implement it yourself |
39 | If you need some form of RPC, you could use the L<AnyEvent::Fork::RPC> |
40 | in whatever way you like, use some message-passing module such |
40 | companion module, which adds simple RPC/job queueing to a process created |
41 | as L<AnyEvent::MP>, some pipe such as L<AnyEvent::ZeroMQ>, use |
41 | by this module. |
42 | L<AnyEvent::Handle> on both sides to send e.g. JSON or Storable messages, |
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43 | and so on. |
|
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44 | |
42 | |
|
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43 | And if you need some automatic process pool management on top of |
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44 | L<AnyEvent::Fork::RPC>, you can look at the L<AnyEvent::Fork::Pool> |
|
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45 | companion module. |
|
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46 | |
|
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47 | Or you can implement it yourself in whatever way you like: use some |
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48 | message-passing module such as L<AnyEvent::MP>, some pipe such as |
|
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49 | L<AnyEvent::ZeroMQ>, use L<AnyEvent::Handle> on both sides to send |
|
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50 | e.g. JSON or Storable messages, and so on. |
|
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51 | |
|
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52 | =head2 COMPARISON TO OTHER MODULES |
|
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53 | |
|
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54 | There is an abundance of modules on CPAN that do "something fork", such as |
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55 | L<Parallel::ForkManager>, L<AnyEvent::ForkManager>, L<AnyEvent::Worker> |
|
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56 | or L<AnyEvent::Subprocess>. There are modules that implement their own |
|
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57 | process management, such as L<AnyEvent::DBI>. |
|
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58 | |
|
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59 | The problems that all these modules try to solve are real, however, none |
|
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60 | of them (from what I have seen) tackle the very real problems of unwanted |
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61 | memory sharing, efficiency, not being able to use event processing or |
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62 | similar modules in the processes they create. |
|
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63 | |
|
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64 | This module doesn't try to replace any of them - instead it tries to solve |
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65 | the problem of creating processes with a minimum of fuss and overhead (and |
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66 | also luxury). Ideally, most of these would use AnyEvent::Fork internally, |
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67 | except they were written before AnyEvent:Fork was available, so obviously |
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68 | had to roll their own. |
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69 | |
45 | =head1 PROBLEM STATEMENT |
70 | =head2 PROBLEM STATEMENT |
46 | |
71 | |
47 | There are two traditional ways to implement parallel processing on UNIX |
72 | There are two traditional ways to implement parallel processing on UNIX |
48 | like operating systems - fork and process, and fork+exec and process. They |
73 | like operating systems - fork and process, and fork+exec and process. They |
49 | have different advantages and disadvantages that I describe below, |
74 | have different advantages and disadvantages that I describe below, |
50 | together with how this module tries to mitigate the disadvantages. |
75 | together with how this module tries to mitigate the disadvantages. |
… | |
… | |
152 | |
177 | |
153 | # now $master_filehandle is connected to the |
178 | # now $master_filehandle is connected to the |
154 | # $slave_filehandle in the new process. |
179 | # $slave_filehandle in the new process. |
155 | }); |
180 | }); |
156 | |
181 | |
157 | # MyModule::worker might look like this |
182 | C<MyModule> might look like this: |
|
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183 | |
|
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184 | package MyModule; |
|
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185 | |
158 | sub MyModule::worker { |
186 | sub worker { |
159 | my ($slave_filehandle) = @_; |
187 | my ($slave_filehandle) = @_; |
160 | |
188 | |
161 | # now $slave_filehandle is connected to the $master_filehandle |
189 | # now $slave_filehandle is connected to the $master_filehandle |
162 | # in the original prorcess. have fun! |
190 | # in the original prorcess. have fun! |
163 | } |
191 | } |
… | |
… | |
182 | } |
210 | } |
183 | |
211 | |
184 | # now do other things - maybe use the filehandle provided by run |
212 | # now do other things - maybe use the filehandle provided by run |
185 | # to wait for the processes to die. or whatever. |
213 | # to wait for the processes to die. or whatever. |
186 | |
214 | |
187 | # My::Server::run might look like this |
215 | C<My::Server> might look like this: |
188 | sub My::Server::run { |
216 | |
|
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217 | package My::Server; |
|
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218 | |
|
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219 | sub run { |
189 | my ($slave, $listener, $id) = @_; |
220 | my ($slave, $listener, $id) = @_; |
190 | |
221 | |
191 | close $slave; # we do not use the socket, so close it to save resources |
