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Revision 1.54 by root, Fri Aug 14 16:15:37 2009 UTC vs.
Revision 1.110 by root, Sun Mar 7 19:29:07 2010 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; # -OR- 15 configure;
17 initialise_node "localhost:4040"; # -OR-
18 initialise_node "slave/", "localhost:4040"
19 16
20 # ports are message endpoints 17 # ports are message destinations
21 18
22 # sending messages 19 # sending messages
23 snd $port, type => data...; 20 snd $port, type => data...;
24 snd $port, @msg; 21 snd $port, @msg;
25 snd @msg_with_first_element_being_a_port; 22 snd @msg_with_first_element_being_a_port;
26 23
27 # creating/using ports, the simple way 24 # creating/using ports, the simple way
28 my $simple_port = port { my @msg = @_; 0 }; 25 my $simple_port = port { my @msg = @_ };
29 26
30 # creating/using ports, tagged message matching 27 # creating/using ports, tagged message matching
31 my $port = port; 28 my $port = port;
32 rcv $port, ping => sub { snd $_[0], "pong"; 0 }; 29 rcv $port, ping => sub { snd $_[0], "pong" };
33 rcv $port, pong => sub { warn "pong received\n"; 0 }; 30 rcv $port, pong => sub { warn "pong received\n" };
34 31
35 # create a port on another node 32 # create a port on another node
36 my $port = spawn $node, $initfunc, @initdata; 33 my $port = spawn $node, $initfunc, @initdata;
37 34
35 # destroy a prot again
36 kil $port; # "normal" kill
37 kil $port, my_error => "everything is broken"; # error kill
38
38 # monitoring 39 # monitoring
39 mon $port, $cb->(@msg) # callback is invoked on death 40 mon $localport, $cb->(@msg) # callback is invoked on death
40 mon $port, $otherport # kill otherport on abnormal death 41 mon $localport, $otherport # kill otherport on abnormal death
41 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 };
42 51
43=head1 CURRENT STATUS 52=head1 CURRENT STATUS
44 53
54 bin/aemp - stable.
45 AnyEvent::MP - stable API, should work 55 AnyEvent::MP - stable API, should work.
46 AnyEvent::MP::Intro - outdated 56 AnyEvent::MP::Intro - explains most concepts.
47 AnyEvent::MP::Kernel - WIP
48 AnyEvent::MP::Transport - mostly stable 57 AnyEvent::MP::Kernel - mostly stable API.
49 58 AnyEvent::MP::Global - stable API.
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
56Despite its simplicity, you can securely message other processes running 64Despite its simplicity, you can securely message other processes running
57on the same or other hosts. 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. 68manual page and the examples under F<eg/>.
61
62At the moment, this module family is severly broken and underdocumented,
63so do not use. This was uploaded mainly to reserve the CPAN namespace -
64stay tuned!
65 69
66=head1 CONCEPTS 70=head1 CONCEPTS
67 71
68=over 4 72=over 4
69 73
70=item port 74=item port
71 75
72A 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).
73 78
74Ports 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
75some messages. Messages will not be queued. 80some messages. Messages send to ports will not be queued, regardless of
81anything was listening for them or not.
76 82
77=item port id - C<noderef#portname> 83=item port ID - C<nodeid#portname>
78 84
79A port ID is the concatenation of a noderef, a hash-mark (C<#>) as 85A port ID is the concatenation of a node ID, a hash-mark (C<#>) as
80separator, and a port name (a printable string of unspecified format). An 86separator, and a port name (a printable string of unspecified format).
81exception is the the node port, whose ID is identical to its node
82reference.
83 87
84=item node 88=item node
85 89
86A node is a single process containing at least one port - the node port, 90A node is a single process containing at least one port - the node port,
87which provides nodes to manage each other remotely, and to create new 91which enables nodes to manage each other remotely, and to create new
88ports. 92ports.
89 93
90Nodes are either private (single-process only), slaves (connected to a 94Nodes are either public (have one or more listening ports) or private
91master node only) or public nodes (connectable from unrelated nodes). 95(no listening ports). Private nodes cannot talk to other private nodes
96currently.
92 97
93=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id> 98=item node ID - C<[A-Z_][a-zA-Z0-9_\-.:]*>
94 99
95A node reference is a string that either simply identifies the node (for 100A node ID is a string that uniquely identifies the node within a
96private and slave nodes), or contains a recipe on how to reach a given 101network. Depending on the configuration used, node IDs can look like a
97node (for public nodes). 102hostname, a hostname and a port, or a random string. AnyEvent::MP itself
103doesn't interpret node IDs in any way.
98 104
99This recipe is simply a comma-separated list of C<address:port> pairs (for 105=item binds - C<ip:port>
100TCP/IP, other protocols might look different).
101 106
102Node references come in two flavours: resolved (containing only numerical 107Nodes can only talk to each other by creating some kind of connection to
103addresses) or unresolved (where hostnames are used instead of addresses). 108each other. To do this, nodes should listen on one or more local transport
109endpoints - binds. Currently, only standard C<ip:port> specifications can
110be used, which specify TCP ports to listen on.
104 111
105Before using an unresolved node reference in a message you first have to 112=item seed nodes
106resolve it. 113
114When a node starts, it knows nothing about the network. To teach the node
115about the network it first has to contact some other node within the
116network. This node is called a seed.
117
118Apart from the fact that other nodes know them as seed nodes and they have
119to have fixed listening addresses, seed nodes are perfectly normal nodes -
120any node can function as a seed node for others.
121
122In addition to discovering the network, seed nodes are also used to
123maintain the network and to connect nodes that otherwise would have
124trouble connecting. They form the backbone of an AnyEvent::MP network.
