[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 1.153 by root, Sat Nov 2 01:30:49 2019 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	configure
143	initialise_node	213
144	snd rcv mon mon_guard kil reg psub spawn	214	NODE $NODE
145	port	215	*SELF
		216
		217	node_of port_is_local
		218
		219	snd kil
		220	port rcv mon mon_guard psub peval spawn cal
		221	db_set db_del db_reg
		222	db_mon db_family db_keys db_values
		223
		224	after
146	);	225	);
147		226
148	our $SELF;	227	our $SELF;
149		228
150	sub _self_die() {	229	sub _self_die() {
…		…
155		234
156	=item $thisnode = NODE / $NODE	235	=item $thisnode = NODE / $NODE
157		236
158	The C<NODE> function returns, and the C<$NODE> variable contains, the node	237	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	238	ID of the node running in the current process. This value is initialised by
160	a call to C<initialise_node>.	239	a call to C<configure>.
161		240
162	=item $nodeid = node_of $port	241	=item $nodeid = node_of $port
163		242
164	Extracts and returns the node ID from a port ID or a node ID.	243	Extracts and returns the node ID from a port ID or a node ID.
165		244
166	=item initialise_node $profile_name, key => value...	245	=item $is_local = port_is_local $port
		246
		247	Returns true iff the port is a local port.
		248
		249	=item configure $profile, key => value...
		250
		251	=item configure key => value...
167		252
168	Before a node can talk to other nodes on the network (i.e. enter	253	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	254	"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	255	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.	256	some other nodes in the network to discover other nodes.
172		257
173	This function initialises a node - it must be called exactly once (or	258	This function configures a node - it must be called exactly once (or
174	never) before calling other AnyEvent::MP functions.	259	never) before calling other AnyEvent::MP functions.
175		260
176	The first argument is a profile name. If it is C<undef> or missing, then	261	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>).	262	F<aemp> command line utility (sans the set/del prefix), with these additions:
178		263
		264	=over 4
		265
		266	=item norc => $boolean (default false)
		267
		268	If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I<not>
		269	be consulted - all configuration options must be specified in the
		270	C<configure> call.
		271
		272	=item force => $boolean (default false)
		273
		274	IF true, then the values specified in the C<configure> will take
		275	precedence over any values configured via the rc file. The default is for
		276	the rc file to override any options specified in the program.
		277
		278	=back
		279
		280	=over 4
		281
		282	=item step 1, gathering configuration from profiles
		283
179	The function first looks up the profile in the aemp configuration (see the	284	The function first looks up a profile in the aemp configuration (see the
180	L<aemp> commandline utility). the profile is calculated as follows:	285	L<aemp> commandline utility). The profile name can be specified via the
		286	named C<profile> parameter or can simply be the first parameter). If it is
		287	missing, then the nodename (F<uname -n>) will be used as profile name.
181		288
		289	The profile data is then gathered as follows:
		290
182	First, all remaining key => value pairs (all of which are conviniently	291	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	292	undocumented at the moment) will be interpreted as configuration
184	any values specified in the global default configuration (see the F<aemp>	293	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	294	default configuration (see the F<aemp> utility), then the chain of
		295	profiles chosen by the profile name (and any C<parent> attributes).
		296
186	the values specified in the profile have highest priority and the values	297	That means that the values specified in the profile have highest priority
187	specified via C<initialise_node> have lowest priority.	298	and the values specified directly via C<configure> have lowest priority,
		299	and can only be used to specify defaults.
188		300
189	If the profile specifies a node ID, then this will become the node ID of	301	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	302	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.	303	a unique randoms tring (C</%u>) appended.
		304
		305	The node ID can contain some C<%> sequences that are expanded: C<%n>
		306	is expanded to the local nodename, C<%u> is replaced by a random
		307	strign to make the node unique. For example, the F<aemp> commandline
		308	utility uses C<aemp/%n/%u> as nodename, which might expand to
		309	C<aemp/cerebro/ZQDGSIkRhEZQDGSIkRhE>.
		310
		311	=item step 2, bind listener sockets
192		312
193	The next step is to look up the binds in the profile, followed by binding	313	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	314	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	315	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	316	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).	317	binds, but it can still talk to all "normal" nodes).
