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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.29 by root, Tue Aug 4 23:16:57 2009 UTC vs.
Revision 1.85 by root, Tue Sep 8 01:54:13 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 it's 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-Z_][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. They should also be relatively responsive - a
		118	seed node that blocks for long periods will slow down everybody else.
		119
		120	=item seeds - C<host:port>
		121
		122	Seeds are transport endpoint(s) (usually a hostname/IP address and a
		123	TCP port) of nodes thta should be used as seed nodes.
		124
		125	The nodes listening on those endpoints are expected to be long-running,
		126	and at least one of those should always be available. When nodes run out
		127	of connections (e.g. due to a network error), they try to re-establish
		128	connections to some seednodes again to join the network.
84		129
85	=back	130	=back
86		131
87	=head1 VARIABLES/FUNCTIONS	132	=head1 VARIABLES/FUNCTIONS
88		133
…		…
90		135
91	=cut	136	=cut
92		137
93	package AnyEvent::MP;	138	package AnyEvent::MP;
94		139
95	use AnyEvent::MP::Base;	140	use AnyEvent::MP::Kernel;
96		141
97	use common::sense;	142	use common::sense;
98		143
99	use Carp ();	144	use Carp ();
100		145
101	use AE ();	146	use AE ();
102		147
103	use base "Exporter";	148	use base "Exporter";
104		149
105	our $VERSION = '0.1';	150	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
		151
106	our @EXPORT = qw(	152	our @EXPORT = qw(
107	NODE $NODE *SELF node_of _any_	153	NODE $NODE *SELF node_of after
108	resolve_node	154	configure
109	become_slave become_public
110	snd rcv mon kil reg psub	155	snd rcv mon mon_guard kil reg psub spawn
111	port	156	port
112	);	157	);
113		158
114	our $SELF;	159	our $SELF;
115		160
…		…
119	kil $SELF, die => $msg;	164	kil $SELF, die => $msg;
120	}	165	}
121		166
122	=item $thisnode = NODE / $NODE	167	=item $thisnode = NODE / $NODE
123		168
124	The C<NODE> function returns, and the C<$NODE> variable contains	169	The C<NODE> function returns, and the C<$NODE> variable contains, the node
125	the noderef of the local node. The value is initialised by a call	170	ID of the node running in the current process. This value is initialised by
126	to C<become_public> or C<become_slave>, after which all local port	171	a call to C<configure>.
127	identifiers become invalid.
128		172
129	=item $noderef = node_of $portid	173	=item $nodeid = node_of $port
130		174
131	Extracts and returns the noderef from a portid or a noderef.	175	Extracts and returns the node ID from a port ID or a node ID.
132		176
133	=item $cv = resolve_node $noderef	177	=item configure $profile, key => value...
134		178
135	Takes an unresolved node reference that may contain hostnames and	179	=item configure key => value...
136	abbreviated IDs, resolves all of them and returns a resolved node
137	reference.
138		180
139	In addition to C<address:port> pairs allowed in resolved noderefs, the	181	Before a node can talk to other nodes on the network (i.e. enter
140	following forms are supported:	182	"distributed mode") it has to configure itself - the minimum a node needs
		183	to know is its own name, and optionally it should know the addresses of
		184	some other nodes in the network to discover other nodes.
		185
		186	This function configures a node - it must be called exactly once (or
		187	never) before calling other AnyEvent::MP functions.
141		188
142	=over 4	189	=over 4
143		190
144	=item the empty string	191	=item step 1, gathering configuration from profiles
145		192
146	An empty-string component gets resolved as if the default port (4040) was	193	The function first looks up a profile in the aemp configuration (see the
147	specified.	194	L<aemp> commandline utility). The profile name can be specified via the
		195	named C<profile> parameter or can simply be the first parameter). If it is
		196	missing, then the nodename (F<uname -n>) will be used as profile name.
148		197
149	=item naked port numbers (e.g. C<1234>)	198	The profile data is then gathered as follows:
150		199
151	These are resolved by prepending the local nodename and a colon, to be	200	First, all remaining key => value pairs (all of which are conveniently
152	further resolved.	201	undocumented at the moment) will be interpreted as configuration
		202	data. Then they will be overwritten by any values specified in the global
		203	default configuration (see the F<aemp> utility), then the chain of
		204	profiles chosen by the profile name (and any C<parent> attributes).
153		205
154	=item hostnames (e.g. C<localhost:1234>, C<localhost>)	206	That means that the values specified in the profile have highest priority
		207	and the values specified directly via C<configure> have lowest priority,
		208	and can only be used to specify defaults.
155		209
156	These are resolved by using AnyEvent::DNS to resolve them, optionally	210	If the profile specifies a node ID, then this will become the node ID of
157	looking up SRV records for the C<aemp=4040> port, if no port was	211	this process. If not, then the profile name will be used as node ID. The
158	specified.	212	special node ID of C<anon/> will be replaced by a random node ID.
