[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 1.125 by root, Sat Mar 3 13:07:19 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<#>)
78	separator, and a port name (a printable string of unspecified format).	88	as separator, and a port name (a printable string of unspecified
		89	format created by AnyEvent::MP).
79		90
80	=item node	91	=item node
81		92
82	A node is a single process containing at least one port - the node port,	93	A node is a single process containing at least one port - the node port,
83	which enables nodes to manage each other remotely, and to create new	94	which enables nodes to manage each other remotely, and to create new
84	ports.	95	ports.
85		96
86	Nodes are either public (have one or more listening ports) or private	97	Nodes are either public (have one or more listening ports) or private
87	(no listening ports). Private nodes cannot talk to other private nodes	98	(no listening ports). Private nodes cannot talk to other private nodes
88	currently.	99	currently, but all nodes can talk to public nodes.
89		100
		101	Nodes is represented by (printable) strings called "node IDs".
		102
90	=item node ID - C<[a-za-Z0-9_\-.:]+>	103	=item node ID - C<[A-Za-z0-9_\-.:]*>
91		104
92	A node ID is a string that uniquely identifies the node within a	105	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	106	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	107	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
95	doesn't interpret node IDs in any way.	108	doesn't interpret node IDs in any way except to uniquely identify a node.
96		109
97	=item binds - C<ip:port>	110	=item binds - C<ip:port>
98		111
99	Nodes can only talk to each other by creating some kind of connection to	112	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	113	each other. To do this, nodes should listen on one or more local transport
		114	endpoints - binds.
		115
101	endpoints - binds. Currently, only standard C<ip:port> specifications can	116	Currently, only standard C<ip:port> specifications can be used, which
102	be used, which specify TCP ports to listen on.	117	specify TCP ports to listen on. So a bind is basically just a tcp socket
		118	in listening mode thta accepts conenctions form other nodes.
103		119
		120	=item seed nodes
		121
		122	When a node starts, it knows nothing about the network it is in - it
		123	needs to connect to at least one other node that is already in the
		124	network. These other nodes are called "seed nodes".
		125
		126	Seed nodes themselves are not special - they are seed nodes only because
		127	some other node I<uses> them as such, but any node can be used as seed
		128	node for other nodes, and eahc node cna use a different set of seed nodes.
		129
		130	In addition to discovering the network, seed nodes are also used to
		131	maintain the network - all nodes using the same seed node form are part of
		132	the same network. If a network is split into multiple subnets because e.g.
		133	the network link between the parts goes down, then using the same seed
		134	nodes for all nodes ensures that eventually the subnets get merged again.
		135
		136	Seed nodes are expected to be long-running, and at least one seed node
		137	should always be available. They should also be relatively responsive - a
		138	seed node that blocks for long periods will slow down everybody else.
		139
		140	For small networks, it's best if every node uses the same set of seed
		141	nodes. For large networks, it can be useful to specify "regional" seed
		142	nodes for most nodes in an area, and use all seed nodes as seed nodes for
		143	each other. What's important is that all seed nodes connections form a
		144	complete graph, so that the network cannot split into separate subnets
		145	forever.
		146
		147	Seed nodes are represented by seed IDs.
		148
104	=item seeds - C<host:port>	149	=item seed IDs - C<host:port>
105		150
106	When a node starts, it knows nothing about the network. To teach the node	151	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	152	TCP port) of nodes that should be used as seed nodes.
108	network. This node is called a seed.
109		153
110	Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes	154	=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		155
116	Apart from being sued for seeding, seednodes are not special in any way -	156	An AEMP network needs a discovery service - nodes need to know how to
117	every public node can be a seednode.	157	connect to other nodes they only know by name. In addition, AEMP offers a
		158	distributed "group database", which maps group names to a list of strings
		159	- for example, to register worker ports.
		160
		161	A network needs at least one global node to work, and allows every node to
		162	be a global node.
		163
		164	Any node that loads the L<AnyEvent::MP::Global> module becomes a global
		165	node and tries to keep connections to all other nodes. So while it can
		166	make sense to make every node "global" in small networks, it usually makes
		167	sense to only make seed nodes into global nodes in large networks (nodes
		168	keep connections to seed nodes and global nodes, so makign them the same
		169	reduces overhead).
