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

Comparing cvsroot/AnyEvent-MP/MP.pm (file contents):
Revision 1.67 by root, Fri Aug 28 22:21:53 2009 UTC vs.
Revision 1.121 by root, Tue Feb 28 18:37:24 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 # 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
13	$SELF # receiving/own port id in rcv callbacks	12	$SELF # receiving/own port id in rcv callbacks
14		13
15	# initialise the node so it can send/receive messages	14	# initialise the node so it can send/receive messages
16	initialise_node;	15	configure;
17		16
18	# ports are message endpoints	17	# ports are message destinations
19		18
20	# sending messages	19	# sending messages
21	snd $port, type => data...;	20	snd $port, type => data...;
22	snd $port, @msg;	21	snd $port, @msg;
23	snd @msg_with_first_element_being_a_port;	22	snd @msg_with_first_element_being_a_port;
24		23
25	# creating/using ports, the simple way	24	# creating/using ports, the simple way
26	my $simple_port = port { my @msg = @_; 0 };	25	my $simple_port = port { my @msg = @_ };
27		26
28	# creating/using ports, tagged message matching	27	# creating/using ports, tagged message matching
29	my $port = port;	28	my $port = port;
30	rcv $port, ping => sub { snd $_[0], "pong"; 0 };	29	rcv $port, ping => sub { snd $_[0], "pong" };
31	rcv $port, pong => sub { warn "pong received\n"; 0 };	30	rcv $port, pong => sub { warn "pong received\n" };
32		31
33	# create a port on another node	32	# create a port on another node
34	my $port = spawn $node, $initfunc, @initdata;	33	my $port = spawn $node, $initfunc, @initdata;
35		34
		35	# destroy a port again
		36	kil $port; # "normal" kill
		37	kil $port, my_error => "everything is broken"; # error kill
		38
36	# monitoring	39	# monitoring
37	mon $port, $cb->(@msg) # callback is invoked on death	40	mon $localport, $cb->(@msg) # callback is invoked on death
38	mon $port, $otherport # kill otherport on abnormal death	41	mon $localport, $otherport # kill otherport on abnormal death
39	mon $port, $otherport, @msg # send message on 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	};
40		51
41	=head1 CURRENT STATUS	52	=head1 CURRENT STATUS
42		53
		54	bin/aemp - stable.
43	AnyEvent::MP - stable API, should work	55	AnyEvent::MP - stable API, should work.
44	AnyEvent::MP::Intro - outdated	56	AnyEvent::MP::Intro - explains most concepts.
45	AnyEvent::MP::Kernel - mostly stable	57	AnyEvent::MP::Kernel - mostly stable API.
46	AnyEvent::MP::Global - mostly stable	58	AnyEvent::MP::Global - stable API.
47	AnyEvent::MP::Node - mostly stable, but internal anyways
48	AnyEvent::MP::Transport - mostly stable, but internal anyways
49
50	stay tuned.
51		59
52	=head1 DESCRIPTION	60	=head1 DESCRIPTION
53		61
54	This module (-family) implements a simple message passing framework.	62	This module (-family) implements a simple message passing framework.
55		63
57	on the same or other hosts, and you can supervise entities remotely.	65	on the same or other hosts, and you can supervise entities remotely.
58		66
59	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	67	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
60	manual page and the examples under F<eg/>.	68	manual page and the examples under F<eg/>.
61		69
62	At the moment, this module family is a bit underdocumented.
63
64	=head1 CONCEPTS	70	=head1 CONCEPTS
65		71
66	=over 4	72	=over 4
67		73
68	=item port	74	=item port
69		75
70	A port is something you can send messages to (with the C<snd> function).	76	Not to be confused with a TCP port, a "port" is something you can send
		77	messages to (with the C<snd> function).
71		78
72	Ports allow you to register C<rcv> handlers that can match all or just	79	Ports allow you to register C<rcv> handlers that can match all or just
73	some messages. Messages send to ports will not be queued, regardless of	80	some messages. Messages send to ports will not be queued, regardless of
74	anything was listening for them or not.	81	anything was listening for them or not.
75		82
		83	Ports are represented by (printable) strings called "port IDs".
		84
76	=item port ID - C<nodeid#portname>	85	=item port ID - C<nodeid#portname>
77		86
78	A port ID is the concatenation of a node ID, a hash-mark (C<#>) as	87	A port ID is the concatenation of a node ID, a hash-mark (C<#>) as
79	separator, and a port name (a printable string of unspecified format).	88	separator, and a port name (a printable string of unspecified format).
80		89
…		…
84	which enables nodes to manage each other remotely, and to create new	93	which enables nodes to manage each other remotely, and to create new
85	ports.	94	ports.