125
126Seed nodes are expected to be long-running, and at least one seed node
127should always be available. They should also be relatively responsive - a
128seed node that blocks for long periods will slow down everybody else.
129
130=item seeds - C<host:port>
131
132Seeds are transport endpoint(s) (usually a hostname/IP address and a
133TCP port) of nodes that should be used as seed nodes.
134
135The nodes listening on those endpoints are expected to be long-running,
136and at least one of those should always be available. When nodes run out
137of connections (e.g. due to a network error), they try to re-establish
138connections to some seednodes again to join the network.
107 139
108=back 140=back
109 141
110=head1 VARIABLES/FUNCTIONS 142=head1 VARIABLES/FUNCTIONS
111 143
123 155
124use AE (); 156use AE ();
125 157
126use base "Exporter"; 158use base "Exporter";
127 159
128our $VERSION = $AnyEvent::MP::Kernel::VERSION; 160our $VERSION = 1.26;
129 161
130our @EXPORT = qw( 162our @EXPORT = qw(
131 NODE $NODE *SELF node_of _any_ 163 NODE $NODE *SELF node_of after
132 resolve_node initialise_node 164 configure
133 snd rcv mon kil reg psub spawn 165 snd rcv mon mon_guard kil psub peval spawn cal
134 port 166 port
135); 167);
136 168
137our $SELF; 169our $SELF;
138 170
142 kil $SELF, die => $msg; 174 kil $SELF, die => $msg;
143} 175}
144 176
145=item $thisnode = NODE / $NODE 177=item $thisnode = NODE / $NODE
146 178
147The C<NODE> function returns, and the C<$NODE> variable contains the 179The C<NODE> function returns, and the C<$NODE> variable contains, the node
148noderef of the local node. The value is initialised by a call to 180ID of the node running in the current process. This value is initialised by
149C<initialise_node>. 181a call to C<configure>.
150 182
151=item $noderef = node_of $port 183=item $nodeid = node_of $port
152 184
153Extracts and returns the noderef from a port ID or a noderef. 185Extracts and returns the node ID from a port ID or a node ID.
154 186
155=item initialise_node $noderef, $seednode, $seednode... 187=item configure $profile, key => value...
156 188
157=item initialise_node "slave/", $master, $master... 189=item configure key => value...
158 190
159Before a node can talk to other nodes on the network it has to initialise 191Before a node can talk to other nodes on the network (i.e. enter
160itself - the minimum a node needs to know is it's own name, and optionally 192"distributed mode") it has to configure itself - the minimum a node needs
161it should know the noderefs of some other nodes in the network. 193to know is its own name, and optionally it should know the addresses of
194some other nodes in the network to discover other nodes.
162 195
196The key/value pairs are basically the same ones as documented for the
197F<aemp> command line utility (sans the set/del prefix).
198
163This function initialises a node - it must be called exactly once (or 199This function configures a node - it must be called exactly once (or
164never) before calling other AnyEvent::MP functions. 200never) before calling other AnyEvent::MP functions.
165 201
166All arguments (optionally except for the first) are noderefs, which can be
167either resolved or unresolved.
168
169The first argument will be looked up in the configuration database first
170(if it is C<undef> then the current nodename will be used instead) to find
171the relevant configuration profile (see L<aemp>). If none is found then
172the default configuration is used. The configuration supplies additional
173seed/master nodes and can override the actual noderef.
174
175There are two types of networked nodes, public nodes and slave nodes:
176
177=over 4 202=over 4
178 203
179=item public nodes 204=item step 1, gathering configuration from profiles
180 205
181For public nodes, C<$noderef> (supplied either directly to 206The function first looks up a profile in the aemp configuration (see the
182C<initialise_node> or indirectly via a profile or the nodename) must be a 207L<aemp> commandline utility). The profile name can be specified via the
183noderef (possibly unresolved, in which case it will be resolved). 208named C<profile> parameter or can simply be the first parameter). If it is
209missing, then the nodename (F<uname -n>) will be used as profile name.
184 210
185After resolving, the node will bind itself on all endpoints and try to 211The profile data is then gathered as follows:
186connect to all additional C<$seednodes> that are specified. Seednodes are
187optional and can be used to quickly bootstrap the node into an existing
188network.
189 212
190=item slave nodes 213First, all remaining key => value pairs (all of which are conveniently
214undocumented at the moment) will be interpreted as configuration
215data. Then they will be overwritten by any values specified in the global
216default configuration (see the F<aemp> utility), then the chain of
217profiles chosen by the profile name (and any C<parent> attributes).
191 218
192When the C<$noderef> (either as given or overriden by the config file) 219That means that the values specified in the profile have highest priority
193is the special string C<slave/>, then the node will become a slave 220and the values specified directly via C<configure> have lowest priority,
194node. Slave nodes cannot be contacted from outside and will route most of 221and can only be used to specify defaults.
195their traffic to the master node that they attach to.
196 222
197At least one additional noderef is required (either by specifying it 223If the profile specifies a node ID, then this will become the node ID of
198directly or because it is part of the configuration profile): The node 224this process. If not, then the profile name will be used as node ID. The
199will try to connect to all of them and will become a slave attached to the 225special node ID of C<anon/> will be replaced by a random node ID.
200first node it can successfully connect to. 226
227=item step 2, bind listener sockets
228
229The next step is to look up the binds in the profile, followed by binding
230aemp protocol listeners on all binds specified (it is possible and valid
231to have no binds, meaning that the node cannot be contacted form the
232outside. This means the node cannot talk to other nodes that also have no
233binds, but it can still talk to all "normal" nodes).
