[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 1.94 by root, Tue Sep 22 14:14:43 2009 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent::MP - multi-processing/message-passing framework	3	AnyEvent::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
		12	$SELF # receiving/own port id in rcv callbacks
		13
		14	# initialise the node so it can send/receive messages
		15	configure;
		16
		17	# ports are message destinations
		18
		19	# sending messages
13	snd $port, type => data...;	20	snd $port, type => data...;
		21	snd $port, @msg;
		22	snd @msg_with_first_element_being_a_port;
14		23
15	$SELF # receiving/own port id in rcv callbacks	24	# creating/using ports, the simple way
		25	my $simple_port = port { my @msg = @_ };
16		26
17	rcv $port, smartmatch => $cb->($port, @msg);	27	# creating/using ports, tagged message matching
18		28	my $port = port;
19	# examples:
20	rcv $port2, ping => sub { snd $_[0], "pong"; 0 };	29	rcv $port, ping => sub { snd $_[0], "pong" };
21	rcv $port1, pong => sub { warn "pong received\n" };	30	rcv $port, pong => sub { warn "pong received\n" };
22	snd $port2, ping => $port1;
23		31
24	# more, smarter, matches (_any_ is exported by this module)	32	# create a port on another node
25	rcv $port, [child_died => $pid] => sub { ...	33	my $port = spawn $node, $initfunc, @initdata;
26	rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3	34
		35	# monitoring
		36	mon $localport, $cb->(@msg) # callback is invoked on death
		37	mon $localport, $otherport # kill otherport on abnormal death
		38	mon $localport, $otherport, @msg # send message on death
		39
		40	=head1 CURRENT STATUS
		41
		42	bin/aemp - stable.
		43	AnyEvent::MP - stable API, should work.
		44	AnyEvent::MP::Intro - explains most concepts.
		45	AnyEvent::MP::Kernel - mostly stable API.
		46	AnyEvent::MP::Global - stable API.
27		47
28	=head1 DESCRIPTION	48	=head1 DESCRIPTION
29		49
30	This module (-family) implements a simple message passing framework.	50	This module (-family) implements a simple message passing framework.
31		51
32	Despite its simplicity, you can securely message other processes running	52	Despite its simplicity, you can securely message other processes running
33	on the same or other hosts.	53	on the same or other hosts, and you can supervise entities remotely.
34		54
35	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	55	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
36	manual page.	56	manual page and the examples under F<eg/>.
37
38	At the moment, this module family is severly broken and 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		57
42	=head1 CONCEPTS	58	=head1 CONCEPTS
43		59
44	=over 4	60	=over 4
45		61
46	=item port	62	=item port
47		63
48	A port is something you can send messages to (with the C<snd> function).	64	Not to be confused with a TCP port, a "port" is something you can send
		65	messages to (with the C<snd> function).
49		66
50	Some ports allow you to register C<rcv> handlers that can match specific	67	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	68	some messages. Messages send to ports will not be queued, regardless of
52	will not be queued.	69	anything was listening for them or not.
53		70
54	=item port id - C<noderef#portname>	71	=item port ID - C<nodeid#portname>
55		72
56	A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as	73	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	74	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		75
61	=item node	76	=item node
62		77
63	A node is a single process containing at least one port - the node	78	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	79	which enables nodes to manage each other remotely, and to create new
65	create new ports, among other things.	80	ports.
66		81
67	Nodes are either private (single-process only), slaves (connected to a	82	Nodes are either public (have one or more listening ports) or private
68	master node only) or public nodes (connectable from unrelated nodes).	83	(no listening ports). Private nodes cannot talk to other private nodes
		84	currently.
69		85
70	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	86	=item node ID - C<[A-Z_][a-zA-Z0-9_\-.:]*>
71		87
72	A node reference is a string that either simply identifies the node (for	88	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	89	network. Depending on the configuration used, node IDs can look like a
74	node (for public nodes).	90	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		91	doesn't interpret node IDs in any way.
75		92
76	This recipe is simply a comma-separated list of C<address:port> pairs (for	93	=item binds - C<ip:port>
77	TCP/IP, other protocols might look different).
78		94
79	Node references come in two flavours: resolved (containing only numerical	95	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).	96	each other. To do this, nodes should listen on one or more local transport
		97	endpoints - binds. Currently, only standard C<ip:port> specifications can
		98	be used, which specify TCP ports to listen on.
81		99
82	Before using an unresolved node reference in a message you first have to	100	=item seed nodes
83	resolve it.	101
		102	When a node starts, it knows nothing about the network. To teach the node
		103	about the network it first has to contact some other node within the
		104	network. This node is called a seed.
		105
		106	Apart from the fact that other nodes know them as seed nodes and they have
		107	to have fixed listening addresses, seed nodes are perfectly normal nodes -
		108	any node can function as a seed node for others.
