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Revision 1.82 by root, Mon Sep 7 18:42:09 2009 UTC

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
13 $SELF # receiving/own port id in rcv callbacks 12 $SELF # receiving/own port id in rcv callbacks
14 13
14 # initialise the node so it can send/receive messages
15 configure;
16
15 # ports are message endpoints 17 # ports are message destinations
16 18
17 # sending messages 19 # sending messages
18 snd $port, type => data...; 20 snd $port, type => data...;
19 snd $port, @msg; 21 snd $port, @msg;
20 snd @msg_with_first_element_being_a_port; 22 snd @msg_with_first_element_being_a_port;
21 23
22 # miniports 24 # creating/using ports, the simple way
23 my $miniport = port { my @msg = @_; 0 }; 25 my $simple_port = port { my @msg = @_ };
24 26
25 # full ports 27 # creating/using ports, tagged message matching
26 my $port = port; 28 my $port = port;
27 rcv $port, smartmatch => $cb->(@msg);
28 rcv $port, ping => sub { snd $_[0], "pong"; 0 }; 29 rcv $port, ping => sub { snd $_[0], "pong" };
29 rcv $port, pong => sub { warn "pong received\n"; 0 }; 30 rcv $port, pong => sub { warn "pong received\n" };
30 31
31 # remote ports 32 # create a port on another node
32 my $port = spawn $node, $initfunc, @initdata; 33 my $port = spawn $node, $initfunc, @initdata;
33
34 # more, smarter, matches (_any_ is exported by this module)
35 rcv $port, [child_died => $pid] => sub { ...
36 rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3
37 34
38 # monitoring 35 # monitoring
39 mon $port, $cb->(@msg) # callback is invoked on death 36 mon $port, $cb->(@msg) # callback is invoked on death
40 mon $port, $otherport # kill otherport on abnormal death 37 mon $port, $otherport # kill otherport on abnormal death
41 mon $port, $otherport, @msg # send message on death 38 mon $port, $otherport, @msg # send message on death
42 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.
46 AnyEvent::MP::Global - stable but incomplete, protocol not yet final.
47
48stay tuned.
49
43=head1 DESCRIPTION 50=head1 DESCRIPTION
44 51
45This module (-family) implements a simple message passing framework. 52This module (-family) implements a simple message passing framework.
46 53
47Despite its simplicity, you can securely message other processes running 54Despite its simplicity, you can securely message other processes running
48on the same or other hosts. 55on the same or other hosts, and you can supervise entities remotely.
49 56
50For an introduction to this module family, see the L<AnyEvent::MP::Intro> 57For an introduction to this module family, see the L<AnyEvent::MP::Intro>
51manual page. 58manual page and the examples under F<eg/>.
52
53At the moment, this module family is severly broken and underdocumented,
54so do not use. This was uploaded mainly to reserve the CPAN namespace -
55stay tuned! The basic API should be finished, however.
56 59
57=head1 CONCEPTS 60=head1 CONCEPTS
58 61
59=over 4 62=over 4
60 63
61=item port 64=item port
62 65
63A port is something you can send messages to (with the C<snd> function). 66Not to be confused with a TCP port, a "port" is something you can send
67messages to (with the C<snd> function).
64 68
65Some ports allow you to register C<rcv> handlers that can match specific 69Ports allow you to register C<rcv> handlers that can match all or just
66messages. All C<rcv> handlers will receive messages they match, messages 70some messages. Messages send to ports will not be queued, regardless of
67will not be queued. 71anything was listening for them or not.
68 72
69=item port id - C<noderef#portname> 73=item port ID - C<nodeid#portname>
70 74
71A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as 75A port ID is the concatenation of a node ID, a hash-mark (C<#>) as
72separator, and a port name (a printable string of unspecified format). An 76separator, and a port name (a printable string of unspecified format).
73exception is the the node port, whose ID is identical to its node
74reference.
75 77
76=item node 78=item node
77 79
78A node is a single process containing at least one port - the node 80A node is a single process containing at least one port - the node port,
79port. You can send messages to node ports to find existing ports or to 81which enables nodes to manage each other remotely, and to create new
80create new ports, among other things. 82ports.
81 83
82Nodes are either private (single-process only), slaves (connected to a 84Nodes are either public (have one or more listening ports) or private
83master node only) or public nodes (connectable from unrelated nodes). 85(no listening ports). Private nodes cannot talk to other private nodes
86currently.
84 87
85=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id> 88=item node ID - C<[a-za-Z0-9_\-.:]+>
86 89
87A node reference is a string that either simply identifies the node (for 90A node ID is a string that uniquely identifies the node within a
88private and slave nodes), or contains a recipe on how to reach a given 91network. Depending on the configuration used, node IDs can look like a
89node (for public nodes). 92hostname, a hostname and a port, or a random string. AnyEvent::MP itself
93doesn't interpret node IDs in any way.
90 94
91This recipe is simply a comma-separated list of C<address:port> pairs (for 95=item binds - C<ip:port>
92TCP/IP, other protocols might look different).
93 96
94Node references come in two flavours: resolved (containing only numerical 97Nodes can only talk to each other by creating some kind of connection to
95addresses) or unresolved (where hostnames are used instead of addresses). 98each other. To do this, nodes should listen on one or more local transport
99endpoints - binds. Currently, only standard C<ip:port> specifications can
100be used, which specify TCP ports to listen on.
96 101
97Before using an unresolved node reference in a message you first have to 102=item seeds - C<host:port>
98resolve it. 103
104When a node starts, it knows nothing about the network. To teach the node
105about the network it first has to contact some other node within the
106network. This node is called a seed.
