… | |
… | |
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 ( |
… | |
… | |
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. |
47 | |
50 | |
48 | First the parent process: |
51 | First the parent process: |
49 | |
52 | |
50 | use AnyEvent; |
53 | use AnyEvent; |
51 | use AnyEvent::Fork; |
|
|
52 | use AnyEvent::Fork::RPC; |
54 | use AnyEvent::Fork::RPC; |
53 | |
55 | |
54 | my $done = AE::cv; |
56 | my $done = AE::cv; |
55 | |
57 | |
56 | my $rpc = AnyEvent::Fork |
58 | my $rpc = AnyEvent::Fork |
… | |
… | |
134 | |
136 | |
135 | And as a final remark, there is a fine module on CPAN that can |
137 | 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 |
138 | asynchronously C<rmdir> and C<unlink> and a lot more, and more efficiently |
137 | than this example, namely L<IO::AIO>. |
139 | than this example, namely L<IO::AIO>. |
138 | |
140 | |
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141 | =head3 Example 1a: the same with the asynchronous backend |
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142 | |
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143 | This example only shows what needs to be changed to use the async backend |
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144 | instead. Doing this is not very useful, the purpose of this example is |
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145 | to show the minimum amount of change that is required to go from the |
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146 | synchronous to the asynchronous backend. |
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147 | |
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148 | To use the async backend in the previous example, you need to add the |
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149 | C<async> parameter to the C<AnyEvent::Fork::RPC::run> call: |
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150 | |
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151 | ->AnyEvent::Fork::RPC::run ("MyWorker::run", |
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152 | async => 1, |
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153 | ... |
|
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154 | |
|
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155 | And since the function call protocol is now changed, you need to adopt |
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156 | C<MyWorker::run> to the async API. |
|
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157 | |
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158 | First, you need to accept the extra initial C<$done> callback: |
|
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159 | |
|
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160 | sub run { |
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161 | my ($done, $cmd, $path) = @_; |
|
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162 | |
|
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163 | And since a response is now generated when C<$done> is called, as opposed |
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164 | to when the function returns, we need to call the C<$done> function with |
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165 | the status: |
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166 | |
|
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167 | $done->($status or (0, "$!")); |
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168 | |
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169 | A few remarks are in order. First, it's quite pointless to use the async |
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170 | backend for this example - but it I<is> possible. Second, you can call |
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171 | C<$done> before or after returning from the function. Third, having both |
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172 | returned from the function and having called the C<$done> callback, the |
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173 | child process may exit at any time, so you should call C<$done> only when |
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174 | you really I<are> done. |
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175 | |
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176 | =head2 Example 2: Asynchronous Backend |
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177 | |
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178 | This example implements multiple count-downs in the child, using |
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179 | L<AnyEvent> timers. While this is a bit silly (one could use timers in te |
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180 | parent just as well), it illustrates the ability to use AnyEvent in the |
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181 | child and the fact that responses can arrive in a different order then the |
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182 | requests. |
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183 | |
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184 | It also shows how to embed the actual child code into a C<__DATA__> |
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185 | section, so it doesn't need any external files at all. |
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186 | |
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187 | And when your parent process is often busy, and you have stricter timing |