86		95
87	Nodes are either public (have one or more listening ports) or private	96	Nodes are either public (have one or more listening ports) or private
88	(no listening ports). Private nodes cannot talk to other private nodes	97	(no listening ports). Private nodes cannot talk to other private nodes
89	currently.	98	currently, but all nodes can talk to public nodes.
90		99
		100	Nodes is represented by (printable) strings called "node IDs".
		101
91	=item node ID - C<[a-za-Z0-9_\-.:]+>	102	=item node ID - C<[A-Za-z0-9_\-.:]*>
92		103
93	A node ID is a string that uniquely identifies the node within a	104	A node ID is a string that uniquely identifies the node within a
94	network. Depending on the configuration used, node IDs can look like a	105	network. Depending on the configuration used, node IDs can look like a
95	hostname, a hostname and a port, or a random string. AnyEvent::MP itself	106	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
96	doesn't interpret node IDs in any way.	107	doesn't interpret node IDs in any way except to uniquely identify a node.
97		108
98	=item binds - C<ip:port>	109	=item binds - C<ip:port>
99		110
100	Nodes can only talk to each other by creating some kind of connection to	111	Nodes can only talk to each other by creating some kind of connection to
101	each other. To do this, nodes should listen on one or more local transport	112	each other. To do this, nodes should listen on one or more local transport
		113	endpoints - binds.
		114
102	endpoints - binds. Currently, only standard C<ip:port> specifications can	115	Currently, only standard C<ip:port> specifications can be used, which
103	be used, which specify TCP ports to listen on.	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.
104		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
105	=item seeds - C<host:port>	148	=item seed IDs - C<host:port>
106		149
107	When a node starts, it knows nothing about the network. To teach the node	150	Seed IDs are transport endpoint(s) (usually a hostname/IP address and a
108	about the network it first has to contact some other node within the	151	TCP port) of nodes that should be used as seed nodes.
109	network. This node is called a seed.
110		152
111	Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes	153	=item global nodes
112	are expected to be long-running, and at least one of those should always
113	be available. When nodes run out of connections (e.g. due to a network
114	error), they try to re-establish connections to some seednodes again to
115	join the network.
116		154
117	Apart from being sued for seeding, seednodes are not special in any way -	155	An AEMP network needs a discovery service - nodes need to know how to
118	every public node can be a seednode.	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).
119		169
120	=back	170	=back
121		171
122	=head1 VARIABLES/FUNCTIONS	172	=head1 VARIABLES/FUNCTIONS
123		173
…		…
125		175
126	=cut	176	=cut
127		177
128	package AnyEvent::MP;	178	package AnyEvent::MP;
129		179
		180	use AnyEvent::MP::Config ();
130	use AnyEvent::MP::Kernel;	181	use AnyEvent::MP::Kernel;
		182	use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID);
131		183
132	use common::sense;	184	use common::sense;
133		185
134	use Carp ();	186	use Carp ();
135		187
136	use AE ();	188	use AE ();
137		189
138	use base "Exporter";	190	use base "Exporter";
139		191
140	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	192	our $VERSION = $AnyEvent::MP::Config::VERSION;
141		193
142	our @EXPORT = qw(	194	our @EXPORT = qw(
143	NODE $NODE *SELF node_of after	195	NODE $NODE *SELF node_of after
144	initialise_node	196	configure
145	snd rcv mon mon_guard kil reg psub spawn	197	snd rcv mon mon_guard kil psub peval spawn cal
146	port	198	port
147	);	199	);
148		200
149	our $SELF;	201	our $SELF;
150		202
…		…
156		208
157	=item $thisnode = NODE / $NODE	209	=item $thisnode = NODE / $NODE
158		210
159	The C<NODE> function returns, and the C<$NODE> variable contains, the node	211	The C<NODE> function returns, and the C<$NODE> variable contains, the node
160	ID of the node running in the current process. This value is initialised by	212	ID of the node running in the current process. This value is initialised by
161	a call to C<initialise_node>.	213	a call to C<configure>.
162		214
163	=item $nodeid = node_of $port	215	=item $nodeid = node_of $port
164		216
165	Extracts and returns the node ID from a port ID or a node ID.	217	Extracts and returns the node ID from a port ID or a node ID.
166		218
167	=item initialise_node $profile_name	219	=item configure $profile, key => value...
		220
		221	=item configure key => value...
168		222
169	Before a node can talk to other nodes on the network (i.e. enter	223	Before a node can talk to other nodes on the network (i.e. enter
170	"distributed mode") it has to initialise itself - the minimum a node needs	224	"distributed mode") it has to configure itself - the minimum a node needs
171	to know is its own name, and optionally it should know the addresses of	225	to know is its own name, and optionally it should know the addresses of
172	some other nodes in the network to discover other nodes.	226	some other nodes in the network to discover other nodes.
173		227
174	This function initialises a node - it must be called exactly once (or	228	This function configures a node - it must be called exactly once (or
175	never) before calling other AnyEvent::MP functions.	229	never) before calling other AnyEvent::MP functions.
