[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 1.83 by root, Tue Sep 8 01:38:16 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 - explains most concepts.
		45	AnyEvent::MP::Kernel - mostly stable.
		46	AnyEvent::MP::Global - stable but incomplete, 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
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		59
42	=head1 CONCEPTS	60	=head1 CONCEPTS
43		61
44	=over 4	62	=over 4
45		63
46	=item port	64	=item port
47		65
48	A port is something you can send messages to (with the C<snd> function).	66	Not to be confused with a TCP port, a "port" is something you can send
		67	messages to (with the C<snd> function).
49		68
50	Some ports allow you to register C<rcv> handlers that can match specific	69	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	70	some messages. Messages send to ports will not be queued, regardless of
52	will not be queued.	71	anything was listening for them or not.
53		72
54	=item port id - C<noderef#portname>	73	=item port ID - C<nodeid#portname>
55		74
56	A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as	75	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	76	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		77
61	=item node	78	=item node
62		79
63	A node is a single process containing at least one port - the node	80	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	81	which enables nodes to manage each other remotely, and to create new
65	create new ports, among other things.	82	ports.
66		83
67	Nodes are either private (single-process only), slaves (connected to a	84	Nodes are either public (have one or more listening ports) or private
68	master node only) or public nodes (connectable from unrelated nodes).	85	(no listening ports). Private nodes cannot talk to other private nodes
		86	currently.
69		87
70	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	88	=item node ID - C<[a-za-Z0-9_\-.:]+>
71		89
72	A node reference is a string that either simply identifies the node (for	90	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	91	network. Depending on the configuration used, node IDs can look like a
74	node (for public nodes).	92	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		93	doesn't interpret node IDs in any way.
75		94
76	This recipe is simply a comma-separated list of C<address:port> pairs (for	95	=item binds - C<ip:port>
77	TCP/IP, other protocols might look different).
78		96
79	Node references come in two flavours: resolved (containing only numerical	97	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).	98	each other. To do this, nodes should listen on one or more local transport
		99	endpoints - binds. Currently, only standard C<ip:port> specifications can
		100	be used, which specify TCP ports to listen on.
81		101
82	Before using an unresolved node reference in a message you first have to	102	=item seed nodes
83	resolve it.	103
		104	When a node starts, it knows nothing about the network. To teach the node
		105	about the network it first has to contact some other node within the
		106	network. This node is called a seed.
		107
		108	Apart from the fact that other nodes know them as seed nodes and they have
		109	to have fixed listening addresses, seed nodes are perfectly normal nodes -
		110	any node can function as a seed node for others.
		111
		112	In addition to discovering the network, seed nodes are also used to
		113	maintain the network and to connect nodes that otherwise would have
		114	trouble connecting. They form the backbone of the AnyEvent::MP network.
		115
		116	Seed nodes are expected to be long-running, and at least one seed node
		117	should always be available.
		118
		119	=item seeds - C<host:port>
		120
		121	Seeds are transport endpoint(s) (usually a hostname/IP address and a
		122	TCP port) of nodes thta should be used as seed nodes.
		123
		124	The nodes listening on those endpoints are expected to be long-running,
		125	and at least one of those should always be available. When nodes run out
		126	of connections (e.g. due to a network error), they try to re-establish
		127	connections to some seednodes again to join the network.
84		128
85	=back	129	=back
86		130
87	=head1 VARIABLES/FUNCTIONS	131	=head1 VARIABLES/FUNCTIONS
88		132
…		…
90		134
91	=cut	135	=cut
92		136
93	package AnyEvent::MP;	137	package AnyEvent::MP;
94		138
95	use AnyEvent::MP::Base;	139	use AnyEvent::MP::Kernel;
96		140
97	use common::sense;	141	use common::sense;
98		142
99	use Carp ();	143	use Carp ();
100		144
101	use AE ();	145	use AE ();
102		146
103	use base "Exporter";	147	use base "Exporter";
104		148
105	our $VERSION = '0.1';	149	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
		150
106	our @EXPORT = qw(	151	our @EXPORT = qw(
107	NODE $NODE *SELF node_of _any_	152	NODE $NODE *SELF node_of after
108	resolve_node initialise_node	153	configure
109	snd rcv mon kil reg psub	154	snd rcv mon mon_guard kil reg psub spawn
110	port	155	port
111	);	156	);
112		157
113	our $SELF;	158	our $SELF;
114		159
…		…
118	kil $SELF, die => $msg;	163	kil $SELF, die => $msg;
119	}	164	}
120		165
121	=item $thisnode = NODE / $NODE	166	=item $thisnode = NODE / $NODE
122		167
123	The C<NODE> function returns, and the C<$NODE> variable contains	168	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	169	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	170	a call to C<configure>.