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188 | requirements, then running timers in a child process suddenly doesn't look |
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189 | so silly anymore. |
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190 | |
|
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191 | Without further ado, here is the code: |
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192 | |
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193 | use AnyEvent; |
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194 | use AnyEvent::Fork::RPC; |
|
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195 | |
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196 | my $done = AE::cv; |
|
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197 | |
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198 | my $rpc = AnyEvent::Fork |
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199 | ->new |
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200 | ->require ("AnyEvent::Fork::RPC::Async") |
|
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201 | ->eval (do { local $/; <DATA> }) |
|
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202 | ->AnyEvent::Fork::RPC::run ("run", |
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203 | async => 1, |
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204 | on_error => sub { warn "FATAL: $_[0]"; exit 1 }, |
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205 | on_event => sub { print $_[0] }, |
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206 | on_destroy => $done, |
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207 | ); |
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208 | |
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209 | for my $count (3, 2, 1) { |
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210 | $rpc->($count, sub { |
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211 | warn "job $count finished\n"; |
|
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212 | }); |
|
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213 | } |
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214 | |
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215 | undef $rpc; |
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216 | |
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217 | $done->recv; |
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218 | |
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219 | __DATA__ |
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220 | |
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221 | # this ends up in main, as we don't use a package declaration |
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222 | |
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223 | use AnyEvent; |
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224 | |
|
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225 | sub run { |
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226 | my ($done, $count) = @_; |
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227 | |
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228 | my $n; |
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229 | |
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230 | AnyEvent::Fork::RPC::event "starting to count up to $count\n"; |
|
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231 | |
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232 | my $w; $w = AE::timer 1, 1, sub { |
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233 | ++$n; |
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234 | |
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235 | AnyEvent::Fork::RPC::event "count $n of $count\n"; |
|
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236 | |
|
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237 | if ($n == $count) { |
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238 | undef $w; |
|
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239 | $done->(); |
|
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240 | } |
|
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241 | }; |
|
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242 | } |
|
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243 | |
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244 | The parent part (the one before the C<__DATA__> section) isn't very |
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245 | different from the earlier examples. It sets async mode, preloads |
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246 | the backend module (so the C<AnyEvent::Fork::RPC::event> function is |
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247 | declared), uses a slightly different C<on_event> handler (which we use |
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248 | simply for logging purposes) and then, instead of loading a module with |
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249 | the actual worker code, it C<eval>'s the code from the data section in the |
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250 | child process. |
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251 | |
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252 | It then starts three countdowns, from 3 to 1 seconds downwards, destroys |
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253 | the rpc object so the example finishes eventually, and then just waits for |
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254 | the stuff to trickle in. |
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255 | |