		213
		214	=item step 2, bind listener sockets
		215
		216	The next step is to look up the binds in the profile, followed by binding
		217	aemp protocol listeners on all binds specified (it is possible and valid
		218	to have no binds, meaning that the node cannot be contacted form the
		219	outside. This means the node cannot talk to other nodes that also have no
		220	binds, but it can still talk to all "normal" nodes).
		221
		222	If the profile does not specify a binds list, then a default of C<*> is
		223	used, meaning the node will bind on a dynamically-assigned port on every
		224	local IP address it finds.
		225
		226	=item step 3, connect to seed nodes
		227
		228	As the last step, the seeds list from the profile is passed to the
		229	L<AnyEvent::MP::Global> module, which will then use it to keep
		230	connectivity with at least one node at any point in time.
159		231
160	=back	232	=back
		233
		234	Example: become a distributed node using the locla node name as profile.
		235	This should be the most common form of invocation for "daemon"-type nodes.
		236
		237	configure
		238
		239	Example: become an anonymous node. This form is often used for commandline
		240	clients.
		241
		242	configure nodeid => "anon/";
		243
		244	Example: configure a node using a profile called seed, which si suitable
		245	for a seed node as it binds on all local addresses on a fixed port (4040,
		246	customary for aemp).
		247
		248	# use the aemp commandline utility
		249	# aemp profile seed nodeid anon/ binds '*:4040'
		250
		251	# then use it
		252	configure profile => "seed";
		253
		254	# or simply use aemp from the shell again:
		255	# aemp run profile seed
		256
		257	# or provide a nicer-to-remember nodeid
		258	# aemp run profile seed nodeid "$(hostname)"
161		259
162	=item $SELF	260	=item $SELF
163		261
164	Contains the current port id while executing C<rcv> callbacks or C<psub>	262	Contains the current port id while executing C<rcv> callbacks or C<psub>
165	blocks.	263	blocks.
166		264
167	=item SELF, %SELF, @SELF...	265	=item *SELF, SELF, %SELF, @SELF...
168		266
169	Due to some quirks in how perl exports variables, it is impossible to	267	Due to some quirks in how perl exports variables, it is impossible to
170	just export C<$SELF>, all the symbols called C<SELF> are exported by this	268	just export C<$SELF>, all the symbols named C<SELF> are exported by this
171	module, but only C<$SELF> is currently used.	269	module, but only C<$SELF> is currently used.
172		270
173	=item snd $portid, type => @data	271	=item snd $port, type => @data
174		272
175	=item snd $portid, @msg	273	=item snd $port, @msg
176		274
177	Send the given message to the given port ID, which can identify either	275	Send the given message to the given port, which can identify either a
178	a local or a remote port, and can be either a string or soemthignt hat	276	local or a remote port, and must be a port ID.
179	stringifies a sa port ID (such as a port object :).
180		277
181	While the message can be about anything, it is highly recommended to use a	278	While the message can be almost anything, it is highly recommended to
182	string as first element (a portid, or some word that indicates a request	279	use a string as first element (a port ID, or some word that indicates a
183	type etc.).	280	request type etc.) and to consist if only simple perl values (scalars,
		281	arrays, hashes) - if you think you need to pass an object, think again.
184		282
185	The message data effectively becomes read-only after a call to this	283	The message data logically becomes read-only after a call to this
186	function: modifying any argument is not allowed and can cause many	284	function: modifying any argument (or values referenced by them) is
187	problems.	285	forbidden, as there can be considerable time between the call to C<snd>
		286	and the time the message is actually being serialised - in fact, it might
		287	never be copied as within the same process it is simply handed to the
		288	receiving port.
188		289
189	The type of data you can transfer depends on the transport protocol: when	290	The type of data you can transfer depends on the transport protocol: when
190	JSON is used, then only strings, numbers and arrays and hashes consisting	291	JSON is used, then only strings, numbers and arrays and hashes consisting
191	of those are allowed (no objects). When Storable is used, then anything	292	of those are allowed (no objects). When Storable is used, then anything
192	that Storable can serialise and deserialise is allowed, and for the local	293	that Storable can serialise and deserialise is allowed, and for the local
193	node, anything can be passed.	294	node, anything can be passed. Best rely only on the common denominator of
		295	these.
194		296
195	=item kil $portid[, @reason]	297	=item $local_port = port
196		298
197	Kill the specified port with the given C<@reason>.	299	Create a new local port object and returns its port ID. Initially it has
		300	no callbacks set and will throw an error when it receives messages.
198		301
199	If no C<@reason> is specified, then the port is killed "normally" (linked	302	=item $local_port = port { my @msg = @_ }
200	ports will not be kileld, or even notified).
201		303
202	Otherwise, linked ports get killed with the same reason (second form of	304	Creates a new local port, and returns its ID. Semantically the same as
203	C<mon>, see below).	305	creating a port and calling C<rcv $port, $callback> on it.
204		306
205	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	307	The block will be called for every message received on the port, with the
206	will be reported as reason C<< die => $@ >>.	308	global variable C<$SELF> set to the port ID. Runtime errors will cause the
		309	port to be C<kil>ed. The message will be passed as-is, no extra argument
		310	(i.e. no port ID) will be passed to the callback.
