… | |
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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 | |
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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 |
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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 | |
41 | |
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 | |
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42 | =head1 EXAMPLES |
42 | =head1 EXAMPLES |
43 | |
43 | |
44 | =head2 Synchronous Backend |
44 | =head2 Example 1: Synchronous Backend |
45 | |
45 | |
46 | 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> |
47 | 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 |
48 | 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 |
49 | silly, but illustrates the use of events. |
49 | silly, but illustrates the use of events. |
… | |
… | |
58 | |
58 | |
59 | my $rpc = AnyEvent::Fork |
59 | my $rpc = AnyEvent::Fork |
60 | ->new |
60 | ->new |
61 | ->require ("MyWorker") |
61 | ->require ("MyWorker") |
62 | ->AnyEvent::Fork::RPC::run ("MyWorker::run", |
62 | ->AnyEvent::Fork::RPC::run ("MyWorker::run", |
63 | on_error => sub { warn "FATAL: $_[0]"; exit 1 }, |
63 | on_error => sub { warn "ERROR: $_[0]"; exit 1 }, |
64 | on_event => sub { warn "$_[0] requests handled\n" }, |
64 | on_event => sub { warn "$_[0] requests handled\n" }, |
65 | on_destroy => $done, |
65 | on_destroy => $done, |
66 | ); |
66 | ); |
67 | |
67 | |
68 | for my $id (1..6) { |
68 | for my $id (1..6) { |
… | |
… | |
137 | |
137 | |
138 | 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 |
139 | 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 |
140 | than this example, namely L<IO::AIO>. |
140 | than this example, namely L<IO::AIO>. |
141 | |
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 | This example implements multiple count-downs in the child, using |
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180 | L<AnyEvent> timers. While this is a bit silly (one could use timers in te |
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181 | parent just as well), it illustrates the ability to use AnyEvent in the |
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182 | child and the fact that responses can arrive in a different order then the |
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183 | requests. |
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184 | |
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185 | It also shows how to embed the actual child code into a C<__DATA__> |
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186 | section, so it doesn't need any external files at all. |
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187 | |
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188 | And when your parent process is often busy, and you have stricter timing |
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189 | requirements, then running timers in a child process suddenly doesn't look |
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190 | so silly anymore. |
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191 | |
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192 | Without further ado, here is the code: |
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193 | |
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194 | use AnyEvent; |
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195 | use AnyEvent::Fork; |
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196 | use AnyEvent::Fork::RPC; |
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197 | |
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198 | my $done = AE::cv; |
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199 | |
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200 | my $rpc = AnyEvent::Fork |
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201 | ->new |
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202 | ->require ("AnyEvent::Fork::RPC::Async") |
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203 | ->eval (do { local $/; <DATA> }) |
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204 | ->AnyEvent::Fork::RPC::run ("run", |
