… | |
… | |
2 | |
2 | |
3 | AnyEvent::Fork::RPC - simple RPC extension for AnyEvent::Fork |
3 | AnyEvent::Fork::RPC - simple RPC extension for AnyEvent::Fork |
4 | |
4 | |
5 | =head1 SYNOPSIS |
5 | =head1 SYNOPSIS |
6 | |
6 | |
|
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7 | use AnyEvent::Fork; |
7 | use AnyEvent::Fork::RPC; |
8 | use AnyEvent::Fork::RPC; |
8 | # use AnyEvent::Fork is not needed |
|
|
9 | |
9 | |
10 | my $rpc = AnyEvent::Fork |
10 | my $rpc = AnyEvent::Fork |
11 | ->new |
11 | ->new |
12 | ->require ("MyModule") |
12 | ->require ("MyModule") |
13 | ->AnyEvent::Fork::RPC::run ( |
13 | ->AnyEvent::Fork::RPC::run ( |
14 | "MyModule::server", |
14 | "MyModule::server", |
15 | ); |
15 | ); |
16 | |
16 | |
|
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17 | use AnyEvent; |
|
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18 | |
17 | my $cv = AE::cv; |
19 | my $cv = AE::cv; |
18 | |
20 | |
19 | $rpc->(1, 2, 3, sub { |
21 | $rpc->(1, 2, 3, sub { |
20 | print "MyModule::server returned @_\n"; |
22 | print "MyModule::server returned @_\n"; |
21 | $cv->send; |
23 | $cv->send; |
… | |
… | |
24 | $cv->recv; |
26 | $cv->recv; |
25 | |
27 | |
26 | =head1 DESCRIPTION |
28 | =head1 DESCRIPTION |
27 | |
29 | |
28 | This module implements a simple RPC protocol and backend for processes |
30 | This module implements a simple RPC protocol and backend for processes |
29 | created via L<AnyEvent::Fork>, allowing you to call a function in the |
31 | created via L<AnyEvent::Fork> or L<AnyEvent::Fork::Remote>, allowing you |
30 | child process and receive its return values (up to 4GB serialised). |
32 | to call a function in the child process and receive its return values (up |
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33 | to 4GB serialised). |
31 | |
34 | |
32 | It implements two different backends: a synchronous one that works like a |
35 | It implements two different backends: a synchronous one that works like a |
33 | normal function call, and an asynchronous one that can run multiple jobs |
36 | normal function call, and an asynchronous one that can run multiple jobs |
34 | concurrently in the child, using AnyEvent. |
37 | concurrently in the child, using AnyEvent. |
35 | |
38 | |
36 | It also implements an asynchronous event mechanism from the child to the |
39 | It also implements an asynchronous event mechanism from the child to the |
37 | parent, that could be used for progress indications or other information. |
40 | parent, that could be used for progress indications or other information. |
38 | |
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39 | Loading this module also always loads L<AnyEvent::Fork>, so you can make a |
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40 | separate C<use AnyEvent::Fork> if you wish, but you don't have to. |
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41 | |
41 | |
42 | =head1 EXAMPLES |
42 | =head1 EXAMPLES |
43 | |
43 | |
44 | =head2 Example 1: Synchronous Backend |
44 | =head2 Example 1: Synchronous Backend |
45 | |
45 | |
… | |
… | |
49 | silly, but illustrates the use of events. |
49 | silly, but illustrates the use of events. |
50 | |
50 | |
51 | First the parent process: |
51 | First the parent process: |
52 | |
52 | |
53 | use AnyEvent; |
53 | use AnyEvent; |
|
|
54 | use AnyEvent::Fork; |
54 | use AnyEvent::Fork::RPC; |
55 | use AnyEvent::Fork::RPC; |
55 | |
56 | |
56 | my $done = AE::cv; |
57 | my $done = AE::cv; |
57 | |
58 | |
58 | my $rpc = AnyEvent::Fork |
59 | my $rpc = AnyEvent::Fork |
59 | ->new |
60 | ->new |
60 | ->require ("MyWorker") |
61 | ->require ("MyWorker") |
61 | ->AnyEvent::Fork::RPC::run ("MyWorker::run", |
62 | ->AnyEvent::Fork::RPC::run ("MyWorker::run", |
62 | on_error => sub { warn "FATAL: $_[0]"; exit 1 }, |
63 | on_error => sub { warn "ERROR: $_[0]"; exit 1 }, |
63 | on_event => sub { warn "$_[0] requests handled\n" }, |
64 | on_event => sub { warn "$_[0] requests handled\n" }, |
64 | on_destroy => $done, |
65 | on_destroy => $done, |
65 | ); |
66 | ); |
66 | |
67 | |
67 | for my $id (1..6) { |
68 | for my $id (1..6) { |
… | |
… | |
174 | you really I<are> done. |
175 | you really I<are> done. |
175 | |
176 | |
176 | =head2 Example 2: Asynchronous Backend |
177 | =head2 Example 2: Asynchronous Backend |
177 | |
178 | |
178 | This example implements multiple count-downs in the child, using |
179 | This example implements multiple count-downs in the child, using |
179 | L<AnyEvent> timers. While this is a bit silly (one could use timers in te |
180 | L<AnyEvent> timers. While this is a bit silly (one could use timers in the |
180 | parent just as well), it illustrates the ability to use AnyEvent in the |
181 | parent just as well), it illustrates the ability to use AnyEvent in the |
181 | child and the fact that responses can arrive in a different order then the |
182 | child and the fact that responses can arrive in a different order then the |
182 | requests. |
183 | requests. |
183 | |
184 | |
184 | It also shows how to embed the actual child code into a C<__DATA__> |
185 | It also shows how to embed the actual child code into a C<__DATA__> |
… | |
… | |
189 | so silly anymore. |
190 | so silly anymore. |
190 | |
191 | |
191 | Without further ado, here is the code: |
192 | Without further ado, here is the code: |
192 | |
193 | |
193 | use AnyEvent; |
