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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.32 by root, Wed Aug 5 19:58:46 2009 UTC vs.
Revision 1.80 by root, Fri Sep 4 22:30:29 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 seeds - C<host:port>
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	Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes
		109	are expected to be long-running, and at least one of those should always
		110	be available. When nodes run out of connections (e.g. due to a network
		111	error), they try to re-establish connections to some seednodes again to
		112	join the network.
		113
		114	Apart from being sued for seeding, seednodes are not special in any way -
		115	every public node can be a seednode.
84		116
85	=back	117	=back
86		118
87	=head1 VARIABLES/FUNCTIONS	119	=head1 VARIABLES/FUNCTIONS
88		120
…		…
90		122
91	=cut	123	=cut
92		124
93	package AnyEvent::MP;	125	package AnyEvent::MP;
94		126
95	use AnyEvent::MP::Base;	127	use AnyEvent::MP::Kernel;
96		128
97	use common::sense;	129	use common::sense;
98		130
99	use Carp ();	131	use Carp ();
100		132
101	use AE ();	133	use AE ();
102		134
103	use base "Exporter";	135	use base "Exporter";
104		136
105	our $VERSION = '0.1';	137	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
		138
106	our @EXPORT = qw(	139	our @EXPORT = qw(
107	NODE $NODE *SELF node_of _any_	140	NODE $NODE *SELF node_of after
108	resolve_node initialise_node	141	configure
109	snd rcv mon kil reg psub	142	snd rcv mon mon_guard kil reg psub spawn
110	port	143	port
111	);	144	);
112		145
113	our $SELF;	146	our $SELF;
114		147
…		…
118	kil $SELF, die => $msg;	151	kil $SELF, die => $msg;
119	}	152	}
120		153
121	=item $thisnode = NODE / $NODE	154	=item $thisnode = NODE / $NODE
122		155
123	The C<NODE> function returns, and the C<$NODE> variable contains	156	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	157	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	158	a call to C<configure>.
126	identifiers become invalid.
127		159
128	=item $noderef = node_of $portid	160	=item $nodeid = node_of $port
129		161
130	Extracts and returns the noderef from a portid or a noderef.	162	Extracts and returns the node ID from a port ID or a node ID.
131		163
132	=item $cv = resolve_node $noderef	164	=item configure $profile, key => value...
133		165
134	Takes an unresolved node reference that may contain hostnames and	166	=item configure key => value...
135	abbreviated IDs, resolves all of them and returns a resolved node
136	reference.
137		167
138	In addition to C<address:port> pairs allowed in resolved noderefs, the	168	Before a node can talk to other nodes on the network (i.e. enter
139	following forms are supported:	169	"distributed mode") it has to configure itself - the minimum a node needs
		170	to know is its own name, and optionally it should know the addresses of
		171	some other nodes in the network to discover other nodes.
		172
		173	This function configures a node - it must be called exactly once (or
		174	never) before calling other AnyEvent::MP functions.
140		175
141	=over 4	176	=over 4
142		177
143	=item the empty string	178	=item step 1, gathering configuration from profiles
144		179
145	An empty-string component gets resolved as if the default port (4040) was	180	The function first looks up a profile in the aemp configuration (see the
146	specified.	181	L<aemp> commandline utility). The profile name can be specified via the
		182	named C<profile> parameter or can simply be the first parameter). If it is
		183	missing, then the nodename (F<uname -n>) will be used as profile name.
147		184
148	=item naked port numbers (e.g. C<1234>)	185	The profile data is then gathered as follows:
149		186
150	These are resolved by prepending the local nodename and a colon, to be	187	First, all remaining key => value pairs (all of which are conveniently
151	further resolved.	188	undocumented at the moment) will be interpreted as configuration
		189	data. Then they will be overwritten by any values specified in the global
		190	default configuration (see the F<aemp> utility), then the chain of
		191	profiles chosen by the profile name (and any C<parent> attributes).
152		192
153	=item hostnames (e.g. C<localhost:1234>, C<localhost>)	193	That means that the values specified in the profile have highest priority
		194	and the values specified directly via C<configure> have lowest priority,
		195	and can only be used to specify defaults.
154		196
155	These are resolved by using AnyEvent::DNS to resolve them, optionally	197	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	198	this process. If not, then the profile name will be used as node ID. The
157	specified.	199	special node ID of C<anon/> will be replaced by a random node ID.
		200
		201	=item step 2, bind listener sockets
		202
		203	The next step is to look up the binds in the profile, followed by binding
		204	aemp protocol listeners on all binds specified (it is possible and valid
		205	to have no binds, meaning that the node cannot be contacted form the
		206	outside. This means the node cannot talk to other nodes that also have no
		207	binds, but it can still talk to all "normal" nodes).