207		311
208	Transport/communication errors are reported as C<< transport_error =>	312	If you want to stop/destroy the port, simply C<kil> it:
209	$message >>.
210		313
211	=item $guard = mon $portid, $cb->(@reason)	314	my $port = port {
		315	my @msg = @_;
		316	...
		317	kil $SELF;
		318	};
212		319
213	=item $guard = mon $portid, $otherport	320	=cut
214		321
215	=item $guard = mon $portid, $otherport, @msg	322	sub rcv($@);
216		323
		324	sub _kilme {
		325	die "received message on port without callback";
		326	}
		327
		328	sub port(;&) {
		329	my $id = "$UNIQ." . $ID++;
		330	my $port = "$NODE#$id";
		331
		332	rcv $port, shift \|\| \&_kilme;
		333
		334	$port
		335	}
		336
		337	=item rcv $local_port, $callback->(@msg)
		338
		339	Replaces the default callback on the specified port. There is no way to
		340	remove the default callback: use C<sub { }> to disable it, or better
		341	C<kil> the port when it is no longer needed.
		342
		343	The global C<$SELF> (exported by this module) contains C<$port> while
		344	executing the callback. Runtime errors during callback execution will
		345	result in the port being C<kil>ed.
		346
		347	The default callback received all messages not matched by a more specific
		348	C<tag> match.
		349
		350	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
		351
		352	Register (or replace) callbacks to be called on messages starting with the
		353	given tag on the given port (and return the port), or unregister it (when
		354	C<$callback> is C<$undef> or missing). There can only be one callback
		355	registered for each tag.
		356
		357	The original message will be passed to the callback, after the first
		358	element (the tag) has been removed. The callback will use the same
		359	environment as the default callback (see above).
		360
		361	Example: create a port and bind receivers on it in one go.
		362
		363	my $port = rcv port,
		364	msg1 => sub { ... },
		365	msg2 => sub { ... },
		366	;
		367
		368	Example: create a port, bind receivers and send it in a message elsewhere
		369	in one go:
		370
		371	snd $otherport, reply =>
		372	rcv port,
		373	msg1 => sub { ... },
		374	...
		375	;
		376
		377	Example: temporarily register a rcv callback for a tag matching some port
		378	(e.g. for a rpc reply) and unregister it after a message was received.
		379
		380	rcv $port, $otherport => sub {
		381	my @reply = @_;
		382
		383	rcv $SELF, $otherport;
		384	};
		385
		386	=cut
		387
		388	sub rcv($@) {
		389	my $port = shift;
		390	my ($nodeid, $portid) = split /#/, $port, 2;
		391
		392	$NODE{$nodeid} == $NODE{""}
		393	or Carp::croak "$port: rcv can only be called on local ports, caught";
		394
		395	while (@_) {
		396	if (ref $_[0]) {
		397	if (my $self = $PORT_DATA{$portid}) {
		398	"AnyEvent::MP::Port" eq ref $self
		399	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		400
		401	$self->[2] = shift;
		402	} else {
		403	my $cb = shift;
		404	$PORT{$portid} = sub {
		405	local $SELF = $port;
		406	eval { &$cb }; _self_die if $@;
		407	};
		408	}
		409	} elsif (defined $_[0]) {
		410	my $self = $PORT_DATA{$portid} \|\|= do {
		411	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
		412
		413	$PORT{$portid} = sub {
		414	local $SELF = $port;
		415
		416	if (my $cb = $self->[1]{$_[0]}) {
		417	shift;
		418	eval { &$cb }; _self_die if $@;
		419	} else {
		420	&{ $self->[0] };
		421	}
		422	};
		423
		424	$self
		425	};
		426
		427	"AnyEvent::MP::Port" eq ref $self
		428	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		429
		430	my ($tag, $cb) = splice @_, 0, 2;
		431
		432	if (defined $cb) {
		433	$self->[1]{$tag} = $cb;
		434	} else {
		435	delete $self->[1]{$tag};
		436	}
		437	}
		438	}
		439
		440	$port
		441	}
		442
		443	=item $closure = psub { BLOCK }
		444
		445	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
		446	closure is executed, sets up the environment in the same way as in C<rcv>
		447	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		448
		449	This is useful when you register callbacks from C<rcv> callbacks:
		450
		451	rcv delayed_reply => sub {
		452	my ($delay, @reply) = @_;
		453	my $timer = AE::timer $delay, 0, psub {
		454	snd @reply, $SELF;
		455	};
		456	};
		457
		458	=cut
		459
		460	sub psub(&) {
		461	my $cb = shift;
		462
		463	my $port = $SELF
		464	or Carp::croak "psub can only be called from within rcv or psub callbacks, not";
		465
		466	sub {
		467	local $SELF = $port;
		468
		469	if (wantarray) {
		470	my @res = eval { &$cb };
		471	_self_die if $@;
		472	@res
		473	} else {
		474	my $res = eval { &$cb };
		475	_self_die if $@;
		476	$res
		477	}
		478	}
		479	}
		480
		481	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
		482
		483	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
		484
		485	=item $guard = mon $port # kill $SELF when $port dies
		486
		487	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
		488
217	Monitor the given port and do something when the port is killed.	489	Monitor the given port and do something when the port is killed or
		490	messages to it were lost, and optionally return a guard that can be used
		491	to stop monitoring again.
