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Revision 1.132 by root, Sat Mar 10 20:34:11 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 # 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
15 # initialise the node so it can send/receive messages 14 # initialise the node so it can send/receive messages
16 configure; 15 configure;
17 16
18 # ports are message endpoints 17 # ports are message destinations
19 18
20 # sending messages 19 # sending messages
21 snd $port, type => data...; 20 snd $port, type => data...;
22 snd $port, @msg; 21 snd $port, @msg;
23 snd @msg_with_first_element_being_a_port; 22 snd @msg_with_first_element_being_a_port;
24 23
25 # creating/using ports, the simple way 24 # creating/using ports, the simple way
26 my $simple_port = port { my @msg = @_; 0 }; 25 my $simple_port = port { my @msg = @_ };
27 26
28 # creating/using ports, tagged message matching 27 # creating/using ports, tagged message matching
29 my $port = port; 28 my $port = port;
30 rcv $port, ping => sub { snd $_[0], "pong"; 0 }; 29 rcv $port, ping => sub { snd $_[0], "pong" };
31 rcv $port, pong => sub { warn "pong received\n"; 0 }; 30 rcv $port, pong => sub { warn "pong received\n" };
32 31
33 # create a port on another node 32 # create a port on another node
34 my $port = spawn $node, $initfunc, @initdata; 33 my $port = spawn $node, $initfunc, @initdata;
35 34
35 # destroy a port again
36 kil $port; # "normal" kill
37 kil $port, my_error => "everything is broken"; # error kill
38
36 # monitoring 39 # monitoring
37 mon $port, $cb->(@msg) # callback is invoked on death 40 mon $port, $cb->(@msg) # callback is invoked on death
38 mon $port, $otherport # kill otherport on abnormal death 41 mon $port, $localport # kill localport on abnormal death
39 mon $port, $otherport, @msg # send message on death 42 mon $port, $localport, @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 };
40 51
41=head1 CURRENT STATUS 52=head1 CURRENT STATUS
42 53
43 bin/aemp - stable. 54 bin/aemp - stable.
44 AnyEvent::MP - stable API, should work. 55 AnyEvent::MP - stable API, should work.
45 AnyEvent::MP::Intro - uptodate, but incomplete. 56 AnyEvent::MP::Intro - explains most concepts.
46 AnyEvent::MP::Kernel - mostly stable. 57 AnyEvent::MP::Kernel - mostly stable API.
47 AnyEvent::MP::Global - stable API, protocol not yet final. 58 AnyEvent::MP::Global - stable API.
48
49 stay tuned.
50 59
51=head1 DESCRIPTION 60=head1 DESCRIPTION
52 61
53This module (-family) implements a simple message passing framework. 62This module (-family) implements a simple message passing framework.
54 63
56on the same or other hosts, and you can supervise entities remotely. 65on the same or other hosts, and you can supervise entities remotely.
57 66
58For an introduction to this module family, see the L<AnyEvent::MP::Intro> 67For an introduction to this module family, see the L<AnyEvent::MP::Intro>
59manual page and the examples under F<eg/>. 68manual page and the examples under F<eg/>.
60 69
61At the moment, this module family is a bit underdocumented.
62
63=head1 CONCEPTS 70=head1 CONCEPTS
64 71
65=over 4 72=over 4
66 73
67=item port 74=item port
68 75
69A port is something you can send messages to (with the C<snd> function). 76Not to be confused with a TCP port, a "port" is something you can send
77messages to (with the C<snd> function).
70 78
71Ports allow you to register C<rcv> handlers that can match all or just 79Ports allow you to register C<rcv> handlers that can match all or just
72some messages. Messages send to ports will not be queued, regardless of 80some messages. Messages send to ports will not be queued, regardless of
73anything was listening for them or not. 81anything was listening for them or not.
74 82
83Ports are represented by (printable) strings called "port IDs".
84
75=item port ID - C<nodeid#portname> 85=item port ID - C<nodeid#portname>
76 86
77A port ID is the concatenation of a node ID, a hash-mark (C<#>) as 87A port ID is the concatenation of a node ID, a hash-mark (C<#>)
78separator, and 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).
79 90
80=item node 91=item node
81 92
82A node is a single process containing at least one port - the node port, 93A node is a single process containing at least one port - the node port,
83which enables nodes to manage each other remotely, and to create new 94which enables nodes to manage each other remotely, and to create new
84ports. 95ports.
85 96
86Nodes are either public (have one or more listening ports) or private 97Nodes are either public (have one or more listening ports) or private
87(no listening ports). Private nodes cannot talk to other private nodes 98(no listening ports). Private nodes cannot talk to other private nodes
88currently. 99currently, but all nodes can talk to public nodes.
89 100
101Nodes is represented by (printable) strings called "node IDs".
102
90=item node ID - C<[a-za-Z0-9_\-.:]+> 103=item node ID - C<[A-Za-z0-9_\-.:]*>
91 104
92A node ID is a string that uniquely identifies the node within a 105A node ID is a string that uniquely identifies the node within a
93network. Depending on the configuration used, node IDs can look like a 106network. Depending on the configuration used, node IDs can look like a
94hostname, a hostname and a port, or a random string. AnyEvent::MP itself 107hostname, a hostname and a port, or a random string. AnyEvent::MP itself
95doesn't interpret node IDs in any way. 108doesn't interpret node IDs in any way except to uniquely identify a node.