		208
		209	If the profile does not specify a binds list, then a default of C<*> is
		210	used, meaning the node will bind on a dynamically-assigned port on every
		211	local IP address it finds.
		212
		213	=item step 3, connect to seed nodes
		214
		215	As the last step, the seeds list from the profile is passed to the
		216	L<AnyEvent::MP::Global> module, which will then use it to keep
		217	connectivity with at least one node at any point in time.
158		218
159	=back	219	=back
		220
		221	Example: become a distributed node using the locla node name as profile.
		222	This should be the most common form of invocation for "daemon"-type nodes.
		223
		224	configure
		225
		226	Example: become an anonymous node. This form is often used for commandline
		227	clients.
		228
		229	configure nodeid => "anon/";
		230
		231	Example: configure a node using a profile called seed, which si suitable
		232	for a seed node as it binds on all local addresses on a fixed port (4040,
		233	customary for aemp).
		234
		235	# use the aemp commandline utility
		236	# aemp profile seed nodeid anon/ binds '*:4040'
		237
		238	# then use it
		239	configure profile => "seed";
		240
		241	# or simply use aemp from the shell again:
		242	# aemp run profile seed
		243
		244	# or provide a nicer-to-remember nodeid
		245	# aemp run profile seed nodeid "$(hostname)"
160		246
161	=item $SELF	247	=item $SELF
162		248
163	Contains the current port id while executing C<rcv> callbacks or C<psub>	249	Contains the current port id while executing C<rcv> callbacks or C<psub>
164	blocks.	250	blocks.
165		251
166	=item SELF, %SELF, @SELF...	252	=item *SELF, SELF, %SELF, @SELF...
167		253
168	Due to some quirks in how perl exports variables, it is impossible to	254	Due to some quirks in how perl exports variables, it is impossible to
169	just export C<$SELF>, all the symbols called C<SELF> are exported by this	255	just export C<$SELF>, all the symbols named C<SELF> are exported by this
170	module, but only C<$SELF> is currently used.	256	module, but only C<$SELF> is currently used.
171		257
172	=item snd $portid, type => @data	258	=item snd $port, type => @data
173		259
174	=item snd $portid, @msg	260	=item snd $port, @msg
175		261
176	Send the given message to the given port ID, which can identify either	262	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	263	local or a remote port, and must be a port ID.
178	stringifies a sa port ID (such as a port object :).
179		264
180	While the message can be about anything, it is highly recommended to use a	265	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	266	use a string as first element (a port ID, or some word that indicates a
182	type etc.).	267	request type etc.) and to consist if only simple perl values (scalars,
		268	arrays, hashes) - if you think you need to pass an object, think again.
183		269
184	The message data effectively becomes read-only after a call to this	270	The message data logically becomes read-only after a call to this
185	function: modifying any argument is not allowed and can cause many	271	function: modifying any argument (or values referenced by them) is
186	problems.	272	forbidden, as there can be considerable time between the call to C<snd>
		273	and the time the message is actually being serialised - in fact, it might
		274	never be copied as within the same process it is simply handed to the
		275	receiving port.
187		276
188	The type of data you can transfer depends on the transport protocol: when	277	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	278	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	279	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	280	that Storable can serialise and deserialise is allowed, and for the local
192	node, anything can be passed.	281	node, anything can be passed. Best rely only on the common denominator of
		282	these.
193		283
194	=item $local_port = port	284	=item $local_port = port
195		285
196	Create a new local port object that can be used either as a pattern	286	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"),	287	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		288
200	=item $portid = port { my @msg = @_; $finished }	289	=item $local_port = port { my @msg = @_ }
201		290
202	Creates a "mini port", that is, a very lightweight port without any	291	Creates a new local port, and returns its ID. Semantically the same as
203	pattern matching behind it, and returns its ID.	292	creating a port and calling C<rcv $port, $callback> on it.
204		293
205	The block will be called for every message received on the port. When the	294	The block will be called for every message received on the port, with the
206	callback returns a true value its job is considered "done" and the port	295	global variable C<$SELF> set to the port ID. Runtime errors will cause the
207	will be destroyed. Otherwise it will stay alive.	296	port to be C<kil>ed. The message will be passed as-is, no extra argument
		297	(i.e. no port ID) will be passed to the callback.
208		298
209	The message will be passed as-is, no extra argument (i.e. no port id) will	299	If you want to stop/destroy the port, simply C<kil> it:
210	be passed to the callback.
211		300
212	If you need the local port id in the callback, this works nicely:	301	my $port = port {
213		302	my @msg = @_;
214	my $port; $port = port {	303	...
