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Revision 1.89 by root, Fri Sep 11 16:47:14 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 34
35 # monitoring
36 mon $port, $cb->(@msg) # callback is invoked on death
37 mon $port, $otherport # kill otherport on abnormal death
38 mon $port, $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.
27 47
28=head1 DESCRIPTION 48=head1 DESCRIPTION
29 49
30This module (-family) implements a simple message passing framework. 50This module (-family) implements a simple message passing framework.
31 51
32Despite its simplicity, you can securely message other processes running 52Despite its simplicity, you can securely message other processes running
33on the same or other hosts. 53on the same or other hosts, and you can supervise entities remotely.
34 54
35For 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>
36manual page. 56manual page and the examples under F<eg/>.
37
38At the moment, this module family is severly broken and underdocumented,
39so do not use. This was uploaded mainly to reserve the CPAN namespace -
40stay tuned! The basic API should be finished, however.
41 57
42=head1 CONCEPTS 58=head1 CONCEPTS
43 59
44=over 4 60=over 4
45 61
46=item port 62=item port
47 63
48A 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).
49 66
50Some 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
51messages. All C<rcv> handlers will receive messages they match, messages 68some messages. Messages send to ports will not be queued, regardless of
52will not be queued. 69anything was listening for them or not.
53 70
54=item port id - C<noderef#portname> 71=item port ID - C<nodeid#portname>
55 72
56A 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
57separator, and a port name (a printable string of unspecified format). An 74separator, and a port name (a printable string of unspecified format).
58exception is the the node port, whose ID is identical to its node
59reference.
60 75
61=item node 76=item node
62 77
63A 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,
64port. 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
65create new ports, among other things. 80ports.
66 81
67Nodes are either private (single-process only), slaves (connected to a 82Nodes are either public (have one or more listening ports) or private
68master node only) or public nodes (connectable from unrelated nodes). 83(no listening ports). Private nodes cannot talk to other private nodes
84currently.
69 85
70=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id> 86=item node ID - C<[A-Z_][a-zA-Z0-9_\-.:]*>
71 87
72A 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
73private 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
74node (for public nodes). 90hostname, a hostname and a port, or a random string. AnyEvent::MP itself
91doesn't interpret node IDs in any way.
75 92
76This recipe is simply a comma-separated list of C<address:port> pairs (for 93=item binds - C<ip:port>
77TCP/IP, other protocols might look different).
78 94
79Node references come in two flavours: resolved (containing only numerical 95Nodes can only talk to each other by creating some kind of connection to
80addresses) 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.
81 99
82Before using an unresolved node reference in a message you first have to 100=item seed nodes
83resolve 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.
84 127
85=back 128=back
86 129
87=head1 VARIABLES/FUNCTIONS 130=head1 VARIABLES/FUNCTIONS
88 131
90 133
91=cut 134=cut
92 135
93package AnyEvent::MP; 136package AnyEvent::MP;
94 137
95use AnyEvent::MP::Base; 138use AnyEvent::MP::Kernel;
96 139
97use common::sense; 140use common::sense;
98 141
99use Carp (); 142use Carp ();
100 143
101use AE (); 144use AE ();
102 145
103use base "Exporter"; 146use base "Exporter";
104 147
105our $VERSION = '0.1'; 148our $VERSION = $AnyEvent::MP::Kernel::VERSION;
149
106our @EXPORT = qw( 150our @EXPORT = qw(
107 NODE $NODE *SELF node_of _any_ 151 NODE $NODE *SELF node_of after
108 resolve_node initialise_node 152 configure
109 snd rcv mon kil reg psub 153 snd rcv mon mon_guard kil reg psub spawn cal
110 port 154 port
111); 155);
112 156
113our $SELF; 157our $SELF;
114 158
118 kil $SELF, die => $msg; 162 kil $SELF, die => $msg;
119} 163}
120 164
121=item $thisnode = NODE / $NODE 165=item $thisnode = NODE / $NODE
122 166
123The C<NODE> function returns, and the C<$NODE> variable contains 167The C<NODE> function returns, and the C<$NODE> variable contains, the node
124the 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
125to C<become_public> or C<become_slave>, after which all local port 169a call to C<configure>.
126identifiers become invalid.
