[ViewVC] Diff of: cvs/AnyEvent-MP/MP.pm

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.32 by root, Wed Aug 5 19:58:46 2009 UTC vs.
Revision 1.68 by root, Fri Aug 28 23:06:33 2009 UTC

…		…
8		8
9	$NODE # contains this node's noderef	9	$NODE # contains this node's noderef
10	NODE # returns this node's noderef	10	NODE # returns this node's noderef
11	NODE $port # returns the noderef of the port	11	NODE $port # returns the noderef of the port
12		12
		13	$SELF # receiving/own port id in rcv callbacks
		14
		15	# initialise the node so it can send/receive messages
		16	initialise_node;
		17
		18	# ports are message endpoints
		19
		20	# sending messages
13	snd $port, type => data...;	21	snd $port, type => data...;
		22	snd $port, @msg;
		23	snd @msg_with_first_element_being_a_port;
14		24
15	$SELF # receiving/own port id in rcv callbacks	25	# creating/using ports, the simple way
		26	my $simple_port = port { my @msg = @_; 0 };
16		27
17	rcv $port, smartmatch => $cb->($port, @msg);	28	# creating/using ports, tagged message matching
18		29	my $port = port;
19	# examples:
20	rcv $port2, ping => sub { snd $_[0], "pong"; 0 };	30	rcv $port, ping => sub { snd $_[0], "pong"; 0 };
21	rcv $port1, pong => sub { warn "pong received\n" };	31	rcv $port, pong => sub { warn "pong received\n"; 0 };
22	snd $port2, ping => $port1;
23		32
24	# more, smarter, matches (_any_ is exported by this module)	33	# create a port on another node
25	rcv $port, [child_died => $pid] => sub { ...	34	my $port = spawn $node, $initfunc, @initdata;
26	rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3	35
		36	# monitoring
		37	mon $port, $cb->(@msg) # callback is invoked on death
		38	mon $port, $otherport # kill otherport on abnormal death
		39	mon $port, $otherport, @msg # send message on death
		40
		41	=head1 CURRENT STATUS
		42
		43	AnyEvent::MP - stable API, should work
		44	AnyEvent::MP::Intro - outdated
		45	AnyEvent::MP::Kernel - mostly stable
		46	AnyEvent::MP::Global - mostly stable
		47	AnyEvent::MP::Node - mostly stable, but internal anyways
		48	AnyEvent::MP::Transport - mostly stable, but internal anyways
		49
		50	stay tuned.
27		51
28	=head1 DESCRIPTION	52	=head1 DESCRIPTION
29		53
30	This module (-family) implements a simple message passing framework.	54	This module (-family) implements a simple message passing framework.
31		55
32	Despite its simplicity, you can securely message other processes running	56	Despite its simplicity, you can securely message other processes running
33	on the same or other hosts.	57	on the same or other hosts, and you can supervise entities remotely.
34		58
35	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	59	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
36	manual page.	60	manual page and the examples under F<eg/>.
37		61
38	At the moment, this module family is severly broken and underdocumented,	62	At the moment, this module family is a bit underdocumented.
39	so do not use. This was uploaded mainly to reserve the CPAN namespace -
40	stay tuned! The basic API should be finished, however.
41		63
42	=head1 CONCEPTS	64	=head1 CONCEPTS
43		65
44	=over 4	66	=over 4
45		67
46	=item port	68	=item port
47		69
48	A port is something you can send messages to (with the C<snd> function).	70	A port is something you can send messages to (with the C<snd> function).
49		71
50	Some ports allow you to register C<rcv> handlers that can match specific	72	Ports allow you to register C<rcv> handlers that can match all or just
51	messages. All C<rcv> handlers will receive messages they match, messages	73	some messages. Messages send to ports will not be queued, regardless of
52	will not be queued.	74	anything was listening for them or not.
53		75
54	=item port id - C<noderef#portname>	76	=item port ID - C<nodeid#portname>
55		77
56	A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as	78	A port ID is the concatenation of a node ID, a hash-mark (C<#>) as
57	separator, and a port name (a printable string of unspecified format). An	79	separator, and a port name (a printable string of unspecified format).
58	exception is the the node port, whose ID is identical to its node
59	reference.
60		80
61	=item node	81	=item node
62		82
63	A node is a single process containing at least one port - the node	83	A node is a single process containing at least one port - the node port,
64	port. You can send messages to node ports to find existing ports or to	84	which enables nodes to manage each other remotely, and to create new
65	create new ports, among other things.	85	ports.
66		86
67	Nodes are either private (single-process only), slaves (connected to a	87	Nodes are either public (have one or more listening ports) or private
68	master node only) or public nodes (connectable from unrelated nodes).	88	(no listening ports). Private nodes cannot talk to other private nodes
		89	currently.
69		90
70	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	91	=item node ID - C<[a-za-Z0-9_\-.:]+>
71		92
72	A node reference is a string that either simply identifies the node (for	93	A node ID is a string that uniquely identifies the node within a
73	private and slave nodes), or contains a recipe on how to reach a given	94	network. Depending on the configuration used, node IDs can look like a
74	node (for public nodes).	95	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		96	doesn't interpret node IDs in any way.
