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Revision 1.90 by root, Tue Sep 22 09:38:28 2009 UTC

1=head1 NAME 1=head1 NAME
2 2
3AnyEvent::MP - multi-processing/message-passing framework 3AnyEvent::MP - erlang-style multi-processing/message-passing framework
4 4
5=head1 SYNOPSIS 5=head1 SYNOPSIS
6 6
7 use AnyEvent::MP; 7 use AnyEvent::MP;
8 8
9 $NODE # contains this node's noderef 9 $NODE # contains this node's node ID
10 NODE # returns this node's noderef 10 NODE # returns this node's node ID
11 NODE $port # returns the noderef of the port
12 11
12 $SELF # receiving/own port id in rcv callbacks
13
14 # initialise the node so it can send/receive messages
15 configure;
16
17 # ports are message destinations
18
19 # sending messages
13 snd $port, type => data...; 20 snd $port, type => data...;
21 snd $port, @msg;
22 snd @msg_with_first_element_being_a_port;
14 23
15 $SELF # receiving/own port id in rcv callbacks 24 # creating/using ports, the simple way
25 my $simple_port = port { my @msg = @_ };
16 26
17 rcv $port, smartmatch => $cb->($port, @msg); 27 # creating/using ports, tagged message matching
18 28 my $port = port;
19 # examples:
20 rcv $port2, ping => sub { snd $_[0], "pong"; 0 }; 29 rcv $port, ping => sub { snd $_[0], "pong" };
21 rcv $port1, pong => sub { warn "pong received\n" }; 30 rcv $port, pong => sub { warn "pong received\n" };
22 snd $port2, ping => $port1;
23 31
24 # more, smarter, matches (_any_ is exported by this module) 32 # create a port on another node
25 rcv $port, [child_died => $pid] => sub { ... 33 my $port = spawn $node, $initfunc, @initdata;
26 rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3
27
28 # linking two ports, so they both crash together
29 lnk $port1, $port2;
30 34
31 # monitoring 35 # monitoring
32 mon $port, $cb->(@msg) # callback is invoked on death 36 mon $localport, $cb->(@msg) # callback is invoked on death
33 mon $port, $otherport # kill otherport on abnormal death 37 mon $localport, $otherport # kill otherport on abnormal death
34 mon $port, $otherport, @msg # send message on death 38 mon $localport, $otherport, @msg # send message on death
39
40=head1 CURRENT STATUS
41
42 bin/aemp - stable.
43 AnyEvent::MP - stable API, should work.
44 AnyEvent::MP::Intro - explains most concepts.
45 AnyEvent::MP::Kernel - mostly stable API.
46 AnyEvent::MP::Global - stable API.
35 47
36=head1 DESCRIPTION 48=head1 DESCRIPTION
37 49
38This module (-family) implements a simple message passing framework. 50This module (-family) implements a simple message passing framework.
39 51
40Despite its simplicity, you can securely message other processes running 52Despite its simplicity, you can securely message other processes running
41on the same or other hosts. 53on the same or other hosts, and you can supervise entities remotely.
42 54
43For an introduction to this module family, see the L<AnyEvent::MP::Intro> 55For an introduction to this module family, see the L<AnyEvent::MP::Intro>
44manual page. 56manual page and the examples under F<eg/>.
45
46At the moment, this module family is severly broken and underdocumented,
47so do not use. This was uploaded mainly to reserve the CPAN namespace -
48stay tuned! The basic API should be finished, however.
49 57
50=head1 CONCEPTS 58=head1 CONCEPTS
51 59
52=over 4 60=over 4
53 61
54=item port 62=item port
55 63
56A port is something you can send messages to (with the C<snd> function). 64Not to be confused with a TCP port, a "port" is something you can send
65messages to (with the C<snd> function).
57 66
58Some ports allow you to register C<rcv> handlers that can match specific 67Ports allow you to register C<rcv> handlers that can match all or just
59messages. All C<rcv> handlers will receive messages they match, messages 68some messages. Messages send to ports will not be queued, regardless of
60will not be queued. 69anything was listening for them or not.
61 70
62=item port id - C<noderef#portname> 71=item port ID - C<nodeid#portname>
63 72
64A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as 73A port ID is the concatenation of a node ID, a hash-mark (C<#>) as
65separator, and a port name (a printable string of unspecified format). An 74separator, and a port name (a printable string of unspecified format).
66exception is the the node port, whose ID is identical to its node
67reference.
68 75
69=item node 76=item node
70 77
71A node is a single process containing at least one port - the node 78A node is a single process containing at least one port - the node port,
72port. You can send messages to node ports to find existing ports or to 79which enables nodes to manage each other remotely, and to create new
73create new ports, among other things. 80ports.
74 81
75Nodes are either private (single-process only), slaves (connected to a 82Nodes are either public (have one or more listening ports) or private
76master node only) or public nodes (connectable from unrelated nodes). 83(no listening ports). Private nodes cannot talk to other private nodes
84currently.
77 85
78=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id> 86=item node ID - C<[A-Z_][a-zA-Z0-9_\-.:]*>
79 87
80A node reference is a string that either simply identifies the node (for 88A node ID is a string that uniquely identifies the node within a
81private and slave nodes), or contains a recipe on how to reach a given 89network. Depending on the configuration used, node IDs can look like a
82node (for public nodes). 90hostname, a hostname and a port, or a random string. AnyEvent::MP itself
91doesn't interpret node IDs in any way.
83 92
84This recipe is simply a comma-separated list of C<address:port> pairs (for 93=item binds - C<ip:port>
85TCP/IP, other protocols might look different).