96 109
97=item binds - C<ip:port> 110=item binds - C<ip:port>
98 111
99Nodes can only talk to each other by creating some kind of connection to 112Nodes can only talk to each other by creating some kind of connection to
100each other. To do this, nodes should listen on one or more local transport 113each other. To do this, nodes should listen on one or more local transport
114endpoints - binds.
115
101endpoints - binds. Currently, only standard C<ip:port> specifications can 116Currently, only standard C<ip:port> specifications can be used, which
102be used, which specify TCP ports to listen on. 117specify TCP ports to listen on. So a bind is basically just a tcp socket
118in listening mode thta accepts conenctions form other nodes.
103 119
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
104=item seeds - C<host:port> 149=item seed IDs - C<host:port>
105 150
106When a node starts, it knows nothing about the network. To teach the node 151Seed IDs are transport endpoint(s) (usually a hostname/IP address and a
107about the network it first has to contact some other node within the 152TCP port) of nodes that should be used as seed nodes.
108network. This node is called a seed.
109 153
110Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes 154=item global nodes
111are expected to be long-running, and at least one of those should always
112be available. When nodes run out of connections (e.g. due to a network
113error), they try to re-establish connections to some seednodes again to
114join the network.
115 155
116Apart from being sued for seeding, seednodes are not special in any way - 156An AEMP network needs a discovery service - nodes need to know how to
117every public node can be a seednode. 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).
118 170
119=back 171=back
120 172
121=head1 VARIABLES/FUNCTIONS 173=head1 VARIABLES/FUNCTIONS
122 174
124 176
125=cut 177=cut
126 178
127package AnyEvent::MP; 179package AnyEvent::MP;
128 180
181use AnyEvent::MP::Config ();
129use AnyEvent::MP::Kernel; 182use AnyEvent::MP::Kernel;
183use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID);
130 184
131use common::sense; 185use common::sense;
132 186
133use Carp (); 187use Carp ();
134 188
135use AE (); 189use AE ();
190use Guard ();
136 191
137use base "Exporter"; 192use base "Exporter";
138 193
139our $VERSION = $AnyEvent::MP::Kernel::VERSION; 194our $VERSION = $AnyEvent::MP::Config::VERSION;
140 195
141our @EXPORT = qw( 196our @EXPORT = qw(
142 NODE $NODE *SELF node_of after 197 NODE $NODE *SELF node_of after
143 configure 198 configure
144 snd rcv mon mon_guard kil reg psub spawn 199 snd rcv mon mon_guard kil psub peval spawn cal
145 port 200 port
201 db_set db_del db_reg
202 db_mon db_family db_keys db_values
146); 203);
147 204
148our $SELF; 205our $SELF;
149 206
150sub _self_die() { 207sub _self_die() {
161 218
162=item $nodeid = node_of $port 219=item $nodeid = node_of $port
163 220
164Extracts and returns the node ID from a port ID or a node ID. 221Extracts and returns the node ID from a port ID or a node ID.
165 222
223=item configure $profile, key => value...
224
166=item configure key => value... 225=item configure key => value...
167 226
168Before a node can talk to other nodes on the network (i.e. enter 227Before a node can talk to other nodes on the network (i.e. enter
169"distributed mode") it has to configure itself - the minimum a node needs 228"distributed mode") it has to configure itself - the minimum a node needs
170to know is its own name, and optionally it should know the addresses of 229to know is its own name, and optionally it should know the addresses of
171some other nodes in the network to discover other nodes. 230some other nodes in the network to discover other nodes.
172 231
173This function configures a node - it must be called exactly once (or 232This function configures a node - it must be called exactly once (or
174never) before calling other AnyEvent::MP functions. 233never) before calling other AnyEvent::MP functions.
175 234
235The key/value pairs are basically the same ones as documented for the
236F<aemp> command line utility (sans the set/del prefix), with these additions:
237
238=over 4
239
240=item norc => $boolean (default false)
241
242If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I<not>
243be consulted - all configuraiton options must be specified in the
244C<configure> call.
245
246=item force => $boolean (default false)
247
248IF true, then the values specified in the C<configure> will take
249precedence over any values configured via the rc file. The default is for
250the rc file to override any options specified in the program.
251
252=item secure => $pass->($nodeid)
253
254In addition to specifying a boolean, you can specify a code reference that
255is called for every remote execution attempt - the execution request is
256granted iff the callback returns a true value.
257
258See F<semp setsecure> for more info.
259
260=back
261
176=over 4 262=over 4
177 263
178=item step 1, gathering configuration from profiles 264=item step 1, gathering configuration from profiles
179 265
180The function first looks up a profile in the aemp configuration (see the 266The function first looks up a profile in the aemp configuration (see the
181L<aemp> commandline utility). The profile name can be specified via the 267L<aemp> commandline utility). The profile name can be specified via the
182named C<profile> parameter. If it is missing, then the nodename (F<uname 268named C<profile> parameter or can simply be the first parameter). If it is
183-n>) will be used as profile name. 269missing, then the nodename (F<uname -n>) will be used as profile name.
184 270
185The profile data is then gathered as follows: 271The profile data is then gathered as follows:
186 272
187First, all remaining key => value pairs (all of which are conviniently 273First, all remaining key => value pairs (all of which are conveniently
188undocumented at the moment) will be interpreted as configuration 274undocumented at the moment) will be interpreted as configuration
189data. Then they will be overwritten by any values specified in the global 275data. Then they will be overwritten by any values specified in the global
190default configuration (see the F<aemp> utility), then the chain of 276default configuration (see the F<aemp> utility), then the chain of
191profiles chosen by the profile name (and any C<parent> attributes). 277profiles chosen by the profile name (and any C<parent> attributes).