107
108Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes
109are expected to be long-running, and at least one of those should always
110be available. When nodes run out of connections (e.g. due to a network
111error), they try to re-establish connections to some seednodes again to
112join the network.
113
114Apart from being sued for seeding, seednodes are not special in any way -
115every public node can be a seednode.
99 116
100=back 117=back
101 118
102=head1 VARIABLES/FUNCTIONS 119=head1 VARIABLES/FUNCTIONS
103 120
105 122
106=cut 123=cut
107 124
108package AnyEvent::MP; 125package AnyEvent::MP;
109 126
110use AnyEvent::MP::Base; 127use AnyEvent::MP::Kernel;
111 128
112use common::sense; 129use common::sense;
113 130
114use Carp (); 131use Carp ();
115 132
116use AE (); 133use AE ();
117 134
118use base "Exporter"; 135use base "Exporter";
119 136
120our $VERSION = '0.1'; 137our $VERSION = $AnyEvent::MP::Kernel::VERSION;
138
121our @EXPORT = qw( 139our @EXPORT = qw(
122 NODE $NODE *SELF node_of _any_ 140 NODE $NODE *SELF node_of after
123 resolve_node initialise_node 141 configure
124 snd rcv mon kil reg psub spawn 142 snd rcv mon mon_guard kil reg psub spawn
125 port 143 port
126); 144);
127 145
128our $SELF; 146our $SELF;
129 147
133 kil $SELF, die => $msg; 151 kil $SELF, die => $msg;
134} 152}
135 153
136=item $thisnode = NODE / $NODE 154=item $thisnode = NODE / $NODE
137 155
138The C<NODE> function returns, and the C<$NODE> variable contains 156The C<NODE> function returns, and the C<$NODE> variable contains, the node
139the noderef of the local node. The value is initialised by a call 157ID of the node running in the current process. This value is initialised by
140to C<become_public> or C<become_slave>, after which all local port 158a call to C<configure>.
141identifiers become invalid.
142 159
143=item $noderef = node_of $port 160=item $nodeid = node_of $port
144 161
145Extracts and returns the noderef from a portid or a noderef. 162Extracts and returns the node ID from a port ID or a node ID.
146 163
147=item initialise_node $noderef, $seednode, $seednode... 164=item configure $profile, key => value...
148 165
149=item initialise_node "slave/", $master, $master... 166=item configure key => value...
150 167
151Before a node can talk to other nodes on the network it has to initialise 168Before a node can talk to other nodes on the network (i.e. enter
152itself - the minimum a node needs to know is it's own name, and optionally 169"distributed mode") it has to configure itself - the minimum a node needs
153it should know the noderefs of some other nodes in the network. 170to know is its own name, and optionally it should know the addresses of
171some other nodes in the network to discover other nodes.
154 172
155This function initialises a node - it must be called exactly once (or 173This function configures a node - it must be called exactly once (or
156never) before calling other AnyEvent::MP functions. 174never) before calling other AnyEvent::MP functions.
157 175
158All arguments are noderefs, which can be either resolved or unresolved.
159
160There are two types of networked nodes, public nodes and slave nodes:
161
162=over 4 176=over 4
163 177
164=item public nodes 178=item step 1, gathering configuration from profiles
165 179
166For public nodes, C<$noderef> must either be a (possibly unresolved) 180The function first looks up a profile in the aemp configuration (see the
167noderef, in which case it will be resolved, or C<undef> (or missing), in 181L<aemp> commandline utility). The profile name can be specified via the
168which case the noderef will be guessed. 182named C<profile> parameter or can simply be the first parameter). If it is
183missing, then the nodename (F<uname -n>) will be used as profile name.
169 184
170Afterwards, the node will bind itself on all endpoints and try to connect 185The profile data is then gathered as follows:
171to all additional C<$seednodes> that are specified. Seednodes are optional
172and can be used to quickly bootstrap the node into an existing network.
173 186
174=item slave nodes 187First, all remaining key => value pairs (all of which are conveniently
188undocumented at the moment) will be interpreted as configuration
189data. Then they will be overwritten by any values specified in the global
190default configuration (see the F<aemp> utility), then the chain of
191profiles chosen by the profile name (and any C<parent> attributes).
175 192
176When the C<$noderef> is the special string C<slave/>, then the node will 193That means that the values specified in the profile have highest priority
177become a slave node. Slave nodes cannot be contacted from outside and will 194and the values specified directly via C<configure> have lowest priority,
178route most of their traffic to the master node that they attach to. 195and can only be used to specify defaults.
179 196
180At least one additional noderef is required: The node will try to connect 197If the profile specifies a node ID, then this will become the node ID of
181to all of them and will become a slave attached to the first node it can 198this process. If not, then the profile name will be used as node ID. The
182successfully connect to. 199special node ID of C<anon/> will be replaced by a random node ID.
200
201=item step 2, bind listener sockets
202
203The next step is to look up the binds in the profile, followed by binding
204aemp protocol listeners on all binds specified (it is possible and valid
205to have no binds, meaning that the node cannot be contacted form the
206outside. This means the node cannot talk to other nodes that also have no
207binds, but it can still talk to all "normal" nodes).
208
209If the profile does not specify a binds list, then a default of C<*> is
210used, meaning the node will bind on a dynamically-assigned port on every
211local IP address it finds.
212
213=item step 3, connect to seed nodes
214
215As the last step, the seeds list from the profile is passed to the
216L<AnyEvent::MP::Global> module, which will then use it to keep
217connectivity with at least one node at any point in time.
183 218
184=back 219=back
185 220
186This function will block until all nodes have been resolved and, for slave 221Example: become a distributed node using the locla node name as profile.
187nodes, until it has successfully established a connection to a master 222This should be the most common form of invocation for "daemon"-type nodes.
