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Revision 1.83 by root, Tue Sep 8 01:38:16 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 seed nodes
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
108Apart from the fact that other nodes know them as seed nodes and they have
109to have fixed listening addresses, seed nodes are perfectly normal nodes -
110any node can function as a seed node for others.
111
112In addition to discovering the network, seed nodes are also used to
113maintain the network and to connect nodes that otherwise would have
114trouble connecting. They form the backbone of the AnyEvent::MP network.
115
116Seed nodes are expected to be long-running, and at least one seed node
117should always be available.
118
119=item seeds - C<host:port>
120
121Seeds are transport endpoint(s) (usually a hostname/IP address and a
122TCP port) of nodes thta should be used as seed nodes.
123
124The nodes listening on those endpoints are expected to be long-running,
125and at least one of those should always be available. When nodes run out
126of connections (e.g. due to a network error), they try to re-establish
127connections to some seednodes again to join the network.
99 128
100=back 129=back
101 130
102=head1 VARIABLES/FUNCTIONS 131=head1 VARIABLES/FUNCTIONS
103 132
105 134
106=cut 135=cut
107 136
108package AnyEvent::MP; 137package AnyEvent::MP;
109 138
110use AnyEvent::MP::Base; 139use AnyEvent::MP::Kernel;
111 140
112use common::sense; 141use common::sense;
113 142
114use Carp (); 143use Carp ();
115 144
116use AE (); 145use AE ();
117 146
118use base "Exporter"; 147use base "Exporter";
119 148
120our $VERSION = '0.1'; 149our $VERSION = $AnyEvent::MP::Kernel::VERSION;
150
121our @EXPORT = qw( 151our @EXPORT = qw(
122 NODE $NODE *SELF node_of _any_ 152 NODE $NODE *SELF node_of after
123 resolve_node initialise_node 153 configure
124 snd rcv mon kil reg psub spawn 154 snd rcv mon mon_guard kil reg psub spawn
125 port 155 port
126); 156);
127 157
128our $SELF; 158our $SELF;
129 159
133 kil $SELF, die => $msg; 163 kil $SELF, die => $msg;
134} 164}
135 165
136=item $thisnode = NODE / $NODE 166=item $thisnode = NODE / $NODE
137 167
138The C<NODE> function returns, and the C<$NODE> variable contains 168The 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 169ID 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 170a call to C<configure>.
141identifiers become invalid.
142 171
143=item $noderef = node_of $port 172=item $nodeid = node_of $port
144 173
145Extracts and returns the noderef from a portid or a noderef. 174Extracts and returns the node ID from a port ID or a node ID.
146 175
147=item initialise_node $noderef, $seednode, $seednode... 176=item configure $profile, key => value...
148 177
149=item initialise_node "slave/", $master, $master... 178=item configure key => value...
150 179
151Before a node can talk to other nodes on the network it has to initialise 180Before a node can talk to other nodes on the network (i.e. enter
152itself - the minimum a node needs to know is it's own name, and optionally 181"distributed mode") it has to configure itself - the minimum a node needs
153it should know the noderefs of some other nodes in the network. 182to know is its own name, and optionally it should know the addresses of
183some other nodes in the network to discover other nodes.
154 184
155This function initialises a node - it must be called exactly once (or 185This function configures a node - it must be called exactly once (or
156never) before calling other AnyEvent::MP functions. 186never) before calling other AnyEvent::MP functions.
157 187
158All arguments are noderefs, which can be either resolved or unresolved.
159
160There are two types of networked nodes, public nodes and slave nodes:
161
162=over 4 188=over 4
163 189
164=item public nodes 190=item step 1, gathering configuration from profiles
165 191
166For public nodes, C<$noderef> must either be a (possibly unresolved) 192The 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 193L<aemp> commandline utility). The profile name can be specified via the
168which case the noderef will be guessed. 194named C<profile> parameter or can simply be the first parameter). If it is
195missing, then the nodename (F<uname -n>) will be used as profile name.
169 196
170Afterwards, the node will bind itself on all endpoints and try to connect 197The profile data is then gathered as follows:
171to all additional C<$seednodes> that are specified. Seednodes are optional
172and can be used to quickly bootstrap the node into an existing network.
173 198
174=item slave nodes 199First, all remaining key => value pairs (all of which are conveniently
200undocumented at the moment) will be interpreted as configuration
201data. Then they will be overwritten by any values specified in the global
202default configuration (see the F<aemp> utility), then the chain of
203profiles chosen by the profile name (and any C<parent> attributes).
175 204
176When the C<$noderef> is the special string C<slave/>, then the node will 205That means that the values specified in the profile have highest priority
177become a slave node. Slave nodes cannot be contacted from outside and will 206and the values specified directly via C<configure> have lowest priority,
178route most of their traffic to the master node that they attach to. 207and can only be used to specify defaults.