75		97
76	This recipe is simply a comma-separated list of C<address:port> pairs (for	98	=item binds - C<ip:port>
77	TCP/IP, other protocols might look different).
78		99
79	Node references come in two flavours: resolved (containing only numerical	100	Nodes can only talk to each other by creating some kind of connection to
80	addresses) or unresolved (where hostnames are used instead of addresses).	101	each other. To do this, nodes should listen on one or more local transport
		102	endpoints - binds. Currently, only standard C<ip:port> specifications can
		103	be used, which specify TCP ports to listen on.
81		104
82	Before using an unresolved node reference in a message you first have to	105	=item seeds - C<host:port>
83	resolve it.	106
		107	When a node starts, it knows nothing about the network. To teach the node
		108	about the network it first has to contact some other node within the
		109	network. This node is called a seed.
		110
		111	Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes
		112	are expected to be long-running, and at least one of those should always
		113	be available. When nodes run out of connections (e.g. due to a network
		114	error), they try to re-establish connections to some seednodes again to
		115	join the network.
		116
		117	Apart from being sued for seeding, seednodes are not special in any way -
		118	every public node can be a seednode.
84		119
85	=back	120	=back
86		121
87	=head1 VARIABLES/FUNCTIONS	122	=head1 VARIABLES/FUNCTIONS
88		123
…		…
90		125
91	=cut	126	=cut
92		127
93	package AnyEvent::MP;	128	package AnyEvent::MP;
94		129
95	use AnyEvent::MP::Base;	130	use AnyEvent::MP::Kernel;
96		131
97	use common::sense;	132	use common::sense;
98		133
99	use Carp ();	134	use Carp ();
100		135
101	use AE ();	136	use AE ();
102		137
103	use base "Exporter";	138	use base "Exporter";
104		139
105	our $VERSION = '0.1';	140	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
		141
106	our @EXPORT = qw(	142	our @EXPORT = qw(
107	NODE $NODE *SELF node_of _any_	143	NODE $NODE *SELF node_of after
108	resolve_node initialise_node	144	initialise_node
109	snd rcv mon kil reg psub	145	snd rcv mon mon_guard kil reg psub spawn
110	port	146	port
111	);	147	);
112		148
113	our $SELF;	149	our $SELF;
114		150
…		…
118	kil $SELF, die => $msg;	154	kil $SELF, die => $msg;
119	}	155	}
120		156
121	=item $thisnode = NODE / $NODE	157	=item $thisnode = NODE / $NODE
122		158
123	The C<NODE> function returns, and the C<$NODE> variable contains	159	The C<NODE> function returns, and the C<$NODE> variable contains, the node
124	the noderef of the local node. The value is initialised by a call	160	ID of the node running in the current process. This value is initialised by
125	to C<become_public> or C<become_slave>, after which all local port	161	a call to C<initialise_node>.
126	identifiers become invalid.
127		162
128	=item $noderef = node_of $portid	163	=item $nodeid = node_of $port
129		164
130	Extracts and returns the noderef from a portid or a noderef.	165	Extracts and returns the node ID from a port ID or a node ID.
131		166
132	=item $cv = resolve_node $noderef	167	=item initialise_node $profile_name
133		168
134	Takes an unresolved node reference that may contain hostnames and	169	Before a node can talk to other nodes on the network (i.e. enter
135	abbreviated IDs, resolves all of them and returns a resolved node	170	"distributed mode") it has to initialise itself - the minimum a node needs
136	reference.	171	to know is its own name, and optionally it should know the addresses of
		172	some other nodes in the network to discover other nodes.
137		173
138	In addition to C<address:port> pairs allowed in resolved noderefs, the	174	This function initialises a node - it must be called exactly once (or
139	following forms are supported:	175	never) before calling other AnyEvent::MP functions.
140		176
141	=over 4	177	The first argument is a profile name. If it is C<undef> or missing, then
		178	the current nodename will be used instead (i.e. F<uname -n>).
142		179
143	=item the empty string	180	The function then looks up the profile in the aemp configuration (see the
		181	L<aemp> commandline utility).
144		182
145	An empty-string component gets resolved as if the default port (4040) was	183	If the profile specifies a node ID, then this will become the node ID of
146	specified.	184	this process. If not, then the profile name will be used as node ID. The
		185	special node ID of C<anon/> will be replaced by a random node ID.
147		186
148	=item naked port numbers (e.g. C<1234>)	187	The next step is to look up the binds in the profile, followed by binding
		188	aemp protocol listeners on all binds specified (it is possible and valid
		189	to have no binds, meaning that the node cannot be contacted form the
		190	outside. This means the node cannot talk to other nodes that also have no
		191	binds, but it can still talk to all "normal" nodes).
149		192
150	These are resolved by prepending the local nodename and a colon, to be	193	If the profile does not specify a binds list, then the node ID will be
151	further resolved.	194	treated as if it were of the form C<host:port>, which will be resolved and
		195	used as binds list.
152		196
153	=item hostnames (e.g. C<localhost:1234>, C<localhost>)	197	Lastly, the seeds list from the profile is passed to the
		198	L<AnyEvent::MP::Global> module, which will then use it to keep
		199	connectivity with at least on of those seed nodes at any point in time.
