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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.15 by root, Sun Aug 2 19:25:27 2009 UTC vs.
Revision 1.119 by root, Sun Feb 26 10:29:59 2012 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent::MP - multi-processing/message-passing framework	3	AnyEvent::MP - erlang-style multi-processing/message-passing framework
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use AnyEvent::MP;	7	use AnyEvent::MP;
8		8
9	NODE # returns this node identifier
10	$NODE # contains this node identifier	9	$NODE # contains this node's node ID
		10	NODE # returns this node's node ID
11		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
12	snd $port, type => data...;	20	snd $port, type => data...;
		21	snd $port, @msg;
		22	snd @msg_with_first_element_being_a_port;
13		23
14	rcv $port, smartmatch => $cb->($port, @msg);	24	# creating/using ports, the simple way
		25	my $simple_port = port { my @msg = @_ };
15		26
16	# examples:	27	# creating/using ports, tagged message matching
		28	my $port = port;
17	rcv $port2, ping => sub { snd $_[0], "pong"; 0 };	29	rcv $port, ping => sub { snd $_[0], "pong" };
18	rcv $port1, pong => sub { warn "pong received\n" };	30	rcv $port, pong => sub { warn "pong received\n" };
19	snd $port2, ping => $port1;
20		31
21	# more, smarter, matches (_any_ is exported by this module)	32	# create a port on another node
22	rcv $port, [child_died => $pid] => sub { ...	33	my $port = spawn $node, $initfunc, @initdata;
23	rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3	34
		35	# destroy a port again
		36	kil $port; # "normal" kill
		37	kil $port, my_error => "everything is broken"; # error kill
		38
		39	# monitoring
		40	mon $localport, $cb->(@msg) # callback is invoked on death
		41	mon $localport, $otherport # kill otherport on abnormal death
		42	mon $localport, $otherport, @msg # send message on death
		43
		44	# temporarily execute code in port context
		45	peval $port, sub { die "kill the port!" };
		46
		47	# execute callbacks in $SELF port context
		48	my $timer = AE::timer 1, 0, psub {
		49	die "kill the port, delayed";
		50	};
		51
		52	=head1 CURRENT STATUS
		53
		54	bin/aemp - stable.
		55	AnyEvent::MP - stable API, should work.
		56	AnyEvent::MP::Intro - explains most concepts.
		57	AnyEvent::MP::Kernel - mostly stable API.
		58	AnyEvent::MP::Global - stable API.
24		59
25	=head1 DESCRIPTION	60	=head1 DESCRIPTION
26		61
27	This module (-family) implements a simple message passing framework.	62	This module (-family) implements a simple message passing framework.
28		63
29	Despite its simplicity, you can securely message other processes running	64	Despite its simplicity, you can securely message other processes running
30	on the same or other hosts.	65	on the same or other hosts, and you can supervise entities remotely.
31		66
32	At the moment, this module family is severly brokena nd underdocumented,	67	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
33	so do not use. This was uploaded mainly to resreve the CPAN namespace -	68	manual page and the examples under F<eg/>.
34	stay tuned!
35		69
36	=head1 CONCEPTS	70	=head1 CONCEPTS
37		71
38	=over 4	72	=over 4
39		73
40	=item port	74	=item port
41		75
42	A port is something you can send messages to with the C<snd> function, and	76	Not to be confused with a TCP port, a "port" is something you can send
43	you can register C<rcv> handlers with. All C<rcv> handlers will receive	77	messages to (with the C<snd> function).
44	messages they match, messages will not be queued.
45		78
		79	Ports allow you to register C<rcv> handlers that can match all or just
		80	some messages. Messages send to ports will not be queued, regardless of
		81	anything was listening for them or not.
		82
		83	Ports are represented by (printable) strings called "port IDs".
		84
46	=item port id - C<noderef#portname>	85	=item port ID - C<nodeid#portname>
47		86
48	A port id is always the noderef, a hash-mark (C<#>) as separator, followed	87	A port ID is the concatenation of a node ID, a hash-mark (C<#>) as
49	by a port name (a printable string of unspecified format).	88	separator, and a port name (a printable string of unspecified format).
50		89
51	=item node	90	=item node
52		91
53	A node is a single process containing at least one port - the node	92	A node is a single process containing at least one port - the node port,
54	port. You can send messages to node ports to let them create new ports,	93	which enables nodes to manage each other remotely, and to create new
55	among other things.	94	ports.
56		95
57	Initially, nodes are either private (single-process only) or hidden	96	Nodes are either public (have one or more listening ports) or private
58	(connected to a master node only). Only when they epxlicitly "become	97	(no listening ports). Private nodes cannot talk to other private nodes
59	public" can you send them messages from unrelated other nodes.	98	currently, but all nodes can talk to public nodes.
60		99
61	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	100	Nodes is represented by (printable) strings called "node IDs".
62		101
		102	=item node ID - C<[A-Za-z0-9_\-.:]*>
		103
63	A noderef is a string that either uniquely identifies a given node (for	104	A node ID is a string that uniquely identifies the node within a
64	private and hidden nodes), or contains a recipe on how to reach a given	105	network. Depending on the configuration used, node IDs can look like a
65	node (for public nodes).	106	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		107	doesn't interpret node IDs in any way except to uniquely identify a node.
		108
		109	=item binds - C<ip:port>
		110
		111	Nodes can only talk to each other by creating some kind of connection to
		112	each other. To do this, nodes should listen on one or more local transport
		113	endpoints - binds.
