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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.73 by root, Mon Aug 31 11:08:25 2009 UTC vs.
Revision 1.141 by root, Fri Mar 23 03:24:41 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	configure;	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;
31	rcv $port, pong => sub { warn "pong received\n" };	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 $port, $cb->(@msg) # callback is invoked on death
38	mon $port, $otherport # kill otherport on abnormal death	41	mon $port, $localport # kill localport on abnormal death
39	mon $port, $otherport, @msg # send message on death	42	mon $port, $localport, @msg # send message on death
40		43
41	=head1 CURRENT STATUS	44	# temporarily execute code in port context
		45	peval $port, sub { die "kill the port!" };
42		46
43	bin/aemp - stable.	47	# execute callbacks in $SELF port context
44	AnyEvent::MP - stable API, should work.	48	my $timer = AE::timer 1, 0, psub {
45	AnyEvent::MP::Intro - uptodate, but incomplete.	49	die "kill the port, delayed";
46	AnyEvent::MP::Kernel - mostly stable.	50	};
47	AnyEvent::MP::Global - stable API, protocol not yet final.
48
49	stay tuned.
50		51
51	=head1 DESCRIPTION	52	=head1 DESCRIPTION
52		53
53	This module (-family) implements a simple message passing framework.	54	This module (-family) implements a simple message passing framework.
54		55
…		…
56	on the same or other hosts, and you can supervise entities remotely.	57	on the same or other hosts, and you can supervise entities remotely.
57		58
58	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	59	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
59	manual page and the examples under F<eg/>.	60	manual page and the examples under F<eg/>.
60		61
61	At the moment, this module family is a bit underdocumented.
62
63	=head1 CONCEPTS	62	=head1 CONCEPTS
64		63
65	=over 4	64	=over 4
66		65
67	=item port	66	=item port
68		67
69	A port is something you can send messages to (with the C<snd> function).	68	Not to be confused with a TCP port, a "port" is something you can send
		69	messages to (with the C<snd> function).
70		70
71	Ports allow you to register C<rcv> handlers that can match all or just	71	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	72	some messages. Messages send to ports will not be queued, regardless of
73	anything was listening for them or not.	73	anything was listening for them or not.
74		74
		75	Ports are represented by (printable) strings called "port IDs".
		76
75	=item port ID - C<nodeid#portname>	77	=item port ID - C<nodeid#portname>
76		78
77	A port ID is the concatenation of a node ID, a hash-mark (C<#>) as	79	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).	80	as separator, and a port name (a printable string of unspecified
		81	format created by AnyEvent::MP).
79		82
80	=item node	83	=item node
81		84
82	A node is a single process containing at least one port - the node port,	85	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	86	which enables nodes to manage each other remotely, and to create new
84	ports.	87	ports.
85		88
86	Nodes are either public (have one or more listening ports) or private	89	Nodes are either public (have one or more listening ports) or private
87	(no listening ports). Private nodes cannot talk to other private nodes	90	(no listening ports). Private nodes cannot talk to other private nodes
88	currently.	91	currently, but all nodes can talk to public nodes.
89		92
		93	Nodes is represented by (printable) strings called "node IDs".
		94
90	=item node ID - C<[a-za-Z0-9_\-.:]+>	95	=item node ID - C<[A-Za-z0-9_\-.:]*>
91		96
92	A node ID is a string that uniquely identifies the node within a	97	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	98	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	99	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
95	doesn't interpret node IDs in any way.	100	doesn't interpret node IDs in any way except to uniquely identify a node.
96		101
97	=item binds - C<ip:port>	102	=item binds - C<ip:port>
98		103
99	Nodes can only talk to each other by creating some kind of connection to	104	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	105	each other. To do this, nodes should listen on one or more local transport
		106	endpoints - binds.
		107
101	endpoints - binds. Currently, only standard C<ip:port> specifications can	108	Currently, only standard C<ip:port> specifications can be used, which
102	be used, which specify TCP ports to listen on.	109	specify TCP ports to listen on. So a bind is basically just a tcp socket
		110	in listening mode thta accepts conenctions form other nodes.
103		111
		112	=item seed nodes
		113
		114	When a node starts, it knows nothing about the network it is in - it
		115	needs to connect to at least one other node that is already in the
		116	network. These other nodes are called "seed nodes".
		117
		118	Seed nodes themselves are not special - they are seed nodes only because
		119	some other node I<uses> them as such, but any node can be used as seed
		120	node for other nodes, and eahc node cna use a different set of seed nodes.
		121
		122	In addition to discovering the network, seed nodes are also used to
		123	maintain the network - all nodes using the same seed node form are part of
		124	the same network. If a network is split into multiple subnets because e.g.
		125	the network link between the parts goes down, then using the same seed
		126	nodes for all nodes ensures that eventually the subnets get merged again.
		127
		128	Seed nodes are expected to be long-running, and at least one seed node
		129	should always be available. They should also be relatively responsive - a
		130	seed node that blocks for long periods will slow down everybody else.
		131
		132	For small networks, it's best if every node uses the same set of seed
		133	nodes. For large networks, it can be useful to specify "regional" seed
		134	nodes for most nodes in an area, and use all seed nodes as seed nodes for
		135	each other. What's important is that all seed nodes connections form a
		136	complete graph, so that the network cannot split into separate subnets
		137	forever.
		138
		139	Seed nodes are represented by seed IDs.
		140
104	=item seeds - C<host:port>	141	=item seed IDs - C<host:port>
105		142
106	When a node starts, it knows nothing about the network. To teach the node	143	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	144	TCP port) of nodes that should be used as seed nodes.
108	network. This node is called a seed.
109		145
110	Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes	146	=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		147
116	Apart from being sued for seeding, seednodes are not special in any way -	148	An AEMP network needs a discovery service - nodes need to know how to
117	every public node can be a seednode.	149	connect to other nodes they only know by name. In addition, AEMP offers a
		150	distributed "group database", which maps group names to a list of strings
		151	- for example, to register worker ports.
		152
		153	A network needs at least one global node to work, and allows every node to
		154	be a global node.
		155
		156	Any node that loads the L<AnyEvent::MP::Global> module becomes a global
		157	node and tries to keep connections to all other nodes. So while it can
		158	make sense to make every node "global" in small networks, it usually makes
		159	sense to only make seed nodes into global nodes in large networks (nodes
		160	keep connections to seed nodes and global nodes, so makign them the same
		161	reduces overhead).