154		200
155	These are resolved by using AnyEvent::DNS to resolve them, optionally	201	Example: become a distributed node listening on the guessed noderef, or
156	looking up SRV records for the C<aemp=4040> port, if no port was	202	the one specified via C<aemp> for the current node. This should be the
157	specified.	203	most common form of invocation for "daemon"-type nodes.
158		204
159	=back	205	initialise_node;
		206
		207	Example: become an anonymous node. This form is often used for commandline
		208	clients.
		209
		210	initialise_node "anon/";
		211
		212	Example: become a distributed node. If there is no profile of the given
		213	name, or no binds list was specified, resolve C<localhost:4044> and bind
		214	on the resulting addresses.
		215
		216	initialise_node "localhost:4044";
160		217
161	=item $SELF	218	=item $SELF
162		219
163	Contains the current port id while executing C<rcv> callbacks or C<psub>	220	Contains the current port id while executing C<rcv> callbacks or C<psub>
164	blocks.	221	blocks.
165		222
166	=item SELF, %SELF, @SELF...	223	=item *SELF, SELF, %SELF, @SELF...
167		224
168	Due to some quirks in how perl exports variables, it is impossible to	225	Due to some quirks in how perl exports variables, it is impossible to
169	just export C<$SELF>, all the symbols called C<SELF> are exported by this	226	just export C<$SELF>, all the symbols named C<SELF> are exported by this
170	module, but only C<$SELF> is currently used.	227	module, but only C<$SELF> is currently used.
171		228
172	=item snd $portid, type => @data	229	=item snd $port, type => @data
173		230
174	=item snd $portid, @msg	231	=item snd $port, @msg
175		232
176	Send the given message to the given port ID, which can identify either	233	Send the given message to the given port, which can identify either a
177	a local or a remote port, and can be either a string or soemthignt hat	234	local or a remote port, and must be a port ID.
178	stringifies a sa port ID (such as a port object :).
179		235
180	While the message can be about anything, it is highly recommended to use a	236	While the message can be almost anything, it is highly recommended to
181	string as first element (a portid, or some word that indicates a request	237	use a string as first element (a port ID, or some word that indicates a
182	type etc.).	238	request type etc.) and to consist if only simple perl values (scalars,
		239	arrays, hashes) - if you think you need to pass an object, think again.
183		240
184	The message data effectively becomes read-only after a call to this	241	The message data logically becomes read-only after a call to this
185	function: modifying any argument is not allowed and can cause many	242	function: modifying any argument (or values referenced by them) is
186	problems.	243	forbidden, as there can be considerable time between the call to C<snd>
		244	and the time the message is actually being serialised - in fact, it might
		245	never be copied as within the same process it is simply handed to the
		246	receiving port.
187		247
188	The type of data you can transfer depends on the transport protocol: when	248	The type of data you can transfer depends on the transport protocol: when
189	JSON is used, then only strings, numbers and arrays and hashes consisting	249	JSON is used, then only strings, numbers and arrays and hashes consisting
190	of those are allowed (no objects). When Storable is used, then anything	250	of those are allowed (no objects). When Storable is used, then anything
191	that Storable can serialise and deserialise is allowed, and for the local	251	that Storable can serialise and deserialise is allowed, and for the local
192	node, anything can be passed.	252	node, anything can be passed. Best rely only on the common denominator of
		253	these.
193		254
194	=item $local_port = port	255	=item $local_port = port
195		256
196	Create a new local port object that can be used either as a pattern	257	Create a new local port object and returns its port ID. Initially it has
197	matching port ("full port") or a single-callback port ("miniport"),	258	no callbacks set and will throw an error when it receives messages.
198	depending on how C<rcv> callbacks are bound to the object.
199		259
200	=item $portid = port { my @msg = @_; $finished }	260	=item $local_port = port { my @msg = @_ }
201		261
202	Creates a "mini port", that is, a very lightweight port without any	262	Creates a new local port, and returns its ID. Semantically the same as
203	pattern matching behind it, and returns its ID.	263	creating a port and calling C<rcv $port, $callback> on it.
204		264
205	The block will be called for every message received on the port. When the	265	The block will be called for every message received on the port, with the
206	callback returns a true value its job is considered "done" and the port	266	global variable C<$SELF> set to the port ID. Runtime errors will cause the
207	will be destroyed. Otherwise it will stay alive.	267	port to be C<kil>ed. The message will be passed as-is, no extra argument
		268	(i.e. no port ID) will be passed to the callback.
208		269
209	The message will be passed as-is, no extra argument (i.e. no port id) will	270	If you want to stop/destroy the port, simply C<kil> it:
210	be passed to the callback.
211		271
212	If you need the local port id in the callback, this works nicely:	272	my $port = port {
213		273	my @msg = @_;
214	my $port; $port = port {	274	...
215	snd $otherport, reply => $port;	275	kil $SELF;
216	};	276	};
217		277
218	=cut	278	=cut
		279
		280	sub rcv($@);
		281
		282	sub _kilme {
		283	die "received message on port without callback";
		284	}
219		285
220	sub port(;&) {	286	sub port(;&) {
221	my $id = "$UNIQ." . $ID++;	287	my $id = "$UNIQ." . $ID++;
222	my $port = "$NODE#$id";	288	my $port = "$NODE#$id";
223		289
		290	rcv $port, shift \|\| \&_kilme;
		291
		292	$port
		293	}
		294
		295	=item rcv $local_port, $callback->(@msg)
		296
		297	Replaces the default callback on the specified port. There is no way to
		298	remove the default callback: use C<sub { }> to disable it, or better
		299	C<kil> the port when it is no longer needed.
		300
		301	The global C<$SELF> (exported by this module) contains C<$port> while
		302	executing the callback. Runtime errors during callback execution will
		303	result in the port being C<kil>ed.