218		492
219	In the first form, the callback is simply called with any number	493	In the first form (callback), the callback is simply called with any
220	of C<@reason> elements (no @reason means that the port was deleted	494	number of C<@reason> elements (no @reason means that the port was deleted
221	"normally"). Note also that I<< the callback B<must> never die >>, so use	495	"normally"). Note also that I<< the callback B<must> never die >>, so use
222	C<eval> if unsure.	496	C<eval> if unsure.
223		497
224	In the second form, the other port will be C<kil>'ed with C<@reason>, iff	498	In the second form (another port given), the other port (C<$rcvport>)
225	a @reason was specified, i.e. on "normal" kils nothing happens, while	499	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
226	under all other conditions, the other port is killed with the same reason.	500	"normal" kils nothing happens, while under all other conditions, the other
		501	port is killed with the same reason.
227		502
		503	The third form (kill self) is the same as the second form, except that
		504	C<$rvport> defaults to C<$SELF>.
		505
228	In the last form, a message of the form C<@msg, @reason> will be C<snd>.	506	In the last form (message), a message of the form C<@msg, @reason> will be
		507	C<snd>.
		508
		509	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		510	alert was raised), they are removed and will not trigger again.
		511
		512	As a rule of thumb, monitoring requests should always monitor a port from
		513	a local port (or callback). The reason is that kill messages might get
		514	lost, just like any other message. Another less obvious reason is that
		515	even monitoring requests can get lost (for example, when the connection
		516	to the other node goes down permanently). When monitoring a port locally
		517	these problems do not exist.
		518
		519	C<mon> effectively guarantees that, in the absence of hardware failures,
		520	after starting the monitor, either all messages sent to the port will
		521	arrive, or the monitoring action will be invoked after possible message
		522	loss has been detected. No messages will be lost "in between" (after
		523	the first lost message no further messages will be received by the
		524	port). After the monitoring action was invoked, further messages might get
		525	delivered again.
		526
		527	Inter-host-connection timeouts and monitoring depend on the transport
		528	used. The only transport currently implemented is TCP, and AnyEvent::MP
		529	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		530	non-idle connection, and usually around two hours for idle conenctions).
		531
		532	This means that monitoring is good for program errors and cleaning up
		533	stuff eventually, but they are no replacement for a timeout when you need
		534	to ensure some maximum latency.
229		535
230	Example: call a given callback when C<$port> is killed.	536	Example: call a given callback when C<$port> is killed.
231		537
232	mon $port, sub { warn "port died because of <@_>\n" };	538	mon $port, sub { warn "port died because of <@_>\n" };
233		539
234	Example: kill ourselves when C<$port> is killed abnormally.	540	Example: kill ourselves when C<$port> is killed abnormally.
235		541
236	mon $port, $self;	542	mon $port;
237		543
238	Example: send us a restart message another C<$port> is killed.	544	Example: send us a restart message when another C<$port> is killed.
239		545
240	mon $port, $self => "restart";	546	mon $port, $self => "restart";
241		547
242	=cut	548	=cut
243		549
244	sub mon {	550	sub mon {
245	my ($noderef, $port, $cb) = ((split /#/, shift, 2), shift);	551	my ($nodeid, $port) = split /#/, shift, 2;
246		552
247	my $node = $NODE{$noderef} \|\| add_node $noderef;	553	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
248		554
249	#TODO: ports must not be references	555	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
250	if (!ref $cb or "AnyEvent::MP::Port" eq ref $cb) {	556
		557	unless (ref $cb) {
251	if (@_) {	558	if (@_) {
252	# send a kill info message	559	# send a kill info message
253	my (@msg) = ($cb, @_);	560	my (@msg) = ($cb, @_);
254	$cb = sub { snd @msg, @_ };	561	$cb = sub { snd @msg, @_ };
255	} else {	562	} else {
…		…
271	is killed, the references will be freed.	578	is killed, the references will be freed.
272		579
273	Optionally returns a guard that will stop the monitoring.	580	Optionally returns a guard that will stop the monitoring.