179 208
180At least one additional noderef is required: The node will try to connect 209If 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 210this process. If not, then the profile name will be used as node ID. The
182successfully connect to. 211special node ID of C<anon/> will be replaced by a random node ID.
212
213=item step 2, bind listener sockets
214
215The next step is to look up the binds in the profile, followed by binding
216aemp protocol listeners on all binds specified (it is possible and valid
217to have no binds, meaning that the node cannot be contacted form the
218outside. This means the node cannot talk to other nodes that also have no
219binds, but it can still talk to all "normal" nodes).
220
221If the profile does not specify a binds list, then a default of C<*> is
222used, meaning the node will bind on a dynamically-assigned port on every
223local IP address it finds.
224
225=item step 3, connect to seed nodes
226
227As the last step, the seeds list from the profile is passed to the
228L<AnyEvent::MP::Global> module, which will then use it to keep
229connectivity with at least one node at any point in time.
183 230
184=back 231=back
185 232
186This function will block until all nodes have been resolved and, for slave 233Example: become a distributed node using the locla node name as profile.
187nodes, until it has successfully established a connection to a master 234This should be the most common form of invocation for "daemon"-type nodes.
188server.
189 235
190Example: become a public node listening on the default node. 236 configure
191 237
192 initialise_node; 238Example: become an anonymous node. This form is often used for commandline
239clients.
193 240
194Example: become a public node, and try to contact some well-known master 241 configure nodeid => "anon/";
195servers to become part of the network.
196 242
197 initialise_node undef, "master1", "master2"; 243Example: configure a node using a profile called seed, which si suitable
244for a seed node as it binds on all local addresses on a fixed port (4040,
245customary for aemp).
198 246
199Example: become a public node listening on port C<4041>. 247 # use the aemp commandline utility
248 # aemp profile seed nodeid anon/ binds '*:4040'
200 249
201 initialise_node 4041; 250 # then use it
251 configure profile => "seed";
202 252
203Example: become a public node, only visible on localhost port 4044. 253 # or simply use aemp from the shell again:
254 # aemp run profile seed
204 255
205 initialise_node "locahost:4044"; 256 # or provide a nicer-to-remember nodeid
206 257 # 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
239 258
240=item $SELF 259=item $SELF
241 260
242Contains the current port id while executing C<rcv> callbacks or C<psub> 261Contains the current port id while executing C<rcv> callbacks or C<psub>
243blocks. 262blocks.
244 263
245=item SELF, %SELF, @SELF... 264=item *SELF, SELF, %SELF, @SELF...
246 265
247Due to some quirks in how perl exports variables, it is impossible to 266Due to some quirks in how perl exports variables, it is impossible to
248just export C<$SELF>, all the symbols called C<SELF> are exported by this 267just export C<$SELF>, all the symbols named C<SELF> are exported by this
249module, but only C<$SELF> is currently used. 268module, but only C<$SELF> is currently used.
250 269
251=item snd $port, type => @data 270=item snd $port, type => @data
252 271
253=item snd $port, @msg 272=item snd $port, @msg
254 273
255Send the given message to the given port ID, which can identify either 274Send 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 275local or a remote port, and must be a port ID.
257stringifies a sa port ID (such as a port object :).
258 276
259While the message can be about anything, it is highly recommended to use a 277While the message can be almost anything, it is highly recommended to
260string as first element (a portid, or some word that indicates a request 278use a string as first element (a port ID, or some word that indicates a
261type etc.). 279request type etc.) and to consist if only simple perl values (scalars,
280arrays, hashes) - if you think you need to pass an object, think again.
262 281
263The message data effectively becomes read-only after a call to this 282The message data logically becomes read-only after a call to this
264function: modifying any argument is not allowed and can cause many 283function: modifying any argument (or values referenced by them) is
265problems. 284forbidden, as there can be considerable time between the call to C<snd>
285and the time the message is actually being serialised - in fact, it might
286never be copied as within the same process it is simply handed to the
287receiving port.
266 288
267The type of data you can transfer depends on the transport protocol: when 289The type of data you can transfer depends on the transport protocol: when
268JSON is used, then only strings, numbers and arrays and hashes consisting 290JSON is used, then only strings, numbers and arrays and hashes consisting
269of those are allowed (no objects). When Storable is used, then anything 291of those are allowed (no objects). When Storable is used, then anything
270that Storable can serialise and deserialise is allowed, and for the local 292that Storable can serialise and deserialise is allowed, and for the local
271node, anything can be passed. 293node, anything can be passed. Best rely only on the common denominator of
294these.