		109
		110	In addition to discovering the network, seed nodes are also used to
		111	maintain the network and to connect nodes that otherwise would have
		112	trouble connecting. They form the backbone of an AnyEvent::MP network.
		113
		114	Seed nodes are expected to be long-running, and at least one seed node
		115	should always be available. They should also be relatively responsive - a
		116	seed node that blocks for long periods will slow down everybody else.
		117
		118	=item seeds - C<host:port>
		119
		120	Seeds are transport endpoint(s) (usually a hostname/IP address and a
		121	TCP port) of nodes thta should be used as seed nodes.
		122
		123	The nodes listening on those endpoints are expected to be long-running,
		124	and at least one of those should always be available. When nodes run out
		125	of connections (e.g. due to a network error), they try to re-establish
		126	connections to some seednodes again to join the network.
84		127
85	=back	128	=back
86		129
87	=head1 VARIABLES/FUNCTIONS	130	=head1 VARIABLES/FUNCTIONS
88		131
90		133
91	=cut	134	=cut
92		135
93	package AnyEvent::MP;	136	package AnyEvent::MP;
94		137
95	use AnyEvent::MP::Base;	138	use AnyEvent::MP::Kernel;
96		139
97	use common::sense;	140	use common::sense;
98		141
99	use Carp ();	142	use Carp ();
100		143
101	use AE ();	144	use AE ();
102		145
103	use base "Exporter";	146	use base "Exporter";
104		147
105	our $VERSION = '0.1';	148	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
		149
106	our @EXPORT = qw(	150	our @EXPORT = qw(
107	NODE $NODE *SELF node_of _any_	151	NODE $NODE *SELF node_of after
108	resolve_node initialise_node	152	configure
109	snd rcv mon kil reg psub	153	snd rcv mon mon_guard kil psub spawn cal
110	port	154	port
111	);	155	);
112		156
113	our $SELF;	157	our $SELF;
114		158
…		…
118	kil $SELF, die => $msg;	162	kil $SELF, die => $msg;
119	}	163	}
120		164
121	=item $thisnode = NODE / $NODE	165	=item $thisnode = NODE / $NODE
122		166
123	The C<NODE> function returns, and the C<$NODE> variable contains	167	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	168	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	169	a call to C<configure>.
126	identifiers become invalid.
127		170
128	=item $noderef = node_of $portid	171	=item $nodeid = node_of $port
129		172
130	Extracts and returns the noderef from a portid or a noderef.	173	Extracts and returns the node ID from a port ID or a node ID.
131		174
132	=item $cv = resolve_node $noderef	175	=item configure $profile, key => value...
133		176
134	Takes an unresolved node reference that may contain hostnames and	177	=item configure key => value...
135	abbreviated IDs, resolves all of them and returns a resolved node
136	reference.
137		178
138	In addition to C<address:port> pairs allowed in resolved noderefs, the	179	Before a node can talk to other nodes on the network (i.e. enter
139	following forms are supported:	180	"distributed mode") it has to configure itself - the minimum a node needs
		181	to know is its own name, and optionally it should know the addresses of
		182	some other nodes in the network to discover other nodes.
		183
		184	This function configures a node - it must be called exactly once (or
		185	never) before calling other AnyEvent::MP functions.
140		186
141	=over 4	187	=over 4
142		188
143	=item the empty string	189	=item step 1, gathering configuration from profiles
144		190
145	An empty-string component gets resolved as if the default port (4040) was	191	The function first looks up a profile in the aemp configuration (see the
146	specified.	192	L<aemp> commandline utility). The profile name can be specified via the
		193	named C<profile> parameter or can simply be the first parameter). If it is
		194	missing, then the nodename (F<uname -n>) will be used as profile name.
147		195
148	=item naked port numbers (e.g. C<1234>)	196	The profile data is then gathered as follows:
149		197
150	These are resolved by prepending the local nodename and a colon, to be	198	First, all remaining key => value pairs (all of which are conveniently
151	further resolved.	199	undocumented at the moment) will be interpreted as configuration
		200	data. Then they will be overwritten by any values specified in the global
		201	default configuration (see the F<aemp> utility), then the chain of
		202	profiles chosen by the profile name (and any C<parent> attributes).
152		203
153	=item hostnames (e.g. C<localhost:1234>, C<localhost>)	204	That means that the values specified in the profile have highest priority
		205	and the values specified directly via C<configure> have lowest priority,
		206	and can only be used to specify defaults.
154		207
155	These are resolved by using AnyEvent::DNS to resolve them, optionally	208	If the profile specifies a node ID, then this will become the node ID of
156	looking up SRV records for the C<aemp=4040> port, if no port was	209	this process. If not, then the profile name will be used as node ID. The
157	specified.	210	special node ID of C<anon/> will be replaced by a random node ID.