176		230
177	The first argument is a profile name. If it is C<undef> or missing, then	231	The key/value pairs are basically the same ones as documented for the
178	the current nodename will be used instead (i.e. F<uname -n>).	232	F<aemp> command line utility (sans the set/del prefix), with two additions:
179		233
		234	=over 4
		235
		236	=item norc => $boolean (default false)
		237
		238	If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I<not>
		239	be consulted - all configuraiton options must be specified in the
		240	C<configure> call.
		241
		242	=item force => $boolean (default false)
		243
		244	IF true, then the values specified in the C<configure> will take
		245	precedence over any values configured via the rc file. The default is for
		246	the rc file to override any options specified in the program.
		247
		248	=back
		249
		250	=over 4
		251
		252	=item step 1, gathering configuration from profiles
		253
180	The function then looks up the profile in the aemp configuration (see the	254	The function first looks up a profile in the aemp configuration (see the
181	L<aemp> commandline utility).	255	L<aemp> commandline utility). The profile name can be specified via the
		256	named C<profile> parameter or can simply be the first parameter). If it is
		257	missing, then the nodename (F<uname -n>) will be used as profile name.
		258
		259	The profile data is then gathered as follows:
		260
		261	First, all remaining key => value pairs (all of which are conveniently
		262	undocumented at the moment) will be interpreted as configuration
		263	data. Then they will be overwritten by any values specified in the global
		264	default configuration (see the F<aemp> utility), then the chain of
		265	profiles chosen by the profile name (and any C<parent> attributes).
		266
		267	That means that the values specified in the profile have highest priority
		268	and the values specified directly via C<configure> have lowest priority,
		269	and can only be used to specify defaults.
182		270
183	If the profile specifies a node ID, then this will become the node ID of	271	If the profile specifies a node ID, then this will become the node ID of
184	this process. If not, then the profile name will be used as node ID. The	272	this process. If not, then the profile name will be used as node ID. The
185	special node ID of C<anon/> will be replaced by a random node ID.	273	special node ID of C<anon/> will be replaced by a random node ID.
		274
		275	=item step 2, bind listener sockets
186		276
187	The next step is to look up the binds in the profile, followed by binding	277	The next step is to look up the binds in the profile, followed by binding
188	aemp protocol listeners on all binds specified (it is possible and valid	278	aemp protocol listeners on all binds specified (it is possible and valid
189	to have no binds, meaning that the node cannot be contacted form the	279	to have no binds, meaning that the node cannot be contacted form the
190	outside. This means the node cannot talk to other nodes that also have no	280	outside. This means the node cannot talk to other nodes that also have no
191	binds, but it can still talk to all "normal" nodes).	281	binds, but it can still talk to all "normal" nodes).
192		282
193	If the profile does not specify a binds list, then the node ID will be	283	If the profile does not specify a binds list, then a default of C<*> is
194	treated as if it were of the form C<host:port>, which will be resolved and	284	used, meaning the node will bind on a dynamically-assigned port on every
195	used as binds list.	285	local IP address it finds.
196		286
		287	=item step 3, connect to seed nodes
		288
197	Lastly, the seeds list from the profile is passed to the	289	As the last step, the seed ID list from the profile is passed to the
198	L<AnyEvent::MP::Global> module, which will then use it to keep	290	L<AnyEvent::MP::Global> module, which will then use it to keep
199	connectivity with at least on of those seed nodes at any point in time.	291	connectivity with at least one node at any point in time.
200		292
201	Example: become a distributed node listening on the guessed noderef, or	293	=back
202	the one specified via C<aemp> for the current node. This should be the	294
		295	Example: become a distributed node using the local node name as profile.
203	most common form of invocation for "daemon"-type nodes.	296	This should be the most common form of invocation for "daemon"-type nodes.
204		297
205	initialise_node;	298	configure
206		299
207	Example: become an anonymous node. This form is often used for commandline	300	Example: become an anonymous node. This form is often used for commandline
208	clients.	301	clients.
209		302
210	initialise_node "anon/";	303	configure nodeid => "anon/";
211		304
212	Example: become a distributed node. If there is no profile of the given	305	Example: configure a node using a profile called seed, which is suitable
213	name, or no binds list was specified, resolve C<localhost:4044> and bind	306	for a seed node as it binds on all local addresses on a fixed port (4040,
214	on the resulting addresses.	307	customary for aemp).
215		308
216	initialise_node "localhost:4044";	309	# use the aemp commandline utility
		310	# aemp profile seed nodeid anon/ binds '*:4040'
		311
		312	# then use it
		313	configure profile => "seed";
		314
		315	# or simply use aemp from the shell again:
		316	# aemp run profile seed
		317
		318	# or provide a nicer-to-remember nodeid
		319	# aemp run profile seed nodeid "$(hostname)"
217		320
218	=item $SELF	321	=item $SELF
219		322
220	Contains the current port id while executing C<rcv> callbacks or C<psub>	323	Contains the current port id while executing C<rcv> callbacks or C<psub>
221	blocks.	324	blocks.
