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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.30 by root, Tue Aug 4 23:35:51 2009 UTC vs.
Revision 1.84 by root, Tue Sep 8 01:42:14 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-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.
		118
		119	=item seeds - C<host:port>
		120
		121	Seeds are transport endpoint(s) (usually a hostname/IP address and a
		122	TCP port) of nodes thta should be used as seed nodes.
		123
		124	The nodes listening on those endpoints are expected to be long-running,
		125	and at least one of those should always be available. When nodes run out
		126	of connections (e.g. due to a network error), they try to re-establish
		127	connections to some seednodes again to join the network.
84		128
85	=back	129	=back
86		130
87	=head1 VARIABLES/FUNCTIONS	131	=head1 VARIABLES/FUNCTIONS
88		132
…		…
90		134
91	=cut	135	=cut
92		136
93	package AnyEvent::MP;	137	package AnyEvent::MP;
94		138
95	use AnyEvent::MP::Base;	139	use AnyEvent::MP::Kernel;
96		140
97	use common::sense;	141	use common::sense;
98		142
99	use Carp ();	143	use Carp ();
100		144
101	use AE ();	145	use AE ();
102		146
103	use base "Exporter";	147	use base "Exporter";
104		148
105	our $VERSION = '0.1';	149	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
		150
106	our @EXPORT = qw(	151	our @EXPORT = qw(
107	NODE $NODE *SELF node_of _any_	152	NODE $NODE *SELF node_of after
108	resolve_node	153	configure
109	become_slave become_public
110	snd rcv mon kil reg psub	154	snd rcv mon mon_guard kil reg psub spawn
111	port	155	port
112	);	156	);
113		157
114	our $SELF;	158	our $SELF;
115		159
…		…
119	kil $SELF, die => $msg;	163	kil $SELF, die => $msg;
120	}	164	}
121		165
122	=item $thisnode = NODE / $NODE	166	=item $thisnode = NODE / $NODE
123		167
124	The C<NODE> function returns, and the C<$NODE> variable contains	168	The C<NODE> function returns, and the C<$NODE> variable contains, the node
125	the noderef of the local node. The value is initialised by a call	169	ID of the node running in the current process. This value is initialised by
126	to C<become_public> or C<become_slave>, after which all local port	170	a call to C<configure>.
127	identifiers become invalid.
128		171
129	=item $noderef = node_of $portid	172	=item $nodeid = node_of $port
130		173
131	Extracts and returns the noderef from a portid or a noderef.	174	Extracts and returns the node ID from a port ID or a node ID.
132		175
133	=item $cv = resolve_node $noderef	176	=item configure $profile, key => value...
134		177
135	Takes an unresolved node reference that may contain hostnames and	178	=item configure key => value...
136	abbreviated IDs, resolves all of them and returns a resolved node
137	reference.
138		179
139	In addition to C<address:port> pairs allowed in resolved noderefs, the	180	Before a node can talk to other nodes on the network (i.e. enter
140	following forms are supported:	181	"distributed mode") it has to configure itself - the minimum a node needs
		182	to know is its own name, and optionally it should know the addresses of
		183	some other nodes in the network to discover other nodes.
		184
		185	This function configures a node - it must be called exactly once (or
		186	never) before calling other AnyEvent::MP functions.
141		187
142	=over 4	188	=over 4
143		189
144	=item the empty string	190	=item step 1, gathering configuration from profiles
145		191
146	An empty-string component gets resolved as if the default port (4040) was	192	The function first looks up a profile in the aemp configuration (see the
147	specified.	193	L<aemp> commandline utility). The profile name can be specified via the
		194	named C<profile> parameter or can simply be the first parameter). If it is
		195	missing, then the nodename (F<uname -n>) will be used as profile name.
148		196
149	=item naked port numbers (e.g. C<1234>)	197	The profile data is then gathered as follows:
150		198
151	These are resolved by prepending the local nodename and a colon, to be	199	First, all remaining key => value pairs (all of which are conveniently
152	further resolved.	200	undocumented at the moment) will be interpreted as configuration
		201	data. Then they will be overwritten by any values specified in the global
		202	default configuration (see the F<aemp> utility), then the chain of
		203	profiles chosen by the profile name (and any C<parent> attributes).
153		204
154	=item hostnames (e.g. C<localhost:1234>, C<localhost>)	205	That means that the values specified in the profile have highest priority
		206	and the values specified directly via C<configure> have lowest priority,
		207	and can only be used to specify defaults.
155		208
156	These are resolved by using AnyEvent::DNS to resolve them, optionally	209	If the profile specifies a node ID, then this will become the node ID of
157	looking up SRV records for the C<aemp=4040> port, if no port was	210	this process. If not, then the profile name will be used as node ID. The
158	specified.	211	special node ID of C<anon/> will be replaced by a random node ID.