198		318
199	If the profile does not specify a binds list, then a default of C<*> is	319	If the profile does not specify a binds list, then a default of C<*> is
200	used.	320	used, meaning the node will bind on a dynamically-assigned port on every
		321	local IP address it finds.
201		322
		323	=item step 3, connect to seed nodes
		324
202	Lastly, the seeds list from the profile is passed to the	325	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	326	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.	327	connectivity with at least one node at any point in time.
205		328
206	Example: become a distributed node listening on the guessed noderef, or	329	=back
207	the one specified via C<aemp> for the current node. This should be the	330
		331	Example: become a distributed node using the local node name as profile.
208	most common form of invocation for "daemon"-type nodes.	332	This should be the most common form of invocation for "daemon"-type nodes.
209		333
210	initialise_node;	334	configure
211		335
212	Example: become an anonymous node. This form is often used for commandline	336	Example: become a semi-anonymous node. This form is often used for
213	clients.	337	commandline clients.
214		338
215	initialise_node "anon/";	339	configure nodeid => "myscript/%n/%u";
216		340
217	Example: become a distributed node. If there is no profile of the given	341	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	342	for a seed node as it binds on all local addresses on a fixed port (4040,
219	on the resulting addresses.	343	customary for aemp).
220		344
221	initialise_node "localhost:4044";	345	# use the aemp commandline utility
		346	# aemp profile seed binds '*:4040'
		347
		348	# then use it
		349	configure profile => "seed";
		350
		351	# or simply use aemp from the shell again:
		352	# aemp run profile seed
		353
		354	# or provide a nicer-to-remember nodeid
		355	# aemp run profile seed nodeid "$(hostname)"
222		356
223	=item $SELF	357	=item $SELF
224		358
225	Contains the current port id while executing C<rcv> callbacks or C<psub>	359	Contains the current port id while executing C<rcv> callbacks or C<psub>
226	blocks.	360	blocks.
…		…
282		416
283	=cut	417	=cut
284		418
285	sub rcv($@);	419	sub rcv($@);
286		420
287	sub _kilme {	421	my $KILME = sub {
288	die "received message on port without callback";	422	(my $tag = substr $_[0], 0, 30) =~ s/([^\x20-\x7e])/./g;
289	}	423	kil $SELF, unhandled_message => "no callback found for message '$tag'";
		424	};
290		425
291	sub port(;&) {	426	sub port(;&) {
292	my $id = "$UNIQ." . $ID++;	427	my $id = $UNIQ . ++$ID;
293	my $port = "$NODE#$id";	428	my $port = "$NODE#$id";
294		429
295	rcv $port, shift \|\| \&_kilme;	430	rcv $port, shift \|\| $KILME;
296		431
297	$port	432	$port
298	}	433	}
299		434
300	=item rcv $local_port, $callback->(@msg)	435	=item rcv $local_port, $callback->(@msg)
…		…
305		440
306	The global C<$SELF> (exported by this module) contains C<$port> while	441	The global C<$SELF> (exported by this module) contains C<$port> while
307	executing the callback. Runtime errors during callback execution will	442	executing the callback. Runtime errors during callback execution will
308	result in the port being C<kil>ed.	443	result in the port being C<kil>ed.
309		444
310	The default callback received all messages not matched by a more specific	445	The default callback receives all messages not matched by a more specific
311	C<tag> match.	446	C<tag> match.
312		447
313	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...	448	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
314		449
315	Register (or replace) callbacks to be called on messages starting with the	450	Register (or replace) callbacks to be called on messages starting with the
…		…
336	msg1 => sub { ... },	471	msg1 => sub { ... },
337	...	472	...
338	;	473	;
339		474
340	Example: temporarily register a rcv callback for a tag matching some port	475	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.	476	(e.g. for an rpc reply) and unregister it after a message was received.