194 | use AnyEvent; |
|
|
195 | use AnyEvent::Fork; |
194 | use AnyEvent::Fork::RPC; |
196 | use AnyEvent::Fork::RPC; |
195 | |
197 | |
196 | my $done = AE::cv; |
198 | my $done = AE::cv; |
197 | |
199 | |
198 | my $rpc = AnyEvent::Fork |
200 | my $rpc = AnyEvent::Fork |
199 | ->new |
201 | ->new |
200 | ->require ("AnyEvent::Fork::RPC::Async") |
202 | ->require ("AnyEvent::Fork::RPC::Async") |
201 | ->eval (do { local $/; <DATA> }) |
203 | ->eval (do { local $/; <DATA> }) |
202 | ->AnyEvent::Fork::RPC::run ("run", |
204 | ->AnyEvent::Fork::RPC::run ("run", |
203 | async => 1, |
205 | async => 1, |
204 | on_error => sub { warn "FATAL: $_[0]"; exit 1 }, |
206 | on_error => sub { warn "ERROR: $_[0]"; exit 1 }, |
205 | on_event => sub { print $_[0] }, |
207 | on_event => sub { print $_[0] }, |
206 | on_destroy => $done, |
208 | on_destroy => $done, |
207 | ); |
209 | ); |
208 | |
210 | |
209 | for my $count (3, 2, 1) { |
211 | for my $count (3, 2, 1) { |
… | |
… | |
285 | |
287 | |
286 | This concludes the async example. Since L<AnyEvent::Fork> does not |
288 | This concludes the async example. Since L<AnyEvent::Fork> does not |
287 | actually fork, you are free to use about any module in the child, not just |
289 | actually fork, you are free to use about any module in the child, not just |
288 | L<AnyEvent>, but also L<IO::AIO>, or L<Tk> for example. |
290 | L<AnyEvent>, but also L<IO::AIO>, or L<Tk> for example. |
289 | |
291 | |
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292 | =head2 Example 3: Asynchronous backend with Coro |
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293 | |
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294 | With L<Coro> you can create a nice asynchronous backend implementation by |
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295 | defining an rpc server function that creates a new Coro thread for every |
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296 | request that calls a function "normally", i.e. the parameters from the |
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297 | parent process are passed to it, and any return values are returned to the |
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298 | parent process, e.g.: |
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299 | |
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300 | package My::Arith; |
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301 | |
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302 | sub add { |
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303 | return $_[0] + $_[1]; |
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304 | } |
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305 | |
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306 | sub mul { |
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307 | return $_[0] * $_[1]; |
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308 | } |
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309 | |
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310 | sub run { |
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311 | my ($done, $func, @arg) = @_; |
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312 | |
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313 | Coro::async_pool { |
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314 | $done->($func->(@arg)); |
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315 | }; |
|
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316 | } |
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317 | |
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318 | The C<run> function creates a new thread for every invocation, using the |
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319 | first argument as function name, and calls the C<$done> callback on it's |
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320 | return values. This makes it quite natural to define the C<add> and C<mul> |
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321 | functions to add or multiply two numbers and return the result. |
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322 | |
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323 | Since this is the asynchronous backend, it's quite possible to define RPC |
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324 | function that do I/O or wait for external events - their execution will |
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325 | overlap as needed. |
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326 | |
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327 | The above could be used like this: |
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328 | |
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329 | my $rpc = AnyEvent::Fork |
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330 | ->new |
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331 | ->require ("MyWorker") |
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332 | ->AnyEvent::Fork::RPC::run ("My::Arith::run", |
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333 | on_error => ..., on_event => ..., on_destroy => ..., |
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334 | ); |
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335 | |