118		170
119	=back	171	=back
120		172
121	=head1 VARIABLES/FUNCTIONS	173	=head1 VARIABLES/FUNCTIONS
122		174
…		…
124		176
125	=cut	177	=cut
126		178
127	package AnyEvent::MP;	179	package AnyEvent::MP;
128		180
		181	use AnyEvent::MP::Config ();
129	use AnyEvent::MP::Kernel;	182	use AnyEvent::MP::Kernel;
		183	use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID);
130		184
131	use common::sense;	185	use common::sense;
132		186
133	use Carp ();	187	use Carp ();
134		188
135	use AE ();	189	use AE ();
		190	use Guard ();
136		191
137	use base "Exporter";	192	use base "Exporter";
138		193
139	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	194	our $VERSION = $AnyEvent::MP::Config::VERSION;
140		195
141	our @EXPORT = qw(	196	our @EXPORT = qw(
142	NODE $NODE *SELF node_of after	197	NODE $NODE *SELF node_of after
143	initialise_node	198	configure
144	snd rcv mon mon_guard kil reg psub spawn	199	snd rcv mon mon_guard kil psub peval spawn cal
145	port	200	port
		201	db_set db_del db_reg
146	);	202	);
147		203
148	our $SELF;	204	our $SELF;
149		205
150	sub _self_die() {	206	sub _self_die() {
…		…
155		211
156	=item $thisnode = NODE / $NODE	212	=item $thisnode = NODE / $NODE
157		213
158	The C<NODE> function returns, and the C<$NODE> variable contains, the node	214	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	215	ID of the node running in the current process. This value is initialised by
160	a call to C<initialise_node>.	216	a call to C<configure>.
161		217
162	=item $nodeid = node_of $port	218	=item $nodeid = node_of $port
163		219
164	Extracts and returns the node ID from a port ID or a node ID.	220	Extracts and returns the node ID from a port ID or a node ID.
165		221
166	=item initialise_node $profile_name, key => value...	222	=item configure $profile, key => value...
		223
		224	=item configure key => value...
167		225
168	Before a node can talk to other nodes on the network (i.e. enter	226	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	227	"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	228	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.	229	some other nodes in the network to discover other nodes.
172		230
173	This function initialises a node - it must be called exactly once (or	231	This function configures a node - it must be called exactly once (or
174	never) before calling other AnyEvent::MP functions.	232	never) before calling other AnyEvent::MP functions.
175		233
176	The first argument is a profile name. If it is C<undef> or missing, then	234	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>).	235	F<aemp> command line utility (sans the set/del prefix), with two additions:
178		236
		237	=over 4
		238
		239	=item norc => $boolean (default false)
		240
		241	If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I<not>
		242	be consulted - all configuraiton options must be specified in the
		243	C<configure> call.
		244
		245	=item force => $boolean (default false)
		246
		247	IF true, then the values specified in the C<configure> will take
		248	precedence over any values configured via the rc file. The default is for
		249	the rc file to override any options specified in the program.
		250
		251	=back
		252
		253	=over 4
		254
		255	=item step 1, gathering configuration from profiles
		256
179	The function first looks up the profile in the aemp configuration (see the	257	The function first looks up a profile in the aemp configuration (see the
180	L<aemp> commandline utility). the profile is calculated as follows:	258	L<aemp> commandline utility). The profile name can be specified via the
		259	named C<profile> parameter or can simply be the first parameter). If it is
		260	missing, then the nodename (F<uname -n>) will be used as profile name.
181		261
		262	The profile data is then gathered as follows:
		263
182	First, all remaining key => value pairs (all of which are conviniently	264	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	265	undocumented at the moment) will be interpreted as configuration
184	any values specified in the global default configuration (see the F<aemp>	266	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	267	default configuration (see the F<aemp> utility), then the chain of
		268	profiles chosen by the profile name (and any C<parent> attributes).
		269
186	the values specified in the profile have highest priority and the values	270	That means that the values specified in the profile have highest priority
187	specified via C<initialise_node> have lowest priority.	271	and the values specified directly via C<configure> have lowest priority,
		272	and can only be used to specify defaults.
