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Revision 1.70 by root, Sun Aug 30 19:49:47 2009 UTC vs.
Revision 1.128 by root, Sun Mar 4 14:28:44 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 initialise_node; 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 $localport, $cb->(@msg) # callback is invoked on death
38 mon $port, $otherport # kill otherport on abnormal death 41 mon $localport, $otherport # kill otherport on abnormal death
39 mon $port, $otherport, @msg # send message on 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 };
40 51
41=head1 CURRENT STATUS 52=head1 CURRENT STATUS
42 53
54 bin/aemp - stable.
43 AnyEvent::MP - stable API, should work 55 AnyEvent::MP - stable API, should work.
44 AnyEvent::MP::Intro - outdated 56 AnyEvent::MP::Intro - explains most concepts.
45 AnyEvent::MP::Kernel - mostly stable 57 AnyEvent::MP::Kernel - mostly stable API.
46 AnyEvent::MP::Global - mostly stable 58 AnyEvent::MP::Global - stable API.
47 AnyEvent::MP::Node - mostly stable, but internal anyways
48 AnyEvent::MP::Transport - mostly stable, but internal anyways
49
50 stay tuned.
51 59
52=head1 DESCRIPTION 60=head1 DESCRIPTION
53 61
54This module (-family) implements a simple message passing framework. 62This module (-family) implements a simple message passing framework.
55 63
57on the same or other hosts, and you can supervise entities remotely. 65on the same or other hosts, and you can supervise entities remotely.
58 66
59For 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>
60manual page and the examples under F<eg/>. 68manual page and the examples under F<eg/>.
61 69
62At the moment, this module family is a bit underdocumented.
63
64=head1 CONCEPTS 70=head1 CONCEPTS
65 71
66=over 4 72=over 4
67 73
68=item port 74=item port
69 75
70A 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).
71 78
72Ports 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
73some messages. Messages send to ports will not be queued, regardless of 80some messages. Messages send to ports will not be queued, regardless of
74anything was listening for them or not. 81anything was listening for them or not.
75 82
83Ports are represented by (printable) strings called "port IDs".
84
76=item port ID - C<nodeid#portname> 85=item port ID - C<nodeid#portname>
77 86
78A 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<#>)
79separator, 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).
80 90
81=item node 91=item node
82 92
83A 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,
84which enables nodes to manage each other remotely, and to create new 94which enables nodes to manage each other remotely, and to create new
85ports. 95ports.
86 96
87Nodes are either public (have one or more listening ports) or private 97Nodes are either public (have one or more listening ports) or private
88(no listening ports). Private nodes cannot talk to other private nodes 98(no listening ports). Private nodes cannot talk to other private nodes
89currently. 99currently, but all nodes can talk to public nodes.
90 100
101Nodes is represented by (printable) strings called "node IDs".
102
91=item node ID - C<[a-za-Z0-9_\-.:]+> 103=item node ID - C<[A-Za-z0-9_\-.:]*>
92 104
93A 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
94network. Depending on the configuration used, node IDs can look like a 106network. Depending on the configuration used, node IDs can look like a
95hostname, 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
96doesn't interpret node IDs in any way. 108doesn't interpret node IDs in any way except to uniquely identify a node.
97 109
98=item binds - C<ip:port> 110=item binds - C<ip:port>
99 111
100Nodes 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
101each 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
102endpoints - binds. Currently, only standard C<ip:port> specifications can 116Currently, only standard C<ip:port> specifications can be used, which
103be 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.
104 119
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
105=item seeds - C<host:port> 149=item seed IDs - C<host:port>
106 150
107When 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
108about the network it first has to contact some other node within the 152TCP port) of nodes that should be used as seed nodes.
109network. This node is called a seed.
110 153
111Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes 154=item global nodes
112are expected to be long-running, and at least one of those should always
113be available. When nodes run out of connections (e.g. due to a network
114error), they try to re-establish connections to some seednodes again to
115join the network.
116 155
117Apart 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
118every 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).