234
235If the profile does not specify a binds list, then a default of C<*> is
236used, meaning the node will bind on a dynamically-assigned port on every
237local IP address it finds.
238
239=item step 3, connect to seed nodes
240
241As the last step, the seeds list from the profile is passed to the
242L<AnyEvent::MP::Global> module, which will then use it to keep
243connectivity with at least one node at any point in time.
201 244
202=back 245=back
203 246
204This function will block until all nodes have been resolved and, for slave 247Example: become a distributed node using the local node name as profile.
205nodes, until it has successfully established a connection to a master 248This should be the most common form of invocation for "daemon"-type nodes.
206server.
207 249
208Example: become a public node listening on the guessed noderef, or the one 250 configure
209specified via C<aemp> for the current node. This should be the most common
210form of invocation for "daemon"-type nodes.
211 251
212 initialise_node; 252Example: become an anonymous node. This form is often used for commandline
253clients.
213 254
214Example: become a slave node to any of the the seednodes specified via 255 configure nodeid => "anon/";
215C<aemp>. This form is often used for commandline clients.
216 256
217 initialise_node "slave/"; 257Example: configure a node using a profile called seed, which si suitable
258for a seed node as it binds on all local addresses on a fixed port (4040,
259customary for aemp).
218 260
219Example: become a slave node to any of the specified master servers. This 261 # use the aemp commandline utility
220form is also often used for commandline clients. 262 # aemp profile seed nodeid anon/ binds '*:4040'
221 263
222 initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net"; 264 # then use it
265 configure profile => "seed";
223 266
224Example: become a public node, and try to contact some well-known master 267 # or simply use aemp from the shell again:
225servers to become part of the network. 268 # aemp run profile seed
226 269
227 initialise_node undef, "master1", "master2"; 270 # or provide a nicer-to-remember nodeid
228 271 # aemp run profile seed nodeid "$(hostname)"
229Example: become a public node listening on port C<4041>.
230
231 initialise_node 4041;
232
233Example: become a public node, only visible on localhost port 4044.
234
235 initialise_node "localhost:4044";
236
237=item $cv = resolve_node $noderef
238
239Takes an unresolved node reference that may contain hostnames and
240abbreviated IDs, resolves all of them and returns a resolved node
241reference.
242
243In addition to C<address:port> pairs allowed in resolved noderefs, the
244following forms are supported:
245
246=over 4
247
248=item the empty string
249
250An empty-string component gets resolved as if the default port (4040) was
251specified.
252
253=item naked port numbers (e.g. C<1234>)
254
255These are resolved by prepending the local nodename and a colon, to be
256further resolved.
257
258=item hostnames (e.g. C<localhost:1234>, C<localhost>)
259
260These are resolved by using AnyEvent::DNS to resolve them, optionally
261looking up SRV records for the C<aemp=4040> port, if no port was
262specified.
263
264=back
265 272
266=item $SELF 273=item $SELF
267 274
268Contains the current port id while executing C<rcv> callbacks or C<psub> 275Contains the current port id while executing C<rcv> callbacks or C<psub>
269blocks. 276blocks.
270 277
271=item SELF, %SELF, @SELF... 278=item *SELF, SELF, %SELF, @SELF...
272 279
273Due to some quirks in how perl exports variables, it is impossible to 280Due to some quirks in how perl exports variables, it is impossible to
274just export C<$SELF>, all the symbols called C<SELF> are exported by this 281just export C<$SELF>, all the symbols named C<SELF> are exported by this
275module, but only C<$SELF> is currently used. 282module, but only C<$SELF> is currently used.
276 283
277=item snd $port, type => @data 284=item snd $port, type => @data
278 285
279=item snd $port, @msg 286=item snd $port, @msg
280 287
281Send the given message to the given port ID, which can identify either 288Send the given message to the given port, which can identify either a
282a local or a remote port, and must be a port ID. 289local or a remote port, and must be a port ID.
283 290
284While the message can be about anything, it is highly recommended to use a 291While the message can be almost anything, it is highly recommended to
285string as first element (a port ID, or some word that indicates a request 292use a string as first element (a port ID, or some word that indicates a
286type etc.). 293request type etc.) and to consist if only simple perl values (scalars,
294arrays, hashes) - if you think you need to pass an object, think again.
287 295
288The message data effectively becomes read-only after a call to this 296The message data logically becomes read-only after a call to this
289function: modifying any argument is not allowed and can cause many 297function: modifying any argument (or values referenced by them) is
290problems. 298forbidden, as there can be considerable time between the call to C<snd>
299and the time the message is actually being serialised - in fact, it might
300never be copied as within the same process it is simply handed to the
301receiving port.
291 302
292The type of data you can transfer depends on the transport protocol: when 303The type of data you can transfer depends on the transport protocol: when
293JSON is used, then only strings, numbers and arrays and hashes consisting 304JSON is used, then only strings, numbers and arrays and hashes consisting
294of those are allowed (no objects). When Storable is used, then anything 305of those are allowed (no objects). When Storable is used, then anything
295that Storable can serialise and deserialise is allowed, and for the local 306that Storable can serialise and deserialise is allowed, and for the local
296node, anything can be passed. 307node, anything can be passed. Best rely only on the common denominator of
308these.
297 309
298=item $local_port = port 310=item $local_port = port
299 311
300Create a new local port object and returns its port ID. Initially it has 312Create a new local port object and returns its port ID. Initially it has
301no callbacks set and will throw an error when it receives messages. 313no callbacks set and will throw an error when it receives messages.
374 msg1 => sub { ... }, 386 msg1 => sub { ... },
375 ... 387 ...