118		162
119	=back	163	=back
120		164
121	=head1 VARIABLES/FUNCTIONS	165	=head1 VARIABLES/FUNCTIONS
122		166
…		…
124		168
125	=cut	169	=cut
126		170
127	package AnyEvent::MP;	171	package AnyEvent::MP;
128		172
		173	use AnyEvent::MP::Config ();
129	use AnyEvent::MP::Kernel;	174	use AnyEvent::MP::Kernel;
		175	use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID);
130		176
131	use common::sense;	177	use common::sense;
132		178
133	use Carp ();	179	use Carp ();
134		180
135	use AE ();	181	use AnyEvent ();
		182	use Guard ();
136		183
137	use base "Exporter";	184	use base "Exporter";
138		185
139	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	186	our $VERSION = $AnyEvent::MP::Config::VERSION;
140		187
141	our @EXPORT = qw(	188	our @EXPORT = qw(
142	NODE $NODE *SELF node_of after	189	NODE $NODE *SELF node_of after
143	configure	190	configure
144	snd rcv mon mon_guard kil reg psub spawn	191	snd rcv mon mon_guard kil psub peval spawn cal
145	port	192	port
		193	db_set db_del db_reg
		194	db_mon db_family db_keys db_values
146	);	195	);
147		196
148	our $SELF;	197	our $SELF;
149		198
150	sub _self_die() {	199	sub _self_die() {
…		…
161		210
162	=item $nodeid = node_of $port	211	=item $nodeid = node_of $port
163		212
164	Extracts and returns the node ID from a port ID or a node ID.	213	Extracts and returns the node ID from a port ID or a node ID.
165		214
		215	=item configure $profile, key => value...
		216
166	=item configure key => value...	217	=item configure key => value...
167		218
168	Before a node can talk to other nodes on the network (i.e. enter	219	Before a node can talk to other nodes on the network (i.e. enter
169	"distributed mode") it has to configure itself - the minimum a node needs	220	"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	221	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.	222	some other nodes in the network to discover other nodes.
172		223
173	This function configures a node - it must be called exactly once (or	224	This function configures a node - it must be called exactly once (or
174	never) before calling other AnyEvent::MP functions.	225	never) before calling other AnyEvent::MP functions.
175		226
		227	The key/value pairs are basically the same ones as documented for the
		228	F<aemp> command line utility (sans the set/del prefix), with these additions:
		229
		230	=over 4
		231
		232	=item norc => $boolean (default false)
		233
		234	If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I<not>
		235	be consulted - all configuraiton options must be specified in the
		236	C<configure> call.
		237
		238	=item force => $boolean (default false)
		239
		240	IF true, then the values specified in the C<configure> will take
		241	precedence over any values configured via the rc file. The default is for
		242	the rc file to override any options specified in the program.
		243
		244	=item secure => $pass->(@msg)
		245
		246	In addition to specifying a boolean, you can specify a code reference that
		247	is called for every code execution attempt - the execution request is
		248	granted iff the callback returns a true value.
		249
		250	Most of the time the callback should look only at
		251	C<$AnyEvent::MP::Kernel::SRCNODE> to make a decision, and not at the
		252	actual message (which can be about anything, and is mostly provided for
		253	diagnostic purposes).
		254
		255	See F<semp setsecure> for more info.
		256
		257	=back
		258
176	=over 4	259	=over 4
177		260
178	=item step 1, gathering configuration from profiles	261	=item step 1, gathering configuration from profiles
179		262
180	The function first looks up a profile in the aemp configuration (see the	263	The function first looks up a profile in the aemp configuration (see the
181	L<aemp> commandline utility). The profile name can be specified via the	264	L<aemp> commandline utility). The profile name can be specified via the
182	named C<profile> parameter. If it is missing, then the nodename (F<uname	265	named C<profile> parameter or can simply be the first parameter). If it is
183	-n>) will be used as profile name.	266	missing, then the nodename (F<uname -n>) will be used as profile name.
184		267
185	The profile data is then gathered as follows:	268	The profile data is then gathered as follows:
186		269
187	First, all remaining key => value pairs (all of which are conviniently	270	First, all remaining key => value pairs (all of which are conveniently
188	undocumented at the moment) will be interpreted as configuration	271	undocumented at the moment) will be interpreted as configuration
189	data. Then they will be overwritten by any values specified in the global	272	data. Then they will be overwritten by any values specified in the global
190	default configuration (see the F<aemp> utility), then the chain of	273	default configuration (see the F<aemp> utility), then the chain of
191	profiles chosen by the profile name (and any C<parent> attributes).	274	profiles chosen by the profile name (and any C<parent> attributes).
192		275
193	That means that the values specified in the profile have highest priority	276	That means that the values specified in the profile have highest priority
194	and the values specified directly via C<configure> have lowest priority,	277	and the values specified directly via C<configure> have lowest priority,
195	and can only be used to specify defaults.	278	and can only be used to specify defaults.
196		279
197	If the profile specifies a node ID, then this will become the node ID of	280	If the profile specifies a node ID, then this will become the node ID of
198	this process. If not, then the profile name will be used as node ID. The	281	this process. If not, then the profile name will be used as node ID, with
199	special node ID of C<anon/> will be replaced by a random node ID.	282	a unique randoms tring (C</%u>) appended.
		283
		284	The node ID can contain some C<%> sequences that are expanded: C<%n>
		285	is expanded to the local nodename, C<%u> is replaced by a random
		286	strign to make the node unique. For example, the F<aemp> commandline
		287	utility uses C<aemp/%n/%u> as nodename, which might expand to
		288	C<aemp/cerebro/ZQDGSIkRhEZQDGSIkRhE>.
200		289
201	=item step 2, bind listener sockets	290	=item step 2, bind listener sockets
202		291
203	The next step is to look up the binds in the profile, followed by binding	292	The next step is to look up the binds in the profile, followed by binding
204	aemp protocol listeners on all binds specified (it is possible and valid	293	aemp protocol listeners on all binds specified (it is possible and valid
…		…
210	used, meaning the node will bind on a dynamically-assigned port on every	299	used, meaning the node will bind on a dynamically-assigned port on every
211	local IP address it finds.	300	local IP address it finds.
212		301
213	=item step 3, connect to seed nodes	302	=item step 3, connect to seed nodes
214		303
215	As the last step, the seeds list from the profile is passed to the	304	As the last step, the seed ID list from the profile is passed to the
216	L<AnyEvent::MP::Global> module, which will then use it to keep	305	L<AnyEvent::MP::Global> module, which will then use it to keep
217	connectivity with at least one node at any point in time.	306	connectivity with at least one node at any point in time.
218		307
219	=back	308	=back
220		309
221	Example: become a distributed node using the locla node name as profile.	310	Example: become a distributed node using the local node name as profile.