		212
		213	=item step 2, bind listener sockets
		214
		215	The next step is to look up the binds in the profile, followed by binding
		216	aemp protocol listeners on all binds specified (it is possible and valid
		217	to have no binds, meaning that the node cannot be contacted form the
		218	outside. This means the node cannot talk to other nodes that also have no
		219	binds, but it can still talk to all "normal" nodes).
		220
		221	If the profile does not specify a binds list, then a default of C<*> is
		222	used, meaning the node will bind on a dynamically-assigned port on every
		223	local IP address it finds.
		224
		225	=item step 3, connect to seed nodes
		226
		227	As the last step, the seeds list from the profile is passed to the
		228	L<AnyEvent::MP::Global> module, which will then use it to keep
		229	connectivity with at least one node at any point in time.
159		230
160	=back	231	=back
		232
		233	Example: become a distributed node using the locla node name as profile.
		234	This should be the most common form of invocation for "daemon"-type nodes.
		235
		236	configure
		237
		238	Example: become an anonymous node. This form is often used for commandline
		239	clients.
		240
		241	configure nodeid => "anon/";
		242
		243	Example: configure a node using a profile called seed, which si suitable
		244	for a seed node as it binds on all local addresses on a fixed port (4040,
		245	customary for aemp).
		246
		247	# use the aemp commandline utility
		248	# aemp profile seed nodeid anon/ binds '*:4040'
		249
		250	# then use it
		251	configure profile => "seed";
		252
		253	# or simply use aemp from the shell again:
		254	# aemp run profile seed
		255
		256	# or provide a nicer-to-remember nodeid
		257	# aemp run profile seed nodeid "$(hostname)"
161		258
162	=item $SELF	259	=item $SELF
163		260
164	Contains the current port id while executing C<rcv> callbacks or C<psub>	261	Contains the current port id while executing C<rcv> callbacks or C<psub>
165	blocks.	262	blocks.
166		263
167	=item SELF, %SELF, @SELF...	264	=item *SELF, SELF, %SELF, @SELF...
168		265
169	Due to some quirks in how perl exports variables, it is impossible to	266	Due to some quirks in how perl exports variables, it is impossible to
170	just export C<$SELF>, all the symbols called C<SELF> are exported by this	267	just export C<$SELF>, all the symbols named C<SELF> are exported by this
171	module, but only C<$SELF> is currently used.	268	module, but only C<$SELF> is currently used.
172		269
173	=item snd $portid, type => @data	270	=item snd $port, type => @data
174		271
175	=item snd $portid, @msg	272	=item snd $port, @msg
176		273
177	Send the given message to the given port ID, which can identify either	274	Send the given message to the given port, which can identify either a
178	a local or a remote port, and can be either a string or soemthignt hat	275	local or a remote port, and must be a port ID.
179	stringifies a sa port ID (such as a port object :).
180		276
181	While the message can be about anything, it is highly recommended to use a	277	While the message can be almost anything, it is highly recommended to
182	string as first element (a portid, or some word that indicates a request	278	use a string as first element (a port ID, or some word that indicates a
183	type etc.).	279	request type etc.) and to consist if only simple perl values (scalars,
		280	arrays, hashes) - if you think you need to pass an object, think again.
184		281
185	The message data effectively becomes read-only after a call to this	282	The message data logically becomes read-only after a call to this
186	function: modifying any argument is not allowed and can cause many	283	function: modifying any argument (or values referenced by them) is
187	problems.	284	forbidden, as there can be considerable time between the call to C<snd>
		285	and the time the message is actually being serialised - in fact, it might
		286	never be copied as within the same process it is simply handed to the
		287	receiving port.
188		288
189	The type of data you can transfer depends on the transport protocol: when	289	The type of data you can transfer depends on the transport protocol: when
190	JSON is used, then only strings, numbers and arrays and hashes consisting	290	JSON is used, then only strings, numbers and arrays and hashes consisting
191	of those are allowed (no objects). When Storable is used, then anything	291	of those are allowed (no objects). When Storable is used, then anything
192	that Storable can serialise and deserialise is allowed, and for the local	292	that Storable can serialise and deserialise is allowed, and for the local
193	node, anything can be passed.	293	node, anything can be passed. Best rely only on the common denominator of
		294	these.
194		295
195	=item kil $portid[, @reason]	296	=item $local_port = port
196		297
197	Kill the specified port with the given C<@reason>.	298	Create a new local port object and returns its port ID. Initially it has
		299	no callbacks set and will throw an error when it receives messages.
198		300
199	If no C<@reason> is specified, then the port is killed "normally" (linked	301	=item $local_port = port { my @msg = @_ }
200	ports will not be kileld, or even notified).
201		302
202	Otherwise, linked ports get killed with the same reason (second form of	303	Creates a new local port, and returns its ID. Semantically the same as
203	C<mon>, see below).	304	creating a port and calling C<rcv $port, $callback> on it.
204		305
205	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	306	The block will be called for every message received on the port, with the
206	will be reported as reason C<< die => $@ >>.	307	global variable C<$SELF> set to the port ID. Runtime errors will cause the
		308	port to be C<kil>ed. The message will be passed as-is, no extra argument
		309	(i.e. no port ID) will be passed to the callback.
