… | |
… | |
9 | $NODE # contains this node's noderef |
9 | $NODE # contains this node's noderef |
10 | NODE # returns this node's noderef |
10 | NODE # returns this node's noderef |
11 | NODE $port # returns the noderef of the port |
11 | NODE $port # returns the noderef of the port |
12 | |
12 | |
13 | $SELF # receiving/own port id in rcv callbacks |
13 | $SELF # receiving/own port id in rcv callbacks |
|
|
14 | |
|
|
15 | # initialise the node so it can send/receive messages |
|
|
16 | initialise_node; # -OR- |
|
|
17 | initialise_node "localhost:4040"; # -OR- |
|
|
18 | initialise_node "slave/", "localhost:4040" |
14 | |
19 | |
15 | # ports are message endpoints |
20 | # ports are message endpoints |
16 | |
21 | |
17 | # sending messages |
22 | # sending messages |
18 | snd $port, type => data...; |
23 | snd $port, type => data...; |
19 | snd $port, @msg; |
24 | snd $port, @msg; |
20 | snd @msg_with_first_element_being_a_port; |
25 | snd @msg_with_first_element_being_a_port; |
21 | |
26 | |
22 | # miniports |
27 | # creating/using ports, the simple way |
23 | my $miniport = port { my @msg = @_; 0 }; |
28 | my $somple_port = port { my @msg = @_; 0 }; |
24 | |
29 | |
25 | # full ports |
30 | # creating/using ports, tagged message matching |
26 | my $port = port; |
31 | my $port = port; |
27 | rcv $port, smartmatch => $cb->(@msg); |
|
|
28 | rcv $port, ping => sub { snd $_[0], "pong"; 0 }; |
32 | rcv $port, ping => sub { snd $_[0], "pong"; 0 }; |
29 | rcv $port, pong => sub { warn "pong received\n"; 0 }; |
33 | rcv $port, pong => sub { warn "pong received\n"; 0 }; |
30 | |
34 | |
31 | # remote ports |
35 | # create a port on another node |
32 | my $port = spawn $node, $initfunc, @initdata; |
36 | my $port = spawn $node, $initfunc, @initdata; |
33 | |
|
|
34 | # more, smarter, matches (_any_ is exported by this module) |
|
|
35 | rcv $port, [child_died => $pid] => sub { ... |
|
|
36 | rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3 |
|
|
37 | |
37 | |
38 | # monitoring |
38 | # monitoring |
39 | mon $port, $cb->(@msg) # callback is invoked on death |
39 | mon $port, $cb->(@msg) # callback is invoked on death |
40 | mon $port, $otherport # kill otherport on abnormal death |
40 | mon $port, $otherport # kill otherport on abnormal death |
41 | mon $port, $otherport, @msg # send message on death |
41 | mon $port, $otherport, @msg # send message on death |
… | |
… | |
143 | kil $SELF, die => $msg; |
143 | kil $SELF, die => $msg; |
144 | } |
144 | } |
145 | |
145 | |
146 | =item $thisnode = NODE / $NODE |
146 | =item $thisnode = NODE / $NODE |
147 | |
147 | |
148 | The C<NODE> function returns, and the C<$NODE> variable contains |
148 | The C<NODE> function returns, and the C<$NODE> variable contains the |
149 | the noderef of the local node. The value is initialised by a call |
149 | noderef of the local node. The value is initialised by a call to |
150 | to C<become_public> or C<become_slave>, after which all local port |
150 | C<initialise_node>. |
151 | identifiers become invalid. |
|
|
152 | |
151 | |
153 | =item $noderef = node_of $port |
152 | =item $noderef = node_of $port |
154 | |
153 | |
155 | Extracts and returns the noderef from a portid or a noderef. |
154 | Extracts and returns the noderef from a port ID or a noderef. |
156 | |
155 | |
157 | =item initialise_node $noderef, $seednode, $seednode... |
156 | =item initialise_node $noderef, $seednode, $seednode... |
158 | |
157 | |
159 | =item initialise_node "slave/", $master, $master... |
158 | =item initialise_node "slave/", $master, $master... |
160 | |
159 | |
… | |
… | |
163 | it should know the noderefs of some other nodes in the network. |
162 | it should know the noderefs of some other nodes in the network. |
164 | |
163 | |
165 | This function initialises a node - it must be called exactly once (or |
164 | This function initialises a node - it must be called exactly once (or |
166 | never) before calling other AnyEvent::MP functions. |
165 | never) before calling other AnyEvent::MP functions. |
167 | |
166 | |