119 170
120=back 171=back
121 172
122=head1 VARIABLES/FUNCTIONS 173=head1 VARIABLES/FUNCTIONS
123 174
125 176
126=cut 177=cut
127 178
128package AnyEvent::MP; 179package AnyEvent::MP;
129 180
181use AnyEvent::MP::Config ();
130use AnyEvent::MP::Kernel; 182use AnyEvent::MP::Kernel;
183use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID);
131 184
132use common::sense; 185use common::sense;
133 186
134use Carp (); 187use Carp ();
135 188
136use AE (); 189use AE ();
190use Guard ();
137 191
138use base "Exporter"; 192use base "Exporter";
139 193
140our $VERSION = $AnyEvent::MP::Kernel::VERSION; 194our $VERSION = $AnyEvent::MP::Config::VERSION;
141 195
142our @EXPORT = qw( 196our @EXPORT = qw(
143 NODE $NODE *SELF node_of after 197 NODE $NODE *SELF node_of after
144 initialise_node 198 configure
145 snd rcv mon mon_guard kil reg psub spawn 199 snd rcv mon mon_guard kil psub peval spawn cal
146 port 200 port
201 db_set db_del db_reg
202 db_mon db_family db_keys db_values
147); 203);
148 204
149our $SELF; 205our $SELF;
150 206
151sub _self_die() { 207sub _self_die() {
156 212
157=item $thisnode = NODE / $NODE 213=item $thisnode = NODE / $NODE
158 214
159The C<NODE> function returns, and the C<$NODE> variable contains, the node 215The C<NODE> function returns, and the C<$NODE> variable contains, the node
160ID of the node running in the current process. This value is initialised by 216ID of the node running in the current process. This value is initialised by
161a call to C<initialise_node>. 217a call to C<configure>.
162 218
163=item $nodeid = node_of $port 219=item $nodeid = node_of $port
164 220
165Extracts 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.
166 222
167=item initialise_node $profile_name, key => value... 223=item configure $profile, key => value...
224
225=item configure key => value...
168 226
169Before 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
170"distributed mode") it has to initialise itself - the minimum a node needs 228"distributed mode") it has to configure itself - the minimum a node needs
171to 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
172some other nodes in the network to discover other nodes. 230some other nodes in the network to discover other nodes.
173 231
174This function initialises a node - it must be called exactly once (or 232This function configures a node - it must be called exactly once (or
175never) before calling other AnyEvent::MP functions. 233never) before calling other AnyEvent::MP functions.
176 234
177The first argument is a profile name. If it is C<undef> or missing, then 235The key/value pairs are basically the same ones as documented for the
178the current nodename will be used instead (i.e. F<uname -n>). 236F<aemp> command line utility (sans the set/del prefix), with these additions:
179 237
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
262=over 4
263
264=item step 1, gathering configuration from profiles
265
180The function first looks up the 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 is calculated as follows: 267L<aemp> commandline utility). The profile name can be specified via the
268named C<profile> parameter or can simply be the first parameter). If it is
269missing, then the nodename (F<uname -n>) will be used as profile name.
182 270
271The profile data is then gathered as follows:
272
183First, all remaining key => value pairs (all of which are conviniently 273First, all remaining key => value pairs (all of which are conveniently
184undocumented at the moment) will be used. Then they will be overwritten by 274undocumented at the moment) will be interpreted as configuration
185any values specified in the global default configuration (see the F<aemp> 275data. Then they will be overwritten by any values specified in the global
186utility), then the chain of profiles selected, if any. That means that 276default configuration (see the F<aemp> utility), then the chain of
277profiles chosen by the profile name (and any C<parent> attributes).
278
187the values specified in the profile have highest priority and the values 279That means that the values specified in the profile have highest priority
188specified via C<initialise_node> have lowest priority. 280and the values specified directly via C<configure> have lowest priority,
281and can only be used to specify defaults.
189 282
190If 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
191this 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
192special 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>.
292
293=item step 2, bind listener sockets
193 294
194The 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
195aemp protocol listeners on all binds specified (it is possible and valid 296aemp protocol listeners on all binds specified (it is possible and valid
196to have no binds, meaning that the node cannot be contacted form the 297to have no binds, meaning that the node cannot be contacted form the
197outside. This means the node cannot talk to other nodes that also have no 298outside. This means the node cannot talk to other nodes that also have no
198binds, but it can still talk to all "normal" nodes). 299binds, but it can still talk to all "normal" nodes).
199 300
200If the profile does not specify a binds list, then a default of C<*> is 301If the profile does not specify a binds list, then a default of C<*> is
201used. 302used, meaning the node will bind on a dynamically-assigned port on every
303local IP address it finds.
202 304
305=item step 3, connect to seed nodes
306
203Lastly, 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
204L<AnyEvent::MP::Global> module, which will then use it to keep 308L<AnyEvent::MP::Global> module, which will then use it to keep
205connectivity with at least on of those seed nodes at any point in time. 309connectivity with at least one node at any point in time.