207		310
208	Transport/communication errors are reported as C<< transport_error =>	311	If you want to stop/destroy the port, simply C<kil> it:
209	$message >>.
210		312
211	=item $guard = mon $portid, $cb->(@reason)	313	my $port = port {
		314	my @msg = @_;
		315	...
		316	kil $SELF;
		317	};
212		318
213	=item $guard = mon $portid, $otherport	319	=cut
214		320
215	=item $guard = mon $portid, $otherport, @msg	321	sub rcv($@);
216		322
		323	sub _kilme {
		324	die "received message on port without callback";
		325	}
		326
		327	sub port(;&) {
		328	my $id = "$UNIQ." . $ID++;
		329	my $port = "$NODE#$id";
		330
		331	rcv $port, shift \|\| \&_kilme;
		332
		333	$port
		334	}
		335
		336	=item rcv $local_port, $callback->(@msg)
		337
		338	Replaces the default callback on the specified port. There is no way to
		339	remove the default callback: use C<sub { }> to disable it, or better
		340	C<kil> the port when it is no longer needed.
		341
		342	The global C<$SELF> (exported by this module) contains C<$port> while
		343	executing the callback. Runtime errors during callback execution will
		344	result in the port being C<kil>ed.
		345
		346	The default callback received all messages not matched by a more specific
		347	C<tag> match.
		348
		349	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
		350
		351	Register (or replace) callbacks to be called on messages starting with the
		352	given tag on the given port (and return the port), or unregister it (when
		353	C<$callback> is C<$undef> or missing). There can only be one callback
		354	registered for each tag.
		355
		356	The original message will be passed to the callback, after the first
		357	element (the tag) has been removed. The callback will use the same
		358	environment as the default callback (see above).
		359
		360	Example: create a port and bind receivers on it in one go.
		361
		362	my $port = rcv port,
		363	msg1 => sub { ... },
		364	msg2 => sub { ... },
		365	;
		366
		367	Example: create a port, bind receivers and send it in a message elsewhere
		368	in one go:
		369
		370	snd $otherport, reply =>
		371	rcv port,
		372	msg1 => sub { ... },
		373	...
		374	;
		375
		376	Example: temporarily register a rcv callback for a tag matching some port
		377	(e.g. for a rpc reply) and unregister it after a message was received.
		378
		379	rcv $port, $otherport => sub {
		380	my @reply = @_;
		381
		382	rcv $SELF, $otherport;
		383	};
		384
		385	=cut
		386
		387	sub rcv($@) {
		388	my $port = shift;
		389	my ($nodeid, $portid) = split /#/, $port, 2;
		390
		391	$NODE{$nodeid} == $NODE{""}
		392	or Carp::croak "$port: rcv can only be called on local ports, caught";
		393
		394	while (@_) {
		395	if (ref $_[0]) {
		396	if (my $self = $PORT_DATA{$portid}) {
		397	"AnyEvent::MP::Port" eq ref $self
		398	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		399
		400	$self->[2] = shift;
		401	} else {
		402	my $cb = shift;
		403	$PORT{$portid} = sub {
		404	local $SELF = $port;
		405	eval { &$cb }; _self_die if $@;
		406	};
		407	}
		408	} elsif (defined $_[0]) {
		409	my $self = $PORT_DATA{$portid} \|\|= do {
		410	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
		411
		412	$PORT{$portid} = sub {
		413	local $SELF = $port;
		414
		415	if (my $cb = $self->[1]{$_[0]}) {
		416	shift;
		417	eval { &$cb }; _self_die if $@;
		418	} else {
		419	&{ $self->[0] };
		420	}
		421	};
		422
		423	$self
		424	};
		425
		426	"AnyEvent::MP::Port" eq ref $self
		427	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		428
		429	my ($tag, $cb) = splice @_, 0, 2;
		430
		431	if (defined $cb) {
		432	$self->[1]{$tag} = $cb;
		433	} else {
		434	delete $self->[1]{$tag};
		435	}
		436	}
		437	}
		438
		439	$port
		440	}
		441
		442	=item $closure = psub { BLOCK }
		443
		444	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
		445	closure is executed, sets up the environment in the same way as in C<rcv>
		446	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		447
		448	This is useful when you register callbacks from C<rcv> callbacks:
		449
		450	rcv delayed_reply => sub {
		451	my ($delay, @reply) = @_;
		452	my $timer = AE::timer $delay, 0, psub {
		453	snd @reply, $SELF;
		454	};
		455	};
		456
		457	=cut
		458
		459	sub psub(&) {
		460	my $cb = shift;
		461
		462	my $port = $SELF
		463	or Carp::croak "psub can only be called from within rcv or psub callbacks, not";
		464
		465	sub {
		466	local $SELF = $port;
		467
		468	if (wantarray) {
		469	my @res = eval { &$cb };
		470	_self_die if $@;
		471	@res
		472	} else {
		473	my $res = eval { &$cb };
		474	_self_die if $@;
		475	$res
		476	}
		477	}
		478	}
		479
		480	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
		481
		482	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
		483
		484	=item $guard = mon $port # kill $SELF when $port dies
		485
		486	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
		487
217	Monitor the given port and do something when the port is killed.	488	Monitor the given port and do something when the port is killed or
		489	messages to it were lost, and optionally return a guard that can be used
		490	to stop monitoring again.