215	snd $otherport, reply => $port;	304	kil $SELF;
216	};	305	};
217		306
218	=cut	307	=cut
		308
		309	sub rcv($@);
		310
		311	sub _kilme {
		312	die "received message on port without callback";
		313	}
219		314
220	sub port(;&) {	315	sub port(;&) {
221	my $id = "$UNIQ." . $ID++;	316	my $id = "$UNIQ." . $ID++;
222	my $port = "$NODE#$id";	317	my $port = "$NODE#$id";
223		318
		319	rcv $port, shift \|\| \&_kilme;
		320
		321	$port
		322	}
		323
		324	=item rcv $local_port, $callback->(@msg)
		325
		326	Replaces the default callback on the specified port. There is no way to
		327	remove the default callback: use C<sub { }> to disable it, or better
		328	C<kil> the port when it is no longer needed.
		329
		330	The global C<$SELF> (exported by this module) contains C<$port> while
		331	executing the callback. Runtime errors during callback execution will
		332	result in the port being C<kil>ed.
		333
		334	The default callback received all messages not matched by a more specific
		335	C<tag> match.
		336
		337	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
		338
		339	Register (or replace) callbacks to be called on messages starting with the
		340	given tag on the given port (and return the port), or unregister it (when
		341	C<$callback> is C<$undef> or missing). There can only be one callback
		342	registered for each tag.
		343
		344	The original message will be passed to the callback, after the first
		345	element (the tag) has been removed. The callback will use the same
		346	environment as the default callback (see above).
		347
		348	Example: create a port and bind receivers on it in one go.
		349
		350	my $port = rcv port,
		351	msg1 => sub { ... },
		352	msg2 => sub { ... },
		353	;
		354
		355	Example: create a port, bind receivers and send it in a message elsewhere
		356	in one go:
		357
		358	snd $otherport, reply =>
		359	rcv port,
		360	msg1 => sub { ... },
		361	...
		362	;
		363
		364	Example: temporarily register a rcv callback for a tag matching some port
		365	(e.g. for a rpc reply) and unregister it after a message was received.
		366
		367	rcv $port, $otherport => sub {
		368	my @reply = @_;
		369
		370	rcv $SELF, $otherport;
		371	};
		372
		373	=cut
		374
		375	sub rcv($@) {
		376	my $port = shift;
		377	my ($nodeid, $portid) = split /#/, $port, 2;
		378
		379	$NODE{$nodeid} == $NODE{""}
		380	or Carp::croak "$port: rcv can only be called on local ports, caught";
		381
224	if (@_) {	382	while (@_) {
		383	if (ref $_[0]) {
		384	if (my $self = $PORT_DATA{$portid}) {
		385	"AnyEvent::MP::Port" eq ref $self
		386	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		387
		388	$self->[2] = shift;
		389	} else {
225	my $cb = shift;	390	my $cb = shift;
226	$PORT{$id} = sub {	391	$PORT{$portid} = sub {
227	local $SELF = $port;	392	local $SELF = $port;
228	eval {	393	eval { &$cb }; _self_die if $@;
229	&$cb	394	};
230	and kil $id;	395	}
		396	} elsif (defined $_[0]) {
		397	my $self = $PORT_DATA{$portid} \|\|= do {
		398	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
		399
		400	$PORT{$portid} = sub {
		401	local $SELF = $port;
		402
		403	if (my $cb = $self->[1]{$_[0]}) {
		404	shift;
		405	eval { &$cb }; _self_die if $@;
		406	} else {
		407	&{ $self->[0] };
		408	}
		409	};
		410
		411	$self
231	};	412	};
232	_self_die if $@;	413
233	};
234	} else {
235	my $self = bless {
236	id => "$NODE#$id",
237	}, "AnyEvent::MP::Port";	414	"AnyEvent::MP::Port" eq ref $self
		415	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
238		416
239	$PORT_DATA{$id} = $self;	417	my ($tag, $cb) = splice @_, 0, 2;
240	$PORT{$id} = sub {
241	local $SELF = $port;
242		418
		419	if (defined $cb) {
		420	$self->[1]{$tag} = $cb;
243	eval {	421	} else {
244	for (@{ $self->{rc0}{$_[0]} }) {	422	delete $self->[1]{$tag};
245	$_ && &{$_->[0]}
246	&& undef $_;
247	}
248
249	for (@{ $self->{rcv}{$_[0]} }) {
250	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
251	&& &{$_->[0]}
252	&& undef $_;
253	}
254
255	for (@{ $self->{any} }) {
256	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
257	&& &{$_->[0]}
258	&& undef $_;
259	}
260	};	423	}
261	_self_die if $@;
262	};
263	}
264
265	$port
266	}
267
268	=item reg $portid, $name
269
270	Registers the given port under the name C<$name>. If the name already
271	exists it is replaced.