206 310
207Example: become a distributed node listening on the guessed noderef, or 311=back
208the one specified via C<aemp> for the current node. This should be the 312
313Example: become a distributed node using the local node name as profile.
209most common form of invocation for "daemon"-type nodes. 314This should be the most common form of invocation for "daemon"-type nodes.
210 315
211 initialise_node; 316 configure
212 317
213Example: become an anonymous node. This form is often used for commandline 318Example: become a semi-anonymous node. This form is often used for
214clients. 319commandline clients.
215 320
216 initialise_node "anon/"; 321 configure nodeid => "myscript/%n/%u";
217 322
218Example: become a distributed node. If there is no profile of the given 323Example: configure a node using a profile called seed, which is suitable
219name, or no binds list was specified, resolve C<localhost:4044> and bind 324for a seed node as it binds on all local addresses on a fixed port (4040,
220on the resulting addresses. 325customary for aemp).
221 326
222 initialise_node "localhost:4044"; 327 # use the aemp commandline utility
328 # aemp profile seed binds '*:4040'
329
330 # then use it
331 configure profile => "seed";
332
333 # or simply use aemp from the shell again:
334 # aemp run profile seed
335
336 # or provide a nicer-to-remember nodeid
337 # aemp run profile seed nodeid "$(hostname)"
223 338
224=item $SELF 339=item $SELF
225 340
226Contains the current port id while executing C<rcv> callbacks or C<psub> 341Contains the current port id while executing C<rcv> callbacks or C<psub>
227blocks. 342blocks.
288sub _kilme { 403sub _kilme {
289 die "received message on port without callback"; 404 die "received message on port without callback";
290} 405}
291 406
292sub port(;&) { 407sub port(;&) {
293 my $id = "$UNIQ." . $ID++; 408 my $id = $UNIQ . ++$ID;
294 my $port = "$NODE#$id"; 409 my $port = "$NODE#$id";
295 410
296 rcv $port, shift || \&_kilme; 411 rcv $port, shift || \&_kilme;
297 412
298 $port 413 $port
337 msg1 => sub { ... }, 452 msg1 => sub { ... },
338 ... 453 ...
339 ; 454 ;
340 455
341Example: temporarily register a rcv callback for a tag matching some port 456Example: temporarily register a rcv callback for a tag matching some port
342(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.
343 458
344 rcv $port, $otherport => sub { 459 rcv $port, $otherport => sub {
345 my @reply = @_; 460 my @reply = @_;
346 461
347 rcv $SELF, $otherport; 462 rcv $SELF, $otherport;
349 464
350=cut 465=cut
351 466
352sub rcv($@) { 467sub rcv($@) {
353 my $port = shift; 468 my $port = shift;
354 my ($noderef, $portid) = split /#/, $port, 2; 469 my ($nodeid, $portid) = split /#/, $port, 2;
355 470
356 $NODE{$noderef} == $NODE{""} 471 $NODE{$nodeid} == $NODE{""}
357 or Carp::croak "$port: rcv can only be called on local ports, caught"; 472 or Carp::croak "$port: rcv can only be called on local ports, caught";
358 473
359 while (@_) { 474 while (@_) {
360 if (ref $_[0]) { 475 if (ref $_[0]) {
361 if (my $self = $PORT_DATA{$portid}) { 476 if (my $self = $PORT_DATA{$portid}) {
362 "AnyEvent::MP::Port" eq ref $self 477 "AnyEvent::MP::Port" eq ref $self
363 or Carp::croak "$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";
364 479
365 $self->[2] = shift; 480 $self->[0] = shift;
366 } else { 481 } else {
367 my $cb = shift; 482 my $cb = shift;
368 $PORT{$portid} = sub { 483 $PORT{$portid} = sub {
369 local $SELF = $port; 484 local $SELF = $port;
370 eval { &$cb }; _self_die if $@; 485 eval { &$cb }; _self_die if $@;
371 }; 486 };
372 } 487 }
373 } elsif (defined $_[0]) { 488 } elsif (defined $_[0]) {
374 my $self = $PORT_DATA{$portid} ||= do { 489 my $self = $PORT_DATA{$portid} ||= do {
375 my $self = bless [$PORT{$port} || sub { }, { }, $port], "AnyEvent::MP::Port"; 490 my $self = bless [$PORT{$portid} || sub { }, { }, $port], "AnyEvent::MP::Port";
376 491
377 $PORT{$portid} = sub { 492 $PORT{$portid} = sub {
378 local $SELF = $port; 493 local $SELF = $port;
379 494
380 if (my $cb = $self->[1]{$_[0]}) { 495 if (my $cb = $self->[1]{$_[0]}) {
402 } 517 }
403 518
404 $port 519 $port
405} 520}
406 521
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
407=item $closure = psub { BLOCK } 559=item $closure = psub { BLOCK }
408 560
409Remembers C<$SELF> and creates a closure out of the BLOCK. When the 561Remembers C<$SELF> and creates a closure out of the BLOCK. When the
410closure 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>
411callbacks, 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 $SELF, sub {
566BLOCK }, @_ } >>.
