[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 1.152 by root, Sun Jul 29 02:23:34 2018 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 $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		51
49	stay tuned.	52	# distributed database - modification
		53	db_set $family => $subkey [=> $value] # add a subkey
		54	db_del $family => $subkey... # delete one or more subkeys
		55	db_reg $family => $port [=> $value] # register a port
		56
		57	# distributed database - queries
		58	db_family $family => $cb->(\%familyhash)
		59	db_keys $family => $cb->(\@keys)
		60	db_values $family => $cb->(\@values)
		61
		62	# distributed database - monitoring a family
		63	db_mon $family => $cb->(\%familyhash, \@added, \@changed, \@deleted)
50		64
51	=head1 DESCRIPTION	65	=head1 DESCRIPTION
52		66
53	This module (-family) implements a simple message passing framework.	67	This module (-family) implements a simple message passing framework.
54		68
56	on the same or other hosts, and you can supervise entities remotely.	70	on the same or other hosts, and you can supervise entities remotely.
57		71
58	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	72	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
59	manual page and the examples under F<eg/>.	73	manual page and the examples under F<eg/>.
60		74
61	At the moment, this module family is a bit underdocumented.
62
63	=head1 CONCEPTS	75	=head1 CONCEPTS
64		76
65	=over 4	77	=over 4
66		78
67	=item port	79	=item port
68		80
69	A port is something you can send messages to (with the C<snd> function).	81	Not to be confused with a TCP port, a "port" is something you can send
		82	messages to (with the C<snd> function).
70		83
71	Ports allow you to register C<rcv> handlers that can match all or just	84	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	85	some messages. Messages send to ports will not be queued, regardless of
73	anything was listening for them or not.	86	anything was listening for them or not.
74		87
		88	Ports are represented by (printable) strings called "port IDs".
		89
75	=item port ID - C<nodeid#portname>	90	=item port ID - C<nodeid#portname>
76		91
77	A port ID is the concatenation of a node ID, a hash-mark (C<#>) as	92	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).	93	as separator, and a port name (a printable string of unspecified
		94	format created by AnyEvent::MP).
79		95
80	=item node	96	=item node
81		97
82	A node is a single process containing at least one port - the node port,	98	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	99	which enables nodes to manage each other remotely, and to create new
84	ports.	100	ports.
85		101
86	Nodes are either public (have one or more listening ports) or private	102	Nodes are either public (have one or more listening ports) or private
87	(no listening ports). Private nodes cannot talk to other private nodes	103	(no listening ports). Private nodes cannot talk to other private nodes
88	currently.	104	currently, but all nodes can talk to public nodes.
89		105
		106	Nodes is represented by (printable) strings called "node IDs".
		107
90	=item node ID - C<[a-za-Z0-9_\-.:]+>	108	=item node ID - C<[A-Za-z0-9_\-.:]*>
91		109
92	A node ID is a string that uniquely identifies the node within a	110	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	111	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	112	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
95	doesn't interpret node IDs in any way.	113	doesn't interpret node IDs in any way except to uniquely identify a node.
96		114
97	=item binds - C<ip:port>	115	=item binds - C<ip:port>
98		116
99	Nodes can only talk to each other by creating some kind of connection to	117	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	118	each other. To do this, nodes should listen on one or more local transport
		119	endpoints - binds.
		120
101	endpoints - binds. Currently, only standard C<ip:port> specifications can	121	Currently, only standard C<ip:port> specifications can be used, which
102	be used, which specify TCP ports to listen on.	122	specify TCP ports to listen on. So a bind is basically just a tcp socket
		123	in listening mode that accepts connections from other nodes.
103		124
		125	=item seed nodes
		126
		127	When a node starts, it knows nothing about the network it is in - it
		128	needs to connect to at least one other node that is already in the
		129	network. These other nodes are called "seed nodes".
		130
		131	Seed nodes themselves are not special - they are seed nodes only because
		132	some other node I<uses> them as such, but any node can be used as seed
		133	node for other nodes, and eahc node can use a different set of seed nodes.
		134
		135	In addition to discovering the network, seed nodes are also used to
		136	maintain the network - all nodes using the same seed node are part of the
		137	same network. If a network is split into multiple subnets because e.g. the
		138	network link between the parts goes down, then using the same seed nodes
		139	for all nodes ensures that eventually the subnets get merged again.
		140
		141	Seed nodes are expected to be long-running, and at least one seed node
		142	should always be available. They should also be relatively responsive - a
		143	seed node that blocks for long periods will slow down everybody else.
		144
		145	For small networks, it's best if every node uses the same set of seed
		146	nodes. For large networks, it can be useful to specify "regional" seed
		147	nodes for most nodes in an area, and use all seed nodes as seed nodes for
		148	each other. What's important is that all seed nodes connections form a
		149	complete graph, so that the network cannot split into separate subnets
		150	forever.
		151
		152	Seed nodes are represented by seed IDs.
		153
104	=item seeds - C<host:port>	154	=item seed IDs - C<host:port>
105		155
106	When a node starts, it knows nothing about the network. To teach the node	156	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	157	TCP port) of nodes that should be used as seed nodes.
108	network. This node is called a seed.
109		158
110	Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes	159	=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		160
116	Apart from being sued for seeding, seednodes are not special in any way -	161	An AEMP network needs a discovery service - nodes need to know how to
117	every public node can be a seednode.	162	connect to other nodes they only know by name. In addition, AEMP offers a
		163	distributed "group database", which maps group names to a list of strings
		164	- for example, to register worker ports.
		165
		166	A network needs at least one global node to work, and allows every node to
		167	be a global node.
		168
		169	Any node that loads the L<AnyEvent::MP::Global> module becomes a global
		170	node and tries to keep connections to all other nodes. So while it can
		171	make sense to make every node "global" in small networks, it usually makes
		172	sense to only make seed nodes into global nodes in large networks (nodes
		173	keep connections to seed nodes and global nodes, so making them the same
		174	reduces overhead).