272
273	A port can only be registered under one well known name.
274
275	A port automatically becomes unregistered when it is killed.
276
277	=cut
278
279	sub reg(@) {
280	my ($portid, $name) = @_;
281
282	$REG{$name} = $portid;
283	}
284
285	=item rcv $portid, $callback->(@msg)
286
287	Replaces the callback on the specified miniport (or newly created port
288	object, see C<port>). Full ports are configured with the following calls:
289
290	=item rcv $portid, tagstring => $callback->(@msg), ...
291
292	=item rcv $portid, $smartmatch => $callback->(@msg), ...
293
294	=item rcv $portid, [$smartmatch...] => $callback->(@msg), ...
295
296	Register callbacks to be called on matching messages on the given full
297	port (or newly created port).
298
299	The callback has to return a true value when its work is done, after
300	which is will be removed, or a false value in which case it will stay
301	registered.
302
303	The global C<$SELF> (exported by this module) contains C<$portid> while
304	executing the callback.
305
306	Runtime errors wdurign callback execution will result in the port being
307	C<kil>ed.
308
309	If the match is an array reference, then it will be matched against the
310	first elements of the message, otherwise only the first element is being
311	matched.
312
313	Any element in the match that is specified as C<_any_> (a function
314	exported by this module) matches any single element of the message.
315
316	While not required, it is highly recommended that the first matching
317	element is a string identifying the message. The one-string-only match is
318	also the most efficient match (by far).
319
320	=cut
321
322	sub rcv($@) {
323	my $portid = shift;
324	my ($noderef, $port) = split /#/, $port, 2;
325
326	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}
327	or Carp::croak "$noderef#$port: rcv can only be called on local ports, caught";
328
329	my $self = $PORT_DATA{$port}
330	or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught";
331
332	"AnyEvent::MP::Port" eq ref $self
333	or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught";
334
335	while (@_) {
336	my ($match, $cb) = splice @_, 0, 2;
337
338	if (!ref $match) {
339	push @{ $self->{rc0}{$match} }, [$cb];
340	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
341	my ($type, @match) = @$match;
342	@match
343	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
344	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
345	} else {
346	push @{ $self->{any} }, [$cb, $match];
347	}	424	}
348	}	425	}
349		426
350	$portid	427	$port
351	}	428	}
352		429
353	=item $closure = psub { BLOCK }	430	=item $closure = psub { BLOCK }
354		431
355	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	432	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
…		…
386	$res	463	$res
387	}	464	}
388	}	465	}
389	}	466	}
390		467
391	=item $guard = mon $portid, $cb->(@reason)	468	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
392		469
393	=item $guard = mon $portid, $otherport	470	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
394		471
395	=item $guard = mon $portid, $otherport, @msg	472	=item $guard = mon $port # kill $SELF when $port dies
396		473
		474	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
		475
397	Monitor the given port and do something when the port is killed.	476	Monitor the given port and do something when the port is killed or
		477	messages to it were lost, and optionally return a guard that can be used
		478	to stop monitoring again.
398		479
399	In the first form, the callback is simply called with any number	480	In the first form (callback), the callback is simply called with any
400	of C<@reason> elements (no @reason means that the port was deleted	481	number of C<@reason> elements (no @reason means that the port was deleted
401	"normally"). Note also that I<< the callback B<must> never die >>, so use	482	"normally"). Note also that I<< the callback B<must> never die >>, so use
402	C<eval> if unsure.	483	C<eval> if unsure.
403		484
404	In the second form, the other port will be C<kil>'ed with C<@reason>, iff	485	In the second form (another port given), the other port (C<$rcvport>)
405	a @reason was specified, i.e. on "normal" kils nothing happens, while	486	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
406	under all other conditions, the other port is killed with the same reason.	487	"normal" kils nothing happens, while under all other conditions, the other
		488	port is killed with the same reason.
407		489
		490	The third form (kill self) is the same as the second form, except that
		491	C<$rvport> defaults to C<$SELF>.
		492
408	In the last form, a message of the form C<@msg, @reason> will be C<snd>.	493	In the last form (message), a message of the form C<@msg, @reason> will be
		494	C<snd>.
		495
		496	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		497	alert was raised), they are removed and will not trigger again.
		498
		499	As a rule of thumb, monitoring requests should always monitor a port from
		500	a local port (or callback). The reason is that kill messages might get
		501	lost, just like any other message. Another less obvious reason is that
		502	even monitoring requests can get lost (for example, when the connection
		503	to the other node goes down permanently). When monitoring a port locally
		504	these problems do not exist.