188		273
189	If the profile specifies a node ID, then this will become the node ID of	274	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	275	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.	276	a slash (C</>) attached.
		277
		278	If the node ID (or profile name) ends with a slash (C</>), then a random
		279	string is appended to make it unique.
		280
		281	=item step 2, bind listener sockets
192		282
193	The next step is to look up the binds in the profile, followed by binding	283	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	284	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	285	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	286	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).	287	binds, but it can still talk to all "normal" nodes).
198		288
199	If the profile does not specify a binds list, then a default of C<*> is	289	If the profile does not specify a binds list, then a default of C<*> is
200	used.	290	used, meaning the node will bind on a dynamically-assigned port on every
		291	local IP address it finds.
201		292
		293	=item step 3, connect to seed nodes
		294
202	Lastly, the seeds list from the profile is passed to the	295	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	296	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.	297	connectivity with at least one node at any point in time.
205		298
206	Example: become a distributed node listening on the guessed noderef, or	299	=back
207	the one specified via C<aemp> for the current node. This should be the	300
		301	Example: become a distributed node using the local node name as profile.
208	most common form of invocation for "daemon"-type nodes.	302	This should be the most common form of invocation for "daemon"-type nodes.
209		303
210	initialise_node;	304	configure
211		305
212	Example: become an anonymous node. This form is often used for commandline	306	Example: become an anonymous node. This form is often used for commandline
213	clients.	307	clients.
214		308
215	initialise_node "anon/";	309	configure nodeid => "anon/";
216		310
217	Example: become a distributed node. If there is no profile of the given	311	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	312	for a seed node as it binds on all local addresses on a fixed port (4040,
219	on the resulting addresses.	313	customary for aemp).
220		314
221	initialise_node "localhost:4044";	315	# use the aemp commandline utility
		316	# aemp profile seed binds '*:4040'
		317
		318	# then use it
		319	configure profile => "seed";
		320
		321	# or simply use aemp from the shell again:
		322	# aemp run profile seed
		323
		324	# or provide a nicer-to-remember nodeid
		325	# aemp run profile seed nodeid "$(hostname)"
222		326
223	=item $SELF	327	=item $SELF
224		328
225	Contains the current port id while executing C<rcv> callbacks or C<psub>	329	Contains the current port id while executing C<rcv> callbacks or C<psub>
226	blocks.	330	blocks.
…		…
287	sub _kilme {	391	sub _kilme {
288	die "received message on port without callback";	392	die "received message on port without callback";
289	}	393	}
290		394
291	sub port(;&) {	395	sub port(;&) {
292	my $id = "$UNIQ." . $ID++;	396	my $id = $UNIQ . ++$ID;
293	my $port = "$NODE#$id";	397	my $port = "$NODE#$id";
294		398
295	rcv $port, shift \|\| \&_kilme;	399	rcv $port, shift \|\| \&_kilme;
296		400
297	$port	401	$port
…		…
336	msg1 => sub { ... },	440	msg1 => sub { ... },
337	...	441	...
338	;	442	;
339		443
340	Example: temporarily register a rcv callback for a tag matching some port	444	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.	445	(e.g. for an rpc reply) and unregister it after a message was received.