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205 | async => 1, |
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206 | on_error => sub { warn "ERROR: $_[0]"; exit 1 }, |
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207 | on_event => sub { print $_[0] }, |
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208 | on_destroy => $done, |
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209 | ); |
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210 | |
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211 | for my $count (3, 2, 1) { |
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212 | $rpc->($count, sub { |
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213 | warn "job $count finished\n"; |
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214 | }); |
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215 | } |
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216 | |
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217 | undef $rpc; |
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218 | |
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219 | $done->recv; |
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220 | |
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221 | __DATA__ |
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222 | |
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223 | # this ends up in main, as we don't use a package declaration |
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224 | |
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225 | use AnyEvent; |
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226 | |
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227 | sub run { |
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228 | my ($done, $count) = @_; |
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229 | |
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230 | my $n; |
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231 | |
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232 | AnyEvent::Fork::RPC::event "starting to count up to $count\n"; |
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233 | |
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234 | my $w; $w = AE::timer 1, 1, sub { |
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235 | ++$n; |
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236 | |
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237 | AnyEvent::Fork::RPC::event "count $n of $count\n"; |
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238 | |
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239 | if ($n == $count) { |
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240 | undef $w; |
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241 | $done->(); |
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242 | } |
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243 | }; |
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244 | } |
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245 | |
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246 | The parent part (the one before the C<__DATA__> section) isn't very |
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247 | different from the earlier examples. It sets async mode, preloads |
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248 | the backend module (so the C<AnyEvent::Fork::RPC::event> function is |
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249 | declared), uses a slightly different C<on_event> handler (which we use |
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250 | simply for logging purposes) and then, instead of loading a module with |
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251 | the actual worker code, it C<eval>'s the code from the data section in the |
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252 | child process. |
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253 | |
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254 | It then starts three countdowns, from 3 to 1 seconds downwards, destroys |
