1 | =head1 NAME |
1 | =head1 NAME |
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 | THE API IS NOT FINISHED, CONSIDER THIS A BETA RELEASE |
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6 | |
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7 | =head1 SYNOPSIS |
5 | =head1 SYNOPSIS |
8 | |
6 | |
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7 | use AnyEvent::Fork; |
9 | use AnyEvent::Fork::RPC; |
8 | use AnyEvent::Fork::RPC; |
10 | # use AnyEvent::Fork is not needed |
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11 | |
9 | |
12 | my $rpc = AnyEvent::Fork |
10 | my $rpc = AnyEvent::Fork |
13 | ->new |
11 | ->new |
14 | ->require ("MyModule") |
12 | ->require ("MyModule") |
15 | ->AnyEvent::Fork::RPC::run ( |
13 | ->AnyEvent::Fork::RPC::run ( |
… | |
… | |
28 | $cv->recv; |
26 | $cv->recv; |
29 | |
27 | |
30 | =head1 DESCRIPTION |
28 | =head1 DESCRIPTION |
31 | |
29 | |
32 | This module implements a simple RPC protocol and backend for processes |
30 | This module implements a simple RPC protocol and backend for processes |
33 | 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 |
34 | 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). |
35 | |
34 | |
36 | 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 |
37 | 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 |
38 | concurrently in the child, using AnyEvent. |
37 | concurrently in the child, using AnyEvent. |
39 | |
38 | |
40 | 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 |
41 | parent, that could be used for progress indications or other information. |
40 | parent, that could be used for progress indications or other information. |
42 | |
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43 | Loading this module also always loads L<AnyEvent::Fork>, so you can make a |
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44 | separate C<use AnyEvent::Fork> if you wish, but you don't have to. |
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45 | |
41 | |
46 | =head1 EXAMPLES |
42 | =head1 EXAMPLES |
47 | |
43 | |
48 | =head2 Example 1: Synchronous Backend |
44 | =head2 Example 1: Synchronous Backend |
49 | |
45 | |
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53 | silly, but illustrates the use of events. |
49 | silly, but illustrates the use of events. |
54 | |
50 | |
55 | First the parent process: |
51 | First the parent process: |
56 | |
52 | |
57 | use AnyEvent; |
53 | use AnyEvent; |
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54 | use AnyEvent::Fork; |
58 | use AnyEvent::Fork::RPC; |
55 | use AnyEvent::Fork::RPC; |
59 | |
56 | |
60 | my $done = AE::cv; |
57 | my $done = AE::cv; |
61 | |
58 | |
62 | my $rpc = AnyEvent::Fork |
59 | my $rpc = AnyEvent::Fork |
63 | ->new |
60 | ->new |
64 | ->require ("MyWorker") |
61 | ->require ("MyWorker") |
65 | ->AnyEvent::Fork::RPC::run ("MyWorker::run", |
62 | ->AnyEvent::Fork::RPC::run ("MyWorker::run", |
66 | on_error => sub { warn "FATAL: $_[0]"; exit 1 }, |
63 | on_error => sub { warn "ERROR: $_[0]"; exit 1 }, |
67 | on_event => sub { warn "$_[0] requests handled\n" }, |
64 | on_event => sub { warn "$_[0] requests handled\n" }, |
68 | on_destroy => $done, |
65 | on_destroy => $done, |
69 | ); |
66 | ); |
70 | |
67 | |
71 | for my $id (1..6) { |
68 | for my $id (1..6) { |
… | |
… | |
178 | you really I<are> done. |
175 | you really I<are> done. |
179 | |
176 | |
180 | =head2 Example 2: Asynchronous Backend |
177 | =head2 Example 2: Asynchronous Backend |
181 | |
178 | |
182 | This example implements multiple count-downs in the child, using |
179 | This example implements multiple count-downs in the child, using |
183 | 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 |
184 | 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 |
185 | 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 |
186 | requests. |
183 | requests. |
187 | |
184 | |
188 | 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__> |
… | |
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193 | so silly anymore. |
190 | so silly anymore. |
194 | |
191 | |
195 | Without further ado, here is the code: |
192 | Without further ado, here is the code: |
196 | |
193 | |
197 | use AnyEvent; |
194 | use AnyEvent; |
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195 | use AnyEvent::Fork; |
198 | use AnyEvent::Fork::RPC; |
196 | use AnyEvent::Fork::RPC; |
199 | |
197 | |
200 | my $done = AE::cv; |
198 | my $done = AE::cv; |
201 | |
199 | |
202 | my $rpc = AnyEvent::Fork |
200 | my $rpc = AnyEvent::Fork |
203 | ->new |
201 | ->new |