272 295
273=item $local_port = port 296=item $local_port = port
274 297
275Create a new local port object that can be used either as a pattern 298Create a new local port object and returns its port ID. Initially it has
276matching port ("full port") or a single-callback port ("miniport"), 299no callbacks set and will throw an error when it receives messages.
277depending on how C<rcv> callbacks are bound to the object.
278 300
279=item $port = port { my @msg = @_; $finished } 301=item $local_port = port { my @msg = @_ }
280 302
281Creates a "miniport", that is, a very lightweight port without any pattern 303Creates 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. 304creating a port and calling C<rcv $port, $callback> on it.
284 305
285The block will be called for every message received on the port. When the 306The block will be called for every message received on the port, with the
286callback returns a true value its job is considered "done" and the port 307global variable C<$SELF> set to the port ID. Runtime errors will cause the
287will be destroyed. Otherwise it will stay alive. 308port to be C<kil>ed. The message will be passed as-is, no extra argument
309(i.e. no port ID) will be passed to the callback.
288 310
289The message will be passed as-is, no extra argument (i.e. no port id) will 311If you want to stop/destroy the port, simply C<kil> it:
290be passed to the callback.
291 312
292If you need the local port id in the callback, this works nicely: 313 my $port = port {
293 314 my @msg = @_;
294 my $port; $port = port { 315 ...
295 snd $otherport, reply => $port; 316 kil $SELF;
296 }; 317 };
297 318
298=cut 319=cut
299 320
300sub rcv($@); 321sub rcv($@);
322
323sub _kilme {
324 die "received message on port without callback";
325}
301 326
302sub port(;&) { 327sub port(;&) {
303 my $id = "$UNIQ." . $ID++; 328 my $id = "$UNIQ." . $ID++;
304 my $port = "$NODE#$id"; 329 my $port = "$NODE#$id";
305 330
306 if (@_) { 331 rcv $port, shift || \&_kilme;
307 rcv $port, shift;
308 } else {
309 $PORT{$id} = sub { }; # nop
310 }
311 332
312 $port 333 $port
313} 334}
314 335
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) 336=item rcv $local_port, $callback->(@msg)
335 337
336Replaces the callback on the specified miniport (after converting it to 338Replaces the default callback on the specified port. There is no way to
337one if required). 339remove the default callback: use C<sub { }> to disable it, or better
338 340C<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...] => $callback->(@msg), ...
344
345Register callbacks to be called on matching messages on the given full
346port (after converting it to one if required) and return the port.
347
348The callback has to return a true value when its work is done, after
349which is will be removed, or a false value in which case it will stay
350registered.
351 341
352The global C<$SELF> (exported by this module) contains C<$port> while 342The global C<$SELF> (exported by this module) contains C<$port> while
353executing the callback. 343executing the callback. Runtime errors during callback execution will
344result in the port being C<kil>ed.
354 345
355Runtime errors during callback execution will result in the port being 346The default callback received all messages not matched by a more specific
356C<kil>ed. 347C<tag> match.
357 348
358If the match is an array reference, then it will be matched against the 349=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
359first elements of the message, otherwise only the first element is being
360matched.
361 350
362Any element in the match that is specified as C<_any_> (a function 351Register (or replace) callbacks to be called on messages starting with the
363exported by this module) matches any single element of the message. 352given tag on the given port (and return the port), or unregister it (when
353C<$callback> is C<$undef> or missing). There can only be one callback
354registered for each tag.
364 355
365While not required, it is highly recommended that the first matching 356The original message will be passed to the callback, after the first
366element is a string identifying the message. The one-string-only match is 357element (the tag) has been removed. The callback will use the same
367also the most efficient match (by far). 358environment as the default callback (see above).
368 359
369Example: create a port and bind receivers on it in one go. 360Example: create a port and bind receivers on it in one go.
370 361
371 my $port = rcv port, 362 my $port = rcv port,
372 msg1 => sub { ...; 0 }, 363 msg1 => sub { ... },
373 msg2 => sub { ...; 0 }, 364 msg2 => sub { ... },
374 ; 365 ;
375 366
376Example: create a port, bind receivers and send it in a message elsewhere 367Example: create a port, bind receivers and send it in a message elsewhere
377in one go: 368in one go:
378 369
379 snd $otherport, reply => 370 snd $otherport, reply =>
380 rcv port, 371 rcv port,
381 msg1 => sub { ...; 0 }, 372 msg1 => sub { ... },
382 ... 373 ...
383 ; 374 ;
384 375
376Example: temporarily register a rcv callback for a tag matching some port
377(e.g. for a rpc reply) and unregister it after a message was received.