86 94
87Node references come in two flavours: resolved (containing only numerical 95Nodes can only talk to each other by creating some kind of connection to
88addresses) or unresolved (where hostnames are used instead of addresses). 96each other. To do this, nodes should listen on one or more local transport
97endpoints - binds. Currently, only standard C<ip:port> specifications can
98be used, which specify TCP ports to listen on.
89 99
90Before using an unresolved node reference in a message you first have to 100=item seed nodes
91resolve it. 101
102When a node starts, it knows nothing about the network. To teach the node
103about the network it first has to contact some other node within the
104network. This node is called a seed.
105
106Apart from the fact that other nodes know them as seed nodes and they have
107to have fixed listening addresses, seed nodes are perfectly normal nodes -
108any node can function as a seed node for others.
109
110In addition to discovering the network, seed nodes are also used to
111maintain the network and to connect nodes that otherwise would have
112trouble connecting. They form the backbone of an AnyEvent::MP network.
113
114Seed nodes are expected to be long-running, and at least one seed node
115should always be available. They should also be relatively responsive - a
116seed node that blocks for long periods will slow down everybody else.
117
118=item seeds - C<host:port>
119
120Seeds are transport endpoint(s) (usually a hostname/IP address and a
121TCP port) of nodes thta should be used as seed nodes.
122
123The nodes listening on those endpoints are expected to be long-running,
124and at least one of those should always be available. When nodes run out
125of connections (e.g. due to a network error), they try to re-establish
126connections to some seednodes again to join the network.
92 127
93=back 128=back
94 129
95=head1 VARIABLES/FUNCTIONS 130=head1 VARIABLES/FUNCTIONS
96 131
98 133
99=cut 134=cut
100 135
101package AnyEvent::MP; 136package AnyEvent::MP;
102 137
103use AnyEvent::MP::Base; 138use AnyEvent::MP::Kernel;
104 139
105use common::sense; 140use common::sense;
106 141
107use Carp (); 142use Carp ();
108 143
109use AE (); 144use AE ();
110 145
111use base "Exporter"; 146use base "Exporter";
112 147
113our $VERSION = '0.1'; 148our $VERSION = $AnyEvent::MP::Kernel::VERSION;
149
114our @EXPORT = qw( 150our @EXPORT = qw(
115 NODE $NODE *SELF node_of _any_ 151 NODE $NODE *SELF node_of after
116 resolve_node initialise_node 152 configure
117 snd rcv mon kil reg psub 153 snd rcv mon mon_guard kil reg psub spawn cal
118 port 154 port
119); 155);
120 156
121our $SELF; 157our $SELF;
122 158
126 kil $SELF, die => $msg; 162 kil $SELF, die => $msg;
127} 163}
128 164
129=item $thisnode = NODE / $NODE 165=item $thisnode = NODE / $NODE
130 166
131The C<NODE> function returns, and the C<$NODE> variable contains 167The C<NODE> function returns, and the C<$NODE> variable contains, the node
132the noderef of the local node. The value is initialised by a call 168ID of the node running in the current process. This value is initialised by
133to C<become_public> or C<become_slave>, after which all local port 169a call to C<configure>.
134identifiers become invalid.
135 170
136=item $noderef = node_of $port 171=item $nodeid = node_of $port
137 172
138Extracts and returns the noderef from a portid or a noderef. 173Extracts and returns the node ID from a port ID or a node ID.
139 174
140=item initialise_node $noderef, $seednode, $seednode... 175=item configure $profile, key => value...
141 176
142=item initialise_node "slave/", $master, $master... 177=item configure key => value...
143 178
144Before a node can talk to other nodes on the network it has to initialise 179Before a node can talk to other nodes on the network (i.e. enter
145itself - the minimum a node needs to know is it's own name, and optionally 180"distributed mode") it has to configure itself - the minimum a node needs
146it should know the noderefs of some other nodes in the network. 181to know is its own name, and optionally it should know the addresses of
182some other nodes in the network to discover other nodes.
147 183
148This function initialises a node - it must be called exactly once (or 184This function configures a node - it must be called exactly once (or
149never) before calling other AnyEvent::MP functions. 185never) before calling other AnyEvent::MP functions.
150 186
151All arguments are noderefs, which can be either resolved or unresolved.
152
153There are two types of networked nodes, public nodes and slave nodes:
154
155=over 4 187=over 4
156 188
157=item public nodes 189=item step 1, gathering configuration from profiles
158 190
159For public nodes, C<$noderef> must either be a (possibly unresolved) 191The function first looks up a profile in the aemp configuration (see the
160noderef, in which case it will be resolved, or C<undef> (or missing), in 192L<aemp> commandline utility). The profile name can be specified via the
161which case the noderef will be guessed. 193named C<profile> parameter or can simply be the first parameter). If it is
194missing, then the nodename (F<uname -n>) will be used as profile name.
162 195
163Afterwards, the node will bind itself on all endpoints and try to connect 196The profile data is then gathered as follows:
164to all additional C<$seednodes> that are specified. Seednodes are optional
165and can be used to quickly bootstrap the node into an existing network.
166 197
167=item slave nodes 198First, all remaining key => value pairs (all of which are conveniently
199undocumented at the moment) will be interpreted as configuration
200data. Then they will be overwritten by any values specified in the global
201default configuration (see the F<aemp> utility), then the chain of
202profiles chosen by the profile name (and any C<parent> attributes).
168 203
169When the C<$noderef> is the special string C<slave/>, then the node will 204That means that the values specified in the profile have highest priority
170become a slave node. Slave nodes cannot be contacted from outside and will 205and the values specified directly via C<configure> have lowest priority,
171route most of their traffic to the master node that they attach to. 206and can only be used to specify defaults.
172 207
173At least one additional noderef is required: The node will try to connect 208If the profile specifies a node ID, then this will become the node ID of
174to all of them and will become a slave attached to the first node it can 209this process. If not, then the profile name will be used as node ID. The
175successfully connect to. 210special node ID of C<anon/> will be replaced by a random node ID.
