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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.71 by root, Sun Aug 30 19:52:56 2009 UTC vs.
Revision 1.122 by root, Wed Feb 29 18:44:59 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 # 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
43	bin/aemp - stable.	54	bin/aemp - stable.
44	AnyEvent::MP - stable API, should work.	55	AnyEvent::MP - stable API, should work.
45	AnyEvent::MP::Intro - uptodate, but incomplete.	56	AnyEvent::MP::Intro - explains most concepts.
46	AnyEvent::MP::Kernel - mostly stable.	57	AnyEvent::MP::Kernel - mostly stable API.
47	AnyEvent::MP::Global - stable API, protocol not yet final.	58	AnyEvent::MP::Global - stable API.
48
49	stay tuned.
50		59
51	=head1 DESCRIPTION	60	=head1 DESCRIPTION
52		61
53	This module (-family) implements a simple message passing framework.	62	This module (-family) implements a simple message passing framework.
54		63
56	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.
57		66
58	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>
59	manual page and the examples under F<eg/>.	68	manual page and the examples under F<eg/>.
60		69
61	At the moment, this module family is a bit underdocumented.
62
63	=head1 CONCEPTS	70	=head1 CONCEPTS
64		71
65	=over 4	72	=over 4
66		73
67	=item port	74	=item port
68		75
69	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).
70		78
71	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
72	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
73	anything was listening for them or not.	81	anything was listening for them or not.
74		82
		83	Ports are represented by (printable) strings called "port IDs".
		84
75	=item port ID - C<nodeid#portname>	85	=item port ID - C<nodeid#portname>
76		86
77	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
78	separator, and a port name (a printable string of unspecified format).	88	separator, and a port name (a printable string of unspecified format).
79		89
…		…
83	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
84	ports.	94	ports.
85		95
86	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
87	(no listening ports). Private nodes cannot talk to other private nodes	97	(no listening ports). Private nodes cannot talk to other private nodes
88	currently.	98	currently, but all nodes can talk to public nodes.
89		99
		100	Nodes is represented by (printable) strings called "node IDs".
		101
90	=item node ID - C<[a-za-Z0-9_\-.:]+>	102	=item node ID - C<[A-Za-z0-9_\-.:]*>
91		103
92	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
93	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
94	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
95	doesn't interpret node IDs in any way.	107	doesn't interpret node IDs in any way except to uniquely identify a node.
96		108
97	=item binds - C<ip:port>	109	=item binds - C<ip:port>
98		110
99	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
100	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
101	endpoints - binds. Currently, only standard C<ip:port> specifications can	115	Currently, only standard C<ip:port> specifications can be used, which
102	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.
103		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
104	=item seeds - C<host:port>	148	=item seed IDs - C<host:port>
105		149
106	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
107	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.
108	network. This node is called a seed.
109		152
110	Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes	153	=item global nodes
111	are expected to be long-running, and at least one of those should always
112	be available. When nodes run out of connections (e.g. due to a network
113	error), they try to re-establish connections to some seednodes again to
114	join the network.
115		154
116	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
117	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).
118		169
119	=back	170	=back
120		171
121	=head1 VARIABLES/FUNCTIONS	172	=head1 VARIABLES/FUNCTIONS
122		173
…		…
124		175
125	=cut	176	=cut
126		177
127	package AnyEvent::MP;	178	package AnyEvent::MP;
128		179
		180	use AnyEvent::MP::Config ();
129	use AnyEvent::MP::Kernel;	181	use AnyEvent::MP::Kernel;
		182	use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID);
130		183
131	use common::sense;	184	use common::sense;
132		185
133	use Carp ();	186	use Carp ();
134		187
135	use AE ();	188	use AE ();
136		189
137	use base "Exporter";	190	use base "Exporter";
138		191
139	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	192	our $VERSION = $AnyEvent::MP::Config::VERSION;
140		193
141	our @EXPORT = qw(	194	our @EXPORT = qw(
142	NODE $NODE *SELF node_of after	195	NODE $NODE *SELF node_of after
143	initialise_node	196	configure
144	snd rcv mon mon_guard kil reg psub spawn	197	snd rcv mon mon_guard kil psub peval spawn cal
145	port	198	port
146	);	199	);
147		200
148	our $SELF;	201	our $SELF;
149		202
…		…
155		208
156	=item $thisnode = NODE / $NODE	209	=item $thisnode = NODE / $NODE
157		210
158	The C<NODE> function returns, and the C<$NODE> variable contains, the node	211	The C<NODE> function returns, and the C<$NODE> variable contains, the node
159	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
160	a call to C<initialise_node>.	213	a call to C<configure>.