222	This should be the most common form of invocation for "daemon"-type nodes.	311	This should be the most common form of invocation for "daemon"-type nodes.
223		312
224	configure	313	configure
225		314
226	Example: become an anonymous node. This form is often used for commandline	315	Example: become a semi-anonymous node. This form is often used for
227	clients.	316	commandline clients.
228		317
229	configure nodeid => "anon/";	318	configure nodeid => "myscript/%n/%u";
230		319
231	Example: configure a node using a profile called seed, which si suitable	320	Example: configure a node using a profile called seed, which is suitable
232	for a seed node as it binds on all local addresses on a fixed port (4040,	321	for a seed node as it binds on all local addresses on a fixed port (4040,
233	customary for aemp).	322	customary for aemp).
234		323
235	# use the aemp commandline utility	324	# use the aemp commandline utility
236	# aemp profile seed setnodeid anon/ setbinds '*:4040'	325	# aemp profile seed binds '*:4040'
237		326
238	# then use it	327	# then use it
239	configure profile => "seed";	328	configure profile => "seed";
240		329
241	# or simply use aemp from the shell again:	330	# or simply use aemp from the shell again:
…		…
306		395
307	=cut	396	=cut
308		397
309	sub rcv($@);	398	sub rcv($@);
310		399
311	sub _kilme {	400	my $KILME = sub {
312	die "received message on port without callback";	401	(my $tag = substr $_[0], 0, 30) =~ s/([\x20-\x7e])/./g;
313	}	402	kil $SELF, unhandled_message => "no callback found for message '$tag'";
		403	};
314		404
315	sub port(;&) {	405	sub port(;&) {
316	my $id = "$UNIQ." . $ID++;	406	my $id = $UNIQ . ++$ID;
317	my $port = "$NODE#$id";	407	my $port = "$NODE#$id";
318		408
319	rcv $port, shift \|\| \&_kilme;	409	rcv $port, shift \|\| $KILME;
320		410
321	$port	411	$port
322	}	412	}
323		413
324	=item rcv $local_port, $callback->(@msg)	414	=item rcv $local_port, $callback->(@msg)
…		…
329		419
330	The global C<$SELF> (exported by this module) contains C<$port> while	420	The global C<$SELF> (exported by this module) contains C<$port> while
331	executing the callback. Runtime errors during callback execution will	421	executing the callback. Runtime errors during callback execution will
332	result in the port being C<kil>ed.	422	result in the port being C<kil>ed.
333		423
334	The default callback received all messages not matched by a more specific	424	The default callback receives all messages not matched by a more specific
335	C<tag> match.	425	C<tag> match.
336		426
337	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...	427	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
338		428
339	Register (or replace) callbacks to be called on messages starting with the	429	Register (or replace) callbacks to be called on messages starting with the
…		…
360	msg1 => sub { ... },	450	msg1 => sub { ... },
361	...	451	...
362	;	452	;
363		453
364	Example: temporarily register a rcv callback for a tag matching some port	454	Example: temporarily register a rcv callback for a tag matching some port
365	(e.g. for a rpc reply) and unregister it after a message was received.	455	(e.g. for an rpc reply) and unregister it after a message was received.
366		456
367	rcv $port, $otherport => sub {	457	rcv $port, $otherport => sub {
368	my @reply = @_;	458	my @reply = @_;
369		459
370	rcv $SELF, $otherport;	460	rcv $SELF, $otherport;
…		…
372		462
373	=cut	463	=cut
374		464
375	sub rcv($@) {	465	sub rcv($@) {
376	my $port = shift;	466	my $port = shift;
377	my ($noderef, $portid) = split /#/, $port, 2;	467	my ($nodeid, $portid) = split /#/, $port, 2;
378		468
379	$NODE{$noderef} == $NODE{""}	469	$NODE{$nodeid} == $NODE{""}
380	or Carp::croak "$port: rcv can only be called on local ports, caught";	470	or Carp::croak "$port: rcv can only be called on local ports, caught";
381		471
382	while (@_) {	472	while (@_) {
383	if (ref $_[0]) {	473	if (ref $_[0]) {
384	if (my $self = $PORT_DATA{$portid}) {	474	if (my $self = $PORT_DATA{$portid}) {
385	"AnyEvent::MP::Port" eq ref $self	475	"AnyEvent::MP::Port" eq ref $self
386	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	476	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
387		477
388	$self->[2] = shift;	478	$self->[0] = shift;
389	} else {	479	} else {
390	my $cb = shift;	480	my $cb = shift;
391	$PORT{$portid} = sub {	481	$PORT{$portid} = sub {
392	local $SELF = $port;	482	local $SELF = $port;
393	eval { &$cb }; _self_die if $@;	483	eval { &$cb }; _self_die if $@;
394	};	484	};
395	}	485	}
396	} elsif (defined $_[0]) {	486	} elsif (defined $_[0]) {
397	my $self = $PORT_DATA{$portid} \|\|= do {	487	my $self = $PORT_DATA{$portid} \|\|= do {
398	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	488	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
399		489
400	$PORT{$portid} = sub {	490	$PORT{$portid} = sub {
401	local $SELF = $port;	491	local $SELF = $port;
402		492
403	if (my $cb = $self->[1]{$_[0]}) {	493	if (my $cb = $self->[1]{$_[0]}) {
…		…
425	}	515	}
426		516
427	$port	517	$port
428	}	518	}
429		519
		520	=item peval $port, $coderef[, @args]
		521
		522	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		523	when the code throews an exception the C<$port> will be killed.
		524
		525	Any remaining args will be passed to the callback. Any return values will
		526	be returned to the caller.
		527
		528	This is useful when you temporarily want to execute code in the context of
		529	a port.
		530
		531	Example: create a port and run some initialisation code in it's context.
		532
		533	my $port = port { ... };
		534
		535	peval $port, sub {
		536	init
		537	or die "unable to init";
		538	};
		539
		540	=cut
		541
		542	sub peval($$) {
		543	local $SELF = shift;
		544	my $cb = shift;
		545
		546	if (wantarray) {
		547	my @res = eval { &$cb };
		548	_self_die if $@;
		549	@res
		550	} else {
		551	my $res = eval { &$cb };
		552	_self_die if $@;
		553	$res
		554	}
		555	}
		556
430	=item $closure = psub { BLOCK }	557	=item $closure = psub { BLOCK }
431		558
432	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	559	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
433	closure is executed, sets up the environment in the same way as in C<rcv>	560	closure is executed, sets up the environment in the same way as in C<rcv>
434	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.	561	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		562
		563	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		564	BLOCK }, @_ } >>.