		304
		305	The default callback received all messages not matched by a more specific
		306	C<tag> match.
		307
		308	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
		309
		310	Register (or replace) callbacks to be called on messages starting with the
		311	given tag on the given port (and return the port), or unregister it (when
		312	C<$callback> is C<$undef> or missing). There can only be one callback
		313	registered for each tag.
		314
		315	The original message will be passed to the callback, after the first
		316	element (the tag) has been removed. The callback will use the same
		317	environment as the default callback (see above).
		318
		319	Example: create a port and bind receivers on it in one go.
		320
		321	my $port = rcv port,
		322	msg1 => sub { ... },
		323	msg2 => sub { ... },
		324	;
		325
		326	Example: create a port, bind receivers and send it in a message elsewhere
		327	in one go:
		328
		329	snd $otherport, reply =>
		330	rcv port,
		331	msg1 => sub { ... },
		332	...
		333	;
		334
		335	Example: temporarily register a rcv callback for a tag matching some port
		336	(e.g. for a rpc reply) and unregister it after a message was received.
		337
		338	rcv $port, $otherport => sub {
		339	my @reply = @_;
		340
		341	rcv $SELF, $otherport;
		342	};
		343
		344	=cut
		345
		346	sub rcv($@) {
		347	my $port = shift;
		348	my ($noderef, $portid) = split /#/, $port, 2;
		349
		350	$NODE{$noderef} == $NODE{""}
		351	or Carp::croak "$port: rcv can only be called on local ports, caught";
		352
224	if (@_) {	353	while (@_) {
		354	if (ref $_[0]) {
		355	if (my $self = $PORT_DATA{$portid}) {
		356	"AnyEvent::MP::Port" eq ref $self
		357	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		358
		359	$self->[2] = shift;
		360	} else {
225	my $cb = shift;	361	my $cb = shift;
226	$PORT{$id} = sub {	362	$PORT{$portid} = sub {
227	local $SELF = $port;	363	local $SELF = $port;
228	eval {	364	eval { &$cb }; _self_die if $@;
229	&$cb	365	};
230	and kil $id;	366	}
		367	} elsif (defined $_[0]) {
		368	my $self = $PORT_DATA{$portid} \|\|= do {
		369	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
		370
		371	$PORT{$portid} = sub {
		372	local $SELF = $port;
		373
		374	if (my $cb = $self->[1]{$_[0]}) {
		375	shift;
		376	eval { &$cb }; _self_die if $@;
		377	} else {
		378	&{ $self->[0] };
		379	}
		380	};
		381
		382	$self
231	};	383	};
232	_self_die if $@;	384
233	};
234	} else {
235	my $self = bless {
236	id => "$NODE#$id",
237	}, "AnyEvent::MP::Port";	385	"AnyEvent::MP::Port" eq ref $self
		386	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
238		387
239	$PORT_DATA{$id} = $self;	388	my ($tag, $cb) = splice @_, 0, 2;
240	$PORT{$id} = sub {
241	local $SELF = $port;
242		389
		390	if (defined $cb) {
		391	$self->[1]{$tag} = $cb;
243	eval {	392	} else {
244	for (@{ $self->{rc0}{$_[0]} }) {	393	delete $self->[1]{$tag};
245	$_ && &{$_->[0]}
246	&& undef $_;
247	}
248
249	for (@{ $self->{rcv}{$_[0]} }) {
250	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
251	&& &{$_->[0]}
252	&& undef $_;
253	}
254
255	for (@{ $self->{any} }) {
256	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
257	&& &{$_->[0]}
258	&& undef $_;
259	}
260	};	394	}
261	_self_die if $@;
262	};
263	}
264
265	$port
266	}
267
268	=item reg $portid, $name
269
270	Registers the given port under the name C<$name>. If the name already
271	exists it is replaced.
272
273	A port can only be registered under one well known name.
274
275	A port automatically becomes unregistered when it is killed.
276
277	=cut
278
279	sub reg(@) {
280	my ($portid, $name) = @_;
281
282	$REG{$name} = $portid;
283	}
284
285	=item rcv $portid, $callback->(@msg)
286
287	Replaces the callback on the specified miniport (or newly created port
288	object, see C<port>). Full ports are configured with the following calls:
289
290	=item rcv $portid, tagstring => $callback->(@msg), ...
291
292	=item rcv $portid, $smartmatch => $callback->(@msg), ...
293
294	=item rcv $portid, [$smartmatch...] => $callback->(@msg), ...
295
296	Register callbacks to be called on matching messages on the given full
297	port (or newly created port).
298
299	The callback has to return a true value when its work is done, after
300	which is will be removed, or a false value in which case it will stay
301	registered.
302
303	The global C<$SELF> (exported by this module) contains C<$portid> while
304	executing the callback.
305
306	Runtime errors wdurign callback execution will result in the port being
307	C<kil>ed.
308
309	If the match is an array reference, then it will be matched against the
310	first elements of the message, otherwise only the first element is being
311	matched.
