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Revision 1.126 by root, Sat Mar 3 19:43:41 2012 UTC

1=head1 NAME 1=head1 NAME
2 2
3AnyEvent::MP - multi-processing/message-passing framework 3AnyEvent::MP - erlang-style multi-processing/message-passing framework
4 4
5=head1 SYNOPSIS 5=head1 SYNOPSIS
6 6
7 use AnyEvent::MP; 7 use AnyEvent::MP;
8 8
9 NODE # returns this node identifier
10 $NODE # contains this node identifier 9 $NODE # contains this node's node ID
10 NODE # returns this node's node ID
11 11
12 $SELF # receiving/own port id in rcv callbacks
13
14 # initialise the node so it can send/receive messages
15 configure;
16
17 # ports are message destinations
18
19 # sending messages
12 snd $port, type => data...; 20 snd $port, type => data...;
21 snd $port, @msg;
22 snd @msg_with_first_element_being_a_port;
13 23
14 rcv $port, smartmatch => $cb->($port, @msg); 24 # creating/using ports, the simple way
25 my $simple_port = port { my @msg = @_ };
15 26
16 # examples: 27 # creating/using ports, tagged message matching
28 my $port = port;
17 rcv $port2, ping => sub { snd $_[0], "pong"; 0 }; 29 rcv $port, ping => sub { snd $_[0], "pong" };
18 rcv $port1, pong => sub { warn "pong received\n" }; 30 rcv $port, pong => sub { warn "pong received\n" };
19 snd $port2, ping => $port1;
20 31
21 # more, smarter, matches (_any_ is exported by this module) 32 # create a port on another node
22 rcv $port, [child_died => $pid] => sub { ... 33 my $port = spawn $node, $initfunc, @initdata;
23 rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3 34
35 # destroy a port again
36 kil $port; # "normal" kill
37 kil $port, my_error => "everything is broken"; # error kill
38
39 # monitoring
40 mon $localport, $cb->(@msg) # callback is invoked on death
41 mon $localport, $otherport # kill otherport on abnormal death
42 mon $localport, $otherport, @msg # send message on death
43
44 # temporarily execute code in port context
45 peval $port, sub { die "kill the port!" };
46
47 # execute callbacks in $SELF port context
48 my $timer = AE::timer 1, 0, psub {
49 die "kill the port, delayed";
50 };
51
52=head1 CURRENT STATUS
53
54 bin/aemp - stable.
55 AnyEvent::MP - stable API, should work.
56 AnyEvent::MP::Intro - explains most concepts.
57 AnyEvent::MP::Kernel - mostly stable API.
58 AnyEvent::MP::Global - stable API.
24 59
25=head1 DESCRIPTION 60=head1 DESCRIPTION
26 61
27This module (-family) implements a simple message passing framework. 62This module (-family) implements a simple message passing framework.
28 63
29Despite its simplicity, you can securely message other processes running 64Despite its simplicity, you can securely message other processes running
30on the same or other hosts. 65on the same or other hosts, and you can supervise entities remotely.
31 66
32At the moment, this module family is severly brokena nd underdocumented, 67For an introduction to this module family, see the L<AnyEvent::MP::Intro>
33so do not use. This was uploaded mainly to resreve the CPAN namespace - 68manual page and the examples under F<eg/>.
34stay tuned!
35 69
36=head1 CONCEPTS 70=head1 CONCEPTS
37 71
38=over 4 72=over 4
39 73
40=item port 74=item port
41 75
42A port is something you can send messages to with the C<snd> function, and 76Not to be confused with a TCP port, a "port" is something you can send
43you can register C<rcv> handlers with. All C<rcv> handlers will receive 77messages to (with the C<snd> function).
44messages they match, messages will not be queued.
45 78
79Ports allow you to register C<rcv> handlers that can match all or just
80some messages. Messages send to ports will not be queued, regardless of
81anything was listening for them or not.
82
83Ports are represented by (printable) strings called "port IDs".
84
46=item port id - C<noderef#portname> 85=item port ID - C<nodeid#portname>
47 86
48A port id is always the noderef, a hash-mark (C<#>) as separator, followed 87A port ID is the concatenation of a node ID, a hash-mark (C<#>)
49by a port name (a printable string of unspecified format). 88as separator, and a port name (a printable string of unspecified
89format created by AnyEvent::MP).
50 90
51=item node 91=item node
52 92
53A node is a single process containing at least one port - the node 93A node is a single process containing at least one port - the node port,
54port. You can send messages to node ports to let them create new ports, 94which enables nodes to manage each other remotely, and to create new
55among other things. 95ports.
56 96
57Initially, nodes are either private (single-process only) or hidden 97Nodes are either public (have one or more listening ports) or private
58(connected to a master node only). Only when they epxlicitly "become 98(no listening ports). Private nodes cannot talk to other private nodes
59public" can you send them messages from unrelated other nodes. 99currently, but all nodes can talk to public nodes.
60 100
61=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id> 101Nodes is represented by (printable) strings called "node IDs".
62 102
103=item node ID - C<[A-Za-z0-9_\-.:]*>
104
63A noderef is a string that either uniquely identifies a given node (for 105A node ID is a string that uniquely identifies the node within a
64private and hidden nodes), or contains a recipe on how to reach a given 106network. Depending on the configuration used, node IDs can look like a
65node (for public nodes). 107hostname, a hostname and a port, or a random string. AnyEvent::MP itself
108doesn't interpret node IDs in any way except to uniquely identify a node.