		114
		115	Currently, only standard C<ip:port> specifications can be used, which
		116	specify TCP ports to listen on. So a bind is basically just a tcp socket
		117	in listening mode thta accepts conenctions form other nodes.
		118
		119	=item seed nodes
		120
		121	When a node starts, it knows nothing about the network it is in - it
		122	needs to connect to at least one other node that is already in the
		123	network. These other nodes are called "seed nodes".
		124
		125	Seed nodes themselves are not special - they are seed nodes only because
		126	some other node I<uses> them as such, but any node can be used as seed
		127	node for other nodes, and eahc node cna use a different set of seed nodes.
		128
		129	In addition to discovering the network, seed nodes are also used to
		130	maintain the network - all nodes using the same seed node form are part of
		131	the same network. If a network is split into multiple subnets because e.g.
		132	the network link between the parts goes down, then using the same seed
		133	nodes for all nodes ensures that eventually the subnets get merged again.
		134
		135	Seed nodes are expected to be long-running, and at least one seed node
		136	should always be available. They should also be relatively responsive - a
		137	seed node that blocks for long periods will slow down everybody else.
		138
		139	For small networks, it's best if every node uses the same set of seed
		140	nodes. For large networks, it can be useful to specify "regional" seed
		141	nodes for most nodes in an area, and use all seed nodes as seed nodes for
		142	each other. What's important is that all seed nodes connections form a
		143	complete graph, so that the network cannot split into separate subnets
		144	forever.
		145
		146	Seed nodes are represented by seed IDs.
		147
		148	=item seed IDs - C<host:port>
		149
		150	Seed IDs are transport endpoint(s) (usually a hostname/IP address and a
		151	TCP port) of nodes that should be used as seed nodes.
		152
		153	=item global nodes
		154
		155	An AEMP network needs a discovery service - nodes need to know how to
		156	connect to other nodes they only know by name. In addition, AEMP offers a
		157	distributed "group database", which maps group names to a list of strings
		158	- for example, to register worker ports.
		159
		160	A network needs at least one global node to work, and allows every node to
		161	be a global node.
		162
		163	Any node that loads the L<AnyEvent::MP::Global> module becomes a global
		164	node and tries to keep connections to all other nodes. So while it can
		165	make sense to make every node "global" in small networks, it usually makes
		166	sense to only make seed nodes into global nodes in large networks (nodes
		167	keep connections to seed nodes and global nodes, so makign them the same
		168	reduces overhead).
66		169
67	=back	170	=back
68		171
69	=head1 VARIABLES/FUNCTIONS	172	=head1 VARIABLES/FUNCTIONS
70		173
72		175
73	=cut	176	=cut
74		177
75	package AnyEvent::MP;	178	package AnyEvent::MP;
76		179
77	use AnyEvent::MP::Base;	180	use AnyEvent::MP::Kernel;
78		181
79	use common::sense;	182	use common::sense;
80		183
81	use Carp ();	184	use Carp ();
82		185
83	use AE ();	186	use AE ();
84		187
85	use base "Exporter";	188	use base "Exporter";
86		189
87	our $VERSION = '0.02';	190	our $VERSION = '1.30';
		191
88	our @EXPORT = qw(	192	our @EXPORT = qw(
89	NODE $NODE $PORT snd rcv _any_	193	NODE $NODE *SELF node_of after
90	create_port create_port_on	194	configure
91	create_miniport	195	snd rcv mon mon_guard kil psub peval spawn cal
92	become_slave become_public	196	port
93	);	197	);
94		198
		199	our $SELF;
		200
		201	sub _self_die() {
		202	my $msg = $@;
		203	$msg =~ s/\n+$// unless ref $msg;
		204	kil $SELF, die => $msg;
		205	}
		206
95	=item NODE / $NODE	207	=item $thisnode = NODE / $NODE
96		208
97	The C<NODE ()> function and the C<$NODE> variable contain the noderef of	209	The C<NODE> function returns, and the C<$NODE> variable contains, the node
98	the local node. The value is initialised by a call to C<become_public> or	210	ID of the node running in the current process. This value is initialised by
99	C<become_slave>, after which all local port identifiers become invalid.	211	a call to C<configure>.
100		212
		213	=item $nodeid = node_of $port
		214
		215	Extracts and returns the node ID from a port ID or a node ID.
		216
		217	=item configure $profile, key => value...
		218
		219	=item configure key => value...
		220
		221	Before a node can talk to other nodes on the network (i.e. enter
		222	"distributed mode") it has to configure itself - the minimum a node needs
		223	to know is its own name, and optionally it should know the addresses of
		224	some other nodes in the network to discover other nodes.
		225
		226	The key/value pairs are basically the same ones as documented for the
		227	F<aemp> command line utility (sans the set/del prefix).
		228
		229	This function configures a node - it must be called exactly once (or
		230	never) before calling other AnyEvent::MP functions.
		231
		232	=over 4
		233
		234	=item step 1, gathering configuration from profiles
		235
		236	The function first looks up a profile in the aemp configuration (see the
		237	L<aemp> commandline utility). The profile name can be specified via the
		238	named C<profile> parameter or can simply be the first parameter). If it is
		239	missing, then the nodename (F<uname -n>) will be used as profile name.