378
379 rcv $port, $otherport => sub {
380 my @reply = @_;
381
382 rcv $SELF, $otherport;
383 };
384
385=cut 385=cut
386 386
387sub rcv($@) { 387sub rcv($@) {
388 my $port = shift; 388 my $port = shift;
389 my ($noderef, $portid) = split /#/, $port, 2; 389 my ($nodeid, $portid) = split /#/, $port, 2;
390 390
391 ($NODE{$noderef} || add_node $noderef) == $NODE{""} 391 $NODE{$nodeid} == $NODE{""}
392 or Carp::croak "$port: rcv can only be called on local ports, caught"; 392 or Carp::croak "$port: rcv can only be called on local ports, caught";
393 393
394 if (@_ == 1) { 394 while (@_) {
395 if (ref $_[0]) {
396 if (my $self = $PORT_DATA{$portid}) {
397 "AnyEvent::MP::Port" eq ref $self
398 or Carp::croak "$port: rcv can only be called on message matching ports, caught";
399
400 $self->[2] = shift;
401 } else {
395 my $cb = shift; 402 my $cb = shift;
396 delete $PORT_DATA{$portid};
397 $PORT{$portid} = sub { 403 $PORT{$portid} = sub {
398 local $SELF = $port; 404 local $SELF = $port;
399 eval { 405 eval { &$cb }; _self_die if $@;
400 &$cb 406 };
401 and kil $port;
402 }; 407 }
403 _self_die if $@; 408 } elsif (defined $_[0]) {
404 };
405 } else {
406 my $self = $PORT_DATA{$portid} ||= do { 409 my $self = $PORT_DATA{$portid} ||= do {
407 my $self = bless { 410 my $self = bless [$PORT{$port} || sub { }, { }, $port], "AnyEvent::MP::Port";
408 id => $port,
409 }, "AnyEvent::MP::Port";
410 411
411 $PORT{$portid} = sub { 412 $PORT{$portid} = sub {
412 local $SELF = $port; 413 local $SELF = $port;
413 414
414 eval {
415 for (@{ $self->{rc0}{$_[0]} }) { 415 if (my $cb = $self->[1]{$_[0]}) {
416 $_ && &{$_->[0]} 416 shift;
417 && undef $_; 417 eval { &$cb }; _self_die if $@;
418 } 418 } else {
419
420 for (@{ $self->{rcv}{$_[0]} }) {
421 $_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
422 && &{$_->[0]} 419 &{ $self->[0] };
423 && undef $_;
424 }
425
426 for (@{ $self->{any} }) {
427 $_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
428 && &{$_->[0]}
429 && undef $_;
430 } 420 }
431 }; 421 };
432 _self_die if $@; 422
423 $self
433 }; 424 };
434 425
435 $self
436 };
437
438 "AnyEvent::MP::Port" eq ref $self 426 "AnyEvent::MP::Port" eq ref $self
439 or Carp::croak "$port: rcv can only be called on message matching ports, caught"; 427 or Carp::croak "$port: rcv can only be called on message matching ports, caught";
440 428
441 while (@_) {
442 my ($match, $cb) = splice @_, 0, 2; 429 my ($tag, $cb) = splice @_, 0, 2;
443 430
444 if (!ref $match) { 431 if (defined $cb) {
445 push @{ $self->{rc0}{$match} }, [$cb]; 432 $self->[1]{$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 { 433 } else {
452 push @{ $self->{any} }, [$cb, $match]; 434 delete $self->[1]{$tag};
453 } 435 }
454 } 436 }
455 } 437 }
456 438
457 $port 439 $port
493 $res 475 $res
494 } 476 }
495 } 477 }
496} 478}
497 479
498=item $guard = mon $port, $cb->(@reason) 480=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
499 481
500=item $guard = mon $port, $rcvport 482=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
501 483
502=item $guard = mon $port 484=item $guard = mon $port # kill $SELF when $port dies
503 485
504=item $guard = mon $port, $rcvport, @msg 486=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
505 487
506Monitor the given port and do something when the port is killed, and 488Monitor the given port and do something when the port is killed or
507optionally return a guard that can be used to stop monitoring again. 489messages to it were lost, and optionally return a guard that can be used
490to stop monitoring again.
508 491
509In the first form (callback), the callback is simply called with any 492In the first form (callback), the callback is simply called with any
510number of C<@reason> elements (no @reason means that the port was deleted 493number of C<@reason> elements (no @reason means that the port was deleted
511"normally"). Note also that I<< the callback B<must> never die >>, so use 494"normally"). Note also that I<< the callback B<must> never die >>, so use
512C<eval> if unsure. 495C<eval> if unsure.