		211
		212	=item step 2, bind listener sockets
		213
		214	The next step is to look up the binds in the profile, followed by binding
		215	aemp protocol listeners on all binds specified (it is possible and valid
		216	to have no binds, meaning that the node cannot be contacted form the
		217	outside. This means the node cannot talk to other nodes that also have no
		218	binds, but it can still talk to all "normal" nodes).
		219
		220	If the profile does not specify a binds list, then a default of C<*> is
		221	used, meaning the node will bind on a dynamically-assigned port on every
		222	local IP address it finds.
		223
		224	=item step 3, connect to seed nodes
		225
		226	As the last step, the seeds list from the profile is passed to the
		227	L<AnyEvent::MP::Global> module, which will then use it to keep
		228	connectivity with at least one node at any point in time.
158		229
159	=back	230	=back
		231
		232	Example: become a distributed node using the local node name as profile.
		233	This should be the most common form of invocation for "daemon"-type nodes.
		234
		235	configure
		236
		237	Example: become an anonymous node. This form is often used for commandline
		238	clients.
		239
		240	configure nodeid => "anon/";
		241
		242	Example: configure a node using a profile called seed, which si suitable
		243	for a seed node as it binds on all local addresses on a fixed port (4040,
		244	customary for aemp).
		245
		246	# use the aemp commandline utility
		247	# aemp profile seed nodeid anon/ binds '*:4040'
		248
		249	# then use it
		250	configure profile => "seed";
		251
		252	# or simply use aemp from the shell again:
		253	# aemp run profile seed
		254
		255	# or provide a nicer-to-remember nodeid
		256	# aemp run profile seed nodeid "$(hostname)"
160		257
161	=item $SELF	258	=item $SELF
162		259
163	Contains the current port id while executing C<rcv> callbacks or C<psub>	260	Contains the current port id while executing C<rcv> callbacks or C<psub>
164	blocks.	261	blocks.
165		262
166	=item SELF, %SELF, @SELF...	263	=item *SELF, SELF, %SELF, @SELF...
167		264
168	Due to some quirks in how perl exports variables, it is impossible to	265	Due to some quirks in how perl exports variables, it is impossible to
169	just export C<$SELF>, all the symbols called C<SELF> are exported by this	266	just export C<$SELF>, all the symbols named C<SELF> are exported by this
170	module, but only C<$SELF> is currently used.	267	module, but only C<$SELF> is currently used.
171		268
172	=item snd $portid, type => @data	269	=item snd $port, type => @data
173		270
174	=item snd $portid, @msg	271	=item snd $port, @msg
175		272
176	Send the given message to the given port ID, which can identify either	273	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	274	local or a remote port, and must be a port ID.
178	stringifies a sa port ID (such as a port object :).
179		275
180	While the message can be about anything, it is highly recommended to use a	276	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	277	use a string as first element (a port ID, or some word that indicates a
182	type etc.).	278	request type etc.) and to consist if only simple perl values (scalars,
		279	arrays, hashes) - if you think you need to pass an object, think again.
183		280
184	The message data effectively becomes read-only after a call to this	281	The message data logically becomes read-only after a call to this
185	function: modifying any argument is not allowed and can cause many	282	function: modifying any argument (or values referenced by them) is
186	problems.	283	forbidden, as there can be considerable time between the call to C<snd>
		284	and the time the message is actually being serialised - in fact, it might
		285	never be copied as within the same process it is simply handed to the
		286	receiving port.
187		287
188	The type of data you can transfer depends on the transport protocol: when	288	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	289	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	290	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	291	that Storable can serialise and deserialise is allowed, and for the local
192	node, anything can be passed.	292	node, anything can be passed. Best rely only on the common denominator of
		293	these.
193		294
194	=item $local_port = port	295	=item $local_port = port
195		296
196	Create a new local port object that can be used either as a pattern	297	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"),	298	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		299
200	=item $portid = port { my @msg = @_; $finished }	300	=item $local_port = port { my @msg = @_ }
201		301
202	Creates a "mini port", that is, a very lightweight port without any	302	Creates a new local port, and returns its ID. Semantically the same as
203	pattern matching behind it, and returns its ID.	303	creating a port and calling C<rcv $port, $callback> on it.
204		304
205	The block will be called for every message received on the port. When the	305	The block will be called for every message received on the port, with the
206	callback returns a true value its job is considered "done" and the port	306	global variable C<$SELF> set to the port ID. Runtime errors will cause the
207	will be destroyed. Otherwise it will stay alive.	307	port to be C<kil>ed. The message will be passed as-is, no extra argument
		308	(i.e. no port ID) will be passed to the callback.
208		309
209	The message will be passed as-is, no extra argument (i.e. no port id) will	310	If you want to stop/destroy the port, simply C<kil> it:
210	be passed to the callback.