109
110=item binds - C<ip:port>
111
112Nodes can only talk to each other by creating some kind of connection to
113each other. To do this, nodes should listen on one or more local transport
114endpoints - binds.
115
116Currently, only standard C<ip:port> specifications can be used, which
117specify TCP ports to listen on. So a bind is basically just a tcp socket
118in listening mode thta accepts conenctions form other nodes.
119
120=item seed nodes
121
122When a node starts, it knows nothing about the network it is in - it
123needs to connect to at least one other node that is already in the
124network. These other nodes are called "seed nodes".
125
126Seed nodes themselves are not special - they are seed nodes only because
127some other node I<uses> them as such, but any node can be used as seed
128node for other nodes, and eahc node cna use a different set of seed nodes.
129
130In addition to discovering the network, seed nodes are also used to
131maintain the network - all nodes using the same seed node form are part of
132the same network. If a network is split into multiple subnets because e.g.
133the network link between the parts goes down, then using the same seed
134nodes for all nodes ensures that eventually the subnets get merged again.
135
136Seed nodes are expected to be long-running, and at least one seed node
137should always be available. They should also be relatively responsive - a
138seed node that blocks for long periods will slow down everybody else.
139
140For small networks, it's best if every node uses the same set of seed
141nodes. For large networks, it can be useful to specify "regional" seed
142nodes for most nodes in an area, and use all seed nodes as seed nodes for
143each other. What's important is that all seed nodes connections form a
144complete graph, so that the network cannot split into separate subnets
145forever.
146
147Seed nodes are represented by seed IDs.
148
149=item seed IDs - C<host:port>
150
151Seed IDs are transport endpoint(s) (usually a hostname/IP address and a
152TCP port) of nodes that should be used as seed nodes.
153
154=item global nodes
155
156An AEMP network needs a discovery service - nodes need to know how to
157connect to other nodes they only know by name. In addition, AEMP offers a
158distributed "group database", which maps group names to a list of strings
159- for example, to register worker ports.
160
161A network needs at least one global node to work, and allows every node to
162be a global node.
163
164Any node that loads the L<AnyEvent::MP::Global> module becomes a global
165node and tries to keep connections to all other nodes. So while it can
166make sense to make every node "global" in small networks, it usually makes
167sense to only make seed nodes into global nodes in large networks (nodes
168keep connections to seed nodes and global nodes, so makign them the same
169reduces overhead).
66 170
67=back 171=back
68 172
69=head1 VARIABLES/FUNCTIONS 173=head1 VARIABLES/FUNCTIONS
70 174
72 176
73=cut 177=cut
74 178
75package AnyEvent::MP; 179package AnyEvent::MP;
76 180
181use AnyEvent::MP::Config ();
77use AnyEvent::MP::Base; 182use AnyEvent::MP::Kernel;
183use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID);
78 184
79use common::sense; 185use common::sense;
80 186
81use Carp (); 187use Carp ();
82 188
83use AE (); 189use AE ();
190use Guard ();
84 191
85use base "Exporter"; 192use base "Exporter";
86 193
87our $VERSION = '0.02'; 194our $VERSION = $AnyEvent::MP::Config::VERSION;
195
88our @EXPORT = qw( 196our @EXPORT = qw(
89 NODE $NODE $PORT snd rcv _any_ 197 NODE $NODE *SELF node_of after
90 create_port create_port_on 198 configure
91 create_miniport 199 snd rcv mon mon_guard kil psub peval spawn cal
92 become_slave become_public 200 port
201 db_set db_del db_reg
93); 202);
94 203
204our $SELF;
205
206sub _self_die() {
207 my $msg = $@;
208 $msg =~ s/\n+$// unless ref $msg;
209 kil $SELF, die => $msg;
210}
211
95=item NODE / $NODE 212=item $thisnode = NODE / $NODE
96 213
97The C<NODE ()> function and the C<$NODE> variable contain the noderef of 214The C<NODE> function returns, and the C<$NODE> variable contains, the node
98the local node. The value is initialised by a call to C<become_public> or 215ID of the node running in the current process. This value is initialised by
99C<become_slave>, after which all local port identifiers become invalid. 216a call to C<configure>.
100 217
218=item $nodeid = node_of $port
219
220Extracts and returns the node ID from a port ID or a node ID.
221
222=item configure $profile, key => value...
223
224=item configure key => value...
225
226Before a node can talk to other nodes on the network (i.e. enter
227"distributed mode") it has to configure itself - the minimum a node needs
228to know is its own name, and optionally it should know the addresses of
229some other nodes in the network to discover other nodes.
230
231This function configures a node - it must be called exactly once (or
232never) before calling other AnyEvent::MP functions.
233
234The key/value pairs are basically the same ones as documented for the
235F<aemp> command line utility (sans the set/del prefix), with two additions:
236
237=over 4
238
239=item norc => $boolean (default false)
240
241If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I<not>
242be consulted - all configuraiton options must be specified in the
243C<configure> call.
244
245=item force => $boolean (default false)
246
247IF true, then the values specified in the C<configure> will take
248precedence over any values configured via the rc file. The default is for
249the rc file to override any options specified in the program.
250
251=back
252
253=over 4
254
255=item step 1, gathering configuration from profiles
256
257The function first looks up a profile in the aemp configuration (see the
258L<aemp> commandline utility). The profile name can be specified via the
259named C<profile> parameter or can simply be the first parameter). If it is
260missing, then the nodename (F<uname -n>) will be used as profile name.