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256 | The worker code uses the event function to log some progress messages, but |
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257 | mostly just creates a recurring one-second timer. |
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258 | |
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259 | The timer callback increments a counter, logs a message, and eventually, |
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260 | when the count has been reached, calls the finish callback. |
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261 | |
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262 | On my system, this results in the following output. Since all timers fire |
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263 | at roughly the same time, the actual order isn't guaranteed, but the order |
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264 | shown is very likely what you would get, too. |
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265 | |
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266 | starting to count up to 3 |
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267 | starting to count up to 2 |
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268 | starting to count up to 1 |
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269 | count 1 of 3 |
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270 | count 1 of 2 |
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271 | count 1 of 1 |
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272 | job 1 finished |
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273 | count 2 of 2 |
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274 | job 2 finished |
|
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275 | count 2 of 3 |
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276 | count 3 of 3 |
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277 | job 3 finished |
|
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278 | |
|
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279 | While the overall ordering isn't guaranteed, the async backend still |
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280 | guarantees that events and responses are delivered to the parent process |
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281 | in the exact same ordering as they were generated in the child process. |
|
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282 | |
|
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283 | And unless your system is I<very> busy, it should clearly show that the |
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284 | job started last will finish first, as it has the lowest count. |
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285 | |
|
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286 | This concludes the async example. Since L<AnyEvent::Fork> does not |
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287 | actually fork, you are free to use about any module in the child, not just |
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288 | L<AnyEvent>, but also L<IO::AIO>, or L<Tk> for example. |
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289 | |
139 | =head1 PARENT PROCESS USAGE |
290 | =head1 PARENT PROCESS USAGE |
140 | |
291 | |
141 | This module exports nothing, and only implements a single function: |
292 | This module exports nothing, and only implements a single function: |
142 | |
293 | |
143 | =over 4 |
294 | =over 4 |
… | |
… | |
150 | |
301 | |
151 | use Errno (); |
302 | use Errno (); |
152 | use Guard (); |
303 | use Guard (); |
153 | |
304 | |
154 | use AnyEvent; |
305 | use AnyEvent; |
155 | #use AnyEvent::Fork; |
306 | use AnyEvent::Fork; # we don't actually depend on it, this is for convenience |
156 | |
307 | |
157 | our $VERSION = 0.1; |
308 | our $VERSION = 0.1; |
158 | |
309 | |
159 | =item my $rpc = AnyEvent::Fork::RPC::run $fork, $function, [key => value...] |
310 | =item my $rpc = AnyEvent::Fork::RPC::run $fork, $function, [key => value...] |
160 | |
311 | |
… | |
… | |
253 | If you need an external module for serialisation, then you can either |
404 | 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> |
405 | 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. |
406 | or C<require> statement into the serialiser string. Or both. |
256 | |
407 | |
257 | =back |
408 | =back |
|
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409 | |
|
|
410 | See the examples section earlier in this document for some actual |
|
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411 | examples. |
258 | |
412 | |
259 | =cut |
413 | =cut |
260 | |
414 | |
261 | our $STRING_SERIALISER = '(sub { pack "(w/a*)*", @_ }, sub { unpack "(w/a*)*", shift })'; |
415 | our $STRING_SERIALISER = '(sub { pack "(w/a*)*", @_ }, sub { unpack "(w/a*)*", shift })'; |
262 | |
416 | |
… | |
… | |
276 | # default for on_event is to raise an error |
430 | # default for on_event is to raise an error |
277 | $on_event ||= sub { $on_error->("event received, but no on_event handler") }; |
431 | $on_event ||= sub { $on_error->("event received, but no on_event handler") }; |
278 | |
432 | |
279 | my ($f, $t) = eval $serialiser; die $@ if $@; |
433 | my ($f, $t) = eval $serialiser; die $@ if $@; |
280 | |
434 | |
281 | my (@rcb, $fh, $shutdown, $wbuf, $ww, $rw); |
435 | my (@rcb, %rcb, $fh, $shutdown, $wbuf, $ww); |
282 | my ($rlen, $rbuf) = 512 - 16; |
436 | my ($rlen, $rbuf, $rw) = 512 - 16; |
283 | |
437 | |