342		446
343	rcv $port, $otherport => sub {	447	rcv $port, $otherport => sub {
344	my @reply = @_;	448	my @reply = @_;
345		449
346	rcv $SELF, $otherport;	450	rcv $SELF, $otherport;
…		…
348		452
349	=cut	453	=cut
350		454
351	sub rcv($@) {	455	sub rcv($@) {
352	my $port = shift;	456	my $port = shift;
353	my ($noderef, $portid) = split /#/, $port, 2;	457	my ($nodeid, $portid) = split /#/, $port, 2;
354		458
355	$NODE{$noderef} == $NODE{""}	459	$NODE{$nodeid} == $NODE{""}
356	or Carp::croak "$port: rcv can only be called on local ports, caught";	460	or Carp::croak "$port: rcv can only be called on local ports, caught";
357		461
358	while (@_) {	462	while (@_) {
359	if (ref $_[0]) {	463	if (ref $_[0]) {
360	if (my $self = $PORT_DATA{$portid}) {	464	if (my $self = $PORT_DATA{$portid}) {
361	"AnyEvent::MP::Port" eq ref $self	465	"AnyEvent::MP::Port" eq ref $self
362	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	466	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
363		467
364	$self->[2] = shift;	468	$self->[0] = shift;
365	} else {	469	} else {
366	my $cb = shift;	470	my $cb = shift;
367	$PORT{$portid} = sub {	471	$PORT{$portid} = sub {
368	local $SELF = $port;	472	local $SELF = $port;
369	eval { &$cb }; _self_die if $@;	473	eval { &$cb }; _self_die if $@;
370	};	474	};
371	}	475	}
372	} elsif (defined $_[0]) {	476	} elsif (defined $_[0]) {
373	my $self = $PORT_DATA{$portid} \|\|= do {	477	my $self = $PORT_DATA{$portid} \|\|= do {
374	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	478	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
375		479
376	$PORT{$portid} = sub {	480	$PORT{$portid} = sub {
377	local $SELF = $port;	481	local $SELF = $port;
378		482
379	if (my $cb = $self->[1]{$_[0]}) {	483	if (my $cb = $self->[1]{$_[0]}) {
…		…
401	}	505	}
402		506
403	$port	507	$port
404	}	508	}
405		509
		510	=item peval $port, $coderef[, @args]
		511
		512	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		513	when the code throews an exception the C<$port> will be killed.
		514
		515	Any remaining args will be passed to the callback. Any return values will
		516	be returned to the caller.
		517
		518	This is useful when you temporarily want to execute code in the context of
		519	a port.
		520
		521	Example: create a port and run some initialisation code in it's context.
		522
		523	my $port = port { ... };
		524
		525	peval $port, sub {
		526	init
		527	or die "unable to init";
		528	};
		529
		530	=cut
		531
		532	sub peval($$) {
		533	local $SELF = shift;
		534	my $cb = shift;
		535
		536	if (wantarray) {
		537	my @res = eval { &$cb };
		538	_self_die if $@;
		539	@res
		540	} else {
		541	my $res = eval { &$cb };
		542	_self_die if $@;
		543	$res
		544	}
		545	}
		546
406	=item $closure = psub { BLOCK }	547	=item $closure = psub { BLOCK }
407		548
408	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	549	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>	550	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.	551	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		552
		553	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		554	BLOCK }, @_ } >>.
411		555
412	This is useful when you register callbacks from C<rcv> callbacks:	556	This is useful when you register callbacks from C<rcv> callbacks:
413		557
414	rcv delayed_reply => sub {	558	rcv delayed_reply => sub {
415	my ($delay, @reply) = @_;	559	my ($delay, @reply) = @_;
…		…
451		595
452	Monitor the given port and do something when the port is killed or	596	Monitor the given port and do something when the port is killed or
453	messages to it were lost, and optionally return a guard that can be used	597	messages to it were lost, and optionally return a guard that can be used
454	to stop monitoring again.	598	to stop monitoring again.
455		599
		600	In the first form (callback), the callback is simply called with any
		601	number of C<@reason> elements (no @reason means that the port was deleted
		602	"normally"). Note also that I<< the callback B<must> never die >>, so use
		603	C<eval> if unsure.
		604
		605	In the second form (another port given), the other port (C<$rcvport>)
		606	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
		607	"normal" kils nothing happens, while under all other conditions, the other
		608	port is killed with the same reason.
		609
		610	The third form (kill self) is the same as the second form, except that
		611	C<$rvport> defaults to C<$SELF>.
		612
		613	In the last form (message), a message of the form C<@msg, @reason> will be
		614	C<snd>.
		615
		616	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		617	alert was raised), they are removed and will not trigger again.
		618
		619	As a rule of thumb, monitoring requests should always monitor a port from
		620	a local port (or callback). The reason is that kill messages might get
		621	lost, just like any other message. Another less obvious reason is that
		622	even monitoring requests can get lost (for example, when the connection
		623	to the other node goes down permanently). When monitoring a port locally
		624	these problems do not exist.