161		214
162	=item $nodeid = node_of $port	215	=item $nodeid = node_of $port
163		216
164	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.
165		218
166	=item initialise_node $profile_name, key => value...	219	=item configure $profile, key => value...
		220
		221	=item configure key => value...
167		222
168	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
169	"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
170	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
171	some other nodes in the network to discover other nodes.	226	some other nodes in the network to discover other nodes.
172		227
173	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
174	never) before calling other AnyEvent::MP functions.	229	never) before calling other AnyEvent::MP functions.
175		230
176	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
177	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:
178		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
179	The function first looks up the profile in the aemp configuration (see the	254	The function first looks up a profile in the aemp configuration (see the
180	L<aemp> commandline utility). the profile is calculated as follows:	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.
181		258
		259	The profile data is then gathered as follows:
		260
182	First, all remaining key => value pairs (all of which are conviniently	261	First, all remaining key => value pairs (all of which are conveniently
183	undocumented at the moment) will be used. Then they will be overwritten by	262	undocumented at the moment) will be interpreted as configuration
184	any values specified in the global default configuration (see the F<aemp>	263	data. Then they will be overwritten by any values specified in the global
185	utility), then the chain of profiles selected, if any. That means that	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
186	the values specified in the profile have highest priority and the values	267	That means that the values specified in the profile have highest priority
187	specified via C<initialise_node> have lowest priority.	268	and the values specified directly via C<configure> have lowest priority,
		269	and can only be used to specify defaults.
188		270
189	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
190	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, with
191	special node ID of C<anon/> will be replaced by a random node ID.	273	a slash (C</>) attached.
		274
		275	If the node ID (or profile name) ends with a slash (C</>), then a random
		276	string is appended to make it unique.
		277
		278	=item step 2, bind listener sockets
192		279
193	The next step is to look up the binds in the profile, followed by binding	280	The next step is to look up the binds in the profile, followed by binding
194	aemp protocol listeners on all binds specified (it is possible and valid	281	aemp protocol listeners on all binds specified (it is possible and valid
195	to have no binds, meaning that the node cannot be contacted form the	282	to have no binds, meaning that the node cannot be contacted form the
196	outside. This means the node cannot talk to other nodes that also have no	283	outside. This means the node cannot talk to other nodes that also have no
197	binds, but it can still talk to all "normal" nodes).	284	binds, but it can still talk to all "normal" nodes).
198		285
199	If the profile does not specify a binds list, then a default of C<*> is	286	If the profile does not specify a binds list, then a default of C<*> is
200	used.	287	used, meaning the node will bind on a dynamically-assigned port on every
		288	local IP address it finds.
201		289
		290	=item step 3, connect to seed nodes
		291
202	Lastly, the seeds list from the profile is passed to the	292	As the last step, the seed ID list from the profile is passed to the
203	L<AnyEvent::MP::Global> module, which will then use it to keep	293	L<AnyEvent::MP::Global> module, which will then use it to keep
204	connectivity with at least on of those seed nodes at any point in time.	294	connectivity with at least one node at any point in time.
205		295
206	Example: become a distributed node listening on the guessed noderef, or	296	=back
207	the one specified via C<aemp> for the current node. This should be the	297
		298	Example: become a distributed node using the local node name as profile.
208	most common form of invocation for "daemon"-type nodes.	299	This should be the most common form of invocation for "daemon"-type nodes.
209		300
210	initialise_node;	301	configure
211		302
212	Example: become an anonymous node. This form is often used for commandline	303	Example: become an anonymous node. This form is often used for commandline
213	clients.	304	clients.