188server.
189 223
190Example: become a public node listening on the default node. 224 configure
191 225
192 initialise_node; 226Example: become an anonymous node. This form is often used for commandline
227clients.
193 228
194Example: become a public node, and try to contact some well-known master 229 configure nodeid => "anon/";
195servers to become part of the network.
196 230
197 initialise_node undef, "master1", "master2"; 231Example: configure a node using a profile called seed, which si suitable
232for a seed node as it binds on all local addresses on a fixed port (4040,
233customary for aemp).
198 234
199Example: become a public node listening on port C<4041>. 235 # use the aemp commandline utility
236 # aemp profile seed nodeid anon/ binds '*:4040'
200 237
201 initialise_node 4041; 238 # then use it
239 configure profile => "seed";
202 240
203Example: become a public node, only visible on localhost port 4044. 241 # or simply use aemp from the shell again:
242 # aemp run profile seed
204 243
205 initialise_node "locahost:4044"; 244 # or provide a nicer-to-remember nodeid
206 245 # aemp run profile seed nodeid "$(hostname)"
207Example: become a slave node to any of the specified master servers.
208
209 initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
210
211=item $cv = resolve_node $noderef
212
213Takes an unresolved node reference that may contain hostnames and
214abbreviated IDs, resolves all of them and returns a resolved node
215reference.
216
217In addition to C<address:port> pairs allowed in resolved noderefs, the
218following forms are supported:
219
220=over 4
221
222=item the empty string
223
224An empty-string component gets resolved as if the default port (4040) was
225specified.
226
227=item naked port numbers (e.g. C<1234>)
228
229These are resolved by prepending the local nodename and a colon, to be
230further resolved.
231
232=item hostnames (e.g. C<localhost:1234>, C<localhost>)
233
234These are resolved by using AnyEvent::DNS to resolve them, optionally
235looking up SRV records for the C<aemp=4040> port, if no port was
236specified.
237
238=back
239 246
240=item $SELF 247=item $SELF
241 248
242Contains the current port id while executing C<rcv> callbacks or C<psub> 249Contains the current port id while executing C<rcv> callbacks or C<psub>
243blocks. 250blocks.
244 251
245=item SELF, %SELF, @SELF... 252=item *SELF, SELF, %SELF, @SELF...
246 253
247Due to some quirks in how perl exports variables, it is impossible to 254Due to some quirks in how perl exports variables, it is impossible to
248just export C<$SELF>, all the symbols called C<SELF> are exported by this 255just export C<$SELF>, all the symbols named C<SELF> are exported by this
249module, but only C<$SELF> is currently used. 256module, but only C<$SELF> is currently used.
250 257
251=item snd $port, type => @data 258=item snd $port, type => @data
252 259
253=item snd $port, @msg 260=item snd $port, @msg
254 261
255Send the given message to the given port ID, which can identify either 262Send the given message to the given port, which can identify either a
256a local or a remote port, and can be either a string or soemthignt hat 263local or a remote port, and must be a port ID.
257stringifies a sa port ID (such as a port object :).
258 264
259While the message can be about anything, it is highly recommended to use a 265While the message can be almost anything, it is highly recommended to
260string as first element (a portid, or some word that indicates a request 266use a string as first element (a port ID, or some word that indicates a
261type etc.). 267request type etc.) and to consist if only simple perl values (scalars,
268arrays, hashes) - if you think you need to pass an object, think again.
262 269
263The message data effectively becomes read-only after a call to this 270The message data logically becomes read-only after a call to this
264function: modifying any argument is not allowed and can cause many 271function: modifying any argument (or values referenced by them) is
265problems. 272forbidden, as there can be considerable time between the call to C<snd>
273and the time the message is actually being serialised - in fact, it might
274never be copied as within the same process it is simply handed to the
275receiving port.
266 276
267The type of data you can transfer depends on the transport protocol: when 277The type of data you can transfer depends on the transport protocol: when
268JSON is used, then only strings, numbers and arrays and hashes consisting 278JSON is used, then only strings, numbers and arrays and hashes consisting
269of those are allowed (no objects). When Storable is used, then anything 279of those are allowed (no objects). When Storable is used, then anything
270that Storable can serialise and deserialise is allowed, and for the local 280that Storable can serialise and deserialise is allowed, and for the local
271node, anything can be passed. 281node, anything can be passed. Best rely only on the common denominator of
282these.
272 283
273=item $local_port = port 284=item $local_port = port
274 285
275Create a new local port object that can be used either as a pattern 286Create a new local port object and returns its port ID. Initially it has
276matching port ("full port") or a single-callback port ("miniport"), 287no callbacks set and will throw an error when it receives messages.
277depending on how C<rcv> callbacks are bound to the object.
278 288
279=item $port = port { my @msg = @_; $finished } 289=item $local_port = port { my @msg = @_ }
280 290
281Creates a "miniport", that is, a very lightweight port without any pattern 291Creates a new local port, and returns its ID. Semantically the same as
282matching behind it, and returns its ID. Semantically the same as creating
283a port and calling C<rcv $port, $callback> on it. 292creating a port and calling C<rcv $port, $callback> on it.
284 293
285The block will be called for every message received on the port. When the 294The block will be called for every message received on the port, with the
286callback returns a true value its job is considered "done" and the port 295global variable C<$SELF> set to the port ID. Runtime errors will cause the
287will be destroyed. Otherwise it will stay alive. 296port to be C<kil>ed. The message will be passed as-is, no extra argument
297(i.e. no port ID) will be passed to the callback.
288 298
289The message will be passed as-is, no extra argument (i.e. no port id) will 299If you want to stop/destroy the port, simply C<kil> it:
290be passed to the callback.