		625
456	C<mon> effectively guarantees that, in the absence of hardware failures,	626	C<mon> effectively guarantees that, in the absence of hardware failures,
457	after starting the monitor, either all messages sent to the port will	627	after starting the monitor, either all messages sent to the port will
458	arrive, or the monitoring action will be invoked after possible message	628	arrive, or the monitoring action will be invoked after possible message
459	loss has been detected. No messages will be lost "in between" (after	629	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	630	the first lost message no further messages will be received by the
461	port). After the monitoring action was invoked, further messages might get	631	port). After the monitoring action was invoked, further messages might get
462	delivered again.	632	delivered again.
463		633
464	Note that monitoring-actions are one-shot: once messages are lost (and a	634	Inter-host-connection timeouts and monitoring depend on the transport
465	monitoring alert was raised), they are removed and will not trigger again.	635	used. The only transport currently implemented is TCP, and AnyEvent::MP
		636	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		637	non-idle connection, and usually around two hours for idle connections).
466		638
467	In the first form (callback), the callback is simply called with any	639	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	640	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	641	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<$SELF>.
479
480	In the last form (message), a message of the form C<@msg, @reason> will be
481	C<snd>.
482
483	As a rule of thumb, monitoring requests should always monitor a port from
484	a local port (or callback). The reason is that kill messages might get
485	lost, just like any other message. Another less obvious reason is that
486	even monitoring requests can get lost (for exmaple, when the connection
487	to the other node goes down permanently). When monitoring a port locally
488	these problems do not exist.
489		642
490	Example: call a given callback when C<$port> is killed.	643	Example: call a given callback when C<$port> is killed.
491		644
492	mon $port, sub { warn "port died because of <@_>\n" };	645	mon $port, sub { warn "port died because of <@_>\n" };
493		646
…		…
500	mon $port, $self => "restart";	653	mon $port, $self => "restart";
501		654
502	=cut	655	=cut
503		656
504	sub mon {	657	sub mon {
505	my ($noderef, $port) = split /#/, shift, 2;	658	my ($nodeid, $port) = split /#/, shift, 2;
506		659
507	my $node = $NODE{$noderef} \|\| add_node $noderef;	660	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
508		661
509	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	662	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
510		663
511	unless (ref $cb) {	664	unless (ref $cb) {
512	if (@_) {	665	if (@_) {
…		…
521	}	674	}
522		675
523	$node->monitor ($port, $cb);	676	$node->monitor ($port, $cb);
524		677
525	defined wantarray	678	defined wantarray
526	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	679	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
527	}	680	}
528		681
529	=item $guard = mon_guard $port, $ref, $ref...	682	=item $guard = mon_guard $port, $ref, $ref...
530		683
531	Monitors the given C<$port> and keeps the passed references. When the port	684	Monitors the given C<$port> and keeps the passed references. When the port
…		…
554		707
555	=item kil $port[, @reason]	708	=item kil $port[, @reason]
556		709
557	Kill the specified port with the given C<@reason>.	710	Kill the specified port with the given C<@reason>.
558		711
559	If no C<@reason> is specified, then the port is killed "normally" (ports	712	If no C<@reason> is specified, then the port is killed "normally" -
560	monitoring other ports will not necessarily die because a port dies	713	monitor callback will be invoked, but the kil will not cause linked ports
561	"normally").	714	(C<mon $mport, $lport> form) to get killed.
562		715
563	Otherwise, linked ports get killed with the same reason (second form of	716	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
564	C<mon>, see above).	717	form) get killed with the same reason.
565		718
566	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	719	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
567	will be reported as reason C<< die => $@ >>.	720	will be reported as reason C<< die => $@ >>.
568		721
569	Transport/communication errors are reported as C<< transport_error =>	722	Transport/communication errors are reported as C<< transport_error =>
…		…
588	the package, then the package above the package and so on (e.g.	741	the package, then the package above the package and so on (e.g.
589	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	742	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
590	exists or it runs out of package names.	743	exists or it runs out of package names.
591		744
592	The init function is then called with the newly-created port as context	745	The init function is then called with the newly-created port as context
593	object (C<$SELF>) and the C<@initdata> values as arguments.	746	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		747	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		748	the port might not get created.