214		305
215	initialise_node "anon/";	306	configure nodeid => "anon/";
216		307
217	Example: become a distributed node. If there is no profile of the given	308	Example: configure a node using a profile called seed, which is suitable
218	name, or no binds list was specified, resolve C<localhost:4044> and bind	309	for a seed node as it binds on all local addresses on a fixed port (4040,
219	on the resulting addresses.	310	customary for aemp).
220		311
221	initialise_node "localhost:4044";	312	# use the aemp commandline utility
		313	# aemp profile seed binds '*:4040'
		314
		315	# then use it
		316	configure profile => "seed";
		317
		318	# or simply use aemp from the shell again:
		319	# aemp run profile seed
		320
		321	# or provide a nicer-to-remember nodeid
		322	# aemp run profile seed nodeid "$(hostname)"
222		323
223	=item $SELF	324	=item $SELF
224		325
225	Contains the current port id while executing C<rcv> callbacks or C<psub>	326	Contains the current port id while executing C<rcv> callbacks or C<psub>
226	blocks.	327	blocks.
…		…
287	sub _kilme {	388	sub _kilme {
288	die "received message on port without callback";	389	die "received message on port without callback";
289	}	390	}
290		391
291	sub port(;&) {	392	sub port(;&) {
292	my $id = "$UNIQ." . $ID++;	393	my $id = "$UNIQ." . ++$ID;
293	my $port = "$NODE#$id";	394	my $port = "$NODE#$id";
294		395
295	rcv $port, shift \|\| \&_kilme;	396	rcv $port, shift \|\| \&_kilme;
296		397
297	$port	398	$port
…		…
336	msg1 => sub { ... },	437	msg1 => sub { ... },
337	...	438	...
338	;	439	;
339		440
340	Example: temporarily register a rcv callback for a tag matching some port	441	Example: temporarily register a rcv callback for a tag matching some port
341	(e.g. for a rpc reply) and unregister it after a message was received.	442	(e.g. for an rpc reply) and unregister it after a message was received.
342		443
343	rcv $port, $otherport => sub {	444	rcv $port, $otherport => sub {
344	my @reply = @_;	445	my @reply = @_;
345		446
346	rcv $SELF, $otherport;	447	rcv $SELF, $otherport;
…		…
348		449
349	=cut	450	=cut
350		451
351	sub rcv($@) {	452	sub rcv($@) {
352	my $port = shift;	453	my $port = shift;
353	my ($noderef, $portid) = split /#/, $port, 2;	454	my ($nodeid, $portid) = split /#/, $port, 2;
354		455
355	$NODE{$noderef} == $NODE{""}	456	$NODE{$nodeid} == $NODE{""}
356	or Carp::croak "$port: rcv can only be called on local ports, caught";	457	or Carp::croak "$port: rcv can only be called on local ports, caught";
357		458
358	while (@_) {	459	while (@_) {
359	if (ref $_[0]) {	460	if (ref $_[0]) {
360	if (my $self = $PORT_DATA{$portid}) {	461	if (my $self = $PORT_DATA{$portid}) {
361	"AnyEvent::MP::Port" eq ref $self	462	"AnyEvent::MP::Port" eq ref $self
362	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	463	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
363		464
364	$self->[2] = shift;	465	$self->[0] = shift;
365	} else {	466	} else {
366	my $cb = shift;	467	my $cb = shift;
367	$PORT{$portid} = sub {	468	$PORT{$portid} = sub {
368	local $SELF = $port;	469	local $SELF = $port;
369	eval { &$cb }; _self_die if $@;	470	eval { &$cb }; _self_die if $@;
370	};	471	};
371	}	472	}
372	} elsif (defined $_[0]) {	473	} elsif (defined $_[0]) {
373	my $self = $PORT_DATA{$portid} \|\|= do {	474	my $self = $PORT_DATA{$portid} \|\|= do {
374	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	475	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
375		476
376	$PORT{$portid} = sub {	477	$PORT{$portid} = sub {
377	local $SELF = $port;	478	local $SELF = $port;
378		479
379	if (my $cb = $self->[1]{$_[0]}) {	480	if (my $cb = $self->[1]{$_[0]}) {
…		…
401	}	502	}
402		503
403	$port	504	$port
404	}	505	}
405		506
		507	=item peval $port, $coderef[, @args]
		508
		509	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		510	when the code throews an exception the C<$port> will be killed.