261
262The profile data is then gathered as follows:
263
264First, all remaining key => value pairs (all of which are conveniently
265undocumented at the moment) will be interpreted as configuration
266data. Then they will be overwritten by any values specified in the global
267default configuration (see the F<aemp> utility), then the chain of
268profiles chosen by the profile name (and any C<parent> attributes).
269
270That means that the values specified in the profile have highest priority
271and the values specified directly via C<configure> have lowest priority,
272and can only be used to specify defaults.
273
274If the profile specifies a node ID, then this will become the node ID of
275this process. If not, then the profile name will be used as node ID, with
276a unique randoms tring (C</%u>) appended.
277
278The node ID can contain some C<%> sequences that are expanded: C<%n>
279is expanded to the local nodename, C<%u> is replaced by a random
280strign to make the node unique. For example, the F<aemp> commandline
281utility uses C<aemp/%n/%u> as nodename, which might expand to
282C<aemp/cerebro/ZQDGSIkRhEZQDGSIkRhE>.
283
284=item step 2, bind listener sockets
285
286The next step is to look up the binds in the profile, followed by binding
287aemp protocol listeners on all binds specified (it is possible and valid
288to have no binds, meaning that the node cannot be contacted form the
289outside. This means the node cannot talk to other nodes that also have no
290binds, but it can still talk to all "normal" nodes).
291
292If the profile does not specify a binds list, then a default of C<*> is
293used, meaning the node will bind on a dynamically-assigned port on every
294local IP address it finds.
295
296=item step 3, connect to seed nodes
297
298As the last step, the seed ID list from the profile is passed to the
299L<AnyEvent::MP::Global> module, which will then use it to keep
300connectivity with at least one node at any point in time.
301
302=back
303
304Example: become a distributed node using the local node name as profile.
305This should be the most common form of invocation for "daemon"-type nodes.
306
307 configure
308
309Example: become a semi-anonymous node. This form is often used for
310commandline clients.
311
312 configure nodeid => "myscript/%n/%u";
313
314Example: configure a node using a profile called seed, which is suitable
315for a seed node as it binds on all local addresses on a fixed port (4040,
316customary for aemp).
317
318 # use the aemp commandline utility
319 # aemp profile seed binds '*:4040'
320
321 # then use it
322 configure profile => "seed";
323
324 # or simply use aemp from the shell again:
325 # aemp run profile seed
326
327 # or provide a nicer-to-remember nodeid
328 # aemp run profile seed nodeid "$(hostname)"
329
330=item $SELF
331
332Contains the current port id while executing C<rcv> callbacks or C<psub>
333blocks.
334
335=item *SELF, SELF, %SELF, @SELF...
336
337Due to some quirks in how perl exports variables, it is impossible to
338just export C<$SELF>, all the symbols named C<SELF> are exported by this
339module, but only C<$SELF> is currently used.
340
101=item snd $portid, type => @data 341=item snd $port, type => @data
102 342
103=item snd $portid, @msg 343=item snd $port, @msg
104 344
105Send the given message to the given port ID, which can identify either 345Send the given message to the given port, which can identify either a
106a local or a remote port, and can be either a string or soemthignt hat 346local or a remote port, and must be a port ID.
107stringifies a sa port ID (such as a port object :).
108 347
109While the message can be about anything, it is highly recommended to use a 348While the message can be almost anything, it is highly recommended to
110string as first element (a portid, or some word that indicates a request 349use a string as first element (a port ID, or some word that indicates a
111type etc.). 350request type etc.) and to consist if only simple perl values (scalars,
351arrays, hashes) - if you think you need to pass an object, think again.
112 352
113The message data effectively becomes read-only after a call to this 353The message data logically becomes read-only after a call to this
114function: modifying any argument is not allowed and can cause many 354function: modifying any argument (or values referenced by them) is
115problems. 355forbidden, as there can be considerable time between the call to C<snd>
356and the time the message is actually being serialised - in fact, it might
357never be copied as within the same process it is simply handed to the
358receiving port.
116 359
117The type of data you can transfer depends on the transport protocol: when 360The type of data you can transfer depends on the transport protocol: when
118JSON is used, then only strings, numbers and arrays and hashes consisting 361JSON is used, then only strings, numbers and arrays and hashes consisting
119of those are allowed (no objects). When Storable is used, then anything 362of those are allowed (no objects). When Storable is used, then anything
120that Storable can serialise and deserialise is allowed, and for the local 363that Storable can serialise and deserialise is allowed, and for the local
121node, anything can be passed. 364node, anything can be passed. Best rely only on the common denominator of
365these.
122 366
123=item $local_port = create_port 367=item $local_port = port
124 368
125Create a new local port object. See the next section for allowed methods. 369Create a new local port object and returns its port ID. Initially it has
370no callbacks set and will throw an error when it receives messages.
126 371
127=cut 372=item $local_port = port { my @msg = @_ }
128 373
129sub create_port { 374Creates a new local port, and returns its ID. Semantically the same as
130 my $id = "$AnyEvent::MP::Base::UNIQ." . $AnyEvent::MP::Base::ID++; 375creating a port and calling C<rcv $port, $callback> on it.
131 376
132 my $self = bless { 377The block will be called for every message received on the port, with the
133 id => "$NODE#$id", 378global variable C<$SELF> set to the port ID. Runtime errors will cause the
134 names => [$id], 379port to be C<kil>ed. The message will be passed as-is, no extra argument
135 }, "AnyEvent::MP::Port"; 380(i.e. no port ID) will be passed to the callback.