		240
		241	The profile data is then gathered as follows:
		242
		243	First, all remaining key => value pairs (all of which are conveniently
		244	undocumented at the moment) will be interpreted as configuration
		245	data. Then they will be overwritten by any values specified in the global
		246	default configuration (see the F<aemp> utility), then the chain of
		247	profiles chosen by the profile name (and any C<parent> attributes).
		248
		249	That means that the values specified in the profile have highest priority
		250	and the values specified directly via C<configure> have lowest priority,
		251	and can only be used to specify defaults.
		252
		253	If the profile specifies a node ID, then this will become the node ID of
		254	this process. If not, then the profile name will be used as node ID. The
		255	special node ID of C<anon/> will be replaced by a random node ID.
		256
		257	=item step 2, bind listener sockets
		258
		259	The next step is to look up the binds in the profile, followed by binding
		260	aemp protocol listeners on all binds specified (it is possible and valid
		261	to have no binds, meaning that the node cannot be contacted form the
		262	outside. This means the node cannot talk to other nodes that also have no
		263	binds, but it can still talk to all "normal" nodes).
		264
		265	If the profile does not specify a binds list, then a default of C<*> is
		266	used, meaning the node will bind on a dynamically-assigned port on every
		267	local IP address it finds.
		268
		269	=item step 3, connect to seed nodes
		270
		271	As the last step, the seed ID list from the profile is passed to the
		272	L<AnyEvent::MP::Global> module, which will then use it to keep
		273	connectivity with at least one node at any point in time.
		274
		275	=back
		276
		277	Example: become a distributed node using the local node name as profile.
		278	This should be the most common form of invocation for "daemon"-type nodes.
		279
		280	configure
		281
		282	Example: become an anonymous node. This form is often used for commandline
		283	clients.
		284
		285	configure nodeid => "anon/";
		286
		287	Example: configure a node using a profile called seed, which si suitable
		288	for a seed node as it binds on all local addresses on a fixed port (4040,
		289	customary for aemp).
		290
		291	# use the aemp commandline utility
		292	# aemp profile seed nodeid anon/ binds '*:4040'
		293
		294	# then use it
		295	configure profile => "seed";
		296
		297	# or simply use aemp from the shell again:
		298	# aemp run profile seed
		299
		300	# or provide a nicer-to-remember nodeid
		301	# aemp run profile seed nodeid "$(hostname)"
		302
		303	=item $SELF
		304
		305	Contains the current port id while executing C<rcv> callbacks or C<psub>
		306	blocks.
		307
		308	=item *SELF, SELF, %SELF, @SELF...
		309
		310	Due to some quirks in how perl exports variables, it is impossible to
		311	just export C<$SELF>, all the symbols named C<SELF> are exported by this
		312	module, but only C<$SELF> is currently used.
		313
101	=item snd $portid, type => @data	314	=item snd $port, type => @data
102		315
103	=item snd $portid, @msg	316	=item snd $port, @msg
104		317
105	Send the given message to the given port ID, which can identify either	318	Send the given message to the given port, which can identify either a
106	a local or a remote port, and can be either a string or soemthignt hat	319	local or a remote port, and must be a port ID.
107	stringifies a sa port ID (such as a port object :).
108		320
109	While the message can be about anything, it is highly recommended to use a	321	While the message can be almost anything, it is highly recommended to
110	string as first element (a portid, or some word that indicates a request	322	use a string as first element (a port ID, or some word that indicates a
111	type etc.).	323	request type etc.) and to consist if only simple perl values (scalars,
		324	arrays, hashes) - if you think you need to pass an object, think again.
112		325
113	The message data effectively becomes read-only after a call to this	326	The message data logically becomes read-only after a call to this
114	function: modifying any argument is not allowed and can cause many	327	function: modifying any argument (or values referenced by them) is
115	problems.	328	forbidden, as there can be considerable time between the call to C<snd>
		329	and the time the message is actually being serialised - in fact, it might
		330	never be copied as within the same process it is simply handed to the
		331	receiving port.
116		332
117	The type of data you can transfer depends on the transport protocol: when	333	The type of data you can transfer depends on the transport protocol: when
118	JSON is used, then only strings, numbers and arrays and hashes consisting	334	JSON is used, then only strings, numbers and arrays and hashes consisting
119	of those are allowed (no objects). When Storable is used, then anything	335	of those are allowed (no objects). When Storable is used, then anything
120	that Storable can serialise and deserialise is allowed, and for the local	336	that Storable can serialise and deserialise is allowed, and for the local
121	node, anything can be passed.	337	node, anything can be passed. Best rely only on the common denominator of
		338	these.
122		339
123	=item $local_port = create_port	340	=item $local_port = port
124		341
125	Create a new local port object. See the next section for allowed methods.	342	Create a new local port object and returns its port ID. Initially it has
		343	no callbacks set and will throw an error when it receives messages.
126		344
127	=cut	345	=item $local_port = port { my @msg = @_ }
128		346
129	sub create_port {	347	Creates a new local port, and returns its ID. Semantically the same as
130	my $id = "$AnyEvent::MP::Base::UNIQ." . ++$AnyEvent::MP::Base::ID;	348	creating a port and calling C<rcv $port, $callback> on it.
131		349
132	my $self = bless {	350	The block will be called for every message received on the port, with the
133	id => "$NODE#$id",	351	global variable C<$SELF> set to the port ID. Runtime errors will cause the
134	names => [$id],	352	port to be C<kil>ed. The message will be passed as-is, no extra argument
135	}, "AnyEvent::MP::Port";	353	(i.e. no port ID) will be passed to the callback.