594		749
595	A common idiom is to pass a local port, immediately monitor the spawned	750	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	751	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	752	local port. This two-way monitoring ensures that both ports get cleaned up
598	when there is a problem.	753	when there is a problem.
599		754
		755	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		756	caller before C<spawn> returns (by delaying invocation when spawn is
		757	called for the local node).
		758
600	Example: spawn a chat server port on C<$othernode>.	759	Example: spawn a chat server port on C<$othernode>.
601		760
602	# this node, executed from within a port context:	761	# this node, executed from within a port context:
603	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	762	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
604	mon $server;	763	mon $server;
…		…
618		777
619	sub _spawn {	778	sub _spawn {
620	my $port = shift;	779	my $port = shift;
621	my $init = shift;	780	my $init = shift;
622		781
		782	# rcv will create the actual port
623	local $SELF = "$NODE#$port";	783	local $SELF = "$NODE#$port";
624	eval {	784	eval {
625	&{ load_func $init }	785	&{ load_func $init }
626	};	786	};
627	_self_die if $@;	787	_self_die if $@;
628	}	788	}
629		789
630	sub spawn(@) {	790	sub spawn(@) {
631	my ($noderef, undef) = split /#/, shift, 2;	791	my ($nodeid, undef) = split /#/, shift, 2;
632		792
633	my $id = "$RUNIQ." . $ID++;	793	my $id = $RUNIQ . ++$ID;
634		794
635	$_[0] =~ /::/	795	$_[0] =~ /::/
636	or Carp::croak "spawn init function must be a fully-qualified name, caught";	796	or Carp::croak "spawn init function must be a fully-qualified name, caught";
637		797
638	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;	798	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
639		799
640	"$noderef#$id"	800	"$nodeid#$id"
641	}	801	}
		802
642		803
643	=item after $timeout, @msg	804	=item after $timeout, @msg
644		805
645	=item after $timeout, $callback	806	=item after $timeout, $callback
646		807
…		…
662	? $action[0]()	823	? $action[0]()
663	: snd @action;	824	: snd @action;
664	};	825	};
665	}	826	}
666		827
		828	=item cal $port, @msg, $callback[, $timeout]
		829
		830	A simple form of RPC - sends a message to the given C<$port> with the
		831	given contents (C<@msg>), but adds a reply port to the message.
		832
		833	The reply port is created temporarily just for the purpose of receiving
		834	the reply, and will be C<kil>ed when no longer needed.
		835
		836	A reply message sent to the port is passed to the C<$callback> as-is.
		837
		838	If an optional time-out (in seconds) is given and it is not C<undef>,
		839	then the callback will be called without any arguments after the time-out
		840	elapsed and the port is C<kil>ed.
		841
		842	If no time-out is given (or it is C<undef>), then the local port will
		843	monitor the remote port instead, so it eventually gets cleaned-up.
		844
		845	Currently this function returns the temporary port, but this "feature"
		846	might go in future versions unless you can make a convincing case that
		847	this is indeed useful for something.
		848
		849	=cut
		850
		851	sub cal(@) {
		852	my $timeout = ref $_[-1] ? undef : pop;
		853	my $cb = pop;
		854
		855	my $port = port {
		856	undef $timeout;
		857	kil $SELF;
		858	&$cb;
		859	};
		860
		861	if (defined $timeout) {
		862	$timeout = AE::timer $timeout, 0, sub {
		863	undef $timeout;
		864	kil $port;
		865	$cb->();
		866	};
		867	} else {
		868	mon $_[0], sub {
		869	kil $port;
		870	$cb->();
		871	};
		872	}
		873
		874	push @_, $port;
		875	&snd;
		876
		877	$port
		878	}
		879
		880	=back
		881
		882	=head1 DISTRIBUTED DATABASE
		883
		884	AnyEvent::MP comes with a simple distributed database. The database will
		885	be mirrored asynchronously at all global nodes. Other nodes bind to one of
		886	the global nodes for their needs.
		887
		888	The database consists of a two-level hash - a hash contains a hash which
		889	contains values.
		890
		891	The top level hash key is called "family", and the second-level hash key
		892	is simply called "key".