412 567
413This is useful when you register callbacks from C<rcv> callbacks: 568This is useful when you register callbacks from C<rcv> callbacks:
414 569
415 rcv delayed_reply => sub { 570 rcv delayed_reply => sub {
416 my ($delay, @reply) = @_; 571 my ($delay, @reply) = @_;
452 607
453Monitor the given port and do something when the port is killed or 608Monitor the given port and do something when the port is killed or
454messages to it were lost, and optionally return a guard that can be used 609messages to it were lost, and optionally return a guard that can be used
455to stop monitoring again. 610to stop monitoring again.
456 611
612In the first form (callback), the callback is simply called with any
613number of C<@reason> elements (no @reason means that the port was deleted
614"normally"). Note also that I<< the callback B<must> never die >>, so use
615C<eval> if unsure.
616
617In the second form (another port given), the other port (C<$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
457C<mon> effectively guarantees that, in the absence of hardware failures, 638C<mon> effectively guarantees that, in the absence of hardware failures,
458after starting the monitor, either all messages sent to the port will 639after starting the monitor, either all messages sent to the port will
459arrive, or the monitoring action will be invoked after possible message 640arrive, or the monitoring action will be invoked after possible message
460loss has been detected. No messages will be lost "in between" (after 641loss has been detected. No messages will be lost "in between" (after
461the first lost message no further messages will be received by the 642the first lost message no further messages will be received by the
462port). After the monitoring action was invoked, further messages might get 643port). After the monitoring action was invoked, further messages might get
463delivered again. 644delivered again.
464 645
465Note that monitoring-actions are one-shot: once messages are lost (and a 646Inter-host-connection timeouts and monitoring depend on the transport
466monitoring 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).
467 650
468In the first form (callback), the callback is simply called with any 651This means that monitoring is good for program errors and cleaning up
469number 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
470"normally"). Note also that I<< the callback B<must> never die >>, so use 653to ensure some maximum latency.
471C<eval> if unsure.
472
473In the second form (another port given), the other port (C<$rcvport>)
474will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
475"normal" kils nothing happens, while under all other conditions, the other
476port is killed with the same reason.
477
478The third form (kill self) is the same as the second form, except that
479C<$rvport> defaults to C<$SELF>.
480
481In the last form (message), a message of the form C<@msg, @reason> will be
482C<snd>.
483
484As a rule of thumb, monitoring requests should always monitor a port from
485a local port (or callback). The reason is that kill messages might get
486lost, just like any other message. Another less obvious reason is that
487even monitoring requests can get lost (for exmaple, when the connection
488to the other node goes down permanently). When monitoring a port locally
489these problems do not exist.
490 654
491Example: call a given callback when C<$port> is killed. 655Example: call a given callback when C<$port> is killed.
492 656
493 mon $port, sub { warn "port died because of <@_>\n" }; 657 mon $port, sub { warn "port died because of <@_>\n" };
494 658
501 mon $port, $self => "restart"; 665 mon $port, $self => "restart";
502 666
503=cut 667=cut
504 668
505sub mon { 669sub mon {
506 my ($noderef, $port) = split /#/, shift, 2; 670 my ($nodeid, $port) = split /#/, shift, 2;
507 671
508 my $node = $NODE{$noderef} || add_node $noderef; 672 my $node = $NODE{$nodeid} || add_node $nodeid;
509 673
510 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,';
511 675
512 unless (ref $cb) { 676 unless (ref $cb) {
513 if (@_) { 677 if (@_) {
522 } 686 }
523 687
524 $node->monitor ($port, $cb); 688 $node->monitor ($port, $cb);
525 689
526 defined wantarray 690 defined wantarray
527 and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) } 691 and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
528} 692}
529 693
530=item $guard = mon_guard $port, $ref, $ref... 694=item $guard = mon_guard $port, $ref, $ref...