168 | All arguments are noderefs, which can be either resolved or unresolved. |
167 | All arguments (optionally except for the first) are noderefs, which can be |
|
|
168 | either resolved or unresolved. |
|
|
169 | |
|
|
170 | The first argument will be looked up in the configuration database first |
|
|
171 | (if it is C<undef> then the current nodename will be used instead) to find |
|
|
172 | the relevant configuration profile (see L<aemp>). If none is found then |
|
|
173 | the default configuration is used. The configuration supplies additional |
|
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174 | seed/master nodes and can override the actual noderef. |
169 | |
175 | |
170 | There are two types of networked nodes, public nodes and slave nodes: |
176 | There are two types of networked nodes, public nodes and slave nodes: |
171 | |
177 | |
172 | =over 4 |
178 | =over 4 |
173 | |
179 | |
174 | =item public nodes |
180 | =item public nodes |
175 | |
181 | |
176 | For public nodes, C<$noderef> must either be a (possibly unresolved) |
182 | For public nodes, C<$noderef> (supplied either directly to |
177 | noderef, in which case it will be resolved, or C<undef> (or missing), in |
183 | C<initialise_node> or indirectly via a profile or the nodename) must be a |
178 | which case the noderef will be guessed. |
184 | noderef (possibly unresolved, in which case it will be resolved). |
179 | |
185 | |
180 | Afterwards, the node will bind itself on all endpoints and try to connect |
186 | After resolving, the node will bind itself on all endpoints and try to |
181 | to all additional C<$seednodes> that are specified. Seednodes are optional |
187 | connect to all additional C<$seednodes> that are specified. Seednodes are |
182 | and can be used to quickly bootstrap the node into an existing network. |
188 | optional and can be used to quickly bootstrap the node into an existing |
|
|
189 | network. |
183 | |
190 | |
184 | =item slave nodes |
191 | =item slave nodes |
185 | |
192 | |
186 | When the C<$noderef> is the special string C<slave/>, then the node will |
193 | When the C<$noderef> (either as given or overriden by the config file) |
|
|
194 | is the special string C<slave/>, then the node will become a slave |
187 | become a slave node. Slave nodes cannot be contacted from outside and will |
195 | node. Slave nodes cannot be contacted from outside and will route most of |
188 | route most of their traffic to the master node that they attach to. |
196 | their traffic to the master node that they attach to. |
189 | |
197 | |
190 | At least one additional noderef is required: The node will try to connect |
198 | At least one additional noderef is required (either by specifying it |
191 | to all of them and will become a slave attached to the first node it can |
199 | directly or because it is part of the configuration profile): The node |
192 | successfully connect to. |
200 | will try to connect to all of them and will become a slave attached to the |
|
|
201 | first node it can successfully connect to. |
193 | |
202 | |
194 | =back |
203 | =back |
195 | |
204 | |
196 | This function will block until all nodes have been resolved and, for slave |
205 | This function will block until all nodes have been resolved and, for slave |
197 | nodes, until it has successfully established a connection to a master |
206 | nodes, until it has successfully established a connection to a master |
198 | server. |
207 | server. |
199 | |
208 | |
200 | Example: become a public node listening on the default node. |
209 | Example: become a public node listening on the guessed noderef, or the one |
|
|
210 | specified via C<aemp> for the current node. This should be the most common |
|
|
211 | form of invocation for "daemon"-type nodes. |
201 | |
212 | |
202 | initialise_node; |
213 | initialise_node; |
|
|
214 | |
|
|
215 | Example: become a slave node to any of the the seednodes specified via |
|
|
216 | C<aemp>. This form is often used for commandline clients. |
|
|
217 | |
|
|
218 | initialise_node "slave/"; |