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255 | the rpc object so the example finishes eventually, and then just waits for |
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256 | the stuff to trickle in. |
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257 | |
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258 | The worker code uses the event function to log some progress messages, but |
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259 | mostly just creates a recurring one-second timer. |
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260 | |
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261 | The timer callback increments a counter, logs a message, and eventually, |
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262 | when the count has been reached, calls the finish callback. |
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263 | |
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264 | On my system, this results in the following output. Since all timers fire |
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265 | at roughly the same time, the actual order isn't guaranteed, but the order |
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266 | shown is very likely what you would get, too. |
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267 | |
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268 | starting to count up to 3 |
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269 | starting to count up to 2 |
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270 | starting to count up to 1 |
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271 | count 1 of 3 |
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272 | count 1 of 2 |
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273 | count 1 of 1 |
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274 | job 1 finished |
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275 | count 2 of 2 |
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276 | job 2 finished |
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277 | count 2 of 3 |
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278 | count 3 of 3 |
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279 | job 3 finished |
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280 | |
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281 | While the overall ordering isn't guaranteed, the async backend still |
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282 | guarantees that events and responses are delivered to the parent process |
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283 | in the exact same ordering as they were generated in the child process. |
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284 | |
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285 | And unless your system is I<very> busy, it should clearly show that the |
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286 | job started last will finish first, as it has the lowest count. |
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287 | |
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288 | This concludes the async example. Since L<AnyEvent::Fork> does not |
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289 | actually fork, you are free to use about any module in the child, not just |
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290 | L<AnyEvent>, but also L<IO::AIO>, or L<Tk> for example. |
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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 | |
142 | =head1 PARENT PROCESS USAGE |
379 | =head1 PARENT PROCESS USAGE |
143 | |
380 | |
144 | This module exports nothing, and only implements a single function: |
381 | This module exports nothing, and only implements a single function: |
145 | |
382 | |
146 | =over 4 |
383 | =over 4 |
… | |
… | |
153 | |
390 | |
154 | use Errno (); |
391 | use Errno (); |
155 | use Guard (); |
392 | use Guard (); |
156 | |
393 | |
157 | use AnyEvent; |
394 | use AnyEvent; |
158 | use AnyEvent::Fork; # we don't actually depend on it, this is for convenience |
|
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159 | |