136 381
137 $AnyEvent::MP::Base::PORT{$id} = sub { 382If you want to stop/destroy the port, simply C<kil> it:
138 unshift @_, $self;
139 383
140 for (@{ $self->{rc0}{$_[1]} }) { 384 my $port = port {
141 $_ && &{$_->[0]} 385 my @msg = @_;
142 && undef $_; 386 ...
387 kil $SELF;
388 };
389
390=cut
391
392sub rcv($@);
393
394sub _kilme {
395 die "received message on port without callback";
396}
397
398sub port(;&) {
399 my $id = $UNIQ . ++$ID;
400 my $port = "$NODE#$id";
401
402 rcv $port, shift || \&_kilme;
403
404 $port
405}
406
407=item rcv $local_port, $callback->(@msg)
408
409Replaces the default callback on the specified port. There is no way to
410remove the default callback: use C<sub { }> to disable it, or better
411C<kil> the port when it is no longer needed.
412
413The global C<$SELF> (exported by this module) contains C<$port> while
414executing the callback. Runtime errors during callback execution will
415result in the port being C<kil>ed.
416
417The default callback received all messages not matched by a more specific
418C<tag> match.
419
420=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
421
422Register (or replace) callbacks to be called on messages starting with the
423given tag on the given port (and return the port), or unregister it (when
424C<$callback> is C<$undef> or missing). There can only be one callback
425registered for each tag.
426
427The original message will be passed to the callback, after the first
428element (the tag) has been removed. The callback will use the same
429environment as the default callback (see above).
430
431Example: create a port and bind receivers on it in one go.
432
433 my $port = rcv port,
434 msg1 => sub { ... },
435 msg2 => sub { ... },
436 ;
437
438Example: create a port, bind receivers and send it in a message elsewhere
439in one go:
440
441 snd $otherport, reply =>
442 rcv port,
443 msg1 => sub { ... },
444 ...
445 ;
446
447Example: temporarily register a rcv callback for a tag matching some port
448(e.g. for an rpc reply) and unregister it after a message was received.
449
450 rcv $port, $otherport => sub {
451 my @reply = @_;
452
453 rcv $SELF, $otherport;
454 };
455
456=cut
457
458sub rcv($@) {
459 my $port = shift;
460 my ($nodeid, $portid) = split /#/, $port, 2;
461
462 $NODE{$nodeid} == $NODE{""}
463 or Carp::croak "$port: rcv can only be called on local ports, caught";
464
465 while (@_) {
466 if (ref $_[0]) {
467 if (my $self = $PORT_DATA{$portid}) {
468 "AnyEvent::MP::Port" eq ref $self
469 or Carp::croak "$port: rcv can only be called on message matching ports, caught";
470
471 $self->[0] = shift;
472 } else {
473 my $cb = shift;
474 $PORT{$portid} = sub {
475 local $SELF = $port;
476 eval { &$cb }; _self_die if $@;
477 };
478 }
479 } elsif (defined $_[0]) {
480 my $self = $PORT_DATA{$portid} ||= do {
481 my $self = bless [$PORT{$portid} || sub { }, { }, $port], "AnyEvent::MP::Port";
482
483 $PORT{$portid} = sub {
484 local $SELF = $port;
485
486 if (my $cb = $self->[1]{$_[0]}) {
487 shift;
488 eval { &$cb }; _self_die if $@;
489 } else {
490 &{ $self->[0] };
491 }
492 };
493
494 $self
495 };
496
497 "AnyEvent::MP::Port" eq ref $self
498 or Carp::croak "$port: rcv can only be called on message matching ports, caught";
499
500 my ($tag, $cb) = splice @_, 0, 2;
501
502 if (defined $cb) {
503 $self->[1]{$tag} = $cb;
504 } else {
505 delete $self->[1]{$tag};
506 }
143 } 507 }
508 }
144 509
145 for (@{ $self->{rcv}{$_[1]} }) { 510 $port
146 $_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1] 511}
147 && &{$_->[0]}
148 && undef $_;
149 }
150 512
151 for (@{ $self->{any} }) { 513=item peval $port, $coderef[, @args]
152 $_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1] 514
153 && &{$_->[0]} 515Evaluates the given C<$codref> within the contetx of C<$port>, that is,
154 && undef $_; 516when the code throews an exception the C<$port> will be killed.
155 } 517
518Any remaining args will be passed to the callback. Any return values will
519be returned to the caller.
520
521This is useful when you temporarily want to execute code in the context of
522a port.
523
524Example: create a port and run some initialisation code in it's context.
525
526 my $port = port { ... };
527
528 peval $port, sub {
529 init
530 or die "unable to init";
156 }; 531 };
157 532
158 $self
159}
160
161=item $portid = miniport { my @msg = @_; $finished }
162
163Creates a "mini port", that is, a very lightweight port without any
164pattern matching behind it, and returns its ID.
165
166The block will be called for every message received on the port. When the
167callback returns a true value its job is considered "done" and the port
168will be destroyed. Otherwise it will stay alive.
169
170The message will be passed as-is, no extra argument (ie.. no port id) will
171be passed to the callback.
172
173If you need the local port id in the callback, this works nicely:
174
175 my $port; $port = miniport {
176 snd $otherport, reply => $port;
177 };
178
179=cut 533=cut
180 534
181sub miniport(&) { 535sub peval($$) {
536 local $SELF = shift;
182 my $cb = shift; 537 my $cb = shift;
183 my $id = "$AnyEvent::MP::Base::UNIQ." . $AnyEvent::MP::Base::ID++;
184 538
185 $AnyEvent::MP::Base::PORT{$id} = sub { 539 if (wantarray) {
186 &$cb 540 my @res = eval { &$cb };
187 and delete $AnyEvent::MP::Base::PORT{$id}; 541 _self_die if $@;
188 }; 542 @res
189
190 "$NODE#$id"
191}
192
193package AnyEvent::MP::Port;
194
195=back
196
197=head1 METHODS FOR PORT OBJECTS
198
199=over 4
200
201=item "$port"
202
203A port object stringifies to its port ID, so can be used directly for
204C<snd> operations.