222 | close $slave; # we do not use the socket, so close it to save resources |
192 | |
223 | |
193 | # we could go ballistic and use e.g. AnyEvent here, or IO::AIO, |
224 | # we could go ballistic and use e.g. AnyEvent here, or IO::AIO, |
… | |
… | |
197 | } |
228 | } |
198 | } |
229 | } |
199 | |
230 | |
200 | =head2 use AnyEvent::Fork as a faster fork+exec |
231 | =head2 use AnyEvent::Fork as a faster fork+exec |
201 | |
232 | |
202 | This runs /bin/echo hi, with stdout redirected to /tmp/log and stderr to |
233 | This runs C</bin/echo hi>, with standard output redirected to F</tmp/log> |
203 | the communications socket. It is usually faster than fork+exec, but still |
234 | and standard error redirected to the communications socket. It is usually |
204 | let's you prepare the environment. |
235 | faster than fork+exec, but still lets you prepare the environment. |
205 | |
236 | |
206 | open my $output, ">/tmp/log" or die "$!"; |
237 | open my $output, ">/tmp/log" or die "$!"; |
207 | |
238 | |
208 | AnyEvent::Fork |
239 | AnyEvent::Fork |
209 | ->new |
240 | ->new |
210 | ->eval (' |
241 | ->eval (' |
|
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242 | # compile a helper function for later use |
211 | sub run { |
243 | sub run { |
212 | my ($fh, $output, @cmd) = @_; |
244 | my ($fh, $output, @cmd) = @_; |
213 | |
245 | |
214 | # perl will clear close-on-exec on STDOUT/STDERR |
246 | # perl will clear close-on-exec on STDOUT/STDERR |
215 | open STDOUT, ">&", $output or die; |
247 | open STDOUT, ">&", $output or die; |
… | |
… | |
222 | ->send_arg ("/bin/echo", "hi") |
254 | ->send_arg ("/bin/echo", "hi") |
223 | ->run ("run", my $cv = AE::cv); |
255 | ->run ("run", my $cv = AE::cv); |
224 | |
256 | |
225 | my $stderr = $cv->recv; |
257 | my $stderr = $cv->recv; |
226 | |
258 | |
|
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259 | =head2 For stingy users: put the worker code into a C<DATA> section. |
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260 | |
|
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261 | When you want to be stingy with files, you cna put your code into the |
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262 | C<DATA> section of your module (or program): |
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263 | |
|
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264 | use AnyEvent::Fork; |
|
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265 | |
|
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266 | AnyEvent::Fork |
|
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267 | ->new |
|
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268 | ->eval (do { local $/; <DATA> }) |
|
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269 | ->run ("doit", sub { ... }); |
|
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270 | |
|
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271 | __DATA__ |
|
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272 | |
|
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273 | sub doit { |
|
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274 | ... do something! |
|
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275 | } |
|
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276 | |
|
|
277 | =head2 For stingy standalone programs: do not rely on external files at |
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278 | all. |
|
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279 | |
|
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280 | For single-file scripts it can be inconvenient to rely on external |
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281 | files - even when using < C<DATA> section, you still need to C<exec> |
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282 | an external perl interpreter, which might not be available when using |
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283 | L<App::Staticperl>, L<Urlader> or L<PAR::Packer> for example. |
|
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284 | |
|
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285 | Two modules help here - L<AnyEvent::Fork::Early> forks a template process |
|
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286 | for all further calls to C<new_exec>, and L<AnyEvent::Fork::Template> |
|
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287 | forks the main program as a template process. |
|
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288 | |
|
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289 | Here is how your main program should look like: |
|
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290 | |
|
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291 | #! perl |
|
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292 | |
|
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293 | # optional, as the very first thing. |
|
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294 | # in case modules want to create their own processes. |
|
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295 | use AnyEvent::Fork::Early; |
|
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296 | |
|
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297 | # next, load all modules you need in your template process |
|
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298 | use Example::My::Module |
|
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299 | use Example::Whatever; |
|
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300 | |
|
|
301 | # next, put your run function definition and anything else you |
|
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302 | # need, but do not use code outside of BEGIN blocks. |
|
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303 | sub worker_run { |
|
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304 | my ($fh, @args) = @_; |
|
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305 | ... |
|
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306 | } |