136		354
137	$AnyEvent::MP::Base::PORT{$id} = sub {	355	If you want to stop/destroy the port, simply C<kil> it:
138	unshift @_, $self;
139		356
140	for (@{ $self->{rc0}{$_[1]} }) {	357	my $port = port {
141	$_ && &{$_->[0]}	358	my @msg = @_;
142	&& undef $_;	359	...
		360	kil $SELF;
		361	};
		362
		363	=cut
		364
		365	sub rcv($@);
		366
		367	sub _kilme {
		368	die "received message on port without callback";
		369	}
		370
		371	sub port(;&) {
		372	my $id = "$UNIQ." . $ID++;
		373	my $port = "$NODE#$id";
		374
		375	rcv $port, shift \|\| \&_kilme;
		376
		377	$port
		378	}
		379
		380	=item rcv $local_port, $callback->(@msg)
		381
		382	Replaces the default callback on the specified port. There is no way to
		383	remove the default callback: use C<sub { }> to disable it, or better
		384	C<kil> the port when it is no longer needed.
		385
		386	The global C<$SELF> (exported by this module) contains C<$port> while
		387	executing the callback. Runtime errors during callback execution will
		388	result in the port being C<kil>ed.
		389
		390	The default callback received all messages not matched by a more specific
		391	C<tag> match.
		392
		393	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
		394
		395	Register (or replace) callbacks to be called on messages starting with the
		396	given tag on the given port (and return the port), or unregister it (when
		397	C<$callback> is C<$undef> or missing). There can only be one callback
		398	registered for each tag.
		399
		400	The original message will be passed to the callback, after the first
		401	element (the tag) has been removed. The callback will use the same
		402	environment as the default callback (see above).
		403
		404	Example: create a port and bind receivers on it in one go.
		405
		406	my $port = rcv port,
		407	msg1 => sub { ... },
		408	msg2 => sub { ... },
		409	;
		410
		411	Example: create a port, bind receivers and send it in a message elsewhere
		412	in one go:
		413
		414	snd $otherport, reply =>
		415	rcv port,
		416	msg1 => sub { ... },
		417	...
		418	;
		419
		420	Example: temporarily register a rcv callback for a tag matching some port
		421	(e.g. for an rpc reply) and unregister it after a message was received.
		422
		423	rcv $port, $otherport => sub {
		424	my @reply = @_;
		425
		426	rcv $SELF, $otherport;
		427	};
		428
		429	=cut
		430
		431	sub rcv($@) {
		432	my $port = shift;
		433	my ($nodeid, $portid) = split /#/, $port, 2;
		434
		435	$NODE{$nodeid} == $NODE{""}
		436	or Carp::croak "$port: rcv can only be called on local ports, caught";
		437
		438	while (@_) {
		439	if (ref $_[0]) {
		440	if (my $self = $PORT_DATA{$portid}) {
		441	"AnyEvent::MP::Port" eq ref $self
		442	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		443
		444	$self->[0] = shift;
		445	} else {
		446	my $cb = shift;
		447	$PORT{$portid} = sub {
		448	local $SELF = $port;
		449	eval { &$cb }; _self_die if $@;
		450	};
		451	}
		452	} elsif (defined $_[0]) {
		453	my $self = $PORT_DATA{$portid} \|\|= do {
		454	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
		455
		456	$PORT{$portid} = sub {
		457	local $SELF = $port;
		458
		459	if (my $cb = $self->[1]{$_[0]}) {
		460	shift;
		461	eval { &$cb }; _self_die if $@;
		462	} else {
		463	&{ $self->[0] };
		464	}
		465	};
		466
		467	$self
		468	};
		469
		470	"AnyEvent::MP::Port" eq ref $self
		471	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		472
		473	my ($tag, $cb) = splice @_, 0, 2;
		474
		475	if (defined $cb) {
		476	$self->[1]{$tag} = $cb;
		477	} else {
		478	delete $self->[1]{$tag};
		479	}
143	}	480	}
		481	}
144		482
145	for (@{ $self->{rcv}{$_[1]} }) {	483	$port
146	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]	484	}
147	&& &{$_->[0]}	485
148	&& undef $_;	486	=item peval $port, $coderef[, @args]
		487
		488	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		489	when the code throews an exception the C<$port> will be killed.
		490
		491	Any remaining args will be passed to the callback. Any return values will
		492	be returned to the caller.
		493
		494	This is useful when you temporarily want to execute code in the context of
		495	a port.
		496
		497	Example: create a port and run some initialisation code in it's context.
		498
		499	my $port = port { ... };
		500
		501	peval $port, sub {
		502	init
		503	or die "unable to init";
		504	};
		505
		506	=cut
		507
		508	sub peval($$) {
		509	local $SELF = shift;
		510	my $cb = shift;
		511
		512	if (wantarray) {
		513	my @res = eval { &$cb };
		514	_self_die if $@;
		515	@res
		516	} else {
		517	my $res = eval { &$cb };
		518	_self_die if $@;
		519	$res
		520	}
		521	}
		522
		523	=item $closure = psub { BLOCK }
		524
		525	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
		526	closure is executed, sets up the environment in the same way as in C<rcv>
		527	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		528
		529	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		530	BLOCK }, @_ } >>.