|
|
219 | |
|
|
220 | Example: become a slave node to any of the specified master servers. This |
|
|
221 | form is also often used for commandline clients. |
|
|
222 | |
|
|
223 | initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net"; |
203 | |
224 | |
204 | Example: become a public node, and try to contact some well-known master |
225 | Example: become a public node, and try to contact some well-known master |
205 | servers to become part of the network. |
226 | servers to become part of the network. |
206 | |
227 | |
207 | initialise_node undef, "master1", "master2"; |
228 | initialise_node undef, "master1", "master2"; |
… | |
… | |
210 | |
231 | |
211 | initialise_node 4041; |
232 | initialise_node 4041; |
212 | |
233 | |
213 | Example: become a public node, only visible on localhost port 4044. |
234 | Example: become a public node, only visible on localhost port 4044. |
214 | |
235 | |
215 | initialise_node "locahost:4044"; |
236 | initialise_node "localhost:4044"; |
216 | |
|
|
217 | Example: become a slave node to any of the specified master servers. |
|
|
218 | |
|
|
219 | initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net"; |
|
|
220 | |
237 | |
221 | =item $cv = resolve_node $noderef |
238 | =item $cv = resolve_node $noderef |
222 | |
239 | |
223 | Takes an unresolved node reference that may contain hostnames and |
240 | Takes an unresolved node reference that may contain hostnames and |
224 | abbreviated IDs, resolves all of them and returns a resolved node |
241 | abbreviated IDs, resolves all of them and returns a resolved node |
… | |
… | |
261 | =item snd $port, type => @data |
278 | =item snd $port, type => @data |
262 | |
279 | |
263 | =item snd $port, @msg |
280 | =item snd $port, @msg |
264 | |
281 | |
265 | Send the given message to the given port ID, which can identify either |
282 | Send the given message to the given port ID, which can identify either |
266 | a local or a remote port, and can be either a string or soemthignt hat |
283 | a local or a remote port, and must be a port ID. |
267 | stringifies a sa port ID (such as a port object :). |
|
|
268 | |
284 | |
269 | While the message can be about anything, it is highly recommended to use a |
285 | While the message can be about anything, it is highly recommended to use a |
270 | string as first element (a portid, or some word that indicates a request |
286 | string as first element (a port ID, or some word that indicates a request |
271 | type etc.). |
287 | type etc.). |
272 | |
288 | |
273 | The message data effectively becomes read-only after a call to this |
289 | The message data effectively becomes read-only after a call to this |
274 | function: modifying any argument is not allowed and can cause many |
290 | function: modifying any argument is not allowed and can cause many |
275 | problems. |
291 | problems. |
… | |
… | |
280 | that Storable can serialise and deserialise is allowed, and for the local |
296 | that Storable can serialise and deserialise is allowed, and for the local |
281 | node, anything can be passed. |
297 | node, anything can be passed. |
282 | |
298 | |
283 | =item $local_port = port |
299 | =item $local_port = port |
284 | |
300 | |
285 | Create a new local port object that can be used either as a pattern |
301 | Create a new local port object and returns its port ID. Initially it has |
286 | matching port ("full port") or a single-callback port ("miniport"), |
302 | no callbacks set and will throw an error when it receives messages. |
287 | depending on how C<rcv> callbacks are bound to the object. |
|
|
288 | |
303 | |
289 | =item $port = port { my @msg = @_; $finished } |
304 | =item $local_port = port { my @msg = @_ } |
290 | |
305 | |
291 | Creates a "miniport", that is, a very lightweight port without any pattern |
306 | Creates a new local port, and returns its ID. Semantically the same as |
292 | matching behind it, and returns its ID. Semantically the same as creating |
|
|
293 | a port and calling C<rcv $port, $callback> on it. |