435		565
436	This is useful when you register callbacks from C<rcv> callbacks:	566	This is useful when you register callbacks from C<rcv> callbacks:
437		567
438	rcv delayed_reply => sub {	568	rcv delayed_reply => sub {
439	my ($delay, @reply) = @_;	569	my ($delay, @reply) = @_;
…		…
463	$res	593	$res
464	}	594	}
465	}	595	}
466	}	596	}
467		597
		598	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
		599
		600	=item $guard = mon $port # kill $SELF when $port dies
		601
468	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies	602	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
469
470	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
471
472	=item $guard = mon $port # kill $SELF when $port dies
473		603
474	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies	604	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
475		605
476	Monitor the given port and do something when the port is killed or	606	Monitor the given port and do something when the port is killed or
477	messages to it were lost, and optionally return a guard that can be used	607	messages to it were lost, and optionally return a guard that can be used
478	to stop monitoring again.	608	to stop monitoring again.
		609
		610	The first two forms distinguish between "normal" and "abnormal" kil's:
		611
		612	In the first form (another port given), if the C<$port> is C<kil>'ed with
		613	a non-empty reason, the other port (C<$rcvport>) will be kil'ed with the
		614	same reason. That is, on "normal" kil's nothing happens, while under all
		615	other conditions, the other port is killed with the same reason.
		616
		617	The second form (kill self) is the same as the first form, except that
		618	C<$rvport> defaults to C<$SELF>.
		619
		620	The remaining forms don't distinguish between "normal" and "abnormal" kil's
		621	- it's up to the callback or receiver to check whether the C<@reason> is
		622	empty and act accordingly.
		623
		624	In the third form (callback), the callback is simply called with any
		625	number of C<@reason> elements (empty @reason means that the port was deleted
		626	"normally"). Note also that I<< the callback B<must> never die >>, so use
		627	C<eval> if unsure.
		628
		629	In the last form (message), a message of the form C<$rcvport, @msg,
		630	@reason> will be C<snd>.
		631
		632	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		633	alert was raised), they are removed and will not trigger again, even if it
		634	turns out that the port is still alive.
		635
		636	As a rule of thumb, monitoring requests should always monitor a remote
		637	port locally (using a local C<$rcvport> or a callback). The reason is that
		638	kill messages might get lost, just like any other message. Another less
		639	obvious reason is that even monitoring requests can get lost (for example,
		640	when the connection to the other node goes down permanently). When
		641	monitoring a port locally these problems do not exist.
479		642
480	C<mon> effectively guarantees that, in the absence of hardware failures,	643	C<mon> effectively guarantees that, in the absence of hardware failures,
481	after starting the monitor, either all messages sent to the port will	644	after starting the monitor, either all messages sent to the port will
482	arrive, or the monitoring action will be invoked after possible message	645	arrive, or the monitoring action will be invoked after possible message
483	loss has been detected. No messages will be lost "in between" (after	646	loss has been detected. No messages will be lost "in between" (after
484	the first lost message no further messages will be received by the	647	the first lost message no further messages will be received by the
485	port). After the monitoring action was invoked, further messages might get	648	port). After the monitoring action was invoked, further messages might get
486	delivered again.	649	delivered again.
487		650
488	Note that monitoring-actions are one-shot: once messages are lost (and a	651	Inter-host-connection timeouts and monitoring depend on the transport
489	monitoring alert was raised), they are removed and will not trigger again.	652	used. The only transport currently implemented is TCP, and AnyEvent::MP
		653	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		654	non-idle connection, and usually around two hours for idle connections).
490		655
491	In the first form (callback), the callback is simply called with any	656	This means that monitoring is good for program errors and cleaning up
492	number of C<@reason> elements (no @reason means that the port was deleted	657	stuff eventually, but they are no replacement for a timeout when you need
493	"normally"). Note also that I<< the callback B<must> never die >>, so use	658	to ensure some maximum latency.
494	C<eval> if unsure.
495
496	In the second form (another port given), the other port (C<$rcvport>)
497	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
498	"normal" kils nothing happens, while under all other conditions, the other
499	port is killed with the same reason.
500
501	The third form (kill self) is the same as the second form, except that
502	C<$rvport> defaults to C<$SELF>.
503
504	In the last form (message), a message of the form C<@msg, @reason> will be
505	C<snd>.
506
507	As a rule of thumb, monitoring requests should always monitor a port from
508	a local port (or callback). The reason is that kill messages might get
509	lost, just like any other message. Another less obvious reason is that
510	even monitoring requests can get lost (for exmaple, when the connection
511	to the other node goes down permanently). When monitoring a port locally
512	these problems do not exist.
513		659
514	Example: call a given callback when C<$port> is killed.	660	Example: call a given callback when C<$port> is killed.
515		661
516	mon $port, sub { warn "port died because of <@_>\n" };	662	mon $port, sub { warn "port died because of <@_>\n" };
517		663
…		…
524	mon $port, $self => "restart";	670	mon $port, $self => "restart";
525		671
526	=cut	672	=cut
527		673
528	sub mon {	674	sub mon {
529	my ($noderef, $port) = split /#/, shift, 2;	675	my ($nodeid, $port) = split /#/, shift, 2;
530		676
531	my $node = $NODE{$noderef} \|\| add_node $noderef;	677	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
532		678
533	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	679	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
534		680
535	unless (ref $cb) {	681	unless (ref $cb) {
536	if (@_) {	682	if (@_) {
…		…
545	}	691	}
546		692
547	$node->monitor ($port, $cb);	693	$node->monitor ($port, $cb);
548		694
549	defined wantarray	695	defined wantarray
550	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	696	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
551	}	697	}
552		698
553	=item $guard = mon_guard $port, $ref, $ref...	699	=item $guard = mon_guard $port, $ref, $ref...
554		700
555	Monitors the given C<$port> and keeps the passed references. When the port	701	Monitors the given C<$port> and keeps the passed references. When the port
…		…
578		724
579	=item kil $port[, @reason]	725	=item kil $port[, @reason]
580		726
581	Kill the specified port with the given C<@reason>.	727	Kill the specified port with the given C<@reason>.
582		728
583	If no C<@reason> is specified, then the port is killed "normally" (ports	729	If no C<@reason> is specified, then the port is killed "normally" -
584	monitoring other ports will not necessarily die because a port dies	730	monitor callback will be invoked, but the kil will not cause linked ports
585	"normally").	731	(C<mon $mport, $lport> form) to get killed.
586		732
587	Otherwise, linked ports get killed with the same reason (second form of	733	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
588	C<mon>, see above).	734	form) get killed with the same reason.
589		735
590	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	736	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
591	will be reported as reason C<< die => $@ >>.	737	will be reported as reason C<< die => $@ >>.
