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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.33 by root, Wed Aug 5 22:40:51 2009 UTC vs.
Revision 1.75 by root, Mon Aug 31 13:18:06 2009 UTC

…		…
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 $port, $cb->(@msg) # callback is invoked on death
		37	mon $port, $otherport # kill otherport on abnormal death
		38	mon $port, $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 - uptodate, but incomplete.
		45	AnyEvent::MP::Kernel - mostly stable.
		46	AnyEvent::MP::Global - stable API, protocol not yet final.
		47
		48	stay tuned.
27		49
28	=head1 DESCRIPTION	50	=head1 DESCRIPTION
29		51
30	This module (-family) implements a simple message passing framework.	52	This module (-family) implements a simple message passing framework.
31		53
32	Despite its simplicity, you can securely message other processes running	54	Despite its simplicity, you can securely message other processes running
33	on the same or other hosts.	55	on the same or other hosts, and you can supervise entities remotely.
34		56
35	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	57	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
36	manual page.	58	manual page and the examples under F<eg/>.
37		59
38	At the moment, this module family is severly broken and underdocumented,	60	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		61
42	=head1 CONCEPTS	62	=head1 CONCEPTS
43		63
44	=over 4	64	=over 4
45		65
46	=item port	66	=item port
47		67
48	A port is something you can send messages to (with the C<snd> function).	68	A port is something you can send messages to (with the C<snd> function).
49		69
50	Some ports allow you to register C<rcv> handlers that can match specific	70	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	71	some messages. Messages send to ports will not be queued, regardless of
52	will not be queued.	72	anything was listening for them or not.
53		73
54	=item port id - C<noderef#portname>	74	=item port ID - C<nodeid#portname>
55		75
56	A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as	76	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	77	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		78
61	=item node	79	=item node
62		80
63	A node is a single process containing at least one port - the node	81	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	82	which enables nodes to manage each other remotely, and to create new
65	create new ports, among other things.	83	ports.
66		84
67	Nodes are either private (single-process only), slaves (connected to a	85	Nodes are either public (have one or more listening ports) or private
68	master node only) or public nodes (connectable from unrelated nodes).	86	(no listening ports). Private nodes cannot talk to other private nodes
		87	currently.
69		88
70	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	89	=item node ID - C<[a-za-Z0-9_\-.:]+>
71		90
72	A node reference is a string that either simply identifies the node (for	91	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	92	network. Depending on the configuration used, node IDs can look like a
74	node (for public nodes).	93	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		94	doesn't interpret node IDs in any way.
75		95
76	This recipe is simply a comma-separated list of C<address:port> pairs (for	96	=item binds - C<ip:port>
77	TCP/IP, other protocols might look different).
78		97
79	Node references come in two flavours: resolved (containing only numerical	98	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).	99	each other. To do this, nodes should listen on one or more local transport
		100	endpoints - binds. Currently, only standard C<ip:port> specifications can
		101	be used, which specify TCP ports to listen on.
81		102
82	Before using an unresolved node reference in a message you first have to	103	=item seeds - C<host:port>
83	resolve it.	104
		105	When a node starts, it knows nothing about the network. To teach the node
		106	about the network it first has to contact some other node within the
		107	network. This node is called a seed.
		108
		109	Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes
		110	are expected to be long-running, and at least one of those should always
		111	be available. When nodes run out of connections (e.g. due to a network
		112	error), they try to re-establish connections to some seednodes again to
		113	join the network.
		114
		115	Apart from being sued for seeding, seednodes are not special in any way -
		116	every public node can be a seednode.
84		117
85	=back	118	=back
86		119
87	=head1 VARIABLES/FUNCTIONS	120	=head1 VARIABLES/FUNCTIONS
88		121
…		…
90		123
91	=cut	124	=cut
92		125
93	package AnyEvent::MP;	126	package AnyEvent::MP;
94		127
95	use AnyEvent::MP::Base;	128	use AnyEvent::MP::Kernel;
96		129
97	use common::sense;	130	use common::sense;
98		131
99	use Carp ();	132	use Carp ();
100		133
101	use AE ();	134	use AE ();
102		135
103	use base "Exporter";	136	use base "Exporter";
104		137
105	our $VERSION = '0.1';	138	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
		139
106	our @EXPORT = qw(	140	our @EXPORT = qw(
107	NODE $NODE *SELF node_of _any_	141	NODE $NODE *SELF node_of after
108	resolve_node initialise_node	142	configure
109	snd rcv mon kil reg psub	143	snd rcv mon mon_guard kil reg psub spawn
110	port	144	port
111	);	145	);
112		146
113	our $SELF;	147	our $SELF;
114		148
…		…
118	kil $SELF, die => $msg;	152	kil $SELF, die => $msg;
119	}	153	}
120		154
121	=item $thisnode = NODE / $NODE	155	=item $thisnode = NODE / $NODE
122		156
123	The C<NODE> function returns, and the C<$NODE> variable contains	157	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	158	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	159	a call to C<configure>.
126	identifiers become invalid.