307 | creating a port and calling C<rcv $port, $callback> on it. |
294 | |
308 | |
295 | The block will be called for every message received on the port. When the |
309 | The block will be called for every message received on the port, with the |
296 | callback returns a true value its job is considered "done" and the port |
310 | global variable C<$SELF> set to the port ID. Runtime errors will cause the |
297 | will be destroyed. Otherwise it will stay alive. |
311 | port to be C<kil>ed. The message will be passed as-is, no extra argument |
|
|
312 | (i.e. no port ID) will be passed to the callback. |
298 | |
313 | |
299 | The message will be passed as-is, no extra argument (i.e. no port id) will |
314 | If you want to stop/destroy the port, simply C<kil> it: |
300 | be passed to the callback. |
|
|
301 | |
315 | |
302 | If you need the local port id in the callback, this works nicely: |
316 | my $port = port { |
303 | |
317 | my @msg = @_; |
304 | my $port; $port = port { |
318 | ... |
305 | snd $otherport, reply => $port; |
319 | kil $SELF; |
306 | }; |
320 | }; |
307 | |
321 | |
308 | =cut |
322 | =cut |
309 | |
323 | |
310 | sub rcv($@); |
324 | sub rcv($@); |
|
|
325 | |
|
|
326 | sub _kilme { |
|
|
327 | die "received message on port without callback"; |
|
|
328 | } |
311 | |
329 | |
312 | sub port(;&) { |
330 | sub port(;&) { |
313 | my $id = "$UNIQ." . $ID++; |
331 | my $id = "$UNIQ." . $ID++; |
314 | my $port = "$NODE#$id"; |
332 | my $port = "$NODE#$id"; |
315 | |
333 | |
316 | if (@_) { |
334 | rcv $port, shift || \&_kilme; |
317 | rcv $port, shift; |
|
|
318 | } else { |
|
|
319 | $PORT{$id} = sub { }; # nop |
|
|
320 | } |
|
|
321 | |
335 | |
322 | $port |
336 | $port |
323 | } |
337 | } |
324 | |
338 | |
325 | =item reg $port, $name |
|
|
326 | |
|
|
327 | =item reg $name |
|
|
328 | |
|
|
329 | Registers the given port (or C<$SELF><<< if missing) under the name |
|
|
330 | C<$name>. If the name already exists it is replaced. |
|
|
331 | |
|
|
332 | A port can only be registered under one well known name. |
|
|
333 | |
|
|
334 | A port automatically becomes unregistered when it is killed. |
|
|
335 | |
|
|
336 | =cut |
|
|
337 | |
|
|
338 | sub reg(@) { |
|
|
339 | my $port = @_ > 1 ? shift : $SELF || Carp::croak 'reg: called with one argument only, but $SELF not set,'; |
|
|
340 | |
|
|
341 | $REG{$_[0]} = $port; |
|
|
342 | } |
|
|
343 | |
|
|
344 | =item rcv $port, $callback->(@msg) |
339 | =item rcv $local_port, $callback->(@msg) |
345 | |
340 | |
346 | Replaces the callback on the specified miniport (after converting it to |
341 | Replaces the default callback on the specified port. There is no way to |
347 | one if required). |
342 | remove the default callback: use C<sub { }> to disable it, or better |
348 | |
343 | C<kil> the port when it is no longer needed. |
349 | =item rcv $port, tagstring => $callback->(@msg), ... |
|
|
350 | |
|
|
351 | =item rcv $port, $smartmatch => $callback->(@msg), ... |
|
|
352 | |
|
|
353 | =item rcv $port, [$smartmatch...] => $callback->(@msg), ... |
|
|
354 | |
|
|
355 | Register callbacks to be called on matching messages on the given full |
|
|
356 | port (after converting it to one if required) and return the port. |
|
|
357 | |
|
|
358 | The callback has to return a true value when its work is done, after |
|
|
359 | which is will be removed, or a false value in which case it will stay |
|
|
360 | registered. |
|
|
361 | |
344 | |
362 | The global C<$SELF> (exported by this module) contains C<$port> while |
345 | The global C<$SELF> (exported by this module) contains C<$port> while |
363 | executing the callback. |
346 | executing the callback. Runtime errors during callback execution will |
|
|
347 | result in the port being C<kil>ed. |
364 | |
348 | |
365 | Runtime errors during callback execution will result in the port being |
349 | The default callback received all messages not matched by a more specific |
366 | C<kil>ed. |
350 | C<tag> match. |
367 | |
351 | |
368 | If the match is an array reference, then it will be matched against the |