531 695
532Monitors the given C<$port> and keeps the passed references. When the port 696Monitors the given C<$port> and keeps the passed references. When the port
555 719
556=item kil $port[, @reason] 720=item kil $port[, @reason]
557 721
558Kill the specified port with the given C<@reason>. 722Kill the specified port with the given C<@reason>.
559 723
560If no C<@reason> is specified, then the port is killed "normally" (ports 724If no C<@reason> is specified, then the port is killed "normally" -
561monitoring other ports will not necessarily die because a port dies 725monitor callback will be invoked, but the kil will not cause linked ports
562"normally"). 726(C<mon $mport, $lport> form) to get killed.
563 727
564Otherwise, linked ports get killed with the same reason (second form of 728If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
565C<mon>, see above). 729form) get killed with the same reason.
566 730
567Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks 731Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
568will be reported as reason C<< die => $@ >>. 732will be reported as reason C<< die => $@ >>.
569 733
570Transport/communication errors are reported as C<< transport_error => 734Transport/communication errors are reported as C<< transport_error =>
589the package, then the package above the package and so on (e.g. 753the package, then the package above the package and so on (e.g.
590C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function 754C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
591exists or it runs out of package names. 755exists or it runs out of package names.
592 756
593The init function is then called with the newly-created port as context 757The init function is then called with the newly-created port as context
594object (C<$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.
595 761
596A 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
597port, and in the remote init function, immediately monitor the passed 763port, and in the remote init function, immediately monitor the passed
598local 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
599when there is a problem. 765when there is a problem.
600 766
767C<spawn> guarantees that the C<$initfunc> has no visible effects on the
768caller before C<spawn> returns (by delaying invocation when spawn is
769called for the local node).
770
601Example: spawn a chat server port on C<$othernode>. 771Example: spawn a chat server port on C<$othernode>.
602 772
603 # this node, executed from within a port context: 773 # this node, executed from within a port context:
604 my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF; 774 my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
605 mon $server; 775 mon $server;
619 789
620sub _spawn { 790sub _spawn {
621 my $port = shift; 791 my $port = shift;
622 my $init = shift; 792 my $init = shift;
623 793
794 # rcv will create the actual port
624 local $SELF = "$NODE#$port"; 795 local $SELF = "$NODE#$port";
625 eval { 796 eval {
626 &{ load_func $init } 797 &{ load_func $init }
627 }; 798 };
628 _self_die if $@; 799 _self_die if $@;
629} 800}
630 801
631sub spawn(@) { 802sub spawn(@) {
632 my ($noderef, undef) = split /#/, shift, 2; 803 my ($nodeid, undef) = split /#/, shift, 2;
633 804
634 my $id = "$RUNIQ." . $ID++; 805 my $id = $RUNIQ . ++$ID;
635 806
636 $_[0] =~ /::/ 807 $_[0] =~ /::/
637 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";
638 809
639 snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_; 810 snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
640 811
641 "$noderef#$id" 812 "$nodeid#$id"
642} 813}
814
643 815
644=item after $timeout, @msg 816=item after $timeout, @msg
645 817
646=item after $timeout, $callback 818=item after $timeout, $callback
647 819
663 ? $action[0]() 835 ? $action[0]()
664 : snd @action; 836 : snd @action;
665 }; 837 };
666} 838}
667 839
840=item cal $port, @msg, $callback[, $timeout]
841
842A simple form of RPC - sends a message to the given C<$port> with the
843given contents (C<@msg>), but adds a reply port to the message.
844
845The reply port is created temporarily just for the purpose of receiving
846the reply, and will be C<kil>ed when no longer needed.
847
848A reply message sent to the port is passed to the C<$callback> as-is.
849
850If an optional time-out (in seconds) is given and it is not C<undef>,
851then the callback will be called without any arguments after the time-out
852elapsed and the port is C<kil>ed.
853
854If no time-out is given (or it is C<undef>), then the local port will
855monitor the remote port instead, so it eventually gets cleaned-up.
856
857Currently this function returns the temporary port, but this "feature"
858might go in future versions unless you can make a convincing case that
859this is indeed useful for something.