		511
		512	Any remaining args will be passed to the callback. Any return values will
		513	be returned to the caller.
		514
		515	This is useful when you temporarily want to execute code in the context of
		516	a port.
		517
		518	Example: create a port and run some initialisation code in it's context.
		519
		520	my $port = port { ... };
		521
		522	peval $port, sub {
		523	init
		524	or die "unable to init";
		525	};
		526
		527	=cut
		528
		529	sub peval($$) {
		530	local $SELF = shift;
		531	my $cb = shift;
		532
		533	if (wantarray) {
		534	my @res = eval { &$cb };
		535	_self_die if $@;
		536	@res
		537	} else {
		538	my $res = eval { &$cb };
		539	_self_die if $@;
		540	$res
		541	}
		542	}
		543
406	=item $closure = psub { BLOCK }	544	=item $closure = psub { BLOCK }
407		545
408	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	546	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
409	closure is executed, sets up the environment in the same way as in C<rcv>	547	closure is executed, sets up the environment in the same way as in C<rcv>
410	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.	548	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		549
		550	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		551	BLOCK }, @_ } >>.
411		552
412	This is useful when you register callbacks from C<rcv> callbacks:	553	This is useful when you register callbacks from C<rcv> callbacks:
413		554
414	rcv delayed_reply => sub {	555	rcv delayed_reply => sub {
415	my ($delay, @reply) = @_;	556	my ($delay, @reply) = @_;
…		…
451		592
452	Monitor the given port and do something when the port is killed or	593	Monitor the given port and do something when the port is killed or
453	messages to it were lost, and optionally return a guard that can be used	594	messages to it were lost, and optionally return a guard that can be used
454	to stop monitoring again.	595	to stop monitoring again.
455		596
		597	In the first form (callback), the callback is simply called with any
		598	number of C<@reason> elements (no @reason means that the port was deleted
		599	"normally"). Note also that I<< the callback B<must> never die >>, so use
		600	C<eval> if unsure.
		601
		602	In the second form (another port given), the other port (C<$rcvport>)
		603	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
		604	"normal" kils nothing happens, while under all other conditions, the other
		605	port is killed with the same reason.
		606
		607	The third form (kill self) is the same as the second form, except that
		608	C<$rvport> defaults to C<$SELF>.
		609
		610	In the last form (message), a message of the form C<@msg, @reason> will be
		611	C<snd>.
		612
		613	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		614	alert was raised), they are removed and will not trigger again.
		615
		616	As a rule of thumb, monitoring requests should always monitor a port from
		617	a local port (or callback). The reason is that kill messages might get
		618	lost, just like any other message. Another less obvious reason is that
		619	even monitoring requests can get lost (for example, when the connection
		620	to the other node goes down permanently). When monitoring a port locally
		621	these problems do not exist.
		622
456	C<mon> effectively guarantees that, in the absence of hardware failures,	623	C<mon> effectively guarantees that, in the absence of hardware failures,
457	after starting the monitor, either all messages sent to the port will	624	after starting the monitor, either all messages sent to the port will
458	arrive, or the monitoring action will be invoked after possible message	625	arrive, or the monitoring action will be invoked after possible message
459	loss has been detected. No messages will be lost "in between" (after	626	loss has been detected. No messages will be lost "in between" (after
460	the first lost message no further messages will be received by the	627	the first lost message no further messages will be received by the
461	port). After the monitoring action was invoked, further messages might get	628	port). After the monitoring action was invoked, further messages might get
462	delivered again.	629	delivered again.
463		630
464	Note that monitoring-actions are one-shot: once messages are lost (and a	631	Inter-host-connection timeouts and monitoring depend on the transport
465	monitoring alert was raised), they are removed and will not trigger again.	632	used. The only transport currently implemented is TCP, and AnyEvent::MP
		633	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		634	non-idle connection, and usually around two hours for idle connections).
466		635
467	In the first form (callback), the callback is simply called with any	636	This means that monitoring is good for program errors and cleaning up
468	number of C<@reason> elements (no @reason means that the port was deleted	637	stuff eventually, but they are no replacement for a timeout when you need
469	"normally"). Note also that I<< the callback B<must> never die >>, so use	638	to ensure some maximum latency.