291 300
292If you need the local port id in the callback, this works nicely: 301 my $port = port {
293 302 my @msg = @_;
294 my $port; $port = port { 303 ...
295 snd $otherport, reply => $port; 304 kil $SELF;
296 }; 305 };
297 306
298=cut 307=cut
299 308
300sub rcv($@); 309sub rcv($@);
310
311sub _kilme {
312 die "received message on port without callback";
313}
301 314
302sub port(;&) { 315sub port(;&) {
303 my $id = "$UNIQ." . $ID++; 316 my $id = "$UNIQ." . $ID++;
304 my $port = "$NODE#$id"; 317 my $port = "$NODE#$id";
305 318
306 if (@_) { 319 rcv $port, shift || \&_kilme;
307 rcv $port, shift;
308 } else {
309 $PORT{$id} = sub { }; # nop
310 }
311 320
312 $port 321 $port
313} 322}
314 323
315=item reg $port, $name
316
317=item reg $name
318
319Registers the given port (or C<$SELF><<< if missing) under the name
320C<$name>. If the name already exists it is replaced.
321
322A port can only be registered under one well known name.
323
324A port automatically becomes unregistered when it is killed.
325
326=cut
327
328sub reg(@) {
329 my $port = @_ > 1 ? shift : $SELF || Carp::croak 'reg: called with one argument only, but $SELF not set,';
330
331 $REG{$_[0]} = $port;
332}
333
334=item rcv $port, $callback->(@msg) 324=item rcv $local_port, $callback->(@msg)
335 325
336Replaces the callback on the specified miniport (after converting it to 326Replaces the default callback on the specified port. There is no way to
337one if required). 327remove the default callback: use C<sub { }> to disable it, or better
338 328C<kil> the port when it is no longer needed.
339=item rcv $port, tagstring => $callback->(@msg), ...
340
341=item rcv $port, $smartmatch => $callback->(@msg), ...
342
343=item rcv $port, [$smartmatch...] => $callback->(@msg), ...
344
345Register callbacks to be called on matching messages on the given full
346port (after converting it to one if required) and return the port.
347
348The callback has to return a true value when its work is done, after
349which is will be removed, or a false value in which case it will stay
350registered.
351 329
352The global C<$SELF> (exported by this module) contains C<$port> while 330The global C<$SELF> (exported by this module) contains C<$port> while
353executing the callback. 331executing the callback. Runtime errors during callback execution will
332result in the port being C<kil>ed.
354 333
355Runtime errors during callback execution will result in the port being 334The default callback received all messages not matched by a more specific
356C<kil>ed. 335C<tag> match.
357 336
358If the match is an array reference, then it will be matched against the 337=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
359first elements of the message, otherwise only the first element is being
360matched.
361 338
362Any element in the match that is specified as C<_any_> (a function 339Register (or replace) callbacks to be called on messages starting with the
363exported by this module) matches any single element of the message. 340given tag on the given port (and return the port), or unregister it (when
341C<$callback> is C<$undef> or missing). There can only be one callback
342registered for each tag.
364 343
365While not required, it is highly recommended that the first matching 344The original message will be passed to the callback, after the first
366element is a string identifying the message. The one-string-only match is 345element (the tag) has been removed. The callback will use the same
367also the most efficient match (by far). 346environment as the default callback (see above).
368 347
369Example: create a port and bind receivers on it in one go. 348Example: create a port and bind receivers on it in one go.
370 349
371 my $port = rcv port, 350 my $port = rcv port,
372 msg1 => sub { ...; 0 }, 351 msg1 => sub { ... },
373 msg2 => sub { ...; 0 }, 352 msg2 => sub { ... },
374 ; 353 ;
375 354
376Example: create a port, bind receivers and send it in a message elsewhere 355Example: create a port, bind receivers and send it in a message elsewhere
377in one go: 356in one go:
378 357
379 snd $otherport, reply => 358 snd $otherport, reply =>
380 rcv port, 359 rcv port,
381 msg1 => sub { ...; 0 }, 360 msg1 => sub { ... },
382 ... 361 ...
383 ; 362 ;
384 363
364Example: temporarily register a rcv callback for a tag matching some port
365(e.g. for a rpc reply) and unregister it after a message was received.