		505
		506	C<mon> effectively guarantees that, in the absence of hardware failures,
		507	after starting the monitor, either all messages sent to the port will
		508	arrive, or the monitoring action will be invoked after possible message
		509	loss has been detected. No messages will be lost "in between" (after
		510	the first lost message no further messages will be received by the
		511	port). After the monitoring action was invoked, further messages might get
		512	delivered again.
		513
		514	Inter-host-connection timeouts and monitoring depend on the transport
		515	used. The only transport currently implemented is TCP, and AnyEvent::MP
		516	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		517	non-idle connection, and usually around two hours for idle conenctions).
		518
		519	This means that monitoring is good for program errors and cleaning up
		520	stuff eventually, but they are no replacement for a timeout when you need
		521	to ensure some maximum latency.
409		522
410	Example: call a given callback when C<$port> is killed.	523	Example: call a given callback when C<$port> is killed.
411		524
412	mon $port, sub { warn "port died because of <@_>\n" };	525	mon $port, sub { warn "port died because of <@_>\n" };
413		526
414	Example: kill ourselves when C<$port> is killed abnormally.	527	Example: kill ourselves when C<$port> is killed abnormally.
415		528
416	mon $port, $self;	529	mon $port;
417		530
418	Example: send us a restart message another C<$port> is killed.	531	Example: send us a restart message when another C<$port> is killed.
419		532
420	mon $port, $self => "restart";	533	mon $port, $self => "restart";
421		534
422	=cut	535	=cut
423		536
424	sub mon {	537	sub mon {
425	my ($noderef, $port) = split /#/, shift, 2;	538	my ($nodeid, $port) = split /#/, shift, 2;
426		539
427	my $node = $NODE{$noderef} \|\| add_node $noderef;	540	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
428		541
429	my $cb = shift;	542	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
430		543
431	unless (ref $cb) {	544	unless (ref $cb) {
432	if (@_) {	545	if (@_) {
433	# send a kill info message	546	# send a kill info message
434	my (@msg) = ($cb, @_);	547	my (@msg) = ($cb, @_);
…		…
452	is killed, the references will be freed.	565	is killed, the references will be freed.
453		566
454	Optionally returns a guard that will stop the monitoring.	567	Optionally returns a guard that will stop the monitoring.
455		568
456	This function is useful when you create e.g. timers or other watchers and	569	This function is useful when you create e.g. timers or other watchers and
457	want to free them when the port gets killed:	570	want to free them when the port gets killed (note the use of C<psub>):
458		571
459	$port->rcv (start => sub {	572	$port->rcv (start => sub {
460	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	573	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
461	undef $timer if 0.9 < rand;	574	undef $timer if 0.9 < rand;
462	});	575	});
463	});	576	});
464		577
465	=cut	578	=cut
466		579
467	sub mon_guard {	580	sub mon_guard {
468	my ($port, @refs) = @_;	581	my ($port, @refs) = @_;
469		582
		583	#TODO: mon-less form?
		584
470	mon $port, sub { 0 && @refs }	585	mon $port, sub { 0 && @refs }
471	}	586	}
472		587
473	=item lnk $port1, $port2
474
475	Link two ports. This is simply a shorthand for:
476
477	mon $port1, $port2;
478	mon $port2, $port1;
479
480	It means that if either one is killed abnormally, the other one gets
481	killed as well.
482
483	=item kil $portid[, @reason]	588	=item kil $port[, @reason]
484		589
485	Kill the specified port with the given C<@reason>.	590	Kill the specified port with the given C<@reason>.
486		591
487	If no C<@reason> is specified, then the port is killed "normally" (linked	592	If no C<@reason> is specified, then the port is killed "normally" (ports
488	ports will not be kileld, or even notified).	593	monitoring other ports will not necessarily die because a port dies
		594	"normally").
489		595
490	Otherwise, linked ports get killed with the same reason (second form of	596	Otherwise, linked ports get killed with the same reason (second form of
491	C<mon>, see below).	597	C<mon>, see above).
492		598
493	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	599	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
494	will be reported as reason C<< die => $@ >>.	600	will be reported as reason C<< die => $@ >>.
495		601
496	Transport/communication errors are reported as C<< transport_error =>	602	Transport/communication errors are reported as C<< transport_error =>
497	$message >>.	603	$message >>.
498		604
		605	=cut
		606
		607	=item $port = spawn $node, $initfunc[, @initdata]
		608
		609	Creates a port on the node C<$node> (which can also be a port ID, in which
		610	case it's the node where that port resides).