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336 | $rpc->(add => 1, 3, Coro::rouse_cb); say Coro::rouse_wait; |
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337 | $rpc->(mul => 3, 2, Coro::rouse_cb); say Coro::rouse_wait; |
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338 | |
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339 | The C<say>'s will print C<4> and C<6>. |
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340 | |
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341 | =head2 Example 4: Forward AnyEvent::Log messages using C<on_event> |
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342 | |
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343 | This partial example shows how to use the C<event> function to forward |
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344 | L<AnyEvent::Log> messages to the parent. |
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345 | |
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346 | For this, the parent needs to provide a suitable C<on_event>: |
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347 | |
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348 | ->AnyEvent::Fork::RPC::run ( |
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349 | on_event => sub { |
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350 | if ($_[0] eq "ae_log") { |
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351 | my (undef, $level, $message) = @_; |
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352 | AE::log $level, $message; |
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353 | } else { |
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354 | # other event types |
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355 | } |
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356 | }, |
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357 | ) |
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358 | |
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359 | In the child, as early as possible, the following code should reconfigure |
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360 | L<AnyEvent::Log> to log via C<AnyEvent::Fork::RPC::event>: |
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361 | |
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362 | $AnyEvent::Log::LOG->log_cb (sub { |
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363 | my ($timestamp, $orig_ctx, $level, $message) = @{+shift}; |
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364 | |
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365 | if (defined &AnyEvent::Fork::RPC::event) { |
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366 | AnyEvent::Fork::RPC::event (ae_log => $level, $message); |
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367 | } else { |
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368 | warn "[$$ before init] $message\n"; |
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369 | } |
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370 | }); |
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371 | |
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372 | There is an important twist - the C<AnyEvent::Fork::RPC::event> function |
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373 | is only defined when the child is fully initialised. If you redirect the |
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374 | log messages in your C<init> function for example, then the C<event> |
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375 | function might not yet be available. This is why the log callback checks |
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376 | whether the fucntion is there using C<defined>, and only then uses it to |
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377 | log the message. |
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378 | |
290 | =head1 PARENT PROCESS USAGE |
379 | =head1 PARENT PROCESS USAGE |
291 | |
380 | |
292 | This module exports nothing, and only implements a single function: |
381 | This module exports nothing, and only implements a single function: |
293 | |
382 | |
294 | =over 4 |
383 | =over 4 |
… | |
… | |
301 | |
390 | |
302 | use Errno (); |
391 | use Errno (); |
303 | use Guard (); |
392 | use Guard (); |
304 | |
393 | |
305 | use AnyEvent; |
394 | use AnyEvent; |
306 | use AnyEvent::Fork; # we don't actually depend on it, this is for convenience |
|
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307 | |
395 | |
308 | our $VERSION = 0.1; |
396 | our $VERSION = 1.21; |
309 | |
397 | |
310 | =item my $rpc = AnyEvent::Fork::RPC::run $fork, $function, [key => value...] |
398 | =item my $rpc = AnyEvent::Fork::RPC::run $fork, $function, [key => value...] |
311 | |
399 | |
312 | The traditional way to call it. But it is way cooler to call it in the |
400 | The traditional way to call it. But it is way cooler to call it in the |
313 | following way: |
401 | following way: |
… | |
… | |
333 | Called on (fatal) errors, with a descriptive (hopefully) message. If |
421 | Called on (fatal) errors, with a descriptive (hopefully) message. If |
334 | this callback is not provided, but C<on_event> is, then the C<on_event> |
422 | this callback is not provided, but C<on_event> is, then the C<on_event> |
335 | callback is called with the first argument being the string C<error>, |