126	identifiers become invalid.
127		171
128	=item $noderef = node_of $port	172	=item $nodeid = node_of $port
129		173
130	Extracts and returns the noderef from a portid or a noderef.	174	Extracts and returns the node ID from a port ID or a node ID.
131		175
132	=item $cv = resolve_node $noderef	176	=item configure $profile, key => value...
133		177
134	Takes an unresolved node reference that may contain hostnames and	178	=item configure key => value...
135	abbreviated IDs, resolves all of them and returns a resolved node
136	reference.
137		179
138	In addition to C<address:port> pairs allowed in resolved noderefs, the	180	Before a node can talk to other nodes on the network (i.e. enter
139	following forms are supported:	181	"distributed mode") it has to configure itself - the minimum a node needs
		182	to know is its own name, and optionally it should know the addresses of
		183	some other nodes in the network to discover other nodes.
		184
		185	This function configures a node - it must be called exactly once (or
		186	never) before calling other AnyEvent::MP functions.
140		187
141	=over 4	188	=over 4
142		189
143	=item the empty string	190	=item step 1, gathering configuration from profiles
144		191
145	An empty-string component gets resolved as if the default port (4040) was	192	The function first looks up a profile in the aemp configuration (see the
146	specified.	193	L<aemp> commandline utility). The profile name can be specified via the
		194	named C<profile> parameter or can simply be the first parameter). If it is
		195	missing, then the nodename (F<uname -n>) will be used as profile name.
147		196
148	=item naked port numbers (e.g. C<1234>)	197	The profile data is then gathered as follows:
149		198
150	These are resolved by prepending the local nodename and a colon, to be	199	First, all remaining key => value pairs (all of which are conveniently
151	further resolved.	200	undocumented at the moment) will be interpreted as configuration
		201	data. Then they will be overwritten by any values specified in the global
		202	default configuration (see the F<aemp> utility), then the chain of
		203	profiles chosen by the profile name (and any C<parent> attributes).
152		204
153	=item hostnames (e.g. C<localhost:1234>, C<localhost>)	205	That means that the values specified in the profile have highest priority
		206	and the values specified directly via C<configure> have lowest priority,
		207	and can only be used to specify defaults.
154		208
155	These are resolved by using AnyEvent::DNS to resolve them, optionally	209	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	210	this process. If not, then the profile name will be used as node ID. The
157	specified.	211	special node ID of C<anon/> will be replaced by a random node ID.
		212
		213	=item step 2, bind listener sockets
		214
		215	The next step is to look up the binds in the profile, followed by binding
		216	aemp protocol listeners on all binds specified (it is possible and valid
		217	to have no binds, meaning that the node cannot be contacted form the
		218	outside. This means the node cannot talk to other nodes that also have no
		219	binds, but it can still talk to all "normal" nodes).
		220
		221	If the profile does not specify a binds list, then a default of C<*> is
		222	used, meaning the node will bind on a dynamically-assigned port on every
		223	local IP address it finds.
		224
		225	=item step 3, connect to seed nodes
		226
		227	As the last step, the seeds list from the profile is passed to the
		228	L<AnyEvent::MP::Global> module, which will then use it to keep
		229	connectivity with at least one node at any point in time.
158		230
159	=back	231	=back
		232
		233	Example: become a distributed node using the locla node name as profile.
		234	This should be the most common form of invocation for "daemon"-type nodes.
		235
		236	configure
		237
		238	Example: become an anonymous node. This form is often used for commandline
		239	clients.
		240
		241	configure nodeid => "anon/";
		242
		243	Example: configure a node using a profile called seed, which si suitable
		244	for a seed node as it binds on all local addresses on a fixed port (4040,
		245	customary for aemp).
		246
		247	# use the aemp commandline utility
		248	# aemp profile seed nodeid anon/ binds '*:4040'
		249
		250	# then use it
		251	configure profile => "seed";
		252
		253	# or simply use aemp from the shell again:
		254	# aemp run profile seed
		255
		256	# or provide a nicer-to-remember nodeid
		257	# aemp run profile seed nodeid "$(hostname)"
160		258
161	=item $SELF	259	=item $SELF
162		260
163	Contains the current port id while executing C<rcv> callbacks or C<psub>	261	Contains the current port id while executing C<rcv> callbacks or C<psub>
164	blocks.	262	blocks.