127		160
128	=item $noderef = node_of $port	161	=item $nodeid = node_of $port
129		162
130	Extracts and returns the noderef from a portid or a noderef.	163	Extracts and returns the node ID from a port ID or a node ID.
131		164
132	=item $cv = resolve_node $noderef	165	=item configure key => value...
133		166
134	Takes an unresolved node reference that may contain hostnames and	167	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	168	"distributed mode") it has to configure itself - the minimum a node needs
136	reference.	169	to know is its own name, and optionally it should know the addresses of
		170	some other nodes in the network to discover other nodes.
137		171
138	In addition to C<address:port> pairs allowed in resolved noderefs, the	172	This function configures a node - it must be called exactly once (or
139	following forms are supported:	173	never) before calling other AnyEvent::MP functions.
140		174
141	=over 4	175	=over 4
142		176
143	=item the empty string	177	=item step 1, gathering configuration from profiles
144		178
145	An empty-string component gets resolved as if the default port (4040) was	179	The function first looks up a profile in the aemp configuration (see the
146	specified.	180	L<aemp> commandline utility). The profile name can be specified via the
		181	named C<profile> parameter. If it is missing, then the nodename (F<uname
		182	-n>) will be used as profile name.
147		183
148	=item naked port numbers (e.g. C<1234>)	184	The profile data is then gathered as follows:
149		185
150	These are resolved by prepending the local nodename and a colon, to be	186	First, all remaining key => value pairs (all of which are conviniently
151	further resolved.	187	undocumented at the moment) will be interpreted as configuration
		188	data. Then they will be overwritten by any values specified in the global
		189	default configuration (see the F<aemp> utility), then the chain of
		190	profiles chosen by the profile name (and any C<parent> attributes).
152		191
153	=item hostnames (e.g. C<localhost:1234>, C<localhost>)	192	That means that the values specified in the profile have highest priority
		193	and the values specified directly via C<configure> have lowest priority,
		194	and can only be used to specify defaults.
154		195
155	These are resolved by using AnyEvent::DNS to resolve them, optionally	196	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	197	this process. If not, then the profile name will be used as node ID. The
157	specified.	198	special node ID of C<anon/> will be replaced by a random node ID.
		199
		200	=item step 2, bind listener sockets
		201
		202	The next step is to look up the binds in the profile, followed by binding
		203	aemp protocol listeners on all binds specified (it is possible and valid
		204	to have no binds, meaning that the node cannot be contacted form the
		205	outside. This means the node cannot talk to other nodes that also have no
		206	binds, but it can still talk to all "normal" nodes).
		207
		208	If the profile does not specify a binds list, then a default of C<*> is
		209	used, meaning the node will bind on a dynamically-assigned port on every
		210	local IP address it finds.
		211
		212	=item step 3, connect to seed nodes
		213
		214	As the last step, the seeds list from the profile is passed to the
		215	L<AnyEvent::MP::Global> module, which will then use it to keep
		216	connectivity with at least one node at any point in time.
158		217
159	=back	218	=back
		219
		220	Example: become a distributed node using the locla node name as profile.
		221	This should be the most common form of invocation for "daemon"-type nodes.
		222
		223	configure
		224
		225	Example: become an anonymous node. This form is often used for commandline
		226	clients.
		227
		228	configure nodeid => "anon/";
		229
		230	Example: configure a node using a profile called seed, which si suitable
		231	for a seed node as it binds on all local addresses on a fixed port (4040,
		232	customary for aemp).
		233
		234	# use the aemp commandline utility
		235	# aemp profile seed nodeid anon/ binds '*:4040'
		236
		237	# then use it
		238	configure profile => "seed";
		239
		240	# or simply use aemp from the shell again:
		241	# aemp run profile seed
		242
		243	# or provide a nicer-to-remember nodeid
		244	# aemp run profile seed nodeid "$(hostname)"
160		245
161	=item $SELF	246	=item $SELF
162		247
163	Contains the current port id while executing C<rcv> callbacks or C<psub>	248	Contains the current port id while executing C<rcv> callbacks or C<psub>
164	blocks.	249	blocks.
165		250
166	=item SELF, %SELF, @SELF...	251	=item *SELF, SELF, %SELF, @SELF...
167		252
168	Due to some quirks in how perl exports variables, it is impossible to	253	Due to some quirks in how perl exports variables, it is impossible to
169	just export C<$SELF>, all the symbols called C<SELF> are exported by this	254	just export C<$SELF>, all the symbols named C<SELF> are exported by this
170	module, but only C<$SELF> is currently used.	255	module, but only C<$SELF> is currently used.
171		256
172	=item snd $port, type => @data	257	=item snd $port, type => @data
173		258
174	=item snd $port, @msg	259	=item snd $port, @msg
175		260
176	Send the given message to the given port ID, which can identify either	261	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	262	local or a remote port, and must be a port ID.
178	stringifies a sa port ID (such as a port object :).
179		263
180	While the message can be about anything, it is highly recommended to use a	264	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	265	use a string as first element (a port ID, or some word that indicates a
182	type etc.).	266	request type etc.) and to consist if only simple perl values (scalars,
		267	arrays, hashes) - if you think you need to pass an object, think again.