423 | callback is called with the first argument being the string C<error>, |
336 | followed by the error message. |
424 | followed by the error message. |
337 | |
425 | |
338 | If neither handler is provided it prints the error to STDERR and will |
426 | If neither handler is provided, then the error is reported with loglevel |
339 | start failing badly. |
427 | C<error> via C<AE::log>. |
340 | |
428 | |
341 | =item on_event => $cb->(...) |
429 | =item on_event => $cb->(...) |
342 | |
430 | |
343 | Called for every call to the C<AnyEvent::Fork::RPC::event> function in the |
431 | Called for every call to the C<AnyEvent::Fork::RPC::event> function in the |
344 | child, with the arguments of that function passed to the callback. |
432 | child, with the arguments of that function passed to the callback. |
… | |
… | |
366 | It is called very early - before the serialisers are created or the |
454 | It is called very early - before the serialisers are created or the |
367 | C<$function> name is resolved into a function reference, so it could be |
455 | C<$function> name is resolved into a function reference, so it could be |
368 | used to load any modules that provide the serialiser or function. It can |
456 | used to load any modules that provide the serialiser or function. It can |
369 | not, however, create events. |
457 | not, however, create events. |
370 | |
458 | |
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459 | =item done => $function (default C<CORE::exit>) |
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460 | |
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461 | The function to call when the asynchronous backend detects an end of file |
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462 | condition when reading from the communications socket I<and> there are no |
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463 | outstanding requests. It's ignored by the synchronous backend. |
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464 | |
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465 | By overriding this you can prolong the life of a RPC process after e.g. |
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466 | the parent has exited by running the event loop in the provided function |
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467 | (or simply calling it, for example, when your child process uses L<EV> you |
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468 | could provide L<EV::loop> as C<done> function). |
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469 | |
|
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470 | Of course, in that case you are responsible for exiting at the appropriate |
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471 | time and not returning from |
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472 | |
371 | =item async => $boolean (default: 0) |
473 | =item async => $boolean (default: 0) |
372 | |
474 | |
373 | The default server used in the child does all I/O blockingly, and only |
475 | The default server used in the child does all I/O blockingly, and only |
374 | allows a single RPC call to execute concurrently. |
476 | allows a single RPC call to execute concurrently. |
375 | |
477 | |
376 | Setting C<async> to a true value switches to another implementation that |
478 | Setting C<async> to a true value switches to another implementation that |
377 | uses L<AnyEvent> in the child and allows multiple concurrent RPC calls. |
479 | uses L<AnyEvent> in the child and allows multiple concurrent RPC calls (it |
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480 | does not support recursion in the event loop however, blocking condvar |
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481 | calls will fail). |
378 | |
482 | |
379 | The actual API in the child is documented in the section that describes |
483 | The actual API in the child is documented in the section that describes |
380 | the calling semantics of the returned C<$rpc> function. |
484 | the calling semantics of the returned C<$rpc> function. |
381 | |
485 | |
382 | If you want to pre-load the actual back-end modules to enable memory |
486 | If you want to pre-load the actual back-end modules to enable memory |
… | |
… | |
384 | synchronous, and C<AnyEvent::Fork::RPC::Async> for asynchronous mode. |
488 | synchronous, and C<AnyEvent::Fork::RPC::Async> for asynchronous mode. |
385 | |
489 | |
386 | If you use a template process and want to fork both sync and async |
490 | If you use a template process and want to fork both sync and async |
387 | children, then it is permissible to load both modules. |
491 | children, then it is permissible to load both modules. |
388 | |
492 | |
389 | =item serialiser => $string (default: '(sub { pack "(w/a*)*", @_ }, sub { unpack "(w/a*)*", shift })') |
493 | =item serialiser => $string (default: $AnyEvent::Fork::RPC::STRING_SERIALISER) |
390 | |
494 | |
391 | All arguments, result data and event data have to be serialised to be |
495 | All arguments, result data and event data have to be serialised to be |
392 | transferred between the processes. For this, they have to be frozen and |
496 | transferred between the processes. For this, they have to be frozen and |
393 | thawed in both parent and child processes. |
497 | thawed in both parent and child processes. |