211
212=item step 2, bind listener sockets
213
214The next step is to look up the binds in the profile, followed by binding
215aemp protocol listeners on all binds specified (it is possible and valid
216to have no binds, meaning that the node cannot be contacted form the
217outside. This means the node cannot talk to other nodes that also have no
218binds, but it can still talk to all "normal" nodes).
219
220If the profile does not specify a binds list, then a default of C<*> is
221used, meaning the node will bind on a dynamically-assigned port on every
222local IP address it finds.
223
224=item step 3, connect to seed nodes
225
226As the last step, the seeds list from the profile is passed to the
227L<AnyEvent::MP::Global> module, which will then use it to keep
228connectivity with at least one node at any point in time.
176 229
177=back 230=back
178 231
179This function will block until all nodes have been resolved and, for slave 232Example: become a distributed node using the local node name as profile.
180nodes, until it has successfully established a connection to a master 233This should be the most common form of invocation for "daemon"-type nodes.
181server.
182 234
183Example: become a public node listening on the default node. 235 configure
184 236
185 initialise_node; 237Example: become an anonymous node. This form is often used for commandline
238clients.
186 239
187Example: become a public node, and try to contact some well-known master 240 configure nodeid => "anon/";
188servers to become part of the network.
189 241
190 initialise_node undef, "master1", "master2"; 242Example: configure a node using a profile called seed, which si suitable
243for a seed node as it binds on all local addresses on a fixed port (4040,
244customary for aemp).
191 245
192Example: become a public node listening on port C<4041>. 246 # use the aemp commandline utility
247 # aemp profile seed nodeid anon/ binds '*:4040'
193 248
194 initialise_node 4041; 249 # then use it
250 configure profile => "seed";
195 251
196Example: become a public node, only visible on localhost port 4044. 252 # or simply use aemp from the shell again:
253 # aemp run profile seed
197 254
198 initialise_node "locahost:4044"; 255 # or provide a nicer-to-remember nodeid
199 256 # aemp run profile seed nodeid "$(hostname)"
200Example: become a slave node to any of the specified master servers.
201
202 initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
203
204=item $cv = resolve_node $noderef
205
206Takes an unresolved node reference that may contain hostnames and
207abbreviated IDs, resolves all of them and returns a resolved node
208reference.
209
210In addition to C<address:port> pairs allowed in resolved noderefs, the
211following forms are supported:
212
213=over 4
214
215=item the empty string
216
217An empty-string component gets resolved as if the default port (4040) was
218specified.
219
220=item naked port numbers (e.g. C<1234>)
221
222These are resolved by prepending the local nodename and a colon, to be
223further resolved.
224
225=item hostnames (e.g. C<localhost:1234>, C<localhost>)
226
227These are resolved by using AnyEvent::DNS to resolve them, optionally
228looking up SRV records for the C<aemp=4040> port, if no port was
229specified.
230
231=back
232 257
233=item $SELF 258=item $SELF
234 259
235Contains the current port id while executing C<rcv> callbacks or C<psub> 260Contains the current port id while executing C<rcv> callbacks or C<psub>
236blocks. 261blocks.
237 262
238=item SELF, %SELF, @SELF... 263=item *SELF, SELF, %SELF, @SELF...
239 264
240Due to some quirks in how perl exports variables, it is impossible to 265Due to some quirks in how perl exports variables, it is impossible to
241just export C<$SELF>, all the symbols called C<SELF> are exported by this 266just export C<$SELF>, all the symbols named C<SELF> are exported by this
242module, but only C<$SELF> is currently used. 267module, but only C<$SELF> is currently used.
243 268
244=item snd $port, type => @data 269=item snd $port, type => @data
245 270
246=item snd $port, @msg 271=item snd $port, @msg
247 272
248Send the given message to the given port ID, which can identify either 273Send the given message to the given port, which can identify either a
249a local or a remote port, and can be either a string or soemthignt hat 274local or a remote port, and must be a port ID.
250stringifies a sa port ID (such as a port object :).
251 275
252While the message can be about anything, it is highly recommended to use a 276While the message can be almost anything, it is highly recommended to
253string as first element (a portid, or some word that indicates a request 277use a string as first element (a port ID, or some word that indicates a
254type etc.). 278request type etc.) and to consist if only simple perl values (scalars,
279arrays, hashes) - if you think you need to pass an object, think again.
255 280
256The message data effectively becomes read-only after a call to this 281The message data logically becomes read-only after a call to this
257function: modifying any argument is not allowed and can cause many 282function: modifying any argument (or values referenced by them) is
258problems. 283forbidden, as there can be considerable time between the call to C<snd>
284and the time the message is actually being serialised - in fact, it might
285never be copied as within the same process it is simply handed to the
286receiving port.
259 287
260The type of data you can transfer depends on the transport protocol: when 288The type of data you can transfer depends on the transport protocol: when
261JSON is used, then only strings, numbers and arrays and hashes consisting 289JSON is used, then only strings, numbers and arrays and hashes consisting
262of those are allowed (no objects). When Storable is used, then anything 290of those are allowed (no objects). When Storable is used, then anything
263that Storable can serialise and deserialise is allowed, and for the local 291that Storable can serialise and deserialise is allowed, and for the local
264node, anything can be passed. 292node, anything can be passed. Best rely only on the common denominator of
293these.
265 294
266=item $local_port = port 295=item $local_port = port
267 296
268Create a new local port object that can be used either as a pattern 297Create a new local port object and returns its port ID. Initially it has
269matching port ("full port") or a single-callback port ("miniport"), 298no callbacks set and will throw an error when it receives messages.