118		175
119	=back	176	=back
120		177
121	=head1 VARIABLES/FUNCTIONS	178	=head1 VARIABLES/FUNCTIONS
122		179
…		…
124		181
125	=cut	182	=cut
126		183
127	package AnyEvent::MP;	184	package AnyEvent::MP;
128		185
		186	use AnyEvent::MP::Config ();
129	use AnyEvent::MP::Kernel;	187	use AnyEvent::MP::Kernel;
		188	use AnyEvent::MP::Kernel qw(
		189	%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID
		190	add_node load_func
		191
		192	NODE $NODE
		193	configure
		194	node_of port_is_local
		195	snd kil
		196	db_set db_del
		197	db_mon db_family db_keys db_values
		198	);
130		199
131	use common::sense;	200	use common::sense;
132		201
133	use Carp ();	202	use Carp ();
134		203
135	use AE ();	204	use AnyEvent ();
		205	use Guard ();
136		206
137	use base "Exporter";	207	use base "Exporter";
138		208
139	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	209	our $VERSION = '2.02'; # also in MP/Config.pm
140		210
141	our @EXPORT = qw(	211	our @EXPORT = qw(
142	NODE $NODE *SELF node_of after	212	NODE $NODE
143	initialise_node	213	configure
144	snd rcv mon mon_guard kil reg psub spawn	214	node_of port_is_local
145	port	215	snd kil
		216	db_set db_del
		217	db_mon db_family db_keys db_values
		218
		219	*SELF
		220
		221	port rcv mon mon_guard psub peval spawn cal
		222	db_set db_del db_reg
		223	db_mon db_family db_keys db_values
		224
		225	after
146	);	226	);
147		227
148	our $SELF;	228	our $SELF;
149		229
150	sub _self_die() {	230	sub _self_die() {
…		…
155		235
156	=item $thisnode = NODE / $NODE	236	=item $thisnode = NODE / $NODE
157		237
158	The C<NODE> function returns, and the C<$NODE> variable contains, the node	238	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	239	ID of the node running in the current process. This value is initialised by
160	a call to C<initialise_node>.	240	a call to C<configure>.
161		241
162	=item $nodeid = node_of $port	242	=item $nodeid = node_of $port
163		243
164	Extracts and returns the node ID from a port ID or a node ID.	244	Extracts and returns the node ID from a port ID or a node ID.
165		245
166	=item initialise_node $profile_name, key => value...	246	=item $is_local = port_is_local $port
		247
		248	Returns true iff the port is a local port.
		249
		250	=item configure $profile, key => value...
		251
		252	=item configure key => value...
167		253
168	Before a node can talk to other nodes on the network (i.e. enter	254	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	255	"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	256	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.	257	some other nodes in the network to discover other nodes.
172		258
173	This function initialises a node - it must be called exactly once (or	259	This function configures a node - it must be called exactly once (or
174	never) before calling other AnyEvent::MP functions.	260	never) before calling other AnyEvent::MP functions.
175		261
176	The first argument is a profile name. If it is C<undef> or missing, then	262	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>).	263	F<aemp> command line utility (sans the set/del prefix), with these additions:
178		264
		265	=over 4
		266
		267	=item norc => $boolean (default false)
		268
		269	If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I<not>
		270	be consulted - all configuration options must be specified in the
		271	C<configure> call.
		272
		273	=item force => $boolean (default false)
		274
		275	IF true, then the values specified in the C<configure> will take
		276	precedence over any values configured via the rc file. The default is for
		277	the rc file to override any options specified in the program.
		278
		279	=back
		280
		281	=over 4
		282
		283	=item step 1, gathering configuration from profiles
		284
179	The function first looks up the profile in the aemp configuration (see the	285	The function first looks up a profile in the aemp configuration (see the
180	L<aemp> commandline utility). the profile is calculated as follows:	286	L<aemp> commandline utility). The profile name can be specified via the
		287	named C<profile> parameter or can simply be the first parameter). If it is
		288	missing, then the nodename (F<uname -n>) will be used as profile name.
181		289
		290	The profile data is then gathered as follows:
		291
182	First, all remaining key => value pairs (all of which are conviniently	292	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	293	undocumented at the moment) will be interpreted as configuration
184	any values specified in the global default configuration (see the F<aemp>	294	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	295	default configuration (see the F<aemp> utility), then the chain of
		296	profiles chosen by the profile name (and any C<parent> attributes).
		297
186	the values specified in the profile have highest priority and the values	298	That means that the values specified in the profile have highest priority
187	specified via C<initialise_node> have lowest priority.	299	and the values specified directly via C<configure> have lowest priority,
		300	and can only be used to specify defaults.
188		301
189	If the profile specifies a node ID, then this will become the node ID of	302	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	303	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.	304	a unique randoms tring (C</%u>) appended.
		305
		306	The node ID can contain some C<%> sequences that are expanded: C<%n>
		307	is expanded to the local nodename, C<%u> is replaced by a random
		308	strign to make the node unique. For example, the F<aemp> commandline
		309	utility uses C<aemp/%n/%u> as nodename, which might expand to
		310	C<aemp/cerebro/ZQDGSIkRhEZQDGSIkRhE>.
		311
		312	=item step 2, bind listener sockets
192		313
193	The next step is to look up the binds in the profile, followed by binding	314	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	315	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	316	to have no binds, meaning that the node cannot be contacted from the
196	outside. This means the node cannot talk to other nodes that also have no	317	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).	318	binds, but it can still talk to all "normal" nodes).
198		319
199	If the profile does not specify a binds list, then a default of C<*> is	320	If the profile does not specify a binds list, then a default of C<*> is
200	used.	321	used, meaning the node will bind on a dynamically-assigned port on every
		322	local IP address it finds.
201		323
		324	=item step 3, connect to seed nodes
		325
202	Lastly, the seeds list from the profile is passed to the	326	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	327	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.	328	connectivity with at least one node at any point in time.
205		329
206	Example: become a distributed node listening on the guessed noderef, or	330	=back
207	the one specified via C<aemp> for the current node. This should be the	331
		332	Example: become a distributed node using the local node name as profile.
208	most common form of invocation for "daemon"-type nodes.	333	This should be the most common form of invocation for "daemon"-type nodes.