205
206=cut
207
208use overload
209 '""' => sub { $_[0]{id} },
210 fallback => 1;
211
212=item $port->rcv (type => $callback->($port, @msg))
213
214=item $port->rcv ($smartmatch => $callback->($port, @msg))
215
216=item $port->rcv ([$smartmatch...] => $callback->($port, @msg))
217
218Register a callback on the given port.
219
220The callback has to return a true value when its work is done, after
221which is will be removed, or a false value in which case it will stay
222registered.
223
224If the match is an array reference, then it will be matched against the
225first elements of the message, otherwise only the first element is being
226matched.
227
228Any element in the match that is specified as C<_any_> (a function
229exported by this module) matches any single element of the message.
230
231While not required, it is highly recommended that the first matching
232element is a string identifying the message. The one-string-only match is
233also the most efficient match (by far).
234
235=cut
236
237sub rcv($@) {
238 my ($self, $match, $cb) = @_;
239
240 if (!ref $match) {
241 push @{ $self->{rc0}{$match} }, [$cb];
242 } elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
243 my ($type, @match) = @$match;
244 @match
245 ? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
246 : push @{ $self->{rc0}{$match->[0]} }, [$cb];
247 } else { 543 } else {
248 push @{ $self->{any} }, [$cb, $match]; 544 my $res = eval { &$cb };
545 _self_die if $@;
546 $res
249 } 547 }
250} 548}
251 549
252=item $port->register ($name) 550=item $closure = psub { BLOCK }
253 551
254Registers the given port under the well known name C<$name>. If the name 552Remembers C<$SELF> and creates a closure out of the BLOCK. When the
255already exists it is replaced. 553closure is executed, sets up the environment in the same way as in C<rcv>
554callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
256 555
257A port can only be registered under one well known name. 556The effect is basically as if it returned C<< sub { peval $SELF, sub {
557BLOCK }, @_ } >>.
258 558
259=cut 559This is useful when you register callbacks from C<rcv> callbacks:
260 560
261sub register { 561 rcv delayed_reply => sub {
262 my ($self, $name) = @_; 562 my ($delay, @reply) = @_;
563 my $timer = AE::timer $delay, 0, psub {
564 snd @reply, $SELF;
565 };
566 };
263 567
264 $self->{wkname} = $name; 568=cut
265 $AnyEvent::MP::Base::WKP{$name} = "$self"; 569
570sub psub(&) {
571 my $cb = shift;
572
573 my $port = $SELF
574 or Carp::croak "psub can only be called from within rcv or psub callbacks, not";
575
576 sub {
577 local $SELF = $port;
578
579 if (wantarray) {
580 my @res = eval { &$cb };
581 _self_die if $@;
582 @res
583 } else {
584 my $res = eval { &$cb };
585 _self_die if $@;
586 $res
587 }
588 }
266} 589}
267 590
268=item $port->destroy 591=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
269 592
270Explicitly destroy/remove/nuke/vaporise the port. 593=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
271 594
272Ports are normally kept alive by there mere existance alone, and need to 595=item $guard = mon $port # kill $SELF when $port dies
273be destroyed explicitly.
274 596
275=cut 597=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
276 598
277sub destroy { 599Monitor the given port and do something when the port is killed or
278 my ($self) = @_; 600messages to it were lost, and optionally return a guard that can be used
601to stop monitoring again.
279 602
280 delete $AnyEvent::MP::Base::WKP{ $self->{wkname} }; 603In the first form (callback), the callback is simply called with any
604number of C<@reason> elements (no @reason means that the port was deleted
605"normally"). Note also that I<< the callback B<must> never die >>, so use
606C<eval> if unsure.
281 607
282 delete $AnyEvent::MP::Base::PORT{$_} 608In the second form (another port given), the other port (C<$rcvport>)
283 for @{ $self->{names} }; 609will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
610"normal" kils nothing happens, while under all other conditions, the other
611port is killed with the same reason.
612
613The third form (kill self) is the same as the second form, except that
614C<$rvport> defaults to C<$SELF>.
615
616In the last form (message), a message of the form C<@msg, @reason> will be
617C<snd>.
618
619Monitoring-actions are one-shot: once messages are lost (and a monitoring
620alert was raised), they are removed and will not trigger again.
621
622As a rule of thumb, monitoring requests should always monitor a port from
623a local port (or callback). The reason is that kill messages might get
624lost, just like any other message. Another less obvious reason is that
625even monitoring requests can get lost (for example, when the connection
626to the other node goes down permanently). When monitoring a port locally
627these problems do not exist.
628
629C<mon> effectively guarantees that, in the absence of hardware failures,
630after starting the monitor, either all messages sent to the port will
631arrive, or the monitoring action will be invoked after possible message
632loss has been detected. No messages will be lost "in between" (after
633the first lost message no further messages will be received by the
634port). After the monitoring action was invoked, further messages might get
635delivered again.
636
637Inter-host-connection timeouts and monitoring depend on the transport
638used. The only transport currently implemented is TCP, and AnyEvent::MP
639relies on TCP to detect node-downs (this can take 10-15 minutes on a
640non-idle connection, and usually around two hours for idle connections).