860
861=cut
862
863sub cal(@) {
864 my $timeout = ref $_[-1] ? undef : pop;
865 my $cb = pop;
866
867 my $port = port {
868 undef $timeout;
869 kil $SELF;
870 &$cb;
871 };
872
873 if (defined $timeout) {
874 $timeout = AE::timer $timeout, 0, sub {
875 undef $timeout;
876 kil $port;
877 $cb->();
878 };
879 } else {
880 mon $_[0], sub {
881 kil $port;
882 $cb->();
883 };
884 }
885
886 push @_, $port;
887 &snd;
888
889 $port
890}
891
892=back
893
894=head1 DISTRIBUTED DATABASE
895
896AnyEvent::MP comes with a simple distributed database. The database will
897be mirrored asynchronously at all global nodes. Other nodes bind to one of
898the global nodes for their needs.
899
900The database consists of a two-level hash - a hash contains a hash which
901contains values.
902
903The top level hash key is called "family", and the second-level hash key
904is called "subkey" or simply "key".
905
906The family must be alphanumeric, i.e. start with a letter and consist
907of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
908pretty much like Perl module names.
909
910As the family namespace is global, it is recommended to prefix family names
911with the name of the application or module using it.
912
913The subkeys must be non-empty strings, with no further restrictions.
914
915The values should preferably be strings, but other perl scalars should
916work as well (such as undef, arrays and hashes).
917
918Every database entry is owned by one node - adding the same family/subkey
919combination on multiple nodes will not cause discomfort for AnyEvent::MP,
920but the result might be nondeterministic, i.e. the key might have
921different values on different nodes.
922
923Different subkeys in the same family can be owned by different nodes
924without problems, and in fact, this is the common method to create worker
925pools. For example, a worker port for image scaling might do this:
926
927 db_set my_image_scalers => $port;
928
929And clients looking for an image scaler will want to get the
930C<my_image_scalers> keys:
931
932 db_keys "my_image_scalers" => 60 => sub {
933 #d##TODO#
934
935=over
936
937=item db_set $family => $subkey [=> $value]
938
939Sets (or replaces) a key to the database - if C<$value> is omitted,
940C<undef> is used instead.
941
942=item db_del $family => $subkey
943
944Deletes a key from the database.
945
946=item $guard = db_reg $family => $subkey [=> $value]
947
948Sets the key on the database and returns a guard. When the guard is
949destroyed, the key is deleted from the database. If C<$value> is missing,
950then C<undef> is used.
951
952=item $guard = db_mon $family => $cb->($familyhash, \@subkeys...)
953
954Creates a monitor on the given database family. Each time a key is set or
955or is deleted the callback is called with a hash containing the database
956family and an arrayref with subkeys that have changed.
957
958Specifically, if one of the passed subkeys exists in the $familyhash, then
959it is currently set to the value in the $familyhash. Otherwise, it has
960been deleted.
961
962The first call will be with the current contents of the family and all
963keys, as if they were just added.
964
965It is possible that the callback is called with a change event even though
966the subkey is already present and the value has not changed.
967
968The monitoring stops when the guard object is destroyed.
969
970Example: on every change to the family "mygroup", print out all keys.
971
972 my $guard = db_mon mygroup => sub {
973 my ($family, $keys) = @_;
974 print "mygroup members: ", (join " ", keys %$family), "\n";
975 };
976
977Exmaple: wait until the family "My::Module::workers" is non-empty.
978
979 my $guard; $guard = db_mon My::Module::workers => sub {
980 my ($family, $keys) = @_;
981 return unless %$family;
982 undef $guard;
983 print "My::Module::workers now nonempty\n";
984 };
985
986Example: print all changes to the family "AnyRvent::Fantasy::Module".
987
988 my $guard = db_mon AnyRvent::Fantasy::Module => sub {
989 my ($family, $keys) = @_;
990
991 for (@$keys) {
992 print "$_: ",
993 (exists $family->{$_}
994 ? $family->{$_}
995 : "(deleted)"),
996 "\n";
997 }
998 };
999
1000=cut
1001
668=back 1002=back
669 1003
670=head1 AnyEvent::MP vs. Distributed Erlang 1004=head1 AnyEvent::MP vs. Distributed Erlang
671 1005
672AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node 1006AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
673== aemp node, Erlang process == aemp port), so many of the documents and 1007== aemp node, Erlang process == aemp port), so many of the documents and
674programming techniques employed by Erlang apply to AnyEvent::MP. Here is a 1008programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
675sample: 1009sample:
676 1010
677 http://www.Erlang.se/doc/programming_rules.shtml 1011 http://www.erlang.se/doc/programming_rules.shtml
678 http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4 1012 http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
679 http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6 1013 http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
680 http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5 1014 http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
681 1015
682Despite the similarities, there are also some important differences: 1016Despite the similarities, there are also some important differences:
683 1017
684=over 4 1018=over 4
685 1019
686=item * Node IDs are arbitrary strings in AEMP. 1020=item * Node IDs are arbitrary strings in AEMP.