209		334
210	initialise_node;	335	configure
211		336
212	Example: become an anonymous node. This form is often used for commandline	337	Example: become a semi-anonymous node. This form is often used for
213	clients.	338	commandline clients.
214		339
215	initialise_node "anon/";	340	configure nodeid => "myscript/%n/%u";
216		341
217	Example: become a distributed node. If there is no profile of the given	342	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	343	for a seed node as it binds on all local addresses on a fixed port (4040,
219	on the resulting addresses.	344	customary for aemp).
220		345
221	initialise_node "localhost:4044";	346	# use the aemp commandline utility
		347	# aemp profile seed binds '*:4040'
		348
		349	# then use it
		350	configure profile => "seed";
		351
		352	# or simply use aemp from the shell again:
		353	# aemp run profile seed
		354
		355	# or provide a nicer-to-remember nodeid
		356	# aemp run profile seed nodeid "$(hostname)"
222		357
223	=item $SELF	358	=item $SELF
224		359
225	Contains the current port id while executing C<rcv> callbacks or C<psub>	360	Contains the current port id while executing C<rcv> callbacks or C<psub>
226	blocks.	361	blocks.
…		…
282		417
283	=cut	418	=cut
284		419
285	sub rcv($@);	420	sub rcv($@);
286		421
287	sub _kilme {	422	my $KILME = sub {
288	die "received message on port without callback";	423	(my $tag = substr $_[0], 0, 30) =~ s/([^\x20-\x7e])/./g;
289	}	424	kil $SELF, unhandled_message => "no callback found for message '$tag'";
		425	};
290		426
291	sub port(;&) {	427	sub port(;&) {
292	my $id = "$UNIQ." . $ID++;	428	my $id = $UNIQ . ++$ID;
293	my $port = "$NODE#$id";	429	my $port = "$NODE#$id";
294		430
295	rcv $port, shift \|\| \&_kilme;	431	rcv $port, shift \|\| $KILME;
296		432
297	$port	433	$port
298	}	434	}
299		435
300	=item rcv $local_port, $callback->(@msg)	436	=item rcv $local_port, $callback->(@msg)
…		…
305		441
306	The global C<$SELF> (exported by this module) contains C<$port> while	442	The global C<$SELF> (exported by this module) contains C<$port> while
307	executing the callback. Runtime errors during callback execution will	443	executing the callback. Runtime errors during callback execution will
308	result in the port being C<kil>ed.	444	result in the port being C<kil>ed.
309		445
310	The default callback received all messages not matched by a more specific	446	The default callback receives all messages not matched by a more specific
311	C<tag> match.	447	C<tag> match.
312		448
313	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...	449	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
314		450
315	Register (or replace) callbacks to be called on messages starting with the	451	Register (or replace) callbacks to be called on messages starting with the
…		…
336	msg1 => sub { ... },	472	msg1 => sub { ... },
337	...	473	...
338	;	474	;
339		475
340	Example: temporarily register a rcv callback for a tag matching some port	476	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.	477	(e.g. for an rpc reply) and unregister it after a message was received.
342		478
343	rcv $port, $otherport => sub {	479	rcv $port, $otherport => sub {
344	my @reply = @_;	480	my @reply = @_;
345		481
346	rcv $SELF, $otherport;	482	rcv $SELF, $otherport;
…		…
348		484
349	=cut	485	=cut
350		486
351	sub rcv($@) {	487	sub rcv($@) {
352	my $port = shift;	488	my $port = shift;
353	my ($noderef, $portid) = split /#/, $port, 2;	489	my ($nodeid, $portid) = split /#/, $port, 2;
354		490
355	$NODE{$noderef} == $NODE{""}	491	$nodeid eq $NODE
356	or Carp::croak "$port: rcv can only be called on local ports, caught";	492	or Carp::croak "$port: rcv can only be called on local ports, caught";
357		493
358	while (@_) {	494	while (@_) {
359	if (ref $_[0]) {	495	if (ref $_[0]) {
360	if (my $self = $PORT_DATA{$portid}) {	496	if (my $self = $PORT_DATA{$portid}) {
361	"AnyEvent::MP::Port" eq ref $self	497	"AnyEvent::MP::Port" eq ref $self
362	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	498	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
363		499
364	$self->[2] = shift;	500	$self->[0] = shift;
365	} else {	501	} else {
366	my $cb = shift;	502	my $cb = shift;
367	$PORT{$portid} = sub {	503	$PORT{$portid} = sub {
368	local $SELF = $port;	504	local $SELF = $port;
369	eval { &$cb }; _self_die if $@;	505	eval { &$cb }; _self_die if $@;
370	};	506	};
371	}	507	}
372	} elsif (defined $_[0]) {	508	} elsif (defined $_[0]) {
373	my $self = $PORT_DATA{$portid} \|\|= do {	509	my $self = $PORT_DATA{$portid} \|\|= do {
374	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	510	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
375		511
376	$PORT{$portid} = sub {	512	$PORT{$portid} = sub {
377	local $SELF = $port;	513	local $SELF = $port;
378		514
379	if (my $cb = $self->[1]{$_[0]}) {	515	if (my $cb = $self->[1]{$_[0]}) {
…		…
401	}	537	}
402		538
403	$port	539	$port
404	}	540	}
405		541
		542	=item peval $port, $coderef[, @args]
		543
		544	Evaluates the given C<$codref> within the context of C<$port>, that is,
		545	when the code throws an exception the C<$port> will be killed.
		546
		547	Any remaining args will be passed to the callback. Any return values will
		548	be returned to the caller.
		549
		550	This is useful when you temporarily want to execute code in the context of
		551	a port.