376 ; 388 ;
377 389
378Example: temporarily register a rcv callback for a tag matching some port 390Example: temporarily register a rcv callback for a tag matching some port
379(e.g. for a rpc reply) and unregister it after a message was received. 391(e.g. for an rpc reply) and unregister it after a message was received.
380 392
381 rcv $port, $otherport => sub { 393 rcv $port, $otherport => sub {
382 my @reply = @_; 394 my @reply = @_;
383 395
384 rcv $SELF, $otherport; 396 rcv $SELF, $otherport;
386 398
387=cut 399=cut
388 400
389sub rcv($@) { 401sub rcv($@) {
390 my $port = shift; 402 my $port = shift;
391 my ($noderef, $portid) = split /#/, $port, 2; 403 my ($nodeid, $portid) = split /#/, $port, 2;
392 404
393 ($NODE{$noderef} || add_node $noderef) == $NODE{""} 405 $NODE{$nodeid} == $NODE{""}
394 or Carp::croak "$port: rcv can only be called on local ports, caught"; 406 or Carp::croak "$port: rcv can only be called on local ports, caught";
395 407
396 while (@_) { 408 while (@_) {
397 if (ref $_[0]) { 409 if (ref $_[0]) {
398 if (my $self = $PORT_DATA{$portid}) { 410 if (my $self = $PORT_DATA{$portid}) {
399 "AnyEvent::MP::Port" eq ref $self 411 "AnyEvent::MP::Port" eq ref $self
400 or Carp::croak "$port: rcv can only be called on message matching ports, caught"; 412 or Carp::croak "$port: rcv can only be called on message matching ports, caught";
401 413
402 $self->[2] = shift; 414 $self->[0] = shift;
403 } else { 415 } else {
404 my $cb = shift; 416 my $cb = shift;
405 $PORT{$portid} = sub { 417 $PORT{$portid} = sub {
406 local $SELF = $port; 418 local $SELF = $port;
407 eval { &$cb }; _self_die if $@; 419 eval { &$cb }; _self_die if $@;
408 }; 420 };
409 } 421 }
410 } elsif (defined $_[0]) { 422 } elsif (defined $_[0]) {
411 my $self = $PORT_DATA{$portid} ||= do { 423 my $self = $PORT_DATA{$portid} ||= do {
412 my $self = bless [$PORT{$port} || sub { }, { }, $port], "AnyEvent::MP::Port"; 424 my $self = bless [$PORT{$portid} || sub { }, { }, $port], "AnyEvent::MP::Port";
413 425
414 $PORT{$portid} = sub { 426 $PORT{$portid} = sub {
415 local $SELF = $port; 427 local $SELF = $port;
416 428
417 if (my $cb = $self->[1]{$_[0]}) { 429 if (my $cb = $self->[1]{$_[0]}) {
439 } 451 }
440 452
441 $port 453 $port
442} 454}
443 455
456=item peval $port, $coderef[, @args]
457
458Evaluates the given C<$codref> within the contetx of C<$port>, that is,
459when the code throews an exception the C<$port> will be killed.
460
461Any remaining args will be passed to the callback. Any return values will
462be returned to the caller.
463
464This is useful when you temporarily want to execute code in the context of
465a port.
466
467Example: create a port and run some initialisation code in it's context.
468
469 my $port = port { ... };
470
471 peval $port, sub {
472 init
473 or die "unable to init";
474 };
475
476=cut
477
478sub peval($$) {
479 local $SELF = shift;
480 my $cb = shift;
481
482 if (wantarray) {
483 my @res = eval { &$cb };
484 _self_die if $@;
485 @res
486 } else {
487 my $res = eval { &$cb };
488 _self_die if $@;
489 $res
490 }
491}
492
444=item $closure = psub { BLOCK } 493=item $closure = psub { BLOCK }
445 494
446Remembers C<$SELF> and creates a closure out of the BLOCK. When the 495Remembers C<$SELF> and creates a closure out of the BLOCK. When the
447closure is executed, sets up the environment in the same way as in C<rcv> 496closure is executed, sets up the environment in the same way as in C<rcv>
448callbacks, i.e. runtime errors will cause the port to get C<kil>ed. 497callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
498
499The effect is basically as if it returned C<< sub { peval $SELF, sub {
500BLOCK } } >>.
449 501
450This is useful when you register callbacks from C<rcv> callbacks: 502This is useful when you register callbacks from C<rcv> callbacks:
451 503
452 rcv delayed_reply => sub { 504 rcv delayed_reply => sub {
453 my ($delay, @reply) = @_; 505 my ($delay, @reply) = @_;
477 $res 529 $res
478 } 530 }
479 } 531 }
480} 532}
481 533
482=item $guard = mon $port, $cb->(@reason) 534=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
483 535
484=item $guard = mon $port, $rcvport 536=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
485 537
486=item $guard = mon $port 538=item $guard = mon $port # kill $SELF when $port dies
487 539
488=item $guard = mon $port, $rcvport, @msg 540=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
489 541
490Monitor the given port and do something when the port is killed or 542Monitor the given port and do something when the port is killed or
491messages to it were lost, and optionally return a guard that can be used 543messages to it were lost, and optionally return a guard that can be used
492to stop monitoring again. 544to stop monitoring again.
493
494C<mon> effectively guarantees that, in the absence of hardware failures,
495that after starting the monitor, either all messages sent to the port
496will arrive, or the monitoring action will be invoked after possible
497message loss has been detected. No messages will be lost "in between"
498(after the first lost message no further messages will be received by the
499port). After the monitoring action was invoked, further messages might get
500delivered again.