270depending on how C<rcv> callbacks are bound to the object.
271 299
272=item $port = port { my @msg = @_; $finished } 300=item $local_port = port { my @msg = @_ }
273 301
274Creates a "miniport", that is, a very lightweight port without any pattern 302Creates a new local port, and returns its ID. Semantically the same as
275matching behind it, and returns its ID. Semantically the same as creating
276a port and calling C<rcv $port, $callback> on it. 303creating a port and calling C<rcv $port, $callback> on it.
277 304
278The block will be called for every message received on the port. When the 305The block will be called for every message received on the port, with the
279callback returns a true value its job is considered "done" and the port 306global variable C<$SELF> set to the port ID. Runtime errors will cause the
280will be destroyed. Otherwise it will stay alive. 307port to be C<kil>ed. The message will be passed as-is, no extra argument
308(i.e. no port ID) will be passed to the callback.
281 309
282The message will be passed as-is, no extra argument (i.e. no port id) will 310If you want to stop/destroy the port, simply C<kil> it:
283be passed to the callback.
284 311
285If you need the local port id in the callback, this works nicely: 312 my $port = port {
286 313 my @msg = @_;
287 my $port; $port = port { 314 ...
288 snd $otherport, reply => $port; 315 kil $SELF;
289 }; 316 };
290 317
291=cut 318=cut
292 319
293sub rcv($@); 320sub rcv($@);
321
322sub _kilme {
323 die "received message on port without callback";
324}
294 325
295sub port(;&) { 326sub port(;&) {
296 my $id = "$UNIQ." . $ID++; 327 my $id = "$UNIQ." . $ID++;
297 my $port = "$NODE#$id"; 328 my $port = "$NODE#$id";
298 329
299 if (@_) { 330 rcv $port, shift || \&_kilme;
300 rcv $port, shift;
301 } else {
302 $PORT{$id} = sub { }; # nop
303 }
304 331
305 $port 332 $port
306} 333}
307 334
308=item reg $port, $name
309
310Registers the given port under the name C<$name>. If the name already
311exists it is replaced.
312
313A port can only be registered under one well known name.
314
315A port automatically becomes unregistered when it is killed.
316
317=cut
318
319sub reg(@) {
320 my ($port, $name) = @_;
321
322 $REG{$name} = $port;
323}
324
325=item rcv $port, $callback->(@msg) 335=item rcv $local_port, $callback->(@msg)
326 336
327Replaces the callback on the specified miniport (after converting it to 337Replaces the default callback on the specified port. There is no way to
328one if required). 338remove the default callback: use C<sub { }> to disable it, or better
329 339C<kil> the port when it is no longer needed.
330=item rcv $port, tagstring => $callback->(@msg), ...
331
332=item rcv $port, $smartmatch => $callback->(@msg), ...
333
334=item rcv $port, [$smartmatch...] => $callback->(@msg), ...
335
336Register callbacks to be called on matching messages on the given full
337port (after converting it to one if required).
338
339The callback has to return a true value when its work is done, after
340which is will be removed, or a false value in which case it will stay
341registered.
342 340
343The global C<$SELF> (exported by this module) contains C<$port> while 341The global C<$SELF> (exported by this module) contains C<$port> while
344executing the callback. 342executing the callback. Runtime errors during callback execution will
343result in the port being C<kil>ed.
345 344
346Runtime errors wdurign callback execution will result in the port being 345The default callback received all messages not matched by a more specific
347C<kil>ed. 346C<tag> match.
348 347
349If the match is an array reference, then it will be matched against the 348=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
350first elements of the message, otherwise only the first element is being
351matched.
352 349
353Any element in the match that is specified as C<_any_> (a function 350Register (or replace) callbacks to be called on messages starting with the
354exported by this module) matches any single element of the message. 351given tag on the given port (and return the port), or unregister it (when
352C<$callback> is C<$undef> or missing). There can only be one callback
353registered for each tag.
355 354
356While not required, it is highly recommended that the first matching 355The original message will be passed to the callback, after the first
357element is a string identifying the message. The one-string-only match is 356element (the tag) has been removed. The callback will use the same
358also the most efficient match (by far). 357environment as the default callback (see above).
358
359Example: create a port and bind receivers on it in one go.
360
361 my $port = rcv port,
362 msg1 => sub { ... },
363 msg2 => sub { ... },
364 ;
365
366Example: create a port, bind receivers and send it in a message elsewhere
367in one go:
368
369 snd $otherport, reply =>
370 rcv port,
371 msg1 => sub { ... },
372 ...
373 ;
374
375Example: temporarily register a rcv callback for a tag matching some port
376(e.g. for a rpc reply) and unregister it after a message was received.