		552
		553	Example: create a port and run some initialisation code in it's context.
		554
		555	my $port = port { ... };
		556
		557	peval $port, sub {
		558	init
		559	or die "unable to init";
		560	};
		561
		562	=cut
		563
		564	sub peval($$) {
		565	local $SELF = shift;
		566	my $cb = shift;
		567
		568	if (wantarray) {
		569	my @res = eval { &$cb };
		570	_self_die if $@;
		571	@res
		572	} else {
		573	my $res = eval { &$cb };
		574	_self_die if $@;
		575	$res
		576	}
		577	}
		578
406	=item $closure = psub { BLOCK }	579	=item $closure = psub { BLOCK }
407		580
408	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	581	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>	582	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.	583	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		584
		585	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		586	BLOCK }, @_ } >>.
411		587
412	This is useful when you register callbacks from C<rcv> callbacks:	588	This is useful when you register callbacks from C<rcv> callbacks:
413		589
414	rcv delayed_reply => sub {	590	rcv delayed_reply => sub {
415	my ($delay, @reply) = @_;	591	my ($delay, @reply) = @_;
…		…
439	$res	615	$res
440	}	616	}
441	}	617	}
442	}	618	}
443		619
		620	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
		621
		622	=item $guard = mon $port # kill $SELF when $port dies
		623
444	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies	624	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
445
446	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
447
448	=item $guard = mon $port # kill $SELF when $port dies
449		625
450	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies	626	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
451		627
452	Monitor the given port and do something when the port is killed or	628	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	629	messages to it were lost, and optionally return a guard that can be used
454	to stop monitoring again.	630	to stop monitoring again.
		631
		632	The first two forms distinguish between "normal" and "abnormal" kil's:
		633
		634	In the first form (another port given), if the C<$port> is C<kil>'ed with
		635	a non-empty reason, the other port (C<$rcvport>) will be kil'ed with the
		636	same reason. That is, on "normal" kil's nothing happens, while under all
		637	other conditions, the other port is killed with the same reason.
		638
		639	The second form (kill self) is the same as the first form, except that
		640	C<$rvport> defaults to C<$SELF>.
		641
		642	The remaining forms don't distinguish between "normal" and "abnormal" kil's
		643	- it's up to the callback or receiver to check whether the C<@reason> is
		644	empty and act accordingly.
		645
		646	In the third form (callback), the callback is simply called with any
		647	number of C<@reason> elements (empty @reason means that the port was deleted
		648	"normally"). Note also that I<< the callback B<must> never die >>, so use
		649	C<eval> if unsure.
		650
		651	In the last form (message), a message of the form C<$rcvport, @msg,
		652	@reason> will be C<snd>.
		653
		654	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		655	alert was raised), they are removed and will not trigger again, even if it
		656	turns out that the port is still alive.
		657
		658	As a rule of thumb, monitoring requests should always monitor a remote
		659	port locally (using a local C<$rcvport> or a callback). The reason is that
		660	kill messages might get lost, just like any other message. Another less
		661	obvious reason is that even monitoring requests can get lost (for example,
		662	when the connection to the other node goes down permanently). When
		663	monitoring a port locally these problems do not exist.
455		664
456	C<mon> effectively guarantees that, in the absence of hardware failures,	665	C<mon> effectively guarantees that, in the absence of hardware failures,
457	after starting the monitor, either all messages sent to the port will	666	after starting the monitor, either all messages sent to the port will
458	arrive, or the monitoring action will be invoked after possible message	667	arrive, or the monitoring action will be invoked after possible message
459	loss has been detected. No messages will be lost "in between" (after	668	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	669	the first lost message no further messages will be received by the
461	port). After the monitoring action was invoked, further messages might get	670	port). After the monitoring action was invoked, further messages might get
462	delivered again.	671	delivered again.
463		672
464	Note that monitoring-actions are one-shot: once messages are lost (and a	673	Inter-host-connection timeouts and monitoring depend on the transport
465	monitoring alert was raised), they are removed and will not trigger again.	674	used. The only transport currently implemented is TCP, and AnyEvent::MP
		675	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		676	non-idle connection, and usually around two hours for idle connections).
466		677
467	In the first form (callback), the callback is simply called with any	678	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	679	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	680	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		681
490	Example: call a given callback when C<$port> is killed.	682	Example: call a given callback when C<$port> is killed.
491		683
492	mon $port, sub { warn "port died because of <@_>\n" };	684	mon $port, sub { warn "port died because of <@_>\n" };
493		685
…		…
500	mon $port, $self => "restart";	692	mon $port, $self => "restart";
501		693
502	=cut	694	=cut
503		695
504	sub mon {	696	sub mon {
505	my ($noderef, $port) = split /#/, shift, 2;	697	my ($nodeid, $port) = split /#/, shift, 2;
506		698
507	my $node = $NODE{$noderef} \|\| add_node $noderef;	699	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
508		700
509	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	701	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
510		702
511	unless (ref $cb) {	703	unless (ref $cb) {
512	if (@_) {	704	if (@_) {
…		…
521	}	713	}
522		714
523	$node->monitor ($port, $cb);	715	$node->monitor ($port, $cb);
524		716
525	defined wantarray	717	defined wantarray
526	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	718	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
527	}	719	}
528		720
529	=item $guard = mon_guard $port, $ref, $ref...	721	=item $guard = mon_guard $port, $ref, $ref...
530		722
531	Monitors the given C<$port> and keeps the passed references. When the port	723	Monitors the given C<$port> and keeps the passed references. When the port
…		…
554		746
555	=item kil $port[, @reason]	747	=item kil $port[, @reason]
556		748
557	Kill the specified port with the given C<@reason>.	749	Kill the specified port with the given C<@reason>.
558		750
559	If no C<@reason> is specified, then the port is killed "normally" (ports	751	If no C<@reason> is specified, then the port is killed "normally" -
560	monitoring other ports will not necessarily die because a port dies	752	monitor callback will be invoked, but the kil will not cause linked ports
561	"normally").	753	(C<mon $mport, $lport> form) to get killed.
562		754
563	Otherwise, linked ports get killed with the same reason (second form of	755	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
564	C<mon>, see above).	756	form) get killed with the same reason.
565		757
566	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	758	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
567	will be reported as reason C<< die => $@ >>.	759	will be reported as reason C<< die => $@ >>.
568		760
569	Transport/communication errors are reported as C<< transport_error =>	761	Transport/communication errors are reported as C<< transport_error =>
570	$message >>.	762	$message >>.