204 | ->require ("AnyEvent::Fork::RPC::Async") |
202 | ->require ("AnyEvent::Fork::RPC::Async") |
205 | ->eval (do { local $/; <DATA> }) |
203 | ->eval (do { local $/; <DATA> }) |
206 | ->AnyEvent::Fork::RPC::run ("run", |
204 | ->AnyEvent::Fork::RPC::run ("run", |
207 | async => 1, |
205 | async => 1, |
208 | on_error => sub { warn "FATAL: $_[0]"; exit 1 }, |
206 | on_error => sub { warn "ERROR: $_[0]"; exit 1 }, |
209 | on_event => sub { print $_[0] }, |
207 | on_event => sub { print $_[0] }, |
210 | on_destroy => $done, |
208 | on_destroy => $done, |
211 | ); |
209 | ); |
212 | |
210 | |
213 | for my $count (3, 2, 1) { |
211 | for my $count (3, 2, 1) { |
… | |
… | |
289 | |
287 | |
290 | This concludes the async example. Since L<AnyEvent::Fork> does not |
288 | This concludes the async example. Since L<AnyEvent::Fork> does not |
291 | 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 |
292 | 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. |
293 | |
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 | |
294 | =head1 PARENT PROCESS USAGE |
379 | =head1 PARENT PROCESS USAGE |
295 | |
380 | |
296 | This module exports nothing, and only implements a single function: |
381 | This module exports nothing, and only implements a single function: |
297 | |
382 | |
298 | =over 4 |
383 | =over 4 |
… | |
… | |
305 | |
390 | |
306 | use Errno (); |
391 | use Errno (); |
307 | use Guard (); |
392 | use Guard (); |
308 | |
393 | |
309 | use AnyEvent; |
394 | use AnyEvent; |
310 | # explicit version on next line, as some cpan-testers test with the 0.1 version, |
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311 | # ignoring dependencies, and this line will at least give a clear indication of that. |
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312 | use AnyEvent::Fork 0.6; # we don't actually depend on it, this is for convenience |
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313 | |
395 | |
314 | our $VERSION = 1.1; |
396 | our $VERSION = 1.23; |
315 | |
397 | |
316 | =item my $rpc = AnyEvent::Fork::RPC::run $fork, $function, [key => value...] |
398 | =item my $rpc = AnyEvent::Fork::RPC::run $fork, $function, [key => value...] |
317 | |
399 | |
318 | 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 |
319 | following way: |
401 | following way: |
… | |
… | |
339 | Called on (fatal) errors, with a descriptive (hopefully) message. If |
421 | Called on (fatal) errors, with a descriptive (hopefully) message. If |
340 | 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> |
341 | 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>, |
342 | followed by the error message. |
424 | followed by the error message. |
343 | |
425 | |
344 | 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 |
345 | start failing badly. |
427 | C<error> via C<AE::log>. |
346 | |
428 | |
347 | =item on_event => $cb->(...) |
429 | =item on_event => $cb->(...) |
348 | |
430 | |
349 | Called for every call to the C<AnyEvent::Fork::RPC::event> function in the |
431 | Called for every call to the C<AnyEvent::Fork::RPC::event> function in the |
350 | child, with the arguments of that function passed to the callback. |
432 | child, with the arguments of that function passed to the callback. |
… | |
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372 | It is called very early - before the serialisers are created or the |
454 | It is called very early - before the serialisers are created or the |
373 | C<$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 |
374 | 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 |
375 | not, however, create events. |
457 | not, however, create events. |
376 | |
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::run> 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 | |
377 | =item async => $boolean (default: 0) |
473 | =item async => $boolean (default: 0) |
378 | |
474 | |
379 | 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 |
380 | allows a single RPC call to execute concurrently. |
476 | allows a single RPC call to execute concurrently. |
381 | |
477 | |
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398 | |
494 | |
399 | 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 |
400 | 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 |
401 | thawed in both parent and child processes. |
497 | thawed in both parent and child processes. |
402 | |
498 | |
403 | By default, only octet strings can be passed between the processes, which |
499 | By default, only octet strings can be passed between the processes, |
404 | is reasonably fast and efficient and requires no extra modules. |