377
378 rcv $port, $otherport => sub {
379 my @reply = @_;
380
381 rcv $SELF, $otherport;
382 };
359 383
360=cut 384=cut
361 385
362sub rcv($@) { 386sub rcv($@) {
363 my $port = shift; 387 my $port = shift;
364 my ($noderef, $portid) = split /#/, $port, 2; 388 my ($nodeid, $portid) = split /#/, $port, 2;
365 389
366 ($NODE{$noderef} || add_node $noderef) == $NODE{""} 390 $NODE{$nodeid} == $NODE{""}
367 or Carp::croak "$port: rcv can only be called on local ports, caught"; 391 or Carp::croak "$port: rcv can only be called on local ports, caught";
368 392
369 if (@_ == 1) { 393 while (@_) {
394 if (ref $_[0]) {
395 if (my $self = $PORT_DATA{$portid}) {
396 "AnyEvent::MP::Port" eq ref $self
397 or Carp::croak "$port: rcv can only be called on message matching ports, caught";
398
399 $self->[2] = shift;
400 } else {
370 my $cb = shift; 401 my $cb = shift;
371 delete $PORT_DATA{$portid};
372 $PORT{$portid} = sub { 402 $PORT{$portid} = sub {
373 local $SELF = $port; 403 local $SELF = $port;
374 eval { 404 eval { &$cb }; _self_die if $@;
375 &$cb 405 };
376 and kil $port;
377 }; 406 }
378 _self_die if $@; 407 } elsif (defined $_[0]) {
379 };
380 } else {
381 my $self = $PORT_DATA{$portid} ||= do { 408 my $self = $PORT_DATA{$portid} ||= do {
382 my $self = bless { 409 my $self = bless [$PORT{$port} || sub { }, { }, $port], "AnyEvent::MP::Port";
383 id => $port,
384 }, "AnyEvent::MP::Port";
385 410
386 $PORT{$portid} = sub { 411 $PORT{$portid} = sub {
387 local $SELF = $port; 412 local $SELF = $port;
388 413
389 eval {
390 for (@{ $self->{rc0}{$_[0]} }) { 414 if (my $cb = $self->[1]{$_[0]}) {
391 $_ && &{$_->[0]} 415 shift;
392 && undef $_; 416 eval { &$cb }; _self_die if $@;
393 } 417 } else {
394
395 for (@{ $self->{rcv}{$_[0]} }) {
396 $_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
397 && &{$_->[0]} 418 &{ $self->[0] };
398 && undef $_;
399 }
400
401 for (@{ $self->{any} }) {
402 $_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
403 && &{$_->[0]}
404 && undef $_;
405 } 419 }
406 }; 420 };
407 _self_die if $@; 421
422 $self
408 }; 423 };
409 424
410 $self
411 };
412
413 "AnyEvent::MP::Port" eq ref $self 425 "AnyEvent::MP::Port" eq ref $self
414 or Carp::croak "$port: rcv can only be called on message matching ports, caught"; 426 or Carp::croak "$port: rcv can only be called on message matching ports, caught";
415 427
416 while (@_) {
417 my ($match, $cb) = splice @_, 0, 2; 428 my ($tag, $cb) = splice @_, 0, 2;
418 429
419 if (!ref $match) { 430 if (defined $cb) {
420 push @{ $self->{rc0}{$match} }, [$cb]; 431 $self->[1]{$tag} = $cb;
421 } elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
422 my ($type, @match) = @$match;
423 @match
424 ? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
425 : push @{ $self->{rc0}{$match->[0]} }, [$cb];
426 } else { 432 } else {
427 push @{ $self->{any} }, [$cb, $match]; 433 delete $self->[1]{$tag};
428 } 434 }
429 } 435 }
430 } 436 }
431 437
432 $port 438 $port
468 $res 474 $res
469 } 475 }
470 } 476 }
471} 477}
472 478
473=item $guard = mon $port, $cb->(@reason) 479=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
474 480
475=item $guard = mon $port, $otherport 481=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
476 482
477=item $guard = mon $port, $otherport, @msg 483=item $guard = mon $port # kill $SELF when $port dies
478 484
485=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
486
479Monitor the given port and do something when the port is killed. 487Monitor the given port and do something when the port is killed or
488messages to it were lost, and optionally return a guard that can be used
489to stop monitoring again.
480 490
481In the first form, the callback is simply called with any number 491In the first form (callback), the callback is simply called with any
482of C<@reason> elements (no @reason means that the port was deleted 492number of C<@reason> elements (no @reason means that the port was deleted
483"normally"). Note also that I<< the callback B<must> never die >>, so use 493"normally"). Note also that I<< the callback B<must> never die >>, so use
484C<eval> if unsure. 494C<eval> if unsure.
485 495
486In the second form, the other port will be C<kil>'ed with C<@reason>, iff 496In the second form (another port given), the other port (C<$rcvport>)
487a @reason was specified, i.e. on "normal" kils nothing happens, while 497will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
488under all other conditions, the other port is killed with the same reason. 498"normal" kils nothing happens, while under all other conditions, the other
499port is killed with the same reason.
489 500
501The third form (kill self) is the same as the second form, except that
502C<$rvport> defaults to C<$SELF>.
503
490In the last form, a message of the form C<@msg, @reason> will be C<snd>. 504In the last form (message), a message of the form C<@msg, @reason> will be
505C<snd>.
506
507Monitoring-actions are one-shot: once messages are lost (and a monitoring
508alert was raised), they are removed and will not trigger again.
509
510As a rule of thumb, monitoring requests should always monitor a port from
511a local port (or callback). The reason is that kill messages might get
512lost, just like any other message. Another less obvious reason is that
513even monitoring requests can get lost (for example, when the connection
514to the other node goes down permanently). When monitoring a port locally
515these problems do not exist.
516
517C<mon> effectively guarantees that, in the absence of hardware failures,
518after starting the monitor, either all messages sent to the port will
519arrive, or the monitoring action will be invoked after possible message
520loss has been detected. No messages will be lost "in between" (after
521the first lost message no further messages will be received by the
522port). After the monitoring action was invoked, further messages might get
523delivered again.
524
525Inter-host-connection timeouts and monitoring depend on the transport
526used. The only transport currently implemented is TCP, and AnyEvent::MP
527relies on TCP to detect node-downs (this can take 10-15 minutes on a
528non-idle connection, and usually around two hours for idle conenctions).
529
530This means that monitoring is good for program errors and cleaning up
531stuff eventually, but they are no replacement for a timeout when you need
532to ensure some maximum latency.
491 533
492Example: call a given callback when C<$port> is killed. 534Example: call a given callback when C<$port> is killed.
493 535
494 mon $port, sub { warn "port died because of <@_>\n" }; 536 mon $port, sub { warn "port died because of <@_>\n" };
495 537
496Example: kill ourselves when C<$port> is killed abnormally. 538Example: kill ourselves when C<$port> is killed abnormally.