352 | =item rcv $local_port, tag => $callback->(@msg_without_tag), ... |
369 | first elements of the message, otherwise only the first element is being |
|
|
370 | matched. |
|
|
371 | |
353 | |
372 | Any element in the match that is specified as C<_any_> (a function |
354 | Register callbacks to be called on messages starting with the given tag on |
373 | exported by this module) matches any single element of the message. |
355 | the given port (and return the port), or unregister it (when C<$callback> |
|
|
356 | is C<$undef>). |
374 | |
357 | |
375 | While not required, it is highly recommended that the first matching |
358 | The original message will be passed to the callback, after the first |
376 | element is a string identifying the message. The one-string-only match is |
359 | element (the tag) has been removed. The callback will use the same |
377 | also the most efficient match (by far). |
360 | environment as the default callback (see above). |
378 | |
361 | |
379 | Example: create a port and bind receivers on it in one go. |
362 | Example: create a port and bind receivers on it in one go. |
380 | |
363 | |
381 | my $port = rcv port, |
364 | my $port = rcv port, |
382 | msg1 => sub { ...; 0 }, |
365 | msg1 => sub { ... }, |
383 | msg2 => sub { ...; 0 }, |
366 | msg2 => sub { ... }, |
384 | ; |
367 | ; |
385 | |
368 | |
386 | Example: create a port, bind receivers and send it in a message elsewhere |
369 | Example: create a port, bind receivers and send it in a message elsewhere |
387 | in one go: |
370 | in one go: |
388 | |
371 | |
389 | snd $otherport, reply => |
372 | snd $otherport, reply => |
390 | rcv port, |
373 | rcv port, |
391 | msg1 => sub { ...; 0 }, |
374 | msg1 => sub { ... }, |
392 | ... |
375 | ... |
393 | ; |
376 | ; |
394 | |
377 | |
395 | =cut |
378 | =cut |
396 | |
379 | |
… | |
… | |
399 | my ($noderef, $portid) = split /#/, $port, 2; |
382 | my ($noderef, $portid) = split /#/, $port, 2; |
400 | |
383 | |
401 | ($NODE{$noderef} || add_node $noderef) == $NODE{""} |
384 | ($NODE{$noderef} || add_node $noderef) == $NODE{""} |
402 | or Carp::croak "$port: rcv can only be called on local ports, caught"; |
385 | or Carp::croak "$port: rcv can only be called on local ports, caught"; |
403 | |
386 | |
404 | if (@_ == 1) { |
387 | while (@_) { |
|
|
388 | if (ref $_[0]) { |
|
|
389 | if (my $self = $PORT_DATA{$portid}) { |
|
|
390 | "AnyEvent::MP::Port" eq ref $self |
|
|
391 | or Carp::croak "$port: rcv can only be called on message matching ports, caught"; |
|
|
392 | |
|
|
393 | $self->[2] = shift; |
|
|
394 | } else { |
405 | my $cb = shift; |
395 | my $cb = shift; |
406 | delete $PORT_DATA{$portid}; |
|
|
407 | $PORT{$portid} = sub { |
396 | $PORT{$portid} = sub { |
408 | local $SELF = $port; |
397 | local $SELF = $port; |
409 | eval { |
398 | eval { &$cb }; _self_die if $@; |
410 | &$cb |
399 | }; |
411 | and kil $port; |
|
|
412 | }; |
400 | } |
413 | _self_die if $@; |
401 | } elsif (defined $_[0]) { |
414 | }; |
|
|
415 | } else { |
|
|
416 | my $self = $PORT_DATA{$portid} ||= do { |
402 | my $self = $PORT_DATA{$portid} ||= do { |
417 | my $self = bless { |
403 | my $self = bless [$PORT{$port} || sub { }, { }, $port], "AnyEvent::MP::Port"; |
418 | id => $port, |
|
|
419 | }, "AnyEvent::MP::Port"; |
|
|
420 | |
404 | |
421 | $PORT{$portid} = sub { |
405 | $PORT{$portid} = sub { |
422 | local $SELF = $port; |
406 | local $SELF = $port; |
423 | |
407 | |
424 | eval { |
|
|
425 | for (@{ $self->{rc0}{$_[0]} }) { |
408 | if (my $cb = $self->[1]{$_[0]}) { |
426 | $_ && &{$_->[0]} |
409 | shift; |
427 | && undef $_; |
410 | eval { &$cb }; _self_die if $@; |
428 | } |
411 | } else { |
429 | |
|
|
430 | for (@{ $self->{rcv}{$_[0]} }) { |
|
|
431 | $_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1] |
|
|
432 | && &{$_->[0]} |
412 | &{ $self->[0] }; |
433 | && undef $_; |
|
|
434 | } |
|
|
435 | |
|
|
436 | for (@{ $self->{any} }) { |
|
|
437 | $_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1] |
|
|
438 | && &{$_->[0]} |
|
|
439 | && undef $_; |
|
|
