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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 | |
7 | use AnyEvent::Fork; |
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8 | use AnyEvent::Fork::RPC; |
7 | use AnyEvent::Fork::RPC; |
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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 ( |
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34 | concurrently in the child, using AnyEvent. |
34 | concurrently in the child, using AnyEvent. |
35 | |
35 | |
36 | It also implements an asynchronous event mechanism from the child to the |
36 | It also implements an asynchronous event mechanism from the child to the |
37 | parent, that could be used for progress indications or other information. |
37 | parent, that could be used for progress indications or other information. |
38 | |
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 | |
39 | =head1 EXAMPLES |
42 | =head1 EXAMPLES |
40 | |
43 | |
41 | =head2 Synchronous Backend |
44 | =head2 Example 1: Synchronous Backend |
42 | |
45 | |
43 | Here is a simple example that implements a backend that executes C<unlink> |
46 | Here is a simple example that implements a backend that executes C<unlink> |
44 | and C<rmdir> calls, and reports their status back. It also reports the |
47 | and C<rmdir> calls, and reports their status back. It also reports the |
45 | number of requests it has processed every three requests, which is clearly |
48 | number of requests it has processed every three requests, which is clearly |
46 | silly, but illustrates the use of events. |
49 | silly, but illustrates the use of events. |
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103 | dies with a fatal error - obviously, you must never let this happen :). |
106 | dies with a fatal error - obviously, you must never let this happen :). |
104 | |
107 | |
105 | Eventually it returns the status value true if the command was successful, |
108 | Eventually it returns the status value true if the command was successful, |
106 | or the status value 0 and the stringified error message. |
109 | or the status value 0 and the stringified error message. |
107 | |
110 | |
108 | On my system, running the first cdoe fragment with the given |
111 | On my system, running the first code fragment with the given |
109 | F<MyWorker.pm> in the current directory yields: |
112 | F<MyWorker.pm> in the current directory yields: |
110 | |
113 | |
111 | /tmp/somepath/1: No such file or directory |
114 | /tmp/somepath/1: No such file or directory |
112 | /tmp/somepath/2: No such file or directory |
115 | /tmp/somepath/2: No such file or directory |
113 | 3 requests handled |
116 | 3 requests handled |
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134 | |
137 | |
135 | And as a final remark, there is a fine module on CPAN that can |
138 | And as a final remark, there is a fine module on CPAN that can |
136 | asynchronously C<rmdir> and C<unlink> and a lot more, and more efficiently |
139 | asynchronously C<rmdir> and C<unlink> and a lot more, and more efficiently |
137 | than this example, namely L<IO::AIO>. |
140 | than this example, namely L<IO::AIO>. |
138 | |
141 | |
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142 | =head3 Example 1a: the same with the asynchronous backend |
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143 | |
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144 | This example only shows what needs to be changed to use the async backend |
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145 | instead. Doing this is not very useful, the purpose of this example is |
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146 | to show the minimum amount of change that is required to go from the |
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147 | synchronous to the asynchronous backend. |
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148 | |
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149 | To use the async backend in the previous example, you need to add the |
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150 | C<async> parameter to the C<AnyEvent::Fork::RPC::run> call: |
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151 | |
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152 | ->AnyEvent::Fork::RPC::run ("MyWorker::run", |
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153 | async => 1, |
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154 | ... |
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155 | |
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156 | And since the function call protocol is now changed, you need to adopt |
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157 | C<MyWorker::run> to the async API. |
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158 | |
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159 | First, you need to accept the extra initial C<$done> callback: |
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160 | |