218		491
219	In the first form, the callback is simply called with any number	492	In the first form (callback), the callback is simply called with any
220	of C<@reason> elements (no @reason means that the port was deleted	493	number of C<@reason> elements (no @reason means that the port was deleted
221	"normally"). Note also that I<< the callback B<must> never die >>, so use	494	"normally"). Note also that I<< the callback B<must> never die >>, so use
222	C<eval> if unsure.	495	C<eval> if unsure.
223		496
224	In the second form, the other port will be C<kil>'ed with C<@reason>, iff	497	In the second form (another port given), the other port (C<$rcvport>)
225	a @reason was specified, i.e. on "normal" kils nothing happens, while	498	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
226	under all other conditions, the other port is killed with the same reason.	499	"normal" kils nothing happens, while under all other conditions, the other
		500	port is killed with the same reason.
227		501
		502	The third form (kill self) is the same as the second form, except that
		503	C<$rvport> defaults to C<$SELF>.
		504
228	In the last form, a message of the form C<@msg, @reason> will be C<snd>.	505	In the last form (message), a message of the form C<@msg, @reason> will be
		506	C<snd>.
		507
		508	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		509	alert was raised), they are removed and will not trigger again.
		510
		511	As a rule of thumb, monitoring requests should always monitor a port from
		512	a local port (or callback). The reason is that kill messages might get
		513	lost, just like any other message. Another less obvious reason is that
		514	even monitoring requests can get lost (for example, when the connection
		515	to the other node goes down permanently). When monitoring a port locally
		516	these problems do not exist.
		517
		518	C<mon> effectively guarantees that, in the absence of hardware failures,
		519	after starting the monitor, either all messages sent to the port will
		520	arrive, or the monitoring action will be invoked after possible message
		521	loss has been detected. No messages will be lost "in between" (after
		522	the first lost message no further messages will be received by the
		523	port). After the monitoring action was invoked, further messages might get
		524	delivered again.
		525
		526	Inter-host-connection timeouts and monitoring depend on the transport
		527	used. The only transport currently implemented is TCP, and AnyEvent::MP
		528	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		529	non-idle connection, and usually around two hours for idle conenctions).
		530
		531	This means that monitoring is good for program errors and cleaning up
		532	stuff eventually, but they are no replacement for a timeout when you need
		533	to ensure some maximum latency.
229		534
230	Example: call a given callback when C<$port> is killed.	535	Example: call a given callback when C<$port> is killed.
231		536
232	mon $port, sub { warn "port died because of <@_>\n" };	537	mon $port, sub { warn "port died because of <@_>\n" };
233		538
234	Example: kill ourselves when C<$port> is killed abnormally.	539	Example: kill ourselves when C<$port> is killed abnormally.
235		540
236	mon $port, $self;	541	mon $port;
237		542
238	Example: send us a restart message another C<$port> is killed.	543	Example: send us a restart message when another C<$port> is killed.
239		544
240	mon $port, $self => "restart";	545	mon $port, $self => "restart";
241		546
242	=cut	547	=cut
243		548
244	sub mon {	549	sub mon {
245	my ($noderef, $port) = split /#/, shift, 2;	550	my ($nodeid, $port) = split /#/, shift, 2;
246		551
247	my $node = $NODE{$noderef} \|\| add_node $noderef;	552	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
248		553
249	my $cb = shift;	554	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
250		555
251	unless (ref $cb) {	556	unless (ref $cb) {
252	if (@_) {	557	if (@_) {
253	# send a kill info message	558	# send a kill info message
254	my (@msg) = ($cb, @_);	559	my (@msg) = ($cb, @_);
…		…
272	is killed, the references will be freed.	577	is killed, the references will be freed.
273		578
274	Optionally returns a guard that will stop the monitoring.	579	Optionally returns a guard that will stop the monitoring.
275		580
276	This function is useful when you create e.g. timers or other watchers and	581	This function is useful when you create e.g. timers or other watchers and
277	want to free them when the port gets killed:	582	want to free them when the port gets killed (note the use of C<psub>):
278		583
279	$port->rcv (start => sub {	584	$port->rcv (start => sub {
280	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	585	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
281	undef $timer if 0.9 < rand;	586	undef $timer if 0.9 < rand;
282	});	587	});
283	});	588	});
284		589
285	=cut	590	=cut
286		591
287	sub mon_guard {	592	sub mon_guard {
288	my ($port, @refs) = @_;	593	my ($port, @refs) = @_;
289		594
		595	#TODO: mon-less form?