470	C<eval> if unsure.
471
472	In the second form (another port given), the other port (C<$rcvport>)
473	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
474	"normal" kils nothing happens, while under all other conditions, the other
475	port is killed with the same reason.
476
477	The third form (kill self) is the same as the second form, except that
478	C<$rvport> defaults to C<$SELF>.
479
480	In the last form (message), a message of the form C<@msg, @reason> will be
481	C<snd>.
482
483	As a rule of thumb, monitoring requests should always monitor a port from
484	a local port (or callback). The reason is that kill messages might get
485	lost, just like any other message. Another less obvious reason is that
486	even monitoring requests can get lost (for exmaple, when the connection
487	to the other node goes down permanently). When monitoring a port locally
488	these problems do not exist.
489		639
490	Example: call a given callback when C<$port> is killed.	640	Example: call a given callback when C<$port> is killed.
491		641
492	mon $port, sub { warn "port died because of <@_>\n" };	642	mon $port, sub { warn "port died because of <@_>\n" };
493		643
…		…
500	mon $port, $self => "restart";	650	mon $port, $self => "restart";
501		651
502	=cut	652	=cut
503		653
504	sub mon {	654	sub mon {
505	my ($noderef, $port) = split /#/, shift, 2;	655	my ($nodeid, $port) = split /#/, shift, 2;
506		656
507	my $node = $NODE{$noderef} \|\| add_node $noderef;	657	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
508		658
509	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	659	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
510		660
511	unless (ref $cb) {	661	unless (ref $cb) {
512	if (@_) {	662	if (@_) {
…		…
521	}	671	}
522		672
523	$node->monitor ($port, $cb);	673	$node->monitor ($port, $cb);
524		674
525	defined wantarray	675	defined wantarray
526	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	676	and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) })
527	}	677	}
528		678
529	=item $guard = mon_guard $port, $ref, $ref...	679	=item $guard = mon_guard $port, $ref, $ref...
530		680
531	Monitors the given C<$port> and keeps the passed references. When the port	681	Monitors the given C<$port> and keeps the passed references. When the port
…		…
554		704
555	=item kil $port[, @reason]	705	=item kil $port[, @reason]
556		706
557	Kill the specified port with the given C<@reason>.	707	Kill the specified port with the given C<@reason>.
558		708
559	If no C<@reason> is specified, then the port is killed "normally" (ports	709	If no C<@reason> is specified, then the port is killed "normally" -
560	monitoring other ports will not necessarily die because a port dies	710	monitor callback will be invoked, but the kil will not cause linked ports
561	"normally").	711	(C<mon $mport, $lport> form) to get killed.
562		712
563	Otherwise, linked ports get killed with the same reason (second form of	713	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
564	C<mon>, see above).	714	form) get killed with the same reason.
565		715
566	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	716	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
567	will be reported as reason C<< die => $@ >>.	717	will be reported as reason C<< die => $@ >>.
568		718
569	Transport/communication errors are reported as C<< transport_error =>	719	Transport/communication errors are reported as C<< transport_error =>
…		…
588	the package, then the package above the package and so on (e.g.	738	the package, then the package above the package and so on (e.g.
589	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	739	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
590	exists or it runs out of package names.	740	exists or it runs out of package names.
591		741
592	The init function is then called with the newly-created port as context	742	The init function is then called with the newly-created port as context
593	object (C<$SELF>) and the C<@initdata> values as arguments.	743	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		744	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		745	the port might not get created.
594		746
595	A common idiom is to pass a local port, immediately monitor the spawned	747	A common idiom is to pass a local port, immediately monitor the spawned
596	port, and in the remote init function, immediately monitor the passed	748	port, and in the remote init function, immediately monitor the passed
597	local port. This two-way monitoring ensures that both ports get cleaned up	749	local port. This two-way monitoring ensures that both ports get cleaned up
598	when there is a problem.	750	when there is a problem.
599		751
		752	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		753	caller before C<spawn> returns (by delaying invocation when spawn is
		754	called for the local node).