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161 | sub run { |
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162 | my ($done, $cmd, $path) = @_; |
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163 | |
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164 | And since a response is now generated when C<$done> is called, as opposed |
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165 | to when the function returns, we need to call the C<$done> function with |
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166 | the status: |
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167 | |
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168 | $done->($status or (0, "$!")); |
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169 | |
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170 | A few remarks are in order. First, it's quite pointless to use the async |
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171 | backend for this example - but it I<is> possible. Second, you can call |
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172 | C<$done> before or after returning from the function. Third, having both |
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173 | returned from the function and having called the C<$done> callback, the |
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174 | child process may exit at any time, so you should call C<$done> only when |
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175 | you really I<are> done. |
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176 | |
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177 | =head2 Example 2: Asynchronous Backend |
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178 | |
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179 | #TODO |
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180 | |
139 | =head1 PARENT PROCESS USAGE |
181 | =head1 PARENT PROCESS USAGE |
140 | |
182 | |
141 | This module exports nothing, and only implements a single function: |
183 | This module exports nothing, and only implements a single function: |
142 | |
184 | |
143 | =over 4 |
185 | =over 4 |
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150 | |
192 | |
151 | use Errno (); |
193 | use Errno (); |
152 | use Guard (); |
194 | use Guard (); |
153 | |
195 | |
154 | use AnyEvent; |
196 | use AnyEvent; |
155 | #use AnyEvent::Fork; |
197 | use AnyEvent::Fork; # we don't actually depend on it, this is for convenience |
156 | |
198 | |
157 | our $VERSION = 0.1; |
199 | our $VERSION = 0.1; |
158 | |
200 | |
159 | =item my $rpc = AnyEvent::Fork::RPC::run $fork, $function, [key => value...] |
201 | =item my $rpc = AnyEvent::Fork::RPC::run $fork, $function, [key => value...] |
160 | |
202 | |
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198 | |
240 | |
199 | Called when the C<$rpc> object has been destroyed and all requests have |
241 | Called when the C<$rpc> object has been destroyed and all requests have |
200 | been successfully handled. This is useful when you queue some requests and |
242 | been successfully handled. This is useful when you queue some requests and |
201 | want the child to go away after it has handled them. The problem is that |
243 | want the child to go away after it has handled them. The problem is that |
202 | the parent must not exit either until all requests have been handled, and |
244 | the parent must not exit either until all requests have been handled, and |
203 | this cna be accomplished by waiting for this callback. |
245 | this can be accomplished by waiting for this callback. |
204 | |
246 | |
205 | =item init => $function (default none) |
247 | =item init => $function (default none) |
206 | |
248 | |
207 | When specified (by name), this function is called in the child as the very |
249 | When specified (by name), this function is called in the child as the very |
208 | first thing when taking over the process, with all the arguments normally |
250 | first thing when taking over the process, with all the arguments normally |
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231 | If you want to pre-load the actual back-end modules to enable memory |
273 | If you want to pre-load the actual back-end modules to enable memory |
232 | sharing, then you should load C<AnyEvent::Fork::RPC::Sync> for |
274 | sharing, then you should load C<AnyEvent::Fork::RPC::Sync> for |
233 | synchronous, and C<AnyEvent::Fork::RPC::Async> for asynchronous mode. |
275 | synchronous, and C<AnyEvent::Fork::RPC::Async> for asynchronous mode. |
234 | |
276 | |
235 | If you use a template process and want to fork both sync and async |
277 | If you use a template process and want to fork both sync and async |
236 | children, then it is permissible to laod both modules. |
278 | children, then it is permissible to load both modules. |
237 | |
279 | |
238 | =item serialiser => $string (default: '(sub { pack "(w/a*)*", @_ }, sub { unpack "(w/a*)*", shift })') |