274		581
275	This function is useful when you create e.g. timers or other watchers and	582	This function is useful when you create e.g. timers or other watchers and
276	want to free them when the port gets killed:	583	want to free them when the port gets killed (note the use of C<psub>):
277		584
278	$port->rcv (start => sub {	585	$port->rcv (start => sub {
279	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	586	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
280	undef $timer if 0.9 < rand;	587	undef $timer if 0.9 < rand;
281	});	588	});
282	});	589	});
283		590
284	=cut	591	=cut
285		592
286	sub mon_guard {	593	sub mon_guard {
287	my ($port, @refs) = @_;	594	my ($port, @refs) = @_;
288		595
		596	#TODO: mon-less form?
		597
289	mon $port, sub { 0 && @refs }	598	mon $port, sub { 0 && @refs }
290	}	599	}
291		600
292	=item lnk $port1, $port2	601	=item kil $port[, @reason]
293		602
294	Link two ports. This is simply a shorthand for:	603	Kill the specified port with the given C<@reason>.
295		604
296	mon $port1, $port2;	605	If no C<@reason> is specified, then the port is killed "normally" (ports
297	mon $port2, $port1;	606	monitoring other ports will not necessarily die because a port dies
		607	"normally").
298		608
299	It means that if either one is killed abnormally, the other one gets	609	Otherwise, linked ports get killed with the same reason (second form of
300	killed as well.	610	C<mon>, see above).
301		611
302	=item $local_port = port	612	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
		613	will be reported as reason C<< die => $@ >>.
303		614
304	Create a new local port object that supports message matching.	615	Transport/communication errors are reported as C<< transport_error =>
		616	$message >>.
305		617
306	=item $portid = port { my @msg = @_; $finished }
307
308	Creates a "mini port", that is, a very lightweight port without any
309	pattern matching behind it, and returns its ID.
310
311	The block will be called for every message received on the port. When the
312	callback returns a true value its job is considered "done" and the port
313	will be destroyed. Otherwise it will stay alive.
314
315	The message will be passed as-is, no extra argument (i.e. no port id) will
316	be passed to the callback.
317
318	If you need the local port id in the callback, this works nicely:
319
320	my $port; $port = miniport {
321	snd $otherport, reply => $port;
322	};
323
324	=cut	618	=cut
325		619
326	sub port(;&) {	620	=item $port = spawn $node, $initfunc[, @initdata]
327	my $id = "$UNIQ." . $ID++;
328	my $port = "$NODE#$id";
329		621
330	if (@_) {	622	Creates a port on the node C<$node> (which can also be a port ID, in which
331	my $cb = shift;	623	case it's the node where that port resides).
332	$PORT{$id} = sub {	624
333	local $SELF = $port;	625	The port ID of the newly created port is returned immediately, and it is
334	eval {	626	possible to immediately start sending messages or to monitor the port.
335	&$cb	627
336	and kil $id;	628	After the port has been created, the init function is called on the remote
		629	node, in the same context as a C<rcv> callback. This function must be a
		630	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
		631	specify a function in the main program, use C<::name>.
		632
		633	If the function doesn't exist, then the node tries to C<require>
		634	the package, then the package above the package and so on (e.g.
		635	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
		636	exists or it runs out of package names.
		637
		638	The init function is then called with the newly-created port as context
		639	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		640	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		641	the port might not get created.
		642
		643	A common idiom is to pass a local port, immediately monitor the spawned
		644	port, and in the remote init function, immediately monitor the passed
		645	local port. This two-way monitoring ensures that both ports get cleaned up
		646	when there is a problem.
		647
		648	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		649	caller before C<spawn> returns (by delaying invocation when spawn is
		650	called for the local node).
		651
		652	Example: spawn a chat server port on C<$othernode>.
		653
		654	# this node, executed from within a port context:
		655	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
		656	mon $server;
		657
		658	# init function on C<$othernode>
		659	sub connect {
		660	my ($srcport) = @_;
		661
		662	mon $srcport;
		663
		664	rcv $SELF, sub {
337	};	665	...
338	_self_die if $@;
339	};
340	} else {
341	my $self = bless {
342	id => "$NODE#$id",
343	}, "AnyEvent::MP::Port";
344
345	$PORT_DATA{$id} = $self;
346	$PORT{$id} = sub {
347	local $SELF = $port;
348
349	eval {
350	for (@{ $self->{rc0}{$_[0]} }) {
351	$_ && &{$_->[0]}
352	&& undef $_;
353	}
354
355	for (@{ $self->{rcv}{$_[0]} }) {
356	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
357	&& &{$_->[0]}
358	&& undef $_;
359	}
360
361	for (@{ $self->{any} }) {
362	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
363	&& &{$_->[0]}
364	&& undef $_;
365	}
366	};
367	_self_die if $@;
368	};	666	};
369	}	667	}
370		668
371	$port
372	}
373
374	=item reg $portid, $name
375
376	Registers the given port under the name C<$name>. If the name already
377	exists it is replaced.
378
379	A port can only be registered under one well known name.
380
381	A port automatically becomes unregistered when it is killed.
382
383	=cut	669	=cut
384		670
385	sub reg(@) {	671	sub _spawn {
386	my ($portid, $name) = @_;	672	my $port = shift;
		673	my $init = shift;
387		674
388	$REG{$name} = $portid;	675	# rcv will create the actual port
389	}	676	local $SELF = "$NODE#$port";
390		677	eval {
391	=item rcv $portid, tagstring => $callback->(@msg), ...	678	&{ load_func $init }
392
393	=item rcv $portid, $smartmatch => $callback->(@msg), ...