183		268
184	The message data effectively becomes read-only after a call to this	269	The message data logically becomes read-only after a call to this
185	function: modifying any argument is not allowed and can cause many	270	function: modifying any argument (or values referenced by them) is
186	problems.	271	forbidden, as there can be considerable time between the call to C<snd>
		272	and the time the message is actually being serialised - in fact, it might
		273	never be copied as within the same process it is simply handed to the
		274	receiving port.
187		275
188	The type of data you can transfer depends on the transport protocol: when	276	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	277	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	278	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	279	that Storable can serialise and deserialise is allowed, and for the local
192	node, anything can be passed.	280	node, anything can be passed. Best rely only on the common denominator of
		281	these.
193		282
194	=item $local_port = port	283	=item $local_port = port
195		284
196	Create a new local port object that can be used either as a pattern	285	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"),	286	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		287
200	=item $port = port { my @msg = @_; $finished }	288	=item $local_port = port { my @msg = @_ }
201		289
202	Creates a "miniport", that is, a very lightweight port without any pattern	290	Creates a new local port, and returns its ID. Semantically the same as
203	matching behind it, and returns its ID. Semantically the same as creating
204	a port and calling C<rcv $port, $callback> on it.	291	creating a port and calling C<rcv $port, $callback> on it.
205		292
206	The block will be called for every message received on the port. When the	293	The block will be called for every message received on the port, with the
207	callback returns a true value its job is considered "done" and the port	294	global variable C<$SELF> set to the port ID. Runtime errors will cause the
208	will be destroyed. Otherwise it will stay alive.	295	port to be C<kil>ed. The message will be passed as-is, no extra argument
		296	(i.e. no port ID) will be passed to the callback.
209		297
210	The message will be passed as-is, no extra argument (i.e. no port id) will	298	If you want to stop/destroy the port, simply C<kil> it:
211	be passed to the callback.
212		299
213	If you need the local port id in the callback, this works nicely:	300	my $port = port {
214		301	my @msg = @_;
215	my $port; $port = port {	302	...
216	snd $otherport, reply => $port;	303	kil $SELF;
217	};	304	};
218		305
219	=cut	306	=cut
220		307
221	sub rcv($@);	308	sub rcv($@);
		309
		310	sub _kilme {
		311	die "received message on port without callback";
		312	}
222		313
223	sub port(;&) {	314	sub port(;&) {
224	my $id = "$UNIQ." . $ID++;	315	my $id = "$UNIQ." . $ID++;
225	my $port = "$NODE#$id";	316	my $port = "$NODE#$id";
226		317
227	if (@_) {	318	rcv $port, shift \|\| \&_kilme;
228	rcv $port, shift;
229	} else {
230	$PORT{$id} = sub { }; # nop
231	}
232		319
233	$port	320	$port
234	}	321	}
235		322
236	=item reg $port, $name
237
238	Registers the given port under the name C<$name>. If the name already
239	exists it is replaced.
240
241	A port can only be registered under one well known name.
242
243	A port automatically becomes unregistered when it is killed.
244
245	=cut
246
247	sub reg(@) {
248	my ($port, $name) = @_;
249
250	$REG{$name} = $port;
251	}
252
253	=item rcv $port, $callback->(@msg)	323	=item rcv $local_port, $callback->(@msg)
254		324
255	Replaces the callback on the specified miniport (after converting it to	325	Replaces the default callback on the specified port. There is no way to
256	one if required).	326	remove the default callback: use C<sub { }> to disable it, or better
257		327	C<kil> the port when it is no longer needed.
258	=item rcv $port, tagstring => $callback->(@msg), ...
259
260	=item rcv $port, $smartmatch => $callback->(@msg), ...
261
262	=item rcv $port, [$smartmatch...] => $callback->(@msg), ...
263
264	Register callbacks to be called on matching messages on the given full
265	port (after converting it to one if required).
266
267	The callback has to return a true value when its work is done, after
268	which is will be removed, or a false value in which case it will stay
269	registered.
270		328
271	The global C<$SELF> (exported by this module) contains C<$port> while	329	The global C<$SELF> (exported by this module) contains C<$port> while
272	executing the callback.	330	executing the callback. Runtime errors during callback execution will
		331	result in the port being C<kil>ed.
273		332
274	Runtime errors wdurign callback execution will result in the port being	333	The default callback received all messages not matched by a more specific
275	C<kil>ed.	334	C<tag> match.
276		335
277	If the match is an array reference, then it will be matched against the	336	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
278	first elements of the message, otherwise only the first element is being
279	matched.
280		337
281	Any element in the match that is specified as C<_any_> (a function	338	Register (or replace) callbacks to be called on messages starting with the
282	exported by this module) matches any single element of the message.	339	given tag on the given port (and return the port), or unregister it (when
		340	C<$callback> is C<$undef> or missing). There can only be one callback
		341	registered for each tag.
283		342
284	While not required, it is highly recommended that the first matching	343	The original message will be passed to the callback, after the first
285	element is a string identifying the message. The one-string-only match is	344	element (the tag) has been removed. The callback will use the same
286	also the most efficient match (by far).	345	environment as the default callback (see above).