165		263
166	=item SELF, %SELF, @SELF...	264	=item *SELF, SELF, %SELF, @SELF...
167		265
168	Due to some quirks in how perl exports variables, it is impossible to	266	Due to some quirks in how perl exports variables, it is impossible to
169	just export C<$SELF>, all the symbols called C<SELF> are exported by this	267	just export C<$SELF>, all the symbols named C<SELF> are exported by this
170	module, but only C<$SELF> is currently used.	268	module, but only C<$SELF> is currently used.
171		269
172	=item snd $port, type => @data	270	=item snd $port, type => @data
173		271
174	=item snd $port, @msg	272	=item snd $port, @msg
175		273
176	Send the given message to the given port ID, which can identify either	274	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	275	local or a remote port, and must be a port ID.
178	stringifies a sa port ID (such as a port object :).
179		276
180	While the message can be about anything, it is highly recommended to use a	277	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	278	use a string as first element (a port ID, or some word that indicates a
182	type etc.).	279	request type etc.) and to consist if only simple perl values (scalars,
		280	arrays, hashes) - if you think you need to pass an object, think again.
183		281
184	The message data effectively becomes read-only after a call to this	282	The message data logically becomes read-only after a call to this
185	function: modifying any argument is not allowed and can cause many	283	function: modifying any argument (or values referenced by them) is
186	problems.	284	forbidden, as there can be considerable time between the call to C<snd>
		285	and the time the message is actually being serialised - in fact, it might
		286	never be copied as within the same process it is simply handed to the
		287	receiving port.
187		288
188	The type of data you can transfer depends on the transport protocol: when	289	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	290	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	291	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	292	that Storable can serialise and deserialise is allowed, and for the local
192	node, anything can be passed.	293	node, anything can be passed. Best rely only on the common denominator of
		294	these.
193		295
194	=item $local_port = port	296	=item $local_port = port
195		297
196	Create a new local port object that can be used either as a pattern	298	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"),	299	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		300
200	=item $port = port { my @msg = @_; $finished }	301	=item $local_port = port { my @msg = @_ }
201		302
202	Creates a "miniport", that is, a very lightweight port without any pattern	303	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.	304	creating a port and calling C<rcv $port, $callback> on it.
205		305
206	The block will be called for every message received on the port. When the	306	The block will be called for every message received on the port, with the
207	callback returns a true value its job is considered "done" and the port	307	global variable C<$SELF> set to the port ID. Runtime errors will cause the
208	will be destroyed. Otherwise it will stay alive.	308	port to be C<kil>ed. The message will be passed as-is, no extra argument
		309	(i.e. no port ID) will be passed to the callback.
209		310
210	The message will be passed as-is, no extra argument (i.e. no port id) will	311	If you want to stop/destroy the port, simply C<kil> it:
211	be passed to the callback.
212		312
213	If you need the local port id in the callback, this works nicely:	313	my $port = port {
214		314	my @msg = @_;
215	my $port; $port = port {	315	...
216	snd $otherport, reply => $port;	316	kil $SELF;
217	};	317	};
218		318
219	=cut	319	=cut
220		320
221	sub rcv($@);	321	sub rcv($@);
		322
		323	sub _kilme {
		324	die "received message on port without callback";
		325	}
222		326
223	sub port(;&) {	327	sub port(;&) {
224	my $id = "$UNIQ." . $ID++;	328	my $id = "$UNIQ." . $ID++;
225	my $port = "$NODE#$id";	329	my $port = "$NODE#$id";
226		330
227	if (@_) {	331	rcv $port, shift \|\| \&_kilme;
228	rcv $port, shift;
229	} else {
230	$PORT{$id} = sub { }; # nop
231	}
232		332
233	$port	333	$port
234	}	334	}
235		335
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)	336	=item rcv $local_port, $callback->(@msg)
254		337
255	Replaces the callback on the specified miniport (after converting it to	338	Replaces the default callback on the specified port. There is no way to
256	one if required).	339	remove the default callback: use C<sub { }> to disable it, or better
257		340	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...] => $callback->(@msg), ...