687 1021
688Erlang relies on special naming and DNS to work everywhere in the same 1022Erlang relies on special naming and DNS to work everywhere in the same
689way. AEMP relies on each node somehow knowing its own address(es) (e.g. by 1023way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
690configuraiton or DNS), but will otherwise discover other odes itself. 1024configuration or DNS), and possibly the addresses of some seed nodes, but
1025will otherwise discover other nodes (and their IDs) itself.
691 1026
692=item * Erlang has a "remote ports are like local ports" philosophy, AEMP 1027=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
693uses "local ports are like remote ports". 1028uses "local ports are like remote ports".
694 1029
695The failure modes for local ports are quite different (runtime errors 1030The failure modes for local ports are quite different (runtime errors
704ports being the special case/exception, where transport errors cannot 1039ports being the special case/exception, where transport errors cannot
705occur. 1040occur.
706 1041
707=item * Erlang uses processes and a mailbox, AEMP does not queue. 1042=item * Erlang uses processes and a mailbox, AEMP does not queue.
708 1043
709Erlang uses processes that selectively receive messages, and therefore 1044Erlang uses processes that selectively receive messages out of order, and
710needs a queue. AEMP is event based, queuing messages would serve no 1045therefore needs a queue. AEMP is event based, queuing messages would serve
711useful purpose. For the same reason the pattern-matching abilities of 1046no useful purpose. For the same reason the pattern-matching abilities
712AnyEvent::MP are more limited, as there is little need to be able to 1047of AnyEvent::MP are more limited, as there is little need to be able to
713filter messages without dequeing them. 1048filter messages without dequeuing them.
714 1049
715(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP). 1050This is not a philosophical difference, but simply stems from AnyEvent::MP
1051being event-based, while Erlang is process-based.
1052
1053You cna have a look at L<Coro::MP> for a more Erlang-like process model on
1054top of AEMP and Coro threads.
716 1055
717=item * Erlang sends are synchronous, AEMP sends are asynchronous. 1056=item * Erlang sends are synchronous, AEMP sends are asynchronous.
718 1057
719Sending messages in Erlang is synchronous and blocks the process (and 1058Sending messages in Erlang is synchronous and blocks the process until
1059a conenction has been established and the message sent (and so does not
720so does not need a queue that can overflow). AEMP sends are immediate, 1060need a queue that can overflow). AEMP sends return immediately, connection
721connection establishment is handled in the background. 1061establishment is handled in the background.
722 1062
723=item * Erlang suffers from silent message loss, AEMP does not. 1063=item * Erlang suffers from silent message loss, AEMP does not.
724 1064
725Erlang makes few guarantees on messages delivery - messages can get lost 1065Erlang implements few guarantees on messages delivery - messages can get
726without any of the processes realising it (i.e. you send messages a, b, 1066lost without any of the processes realising it (i.e. you send messages a,
727and c, and the other side only receives messages a and c). 1067b, and c, and the other side only receives messages a and c).
728 1068
729AEMP guarantees correct ordering, and the guarantee that after one message 1069AEMP guarantees (modulo hardware errors) correct ordering, and the
730is lost, all following ones sent to the same port are lost as well, until 1070guarantee that after one message is lost, all following ones sent to the
731monitoring raises an error, so there are no silent "holes" in the message 1071same port are lost as well, until monitoring raises an error, so there are
732sequence. 1072no silent "holes" in the message sequence.
1073
1074If you want your software to be very reliable, you have to cope with
1075corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
1076simply tries to work better in common error cases, such as when a network
1077link goes down.
733 1078
734=item * Erlang can send messages to the wrong port, AEMP does not. 1079=item * Erlang can send messages to the wrong port, AEMP does not.
735 1080
736In Erlang it is quite likely that a node that restarts reuses a process ID 1081In Erlang it is quite likely that a node that restarts reuses an Erlang
737known to other nodes for a completely different process, causing messages 1082process ID known to other nodes for a completely different process,
738destined for that process to end up in an unrelated process. 1083causing messages destined for that process to end up in an unrelated
1084process.