394 | |
498 | |
395 | By default, only octet strings can be passed between the processes, which |
499 | By default, only octet strings can be passed between the processes, which |
396 | is reasonably fast and efficient. |
500 | is reasonably fast and efficient and requires no extra modules. |
397 | |
501 | |
398 | For more complicated use cases, you can provide your own freeze and thaw |
502 | For more complicated use cases, you can provide your own freeze and thaw |
399 | functions, by specifying a string with perl source code. It's supposed to |
503 | functions, by specifying a string with perl source code. It's supposed to |
400 | return two code references when evaluated: the first receives a list of |
504 | return two code references when evaluated: the first receives a list of |
401 | perl values and must return an octet string. The second receives the octet |
505 | perl values and must return an octet string. The second receives the octet |
… | |
… | |
403 | |
507 | |
404 | If you need an external module for serialisation, then you can either |
508 | If you need an external module for serialisation, then you can either |
405 | pre-load it into your L<AnyEvent::Fork> process, or you can add a C<use> |
509 | pre-load it into your L<AnyEvent::Fork> process, or you can add a C<use> |
406 | or C<require> statement into the serialiser string. Or both. |
510 | or C<require> statement into the serialiser string. Or both. |
407 | |
511 | |
|
|
512 | Here are some examples - some of them are also available as global |
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513 | variables that make them easier to use. |
|
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514 | |
|
|
515 | =over 4 |
|
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516 | |
|
|
517 | =item octet strings - C<$AnyEvent::Fork::RPC::STRING_SERIALISER> |
|
|
518 | |
|
|
519 | This serialiser concatenates length-prefixes octet strings, and is the |
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520 | default. That means you can only pass (and return) strings containing |
|
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521 | character codes 0-255. |
|
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522 | |
|
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523 | Implementation: |
|
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524 | |
|
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525 | ( |
|
|
526 | sub { pack "(w/a*)*", @_ }, |
|
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527 | sub { unpack "(w/a*)*", shift } |
|
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528 | ) |
|
|
529 | |
|
|
530 | =item json - C<$AnyEvent::Fork::RPC::JSON_SERIALISER> |
|
|
531 | |
|
|
532 | This serialiser creates JSON arrays - you have to make sure the L<JSON> |
|
|
533 | module is installed for this serialiser to work. It can be beneficial for |
|
|
534 | sharing when you preload the L<JSON> module in a template process. |
|
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535 | |
|
|
536 | L<JSON> (with L<JSON::XS> installed) is slower than the octet string |
|
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537 | serialiser, but usually much faster than L<Storable>, unless big chunks of |
|
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538 | binary data need to be transferred. |
|
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539 | |
|
|
540 | Implementation: |
|
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541 | |
|
|
542 | use JSON (); |
|
|
543 | ( |
|
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544 | sub { JSON::encode_json \@_ }, |
|
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545 | sub { @{ JSON::decode_json shift } } |
|
|
546 | ) |
|
|
547 | |
|
|
548 | =item storable - C<$AnyEvent::Fork::RPC::STORABLE_SERIALISER> |
|
|
549 | |
|
|
550 | This serialiser uses L<Storable>, which means it has high chance of |
|
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551 | serialising just about anything you throw at it, at the cost of having |
|
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552 | very high overhead per operation. It also comes with perl. It should be |
|
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553 | used when you need to serialise complex data structures. |
|
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554 | |
|
|
555 | Implementation: |
|
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556 | |
|
|
557 | use Storable (); |
|
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558 | ( |
|
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559 | sub { Storable::freeze \@_ }, |
|
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560 | sub { @{ Storable::thaw shift } } |
|
|
561 | ) |
|
|
562 | |
|
|
563 | =item portable storable - C<$AnyEvent::Fork::RPC::NSTORABLE_SERIALISER> |
|
|
564 | |
|
|
565 | This serialiser also uses L<Storable>, but uses it's "network" format |
|
|
566 | to serialise data, which makes it possible to talk to different |
|
|
567 | perl binaries (for example, when talking to a process created with |
|
|
568 | L<AnyEvent::Fork::Remote>). |
|
|
569 | |
|
|
570 | Implementation: |
|
|
571 | |
|
|
572 | use Storable (); |
|
|
573 | ( |
|
|
574 | sub { Storable::nfreeze \@_ }, |
|
|
575 | sub { @{ Storable::thaw shift } } |
|
|