592		738
593	Transport/communication errors are reported as C<< transport_error =>	739	Transport/communication errors are reported as C<< transport_error =>
594	$message >>.	740	$message >>.
595		741
596	=cut	742	Common idioms:
		743
		744	# silently remove yourself, do not kill linked ports
		745	kil $SELF;
		746
		747	# report a failure in some detail
		748	kil $SELF, failure_mode_1 => "it failed with too high temperature";
		749
		750	# do not waste much time with killing, just die when something goes wrong
		751	open my $fh, "<file"
		752	or die "file: $!";
597		753
598	=item $port = spawn $node, $initfunc[, @initdata]	754	=item $port = spawn $node, $initfunc[, @initdata]
599		755
600	Creates a port on the node C<$node> (which can also be a port ID, in which	756	Creates a port on the node C<$node> (which can also be a port ID, in which
601	case it's the node where that port resides).	757	case it's the node where that port resides).
…		…
612	the package, then the package above the package and so on (e.g.	768	the package, then the package above the package and so on (e.g.
613	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	769	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
614	exists or it runs out of package names.	770	exists or it runs out of package names.
615		771
616	The init function is then called with the newly-created port as context	772	The init function is then called with the newly-created port as context
617	object (C<$SELF>) and the C<@initdata> values as arguments.	773	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		774	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		775	the port might not get created.
618		776
619	A common idiom is to pass a local port, immediately monitor the spawned	777	A common idiom is to pass a local port, immediately monitor the spawned
620	port, and in the remote init function, immediately monitor the passed	778	port, and in the remote init function, immediately monitor the passed
621	local port. This two-way monitoring ensures that both ports get cleaned up	779	local port. This two-way monitoring ensures that both ports get cleaned up
622	when there is a problem.	780	when there is a problem.
623		781
		782	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		783	caller before C<spawn> returns (by delaying invocation when spawn is
		784	called for the local node).
		785
624	Example: spawn a chat server port on C<$othernode>.	786	Example: spawn a chat server port on C<$othernode>.
625		787
626	# this node, executed from within a port context:	788	# this node, executed from within a port context:
627	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	789	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
628	mon $server;	790	mon $server;
…		…
642		804
643	sub _spawn {	805	sub _spawn {
644	my $port = shift;	806	my $port = shift;
645	my $init = shift;	807	my $init = shift;
646		808
		809	# rcv will create the actual port
647	local $SELF = "$NODE#$port";	810	local $SELF = "$NODE#$port";
648	eval {	811	eval {
649	&{ load_func $init }	812	&{ load_func $init }
650	};	813	};
651	_self_die if $@;	814	_self_die if $@;
652	}	815	}
653		816
654	sub spawn(@) {	817	sub spawn(@) {
655	my ($noderef, undef) = split /#/, shift, 2;	818	my ($nodeid, undef) = split /#/, shift, 2;
656		819
657	my $id = "$RUNIQ." . $ID++;	820	my $id = $RUNIQ . ++$ID;
658		821
659	$_[0] =~ /::/	822	$_[0] =~ /::/
660	or Carp::croak "spawn init function must be a fully-qualified name, caught";	823	or Carp::croak "spawn init function must be a fully-qualified name, caught";
661		824
662	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;	825	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
663		826
664	"$noderef#$id"	827	"$nodeid#$id"
665	}	828	}
		829
666		830
667	=item after $timeout, @msg	831	=item after $timeout, @msg
668		832
669	=item after $timeout, $callback	833	=item after $timeout, $callback
670		834
…		…
686	? $action[0]()	850	? $action[0]()
687	: snd @action;	851	: snd @action;
688	};	852	};
689	}	853	}
690		854
		855	#=item $cb2 = timeout $seconds, $cb[, @args]
		856
		857	=item cal $port, @msg, $callback[, $timeout]
		858
		859	A simple form of RPC - sends a message to the given C<$port> with the
		860	given contents (C<@msg>), but adds a reply port to the message.
		861
		862	The reply port is created temporarily just for the purpose of receiving
		863	the reply, and will be C<kil>ed when no longer needed.
		864
		865	A reply message sent to the port is passed to the C<$callback> as-is.
		866
		867	If an optional time-out (in seconds) is given and it is not C<undef>,
		868	then the callback will be called without any arguments after the time-out
		869	elapsed and the port is C<kil>ed.
		870
		871	If no time-out is given (or it is C<undef>), then the local port will
		872	monitor the remote port instead, so it eventually gets cleaned-up.
		873
		874	Currently this function returns the temporary port, but this "feature"
		875	might go in future versions unless you can make a convincing case that
		876	this is indeed useful for something.
		877
		878	=cut
		879
		880	sub cal(@) {
		881	my $timeout = ref $_[-1] ? undef : pop;
		882	my $cb = pop;
		883
		884	my $port = port {
		885	undef $timeout;
		886	kil $SELF;
		887	&$cb;
		888	};
		889
		890	if (defined $timeout) {
		891	$timeout = AE::timer $timeout, 0, sub {
		892	undef $timeout;
		893	kil $port;
		894	$cb->();
		895	};
		896	} else {
		897	mon $_[0], sub {
		898	kil $port;
		899	$cb->();
		900	};
		901	}
		902
		903	push @_, $port;
		904	&snd;
		905
		906	$port
		907	}
		908
		909	=back
		910
		911	=head1 DISTRIBUTED DATABASE
		912
		913	AnyEvent::MP comes with a simple distributed database. The database will
		914	be mirrored asynchronously on all global nodes. Other nodes bind to one
		915	of the global nodes for their needs. Every node has a "local database"
		916	which contains all the values that are set locally. All local databases
		917	are merged together to form the global database, which can be queried.
		918
		919	The database structure is that of a two-level hash - the database hash
		920	contains hashes which contain values, similarly to a perl hash of hashes,
		921	i.e.:
		922
		923	$DATABASE{$family}{$subkey} = $value
		924
		925	The top level hash key is called "family", and the second-level hash key
		926	is called "subkey" or simply "key".
		927
		928	The family must be alphanumeric, i.e. start with a letter and consist
		929	of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
		930	pretty much like Perl module names.
		931
		932	As the family namespace is global, it is recommended to prefix family names
		933	with the name of the application or module using it.
		934
		935	The subkeys must be non-empty strings, with no further restrictions.
		936
		937	The values should preferably be strings, but other perl scalars should
		938	work as well (such as C<undef>, arrays and hashes).