211		311
212	If you need the local port id in the callback, this works nicely:	312	my $port = port {
213		313	my @msg = @_;
214	my $port; $port = port {	314	...
215	snd $otherport, reply => $port;	315	kil $SELF;
216	};	316	};
217		317
218	=cut	318	=cut
		319
		320	sub rcv($@);
		321
		322	sub _kilme {
		323	die "received message on port without callback";
		324	}
219		325
220	sub port(;&) {	326	sub port(;&) {
221	my $id = "$UNIQ." . $ID++;	327	my $id = "$UNIQ." . $ID++;
222	my $port = "$NODE#$id";	328	my $port = "$NODE#$id";
223		329
		330	rcv $port, shift \|\| \&_kilme;
		331
		332	$port
		333	}
		334
		335	=item rcv $local_port, $callback->(@msg)
		336
		337	Replaces the default callback on the specified port. There is no way to
		338	remove the default callback: use C<sub { }> to disable it, or better
		339	C<kil> the port when it is no longer needed.
		340
		341	The global C<$SELF> (exported by this module) contains C<$port> while
		342	executing the callback. Runtime errors during callback execution will
		343	result in the port being C<kil>ed.
		344
		345	The default callback received all messages not matched by a more specific
		346	C<tag> match.
		347
		348	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
		349
		350	Register (or replace) callbacks to be called on messages starting with the
		351	given tag on the given port (and return the port), or unregister it (when
		352	C<$callback> is C<$undef> or missing). There can only be one callback
		353	registered for each tag.
		354
		355	The original message will be passed to the callback, after the first
		356	element (the tag) has been removed. The callback will use the same
		357	environment as the default callback (see above).
		358
		359	Example: create a port and bind receivers on it in one go.
		360
		361	my $port = rcv port,
		362	msg1 => sub { ... },
		363	msg2 => sub { ... },
		364	;
		365
		366	Example: create a port, bind receivers and send it in a message elsewhere
		367	in one go:
		368
		369	snd $otherport, reply =>
		370	rcv port,
		371	msg1 => sub { ... },
		372	...
		373	;
		374
		375	Example: temporarily register a rcv callback for a tag matching some port
		376	(e.g. for a rpc reply) and unregister it after a message was received.
		377
		378	rcv $port, $otherport => sub {
		379	my @reply = @_;
		380
		381	rcv $SELF, $otherport;
		382	};
		383
		384	=cut
		385
		386	sub rcv($@) {
		387	my $port = shift;
		388	my ($nodeid, $portid) = split /#/, $port, 2;
		389
		390	$NODE{$nodeid} == $NODE{""}
		391	or Carp::croak "$port: rcv can only be called on local ports, caught";
		392
224	if (@_) {	393	while (@_) {
		394	if (ref $_[0]) {
		395	if (my $self = $PORT_DATA{$portid}) {
		396	"AnyEvent::MP::Port" eq ref $self
		397	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		398
		399	$self->[2] = shift;
		400	} else {
225	my $cb = shift;	401	my $cb = shift;
226	$PORT{$id} = sub {	402	$PORT{$portid} = sub {
227	local $SELF = $port;	403	local $SELF = $port;
228	eval {	404	eval { &$cb }; _self_die if $@;
229	&$cb	405	};
230	and kil $id;	406	}
		407	} elsif (defined $_[0]) {
		408	my $self = $PORT_DATA{$portid} \|\|= do {
		409	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
		410
		411	$PORT{$portid} = sub {
		412	local $SELF = $port;
		413
		414	if (my $cb = $self->[1]{$_[0]}) {
		415	shift;
		416	eval { &$cb }; _self_die if $@;
		417	} else {
		418	&{ $self->[0] };
		419	}
		420	};
		421
		422	$self
231	};	423	};
232	_self_die if $@;	424
233	};
234	} else {
235	my $self = bless {
236	id => "$NODE#$id",
237	}, "AnyEvent::MP::Port";	425	"AnyEvent::MP::Port" eq ref $self
		426	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
238		427
239	$PORT_DATA{$id} = $self;	428	my ($tag, $cb) = splice @_, 0, 2;
240	$PORT{$id} = sub {
241	local $SELF = $port;
242		429
		430	if (defined $cb) {
		431	$self->[1]{$tag} = $cb;
243	eval {	432	} else {
244	for (@{ $self->{rc0}{$_[0]} }) {	433	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	};	434	}
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	}	435	}
348	}	436	}
349		437
350	$portid	438	$port
351	}	439	}
352		440
353	=item $closure = psub { BLOCK }	441	=item $closure = psub { BLOCK }
354		442
355	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	443	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
…		…
386	$res	474	$res
387	}	475	}
388	}	476	}
389	}	477	}
390		478
391	=item $guard = mon $portid, $cb->(@reason)	479	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
392		480
393	=item $guard = mon $portid, $otherport	481	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
394		482
395	=item $guard = mon $portid, $otherport, @msg	483	=item $guard = mon $port # kill $SELF when $port dies
396		484
		485	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
		486
397	Monitor the given port and do something when the port is killed.	487	Monitor the given port and do something when the port is killed or
		488	messages to it were lost, and optionally return a guard that can be used
		489	to stop monitoring again.