127 170
128=item $noderef = node_of $port 171=item $nodeid = node_of $port
129 172
130Extracts and returns the noderef from a portid or a noderef. 173Extracts and returns the node ID from a port ID or a node ID.
131 174
132=item initialise_node $noderef, $seednode, $seednode... 175=item configure $profile, key => value...
133 176
134=item initialise_node "slave/", $master, $master... 177=item configure key => value...
135 178
136Before a node can talk to other nodes on the network it has to initialise 179Before a node can talk to other nodes on the network (i.e. enter
137itself - the minimum a node needs to know is it's own name, and optionally 180"distributed mode") it has to configure itself - the minimum a node needs
138it should know the noderefs of some other nodes in the network. 181to know is its own name, and optionally it should know the addresses of
182some other nodes in the network to discover other nodes.
139 183
140This function initialises a node - it must be called exactly once (or 184This function configures a node - it must be called exactly once (or
141never) before calling other AnyEvent::MP functions. 185never) before calling other AnyEvent::MP functions.
142 186
143All arguments are noderefs, which can be either resolved or unresolved.
144
145There are two types of networked nodes, public nodes and slave nodes:
146
147=over 4 187=over 4
148 188
149=item public nodes 189=item step 1, gathering configuration from profiles
150 190
151For public nodes, C<$noderef> must either be a (possibly unresolved) 191The function first looks up a profile in the aemp configuration (see the
152noderef, 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
153which 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.
154 195
155Afterwards, the node will bind itself on all endpoints and try to connect 196The profile data is then gathered as follows:
156to all additional C<$seednodes> that are specified. Seednodes are optional
157and can be used to quickly bootstrap the node into an existing network.
158 197
159=item slave nodes 198First, all remaining key => value pairs (all of which are conveniently
199undocumented at the moment) will be interpreted as configuration
200data. Then they will be overwritten by any values specified in the global
201default configuration (see the F<aemp> utility), then the chain of
202profiles chosen by the profile name (and any C<parent> attributes).
160 203
161When the C<$noderef> is the special string C<slave/>, then the node will 204That means that the values specified in the profile have highest priority
162become a slave node. Slave nodes cannot be contacted from outside and will 205and the values specified directly via C<configure> have lowest priority,
163route most of their traffic to the master node that they attach to. 206and can only be used to specify defaults.
164 207
165At 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
166to 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
167successfully 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.
168 229
169=back 230=back
170 231
171This function will block until all nodes have been resolved and, for slave 232Example: become a distributed node using the local node name as profile.
172nodes, until it has successfully established a connection to a master 233This should be the most common form of invocation for "daemon"-type nodes.
173server.
174 234
175Example: become a public node listening on the default node. 235 configure
176 236
177 initialise_node; 237Example: become an anonymous node. This form is often used for commandline
238clients.
178 239
179Example: become a public node, and try to contact some well-known master 240 configure nodeid => "anon/";
180servers to become part of the network.
181 241
182 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).
183 245
184Example: become a public node listening on port C<4041>. 246 # use the aemp commandline utility
247 # aemp profile seed nodeid anon/ binds '*:4040'
185 248
186 initialise_node 4041; 249 # then use it
250 configure profile => "seed";
187 251
188Example: become a public node, only visible on localhost port 4044. 252 # or simply use aemp from the shell again:
253 # aemp run profile seed
189 254
190 initialise_node "locahost:4044"; 255 # or provide a nicer-to-remember nodeid
191 256 # aemp run profile seed nodeid "$(hostname)"
192Example: become a slave node to any of the specified master servers.
193
194 initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
195
196=item $cv = resolve_node $noderef
197
198Takes an unresolved node reference that may contain hostnames and
199abbreviated IDs, resolves all of them and returns a resolved node
200reference.
201
202In addition to C<address:port> pairs allowed in resolved noderefs, the
203following forms are supported:
204
205=over 4
206
207=item the empty string
208
209An empty-string component gets resolved as if the default port (4040) was
210specified.
211
212=item naked port numbers (e.g. C<1234>)
213
214These are resolved by prepending the local nodename and a colon, to be
215further resolved.
216
217=item hostnames (e.g. C<localhost:1234>, C<localhost>)
218
219These are resolved by using AnyEvent::DNS to resolve them, optionally
220looking up SRV records for the C<aemp=4040> port, if no port was
221specified.