…		…
282	sub _kilme {	385	sub _kilme {
283	die "received message on port without callback";	386	die "received message on port without callback";
284	}	387	}
285		388
286	sub port(;&) {	389	sub port(;&) {
287	my $id = "$UNIQ." . $ID++;	390	my $id = "$UNIQ." . ++$ID;
288	my $port = "$NODE#$id";	391	my $port = "$NODE#$id";
289		392
290	rcv $port, shift \|\| \&_kilme;	393	rcv $port, shift \|\| \&_kilme;
291		394
292	$port	395	$port
…		…
331	msg1 => sub { ... },	434	msg1 => sub { ... },
332	...	435	...
333	;	436	;
334		437
335	Example: temporarily register a rcv callback for a tag matching some port	438	Example: temporarily register a rcv callback for a tag matching some port
336	(e.g. for a rpc reply) and unregister it after a message was received.	439	(e.g. for an rpc reply) and unregister it after a message was received.
337		440
338	rcv $port, $otherport => sub {	441	rcv $port, $otherport => sub {
339	my @reply = @_;	442	my @reply = @_;
340		443
341	rcv $SELF, $otherport;	444	rcv $SELF, $otherport;
…		…
343		446
344	=cut	447	=cut
345		448
346	sub rcv($@) {	449	sub rcv($@) {
347	my $port = shift;	450	my $port = shift;
348	my ($noderef, $portid) = split /#/, $port, 2;	451	my ($nodeid, $portid) = split /#/, $port, 2;
349		452
350	$NODE{$noderef} == $NODE{""}	453	$NODE{$nodeid} == $NODE{""}
351	or Carp::croak "$port: rcv can only be called on local ports, caught";	454	or Carp::croak "$port: rcv can only be called on local ports, caught";
352		455
353	while (@_) {	456	while (@_) {
354	if (ref $_[0]) {	457	if (ref $_[0]) {
355	if (my $self = $PORT_DATA{$portid}) {	458	if (my $self = $PORT_DATA{$portid}) {
356	"AnyEvent::MP::Port" eq ref $self	459	"AnyEvent::MP::Port" eq ref $self
357	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	460	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
358		461
359	$self->[2] = shift;	462	$self->[0] = shift;
360	} else {	463	} else {
361	my $cb = shift;	464	my $cb = shift;
362	$PORT{$portid} = sub {	465	$PORT{$portid} = sub {
363	local $SELF = $port;	466	local $SELF = $port;
364	eval { &$cb }; _self_die if $@;	467	eval { &$cb }; _self_die if $@;
365	};	468	};
366	}	469	}
367	} elsif (defined $_[0]) {	470	} elsif (defined $_[0]) {
368	my $self = $PORT_DATA{$portid} \|\|= do {	471	my $self = $PORT_DATA{$portid} \|\|= do {
369	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	472	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
370		473
371	$PORT{$portid} = sub {	474	$PORT{$portid} = sub {
372	local $SELF = $port;	475	local $SELF = $port;
373		476
374	if (my $cb = $self->[1]{$_[0]}) {	477	if (my $cb = $self->[1]{$_[0]}) {
…		…
396	}	499	}
397		500
398	$port	501	$port
399	}	502	}
400		503
		504	=item peval $port, $coderef[, @args]
		505
		506	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		507	when the code throews an exception the C<$port> will be killed.
		508
		509	Any remaining args will be passed to the callback. Any return values will
		510	be returned to the caller.
		511
		512	This is useful when you temporarily want to execute code in the context of
		513	a port.
		514
		515	Example: create a port and run some initialisation code in it's context.
		516
		517	my $port = port { ... };
		518
		519	peval $port, sub {
		520	init
		521	or die "unable to init";
		522	};
		523
		524	=cut
		525
		526	sub peval($$) {
		527	local $SELF = shift;
		528	my $cb = shift;
		529
		530	if (wantarray) {
		531	my @res = eval { &$cb };
		532	_self_die if $@;
		533	@res
		534	} else {
		535	my $res = eval { &$cb };
		536	_self_die if $@;
		537	$res
		538	}
		539	}
		540
401	=item $closure = psub { BLOCK }	541	=item $closure = psub { BLOCK }
402		542
403	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	543	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
404	closure is executed, sets up the environment in the same way as in C<rcv>	544	closure is executed, sets up the environment in the same way as in C<rcv>
405	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.	545	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		546
		547	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		548	BLOCK }, @_ } >>.