		893
		894	The family must be alphanumeric, i.e. start with a letter and consist
		895	of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
		896	pretty much like Perl module names.
		897
		898	As the family namespace is global, it is recommended to prefix family names
		899	with the name of the application or module using it.
		900
		901	The keys must be strings, with no other limitations.
		902
		903	The values should preferably be strings, but other perl scalars should
		904	work as well (such as undef, arrays and hashes).
		905
		906	Every database entry is owned by one node - adding the same family/key
		907	combination on multiple nodes will not cause discomfort for AnyEvent::MP,
		908	but the result might be nondeterministic, i.e. the key might have
		909	different values on different nodes.
		910
		911	=item db_set $family => $key => $value
		912
		913	Sets (or replaces) a key to the database.
		914
		915	=item db_del $family => $key
		916
		917	Deletes a key from the database.
		918
		919	=item $guard = db_reg $family => $key [=> $value]
		920
		921	Sets the key on the database and returns a guard. When the guard is
		922	destroyed, the key is deleted from the database. If C<$value> is missing,
		923	then C<undef> is used.
		924
		925	=cut
		926
667	=back	927	=back
668		928
669	=head1 AnyEvent::MP vs. Distributed Erlang	929	=head1 AnyEvent::MP vs. Distributed Erlang
670		930
671	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	931	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	932	== 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	933	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
674	sample:	934	sample:
675		935
676	http://www.Erlang.se/doc/programming_rules.shtml	936	http://www.erlang.se/doc/programming_rules.shtml
677	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	937	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	938	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	939	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
680		940
681	Despite the similarities, there are also some important differences:	941	Despite the similarities, there are also some important differences:
682		942
683	=over 4	943	=over 4
684		944
685	=item * Node IDs are arbitrary strings in AEMP.	945	=item * Node IDs are arbitrary strings in AEMP.
686		946
687	Erlang relies on special naming and DNS to work everywhere in the same	947	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	948	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.	949	configuration or DNS), and possibly the addresses of some seed nodes, but
		950	will otherwise discover other nodes (and their IDs) itself.
690		951
691	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	952	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
692	uses "local ports are like remote ports".	953	uses "local ports are like remote ports".
693		954
694	The failure modes for local ports are quite different (runtime errors	955	The failure modes for local ports are quite different (runtime errors
…		…
703	ports being the special case/exception, where transport errors cannot	964	ports being the special case/exception, where transport errors cannot
704	occur.	965	occur.
705		966
706	=item * Erlang uses processes and a mailbox, AEMP does not queue.	967	=item * Erlang uses processes and a mailbox, AEMP does not queue.
707		968
708	Erlang uses processes that selectively receive messages, and therefore	969	Erlang uses processes that selectively receive messages out of order, and
709	needs a queue. AEMP is event based, queuing messages would serve no	970	therefore needs a queue. AEMP is event based, queuing messages would serve
710	useful purpose. For the same reason the pattern-matching abilities of	971	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	972	of AnyEvent::MP are more limited, as there is little need to be able to
712	filter messages without dequeing them.	973	filter messages without dequeuing them.
713		974
714	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	975	This is not a philosophical difference, but simply stems from AnyEvent::MP
		976	being event-based, while Erlang is process-based.
		977
		978	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		979	top of AEMP and Coro threads.
715		980
716	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	981	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
717		982
718	Sending messages in Erlang is synchronous and blocks the process (and	983	Sending messages in Erlang is synchronous and blocks the process until
		984	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,	985	need a queue that can overflow). AEMP sends return immediately, connection
720	connection establishment is handled in the background.	986	establishment is handled in the background.
721		987
722	=item * Erlang suffers from silent message loss, AEMP does not.	988	=item * Erlang suffers from silent message loss, AEMP does not.
723		989
724	Erlang makes few guarantees on messages delivery - messages can get lost	990	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,	991	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).	992	b, and c, and the other side only receives messages a and c).
727		993
728	AEMP guarantees correct ordering, and the guarantee that after one message	994	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	995	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	996	same port are lost as well, until monitoring raises an error, so there are
731	sequence.	997	no silent "holes" in the message sequence.
		998
		999	If you want your software to be very reliable, you have to cope with
		1000	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
		1001	simply tries to work better in common error cases, such as when a network
		1002	link goes down.