497 539
498 mon $port, $self; 540 mon $port;
499 541
500Example: send us a restart message another C<$port> is killed. 542Example: send us a restart message when another C<$port> is killed.
501 543
502 mon $port, $self => "restart"; 544 mon $port, $self => "restart";
503 545
504=cut 546=cut
505 547
506sub mon { 548sub mon {
507 my ($noderef, $port) = split /#/, shift, 2; 549 my ($nodeid, $port) = split /#/, shift, 2;
508 550
509 my $node = $NODE{$noderef} || add_node $noderef; 551 my $node = $NODE{$nodeid} || add_node $nodeid;
510 552
511 my $cb = shift; 553 my $cb = @_ ? shift : $SELF || Carp::croak 'mon: called with one argument only, but $SELF not set,';
512 554
513 unless (ref $cb) { 555 unless (ref $cb) {
514 if (@_) { 556 if (@_) {
515 # send a kill info message 557 # send a kill info message
516 my (@msg) = ($cb, @_); 558 my (@msg) = ($cb, @_);
534is killed, the references will be freed. 576is killed, the references will be freed.
535 577
536Optionally returns a guard that will stop the monitoring. 578Optionally returns a guard that will stop the monitoring.
537 579
538This function is useful when you create e.g. timers or other watchers and 580This function is useful when you create e.g. timers or other watchers and
539want to free them when the port gets killed: 581want to free them when the port gets killed (note the use of C<psub>):
540 582
541 $port->rcv (start => sub { 583 $port->rcv (start => sub {
542 my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub { 584 my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
543 undef $timer if 0.9 < rand; 585 undef $timer if 0.9 < rand;
544 }); 586 });
545 }); 587 });
546 588
547=cut 589=cut
548 590
549sub mon_guard { 591sub mon_guard {
550 my ($port, @refs) = @_; 592 my ($port, @refs) = @_;
551 593
594 #TODO: mon-less form?
595
552 mon $port, sub { 0 && @refs } 596 mon $port, sub { 0 && @refs }
553} 597}
554 598
555=item lnk $port1, $port2
556
557Link two ports. This is simply a shorthand for:
558
559 mon $port1, $port2;
560 mon $port2, $port1;
561
562It means that if either one is killed abnormally, the other one gets
563killed as well.
564
565=item kil $port[, @reason] 599=item kil $port[, @reason]
566 600
567Kill the specified port with the given C<@reason>. 601Kill the specified port with the given C<@reason>.
568 602
569If no C<@reason> is specified, then the port is killed "normally" (linked 603If no C<@reason> is specified, then the port is killed "normally" (ports
570ports will not be kileld, or even notified). 604monitoring other ports will not necessarily die because a port dies
605"normally").
571 606
572Otherwise, linked ports get killed with the same reason (second form of 607Otherwise, linked ports get killed with the same reason (second form of
573C<mon>, see below). 608C<mon>, see above).
574 609
575Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks 610Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
576will be reported as reason C<< die => $@ >>. 611will be reported as reason C<< die => $@ >>.
577 612
578Transport/communication errors are reported as C<< transport_error => 613Transport/communication errors are reported as C<< transport_error =>
579$message >>. 614$message >>.
580 615
581=back
582
583=head1 NODE MESSAGES
584
585Nodes understand the following messages sent to them. Many of them take
586arguments called C<@reply>, which will simply be used to compose a reply
587message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
588the remaining arguments are simply the message data.
589
590While other messages exist, they are not public and subject to change.
591
592=over 4
593
594=cut 616=cut
595 617
596=item lookup => $name, @reply 618=item $port = spawn $node, $initfunc[, @initdata]
597 619
598Replies with the port ID of the specified well-known port, or C<undef>. 620Creates a port on the node C<$node> (which can also be a port ID, in which
621case it's the node where that port resides).
599 622
600=item devnull => ... 623The port ID of the newly created port is returned immediately, and it is
624possible to immediately start sending messages or to monitor the port.
601 625
602Generic data sink/CPU heat conversion. 626After the port has been created, the init function is called on the remote
627node, in the same context as a C<rcv> callback. This function must be a
628fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
629specify a function in the main program, use C<::name>.
603 630
604=item relay => $port, @msg 631If the function doesn't exist, then the node tries to C<require>
632the package, then the package above the package and so on (e.g.
633C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
634exists or it runs out of package names.
605 635
606Simply forwards the message to the given port. 636The init function is then called with the newly-created port as context
637object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
638call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
639the port might not get created.
607 640
608=item eval => $string[ @reply] 641A common idiom is to pass a local port, immediately monitor the spawned
642port, and in the remote init function, immediately monitor the passed
643local port. This two-way monitoring ensures that both ports get cleaned up
644when there is a problem.
609 645
610Evaluates the given string. If C<@reply> is given, then a message of the 646C<spawn> guarantees that the C<$initfunc> has no visible effects on the
611form C<@reply, $@, @evalres> is sent. 647caller before C<spawn> returns (by delaying invocation when spawn is
648called for the local node).
612 649
613Example: crash another node. 650Example: spawn a chat server port on C<$othernode>.
614 651
615 snd $othernode, eval => "exit"; 652 # this node, executed from within a port context:
653 my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
654 mon $server;
616 655
617=item time => @reply 656 # init function on C<$othernode>
657 sub connect {
658 my ($srcport) = @_;
618 659
619Replies the the current node time to C<@reply>. 660 mon $srcport;
620 661
621Example: tell the current node to send the current time to C<$myport> in a 662 rcv $SELF, sub {
622C<timereply> message. 663 ...