576 | ) |
|
|
577 | |
|
|
578 | =back |
|
|
579 | |
408 | =back |
580 | =back |
409 | |
581 | |
410 | See the examples section earlier in this document for some actual |
582 | See the examples section earlier in this document for some actual |
411 | examples. |
583 | examples. |
412 | |
584 | |
413 | =cut |
585 | =cut |
414 | |
586 | |
415 | our $STRING_SERIALISER = '(sub { pack "(w/a*)*", @_ }, sub { unpack "(w/a*)*", shift })'; |
587 | our $STRING_SERIALISER = '(sub { pack "(w/a*)*", @_ }, sub { unpack "(w/a*)*", shift })'; |
|
|
588 | our $JSON_SERIALISER = 'use JSON (); (sub { JSON::encode_json \@_ }, sub { @{ JSON::decode_json shift } })'; |
|
|
589 | our $STORABLE_SERIALISER = 'use Storable (); (sub { Storable::freeze \@_ }, sub { @{ Storable::thaw shift } })'; |
|
|
590 | our $NSTORABLE_SERIALISER = 'use Storable (); (sub { Storable::nfreeze \@_ }, sub { @{ Storable::thaw shift } })'; |
416 | |
591 | |
417 | sub run { |
592 | sub run { |
418 | my ($self, $function, %arg) = @_; |
593 | my ($self, $function, %arg) = @_; |
419 | |
594 | |
420 | my $serialiser = delete $arg{serialiser} || $STRING_SERIALISER; |
595 | my $serialiser = delete $arg{serialiser} || $STRING_SERIALISER; |
… | |
… | |
423 | my $on_destroy = delete $arg{on_destroy}; |
598 | my $on_destroy = delete $arg{on_destroy}; |
424 | |
599 | |
425 | # default for on_error is to on_event, if specified |
600 | # default for on_error is to on_event, if specified |
426 | $on_error ||= $on_event |
601 | $on_error ||= $on_event |
427 | ? sub { $on_event->(error => shift) } |
602 | ? sub { $on_event->(error => shift) } |
428 | : sub { die "AnyEvent::Fork::RPC: uncaught error: $_[0].\n" }; |
603 | : sub { AE::log die => "AnyEvent::Fork::RPC: uncaught error: $_[0]." }; |
429 | |
604 | |
430 | # default for on_event is to raise an error |
605 | # default for on_event is to raise an error |
431 | $on_event ||= sub { $on_error->("event received, but no on_event handler") }; |
606 | $on_event ||= sub { $on_error->("event received, but no on_event handler") }; |
432 | |
607 | |
433 | my ($f, $t) = eval $serialiser; die $@ if $@; |
608 | my ($f, $t) = eval $serialiser; die $@ if $@; |
… | |
… | |
454 | }; |
629 | }; |
455 | |
630 | |
456 | my $module = "AnyEvent::Fork::RPC::" . ($arg{async} ? "Async" : "Sync"); |
631 | my $module = "AnyEvent::Fork::RPC::" . ($arg{async} ? "Async" : "Sync"); |
457 | |
632 | |
458 | $self->require ($module) |
633 | $self->require ($module) |
459 | ->send_arg ($function, $arg{init}, $serialiser) |
634 | ->send_arg ($function, $arg{init}, $serialiser, $arg{done} || "$module\::do_exit") |
460 | ->run ("$module\::run", sub { |
635 | ->run ("$module\::run", sub { |
461 | $fh = shift; |
636 | $fh = shift; |
462 | |
637 | |
463 | my ($id, $len); |
638 | my ($id, $len); |
464 | $rw = AE::io $fh, 0, sub { |
639 | $rw = AE::io $fh, 0, sub { |
465 | $rlen = $rlen * 2 + 16 if $rlen - 128 < length $rbuf; |
640 | $rlen = $rlen * 2 + 16 if $rlen - 128 < length $rbuf; |
466 | $len = sysread $fh, $rbuf, $rlen - length $rbuf, length $rbuf; |
641 | $len = sysread $fh, $rbuf, $rlen - length $rbuf, length $rbuf; |
467 | |
642 | |
468 | if ($len) { |
643 | if ($len) { |
469 | while (8 <= length $rbuf) { |
644 | while (8 <= length $rbuf) { |
470 | ($id, $len) = unpack "LL", $rbuf; |
645 | ($id, $len) = unpack "NN", $rbuf; |
471 | 8 + $len <= length $rbuf |
646 | 8 + $len <= length $rbuf |
472 | or last; |
647 | or last; |
473 | |
648 | |
474 | my @r = $t->(substr $rbuf, 8, $len); |
649 | my @r = $t->(substr $rbuf, 8, $len); |
475 | substr $rbuf, 0, 8 + $len, ""; |
650 | substr $rbuf, 0, 8 + $len, ""; |
… | |
… | |
489 | } |
664 | } |
490 | } elsif (defined $len) { |
665 | } elsif (defined $len) { |
491 | undef $rw; undef $ww; # it ends here |
666 | undef $rw; undef $ww; # it ends here |
492 | |
667 | |
493 | if (@rcb || %rcb) { |
668 | if (@rcb || %rcb) { |
494 | use Data::Dump;ddx[\@rcb,\%rcb];#d# |
|
|
495 | $on_error->("unexpected eof"); |
669 | $on_error->("unexpected eof"); |
496 | } else { |
670 | } else { |
497 | $on_destroy->(); |
671 | $on_destroy->() |
|
|
672 | if $on_destroy; |
498 | } |
673 | } |
499 | } elsif ($! != Errno::EAGAIN && $! != Errno::EWOULDBLOCK) { |
674 | } elsif ($! != Errno::EAGAIN && $! != Errno::EWOULDBLOCK) { |
500 | undef $rw; undef $ww; # it ends here |
675 | undef $rw; undef $ww; # it ends here |
501 | $on_error->("read: $!"); |
676 | $on_error->("read: $!"); |
502 | } |
677 | } |
… | |
… | |
505 | $ww ||= AE::io $fh, 1, $wcb; |
680 | $ww ||= AE::io $fh, 1, $wcb; |
506 | }); |
681 | }); |
507 | |
682 | |
508 | my $guard = Guard::guard { |
683 | my $guard = Guard::guard { |
509 | $shutdown = 1; |
684 | $shutdown = 1; |
510 | $ww ||= $fh && AE::io $fh, 1, $wcb; |
685 | |
|
|
686 | shutdown $fh, 1 if $fh && !$ww; |
511 | }; |
687 | }; |
512 | |
688 | |
513 | my $id; |
689 | my $id; |
514 | |
690 | |
515 | $arg{async} |
691 | $arg{async} |
… | |
… | |
517 | $id = ($id == 0xffffffff ? 0 : $id) + 1; |
693 | $id = ($id == 0xffffffff ? 0 : $id) + 1; |
518 | $id = ($id == 0xffffffff ? 0 : $id) + 1 while exists $rcb{$id}; # rarely loops |
694 | $id = ($id == 0xffffffff ? 0 : $id) + 1 while exists $rcb{$id}; # rarely loops |
519 | |
695 | |
520 | $rcb{$id} = pop; |
696 | $rcb{$id} = pop; |
521 | |
697 | |
522 | $guard; # keep it alive |
698 | $guard if 0; # keep it alive |
523 | |
699 | |