192 278
193That means that the values specified in the profile have highest priority 279That means that the values specified in the profile have highest priority
194and the values specified directly via C<configure> have lowest priority, 280and the values specified directly via C<configure> have lowest priority,
195and can only be used to specify defaults. 281and can only be used to specify defaults.
196 282
197If the profile specifies a node ID, then this will become the node ID of 283If the profile specifies a node ID, then this will become the node ID of
198this process. If not, then the profile name will be used as node ID. The 284this process. If not, then the profile name will be used as node ID, with
199special node ID of C<anon/> will be replaced by a random node ID. 285a unique randoms tring (C</%u>) appended.
286
287The node ID can contain some C<%> sequences that are expanded: C<%n>
288is expanded to the local nodename, C<%u> is replaced by a random
289strign to make the node unique. For example, the F<aemp> commandline
290utility uses C<aemp/%n/%u> as nodename, which might expand to
291C<aemp/cerebro/ZQDGSIkRhEZQDGSIkRhE>.
200 292
201=item step 2, bind listener sockets 293=item step 2, bind listener sockets
202 294
203The next step is to look up the binds in the profile, followed by binding 295The next step is to look up the binds in the profile, followed by binding
204aemp protocol listeners on all binds specified (it is possible and valid 296aemp protocol listeners on all binds specified (it is possible and valid
210used, meaning the node will bind on a dynamically-assigned port on every 302used, meaning the node will bind on a dynamically-assigned port on every
211local IP address it finds. 303local IP address it finds.
212 304
213=item step 3, connect to seed nodes 305=item step 3, connect to seed nodes
214 306
215As the last step, the seeds list from the profile is passed to the 307As the last step, the seed ID list from the profile is passed to the
216L<AnyEvent::MP::Global> module, which will then use it to keep 308L<AnyEvent::MP::Global> module, which will then use it to keep
217connectivity with at least one node at any point in time. 309connectivity with at least one node at any point in time.
218 310
219=back 311=back
220 312
221Example: become a distributed node using the locla node name as profile. 313Example: become a distributed node using the local node name as profile.
222This should be the most common form of invocation for "daemon"-type nodes. 314This should be the most common form of invocation for "daemon"-type nodes.
223 315
224 configure 316 configure
225 317
226Example: become an anonymous node. This form is often used for commandline 318Example: become a semi-anonymous node. This form is often used for
227clients. 319commandline clients.
228 320
229 configure nodeid => "anon/"; 321 configure nodeid => "myscript/%n/%u";
230 322
231Example: configure a node using a profile called seed, which si suitable 323Example: configure a node using a profile called seed, which is suitable
232for a seed node as it binds on all local addresses on a fixed port (4040, 324for a seed node as it binds on all local addresses on a fixed port (4040,
233customary for aemp). 325customary for aemp).
234 326
235 # use the aemp commandline utility 327 # use the aemp commandline utility
236 # aemp profile seed setnodeid anon/ setbinds '*:4040' 328 # aemp profile seed binds '*:4040'
237 329
238 # then use it 330 # then use it
239 configure profile => "seed"; 331 configure profile => "seed";
240 332
241 # or simply use aemp from the shell again: 333 # or simply use aemp from the shell again:
306 398
307=cut 399=cut
308 400
309sub rcv($@); 401sub rcv($@);
310 402
311sub _kilme { 403my $KILME = sub {
312 die "received message on port without callback"; 404 die "received message on port without callback";
313} 405};
314 406
315sub port(;&) { 407sub port(;&) {
316 my $id = "$UNIQ." . $ID++; 408 my $id = $UNIQ . ++$ID;
317 my $port = "$NODE#$id"; 409 my $port = "$NODE#$id";
318 410
319 rcv $port, shift || \&_kilme; 411 rcv $port, shift || $KILME;
320 412
321 $port 413 $port
322} 414}
323 415
324=item rcv $local_port, $callback->(@msg) 416=item rcv $local_port, $callback->(@msg)
360 msg1 => sub { ... }, 452 msg1 => sub { ... },
361 ... 453 ...
362 ; 454 ;
363 455
364Example: temporarily register a rcv callback for a tag matching some port 456Example: temporarily register a rcv callback for a tag matching some port
365(e.g. for a rpc reply) and unregister it after a message was received. 457(e.g. for an rpc reply) and unregister it after a message was received.