		346
		347	Example: create a port and bind receivers on it in one go.
		348
		349	my $port = rcv port,
		350	msg1 => sub { ... },
		351	msg2 => sub { ... },
		352	;
		353
		354	Example: create a port, bind receivers and send it in a message elsewhere
		355	in one go:
		356
		357	snd $otherport, reply =>
		358	rcv port,
		359	msg1 => sub { ... },
		360	...
		361	;
		362
		363	Example: temporarily register a rcv callback for a tag matching some port
		364	(e.g. for a rpc reply) and unregister it after a message was received.
		365
		366	rcv $port, $otherport => sub {
		367	my @reply = @_;
		368
		369	rcv $SELF, $otherport;
		370	};
287		371
288	=cut	372	=cut
289		373
290	sub rcv($@) {	374	sub rcv($@) {
291	my $port = shift;	375	my $port = shift;
292	my ($noderef, $portid) = split /#/, $port, 2;	376	my ($nodeid, $portid) = split /#/, $port, 2;
293		377
294	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	378	$NODE{$nodeid} == $NODE{""}
295	or Carp::croak "$port: rcv can only be called on local ports, caught";	379	or Carp::croak "$port: rcv can only be called on local ports, caught";
296		380
297	if (@_ == 1) {	381	while (@_) {
		382	if (ref $_[0]) {
		383	if (my $self = $PORT_DATA{$portid}) {
		384	"AnyEvent::MP::Port" eq ref $self
		385	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		386
		387	$self->[2] = shift;
		388	} else {
298	my $cb = shift;	389	my $cb = shift;
299	delete $PORT_DATA{$portid};
300	$PORT{$portid} = sub {	390	$PORT{$portid} = sub {
301	local $SELF = $port;	391	local $SELF = $port;
302	eval {	392	eval { &$cb }; _self_die if $@;
303	&$cb	393	};
304	and kil $port;
305	};	394	}
306	_self_die if $@;	395	} elsif (defined $_[0]) {
307	};
308	} else {
309	my $self = $PORT_DATA{$portid} \|\|= do {	396	my $self = $PORT_DATA{$portid} \|\|= do {
310	my $self = bless {	397	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
311	id => $port,
312	}, "AnyEvent::MP::Port";
313		398
314	$PORT{$portid} = sub {	399	$PORT{$portid} = sub {
315	local $SELF = $port;	400	local $SELF = $port;
316		401
317	eval {
318	for (@{ $self->{rc0}{$_[0]} }) {	402	if (my $cb = $self->[1]{$_[0]}) {
319	$_ && &{$_->[0]}	403	shift;
320	&& undef $_;	404	eval { &$cb }; _self_die if $@;
321	}	405	} else {
322
323	for (@{ $self->{rcv}{$_[0]} }) {
324	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
325	&& &{$_->[0]}	406	&{ $self->[0] };
326	&& undef $_;
327	}
328
329	for (@{ $self->{any} }) {
330	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
331	&& &{$_->[0]}
332	&& undef $_;
333	}	407	}
334	};	408	};
335	_self_die if $@;	409
		410	$self
336	};	411	};
337		412
338	$self
339	};
340
341	"AnyEvent::MP::Port" eq ref $self	413	"AnyEvent::MP::Port" eq ref $self
342	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	414	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
343		415
344	while (@_) {
345	my ($match, $cb) = splice @_, 0, 2;	416	my ($tag, $cb) = splice @_, 0, 2;
346		417
347	if (!ref $match) {	418	if (defined $cb) {
348	push @{ $self->{rc0}{$match} }, [$cb];	419	$self->[1]{$tag} = $cb;
349	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
350	my ($type, @match) = @$match;
351	@match
352	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
353	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
354	} else {	420	} else {
355	push @{ $self->{any} }, [$cb, $match];	421	delete $self->[1]{$tag};
356	}	422	}
357	}	423	}
358	}	424	}
359		425
360	$port	426	$port
…		…
396	$res	462	$res
397	}	463	}
398	}	464	}
399	}	465	}
400		466
401	=item $guard = mon $port, $cb->(@reason)	467	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
402		468
403	=item $guard = mon $port, $otherport	469	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
404		470
405	=item $guard = mon $port, $otherport, @msg	471	=item $guard = mon $port # kill $SELF when $port dies
406		472
		473	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
		474
407	Monitor the given port and do something when the port is killed.	475	Monitor the given port and do something when the port is killed or
		476	messages to it were lost, and optionally return a guard that can be used
		477	to stop monitoring again.
408		478
		479	C<mon> effectively guarantees that, in the absence of hardware failures,
		480	after starting the monitor, either all messages sent to the port will
		481	arrive, or the monitoring action will be invoked after possible message
		482	loss has been detected. No messages will be lost "in between" (after
		483	the first lost message no further messages will be received by the
		484	port). After the monitoring action was invoked, further messages might get
		485	delivered again.
		486
		487	Note that monitoring-actions are one-shot: once messages are lost (and a
		488	monitoring alert was raised), they are removed and will not trigger again.