500 | which is reasonably fast and efficient and requires no extra modules |
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501 | (the C<AnyEvent::Fork::RPC> distribution does not provide these extra |
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502 | serialiser modules). |
405 | |
503 | |
406 | For more complicated use cases, you can provide your own freeze and thaw |
504 | For more complicated use cases, you can provide your own freeze and thaw |
407 | functions, by specifying a string with perl source code. It's supposed to |
505 | functions, by specifying a string with perl source code. It's supposed to |
408 | return two code references when evaluated: the first receives a list of |
506 | return two code references when evaluated: the first receives a list of |
409 | perl values and must return an octet string. The second receives the octet |
507 | perl values and must return an octet string. The second receives the octet |
… | |
… | |
411 | |
509 | |
412 | If you need an external module for serialisation, then you can either |
510 | If you need an external module for serialisation, then you can either |
413 | pre-load it into your L<AnyEvent::Fork> process, or you can add a C<use> |
511 | pre-load it into your L<AnyEvent::Fork> process, or you can add a C<use> |
414 | or C<require> statement into the serialiser string. Or both. |
512 | or C<require> statement into the serialiser string. Or both. |
415 | |
513 | |
416 | Here are some examples - some of them are also available as global |
514 | Here are some examples - all of them are also available as global |
417 | variables that make them easier to use. |
515 | variables that make them easier to use. |
418 | |
516 | |
419 | =over 4 |
517 | =over 4 |
420 | |
518 | |
421 | =item octet strings - C<$AnyEvent::Fork::RPC::STRING_SERIALISER> |
519 | =item C<$AnyEvent::Fork::RPC::STRING_SERIALISER> - octet strings only |
422 | |
520 | |
423 | This serialiser concatenates length-prefixes octet strings, and is the |
521 | This serialiser (currently the default) concatenates length-prefixes octet |
424 | default. |
522 | strings, and is the default. That means you can only pass (and return) |
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523 | strings containing character codes 0-255. |
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524 | |
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525 | The main advantages of this serialiser are the high speed and that it |
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526 | doesn't need another module. The main disadvantage is that you are very |
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527 | limited in what you can pass - only octet strings. |
425 | |
528 | |
426 | Implementation: |
529 | Implementation: |
427 | |
530 | |
428 | ( |
531 | ( |
429 | sub { pack "(w/a*)*", @_ }, |
532 | sub { pack "(w/a*)*", @_ }, |
430 | sub { unpack "(w/a*)*", shift } |
533 | sub { unpack "(w/a*)*", shift } |
431 | ) |
534 | ) |
432 | |
535 | |
433 | =item json - C<$AnyEvent::Fork::RPC::JSON_SERIALISER> |
536 | =item C<$AnyEvent::Fork::RPC::CBOR_XS_SERIALISER> - uses L<CBOR::XS> |
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537 | |
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538 | This serialiser creates CBOR::XS arrays - you have to make sure the |
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539 | L<CBOR::XS> module is installed for this serialiser to work. It can be |
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540 | beneficial for sharing when you preload the L<CBOR::XS> module in a template |
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541 | process. |
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542 | |
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543 | L<CBOR::XS> is about as fast as the octet string serialiser, but supports |
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544 | complex data structures (similar to JSON) and is faster than any of the |
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545 | other serialisers. If you have the L<CBOR::XS> module available, it's the |
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546 | best choice. |
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547 | |
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548 | The encoder enables C<allow_sharing> (so this serialisation method can |
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549 | encode cyclic and self-referencing data structures). |