		755
600	Example: spawn a chat server port on C<$othernode>.	756	Example: spawn a chat server port on C<$othernode>.
601		757
602	# this node, executed from within a port context:	758	# this node, executed from within a port context:
603	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	759	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
604	mon $server;	760	mon $server;
…		…
618		774
619	sub _spawn {	775	sub _spawn {
620	my $port = shift;	776	my $port = shift;
621	my $init = shift;	777	my $init = shift;
622		778
		779	# rcv will create the actual port
623	local $SELF = "$NODE#$port";	780	local $SELF = "$NODE#$port";
624	eval {	781	eval {
625	&{ load_func $init }	782	&{ load_func $init }
626	};	783	};
627	_self_die if $@;	784	_self_die if $@;
628	}	785	}
629		786
630	sub spawn(@) {	787	sub spawn(@) {
631	my ($noderef, undef) = split /#/, shift, 2;	788	my ($nodeid, undef) = split /#/, shift, 2;
632		789
633	my $id = "$RUNIQ." . $ID++;	790	my $id = "$RUNIQ." . ++$ID;
634		791
635	$_[0] =~ /::/	792	$_[0] =~ /::/
636	or Carp::croak "spawn init function must be a fully-qualified name, caught";	793	or Carp::croak "spawn init function must be a fully-qualified name, caught";
637		794
638	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;	795	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
639		796
640	"$noderef#$id"	797	"$nodeid#$id"
641	}	798	}
		799
642		800
643	=item after $timeout, @msg	801	=item after $timeout, @msg
644		802
645	=item after $timeout, $callback	803	=item after $timeout, $callback
646		804
…		…
662	? $action[0]()	820	? $action[0]()
663	: snd @action;	821	: snd @action;
664	};	822	};
665	}	823	}
666		824
		825	=item cal $port, @msg, $callback[, $timeout]
		826
		827	A simple form of RPC - sends a message to the given C<$port> with the
		828	given contents (C<@msg>), but adds a reply port to the message.
		829
		830	The reply port is created temporarily just for the purpose of receiving
		831	the reply, and will be C<kil>ed when no longer needed.
		832
		833	A reply message sent to the port is passed to the C<$callback> as-is.
		834
		835	If an optional time-out (in seconds) is given and it is not C<undef>,
		836	then the callback will be called without any arguments after the time-out
		837	elapsed and the port is C<kil>ed.
		838
		839	If no time-out is given (or it is C<undef>), then the local port will
		840	monitor the remote port instead, so it eventually gets cleaned-up.
		841
		842	Currently this function returns the temporary port, but this "feature"
		843	might go in future versions unless you can make a convincing case that
		844	this is indeed useful for something.
		845
		846	=cut
		847
		848	sub cal(@) {
		849	my $timeout = ref $_[-1] ? undef : pop;
		850	my $cb = pop;
		851
		852	my $port = port {
		853	undef $timeout;
		854	kil $SELF;
		855	&$cb;
		856	};
		857
		858	if (defined $timeout) {
		859	$timeout = AE::timer $timeout, 0, sub {
		860	undef $timeout;
		861	kil $port;
		862	$cb->();
		863	};
		864	} else {
		865	mon $_[0], sub {
		866	kil $port;
		867	$cb->();
		868	};
		869	}
		870
		871	push @_, $port;
		872	&snd;
		873
		874	$port
		875	}
		876
667	=back	877	=back
668		878
669	=head1 AnyEvent::MP vs. Distributed Erlang	879	=head1 AnyEvent::MP vs. Distributed Erlang
670		880
671	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	881	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
672	== aemp node, Erlang process == aemp port), so many of the documents and	882	== aemp node, Erlang process == aemp port), so many of the documents and
673	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	883	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
674	sample:	884	sample:
675		885
676	http://www.Erlang.se/doc/programming_rules.shtml	886	http://www.erlang.se/doc/programming_rules.shtml
677	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	887	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
678	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	888	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
679	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	889	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
680		890
681	Despite the similarities, there are also some important differences:	891	Despite the similarities, there are also some important differences:
682		892
683	=over 4	893	=over 4
684		894
685	=item * Node IDs are arbitrary strings in AEMP.	895	=item * Node IDs are arbitrary strings in AEMP.