		489
409	In the first form, the callback is simply called with any number	490	In the first form (callback), the callback is simply called with any
410	of C<@reason> elements (no @reason means that the port was deleted	491	number of C<@reason> elements (no @reason means that the port was deleted
411	"normally"). Note also that I<< the callback B<must> never die >>, so use	492	"normally"). Note also that I<< the callback B<must> never die >>, so use
412	C<eval> if unsure.	493	C<eval> if unsure.
413		494
414	In the second form, the other port will be C<kil>'ed with C<@reason>, iff	495	In the second form (another port given), the other port (C<$rcvport>)
415	a @reason was specified, i.e. on "normal" kils nothing happens, while	496	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
416	under all other conditions, the other port is killed with the same reason.	497	"normal" kils nothing happens, while under all other conditions, the other
		498	port is killed with the same reason.
417		499
		500	The third form (kill self) is the same as the second form, except that
		501	C<$rvport> defaults to C<$SELF>.
		502
418	In the last form, a message of the form C<@msg, @reason> will be C<snd>.	503	In the last form (message), a message of the form C<@msg, @reason> will be
		504	C<snd>.
		505
		506	As a rule of thumb, monitoring requests should always monitor a port from
		507	a local port (or callback). The reason is that kill messages might get
		508	lost, just like any other message. Another less obvious reason is that
		509	even monitoring requests can get lost (for exmaple, when the connection
		510	to the other node goes down permanently). When monitoring a port locally
		511	these problems do not exist.
419		512
420	Example: call a given callback when C<$port> is killed.	513	Example: call a given callback when C<$port> is killed.
421		514
422	mon $port, sub { warn "port died because of <@_>\n" };	515	mon $port, sub { warn "port died because of <@_>\n" };
423		516
424	Example: kill ourselves when C<$port> is killed abnormally.	517	Example: kill ourselves when C<$port> is killed abnormally.
425		518
426	mon $port, $self;	519	mon $port;
427		520
428	Example: send us a restart message another C<$port> is killed.	521	Example: send us a restart message when another C<$port> is killed.
429		522
430	mon $port, $self => "restart";	523	mon $port, $self => "restart";
431		524
432	=cut	525	=cut
433		526
434	sub mon {	527	sub mon {
435	my ($noderef, $port) = split /#/, shift, 2;	528	my ($nodeid, $port) = split /#/, shift, 2;
436		529
437	my $node = $NODE{$noderef} \|\| add_node $noderef;	530	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
438		531
439	my $cb = shift;	532	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
440		533
441	unless (ref $cb) {	534	unless (ref $cb) {
442	if (@_) {	535	if (@_) {
443	# send a kill info message	536	# send a kill info message
444	my (@msg) = ($cb, @_);	537	my (@msg) = ($cb, @_);
…		…
462	is killed, the references will be freed.	555	is killed, the references will be freed.
463		556
464	Optionally returns a guard that will stop the monitoring.	557	Optionally returns a guard that will stop the monitoring.
465		558
466	This function is useful when you create e.g. timers or other watchers and	559	This function is useful when you create e.g. timers or other watchers and
467	want to free them when the port gets killed:	560	want to free them when the port gets killed (note the use of C<psub>):
468		561
469	$port->rcv (start => sub {	562	$port->rcv (start => sub {
470	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	563	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
471	undef $timer if 0.9 < rand;	564	undef $timer if 0.9 < rand;
472	});	565	});
473	});	566	});
474		567
475	=cut	568	=cut
476		569
477	sub mon_guard {	570	sub mon_guard {
478	my ($port, @refs) = @_;	571	my ($port, @refs) = @_;
479		572
		573	#TODO: mon-less form?
		574
480	mon $port, sub { 0 && @refs }	575	mon $port, sub { 0 && @refs }
481	}	576	}
482		577
483	=item lnk $port1, $port2
484
485	Link two ports. This is simply a shorthand for:
486
487	mon $port1, $port2;
488	mon $port2, $port1;
489
490	It means that if either one is killed abnormally, the other one gets
491	killed as well.
492
493	=item kil $port[, @reason]	578	=item kil $port[, @reason]
494		579
495	Kill the specified port with the given C<@reason>.	580	Kill the specified port with the given C<@reason>.
496		581
497	If no C<@reason> is specified, then the port is killed "normally" (linked	582	If no C<@reason> is specified, then the port is killed "normally" (ports
498	ports will not be kileld, or even notified).	583	monitoring other ports will not necessarily die because a port dies
		584	"normally").
499		585
500	Otherwise, linked ports get killed with the same reason (second form of	586	Otherwise, linked ports get killed with the same reason (second form of
501	C<mon>, see below).	587	C<mon>, see above).
502		588
503	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	589	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
504	will be reported as reason C<< die => $@ >>.	590	will be reported as reason C<< die => $@ >>.
505		591
506	Transport/communication errors are reported as C<< transport_error =>	592	Transport/communication errors are reported as C<< transport_error =>
507	$message >>.	593	$message >>.