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550 | |
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551 | Implementation: |
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552 | |
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553 | use CBOR::XS (); |
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554 | ( |
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555 | sub { CBOR::XS::encode_cbor_sharing \@_ }, |
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556 | sub { @{ CBOR::XS::decode_cbor shift } } |
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557 | ) |
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558 | |
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559 | =item C<$AnyEvent::Fork::RPC::JSON_SERIALISER> - uses L<JSON::XS> or L<JSON> |
434 | |
560 | |
435 | This serialiser creates JSON arrays - you have to make sure the L<JSON> |
561 | This serialiser creates JSON arrays - you have to make sure the L<JSON> |
436 | module is installed for this serialiser to work. It can be beneficial for |
562 | module is installed for this serialiser to work. It can be beneficial for |
437 | sharing when you preload the L<JSON> module in a template process. |
563 | sharing when you preload the L<JSON> module in a template process. |
438 | |
564 | |
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446 | ( |
572 | ( |
447 | sub { JSON::encode_json \@_ }, |
573 | sub { JSON::encode_json \@_ }, |
448 | sub { @{ JSON::decode_json shift } } |
574 | sub { @{ JSON::decode_json shift } } |
449 | ) |
575 | ) |
450 | |
576 | |
451 | =item storable - C<$AnyEvent::Fork::RPC::STORABLE_SERIALISER> |
577 | =item C<$AnyEvent::Fork::RPC::STORABLE_SERIALISER> - L<Storable> |
452 | |
578 | |
453 | This serialiser uses L<Storable>, which means it has high chance of |
579 | This serialiser uses L<Storable>, which means it has high chance of |
454 | serialising just about anything you throw at it, at the cost of having |
580 | serialising just about anything you throw at it, at the cost of having |
455 | very high overhead per operation. It also comes with perl. |
581 | very high overhead per operation. It also comes with perl. It should be |
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582 | used when you need to serialise complex data structures. |
456 | |
583 | |
457 | Implementation: |
584 | Implementation: |
458 | |
585 | |
459 | use Storable (); |
586 | use Storable (); |
460 | ( |
587 | ( |
461 | sub { Storable::freeze \@_ }, |
588 | sub { Storable::freeze \@_ }, |
462 | sub { @{ Storable::thaw shift } } |
589 | sub { @{ Storable::thaw shift } } |
463 | ) |
590 | ) |
464 | |
591 | |
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592 | =item C<$AnyEvent::Fork::RPC::NSTORABLE_SERIALISER> - portable Storable |
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593 | |
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594 | This serialiser also uses L<Storable>, but uses it's "network" format |
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595 | to serialise data, which makes it possible to talk to different |
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596 | perl binaries (for example, when talking to a process created with |
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597 | L<AnyEvent::Fork::Remote>). |
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598 | |
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599 | Implementation: |
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600 | |
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601 | use Storable (); |
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602 | ( |
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603 | sub { Storable::nfreeze \@_ }, |
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604 | sub { @{ Storable::thaw shift } } |
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605 | ) |
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606 | |
465 | =back |
607 | =back |
466 | |
608 | |
467 | =back |
609 | =back |
468 | |
610 | |
469 | See the examples section earlier in this document for some actual |
611 | See the examples section earlier in this document for some actual |
470 | examples. |
612 | examples. |
471 | |
613 | |
472 | =cut |
614 | =cut |
473 | |
615 | |
474 | our $STRING_SERIALISER = '(sub { pack "(w/a*)*", @_ }, sub { unpack "(w/a*)*", shift })'; |
616 | our $STRING_SERIALISER = '(sub { pack "(w/a*)*", @_ }, sub { unpack "(w/a*)*", shift })'; |
|
|
617 | our $CBOR_XS_SERIALISER = 'use CBOR::XS (); (sub { CBOR::XS::encode_cbor_sharing \@_ }, sub { @{ CBOR::XS::decode_cbor shift } })'; |