263
264	Register callbacks to be called on matching messages on the given full
265	port (after converting it to one if required).
266
267	The callback has to return a true value when its work is done, after
268	which is will be removed, or a false value in which case it will stay
269	registered.
270		341
271	The global C<$SELF> (exported by this module) contains C<$port> while	342	The global C<$SELF> (exported by this module) contains C<$port> while
272	executing the callback.	343	executing the callback. Runtime errors during callback execution will
		344	result in the port being C<kil>ed.
273		345
274	Runtime errors wdurign callback execution will result in the port being	346	The default callback received all messages not matched by a more specific
275	C<kil>ed.	347	C<tag> match.
276		348
277	If the match is an array reference, then it will be matched against the	349	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
278	first elements of the message, otherwise only the first element is being
279	matched.
280		350
281	Any element in the match that is specified as C<_any_> (a function	351	Register (or replace) callbacks to be called on messages starting with the
282	exported by this module) matches any single element of the message.	352	given tag on the given port (and return the port), or unregister it (when
		353	C<$callback> is C<$undef> or missing). There can only be one callback
		354	registered for each tag.
283		355
284	While not required, it is highly recommended that the first matching	356	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	357	element (the tag) has been removed. The callback will use the same
286	also the most efficient match (by far).	358	environment as the default callback (see above).
		359
		360	Example: create a port and bind receivers on it in one go.
		361
		362	my $port = rcv port,
		363	msg1 => sub { ... },
		364	msg2 => sub { ... },
		365	;
		366
		367	Example: create a port, bind receivers and send it in a message elsewhere
		368	in one go:
		369
		370	snd $otherport, reply =>
		371	rcv port,
		372	msg1 => sub { ... },
		373	...
		374	;
		375
		376	Example: temporarily register a rcv callback for a tag matching some port
		377	(e.g. for a rpc reply) and unregister it after a message was received.
		378
		379	rcv $port, $otherport => sub {
		380	my @reply = @_;
		381
		382	rcv $SELF, $otherport;
		383	};
287		384
288	=cut	385	=cut
289		386
290	sub rcv($@) {	387	sub rcv($@) {
291	my $port = shift;	388	my $port = shift;
292	my ($noderef, $portid) = split /#/, $port, 2;	389	my ($nodeid, $portid) = split /#/, $port, 2;
293		390
294	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	391	$NODE{$nodeid} == $NODE{""}
295	or Carp::croak "$port: rcv can only be called on local ports, caught";	392	or Carp::croak "$port: rcv can only be called on local ports, caught";
296		393
297	if (@_ == 1) {	394	while (@_) {
		395	if (ref $_[0]) {
		396	if (my $self = $PORT_DATA{$portid}) {
		397	"AnyEvent::MP::Port" eq ref $self
		398	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		399
		400	$self->[2] = shift;
		401	} else {
298	my $cb = shift;	402	my $cb = shift;
299	delete $PORT_DATA{$portid};
300	$PORT{$portid} = sub {	403	$PORT{$portid} = sub {
301	local $SELF = $port;	404	local $SELF = $port;
302	eval {	405	eval { &$cb }; _self_die if $@;
303	&$cb	406	};
304	and kil $port;
305	};	407	}
306	_self_die if $@;	408	} elsif (defined $_[0]) {
307	};
308	} else {
309	my $self = $PORT_DATA{$portid} \|\|= do {	409	my $self = $PORT_DATA{$portid} \|\|= do {
310	my $self = bless {	410	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
311	id => $port,
312	}, "AnyEvent::MP::Port";
313		411
314	$PORT{$portid} = sub {	412	$PORT{$portid} = sub {
315	local $SELF = $port;	413	local $SELF = $port;
316		414
317	eval {
318	for (@{ $self->{rc0}{$_[0]} }) {	415	if (my $cb = $self->[1]{$_[0]}) {
319	$_ && &{$_->[0]}	416	shift;
320	&& undef $_;	417	eval { &$cb }; _self_die if $@;
321	}	418	} else {
322
323	for (@{ $self->{rcv}{$_[0]} }) {
324	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
325	&& &{$_->[0]}	419	&{ $self->[0] };
326	&& undef $_;
327	}
328
329	for (@{ $self->{any} }) {
330	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
331	&& &{$_->[0]}
332	&& undef $_;
333	}	420	}
334	};	421	};
335	_self_die if $@;	422
		423	$self
336	};	424	};
337		425
338	$self
339	};
340
341	"AnyEvent::MP::Port" eq ref $self	426	"AnyEvent::MP::Port" eq ref $self
342	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	427	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
343		428
344	while (@_) {
345	my ($match, $cb) = splice @_, 0, 2;	429	my ($tag, $cb) = splice @_, 0, 2;
346		430
347	if (!ref $match) {	431	if (defined $cb) {
348	push @{ $self->{rc0}{$match} }, [$cb];	432	$self->[1]{$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 {	433	} else {
355	push @{ $self->{any} }, [$cb, $match];	434	delete $self->[1]{$tag};
356	}	435	}
357	}	436	}
358	}	437	}
359		438
360	$port	439	$port
…		…
396	$res	475	$res
397	}	476	}
398	}	477	}
399	}	478	}
400		479
401	=item $guard = mon $port, $cb->(@reason)	480	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
402		481
403	=item $guard = mon $port, $otherport	482	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
404		483
405	=item $guard = mon $port, $otherport, @msg	484	=item $guard = mon $port # kill $SELF when $port dies
406		485
		486	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
		487
407	Monitor the given port and do something when the port is killed.	488	Monitor the given port and do something when the port is killed or
		489	messages to it were lost, and optionally return a guard that can be used
		490	to stop monitoring again.