395 | |
160 | our $VERSION = 0.1; |
396 | our $VERSION = 1.1; |
161 | |
397 | |
162 | =item my $rpc = AnyEvent::Fork::RPC::run $fork, $function, [key => value...] |
398 | =item my $rpc = AnyEvent::Fork::RPC::run $fork, $function, [key => value...] |
163 | |
399 | |
164 | 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 |
165 | following way: |
401 | following way: |
… | |
… | |
185 | Called on (fatal) errors, with a descriptive (hopefully) message. If |
421 | Called on (fatal) errors, with a descriptive (hopefully) message. If |
186 | 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> |
187 | 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>, |
188 | followed by the error message. |
424 | followed by the error message. |
189 | |
425 | |
190 | 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 |
191 | start failing badly. |
427 | C<error> via C<AE::log>. |
192 | |
428 | |
193 | =item on_event => $cb->(...) |
429 | =item on_event => $cb->(...) |
194 | |
430 | |
195 | Called for every call to the C<AnyEvent::Fork::RPC::event> function in the |
431 | Called for every call to the C<AnyEvent::Fork::RPC::event> function in the |
196 | child, with the arguments of that function passed to the callback. |
432 | child, with the arguments of that function passed to the callback. |
… | |
… | |
224 | |
460 | |
225 | The default server used in the child does all I/O blockingly, and only |
461 | The default server used in the child does all I/O blockingly, and only |
226 | allows a single RPC call to execute concurrently. |
462 | allows a single RPC call to execute concurrently. |
227 | |
463 | |
228 | Setting C<async> to a true value switches to another implementation that |
464 | Setting C<async> to a true value switches to another implementation that |
229 | uses L<AnyEvent> in the child and allows multiple concurrent RPC calls. |
465 | uses L<AnyEvent> in the child and allows multiple concurrent RPC calls (it |
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466 | does not support recursion in the event loop however, blocking condvar |
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467 | calls will fail). |
230 | |
468 | |
231 | The actual API in the child is documented in the section that describes |
469 | The actual API in the child is documented in the section that describes |
232 | the calling semantics of the returned C<$rpc> function. |
470 | the calling semantics of the returned C<$rpc> function. |
233 | |
471 | |
234 | If you want to pre-load the actual back-end modules to enable memory |
472 | If you want to pre-load the actual back-end modules to enable memory |
… | |
… | |
236 | synchronous, and C<AnyEvent::Fork::RPC::Async> for asynchronous mode. |
474 | synchronous, and C<AnyEvent::Fork::RPC::Async> for asynchronous mode. |
237 | |
475 | |
238 | If you use a template process and want to fork both sync and async |
476 | If you use a template process and want to fork both sync and async |
239 | children, then it is permissible to load both modules. |
477 | children, then it is permissible to load both modules. |
240 | |
478 | |
241 | =item serialiser => $string (default: '(sub { pack "(w/a*)*", @_ }, sub { unpack "(w/a*)*", shift })') |
479 | =item serialiser => $string (default: $AnyEvent::Fork::RPC::STRING_SERIALISER) |
242 | |
480 | |
243 | All arguments, result data and event data have to be serialised to be |
481 | All arguments, result data and event data have to be serialised to be |
244 | transferred between the processes. For this, they have to be frozen and |
482 | transferred between the processes. For this, they have to be frozen and |
245 | thawed in both parent and child processes. |
483 | thawed in both parent and child processes. |
246 | |
484 | |
247 | By default, only octet strings can be passed between the processes, which |
485 | By default, only octet strings can be passed between the processes, which |
248 | is reasonably fast and efficient. |
486 | is reasonably fast and efficient and requires no extra modules. |
249 | |
487 | |
250 | For more complicated use cases, you can provide your own freeze and thaw |
488 | For more complicated use cases, you can provide your own freeze and thaw |