501 545
502In the first form (callback), the callback is simply called with any 546In the first form (callback), the callback is simply called with any
503number of C<@reason> elements (no @reason means that the port was deleted 547number of C<@reason> elements (no @reason means that the port was deleted
504"normally"). Note also that I<< the callback B<must> never die >>, so use 548"normally"). Note also that I<< the callback B<must> never die >>, so use
505C<eval> if unsure. 549C<eval> if unsure.
506 550
507In the second form (another port given), the other port (C<$rcvport>) 551In the second form (another port given), the other port (C<$rcvport>)
508will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on 552will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
509"normal" kils nothing happens, while under all other conditions, the other 553"normal" kils nothing happens, while under all other conditions, the other
510port is killed with the same reason. 554port is killed with the same reason.
511 555
512The third form (kill self) is the same as the second form, except that 556The third form (kill self) is the same as the second form, except that
513C<$rvport> defaults to C<$SELF>. 557C<$rvport> defaults to C<$SELF>.
514 558
515In the last form (message), a message of the form C<@msg, @reason> will be 559In the last form (message), a message of the form C<@msg, @reason> will be
516C<snd>. 560C<snd>.
561
562Monitoring-actions are one-shot: once messages are lost (and a monitoring
563alert was raised), they are removed and will not trigger again.
517 564
518As a rule of thumb, monitoring requests should always monitor a port from 565As a rule of thumb, monitoring requests should always monitor a port from
519a local port (or callback). The reason is that kill messages might get 566a local port (or callback). The reason is that kill messages might get
520lost, just like any other message. Another less obvious reason is that 567lost, just like any other message. Another less obvious reason is that
521even monitoring requests can get lost (for exmaple, when the connection 568even monitoring requests can get lost (for example, when the connection
522to the other node goes down permanently). When monitoring a port locally 569to the other node goes down permanently). When monitoring a port locally
523these problems do not exist. 570these problems do not exist.
524 571
572C<mon> effectively guarantees that, in the absence of hardware failures,
573after starting the monitor, either all messages sent to the port will
574arrive, or the monitoring action will be invoked after possible message
575loss has been detected. No messages will be lost "in between" (after
576the first lost message no further messages will be received by the
577port). After the monitoring action was invoked, further messages might get
578delivered again.
579
580Inter-host-connection timeouts and monitoring depend on the transport
581used. The only transport currently implemented is TCP, and AnyEvent::MP
582relies on TCP to detect node-downs (this can take 10-15 minutes on a
583non-idle connection, and usually around two hours for idle connections).
584
585This means that monitoring is good for program errors and cleaning up
586stuff eventually, but they are no replacement for a timeout when you need
587to ensure some maximum latency.
588
525Example: call a given callback when C<$port> is killed. 589Example: call a given callback when C<$port> is killed.
526 590
527 mon $port, sub { warn "port died because of <@_>\n" }; 591 mon $port, sub { warn "port died because of <@_>\n" };
528 592
529Example: kill ourselves when C<$port> is killed abnormally. 593Example: kill ourselves when C<$port> is killed abnormally.
535 mon $port, $self => "restart"; 599 mon $port, $self => "restart";
536 600
537=cut 601=cut
538 602
539sub mon { 603sub mon {
540 my ($noderef, $port) = split /#/, shift, 2; 604 my ($nodeid, $port) = split /#/, shift, 2;
541 605
542 my $node = $NODE{$noderef} || add_node $noderef; 606 my $node = $NODE{$nodeid} || add_node $nodeid;
543 607
544 my $cb = @_ ? shift : $SELF || Carp::croak 'mon: called with one argument only, but $SELF not set,'; 608 my $cb = @_ ? shift : $SELF || Carp::croak 'mon: called with one argument only, but $SELF not set,';
545 609
546 unless (ref $cb) { 610 unless (ref $cb) {
547 if (@_) { 611 if (@_) {
556 } 620 }
557 621
558 $node->monitor ($port, $cb); 622 $node->monitor ($port, $cb);
559 623
560 defined wantarray 624 defined wantarray
561 and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) } 625 and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) })
562} 626}
563 627
564=item $guard = mon_guard $port, $ref, $ref... 628=item $guard = mon_guard $port, $ref, $ref...
565 629
566Monitors the given C<$port> and keeps the passed references. When the port 630Monitors the given C<$port> and keeps the passed references. When the port
567is killed, the references will be freed. 631is killed, the references will be freed.
568 632
569Optionally returns a guard that will stop the monitoring. 633Optionally returns a guard that will stop the monitoring.
570 634
571This function is useful when you create e.g. timers or other watchers and 635This function is useful when you create e.g. timers or other watchers and
572want to free them when the port gets killed: 636want to free them when the port gets killed (note the use of C<psub>):
573 637
574 $port->rcv (start => sub { 638 $port->rcv (start => sub {
575 my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub { 639 my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
576 undef $timer if 0.9 < rand; 640 undef $timer if 0.9 < rand;
577 }); 641 });
578 }); 642 });
579 643
580=cut 644=cut
589 653
590=item kil $port[, @reason] 654=item kil $port[, @reason]
591 655
592Kill the specified port with the given C<@reason>. 656Kill the specified port with the given C<@reason>.
593 657
594If no C<@reason> is specified, then the port is killed "normally" (linked 658If no C<@reason> is specified, then the port is killed "normally" -
595ports will not be kileld, or even notified). 659monitor callback will be invoked, but the kil will not cause linked ports
660(C<mon $mport, $lport> form) to get killed.
596 661
597Otherwise, linked ports get killed with the same reason (second form of 662If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
598C<mon>, see below). 663form) get killed with the same reason.