|
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307 | |
|
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308 | # now preserve everything so far as AnyEvent::Fork object |
|
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309 | # in §TEMPLATE. |
|
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310 | use AnyEvent::Fork::Template; |
|
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311 | |
|
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312 | # do not put code outside of BEGIN blocks until here |
|
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313 | |
|
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314 | # now use the $TEMPLATE process in any way you like |
|
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315 | |
|
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316 | # for example: create 10 worker processes |
|
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317 | my @worker; |
|
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318 | my $cv = AE::cv; |
|
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319 | for (1..10) { |
|
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320 | $cv->begin; |
|
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321 | $TEMPLATE->fork->send_arg ($_)->run ("worker_run", sub { |
|
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322 | push @worker, shift; |
|
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323 | $cv->end; |
|
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324 | }); |
|
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325 | } |
|
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326 | $cv->recv; |
|
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327 | |
227 | =head1 CONCEPTS |
328 | =head1 CONCEPTS |
228 | |
329 | |
229 | This module can create new processes either by executing a new perl |
330 | This module can create new processes either by executing a new perl |
230 | process, or by forking from an existing "template" process. |
331 | process, or by forking from an existing "template" process. |
|
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332 | |
|
|
333 | All these processes are called "child processes" (whether they are direct |
|
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334 | children or not), while the process that manages them is called the |
|
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335 | "parent process". |
231 | |
336 | |
232 | Each such process comes with its own file handle that can be used to |
337 | Each such process comes with its own file handle that can be used to |
233 | communicate with it (it's actually a socket - one end in the new process, |
338 | communicate with it (it's actually a socket - one end in the new process, |
234 | one end in the main process), and among the things you can do in it are |
339 | one end in the main process), and among the things you can do in it are |
235 | load modules, fork new processes, send file handles to it, and execute |
340 | load modules, fork new processes, send file handles to it, and execute |
… | |
… | |
314 | =head1 THE C<AnyEvent::Fork> CLASS |
419 | =head1 THE C<AnyEvent::Fork> CLASS |
315 | |
420 | |
316 | This module exports nothing, and only implements a single class - |
421 | This module exports nothing, and only implements a single class - |
317 | C<AnyEvent::Fork>. |
422 | C<AnyEvent::Fork>. |
318 | |
423 | |
319 | There are two constructors that both create new processes - C<new> and |
424 | There are two class constructors that both create new processes - C<new> |
320 | C<new_exec>. The C<fork> method creates a new process by forking an |
425 | and C<new_exec>. The C<fork> method creates a new process by forking an |
321 | existing one and could be considered a third constructor. |
426 | existing one and could be considered a third constructor. |
322 | |
427 | |
323 | Most of the remaining methods deal with preparing the new process, by |
428 | Most of the remaining methods deal with preparing the new process, by |
324 | loading code, evaluating code and sending data to the new process. They |
429 | loading code, evaluating code and sending data to the new process. They |
325 | usually return the process object, so you can chain method calls. |
430 | usually return the process object, so you can chain method calls. |
326 | |
431 | |
327 | If a process object is destroyed before calling its C<run> method, then |
432 | If a process object is destroyed before calling its C<run> method, then |
328 | the process simply exits. After C<run> is called, all responsibility is |
433 | the process simply exits. After C<run> is called, all responsibility is |
329 | passed to the specified function. |
434 | passed to the specified function. |
330 | |
435 | |
|
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436 | As long as there is any outstanding work to be done, process objects |
|
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437 | resist being destroyed, so there is no reason to store them unless you |
|
|
438 | need them later - configure and forget works just fine. |
|
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439 | |
331 | =over 4 |
440 | =over 4 |
332 | |
441 | |
333 | =cut |
442 | =cut |
334 | |
443 | |
335 | package AnyEvent::Fork; |
444 | package AnyEvent::Fork; |
… | |
… | |
341 | use AnyEvent; |
450 | use AnyEvent; |
342 | use AnyEvent::Util (); |
451 | use AnyEvent::Util (); |
343 | |
452 | |
344 | use IO::FDPass; |
453 | use IO::FDPass; |
345 | |
454 | |
346 | our $VERSION = 0.5; |
455 | our $VERSION = '1.0'; |
347 | |
|
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348 | our $PERL; # the path to the perl interpreter, deduces with various forms of magic |
|
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349 | |
|
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350 | =item my $pool = new AnyEvent::Fork key => value... |
|
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351 | |
|