408		491
409	In the first form, the callback is simply called with any number	492	In the first form (callback), the callback is simply called with any
410	of C<@reason> elements (no @reason means that the port was deleted	493	number of C<@reason> elements (no @reason means that the port was deleted
411	"normally"). Note also that I<< the callback B<must> never die >>, so use	494	"normally"). Note also that I<< the callback B<must> never die >>, so use
412	C<eval> if unsure.	495	C<eval> if unsure.
413		496
414	In the second form, the other port will be C<kil>'ed with C<@reason>, iff	497	In the second form (another port given), the other port (C<$rcvport>)
415	a @reason was specified, i.e. on "normal" kils nothing happens, while	498	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
416	under all other conditions, the other port is killed with the same reason.	499	"normal" kils nothing happens, while under all other conditions, the other
		500	port is killed with the same reason.
417		501
		502	The third form (kill self) is the same as the second form, except that
		503	C<$rvport> defaults to C<$SELF>.
		504
418	In the last form, a message of the form C<@msg, @reason> will be C<snd>.	505	In the last form (message), a message of the form C<@msg, @reason> will be
		506	C<snd>.
		507
		508	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		509	alert was raised), they are removed and will not trigger again.
		510
		511	As a rule of thumb, monitoring requests should always monitor a port from
		512	a local port (or callback). The reason is that kill messages might get
		513	lost, just like any other message. Another less obvious reason is that
		514	even monitoring requests can get lost (for example, when the connection
		515	to the other node goes down permanently). When monitoring a port locally
		516	these problems do not exist.
		517
		518	C<mon> effectively guarantees that, in the absence of hardware failures,
		519	after starting the monitor, either all messages sent to the port will
		520	arrive, or the monitoring action will be invoked after possible message
		521	loss has been detected. No messages will be lost "in between" (after
		522	the first lost message no further messages will be received by the
		523	port). After the monitoring action was invoked, further messages might get
		524	delivered again.
		525
		526	Inter-host-connection timeouts and monitoring depend on the transport
		527	used. The only transport currently implemented is TCP, and AnyEvent::MP
		528	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		529	non-idle connection, and usually around two hours for idle conenctions).
		530
		531	This means that monitoring is good for program errors and cleaning up
		532	stuff eventually, but they are no replacement for a timeout when you need
		533	to ensure some maximum latency.
419		534
420	Example: call a given callback when C<$port> is killed.	535	Example: call a given callback when C<$port> is killed.
421		536
422	mon $port, sub { warn "port died because of <@_>\n" };	537	mon $port, sub { warn "port died because of <@_>\n" };
423		538
424	Example: kill ourselves when C<$port> is killed abnormally.	539	Example: kill ourselves when C<$port> is killed abnormally.
425		540
426	mon $port, $self;	541	mon $port;
427		542
428	Example: send us a restart message another C<$port> is killed.	543	Example: send us a restart message when another C<$port> is killed.