599 664
600Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks 665Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
601will be reported as reason C<< die => $@ >>. 666will be reported as reason C<< die => $@ >>.
602 667
603Transport/communication errors are reported as C<< transport_error => 668Transport/communication errors are reported as C<< transport_error =>
608=item $port = spawn $node, $initfunc[, @initdata] 673=item $port = spawn $node, $initfunc[, @initdata]
609 674
610Creates a port on the node C<$node> (which can also be a port ID, in which 675Creates a port on the node C<$node> (which can also be a port ID, in which
611case it's the node where that port resides). 676case it's the node where that port resides).
612 677
613The port ID of the newly created port is return immediately, and it is 678The port ID of the newly created port is returned immediately, and it is
614permissible to immediately start sending messages or monitor the port. 679possible to immediately start sending messages or to monitor the port.
615 680
616After the port has been created, the init function is 681After the port has been created, the init function is called on the remote
617called. This function must be a fully-qualified function name 682node, in the same context as a C<rcv> callback. This function must be a
618(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main 683fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
619program, use C<::name>. 684specify a function in the main program, use C<::name>.
620 685
621If the function doesn't exist, then the node tries to C<require> 686If the function doesn't exist, then the node tries to C<require>
622the package, then the package above the package and so on (e.g. 687the package, then the package above the package and so on (e.g.
623C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function 688C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
624exists or it runs out of package names. 689exists or it runs out of package names.
625 690
626The init function is then called with the newly-created port as context 691The init function is then called with the newly-created port as context
627object (C<$SELF>) and the C<@initdata> values as arguments. 692object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
693call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
694the port might not get created.
628 695
629A common idiom is to pass your own port, monitor the spawned port, and 696A common idiom is to pass a local port, immediately monitor the spawned
630in the init function, monitor the original port. This two-way monitoring 697port, and in the remote init function, immediately monitor the passed
631ensures that both ports get cleaned up when there is a problem. 698local port. This two-way monitoring ensures that both ports get cleaned up
699when there is a problem.
700
701C<spawn> guarantees that the C<$initfunc> has no visible effects on the
702caller before C<spawn> returns (by delaying invocation when spawn is
703called for the local node).
632 704
633Example: spawn a chat server port on C<$othernode>. 705Example: spawn a chat server port on C<$othernode>.
634 706
635 # this node, executed from within a port context: 707 # this node, executed from within a port context:
636 my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF; 708 my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
651 723
652sub _spawn { 724sub _spawn {
653 my $port = shift; 725 my $port = shift;
654 my $init = shift; 726 my $init = shift;
655 727
728 # rcv will create the actual port
656 local $SELF = "$NODE#$port"; 729 local $SELF = "$NODE#$port";
657 eval { 730 eval {
658 &{ load_func $init } 731 &{ load_func $init }
659 }; 732 };
660 _self_die if $@; 733 _self_die if $@;
661} 734}
662 735
663sub spawn(@) { 736sub spawn(@) {
664 my ($noderef, undef) = split /#/, shift, 2; 737 my ($nodeid, undef) = split /#/, shift, 2;
665 738
666 my $id = "$RUNIQ." . $ID++; 739 my $id = "$RUNIQ." . $ID++;
667 740
668 $_[0] =~ /::/ 741 $_[0] =~ /::/
669 or Carp::croak "spawn init function must be a fully-qualified name, caught"; 742 or Carp::croak "spawn init function must be a fully-qualified name, caught";
670 743
671 ($NODE{$noderef} || add_node $noderef) 744 snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
672 ->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
673 745
674 "$noderef#$id" 746 "$nodeid#$id"
675} 747}
676 748
677=back 749=item after $timeout, @msg
678 750
679=head1 NODE MESSAGES 751=item after $timeout, $callback
680 752
681Nodes understand the following messages sent to them. Many of them take 753Either sends the given message, or call the given callback, after the
682arguments called C<@reply>, which will simply be used to compose a reply 754specified number of seconds.
683message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
684the remaining arguments are simply the message data.
685 755
686While other messages exist, they are not public and subject to change. 756This is simply a utility function that comes in handy at times - the
757AnyEvent::MP author is not convinced of the wisdom of having it, though,
758so it may go away in the future.
687 759
688=over 4
689
690=cut 760=cut
691 761
692=item lookup => $name, @reply 762sub after($@) {
763 my ($timeout, @action) = @_;
693 764
694Replies with the port ID of the specified well-known port, or C<undef>. 765 my $t; $t = AE::timer $timeout, 0, sub {
766 undef $t;
767 ref $action[0]
768 ? $action[0]()
769 : snd @action;
770 };
771}
695 772
696=item devnull => ... 773=item cal $port, @msg, $callback[, $timeout]
697 774
698Generic data sink/CPU heat conversion. 775A simple form of RPC - sends a message to the given C<$port> with the
776given contents (C<@msg>), but adds a reply port to the message.
699 777
700=item relay => $port, @msg 778The reply port is created temporarily just for the purpose of receiving
779the reply, and will be C<kil>ed when no longer needed.
701 780
702Simply forwards the message to the given port. 781A reply message sent to the port is passed to the C<$callback> as-is.
703 782
704=item eval => $string[ @reply] 783If an optional time-out (in seconds) is given and it is not C<undef>,
784then the callback will be called without any arguments after the time-out
785elapsed and the port is C<kil>ed.
705 786
706Evaluates the given string. If C<@reply> is given, then a message of the 787If no time-out is given (or it is C<undef>), then the local port will
707form C<@reply, $@, @evalres> is sent. 788monitor the remote port instead, so it eventually gets cleaned-up.