686		896
687	Erlang relies on special naming and DNS to work everywhere in the same	897	Erlang relies on special naming and DNS to work everywhere in the same
688	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by	898	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
689	configuraiton or DNS), but will otherwise discover other odes itself.	899	configuration or DNS), and possibly the addresses of some seed nodes, but
		900	will otherwise discover other nodes (and their IDs) itself.
690		901
691	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	902	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
692	uses "local ports are like remote ports".	903	uses "local ports are like remote ports".
693		904
694	The failure modes for local ports are quite different (runtime errors	905	The failure modes for local ports are quite different (runtime errors
…		…
703	ports being the special case/exception, where transport errors cannot	914	ports being the special case/exception, where transport errors cannot
704	occur.	915	occur.
705		916
706	=item * Erlang uses processes and a mailbox, AEMP does not queue.	917	=item * Erlang uses processes and a mailbox, AEMP does not queue.
707		918
708	Erlang uses processes that selectively receive messages, and therefore	919	Erlang uses processes that selectively receive messages out of order, and
709	needs a queue. AEMP is event based, queuing messages would serve no	920	therefore needs a queue. AEMP is event based, queuing messages would serve
710	useful purpose. For the same reason the pattern-matching abilities of	921	no useful purpose. For the same reason the pattern-matching abilities
711	AnyEvent::MP are more limited, as there is little need to be able to	922	of AnyEvent::MP are more limited, as there is little need to be able to
712	filter messages without dequeing them.	923	filter messages without dequeuing them.
713		924
714	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	925	This is not a philosophical difference, but simply stems from AnyEvent::MP
		926	being event-based, while Erlang is process-based.
		927
		928	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		929	top of AEMP and Coro threads.
715		930
716	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	931	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
717		932
718	Sending messages in Erlang is synchronous and blocks the process (and	933	Sending messages in Erlang is synchronous and blocks the process until
		934	a conenction has been established and the message sent (and so does not
719	so does not need a queue that can overflow). AEMP sends are immediate,	935	need a queue that can overflow). AEMP sends return immediately, connection
720	connection establishment is handled in the background.	936	establishment is handled in the background.
721		937
722	=item * Erlang suffers from silent message loss, AEMP does not.	938	=item * Erlang suffers from silent message loss, AEMP does not.
723		939
724	Erlang makes few guarantees on messages delivery - messages can get lost	940	Erlang implements few guarantees on messages delivery - messages can get
725	without any of the processes realising it (i.e. you send messages a, b,	941	lost without any of the processes realising it (i.e. you send messages a,
726	and c, and the other side only receives messages a and c).	942	b, and c, and the other side only receives messages a and c).
727		943
728	AEMP guarantees correct ordering, and the guarantee that after one message	944	AEMP guarantees (modulo hardware errors) correct ordering, and the
729	is lost, all following ones sent to the same port are lost as well, until	945	guarantee that after one message is lost, all following ones sent to the
730	monitoring raises an error, so there are no silent "holes" in the message	946	same port are lost as well, until monitoring raises an error, so there are
731	sequence.	947	no silent "holes" in the message sequence.
		948
		949	If you want your software to be very reliable, you have to cope with
		950	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
		951	simply tries to work better in common error cases, such as when a network
		952	link goes down.
732		953
733	=item * Erlang can send messages to the wrong port, AEMP does not.	954	=item * Erlang can send messages to the wrong port, AEMP does not.
734		955
735	In Erlang it is quite likely that a node that restarts reuses a process ID	956	In Erlang it is quite likely that a node that restarts reuses an Erlang
736	known to other nodes for a completely different process, causing messages	957	process ID known to other nodes for a completely different process,
737	destined for that process to end up in an unrelated process.	958	causing messages destined for that process to end up in an unrelated
		959	process.
738		960
739	AEMP never reuses port IDs, so old messages or old port IDs floating	961	AEMP does not reuse port IDs, so old messages or old port IDs floating
740	around in the network will not be sent to an unrelated port.	962	around in the network will not be sent to an unrelated port.