406		549
407	This is useful when you register callbacks from C<rcv> callbacks:	550	This is useful when you register callbacks from C<rcv> callbacks:
408		551
409	rcv delayed_reply => sub {	552	rcv delayed_reply => sub {
410	my ($delay, @reply) = @_;	553	my ($delay, @reply) = @_;
…		…
446		589
447	Monitor the given port and do something when the port is killed or	590	Monitor the given port and do something when the port is killed or
448	messages to it were lost, and optionally return a guard that can be used	591	messages to it were lost, and optionally return a guard that can be used
449	to stop monitoring again.	592	to stop monitoring again.
450		593
		594	In the first form (callback), the callback is simply called with any
		595	number of C<@reason> elements (no @reason means that the port was deleted
		596	"normally"). Note also that I<< the callback B<must> never die >>, so use
		597	C<eval> if unsure.
		598
		599	In the second form (another port given), the other port (C<$rcvport>)
		600	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
		601	"normal" kils nothing happens, while under all other conditions, the other
		602	port is killed with the same reason.
		603
		604	The third form (kill self) is the same as the second form, except that
		605	C<$rvport> defaults to C<$SELF>.
		606
		607	In the last form (message), a message of the form C<@msg, @reason> will be
		608	C<snd>.
		609
		610	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		611	alert was raised), they are removed and will not trigger again.
		612
		613	As a rule of thumb, monitoring requests should always monitor a port from
		614	a local port (or callback). The reason is that kill messages might get
		615	lost, just like any other message. Another less obvious reason is that
		616	even monitoring requests can get lost (for example, when the connection
		617	to the other node goes down permanently). When monitoring a port locally
		618	these problems do not exist.
		619
451	C<mon> effectively guarantees that, in the absence of hardware failures,	620	C<mon> effectively guarantees that, in the absence of hardware failures,
452	after starting the monitor, either all messages sent to the port will	621	after starting the monitor, either all messages sent to the port will
453	arrive, or the monitoring action will be invoked after possible message	622	arrive, or the monitoring action will be invoked after possible message
454	loss has been detected. No messages will be lost "in between" (after	623	loss has been detected. No messages will be lost "in between" (after
455	the first lost message no further messages will be received by the	624	the first lost message no further messages will be received by the
456	port). After the monitoring action was invoked, further messages might get	625	port). After the monitoring action was invoked, further messages might get
457	delivered again.	626	delivered again.
458		627
459	Note that monitoring-actions are one-shot: once messages are lost (and a	628	Inter-host-connection timeouts and monitoring depend on the transport
460	monitoring alert was raised), they are removed and will not trigger again.	629	used. The only transport currently implemented is TCP, and AnyEvent::MP
		630	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		631	non-idle connection, and usually around two hours for idle connections).
461		632
462	In the first form (callback), the callback is simply called with any	633	This means that monitoring is good for program errors and cleaning up
463	number of C<@reason> elements (no @reason means that the port was deleted	634	stuff eventually, but they are no replacement for a timeout when you need
464	"normally"). Note also that I<< the callback B<must> never die >>, so use	635	to ensure some maximum latency.
465	C<eval> if unsure.
466
467	In the second form (another port given), the other port (C<$rcvport>)
468	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
469	"normal" kils nothing happens, while under all other conditions, the other
470	port is killed with the same reason.
471
472	The third form (kill self) is the same as the second form, except that
473	C<$rvport> defaults to C<$SELF>.
474
475	In the last form (message), a message of the form C<@msg, @reason> will be
476	C<snd>.
477
478	As a rule of thumb, monitoring requests should always monitor a port from
479	a local port (or callback). The reason is that kill messages might get
480	lost, just like any other message. Another less obvious reason is that
481	even monitoring requests can get lost (for exmaple, when the connection
482	to the other node goes down permanently). When monitoring a port locally
483	these problems do not exist.
484		636
485	Example: call a given callback when C<$port> is killed.	637	Example: call a given callback when C<$port> is killed.
486		638
487	mon $port, sub { warn "port died because of <@_>\n" };	639	mon $port, sub { warn "port died because of <@_>\n" };
488		640
…		…
495	mon $port, $self => "restart";	647	mon $port, $self => "restart";
496		648
497	=cut	649	=cut
498		650
499	sub mon {	651	sub mon {
500	my ($noderef, $port) = split /#/, shift, 2;	652	my ($nodeid, $port) = split /#/, shift, 2;
501		653
502	my $node = $NODE{$noderef} \|\| add_node $noderef;	654	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
503		655
504	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	656	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
505		657
506	unless (ref $cb) {	658	unless (ref $cb) {
507	if (@_) {	659	if (@_) {
…		…
516	}	668	}
517		669
518	$node->monitor ($port, $cb);	670	$node->monitor ($port, $cb);
519		671
520	defined wantarray	672	defined wantarray
521	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	673	and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) })
522	}	674	}
523		675
524	=item $guard = mon_guard $port, $ref, $ref...	676	=item $guard = mon_guard $port, $ref, $ref...