251 | functions, by specifying a string with perl source code. It's supposed to |
489 | functions, by specifying a string with perl source code. It's supposed to |
252 | return two code references when evaluated: the first receives a list of |
490 | return two code references when evaluated: the first receives a list of |
253 | perl values and must return an octet string. The second receives the octet |
491 | perl values and must return an octet string. The second receives the octet |
… | |
… | |
255 | |
493 | |
256 | If you need an external module for serialisation, then you can either |
494 | If you need an external module for serialisation, then you can either |
257 | pre-load it into your L<AnyEvent::Fork> process, or you can add a C<use> |
495 | pre-load it into your L<AnyEvent::Fork> process, or you can add a C<use> |
258 | or C<require> statement into the serialiser string. Or both. |
496 | or C<require> statement into the serialiser string. Or both. |
259 | |
497 | |
|
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498 | Here are some examples - some of them are also available as global |
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499 | variables that make them easier to use. |
|
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500 | |
|
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501 | =over 4 |
|
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502 | |
|
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503 | =item octet strings - C<$AnyEvent::Fork::RPC::STRING_SERIALISER> |
|
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504 | |
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505 | This serialiser concatenates length-prefixes octet strings, and is the |
|
|
506 | default. That means you can only pass (and return) strings containing |
|
|
507 | character codes 0-255. |
|
|
508 | |
|
|
509 | Implementation: |
|
|
510 | |
|
|
511 | ( |
|
|
512 | sub { pack "(w/a*)*", @_ }, |
|
|
513 | sub { unpack "(w/a*)*", shift } |
|
|
514 | ) |
|
|
515 | |
|
|
516 | =item json - C<$AnyEvent::Fork::RPC::JSON_SERIALISER> |
|
|
517 | |
|
|
518 | This serialiser creates JSON arrays - you have to make sure the L<JSON> |
|
|
519 | module is installed for this serialiser to work. It can be beneficial for |
|
|
520 | sharing when you preload the L<JSON> module in a template process. |
|
|
521 | |
|
|
522 | L<JSON> (with L<JSON::XS> installed) is slower than the octet string |
|
|
523 | serialiser, but usually much faster than L<Storable>, unless big chunks of |
|
|
524 | binary data need to be transferred. |
|
|
525 | |
|
|
526 | Implementation: |
|
|
527 | |
|
|
528 | use JSON (); |
|
|
529 | ( |
|
|
530 | sub { JSON::encode_json \@_ }, |
|
|
531 | sub { @{ JSON::decode_json shift } } |
|
|
532 | ) |
|
|
533 | |
|
|
534 | =item storable - C<$AnyEvent::Fork::RPC::STORABLE_SERIALISER> |
|
|
535 | |
|
|
536 | This serialiser uses L<Storable>, which means it has high chance of |
|
|
537 | serialising just about anything you throw at it, at the cost of having |
|
|
538 | very high overhead per operation. It also comes with perl. It should be |
|
|
539 | used when you need to serialise complex data structures. |
|
|
540 | |
|
|
541 | Implementation: |
|
|
542 | |
|
|
543 | use Storable (); |
|
|
544 | ( |
|
|
545 | sub { Storable::freeze \@_ }, |
|
|
546 | sub { @{ Storable::thaw shift } } |
|
|
547 | ) |
|
|
548 | |
|
|
549 | =item portable storable - C<$AnyEvent::Fork::RPC::NSTORABLE_SERIALISER> |
|
|
550 | |
|
|
551 | This serialiser also uses L<Storable>, but uses it's "network" format |
|
|
552 | to serialise data, which makes it possible to talk to different |
|
|
553 | perl binaries (for example, when talking to a process created with |
|
|
554 | L<AnyEvent::Fork::Remote>). |
|
|
555 | |
|
|
556 | Implementation: |
|
|
557 | |
|
|
558 | use Storable (); |
|
|
559 | ( |
|
|
560 | sub { Storable::nfreeze \@_ }, |
|
|
561 | sub { @{ Storable::thaw shift } } |
|
|
562 | ) |
|
|
563 | |
|
|
564 | =back |
|
|
565 | |
260 | =back |
566 | =back |
261 | |
567 | |
262 | See the examples section earlier in this document for some actual |