222
223=back
224 257
225=item $SELF 258=item $SELF
226 259
227Contains the current port id while executing C<rcv> callbacks or C<psub> 260Contains the current port id while executing C<rcv> callbacks or C<psub>
228blocks. 261blocks.
229 262
230=item SELF, %SELF, @SELF... 263=item *SELF, SELF, %SELF, @SELF...
231 264
232Due to some quirks in how perl exports variables, it is impossible to 265Due to some quirks in how perl exports variables, it is impossible to
233just export C<$SELF>, all the symbols called C<SELF> are exported by this 266just export C<$SELF>, all the symbols named C<SELF> are exported by this
234module, but only C<$SELF> is currently used. 267module, but only C<$SELF> is currently used.
235 268
236=item snd $port, type => @data 269=item snd $port, type => @data
237 270
238=item snd $port, @msg 271=item snd $port, @msg
239 272
240Send 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
241a 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.
242stringifies a sa port ID (such as a port object :).
243 275
244While 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
245string 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
246type 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.
247 280
248The message data effectively becomes read-only after a call to this 281The message data logically becomes read-only after a call to this
249function: modifying any argument is not allowed and can cause many 282function: modifying any argument (or values referenced by them) is
250problems. 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.
251 287
252The 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
253JSON is used, then only strings, numbers and arrays and hashes consisting 289JSON is used, then only strings, numbers and arrays and hashes consisting
254of those are allowed (no objects). When Storable is used, then anything 290of those are allowed (no objects). When Storable is used, then anything
255that Storable can serialise and deserialise is allowed, and for the local 291that Storable can serialise and deserialise is allowed, and for the local
256node, anything can be passed. 292node, anything can be passed. Best rely only on the common denominator of
293these.
257 294
258=item $local_port = port 295=item $local_port = port
259 296
260Create 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
261matching port ("full port") or a single-callback port ("miniport"), 298no callbacks set and will throw an error when it receives messages.
262depending on how C<rcv> callbacks are bound to the object.
263 299
264=item $port = port { my @msg = @_; $finished } 300=item $local_port = port { my @msg = @_ }
265 301
266Creates a "miniport", that is, a very lightweight port without any pattern 302Creates a new local port, and returns its ID. Semantically the same as
267matching behind it, and returns its ID. Semantically the same as creating
268a port and calling C<rcv $port, $callback> on it. 303creating a port and calling C<rcv $port, $callback> on it.
269 304
270The block will be called for every message received on the port. When the 305The block will be called for every message received on the port, with the
271callback returns a true value its job is considered "done" and the port 306global variable C<$SELF> set to the port ID. Runtime errors will cause the
272will 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.
273 309
274The 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:
275be passed to the callback.
276 311
277If you need the local port id in the callback, this works nicely: 312 my $port = port {
278 313 my @msg = @_;
279 my $port; $port = port { 314 ...
280 snd $otherport, reply => $port; 315 kil $SELF;
281 }; 316 };
282 317
283=cut 318=cut
284 319
285sub rcv($@); 320sub rcv($@);
321
322sub _kilme {
323 die "received message on port without callback";
324}
286 325
287sub port(;&) { 326sub port(;&) {
288 my $id = "$UNIQ." . $ID++; 327 my $id = "$UNIQ." . $ID++;
289 my $port = "$NODE#$id"; 328 my $port = "$NODE#$id";
290 329
291 if (@_) { 330 rcv $port, shift || \&_kilme;
292 rcv $port, shift;
293 } else {
294 $PORT{$id} = sub { }; # nop
295 }
296 331
297 $port 332 $port
298} 333}
299 334
300=item reg $port, $name
301
302Registers the given port under the name C<$name>. If the name already
303exists it is replaced.
304
305A port can only be registered under one well known name.
306
307A port automatically becomes unregistered when it is killed.
308
309=cut
310
311sub reg(@) {
312 my ($port, $name) = @_;
313
314 $REG{$name} = $port;
315}
316
317=item rcv $port, $callback->(@msg) 335=item rcv $local_port, $callback->(@msg)
318 336
319Replaces the callback on the specified miniport (after converting it to 337Replaces the default callback on the specified port. There is no way to
320one if required). 338remove the default callback: use C<sub { }> to disable it, or better
321 339C<kil> the port when it is no longer needed.