		596
290	mon $port, sub { 0 && @refs }	597	mon $port, sub { 0 && @refs }
291	}	598	}
292		599
293	=item lnk $port1, $port2	600	=item kil $port[, @reason]
294		601
295	Link two ports. This is simply a shorthand for:	602	Kill the specified port with the given C<@reason>.
296		603
297	mon $port1, $port2;	604	If no C<@reason> is specified, then the port is killed "normally" (ports
298	mon $port2, $port1;	605	monitoring other ports will not necessarily die because a port dies
		606	"normally").
299		607
300	It means that if either one is killed abnormally, the other one gets	608	Otherwise, linked ports get killed with the same reason (second form of
301	killed as well.	609	C<mon>, see above).
302		610
303	=item $local_port = port	611	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
		612	will be reported as reason C<< die => $@ >>.
304		613
305	Create a new local port object that supports message matching.	614	Transport/communication errors are reported as C<< transport_error =>
		615	$message >>.
306		616
307	=item $portid = port { my @msg = @_; $finished }
308
309	Creates a "mini port", that is, a very lightweight port without any
310	pattern matching behind it, and returns its ID.
311
312	The block will be called for every message received on the port. When the
313	callback returns a true value its job is considered "done" and the port
314	will be destroyed. Otherwise it will stay alive.
315
316	The message will be passed as-is, no extra argument (i.e. no port id) will
317	be passed to the callback.
318
319	If you need the local port id in the callback, this works nicely:
320
321	my $port; $port = miniport {
322	snd $otherport, reply => $port;
323	};
324
325	=cut	617	=cut
326		618
327	sub port(;&) {	619	=item $port = spawn $node, $initfunc[, @initdata]
328	my $id = "$UNIQ." . $ID++;
329	my $port = "$NODE#$id";
330		620
331	if (@_) {	621	Creates a port on the node C<$node> (which can also be a port ID, in which
332	my $cb = shift;	622	case it's the node where that port resides).
333	$PORT{$id} = sub {	623
334	local $SELF = $port;	624	The port ID of the newly created port is returned immediately, and it is
335	eval {	625	possible to immediately start sending messages or to monitor the port.
336	&$cb	626
337	and kil $id;	627	After the port has been created, the init function is called on the remote
		628	node, in the same context as a C<rcv> callback. This function must be a
		629	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
		630	specify a function in the main program, use C<::name>.
		631
		632	If the function doesn't exist, then the node tries to C<require>
		633	the package, then the package above the package and so on (e.g.
		634	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
		635	exists or it runs out of package names.
		636
		637	The init function is then called with the newly-created port as context
		638	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		639	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		640	the port might not get created.
		641
		642	A common idiom is to pass a local port, immediately monitor the spawned
		643	port, and in the remote init function, immediately monitor the passed
		644	local port. This two-way monitoring ensures that both ports get cleaned up
		645	when there is a problem.
		646
		647	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		648	caller before C<spawn> returns (by delaying invocation when spawn is
		649	called for the local node).
		650
		651	Example: spawn a chat server port on C<$othernode>.
		652
		653	# this node, executed from within a port context:
		654	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
		655	mon $server;
		656
		657	# init function on C<$othernode>
		658	sub connect {
		659	my ($srcport) = @_;
		660
		661	mon $srcport;
		662
		663	rcv $SELF, sub {
338	};	664	...
339	_self_die if $@;
340	};
341	} else {
342	my $self = bless {
343	id => "$NODE#$id",
344	}, "AnyEvent::MP::Port";
345
346	$PORT_DATA{$id} = $self;
347	$PORT{$id} = sub {
348	local $SELF = $port;
349
350	eval {
351	for (@{ $self->{rc0}{$_[0]} }) {
352	$_ && &{$_->[0]}
353	&& undef $_;
354	}
355
356	for (@{ $self->{rcv}{$_[0]} }) {
357	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
358	&& &{$_->[0]}
359	&& undef $_;
360	}
361
362	for (@{ $self->{any} }) {
363	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
364	&& &{$_->[0]}
365	&& undef $_;
366	}
367	};
368	_self_die if $@;
369	};	665	};
370	}	666	}
371		667
372	$port
373	}
374
375	=item reg $portid, $name
376
377	Registers the given port under the name C<$name>. If the name already
378	exists it is replaced.
379
380	A port can only be registered under one well known name.
381
382	A port automatically becomes unregistered when it is killed.
383
384	=cut	668	=cut
385		669
386	sub reg(@) {	670	sub _spawn {
387	my ($portid, $name) = @_;	671	my $port = shift;
		672	my $init = shift;
388		673
389	$REG{$name} = $portid;	674	# rcv will create the actual port
390	}	675	local $SELF = "$NODE#$port";
391		676	eval {
392	=item rcv $portid, tagstring => $callback->(@msg), ...	677	&{ load_func $init }
393
394	=item rcv $portid, $smartmatch => $callback->(@msg), ...