366 458
367 rcv $port, $otherport => sub { 459 rcv $port, $otherport => sub {
368 my @reply = @_; 460 my @reply = @_;
369 461
370 rcv $SELF, $otherport; 462 rcv $SELF, $otherport;
372 464
373=cut 465=cut
374 466
375sub rcv($@) { 467sub rcv($@) {
376 my $port = shift; 468 my $port = shift;
377 my ($noderef, $portid) = split /#/, $port, 2; 469 my ($nodeid, $portid) = split /#/, $port, 2;
378 470
379 $NODE{$noderef} == $NODE{""} 471 $NODE{$nodeid} == $NODE{""}
380 or Carp::croak "$port: rcv can only be called on local ports, caught"; 472 or Carp::croak "$port: rcv can only be called on local ports, caught";
381 473
382 while (@_) { 474 while (@_) {
383 if (ref $_[0]) { 475 if (ref $_[0]) {
384 if (my $self = $PORT_DATA{$portid}) { 476 if (my $self = $PORT_DATA{$portid}) {
385 "AnyEvent::MP::Port" eq ref $self 477 "AnyEvent::MP::Port" eq ref $self
386 or Carp::croak "$port: rcv can only be called on message matching ports, caught"; 478 or Carp::croak "$port: rcv can only be called on message matching ports, caught";
387 479
388 $self->[2] = shift; 480 $self->[0] = shift;
389 } else { 481 } else {
390 my $cb = shift; 482 my $cb = shift;
391 $PORT{$portid} = sub { 483 $PORT{$portid} = sub {
392 local $SELF = $port; 484 local $SELF = $port;
393 eval { &$cb }; _self_die if $@; 485 eval { &$cb }; _self_die if $@;
394 }; 486 };
395 } 487 }
396 } elsif (defined $_[0]) { 488 } elsif (defined $_[0]) {
397 my $self = $PORT_DATA{$portid} ||= do { 489 my $self = $PORT_DATA{$portid} ||= do {
398 my $self = bless [$PORT{$port} || sub { }, { }, $port], "AnyEvent::MP::Port"; 490 my $self = bless [$PORT{$portid} || sub { }, { }, $port], "AnyEvent::MP::Port";
399 491
400 $PORT{$portid} = sub { 492 $PORT{$portid} = sub {
401 local $SELF = $port; 493 local $SELF = $port;
402 494
403 if (my $cb = $self->[1]{$_[0]}) { 495 if (my $cb = $self->[1]{$_[0]}) {
425 } 517 }
426 518
427 $port 519 $port
428} 520}
429 521
522=item peval $port, $coderef[, @args]
523
524Evaluates the given C<$codref> within the contetx of C<$port>, that is,
525when the code throews an exception the C<$port> will be killed.
526
527Any remaining args will be passed to the callback. Any return values will
528be returned to the caller.
529
530This is useful when you temporarily want to execute code in the context of
531a port.
532
533Example: create a port and run some initialisation code in it's context.
534
535 my $port = port { ... };
536
537 peval $port, sub {
538 init
539 or die "unable to init";
540 };
541
542=cut
543
544sub peval($$) {
545 local $SELF = shift;
546 my $cb = shift;
547
548 if (wantarray) {
549 my @res = eval { &$cb };
550 _self_die if $@;
551 @res
552 } else {
553 my $res = eval { &$cb };
554 _self_die if $@;
555 $res
556 }
557}
558
430=item $closure = psub { BLOCK } 559=item $closure = psub { BLOCK }
431 560
432Remembers C<$SELF> and creates a closure out of the BLOCK. When the 561Remembers C<$SELF> and creates a closure out of the BLOCK. When the
433closure is executed, sets up the environment in the same way as in C<rcv> 562closure is executed, sets up the environment in the same way as in C<rcv>
434callbacks, i.e. runtime errors will cause the port to get C<kil>ed. 563callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
564
565The effect is basically as if it returned C<< sub { peval $SELF, sub {
566BLOCK }, @_ } >>.
435 567
436This is useful when you register callbacks from C<rcv> callbacks: 568This is useful when you register callbacks from C<rcv> callbacks:
437 569
438 rcv delayed_reply => sub { 570 rcv delayed_reply => sub {
439 my ($delay, @reply) = @_; 571 my ($delay, @reply) = @_;
475 607
476Monitor the given port and do something when the port is killed or 608Monitor the given port and do something when the port is killed or
477messages to it were lost, and optionally return a guard that can be used 609messages to it were lost, and optionally return a guard that can be used
478to stop monitoring again. 610to stop monitoring again.
479 611
612In the first form (callback), the callback is simply called with any
613number of C<@reason> elements (no @reason means that the port was deleted
614"normally"). Note also that I<< the callback B<must> never die >>, so use
615C<eval> if unsure.
616
617In the second form (another port given), the other port (C<$rcvport>)
618will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
619"normal" kils nothing happens, while under all other conditions, the other
620port is killed with the same reason.
621
622The third form (kill self) is the same as the second form, except that
623C<$rvport> defaults to C<$SELF>.
624
625In the last form (message), a message of the form C<@msg, @reason> will be
626C<snd>.
627
628Monitoring-actions are one-shot: once messages are lost (and a monitoring
629alert was raised), they are removed and will not trigger again.
630
631As a rule of thumb, monitoring requests should always monitor a port from
632a local port (or callback). The reason is that kill messages might get
633lost, just like any other message. Another less obvious reason is that
634even monitoring requests can get lost (for example, when the connection
635to the other node goes down permanently). When monitoring a port locally
636these problems do not exist.
637
480C<mon> effectively guarantees that, in the absence of hardware failures, 638C<mon> effectively guarantees that, in the absence of hardware failures,
481after starting the monitor, either all messages sent to the port will 639after starting the monitor, either all messages sent to the port will
482arrive, or the monitoring action will be invoked after possible message 640arrive, or the monitoring action will be invoked after possible message
483loss has been detected. No messages will be lost "in between" (after 641loss has been detected. No messages will be lost "in between" (after
484the first lost message no further messages will be received by the 642the first lost message no further messages will be received by the
485port). After the monitoring action was invoked, further messages might get 643port). After the monitoring action was invoked, further messages might get
486delivered again. 644delivered again.
487 645
488Note that monitoring-actions are one-shot: once messages are lost (and a 646Inter-host-connection timeouts and monitoring depend on the transport
489monitoring alert was raised), they are removed and will not trigger again. 647used. The only transport currently implemented is TCP, and AnyEvent::MP
648relies on TCP to detect node-downs (this can take 10-15 minutes on a
649non-idle connection, and usually around two hours for idle connections).