525		677
526	Monitors the given C<$port> and keeps the passed references. When the port	678	Monitors the given C<$port> and keeps the passed references. When the port
…		…
549		701
550	=item kil $port[, @reason]	702	=item kil $port[, @reason]
551		703
552	Kill the specified port with the given C<@reason>.	704	Kill the specified port with the given C<@reason>.
553		705
554	If no C<@reason> is specified, then the port is killed "normally" (ports	706	If no C<@reason> is specified, then the port is killed "normally" -
555	monitoring other ports will not necessarily die because a port dies	707	monitor callback will be invoked, but the kil will not cause linked ports
556	"normally").	708	(C<mon $mport, $lport> form) to get killed.
557		709
558	Otherwise, linked ports get killed with the same reason (second form of	710	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
559	C<mon>, see above).	711	form) get killed with the same reason.
560		712
561	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	713	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
562	will be reported as reason C<< die => $@ >>.	714	will be reported as reason C<< die => $@ >>.
563		715
564	Transport/communication errors are reported as C<< transport_error =>	716	Transport/communication errors are reported as C<< transport_error =>
…		…
583	the package, then the package above the package and so on (e.g.	735	the package, then the package above the package and so on (e.g.
584	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	736	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
585	exists or it runs out of package names.	737	exists or it runs out of package names.
586		738
587	The init function is then called with the newly-created port as context	739	The init function is then called with the newly-created port as context
588	object (C<$SELF>) and the C<@initdata> values as arguments.	740	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		741	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		742	the port might not get created.
589		743
590	A common idiom is to pass a local port, immediately monitor the spawned	744	A common idiom is to pass a local port, immediately monitor the spawned
591	port, and in the remote init function, immediately monitor the passed	745	port, and in the remote init function, immediately monitor the passed
592	local port. This two-way monitoring ensures that both ports get cleaned up	746	local port. This two-way monitoring ensures that both ports get cleaned up
593	when there is a problem.	747	when there is a problem.
594		748
		749	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		750	caller before C<spawn> returns (by delaying invocation when spawn is
		751	called for the local node).
		752
595	Example: spawn a chat server port on C<$othernode>.	753	Example: spawn a chat server port on C<$othernode>.
596		754
597	# this node, executed from within a port context:	755	# this node, executed from within a port context:
598	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	756	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
599	mon $server;	757	mon $server;
…		…
613		771
614	sub _spawn {	772	sub _spawn {
615	my $port = shift;	773	my $port = shift;
616	my $init = shift;	774	my $init = shift;
617		775
		776	# rcv will create the actual port
618	local $SELF = "$NODE#$port";	777	local $SELF = "$NODE#$port";
619	eval {	778	eval {
620	&{ load_func $init }	779	&{ load_func $init }
621	};	780	};
622	_self_die if $@;	781	_self_die if $@;
623	}	782	}
624		783
625	sub spawn(@) {	784	sub spawn(@) {
626	my ($noderef, undef) = split /#/, shift, 2;	785	my ($nodeid, undef) = split /#/, shift, 2;
627		786
628	my $id = "$RUNIQ." . $ID++;	787	my $id = "$RUNIQ." . ++$ID;
629		788
630	$_[0] =~ /::/	789	$_[0] =~ /::/
631	or Carp::croak "spawn init function must be a fully-qualified name, caught";	790	or Carp::croak "spawn init function must be a fully-qualified name, caught";
632		791
633	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;	792	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
634		793
635	"$noderef#$id"	794	"$nodeid#$id"
636	}	795	}
		796
637		797
638	=item after $timeout, @msg	798	=item after $timeout, @msg
639		799
640	=item after $timeout, $callback	800	=item after $timeout, $callback
641		801
…		…
657	? $action[0]()	817	? $action[0]()
658	: snd @action;	818	: snd @action;
659	};	819	};
660	}	820	}
661		821
		822	=item cal $port, @msg, $callback[, $timeout]
		823
		824	A simple form of RPC - sends a message to the given C<$port> with the
		825	given contents (C<@msg>), but adds a reply port to the message.
		826
		827	The reply port is created temporarily just for the purpose of receiving
		828	the reply, and will be C<kil>ed when no longer needed.
		829
		830	A reply message sent to the port is passed to the C<$callback> as-is.
		831
		832	If an optional time-out (in seconds) is given and it is not C<undef>,
		833	then the callback will be called without any arguments after the time-out
		834	elapsed and the port is C<kil>ed.
		835
		836	If no time-out is given (or it is C<undef>), then the local port will
		837	monitor the remote port instead, so it eventually gets cleaned-up.
		838
		839	Currently this function returns the temporary port, but this "feature"
		840	might go in future versions unless you can make a convincing case that
		841	this is indeed useful for something.