		531
		532	This is useful when you register callbacks from C<rcv> callbacks:
		533
		534	rcv delayed_reply => sub {
		535	my ($delay, @reply) = @_;
		536	my $timer = AE::timer $delay, 0, psub {
		537	snd @reply, $SELF;
		538	};
		539	};
		540
		541	=cut
		542
		543	sub psub(&) {
		544	my $cb = shift;
		545
		546	my $port = $SELF
		547	or Carp::croak "psub can only be called from within rcv or psub callbacks, not";
		548
		549	sub {
		550	local $SELF = $port;
		551
		552	if (wantarray) {
		553	my @res = eval { &$cb };
		554	_self_die if $@;
		555	@res
		556	} else {
		557	my $res = eval { &$cb };
		558	_self_die if $@;
		559	$res
149	}	560	}
		561	}
		562	}
150		563
151	for (@{ $self->{any} }) {	564	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
152	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]	565
153	&& &{$_->[0]}	566	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
154	&& undef $_;	567
		568	=item $guard = mon $port # kill $SELF when $port dies
		569
		570	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
		571
		572	Monitor the given port and do something when the port is killed or
		573	messages to it were lost, and optionally return a guard that can be used
		574	to stop monitoring again.
		575
		576	In the first form (callback), the callback is simply called with any
		577	number of C<@reason> elements (no @reason means that the port was deleted
		578	"normally"). Note also that I<< the callback B<must> never die >>, so use
		579	C<eval> if unsure.
		580
		581	In the second form (another port given), the other port (C<$rcvport>)
		582	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
		583	"normal" kils nothing happens, while under all other conditions, the other
		584	port is killed with the same reason.
		585
		586	The third form (kill self) is the same as the second form, except that
		587	C<$rvport> defaults to C<$SELF>.
		588
		589	In the last form (message), a message of the form C<@msg, @reason> will be
		590	C<snd>.
		591
		592	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		593	alert was raised), they are removed and will not trigger again.
		594
		595	As a rule of thumb, monitoring requests should always monitor a port from
		596	a local port (or callback). The reason is that kill messages might get
		597	lost, just like any other message. Another less obvious reason is that
		598	even monitoring requests can get lost (for example, when the connection
		599	to the other node goes down permanently). When monitoring a port locally
		600	these problems do not exist.
		601
		602	C<mon> effectively guarantees that, in the absence of hardware failures,
		603	after starting the monitor, either all messages sent to the port will
		604	arrive, or the monitoring action will be invoked after possible message
		605	loss has been detected. No messages will be lost "in between" (after
		606	the first lost message no further messages will be received by the
		607	port). After the monitoring action was invoked, further messages might get
		608	delivered again.
		609
		610	Inter-host-connection timeouts and monitoring depend on the transport
		611	used. The only transport currently implemented is TCP, and AnyEvent::MP
		612	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		613	non-idle connection, and usually around two hours for idle connections).
		614
		615	This means that monitoring is good for program errors and cleaning up
		616	stuff eventually, but they are no replacement for a timeout when you need
		617	to ensure some maximum latency.
		618
		619	Example: call a given callback when C<$port> is killed.
		620
		621	mon $port, sub { warn "port died because of <@_>\n" };
		622
		623	Example: kill ourselves when C<$port> is killed abnormally.
		624
		625	mon $port;
		626
		627	Example: send us a restart message when another C<$port> is killed.
		628
		629	mon $port, $self => "restart";
		630
		631	=cut
		632
		633	sub mon {
		634	my ($nodeid, $port) = split /#/, shift, 2;
		635
		636	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
		637
		638	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
		639
		640	unless (ref $cb) {
		641	if (@_) {
		642	# send a kill info message
		643	my (@msg) = ($cb, @_);
		644	$cb = sub { snd @msg, @_ };
		645	} else {
		646	# simply kill other port
		647	my $port = $cb;
		648	$cb = sub { kil $port, @_ if @_ };
155	}	649	}
		650	}
		651
		652	$node->monitor ($port, $cb);
		653
		654	defined wantarray
		655	and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) })
		656	}
		657
		658	=item $guard = mon_guard $port, $ref, $ref...
		659
		660	Monitors the given C<$port> and keeps the passed references. When the port
		661	is killed, the references will be freed.
		662
		663	Optionally returns a guard that will stop the monitoring.
		664
		665	This function is useful when you create e.g. timers or other watchers and
		666	want to free them when the port gets killed (note the use of C<psub>):
		667
		668	$port->rcv (start => sub {
		669	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
		670	undef $timer if 0.9 < rand;
		671	});
		672	});
		673
		674	=cut
		675
		676	sub mon_guard {
		677	my ($port, @refs) = @_;
		678
		679	#TODO: mon-less form?
		680
		681	mon $port, sub { 0 && @refs }
		682	}
		683
		684	=item kil $port[, @reason]
		685
		686	Kill the specified port with the given C<@reason>.
		687
		688	If no C<@reason> is specified, then the port is killed "normally" -
		689	monitor callback will be invoked, but the kil will not cause linked ports
		690	(C<mon $mport, $lport> form) to get killed.
		691
		692	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
		693	form) get killed with the same reason.
		694
		695	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
		696	will be reported as reason C<< die => $@ >>.
		697
		698	Transport/communication errors are reported as C<< transport_error =>
		699	$message >>.
		700
		701	=cut
		702
		703	=item $port = spawn $node, $initfunc[, @initdata]
		704
		705	Creates a port on the node C<$node> (which can also be a port ID, in which
		706	case it's the node where that port resides).