312
313	Any element in the match that is specified as C<_any_> (a function
314	exported by this module) matches any single element of the message.
315
316	While not required, it is highly recommended that the first matching
317	element is a string identifying the message. The one-string-only match is
318	also the most efficient match (by far).
319
320	=cut
321
322	sub rcv($@) {
323	my $portid = shift;
324	my ($noderef, $port) = split /#/, $port, 2;
325
326	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}
327	or Carp::croak "$noderef#$port: rcv can only be called on local ports, caught";
328
329	my $self = $PORT_DATA{$port}
330	or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught";
331
332	"AnyEvent::MP::Port" eq ref $self
333	or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught";
334
335	while (@_) {
336	my ($match, $cb) = splice @_, 0, 2;
337
338	if (!ref $match) {
339	push @{ $self->{rc0}{$match} }, [$cb];
340	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
341	my ($type, @match) = @$match;
342	@match
343	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
344	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
345	} else {
346	push @{ $self->{any} }, [$cb, $match];
347	}	395	}
348	}	396	}
349		397
350	$portid	398	$port
351	}	399	}
352		400
353	=item $closure = psub { BLOCK }	401	=item $closure = psub { BLOCK }
354		402
355	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	403	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
…		…
386	$res	434	$res
387	}	435	}
388	}	436	}
389	}	437	}
390		438
391	=item $guard = mon $portid, $cb->(@reason)	439	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
392		440
393	=item $guard = mon $portid, $otherport	441	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
394		442
395	=item $guard = mon $portid, $otherport, @msg	443	=item $guard = mon $port # kill $SELF when $port dies
396		444
		445	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
		446
397	Monitor the given port and do something when the port is killed.	447	Monitor the given port and do something when the port is killed or
		448	messages to it were lost, and optionally return a guard that can be used
		449	to stop monitoring again.
398		450
		451	C<mon> effectively guarantees that, in the absence of hardware failures,
		452	after starting the monitor, either all messages sent to the port will
		453	arrive, or the monitoring action will be invoked after possible message
		454	loss has been detected. No messages will be lost "in between" (after
		455	the first lost message no further messages will be received by the
		456	port). After the monitoring action was invoked, further messages might get
		457	delivered again.
		458
		459	Note that monitoring-actions are one-shot: once messages are lost (and a
		460	monitoring alert was raised), they are removed and will not trigger again.
		461
399	In the first form, the callback is simply called with any number	462	In the first form (callback), the callback is simply called with any
400	of C<@reason> elements (no @reason means that the port was deleted	463	number of C<@reason> elements (no @reason means that the port was deleted
401	"normally"). Note also that I<< the callback B<must> never die >>, so use	464	"normally"). Note also that I<< the callback B<must> never die >>, so use
402	C<eval> if unsure.	465	C<eval> if unsure.
403		466
404	In the second form, the other port will be C<kil>'ed with C<@reason>, iff	467	In the second form (another port given), the other port (C<$rcvport>)
405	a @reason was specified, i.e. on "normal" kils nothing happens, while	468	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
406	under all other conditions, the other port is killed with the same reason.	469	"normal" kils nothing happens, while under all other conditions, the other
		470	port is killed with the same reason.
407		471
		472	The third form (kill self) is the same as the second form, except that
		473	C<$rvport> defaults to C<$SELF>.
		474
408	In the last form, a message of the form C<@msg, @reason> will be C<snd>.	475	In the last form (message), a message of the form C<@msg, @reason> will be
		476	C<snd>.
		477
		478	As a rule of thumb, monitoring requests should always monitor a port from
		479	a local port (or callback). The reason is that kill messages might get
		480	lost, just like any other message. Another less obvious reason is that
		481	even monitoring requests can get lost (for exmaple, when the connection
		482	to the other node goes down permanently). When monitoring a port locally
		483	these problems do not exist.
409		484
410	Example: call a given callback when C<$port> is killed.	485	Example: call a given callback when C<$port> is killed.
411		486
412	mon $port, sub { warn "port died because of <@_>\n" };	487	mon $port, sub { warn "port died because of <@_>\n" };
413		488
414	Example: kill ourselves when C<$port> is killed abnormally.	489	Example: kill ourselves when C<$port> is killed abnormally.
415		490
416	mon $port, $self;	491	mon $port;
417		492
418	Example: send us a restart message another C<$port> is killed.	493	Example: send us a restart message when another C<$port> is killed.
419		494
420	mon $port, $self => "restart";	495	mon $port, $self => "restart";
421		496
422	=cut	497	=cut
423		498
424	sub mon {	499	sub mon {
425	my ($noderef, $port) = split /#/, shift, 2;	500	my ($noderef, $port) = split /#/, shift, 2;
426		501
427	my $node = $NODE{$noderef} \|\| add_node $noderef;	502	my $node = $NODE{$noderef} \|\| add_node $noderef;
428		503
429	my $cb = shift;	504	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
430		505
431	unless (ref $cb) {	506	unless (ref $cb) {
432	if (@_) {	507	if (@_) {
433	# send a kill info message	508	# send a kill info message
434	my (@msg) = ($cb, @_);	509	my (@msg) = ($cb, @_);
…		…
452	is killed, the references will be freed.	527	is killed, the references will be freed.