		611
		612	The port ID of the newly created port is returned immediately, and it is
		613	possible to immediately start sending messages or to monitor the port.
		614
		615	After the port has been created, the init function is called on the remote
		616	node, in the same context as a C<rcv> callback. This function must be a
		617	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
		618	specify a function in the main program, use C<::name>.
		619
		620	If the function doesn't exist, then the node tries to C<require>
		621	the package, then the package above the package and so on (e.g.
		622	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
		623	exists or it runs out of package names.
		624
		625	The init function is then called with the newly-created port as context
		626	object (C<$SELF>) and the C<@initdata> values as arguments.
		627
		628	A common idiom is to pass a local port, immediately monitor the spawned
		629	port, and in the remote init function, immediately monitor the passed
		630	local port. This two-way monitoring ensures that both ports get cleaned up
		631	when there is a problem.
		632
		633	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		634	caller before C<spawn> returns (by delaying invocation when spawn is
		635	called for the local node).
		636
		637	Example: spawn a chat server port on C<$othernode>.
		638
		639	# this node, executed from within a port context:
		640	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
		641	mon $server;
		642
		643	# init function on C<$othernode>
		644	sub connect {
		645	my ($srcport) = @_;
		646
		647	mon $srcport;
		648
		649	rcv $SELF, sub {
		650	...
		651	};
		652	}
		653
		654	=cut
		655
		656	sub _spawn {
		657	my $port = shift;
		658	my $init = shift;
		659
		660	local $SELF = "$NODE#$port";
		661	eval {
		662	&{ load_func $init }
		663	};
		664	_self_die if $@;
		665	}
		666
		667	sub spawn(@) {
		668	my ($nodeid, undef) = split /#/, shift, 2;
		669
		670	my $id = "$RUNIQ." . $ID++;
		671
		672	$_[0] =~ /::/
		673	or Carp::croak "spawn init function must be a fully-qualified name, caught";
		674
		675	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
		676
		677	"$nodeid#$id"
		678	}
		679
		680	=item after $timeout, @msg
		681
		682	=item after $timeout, $callback
		683
		684	Either sends the given message, or call the given callback, after the
		685	specified number of seconds.
		686
		687	This is simply a utility function that comes in handy at times - the
		688	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		689	so it may go away in the future.
		690
		691	=cut
		692
		693	sub after($@) {
		694	my ($timeout, @action) = @_;
		695
		696	my $t; $t = AE::timer $timeout, 0, sub {
		697	undef $t;
		698	ref $action[0]
		699	? $action[0]()
		700	: snd @action;
		701	};
		702	}
		703
499	=back	704	=back
500		705
501	=head1 FUNCTIONS FOR NODES	706	=head1 AnyEvent::MP vs. Distributed Erlang
		707
		708	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
		709	== aemp node, Erlang process == aemp port), so many of the documents and
		710	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
		711	sample:
		712
		713	http://www.Erlang.se/doc/programming_rules.shtml
		714	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
		715	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6
		716	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
		717
		718	Despite the similarities, there are also some important differences:
502		719
503	=over 4	720	=over 4
504		721
505	=item become_public $noderef	722	=item * Node IDs are arbitrary strings in AEMP.
506		723
507	Tells the node to become a public node, i.e. reachable from other nodes.
508
509	The first argument is the (unresolved) node reference of the local node
510	(if missing then the empty string is used).
511
512	It is quite common to not specify anything, in which case the local node
513	tries to listen on the default port, or to only specify a port number, in
514	which case AnyEvent::MP tries to guess the local addresses.
515
516	=cut
517
518	=back
519
520	=head1 NODE MESSAGES
521
522	Nodes understand the following messages sent to them. Many of them take
523	arguments called C<@reply>, which will simply be used to compose a reply
524	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
525	the remaining arguments are simply the message data.
526
527	While other messages exist, they are not public and subject to change.
528
529	=over 4
530
531	=cut
532
533	=item lookup => $name, @reply
534
535	Replies with the port ID of the specified well-known port, or C<undef>.
536
537	=item devnull => ...
538
539	Generic data sink/CPU heat conversion.
540
541	=item relay => $port, @msg
542
543	Simply forwards the message to the given port.
544
545	=item eval => $string[ @reply]
546
547	Evaluates the given string. If C<@reply> is given, then a message of the
548	form C<@reply, $@, @evalres> is sent.