508		594
		595	=cut
		596
		597	=item $port = spawn $node, $initfunc[, @initdata]
		598
		599	Creates a port on the node C<$node> (which can also be a port ID, in which
		600	case it's the node where that port resides).
		601
		602	The port ID of the newly created port is returned immediately, and it is
		603	possible to immediately start sending messages or to monitor the port.
		604
		605	After the port has been created, the init function is called on the remote
		606	node, in the same context as a C<rcv> callback. This function must be a
		607	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
		608	specify a function in the main program, use C<::name>.
		609
		610	If the function doesn't exist, then the node tries to C<require>
		611	the package, then the package above the package and so on (e.g.
		612	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
		613	exists or it runs out of package names.
		614
		615	The init function is then called with the newly-created port as context
		616	object (C<$SELF>) and the C<@initdata> values as arguments.
		617
		618	A common idiom is to pass a local port, immediately monitor the spawned
		619	port, and in the remote init function, immediately monitor the passed
		620	local port. This two-way monitoring ensures that both ports get cleaned up
		621	when there is a problem.
		622
		623	Example: spawn a chat server port on C<$othernode>.
		624
		625	# this node, executed from within a port context:
		626	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
		627	mon $server;
		628
		629	# init function on C<$othernode>
		630	sub connect {
		631	my ($srcport) = @_;
		632
		633	mon $srcport;
		634
		635	rcv $SELF, sub {
		636	...
		637	};
		638	}
		639
		640	=cut
		641
		642	sub _spawn {
		643	my $port = shift;
		644	my $init = shift;
		645
		646	local $SELF = "$NODE#$port";
		647	eval {
		648	&{ load_func $init }
		649	};
		650	_self_die if $@;
		651	}
		652
		653	sub spawn(@) {
		654	my ($nodeid, undef) = split /#/, shift, 2;
		655
		656	my $id = "$RUNIQ." . $ID++;
		657
		658	$_[0] =~ /::/
		659	or Carp::croak "spawn init function must be a fully-qualified name, caught";
		660
		661	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
		662
		663	"$nodeid#$id"
		664	}
		665
		666	=item after $timeout, @msg
		667
		668	=item after $timeout, $callback
		669
		670	Either sends the given message, or call the given callback, after the
		671	specified number of seconds.
		672
		673	This is simply a utility function that comes in handy at times - the
		674	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		675	so it may go away in the future.
		676
		677	=cut
		678
		679	sub after($@) {
		680	my ($timeout, @action) = @_;
		681
		682	my $t; $t = AE::timer $timeout, 0, sub {
		683	undef $t;
		684	ref $action[0]
		685	? $action[0]()
		686	: snd @action;
		687	};
		688	}
		689
509	=back	690	=back
510		691
511	=head1 FUNCTIONS FOR NODES	692	=head1 AnyEvent::MP vs. Distributed Erlang
		693
		694	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
		695	== aemp node, Erlang process == aemp port), so many of the documents and
		696	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
		697	sample:
		698
		699	http://www.Erlang.se/doc/programming_rules.shtml
		700	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
		701	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6
		702	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
		703
		704	Despite the similarities, there are also some important differences:
512		705
513	=over 4	706	=over 4
514		707
515	=item initialise_node $noderef, $seednode, $seednode...	708	=item * Node IDs are arbitrary strings in AEMP.
516		709
517	=item initialise_node "slave/", $master, $master...
518
519	Initialises a node - must be called exactly once before calling other
520	AnyEvent::MP functions when talking to other nodes is required.
521
522	All arguments are noderefs, which can be either resolved or unresolved.
523
524	There are two types of networked nodes, public nodes and slave nodes:
525
526	=over 4
527
528	=item public nodes
529
530	For public nodes, C<$noderef> must either be a (possibly unresolved)
531	noderef, in which case it will be resolved, or C<undef> (or missing), in
532	which case the noderef will be guessed.
533
534	Afterwards, the node will bind itself on all endpoints and try to connect
535	to all additional C<$seednodes> that are specified. Seednodes are optional
536	and can be used to quickly bootstrap the node into an existing network.
537
538	=item slave nodes
539
540	When the C<$noderef> is the special string C<slave/>, then the node will
541	become a slave node. Slave nodes cannot be contacted from outside and will
542	route most of their traffic to the master node that they attach to.
543
544	At least one additional noderef is required: The node will try to connect
545	to all of them and will become a slave attached to the first node it can
546	successfully connect to.
547
548	=back
549
550	This function will block until all nodes have been resolved and, for slave
551	nodes, until it has successfully established a connection to a master
552	server.
553
554	Example: become a public node listening on the default node.
555
556	initialise_node;
557
558	Example: become a public node, and try to contact some well-known master
559	servers to become part of the network.
560
561	initialise_node undef, "master1", "master2";
562
563	Example: become a public node listening on port C<4041>.
564
565	initialise_node 4041;
566
567	Example: become a public node, only visible on localhost port 4044.
568
569	initialise_node "locahost:4044";
570
571	Example: become a slave node to any of the specified master servers.
572
573	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
574
575	=cut
576
577	=back
578
579	=head1 NODE MESSAGES
580
581	Nodes understand the following messages sent to them. Many of them take
582	arguments called C<@reply>, which will simply be used to compose a reply
583	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
584	the remaining arguments are simply the message data.