395
396	=item rcv $portid, [$smartmatch...] => $callback->(@msg), ...
397
398	Register callbacks to be called on matching messages on the given port.
399
400	The callback has to return a true value when its work is done, after
401	which is will be removed, or a false value in which case it will stay
402	registered.
403
404	The global C<$SELF> (exported by this module) contains C<$portid> while
405	executing the callback.
406
407	Runtime errors wdurign callback execution will result in the port being
408	C<kil>ed.
409
410	If the match is an array reference, then it will be matched against the
411	first elements of the message, otherwise only the first element is being
412	matched.
413
414	Any element in the match that is specified as C<_any_> (a function
415	exported by this module) matches any single element of the message.
416
417	While not required, it is highly recommended that the first matching
418	element is a string identifying the message. The one-string-only match is
419	also the most efficient match (by far).
420
421	=cut
422
423	sub rcv($@) {
424	my ($noderef, $port) = split /#/, shift, 2;
425
426	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}
427	or Carp::croak "$noderef#$port: rcv can only be called on local ports, caught";
428
429	my $self = $PORT_DATA{$port}
430	or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught";
431
432	"AnyEvent::MP::Port" eq ref $self
433	or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught";
434
435	while (@_) {
436	my ($match, $cb) = splice @_, 0, 2;
437
438	if (!ref $match) {
439	push @{ $self->{rc0}{$match} }, [$cb];
440	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
441	my ($type, @match) = @$match;
442	@match
443	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
444	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
445	} else {
446	push @{ $self->{any} }, [$cb, $match];
447	}
448	}
449	}
450
451	=item $closure = psub { BLOCK }
452
453	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
454	closure is executed, sets up the environment in the same way as in C<rcv>
455	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
456
457	This is useful when you register callbacks from C<rcv> callbacks:
458
459	rcv delayed_reply => sub {
460	my ($delay, @reply) = @_;
461	my $timer = AE::timer $delay, 0, psub {
462	snd @reply, $SELF;
463	};
464	};	678	};
465
466	=cut
467
468	sub psub(&) {
469	my $cb = shift;
470
471	my $port = $SELF
472	or Carp::croak "psub can only be called from within rcv or psub callbacks, not";
473
474	sub {
475	local $SELF = $port;
476
477	if (wantarray) {
478	my @res = eval { &$cb };
479	_self_die if $@;	679	_self_die if $@;
480	@res	680	}
481	} else {	681
482	my $res = eval { &$cb };	682	sub spawn(@) {
483	_self_die if $@;	683	my ($nodeid, undef) = split /#/, shift, 2;
484	$res	684
485	}	685	my $id = "$RUNIQ." . $ID++;
		686
		687	$_[0] =~ /::/
		688	or Carp::croak "spawn init function must be a fully-qualified name, caught";
		689
		690	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
		691
		692	"$nodeid#$id"
		693	}
		694
		695	=item after $timeout, @msg
		696
		697	=item after $timeout, $callback
		698
		699	Either sends the given message, or call the given callback, after the
		700	specified number of seconds.
		701
		702	This is simply a utility function that comes in handy at times - the
		703	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		704	so it may go away in the future.
		705
		706	=cut
		707
		708	sub after($@) {
		709	my ($timeout, @action) = @_;
		710
		711	my $t; $t = AE::timer $timeout, 0, sub {
		712	undef $t;
		713	ref $action[0]
		714	? $action[0]()
		715	: snd @action;
486	}	716	};
487	}	717	}
488		718
489	=back	719	=back
490		720
491	=head1 FUNCTIONS FOR NODES	721	=head1 AnyEvent::MP vs. Distributed Erlang
		722
		723	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
		724	== aemp node, Erlang process == aemp port), so many of the documents and
		725	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
		726	sample:
		727
		728	http://www.Erlang.se/doc/programming_rules.shtml
		729	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
		730	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6
		731	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
		732
		733	Despite the similarities, there are also some important differences:
492		734
493	=over 4	735	=over 4
494		736
495	=item become_public $noderef	737	=item * Node IDs are arbitrary strings in AEMP.
496		738
497	Tells the node to become a public node, i.e. reachable from other nodes.
498
499	The first argument is the (unresolved) node reference of the local node
500	(if missing then the empty string is used).
501
502	It is quite common to not specify anything, in which case the local node
503	tries to listen on the default port, or to only specify a port number, in
504	which case AnyEvent::MP tries to guess the local addresses.
505
506	=cut
507
508	=back
509
510	=head1 NODE MESSAGES
511
512	Nodes understand the following messages sent to them. Many of them take
513	arguments called C<@reply>, which will simply be used to compose a reply
514	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
515	the remaining arguments are simply the message data.