708 789
709Example: crash another node. 790Currently this function returns the temporary port, but this "feature"
791might go in future versions unless you can make a convincing case that
792this is indeed useful for something.
710 793
711 snd $othernode, eval => "exit"; 794=cut
712 795
713=item time => @reply 796sub cal(@) {
797 my $timeout = ref $_[-1] ? undef : pop;
798 my $cb = pop;
714 799
715Replies the the current node time to C<@reply>. 800 my $port = port {
801 undef $timeout;
802 kil $SELF;
803 &$cb;
804 };
716 805
717Example: tell the current node to send the current time to C<$myport> in a 806 if (defined $timeout) {
718C<timereply> message. 807 $timeout = AE::timer $timeout, 0, sub {
808 undef $timeout;
809 kil $port;
810 $cb->();
811 };
812 } else {
813 mon $_[0], sub {
814 kil $port;
815 $cb->();
816 };
817 }
719 818
720 snd $NODE, time => $myport, timereply => 1, 2; 819 push @_, $port;
721 # => snd $myport, timereply => 1, 2, <time> 820 &snd;
821
822 $port
823}
722 824
723=back 825=back
724 826
725=head1 AnyEvent::MP vs. Distributed Erlang 827=head1 AnyEvent::MP vs. Distributed Erlang
726 828
727AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node 829AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
728== aemp node, Erlang process == aemp port), so many of the documents and 830== aemp node, Erlang process == aemp port), so many of the documents and
729programming techniques employed by Erlang apply to AnyEvent::MP. Here is a 831programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
730sample: 832sample:
731 833
732 http://www.Erlang.se/doc/programming_rules.shtml 834 http://www.erlang.se/doc/programming_rules.shtml
733 http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4 835 http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
734 http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6 836 http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
735 http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5 837 http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
736 838
737Despite the similarities, there are also some important differences: 839Despite the similarities, there are also some important differences:
738 840
739=over 4 841=over 4
740 842
741=item * Node references contain the recipe on how to contact them. 843=item * Node IDs are arbitrary strings in AEMP.
742 844
743Erlang relies on special naming and DNS to work everywhere in the 845Erlang relies on special naming and DNS to work everywhere in the same
744same way. AEMP relies on each node knowing it's own address(es), with 846way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
745convenience functionality. 847configuration or DNS), and possibly the addresses of some seed nodes, but
746 848will otherwise discover other nodes (and their IDs) itself.
747This means that AEMP requires a less tightly controlled environment at the
748cost of longer node references and a slightly higher management overhead.
749 849
750=item * Erlang has a "remote ports are like local ports" philosophy, AEMP 850=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
751uses "local ports are like remote ports". 851uses "local ports are like remote ports".
752 852
753The failure modes for local ports are quite different (runtime errors 853The failure modes for local ports are quite different (runtime errors
766 866
767Erlang uses processes that selectively receive messages, and therefore 867Erlang uses processes that selectively receive messages, and therefore
768needs a queue. AEMP is event based, queuing messages would serve no 868needs a queue. AEMP is event based, queuing messages would serve no
769useful purpose. For the same reason the pattern-matching abilities of 869useful purpose. For the same reason the pattern-matching abilities of
770AnyEvent::MP are more limited, as there is little need to be able to 870AnyEvent::MP are more limited, as there is little need to be able to
771filter messages without dequeing them. 871filter messages without dequeuing them.
772 872
773(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP). 873(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
774 874
775=item * Erlang sends are synchronous, AEMP sends are asynchronous. 875=item * Erlang sends are synchronous, AEMP sends are asynchronous.
776 876
778so does not need a queue that can overflow). AEMP sends are immediate, 878so does not need a queue that can overflow). AEMP sends are immediate,
779connection establishment is handled in the background. 879connection establishment is handled in the background.
780 880
781=item * Erlang suffers from silent message loss, AEMP does not. 881=item * Erlang suffers from silent message loss, AEMP does not.
782 882
783Erlang makes few guarantees on messages delivery - messages can get lost 883Erlang implements few guarantees on messages delivery - messages can get
784without any of the processes realising it (i.e. you send messages a, b, 884lost without any of the processes realising it (i.e. you send messages a,
785and c, and the other side only receives messages a and c). 885b, and c, and the other side only receives messages a and c).
786 886
787AEMP guarantees correct ordering, and the guarantee that there are no 887AEMP guarantees correct ordering, and the guarantee that after one message
788holes in the message sequence. 888is lost, all following ones sent to the same port are lost as well, until
789 889monitoring raises an error, so there are no silent "holes" in the message
790=item * In Erlang, processes can be declared dead and later be found to be 890sequence.
791alive.
792
793In Erlang it can happen that a monitored process is declared dead and
794linked processes get killed, but later it turns out that the process is
795still alive - and can receive messages.
796
797In AEMP, when port monitoring detects a port as dead, then that port will
798eventually be killed - it cannot happen that a node detects a port as dead
799and then later sends messages to it, finding it is still alive.
800 891
801=item * Erlang can send messages to the wrong port, AEMP does not. 892=item * Erlang can send messages to the wrong port, AEMP does not.
802 893
803In Erlang it is quite likely that a node that restarts reuses a process ID 894In Erlang it is quite likely that a node that restarts reuses a process ID
804known to other nodes for a completely different process, causing messages 895known to other nodes for a completely different process, causing messages
808around in the network will not be sent to an unrelated port. 899around in the network will not be sent to an unrelated port.
809 900
810=item * Erlang uses unprotected connections, AEMP uses secure 901=item * Erlang uses unprotected connections, AEMP uses secure
811authentication and can use TLS. 902authentication and can use TLS.