568 | See the examples section earlier in this document for some actual |
263 | examples. |
569 | examples. |
264 | |
570 | |
265 | =cut |
571 | =cut |
266 | |
572 | |
267 | our $STRING_SERIALISER = '(sub { pack "(w/a*)*", @_ }, sub { unpack "(w/a*)*", shift })'; |
573 | our $STRING_SERIALISER = '(sub { pack "(w/a*)*", @_ }, sub { unpack "(w/a*)*", shift })'; |
|
|
574 | our $JSON_SERIALISER = 'use JSON (); (sub { JSON::encode_json \@_ }, sub { @{ JSON::decode_json shift } })'; |
|
|
575 | our $STORABLE_SERIALISER = 'use Storable (); (sub { Storable::freeze \@_ }, sub { @{ Storable::thaw shift } })'; |
|
|
576 | our $NSTORABLE_SERIALISER = 'use Storable (); (sub { Storable::nfreeze \@_ }, sub { @{ Storable::thaw shift } })'; |
268 | |
577 | |
269 | sub run { |
578 | sub run { |
270 | my ($self, $function, %arg) = @_; |
579 | my ($self, $function, %arg) = @_; |
271 | |
580 | |
272 | my $serialiser = delete $arg{serialiser} || $STRING_SERIALISER; |
581 | my $serialiser = delete $arg{serialiser} || $STRING_SERIALISER; |
… | |
… | |
275 | my $on_destroy = delete $arg{on_destroy}; |
584 | my $on_destroy = delete $arg{on_destroy}; |
276 | |
585 | |
277 | # default for on_error is to on_event, if specified |
586 | # default for on_error is to on_event, if specified |
278 | $on_error ||= $on_event |
587 | $on_error ||= $on_event |
279 | ? sub { $on_event->(error => shift) } |
588 | ? sub { $on_event->(error => shift) } |
280 | : sub { die "AnyEvent::Fork::RPC: uncaught error: $_[0].\n" }; |
589 | : sub { AE::log die => "AnyEvent::Fork::RPC: uncaught error: $_[0]." }; |
281 | |
590 | |
282 | # default for on_event is to raise an error |
591 | # default for on_event is to raise an error |
283 | $on_event ||= sub { $on_error->("event received, but no on_event handler") }; |
592 | $on_event ||= sub { $on_error->("event received, but no on_event handler") }; |
284 | |
593 | |
285 | my ($f, $t) = eval $serialiser; die $@ if $@; |
594 | my ($f, $t) = eval $serialiser; die $@ if $@; |
… | |
… | |
317 | $rlen = $rlen * 2 + 16 if $rlen - 128 < length $rbuf; |
626 | $rlen = $rlen * 2 + 16 if $rlen - 128 < length $rbuf; |
318 | $len = sysread $fh, $rbuf, $rlen - length $rbuf, length $rbuf; |
627 | $len = sysread $fh, $rbuf, $rlen - length $rbuf, length $rbuf; |
319 | |
628 | |
320 | if ($len) { |
629 | if ($len) { |
321 | while (8 <= length $rbuf) { |
630 | while (8 <= length $rbuf) { |
322 | ($id, $len) = unpack "LL", $rbuf; |
631 | ($id, $len) = unpack "NN", $rbuf; |
323 | 8 + $len <= length $rbuf |
632 | 8 + $len <= length $rbuf |
324 | or last; |
633 | or last; |
325 | |
634 | |
326 | my @r = $t->(substr $rbuf, 8, $len); |
635 | my @r = $t->(substr $rbuf, 8, $len); |
327 | substr $rbuf, 0, 8 + $len, ""; |
636 | substr $rbuf, 0, 8 + $len, ""; |
… | |
… | |
341 | } |
650 | } |
342 | } elsif (defined $len) { |
651 | } elsif (defined $len) { |
343 | undef $rw; undef $ww; # it ends here |
652 | undef $rw; undef $ww; # it ends here |
344 | |
653 | |
345 | if (@rcb || %rcb) { |
654 | if (@rcb || %rcb) { |
346 | use Data::Dump;ddx[\@rcb,\%rcb];#d# |
|
|
347 | $on_error->("unexpected eof"); |
655 | $on_error->("unexpected eof"); |
348 | } else { |
656 | } else { |
349 | $on_destroy->(); |
657 | $on_destroy->() |
|
|
658 | if $on_destroy; |
350 | } |
659 | } |
351 | } elsif ($! != Errno::EAGAIN && $! != Errno::EWOULDBLOCK) { |
660 | } elsif ($! != Errno::EAGAIN && $! != Errno::EWOULDBLOCK) { |
352 | undef $rw; undef $ww; # it ends here |
661 | undef $rw; undef $ww; # it ends here |
353 | $on_error->("read: $!"); |
662 | $on_error->("read: $!"); |
354 | } |
663 | } |
… | |
… | |
357 | $ww ||= AE::io $fh, 1, $wcb; |
666 | $ww ||= AE::io $fh, 1, $wcb; |
358 | }); |
667 | }); |
359 | |
668 | |
360 | my $guard = Guard::guard { |
669 | my $guard = Guard::guard { |
361 | $shutdown = 1; |
670 | $shutdown = 1; |
362 | $ww ||= $fh && AE::io $fh, 1, $wcb; |
671 | |
|
|
672 | shutdown $fh, 1 if $fh && !$ww; |
363 | }; |
673 | }; |
364 | |
674 | |
365 | my $id; |
675 | my $id; |
366 | |
676 | |
367 | $arg{async} |
677 | $arg{async} |
… | |
… | |
369 | $id = ($id == 0xffffffff ? 0 : $id) + 1; |
679 | $id = ($id == 0xffffffff ? 0 : $id) + 1; |