		707
		708	The port ID of the newly created port is returned immediately, and it is
		709	possible to immediately start sending messages or to monitor the port.
		710
		711	After the port has been created, the init function is called on the remote
		712	node, in the same context as a C<rcv> callback. This function must be a
		713	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
		714	specify a function in the main program, use C<::name>.
		715
		716	If the function doesn't exist, then the node tries to C<require>
		717	the package, then the package above the package and so on (e.g.
		718	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
		719	exists or it runs out of package names.
		720
		721	The init function is then called with the newly-created port as context
		722	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		723	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		724	the port might not get created.
		725
		726	A common idiom is to pass a local port, immediately monitor the spawned
		727	port, and in the remote init function, immediately monitor the passed
		728	local port. This two-way monitoring ensures that both ports get cleaned up
		729	when there is a problem.
		730
		731	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		732	caller before C<spawn> returns (by delaying invocation when spawn is
		733	called for the local node).
		734
		735	Example: spawn a chat server port on C<$othernode>.
		736
		737	# this node, executed from within a port context:
		738	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
		739	mon $server;
		740
		741	# init function on C<$othernode>
		742	sub connect {
		743	my ($srcport) = @_;
		744
		745	mon $srcport;
		746
		747	rcv $SELF, sub {
		748	...
		749	};
		750	}
		751
		752	=cut
		753
		754	sub _spawn {
		755	my $port = shift;
		756	my $init = shift;
		757
		758	# rcv will create the actual port
		759	local $SELF = "$NODE#$port";
		760	eval {
		761	&{ load_func $init }
156	};	762	};
157		763	_self_die if $@;
158	$self
159	}	764	}
160		765
161	=item $portid = miniport { my @msg = @_; $finished }	766	sub spawn(@) {
		767	my ($nodeid, undef) = split /#/, shift, 2;
162		768
163	Creates a "mini port", that is, a very lightweight port without any	769	my $id = "$RUNIQ." . $ID++;
164	pattern matching behind it, and returns its ID.
165		770
166	The block will be called for every message received on the port. When the	771	$_[0] =~ /::/
167	callback returns a true value its job is considered "done" and the port	772	or Carp::croak "spawn init function must be a fully-qualified name, caught";
168	will be destroyed. Otherwise it will stay alive.
169		773
170	The message will be passed as-is, no extra argument (ie.. no port id) will	774	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
171	be passed to the callback.
172		775
173	If you need the local port id in the callback, this works nicely:	776	"$nodeid#$id"
		777	}
174		778
175	my $port; $port = miniport {	779	=item after $timeout, @msg
176	snd $otherport, reply => $port;	780
		781	=item after $timeout, $callback
		782
		783	Either sends the given message, or call the given callback, after the
		784	specified number of seconds.
		785
		786	This is simply a utility function that comes in handy at times - the
		787	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		788	so it may go away in the future.
		789
		790	=cut
		791
		792	sub after($@) {
		793	my ($timeout, @action) = @_;
		794
		795	my $t; $t = AE::timer $timeout, 0, sub {
		796	undef $t;
		797	ref $action[0]
		798	? $action[0]()
		799	: snd @action;
177	};	800	};
		801	}
178		802
179	=cut	803	=item cal $port, @msg, $callback[, $timeout]
180		804
181	sub miniport(&) {	805	A simple form of RPC - sends a message to the given C<$port> with the
		806	given contents (C<@msg>), but adds a reply port to the message.
		807
		808	The reply port is created temporarily just for the purpose of receiving
		809	the reply, and will be C<kil>ed when no longer needed.
		810
		811	A reply message sent to the port is passed to the C<$callback> as-is.
		812
		813	If an optional time-out (in seconds) is given and it is not C<undef>,
		814	then the callback will be called without any arguments after the time-out
		815	elapsed and the port is C<kil>ed.
		816
		817	If no time-out is given (or it is C<undef>), then the local port will
		818	monitor the remote port instead, so it eventually gets cleaned-up.
		819
		820	Currently this function returns the temporary port, but this "feature"
		821	might go in future versions unless you can make a convincing case that
		822	this is indeed useful for something.
		823
		824	=cut
		825
		826	sub cal(@) {
		827	my $timeout = ref $_[-1] ? undef : pop;
182	my $cb = shift;	828	my $cb = pop;
183	my $id = "$AnyEvent::MP::Base::UNIQ." . ++$AnyEvent::MP::Base::ID;
184		829
185	$AnyEvent::MP::Base::PORT{$id} = sub {	830	my $port = port {
		831	undef $timeout;
		832	kil $SELF;
186	&$cb	833	&$cb;
187	and delete $AnyEvent::MP::Base::PORT{$id};
188	};	834	};
189		835
190	"$NODE#$id"	836	if (defined $timeout) {
191	}	837	$timeout = AE::timer $timeout, 0, sub {
		838	undef $timeout;
		839	kil $port;
		840	$cb->();
		841	};
		842	} else {
		843	mon $_[0], sub {
		844	kil $port;
		845	$cb->();
		846	};
		847	}
192		848
193	package AnyEvent::MP::Port;	849	push @_, $port;
		850	&snd;
		851
		852	$port
		853	}
194		854
195	=back	855	=back
196		856
197	=head1 METHODS FOR PORT OBJECTS	857	=head1 AnyEvent::MP vs. Distributed Erlang
		858
		859	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
		860	== aemp node, Erlang process == aemp port), so many of the documents and
		861	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
		862	sample:
		863
		864	http://www.erlang.se/doc/programming_rules.shtml
		865	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
		866	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
		867	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
		868
		869	Despite the similarities, there are also some important differences:
198		870
199	=over 4	871	=over 4
200		872
201	=item "$port"	873	=item * Node IDs are arbitrary strings in AEMP.