513 496
514In the second form (another port given), the other port (C<$rcvport) 497In the second form (another port given), the other port (C<$rcvport>)
515will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on 498will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
516"normal" kils nothing happens, while under all other conditions, the other 499"normal" kils nothing happens, while under all other conditions, the other
517port is killed with the same reason. 500port is killed with the same reason.
518 501
519The third form (kill self) is the same as the second form, except that 502The third form (kill self) is the same as the second form, except that
520C<$rvport> defaults to C<$SELF>. 503C<$rvport> defaults to C<$SELF>.
521 504
522In the last form (message), a message of the form C<@msg, @reason> will be 505In the last form (message), a message of the form C<@msg, @reason> will be
523C<snd>. 506C<snd>.
507
508Monitoring-actions are one-shot: once messages are lost (and a monitoring
509alert was raised), they are removed and will not trigger again.
524 510
525As a rule of thumb, monitoring requests should always monitor a port from 511As 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 512a local port (or callback). The reason is that kill messages might get
527lost, just like any other message. Another less obvious reason is that 513lost, just like any other message. Another less obvious reason is that
528even monitoring requests can get lost (for exmaple, when the connection 514even monitoring requests can get lost (for example, when the connection
529to the other node goes down permanently). When monitoring a port locally 515to the other node goes down permanently). When monitoring a port locally
530these problems do not exist. 516these problems do not exist.
531 517
518C<mon> effectively guarantees that, in the absence of hardware failures,
519after starting the monitor, either all messages sent to the port will
520arrive, or the monitoring action will be invoked after possible message
521loss has been detected. No messages will be lost "in between" (after
522the first lost message no further messages will be received by the
523port). After the monitoring action was invoked, further messages might get
524delivered again.
525
526Inter-host-connection timeouts and monitoring depend on the transport
527used. The only transport currently implemented is TCP, and AnyEvent::MP
528relies on TCP to detect node-downs (this can take 10-15 minutes on a
529non-idle connection, and usually around two hours for idle conenctions).
530
531This means that monitoring is good for program errors and cleaning up
532stuff eventually, but they are no replacement for a timeout when you need
533to ensure some maximum latency.
534
532Example: call a given callback when C<$port> is killed. 535Example: call a given callback when C<$port> is killed.
533 536
534 mon $port, sub { warn "port died because of <@_>\n" }; 537 mon $port, sub { warn "port died because of <@_>\n" };
535 538
536Example: kill ourselves when C<$port> is killed abnormally. 539Example: kill ourselves when C<$port> is killed abnormally.
542 mon $port, $self => "restart"; 545 mon $port, $self => "restart";
543 546
544=cut 547=cut
545 548
546sub mon { 549sub mon {
547 my ($noderef, $port) = split /#/, shift, 2; 550 my ($nodeid, $port) = split /#/, shift, 2;
548 551
549 my $node = $NODE{$noderef} || add_node $noderef; 552 my $node = $NODE{$nodeid} || add_node $nodeid;
550 553
551 my $cb = @_ ? shift : $SELF || Carp::croak 'mon: called with one argument only, but $SELF not set,'; 554 my $cb = @_ ? shift : $SELF || Carp::croak 'mon: called with one argument only, but $SELF not set,';
552 555
553 unless (ref $cb) { 556 unless (ref $cb) {
554 if (@_) { 557 if (@_) {
574is killed, the references will be freed. 577is killed, the references will be freed.
575 578
576Optionally returns a guard that will stop the monitoring. 579Optionally returns a guard that will stop the monitoring.
577 580
578This function is useful when you create e.g. timers or other watchers and 581This function is useful when you create e.g. timers or other watchers and
579want to free them when the port gets killed: 582want to free them when the port gets killed (note the use of C<psub>):
580 583
581 $port->rcv (start => sub { 584 $port->rcv (start => sub {
582 my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub { 585 my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
583 undef $timer if 0.9 < rand; 586 undef $timer if 0.9 < rand;
584 }); 587 });
585 }); 588 });
586 589
587=cut 590=cut
596 599
597=item kil $port[, @reason] 600=item kil $port[, @reason]
598 601
599Kill the specified port with the given C<@reason>. 602Kill the specified port with the given C<@reason>.
600 603
601If no C<@reason> is specified, then the port is killed "normally" (linked 604If no C<@reason> is specified, then the port is killed "normally" (ports
602ports will not be kileld, or even notified). 605monitoring other ports will not necessarily die because a port dies
606"normally").
603 607
604Otherwise, linked ports get killed with the same reason (second form of 608Otherwise, linked ports get killed with the same reason (second form of
605C<mon>, see below). 609C<mon>, see above).
606 610
607Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks 611Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
608will be reported as reason C<< die => $@ >>. 612will be reported as reason C<< die => $@ >>.