585
586	While other messages exist, they are not public and subject to change.
587
588	=over 4
589
590	=cut
591
592	=item lookup => $name, @reply
593
594	Replies with the port ID of the specified well-known port, or C<undef>.
595
596	=item devnull => ...
597
598	Generic data sink/CPU heat conversion.
599
600	=item relay => $port, @msg
601
602	Simply forwards the message to the given port.
603
604	=item eval => $string[ @reply]
605
606	Evaluates the given string. If C<@reply> is given, then a message of the
607	form C<@reply, $@, @evalres> is sent.
608
609	Example: crash another node.
610
611	snd $othernode, eval => "exit";
612
613	=item time => @reply
614
615	Replies the the current node time to C<@reply>.
616
617	Example: tell the current node to send the current time to C<$myport> in a
618	C<timereply> message.
619
620	snd $NODE, time => $myport, timereply => 1, 2;
621	# => snd $myport, timereply => 1, 2, <time>
622
623	=back
624
625	=head1 AnyEvent::MP vs. Distributed Erlang
626
627	AnyEvent::MP got lots of its ideas from distributed erlang (erlang node
628	== aemp node, erlang process == aemp port), so many of the documents and
629	programming techniques employed by erlang apply to AnyEvent::MP. Here is a
630	sample:
631
632	http://www.erlang.se/doc/programming_rules.shtml
633	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
634	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
635	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
636
637	Despite the similarities, there are also some important differences:
638
639	=over 4
640
641	=item * Node references contain the recipe on how to contact them.
642
643	Erlang relies on special naming and DNS to work everywhere in the	710	Erlang relies on special naming and DNS to work everywhere in the same
644	same way. AEMP relies on each node knowing it's own address(es), with	711	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
645	convenience functionality.	712	configuraiton or DNS), but will otherwise discover other odes itself.
646		713
647	This means that AEMP requires a less tightly controlled environment at the	714	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
648	cost of longer node references and a slightly higher management overhead.	715	uses "local ports are like remote ports".
		716
		717	The failure modes for local ports are quite different (runtime errors
		718	only) then for remote ports - when a local port dies, you I<know> it dies,
		719	when a connection to another node dies, you know nothing about the other
		720	port.
		721
		722	Erlang pretends remote ports are as reliable as local ports, even when
		723	they are not.
		724
		725	AEMP encourages a "treat remote ports differently" philosophy, with local
		726	ports being the special case/exception, where transport errors cannot
		727	occur.
649		728
650	=item * Erlang uses processes and a mailbox, AEMP does not queue.	729	=item * Erlang uses processes and a mailbox, AEMP does not queue.
651		730
652	Erlang uses processes that selctively receive messages, and therefore	731	Erlang uses processes that selectively receive messages, and therefore
653	needs a queue. AEMP is event based, queuing messages would serve no useful	732	needs a queue. AEMP is event based, queuing messages would serve no
654	purpose.	733	useful purpose. For the same reason the pattern-matching abilities of
		734	AnyEvent::MP are more limited, as there is little need to be able to
		735	filter messages without dequeing them.
655		736
656	(But see L<Coro::MP> for a more erlang-like process model on top of AEMP).	737	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
657		738
658	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	739	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
659		740
660	Sending messages in erlang is synchronous and blocks the process. AEMP	741	Sending messages in Erlang is synchronous and blocks the process (and
661	sends are immediate, connection establishment is handled in the	742	so does not need a queue that can overflow). AEMP sends are immediate,
662	background.	743	connection establishment is handled in the background.
663		744
664	=item * Erlang can silently lose messages, AEMP cannot.	745	=item * Erlang suffers from silent message loss, AEMP does not.
665		746
666	Erlang makes few guarantees on messages delivery - messages can get lost	747	Erlang makes few guarantees on messages delivery - messages can get lost
667	without any of the processes realising it (i.e. you send messages a, b,	748	without any of the processes realising it (i.e. you send messages a, b,
668	and c, and the other side only receives messages a and c).	749	and c, and the other side only receives messages a and c).
669		750
670	AEMP guarantees correct ordering, and the guarantee that there are no	751	AEMP guarantees correct ordering, and the guarantee that after one message
671	holes in the message sequence.	752	is lost, all following ones sent to the same port are lost as well, until
672		753	monitoring raises an error, so there are no silent "holes" in the message
673	=item * In erlang, processes can be declared dead and later be found to be	754	sequence.
674	alive.
675
676	In erlang it can happen that a monitored process is declared dead and
677	linked processes get killed, but later it turns out that the process is
678	still alive - and can receive messages.
679
680	In AEMP, when port monitoring detects a port as dead, then that port will
681	eventually be killed - it cannot happen that a node detects a port as dead
682	and then later sends messages to it, finding it is still alive.
683		755
684	=item * Erlang can send messages to the wrong port, AEMP does not.	756	=item * Erlang can send messages to the wrong port, AEMP does not.