732		1003
733	=item * Erlang can send messages to the wrong port, AEMP does not.	1004	=item * Erlang can send messages to the wrong port, AEMP does not.
734		1005
735	In Erlang it is quite likely that a node that restarts reuses a process ID	1006	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	1007	process ID known to other nodes for a completely different process,
737	destined for that process to end up in an unrelated process.	1008	causing messages destined for that process to end up in an unrelated
		1009	process.
738		1010
739	AEMP never reuses port IDs, so old messages or old port IDs floating	1011	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.	1012	around in the network will not be sent to an unrelated port.
741		1013
742	=item * Erlang uses unprotected connections, AEMP uses secure	1014	=item * Erlang uses unprotected connections, AEMP uses secure
743	authentication and can use TLS.	1015	authentication and can use TLS.
744		1016
…		…
747		1019
748	=item * The AEMP protocol is optimised for both text-based and binary	1020	=item * The AEMP protocol is optimised for both text-based and binary
749	communications.	1021	communications.
750		1022
751	The AEMP protocol, unlike the Erlang protocol, supports both programming	1023	The AEMP protocol, unlike the Erlang protocol, supports both programming
752	language independent text-only protocols (good for debugging) and binary,	1024	language independent text-only protocols (good for debugging), and binary,
753	language-specific serialisers (e.g. Storable). By default, unless TLS is	1025	language-specific serialisers (e.g. Storable). By default, unless TLS is
754	used, the protocol is actually completely text-based.	1026	used, the protocol is actually completely text-based.
755		1027
756	It has also been carefully designed to be implementable in other languages	1028	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	1029	with a minimum of work while gracefully degrading functionality to make the
758	protocol simple.	1030	protocol simple.
759		1031
760	=item * AEMP has more flexible monitoring options than Erlang.	1032	=item * AEMP has more flexible monitoring options than Erlang.
761		1033
762	In Erlang, you can chose to receive I<all> exit signals as messages	1034	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	1035	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	1036	difficult to implement.
765	Erlang, as one can choose between automatic kill, exit message or callback	1037
766	on a per-process basis.	1038	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		1039	between automatic kill, exit message or callback on a per-port basis.
767		1040
768	=item * Erlang tries to hide remote/local connections, AEMP does not.	1041	=item * Erlang tries to hide remote/local connections, AEMP does not.
769		1042
770	Monitoring in Erlang is not an indicator of process death/crashes, in the	1043	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).	1044	same way as linking is (except linking is unreliable in Erlang).
…		…
793	overhead, as well as having to keep a proxy object everywhere.	1066	overhead, as well as having to keep a proxy object everywhere.
794		1067
795	Strings can easily be printed, easily serialised etc. and need no special	1068	Strings can easily be printed, easily serialised etc. and need no special
796	procedures to be "valid".	1069	procedures to be "valid".
797		1070
798	And as a result, a miniport consists of a single closure stored in a	1071	And as a result, a port with just a default receiver consists of a single
799	global hash - it can't become much cheaper.	1072	code reference stored in a global hash - it can't become much cheaper.
800		1073
801	=item Why favour JSON, why not a real serialising format such as Storable?	1074	=item Why favour JSON, why not a real serialising format such as Storable?
802		1075
803	In fact, any AnyEvent::MP node will happily accept Storable as framing	1076	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	1077	format, but currently there is no way to make a node use Storable by
…		…
820		1093
821	L<AnyEvent::MP::Intro> - a gentle introduction.	1094	L<AnyEvent::MP::Intro> - a gentle introduction.
822		1095
823	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.	1096	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
824		1097
825	L<AnyEvent::MP::Global> - network maintainance and port groups, to find	1098	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
826	your applications.	1099	your applications.
		1100
		1101	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		1102
		1103	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		1104	all nodes.
827		1105
828	L<AnyEvent>.	1106	L<AnyEvent>.
829		1107
830	=head1 AUTHOR	1108	=head1 AUTHOR
831		1109

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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 1.125 by root, Sat Mar 3 13:07:19 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 1.125 by root, Sat Mar 3 13:07:19 2012 UTC