394
395	=item rcv $portid, [$smartmatch...] => $callback->(@msg), ...
396
397	Register callbacks to be called on matching messages on the given port.
398
399	The callback has to return a true value when its work is done, after
400	which is will be removed, or a false value in which case it will stay
401	registered.
402
403	The global C<$SELF> (exported by this module) contains C<$portid> while
404	executing the callback.
405
406	Runtime errors wdurign callback execution will result in the port being
407	C<kil>ed.
408
409	If the match is an array reference, then it will be matched against the
410	first elements of the message, otherwise only the first element is being
411	matched.
412
413	Any element in the match that is specified as C<_any_> (a function
414	exported by this module) matches any single element of the message.
415
416	While not required, it is highly recommended that the first matching
417	element is a string identifying the message. The one-string-only match is
418	also the most efficient match (by far).
419
420	=cut
421
422	sub rcv($@) {
423	my ($noderef, $port) = split /#/, shift, 2;
424
425	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}
426	or Carp::croak "$noderef#$port: rcv can only be called on local ports, caught";
427
428	my $self = $PORT_DATA{$port}
429	or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught";
430
431	"AnyEvent::MP::Port" eq ref $self
432	or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught";
433
434	while (@_) {
435	my ($match, $cb) = splice @_, 0, 2;
436
437	if (!ref $match) {
438	push @{ $self->{rc0}{$match} }, [$cb];
439	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
440	my ($type, @match) = @$match;
441	@match
442	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
443	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
444	} else {
445	push @{ $self->{any} }, [$cb, $match];
446	}
447	}
448	}
449
450	=item $closure = psub { BLOCK }
451
452	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
453	closure is executed, sets up the environment in the same way as in C<rcv>
454	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
455
456	This is useful when you register callbacks from C<rcv> callbacks:
457
458	rcv delayed_reply => sub {
459	my ($delay, @reply) = @_;
460	my $timer = AE::timer $delay, 0, psub {
461	snd @reply, $SELF;
462	};
463	};	679	};
464
465	=cut
466
467	sub psub(&) {
468	my $cb = shift;
469
470	my $port = $SELF
471	or Carp::croak "psub can only be called from within rcv or psub callbacks, not";
472
473	sub {
474	local $SELF = $port;
475
476	if (wantarray) {
477	my @res = eval { &$cb };
478	_self_die if $@;	680	_self_die if $@;
479	@res	681	}
480	} else {	682
481	my $res = eval { &$cb };	683	sub spawn(@) {
482	_self_die if $@;	684	my ($nodeid, undef) = split /#/, shift, 2;
483	$res	685
484	}	686	my $id = "$RUNIQ." . $ID++;
		687
		688	$_[0] =~ /::/
		689	or Carp::croak "spawn init function must be a fully-qualified name, caught";
		690
		691	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
		692
		693	"$nodeid#$id"
		694	}
		695
		696	=item after $timeout, @msg
		697
		698	=item after $timeout, $callback
		699
		700	Either sends the given message, or call the given callback, after the
		701	specified number of seconds.
		702
		703	This is simply a utility function that comes in handy at times - the
		704	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		705	so it may go away in the future.
		706
		707	=cut
		708
		709	sub after($@) {
		710	my ($timeout, @action) = @_;
		711
		712	my $t; $t = AE::timer $timeout, 0, sub {
		713	undef $t;
		714	ref $action[0]
		715	? $action[0]()
		716	: snd @action;
485	}	717	};
486	}	718	}
487		719
488	=back	720	=back
489		721
490	=head1 FUNCTIONS FOR NODES	722	=head1 AnyEvent::MP vs. Distributed Erlang
		723
		724	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
		725	== aemp node, Erlang process == aemp port), so many of the documents and
		726	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
		727	sample:
		728
		729	http://www.Erlang.se/doc/programming_rules.shtml
		730	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
		731	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6
		732	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
		733
		734	Despite the similarities, there are also some important differences:
491		735
492	=over 4	736	=over 4
493		737
494	=item become_public $noderef	738	=item * Node IDs are arbitrary strings in AEMP.
495		739
496	Tells the node to become a public node, i.e. reachable from other nodes.
497
498	The first argument is the (unresolved) node reference of the local node
499	(if missing then the empty string is used).
500
501	It is quite common to not specify anything, in which case the local node
502	tries to listen on the default port, or to only specify a port number, in
503	which case AnyEvent::MP tries to guess the local addresses.
504
505	=cut
506
507	=back
508
509	=head1 NODE MESSAGES
510
511	Nodes understand the following messages sent to them. Many of them take
512	arguments called C<@reply>, which will simply be used to compose a reply
513	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
514	the remaining arguments are simply the message data.