284 | my $wcb = sub { |
438 | my $wcb = sub { |
285 | my $len = syswrite $fh, $wbuf; |
439 | my $len = syswrite $fh, $wbuf; |
286 | |
440 | |
287 | if (!defined $len) { |
441 | unless (defined $len) { |
288 | if ($! != Errno::EAGAIN && $! != Errno::EWOULDBLOCK) { |
442 | if ($! != Errno::EAGAIN && $! != Errno::EWOULDBLOCK) { |
289 | undef $rw; undef $ww; # it ends here |
443 | undef $rw; undef $ww; # it ends here |
290 | $on_error->("$!"); |
444 | $on_error->("$!"); |
291 | } |
445 | } |
292 | } |
446 | } |
… | |
… | |
303 | |
457 | |
304 | $self->require ($module) |
458 | $self->require ($module) |
305 | ->send_arg ($function, $arg{init}, $serialiser) |
459 | ->send_arg ($function, $arg{init}, $serialiser) |
306 | ->run ("$module\::run", sub { |
460 | ->run ("$module\::run", sub { |
307 | $fh = shift; |
461 | $fh = shift; |
|
|
462 | |
|
|
463 | my ($id, $len); |
308 | $rw = AE::io $fh, 0, sub { |
464 | $rw = AE::io $fh, 0, sub { |
309 | $rlen = $rlen * 2 + 16 if $rlen - 128 < length $rbuf; |
465 | $rlen = $rlen * 2 + 16 if $rlen - 128 < length $rbuf; |
310 | my $len = sysread $fh, $rbuf, $rlen - length $rbuf, length $rbuf; |
466 | $len = sysread $fh, $rbuf, $rlen - length $rbuf, length $rbuf; |
311 | |
467 | |
312 | if ($len) { |
468 | if ($len) { |
313 | while (5 <= length $rbuf) { |
469 | while (8 <= length $rbuf) { |
314 | $len = unpack "L", $rbuf; |
470 | ($id, $len) = unpack "LL", $rbuf; |
315 | 4 + $len <= length $rbuf |
471 | 8 + $len <= length $rbuf |
316 | or last; |
472 | or last; |
317 | |
473 | |
318 | my @r = $t->(substr $rbuf, 4, $len); |
474 | my @r = $t->(substr $rbuf, 8, $len); |
319 | substr $rbuf, 0, $len + 4, ""; |
475 | substr $rbuf, 0, 8 + $len, ""; |
|
|
476 | |
|
|
477 | if ($id) { |
|
|
478 | if (@rcb) { |
|
|
479 | (shift @rcb)->(@r); |
|
|
480 | } elsif (my $cb = delete $rcb{$id}) { |
|
|
481 | $cb->(@r); |
|
|
482 | } else { |
|
|
483 | undef $rw; undef $ww; |
|
|
484 | $on_error->("unexpected data from child"); |
320 | |
485 | } |
321 | if (pop @r) { |
486 | } else { |
322 | $on_event->(@r); |
487 | $on_event->(@r); |
323 | } elsif (@rcb) { |
|
|
324 | (shift @rcb)->(@r); |
|
|
325 | } else { |
|
|
326 | undef $rw; undef $ww; |
|
|
327 | $on_error->("unexpected data from child"); |
|
|
328 | } |
488 | } |
329 | } |
489 | } |
330 | } elsif (defined $len) { |
490 | } elsif (defined $len) { |
331 | undef $rw; undef $ww; # it ends here |
491 | undef $rw; undef $ww; # it ends here |
332 | |
492 | |
333 | if (@rcb) { |
493 | if (@rcb || %rcb) { |
|
|
494 | use Data::Dump;ddx[\@rcb,\%rcb];#d# |
334 | $on_error->("unexpected eof"); |
495 | $on_error->("unexpected eof"); |
335 | } else { |
496 | } else { |
336 | $on_destroy->(); |
497 | $on_destroy->(); |
337 | } |
498 | } |
338 | } elsif ($! != Errno::EAGAIN && $! != Errno::EWOULDBLOCK) { |
499 | } elsif ($! != Errno::EAGAIN && $! != Errno::EWOULDBLOCK) { |
… | |
… | |
347 | my $guard = Guard::guard { |
508 | my $guard = Guard::guard { |
348 | $shutdown = 1; |
509 | $shutdown = 1; |
349 | $ww ||= $fh && AE::io $fh, 1, $wcb; |
510 | $ww ||= $fh && AE::io $fh, 1, $wcb; |
350 | }; |
511 | }; |
351 | |
512 | |
|
|
513 | my $id; |
|
|
514 | |
|
|
515 | $arg{async} |
352 | sub { |
516 | ? sub { |
353 | push @rcb, pop; |
517 | $id = ($id == 0xffffffff ? 0 : $id) + 1; |
|
|
518 | $id = ($id == 0xffffffff ? 0 : $id) + 1 while exists $rcb{$id}; # rarely loops |
354 | |
519 | |
|
|
520 | $rcb{$id} = pop; |
|
|
521 | |
355 | $guard; # keep it alive |
522 | $guard; # keep it alive |
356 | |
523 | |
357 | $wbuf .= pack "L/a*", &$f; |
524 | $wbuf .= pack "LL/a*", $id, &$f; |
358 | $ww ||= $fh && AE::io $fh, 1, $wcb; |
525 | $ww ||= $fh && AE::io $fh, 1, $wcb; |
359 | } |
526 | } |
|
|
527 | : sub { |
|
|
528 | push @rcb, pop; |
|
|
529 | |
|
|
530 | $guard; # keep it alive |
|
|
531 | |
|
|
532 | $wbuf .= pack "L/a*", &$f; |
|
|
533 | $ww ||= $fh && AE::io $fh, 1, $wcb; |
|
|
534 | } |
360 | } |
535 | } |
361 | |
536 | |
362 | =item $rpc->(..., $cb->(...)) |
537 | =item $rpc->(..., $cb->(...)) |
363 | |
538 | |
364 | The RPC object returned by C<AnyEvent::Fork::RPC::run> is actually a code |
539 | The RPC object returned by C<AnyEvent::Fork::RPC::run> is actually a code |
… | |
… | |
379 | |
554 | |
380 | The other thing that can be done with the RPC object is to destroy it. In |
555 | 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 |
556 | this case, the child process will execute all remaining RPC calls, report |
382 | their results, and then exit. |
557 | their results, and then exit. |
383 | |
558 | |
|
|
559 | See the examples section earlier in this document for some actual |
|
|
560 | examples. |
|
|
561 | |
384 | =back |
562 | =back |
385 | |
563 | |
386 | =head1 CHILD PROCESS USAGE |
564 | =head1 CHILD PROCESS USAGE |
387 | |
565 | |
388 | The following function is not available in this module. They are only |
566 | The following function is not available in this module. They are only |
… | |
… | |
396 | |
574 | |
397 | Send an event to the parent. Events are a bit like RPC calls made by the |
575 | 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 |
576 | child process to the parent, except that there is no notion of return |
399 | values. |
577 | values. |
400 | |
578 | |
|
|
579 | See the examples section earlier in this document for some actual |
|
|
580 | examples. |
|
|
581 | |
401 | =back |
582 | =back |
402 | |
583 | |
403 | =head1 SEE ALSO |
584 | =head1 SEE ALSO |
404 | |
585 | |
405 | L<AnyEvent::Fork> (to create the processes in the first place), |
586 | L<AnyEvent::Fork> (to create the processes in the first place), |