322=item rcv $port, tagstring => $callback->(@msg), ...
323
324=item rcv $port, $smartmatch => $callback->(@msg), ...
325
326=item rcv $port, [$smartmatch...] => $callback->(@msg), ...
327
328Register callbacks to be called on matching messages on the given full
329port (after converting it to one if required).
330
331The callback has to return a true value when its work is done, after
332which is will be removed, or a false value in which case it will stay
333registered.
334 340
335The global C<$SELF> (exported by this module) contains C<$port> while 341The global C<$SELF> (exported by this module) contains C<$port> while
336executing the callback. 342executing the callback. Runtime errors during callback execution will
343result in the port being C<kil>ed.
337 344
338Runtime errors wdurign callback execution will result in the port being 345The default callback received all messages not matched by a more specific
339C<kil>ed. 346C<tag> match.
340 347
341If the match is an array reference, then it will be matched against the 348=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
342first elements of the message, otherwise only the first element is being
343matched.
344 349
345Any element in the match that is specified as C<_any_> (a function 350Register (or replace) callbacks to be called on messages starting with the
346exported by this module) matches any single element of the message. 351given tag on the given port (and return the port), or unregister it (when
352C<$callback> is C<$undef> or missing). There can only be one callback
353registered for each tag.
347 354
348While not required, it is highly recommended that the first matching 355The original message will be passed to the callback, after the first
349element is a string identifying the message. The one-string-only match is 356element (the tag) has been removed. The callback will use the same
350also 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, $otherport;
382 };
351 383
352=cut 384=cut
353 385
354sub rcv($@) { 386sub rcv($@) {
355 my $port = shift; 387 my $port = shift;
356 my ($noderef, $portid) = split /#/, $port, 2; 388 my ($nodeid, $portid) = split /#/, $port, 2;
357 389
358 ($NODE{$noderef} || add_node $noderef) == $NODE{""} 390 $NODE{$nodeid} == $NODE{""}
359 or Carp::croak "$port: rcv can only be called on local ports, caught"; 391 or Carp::croak "$port: rcv can only be called on local ports, caught";
360 392
361 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 {
362 my $cb = shift; 401 my $cb = shift;
363 delete $PORT_DATA{$portid};
364 $PORT{$portid} = sub { 402 $PORT{$portid} = sub {
365 local $SELF = $port; 403 local $SELF = $port;
366 eval { 404 eval { &$cb }; _self_die if $@;
367 &$cb 405 };
368 and kil $port;
369 }; 406 }
370 _self_die if $@; 407 } elsif (defined $_[0]) {
371 };
372 } else {
373 my $self = $PORT_DATA{$portid} ||= do { 408 my $self = $PORT_DATA{$portid} ||= do {
374 my $self = bless { 409 my $self = bless [$PORT{$port} || sub { }, { }, $port], "AnyEvent::MP::Port";
375 id => $port,
376 }, "AnyEvent::MP::Port";
377 410
378 $PORT{$portid} = sub { 411 $PORT{$portid} = sub {
379 local $SELF = $port; 412 local $SELF = $port;
380 413
381 eval {
382 for (@{ $self->{rc0}{$_[0]} }) { 414 if (my $cb = $self->[1]{$_[0]}) {
383 $_ && &{$_->[0]} 415 shift;
384 && undef $_; 416 eval { &$cb }; _self_die if $@;
385 } 417 } else {
386
387 for (@{ $self->{rcv}{$_[0]} }) {
388 $_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
389 && &{$_->[0]} 418 &{ $self->[0] };
390 && undef $_;
391 }
392
393 for (@{ $self->{any} }) {
394 $_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
395 && &{$_->[0]}
396 && undef $_;
397 } 419 }
398 }; 420 };
399 _self_die if $@; 421
422 $self
400 }; 423 };
401 424
402 $self
403 };
404
405 "AnyEvent::MP::Port" eq ref $self 425 "AnyEvent::MP::Port" eq ref $self
406 or Carp::croak "$port: rcv can only be called on message matching ports, caught"; 426 or Carp::croak "$port: rcv can only be called on message matching ports, caught";
407 427
408 while (@_) {
409 my ($match, $cb) = splice @_, 0, 2; 428 my ($tag, $cb) = splice @_, 0, 2;
410 429
411 if (!ref $match) { 430 if (defined $cb) {
412 push @{ $self->{rc0}{$match} }, [$cb]; 431 $self->[1]{$tag} = $cb;
413 } elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
414 my ($type, @match) = @$match;
415 @match
416 ? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
417 : push @{ $self->{rc0}{$match->[0]} }, [$cb];
418 } else { 432 } else {
419 push @{ $self->{any} }, [$cb, $match]; 433 delete $self->[1]{$tag};
420 } 434 }
421 } 435 }
422 } 436 }
423 437
424 $port 438 $port
460 $res 474 $res
461 } 475 }
462 } 476 }
463} 477}
464 478
465=item $guard = mon $port, $cb->(@reason) 479=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
466 480
467=item $guard = mon $port, $otherport 481=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
468 482
469=item $guard = mon $port, $otherport, @msg 483=item $guard = mon $port # kill $SELF when $port dies
470 484
485=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
486
471Monitor the given port and do something when the port is killed. 487Monitor the given port and do something when the port is killed or
488messages to it were lost, and optionally return a guard that can be used
489to stop monitoring again.