280 | =item serialiser => $string (default: '(sub { pack "(w/a*)*", @_ }, sub { unpack "(w/a*)*", shift })') |
239 | |
281 | |
240 | All arguments, result data and event data have to be serialised to be |
282 | All arguments, result data and event data have to be serialised to be |
241 | transferred between the processes. For this, they have to be frozen and |
283 | transferred between the processes. For this, they have to be frozen and |
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253 | If you need an external module for serialisation, then you can either |
295 | If you need an external module for serialisation, then you can either |
254 | pre-load it into your L<AnyEvent::Fork> process, or you can add a C<use> |
296 | pre-load it into your L<AnyEvent::Fork> process, or you can add a C<use> |
255 | or C<require> statement into the serialiser string. Or both. |
297 | or C<require> statement into the serialiser string. Or both. |
256 | |
298 | |
257 | =back |
299 | =back |
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300 | |
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301 | See the examples section earlier in this document for some actual |
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302 | examples. |
258 | |
303 | |
259 | =cut |
304 | =cut |
260 | |
305 | |
261 | our $STRING_SERIALISER = '(sub { pack "(w/a*)*", @_ }, sub { unpack "(w/a*)*", shift })'; |
306 | our $STRING_SERIALISER = '(sub { pack "(w/a*)*", @_ }, sub { unpack "(w/a*)*", shift })'; |
262 | |
307 | |
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276 | # default for on_event is to raise an error |
321 | # default for on_event is to raise an error |
277 | $on_event ||= sub { $on_error->("event received, but no on_event handler") }; |
322 | $on_event ||= sub { $on_error->("event received, but no on_event handler") }; |
278 | |
323 | |
279 | my ($f, $t) = eval $serialiser; die $@ if $@; |
324 | my ($f, $t) = eval $serialiser; die $@ if $@; |
280 | |
325 | |
281 | my (@rcb, $fh, $shutdown, $wbuf, $ww, $rw); |
326 | my (@rcb, %rcb, $fh, $shutdown, $wbuf, $ww); |
282 | my ($rlen, $rbuf) = 512 - 16; |
327 | my ($rlen, $rbuf, $rw) = 512 - 16; |
283 | |
328 | |
284 | my $wcb = sub { |
329 | my $wcb = sub { |
285 | my $len = syswrite $fh, $wbuf; |
330 | my $len = syswrite $fh, $wbuf; |
286 | |
331 | |
287 | if (!defined $len) { |
332 | unless (defined $len) { |
288 | if ($! != Errno::EAGAIN && $! != Errno::EWOULDBLOCK) { |
333 | if ($! != Errno::EAGAIN && $! != Errno::EWOULDBLOCK) { |
289 | undef $rw; undef $ww; # it ends here |
334 | undef $rw; undef $ww; # it ends here |
290 | $on_error->("$!"); |
335 | $on_error->("$!"); |
291 | } |
336 | } |
292 | } |
337 | } |
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303 | |
348 | |
304 | $self->require ($module) |
349 | $self->require ($module) |
305 | ->send_arg ($function, $arg{init}, $serialiser) |
350 | ->send_arg ($function, $arg{init}, $serialiser) |
306 | ->run ("$module\::run", sub { |
351 | ->run ("$module\::run", sub { |
307 | $fh = shift; |
352 | $fh = shift; |
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353 | |
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354 | my ($id, $len); |
308 | $rw = AE::io $fh, 0, sub { |
355 | $rw = AE::io $fh, 0, sub { |
309 | $rlen = $rlen * 2 + 16 if $rlen - 128 < length $rbuf; |
356 | $rlen = $rlen * 2 + 16 if $rlen - 128 < length $rbuf; |
310 | my $len = sysread $fh, $rbuf, $rlen - length $rbuf, length $rbuf; |
357 | $len = sysread $fh, $rbuf, $rlen - length $rbuf, length $rbuf; |
311 | |
358 | |
312 | if ($len) { |
359 | if ($len) { |
313 | while (5 <= length $rbuf) { |
360 | while (8 <= length $rbuf) { |
314 | $len = unpack "L", $rbuf; |
361 | ($id, $len) = unpack "LL", $rbuf; |
315 | 4 + $len <= length $rbuf |
362 | 8 + $len <= length $rbuf |
316 | or last; |
363 | or last; |
317 | |
364 | |
318 | my @r = $t->(substr $rbuf, 4, $len); |
365 | my @r = $t->(substr $rbuf, 8, $len); |
319 | substr $rbuf, 0, $len + 4, ""; |
366 | substr $rbuf, 0, 8 + $len, ""; |
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367 | |
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368 | if ($id) { |
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369 | if (@rcb) { |
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370 | (shift @rcb)->(@r); |
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371 | } elsif (my $cb = delete $rcb{$id}) { |
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372 | $cb->(@r); |
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373 | } else { |
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374 | undef $rw; undef $ww; |
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375 | $on_error->("unexpected data from child"); |
320 | |
376 | } |
321 | if (pop @r) { |
377 | } else { |
322 | $on_event->(@r); |
378 | $on_event->(@r); |
323 | } elsif (@rcb) { |
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324 | (shift @rcb)->(@r); |