		939
		940	Every database entry is owned by one node - adding the same family/subkey
		941	combination on multiple nodes will not cause discomfort for AnyEvent::MP,
		942	but the result might be nondeterministic, i.e. the key might have
		943	different values on different nodes.
		944
		945	Different subkeys in the same family can be owned by different nodes
		946	without problems, and in fact, this is the common method to create worker
		947	pools. For example, a worker port for image scaling might do this:
		948
		949	db_set my_image_scalers => $port;
		950
		951	And clients looking for an image scaler will want to get the
		952	C<my_image_scalers> keys from time to time:
		953
		954	db_keys my_image_scalers => sub {
		955	@ports = @{ $_[0] };
		956	};
		957
		958	Or better yet, they want to monitor the database family, so they always
		959	have a reasonable up-to-date copy:
		960
		961	db_mon my_image_scalers => sub {
		962	@ports = keys %{ $_[0] };
		963	};
		964
		965	In general, you can set or delete single subkeys, but query and monitor
		966	whole families only.
		967
		968	If you feel the need to monitor or query a single subkey, try giving it
		969	it's own family.
		970
		971	=over
		972
		973	=item $guard = db_set $family => $subkey [=> $value]
		974
		975	Sets (or replaces) a key to the database - if C<$value> is omitted,
		976	C<undef> is used instead.
		977
		978	When called in non-void context, C<db_set> returns a guard that
		979	automatically calls C<db_del> when it is destroyed.
		980
		981	=item db_del $family => $subkey...
		982
		983	Deletes one or more subkeys from the database family.
		984
		985	=item $guard = db_reg $family => $port => $value
		986
		987	=item $guard = db_reg $family => $port
		988
		989	=item $guard = db_reg $family
		990
		991	Registers a port in the given family and optionally returns a guard to
		992	remove it.
		993
		994	This function basically does the same as:
		995
		996	db_set $family => $port => $value
		997
		998	Except that the port is monitored and automatically removed from the
		999	database family when it is kil'ed.
		1000
		1001	If C<$value> is missing, C<undef> is used. If C<$port> is missing, then
		1002	C<$SELF> is used.
		1003
		1004	This function is most useful to register a port in some port group (which
		1005	is just another name for a database family), and have it removed when the
		1006	port is gone. This works best when the port is a local port.
		1007
		1008	=cut
		1009
		1010	sub db_reg($$;$) {
		1011	my $family = shift;
		1012	my $port = @_ ? shift : $SELF;
		1013
		1014	my $clr = sub { db_del $family => $port };
		1015	mon $port, $clr;
		1016
		1017	db_set $family => $port => $_[0];
		1018
		1019	defined wantarray
		1020	and &Guard::guard ($clr)
		1021	}
		1022
		1023	=item db_family $family => $cb->(\%familyhash)
		1024
		1025	Queries the named database C<$family> and call the callback with the
		1026	family represented as a hash. You can keep and freely modify the hash.
		1027
		1028	=item db_keys $family => $cb->(\@keys)
		1029
		1030	Same as C<db_family>, except it only queries the family I<subkeys> and passes
		1031	them as array reference to the callback.
		1032
		1033	=item db_values $family => $cb->(\@values)
		1034
		1035	Same as C<db_family>, except it only queries the family I<values> and passes them
		1036	as array reference to the callback.
		1037
		1038	=item $guard = db_mon $family => $cb->($familyhash, \@added, \@changed, \@deleted)
		1039
		1040	Creates a monitor on the given database family. Each time a key is set
		1041	or or is deleted the callback is called with a hash containing the
		1042	database family and three lists of added, changed and deleted subkeys,
		1043	respectively. If no keys have changed then the array reference might be
		1044	C<undef> or even missing.
		1045
		1046	If not called in void context, a guard object is returned that, when
		1047	destroyed, stops the monitor.
		1048
		1049	The family hash reference and the key arrays belong to AnyEvent::MP and
		1050	B<must not be modified or stored> by the callback. When in doubt, make a
		1051	copy.
		1052
		1053	As soon as possible after the monitoring starts, the callback will be
		1054	called with the intiial contents of the family, even if it is empty,
		1055	i.e. there will always be a timely call to the callback with the current
		1056	contents.
		1057
		1058	It is possible that the callback is called with a change event even though
		1059	the subkey is already present and the value has not changed.
		1060
		1061	The monitoring stops when the guard object is destroyed.
		1062
		1063	Example: on every change to the family "mygroup", print out all keys.
		1064
		1065	my $guard = db_mon mygroup => sub {
		1066	my ($family, $a, $c, $d) = @_;
		1067	print "mygroup members: ", (join " ", keys %$family), "\n";
		1068	};
		1069
		1070	Exmaple: wait until the family "My::Module::workers" is non-empty.
		1071
		1072	my $guard; $guard = db_mon My::Module::workers => sub {
		1073	my ($family, $a, $c, $d) = @_;
		1074	return unless %$family;
		1075	undef $guard;
		1076	print "My::Module::workers now nonempty\n";
		1077	};
		1078
		1079	Example: print all changes to the family "AnyRvent::Fantasy::Module".
		1080
		1081	my $guard = db_mon AnyRvent::Fantasy::Module => sub {
		1082	my ($family, $a, $c, $d) = @_;
		1083
		1084	print "+$_=$family->{$_}\n" for @$a;
		1085	print "*$_=$family->{$_}\n" for @$c;
		1086	print "-$_=$family->{$_}\n" for @$d;
		1087	};
		1088
		1089	=cut
		1090
691	=back	1091	=back
692		1092
693	=head1 AnyEvent::MP vs. Distributed Erlang	1093	=head1 AnyEvent::MP vs. Distributed Erlang
694		1094
695	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	1095	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
696	== aemp node, Erlang process == aemp port), so many of the documents and	1096	== aemp node, Erlang process == aemp port), so many of the documents and
697	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	1097	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
698	sample:	1098	sample:
699		1099
700	http://www.Erlang.se/doc/programming_rules.shtml	1100	http://www.erlang.se/doc/programming_rules.shtml
701	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	1101	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
702	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	1102	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
703	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	1103	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
704		1104
705	Despite the similarities, there are also some important differences:	1105	Despite the similarities, there are also some important differences:
706		1106
707	=over 4	1107	=over 4
708		1108
709	=item * Node IDs are arbitrary strings in AEMP.	1109	=item * Node IDs are arbitrary strings in AEMP.
710		1110
711	Erlang relies on special naming and DNS to work everywhere in the same	1111	Erlang relies on special naming and DNS to work everywhere in the same
712	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by	1112	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
713	configuraiton or DNS), but will otherwise discover other odes itself.	1113	configuration or DNS), and possibly the addresses of some seed nodes, but
		1114	will otherwise discover other nodes (and their IDs) itself.