685		757
686	In erlang it is quite possible that a node that restarts reuses a process	758	In Erlang it is quite likely that a node that restarts reuses a process ID
687	ID known to other nodes for a completely different process, causing	759	known to other nodes for a completely different process, causing messages
688	messages destined for that process to end up in an unrelated process.	760	destined for that process to end up in an unrelated process.
689		761
690	AEMP never reuses port IDs, so old messages or old port IDs floating	762	AEMP never reuses port IDs, so old messages or old port IDs floating
691	around in the network will not be sent to an unrelated port.	763	around in the network will not be sent to an unrelated port.
692		764
693	=item * Erlang uses unprotected connections, AEMP uses secure	765	=item * Erlang uses unprotected connections, AEMP uses secure
694	authentication and can use TLS.	766	authentication and can use TLS.
695		767
696	AEMP can use a proven protocol - SSL/TLS - to protect connections and	768	AEMP can use a proven protocol - TLS - to protect connections and
697	securely authenticate nodes.	769	securely authenticate nodes.
698		770
699	=item * The AEMP protocol is optimised for both text-based and binary	771	=item * The AEMP protocol is optimised for both text-based and binary
700	communications.	772	communications.
701		773
702	The AEMP protocol, unlike the erlang protocol, supports both	774	The AEMP protocol, unlike the Erlang protocol, supports both programming
703	language-independent text-only protocols (good for debugging) and binary,	775	language independent text-only protocols (good for debugging) and binary,
704	language-specific serialisers (e.g. Storable).	776	language-specific serialisers (e.g. Storable). By default, unless TLS is
		777	used, the protocol is actually completely text-based.
705		778
706	It has also been carefully designed to be implementable in other languages	779	It has also been carefully designed to be implementable in other languages
707	with a minimum of work while gracefully degrading fucntionality to make the	780	with a minimum of work while gracefully degrading functionality to make the
708	protocol simple.	781	protocol simple.
709		782
		783	=item * AEMP has more flexible monitoring options than Erlang.
		784
		785	In Erlang, you can chose to receive I<all> exit signals as messages
		786	or I<none>, there is no in-between, so monitoring single processes is
		787	difficult to implement. Monitoring in AEMP is more flexible than in
		788	Erlang, as one can choose between automatic kill, exit message or callback
		789	on a per-process basis.
		790
		791	=item * Erlang tries to hide remote/local connections, AEMP does not.
		792
		793	Monitoring in Erlang is not an indicator of process death/crashes, in the
		794	same way as linking is (except linking is unreliable in Erlang).
		795
		796	In AEMP, you don't "look up" registered port names or send to named ports
		797	that might or might not be persistent. Instead, you normally spawn a port
		798	on the remote node. The init function monitors you, and you monitor the
		799	remote port. Since both monitors are local to the node, they are much more
		800	reliable (no need for C<spawn_link>).
		801
		802	This also saves round-trips and avoids sending messages to the wrong port
		803	(hard to do in Erlang).
		804
710	=back	805	=back
711		806
		807	=head1 RATIONALE
		808
		809	=over 4
		810
		811	=item Why strings for port and node IDs, why not objects?
		812
		813	We considered "objects", but found that the actual number of methods
		814	that can be called are quite low. Since port and node IDs travel over
		815	the network frequently, the serialising/deserialising would add lots of
		816	overhead, as well as having to keep a proxy object everywhere.
		817
		818	Strings can easily be printed, easily serialised etc. and need no special
		819	procedures to be "valid".
		820
		821	And as a result, a miniport consists of a single closure stored in a
		822	global hash - it can't become much cheaper.
		823
		824	=item Why favour JSON, why not a real serialising format such as Storable?
		825
		826	In fact, any AnyEvent::MP node will happily accept Storable as framing
		827	format, but currently there is no way to make a node use Storable by
		828	default (although all nodes will accept it).
		829
		830	The default framing protocol is JSON because a) JSON::XS is many times
		831	faster for small messages and b) most importantly, after years of
		832	experience we found that object serialisation is causing more problems
		833	than it solves: Just like function calls, objects simply do not travel
		834	easily over the network, mostly because they will always be a copy, so you
		835	always have to re-think your design.
		836
		837	Keeping your messages simple, concentrating on data structures rather than
		838	objects, will keep your messages clean, tidy and efficient.
		839
		840	=back
		841
712	=head1 SEE ALSO	842	=head1 SEE ALSO
		843
		844	L<AnyEvent::MP::Intro> - a gentle introduction.
		845
		846	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		847
		848	L<AnyEvent::MP::Global> - network maintainance and port groups, to find
		849	your applications.
713		850
714	L<AnyEvent>.	851	L<AnyEvent>.
715		852
716	=head1 AUTHOR	853	=head1 AUTHOR
717		854

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Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.33 by root, Wed Aug 5 22:40:51 2009 UTC vs. Revision 1.75 by root, Mon Aug 31 13:18:06 2009 UTC

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Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.33 by root, Wed Aug 5 22:40:51 2009 UTC vs.
Revision 1.75 by root, Mon Aug 31 13:18:06 2009 UTC