664 };
665 }
623 666
624 snd $NODE, time => $myport, timereply => 1, 2; 667=cut
625 # => snd $myport, timereply => 1, 2, <time> 668
669sub _spawn {
670 my $port = shift;
671 my $init = shift;
672
673 # rcv will create the actual port
674 local $SELF = "$NODE#$port";
675 eval {
676 &{ load_func $init }
677 };
678 _self_die if $@;
679}
680
681sub spawn(@) {
682 my ($nodeid, undef) = split /#/, shift, 2;
683
684 my $id = "$RUNIQ." . $ID++;
685
686 $_[0] =~ /::/
687 or Carp::croak "spawn init function must be a fully-qualified name, caught";
688
689 snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
690
691 "$nodeid#$id"
692}
693
694=item after $timeout, @msg
695
696=item after $timeout, $callback
697
698Either sends the given message, or call the given callback, after the
699specified number of seconds.
700
701This is simply a utility function that comes in handy at times - the
702AnyEvent::MP author is not convinced of the wisdom of having it, though,
703so it may go away in the future.
704
705=cut
706
707sub after($@) {
708 my ($timeout, @action) = @_;
709
710 my $t; $t = AE::timer $timeout, 0, sub {
711 undef $t;
712 ref $action[0]
713 ? $action[0]()
714 : snd @action;
715 };
716}
717
718=item cal $port, @msg, $callback[, $timeout]
719
720A simple form of RPC - sends a message to the given C<$port> with the
721given contents (C<@msg>), but adds a reply port to the message.
722
723The reply port is created temporarily just for the purpose of receiving
724the reply, and will be C<kil>ed when no longer needed.
725
726A reply message sent to the port is passed to the C<$callback> as-is.
727
728If an optional time-out (in seconds) is given and it is not C<undef>,
729then the callback will be called without any arguments after the time-out
730elapsed and the port is C<kil>ed.
731
732If no time-out is given, then the local port will monitor the remote port
733instead, so it eventually gets cleaned-up.
734
735Currently this function returns the temporary port, but this "feature"
736might go in future versions unless you can make a convincing case that
737this is indeed useful for something.
738
739=cut
740
741sub cal(@) {
742 my $timeout = ref $_[-1] ? undef : pop;
743 my $cb = pop;
744
745 my $port = port {
746 undef $timeout;
747 kil $SELF;
748 &$cb;
749 };
750
751 if (defined $timeout) {
752 $timeout = AE::timer $timeout, 0, sub {
753 undef $timeout;
754 kil $port;
755 $cb->();
756 };
757 } else {
758 mon $_[0], sub {
759 kil $port;
760 $cb->();
761 };
762 }
763
764 push @_, $port;
765 &snd;
766
767 $port
768}
626 769
627=back 770=back
628 771
629=head1 AnyEvent::MP vs. Distributed Erlang 772=head1 AnyEvent::MP vs. Distributed Erlang
630 773
640 783
641Despite the similarities, there are also some important differences: 784Despite the similarities, there are also some important differences:
642 785
643=over 4 786=over 4
644 787
645=item * Node references contain the recipe on how to contact them. 788=item * Node IDs are arbitrary strings in AEMP.
646 789
647Erlang relies on special naming and DNS to work everywhere in the 790Erlang relies on special naming and DNS to work everywhere in the same
648same way. AEMP relies on each node knowing it's own address(es), with 791way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
649convenience functionality. 792configuration or DNS), but will otherwise discover other odes itself.
650 793
651This means that AEMP requires a less tightly controlled environment at the 794=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
652cost of longer node references and a slightly higher management overhead. 795uses "local ports are like remote ports".
796
797The failure modes for local ports are quite different (runtime errors
798only) then for remote ports - when a local port dies, you I<know> it dies,
799when a connection to another node dies, you know nothing about the other
800port.
801
802Erlang pretends remote ports are as reliable as local ports, even when
803they are not.
804
805AEMP encourages a "treat remote ports differently" philosophy, with local
806ports being the special case/exception, where transport errors cannot
807occur.
653 808
654=item * Erlang uses processes and a mailbox, AEMP does not queue. 809=item * Erlang uses processes and a mailbox, AEMP does not queue.
655 810
656Erlang uses processes that selctively receive messages, and therefore 811Erlang uses processes that selectively receive messages, and therefore
657needs a queue. AEMP is event based, queuing messages would serve no useful 812needs a queue. AEMP is event based, queuing messages would serve no
658purpose. 813useful purpose. For the same reason the pattern-matching abilities of
814AnyEvent::MP are more limited, as there is little need to be able to
815filter messages without dequeuing them.
659 816
660(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP). 817(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
661 818
662=item * Erlang sends are synchronous, AEMP sends are asynchronous. 819=item * Erlang sends are synchronous, AEMP sends are asynchronous.
663 820
664Sending messages in Erlang is synchronous and blocks the process. AEMP 821Sending messages in Erlang is synchronous and blocks the process (and
665sends are immediate, connection establishment is handled in the 822so does not need a queue that can overflow). AEMP sends are immediate,
666background. 823connection establishment is handled in the background.
667 824
668=item * Erlang can silently lose messages, AEMP cannot. 825=item * Erlang suffers from silent message loss, AEMP does not.
669 826
670Erlang makes few guarantees on messages delivery - messages can get lost 827Erlang makes few guarantees on messages delivery - messages can get lost
671without any of the processes realising it (i.e. you send messages a, b, 828without any of the processes realising it (i.e. you send messages a, b,
672and c, and the other side only receives messages a and c). 829and c, and the other side only receives messages a and c).
673 830
674AEMP guarantees correct ordering, and the guarantee that there are no 831AEMP guarantees correct ordering, and the guarantee that after one message
675holes in the message sequence. 832is lost, all following ones sent to the same port are lost as well, until
676 833monitoring raises an error, so there are no silent "holes" in the message
677=item * In Erlang, processes can be declared dead and later be found to be 834sequence.