429		544
430	mon $port, $self => "restart";	545	mon $port, $self => "restart";
431		546
432	=cut	547	=cut
433		548
434	sub mon {	549	sub mon {
435	my ($noderef, $port) = split /#/, shift, 2;	550	my ($nodeid, $port) = split /#/, shift, 2;
436		551
437	my $node = $NODE{$noderef} \|\| add_node $noderef;	552	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
438		553
439	my $cb = shift;	554	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
440		555
441	unless (ref $cb) {	556	unless (ref $cb) {
442	if (@_) {	557	if (@_) {
443	# send a kill info message	558	# send a kill info message
444	my (@msg) = ($cb, @_);	559	my (@msg) = ($cb, @_);
…		…
462	is killed, the references will be freed.	577	is killed, the references will be freed.
463		578
464	Optionally returns a guard that will stop the monitoring.	579	Optionally returns a guard that will stop the monitoring.
465		580
466	This function is useful when you create e.g. timers or other watchers and	581	This function is useful when you create e.g. timers or other watchers and
467	want to free them when the port gets killed:	582	want to free them when the port gets killed (note the use of C<psub>):
468		583
469	$port->rcv (start => sub {	584	$port->rcv (start => sub {
470	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	585	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
471	undef $timer if 0.9 < rand;	586	undef $timer if 0.9 < rand;
472	});	587	});
473	});	588	});
474		589
475	=cut	590	=cut
476		591
477	sub mon_guard {	592	sub mon_guard {
478	my ($port, @refs) = @_;	593	my ($port, @refs) = @_;
479		594
		595	#TODO: mon-less form?
		596
480	mon $port, sub { 0 && @refs }	597	mon $port, sub { 0 && @refs }
481	}	598	}
482		599
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]	600	=item kil $port[, @reason]
494		601
495	Kill the specified port with the given C<@reason>.	602	Kill the specified port with the given C<@reason>.
496		603
497	If no C<@reason> is specified, then the port is killed "normally" (linked	604	If no C<@reason> is specified, then the port is killed "normally" (ports
498	ports will not be kileld, or even notified).	605	monitoring other ports will not necessarily die because a port dies
		606	"normally").
499		607
500	Otherwise, linked ports get killed with the same reason (second form of	608	Otherwise, linked ports get killed with the same reason (second form of
501	C<mon>, see below).	609	C<mon>, see above).
502		610
503	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	611	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
504	will be reported as reason C<< die => $@ >>.	612	will be reported as reason C<< die => $@ >>.
505		613
506	Transport/communication errors are reported as C<< transport_error =>	614	Transport/communication errors are reported as C<< transport_error =>
507	$message >>.	615	$message >>.
508		616
		617	=cut
		618
		619	=item $port = spawn $node, $initfunc[, @initdata]
		620
		621	Creates a port on the node C<$node> (which can also be a port ID, in which
		622	case it's the node where that port resides).
		623
		624	The port ID of the newly created port is returned immediately, and it is
		625	possible to immediately start sending messages or to monitor the port.
		626
		627	After the port has been created, the init function is called on the remote
		628	node, in the same context as a C<rcv> callback. This function must be a
		629	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
		630	specify a function in the main program, use C<::name>.
		631
		632	If the function doesn't exist, then the node tries to C<require>
		633	the package, then the package above the package and so on (e.g.
		634	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
		635	exists or it runs out of package names.
		636
		637	The init function is then called with the newly-created port as context
		638	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		639	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		640	the port might not get created.
		641
		642	A common idiom is to pass a local port, immediately monitor the spawned
		643	port, and in the remote init function, immediately monitor the passed
		644	local port. This two-way monitoring ensures that both ports get cleaned up
		645	when there is a problem.
		646
		647	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		648	caller before C<spawn> returns (by delaying invocation when spawn is
		649	called for the local node).
		650
		651	Example: spawn a chat server port on C<$othernode>.
		652
		653	# this node, executed from within a port context:
		654	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
		655	mon $server;
		656
		657	# init function on C<$othernode>
		658	sub connect {
		659	my ($srcport) = @_;
		660
		661	mon $srcport;
		662
		663	rcv $SELF, sub {
		664	...