490 650
491In the first form (callback), the callback is simply called with any 651This means that monitoring is good for program errors and cleaning up
492number of C<@reason> elements (no @reason means that the port was deleted 652stuff eventually, but they are no replacement for a timeout when you need
493"normally"). Note also that I<< the callback B<must> never die >>, so use 653to ensure some maximum latency.
494C<eval> if unsure.
495
496In the second form (another port given), the other port (C<$rcvport>)
497will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
498"normal" kils nothing happens, while under all other conditions, the other
499port is killed with the same reason.
500
501The third form (kill self) is the same as the second form, except that
502C<$rvport> defaults to C<$SELF>.
503
504In the last form (message), a message of the form C<@msg, @reason> will be
505C<snd>.
506
507As a rule of thumb, monitoring requests should always monitor a port from
508a local port (or callback). The reason is that kill messages might get
509lost, just like any other message. Another less obvious reason is that
510even monitoring requests can get lost (for exmaple, when the connection
511to the other node goes down permanently). When monitoring a port locally
512these problems do not exist.
513 654
514Example: call a given callback when C<$port> is killed. 655Example: call a given callback when C<$port> is killed.
515 656
516 mon $port, sub { warn "port died because of <@_>\n" }; 657 mon $port, sub { warn "port died because of <@_>\n" };
517 658
524 mon $port, $self => "restart"; 665 mon $port, $self => "restart";
525 666
526=cut 667=cut
527 668
528sub mon { 669sub mon {
529 my ($noderef, $port) = split /#/, shift, 2; 670 my ($nodeid, $port) = split /#/, shift, 2;
530 671
531 my $node = $NODE{$noderef} || add_node $noderef; 672 my $node = $NODE{$nodeid} || add_node $nodeid;
532 673
533 my $cb = @_ ? shift : $SELF || Carp::croak 'mon: called with one argument only, but $SELF not set,'; 674 my $cb = @_ ? shift : $SELF || Carp::croak 'mon: called with one argument only, but $SELF not set,';
534 675
535 unless (ref $cb) { 676 unless (ref $cb) {
536 if (@_) { 677 if (@_) {
545 } 686 }
546 687
547 $node->monitor ($port, $cb); 688 $node->monitor ($port, $cb);
548 689
549 defined wantarray 690 defined wantarray
550 and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) } 691 and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
551} 692}
552 693
553=item $guard = mon_guard $port, $ref, $ref... 694=item $guard = mon_guard $port, $ref, $ref...
554 695
555Monitors the given C<$port> and keeps the passed references. When the port 696Monitors the given C<$port> and keeps the passed references. When the port
578 719
579=item kil $port[, @reason] 720=item kil $port[, @reason]
580 721
581Kill the specified port with the given C<@reason>. 722Kill the specified port with the given C<@reason>.
582 723
583If no C<@reason> is specified, then the port is killed "normally" (ports 724If no C<@reason> is specified, then the port is killed "normally" -
584monitoring other ports will not necessarily die because a port dies 725monitor callback will be invoked, but the kil will not cause linked ports
585"normally"). 726(C<mon $mport, $lport> form) to get killed.
586 727
587Otherwise, linked ports get killed with the same reason (second form of 728If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
588C<mon>, see above). 729form) get killed with the same reason.
589 730
590Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks 731Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
591will be reported as reason C<< die => $@ >>. 732will be reported as reason C<< die => $@ >>.
592 733
593Transport/communication errors are reported as C<< transport_error => 734Transport/communication errors are reported as C<< transport_error =>
612the package, then the package above the package and so on (e.g. 753the package, then the package above the package and so on (e.g.
613C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function 754C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
614exists or it runs out of package names. 755exists or it runs out of package names.
615 756
616The init function is then called with the newly-created port as context 757The init function is then called with the newly-created port as context
617object (C<$SELF>) and the C<@initdata> values as arguments. 758object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
759call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
760the port might not get created.
618 761
619A common idiom is to pass a local port, immediately monitor the spawned 762A common idiom is to pass a local port, immediately monitor the spawned
620port, and in the remote init function, immediately monitor the passed 763port, and in the remote init function, immediately monitor the passed
621local port. This two-way monitoring ensures that both ports get cleaned up 764local port. This two-way monitoring ensures that both ports get cleaned up
622when there is a problem. 765when there is a problem.
623 766
767C<spawn> guarantees that the C<$initfunc> has no visible effects on the
768caller before C<spawn> returns (by delaying invocation when spawn is
769called for the local node).
770
624Example: spawn a chat server port on C<$othernode>. 771Example: spawn a chat server port on C<$othernode>.