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352 | Create a new process pool. The following named parameters are supported: |
|
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353 | |
|
|
354 | =over 4 |
|
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355 | |
|
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356 | =back |
|
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357 | |
|
|
358 | =cut |
|
|
359 | |
456 | |
360 | # the early fork template process |
457 | # the early fork template process |
361 | our $EARLY; |
458 | our $EARLY; |
362 | |
459 | |
363 | # the empty template process |
460 | # the empty template process |
364 | our $TEMPLATE; |
461 | our $TEMPLATE; |
|
|
462 | |
|
|
463 | sub QUEUE() { 0 } |
|
|
464 | sub FH() { 1 } |
|
|
465 | sub WW() { 2 } |
|
|
466 | sub PID() { 3 } |
|
|
467 | sub CB() { 4 } |
|
|
468 | |
|
|
469 | sub _new { |
|
|
470 | my ($self, $fh, $pid) = @_; |
|
|
471 | |
|
|
472 | AnyEvent::Util::fh_nonblocking $fh, 1; |
|
|
473 | |
|
|
474 | $self = bless [ |
|
|
475 | [], # write queue - strings or fd's |
|
|
476 | $fh, |
|
|
477 | undef, # AE watcher |
|
|
478 | $pid, |
|
|
479 | ], $self; |
|
|
480 | |
|
|
481 | $self |
|
|
482 | } |
365 | |
483 | |
366 | sub _cmd { |
484 | sub _cmd { |
367 | my $self = shift; |
485 | my $self = shift; |
368 | |
486 | |
369 | # ideally, we would want to use "a (w/a)*" as format string, but perl |
487 | # ideally, we would want to use "a (w/a)*" as format string, but perl |
370 | # versions from at least 5.8.9 to 5.16.3 are all buggy and can't unpack |
488 | # versions from at least 5.8.9 to 5.16.3 are all buggy and can't unpack |
371 | # it. |
489 | # it. |
372 | push @{ $self->[2] }, pack "a L/a*", $_[0], $_[1]; |
490 | push @{ $self->[QUEUE] }, pack "a N/a*", $_[0], $_[1]; |
373 | |
491 | |
374 | $self->[3] ||= AE::io $self->[1], 1, sub { |
492 | $self->[WW] ||= AE::io $self->[FH], 1, sub { |
375 | do { |
493 | do { |
376 | # send the next "thing" in the queue - either a reference to an fh, |
494 | # send the next "thing" in the queue - either a reference to an fh, |
377 | # or a plain string. |
495 | # or a plain string. |
378 | |
496 | |
379 | if (ref $self->[2][0]) { |
497 | if (ref $self->[QUEUE][0]) { |
380 | # send fh |
498 | # send fh |
381 | unless (IO::FDPass::send fileno $self->[1], fileno ${ $self->[2][0] }) { |
499 | unless (IO::FDPass::send fileno $self->[FH], fileno ${ $self->[QUEUE][0] }) { |
382 | return if $! == Errno::EAGAIN || $! == Errno::EWOULDBLOCK; |
500 | return if $! == Errno::EAGAIN || $! == Errno::EWOULDBLOCK; |
383 | undef $self->[3]; |
501 | undef $self->[WW]; |
384 | die "AnyEvent::Fork: file descriptor send failure: $!"; |
502 | die "AnyEvent::Fork: file descriptor send failure: $!"; |
385 | } |
503 | } |
386 | |
504 | |
387 | shift @{ $self->[2] }; |
505 | shift @{ $self->[QUEUE] }; |
388 | |
506 | |
389 | } else { |
507 | } else { |
390 | # send string |
508 | # send string |
391 | my $len = syswrite $self->[1], $self->[2][0]; |
509 | my $len = syswrite $self->[FH], $self->[QUEUE][0]; |
392 | |
510 | |
393 | unless ($len) { |
511 | unless ($len) { |
394 | return if $! == Errno::EAGAIN || $! == Errno::EWOULDBLOCK; |
512 | return if $! == Errno::EAGAIN || $! == Errno::EWOULDBLOCK; |
395 | undef $self->[3]; |
513 | undef $self->[WW]; |
396 | die "AnyEvent::Fork: command write failure: $!"; |
514 | die "AnyEvent::Fork: command write failure: $!"; |
397 | } |
515 | } |
398 | |
516 | |
399 | substr $self->[2][0], 0, $len, ""; |
517 | substr $self->[QUEUE][0], 0, $len, ""; |
400 | shift @{ $self->[2] } unless length $self->[2][0]; |
518 | shift @{ $self->[QUEUE] } unless length $self->[QUEUE][0]; |
401 | } |
519 | } |
402 | } while @{ $self->[2] }; |
520 | } while @{ $self->[QUEUE] }; |
403 | |
521 | |
404 | # everything written |
522 | # everything written |
405 | undef $self->[3]; |
523 | undef $self->[WW]; |
406 | |
524 | |
407 | # invoke run callback, if any |
525 | # invoke run callback, if any |
408 | $self->[4]->($self->[1]) if $self->[4]; |
526 | if ($self->[CB]) { |
|
|
527 | $self->[CB]->($self->[FH]); |
|
|
528 | @$self = (); |
|
|
529 | } |
409 | }; |
530 | }; |
410 | |
531 | |
411 | () # make sure we don't leak the watcher |
532 | () # make sure we don't leak the watcher |
412 | } |
|
|
413 | |
|
|
414 | sub _new { |
|
|
415 | my ($self, $fh, $pid) = @_; |
|
|
416 | |
|
|
417 | AnyEvent::Util::fh_nonblocking $fh, 1; |
|
|
418 | |
|
|
419 | $self = bless [ |
|
|
420 | $pid, |
|
|
421 | $fh, |
|
|
422 | [], # write queue - strings or fd's |
|
|
423 | undef, # AE watcher |
|
|
424 | ], $self; |
|
|
425 | |
|
|
426 | $self |
|
|
427 | } |
533 | } |
428 | |
534 | |
429 | # fork template from current process, used by AnyEvent::Fork::Early/Template |
535 | # fork template from current process, used by AnyEvent::Fork::Early/Template |
430 | sub _new_fork { |
536 | sub _new_fork { |
431 | my ($fh, $slave) = AnyEvent::Util::portable_socketpair; |
537 | my ($fh, $slave) = AnyEvent::Util::portable_socketpair; |
… | |
… | |
436 | if ($pid eq 0) { |
542 | if ($pid eq 0) { |
437 | require AnyEvent::Fork::Serve; |
543 | require AnyEvent::Fork::Serve; |
438 | $AnyEvent::Fork::Serve::OWNER = $parent; |
544 | $AnyEvent::Fork::Serve::OWNER = $parent; |
439 | close $fh; |
545 | close $fh; |
440 | $0 = "$_[1] of $parent"; |
546 | $0 = "$_[1] of $parent"; |
441 | $SIG{CHLD} = 'IGNORE'; |
|
|
442 | AnyEvent::Fork::Serve::serve ($slave); |
547 | AnyEvent::Fork::Serve::serve ($slave); |
443 | exit 0; |
548 | exit 0; |
444 | } elsif (!$pid) { |
549 | } elsif (!$pid) { |
445 | die "AnyEvent::Fork::Early/Template: unable to fork template process: $!"; |
550 | die "AnyEvent::Fork::Early/Template: unable to fork template process: $!"; |
446 | } |
551 | } |
… | |
… | |
453 | Create a new "empty" perl interpreter process and returns its process |
558 | Create a new "empty" perl interpreter process and returns its process |
454 | object for further manipulation. |
559 | object for further manipulation. |