516
517	While other messages exist, they are not public and subject to change.
518
519	=over 4
520
521	=cut
522
523	=item lookup => $name, @reply
524
525	Replies with the port ID of the specified well-known port, or C<undef>.
526
527	=item devnull => ...
528
529	Generic data sink/CPU heat conversion.
530
531	=item relay => $port, @msg
532
533	Simply forwards the message to the given port.
534
535	=item eval => $string[ @reply]
536
537	Evaluates the given string. If C<@reply> is given, then a message of the
538	form C<@reply, $@, @evalres> is sent.
539
540	Example: crash another node.
541
542	snd $othernode, eval => "exit";
543
544	=item time => @reply
545
546	Replies the the current node time to C<@reply>.
547
548	Example: tell the current node to send the current time to C<$myport> in a
549	C<timereply> message.
550
551	snd $NODE, time => $myport, timereply => 1, 2;
552	# => snd $myport, timereply => 1, 2, <time>
553
554	=back
555
556	=head1 AnyEvent::MP vs. Distributed Erlang
557
558	AnyEvent::MP got lots of its ideas from distributed erlang (erlang node
559	== aemp node, erlang process == aemp port), so many of the documents and
560	programming techniques employed by erlang apply to AnyEvent::MP. Here is a
561	sample:
562
563	http://www.erlang.se/doc/programming_rules.shtml
564	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
565	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
566	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
567
568	Despite the similarities, there are also some important differences:
569
570	=over 4
571
572	=item * Node references contain the recipe on how to contact them.
573
574	Erlang relies on special naming and DNS to work everywhere in the	739	Erlang relies on special naming and DNS to work everywhere in the same
575	same way. AEMP relies on each node knowing it's own address(es), with	740	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
576	convenience functionality.	741	configuration or DNS), but will otherwise discover other odes itself.
577		742
578	This means that AEMP requires a less tightly controlled environment at the	743	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
579	cost of longer node references and a slightly higher management overhead.	744	uses "local ports are like remote ports".
		745
		746	The failure modes for local ports are quite different (runtime errors
		747	only) then for remote ports - when a local port dies, you I<know> it dies,
		748	when a connection to another node dies, you know nothing about the other
		749	port.
		750
		751	Erlang pretends remote ports are as reliable as local ports, even when
		752	they are not.
		753
		754	AEMP encourages a "treat remote ports differently" philosophy, with local
		755	ports being the special case/exception, where transport errors cannot
		756	occur.
580		757
581	=item * Erlang uses processes and a mailbox, AEMP does not queue.	758	=item * Erlang uses processes and a mailbox, AEMP does not queue.
582		759
583	Erlang uses processes that selctively receive messages, and therefore	760	Erlang uses processes that selectively receive messages, and therefore
584	needs a queue. AEMP is event based, queuing messages would serve no useful	761	needs a queue. AEMP is event based, queuing messages would serve no
585	purpose.	762	useful purpose. For the same reason the pattern-matching abilities of
		763	AnyEvent::MP are more limited, as there is little need to be able to
		764	filter messages without dequeuing them.
586		765
587	(But see L<Coro::MP> for a more erlang-like process model on top of AEMP).	766	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
588		767
589	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	768	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
590		769
591	Sending messages in erlang is synchronous and blocks the process. AEMP	770	Sending messages in Erlang is synchronous and blocks the process (and
592	sends are immediate, connection establishment is handled in the	771	so does not need a queue that can overflow). AEMP sends are immediate,
593	background.	772	connection establishment is handled in the background.
594		773
595	=item * Erlang can silently lose messages, AEMP cannot.	774	=item * Erlang suffers from silent message loss, AEMP does not.
596		775
597	Erlang makes few guarantees on messages delivery - messages can get lost	776	Erlang makes few guarantees on messages delivery - messages can get lost
598	without any of the processes realising it (i.e. you send messages a, b,	777	without any of the processes realising it (i.e. you send messages a, b,
599	and c, and the other side only receives messages a and c).	778	and c, and the other side only receives messages a and c).
600		779
601	AEMP guarantees correct ordering, and the guarantee that there are no	780	AEMP guarantees correct ordering, and the guarantee that after one message
602	holes in the message sequence.	781	is lost, all following ones sent to the same port are lost as well, until
603		782	monitoring raises an error, so there are no silent "holes" in the message
604	=item * In erlang, processes can be declared dead and later be found to be	783	sequence.
605	alive.
606
607	In erlang it can happen that a monitored process is declared dead and
608	linked processes get killed, but later it turns out that the process is
609	still alive - and can receive messages.
610
611	In AEMP, when port monitoring detects a port as dead, then that port will
612	eventually be killed - it cannot happen that a node detects a port as dead
613	and then later sends messages to it, finding it is still alive.
614		784
615	=item * Erlang can send messages to the wrong port, AEMP does not.	785	=item * Erlang can send messages to the wrong port, AEMP does not.