		665	};
		666	}
		667
		668	=cut
		669
		670	sub _spawn {
		671	my $port = shift;
		672	my $init = shift;
		673
		674	# rcv will create the actual port
		675	local $SELF = "$NODE#$port";
		676	eval {
		677	&{ load_func $init }
		678	};
		679	_self_die if $@;
		680	}
		681
		682	sub spawn(@) {
		683	my ($nodeid, undef) = split /#/, shift, 2;
		684
		685	my $id = "$RUNIQ." . $ID++;
		686
		687	$_[0] =~ /::/
		688	or Carp::croak "spawn init function must be a fully-qualified name, caught";
		689
		690	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
		691
		692	"$nodeid#$id"
		693	}
		694
		695	=item after $timeout, @msg
		696
		697	=item after $timeout, $callback
		698
		699	Either sends the given message, or call the given callback, after the
		700	specified number of seconds.
		701
		702	This is simply a utility function that comes in handy at times - the
		703	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		704	so it may go away in the future.
		705
		706	=cut
		707
		708	sub after($@) {
		709	my ($timeout, @action) = @_;
		710
		711	my $t; $t = AE::timer $timeout, 0, sub {
		712	undef $t;
		713	ref $action[0]
		714	? $action[0]()
		715	: snd @action;
		716	};
		717	}
		718
509	=back	719	=back
510		720
511	=head1 FUNCTIONS FOR NODES	721	=head1 AnyEvent::MP vs. Distributed Erlang
		722
		723	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
		724	== aemp node, Erlang process == aemp port), so many of the documents and
		725	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
		726	sample:
		727
		728	http://www.Erlang.se/doc/programming_rules.shtml
		729	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
		730	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6
		731	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
		732
		733	Despite the similarities, there are also some important differences:
512		734
513	=over 4	735	=over 4
514		736
515	=item initialise_node $noderef, $seednode, $seednode...	737	=item * Node IDs are arbitrary strings in AEMP.
516		738
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	739	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	740	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
645	convenience functionality.	741	configuration or DNS), but will otherwise discover other odes itself.
646		742
647	This means that AEMP requires a less tightly controlled environment at the	743	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
648	cost of longer node references and a slightly higher management overhead.	744	uses "local ports are like remote ports".
		745
		746	The failure modes for local ports are quite different (runtime errors
		747	only) then for remote ports - when a local port dies, you I<know> it dies,
		748	when a connection to another node dies, you know nothing about the other
		749	port.
		750
		751	Erlang pretends remote ports are as reliable as local ports, even when
		752	they are not.
		753
		754	AEMP encourages a "treat remote ports differently" philosophy, with local
		755	ports being the special case/exception, where transport errors cannot
		756	occur.
649		757
650	=item * Erlang uses processes and a mailbox, AEMP does not queue.	758	=item * Erlang uses processes and a mailbox, AEMP does not queue.
651		759
652	Erlang uses processes that selctively receive messages, and therefore	760	Erlang uses processes that selectively receive messages, and therefore
653	needs a queue. AEMP is event based, queuing messages would serve no useful	761	needs a queue. AEMP is event based, queuing messages would serve no
654	purpose.	762	useful purpose. For the same reason the pattern-matching abilities of
		763	AnyEvent::MP are more limited, as there is little need to be able to
		764	filter messages without dequeuing them.
655		765
656	(But see L<Coro::MP> for a more erlang-like process model on top of AEMP).	766	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
657		767
658	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	768	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
659		769
660	Sending messages in erlang is synchronous and blocks the process. AEMP	770	Sending messages in Erlang is synchronous and blocks the process (and
661	sends are immediate, connection establishment is handled in the	771	so does not need a queue that can overflow). AEMP sends are immediate,
662	background.	772	connection establishment is handled in the background.
663		773
664	=item * Erlang can silently lose messages, AEMP cannot.	774	=item * Erlang suffers from silent message loss, AEMP does not.
665		775
666	Erlang makes few guarantees on messages delivery - messages can get lost	776	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,	777	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).	778	and c, and the other side only receives messages a and c).
669		779
670	AEMP guarantees correct ordering, and the guarantee that there are no	780	AEMP guarantees correct ordering, and the guarantee that after one message
671	holes in the message sequence.	781	is lost, all following ones sent to the same port are lost as well, until
672		782	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	783	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		784
684	=item * Erlang can send messages to the wrong port, AEMP does not.	785	=item * Erlang can send messages to the wrong port, AEMP does not.
685		786
686	In erlang it is quite possible that a node that restarts reuses a process	787	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	788	known to other nodes for a completely different process, causing messages
688	messages destined for that process to end up in an unrelated process.	789	destined for that process to end up in an unrelated process.
689		790
690	AEMP never reuses port IDs, so old messages or old port IDs floating	791	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.	792	around in the network will not be sent to an unrelated port.