714		1115
715	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	1116	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
716	uses "local ports are like remote ports".	1117	uses "local ports are like remote ports".
717		1118
718	The failure modes for local ports are quite different (runtime errors	1119	The failure modes for local ports are quite different (runtime errors
…		…
727	ports being the special case/exception, where transport errors cannot	1128	ports being the special case/exception, where transport errors cannot
728	occur.	1129	occur.
729		1130
730	=item * Erlang uses processes and a mailbox, AEMP does not queue.	1131	=item * Erlang uses processes and a mailbox, AEMP does not queue.
731		1132
732	Erlang uses processes that selectively receive messages, and therefore	1133	Erlang uses processes that selectively receive messages out of order, and
733	needs a queue. AEMP is event based, queuing messages would serve no	1134	therefore needs a queue. AEMP is event based, queuing messages would serve
734	useful purpose. For the same reason the pattern-matching abilities of	1135	no useful purpose. For the same reason the pattern-matching abilities
735	AnyEvent::MP are more limited, as there is little need to be able to	1136	of AnyEvent::MP are more limited, as there is little need to be able to
736	filter messages without dequeing them.	1137	filter messages without dequeuing them.
737		1138
738	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	1139	This is not a philosophical difference, but simply stems from AnyEvent::MP
		1140	being event-based, while Erlang is process-based.
		1141
		1142	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		1143	top of AEMP and Coro threads.
739		1144
740	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	1145	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
741		1146
742	Sending messages in Erlang is synchronous and blocks the process (and	1147	Sending messages in Erlang is synchronous and blocks the process until
		1148	a conenction has been established and the message sent (and so does not
743	so does not need a queue that can overflow). AEMP sends are immediate,	1149	need a queue that can overflow). AEMP sends return immediately, connection
744	connection establishment is handled in the background.	1150	establishment is handled in the background.
745		1151
746	=item * Erlang suffers from silent message loss, AEMP does not.	1152	=item * Erlang suffers from silent message loss, AEMP does not.
747		1153
748	Erlang makes few guarantees on messages delivery - messages can get lost	1154	Erlang implements few guarantees on messages delivery - messages can get
749	without any of the processes realising it (i.e. you send messages a, b,	1155	lost without any of the processes realising it (i.e. you send messages a,
750	and c, and the other side only receives messages a and c).	1156	b, and c, and the other side only receives messages a and c).
751		1157
752	AEMP guarantees correct ordering, and the guarantee that after one message	1158	AEMP guarantees (modulo hardware errors) correct ordering, and the
753	is lost, all following ones sent to the same port are lost as well, until	1159	guarantee that after one message is lost, all following ones sent to the
754	monitoring raises an error, so there are no silent "holes" in the message	1160	same port are lost as well, until monitoring raises an error, so there are
755	sequence.	1161	no silent "holes" in the message sequence.
		1162
		1163	If you want your software to be very reliable, you have to cope with
		1164	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
		1165	simply tries to work better in common error cases, such as when a network
		1166	link goes down.
756		1167
757	=item * Erlang can send messages to the wrong port, AEMP does not.	1168	=item * Erlang can send messages to the wrong port, AEMP does not.
758		1169
759	In Erlang it is quite likely that a node that restarts reuses a process ID	1170	In Erlang it is quite likely that a node that restarts reuses an Erlang
760	known to other nodes for a completely different process, causing messages	1171	process ID known to other nodes for a completely different process,
761	destined for that process to end up in an unrelated process.	1172	causing messages destined for that process to end up in an unrelated
		1173	process.
762		1174
763	AEMP never reuses port IDs, so old messages or old port IDs floating	1175	AEMP does not reuse port IDs, so old messages or old port IDs floating
764	around in the network will not be sent to an unrelated port.	1176	around in the network will not be sent to an unrelated port.
765		1177
766	=item * Erlang uses unprotected connections, AEMP uses secure	1178	=item * Erlang uses unprotected connections, AEMP uses secure
767	authentication and can use TLS.	1179	authentication and can use TLS.
768		1180
…		…
771		1183
772	=item * The AEMP protocol is optimised for both text-based and binary	1184	=item * The AEMP protocol is optimised for both text-based and binary
773	communications.	1185	communications.
774		1186
775	The AEMP protocol, unlike the Erlang protocol, supports both programming	1187	The AEMP protocol, unlike the Erlang protocol, supports both programming
776	language independent text-only protocols (good for debugging) and binary,	1188	language independent text-only protocols (good for debugging), and binary,
777	language-specific serialisers (e.g. Storable). By default, unless TLS is	1189	language-specific serialisers (e.g. Storable). By default, unless TLS is
778	used, the protocol is actually completely text-based.	1190	used, the protocol is actually completely text-based.
779		1191
780	It has also been carefully designed to be implementable in other languages	1192	It has also been carefully designed to be implementable in other languages
781	with a minimum of work while gracefully degrading functionality to make the	1193	with a minimum of work while gracefully degrading functionality to make the
782	protocol simple.	1194	protocol simple.
783		1195
784	=item * AEMP has more flexible monitoring options than Erlang.	1196	=item * AEMP has more flexible monitoring options than Erlang.
785		1197
786	In Erlang, you can chose to receive I<all> exit signals as messages	1198	In Erlang, you can chose to receive I<all> exit signals as messages or
787	or I<none>, there is no in-between, so monitoring single processes is	1199	I<none>, there is no in-between, so monitoring single Erlang processes is
788	difficult to implement. Monitoring in AEMP is more flexible than in	1200	difficult to implement.
789	Erlang, as one can choose between automatic kill, exit message or callback	1201
790	on a per-process basis.	1202	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		1203	between automatic kill, exit message or callback on a per-port basis.
791		1204
792	=item * Erlang tries to hide remote/local connections, AEMP does not.	1205	=item * Erlang tries to hide remote/local connections, AEMP does not.
793		1206
794	Monitoring in Erlang is not an indicator of process death/crashes, in the	1207	Monitoring in Erlang is not an indicator of process death/crashes, in the
795	same way as linking is (except linking is unreliable in Erlang).	1208	same way as linking is (except linking is unreliable in Erlang).
…		…
817	overhead, as well as having to keep a proxy object everywhere.	1230	overhead, as well as having to keep a proxy object everywhere.
818		1231
819	Strings can easily be printed, easily serialised etc. and need no special	1232	Strings can easily be printed, easily serialised etc. and need no special
820	procedures to be "valid".	1233	procedures to be "valid".