475 | our $JSON_SERIALISER = 'use JSON (); (sub { JSON::encode_json \@_ }, sub { @{ JSON::decode_json shift } })'; |
618 | our $JSON_SERIALISER = 'use JSON (); (sub { JSON::encode_json \@_ }, sub { @{ JSON::decode_json shift } })'; |
476 | our $STORABLE_SERIALISER = 'use Storable (); (sub { Storable::freeze \@_ }, sub { @{ Storable::thaw shift } })'; |
619 | our $STORABLE_SERIALISER = 'use Storable (); (sub { Storable::freeze \@_ }, sub { @{ Storable::thaw shift } })'; |
|
|
620 | our $NSTORABLE_SERIALISER = 'use Storable (); (sub { Storable::nfreeze \@_ }, sub { @{ Storable::thaw shift } })'; |
477 | |
621 | |
478 | sub run { |
622 | sub run { |
479 | my ($self, $function, %arg) = @_; |
623 | my ($self, $function, %arg) = @_; |
480 | |
624 | |
481 | my $serialiser = delete $arg{serialiser} || $STRING_SERIALISER; |
625 | my $serialiser = delete $arg{serialiser} || $STRING_SERIALISER; |
… | |
… | |
484 | my $on_destroy = delete $arg{on_destroy}; |
628 | my $on_destroy = delete $arg{on_destroy}; |
485 | |
629 | |
486 | # default for on_error is to on_event, if specified |
630 | # default for on_error is to on_event, if specified |
487 | $on_error ||= $on_event |
631 | $on_error ||= $on_event |
488 | ? sub { $on_event->(error => shift) } |
632 | ? sub { $on_event->(error => shift) } |
489 | : sub { die "AnyEvent::Fork::RPC: uncaught error: $_[0].\n" }; |
633 | : sub { AE::log die => "AnyEvent::Fork::RPC: uncaught error: $_[0]." }; |
490 | |
634 | |
491 | # default for on_event is to raise an error |
635 | # default for on_event is to raise an error |
492 | $on_event ||= sub { $on_error->("event received, but no on_event handler") }; |
636 | $on_event ||= sub { $on_error->("event received, but no on_event handler") }; |
493 | |
637 | |
494 | my ($f, $t) = eval $serialiser; die $@ if $@; |
638 | my ($f, $t) = eval $serialiser; die $@ if $@; |
… | |
… | |
515 | }; |
659 | }; |
516 | |
660 | |
517 | my $module = "AnyEvent::Fork::RPC::" . ($arg{async} ? "Async" : "Sync"); |
661 | my $module = "AnyEvent::Fork::RPC::" . ($arg{async} ? "Async" : "Sync"); |
518 | |
662 | |
519 | $self->require ($module) |
663 | $self->require ($module) |
520 | ->send_arg ($function, $arg{init}, $serialiser) |
664 | ->send_arg ($function, $arg{init}, $serialiser, $arg{done} || "$module\::do_exit") |
521 | ->run ("$module\::run", sub { |
665 | ->run ("$module\::run", sub { |
522 | $fh = shift; |
666 | $fh = shift; |
523 | |
667 | |
524 | my ($id, $len); |
668 | my ($id, $len); |
525 | $rw = AE::io $fh, 0, sub { |
669 | $rw = AE::io $fh, 0, sub { |
… | |
… | |
639 | values. |
783 | values. |
640 | |
784 | |
641 | See the examples section earlier in this document for some actual |
785 | See the examples section earlier in this document for some actual |
642 | examples. |
786 | examples. |
643 | |
787 | |
|
|
788 | Note: the event data, like any data send to the parent, might not be sent |
|
|
789 | immediatelly but queued for later sending, so there is no guarantee that |
|
|
790 | the event has been sent to the parent when the call returns - when you |
|
|
791 | e.g. exit directly after calling this function, the parent might never |
|
|
792 | receive the event. |
|
|
793 | |
|
|
794 | =back |
|
|
795 | |
|
|
796 | =head2 PROCESS EXIT |
|
|
797 | |
|
|
798 | If and when the child process exits depends on the backend and |
|
|
799 | configuration. Apart from explicit exits (e.g. by calling C<exit>) or |
|
|
800 | runtime conditions (uncaught exceptions, signals etc.), the backends exit |
|
|
801 | under these conditions: |
|
|
802 | |
|
|
803 | =over 4 |
|
|
804 | |
|
|
805 | =item Synchronous Backend |
|
|
806 | |
|
|
807 | The synchronous backend is very simple: when the process waits for another |
|
|
808 | request to arrive and the writing side (usually in the parent) is closed, |
|
|
809 | it will exit normally, i.e. as if your main program reached the end of the |
|
|
810 | file. |
|
|
811 | |
|
|
812 | That means that if your parent process exits, the RPC process will usually |
|
|
813 | exit as well, either because it is idle anyway, or because it executes a |
|
|
814 | request. In the latter case, you will likely get an error when the RPc |
|
|
815 | process tries to send the results to the parent (because agruably, you |
|
|
816 | shouldn't exit your parent while there are still outstanding requests). |
|
|
817 | |
|
|
818 | The process is usually quiescent when it happens, so it should rarely be a |
|
|
819 | problem, and C<END> handlers can be used to clean up. |
|
|
820 | |
|