342		477
343	rcv $port, $otherport => sub {	478	rcv $port, $otherport => sub {
344	my @reply = @_;	479	my @reply = @_;
345		480
346	rcv $SELF, $otherport;	481	rcv $SELF, $otherport;
…		…
348		483
349	=cut	484	=cut
350		485
351	sub rcv($@) {	486	sub rcv($@) {
352	my $port = shift;	487	my $port = shift;
353	my ($noderef, $portid) = split /#/, $port, 2;	488	my ($nodeid, $portid) = split /#/, $port, 2;
354		489
355	$NODE{$noderef} == $NODE{""}	490	$nodeid eq $NODE
356	or Carp::croak "$port: rcv can only be called on local ports, caught";	491	or Carp::croak "$port: rcv can only be called on local ports, caught";
357		492
358	while (@_) {	493	while (@_) {
359	if (ref $_[0]) {	494	if (ref $_[0]) {
360	if (my $self = $PORT_DATA{$portid}) {	495	if (my $self = $PORT_DATA{$portid}) {
361	"AnyEvent::MP::Port" eq ref $self	496	"AnyEvent::MP::Port" eq ref $self
362	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	497	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
363		498
364	$self->[2] = shift;	499	$self->[0] = shift;
365	} else {	500	} else {
366	my $cb = shift;	501	my $cb = shift;
367	$PORT{$portid} = sub {	502	$PORT{$portid} = sub {
368	local $SELF = $port;	503	local $SELF = $port;
369	eval { &$cb }; _self_die if $@;	504	eval { &$cb }; _self_die if $@;
370	};	505	};
371	}	506	}
372	} elsif (defined $_[0]) {	507	} elsif (defined $_[0]) {
373	my $self = $PORT_DATA{$portid} \|\|= do {	508	my $self = $PORT_DATA{$portid} \|\|= do {
374	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	509	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
375		510
376	$PORT{$portid} = sub {	511	$PORT{$portid} = sub {
377	local $SELF = $port;	512	local $SELF = $port;
378		513
379	if (my $cb = $self->[1]{$_[0]}) {	514	if (my $cb = $self->[1]{$_[0]}) {
…		…
401	}	536	}
402		537
403	$port	538	$port
404	}	539	}
405		540
		541	=item peval $port, $coderef[, @args]
		542
		543	Evaluates the given C<$codref> within the context of C<$port>, that is,
		544	when the code throws an exception the C<$port> will be killed.
		545
		546	Any remaining args will be passed to the callback. Any return values will
		547	be returned to the caller.
		548
		549	This is useful when you temporarily want to execute code in the context of
		550	a port.
		551
		552	Example: create a port and run some initialisation code in it's context.
		553
		554	my $port = port { ... };
		555
		556	peval $port, sub {
		557	init
		558	or die "unable to init";
		559	};
		560
		561	=cut
		562
		563	sub peval($$) {
		564	local $SELF = shift;
		565	my $cb = shift;
		566
		567	if (wantarray) {
		568	my @res = eval { &$cb };
		569	_self_die if $@;
		570	@res
		571	} else {
		572	my $res = eval { &$cb };
		573	_self_die if $@;
		574	$res
		575	}
		576	}
		577
406	=item $closure = psub { BLOCK }	578	=item $closure = psub { BLOCK }
407		579
408	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	580	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>	581	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.	582	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		583
		584	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		585	BLOCK }, @_ } >>.
411		586
412	This is useful when you register callbacks from C<rcv> callbacks:	587	This is useful when you register callbacks from C<rcv> callbacks:
413		588
414	rcv delayed_reply => sub {	589	rcv delayed_reply => sub {
415	my ($delay, @reply) = @_;	590	my ($delay, @reply) = @_;
…		…
439	$res	614	$res
440	}	615	}
441	}	616	}
442	}	617	}
443		618
		619	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
		620
		621	=item $guard = mon $port # kill $SELF when $port dies
		622
444	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies	623	=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		624
450	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies	625	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
451		626
452	Monitor the given port and do something when the port is killed or	627	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	628	messages to it were lost, and optionally return a guard that can be used
454	to stop monitoring again.	629	to stop monitoring again.
		630
		631	The first two forms distinguish between "normal" and "abnormal" kil's:
		632
		633	In the first form (another port given), if the C<$port> is C<kil>'ed with
		634	a non-empty reason, the other port (C<$rcvport>) will be kil'ed with the
		635	same reason. That is, on "normal" kil's nothing happens, while under all
		636	other conditions, the other port is killed with the same reason.