741		963
742	=item * Erlang uses unprotected connections, AEMP uses secure	964	=item * Erlang uses unprotected connections, AEMP uses secure
743	authentication and can use TLS.	965	authentication and can use TLS.
744		966
…		…
747		969
748	=item * The AEMP protocol is optimised for both text-based and binary	970	=item * The AEMP protocol is optimised for both text-based and binary
749	communications.	971	communications.
750		972
751	The AEMP protocol, unlike the Erlang protocol, supports both programming	973	The AEMP protocol, unlike the Erlang protocol, supports both programming
752	language independent text-only protocols (good for debugging) and binary,	974	language independent text-only protocols (good for debugging), and binary,
753	language-specific serialisers (e.g. Storable). By default, unless TLS is	975	language-specific serialisers (e.g. Storable). By default, unless TLS is
754	used, the protocol is actually completely text-based.	976	used, the protocol is actually completely text-based.
755		977
756	It has also been carefully designed to be implementable in other languages	978	It has also been carefully designed to be implementable in other languages
757	with a minimum of work while gracefully degrading functionality to make the	979	with a minimum of work while gracefully degrading functionality to make the
758	protocol simple.	980	protocol simple.
759		981
760	=item * AEMP has more flexible monitoring options than Erlang.	982	=item * AEMP has more flexible monitoring options than Erlang.
761		983
762	In Erlang, you can chose to receive I<all> exit signals as messages	984	In Erlang, you can chose to receive I<all> exit signals as messages or
763	or I<none>, there is no in-between, so monitoring single processes is	985	I<none>, there is no in-between, so monitoring single Erlang processes is
764	difficult to implement. Monitoring in AEMP is more flexible than in	986	difficult to implement.
765	Erlang, as one can choose between automatic kill, exit message or callback	987
766	on a per-process basis.	988	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		989	between automatic kill, exit message or callback on a per-port basis.
767		990
768	=item * Erlang tries to hide remote/local connections, AEMP does not.	991	=item * Erlang tries to hide remote/local connections, AEMP does not.
769		992
770	Monitoring in Erlang is not an indicator of process death/crashes, in the	993	Monitoring in Erlang is not an indicator of process death/crashes, in the
771	same way as linking is (except linking is unreliable in Erlang).	994	same way as linking is (except linking is unreliable in Erlang).
…		…
793	overhead, as well as having to keep a proxy object everywhere.	1016	overhead, as well as having to keep a proxy object everywhere.
794		1017
795	Strings can easily be printed, easily serialised etc. and need no special	1018	Strings can easily be printed, easily serialised etc. and need no special
796	procedures to be "valid".	1019	procedures to be "valid".
797		1020
798	And as a result, a miniport consists of a single closure stored in a	1021	And as a result, a port with just a default receiver consists of a single
799	global hash - it can't become much cheaper.	1022	code reference stored in a global hash - it can't become much cheaper.
800		1023
801	=item Why favour JSON, why not a real serialising format such as Storable?	1024	=item Why favour JSON, why not a real serialising format such as Storable?
802		1025
803	In fact, any AnyEvent::MP node will happily accept Storable as framing	1026	In fact, any AnyEvent::MP node will happily accept Storable as framing
804	format, but currently there is no way to make a node use Storable by	1027	format, but currently there is no way to make a node use Storable by
…		…
820		1043
821	L<AnyEvent::MP::Intro> - a gentle introduction.	1044	L<AnyEvent::MP::Intro> - a gentle introduction.
822		1045
823	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.	1046	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
824		1047
825	L<AnyEvent::MP::Global> - network maintainance and port groups, to find	1048	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
826	your applications.	1049	your applications.
		1050
		1051	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		1052
		1053	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		1054	all nodes.
827		1055
828	L<AnyEvent>.	1056	L<AnyEvent>.
829		1057
830	=head1 AUTHOR	1058	=head1 AUTHOR
831		1059

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Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.71 by root, Sun Aug 30 19:52:56 2009 UTC vs. Revision 1.122 by root, Wed Feb 29 18:44:59 2012 UTC

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Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.71 by root, Sun Aug 30 19:52:56 2009 UTC vs.
Revision 1.122 by root, Wed Feb 29 18:44:59 2012 UTC