472 490
473In the first form, the callback is simply called with any number 491In the first form (callback), the callback is simply called with any
474of C<@reason> elements (no @reason means that the port was deleted 492number of C<@reason> elements (no @reason means that the port was deleted
475"normally"). Note also that I<< the callback B<must> never die >>, so use 493"normally"). Note also that I<< the callback B<must> never die >>, so use
476C<eval> if unsure. 494C<eval> if unsure.
477 495
478In the second form, the other port will be C<kil>'ed with C<@reason>, iff 496In the second form (another port given), the other port (C<$rcvport>)
479a @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
480under 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.
481 500
501The third form (kill self) is the same as the second form, except that
502C<$rvport> defaults to C<$SELF>.
503
482In 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.
483 533
484Example: call a given callback when C<$port> is killed. 534Example: call a given callback when C<$port> is killed.
485 535
486 mon $port, sub { warn "port died because of <@_>\n" }; 536 mon $port, sub { warn "port died because of <@_>\n" };
487 537
488Example: kill ourselves when C<$port> is killed abnormally. 538Example: kill ourselves when C<$port> is killed abnormally.
489 539
490 mon $port, $self; 540 mon $port;
491 541
492Example: send us a restart message another C<$port> is killed. 542Example: send us a restart message when another C<$port> is killed.
493 543
494 mon $port, $self => "restart"; 544 mon $port, $self => "restart";
495 545
496=cut 546=cut
497 547
498sub mon { 548sub mon {
499 my ($noderef, $port) = split /#/, shift, 2; 549 my ($nodeid, $port) = split /#/, shift, 2;
500 550
501 my $node = $NODE{$noderef} || add_node $noderef; 551 my $node = $NODE{$nodeid} || add_node $nodeid;
502 552
503 my $cb = shift; 553 my $cb = @_ ? shift : $SELF || Carp::croak 'mon: called with one argument only, but $SELF not set,';
504 554
505 unless (ref $cb) { 555 unless (ref $cb) {
506 if (@_) { 556 if (@_) {
507 # send a kill info message 557 # send a kill info message
508 my (@msg) = ($cb, @_); 558 my (@msg) = ($cb, @_);
526is killed, the references will be freed. 576is killed, the references will be freed.
527 577
528Optionally returns a guard that will stop the monitoring. 578Optionally returns a guard that will stop the monitoring.
529 579
530This 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
531want to free them when the port gets killed: 581want to free them when the port gets killed (note the use of C<psub>):
532 582
533 $port->rcv (start => sub { 583 $port->rcv (start => sub {
534 my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub { 584 my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
535 undef $timer if 0.9 < rand; 585 undef $timer if 0.9 < rand;
536 }); 586 });
537 }); 587 });
538 588
539=cut 589=cut
540 590
541sub mon_guard { 591sub mon_guard {
542 my ($port, @refs) = @_; 592 my ($port, @refs) = @_;
543 593
594 #TODO: mon-less form?