641
642This means that monitoring is good for program errors and cleaning up
643stuff eventually, but they are no replacement for a timeout when you need
644to ensure some maximum latency.
645
646Example: call a given callback when C<$port> is killed.
647
648 mon $port, sub { warn "port died because of <@_>\n" };
649
650Example: kill ourselves when C<$port> is killed abnormally.
651
652 mon $port;
653
654Example: send us a restart message when another C<$port> is killed.
655
656 mon $port, $self => "restart";
657
658=cut
659
660sub mon {
661 my ($nodeid, $port) = split /#/, shift, 2;
662
663 my $node = $NODE{$nodeid} || add_node $nodeid;
664
665 my $cb = @_ ? shift : $SELF || Carp::croak 'mon: called with one argument only, but $SELF not set,';
666
667 unless (ref $cb) {
668 if (@_) {
669 # send a kill info message
670 my (@msg) = ($cb, @_);
671 $cb = sub { snd @msg, @_ };
672 } else {
673 # simply kill other port
674 my $port = $cb;
675 $cb = sub { kil $port, @_ if @_ };
676 }
677 }
678
679 $node->monitor ($port, $cb);
680
681 defined wantarray
682 and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
284} 683}
285 684
685=item $guard = mon_guard $port, $ref, $ref...
686
687Monitors the given C<$port> and keeps the passed references. When the port
688is killed, the references will be freed.
689
690Optionally returns a guard that will stop the monitoring.
691
692This function is useful when you create e.g. timers or other watchers and
693want to free them when the port gets killed (note the use of C<psub>):
694
695 $port->rcv (start => sub {
696 my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
697 undef $timer if 0.9 < rand;
698 });
699 });
700
701=cut
702
703sub mon_guard {
704 my ($port, @refs) = @_;
705
706 #TODO: mon-less form?
707
708 mon $port, sub { 0 && @refs }
709}
710
711=item kil $port[, @reason]
712
713Kill the specified port with the given C<@reason>.
714
715If no C<@reason> is specified, then the port is killed "normally" -
716monitor callback will be invoked, but the kil will not cause linked ports
717(C<mon $mport, $lport> form) to get killed.
718
719If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
720form) get killed with the same reason.
721
722Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
723will be reported as reason C<< die => $@ >>.
724
725Transport/communication errors are reported as C<< transport_error =>
726$message >>.
727
728=cut
729
730=item $port = spawn $node, $initfunc[, @initdata]
731
732Creates a port on the node C<$node> (which can also be a port ID, in which
733case it's the node where that port resides).
734
735The port ID of the newly created port is returned immediately, and it is
736possible to immediately start sending messages or to monitor the port.
737
738After the port has been created, the init function is called on the remote
739node, in the same context as a C<rcv> callback. This function must be a
740fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
741specify a function in the main program, use C<::name>.
742
743If the function doesn't exist, then the node tries to C<require>
744the package, then the package above the package and so on (e.g.
745C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
746exists or it runs out of package names.
747
748The init function is then called with the newly-created port as context
749object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
750call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
751the port might not get created.
752
753A common idiom is to pass a local port, immediately monitor the spawned
754port, and in the remote init function, immediately monitor the passed
755local port. This two-way monitoring ensures that both ports get cleaned up
756when there is a problem.
757
758C<spawn> guarantees that the C<$initfunc> has no visible effects on the
759caller before C<spawn> returns (by delaying invocation when spawn is
760called for the local node).
761
762Example: spawn a chat server port on C<$othernode>.
763
764 # this node, executed from within a port context:
765 my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
766 mon $server;
767
768 # init function on C<$othernode>
769 sub connect {
770 my ($srcport) = @_;
771
772 mon $srcport;
773
774 rcv $SELF, sub {
775 ...
776 };
777 }
778
779=cut
780
781sub _spawn {
782 my $port = shift;
783 my $init = shift;
784
785 # rcv will create the actual port
786 local $SELF = "$NODE#$port";
787 eval {
788 &{ load_func $init }
789 };
790 _self_die if $@;
791}
792
793sub spawn(@) {
794 my ($nodeid, undef) = split /#/, shift, 2;
795
796 my $id = $RUNIQ . ++$ID;
797
798 $_[0] =~ /::/
799 or Carp::croak "spawn init function must be a fully-qualified name, caught";
800
801 snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
802
803 "$nodeid#$id"
804}
805
806
807=item after $timeout, @msg
808
809=item after $timeout, $callback
810
811Either sends the given message, or call the given callback, after the
812specified number of seconds.
813
814This is simply a utility function that comes in handy at times - the
815AnyEvent::MP author is not convinced of the wisdom of having it, though,
816so it may go away in the future.
817
818=cut
819
820sub after($@) {
821 my ($timeout, @action) = @_;
822
823 my $t; $t = AE::timer $timeout, 0, sub {
824 undef $t;
825 ref $action[0]
826 ? $action[0]()
827 : snd @action;
828 };
829}
830
831=item cal $port, @msg, $callback[, $timeout]
832
833A simple form of RPC - sends a message to the given C<$port> with the
834given contents (C<@msg>), but adds a reply port to the message.
835
836The reply port is created temporarily just for the purpose of receiving
837the reply, and will be C<kil>ed when no longer needed.
838
839A reply message sent to the port is passed to the C<$callback> as-is.
840
841If an optional time-out (in seconds) is given and it is not C<undef>,
842then the callback will be called without any arguments after the time-out
843elapsed and the port is C<kil>ed.
844
845If no time-out is given (or it is C<undef>), then the local port will
846monitor the remote port instead, so it eventually gets cleaned-up.