		842
		843	=cut
		844
		845	sub cal(@) {
		846	my $timeout = ref $_[-1] ? undef : pop;
		847	my $cb = pop;
		848
		849	my $port = port {
		850	undef $timeout;
		851	kil $SELF;
		852	&$cb;
		853	};
		854
		855	if (defined $timeout) {
		856	$timeout = AE::timer $timeout, 0, sub {
		857	undef $timeout;
		858	kil $port;
		859	$cb->();
		860	};
		861	} else {
		862	mon $_[0], sub {
		863	kil $port;
		864	$cb->();
		865	};
		866	}
		867
		868	push @_, $port;
		869	&snd;
		870
		871	$port
		872	}
		873
662	=back	874	=back
663		875
664	=head1 AnyEvent::MP vs. Distributed Erlang	876	=head1 AnyEvent::MP vs. Distributed Erlang
665		877
666	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	878	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
667	== aemp node, Erlang process == aemp port), so many of the documents and	879	== aemp node, Erlang process == aemp port), so many of the documents and
668	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	880	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
669	sample:	881	sample:
670		882
671	http://www.Erlang.se/doc/programming_rules.shtml	883	http://www.erlang.se/doc/programming_rules.shtml
672	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	884	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
673	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	885	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
674	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	886	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
675		887
676	Despite the similarities, there are also some important differences:	888	Despite the similarities, there are also some important differences:
677		889
678	=over 4	890	=over 4
679		891
680	=item * Node IDs are arbitrary strings in AEMP.	892	=item * Node IDs are arbitrary strings in AEMP.
681		893
682	Erlang relies on special naming and DNS to work everywhere in the same	894	Erlang relies on special naming and DNS to work everywhere in the same
683	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by	895	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
684	configuraiton or DNS), but will otherwise discover other odes itself.	896	configuration or DNS), and possibly the addresses of some seed nodes, but
		897	will otherwise discover other nodes (and their IDs) itself.
685		898
686	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	899	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
687	uses "local ports are like remote ports".	900	uses "local ports are like remote ports".
688		901
689	The failure modes for local ports are quite different (runtime errors	902	The failure modes for local ports are quite different (runtime errors
…		…
698	ports being the special case/exception, where transport errors cannot	911	ports being the special case/exception, where transport errors cannot
699	occur.	912	occur.
700		913
701	=item * Erlang uses processes and a mailbox, AEMP does not queue.	914	=item * Erlang uses processes and a mailbox, AEMP does not queue.
702		915
703	Erlang uses processes that selectively receive messages, and therefore	916	Erlang uses processes that selectively receive messages out of order, and
704	needs a queue. AEMP is event based, queuing messages would serve no	917	therefore needs a queue. AEMP is event based, queuing messages would serve
705	useful purpose. For the same reason the pattern-matching abilities of	918	no useful purpose. For the same reason the pattern-matching abilities
706	AnyEvent::MP are more limited, as there is little need to be able to	919	of AnyEvent::MP are more limited, as there is little need to be able to
707	filter messages without dequeing them.	920	filter messages without dequeuing them.
708		921
709	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	922	This is not a philosophical difference, but simply stems from AnyEvent::MP
		923	being event-based, while Erlang is process-based.
		924
		925	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		926	top of AEMP and Coro threads.
710		927
711	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	928	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
712		929
713	Sending messages in Erlang is synchronous and blocks the process (and	930	Sending messages in Erlang is synchronous and blocks the process until
		931	a conenction has been established and the message sent (and so does not
714	so does not need a queue that can overflow). AEMP sends are immediate,	932	need a queue that can overflow). AEMP sends return immediately, connection
715	connection establishment is handled in the background.	933	establishment is handled in the background.
716		934
717	=item * Erlang suffers from silent message loss, AEMP does not.	935	=item * Erlang suffers from silent message loss, AEMP does not.
718		936
719	Erlang makes few guarantees on messages delivery - messages can get lost	937	Erlang implements few guarantees on messages delivery - messages can get
720	without any of the processes realising it (i.e. you send messages a, b,	938	lost without any of the processes realising it (i.e. you send messages a,
721	and c, and the other side only receives messages a and c).	939	b, and c, and the other side only receives messages a and c).
722		940
723	AEMP guarantees correct ordering, and the guarantee that after one message	941	AEMP guarantees (modulo hardware errors) correct ordering, and the
724	is lost, all following ones sent to the same port are lost as well, until	942	guarantee that after one message is lost, all following ones sent to the
725	monitoring raises an error, so there are no silent "holes" in the message	943	same port are lost as well, until monitoring raises an error, so there are
726	sequence.	944	no silent "holes" in the message sequence.
		945
		946	If you want your software to be very reliable, you have to cope with
		947	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
		948	simply tries to work better in common error cases, such as when a network
		949	link goes down.