370 | $id = ($id == 0xffffffff ? 0 : $id) + 1 while exists $rcb{$id}; # rarely loops |
680 | $id = ($id == 0xffffffff ? 0 : $id) + 1 while exists $rcb{$id}; # rarely loops |
371 | |
681 | |
372 | $rcb{$id} = pop; |
682 | $rcb{$id} = pop; |
373 | |
683 | |
374 | $guard; # keep it alive |
684 | $guard if 0; # keep it alive |
375 | |
685 | |
376 | $wbuf .= pack "LL/a*", $id, &$f; |
686 | $wbuf .= pack "NN/a*", $id, &$f; |
377 | $ww ||= $fh && AE::io $fh, 1, $wcb; |
687 | $ww ||= $fh && AE::io $fh, 1, $wcb; |
378 | } |
688 | } |
379 | : sub { |
689 | : sub { |
380 | push @rcb, pop; |
690 | push @rcb, pop; |
381 | |
691 | |
382 | $guard; # keep it alive |
692 | $guard; # keep it alive |
383 | |
693 | |
384 | $wbuf .= pack "L/a*", &$f; |
694 | $wbuf .= pack "N/a*", &$f; |
385 | $ww ||= $fh && AE::io $fh, 1, $wcb; |
695 | $ww ||= $fh && AE::io $fh, 1, $wcb; |
386 | } |
696 | } |
387 | } |
697 | } |
388 | |
698 | |
389 | =item $rpc->(..., $cb->(...)) |
699 | =item $rpc->(..., $cb->(...)) |
… | |
… | |
431 | See the examples section earlier in this document for some actual |
741 | See the examples section earlier in this document for some actual |
432 | examples. |
742 | examples. |
433 | |
743 | |
434 | =back |
744 | =back |
435 | |
745 | |
|
|
746 | =head1 ADVANCED TOPICS |
|
|
747 | |
|
|
748 | =head2 Choosing a backend |
|
|
749 | |
|
|
750 | So how do you decide which backend to use? Well, that's your problem to |
|
|
751 | solve, but here are some thoughts on the matter: |
|
|
752 | |
|
|
753 | =over 4 |
|
|
754 | |
|
|
755 | =item Synchronous |
|
|
756 | |
|
|
757 | The synchronous backend does not rely on any external modules (well, |
|
|
758 | except L<common::sense>, which works around a bug in how perl's warning |
|
|
759 | system works). This keeps the process very small, for example, on my |
|
|
760 | system, an empty perl interpreter uses 1492kB RSS, which becomes 2020kB |
|
|
761 | after C<use warnings; use strict> (for people who grew up with C64s around |
|
|
762 | them this is probably shocking every single time they see it). The worker |
|
|
763 | process in the first example in this document uses 1792kB. |
|
|
764 | |
|
|
765 | Since the calls are done synchronously, slow jobs will keep newer jobs |
|
|
766 | from executing. |
|
|
767 | |
|
|
768 | The synchronous backend also has no overhead due to running an event loop |
|
|
769 | - reading requests is therefore very efficient, while writing responses is |
|
|
770 | less so, as every response results in a write syscall. |
|
|
771 | |
|
|
772 | If the parent process is busy and a bit slow reading responses, the child |
|
|
773 | waits instead of processing further requests. This also limits the amount |
|
|
774 | of memory needed for buffering, as never more than one response has to be |
|
|
775 | buffered. |
|
|
776 | |
|
|
777 | The API in the child is simple - you just have to define a function that |
|
|
778 | does something and returns something. |
|
|
779 | |
|
|
780 | It's hard to use modules or code that relies on an event loop, as the |
|
|
781 | child cannot execute anything while it waits for more input. |
|
|
782 | |
|
|
783 | =item Asynchronous |
|
|
784 | |
|
|
785 | The asynchronous backend relies on L<AnyEvent>, which tries to be small, |
|
|
786 | but still comes at a price: On my system, the worker from example 1a uses |
|
|
787 | 3420kB RSS (for L<AnyEvent>, which loads L<EV>, which needs L<XSLoader> |
|
|
788 | which in turn loads a lot of other modules such as L<warnings>, L<strict>, |
|
|
789 | L<vars>, L<Exporter>...). |
|
|
790 | |
|
|
791 | It batches requests and responses reasonably efficiently, doing only as |
|
|
792 | few reads and writes as needed, but needs to poll for events via the event |
|
|
793 | loop. |
|
|
794 | |
|
|
795 | Responses are queued when the parent process is busy. This means the child |
|
|
796 | can continue to execute any queued requests. It also means that a child |
|
|
797 | might queue a lot of responses in memory when it generates them and the |
|
|
798 | parent process is slow accepting them. |
|
|
799 | |
|
|
800 | The API is not a straightforward RPC pattern - you have to call a |
|
|