455 | |
560 | |
456 | The new process is forked from a template process that is kept around |
561 | The new process is forked from a template process that is kept around |
457 | for this purpose. When it doesn't exist yet, it is created by a call to |
562 | for this purpose. When it doesn't exist yet, it is created by a call to |
458 | C<new_exec> and kept around for future calls. |
563 | C<new_exec> first and then stays around for future calls. |
459 | |
|
|
460 | When the process object is destroyed, it will release the file handle |
|
|
461 | that connects it with the new process. When the new process has not yet |
|
|
462 | called C<run>, then the process will exit. Otherwise, what happens depends |
|
|
463 | entirely on the code that is executed. |
|
|
464 | |
564 | |
465 | =cut |
565 | =cut |
466 | |
566 | |
467 | sub new { |
567 | sub new { |
468 | my $class = shift; |
568 | my $class = shift; |
… | |
… | |
558 | } |
658 | } |
559 | |
659 | |
560 | =item $pid = $proc->pid |
660 | =item $pid = $proc->pid |
561 | |
661 | |
562 | Returns the process id of the process I<iff it is a direct child of the |
662 | Returns the process id of the process I<iff it is a direct child of the |
563 | process> running AnyEvent::Fork, and C<undef> otherwise. |
663 | process running AnyEvent::Fork>, and C<undef> otherwise. |
564 | |
664 | |
565 | Normally, only processes created via C<< AnyEvent::Fork->new_exec >> and |
665 | Normally, only processes created via C<< AnyEvent::Fork->new_exec >> and |
566 | L<AnyEvent::Fork::Template> are direct children, and you are responsible |
666 | L<AnyEvent::Fork::Template> are direct children, and you are responsible |
567 | to clean up their zombies when they die. |
667 | to clean up their zombies when they die. |
568 | |
668 | |
569 | All other processes are not direct children, and will be cleaned up by |
669 | All other processes are not direct children, and will be cleaned up by |
570 | AnyEvent::Fork. |
670 | AnyEvent::Fork itself. |
571 | |
671 | |
572 | =cut |
672 | =cut |
573 | |
673 | |
574 | sub pid { |
674 | sub pid { |
575 | $_[0][0] |
675 | $_[0][PID] |
576 | } |
676 | } |
577 | |
677 | |
578 | =item $proc = $proc->eval ($perlcode, @args) |
678 | =item $proc = $proc->eval ($perlcode, @args) |
579 | |
679 | |
580 | Evaluates the given C<$perlcode> as ... perl code, while setting C<@_> to |
680 | Evaluates the given C<$perlcode> as ... Perl code, while setting C<@_> to |
581 | the strings specified by C<@args>, in the "main" package. |
681 | the strings specified by C<@args>, in the "main" package. |
582 | |
682 | |
583 | This call is meant to do any custom initialisation that might be required |
683 | This call is meant to do any custom initialisation that might be required |
584 | (for example, the C<require> method uses it). It's not supposed to be used |
684 | (for example, the C<require> method uses it). It's not supposed to be used |
585 | to completely take over the process, use C<run> for that. |
685 | to completely take over the process, use C<run> for that. |
586 | |
686 | |
587 | The code will usually be executed after this call returns, and there is no |
687 | The code will usually be executed after this call returns, and there is no |
588 | way to pass anything back to the calling process. Any evaluation errors |
688 | way to pass anything back to the calling process. Any evaluation errors |
589 | will be reported to stderr and cause the process to exit. |
689 | will be reported to stderr and cause the process to exit. |
590 | |
690 | |
591 | If you want to execute some code to take over the process (see the |
691 | If you want to execute some code (that isn't in a module) to take over the |
592 | "fork+exec" example in the SYNOPSIS), you should compile a function via |
692 | process, you should compile a function via C<eval> first, and then call |
593 | C<eval> first, and then call it via C<run>. This also gives you access to |
693 | it via C<run>. This also gives you access to any arguments passed via the |
594 | any arguments passed via the C<send_xxx> methods, such as file handles. |
694 | C<send_xxx> methods, such as file handles. See the L<use AnyEvent::Fork as |
|
|
695 | a faster fork+exec> example to see it in action. |
595 | |
696 | |
596 | Returns the process object for easy chaining of method calls. |
697 | Returns the process object for easy chaining of method calls. |
597 | |
698 | |
598 | =cut |
699 | =cut |
599 | |
700 | |
… | |
… | |
625 | =item $proc = $proc->send_fh ($handle, ...) |
726 | =item $proc = $proc->send_fh ($handle, ...) |
626 | |
727 | |
627 | Send one or more file handles (I<not> file descriptors) to the process, |
728 | Send one or more file handles (I<not> file descriptors) to the process, |
628 | to prepare a call to C<run>. |
729 | to prepare a call to C<run>. |
629 | |
730 | |
630 | The process object keeps a reference to the handles until this is done, |
731 | The process object keeps a reference to the handles until they have |
631 | so you must not explicitly close the handles. This is most easily |
732 | been passed over to the process, so you must not explicitly close the |
632 | accomplished by simply not storing the file handles anywhere after passing |
733 | handles. This is most easily accomplished by simply not storing the file |
633 | them to this method. |
734 | handles anywhere after passing them to this method - when AnyEvent::Fork |
|
|
735 | is finished using them, perl will automatically close them. |
634 | |
736 | |
635 | Returns the process object for easy chaining of method calls. |
737 | Returns the process object for easy chaining of method calls. |
636 | |
738 | |
637 | Example: pass a file handle to a process, and release it without |
739 | Example: pass a file handle to a process, and release it without |
638 | closing. It will be closed automatically when it is no longer used. |
740 | closing. It will be closed automatically when it is no longer used. |
… | |
… | |
645 | sub send_fh { |