524 | $wbuf .= pack "LL/a*", $id, &$f; |
700 | $wbuf .= pack "NN/a*", $id, &$f; |
525 | $ww ||= $fh && AE::io $fh, 1, $wcb; |
701 | $ww ||= $fh && AE::io $fh, 1, $wcb; |
526 | } |
702 | } |
527 | : sub { |
703 | : sub { |
528 | push @rcb, pop; |
704 | push @rcb, pop; |
529 | |
705 | |
530 | $guard; # keep it alive |
706 | $guard; # keep it alive |
531 | |
707 | |
532 | $wbuf .= pack "L/a*", &$f; |
708 | $wbuf .= pack "N/a*", &$f; |
533 | $ww ||= $fh && AE::io $fh, 1, $wcb; |
709 | $ww ||= $fh && AE::io $fh, 1, $wcb; |
534 | } |
710 | } |
535 | } |
711 | } |
536 | |
712 | |
537 | =item $rpc->(..., $cb->(...)) |
713 | =item $rpc->(..., $cb->(...)) |
… | |
… | |
579 | See the examples section earlier in this document for some actual |
755 | See the examples section earlier in this document for some actual |
580 | examples. |
756 | examples. |
581 | |
757 | |
582 | =back |
758 | =back |
583 | |
759 | |
|
|
760 | =head2 PROCESS EXIT |
|
|
761 | |
|
|
762 | If and when the child process exits depends on the backend and |
|
|
763 | configuration. Apart from explicit exits (e.g. by calling C<exit>) or |
|
|
764 | runtime conditions (uncaught exceptions, signals etc.), the backends exit |
|
|
765 | under these conditions: |
|
|
766 | |
|
|
767 | =over 4 |
|
|
768 | |
|
|
769 | =item Synchronous Backend |
|
|
770 | |
|
|
771 | The synchronous backend is very simple: when the process waits for another |
|
|
772 | request to arrive and the writing side (usually in the parent) is closed, |
|
|
773 | it will exit normally, i.e. as if your main program reached the end of the |
|
|
774 | file. |
|
|
775 | |
|
|
776 | That means that if your parent process exits, the RPC process will usually |
|
|
777 | exit as well, either because it is idle anyway, or because it executes a |
|
|
778 | request. In the latter case, you will likely get an error when the RPc |
|
|
779 | process tries to send the results to the parent (because agruably, you |
|
|
780 | shouldn't exit your parent while there are still outstanding requests). |
|
|
781 | |
|
|
782 | The process is usually quiescent when it happens, so it should rarely be a |
|
|
783 | problem, and C<END> handlers can be used to clean up. |
|
|
784 | |
|
|
785 | =item Asynchronous Backend |
|
|
786 | |
|
|
787 | For the asynchronous backend, things are more complicated: Whenever it |
|
|
788 | listens for another request by the parent, it might detect that the socket |
|
|
789 | was closed (e.g. because the parent exited). It will sotp listening for |
|
|
790 | new requests and instead try to write out any remaining data (if any) or |
|
|
791 | simply check whether the socket can be written to. After this, the RPC |
|
|
792 | process is effectively done - no new requests are incoming, no outstanding |
|
|
793 | request data can be written back. |
|
|
794 | |
|
|
795 | Since chances are high that there are event watchers that the RPC server |
|
|
796 | knows nothing about (why else would one use the async backend if not for |
|
|
797 | the ability to register watchers?), the event loop would often happily |
|
|
798 | continue. |
|
|
799 | |
|
|
800 | This is why the asynchronous backend explicitly calls C<CORE::exit> when |
|
|
801 | it is done (under other circumstances, such as when there is an I/O error |
|
|
802 | and there is outstanding data to write, it will log a fatal message via |
|
|
803 | L<AnyEvent::Log>, also causing the program to exit). |
|
|
804 | |
|
|
805 | You can override this by specifying a function name to call via the C<done> |
|
|
806 | parameter instead. |
|
|
807 | |
|
|
808 | =back |
|
|
809 | |
|
|
810 | =head1 ADVANCED TOPICS |
|
|
811 | |
|
|
812 | =head2 Choosing a backend |
|
|
813 | |
|
|
814 | So how do you decide which backend to use? Well, that's your problem to |
|
|
815 | solve, but here are some thoughts on the matter: |
|
|
816 | |
|
|
817 | =over 4 |
|
|
818 | |
|
|
819 | =item Synchronous |
|
|
820 | |
|
|
821 | The synchronous backend does not rely on any external modules (well, |
|
|
822 | except L<common::sense>, which works around a bug in how perl's warning |
|
|
823 | system works). This keeps the process very small, for example, on my |
|
|
824 | system, an empty perl interpreter uses 1492kB RSS, which becomes 2020kB |
|
|
825 | after C<use warnings; use strict> (for people who grew up with C64s around |
|
|
826 | them this is probably shocking every single time they see it). The worker |
|
|
827 | process in the first example in this document uses 1792kB. |
|
|
828 | |
|
|
829 | Since the calls are done synchronously, slow jobs will keep newer jobs |
|
|
830 | from executing. |
|
|
831 | |
|
|
832 | The synchronous backend also has no overhead due to running an event loop |
|
|
833 | - reading requests is therefore very efficient, while writing responses is |
|
|
834 | less so, as every response results in a write syscall. |
|
|
835 | |
|
|
836 | If the parent process is busy and a bit slow reading responses, the child |
|
|
837 | waits instead of processing further requests. This also limits the amount |
|
|
838 | of memory needed for buffering, as never more than one response has to be |
|
|
839 | buffered. |
|
|
840 | |
|
|
841 | The API in the child is simple - you just have to define a function that |
|
|
842 | does something and returns something. |
|
|
843 | |
|
|