739 1085
740AEMP never reuses port IDs, so old messages or old port IDs floating 1086AEMP does not reuse port IDs, so old messages or old port IDs floating
741around in the network will not be sent to an unrelated port. 1087around in the network will not be sent to an unrelated port.
742 1088
743=item * Erlang uses unprotected connections, AEMP uses secure 1089=item * Erlang uses unprotected connections, AEMP uses secure
744authentication and can use TLS. 1090authentication and can use TLS.
745 1091
748 1094
749=item * The AEMP protocol is optimised for both text-based and binary 1095=item * The AEMP protocol is optimised for both text-based and binary
750communications. 1096communications.
751 1097
752The AEMP protocol, unlike the Erlang protocol, supports both programming 1098The AEMP protocol, unlike the Erlang protocol, supports both programming
753language independent text-only protocols (good for debugging) and binary, 1099language independent text-only protocols (good for debugging), and binary,
754language-specific serialisers (e.g. Storable). By default, unless TLS is 1100language-specific serialisers (e.g. Storable). By default, unless TLS is
755used, the protocol is actually completely text-based. 1101used, the protocol is actually completely text-based.
756 1102
757It has also been carefully designed to be implementable in other languages 1103It has also been carefully designed to be implementable in other languages
758with a minimum of work while gracefully degrading functionality to make the 1104with a minimum of work while gracefully degrading functionality to make the
759protocol simple. 1105protocol simple.
760 1106
761=item * AEMP has more flexible monitoring options than Erlang. 1107=item * AEMP has more flexible monitoring options than Erlang.
762 1108
763In Erlang, you can chose to receive I<all> exit signals as messages 1109In Erlang, you can chose to receive I<all> exit signals as messages or
764or I<none>, there is no in-between, so monitoring single processes is 1110I<none>, there is no in-between, so monitoring single Erlang processes is
765difficult to implement. Monitoring in AEMP is more flexible than in 1111difficult to implement.
766Erlang, as one can choose between automatic kill, exit message or callback 1112
767on a per-process basis. 1113Monitoring in AEMP is more flexible than in Erlang, as one can choose
1114between automatic kill, exit message or callback on a per-port basis.
768 1115
769=item * Erlang tries to hide remote/local connections, AEMP does not. 1116=item * Erlang tries to hide remote/local connections, AEMP does not.
770 1117
771Monitoring in Erlang is not an indicator of process death/crashes, in the 1118Monitoring in Erlang is not an indicator of process death/crashes, in the
772same way as linking is (except linking is unreliable in Erlang). 1119same way as linking is (except linking is unreliable in Erlang).
794overhead, as well as having to keep a proxy object everywhere. 1141overhead, as well as having to keep a proxy object everywhere.
795 1142
796Strings can easily be printed, easily serialised etc. and need no special 1143Strings can easily be printed, easily serialised etc. and need no special
797procedures to be "valid". 1144procedures to be "valid".
798 1145
799And as a result, a miniport consists of a single closure stored in a 1146And as a result, a port with just a default receiver consists of a single
800global hash - it can't become much cheaper. 1147code reference stored in a global hash - it can't become much cheaper.
801 1148
802=item Why favour JSON, why not a real serialising format such as Storable? 1149=item Why favour JSON, why not a real serialising format such as Storable?
803 1150
804In fact, any AnyEvent::MP node will happily accept Storable as framing 1151In fact, any AnyEvent::MP node will happily accept Storable as framing
805format, but currently there is no way to make a node use Storable by 1152format, but currently there is no way to make a node use Storable by
821 1168
822L<AnyEvent::MP::Intro> - a gentle introduction. 1169L<AnyEvent::MP::Intro> - a gentle introduction.
823 1170
824L<AnyEvent::MP::Kernel> - more, lower-level, stuff. 1171L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
825 1172
826L<AnyEvent::MP::Global> - network maintainance and port groups, to find 1173L<AnyEvent::MP::Global> - network maintenance and port groups, to find
827your applications. 1174your applications.
1175
1176L<AnyEvent::MP::DataConn> - establish data connections between nodes.
1177
1178L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
1179all nodes.
828 1180
829L<AnyEvent>. 1181L<AnyEvent>.
830 1182
831=head1 AUTHOR 1183=head1 AUTHOR
832 1184

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