202		874
203	A port object stringifies to its port ID, so can be used directly for	875	Erlang relies on special naming and DNS to work everywhere in the same
204	C<snd> operations.	876	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
		877	configuration or DNS), and possibly the addresses of some seed nodes, but
		878	will otherwise discover other nodes (and their IDs) itself.
205		879
206	=cut	880	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
		881	uses "local ports are like remote ports".
207		882
208	use overload	883	The failure modes for local ports are quite different (runtime errors
209	'""' => sub { $_[0]{id} },	884	only) then for remote ports - when a local port dies, you I<know> it dies,
210	fallback => 1;	885	when a connection to another node dies, you know nothing about the other
		886	port.
211		887
212	=item $port->rcv (type => $callback->($port, @msg))	888	Erlang pretends remote ports are as reliable as local ports, even when
		889	they are not.
213		890
214	=item $port->rcv ($smartmatch => $callback->($port, @msg))	891	AEMP encourages a "treat remote ports differently" philosophy, with local
		892	ports being the special case/exception, where transport errors cannot
		893	occur.
215		894
216	=item $port->rcv ([$smartmatch...] => $callback->($port, @msg))	895	=item * Erlang uses processes and a mailbox, AEMP does not queue.
217		896
218	Register a callback on the given port.	897	Erlang uses processes that selectively receive messages out of order, and
		898	therefore needs a queue. AEMP is event based, queuing messages would serve
		899	no useful purpose. For the same reason the pattern-matching abilities
		900	of AnyEvent::MP are more limited, as there is little need to be able to
		901	filter messages without dequeuing them.
219		902
220	The callback has to return a true value when its work is done, after	903	This is not a philosophical difference, but simply stems from AnyEvent::MP
221	which is will be removed, or a false value in which case it will stay	904	being event-based, while Erlang is process-based.
222	registered.
223		905
224	If the match is an array reference, then it will be matched against the	906	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
225	first elements of the message, otherwise only the first element is being	907	top of AEMP and Coro threads.
226	matched.
227		908
228	Any element in the match that is specified as C<_any_> (a function	909	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
229	exported by this module) matches any single element of the message.
230		910
231	While not required, it is highly recommended that the first matching	911	Sending messages in Erlang is synchronous and blocks the process until
232	element is a string identifying the message. The one-string-only match is	912	a conenction has been established and the message sent (and so does not
233	also the most efficient match (by far).	913	need a queue that can overflow). AEMP sends return immediately, connection
		914	establishment is handled in the background.
234		915
235	=cut	916	=item * Erlang suffers from silent message loss, AEMP does not.
236		917
237	sub rcv($@) {	918	Erlang implements few guarantees on messages delivery - messages can get
238	my ($self, $match, $cb) = @_;	919	lost without any of the processes realising it (i.e. you send messages a,
		920	b, and c, and the other side only receives messages a and c).
239		921
240	if (!ref $match) {	922	AEMP guarantees (modulo hardware errors) correct ordering, and the
241	push @{ $self->{rc0}{$match} }, [$cb];	923	guarantee that after one message is lost, all following ones sent to the
242	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {	924	same port are lost as well, until monitoring raises an error, so there are
243	my ($type, @match) = @$match;	925	no silent "holes" in the message sequence.
244	@match
245	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
246	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
247	} else {
248	push @{ $self->{any} }, [$cb, $match];
249	}
250	}
251		926
252	=item $port->register ($name)	927	If you want your software to be very reliable, you have to cope with
		928	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
		929	simply tries to work better in common error cases, such as when a network
		930	link goes down.
253		931
254	Registers the given port under the well known name C<$name>. If the name	932	=item * Erlang can send messages to the wrong port, AEMP does not.
255	already exists it is replaced.
256		933
257	A port can only be registered under one well known name.	934	In Erlang it is quite likely that a node that restarts reuses an Erlang
		935	process ID known to other nodes for a completely different process,
		936	causing messages destined for that process to end up in an unrelated
		937	process.
258		938
259	=cut	939	AEMP does not reuse port IDs, so old messages or old port IDs floating
		940	around in the network will not be sent to an unrelated port.
260		941
261	sub register {	942	=item * Erlang uses unprotected connections, AEMP uses secure
262	my ($self, $name) = @_;	943	authentication and can use TLS.
263		944
264	$self->{wkname} = $name;	945	AEMP can use a proven protocol - TLS - to protect connections and
265	$AnyEvent::MP::Base::WKP{$name} = "$self";	946	securely authenticate nodes.
266	}
267		947
268	=item $port->destroy	948	=item * The AEMP protocol is optimised for both text-based and binary
		949	communications.
269		950
270	Explicitly destroy/remove/nuke/vaporise the port.	951	The AEMP protocol, unlike the Erlang protocol, supports both programming
		952	language independent text-only protocols (good for debugging), and binary,
		953	language-specific serialisers (e.g. Storable). By default, unless TLS is
		954	used, the protocol is actually completely text-based.
271		955
272	Ports are normally kept alive by there mere existance alone, and need to	956	It has also been carefully designed to be implementable in other languages
273	be destroyed explicitly.	957	with a minimum of work while gracefully degrading functionality to make the
		958	protocol simple.