678alive.
679
680In Erlang it can happen that a monitored process is declared dead and
681linked processes get killed, but later it turns out that the process is
682still alive - and can receive messages.
683
684In AEMP, when port monitoring detects a port as dead, then that port will
685eventually be killed - it cannot happen that a node detects a port as dead
686and then later sends messages to it, finding it is still alive.
687 835
688=item * Erlang can send messages to the wrong port, AEMP does not. 836=item * Erlang can send messages to the wrong port, AEMP does not.
689 837
690In Erlang it is quite possible that a node that restarts reuses a process 838In Erlang it is quite likely that a node that restarts reuses a process ID
691ID known to other nodes for a completely different process, causing 839known to other nodes for a completely different process, causing messages
692messages destined for that process to end up in an unrelated process. 840destined for that process to end up in an unrelated process.
693 841
694AEMP never reuses port IDs, so old messages or old port IDs floating 842AEMP never reuses port IDs, so old messages or old port IDs floating
695around in the network will not be sent to an unrelated port. 843around in the network will not be sent to an unrelated port.
696 844
697=item * Erlang uses unprotected connections, AEMP uses secure 845=item * Erlang uses unprotected connections, AEMP uses secure
698authentication and can use TLS. 846authentication and can use TLS.
699 847
700AEMP can use a proven protocol - SSL/TLS - to protect connections and 848AEMP can use a proven protocol - TLS - to protect connections and
701securely authenticate nodes. 849securely authenticate nodes.
702 850
703=item * The AEMP protocol is optimised for both text-based and binary 851=item * The AEMP protocol is optimised for both text-based and binary
704communications. 852communications.
705 853
706The AEMP protocol, unlike the Erlang protocol, supports both 854The AEMP protocol, unlike the Erlang protocol, supports both programming
707language-independent text-only protocols (good for debugging) and binary, 855language independent text-only protocols (good for debugging) and binary,
708language-specific serialisers (e.g. Storable). 856language-specific serialisers (e.g. Storable). By default, unless TLS is
857used, the protocol is actually completely text-based.
709 858
710It has also been carefully designed to be implementable in other languages 859It has also been carefully designed to be implementable in other languages
711with a minimum of work while gracefully degrading fucntionality to make the 860with a minimum of work while gracefully degrading functionality to make the
712protocol simple. 861protocol simple.
713 862
714=item * AEMP has more flexible monitoring options than Erlang. 863=item * AEMP has more flexible monitoring options than Erlang.
715 864
716In Erlang, you can chose to receive I<all> exit signals as messages 865In Erlang, you can chose to receive I<all> exit signals as messages
717or I<none>, there is no in-between, so monitoring single processes is 866or I<none>, there is no in-between, so monitoring single processes is
718difficult to implement. Monitoring in AEMP is more flexible than in 867difficult to implement. Monitoring in AEMP is more flexible than in
719Erlang, as one can choose between automatic kill, exit message or callback 868Erlang, as one can choose between automatic kill, exit message or callback
720on a per-process basis. 869on a per-process basis.
721 870
722=item * Erlang has different semantics for monitoring and linking, AEMP has the same. 871=item * Erlang tries to hide remote/local connections, AEMP does not.
723 872
724Monitoring in Erlang is not an indicator of process death/crashes, 873Monitoring in Erlang is not an indicator of process death/crashes, in the
725as linking is (except linking is unreliable in Erlang). In AEMP, the 874same way as linking is (except linking is unreliable in Erlang).
726semantics of monitoring and linking are identical, linking is simply 875
727two-way monitoring with automatic kill. 876In AEMP, you don't "look up" registered port names or send to named ports
877that might or might not be persistent. Instead, you normally spawn a port
878on the remote node. The init function monitors you, and you monitor the
879remote port. Since both monitors are local to the node, they are much more
880reliable (no need for C<spawn_link>).
881
882This also saves round-trips and avoids sending messages to the wrong port
883(hard to do in Erlang).
728 884
729=back 885=back
730 886
887=head1 RATIONALE
888
889=over 4
890
891=item Why strings for port and node IDs, why not objects?
892
893We considered "objects", but found that the actual number of methods
894that can be called are quite low. Since port and node IDs travel over
895the network frequently, the serialising/deserialising would add lots of
896overhead, as well as having to keep a proxy object everywhere.
897
898Strings can easily be printed, easily serialised etc. and need no special
899procedures to be "valid".
900
901And as a result, a miniport consists of a single closure stored in a
902global hash - it can't become much cheaper.
903
904=item Why favour JSON, why not a real serialising format such as Storable?
905
906In fact, any AnyEvent::MP node will happily accept Storable as framing
907format, but currently there is no way to make a node use Storable by
908default (although all nodes will accept it).
909
910The default framing protocol is JSON because a) JSON::XS is many times
911faster for small messages and b) most importantly, after years of
912experience we found that object serialisation is causing more problems
913than it solves: Just like function calls, objects simply do not travel
914easily over the network, mostly because they will always be a copy, so you
915always have to re-think your design.
916
917Keeping your messages simple, concentrating on data structures rather than
918objects, will keep your messages clean, tidy and efficient.
919
920=back
921
731=head1 SEE ALSO 922=head1 SEE ALSO
923
924L<AnyEvent::MP::Intro> - a gentle introduction.
925
926L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
927
928L<AnyEvent::MP::Global> - network maintainance and port groups, to find
929your applications.
930
931L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
932all nodes.
732 933
733L<AnyEvent>. 934L<AnyEvent>.
734 935
735=head1 AUTHOR 936=head1 AUTHOR
736 937

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