453		528
454	Optionally returns a guard that will stop the monitoring.	529	Optionally returns a guard that will stop the monitoring.
455		530
456	This function is useful when you create e.g. timers or other watchers and	531	This function is useful when you create e.g. timers or other watchers and
457	want to free them when the port gets killed:	532	want to free them when the port gets killed (note the use of C<psub>):
458		533
459	$port->rcv (start => sub {	534	$port->rcv (start => sub {
460	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	535	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
461	undef $timer if 0.9 < rand;	536	undef $timer if 0.9 < rand;
462	});	537	});
463	});	538	});
464		539
465	=cut	540	=cut
466		541
467	sub mon_guard {	542	sub mon_guard {
468	my ($port, @refs) = @_;	543	my ($port, @refs) = @_;
469		544
		545	#TODO: mon-less form?
		546
470	mon $port, sub { 0 && @refs }	547	mon $port, sub { 0 && @refs }
471	}	548	}
472		549
473	=item lnk $port1, $port2
474
475	Link two ports. This is simply a shorthand for:
476
477	mon $port1, $port2;
478	mon $port2, $port1;
479
480	It means that if either one is killed abnormally, the other one gets
481	killed as well.
482
483	=item kil $portid[, @reason]	550	=item kil $port[, @reason]
484		551
485	Kill the specified port with the given C<@reason>.	552	Kill the specified port with the given C<@reason>.
486		553
487	If no C<@reason> is specified, then the port is killed "normally" (linked	554	If no C<@reason> is specified, then the port is killed "normally" (ports
488	ports will not be kileld, or even notified).	555	monitoring other ports will not necessarily die because a port dies
		556	"normally").
489		557
490	Otherwise, linked ports get killed with the same reason (second form of	558	Otherwise, linked ports get killed with the same reason (second form of
491	C<mon>, see below).	559	C<mon>, see above).
492		560
493	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	561	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
494	will be reported as reason C<< die => $@ >>.	562	will be reported as reason C<< die => $@ >>.
495		563
496	Transport/communication errors are reported as C<< transport_error =>	564	Transport/communication errors are reported as C<< transport_error =>
497	$message >>.	565	$message >>.
498		566
		567	=cut
		568
		569	=item $port = spawn $node, $initfunc[, @initdata]
		570
		571	Creates a port on the node C<$node> (which can also be a port ID, in which
		572	case it's the node where that port resides).
		573
		574	The port ID of the newly created port is returned immediately, and it is
		575	possible to immediately start sending messages or to monitor the port.
		576
		577	After the port has been created, the init function is called on the remote
		578	node, in the same context as a C<rcv> callback. This function must be a
		579	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
		580	specify a function in the main program, use C<::name>.
		581
		582	If the function doesn't exist, then the node tries to C<require>
		583	the package, then the package above the package and so on (e.g.
		584	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
		585	exists or it runs out of package names.
		586
		587	The init function is then called with the newly-created port as context
		588	object (C<$SELF>) and the C<@initdata> values as arguments.
		589
		590	A common idiom is to pass a local port, immediately monitor the spawned
		591	port, and in the remote init function, immediately monitor the passed
		592	local port. This two-way monitoring ensures that both ports get cleaned up
		593	when there is a problem.
		594
		595	Example: spawn a chat server port on C<$othernode>.
		596
		597	# this node, executed from within a port context:
		598	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
		599	mon $server;
		600
		601	# init function on C<$othernode>
		602	sub connect {
		603	my ($srcport) = @_;
		604
		605	mon $srcport;
		606
		607	rcv $SELF, sub {
		608	...
		609	};
		610	}
		611
		612	=cut
		613
		614	sub _spawn {
		615	my $port = shift;
		616	my $init = shift;
		617
		618	local $SELF = "$NODE#$port";
		619	eval {
		620	&{ load_func $init }
		621	};
		622	_self_die if $@;
		623	}
		624
		625	sub spawn(@) {
		626	my ($noderef, undef) = split /#/, shift, 2;
		627
		628	my $id = "$RUNIQ." . $ID++;
		629
		630	$_[0] =~ /::/
		631	or Carp::croak "spawn init function must be a fully-qualified name, caught";
		632
		633	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;
		634
		635	"$noderef#$id"
		636	}
		637
		638	=item after $timeout, @msg
		639
		640	=item after $timeout, $callback
		641
		642	Either sends the given message, or call the given callback, after the
		643	specified number of seconds.
		644
		645	This is simply a utility function that comes in handy at times - the
		646	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		647	so it may go away in the future.
		648
		649	=cut
		650
		651	sub after($@) {
		652	my ($timeout, @action) = @_;
		653
		654	my $t; $t = AE::timer $timeout, 0, sub {
		655	undef $t;
		656	ref $action[0]
		657	? $action[0]()
		658	: snd @action;
		659	};
		660	}
		661
499	=back	662	=back
500		663
501	=head1 FUNCTIONS FOR NODES	664	=head1 AnyEvent::MP vs. Distributed Erlang
		665
		666	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
		667	== aemp node, Erlang process == aemp port), so many of the documents and
		668	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
		669	sample:
		670
		671	http://www.Erlang.se/doc/programming_rules.shtml
		672	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
		673	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6
		674	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
		675
		676	Despite the similarities, there are also some important differences:
502		677
503	=over 4	678	=over 4
504		679
505	=item become_public $noderef	680	=item * Node IDs are arbitrary strings in AEMP.