625 772
626 # this node, executed from within a port context: 773 # this node, executed from within a port context:
627 my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF; 774 my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
628 mon $server; 775 mon $server;
642 789
643sub _spawn { 790sub _spawn {
644 my $port = shift; 791 my $port = shift;
645 my $init = shift; 792 my $init = shift;
646 793
794 # rcv will create the actual port
647 local $SELF = "$NODE#$port"; 795 local $SELF = "$NODE#$port";
648 eval { 796 eval {
649 &{ load_func $init } 797 &{ load_func $init }
650 }; 798 };
651 _self_die if $@; 799 _self_die if $@;
652} 800}
653 801
654sub spawn(@) { 802sub spawn(@) {
655 my ($noderef, undef) = split /#/, shift, 2; 803 my ($nodeid, undef) = split /#/, shift, 2;
656 804
657 my $id = "$RUNIQ." . $ID++; 805 my $id = $RUNIQ . ++$ID;
658 806
659 $_[0] =~ /::/ 807 $_[0] =~ /::/
660 or Carp::croak "spawn init function must be a fully-qualified name, caught"; 808 or Carp::croak "spawn init function must be a fully-qualified name, caught";
661 809
662 snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_; 810 snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
663 811
664 "$noderef#$id" 812 "$nodeid#$id"
665} 813}
814
666 815
667=item after $timeout, @msg 816=item after $timeout, @msg
668 817
669=item after $timeout, $callback 818=item after $timeout, $callback
670 819
686 ? $action[0]() 835 ? $action[0]()
687 : snd @action; 836 : snd @action;
688 }; 837 };
689} 838}
690 839
840#=item $cb2 = timeout $seconds, $cb[, @args]
841
842=item cal $port, @msg, $callback[, $timeout]
843
844A simple form of RPC - sends a message to the given C<$port> with the
845given contents (C<@msg>), but adds a reply port to the message.
846
847The reply port is created temporarily just for the purpose of receiving
848the reply, and will be C<kil>ed when no longer needed.
849
850A reply message sent to the port is passed to the C<$callback> as-is.
851
852If an optional time-out (in seconds) is given and it is not C<undef>,
853then the callback will be called without any arguments after the time-out
854elapsed and the port is C<kil>ed.
855
856If no time-out is given (or it is C<undef>), then the local port will
857monitor the remote port instead, so it eventually gets cleaned-up.
858
859Currently this function returns the temporary port, but this "feature"
860might go in future versions unless you can make a convincing case that
861this is indeed useful for something.
862
863=cut
864
865sub cal(@) {
866 my $timeout = ref $_[-1] ? undef : pop;
867 my $cb = pop;
868
869 my $port = port {
870 undef $timeout;
871 kil $SELF;
872 &$cb;
873 };
874
875 if (defined $timeout) {
876 $timeout = AE::timer $timeout, 0, sub {
877 undef $timeout;
878 kil $port;
879 $cb->();
880 };
881 } else {
882 mon $_[0], sub {
883 kil $port;
884 $cb->();
885 };
886 }
887
888 push @_, $port;
889 &snd;
890
891 $port
892}
893
894=back
895
896=head1 DISTRIBUTED DATABASE
897
898AnyEvent::MP comes with a simple distributed database. The database will
899be mirrored asynchronously on all global nodes. Other nodes bind to one
900of the global nodes for their needs. Every node has a "local database"
901which contains all the values that are set locally. All local databases
902are merged together to form the global database, which can be queried.
903
904The database structure is that of a two-level hash - the database hash
905contains hashes which contain values, similarly to a perl hash of hashes,
906i.e.:
907
908 $DATABASE{$family}{$subkey} = $value
909
910The top level hash key is called "family", and the second-level hash key
911is called "subkey" or simply "key".
912
913The family must be alphanumeric, i.e. start with a letter and consist
914of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
915pretty much like Perl module names.
916
917As the family namespace is global, it is recommended to prefix family names
918with the name of the application or module using it.
919
920The subkeys must be non-empty strings, with no further restrictions.
921
922The values should preferably be strings, but other perl scalars should
923work as well (such as C<undef>, arrays and hashes).
924
925Every database entry is owned by one node - adding the same family/subkey
926combination on multiple nodes will not cause discomfort for AnyEvent::MP,
927but the result might be nondeterministic, i.e. the key might have
928different values on different nodes.
929
930Different subkeys in the same family can be owned by different nodes
931without problems, and in fact, this is the common method to create worker
932pools. For example, a worker port for image scaling might do this:
933
934 db_set my_image_scalers => $port;
935
936And clients looking for an image scaler will want to get the
937C<my_image_scalers> keys from time to time:
938
939 db_keys my_image_scalers => sub {
940 @ports = @{ $_[0] };
941 };
942
943Or better yet, they want to monitor the database family, so they always
944have a reasonable up-to-date copy:
945
946 db_mon my_image_scalers => sub {
947 @ports = keys %{ $_[0] };
948 };
949
950In general, you can set or delete single subkeys, but query and monitor
951whole families only.
952
953If you feel the need to monitor or query a single subkey, try giving it
954it's own family.
955
956=over
957
958=item db_set $family => $subkey [=> $value]
959
960Sets (or replaces) a key to the database - if C<$value> is omitted,
961C<undef> is used instead.
962
963=item db_del $family => $subkey...
964
965Deletes one or more subkeys from the database family.
966
967=item $guard = db_reg $family => $subkey [=> $value]
968
969Sets the key on the database and returns a guard. When the guard is
970destroyed, the key is deleted from the database. If C<$value> is missing,
971then C<undef> is used.
972
973=item db_family $family => $cb->(\%familyhash)
974
975Queries the named database C<$family> and call the callback with the
976family represented as a hash. You can keep and freely modify the hash.
977
978=item db_keys $family => $cb->(\@keys)
979
980Same as C<db_family>, except it only queries the family I<subkeys> and passes
981them as array reference to the callback.
982
983=item db_values $family => $cb->(\@values)
984
985Same as C<db_family>, except it only queries the family I<values> and passes them
986as array reference to the callback.
987
988=item $guard = db_mon $family => $cb->($familyhash, \@added, \@changed, \@deleted)
989
990Creates a monitor on the given database family. Each time a key is set
991or or is deleted the callback is called with a hash containing the
992database family and three lists of added, changed and deleted subkeys,
993respectively. If no keys have changed then the array reference might be
994C<undef> or even missing.