609 613
610Transport/communication errors are reported as C<< transport_error => 614Transport/communication errors are reported as C<< transport_error =>
615=item $port = spawn $node, $initfunc[, @initdata] 619=item $port = spawn $node, $initfunc[, @initdata]
616 620
617Creates a port on the node C<$node> (which can also be a port ID, in which 621Creates a port on the node C<$node> (which can also be a port ID, in which
618case it's the node where that port resides). 622case it's the node where that port resides).
619 623
620The port ID of the newly created port is return immediately, and it is 624The port ID of the newly created port is returned immediately, and it is
621permissible to immediately start sending messages or monitor the port. 625possible to immediately start sending messages or to monitor the port.
622 626
623After the port has been created, the init function is 627After the port has been created, the init function is called on the remote
624called. This function must be a fully-qualified function name 628node, in the same context as a C<rcv> callback. This function must be a
625(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main 629fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
626program, use C<::name>. 630specify a function in the main program, use C<::name>.
627 631
628If the function doesn't exist, then the node tries to C<require> 632If the function doesn't exist, then the node tries to C<require>
629the package, then the package above the package and so on (e.g. 633the package, then the package above the package and so on (e.g.
630C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function 634C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
631exists or it runs out of package names. 635exists or it runs out of package names.
632 636
633The init function is then called with the newly-created port as context 637The init function is then called with the newly-created port as context
634object (C<$SELF>) and the C<@initdata> values as arguments. 638object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
639call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
640the port might not get created.
635 641
636A common idiom is to pass your own port, monitor the spawned port, and 642A common idiom is to pass a local port, immediately monitor the spawned
637in the init function, monitor the original port. This two-way monitoring 643port, and in the remote init function, immediately monitor the passed
638ensures that both ports get cleaned up when there is a problem. 644local port. This two-way monitoring ensures that both ports get cleaned up
645when there is a problem.
646
647C<spawn> guarantees that the C<$initfunc> has no visible effects on the
648caller before C<spawn> returns (by delaying invocation when spawn is
649called for the local node).
639 650
640Example: spawn a chat server port on C<$othernode>. 651Example: spawn a chat server port on C<$othernode>.
641 652
642 # this node, executed from within a port context: 653 # this node, executed from within a port context:
643 my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF; 654 my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
658 669
659sub _spawn { 670sub _spawn {
660 my $port = shift; 671 my $port = shift;
661 my $init = shift; 672 my $init = shift;
662 673
674 # rcv will create the actual port
663 local $SELF = "$NODE#$port"; 675 local $SELF = "$NODE#$port";
664 eval { 676 eval {
665 &{ load_func $init } 677 &{ load_func $init }
666 }; 678 };
667 _self_die if $@; 679 _self_die if $@;
668} 680}
669 681
670sub spawn(@) { 682sub spawn(@) {
671 my ($noderef, undef) = split /#/, shift, 2; 683 my ($nodeid, undef) = split /#/, shift, 2;
672 684
673 my $id = "$RUNIQ." . $ID++; 685 my $id = "$RUNIQ." . $ID++;
674 686
675 $_[0] =~ /::/ 687 $_[0] =~ /::/
676 or Carp::croak "spawn init function must be a fully-qualified name, caught"; 688 or Carp::croak "spawn init function must be a fully-qualified name, caught";
677 689
678 ($NODE{$noderef} || add_node $noderef) 690 snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
679 ->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
680 691
681 "$noderef#$id" 692 "$nodeid#$id"
682} 693}
683 694
684=back 695=item after $timeout, @msg
685 696
686=head1 NODE MESSAGES 697=item after $timeout, $callback
687 698
688Nodes understand the following messages sent to them. Many of them take 699Either sends the given message, or call the given callback, after the
689arguments called C<@reply>, which will simply be used to compose a reply 700specified number of seconds.
690message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
691the remaining arguments are simply the message data.
692 701
693While other messages exist, they are not public and subject to change. 702This is simply a utility function that comes in handy at times - the
703AnyEvent::MP author is not convinced of the wisdom of having it, though,
704so it may go away in the future.
694 705
695=over 4
696
697=cut 706=cut
698 707
699=item lookup => $name, @reply 708sub after($@) {
709 my ($timeout, @action) = @_;
700 710
701Replies with the port ID of the specified well-known port, or C<undef>. 711 my $t; $t = AE::timer $timeout, 0, sub {
702 712 undef $t;
703=item devnull => ... 713 ref $action[0]
704 714 ? $action[0]()
705Generic data sink/CPU heat conversion. 715 : snd @action;
706 716 };
707=item relay => $port, @msg 717}
708
709Simply forwards the message to the given port.