821		1234
822	And as a result, a miniport consists of a single closure stored in a	1235	And as a result, a port with just a default receiver consists of a single
823	global hash - it can't become much cheaper.	1236	code reference stored in a global hash - it can't become much cheaper.
824		1237
825	=item Why favour JSON, why not a real serialising format such as Storable?	1238	=item Why favour JSON, why not a real serialising format such as Storable?
826		1239
827	In fact, any AnyEvent::MP node will happily accept Storable as framing	1240	In fact, any AnyEvent::MP node will happily accept Storable as framing
828	format, but currently there is no way to make a node use Storable by	1241	format, but currently there is no way to make a node use Storable by
…		…
838	Keeping your messages simple, concentrating on data structures rather than	1251	Keeping your messages simple, concentrating on data structures rather than
839	objects, will keep your messages clean, tidy and efficient.	1252	objects, will keep your messages clean, tidy and efficient.
840		1253
841	=back	1254	=back
842		1255
		1256	=head1 PORTING FROM AnyEvent::MP VERSION 1.X
		1257
		1258	AEMP version 2 has a few major incompatible changes compared to version 1:
		1259
		1260	=over 4
		1261
		1262	=item AnyEvent::MP::Global no longer has group management functions.
		1263
		1264	At least not officially - the grp_* functions are still exported and might
		1265	work, but they will be removed in some later release.
		1266
		1267	AnyEvent::MP now comes with a distributed database that is more
		1268	powerful. Its database families map closely to port groups, but the API
		1269	has changed (the functions are also now exported by AnyEvent::MP). Here is
		1270	a rough porting guide:
		1271
		1272	grp_reg $group, $port # old
		1273	db_reg $group, $port # new
		1274
		1275	$list = grp_get $group # old
		1276	db_keys $group, sub { my $list = shift } # new
		1277
		1278	grp_mon $group, $cb->(\@ports, $add, $del) # old
		1279	db_mon $group, $cb->(\%ports, $add, $change, $del) # new
		1280
		1281	C<grp_reg> is a no-brainer (just replace by C<db_reg>), but C<grp_get> is
		1282	no longer instant, because the local node might not have a copy of the
		1283	group. You can either modify your code to allow for a callback, or use
		1284	C<db_mon> to keep an updated copy of the group:
		1285
		1286	my $local_group_copy;
		1287	db_mon $group => sub { $local_group_copy = $_[0] };
		1288
		1289	# now "keys %$local_group_copy" always returns the most up-to-date
		1290	# list of ports in the group.
		1291
		1292	C<grp_mon> can be replaced by C<db_mon> with minor changes - C<db_mon>
		1293	passes a hash as first argument, and an extra C<$chg> argument that can be
		1294	ignored:
		1295
		1296	db_mon $group => sub {
		1297	my ($ports, $add, $chg, $lde) = @_;
		1298	$ports = [keys %$ports];
		1299
		1300	# now $ports, $add and $del are the same as
		1301	# were originally passed by grp_mon.
		1302	...
		1303	};
		1304
		1305	=item Nodes not longer connect to all other nodes.
		1306
		1307	In AEMP 1.x, every node automatically loads the L<AnyEvent::MP::Global>
		1308	module, which in turn would create connections to all other nodes in the
		1309	network (helped by the seed nodes).
		1310
		1311	In version 2.x, global nodes still connect to all other global nodes, but
		1312	other nodes don't - now every node either is a global node itself, or
		1313	attaches itself to another global node.
		1314
		1315	If a node isn't a global node itself, then it attaches itself to one
		1316	of its seed nodes. If that seed node isn't a global node yet, it will
		1317	automatically be upgraded to a global node.
		1318
		1319	So in many cases, nothing needs to be changed - one just has to make sure
		1320	that all seed nodes are meshed together with the other seed nodes (as with
		1321	AEMP 1.x), and other nodes specify them as seed nodes. This is most easily
		1322	achieved by specifying the same set of seed nodes for all nodes in the
		1323	network.
		1324
		1325	Not opening a connection to every other node is usually an advantage,
		1326	except when you need the lower latency of an already established
		1327	connection. To ensure a node establishes a connection to another node,
		1328	you can monitor the node port (C<mon $node, ...>), which will attempt to
		1329	create the connection (and notify you when the connection fails).
		1330
		1331	=item Listener-less nodes (nodes without binds) are gone.
		1332
		1333	And are not coming back, at least not in their old form. If no C<binds>
		1334	are specified for a node, AnyEvent::MP assumes a default of C<:>.
		1335
		1336	There are vague plans to implement some form of routing domains, which
		1337	might or might not bring back listener-less nodes, but don't count on it.
		1338
		1339	The fact that most connections are now optional somewhat mitigates this,
		1340	as a node can be effectively unreachable from the outside without any
		1341	problems, as long as it isn't a global node and only reaches out to other
		1342	nodes (as opposed to being contacted from other nodes).
		1343
		1344	=item $AnyEvent::MP::Kernel::WARN has gone.
		1345
		1346	AnyEvent has acquired a logging framework (L<AnyEvent::Log>), and AEMP now
		1347	uses this, and so should your programs.
		1348
		1349	Every module now documents what kinds of messages it generates, with
		1350	AnyEvent::MP acting as a catch all.
		1351
		1352	On the positive side, this means that instead of setting
		1353	C<PERL_ANYEVENT_MP_WARNLEVEL>, you can get away by setting C<AE_VERBOSE> -
		1354	much less to type.
		1355
		1356	=back
		1357
		1358	=head1 LOGGING
		1359
		1360	AnyEvent::MP does not normally log anything by itself, but sinc eit is the
		1361	root of the contetx hierarchy for AnyEvent::MP modules, it will receive
		1362	all log messages by submodules.
		1363
843	=head1 SEE ALSO	1364	=head1 SEE ALSO
844		1365
845	L<AnyEvent::MP::Intro> - a gentle introduction.	1366	L<AnyEvent::MP::Intro> - a gentle introduction.
846		1367
847	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.	1368	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
848		1369
849	L<AnyEvent::MP::Global> - network maintainance and port groups, to find	1370	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
850	your applications.	1371	your applications.
		1372
		1373	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		1374
		1375	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		1376	all nodes.
851		1377
852	L<AnyEvent>.	1378	L<AnyEvent>.
853		1379
854	=head1 AUTHOR	1380	=head1 AUTHOR
855		1381

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Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.73 by root, Mon Aug 31 11:08:25 2009 UTC vs. Revision 1.141 by root, Fri Mar 23 03:24:41 2012 UTC

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Revision 1.73 by root, Mon Aug 31 11:08:25 2009 UTC vs.
Revision 1.141 by root, Fri Mar 23 03:24:41 2012 UTC