366
367 rcv $port, $otherport => sub {
368 my @reply = @_;
369
370 rcv $SELF, $otherport;
371 };
372
385=cut 373=cut
386 374
387sub rcv($@) { 375sub rcv($@) {
388 my $port = shift; 376 my $port = shift;
389 my ($noderef, $portid) = split /#/, $port, 2; 377 my ($nodeid, $portid) = split /#/, $port, 2;
390 378
391 ($NODE{$noderef} || add_node $noderef) == $NODE{""} 379 $NODE{$nodeid} == $NODE{""}
392 or Carp::croak "$port: rcv can only be called on local ports, caught"; 380 or Carp::croak "$port: rcv can only be called on local ports, caught";
393 381
394 if (@_ == 1) { 382 while (@_) {
383 if (ref $_[0]) {
384 if (my $self = $PORT_DATA{$portid}) {
385 "AnyEvent::MP::Port" eq ref $self
386 or Carp::croak "$port: rcv can only be called on message matching ports, caught";
387
388 $self->[2] = shift;
389 } else {
395 my $cb = shift; 390 my $cb = shift;
396 delete $PORT_DATA{$portid};
397 $PORT{$portid} = sub { 391 $PORT{$portid} = sub {
398 local $SELF = $port; 392 local $SELF = $port;
399 eval { 393 eval { &$cb }; _self_die if $@;
400 &$cb 394 };
401 and kil $port;
402 }; 395 }
403 _self_die if $@; 396 } elsif (defined $_[0]) {
404 };
405 } else {
406 my $self = $PORT_DATA{$portid} ||= do { 397 my $self = $PORT_DATA{$portid} ||= do {
407 my $self = bless { 398 my $self = bless [$PORT{$port} || sub { }, { }, $port], "AnyEvent::MP::Port";
408 id => $port,
409 }, "AnyEvent::MP::Port";
410 399
411 $PORT{$portid} = sub { 400 $PORT{$portid} = sub {
412 local $SELF = $port; 401 local $SELF = $port;
413 402
414 eval {
415 for (@{ $self->{rc0}{$_[0]} }) { 403 if (my $cb = $self->[1]{$_[0]}) {
416 $_ && &{$_->[0]} 404 shift;
417 && undef $_; 405 eval { &$cb }; _self_die if $@;
418 } 406 } else {
419
420 for (@{ $self->{rcv}{$_[0]} }) {
421 $_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
422 && &{$_->[0]} 407 &{ $self->[0] };
423 && undef $_;
424 }
425
426 for (@{ $self->{any} }) {
427 $_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
428 && &{$_->[0]}
429 && undef $_;
430 } 408 }
431 }; 409 };
432 _self_die if $@; 410
411 $self
433 }; 412 };
434 413
435 $self
436 };
437
438 "AnyEvent::MP::Port" eq ref $self 414 "AnyEvent::MP::Port" eq ref $self
439 or Carp::croak "$port: rcv can only be called on message matching ports, caught"; 415 or Carp::croak "$port: rcv can only be called on message matching ports, caught";
440 416
441 while (@_) {
442 my ($match, $cb) = splice @_, 0, 2; 417 my ($tag, $cb) = splice @_, 0, 2;
443 418
444 if (!ref $match) { 419 if (defined $cb) {
445 push @{ $self->{rc0}{$match} }, [$cb]; 420 $self->[1]{$tag} = $cb;
446 } elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
447 my ($type, @match) = @$match;
448 @match
449 ? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
450 : push @{ $self->{rc0}{$match->[0]} }, [$cb];
451 } else { 421 } else {
452 push @{ $self->{any} }, [$cb, $match]; 422 delete $self->[1]{$tag};
453 } 423 }
454 } 424 }
455 } 425 }
456 426
457 $port 427 $port
493 $res 463 $res
494 } 464 }
495 } 465 }
496} 466}
497 467
498=item $guard = mon $port, $cb->(@reason) 468=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
499 469
500=item $guard = mon $port, $rcvport 470=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
501 471
502=item $guard = mon $port 472=item $guard = mon $port # kill $SELF when $port dies
503 473
504=item $guard = mon $port, $rcvport, @msg 474=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
505 475
506Monitor the given port and do something when the port is killed, and 476Monitor the given port and do something when the port is killed or
507optionally return a guard that can be used to stop monitoring again. 477messages to it were lost, and optionally return a guard that can be used
478to stop monitoring again.
508 479
509In the first form (callback), the callback is simply called with any 480In the first form (callback), the callback is simply called with any
510number of C<@reason> elements (no @reason means that the port was deleted 481number of C<@reason> elements (no @reason means that the port was deleted
511"normally"). Note also that I<< the callback B<must> never die >>, so use 482"normally"). Note also that I<< the callback B<must> never die >>, so use
512C<eval> if unsure. 483C<eval> if unsure.
513 484
514In the second form (another port given), the other port (C<$rcvport) 485In the second form (another port given), the other port (C<$rcvport>)
515will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on 486will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
516"normal" kils nothing happens, while under all other conditions, the other 487"normal" kils nothing happens, while under all other conditions, the other
517port is killed with the same reason. 488port is killed with the same reason.
518 489
519The third form (kill self) is the same as the second form, except that 490The third form (kill self) is the same as the second form, except that
520C<$rvport> defaults to C<$SELF>. 491C<$rvport> defaults to C<$SELF>.
521 492
522In the last form (message), a message of the form C<@msg, @reason> will be 493In the last form (message), a message of the form C<@msg, @reason> will be
523C<snd>. 494C<snd>.
495
496Monitoring-actions are one-shot: once messages are lost (and a monitoring
497alert was raised), they are removed and will not trigger again.
524 498
525As a rule of thumb, monitoring requests should always monitor a port from 499As a rule of thumb, monitoring requests should always monitor a port from
526a local port (or callback). The reason is that kill messages might get 500a local port (or callback). The reason is that kill messages might get
527lost, just like any other message. Another less obvious reason is that 501lost, just like any other message. Another less obvious reason is that
528even monitoring requests can get lost (for exmaple, when the connection 502even monitoring requests can get lost (for example, when the connection
529to the other node goes down permanently). When monitoring a port locally 503to the other node goes down permanently). When monitoring a port locally
530these problems do not exist. 504these problems do not exist.
531 505
506C<mon> effectively guarantees that, in the absence of hardware failures,
507after starting the monitor, either all messages sent to the port will
508arrive, or the monitoring action will be invoked after possible message
509loss has been detected. No messages will be lost "in between" (after
510the first lost message no further messages will be received by the
511port). After the monitoring action was invoked, further messages might get
512delivered again.
513
514Inter-host-connection timeouts and monitoring depend on the transport
515used. The only transport currently implemented is TCP, and AnyEvent::MP
516relies on TCP to detect node-downs (this can take 10-15 minutes on a
517non-idle connection, and usually around two hours for idle conenctions).
518
519This means that monitoring is good for program errors and cleaning up
520stuff eventually, but they are no replacement for a timeout when you need
521to ensure some maximum latency.