812 903
813AEMP can use a proven protocol - SSL/TLS - to protect connections and 904AEMP can use a proven protocol - TLS - to protect connections and
814securely authenticate nodes. 905securely authenticate nodes.
815 906
816=item * The AEMP protocol is optimised for both text-based and binary 907=item * The AEMP protocol is optimised for both text-based and binary
817communications. 908communications.
818 909
819The AEMP protocol, unlike the Erlang protocol, supports both 910The AEMP protocol, unlike the Erlang protocol, supports both programming
820language-independent text-only protocols (good for debugging) and binary, 911language independent text-only protocols (good for debugging) and binary,
821language-specific serialisers (e.g. Storable). 912language-specific serialisers (e.g. Storable). By default, unless TLS is
913used, the protocol is actually completely text-based.
822 914
823It has also been carefully designed to be implementable in other languages 915It has also been carefully designed to be implementable in other languages
824with a minimum of work while gracefully degrading fucntionality to make the 916with a minimum of work while gracefully degrading functionality to make the
825protocol simple. 917protocol simple.
826 918
827=item * AEMP has more flexible monitoring options than Erlang. 919=item * AEMP has more flexible monitoring options than Erlang.
828 920
829In Erlang, you can chose to receive I<all> exit signals as messages 921In Erlang, you can chose to receive I<all> exit signals as messages
832Erlang, as one can choose between automatic kill, exit message or callback 924Erlang, as one can choose between automatic kill, exit message or callback
833on a per-process basis. 925on a per-process basis.
834 926
835=item * Erlang tries to hide remote/local connections, AEMP does not. 927=item * Erlang tries to hide remote/local connections, AEMP does not.
836 928
837Monitoring in Erlang is not an indicator of process death/crashes, 929Monitoring in Erlang is not an indicator of process death/crashes, in the
838as linking is (except linking is unreliable in Erlang). 930same way as linking is (except linking is unreliable in Erlang).
839 931
840In AEMP, you don't "look up" registered port names or send to named ports 932In AEMP, you don't "look up" registered port names or send to named ports
841that might or might not be persistent. Instead, you normally spawn a port 933that might or might not be persistent. Instead, you normally spawn a port
842on the remote node. The init function monitors the you, and you monitor 934on the remote node. The init function monitors you, and you monitor the
843the remote port. Since both monitors are local to the node, they are much 935remote port. Since both monitors are local to the node, they are much more
844more reliable. 936reliable (no need for C<spawn_link>).
845 937
846This also saves round-trips and avoids sending messages to the wrong port 938This also saves round-trips and avoids sending messages to the wrong port
847(hard to do in Erlang). 939(hard to do in Erlang).
848 940
849=back 941=back
850 942
851=head1 RATIONALE 943=head1 RATIONALE
852 944
853=over 4 945=over 4
854 946
855=item Why strings for ports and noderefs, why not objects? 947=item Why strings for port and node IDs, why not objects?
856 948
857We considered "objects", but found that the actual number of methods 949We considered "objects", but found that the actual number of methods
858thatc an be called are very low. Since port IDs and noderefs travel over 950that can be called are quite low. Since port and node IDs travel over
859the network frequently, the serialising/deserialising would add lots of 951the network frequently, the serialising/deserialising would add lots of
860overhead, as well as having to keep a proxy object. 952overhead, as well as having to keep a proxy object everywhere.
861 953
862Strings can easily be printed, easily serialised etc. and need no special 954Strings can easily be printed, easily serialised etc. and need no special
863procedures to be "valid". 955procedures to be "valid".
864 956
865And a a miniport consists of a single closure stored in a global hash - it 957And as a result, a port with just a default receiver consists of a single
866can't become much cheaper. 958closure stored in a global hash - it can't become much cheaper.
867 959
868=item Why favour JSON, why not real serialising format such as Storable? 960=item Why favour JSON, why not a real serialising format such as Storable?
869 961
870In fact, any AnyEvent::MP node will happily accept Storable as framing 962In fact, any AnyEvent::MP node will happily accept Storable as framing
871format, but currently there is no way to make a node use Storable by 963format, but currently there is no way to make a node use Storable by
872default. 964default (although all nodes will accept it).
873 965
874The default framing protocol is JSON because a) JSON::XS is many times 966The default framing protocol is JSON because a) JSON::XS is many times
875faster for small messages and b) most importantly, after years of 967faster for small messages and b) most importantly, after years of
876experience we found that object serialisation is causing more problems 968experience we found that object serialisation is causing more problems
877than it gains: Just like function calls, objects simply do not travel 969than it solves: Just like function calls, objects simply do not travel
878easily over the network, mostly because they will always be a copy, so you 970easily over the network, mostly because they will always be a copy, so you
879always have to re-think your design. 971always have to re-think your design.
880 972
881Keeping your messages simple, concentrating on data structures rather than 973Keeping your messages simple, concentrating on data structures rather than
882objects, will keep your messages clean, tidy and efficient. 974objects, will keep your messages clean, tidy and efficient.
883 975
884=back 976=back
885 977
886=head1 SEE ALSO 978=head1 SEE ALSO
887 979
980L<AnyEvent::MP::Intro> - a gentle introduction.
981
982L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
983
984L<AnyEvent::MP::Global> - network maintainance and port groups, to find
985your applications.
986
987L<AnyEvent::MP::DataConn> - establish data connections between nodes.
988
989L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
990all nodes.
991
888L<AnyEvent>. 992L<AnyEvent>.
889 993
890=head1 AUTHOR 994=head1 AUTHOR
891 995
892 Marc Lehmann <schmorp@schmorp.de> 996 Marc Lehmann <schmorp@schmorp.de>

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