571		763
572	=cut	764	Common idioms:
		765
		766	# silently remove yourself, do not kill linked ports
		767	kil $SELF;
		768
		769	# report a failure in some detail
		770	kil $SELF, failure_mode_1 => "it failed with too high temperature";
		771
		772	# do not waste much time with killing, just die when something goes wrong
		773	open my $fh, "<file"
		774	or die "file: $!";
573		775
574	=item $port = spawn $node, $initfunc[, @initdata]	776	=item $port = spawn $node, $initfunc[, @initdata]
575		777
576	Creates a port on the node C<$node> (which can also be a port ID, in which	778	Creates a port on the node C<$node> (which can also be a port ID, in which
577	case it's the node where that port resides).	779	case it's the node where that port resides).
…		…
588	the package, then the package above the package and so on (e.g.	790	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	791	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
590	exists or it runs out of package names.	792	exists or it runs out of package names.
591		793
592	The init function is then called with the newly-created port as context	794	The init function is then called with the newly-created port as context
593	object (C<$SELF>) and the C<@initdata> values as arguments.	795	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		796	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		797	the port might not get created.
594		798
595	A common idiom is to pass a local port, immediately monitor the spawned	799	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	800	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	801	local port. This two-way monitoring ensures that both ports get cleaned up
598	when there is a problem.	802	when there is a problem.
599		803
		804	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		805	caller before C<spawn> returns (by delaying invocation when spawn is
		806	called for the local node).
		807
600	Example: spawn a chat server port on C<$othernode>.	808	Example: spawn a chat server port on C<$othernode>.
601		809
602	# this node, executed from within a port context:	810	# this node, executed from within a port context:
603	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	811	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
604	mon $server;	812	mon $server;
…		…
618		826
619	sub _spawn {	827	sub _spawn {
620	my $port = shift;	828	my $port = shift;
621	my $init = shift;	829	my $init = shift;
622		830
		831	# rcv will create the actual port
623	local $SELF = "$NODE#$port";	832	local $SELF = "$NODE#$port";
624	eval {	833	eval {
625	&{ load_func $init }	834	&{ load_func $init }
626	};	835	};
627	_self_die if $@;	836	_self_die if $@;
628	}	837	}
629		838
630	sub spawn(@) {	839	sub spawn(@) {
631	my ($noderef, undef) = split /#/, shift, 2;	840	my ($nodeid, undef) = split /#/, shift, 2;
632		841
633	my $id = "$RUNIQ." . $ID++;	842	my $id = $RUNIQ . ++$ID;
634		843
635	$_[0] =~ /::/	844	$_[0] =~ /::/
636	or Carp::croak "spawn init function must be a fully-qualified name, caught";	845	or Carp::croak "spawn init function must be a fully-qualified name, caught";
637		846
638	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;	847	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
639		848
640	"$noderef#$id"	849	"$nodeid#$id"
641	}	850	}
		851
642		852
643	=item after $timeout, @msg	853	=item after $timeout, @msg
644		854
645	=item after $timeout, $callback	855	=item after $timeout, $callback
646		856
…		…
662	? $action[0]()	872	? $action[0]()
663	: snd @action;	873	: snd @action;
664	};	874	};
665	}	875	}
666		876
		877	#=item $cb2 = timeout $seconds, $cb[, @args]
		878
		879	=item cal $port, @msg, $callback[, $timeout]
		880
		881	A simple form of RPC - sends a message to the given C<$port> with the
		882	given contents (C<@msg>), but adds a reply port to the message.
		883
		884	The reply port is created temporarily just for the purpose of receiving
		885	the reply, and will be C<kil>ed when no longer needed.
		886
		887	A reply message sent to the port is passed to the C<$callback> as-is.
		888
		889	If an optional time-out (in seconds) is given and it is not C<undef>,
		890	then the callback will be called without any arguments after the time-out
		891	elapsed and the port is C<kil>ed.
		892
		893	If no time-out is given (or it is C<undef>), then the local port will
		894	monitor the remote port instead, so it eventually gets cleaned-up.
		895
		896	Currently this function returns the temporary port, but this "feature"
		897	might go in future versions unless you can make a convincing case that
		898	this is indeed useful for something.
		899
		900	=cut
		901
		902	sub cal(@) {
		903	my $timeout = ref $_[-1] ? undef : pop;
		904	my $cb = pop;
		905
		906	my $port = port {
		907	undef $timeout;
		908	kil $SELF;
		909	&$cb;
		910	};
		911
		912	if (defined $timeout) {
		913	$timeout = AE::timer $timeout, 0, sub {
		914	undef $timeout;
		915	kil $port;
		916	$cb->();
		917	};
		918	} else {
		919	mon $_[0], sub {
		920	kil $port;
		921	$cb->();
		922	};
		923	}
		924
		925	push @_, $port;
		926	&snd;
		927
		928	$port
		929	}
		930
		931	=back
		932
		933	=head1 DISTRIBUTED DATABASE
		934
		935	AnyEvent::MP comes with a simple distributed database. The database will
		936	be mirrored asynchronously on all global nodes. Other nodes bind to one
		937	of the global nodes for their needs. Every node has a "local database"
		938	which contains all the values that are set locally. All local databases
		939	are merged together to form the global database, which can be queried.
		940
		941	The database structure is that of a two-level hash - the database hash
		942	contains hashes which contain values, similarly to a perl hash of hashes,
		943	i.e.:
		944
		945	$DATABASE{$family}{$subkey} = $value
		946
		947	The top level hash key is called "family", and the second-level hash key
		948	is called "subkey" or simply "key".
		949
		950	The family must be alphanumeric, i.e. start with a letter and consist
		951	of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
		952	pretty much like Perl module names.
		953
		954	As the family namespace is global, it is recommended to prefix family names
		955	with the name of the application or module using it.
		956
		957	The subkeys must be non-empty strings, with no further restrictions.
		958
		959	The values should preferably be strings, but other perl scalars should
		960	work as well (such as C<undef>, arrays and hashes).