847
848Currently this function returns the temporary port, but this "feature"
849might go in future versions unless you can make a convincing case that
850this is indeed useful for something.
851
852=cut
853
854sub cal(@) {
855 my $timeout = ref $_[-1] ? undef : pop;
856 my $cb = pop;
857
858 my $port = port {
859 undef $timeout;
860 kil $SELF;
861 &$cb;
862 };
863
864 if (defined $timeout) {
865 $timeout = AE::timer $timeout, 0, sub {
866 undef $timeout;
867 kil $port;
868 $cb->();
869 };
870 } else {
871 mon $_[0], sub {
872 kil $port;
873 $cb->();
874 };
875 }
876
877 push @_, $port;
878 &snd;
879
880 $port
881}
882
286=back 883=back
287 884
288=head1 FUNCTIONS FOR NODES 885=head1 DISTRIBUTED DATABASE
886
887AnyEvent::MP comes with a simple distributed database. The database will
888be mirrored asynchronously at all global nodes. Other nodes bind to one of
889the global nodes for their needs.
890
891The database consists of a two-level hash - a hash contains a hash which
892contains values.
893
894The top level hash key is called "family", and the second-level hash key
895is called "subkey" or simply "key".
896
897The family must be alphanumeric, i.e. start with a letter and consist
898of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
899pretty much like Perl module names.
900
901As the family namespace is global, it is recommended to prefix family names
902with the name of the application or module using it.
903
904The subkeys must be non-empty strings, with no further restrictions.
905
906The values should preferably be strings, but other perl scalars should
907work as well (such as undef, arrays and hashes).
908
909Every database entry is owned by one node - adding the same family/subkey
910combination on multiple nodes will not cause discomfort for AnyEvent::MP,
911but the result might be nondeterministic, i.e. the key might have
912different values on different nodes.
913
914Different subkeys in the same family can be owned by different nodes
915without problems, and in fact, this is the common method to create worker
916pools. For example, a worker port for image scaling might do this:
917
918 db_set my_image_scalers => $port;
919
920And clients looking for an image scaler will want to get the
921C<my_image_scalers> keys:
922
923 db_keys "my_image_scalers" => 60 => sub {
924 #d##TODO#
925
926=over
927
928=item db_set $family => $subkey [=> $value]
929
930Sets (or replaces) a key to the database - if C<$value> is omitted,
931C<undef> is used instead.
932
933=item db_del $family => $subkey
934
935Deletes a key from the database.
936
937=item $guard = db_reg $family => $subkey [=> $value]
938
939Sets the key on the database and returns a guard. When the guard is
940destroyed, the key is deleted from the database. If C<$value> is missing,
941then C<undef> is used.
942
943=cut
944
945=back
946
947=head1 AnyEvent::MP vs. Distributed Erlang
948
949AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
950== aemp node, Erlang process == aemp port), so many of the documents and
951programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
952sample:
953
954 http://www.erlang.se/doc/programming_rules.shtml
955 http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
956 http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
957 http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
958
959Despite the similarities, there are also some important differences:
289 960
290=over 4 961=over 4
291 962
292=item mon $noderef, $callback->($noderef, $status, $) 963=item * Node IDs are arbitrary strings in AEMP.
293 964
294Monitors the given noderef. 965Erlang relies on special naming and DNS to work everywhere in the same
966way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
967configuration or DNS), and possibly the addresses of some seed nodes, but
968will otherwise discover other nodes (and their IDs) itself.
295 969
296=item become_public endpoint... 970=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
971uses "local ports are like remote ports".
297 972
298Tells the node to become a public node, i.e. reachable from other nodes. 973The failure modes for local ports are quite different (runtime errors
974only) then for remote ports - when a local port dies, you I<know> it dies,
975when a connection to another node dies, you know nothing about the other
976port.
299 977
300If no arguments are given, or the first argument is C<undef>, then 978Erlang pretends remote ports are as reliable as local ports, even when
301AnyEvent::MP tries to bind on port C<4040> on all IP addresses that the 979they are not.
302local nodename resolves to.
303 980
304Otherwise the first argument must be an array-reference with transport 981AEMP encourages a "treat remote ports differently" philosophy, with local
305endpoints ("ip:port", "hostname:port") or port numbers (in which case the 982ports being the special case/exception, where transport errors cannot
306local nodename is used as hostname). The endpoints are all resolved and 983occur.
307will become the node reference.
308 984
309=cut 985=item * Erlang uses processes and a mailbox, AEMP does not queue.
986
987Erlang uses processes that selectively receive messages out of order, and
988therefore needs a queue. AEMP is event based, queuing messages would serve
989no useful purpose. For the same reason the pattern-matching abilities
990of AnyEvent::MP are more limited, as there is little need to be able to
991filter messages without dequeuing them.
992
993This is not a philosophical difference, but simply stems from AnyEvent::MP
994being event-based, while Erlang is process-based.
995
996You cna have a look at L<Coro::MP> for a more Erlang-like process model on
997top of AEMP and Coro threads.
998
999=item * Erlang sends are synchronous, AEMP sends are asynchronous.
1000
1001Sending messages in Erlang is synchronous and blocks the process until
1002a conenction has been established and the message sent (and so does not
1003need a queue that can overflow). AEMP sends return immediately, connection
1004establishment is handled in the background.
1005
1006=item * Erlang suffers from silent message loss, AEMP does not.
1007
1008Erlang implements few guarantees on messages delivery - messages can get
1009lost without any of the processes realising it (i.e. you send messages a,
1010b, and c, and the other side only receives messages a and c).