515
516	While other messages exist, they are not public and subject to change.
517
518	=over 4
519
520	=cut
521
522	=item lookup => $name, @reply
523
524	Replies with the port ID of the specified well-known port, or C<undef>.
525
526	=item devnull => ...
527
528	Generic data sink/CPU heat conversion.
529
530	=item relay => $port, @msg
531
532	Simply forwards the message to the given port.
533
534	=item eval => $string[ @reply]
535
536	Evaluates the given string. If C<@reply> is given, then a message of the
537	form C<@reply, $@, @evalres> is sent.
538
539	Example: crash another node.
540
541	snd $othernode, eval => "exit";
542
543	=item time => @reply
544
545	Replies the the current node time to C<@reply>.
546
547	Example: tell the current node to send the current time to C<$myport> in a
548	C<timereply> message.
549
550	snd $NODE, time => $myport, timereply => 1, 2;
551	# => snd $myport, timereply => 1, 2, <time>
552
553	=back
554
555	=head1 AnyEvent::MP vs. Distributed Erlang
556
557	AnyEvent::MP got lots of its ideas from distributed erlang (erlang node
558	== aemp node, erlang process == aemp port), so many of the documents and
559	programming techniques employed by erlang apply to AnyEvent::MP. Here is a
560	sample:
561
562	http://www.erlang.se/doc/programming_rules.shtml
563	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
564	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
565	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
566
567	Despite the similarities, there are also some important differences:
568
569	=over 4
570
571	=item * Node references contain the recipe on how to contact them.
572
573	Erlang relies on special naming and DNS to work everywhere in the	740	Erlang relies on special naming and DNS to work everywhere in the same
574	same way. AEMP relies on each node knowing it's own address(es), with	741	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
575	convenience functionality.	742	configuration or DNS), but will otherwise discover other odes itself.
576		743
577	This means that AEMP requires a less tightly controlled environment at the	744	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
578	cost of longer node references and a slightly higher management overhead.	745	uses "local ports are like remote ports".
		746
		747	The failure modes for local ports are quite different (runtime errors
		748	only) then for remote ports - when a local port dies, you I<know> it dies,
		749	when a connection to another node dies, you know nothing about the other
		750	port.
		751
		752	Erlang pretends remote ports are as reliable as local ports, even when
		753	they are not.
		754
		755	AEMP encourages a "treat remote ports differently" philosophy, with local
		756	ports being the special case/exception, where transport errors cannot
		757	occur.
579		758
580	=item * Erlang uses processes and a mailbox, AEMP does not queue.	759	=item * Erlang uses processes and a mailbox, AEMP does not queue.
581		760
582	Erlang uses processes that selctively receive messages, and therefore	761	Erlang uses processes that selectively receive messages, and therefore
583	needs a queue. AEMP is event based, queuing messages would serve no useful	762	needs a queue. AEMP is event based, queuing messages would serve no
584	purpose.	763	useful purpose. For the same reason the pattern-matching abilities of
		764	AnyEvent::MP are more limited, as there is little need to be able to
		765	filter messages without dequeuing them.
585		766
586	(But see L<Coro::MP> for a more erlang-like process model on top of AEMP).	767	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
587		768
588	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	769	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
589		770
590	Sending messages in erlang is synchronous and blocks the process. AEMP	771	Sending messages in Erlang is synchronous and blocks the process (and
591	sends are immediate, connection establishment is handled in the	772	so does not need a queue that can overflow). AEMP sends are immediate,
592	background.	773	connection establishment is handled in the background.
593		774
594	=item * Erlang can silently lose messages, AEMP cannot.	775	=item * Erlang suffers from silent message loss, AEMP does not.
595		776
596	Erlang makes few guarantees on messages delivery - messages can get lost	777	Erlang makes few guarantees on messages delivery - messages can get lost
597	without any of the processes realising it (i.e. you send messages a, b,	778	without any of the processes realising it (i.e. you send messages a, b,
598	and c, and the other side only receives messages a and c).	779	and c, and the other side only receives messages a and c).
599		780
600	AEMP guarantees correct ordering, and the guarantee that there are no	781	AEMP guarantees correct ordering, and the guarantee that after one message
601	holes in the message sequence.	782	is lost, all following ones sent to the same port are lost as well, until
602		783	monitoring raises an error, so there are no silent "holes" in the message
603	=item * In erlang, processes can be declared dead and later be found to be	784	sequence.
604	alive.
605
606	In erlang it can happen that a monitored process is declared dead and
607	linked processes get killed, but later it turns out that the process is
608	still alive - and can receive messages.
609
610	In AEMP, when port monitoring detects a port as dead, then that port will
611	eventually be killed - it cannot happen that a node detects a port as dead
612	and then later sends messages to it, finding it is still alive.
613		785
614	=item * Erlang can send messages to the wrong port, AEMP does not.	786	=item * Erlang can send messages to the wrong port, AEMP does not.