595
544 mon $port, sub { 0 && @refs } 596 mon $port, sub { 0 && @refs }
545} 597}
546 598
547=item lnk $port1, $port2
548
549Link two ports. This is simply a shorthand for:
550
551 mon $port1, $port2;
552 mon $port2, $port1;
553
554It means that if either one is killed abnormally, the other one gets
555killed as well.
556
557=item kil $port[, @reason] 599=item kil $port[, @reason]
558 600
559Kill the specified port with the given C<@reason>. 601Kill the specified port with the given C<@reason>.
560 602
561If 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
562ports will not be kileld, or even notified). 604monitoring other ports will not necessarily die because a port dies
605"normally").
563 606
564Otherwise, linked ports get killed with the same reason (second form of 607Otherwise, linked ports get killed with the same reason (second form of
565C<mon>, see below). 608C<mon>, see above).
566 609
567Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks 610Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
568will be reported as reason C<< die => $@ >>. 611will be reported as reason C<< die => $@ >>.
569 612
570Transport/communication errors are reported as C<< transport_error => 613Transport/communication errors are reported as C<< transport_error =>
571$message >>. 614$message >>.
572 615
616=cut
617
618=item $port = spawn $node, $initfunc[, @initdata]
619
620Creates a port on the node C<$node> (which can also be a port ID, in which
621case it's the node where that port resides).
622
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.
625
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>.
630
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.
635
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.
640
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.
645
646C<spawn> guarantees that the C<$initfunc> has no visible effects on the
647caller before C<spawn> returns (by delaying invocation when spawn is
648called for the local node).
649
650Example: spawn a chat server port on C<$othernode>.
651
652 # this node, executed from within a port context:
653 my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
654 mon $server;
655
656 # init function on C<$othernode>
657 sub connect {
658 my ($srcport) = @_;
659
660 mon $srcport;
661
662 rcv $SELF, sub {
663 ...
664 };
665 }
666
667=cut
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 $port
768}
769
573=back 770=back
574 771
575=head1 NODE MESSAGES 772=head1 AnyEvent::MP vs. Distributed Erlang
576 773
577Nodes understand the following messages sent to them. Many of them take 774AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
578arguments called C<@reply>, which will simply be used to compose a reply 775== aemp node, Erlang process == aemp port), so many of the documents and
579message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and 776programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
580the remaining arguments are simply the message data. 777sample:
581 778
582While other messages exist, they are not public and subject to change. 779 http://www.Erlang.se/doc/programming_rules.shtml
780 http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
781 http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6
782 http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
783
784Despite the similarities, there are also some important differences:
583 785
584=over 4 786=over 4
585 787
586=cut 788=item * Node IDs are arbitrary strings in AEMP.
587 789
588=item lookup => $name, @reply
589
590Replies with the port ID of the specified well-known port, or C<undef>.
591
592=item devnull => ...
593
594Generic data sink/CPU heat conversion.
595
596=item relay => $port, @msg
597
598Simply forwards the message to the given port.
599
600=item eval => $string[ @reply]
601
602Evaluates the given string. If C<@reply> is given, then a message of the
603form C<@reply, $@, @evalres> is sent.
604
605Example: crash another node.
606
607 snd $othernode, eval => "exit";
608
609=item time => @reply
610
611Replies the the current node time to C<@reply>.
612
613Example: tell the current node to send the current time to C<$myport> in a
614C<timereply> message.
615
616 snd $NODE, time => $myport, timereply => 1, 2;
617 # => snd $myport, timereply => 1, 2, <time>
618
619=back
620
621=head1 AnyEvent::MP vs. Distributed Erlang
622
623AnyEvent::MP got lots of its ideas from distributed erlang (erlang node
624== aemp node, erlang process == aemp port), so many of the documents and
625programming techniques employed by erlang apply to AnyEvent::MP. Here is a
626sample:
627
628 http://www.erlang.se/doc/programming_rules.shtml
629 http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
630 http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
631 http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
632
633Despite the similarities, there are also some important differences:
634
635=over 4
636
637=item * Node references contain the recipe on how to contact them.
638
639Erlang relies on special naming and DNS to work everywhere in the 790Erlang relies on special naming and DNS to work everywhere in the same
640same 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
641convenience functionality. 792configuration or DNS), but will otherwise discover other odes itself.
642 793
643This means that AEMP requires a less tightly controlled environment at the 794=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
644cost 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.