398		490
399	In the first form, the callback is simply called with any number	491	In the first form (callback), the callback is simply called with any
400	of C<@reason> elements (no @reason means that the port was deleted	492	number of C<@reason> elements (no @reason means that the port was deleted
401	"normally"). Note also that I<< the callback B<must> never die >>, so use	493	"normally"). Note also that I<< the callback B<must> never die >>, so use
402	C<eval> if unsure.	494	C<eval> if unsure.
403		495
404	In the second form, the other port will be C<kil>'ed with C<@reason>, iff	496	In the second form (another port given), the other port (C<$rcvport>)
405	a @reason was specified, i.e. on "normal" kils nothing happens, while	497	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
406	under all other conditions, the other port is killed with the same reason.	498	"normal" kils nothing happens, while under all other conditions, the other
		499	port is killed with the same reason.
407		500
		501	The third form (kill self) is the same as the second form, except that
		502	C<$rvport> defaults to C<$SELF>.
		503
408	In the last form, a message of the form C<@msg, @reason> will be C<snd>.	504	In the last form (message), a message of the form C<@msg, @reason> will be
		505	C<snd>.
		506
		507	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		508	alert was raised), they are removed and will not trigger again.
		509
		510	As a rule of thumb, monitoring requests should always monitor a port from
		511	a local port (or callback). The reason is that kill messages might get
		512	lost, just like any other message. Another less obvious reason is that
		513	even monitoring requests can get lost (for example, when the connection
		514	to the other node goes down permanently). When monitoring a port locally
		515	these problems do not exist.
		516
		517	C<mon> effectively guarantees that, in the absence of hardware failures,
		518	after starting the monitor, either all messages sent to the port will
		519	arrive, or the monitoring action will be invoked after possible message
		520	loss has been detected. No messages will be lost "in between" (after
		521	the first lost message no further messages will be received by the
		522	port). After the monitoring action was invoked, further messages might get
		523	delivered again.
		524
		525	Inter-host-connection timeouts and monitoring depend on the transport
		526	used. The only transport currently implemented is TCP, and AnyEvent::MP
		527	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		528	non-idle connection, and usually around two hours for idle conenctions).
		529
		530	This means that monitoring is good for program errors and cleaning up
		531	stuff eventually, but they are no replacement for a timeout when you need
		532	to ensure some maximum latency.
409		533
410	Example: call a given callback when C<$port> is killed.	534	Example: call a given callback when C<$port> is killed.
411		535
412	mon $port, sub { warn "port died because of <@_>\n" };	536	mon $port, sub { warn "port died because of <@_>\n" };
413		537
414	Example: kill ourselves when C<$port> is killed abnormally.	538	Example: kill ourselves when C<$port> is killed abnormally.
415		539
416	mon $port, $self;	540	mon $port;
417		541
418	Example: send us a restart message another C<$port> is killed.	542	Example: send us a restart message when another C<$port> is killed.
419		543
420	mon $port, $self => "restart";	544	mon $port, $self => "restart";
421		545
422	=cut	546	=cut
423		547
424	sub mon {	548	sub mon {
425	my ($noderef, $port) = split /#/, shift, 2;	549	my ($nodeid, $port) = split /#/, shift, 2;
426		550
427	my $node = $NODE{$noderef} \|\| add_node $noderef;	551	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
428		552
429	my $cb = shift;	553	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
430		554
431	unless (ref $cb) {	555	unless (ref $cb) {
432	if (@_) {	556	if (@_) {
433	# send a kill info message	557	# send a kill info message
434	my (@msg) = ($cb, @_);	558	my (@msg) = ($cb, @_);
…		…
441	}	565	}
442		566
443	$node->monitor ($port, $cb);	567	$node->monitor ($port, $cb);
444		568
445	defined wantarray	569	defined wantarray
446	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	570	and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) })
447	}	571	}
448		572
449	=item $guard = mon_guard $port, $ref, $ref...	573	=item $guard = mon_guard $port, $ref, $ref...
450		574
451	Monitors the given C<$port> and keeps the passed references. When the port	575	Monitors the given C<$port> and keeps the passed references. When the port
452	is killed, the references will be freed.	576	is killed, the references will be freed.
453		577
454	Optionally returns a guard that will stop the monitoring.	578	Optionally returns a guard that will stop the monitoring.