615		787
616	In erlang it is quite possible that a node that restarts reuses a process	788	In Erlang it is quite likely that a node that restarts reuses a process ID
617	ID known to other nodes for a completely different process, causing	789	known to other nodes for a completely different process, causing messages
618	messages destined for that process to end up in an unrelated process.	790	destined for that process to end up in an unrelated process.
619		791
620	AEMP never reuses port IDs, so old messages or old port IDs floating	792	AEMP never reuses port IDs, so old messages or old port IDs floating
621	around in the network will not be sent to an unrelated port.	793	around in the network will not be sent to an unrelated port.
622		794
623	=item * Erlang uses unprotected connections, AEMP uses secure	795	=item * Erlang uses unprotected connections, AEMP uses secure
624	authentication and can use TLS.	796	authentication and can use TLS.
625		797
626	AEMP can use a proven protocol - SSL/TLS - to protect connections and	798	AEMP can use a proven protocol - TLS - to protect connections and
627	securely authenticate nodes.	799	securely authenticate nodes.
628		800
629	=item * The AEMP protocol is optimised for both text-based and binary	801	=item * The AEMP protocol is optimised for both text-based and binary
630	communications.	802	communications.
631		803
632	The AEMP protocol, unlike the erlang protocol, supports both	804	The AEMP protocol, unlike the Erlang protocol, supports both programming
633	language-independent text-only protocols (good for debugging) and binary,	805	language independent text-only protocols (good for debugging) and binary,
634	language-specific serialisers (e.g. Storable).	806	language-specific serialisers (e.g. Storable). By default, unless TLS is
		807	used, the protocol is actually completely text-based.
635		808
636	It has also been carefully designed to be implementable in other languages	809	It has also been carefully designed to be implementable in other languages
637	with a minimum of work while gracefully degrading fucntionality to make the	810	with a minimum of work while gracefully degrading functionality to make the
638	protocol simple.	811	protocol simple.
639		812
		813	=item * AEMP has more flexible monitoring options than Erlang.
		814
		815	In Erlang, you can chose to receive I<all> exit signals as messages
		816	or I<none>, there is no in-between, so monitoring single processes is
		817	difficult to implement. Monitoring in AEMP is more flexible than in
		818	Erlang, as one can choose between automatic kill, exit message or callback
		819	on a per-process basis.
		820
		821	=item * Erlang tries to hide remote/local connections, AEMP does not.
		822
		823	Monitoring in Erlang is not an indicator of process death/crashes, in the
		824	same way as linking is (except linking is unreliable in Erlang).
		825
		826	In AEMP, you don't "look up" registered port names or send to named ports
		827	that might or might not be persistent. Instead, you normally spawn a port
		828	on the remote node. The init function monitors you, and you monitor the
		829	remote port. Since both monitors are local to the node, they are much more
		830	reliable (no need for C<spawn_link>).
		831
		832	This also saves round-trips and avoids sending messages to the wrong port
		833	(hard to do in Erlang).
		834
640	=back	835	=back
641		836
		837	=head1 RATIONALE
		838
		839	=over 4
		840
		841	=item Why strings for port and node IDs, why not objects?
		842
		843	We considered "objects", but found that the actual number of methods
		844	that can be called are quite low. Since port and node IDs travel over
		845	the network frequently, the serialising/deserialising would add lots of
		846	overhead, as well as having to keep a proxy object everywhere.
		847
		848	Strings can easily be printed, easily serialised etc. and need no special
		849	procedures to be "valid".
		850
		851	And as a result, a miniport consists of a single closure stored in a
		852	global hash - it can't become much cheaper.
		853
		854	=item Why favour JSON, why not a real serialising format such as Storable?
		855
		856	In fact, any AnyEvent::MP node will happily accept Storable as framing
		857	format, but currently there is no way to make a node use Storable by
		858	default (although all nodes will accept it).
		859
		860	The default framing protocol is JSON because a) JSON::XS is many times
		861	faster for small messages and b) most importantly, after years of
		862	experience we found that object serialisation is causing more problems
		863	than it solves: Just like function calls, objects simply do not travel
		864	easily over the network, mostly because they will always be a copy, so you
		865	always have to re-think your design.
		866
		867	Keeping your messages simple, concentrating on data structures rather than
		868	objects, will keep your messages clean, tidy and efficient.
		869
		870	=back
		871
642	=head1 SEE ALSO	872	=head1 SEE ALSO
		873
		874	L<AnyEvent::MP::Intro> - a gentle introduction.
		875
		876	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		877
		878	L<AnyEvent::MP::Global> - network maintainance and port groups, to find
		879	your applications.
		880
		881	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		882	all nodes.
643		883
644	L<AnyEvent>.	884	L<AnyEvent>.
645		885
646	=head1 AUTHOR	886	=head1 AUTHOR
647		887

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Revision 1.29 by root, Tue Aug 4 23:16:57 2009 UTC vs.
Revision 1.85 by root, Tue Sep 8 01:54:13 2009 UTC