274		959
275	=cut	960	=item * AEMP has more flexible monitoring options than Erlang.
276		961
277	sub destroy {	962	In Erlang, you can chose to receive I<all> exit signals as messages or
278	my ($self) = @_;	963	I<none>, there is no in-between, so monitoring single Erlang processes is
		964	difficult to implement.
279		965
280	delete $AnyEvent::MP::Base::WKP{ $self->{wkname} };	966	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		967	between automatic kill, exit message or callback on a per-port basis.
281		968
282	delete $AnyEvent::MP::Base::PORT{$_}	969	=item * Erlang tries to hide remote/local connections, AEMP does not.
283	for @{ $self->{names} };	970
284	}	971	Monitoring in Erlang is not an indicator of process death/crashes, in the
		972	same way as linking is (except linking is unreliable in Erlang).
		973
		974	In AEMP, you don't "look up" registered port names or send to named ports
		975	that might or might not be persistent. Instead, you normally spawn a port
		976	on the remote node. The init function monitors you, and you monitor the
		977	remote port. Since both monitors are local to the node, they are much more
		978	reliable (no need for C<spawn_link>).
		979
		980	This also saves round-trips and avoids sending messages to the wrong port
		981	(hard to do in Erlang).
285		982
286	=back	983	=back
287		984
288	=head1 FUNCTIONS FOR NODES	985	=head1 RATIONALE
289		986
290	=over 4	987	=over 4
291		988
292	=item mon $noderef, $callback->($noderef, $status, $)	989	=item Why strings for port and node IDs, why not objects?
293		990
294	Monitors the given noderef.	991	We considered "objects", but found that the actual number of methods
		992	that can be called are quite low. Since port and node IDs travel over
		993	the network frequently, the serialising/deserialising would add lots of
		994	overhead, as well as having to keep a proxy object everywhere.
295		995
296	=item become_public endpoint...	996	Strings can easily be printed, easily serialised etc. and need no special
		997	procedures to be "valid".
297		998
298	Tells the node to become a public node, i.e. reachable from other nodes.	999	And as a result, a port with just a default receiver consists of a single
		1000	code reference stored in a global hash - it can't become much cheaper.
299		1001
300	If no arguments are given, or the first argument is C<undef>, then	1002	=item Why favour JSON, why not a real serialising format such as Storable?
301	AnyEvent::MP tries to bind on port C<4040> on all IP addresses that the
302	local nodename resolves to.
303		1003
304	Otherwise the first argument must be an array-reference with transport	1004	In fact, any AnyEvent::MP node will happily accept Storable as framing
305	endpoints ("ip:port", "hostname:port") or port numbers (in which case the	1005	format, but currently there is no way to make a node use Storable by
306	local nodename is used as hostname). The endpoints are all resolved and	1006	default (although all nodes will accept it).
307	will become the node reference.
308		1007
309	=cut	1008	The default framing protocol is JSON because a) JSON::XS is many times
		1009	faster for small messages and b) most importantly, after years of
		1010	experience we found that object serialisation is causing more problems
		1011	than it solves: Just like function calls, objects simply do not travel
		1012	easily over the network, mostly because they will always be a copy, so you
		1013	always have to re-think your design.
		1014
		1015	Keeping your messages simple, concentrating on data structures rather than
		1016	objects, will keep your messages clean, tidy and efficient.
310		1017
311	=back	1018	=back
312		1019
313	=head1 NODE MESSAGES
314
315	Nodes understand the following messages sent to them. Many of them take
316	arguments called C<@reply>, which will simply be used to compose a reply
317	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
318	the remaining arguments are simply the message data.
319
320	=over 4
321
322	=cut
323
324	=item wkp => $name, @reply
325
326	Replies with the port ID of the specified well-known port, or C<undef>.
327
328	=item devnull => ...
329
330	Generic data sink/CPU heat conversion.
331
332	=item relay => $port, @msg
333
334	Simply forwards the message to the given port.
335
336	=item eval => $string[ @reply]
337
338	Evaluates the given string. If C<@reply> is given, then a message of the
339	form C<@reply, $@, @evalres> is sent.
340
341	Example: crash another node.
342
343	snd $othernode, eval => "exit";
344
345	=item time => @reply
346
347	Replies the the current node time to C<@reply>.
348
349	Example: tell the current node to send the current time to C<$myport> in a
350	C<timereply> message.
351
352	snd $NODE, time => $myport, timereply => 1, 2;
353	# => snd $myport, timereply => 1, 2, <time>
354
355	=back
356
357	=head1 SEE ALSO	1020	=head1 SEE ALSO
		1021
		1022	L<AnyEvent::MP::Intro> - a gentle introduction.
		1023
		1024	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		1025
		1026	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
		1027	your applications.
		1028
		1029	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		1030
		1031	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		1032	all nodes.
358		1033
359	L<AnyEvent>.	1034	L<AnyEvent>.
360		1035
361	=head1 AUTHOR	1036	=head1 AUTHOR
362		1037

Diff Legend

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

Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.15 by root, Sun Aug 2 19:25:27 2009 UTC vs. Revision 1.119 by root, Sun Feb 26 10:29:59 2012 UTC

Diff Legend

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.15 by root, Sun Aug 2 19:25:27 2009 UTC vs.
Revision 1.119 by root, Sun Feb 26 10:29:59 2012 UTC