747 | sub send_fh { |
646 | my ($self, @fh) = @_; |
748 | my ($self, @fh) = @_; |
647 | |
749 | |
648 | for my $fh (@fh) { |
750 | for my $fh (@fh) { |
649 | $self->_cmd ("h"); |
751 | $self->_cmd ("h"); |
650 | push @{ $self->[2] }, \$fh; |
752 | push @{ $self->[QUEUE] }, \$fh; |
651 | } |
753 | } |
652 | |
754 | |
653 | $self |
755 | $self |
654 | } |
756 | } |
655 | |
757 | |
656 | =item $proc = $proc->send_arg ($string, ...) |
758 | =item $proc = $proc->send_arg ($string, ...) |
657 | |
759 | |
658 | Send one or more argument strings to the process, to prepare a call to |
760 | Send one or more argument strings to the process, to prepare a call to |
659 | C<run>. The strings can be any octet string. |
761 | C<run>. The strings can be any octet strings. |
660 | |
762 | |
661 | The protocol is optimised to pass a moderate number of relatively short |
763 | The protocol is optimised to pass a moderate number of relatively short |
662 | strings - while you can pass up to 4GB of data in one go, this is more |
764 | strings - while you can pass up to 4GB of data in one go, this is more |
663 | meant to pass some ID information or other startup info, not big chunks of |
765 | meant to pass some ID information or other startup info, not big chunks of |
664 | data. |
766 | data. |
… | |
… | |
680 | Enter the function specified by the function name in C<$func> in the |
782 | Enter the function specified by the function name in C<$func> in the |
681 | process. The function is called with the communication socket as first |
783 | process. The function is called with the communication socket as first |
682 | argument, followed by all file handles and string arguments sent earlier |
784 | argument, followed by all file handles and string arguments sent earlier |
683 | via C<send_fh> and C<send_arg> methods, in the order they were called. |
785 | via C<send_fh> and C<send_arg> methods, in the order they were called. |
684 | |
786 | |
|
|
787 | The process object becomes unusable on return from this function - any |
|
|
788 | further method calls result in undefined behaviour. |
|
|
789 | |
685 | The function name should be fully qualified, but if it isn't, it will be |
790 | The function name should be fully qualified, but if it isn't, it will be |
686 | looked up in the main package. |
791 | looked up in the C<main> package. |
687 | |
792 | |
688 | If the called function returns, doesn't exist, or any error occurs, the |
793 | If the called function returns, doesn't exist, or any error occurs, the |
689 | process exits. |
794 | process exits. |
690 | |
795 | |
691 | Preparing the process is done in the background - when all commands have |
796 | Preparing the process is done in the background - when all commands have |
692 | been sent, the callback is invoked with the local communications socket |
797 | been sent, the callback is invoked with the local communications socket |
693 | as argument. At this point you can start using the socket in any way you |
798 | as argument. At this point you can start using the socket in any way you |
694 | like. |
799 | like. |
695 | |
|
|
696 | The process object becomes unusable on return from this function - any |
|
|
697 | further method calls result in undefined behaviour. |
|
|
698 | |
800 | |
699 | If the communication socket isn't used, it should be closed on both sides, |
801 | If the communication socket isn't used, it should be closed on both sides, |
700 | to save on kernel memory. |
802 | to save on kernel memory. |
701 | |
803 | |
702 | The socket is non-blocking in the parent, and blocking in the newly |
804 | The socket is non-blocking in the parent, and blocking in the newly |
… | |
… | |
741 | =cut |
843 | =cut |
742 | |
844 | |
743 | sub run { |
845 | sub run { |
744 | my ($self, $func, $cb) = @_; |
846 | my ($self, $func, $cb) = @_; |
745 | |
847 | |
746 | $self->[4] = $cb; |
848 | $self->[CB] = $cb; |
747 | $self->_cmd (r => $func); |
849 | $self->_cmd (r => $func); |
|
|
850 | } |
|
|
851 | |
|
|
852 | =back |
|
|
853 | |
|
|
854 | =head2 ADVANCED METHODS |
|
|
855 | |
|
|
856 | =over 4 |
|
|
857 | |
|
|
858 | =item new_from_stdio AnyEvent::Fork $fh |
|
|
859 | |
|
|
860 | Assume that you have a perl interpreter running (without any special |
|
|
861 | options or a program) somewhere and it has it's STDIN and STDOUT connected |
|
|
862 | to the C<$fh> somehow. I.e. exactly the state perl is in when you start it |
|
|
863 | without any arguments: |
|
|
864 | |
|
|
865 | perl |
|
|
866 | |
|
|
867 | Then you can create an C<AnyEvent::Fork> object out of this perl |
|
|
868 | interpreter with this constructor. |
|
|
869 | |
|
|
870 | When the usefulness of this isn't immediately clear, imagine you manage to |
|
|
871 | run a perl interpreter remotely (F<ssh remotemachine perl>), then you can |
|
|
872 | manage it mostly like a local C<AnyEvent::Fork> child. |
|
|
873 | |
|
|
874 | This works without any module support, i.e. the remote F<perl> does not |
|
|
875 | need to have any special modules installed. |
|
|
876 | |
|
|
877 | There are a number of limitations though: C<send_fh> will only work if the |
|
|
878 | L<IO::FDPass> module is loadable by the remote perl and the two processes |
|
|
879 | are connected in a way that let's L<IO::FDPass> do it's work. |
|
|
880 | |
|
|
881 | This will therefore not work over a network connection. From this follows |
|
|
882 | that C<fork> will also not work under these circumstances, as it relies on |
|
|
883 | C<send_fh> internally. |
|
|
884 | |
|
|
885 | Although not a limitation of this module, keep in mind that the |
|
|
886 | "communications socket" is simply C<STDIN>, and depending on how you |
|
|
887 | started F<perl> (e.g. via F<ssh>), it might only be half-duplex. This is |
|
|
888 | fine for C<AnyEvent::Fork>, but your C<run> function might want to use |
|
|
889 | C<STDIN> (or the "communications socket") for input and C<STDOUT> for |
|
|
890 | output. |
|
|
891 | |
|
|