995
996If not called in void context, a guard object is returned that, when
997destroyed, stops the monitor.
998
999The family hash reference and the key arrays belong to AnyEvent::MP and
1000B<must not be modified or stored> by the callback. When in doubt, make a
1001copy.
1002
1003As soon as possible after the monitoring starts, the callback will be
1004called with the intiial contents of the family, even if it is empty,
1005i.e. there will always be a timely call to the callback with the current
1006contents.
1007
1008It is possible that the callback is called with a change event even though
1009the subkey is already present and the value has not changed.
1010
1011The monitoring stops when the guard object is destroyed.
1012
1013Example: on every change to the family "mygroup", print out all keys.
1014
1015 my $guard = db_mon mygroup => sub {
1016 my ($family, $a, $c, $d) = @_;
1017 print "mygroup members: ", (join " ", keys %$family), "\n";
1018 };
1019
1020Exmaple: wait until the family "My::Module::workers" is non-empty.
1021
1022 my $guard; $guard = db_mon My::Module::workers => sub {
1023 my ($family, $a, $c, $d) = @_;
1024 return unless %$family;
1025 undef $guard;
1026 print "My::Module::workers now nonempty\n";
1027 };
1028
1029Example: print all changes to the family "AnyRvent::Fantasy::Module".
1030
1031 my $guard = db_mon AnyRvent::Fantasy::Module => sub {
1032 my ($family, $a, $c, $d) = @_;
1033
1034 print "+$_=$family->{$_}\n" for @$a;
1035 print "*$_=$family->{$_}\n" for @$c;
1036 print "-$_=$family->{$_}\n" for @$d;
1037 };
1038
1039=cut
1040
691=back 1041=back
692 1042
693=head1 AnyEvent::MP vs. Distributed Erlang 1043=head1 AnyEvent::MP vs. Distributed Erlang
694 1044
695AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node 1045AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
696== aemp node, Erlang process == aemp port), so many of the documents and 1046== aemp node, Erlang process == aemp port), so many of the documents and
697programming techniques employed by Erlang apply to AnyEvent::MP. Here is a 1047programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
698sample: 1048sample:
699 1049
700 http://www.Erlang.se/doc/programming_rules.shtml 1050 http://www.erlang.se/doc/programming_rules.shtml
701 http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4 1051 http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
702 http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6 1052 http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
703 http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5 1053 http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
704 1054
705Despite the similarities, there are also some important differences: 1055Despite the similarities, there are also some important differences:
706 1056
707=over 4 1057=over 4
708 1058
709=item * Node IDs are arbitrary strings in AEMP. 1059=item * Node IDs are arbitrary strings in AEMP.
710 1060
711Erlang relies on special naming and DNS to work everywhere in the same 1061Erlang relies on special naming and DNS to work everywhere in the same
712way. AEMP relies on each node somehow knowing its own address(es) (e.g. by 1062way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
713configuraiton or DNS), but will otherwise discover other odes itself. 1063configuration or DNS), and possibly the addresses of some seed nodes, but
1064will otherwise discover other nodes (and their IDs) itself.
714 1065
715=item * Erlang has a "remote ports are like local ports" philosophy, AEMP 1066=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
716uses "local ports are like remote ports". 1067uses "local ports are like remote ports".
717 1068
718The failure modes for local ports are quite different (runtime errors 1069The failure modes for local ports are quite different (runtime errors
727ports being the special case/exception, where transport errors cannot 1078ports being the special case/exception, where transport errors cannot
728occur. 1079occur.
729 1080
730=item * Erlang uses processes and a mailbox, AEMP does not queue. 1081=item * Erlang uses processes and a mailbox, AEMP does not queue.
731 1082
732Erlang uses processes that selectively receive messages, and therefore 1083Erlang uses processes that selectively receive messages out of order, and
733needs a queue. AEMP is event based, queuing messages would serve no 1084therefore needs a queue. AEMP is event based, queuing messages would serve
734useful purpose. For the same reason the pattern-matching abilities of 1085no useful purpose. For the same reason the pattern-matching abilities
735AnyEvent::MP are more limited, as there is little need to be able to 1086of AnyEvent::MP are more limited, as there is little need to be able to
736filter messages without dequeing them. 1087filter messages without dequeuing them.
737 1088
738(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP). 1089This is not a philosophical difference, but simply stems from AnyEvent::MP
1090being event-based, while Erlang is process-based.
1091
1092You cna have a look at L<Coro::MP> for a more Erlang-like process model on
1093top of AEMP and Coro threads.
739 1094
740=item * Erlang sends are synchronous, AEMP sends are asynchronous. 1095=item * Erlang sends are synchronous, AEMP sends are asynchronous.
741 1096
742Sending messages in Erlang is synchronous and blocks the process (and 1097Sending messages in Erlang is synchronous and blocks the process until
1098a conenction has been established and the message sent (and so does not
743so does not need a queue that can overflow). AEMP sends are immediate, 1099need a queue that can overflow). AEMP sends return immediately, connection
744connection establishment is handled in the background. 1100establishment is handled in the background.
745 1101
746=item * Erlang suffers from silent message loss, AEMP does not. 1102=item * Erlang suffers from silent message loss, AEMP does not.
747 1103
748Erlang makes few guarantees on messages delivery - messages can get lost 1104Erlang implements few guarantees on messages delivery - messages can get
749without any of the processes realising it (i.e. you send messages a, b, 1105lost without any of the processes realising it (i.e. you send messages a,
750and c, and the other side only receives messages a and c). 1106b, and c, and the other side only receives messages a and c).