		961
		962	Every database entry is owned by one node - adding the same family/subkey
		963	combination on multiple nodes will not cause discomfort for AnyEvent::MP,
		964	but the result might be nondeterministic, i.e. the key might have
		965	different values on different nodes.
		966
		967	Different subkeys in the same family can be owned by different nodes
		968	without problems, and in fact, this is the common method to create worker
		969	pools. For example, a worker port for image scaling might do this:
		970
		971	db_set my_image_scalers => $port;
		972
		973	And clients looking for an image scaler will want to get the
		974	C<my_image_scalers> keys from time to time:
		975
		976	db_keys my_image_scalers => sub {
		977	@ports = @{ $_[0] };
		978	};
		979
		980	Or better yet, they want to monitor the database family, so they always
		981	have a reasonable up-to-date copy:
		982
		983	db_mon my_image_scalers => sub {
		984	@ports = keys %{ $_[0] };
		985	};
		986
		987	In general, you can set or delete single subkeys, but query and monitor
		988	whole families only.
		989
		990	If you feel the need to monitor or query a single subkey, try giving it
		991	it's own family.
		992
		993	=over
		994
		995	=item $guard = db_set $family => $subkey [=> $value]
		996
		997	Sets (or replaces) a key to the database - if C<$value> is omitted,
		998	C<undef> is used instead.
		999
		1000	When called in non-void context, C<db_set> returns a guard that
		1001	automatically calls C<db_del> when it is destroyed.
		1002
		1003	=item db_del $family => $subkey...
		1004
		1005	Deletes one or more subkeys from the database family.
		1006
		1007	=item $guard = db_reg $family => $port => $value
		1008
		1009	=item $guard = db_reg $family => $port
		1010
		1011	=item $guard = db_reg $family
		1012
		1013	Registers a port in the given family and optionally returns a guard to
		1014	remove it.
		1015
		1016	This function basically does the same as:
		1017
		1018	db_set $family => $port => $value
		1019
		1020	Except that the port is monitored and automatically removed from the
		1021	database family when it is kil'ed.
		1022
		1023	If C<$value> is missing, C<undef> is used. If C<$port> is missing, then
		1024	C<$SELF> is used.
		1025
		1026	This function is most useful to register a port in some port group (which
		1027	is just another name for a database family), and have it removed when the
		1028	port is gone. This works best when the port is a local port.
		1029
		1030	=cut
		1031
		1032	sub db_reg($$;$) {
		1033	my $family = shift;
		1034	my $port = @_ ? shift : $SELF;
		1035
		1036	my $clr = sub { db_del $family => $port };
		1037	mon $port, $clr;
		1038
		1039	db_set $family => $port => $_[0];
		1040
		1041	defined wantarray
		1042	and &Guard::guard ($clr)
		1043	}
		1044
		1045	=item db_family $family => $cb->(\%familyhash)
		1046
		1047	Queries the named database C<$family> and call the callback with the
		1048	family represented as a hash. You can keep and freely modify the hash.
		1049
		1050	=item db_keys $family => $cb->(\@keys)
		1051
		1052	Same as C<db_family>, except it only queries the family I<subkeys> and passes
		1053	them as array reference to the callback.
		1054
		1055	=item db_values $family => $cb->(\@values)
		1056
		1057	Same as C<db_family>, except it only queries the family I<values> and passes them
		1058	as array reference to the callback.
		1059
		1060	=item $guard = db_mon $family => $cb->(\%familyhash, \@added, \@changed, \@deleted)
		1061
		1062	Creates a monitor on the given database family. Each time a key is
		1063	set or is deleted the callback is called with a hash containing the
		1064	database family and three lists of added, changed and deleted subkeys,
		1065	respectively. If no keys have changed then the array reference might be
		1066	C<undef> or even missing.
		1067
		1068	If not called in void context, a guard object is returned that, when
		1069	destroyed, stops the monitor.
		1070
		1071	The family hash reference and the key arrays belong to AnyEvent::MP and
		1072	B<must not be modified or stored> by the callback. When in doubt, make a
		1073	copy.
		1074
		1075	As soon as possible after the monitoring starts, the callback will be
		1076	called with the intiial contents of the family, even if it is empty,
		1077	i.e. there will always be a timely call to the callback with the current
		1078	contents.
		1079
		1080	It is possible that the callback is called with a change event even though
		1081	the subkey is already present and the value has not changed.
		1082
		1083	The monitoring stops when the guard object is destroyed.
		1084
		1085	Example: on every change to the family "mygroup", print out all keys.
		1086
		1087	my $guard = db_mon mygroup => sub {
		1088	my ($family, $a, $c, $d) = @_;
		1089	print "mygroup members: ", (join " ", keys %$family), "\n";
		1090	};
		1091
		1092	Exmaple: wait until the family "My::Module::workers" is non-empty.
		1093
		1094	my $guard; $guard = db_mon My::Module::workers => sub {
		1095	my ($family, $a, $c, $d) = @_;
		1096	return unless %$family;
		1097	undef $guard;
		1098	print "My::Module::workers now nonempty\n";
		1099	};
		1100
		1101	Example: print all changes to the family "AnyEvent::Fantasy::Module".
		1102
		1103	my $guard = db_mon AnyEvent::Fantasy::Module => sub {
		1104	my ($family, $a, $c, $d) = @_;
		1105
		1106	print "+$_=$family->{$_}\n" for @$a;
		1107	print "*$_=$family->{$_}\n" for @$c;
		1108	print "-$_=$family->{$_}\n" for @$d;
		1109	};
		1110
		1111	=cut
		1112
667	=back	1113	=back
668		1114
669	=head1 AnyEvent::MP vs. Distributed Erlang	1115	=head1 AnyEvent::MP vs. Distributed Erlang
670		1116
671	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	1117	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	1118	== 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	1119	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
674	sample:	1120	sample:
675		1121
676	http://www.Erlang.se/doc/programming_rules.shtml	1122	http://www.erlang.se/doc/programming_rules.shtml
677	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	1123	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	1124	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	1125	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
680		1126
681	Despite the similarities, there are also some important differences:	1127	Despite the similarities, there are also some important differences:
682		1128
683	=over 4	1129	=over 4
684		1130
685	=item * Node IDs are arbitrary strings in AEMP.	1131	=item * Node IDs are arbitrary strings in AEMP.