		637
		638	The second form (kill self) is the same as the first form, except that
		639	C<$rvport> defaults to C<$SELF>.
		640
		641	The remaining forms don't distinguish between "normal" and "abnormal" kil's
		642	- it's up to the callback or receiver to check whether the C<@reason> is
		643	empty and act accordingly.
		644
		645	In the third form (callback), the callback is simply called with any
		646	number of C<@reason> elements (empty @reason means that the port was deleted
		647	"normally"). Note also that I<< the callback B<must> never die >>, so use
		648	C<eval> if unsure.
		649
		650	In the last form (message), a message of the form C<$rcvport, @msg,
		651	@reason> will be C<snd>.
		652
		653	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		654	alert was raised), they are removed and will not trigger again, even if it
		655	turns out that the port is still alive.
		656
		657	As a rule of thumb, monitoring requests should always monitor a remote
		658	port locally (using a local C<$rcvport> or a callback). The reason is that
		659	kill messages might get lost, just like any other message. Another less
		660	obvious reason is that even monitoring requests can get lost (for example,
		661	when the connection to the other node goes down permanently). When
		662	monitoring a port locally these problems do not exist.
455		663
456	C<mon> effectively guarantees that, in the absence of hardware failures,	664	C<mon> effectively guarantees that, in the absence of hardware failures,
457	after starting the monitor, either all messages sent to the port will	665	after starting the monitor, either all messages sent to the port will
458	arrive, or the monitoring action will be invoked after possible message	666	arrive, or the monitoring action will be invoked after possible message
459	loss has been detected. No messages will be lost "in between" (after	667	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	668	the first lost message no further messages will be received by the
461	port). After the monitoring action was invoked, further messages might get	669	port). After the monitoring action was invoked, further messages might get
462	delivered again.	670	delivered again.
463		671
464	Note that monitoring-actions are one-shot: once messages are lost (and a	672	Inter-host-connection timeouts and monitoring depend on the transport
465	monitoring alert was raised), they are removed and will not trigger again.	673	used. The only transport currently implemented is TCP, and AnyEvent::MP
		674	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		675	non-idle connection, and usually around two hours for idle connections).
466		676
467	In the first form (callback), the callback is simply called with any	677	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	678	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	679	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		680
490	Example: call a given callback when C<$port> is killed.	681	Example: call a given callback when C<$port> is killed.
491		682
492	mon $port, sub { warn "port died because of <@_>\n" };	683	mon $port, sub { warn "port died because of <@_>\n" };
493		684
…		…
500	mon $port, $self => "restart";	691	mon $port, $self => "restart";
501		692
502	=cut	693	=cut
503		694
504	sub mon {	695	sub mon {
505	my ($noderef, $port) = split /#/, shift, 2;	696	my ($nodeid, $port) = split /#/, shift, 2;
506		697
507	my $node = $NODE{$noderef} \|\| add_node $noderef;	698	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
508		699
509	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	700	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
510		701
511	unless (ref $cb) {	702	unless (ref $cb) {
512	if (@_) {	703	if (@_) {
…		…
521	}	712	}
522		713
523	$node->monitor ($port, $cb);	714	$node->monitor ($port, $cb);
524		715
525	defined wantarray	716	defined wantarray
526	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	717	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
527	}	718	}
528		719
529	=item $guard = mon_guard $port, $ref, $ref...	720	=item $guard = mon_guard $port, $ref, $ref...
530		721
531	Monitors the given C<$port> and keeps the passed references. When the port	722	Monitors the given C<$port> and keeps the passed references. When the port
…		…
554		745
555	=item kil $port[, @reason]	746	=item kil $port[, @reason]
556		747
557	Kill the specified port with the given C<@reason>.	748	Kill the specified port with the given C<@reason>.
558		749
559	If no C<@reason> is specified, then the port is killed "normally" (ports	750	If no C<@reason> is specified, then the port is killed "normally" -
560	monitoring other ports will not necessarily die because a port dies	751	monitor callback will be invoked, but the kil will not cause linked ports
561	"normally").	752	(C<mon $mport, $lport> form) to get killed.
562		753
563	Otherwise, linked ports get killed with the same reason (second form of	754	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
564	C<mon>, see above).	755	form) get killed with the same reason.
565		756
566	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	757	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
567	will be reported as reason C<< die => $@ >>.	758	will be reported as reason C<< die => $@ >>.