506		681
507	Tells the node to become a public node, i.e. reachable from other nodes.
508
509	The first argument is the (unresolved) node reference of the local node
510	(if missing then the empty string is used).
511
512	It is quite common to not specify anything, in which case the local node
513	tries to listen on the default port, or to only specify a port number, in
514	which case AnyEvent::MP tries to guess the local addresses.
515
516	=cut
517
518	=back
519
520	=head1 NODE MESSAGES
521
522	Nodes understand the following messages sent to them. Many of them take
523	arguments called C<@reply>, which will simply be used to compose a reply
524	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
525	the remaining arguments are simply the message data.
526
527	While other messages exist, they are not public and subject to change.
528
529	=over 4
530
531	=cut
532
533	=item lookup => $name, @reply
534
535	Replies with the port ID of the specified well-known port, or C<undef>.
536
537	=item devnull => ...
538
539	Generic data sink/CPU heat conversion.
540
541	=item relay => $port, @msg
542
543	Simply forwards the message to the given port.
544
545	=item eval => $string[ @reply]
546
547	Evaluates the given string. If C<@reply> is given, then a message of the
548	form C<@reply, $@, @evalres> is sent.
549
550	Example: crash another node.
551
552	snd $othernode, eval => "exit";
553
554	=item time => @reply
555
556	Replies the the current node time to C<@reply>.
557
558	Example: tell the current node to send the current time to C<$myport> in a
559	C<timereply> message.
560
561	snd $NODE, time => $myport, timereply => 1, 2;
562	# => snd $myport, timereply => 1, 2, <time>
563
564	=back
565
566	=head1 AnyEvent::MP vs. Distributed Erlang
567
568	AnyEvent::MP got lots of its ideas from distributed erlang (erlang node
569	== aemp node, erlang process == aemp port), so many of the documents and
570	programming techniques employed by erlang apply to AnyEvent::MP. Here is a
571	sample:
572
573	http://www.erlang.se/doc/programming_rules.shtml
574	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
575	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
576	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
577
578	Despite the similarities, there are also some important differences:
579
580	=over 4
581
582	=item * Node references contain the recipe on how to contact them.
583
584	Erlang relies on special naming and DNS to work everywhere in the	682	Erlang relies on special naming and DNS to work everywhere in the same
585	same way. AEMP relies on each node knowing it's own address(es), with	683	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
586	convenience functionality.	684	configuraiton or DNS), but will otherwise discover other odes itself.
587		685
588	This means that AEMP requires a less tightly controlled environment at the	686	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
589	cost of longer node references and a slightly higher management overhead.	687	uses "local ports are like remote ports".
		688
		689	The failure modes for local ports are quite different (runtime errors
		690	only) then for remote ports - when a local port dies, you I<know> it dies,
		691	when a connection to another node dies, you know nothing about the other
		692	port.
		693
		694	Erlang pretends remote ports are as reliable as local ports, even when
		695	they are not.
		696
		697	AEMP encourages a "treat remote ports differently" philosophy, with local
		698	ports being the special case/exception, where transport errors cannot
		699	occur.
590		700
591	=item * Erlang uses processes and a mailbox, AEMP does not queue.	701	=item * Erlang uses processes and a mailbox, AEMP does not queue.
592		702
593	Erlang uses processes that selctively receive messages, and therefore	703	Erlang uses processes that selectively receive messages, and therefore
594	needs a queue. AEMP is event based, queuing messages would serve no useful	704	needs a queue. AEMP is event based, queuing messages would serve no
595	purpose.	705	useful purpose. For the same reason the pattern-matching abilities of
		706	AnyEvent::MP are more limited, as there is little need to be able to
		707	filter messages without dequeing them.
596		708
597	(But see L<Coro::MP> for a more erlang-like process model on top of AEMP).	709	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
598		710
599	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	711	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
600		712
601	Sending messages in erlang is synchronous and blocks the process. AEMP	713	Sending messages in Erlang is synchronous and blocks the process (and
602	sends are immediate, connection establishment is handled in the	714	so does not need a queue that can overflow). AEMP sends are immediate,
603	background.	715	connection establishment is handled in the background.
604		716
605	=item * Erlang can silently lose messages, AEMP cannot.	717	=item * Erlang suffers from silent message loss, AEMP does not.
606		718
607	Erlang makes few guarantees on messages delivery - messages can get lost	719	Erlang makes few guarantees on messages delivery - messages can get lost
608	without any of the processes realising it (i.e. you send messages a, b,	720	without any of the processes realising it (i.e. you send messages a, b,
609	and c, and the other side only receives messages a and c).	721	and c, and the other side only receives messages a and c).
610		722
611	AEMP guarantees correct ordering, and the guarantee that there are no	723	AEMP guarantees correct ordering, and the guarantee that after one message
612	holes in the message sequence.	724	is lost, all following ones sent to the same port are lost as well, until
613		725	monitoring raises an error, so there are no silent "holes" in the message
614	=item * In erlang, processes can be declared dead and later be found to be	726	sequence.
615	alive.