549
550	Example: crash another node.
551
552	snd $othernode, eval => "exit";
553
554	=item time => @reply
555
556	Replies the the current node time to C<@reply>.
557
558	Example: tell the current node to send the current time to C<$myport> in a
559	C<timereply> message.
560
561	snd $NODE, time => $myport, timereply => 1, 2;
562	# => snd $myport, timereply => 1, 2, <time>
563
564	=back
565
566	=head1 AnyEvent::MP vs. Distributed Erlang
567
568	AnyEvent::MP got lots of its ideas from distributed erlang (erlang node
569	== aemp node, erlang process == aemp port), so many of the documents and
570	programming techniques employed by erlang apply to AnyEvent::MP. Here is a
571	sample:
572
573	http://www.erlang.se/doc/programming_rules.shtml
574	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
575	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
576	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
577
578	Despite the similarities, there are also some important differences:
579
580	=over 4
581
582	=item * Node references contain the recipe on how to contact them.
583
584	Erlang relies on special naming and DNS to work everywhere in the	724	Erlang relies on special naming and DNS to work everywhere in the same
585	same way. AEMP relies on each node knowing it's own address(es), with	725	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
586	convenience functionality.	726	configuration or DNS), but will otherwise discover other odes itself.
587		727
588	This means that AEMP requires a less tightly controlled environment at the	728	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
589	cost of longer node references and a slightly higher management overhead.	729	uses "local ports are like remote ports".
		730
		731	The failure modes for local ports are quite different (runtime errors
		732	only) then for remote ports - when a local port dies, you I<know> it dies,
		733	when a connection to another node dies, you know nothing about the other
		734	port.
		735
		736	Erlang pretends remote ports are as reliable as local ports, even when
		737	they are not.
		738
		739	AEMP encourages a "treat remote ports differently" philosophy, with local
		740	ports being the special case/exception, where transport errors cannot
		741	occur.
590		742
591	=item * Erlang uses processes and a mailbox, AEMP does not queue.	743	=item * Erlang uses processes and a mailbox, AEMP does not queue.
592		744
593	Erlang uses processes that selctively receive messages, and therefore	745	Erlang uses processes that selectively receive messages, and therefore
594	needs a queue. AEMP is event based, queuing messages would serve no useful	746	needs a queue. AEMP is event based, queuing messages would serve no
595	purpose.	747	useful purpose. For the same reason the pattern-matching abilities of
		748	AnyEvent::MP are more limited, as there is little need to be able to
		749	filter messages without dequeuing them.
596		750
597	(But see L<Coro::MP> for a more erlang-like process model on top of AEMP).	751	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
598		752
599	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	753	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
600		754
601	Sending messages in erlang is synchronous and blocks the process. AEMP	755	Sending messages in Erlang is synchronous and blocks the process (and
602	sends are immediate, connection establishment is handled in the	756	so does not need a queue that can overflow). AEMP sends are immediate,
603	background.	757	connection establishment is handled in the background.
604		758
605	=item * Erlang can silently lose messages, AEMP cannot.	759	=item * Erlang suffers from silent message loss, AEMP does not.
606		760
607	Erlang makes few guarantees on messages delivery - messages can get lost	761	Erlang makes few guarantees on messages delivery - messages can get lost
608	without any of the processes realising it (i.e. you send messages a, b,	762	without any of the processes realising it (i.e. you send messages a, b,
609	and c, and the other side only receives messages a and c).	763	and c, and the other side only receives messages a and c).
610		764
611	AEMP guarantees correct ordering, and the guarantee that there are no	765	AEMP guarantees correct ordering, and the guarantee that after one message
612	holes in the message sequence.	766	is lost, all following ones sent to the same port are lost as well, until
613		767	monitoring raises an error, so there are no silent "holes" in the message
614	=item * In erlang, processes can be declared dead and later be found to be	768	sequence.
615	alive.
616
617	In erlang it can happen that a monitored process is declared dead and
618	linked processes get killed, but later it turns out that the process is
619	still alive - and can receive messages.
620
621	In AEMP, when port monitoring detects a port as dead, then that port will
622	eventually be killed - it cannot happen that a node detects a port as dead
623	and then later sends messages to it, finding it is still alive.
624		769
625	=item * Erlang can send messages to the wrong port, AEMP does not.	770	=item * Erlang can send messages to the wrong port, AEMP does not.
626		771
627	In erlang it is quite possible that a node that restarts reuses a process	772	In Erlang it is quite likely that a node that restarts reuses a process ID
628	ID known to other nodes for a completely different process, causing	773	known to other nodes for a completely different process, causing messages
629	messages destined for that process to end up in an unrelated process.	774	destined for that process to end up in an unrelated process.
630		775
631	AEMP never reuses port IDs, so old messages or old port IDs floating	776	AEMP never reuses port IDs, so old messages or old port IDs floating
632	around in the network will not be sent to an unrelated port.	777	around in the network will not be sent to an unrelated port.