686		1132
687	Erlang relies on special naming and DNS to work everywhere in the same	1133	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	1134	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.	1135	configuration or DNS), and possibly the addresses of some seed nodes, but
		1136	will otherwise discover other nodes (and their IDs) itself.
690		1137
691	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	1138	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
692	uses "local ports are like remote ports".	1139	uses "local ports are like remote ports".
693		1140
694	The failure modes for local ports are quite different (runtime errors	1141	The failure modes for local ports are quite different (runtime errors
…		…
703	ports being the special case/exception, where transport errors cannot	1150	ports being the special case/exception, where transport errors cannot
704	occur.	1151	occur.
705		1152
706	=item * Erlang uses processes and a mailbox, AEMP does not queue.	1153	=item * Erlang uses processes and a mailbox, AEMP does not queue.
707		1154
708	Erlang uses processes that selectively receive messages, and therefore	1155	Erlang uses processes that selectively receive messages out of order, and
709	needs a queue. AEMP is event based, queuing messages would serve no	1156	therefore needs a queue. AEMP is event based, queuing messages would serve
710	useful purpose. For the same reason the pattern-matching abilities of	1157	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	1158	of AnyEvent::MP are more limited, as there is little need to be able to
712	filter messages without dequeing them.	1159	filter messages without dequeuing them.
713		1160
714	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	1161	This is not a philosophical difference, but simply stems from AnyEvent::MP
		1162	being event-based, while Erlang is process-based.
		1163
		1164	You can have a look at L<Coro::MP> for a more Erlang-like process model on
		1165	top of AEMP and Coro threads.
715		1166
716	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	1167	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
717		1168
718	Sending messages in Erlang is synchronous and blocks the process (and	1169	Sending messages in Erlang is synchronous and blocks the process until
		1170	a connection 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,	1171	need a queue that can overflow). AEMP sends return immediately, connection
720	connection establishment is handled in the background.	1172	establishment is handled in the background.
721		1173
722	=item * Erlang suffers from silent message loss, AEMP does not.	1174	=item * Erlang suffers from silent message loss, AEMP does not.
723		1175
724	Erlang makes few guarantees on messages delivery - messages can get lost	1176	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,	1177	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).	1178	b, and c, and the other side only receives messages a and c).
727		1179
728	AEMP guarantees correct ordering, and the guarantee that after one message	1180	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	1181	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	1182	same port are lost as well, until monitoring raises an error, so there are
731	sequence.	1183	no silent "holes" in the message sequence.
		1184
		1185	If you want your software to be very reliable, you have to cope with
		1186	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
		1187	simply tries to work better in common error cases, such as when a network
		1188	link goes down.
732		1189
733	=item * Erlang can send messages to the wrong port, AEMP does not.	1190	=item * Erlang can send messages to the wrong port, AEMP does not.
734		1191
735	In Erlang it is quite likely that a node that restarts reuses a process ID	1192	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	1193	process ID known to other nodes for a completely different process,
737	destined for that process to end up in an unrelated process.	1194	causing messages destined for that process to end up in an unrelated
		1195	process.
738		1196
739	AEMP never reuses port IDs, so old messages or old port IDs floating	1197	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.	1198	around in the network will not be sent to an unrelated port.
741		1199
742	=item * Erlang uses unprotected connections, AEMP uses secure	1200	=item * Erlang uses unprotected connections, AEMP uses secure
743	authentication and can use TLS.	1201	authentication and can use TLS.
744		1202
…		…
747		1205
748	=item * The AEMP protocol is optimised for both text-based and binary	1206	=item * The AEMP protocol is optimised for both text-based and binary
749	communications.	1207	communications.
750		1208
751	The AEMP protocol, unlike the Erlang protocol, supports both programming	1209	The AEMP protocol, unlike the Erlang protocol, supports both programming
752	language independent text-only protocols (good for debugging) and binary,	1210	language independent text-only protocols (good for debugging), and binary,
753	language-specific serialisers (e.g. Storable). By default, unless TLS is	1211	language-specific serialisers (e.g. Storable). By default, unless TLS is
754	used, the protocol is actually completely text-based.	1212	used, the protocol is actually completely text-based.
755		1213
756	It has also been carefully designed to be implementable in other languages	1214	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	1215	with a minimum of work while gracefully degrading functionality to make the
758	protocol simple.	1216	protocol simple.
759		1217
760	=item * AEMP has more flexible monitoring options than Erlang.	1218	=item * AEMP has more flexible monitoring options than Erlang.
761		1219
762	In Erlang, you can chose to receive I<all> exit signals as messages	1220	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	1221	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	1222	difficult to implement.
765	Erlang, as one can choose between automatic kill, exit message or callback	1223
766	on a per-process basis.	1224	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		1225	between automatic kill, exit message or callback on a per-port basis.
767		1226
768	=item * Erlang tries to hide remote/local connections, AEMP does not.	1227	=item * Erlang tries to hide remote/local connections, AEMP does not.
769		1228
770	Monitoring in Erlang is not an indicator of process death/crashes, in the	1229	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).	1230	same way as linking is (except linking is unreliable in Erlang).
…		…
793	overhead, as well as having to keep a proxy object everywhere.	1252	overhead, as well as having to keep a proxy object everywhere.
794		1253
795	Strings can easily be printed, easily serialised etc. and need no special	1254	Strings can easily be printed, easily serialised etc. and need no special
796	procedures to be "valid".	1255	procedures to be "valid".
797		1256
798	And as a result, a miniport consists of a single closure stored in a	1257	And as a result, a port with just a default receiver consists of a single
799	global hash - it can't become much cheaper.	1258	code reference stored in a global hash - it can't become much cheaper.
800		1259
801	=item Why favour JSON, why not a real serialising format such as Storable?	1260	=item Why favour JSON, why not a real serialising format such as Storable?