568		759
569	Transport/communication errors are reported as C<< transport_error =>	760	Transport/communication errors are reported as C<< transport_error =>
570	$message >>.	761	$message >>.
571		762
572	=cut	763	Common idioms:
		764
		765	# silently remove yourself, do not kill linked ports
		766	kil $SELF;
		767
		768	# report a failure in some detail
		769	kil $SELF, failure_mode_1 => "it failed with too high temperature";
		770
		771	# do not waste much time with killing, just die when something goes wrong
		772	open my $fh, "<file"
		773	or die "file: $!";
573		774
574	=item $port = spawn $node, $initfunc[, @initdata]	775	=item $port = spawn $node, $initfunc[, @initdata]
575		776
576	Creates a port on the node C<$node> (which can also be a port ID, in which	777	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).	778	case it's the node where that port resides).
…		…
588	the package, then the package above the package and so on (e.g.	789	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	790	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
590	exists or it runs out of package names.	791	exists or it runs out of package names.
591		792
592	The init function is then called with the newly-created port as context	793	The init function is then called with the newly-created port as context
593	object (C<$SELF>) and the C<@initdata> values as arguments.	794	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		795	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		796	the port might not get created.
594		797
595	A common idiom is to pass a local port, immediately monitor the spawned	798	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	799	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	800	local port. This two-way monitoring ensures that both ports get cleaned up
598	when there is a problem.	801	when there is a problem.
599		802
		803	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		804	caller before C<spawn> returns (by delaying invocation when spawn is
		805	called for the local node).
		806
600	Example: spawn a chat server port on C<$othernode>.	807	Example: spawn a chat server port on C<$othernode>.
601		808
602	# this node, executed from within a port context:	809	# this node, executed from within a port context:
603	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	810	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
604	mon $server;	811	mon $server;
…		…
618		825
619	sub _spawn {	826	sub _spawn {
620	my $port = shift;	827	my $port = shift;
621	my $init = shift;	828	my $init = shift;
622		829
		830	# rcv will create the actual port
623	local $SELF = "$NODE#$port";	831	local $SELF = "$NODE#$port";
624	eval {	832	eval {
625	&{ load_func $init }	833	&{ load_func $init }
626	};	834	};
627	_self_die if $@;	835	_self_die if $@;
628	}	836	}
629		837
630	sub spawn(@) {	838	sub spawn(@) {
631	my ($noderef, undef) = split /#/, shift, 2;	839	my ($nodeid, undef) = split /#/, shift, 2;
632		840
633	my $id = "$RUNIQ." . $ID++;	841	my $id = $RUNIQ . ++$ID;
634		842
635	$_[0] =~ /::/	843	$_[0] =~ /::/
636	or Carp::croak "spawn init function must be a fully-qualified name, caught";	844	or Carp::croak "spawn init function must be a fully-qualified name, caught";
637		845
638	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;	846	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
639		847
640	"$noderef#$id"	848	"$nodeid#$id"
641	}	849	}
		850
642		851
643	=item after $timeout, @msg	852	=item after $timeout, @msg
644		853
645	=item after $timeout, $callback	854	=item after $timeout, $callback
646		855
…		…
662	? $action[0]()	871	? $action[0]()
663	: snd @action;	872	: snd @action;
664	};	873	};
665	}	874	}
666		875
		876	#=item $cb2 = timeout $seconds, $cb[, @args]
		877
		878	=item cal $port, @msg, $callback[, $timeout]
		879
		880	A simple form of RPC - sends a message to the given C<$port> with the
		881	given contents (C<@msg>), but adds a reply port to the message.
		882
		883	The reply port is created temporarily just for the purpose of receiving
		884	the reply, and will be C<kil>ed when no longer needed.
		885
		886	A reply message sent to the port is passed to the C<$callback> as-is.
		887
		888	If an optional time-out (in seconds) is given and it is not C<undef>,
		889	then the callback will be called without any arguments after the time-out
		890	elapsed and the port is C<kil>ed.
		891
		892	If no time-out is given (or it is C<undef>), then the local port will
		893	monitor the remote port instead, so it eventually gets cleaned-up.
		894
		895	Currently this function returns the temporary port, but this "feature"
		896	might go in future versions unless you can make a convincing case that
		897	this is indeed useful for something.