616
617	In erlang it can happen that a monitored process is declared dead and
618	linked processes get killed, but later it turns out that the process is
619	still alive - and can receive messages.
620
621	In AEMP, when port monitoring detects a port as dead, then that port will
622	eventually be killed - it cannot happen that a node detects a port as dead
623	and then later sends messages to it, finding it is still alive.
624		727
625	=item * Erlang can send messages to the wrong port, AEMP does not.	728	=item * Erlang can send messages to the wrong port, AEMP does not.
626		729
627	In erlang it is quite possible that a node that restarts reuses a process	730	In Erlang it is quite likely that a node that restarts reuses a process ID
628	ID known to other nodes for a completely different process, causing	731	known to other nodes for a completely different process, causing messages
629	messages destined for that process to end up in an unrelated process.	732	destined for that process to end up in an unrelated process.
630		733
631	AEMP never reuses port IDs, so old messages or old port IDs floating	734	AEMP never reuses port IDs, so old messages or old port IDs floating
632	around in the network will not be sent to an unrelated port.	735	around in the network will not be sent to an unrelated port.
633		736
634	=item * Erlang uses unprotected connections, AEMP uses secure	737	=item * Erlang uses unprotected connections, AEMP uses secure
635	authentication and can use TLS.	738	authentication and can use TLS.
636		739
637	AEMP can use a proven protocol - SSL/TLS - to protect connections and	740	AEMP can use a proven protocol - TLS - to protect connections and
638	securely authenticate nodes.	741	securely authenticate nodes.
639		742
640	=item * The AEMP protocol is optimised for both text-based and binary	743	=item * The AEMP protocol is optimised for both text-based and binary
641	communications.	744	communications.
642		745
643	The AEMP protocol, unlike the erlang protocol, supports both	746	The AEMP protocol, unlike the Erlang protocol, supports both programming
644	language-independent text-only protocols (good for debugging) and binary,	747	language independent text-only protocols (good for debugging) and binary,
645	language-specific serialisers (e.g. Storable).	748	language-specific serialisers (e.g. Storable). By default, unless TLS is
		749	used, the protocol is actually completely text-based.
646		750
647	It has also been carefully designed to be implementable in other languages	751	It has also been carefully designed to be implementable in other languages
648	with a minimum of work while gracefully degrading fucntionality to make the	752	with a minimum of work while gracefully degrading functionality to make the
649	protocol simple.	753	protocol simple.
650		754
		755	=item * AEMP has more flexible monitoring options than Erlang.
		756
		757	In Erlang, you can chose to receive I<all> exit signals as messages
		758	or I<none>, there is no in-between, so monitoring single processes is
		759	difficult to implement. Monitoring in AEMP is more flexible than in
		760	Erlang, as one can choose between automatic kill, exit message or callback
		761	on a per-process basis.
		762
		763	=item * Erlang tries to hide remote/local connections, AEMP does not.
		764
		765	Monitoring in Erlang is not an indicator of process death/crashes, in the
		766	same way as linking is (except linking is unreliable in Erlang).
		767
		768	In AEMP, you don't "look up" registered port names or send to named ports
		769	that might or might not be persistent. Instead, you normally spawn a port
		770	on the remote node. The init function monitors you, and you monitor the
		771	remote port. Since both monitors are local to the node, they are much more
		772	reliable (no need for C<spawn_link>).
		773
		774	This also saves round-trips and avoids sending messages to the wrong port
		775	(hard to do in Erlang).
		776
651	=back	777	=back
652		778
		779	=head1 RATIONALE
		780
		781	=over 4
		782
		783	=item Why strings for port and node IDs, why not objects?
		784
		785	We considered "objects", but found that the actual number of methods
		786	that can be called are quite low. Since port and node IDs travel over
		787	the network frequently, the serialising/deserialising would add lots of
		788	overhead, as well as having to keep a proxy object everywhere.
		789
		790	Strings can easily be printed, easily serialised etc. and need no special
		791	procedures to be "valid".
		792
		793	And as a result, a miniport consists of a single closure stored in a
		794	global hash - it can't become much cheaper.
		795
		796	=item Why favour JSON, why not a real serialising format such as Storable?
		797
		798	In fact, any AnyEvent::MP node will happily accept Storable as framing
		799	format, but currently there is no way to make a node use Storable by
		800	default (although all nodes will accept it).
		801
		802	The default framing protocol is JSON because a) JSON::XS is many times
		803	faster for small messages and b) most importantly, after years of
		804	experience we found that object serialisation is causing more problems
		805	than it solves: Just like function calls, objects simply do not travel
		806	easily over the network, mostly because they will always be a copy, so you
		807	always have to re-think your design.
		808
		809	Keeping your messages simple, concentrating on data structures rather than
		810	objects, will keep your messages clean, tidy and efficient.
		811
		812	=back
		813
653	=head1 SEE ALSO	814	=head1 SEE ALSO
		815
		816	L<AnyEvent::MP::Intro> - a gentle introduction.
		817
		818	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		819
		820	L<AnyEvent::MP::Global> - network maintainance and port groups, to find
		821	your applications.
654		822
655	L<AnyEvent>.	823	L<AnyEvent>.
656		824
657	=head1 AUTHOR	825	=head1 AUTHOR
658		826

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Revision 1.68 by root, Fri Aug 28 23:06:33 2009 UTC