440 | } |
413 | } |
441 | }; |
414 | }; |
442 | _self_die if $@; |
415 | |
|
|
416 | $self |
443 | }; |
417 | }; |
444 | |
418 | |
445 | $self |
|
|
446 | }; |
|
|
447 | |
|
|
448 | "AnyEvent::MP::Port" eq ref $self |
419 | "AnyEvent::MP::Port" eq ref $self |
449 | or Carp::croak "$port: rcv can only be called on message matching ports, caught"; |
420 | or Carp::croak "$port: rcv can only be called on message matching ports, caught"; |
450 | |
421 | |
451 | while (@_) { |
|
|
452 | my ($match, $cb) = splice @_, 0, 2; |
422 | my ($tag, $cb) = splice @_, 0, 2; |
453 | |
423 | |
454 | if (!ref $match) { |
424 | if (defined $cb) { |
455 | push @{ $self->{rc0}{$match} }, [$cb]; |
425 | $self->[1]{$tag} = $cb; |
456 | } elsif (("ARRAY" eq ref $match && !ref $match->[0])) { |
|
|
457 | my ($type, @match) = @$match; |
|
|
458 | @match |
|
|
459 | ? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match] |
|
|
460 | : push @{ $self->{rc0}{$match->[0]} }, [$cb]; |
|
|
461 | } else { |
426 | } else { |
462 | push @{ $self->{any} }, [$cb, $match]; |
427 | delete $self->[1]{$tag}; |
463 | } |
428 | } |
464 | } |
429 | } |
465 | } |
430 | } |
466 | |
431 | |
467 | $port |
432 | $port |
… | |
… | |
771 | convenience functionality. |
736 | convenience functionality. |
772 | |
737 | |
773 | This means that AEMP requires a less tightly controlled environment at the |
738 | This means that AEMP requires a less tightly controlled environment at the |
774 | cost of longer node references and a slightly higher management overhead. |
739 | cost of longer node references and a slightly higher management overhead. |
775 | |
740 | |
|
|
741 | =item Erlang has a "remote ports are like local ports" philosophy, AEMP |
|
|
742 | uses "local ports are like remote ports". |
|
|
743 | |
|
|
744 | The failure modes for local ports are quite different (runtime errors |
|
|
745 | only) then for remote ports - when a local port dies, you I<know> it dies, |
|
|
746 | when a connection to another node dies, you know nothing about the other |
|
|
747 | port. |
|
|
748 | |
|
|
749 | Erlang pretends remote ports are as reliable as local ports, even when |
|
|
750 | they are not. |
|
|
751 | |
|
|
752 | AEMP encourages a "treat remote ports differently" philosophy, with local |
|
|
753 | ports being the special case/exception, where transport errors cannot |
|
|
754 | occur. |
|
|
755 | |
776 | =item * Erlang uses processes and a mailbox, AEMP does not queue. |
756 | =item * Erlang uses processes and a mailbox, AEMP does not queue. |
777 | |
757 | |
778 | Erlang uses processes that selctively receive messages, and therefore |
758 | Erlang uses processes that selectively receive messages, and therefore |
779 | needs a queue. AEMP is event based, queuing messages would serve no useful |
759 | needs a queue. AEMP is event based, queuing messages would serve no |
780 | purpose. |
760 | useful purpose. For the same reason the pattern-matching abilities of |
|
|
761 | AnyEvent::MP are more limited, as there is little need to be able to |
|
|
762 | filter messages without dequeing them. |
781 | |
763 | |
782 | (But see L<Coro::MP> for a more Erlang-like process model on top of AEMP). |
764 | (But see L<Coro::MP> for a more Erlang-like process model on top of AEMP). |
783 | |
765 | |
784 | =item * Erlang sends are synchronous, AEMP sends are asynchronous. |
766 | =item * Erlang sends are synchronous, AEMP sends are asynchronous. |
785 | |
767 | |
786 | Sending messages in Erlang is synchronous and blocks the process. AEMP |
768 | Sending messages in Erlang is synchronous and blocks the process (and |
787 | sends are immediate, connection establishment is handled in the |
769 | so does not need a queue that can overflow). AEMP sends are immediate, |
788 | background. |
770 | connection establishment is handled in the background. |
789 | |
771 | |
790 | =item * Erlang can silently lose messages, AEMP cannot. |
772 | =item * Erlang suffers from silent message loss, AEMP does not. |
791 | |
773 | |