616		786
617	In erlang it is quite possible that a node that restarts reuses a process	787	In Erlang it is quite likely that a node that restarts reuses a process ID
618	ID known to other nodes for a completely different process, causing	788	known to other nodes for a completely different process, causing messages
619	messages destined for that process to end up in an unrelated process.	789	destined for that process to end up in an unrelated process.
620		790
621	AEMP never reuses port IDs, so old messages or old port IDs floating	791	AEMP never reuses port IDs, so old messages or old port IDs floating
622	around in the network will not be sent to an unrelated port.	792	around in the network will not be sent to an unrelated port.
623		793
624	=item * Erlang uses unprotected connections, AEMP uses secure	794	=item * Erlang uses unprotected connections, AEMP uses secure
625	authentication and can use TLS.	795	authentication and can use TLS.
626		796
627	AEMP can use a proven protocol - SSL/TLS - to protect connections and	797	AEMP can use a proven protocol - TLS - to protect connections and
628	securely authenticate nodes.	798	securely authenticate nodes.
629		799
630	=item * The AEMP protocol is optimised for both text-based and binary	800	=item * The AEMP protocol is optimised for both text-based and binary
631	communications.	801	communications.
632		802
633	The AEMP protocol, unlike the erlang protocol, supports both	803	The AEMP protocol, unlike the Erlang protocol, supports both programming
634	language-independent text-only protocols (good for debugging) and binary,	804	language independent text-only protocols (good for debugging) and binary,
635	language-specific serialisers (e.g. Storable).	805	language-specific serialisers (e.g. Storable). By default, unless TLS is
		806	used, the protocol is actually completely text-based.
636		807
637	It has also been carefully designed to be implementable in other languages	808	It has also been carefully designed to be implementable in other languages
638	with a minimum of work while gracefully degrading fucntionality to make the	809	with a minimum of work while gracefully degrading functionality to make the
639	protocol simple.	810	protocol simple.
640		811
		812	=item * AEMP has more flexible monitoring options than Erlang.
		813
		814	In Erlang, you can chose to receive I<all> exit signals as messages
		815	or I<none>, there is no in-between, so monitoring single processes is
		816	difficult to implement. Monitoring in AEMP is more flexible than in
		817	Erlang, as one can choose between automatic kill, exit message or callback
		818	on a per-process basis.
		819
		820	=item * Erlang tries to hide remote/local connections, AEMP does not.
		821
		822	Monitoring in Erlang is not an indicator of process death/crashes, in the
		823	same way as linking is (except linking is unreliable in Erlang).
		824
		825	In AEMP, you don't "look up" registered port names or send to named ports
		826	that might or might not be persistent. Instead, you normally spawn a port
		827	on the remote node. The init function monitors you, and you monitor the
		828	remote port. Since both monitors are local to the node, they are much more
		829	reliable (no need for C<spawn_link>).
		830
		831	This also saves round-trips and avoids sending messages to the wrong port
		832	(hard to do in Erlang).
		833
641	=back	834	=back
642		835
		836	=head1 RATIONALE
		837
		838	=over 4
		839
		840	=item Why strings for port and node IDs, why not objects?
		841
		842	We considered "objects", but found that the actual number of methods
		843	that can be called are quite low. Since port and node IDs travel over
		844	the network frequently, the serialising/deserialising would add lots of
		845	overhead, as well as having to keep a proxy object everywhere.
		846
		847	Strings can easily be printed, easily serialised etc. and need no special
		848	procedures to be "valid".
		849
		850	And as a result, a miniport consists of a single closure stored in a
		851	global hash - it can't become much cheaper.
		852
		853	=item Why favour JSON, why not a real serialising format such as Storable?
		854
		855	In fact, any AnyEvent::MP node will happily accept Storable as framing
		856	format, but currently there is no way to make a node use Storable by
		857	default (although all nodes will accept it).
		858
		859	The default framing protocol is JSON because a) JSON::XS is many times
		860	faster for small messages and b) most importantly, after years of
		861	experience we found that object serialisation is causing more problems
		862	than it solves: Just like function calls, objects simply do not travel
		863	easily over the network, mostly because they will always be a copy, so you
		864	always have to re-think your design.
		865
		866	Keeping your messages simple, concentrating on data structures rather than
		867	objects, will keep your messages clean, tidy and efficient.
		868
		869	=back
		870
643	=head1 SEE ALSO	871	=head1 SEE ALSO
		872
		873	L<AnyEvent::MP::Intro> - a gentle introduction.
		874
		875	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		876
		877	L<AnyEvent::MP::Global> - network maintainance and port groups, to find
		878	your applications.
		879
		880	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		881	all nodes.
644		882
645	L<AnyEvent>.	883	L<AnyEvent>.
646		884
647	=head1 AUTHOR	885	=head1 AUTHOR
648		886

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Revision 1.30 by root, Tue Aug 4 23:35:51 2009 UTC vs.
Revision 1.84 by root, Tue Sep 8 01:42:14 2009 UTC