455		579
456	This function is useful when you create e.g. timers or other watchers and	580	This function is useful when you create e.g. timers or other watchers and
457	want to free them when the port gets killed:	581	want to free them when the port gets killed (note the use of C<psub>):
458		582
459	$port->rcv (start => sub {	583	$port->rcv (start => sub {
460	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	584	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
461	undef $timer if 0.9 < rand;	585	undef $timer if 0.9 < rand;
462	});	586	});
463	});	587	});
464		588
465	=cut	589	=cut
466		590
467	sub mon_guard {	591	sub mon_guard {
468	my ($port, @refs) = @_;	592	my ($port, @refs) = @_;
469		593
		594	#TODO: mon-less form?
		595
470	mon $port, sub { 0 && @refs }	596	mon $port, sub { 0 && @refs }
471	}	597	}
472		598
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]	599	=item kil $port[, @reason]
484		600
485	Kill the specified port with the given C<@reason>.	601	Kill the specified port with the given C<@reason>.
486		602
487	If no C<@reason> is specified, then the port is killed "normally" (linked	603	If no C<@reason> is specified, then the port is killed "normally" (ports
488	ports will not be kileld, or even notified).	604	monitoring other ports will not necessarily die because a port dies
		605	"normally").
489		606
490	Otherwise, linked ports get killed with the same reason (second form of	607	Otherwise, linked ports get killed with the same reason (second form of
491	C<mon>, see below).	608	C<mon>, see above).
492		609
493	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	610	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
494	will be reported as reason C<< die => $@ >>.	611	will be reported as reason C<< die => $@ >>.
495		612
496	Transport/communication errors are reported as C<< transport_error =>	613	Transport/communication errors are reported as C<< transport_error =>
497	$message >>.	614	$message >>.
498		615
		616	=cut
		617
		618	=item $port = spawn $node, $initfunc[, @initdata]
		619
		620	Creates a port on the node C<$node> (which can also be a port ID, in which
		621	case it's the node where that port resides).
		622
		623	The port ID of the newly created port is returned immediately, and it is
		624	possible to immediately start sending messages or to monitor the port.
		625
		626	After the port has been created, the init function is called on the remote
		627	node, in the same context as a C<rcv> callback. This function must be a
		628	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
		629	specify a function in the main program, use C<::name>.
		630
		631	If the function doesn't exist, then the node tries to C<require>
		632	the package, then the package above the package and so on (e.g.
		633	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
		634	exists or it runs out of package names.
		635
		636	The init function is then called with the newly-created port as context
		637	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		638	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		639	the port might not get created.
		640
		641	A common idiom is to pass a local port, immediately monitor the spawned
		642	port, and in the remote init function, immediately monitor the passed
		643	local port. This two-way monitoring ensures that both ports get cleaned up
		644	when there is a problem.
		645
		646	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		647	caller before C<spawn> returns (by delaying invocation when spawn is
		648	called for the local node).
		649
		650	Example: spawn a chat server port on C<$othernode>.
		651
		652	# this node, executed from within a port context:
		653	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
		654	mon $server;
		655
		656	# init function on C<$othernode>
		657	sub connect {
		658	my ($srcport) = @_;
		659
		660	mon $srcport;
		661
		662	rcv $SELF, sub {
		663	...
		664	};
		665	}
		666
		667	=cut
		668
		669	sub _spawn {
		670	my $port = shift;
		671	my $init = shift;
		672
		673	# rcv will create the actual port
		674	local $SELF = "$NODE#$port";
		675	eval {
		676	&{ load_func $init }
		677	};
		678	_self_die if $@;
		679	}
		680
		681	sub spawn(@) {
		682	my ($nodeid, undef) = split /#/, shift, 2;
		683
		684	my $id = "$RUNIQ." . $ID++;
		685
		686	$_[0] =~ /::/
		687	or Carp::croak "spawn init function must be a fully-qualified name, caught";
		688
		689	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
		690
		691	"$nodeid#$id"
		692	}
		693
		694	=item after $timeout, @msg
		695
		696	=item after $timeout, $callback
		697
		698	Either sends the given message, or call the given callback, after the
		699	specified number of seconds.
		700
		701	This is simply a utility function that comes in handy at times - the
		702	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		703	so it may go away in the future.
		704
		705	=cut
		706
		707	sub after($@) {
		708	my ($timeout, @action) = @_;
		709
		710	my $t; $t = AE::timer $timeout, 0, sub {
		711	undef $t;
		712	ref $action[0]
		713	? $action[0]()
		714	: snd @action;
		715	};
		716	}
		717
		718	=item cal $port, @msg, $callback[, $timeout]
		719
		720	A simple form of RPC - sends a message to the given C<$port> with the
		721	given contents (C<@msg>), but adds a reply port to the message.
		722
		723	The reply port is created temporarily just for the purpose of receiving
		724	the reply, and will be C<kil>ed when no longer needed.