710
711=item eval => $string[ @reply]
712
713Evaluates the given string. If C<@reply> is given, then a message of the
714form C<@reply, $@, @evalres> is sent.
715
716Example: crash another node.
717
718 snd $othernode, eval => "exit";
719
720=item time => @reply
721
722Replies the the current node time to C<@reply>.
723
724Example: tell the current node to send the current time to C<$myport> in a
725C<timereply> message.
726
727 snd $NODE, time => $myport, timereply => 1, 2;
728 # => snd $myport, timereply => 1, 2, <time>
729 718
730=back 719=back
731 720
732=head1 AnyEvent::MP vs. Distributed Erlang 721=head1 AnyEvent::MP vs. Distributed Erlang
733 722
743 732
744Despite the similarities, there are also some important differences: 733Despite the similarities, there are also some important differences:
745 734
746=over 4 735=over 4
747 736
748=item * Node references contain the recipe on how to contact them. 737=item * Node IDs are arbitrary strings in AEMP.
749 738
750Erlang relies on special naming and DNS to work everywhere in the 739Erlang relies on special naming and DNS to work everywhere in the same
751same way. AEMP relies on each node knowing it's own address(es), with 740way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
752convenience functionality. 741configuration or DNS), but will otherwise discover other odes itself.
753 742
754This means that AEMP requires a less tightly controlled environment at the 743=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
755cost of longer node references and a slightly higher management overhead. 744uses "local ports are like remote ports".
745
746The failure modes for local ports are quite different (runtime errors
747only) then for remote ports - when a local port dies, you I<know> it dies,
748when a connection to another node dies, you know nothing about the other
749port.
750
751Erlang pretends remote ports are as reliable as local ports, even when
752they are not.
753
754AEMP encourages a "treat remote ports differently" philosophy, with local
755ports being the special case/exception, where transport errors cannot
756occur.
756 757
757=item * Erlang uses processes and a mailbox, AEMP does not queue. 758=item * Erlang uses processes and a mailbox, AEMP does not queue.
758 759
759Erlang uses processes that selctively receive messages, and therefore 760Erlang uses processes that selectively receive messages, and therefore
760needs a queue. AEMP is event based, queuing messages would serve no useful 761needs a queue. AEMP is event based, queuing messages would serve no
761purpose. 762useful purpose. For the same reason the pattern-matching abilities of
763AnyEvent::MP are more limited, as there is little need to be able to
764filter messages without dequeuing them.
762 765
763(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP). 766(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
764 767
765=item * Erlang sends are synchronous, AEMP sends are asynchronous. 768=item * Erlang sends are synchronous, AEMP sends are asynchronous.
766 769
767Sending messages in Erlang is synchronous and blocks the process. AEMP 770Sending messages in Erlang is synchronous and blocks the process (and
768sends are immediate, connection establishment is handled in the 771so does not need a queue that can overflow). AEMP sends are immediate,
769background. 772connection establishment is handled in the background.
770 773
771=item * Erlang can silently lose messages, AEMP cannot. 774=item * Erlang suffers from silent message loss, AEMP does not.
772 775
773Erlang makes few guarantees on messages delivery - messages can get lost 776Erlang makes few guarantees on messages delivery - messages can get lost
774without any of the processes realising it (i.e. you send messages a, b, 777without any of the processes realising it (i.e. you send messages a, b,
775and c, and the other side only receives messages a and c). 778and c, and the other side only receives messages a and c).
776 779
777AEMP guarantees correct ordering, and the guarantee that there are no 780AEMP guarantees correct ordering, and the guarantee that after one message
778holes in the message sequence. 781is lost, all following ones sent to the same port are lost as well, until
779 782monitoring raises an error, so there are no silent "holes" in the message
780=item * In Erlang, processes can be declared dead and later be found to be 783sequence.
781alive.
782
783In Erlang it can happen that a monitored process is declared dead and
784linked processes get killed, but later it turns out that the process is
785still alive - and can receive messages.
786
787In AEMP, when port monitoring detects a port as dead, then that port will
788eventually be killed - it cannot happen that a node detects a port as dead
789and then later sends messages to it, finding it is still alive.
790 784
791=item * Erlang can send messages to the wrong port, AEMP does not. 785=item * Erlang can send messages to the wrong port, AEMP does not.
792 786
793In Erlang it is quite possible that a node that restarts reuses a process 787In Erlang it is quite likely that a node that restarts reuses a process ID
794ID known to other nodes for a completely different process, causing 788known to other nodes for a completely different process, causing messages
795messages destined for that process to end up in an unrelated process. 789destined for that process to end up in an unrelated process.