692		793
693	=item * Erlang uses unprotected connections, AEMP uses secure	794	=item * Erlang uses unprotected connections, AEMP uses secure
694	authentication and can use TLS.	795	authentication and can use TLS.
695		796
696	AEMP can use a proven protocol - SSL/TLS - to protect connections and	797	AEMP can use a proven protocol - TLS - to protect connections and
697	securely authenticate nodes.	798	securely authenticate nodes.
698		799
699	=item * The AEMP protocol is optimised for both text-based and binary	800	=item * The AEMP protocol is optimised for both text-based and binary
700	communications.	801	communications.
701		802
702	The AEMP protocol, unlike the erlang protocol, supports both	803	The AEMP protocol, unlike the Erlang protocol, supports both programming
703	language-independent text-only protocols (good for debugging) and binary,	804	language independent text-only protocols (good for debugging) and binary,
704	language-specific serialisers (e.g. Storable).	805	language-specific serialisers (e.g. Storable). By default, unless TLS is
		806	used, the protocol is actually completely text-based.
705		807
706	It has also been carefully designed to be implementable in other languages	808	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	809	with a minimum of work while gracefully degrading functionality to make the
708	protocol simple.	810	protocol simple.
709		811
		812	=item * AEMP has more flexible monitoring options than Erlang.
		813
		814	In Erlang, you can chose to receive I<all> exit signals as messages
		815	or I<none>, there is no in-between, so monitoring single processes is
		816	difficult to implement. Monitoring in AEMP is more flexible than in
		817	Erlang, as one can choose between automatic kill, exit message or callback
		818	on a per-process basis.
		819
		820	=item * Erlang tries to hide remote/local connections, AEMP does not.
		821
		822	Monitoring in Erlang is not an indicator of process death/crashes, in the
		823	same way as linking is (except linking is unreliable in Erlang).
		824
		825	In AEMP, you don't "look up" registered port names or send to named ports
		826	that might or might not be persistent. Instead, you normally spawn a port
		827	on the remote node. The init function monitors you, and you monitor the
		828	remote port. Since both monitors are local to the node, they are much more
		829	reliable (no need for C<spawn_link>).
		830
		831	This also saves round-trips and avoids sending messages to the wrong port
		832	(hard to do in Erlang).
		833
710	=back	834	=back
711		835
		836	=head1 RATIONALE
		837
		838	=over 4
		839
		840	=item Why strings for port and node IDs, why not objects?
		841
		842	We considered "objects", but found that the actual number of methods
		843	that can be called are quite low. Since port and node IDs travel over
		844	the network frequently, the serialising/deserialising would add lots of
		845	overhead, as well as having to keep a proxy object everywhere.
		846
		847	Strings can easily be printed, easily serialised etc. and need no special
		848	procedures to be "valid".
		849
		850	And as a result, a miniport consists of a single closure stored in a
		851	global hash - it can't become much cheaper.
		852
		853	=item Why favour JSON, why not a real serialising format such as Storable?
		854
		855	In fact, any AnyEvent::MP node will happily accept Storable as framing
		856	format, but currently there is no way to make a node use Storable by
		857	default (although all nodes will accept it).
		858
		859	The default framing protocol is JSON because a) JSON::XS is many times
		860	faster for small messages and b) most importantly, after years of
		861	experience we found that object serialisation is causing more problems
		862	than it solves: Just like function calls, objects simply do not travel
		863	easily over the network, mostly because they will always be a copy, so you
		864	always have to re-think your design.
		865
		866	Keeping your messages simple, concentrating on data structures rather than
		867	objects, will keep your messages clean, tidy and efficient.
		868
		869	=back
		870
712	=head1 SEE ALSO	871	=head1 SEE ALSO
		872
		873	L<AnyEvent::MP::Intro> - a gentle introduction.
		874
		875	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		876
		877	L<AnyEvent::MP::Global> - network maintainance and port groups, to find
		878	your applications.
		879
		880	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		881	all nodes.
713		882
714	L<AnyEvent>.	883	L<AnyEvent>.
715		884
716	=head1 AUTHOR	885	=head1 AUTHOR
717		886

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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 1.83 by root, Tue Sep 8 01:38:16 2009 UTC

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Revision 1.33 by root, Wed Aug 5 22:40:51 2009 UTC vs.
Revision 1.83 by root, Tue Sep 8 01:38:16 2009 UTC