		725
		726	A reply message sent to the port is passed to the C<$callback> as-is.
		727
		728	If an optional time-out (in seconds) is given and it is not C<undef>,
		729	then the callback will be called without any arguments after the time-out
		730	elapsed and the port is C<kil>ed.
		731
		732	If no time-out is given, then the local port will monitor the remote port
		733	instead, so it eventually gets cleaned-up.
		734
		735	Currently this function returns the temporary port, but this "feature"
		736	might go in future versions unless you can make a convincing case that
		737	this is indeed useful for something.
		738
		739	=cut
		740
		741	sub cal(@) {
		742	my $timeout = ref $_[-1] ? undef : pop;
		743	my $cb = pop;
		744
		745	my $port = port {
		746	undef $timeout;
		747	kil $SELF;
		748	&$cb;
		749	};
		750
		751	if (defined $timeout) {
		752	$timeout = AE::timer $timeout, 0, sub {
		753	undef $timeout;
		754	kil $port;
		755	$cb->();
		756	};
		757	} else {
		758	mon $_[0], sub {
		759	kil $port;
		760	$cb->();
		761	};
		762	}
		763
		764	push @_, $port;
		765	&snd;
		766
		767	$port
		768	}
		769
499	=back	770	=back
500		771
501	=head1 FUNCTIONS FOR NODES	772	=head1 AnyEvent::MP vs. Distributed Erlang
		773
		774	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
		775	== aemp node, Erlang process == aemp port), so many of the documents and
		776	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
		777	sample:
		778
		779	http://www.Erlang.se/doc/programming_rules.shtml
		780	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
		781	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6
		782	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
		783
		784	Despite the similarities, there are also some important differences:
502		785
503	=over 4	786	=over 4
504		787
505	=item become_public $noderef	788	=item * Node IDs are arbitrary strings in AEMP.
506		789
507	Tells the node to become a public node, i.e. reachable from other nodes.
508
509	The first argument is the (unresolved) node reference of the local node
510	(if missing then the empty string is used).
511
512	It is quite common to not specify anything, in which case the local node
513	tries to listen on the default port, or to only specify a port number, in
514	which case AnyEvent::MP tries to guess the local addresses.
515
516	=cut
517
518	=back
519
520	=head1 NODE MESSAGES
521
522	Nodes understand the following messages sent to them. Many of them take
523	arguments called C<@reply>, which will simply be used to compose a reply
524	message - C<$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	790	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	791	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
586	convenience functionality.	792	configuration or DNS), but will otherwise discover other odes itself.
587		793
588	This means that AEMP requires a less tightly controlled environment at the	794	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
589	cost of longer node references and a slightly higher management overhead.	795	uses "local ports are like remote ports".
		796
		797	The failure modes for local ports are quite different (runtime errors
		798	only) then for remote ports - when a local port dies, you I<know> it dies,
		799	when a connection to another node dies, you know nothing about the other
		800	port.
		801
		802	Erlang pretends remote ports are as reliable as local ports, even when
		803	they are not.
		804
		805	AEMP encourages a "treat remote ports differently" philosophy, with local
		806	ports being the special case/exception, where transport errors cannot
		807	occur.
590		808
591	=item * Erlang uses processes and a mailbox, AEMP does not queue.	809	=item * Erlang uses processes and a mailbox, AEMP does not queue.
592		810
593	Erlang uses processes that selctively receive messages, and therefore	811	Erlang uses processes that selectively receive messages, and therefore
594	needs a queue. AEMP is event based, queuing messages would serve no useful	812	needs a queue. AEMP is event based, queuing messages would serve no
595	purpose.	813	useful purpose. For the same reason the pattern-matching abilities of
		814	AnyEvent::MP are more limited, as there is little need to be able to
		815	filter messages without dequeuing them.
596		816
597	(But see L<Coro::MP> for a more erlang-like process model on top of AEMP).	817	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
598		818
599	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	819	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
600		820
601	Sending messages in erlang is synchronous and blocks the process. AEMP	821	Sending messages in Erlang is synchronous and blocks the process (and
602	sends are immediate, connection establishment is handled in the	822	so does not need a queue that can overflow). AEMP sends are immediate,
603	background.	823	connection establishment is handled in the background.
604		824
605	=item * Erlang can silently lose messages, AEMP cannot.	825	=item * Erlang suffers from silent message loss, AEMP does not.
606		826
607	Erlang makes few guarantees on messages delivery - messages can get lost	827	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,	828	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).	829	and c, and the other side only receives messages a and c).
610		830
611	AEMP guarantees correct ordering, and the guarantee that there are no	831	AEMP guarantees correct ordering, and the guarantee that after one message
612	holes in the message sequence.	832	is lost, all following ones sent to the same port are lost as well, until
613		833	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	834	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		835
625	=item * Erlang can send messages to the wrong port, AEMP does not.	836	=item * Erlang can send messages to the wrong port, AEMP does not.