645 808
646=item * Erlang uses processes and a mailbox, AEMP does not queue. 809=item * Erlang uses processes and a mailbox, AEMP does not queue.
647 810
648Erlang uses processes that selctively receive messages, and therefore 811Erlang uses processes that selectively receive messages, and therefore
649needs a queue. AEMP is event based, queuing messages would serve no useful 812needs a queue. AEMP is event based, queuing messages would serve no
650purpose. 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.
651 816
652(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).
653 818
654=item * Erlang sends are synchronous, AEMP sends are asynchronous. 819=item * Erlang sends are synchronous, AEMP sends are asynchronous.
655 820
656Sending messages in erlang is synchronous and blocks the process. AEMP 821Sending messages in Erlang is synchronous and blocks the process (and
657sends are immediate, connection establishment is handled in the 822so does not need a queue that can overflow). AEMP sends are immediate,
658background. 823connection establishment is handled in the background.
659 824
660=item * Erlang can silently lose messages, AEMP cannot. 825=item * Erlang suffers from silent message loss, AEMP does not.
661 826
662Erlang makes few guarantees on messages delivery - messages can get lost 827Erlang makes few guarantees on messages delivery - messages can get lost
663without 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,
664and c, and the other side only receives messages a and c). 829and c, and the other side only receives messages a and c).
665 830
666AEMP guarantees correct ordering, and the guarantee that there are no 831AEMP guarantees correct ordering, and the guarantee that after one message
667holes in the message sequence. 832is lost, all following ones sent to the same port are lost as well, until
668 833monitoring raises an error, so there are no silent "holes" in the message
669=item * In erlang, processes can be declared dead and later be found to be 834sequence.
670alive.
671
672In erlang it can happen that a monitored process is declared dead and
673linked processes get killed, but later it turns out that the process is
674still alive - and can receive messages.
675
676In AEMP, when port monitoring detects a port as dead, then that port will
677eventually be killed - it cannot happen that a node detects a port as dead
678and then later sends messages to it, finding it is still alive.
679 835
680=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.
681 837
682In 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
683ID known to other nodes for a completely different process, causing 839known to other nodes for a completely different process, causing messages
684messages destined for that process to end up in an unrelated process. 840destined for that process to end up in an unrelated process.
685 841
686AEMP 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
687around in the network will not be sent to an unrelated port. 843around in the network will not be sent to an unrelated port.
688 844
689=item * Erlang uses unprotected connections, AEMP uses secure 845=item * Erlang uses unprotected connections, AEMP uses secure
690authentication and can use TLS. 846authentication and can use TLS.
691 847
692AEMP can use a proven protocol - SSL/TLS - to protect connections and 848AEMP can use a proven protocol - TLS - to protect connections and
693securely authenticate nodes. 849securely authenticate nodes.
694 850
695=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
696communications. 852communications.
697 853
698The AEMP protocol, unlike the erlang protocol, supports both 854The AEMP protocol, unlike the Erlang protocol, supports both programming
699language-independent text-only protocols (good for debugging) and binary, 855language independent text-only protocols (good for debugging) and binary,
700language-specific serialisers (e.g. Storable). 856language-specific serialisers (e.g. Storable). By default, unless TLS is
857used, the protocol is actually completely text-based.
701 858
702It has also been carefully designed to be implementable in other languages 859It has also been carefully designed to be implementable in other languages
703with a minimum of work while gracefully degrading fucntionality to make the 860with a minimum of work while gracefully degrading functionality to make the
704protocol simple. 861protocol simple.
705 862
863=item * AEMP has more flexible monitoring options than Erlang.
864
865In Erlang, you can chose to receive I<all> exit signals as messages
866or I<none>, there is no in-between, so monitoring single processes is
867difficult to implement. Monitoring in AEMP is more flexible than in
868Erlang, as one can choose between automatic kill, exit message or callback
869on a per-process basis.
870
871=item * Erlang tries to hide remote/local connections, AEMP does not.
872
873Monitoring in Erlang is not an indicator of process death/crashes, in the
874same way as linking is (except linking is unreliable in Erlang).
875
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).
884
706=back 885=back
707 886
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
708=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.
709 933
710L<AnyEvent>. 934L<AnyEvent>.
711 935
712=head1 AUTHOR 936=head1 AUTHOR
713 937

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