796 790
797AEMP never reuses port IDs, so old messages or old port IDs floating 791AEMP never reuses port IDs, so old messages or old port IDs floating
798around in the network will not be sent to an unrelated port. 792around in the network will not be sent to an unrelated port.
799 793
800=item * Erlang uses unprotected connections, AEMP uses secure 794=item * Erlang uses unprotected connections, AEMP uses secure
801authentication and can use TLS. 795authentication and can use TLS.
802 796
803AEMP can use a proven protocol - SSL/TLS - to protect connections and 797AEMP can use a proven protocol - TLS - to protect connections and
804securely authenticate nodes. 798securely authenticate nodes.
805 799
806=item * The AEMP protocol is optimised for both text-based and binary 800=item * The AEMP protocol is optimised for both text-based and binary
807communications. 801communications.
808 802
809The AEMP protocol, unlike the Erlang protocol, supports both 803The AEMP protocol, unlike the Erlang protocol, supports both programming
810language-independent text-only protocols (good for debugging) and binary, 804language independent text-only protocols (good for debugging) and binary,
811language-specific serialisers (e.g. Storable). 805language-specific serialisers (e.g. Storable). By default, unless TLS is
806used, the protocol is actually completely text-based.
812 807
813It has also been carefully designed to be implementable in other languages 808It has also been carefully designed to be implementable in other languages
814with a minimum of work while gracefully degrading fucntionality to make the 809with a minimum of work while gracefully degrading functionality to make the
815protocol simple. 810protocol simple.
816 811
817=item * AEMP has more flexible monitoring options than Erlang. 812=item * AEMP has more flexible monitoring options than Erlang.
818 813
819In Erlang, you can chose to receive I<all> exit signals as messages 814In Erlang, you can chose to receive I<all> exit signals as messages
822Erlang, as one can choose between automatic kill, exit message or callback 817Erlang, as one can choose between automatic kill, exit message or callback
823on a per-process basis. 818on a per-process basis.
824 819
825=item * Erlang tries to hide remote/local connections, AEMP does not. 820=item * Erlang tries to hide remote/local connections, AEMP does not.
826 821
827Monitoring in Erlang is not an indicator of process death/crashes, 822Monitoring in Erlang is not an indicator of process death/crashes, in the
828as linking is (except linking is unreliable in Erlang). 823same way as linking is (except linking is unreliable in Erlang).
829 824
830In AEMP, you don't "look up" registered port names or send to named ports 825In AEMP, you don't "look up" registered port names or send to named ports
831that might or might not be persistent. Instead, you normally spawn a port 826that might or might not be persistent. Instead, you normally spawn a port
832on the remote node. The init function monitors the you, and you monitor 827on the remote node. The init function monitors you, and you monitor the
833the remote port. Since both monitors are local to the node, they are much 828remote port. Since both monitors are local to the node, they are much more
834more reliable. 829reliable (no need for C<spawn_link>).
835 830
836This also saves round-trips and avoids sending messages to the wrong port 831This also saves round-trips and avoids sending messages to the wrong port
837(hard to do in Erlang). 832(hard to do in Erlang).
838 833
839=back 834=back
840 835
836=head1 RATIONALE
837
838=over 4
839
840=item Why strings for port and node IDs, why not objects?
841
842We considered "objects", but found that the actual number of methods
843that can be called are quite low. Since port and node IDs travel over
844the network frequently, the serialising/deserialising would add lots of
845overhead, as well as having to keep a proxy object everywhere.
846
847Strings can easily be printed, easily serialised etc. and need no special
848procedures to be "valid".
849
850And as a result, a miniport consists of a single closure stored in a
851global hash - it can't become much cheaper.
852
853=item Why favour JSON, why not a real serialising format such as Storable?
854
855In fact, any AnyEvent::MP node will happily accept Storable as framing
856format, but currently there is no way to make a node use Storable by
857default (although all nodes will accept it).
858
859The default framing protocol is JSON because a) JSON::XS is many times
860faster for small messages and b) most importantly, after years of
861experience we found that object serialisation is causing more problems
862than it solves: Just like function calls, objects simply do not travel
863easily over the network, mostly because they will always be a copy, so you
864always have to re-think your design.
865
866Keeping your messages simple, concentrating on data structures rather than
867objects, will keep your messages clean, tidy and efficient.
868
869=back
870
841=head1 SEE ALSO 871=head1 SEE ALSO
872
873L<AnyEvent::MP::Intro> - a gentle introduction.
874
875L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
876
877L<AnyEvent::MP::Global> - network maintainance and port groups, to find
878your applications.
879
880L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
881all nodes.
842 882
843L<AnyEvent>. 883L<AnyEvent>.
844 884
845=head1 AUTHOR 885=head1 AUTHOR
846 886

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