|
821 | =item Asynchronous Backend |
|
|
822 | |
|
|
823 | For the asynchronous backend, things are more complicated: Whenever it |
|
|
824 | listens for another request by the parent, it might detect that the socket |
|
|
825 | was closed (e.g. because the parent exited). It will sotp listening for |
|
|
826 | new requests and instead try to write out any remaining data (if any) or |
|
|
827 | simply check whether the socket can be written to. After this, the RPC |
|
|
828 | process is effectively done - no new requests are incoming, no outstanding |
|
|
829 | request data can be written back. |
|
|
830 | |
|
|
831 | Since chances are high that there are event watchers that the RPC server |
|
|
832 | knows nothing about (why else would one use the async backend if not for |
|
|
833 | the ability to register watchers?), the event loop would often happily |
|
|
834 | continue. |
|
|
835 | |
|
|
836 | This is why the asynchronous backend explicitly calls C<CORE::exit> when |
|
|
837 | it is done (under other circumstances, such as when there is an I/O error |
|
|
838 | and there is outstanding data to write, it will log a fatal message via |
|
|
839 | L<AnyEvent::Log>, also causing the program to exit). |
|
|
840 | |
|
|
841 | You can override this by specifying a function name to call via the C<done> |
|
|
842 | parameter instead. |
|
|
843 | |
644 | =back |
844 | =back |
645 | |
845 | |
646 | =head1 ADVANCED TOPICS |
846 | =head1 ADVANCED TOPICS |
647 | |
847 | |
648 | =head2 Choosing a backend |
848 | =head2 Choosing a backend |
… | |
… | |
703 | are queued and the jobs are slow, they will all run concurrently. The |
903 | are queued and the jobs are slow, they will all run concurrently. The |
704 | child must implement some queueing/limiting mechanism if this causes |
904 | child must implement some queueing/limiting mechanism if this causes |
705 | problems. Alternatively, the parent could limit the amount of rpc calls |
905 | problems. Alternatively, the parent could limit the amount of rpc calls |
706 | that are outstanding. |
906 | that are outstanding. |
707 | |
907 | |
708 | Blocking use of condvars is not supported. |
908 | Blocking use of condvars is not supported (in the main thread, outside of |
|
|
909 | e.g. L<Coro> threads). |
709 | |
910 | |
710 | Using event-based modules such as L<IO::AIO>, L<Gtk2>, L<Tk> and so on is |
911 | Using event-based modules such as L<IO::AIO>, L<Gtk2>, L<Tk> and so on is |
711 | easy. |
912 | easy. |
712 | |
913 | |
713 | =back |
914 | =back |
… | |
… | |
730 | half it has passed earlier. |
931 | half it has passed earlier. |
731 | |
932 | |
732 | Here is some (untested) pseudocode to that effect: |
933 | Here is some (untested) pseudocode to that effect: |
733 | |
934 | |
734 | use AnyEvent::Util; |
935 | use AnyEvent::Util; |
|
|
936 | use AnyEvent::Fork; |
735 | use AnyEvent::Fork::RPC; |
937 | use AnyEvent::Fork::RPC; |
736 | use IO::FDPass; |
938 | use IO::FDPass; |
737 | |
939 | |
738 | my ($s1, $s2) = AnyEvent::Util::portable_socketpair; |
940 | my ($s1, $s2) = AnyEvent::Util::portable_socketpair; |
739 | |
941 | |
… | |
… | |
778 | gory details. |
980 | gory details. |
779 | |
981 | |
780 | =head1 EXCEPTIONS |
982 | =head1 EXCEPTIONS |
781 | |
983 | |
782 | There are no provisions whatsoever for catching exceptions at this time - |
984 | There are no provisions whatsoever for catching exceptions at this time - |
783 | in the child, exeptions might kill the process, causing calls to be lost |
985 | in the child, exceptions might kill the process, causing calls to be lost |
784 | and the parent encountering a fatal error. In the parent, exceptions in |
986 | and the parent encountering a fatal error. In the parent, exceptions in |
785 | the result callback will not be caught and cause undefined behaviour. |
987 | the result callback will not be caught and cause undefined behaviour. |
786 | |
988 | |
787 | =head1 SEE ALSO |
989 | =head1 SEE ALSO |
788 | |
990 | |
789 | L<AnyEvent::Fork>, to create the processes in the first place. |
991 | L<AnyEvent::Fork>, to create the processes in the first place. |
790 | |
992 | |
|
|
993 | L<AnyEvent::Fork::Remote>, likewise, but helpful for remote processes. |
|
|
994 | |
791 | L<AnyEvent::Fork::Pool>, to manage whole pools of processes. |
995 | L<AnyEvent::Fork::Pool>, to manage whole pools of processes. |
792 | |
996 | |
793 | =head1 AUTHOR AND CONTACT INFORMATION |
997 | =head1 AUTHOR AND CONTACT INFORMATION |
794 | |
998 | |
795 | Marc Lehmann <schmorp@schmorp.de> |
999 | Marc Lehmann <schmorp@schmorp.de> |