633		778
634	=item * Erlang uses unprotected connections, AEMP uses secure	779	=item * Erlang uses unprotected connections, AEMP uses secure
635	authentication and can use TLS.	780	authentication and can use TLS.
636		781
637	AEMP can use a proven protocol - SSL/TLS - to protect connections and	782	AEMP can use a proven protocol - TLS - to protect connections and
638	securely authenticate nodes.	783	securely authenticate nodes.
639		784
640	=item * The AEMP protocol is optimised for both text-based and binary	785	=item * The AEMP protocol is optimised for both text-based and binary
641	communications.	786	communications.
642		787
643	The AEMP protocol, unlike the erlang protocol, supports both	788	The AEMP protocol, unlike the Erlang protocol, supports both programming
644	language-independent text-only protocols (good for debugging) and binary,	789	language independent text-only protocols (good for debugging) and binary,
645	language-specific serialisers (e.g. Storable).	790	language-specific serialisers (e.g. Storable). By default, unless TLS is
		791	used, the protocol is actually completely text-based.
646		792
647	It has also been carefully designed to be implementable in other languages	793	It has also been carefully designed to be implementable in other languages
648	with a minimum of work while gracefully degrading fucntionality to make the	794	with a minimum of work while gracefully degrading functionality to make the
649	protocol simple.	795	protocol simple.
650		796
		797	=item * AEMP has more flexible monitoring options than Erlang.
		798
		799	In Erlang, you can chose to receive I<all> exit signals as messages
		800	or I<none>, there is no in-between, so monitoring single processes is
		801	difficult to implement. Monitoring in AEMP is more flexible than in
		802	Erlang, as one can choose between automatic kill, exit message or callback
		803	on a per-process basis.
		804
		805	=item * Erlang tries to hide remote/local connections, AEMP does not.
		806
		807	Monitoring in Erlang is not an indicator of process death/crashes, in the
		808	same way as linking is (except linking is unreliable in Erlang).
		809
		810	In AEMP, you don't "look up" registered port names or send to named ports
		811	that might or might not be persistent. Instead, you normally spawn a port
		812	on the remote node. The init function monitors you, and you monitor the
		813	remote port. Since both monitors are local to the node, they are much more
		814	reliable (no need for C<spawn_link>).
		815
		816	This also saves round-trips and avoids sending messages to the wrong port
		817	(hard to do in Erlang).
		818
651	=back	819	=back
652		820
		821	=head1 RATIONALE
		822
		823	=over 4
		824
		825	=item Why strings for port and node IDs, why not objects?
		826
		827	We considered "objects", but found that the actual number of methods
		828	that can be called are quite low. Since port and node IDs travel over
		829	the network frequently, the serialising/deserialising would add lots of
		830	overhead, as well as having to keep a proxy object everywhere.
		831
		832	Strings can easily be printed, easily serialised etc. and need no special
		833	procedures to be "valid".
		834
		835	And as a result, a miniport consists of a single closure stored in a
		836	global hash - it can't become much cheaper.
		837
		838	=item Why favour JSON, why not a real serialising format such as Storable?
		839
		840	In fact, any AnyEvent::MP node will happily accept Storable as framing
		841	format, but currently there is no way to make a node use Storable by
		842	default (although all nodes will accept it).
		843
		844	The default framing protocol is JSON because a) JSON::XS is many times
		845	faster for small messages and b) most importantly, after years of
		846	experience we found that object serialisation is causing more problems
		847	than it solves: Just like function calls, objects simply do not travel
		848	easily over the network, mostly because they will always be a copy, so you
		849	always have to re-think your design.
		850
		851	Keeping your messages simple, concentrating on data structures rather than
		852	objects, will keep your messages clean, tidy and efficient.
		853
		854	=back
		855
653	=head1 SEE ALSO	856	=head1 SEE ALSO
		857
		858	L<AnyEvent::MP::Intro> - a gentle introduction.
		859
		860	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		861
		862	L<AnyEvent::MP::Global> - network maintainance and port groups, to find
		863	your applications.
654		864
655	L<AnyEvent>.	865	L<AnyEvent>.
656		866
657	=head1 AUTHOR	867	=head1 AUTHOR
658		868

Diff Legend

-–
+Removed lines
-+
+Added lines
-<
+Changed lines
->
+Changed lines

Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.32 by root, Wed Aug 5 19:58:46 2009 UTC vs. Revision 1.80 by root, Fri Sep 4 22:30:29 2009 UTC

Diff Legend

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.32 by root, Wed Aug 5 19:58:46 2009 UTC vs.
Revision 1.80 by root, Fri Sep 4 22:30:29 2009 UTC