892 | You can support both cases by checking the C<fileno> of the handle passed |
|
|
893 | to your run function: |
|
|
894 | |
|
|
895 | sub run { |
|
|
896 | my ($rfh) = @_; |
|
|
897 | |
|
|
898 | my $wfh = fileno $rfh ? $rfh : *STDOUT; |
|
|
899 | |
|
|
900 | # now use $rfh for reading and $wfh for writing |
|
|
901 | } |
|
|
902 | |
|
|
903 | =cut |
|
|
904 | |
|
|
905 | sub new_from_stdio { |
|
|
906 | my ($class, $fh) = @_; |
|
|
907 | |
|
|
908 | my $self = $class->_new ($fh); |
|
|
909 | |
|
|
910 | # send startup code |
|
|
911 | push @{ $self->[QUEUE] }, |
|
|
912 | (do "AnyEvent/Fork/serve.pl") |
|
|
913 | . <<'EOF'; |
|
|
914 | |
|
|
915 | $OWNER = "another process"; |
|
|
916 | $0 = "AnyEvent::Fork/stdio of $OWNER"; |
|
|
917 | |
|
|
918 | serve *STDIN; |
|
|
919 | __END__ |
|
|
920 | EOF |
|
|
921 | |
|
|
922 | # the data is only sent when the user requests additional things, which |
|
|
923 | # is likely early enough for our purposes. |
|
|
924 | |
|
|
925 | $self |
|
|
926 | } |
|
|
927 | |
|
|
928 | =back |
|
|
929 | |
|
|
930 | =head2 EXPERIMENTAL METHODS |
|
|
931 | |
|
|
932 | These methods might go away completely or change behaviour, a any time. |
|
|
933 | |
|
|
934 | =over 4 |
|
|
935 | |
|
|
936 | =item $proc->to_fh ($cb->($fh)) # EXPERIMENTAL, MIGHT BE REMOVED |
|
|
937 | |
|
|
938 | Flushes all commands out to the process and then calls the callback with |
|
|
939 | the communications socket. |
|
|
940 | |
|
|
941 | The process object becomes unusable on return from this function - any |
|
|
942 | further method calls result in undefined behaviour. |
|
|
943 | |
|
|
944 | The point of this method is to give you a file handle thta you cna pass |
|
|
945 | to another process. In that other process, you can call C<new_from_fh |
|
|
946 | AnyEvent::Fork> to create a new C<AnyEvent::Fork> object from it, thereby |
|
|
947 | effectively passing a fork object to another process. |
|
|
948 | |
|
|
949 | =cut |
|
|
950 | |
|
|
951 | sub to_fh { |
|
|
952 | my ($self, $cb) = @_; |
|
|
953 | |
|
|
954 | $self->[CB] = $cb; |
|
|
955 | |
|
|
956 | unless ($self->[WW]) { |
|
|
957 | $self->[CB]->($self->[FH]); |
|
|
958 | @$self = (); |
|
|
959 | } |
|
|
960 | } |
|
|
961 | |
|
|
962 | =item new_from_fh AnyEvent::Fork $fh # EXPERIMENTAL, MIGHT BE REMOVED |
|
|
963 | |
|
|
964 | Takes a file handle originally rceeived by the C<to_fh> method and creates |
|
|
965 | a new C<AnyEvent:Fork> object. The child process itself will not change in |
|
|
966 | any way, i.e. it will keep all the modifications done to it before calling |
|
|
967 | C<to_fh>. |
|
|
968 | |
|
|
969 | The new object is very much like the original object, except that the |
|
|
970 | C<pid> method will return C<undef> even if the process is a direct child. |
|
|
971 | |
|
|
972 | =cut |
|
|
973 | |
|
|
974 | sub new_from_fh { |
|
|
975 | my ($class, $fh) = @_; |
|
|
976 | |
|
|
977 | $class->_new ($fh) |
748 | } |
978 | } |
749 | |
979 | |
750 | =back |
980 | =back |
751 | |
981 | |
752 | =head1 PERFORMANCE |
982 | =head1 PERFORMANCE |
… | |
… | |
762 | |
992 | |
763 | 2079 new processes per second, using manual socketpair + fork |
993 | 2079 new processes per second, using manual socketpair + fork |
764 | |
994 | |
765 | Then I did the same thing, but instead of calling fork, I called |
995 | Then I did the same thing, but instead of calling fork, I called |
766 | AnyEvent::Fork->new->run ("CORE::exit") and then again waited for the |
996 | AnyEvent::Fork->new->run ("CORE::exit") and then again waited for the |
767 | socket form the child to close on exit. This does the same thing as manual |
997 | socket from the child to close on exit. This does the same thing as manual |
768 | socket pair + fork, except that what is forked is the template process |
998 | socket pair + fork, except that what is forked is the template process |
769 | (2440kB), and the socket needs to be passed to the server at the other end |
999 | (2440kB), and the socket needs to be passed to the server at the other end |
770 | of the socket first. |
1000 | of the socket first. |
771 | |
1001 | |
772 | 2307 new processes per second, using AnyEvent::Fork->new |
1002 | 2307 new processes per second, using AnyEvent::Fork->new |
… | |
… | |
777 | 479 vfork+execs per second, using AnyEvent::Fork->new_exec |
1007 | 479 vfork+execs per second, using AnyEvent::Fork->new_exec |
778 | |
1008 | |
779 | So how can C<< AnyEvent->new >> be faster than a standard fork, even |
1009 | So how can C<< AnyEvent->new >> be faster than a standard fork, even |
780 | though it uses the same operations, but adds a lot of overhead? |
1010 | though it uses the same operations, but adds a lot of overhead? |
781 | |
1011 | |
782 | The difference is simply the process size: forking the 6MB process takes |
1012 | The difference is simply the process size: forking the 5MB process takes |
783 | so much longer than forking the 2.5MB template process that the overhead |
1013 | so much longer than forking the 2.5MB template process that the extra |
784 | introduced is canceled out. |
1014 | overhead is canceled out. |
785 | |
1015 | |
786 | If the benchmark process grows, the normal fork becomes even slower: |
1016 | If the benchmark process grows, the normal fork becomes even slower: |
787 | |
1017 | |
788 | 1340 new processes, manual fork in a 20MB process |
1018 | 1340 new processes, manual fork of a 20MB process |
789 | 731 new processes, manual fork in a 200MB process |
1019 | 731 new processes, manual fork of a 200MB process |
790 | 235 new processes, manual fork in a 2000MB process |
1020 | 235 new processes, manual fork of a 2000MB process |
791 | |
1021 | |
792 | What that means (to me) is that I can use this module without having a |
1022 | What that means (to me) is that I can use this module without having a bad |
793 | very bad conscience because of the extra overhead required to start new |
1023 | conscience because of the extra overhead required to start new processes. |
794 | processes. |
|
|
795 | |
1024 | |