		898
		899	=cut
		900
		901	sub cal(@) {
		902	my $timeout = ref $_[-1] ? undef : pop;
		903	my $cb = pop;
		904
		905	my $port = port {
		906	undef $timeout;
		907	kil $SELF;
		908	&$cb;
		909	};
		910
		911	if (defined $timeout) {
		912	$timeout = AE::timer $timeout, 0, sub {
		913	undef $timeout;
		914	kil $port;
		915	$cb->();
		916	};
		917	} else {
		918	mon $_[0], sub {
		919	kil $port;
		920	$cb->();
		921	};
		922	}
		923
		924	push @_, $port;
		925	&snd;
		926
		927	$port
		928	}
		929
		930	=back
		931
		932	=head1 DISTRIBUTED DATABASE
		933
		934	AnyEvent::MP comes with a simple distributed database. The database will
		935	be mirrored asynchronously on all global nodes. Other nodes bind to one
		936	of the global nodes for their needs. Every node has a "local database"
		937	which contains all the values that are set locally. All local databases
		938	are merged together to form the global database, which can be queried.
		939
		940	The database structure is that of a two-level hash - the database hash
		941	contains hashes which contain values, similarly to a perl hash of hashes,
		942	i.e.:
		943
		944	$DATABASE{$family}{$subkey} = $value
		945
		946	The top level hash key is called "family", and the second-level hash key
		947	is called "subkey" or simply "key".
		948
		949	The family must be alphanumeric, i.e. start with a letter and consist
		950	of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
		951	pretty much like Perl module names.
		952
		953	As the family namespace is global, it is recommended to prefix family names
		954	with the name of the application or module using it.
		955
		956	The subkeys must be non-empty strings, with no further restrictions.
		957
		958	The values should preferably be strings, but other perl scalars should
		959	work as well (such as C<undef>, arrays and hashes).
		960
		961	Every database entry is owned by one node - adding the same family/subkey
		962	combination on multiple nodes will not cause discomfort for AnyEvent::MP,
		963	but the result might be nondeterministic, i.e. the key might have
		964	different values on different nodes.
		965
		966	Different subkeys in the same family can be owned by different nodes
		967	without problems, and in fact, this is the common method to create worker
		968	pools. For example, a worker port for image scaling might do this:
		969
		970	db_set my_image_scalers => $port;
		971
		972	And clients looking for an image scaler will want to get the
		973	C<my_image_scalers> keys from time to time:
		974
		975	db_keys my_image_scalers => sub {
		976	@ports = @{ $_[0] };
		977	};
		978
		979	Or better yet, they want to monitor the database family, so they always
		980	have a reasonable up-to-date copy:
		981
		982	db_mon my_image_scalers => sub {
		983	@ports = keys %{ $_[0] };
		984	};
		985
		986	In general, you can set or delete single subkeys, but query and monitor
		987	whole families only.
		988
		989	If you feel the need to monitor or query a single subkey, try giving it
		990	it's own family.
		991
		992	=over
		993
		994	=item $guard = db_set $family => $subkey [=> $value]
		995
		996	Sets (or replaces) a key to the database - if C<$value> is omitted,
		997	C<undef> is used instead.
		998
		999	When called in non-void context, C<db_set> returns a guard that
		1000	automatically calls C<db_del> when it is destroyed.
		1001
		1002	=item db_del $family => $subkey...
		1003
		1004	Deletes one or more subkeys from the database family.
		1005
		1006	=item $guard = db_reg $family => $port => $value
		1007
		1008	=item $guard = db_reg $family => $port
		1009
		1010	=item $guard = db_reg $family
		1011
		1012	Registers a port in the given family and optionally returns a guard to
		1013	remove it.
		1014
		1015	This function basically does the same as:
		1016
		1017	db_set $family => $port => $value
		1018
		1019	Except that the port is monitored and automatically removed from the
		1020	database family when it is kil'ed.
		1021
		1022	If C<$value> is missing, C<undef> is used. If C<$port> is missing, then
		1023	C<$SELF> is used.
		1024
		1025	This function is most useful to register a port in some port group (which
		1026	is just another name for a database family), and have it removed when the
		1027	port is gone. This works best when the port is a local port.