802		1261
803	In fact, any AnyEvent::MP node will happily accept Storable as framing	1262	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	1263	format, but currently there is no way to make a node use Storable by
…		…
814	Keeping your messages simple, concentrating on data structures rather than	1273	Keeping your messages simple, concentrating on data structures rather than
815	objects, will keep your messages clean, tidy and efficient.	1274	objects, will keep your messages clean, tidy and efficient.
816		1275
817	=back	1276	=back
818		1277
		1278	=head1 PORTING FROM AnyEvent::MP VERSION 1.X
		1279
		1280	AEMP version 2 has a few major incompatible changes compared to version 1:
		1281
		1282	=over 4
		1283
		1284	=item AnyEvent::MP::Global no longer has group management functions.
		1285
		1286	At least not officially - the grp_* functions are still exported and might
		1287	work, but they will be removed in some later release.
		1288
		1289	AnyEvent::MP now comes with a distributed database that is more
		1290	powerful. Its database families map closely to port groups, but the API
		1291	has changed (the functions are also now exported by AnyEvent::MP). Here is
		1292	a rough porting guide:
		1293
		1294	grp_reg $group, $port # old
		1295	db_reg $group, $port # new
		1296
		1297	$list = grp_get $group # old
		1298	db_keys $group, sub { my $list = shift } # new
		1299
		1300	grp_mon $group, $cb->(\@ports, $add, $del) # old
		1301	db_mon $group, $cb->(\%ports, $add, $change, $del) # new
		1302
		1303	C<grp_reg> is a no-brainer (just replace by C<db_reg>), but C<grp_get> is
		1304	no longer instant, because the local node might not have a copy of the
		1305	group. You can either modify your code to allow for a callback, or use
		1306	C<db_mon> to keep an updated copy of the group:
		1307
		1308	my $local_group_copy;
		1309	db_mon $group => sub { $local_group_copy = $_[0] };
		1310
		1311	# now "keys %$local_group_copy" always returns the most up-to-date
		1312	# list of ports in the group.
		1313
		1314	C<grp_mon> can be replaced by C<db_mon> with minor changes - C<db_mon>
		1315	passes a hash as first argument, and an extra C<$chg> argument that can be
		1316	ignored:
		1317
		1318	db_mon $group => sub {
		1319	my ($ports, $add, $chg, $del) = @_;
		1320	$ports = [keys %$ports];
		1321
		1322	# now $ports, $add and $del are the same as
		1323	# were originally passed by grp_mon.
		1324	...
		1325	};
		1326
		1327	=item Nodes not longer connect to all other nodes.
		1328
		1329	In AEMP 1.x, every node automatically loads the L<AnyEvent::MP::Global>
		1330	module, which in turn would create connections to all other nodes in the
		1331	network (helped by the seed nodes).
		1332
		1333	In version 2.x, global nodes still connect to all other global nodes, but
		1334	other nodes don't - now every node either is a global node itself, or
		1335	attaches itself to another global node.
		1336
		1337	If a node isn't a global node itself, then it attaches itself to one
		1338	of its seed nodes. If that seed node isn't a global node yet, it will
		1339	automatically be upgraded to a global node.
		1340
		1341	So in many cases, nothing needs to be changed - one just has to make sure
		1342	that all seed nodes are meshed together with the other seed nodes (as with
		1343	AEMP 1.x), and other nodes specify them as seed nodes. This is most easily
		1344	achieved by specifying the same set of seed nodes for all nodes in the
		1345	network.
		1346
		1347	Not opening a connection to every other node is usually an advantage,
		1348	except when you need the lower latency of an already established
		1349	connection. To ensure a node establishes a connection to another node,
		1350	you can monitor the node port (C<mon $node, ...>), which will attempt to
		1351	create the connection (and notify you when the connection fails).
		1352
		1353	=item Listener-less nodes (nodes without binds) are gone.
		1354
		1355	And are not coming back, at least not in their old form. If no C<binds>
		1356	are specified for a node, AnyEvent::MP assumes a default of C<:>.
		1357
		1358	There are vague plans to implement some form of routing domains, which
		1359	might or might not bring back listener-less nodes, but don't count on it.
		1360
		1361	The fact that most connections are now optional somewhat mitigates this,
		1362	as a node can be effectively unreachable from the outside without any
		1363	problems, as long as it isn't a global node and only reaches out to other
		1364	nodes (as opposed to being contacted from other nodes).
		1365
		1366	=item $AnyEvent::MP::Kernel::WARN has gone.
		1367
		1368	AnyEvent has acquired a logging framework (L<AnyEvent::Log>), and AEMP now
		1369	uses this, and so should your programs.
		1370
		1371	Every module now documents what kinds of messages it generates, with
		1372	AnyEvent::MP acting as a catch all.
		1373
		1374	On the positive side, this means that instead of setting
		1375	C<PERL_ANYEVENT_MP_WARNLEVEL>, you can get away by setting C<AE_VERBOSE> -
		1376	much less to type.
		1377
		1378	=back
		1379
		1380	=head1 LOGGING
		1381
		1382	AnyEvent::MP does not normally log anything by itself, but since it is the
		1383	root of the context hierarchy for AnyEvent::MP modules, it will receive
		1384	all log messages by submodules.
		1385
819	=head1 SEE ALSO	1386	=head1 SEE ALSO
820		1387
821	L<AnyEvent::MP::Intro> - a gentle introduction.	1388	L<AnyEvent::MP::Intro> - a gentle introduction.
822		1389
823	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.	1390	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
824		1391
825	L<AnyEvent::MP::Global> - network maintainance and port groups, to find	1392	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
826	your applications.	1393	your applications.
		1394
		1395	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		1396
		1397	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		1398	all nodes.
827		1399
828	L<AnyEvent>.	1400	L<AnyEvent>.
829		1401
830	=head1 AUTHOR	1402	=head1 AUTHOR
831		1403

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Revision 1.71 by root, Sun Aug 30 19:52:56 2009 UTC vs.
Revision 1.152 by root, Sun Jul 29 02:23:34 2018 UTC