1011
1012AEMP guarantees (modulo hardware errors) correct ordering, and the
1013guarantee that after one message is lost, all following ones sent to the
1014same port are lost as well, until monitoring raises an error, so there are
1015no silent "holes" in the message sequence.
1016
1017If you want your software to be very reliable, you have to cope with
1018corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
1019simply tries to work better in common error cases, such as when a network
1020link goes down.
1021
1022=item * Erlang can send messages to the wrong port, AEMP does not.
1023
1024In Erlang it is quite likely that a node that restarts reuses an Erlang
1025process ID known to other nodes for a completely different process,
1026causing messages destined for that process to end up in an unrelated
1027process.
1028
1029AEMP does not reuse port IDs, so old messages or old port IDs floating
1030around in the network will not be sent to an unrelated port.
1031
1032=item * Erlang uses unprotected connections, AEMP uses secure
1033authentication and can use TLS.
1034
1035AEMP can use a proven protocol - TLS - to protect connections and
1036securely authenticate nodes.
1037
1038=item * The AEMP protocol is optimised for both text-based and binary
1039communications.
1040
1041The AEMP protocol, unlike the Erlang protocol, supports both programming
1042language independent text-only protocols (good for debugging), and binary,
1043language-specific serialisers (e.g. Storable). By default, unless TLS is
1044used, the protocol is actually completely text-based.
1045
1046It has also been carefully designed to be implementable in other languages
1047with a minimum of work while gracefully degrading functionality to make the
1048protocol simple.
1049
1050=item * AEMP has more flexible monitoring options than Erlang.
1051
1052In Erlang, you can chose to receive I<all> exit signals as messages or
1053I<none>, there is no in-between, so monitoring single Erlang processes is
1054difficult to implement.
1055
1056Monitoring in AEMP is more flexible than in Erlang, as one can choose
1057between automatic kill, exit message or callback on a per-port basis.
1058
1059=item * Erlang tries to hide remote/local connections, AEMP does not.
1060
1061Monitoring in Erlang is not an indicator of process death/crashes, in the
1062same way as linking is (except linking is unreliable in Erlang).
1063
1064In AEMP, you don't "look up" registered port names or send to named ports
1065that might or might not be persistent. Instead, you normally spawn a port
1066on the remote node. The init function monitors you, and you monitor the
1067remote port. Since both monitors are local to the node, they are much more
1068reliable (no need for C<spawn_link>).
1069
1070This also saves round-trips and avoids sending messages to the wrong port
1071(hard to do in Erlang).
310 1072
311=back 1073=back
312 1074
313=head1 NODE MESSAGES 1075=head1 RATIONALE
314
315Nodes understand the following messages sent to them. Many of them take
316arguments called C<@reply>, which will simply be used to compose a reply
317message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
318the remaining arguments are simply the message data.
319 1076
320=over 4 1077=over 4
321 1078
322=cut 1079=item Why strings for port and node IDs, why not objects?
323 1080
324=item wkp => $name, @reply 1081We considered "objects", but found that the actual number of methods
1082that can be called are quite low. Since port and node IDs travel over
1083the network frequently, the serialising/deserialising would add lots of
1084overhead, as well as having to keep a proxy object everywhere.
325 1085
326Replies with the port ID of the specified well-known port, or C<undef>. 1086Strings can easily be printed, easily serialised etc. and need no special
1087procedures to be "valid".
327 1088
328=item devnull => ... 1089And as a result, a port with just a default receiver consists of a single
1090code reference stored in a global hash - it can't become much cheaper.
329 1091
330Generic data sink/CPU heat conversion. 1092=item Why favour JSON, why not a real serialising format such as Storable?
331 1093
332=item relay => $port, @msg 1094In fact, any AnyEvent::MP node will happily accept Storable as framing
1095format, but currently there is no way to make a node use Storable by
1096default (although all nodes will accept it).
333 1097
334Simply forwards the message to the given port. 1098The default framing protocol is JSON because a) JSON::XS is many times
1099faster for small messages and b) most importantly, after years of
1100experience we found that object serialisation is causing more problems
1101than it solves: Just like function calls, objects simply do not travel
1102easily over the network, mostly because they will always be a copy, so you
1103always have to re-think your design.
335 1104
336=item eval => $string[ @reply] 1105Keeping your messages simple, concentrating on data structures rather than
337 1106objects, will keep your messages clean, tidy and efficient.
338Evaluates the given string. If C<@reply> is given, then a message of the
339form C<@reply, $@, @evalres> is sent.
340
341Example: crash another node.
342
343 snd $othernode, eval => "exit";
344
345=item time => @reply
346
347Replies the the current node time to C<@reply>.
348
349Example: tell the current node to send the current time to C<$myport> in a
350C<timereply> message.
351
352 snd $NODE, time => $myport, timereply => 1, 2;
353 # => snd $myport, timereply => 1, 2, <time>
354 1107
355=back 1108=back
356 1109
357=head1 SEE ALSO 1110=head1 SEE ALSO
1111
1112L<AnyEvent::MP::Intro> - a gentle introduction.
1113
1114L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
1115
1116L<AnyEvent::MP::Global> - network maintenance and port groups, to find
1117your applications.
1118
1119L<AnyEvent::MP::DataConn> - establish data connections between nodes.
1120
1121L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
1122all nodes.
358 1123
359L<AnyEvent>. 1124L<AnyEvent>.
360 1125
361=head1 AUTHOR 1126=head1 AUTHOR
362 1127

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