522
532Example: call a given callback when C<$port> is killed. 523Example: call a given callback when C<$port> is killed.
533 524
534 mon $port, sub { warn "port died because of <@_>\n" }; 525 mon $port, sub { warn "port died because of <@_>\n" };
535 526
536Example: kill ourselves when C<$port> is killed abnormally. 527Example: kill ourselves when C<$port> is killed abnormally.
542 mon $port, $self => "restart"; 533 mon $port, $self => "restart";
543 534
544=cut 535=cut
545 536
546sub mon { 537sub mon {
547 my ($noderef, $port) = split /#/, shift, 2; 538 my ($nodeid, $port) = split /#/, shift, 2;
548 539
549 my $node = $NODE{$noderef} || add_node $noderef; 540 my $node = $NODE{$nodeid} || add_node $nodeid;
550 541
551 my $cb = @_ ? $_[0] : $SELF || Carp::croak 'mon: called with one argument only, but $SELF not set,'; 542 my $cb = @_ ? shift : $SELF || Carp::croak 'mon: called with one argument only, but $SELF not set,';
552 543
553 unless (ref $cb) { 544 unless (ref $cb) {
554 if (@_) { 545 if (@_) {
555 # send a kill info message 546 # send a kill info message
556 my (@msg) = @_; 547 my (@msg) = ($cb, @_);
557 $cb = sub { snd @msg, @_ }; 548 $cb = sub { snd @msg, @_ };
558 } else { 549 } else {
559 # simply kill other port 550 # simply kill other port
560 my $port = $cb; 551 my $port = $cb;
561 $cb = sub { kil $port, @_ if @_ }; 552 $cb = sub { kil $port, @_ if @_ };
574is killed, the references will be freed. 565is killed, the references will be freed.
575 566
576Optionally returns a guard that will stop the monitoring. 567Optionally returns a guard that will stop the monitoring.
577 568
578This function is useful when you create e.g. timers or other watchers and 569This function is useful when you create e.g. timers or other watchers and
579want to free them when the port gets killed: 570want to free them when the port gets killed (note the use of C<psub>):
580 571
581 $port->rcv (start => sub { 572 $port->rcv (start => sub {
582 my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub { 573 my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
583 undef $timer if 0.9 < rand; 574 undef $timer if 0.9 < rand;
584 }); 575 });
585 }); 576 });
586 577
587=cut 578=cut
596 587
597=item kil $port[, @reason] 588=item kil $port[, @reason]
598 589
599Kill the specified port with the given C<@reason>. 590Kill the specified port with the given C<@reason>.
600 591
601If no C<@reason> is specified, then the port is killed "normally" (linked 592If no C<@reason> is specified, then the port is killed "normally" (ports
602ports will not be kileld, or even notified). 593monitoring other ports will not necessarily die because a port dies
594"normally").
603 595
604Otherwise, linked ports get killed with the same reason (second form of 596Otherwise, linked ports get killed with the same reason (second form of
605C<mon>, see below). 597C<mon>, see above).
606 598
607Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks 599Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
608will be reported as reason C<< die => $@ >>. 600will be reported as reason C<< die => $@ >>.
609 601
610Transport/communication errors are reported as C<< transport_error => 602Transport/communication errors are reported as C<< transport_error =>
615=item $port = spawn $node, $initfunc[, @initdata] 607=item $port = spawn $node, $initfunc[, @initdata]
616 608
617Creates a port on the node C<$node> (which can also be a port ID, in which 609Creates a port on the node C<$node> (which can also be a port ID, in which
618case it's the node where that port resides). 610case it's the node where that port resides).
619 611
620The port ID of the newly created port is return immediately, and it is 612The port ID of the newly created port is returned immediately, and it is
621permissible to immediately start sending messages or monitor the port. 613possible to immediately start sending messages or to monitor the port.
622 614
623After the port has been created, the init function is 615After the port has been created, the init function is called on the remote
624called. This fucntion must be a fully-qualified function name 616node, in the same context as a C<rcv> callback. This function must be a
625(e.g. C<MyApp::Chat::Server::init>). 617fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
618specify a function in the main program, use C<::name>.
626 619
627If the function doesn't exist, then the node tries to C<require> 620If the function doesn't exist, then the node tries to C<require>
628the package, then the package above the package and so on (e.g. 621the package, then the package above the package and so on (e.g.
629C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function 622C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
630exists or it runs out of package names. 623exists or it runs out of package names.
631 624
632The init function is then called with the newly-created port as context 625The init function is then called with the newly-created port as context
633object (C<$SELF>) and the C<@initdata> values as arguments. 626object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
627call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
628the port might not get created.
634 629
635A common idiom is to pass your own port, monitor the spawned port, and 630A common idiom is to pass a local port, immediately monitor the spawned
636in the init function, monitor the original port. This two-way monitoring 631port, and in the remote init function, immediately monitor the passed
637ensures that both ports get cleaned up when there is a problem. 632local port. This two-way monitoring ensures that both ports get cleaned up
633when there is a problem.
634
635C<spawn> guarantees that the C<$initfunc> has no visible effects on the
636caller before C<spawn> returns (by delaying invocation when spawn is
637called for the local node).
638 638
639Example: spawn a chat server port on C<$othernode>. 639Example: spawn a chat server port on C<$othernode>.