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325 | } else { |
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326 | undef $rw; undef $ww; |
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327 | $on_error->("unexpected data from child"); |
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328 | } |
379 | } |
329 | } |
380 | } |
330 | } elsif (defined $len) { |
381 | } elsif (defined $len) { |
331 | undef $rw; undef $ww; # it ends here |
382 | undef $rw; undef $ww; # it ends here |
332 | |
383 | |
333 | if (@rcb) { |
384 | if (@rcb || %rcb) { |
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385 | use Data::Dump;ddx[\@rcb,\%rcb];#d# |
334 | $on_error->("unexpected eof"); |
386 | $on_error->("unexpected eof"); |
335 | } else { |
387 | } else { |
336 | $on_destroy->(); |
388 | $on_destroy->(); |
337 | } |
389 | } |
338 | } elsif ($! != Errno::EAGAIN && $! != Errno::EWOULDBLOCK) { |
390 | } elsif ($! != Errno::EAGAIN && $! != Errno::EWOULDBLOCK) { |
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347 | my $guard = Guard::guard { |
399 | my $guard = Guard::guard { |
348 | $shutdown = 1; |
400 | $shutdown = 1; |
349 | $ww ||= $fh && AE::io $fh, 1, $wcb; |
401 | $ww ||= $fh && AE::io $fh, 1, $wcb; |
350 | }; |
402 | }; |
351 | |
403 | |
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404 | my $id; |
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405 | |
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406 | $arg{async} |
352 | sub { |
407 | ? sub { |
353 | push @rcb, pop; |
408 | $id = ($id == 0xffffffff ? 0 : $id) + 1; |
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409 | $id = ($id == 0xffffffff ? 0 : $id) + 1 while exists $rcb{$id}; # rarely loops |
354 | |
410 | |
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411 | $rcb{$id} = pop; |
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412 | |
355 | $guard; # keep it alive |
413 | $guard; # keep it alive |
356 | |
414 | |
357 | $wbuf .= pack "L/a*", &$f; |
415 | $wbuf .= pack "LL/a*", $id, &$f; |
358 | $ww ||= $fh && AE::io $fh, 1, $wcb; |
416 | $ww ||= $fh && AE::io $fh, 1, $wcb; |
359 | } |
417 | } |
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418 | : sub { |
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419 | push @rcb, pop; |
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420 | |
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421 | $guard; # keep it alive |
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422 | |
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423 | $wbuf .= pack "L/a*", &$f; |
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424 | $ww ||= $fh && AE::io $fh, 1, $wcb; |
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425 | } |
360 | } |
426 | } |
361 | |
427 | |
362 | =item $rpc->(..., $cb->(...)) |
428 | =item $rpc->(..., $cb->(...)) |
363 | |
429 | |
364 | The RPC object returned by C<AnyEvent::Fork::RPC::run> is actually a code |
430 | The RPC object returned by C<AnyEvent::Fork::RPC::run> is actually a code |
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379 | |
445 | |
380 | The other thing that can be done with the RPC object is to destroy it. In |
446 | The other thing that can be done with the RPC object is to destroy it. In |
381 | this case, the child process will execute all remaining RPC calls, report |
447 | this case, the child process will execute all remaining RPC calls, report |
382 | their results, and then exit. |
448 | their results, and then exit. |
383 | |
449 | |
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450 | See the examples section earlier in this document for some actual |
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451 | examples. |
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452 | |
384 | =back |
453 | =back |
385 | |
454 | |
386 | =head1 CHILD PROCESS USAGE |
455 | =head1 CHILD PROCESS USAGE |
387 | |
456 | |
388 | The following function is not available in this module. They are only |
457 | The following function is not available in this module. They are only |
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396 | |
465 | |
397 | Send an event to the parent. Events are a bit like RPC calls made by the |
466 | Send an event to the parent. Events are a bit like RPC calls made by the |
398 | child process to the parent, except that there is no notion of return |
467 | child process to the parent, except that there is no notion of return |
399 | values. |
468 | values. |
400 | |
469 | |
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470 | See the examples section earlier in this document for some actual |
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471 | examples. |
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472 | |
401 | =back |
473 | =back |
402 | |
474 | |
403 | =head1 SEE ALSO |
475 | =head1 SEE ALSO |
404 | |
476 | |
405 | L<AnyEvent::Fork> (to create the processes in the first place), |
477 | L<AnyEvent::Fork> (to create the processes in the first place), |