626		837
627	In erlang it is quite possible that a node that restarts reuses a process	838	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	839	known to other nodes for a completely different process, causing messages
629	messages destined for that process to end up in an unrelated process.	840	destined for that process to end up in an unrelated process.
630		841
631	AEMP never reuses port IDs, so old messages or old port IDs floating	842	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.	843	around in the network will not be sent to an unrelated port.
633		844
634	=item * Erlang uses unprotected connections, AEMP uses secure	845	=item * Erlang uses unprotected connections, AEMP uses secure
635	authentication and can use TLS.	846	authentication and can use TLS.
636		847
637	AEMP can use a proven protocol - SSL/TLS - to protect connections and	848	AEMP can use a proven protocol - TLS - to protect connections and
638	securely authenticate nodes.	849	securely authenticate nodes.
639		850
640	=item * The AEMP protocol is optimised for both text-based and binary	851	=item * The AEMP protocol is optimised for both text-based and binary
641	communications.	852	communications.
642		853
643	The AEMP protocol, unlike the erlang protocol, supports both	854	The AEMP protocol, unlike the Erlang protocol, supports both programming
644	language-independent text-only protocols (good for debugging) and binary,	855	language independent text-only protocols (good for debugging) and binary,
645	language-specific serialisers (e.g. Storable).	856	language-specific serialisers (e.g. Storable). By default, unless TLS is
		857	used, the protocol is actually completely text-based.
646		858
647	It has also been carefully designed to be implementable in other languages	859	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	860	with a minimum of work while gracefully degrading functionality to make the
649	protocol simple.	861	protocol simple.
650		862
		863	=item * AEMP has more flexible monitoring options than Erlang.
		864
		865	In Erlang, you can chose to receive I<all> exit signals as messages
		866	or I<none>, there is no in-between, so monitoring single processes is
		867	difficult to implement. Monitoring in AEMP is more flexible than in
		868	Erlang, as one can choose between automatic kill, exit message or callback
		869	on a per-process basis.
		870
		871	=item * Erlang tries to hide remote/local connections, AEMP does not.
		872
		873	Monitoring in Erlang is not an indicator of process death/crashes, in the
		874	same way as linking is (except linking is unreliable in Erlang).
		875
		876	In AEMP, you don't "look up" registered port names or send to named ports
		877	that might or might not be persistent. Instead, you normally spawn a port
		878	on the remote node. The init function monitors you, and you monitor the
		879	remote port. Since both monitors are local to the node, they are much more
		880	reliable (no need for C<spawn_link>).
		881
		882	This also saves round-trips and avoids sending messages to the wrong port
		883	(hard to do in Erlang).
		884
651	=back	885	=back
652		886
		887	=head1 RATIONALE
		888
		889	=over 4
		890
		891	=item Why strings for port and node IDs, why not objects?
		892
		893	We considered "objects", but found that the actual number of methods
		894	that can be called are quite low. Since port and node IDs travel over
		895	the network frequently, the serialising/deserialising would add lots of
		896	overhead, as well as having to keep a proxy object everywhere.
		897
		898	Strings can easily be printed, easily serialised etc. and need no special
		899	procedures to be "valid".
		900
		901	And as a result, a miniport consists of a single closure stored in a
		902	global hash - it can't become much cheaper.
		903
		904	=item Why favour JSON, why not a real serialising format such as Storable?
		905
		906	In fact, any AnyEvent::MP node will happily accept Storable as framing
		907	format, but currently there is no way to make a node use Storable by
		908	default (although all nodes will accept it).
		909
		910	The default framing protocol is JSON because a) JSON::XS is many times
		911	faster for small messages and b) most importantly, after years of
		912	experience we found that object serialisation is causing more problems
		913	than it solves: Just like function calls, objects simply do not travel
		914	easily over the network, mostly because they will always be a copy, so you
		915	always have to re-think your design.
		916
		917	Keeping your messages simple, concentrating on data structures rather than
		918	objects, will keep your messages clean, tidy and efficient.
		919
		920	=back
		921
653	=head1 SEE ALSO	922	=head1 SEE ALSO
		923
		924	L<AnyEvent::MP::Intro> - a gentle introduction.
		925
		926	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		927
		928	L<AnyEvent::MP::Global> - network maintainance and port groups, to find
		929	your applications.
		930
		931	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		932	all nodes.
654		933
655	L<AnyEvent>.	934	L<AnyEvent>.
656		935
657	=head1 AUTHOR	936	=head1 AUTHOR
658		937

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Revision 1.32 by root, Wed Aug 5 19:58:46 2009 UTC vs.
Revision 1.94 by root, Tue Sep 22 14:14:43 2009 UTC