751 1107
752AEMP guarantees correct ordering, and the guarantee that after one message 1108AEMP guarantees (modulo hardware errors) correct ordering, and the
753is lost, all following ones sent to the same port are lost as well, until 1109guarantee that after one message is lost, all following ones sent to the
754monitoring raises an error, so there are no silent "holes" in the message 1110same port are lost as well, until monitoring raises an error, so there are
755sequence. 1111no silent "holes" in the message sequence.
1112
1113If you want your software to be very reliable, you have to cope with
1114corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
1115simply tries to work better in common error cases, such as when a network
1116link goes down.
756 1117
757=item * Erlang can send messages to the wrong port, AEMP does not. 1118=item * Erlang can send messages to the wrong port, AEMP does not.
758 1119
759In Erlang it is quite likely that a node that restarts reuses a process ID 1120In Erlang it is quite likely that a node that restarts reuses an Erlang
760known to other nodes for a completely different process, causing messages 1121process ID known to other nodes for a completely different process,
761destined for that process to end up in an unrelated process. 1122causing messages destined for that process to end up in an unrelated
1123process.
762 1124
763AEMP never reuses port IDs, so old messages or old port IDs floating 1125AEMP does not reuse port IDs, so old messages or old port IDs floating
764around in the network will not be sent to an unrelated port. 1126around in the network will not be sent to an unrelated port.
765 1127
766=item * Erlang uses unprotected connections, AEMP uses secure 1128=item * Erlang uses unprotected connections, AEMP uses secure
767authentication and can use TLS. 1129authentication and can use TLS.
768 1130
771 1133
772=item * The AEMP protocol is optimised for both text-based and binary 1134=item * The AEMP protocol is optimised for both text-based and binary
773communications. 1135communications.
774 1136
775The AEMP protocol, unlike the Erlang protocol, supports both programming 1137The AEMP protocol, unlike the Erlang protocol, supports both programming
776language independent text-only protocols (good for debugging) and binary, 1138language independent text-only protocols (good for debugging), and binary,
777language-specific serialisers (e.g. Storable). By default, unless TLS is 1139language-specific serialisers (e.g. Storable). By default, unless TLS is
778used, the protocol is actually completely text-based. 1140used, the protocol is actually completely text-based.
779 1141
780It has also been carefully designed to be implementable in other languages 1142It has also been carefully designed to be implementable in other languages
781with a minimum of work while gracefully degrading functionality to make the 1143with a minimum of work while gracefully degrading functionality to make the
782protocol simple. 1144protocol simple.
783 1145
784=item * AEMP has more flexible monitoring options than Erlang. 1146=item * AEMP has more flexible monitoring options than Erlang.
785 1147
786In Erlang, you can chose to receive I<all> exit signals as messages 1148In Erlang, you can chose to receive I<all> exit signals as messages or
787or I<none>, there is no in-between, so monitoring single processes is 1149I<none>, there is no in-between, so monitoring single Erlang processes is
788difficult to implement. Monitoring in AEMP is more flexible than in 1150difficult to implement.
789Erlang, as one can choose between automatic kill, exit message or callback 1151
790on a per-process basis. 1152Monitoring in AEMP is more flexible than in Erlang, as one can choose
1153between automatic kill, exit message or callback on a per-port basis.
791 1154
792=item * Erlang tries to hide remote/local connections, AEMP does not. 1155=item * Erlang tries to hide remote/local connections, AEMP does not.
793 1156
794Monitoring in Erlang is not an indicator of process death/crashes, in the 1157Monitoring in Erlang is not an indicator of process death/crashes, in the
795same way as linking is (except linking is unreliable in Erlang). 1158same way as linking is (except linking is unreliable in Erlang).
817overhead, as well as having to keep a proxy object everywhere. 1180overhead, as well as having to keep a proxy object everywhere.
818 1181
819Strings can easily be printed, easily serialised etc. and need no special 1182Strings can easily be printed, easily serialised etc. and need no special
820procedures to be "valid". 1183procedures to be "valid".
821 1184
822And as a result, a miniport consists of a single closure stored in a 1185And as a result, a port with just a default receiver consists of a single
823global hash - it can't become much cheaper. 1186code reference stored in a global hash - it can't become much cheaper.
824 1187
825=item Why favour JSON, why not a real serialising format such as Storable? 1188=item Why favour JSON, why not a real serialising format such as Storable?
826 1189
827In fact, any AnyEvent::MP node will happily accept Storable as framing 1190In fact, any AnyEvent::MP node will happily accept Storable as framing
828format, but currently there is no way to make a node use Storable by 1191format, but currently there is no way to make a node use Storable by
844 1207
845L<AnyEvent::MP::Intro> - a gentle introduction. 1208L<AnyEvent::MP::Intro> - a gentle introduction.
846 1209
847L<AnyEvent::MP::Kernel> - more, lower-level, stuff. 1210L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
848 1211
849L<AnyEvent::MP::Global> - network maintainance and port groups, to find 1212L<AnyEvent::MP::Global> - network maintenance and port groups, to find
850your applications. 1213your applications.
1214
1215L<AnyEvent::MP::DataConn> - establish data connections between nodes.
1216
1217L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
1218all nodes.
851 1219
852L<AnyEvent>. 1220L<AnyEvent>.
853 1221
854=head1 AUTHOR 1222=head1 AUTHOR
855 1223

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