796 | =head1 TYPICAL PROBLEMS |
1025 | =head1 TYPICAL PROBLEMS |
797 | |
1026 | |
798 | This section lists typical problems that remain. I hope by recognising |
1027 | This section lists typical problems that remain. I hope by recognising |
799 | them, most can be avoided. |
1028 | them, most can be avoided. |
800 | |
1029 | |
801 | =over 4 |
1030 | =over 4 |
802 | |
1031 | |
803 | =item "leaked" file descriptors for exec'ed processes |
1032 | =item leaked file descriptors for exec'ed processes |
804 | |
1033 | |
805 | POSIX systems inherit file descriptors by default when exec'ing a new |
1034 | POSIX systems inherit file descriptors by default when exec'ing a new |
806 | process. While perl itself laudably sets the close-on-exec flags on new |
1035 | process. While perl itself laudably sets the close-on-exec flags on new |
807 | file handles, most C libraries don't care, and even if all cared, it's |
1036 | file handles, most C libraries don't care, and even if all cared, it's |
808 | often not possible to set the flag in a race-free manner. |
1037 | often not possible to set the flag in a race-free manner. |
… | |
… | |
828 | libraries or the code that leaks those file descriptors. |
1057 | libraries or the code that leaks those file descriptors. |
829 | |
1058 | |
830 | Fortunately, most of these leaked descriptors do no harm, other than |
1059 | Fortunately, most of these leaked descriptors do no harm, other than |
831 | sitting on some resources. |
1060 | sitting on some resources. |
832 | |
1061 | |
833 | =item "leaked" file descriptors for fork'ed processes |
1062 | =item leaked file descriptors for fork'ed processes |
834 | |
1063 | |
835 | Normally, L<AnyEvent::Fork> does start new processes by exec'ing them, |
1064 | Normally, L<AnyEvent::Fork> does start new processes by exec'ing them, |
836 | which closes file descriptors not marked for being inherited. |
1065 | which closes file descriptors not marked for being inherited. |
837 | |
1066 | |
838 | However, L<AnyEvent::Fork::Early> and L<AnyEvent::Fork::Template> offer |
1067 | However, L<AnyEvent::Fork::Early> and L<AnyEvent::Fork::Template> offer |
… | |
… | |
847 | |
1076 | |
848 | The solution is to either not load these modules before use'ing |
1077 | The solution is to either not load these modules before use'ing |
849 | L<AnyEvent::Fork::Early> or L<AnyEvent::Fork::Template>, or to delay |
1078 | L<AnyEvent::Fork::Early> or L<AnyEvent::Fork::Template>, or to delay |
850 | initialising them, for example, by calling C<init Gtk2> manually. |
1079 | initialising them, for example, by calling C<init Gtk2> manually. |
851 | |
1080 | |
852 | =item exit runs destructors |
1081 | =item exiting calls object destructors |
853 | |
1082 | |
854 | This only applies to users of Lc<AnyEvent::Fork:Early> and |
1083 | This only applies to users of L<AnyEvent::Fork:Early> and |
855 | L<AnyEvent::Fork::Template>. |
1084 | L<AnyEvent::Fork::Template>, or when initialising code creates objects |
|
|
1085 | that reference external resources. |
856 | |
1086 | |
857 | When a process created by AnyEvent::Fork exits, it might do so by calling |
1087 | When a process created by AnyEvent::Fork exits, it might do so by calling |
858 | exit, or simply letting perl reach the end of the program. At which point |
1088 | exit, or simply letting perl reach the end of the program. At which point |
859 | Perl runs all destructors. |
1089 | Perl runs all destructors. |
860 | |
1090 | |
… | |
… | |
879 | to make it so, mostly due to the bloody broken perl that nobody seems to |
1109 | to make it so, mostly due to the bloody broken perl that nobody seems to |
880 | care about. The fork emulation is a bad joke - I have yet to see something |
1110 | care about. The fork emulation is a bad joke - I have yet to see something |
881 | useful that you can do with it without running into memory corruption |
1111 | useful that you can do with it without running into memory corruption |
882 | issues or other braindamage. Hrrrr. |
1112 | issues or other braindamage. Hrrrr. |
883 | |
1113 | |
884 | Cygwin perl is not supported at the moment, as it should implement fd |
1114 | Since fork is endlessly broken on win32 perls (it doesn't even remotely |
885 | passing, but doesn't, and rolling my own is hard, as cygwin doesn't |
1115 | work within it's documented limits) and quite obviously it's not getting |
886 | support enough functionality to do it. |
1116 | improved any time soon, the best way to proceed on windows would be to |
|
|
1117 | always use C<new_exec> and thus never rely on perl's fork "emulation". |
|
|
1118 | |
|
|
1119 | Cygwin perl is not supported at the moment due to some hilarious |
|
|
1120 | shortcomings of its API - see L<IO::FDPoll> for more details. If you never |
|
|
1121 | use C<send_fh> and always use C<new_exec> to create processes, it should |
|
|
1122 | work though. |
887 | |
1123 | |
888 | =head1 SEE ALSO |
1124 | =head1 SEE ALSO |
889 | |
1125 | |
890 | L<AnyEvent::Fork::Early> (to avoid executing a perl interpreter), |
1126 | L<AnyEvent::Fork::Early>, to avoid executing a perl interpreter at all |
|
|
1127 | (part of this distribution). |
|
|
1128 | |
891 | L<AnyEvent::Fork::Template> (to create a process by forking the main |
1129 | L<AnyEvent::Fork::Template>, to create a process by forking the main |
892 | program at a convenient time). |
1130 | program at a convenient time (part of this distribution). |
893 | |
1131 | |
894 | =head1 AUTHOR |
1132 | L<AnyEvent::Fork::RPC>, for simple RPC to child processes (on CPAN). |
|
|
1133 | |
|
|
1134 | L<AnyEvent::Fork::Pool>, for simple worker process pool (on CPAN). |
|
|
1135 | |
|
|
1136 | =head1 AUTHOR AND CONTACT INFORMATION |
895 | |
1137 | |
896 | Marc Lehmann <schmorp@schmorp.de> |
1138 | Marc Lehmann <schmorp@schmorp.de> |
897 | http://home.schmorp.de/ |
1139 | http://software.schmorp.de/pkg/AnyEvent-Fork |
898 | |
1140 | |
899 | =cut |
1141 | =cut |
900 | |
1142 | |
901 | 1 |
1143 | 1 |
902 | |
1144 | |