727		950
728	=item * Erlang can send messages to the wrong port, AEMP does not.	951	=item * Erlang can send messages to the wrong port, AEMP does not.
729		952
730	In Erlang it is quite likely that a node that restarts reuses a process ID	953	In Erlang it is quite likely that a node that restarts reuses an Erlang
731	known to other nodes for a completely different process, causing messages	954	process ID known to other nodes for a completely different process,
732	destined for that process to end up in an unrelated process.	955	causing messages destined for that process to end up in an unrelated
		956	process.
733		957
734	AEMP never reuses port IDs, so old messages or old port IDs floating	958	AEMP does not reuse port IDs, so old messages or old port IDs floating
735	around in the network will not be sent to an unrelated port.	959	around in the network will not be sent to an unrelated port.
736		960
737	=item * Erlang uses unprotected connections, AEMP uses secure	961	=item * Erlang uses unprotected connections, AEMP uses secure
738	authentication and can use TLS.	962	authentication and can use TLS.
739		963
…		…
742		966
743	=item * The AEMP protocol is optimised for both text-based and binary	967	=item * The AEMP protocol is optimised for both text-based and binary
744	communications.	968	communications.
745		969
746	The AEMP protocol, unlike the Erlang protocol, supports both programming	970	The AEMP protocol, unlike the Erlang protocol, supports both programming
747	language independent text-only protocols (good for debugging) and binary,	971	language independent text-only protocols (good for debugging), and binary,
748	language-specific serialisers (e.g. Storable). By default, unless TLS is	972	language-specific serialisers (e.g. Storable). By default, unless TLS is
749	used, the protocol is actually completely text-based.	973	used, the protocol is actually completely text-based.
750		974
751	It has also been carefully designed to be implementable in other languages	975	It has also been carefully designed to be implementable in other languages
752	with a minimum of work while gracefully degrading functionality to make the	976	with a minimum of work while gracefully degrading functionality to make the
753	protocol simple.	977	protocol simple.
754		978
755	=item * AEMP has more flexible monitoring options than Erlang.	979	=item * AEMP has more flexible monitoring options than Erlang.
756		980
757	In Erlang, you can chose to receive I<all> exit signals as messages	981	In Erlang, you can chose to receive I<all> exit signals as messages or
758	or I<none>, there is no in-between, so monitoring single processes is	982	I<none>, there is no in-between, so monitoring single Erlang processes is
759	difficult to implement. Monitoring in AEMP is more flexible than in	983	difficult to implement.
760	Erlang, as one can choose between automatic kill, exit message or callback	984
761	on a per-process basis.	985	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		986	between automatic kill, exit message or callback on a per-port basis.
762		987
763	=item * Erlang tries to hide remote/local connections, AEMP does not.	988	=item * Erlang tries to hide remote/local connections, AEMP does not.
764		989
765	Monitoring in Erlang is not an indicator of process death/crashes, in the	990	Monitoring in Erlang is not an indicator of process death/crashes, in the
766	same way as linking is (except linking is unreliable in Erlang).	991	same way as linking is (except linking is unreliable in Erlang).
…		…
788	overhead, as well as having to keep a proxy object everywhere.	1013	overhead, as well as having to keep a proxy object everywhere.
789		1014
790	Strings can easily be printed, easily serialised etc. and need no special	1015	Strings can easily be printed, easily serialised etc. and need no special
791	procedures to be "valid".	1016	procedures to be "valid".
792		1017
793	And as a result, a miniport consists of a single closure stored in a	1018	And as a result, a port with just a default receiver consists of a single
794	global hash - it can't become much cheaper.	1019	code reference stored in a global hash - it can't become much cheaper.
795		1020
796	=item Why favour JSON, why not a real serialising format such as Storable?	1021	=item Why favour JSON, why not a real serialising format such as Storable?
797		1022
798	In fact, any AnyEvent::MP node will happily accept Storable as framing	1023	In fact, any AnyEvent::MP node will happily accept Storable as framing
799	format, but currently there is no way to make a node use Storable by	1024	format, but currently there is no way to make a node use Storable by
…		…
811		1036
812	=back	1037	=back
813		1038
814	=head1 SEE ALSO	1039	=head1 SEE ALSO
815		1040
		1041	L<AnyEvent::MP::Intro> - a gentle introduction.
		1042
		1043	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		1044
		1045	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
		1046	your applications.
		1047
		1048	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		1049
		1050	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		1051	all nodes.
		1052
816	L<AnyEvent>.	1053	L<AnyEvent>.
817		1054
818	=head1 AUTHOR	1055	=head1 AUTHOR
819		1056
820	Marc Lehmann <schmorp@schmorp.de>	1057	Marc Lehmann <schmorp@schmorp.de>

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Revision 1.67 by root, Fri Aug 28 22:21:53 2009 UTC vs.
Revision 1.121 by root, Tue Feb 28 18:37:24 2012 UTC