640 640
641 # this node, executed from within a port context: 641 # this node, executed from within a port context:
642 my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF; 642 my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
657 657
658sub _spawn { 658sub _spawn {
659 my $port = shift; 659 my $port = shift;
660 my $init = shift; 660 my $init = shift;
661 661
662 # rcv will create the actual port
662 local $SELF = "$NODE#$port"; 663 local $SELF = "$NODE#$port";
663 eval { 664 eval {
664 &{ load_func $init } 665 &{ load_func $init }
665 }; 666 };
666 _self_die if $@; 667 _self_die if $@;
667} 668}
668 669
669sub spawn(@) { 670sub spawn(@) {
670 my ($noderef, undef) = split /#/, shift, 2; 671 my ($nodeid, undef) = split /#/, shift, 2;
671 672
672 my $id = "$RUNIQ." . $ID++; 673 my $id = "$RUNIQ." . $ID++;
673 674
674 ($NODE{$noderef} || add_node $noderef) 675 $_[0] =~ /::/
675 ->send (["", "AnyEvent::MP::_spawn" => $id, @_]); 676 or Carp::croak "spawn init function must be a fully-qualified name, caught";
676 677
678 snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
679
677 "$noderef#$id" 680 "$nodeid#$id"
678} 681}
679 682
680=back 683=item after $timeout, @msg
681 684
682=head1 NODE MESSAGES 685=item after $timeout, $callback
683 686
684Nodes understand the following messages sent to them. Many of them take 687Either sends the given message, or call the given callback, after the
685arguments called C<@reply>, which will simply be used to compose a reply 688specified number of seconds.
686message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
687the remaining arguments are simply the message data.
688 689
689While other messages exist, they are not public and subject to change. 690This is simply a utility function that comes in handy at times - the
691AnyEvent::MP author is not convinced of the wisdom of having it, though,
692so it may go away in the future.
690 693
691=over 4
692
693=cut 694=cut
694 695
695=item lookup => $name, @reply 696sub after($@) {
697 my ($timeout, @action) = @_;
696 698
697Replies with the port ID of the specified well-known port, or C<undef>. 699 my $t; $t = AE::timer $timeout, 0, sub {
698 700 undef $t;
699=item devnull => ... 701 ref $action[0]
700 702 ? $action[0]()
701Generic data sink/CPU heat conversion. 703 : snd @action;
702 704 };
703=item relay => $port, @msg 705}
704
705Simply forwards the message to the given port.
706
707=item eval => $string[ @reply]
708
709Evaluates the given string. If C<@reply> is given, then a message of the
710form C<@reply, $@, @evalres> is sent.
711
712Example: crash another node.
713
714 snd $othernode, eval => "exit";
715
716=item time => @reply
717
718Replies the the current node time to C<@reply>.
719
720Example: tell the current node to send the current time to C<$myport> in a
721C<timereply> message.
722
723 snd $NODE, time => $myport, timereply => 1, 2;
724 # => snd $myport, timereply => 1, 2, <time>
725 706
726=back 707=back
727 708
728=head1 AnyEvent::MP vs. Distributed Erlang 709=head1 AnyEvent::MP vs. Distributed Erlang
729 710
739 720
740Despite the similarities, there are also some important differences: 721Despite the similarities, there are also some important differences:
741 722
742=over 4 723=over 4
743 724
744=item * Node references contain the recipe on how to contact them. 725=item * Node IDs are arbitrary strings in AEMP.
745 726
746Erlang relies on special naming and DNS to work everywhere in the 727Erlang relies on special naming and DNS to work everywhere in the same
747same way. AEMP relies on each node knowing it's own address(es), with 728way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
748convenience functionality. 729configuration or DNS), but will otherwise discover other odes itself.
749 730
750This means that AEMP requires a less tightly controlled environment at the 731=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
751cost of longer node references and a slightly higher management overhead. 732uses "local ports are like remote ports".
733
734The failure modes for local ports are quite different (runtime errors
735only) then for remote ports - when a local port dies, you I<know> it dies,
736when a connection to another node dies, you know nothing about the other
737port.
738
739Erlang pretends remote ports are as reliable as local ports, even when
740they are not.
741
742AEMP encourages a "treat remote ports differently" philosophy, with local
743ports being the special case/exception, where transport errors cannot
744occur.
752 745
753=item * Erlang uses processes and a mailbox, AEMP does not queue. 746=item * Erlang uses processes and a mailbox, AEMP does not queue.
754 747
755Erlang uses processes that selctively receive messages, and therefore 748Erlang uses processes that selectively receive messages, and therefore
756needs a queue. AEMP is event based, queuing messages would serve no useful 749needs a queue. AEMP is event based, queuing messages would serve no
757purpose. 750useful purpose. For the same reason the pattern-matching abilities of
751AnyEvent::MP are more limited, as there is little need to be able to
752filter messages without dequeuing them.
758 753
759(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP). 754(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
760 755
761=item * Erlang sends are synchronous, AEMP sends are asynchronous. 756=item * Erlang sends are synchronous, AEMP sends are asynchronous.
762 757
763Sending messages in Erlang is synchronous and blocks the process. AEMP 758Sending messages in Erlang is synchronous and blocks the process (and
764sends are immediate, connection establishment is handled in the 759so does not need a queue that can overflow). AEMP sends are immediate,
765background. 760connection establishment is handled in the background.
766 761
767=item * Erlang can silently lose messages, AEMP cannot. 762=item * Erlang suffers from silent message loss, AEMP does not.
768 763
769Erlang makes few guarantees on messages delivery - messages can get lost 764Erlang makes few guarantees on messages delivery - messages can get lost
770without any of the processes realising it (i.e. you send messages a, b, 765without any of the processes realising it (i.e. you send messages a, b,
771and c, and the other side only receives messages a and c). 766and c, and the other side only receives messages a and c).
772 767
773AEMP guarantees correct ordering, and the guarantee that there are no 768AEMP guarantees correct ordering, and the guarantee that after one message
774holes in the message sequence. 769is lost, all following ones sent to the same port are lost as well, until
775 770monitoring raises an error, so there are no silent "holes" in the message
776=item * In Erlang, processes can be declared dead and later be found to be 771sequence.