792 | Erlang makes few guarantees on messages delivery - messages can get lost |
774 | Erlang makes few guarantees on messages delivery - messages can get lost |
793 | without any of the processes realising it (i.e. you send messages a, b, |
775 | without any of the processes realising it (i.e. you send messages a, b, |
794 | and c, and the other side only receives messages a and c). |
776 | and c, and the other side only receives messages a and c). |
795 | |
777 | |
… | |
… | |
807 | eventually be killed - it cannot happen that a node detects a port as dead |
789 | eventually be killed - it cannot happen that a node detects a port as dead |
808 | and then later sends messages to it, finding it is still alive. |
790 | and then later sends messages to it, finding it is still alive. |
809 | |
791 | |
810 | =item * Erlang can send messages to the wrong port, AEMP does not. |
792 | =item * Erlang can send messages to the wrong port, AEMP does not. |
811 | |
793 | |
812 | In Erlang it is quite possible that a node that restarts reuses a process |
794 | In Erlang it is quite likely that a node that restarts reuses a process ID |
813 | ID known to other nodes for a completely different process, causing |
795 | known to other nodes for a completely different process, causing messages |
814 | messages destined for that process to end up in an unrelated process. |
796 | destined for that process to end up in an unrelated process. |
815 | |
797 | |
816 | AEMP never reuses port IDs, so old messages or old port IDs floating |
798 | AEMP never reuses port IDs, so old messages or old port IDs floating |
817 | around in the network will not be sent to an unrelated port. |
799 | around in the network will not be sent to an unrelated port. |
818 | |
800 | |
819 | =item * Erlang uses unprotected connections, AEMP uses secure |
801 | =item * Erlang uses unprotected connections, AEMP uses secure |
… | |
… | |
855 | This also saves round-trips and avoids sending messages to the wrong port |
837 | This also saves round-trips and avoids sending messages to the wrong port |
856 | (hard to do in Erlang). |
838 | (hard to do in Erlang). |
857 | |
839 | |
858 | =back |
840 | =back |
859 | |
841 | |
|
|
842 | =head1 RATIONALE |
|
|
843 | |
|
|
844 | =over 4 |
|
|
845 | |
|
|
846 | =item Why strings for ports and noderefs, why not objects? |
|
|
847 | |
|
|
848 | We considered "objects", but found that the actual number of methods |
|
|
849 | thatc an be called are very low. Since port IDs and noderefs travel over |
|
|
850 | the network frequently, the serialising/deserialising would add lots of |
|
|
851 | overhead, as well as having to keep a proxy object. |
|
|
852 | |
|
|
853 | Strings can easily be printed, easily serialised etc. and need no special |
|
|
854 | procedures to be "valid". |
|
|
855 | |
|
|
856 | And a a miniport consists of a single closure stored in a global hash - it |
|
|
857 | can't become much cheaper. |
|
|
858 | |
|
|
859 | =item Why favour JSON, why not real serialising format such as Storable? |
|
|
860 | |
|
|
861 | In fact, any AnyEvent::MP node will happily accept Storable as framing |
|
|
862 | format, but currently there is no way to make a node use Storable by |
|
|
863 | default. |
|
|
864 | |
|
|
865 | The default framing protocol is JSON because a) JSON::XS is many times |
|
|
866 | faster for small messages and b) most importantly, after years of |
|
|
867 | experience we found that object serialisation is causing more problems |
|
|
868 | than it gains: Just like function calls, objects simply do not travel |
|
|
869 | easily over the network, mostly because they will always be a copy, so you |
|
|
870 | always have to re-think your design. |
|
|
871 | |
|
|
872 | Keeping your messages simple, concentrating on data structures rather than |
|
|
873 | objects, will keep your messages clean, tidy and efficient. |
|
|
874 | |
|
|
875 | =back |
|
|
876 | |
860 | =head1 SEE ALSO |
877 | =head1 SEE ALSO |
861 | |
878 | |
862 | L<AnyEvent>. |
879 | L<AnyEvent>. |
863 | |
880 | |
864 | =head1 AUTHOR |
881 | =head1 AUTHOR |