844 | It's hard to use modules or code that relies on an event loop, as the |
|
|
845 | child cannot execute anything while it waits for more input. |
|
|
846 | |
|
|
847 | =item Asynchronous |
|
|
848 | |
|
|
849 | The asynchronous backend relies on L<AnyEvent>, which tries to be small, |
|
|
850 | but still comes at a price: On my system, the worker from example 1a uses |
|
|
851 | 3420kB RSS (for L<AnyEvent>, which loads L<EV>, which needs L<XSLoader> |
|
|
852 | which in turn loads a lot of other modules such as L<warnings>, L<strict>, |
|
|
853 | L<vars>, L<Exporter>...). |
|
|
854 | |
|
|
855 | It batches requests and responses reasonably efficiently, doing only as |
|
|
856 | few reads and writes as needed, but needs to poll for events via the event |
|
|
857 | loop. |
|
|
858 | |
|
|
859 | Responses are queued when the parent process is busy. This means the child |
|
|
860 | can continue to execute any queued requests. It also means that a child |
|
|
861 | might queue a lot of responses in memory when it generates them and the |
|
|
862 | parent process is slow accepting them. |
|
|
863 | |
|
|
864 | The API is not a straightforward RPC pattern - you have to call a |
|
|
865 | "done" callback to pass return values and signal completion. Also, more |
|
|
866 | importantly, the API starts jobs as fast as possible - when 1000 jobs |
|
|
867 | are queued and the jobs are slow, they will all run concurrently. The |
|
|
868 | child must implement some queueing/limiting mechanism if this causes |
|
|
869 | problems. Alternatively, the parent could limit the amount of rpc calls |
|
|
870 | that are outstanding. |
|
|
871 | |
|
|
872 | Blocking use of condvars is not supported. |
|
|
873 | |
|
|
874 | Using event-based modules such as L<IO::AIO>, L<Gtk2>, L<Tk> and so on is |
|
|
875 | easy. |
|
|
876 | |
|
|
877 | =back |
|
|
878 | |
|
|
879 | =head2 Passing file descriptors |
|
|
880 | |
|
|
881 | Unlike L<AnyEvent::Fork>, this module has no in-built file handle or file |
|
|
882 | descriptor passing abilities. |
|
|
883 | |
|
|
884 | The reason is that passing file descriptors is extraordinary tricky |
|
|
885 | business, and conflicts with efficient batching of messages. |
|
|
886 | |
|
|
887 | There still is a method you can use: Create a |
|
|
888 | C<AnyEvent::Util::portable_socketpair> and C<send_fh> one half of it to |
|
|
889 | the process before you pass control to C<AnyEvent::Fork::RPC::run>. |
|
|
890 | |
|
|
891 | Whenever you want to pass a file descriptor, send an rpc request to the |
|
|
892 | child process (so it expects the descriptor), then send it over the other |
|
|
893 | half of the socketpair. The child should fetch the descriptor from the |
|
|
894 | half it has passed earlier. |
|
|
895 | |
|
|
896 | Here is some (untested) pseudocode to that effect: |
|
|
897 | |
|
|
898 | use AnyEvent::Util; |
|
|
899 | use AnyEvent::Fork; |
|
|
900 | use AnyEvent::Fork::RPC; |
|
|
901 | use IO::FDPass; |
|
|
902 | |
|
|
903 | my ($s1, $s2) = AnyEvent::Util::portable_socketpair; |
|
|
904 | |
|
|
905 | my $rpc = AnyEvent::Fork |
|
|
906 | ->new |
|
|
907 | ->send_fh ($s2) |
|
|
908 | ->require ("MyWorker") |
|
|
909 | ->AnyEvent::Fork::RPC::run ("MyWorker::run" |
|
|
910 | init => "MyWorker::init", |
|
|
911 | ); |
|
|
912 | |
|
|
913 | undef $s2; # no need to keep it around |
|
|
914 | |
|
|
915 | # pass an fd |
|
|
916 | $rpc->("i'll send some fd now, please expect it!", my $cv = AE::cv); |
|
|
917 | |
|
|
918 | IO::FDPass fileno $s1, fileno $handle_to_pass; |
|
|
919 | |
|
|
920 | $cv->recv; |
|
|
921 | |
|
|
922 | The MyWorker module could look like this: |
|
|
923 | |
|
|
924 | package MyWorker; |
|
|
925 | |
|
|
926 | use IO::FDPass; |
|
|
927 | |
|
|
928 | my $s2; |
|
|
929 | |
|
|
930 | sub init { |
|
|
931 | $s2 = $_[0]; |
|
|
932 | } |
|
|
933 | |
|
|
934 | sub run { |
|
|
935 | if ($_[0] eq "i'll send some fd now, please expect it!") { |
|
|
936 | my $fd = IO::FDPass::recv fileno $s2; |
|
|
937 | ... |
|
|
938 | } |
|
|
939 | } |
|
|
940 | |
|
|
941 | Of course, this might be blocking if you pass a lot of file descriptors, |
|
|
942 | so you might want to look into L<AnyEvent::FDpasser> which can handle the |
|
|
943 | gory details. |
|
|
944 | |
|
|
945 | =head1 EXCEPTIONS |
|
|
946 | |
|
|
947 | There are no provisions whatsoever for catching exceptions at this time - |
|
|
948 | in the child, exeptions might kill the process, causing calls to be lost |
|
|
949 | and the parent encountering a fatal error. In the parent, exceptions in |
|
|
950 | the result callback will not be caught and cause undefined behaviour. |
|
|
951 | |
584 | =head1 SEE ALSO |
952 | =head1 SEE ALSO |
585 | |
953 | |
586 | L<AnyEvent::Fork> (to create the processes in the first place), |
954 | L<AnyEvent::Fork>, to create the processes in the first place. |
|
|
955 | |
|
|
956 | L<AnyEvent::Fork::Remote>, likewise, but helpful for remote processes. |
|
|
957 | |
587 | L<AnyEvent::Fork::Pool> (to manage whole pools of processes). |
958 | L<AnyEvent::Fork::Pool>, to manage whole pools of processes. |
588 | |
959 | |
589 | =head1 AUTHOR AND CONTACT INFORMATION |
960 | =head1 AUTHOR AND CONTACT INFORMATION |
590 | |
961 | |
591 | Marc Lehmann <schmorp@schmorp.de> |
962 | Marc Lehmann <schmorp@schmorp.de> |
592 | http://software.schmorp.de/pkg/AnyEvent-Fork-RPC |
963 | http://software.schmorp.de/pkg/AnyEvent-Fork-RPC |