777alive.
778
779In Erlang it can happen that a monitored process is declared dead and
780linked processes get killed, but later it turns out that the process is
781still alive - and can receive messages.
782
783In AEMP, when port monitoring detects a port as dead, then that port will
784eventually be killed - it cannot happen that a node detects a port as dead
785and then later sends messages to it, finding it is still alive.
786 772
787=item * Erlang can send messages to the wrong port, AEMP does not. 773=item * Erlang can send messages to the wrong port, AEMP does not.
788 774
789In Erlang it is quite possible that a node that restarts reuses a process 775In Erlang it is quite likely that a node that restarts reuses a process ID
790ID known to other nodes for a completely different process, causing 776known to other nodes for a completely different process, causing messages
791messages destined for that process to end up in an unrelated process. 777destined for that process to end up in an unrelated process.
792 778
793AEMP never reuses port IDs, so old messages or old port IDs floating 779AEMP never reuses port IDs, so old messages or old port IDs floating
794around in the network will not be sent to an unrelated port. 780around in the network will not be sent to an unrelated port.
795 781
796=item * Erlang uses unprotected connections, AEMP uses secure 782=item * Erlang uses unprotected connections, AEMP uses secure
797authentication and can use TLS. 783authentication and can use TLS.
798 784
799AEMP can use a proven protocol - SSL/TLS - to protect connections and 785AEMP can use a proven protocol - TLS - to protect connections and
800securely authenticate nodes. 786securely authenticate nodes.
801 787
802=item * The AEMP protocol is optimised for both text-based and binary 788=item * The AEMP protocol is optimised for both text-based and binary
803communications. 789communications.
804 790
805The AEMP protocol, unlike the Erlang protocol, supports both 791The AEMP protocol, unlike the Erlang protocol, supports both programming
806language-independent text-only protocols (good for debugging) and binary, 792language independent text-only protocols (good for debugging) and binary,
807language-specific serialisers (e.g. Storable). 793language-specific serialisers (e.g. Storable). By default, unless TLS is
794used, the protocol is actually completely text-based.
808 795
809It has also been carefully designed to be implementable in other languages 796It has also been carefully designed to be implementable in other languages
810with a minimum of work while gracefully degrading fucntionality to make the 797with a minimum of work while gracefully degrading functionality to make the
811protocol simple. 798protocol simple.
812 799
813=item * AEMP has more flexible monitoring options than Erlang. 800=item * AEMP has more flexible monitoring options than Erlang.
814 801
815In Erlang, you can chose to receive I<all> exit signals as messages 802In Erlang, you can chose to receive I<all> exit signals as messages
818Erlang, as one can choose between automatic kill, exit message or callback 805Erlang, as one can choose between automatic kill, exit message or callback
819on a per-process basis. 806on a per-process basis.
820 807
821=item * Erlang tries to hide remote/local connections, AEMP does not. 808=item * Erlang tries to hide remote/local connections, AEMP does not.
822 809
823Monitoring in Erlang is not an indicator of process death/crashes, 810Monitoring in Erlang is not an indicator of process death/crashes, in the
824as linking is (except linking is unreliable in Erlang). 811same way as linking is (except linking is unreliable in Erlang).
825 812
826In AEMP, you don't "look up" registered port names or send to named ports 813In AEMP, you don't "look up" registered port names or send to named ports
827that might or might not be persistent. Instead, you normally spawn a port 814that might or might not be persistent. Instead, you normally spawn a port
828on the remote node. The init function monitors the you, and you monitor 815on the remote node. The init function monitors you, and you monitor the
829the remote port. Since both monitors are local to the node, they are much 816remote port. Since both monitors are local to the node, they are much more
830more reliable. 817reliable (no need for C<spawn_link>).
831 818
832This also saves round-trips and avoids sending messages to the wrong port 819This also saves round-trips and avoids sending messages to the wrong port
833(hard to do in Erlang). 820(hard to do in Erlang).
834 821
835=back 822=back
836 823
824=head1 RATIONALE
825
826=over 4
827
828=item Why strings for port and node IDs, why not objects?
829
830We considered "objects", but found that the actual number of methods
831that can be called are quite low. Since port and node IDs travel over
832the network frequently, the serialising/deserialising would add lots of
833overhead, as well as having to keep a proxy object everywhere.
834
835Strings can easily be printed, easily serialised etc. and need no special
836procedures to be "valid".
837
838And as a result, a miniport consists of a single closure stored in a
839global hash - it can't become much cheaper.
840
841=item Why favour JSON, why not a real serialising format such as Storable?
842
843In fact, any AnyEvent::MP node will happily accept Storable as framing
844format, but currently there is no way to make a node use Storable by
845default (although all nodes will accept it).
846
847The default framing protocol is JSON because a) JSON::XS is many times
848faster for small messages and b) most importantly, after years of
849experience we found that object serialisation is causing more problems
850than it solves: Just like function calls, objects simply do not travel
851easily over the network, mostly because they will always be a copy, so you
852always have to re-think your design.
853
854Keeping your messages simple, concentrating on data structures rather than
855objects, will keep your messages clean, tidy and efficient.
856
857=back
858
837=head1 SEE ALSO 859=head1 SEE ALSO
860
861L<AnyEvent::MP::Intro> - a gentle introduction.
862
863L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
864
865L<AnyEvent::MP::Global> - network maintainance and port groups, to find
866your applications.
867
868L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
869all nodes.
838 870
839L<AnyEvent>. 871L<AnyEvent>.
840 872
841=head1 AUTHOR 873=head1 AUTHOR
842 874

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