801 | "done" callback to pass return values and signal completion. Also, more |
|
|
802 | importantly, the API starts jobs as fast as possible - when 1000 jobs |
|
|
803 | are queued and the jobs are slow, they will all run concurrently. The |
|
|
804 | child must implement some queueing/limiting mechanism if this causes |
|
|
805 | problems. Alternatively, the parent could limit the amount of rpc calls |
|
|
806 | that are outstanding. |
|
|
807 | |
|
|
808 | Blocking use of condvars is not supported. |
|
|
809 | |
|
|
810 | Using event-based modules such as L<IO::AIO>, L<Gtk2>, L<Tk> and so on is |
|
|
811 | easy. |
|
|
812 | |
|
|
813 | =back |
|
|
814 | |
|
|
815 | =head2 Passing file descriptors |
|
|
816 | |
|
|
817 | Unlike L<AnyEvent::Fork>, this module has no in-built file handle or file |
|
|
818 | descriptor passing abilities. |
|
|
819 | |
|
|
820 | The reason is that passing file descriptors is extraordinary tricky |
|
|
821 | business, and conflicts with efficient batching of messages. |
|
|
822 | |
|
|
823 | There still is a method you can use: Create a |
|
|
824 | C<AnyEvent::Util::portable_socketpair> and C<send_fh> one half of it to |
|
|
825 | the process before you pass control to C<AnyEvent::Fork::RPC::run>. |
|
|
826 | |
|
|
827 | Whenever you want to pass a file descriptor, send an rpc request to the |
|
|
828 | child process (so it expects the descriptor), then send it over the other |
|
|
829 | half of the socketpair. The child should fetch the descriptor from the |
|
|
830 | half it has passed earlier. |
|
|
831 | |
|
|
832 | Here is some (untested) pseudocode to that effect: |
|
|
833 | |
|
|
834 | use AnyEvent::Util; |
|
|
835 | use AnyEvent::Fork; |
|
|
836 | use AnyEvent::Fork::RPC; |
|
|
837 | use IO::FDPass; |
|
|
838 | |
|
|
839 | my ($s1, $s2) = AnyEvent::Util::portable_socketpair; |
|
|
840 | |
|
|
841 | my $rpc = AnyEvent::Fork |
|
|
842 | ->new |
|
|
843 | ->send_fh ($s2) |
|
|
844 | ->require ("MyWorker") |
|
|
845 | ->AnyEvent::Fork::RPC::run ("MyWorker::run" |
|
|
846 | init => "MyWorker::init", |
|
|
847 | ); |
|
|
848 | |
|
|
849 | undef $s2; # no need to keep it around |
|
|
850 | |
|
|
851 | # pass an fd |
|
|
852 | $rpc->("i'll send some fd now, please expect it!", my $cv = AE::cv); |
|
|
853 | |
|
|
854 | IO::FDPass fileno $s1, fileno $handle_to_pass; |
|
|
855 | |
|
|
856 | $cv->recv; |
|
|
857 | |
|
|
858 | The MyWorker module could look like this: |
|
|
859 | |
|
|
860 | package MyWorker; |
|
|
861 | |
|
|
862 | use IO::FDPass; |
|
|
863 | |
|
|
864 | my $s2; |
|
|
865 | |
|
|
866 | sub init { |
|
|
867 | $s2 = $_[0]; |
|
|
868 | } |
|
|
869 | |
|
|
870 | sub run { |
|
|
871 | if ($_[0] eq "i'll send some fd now, please expect it!") { |
|
|
872 | my $fd = IO::FDPass::recv fileno $s2; |
|
|
873 | ... |
|
|
874 | } |
|
|
875 | } |
|
|
876 | |
|
|
877 | Of course, this might be blocking if you pass a lot of file descriptors, |
|
|
878 | so you might want to look into L<AnyEvent::FDpasser> which can handle the |
|
|
879 | gory details. |
|
|
880 | |
|
|
881 | =head1 EXCEPTIONS |
|
|
882 | |
|
|
883 | There are no provisions whatsoever for catching exceptions at this time - |
|
|
884 | in the child, exeptions might kill the process, causing calls to be lost |
|
|
885 | and the parent encountering a fatal error. In the parent, exceptions in |
|
|
886 | the result callback will not be caught and cause undefined behaviour. |
|
|
887 | |
436 | =head1 SEE ALSO |
888 | =head1 SEE ALSO |
437 | |
889 | |
438 | L<AnyEvent::Fork> (to create the processes in the first place), |
890 | L<AnyEvent::Fork>, to create the processes in the first place. |
|
|
891 | |
|
|
892 | L<AnyEvent::Fork::Remote>, likewise, but helpful for remote processes. |
|
|
893 | |
439 | L<AnyEvent::Fork::Pool> (to manage whole pools of processes). |
894 | L<AnyEvent::Fork::Pool>, to manage whole pools of processes. |
440 | |
895 | |
441 | =head1 AUTHOR AND CONTACT INFORMATION |
896 | =head1 AUTHOR AND CONTACT INFORMATION |
442 | |
897 | |
443 | Marc Lehmann <schmorp@schmorp.de> |
898 | Marc Lehmann <schmorp@schmorp.de> |
444 | http://software.schmorp.de/pkg/AnyEvent-Fork-RPC |
899 | http://software.schmorp.de/pkg/AnyEvent-Fork-RPC |