		1028
		1029	=cut
		1030
		1031	sub db_reg($$;$) {
		1032	my $family = shift;
		1033	my $port = @_ ? shift : $SELF;
		1034
		1035	my $clr = sub { db_del $family => $port };
		1036	mon $port, $clr;
		1037
		1038	db_set $family => $port => $_[0];
		1039
		1040	defined wantarray
		1041	and &Guard::guard ($clr)
		1042	}
		1043
		1044	=item db_family $family => $cb->(\%familyhash)
		1045
		1046	Queries the named database C<$family> and call the callback with the
		1047	family represented as a hash. You can keep and freely modify the hash.
		1048
		1049	=item db_keys $family => $cb->(\@keys)
		1050
		1051	Same as C<db_family>, except it only queries the family I<subkeys> and passes
		1052	them as array reference to the callback.
		1053
		1054	=item db_values $family => $cb->(\@values)
		1055
		1056	Same as C<db_family>, except it only queries the family I<values> and passes them
		1057	as array reference to the callback.
		1058
		1059	=item $guard = db_mon $family => $cb->(\%familyhash, \@added, \@changed, \@deleted)
		1060
		1061	Creates a monitor on the given database family. Each time a key is
		1062	set or is deleted the callback is called with a hash containing the
		1063	database family and three lists of added, changed and deleted subkeys,
		1064	respectively. If no keys have changed then the array reference might be
		1065	C<undef> or even missing.
		1066
		1067	If not called in void context, a guard object is returned that, when
		1068	destroyed, stops the monitor.
		1069
		1070	The family hash reference and the key arrays belong to AnyEvent::MP and
		1071	B<must not be modified or stored> by the callback. When in doubt, make a
		1072	copy.
		1073
		1074	As soon as possible after the monitoring starts, the callback will be
		1075	called with the intiial contents of the family, even if it is empty,
		1076	i.e. there will always be a timely call to the callback with the current
		1077	contents.
		1078
		1079	It is possible that the callback is called with a change event even though
		1080	the subkey is already present and the value has not changed.
		1081
		1082	The monitoring stops when the guard object is destroyed.
		1083
		1084	Example: on every change to the family "mygroup", print out all keys.
		1085
		1086	my $guard = db_mon mygroup => sub {
		1087	my ($family, $a, $c, $d) = @_;
		1088	print "mygroup members: ", (join " ", keys %$family), "\n";
		1089	};
		1090
		1091	Exmaple: wait until the family "My::Module::workers" is non-empty.
		1092
		1093	my $guard; $guard = db_mon My::Module::workers => sub {
		1094	my ($family, $a, $c, $d) = @_;
		1095	return unless %$family;
		1096	undef $guard;
		1097	print "My::Module::workers now nonempty\n";
		1098	};
		1099
		1100	Example: print all changes to the family "AnyEvent::Fantasy::Module".
		1101
		1102	my $guard = db_mon AnyEvent::Fantasy::Module => sub {
		1103	my ($family, $a, $c, $d) = @_;
		1104
		1105	print "+$_=$family->{$_}\n" for @$a;
		1106	print "*$_=$family->{$_}\n" for @$c;
		1107	print "-$_=$family->{$_}\n" for @$d;
		1108	};
		1109
		1110	=cut
		1111
667	=back	1112	=back
668		1113
669	=head1 AnyEvent::MP vs. Distributed Erlang	1114	=head1 AnyEvent::MP vs. Distributed Erlang
670		1115
671	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	1116	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	1117	== 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	1118	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
674	sample:	1119	sample:
675		1120
676	http://www.Erlang.se/doc/programming_rules.shtml	1121	http://www.erlang.se/doc/programming_rules.shtml
677	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	1122	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	1123	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	1124	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
680		1125
681	Despite the similarities, there are also some important differences:	1126	Despite the similarities, there are also some important differences:
682		1127
683	=over 4	1128	=over 4
684		1129
685	=item * Node IDs are arbitrary strings in AEMP.	1130	=item * Node IDs are arbitrary strings in AEMP.
686		1131
687	Erlang relies on special naming and DNS to work everywhere in the same	1132	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	1133	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.	1134	configuration or DNS), and possibly the addresses of some seed nodes, but
		1135	will otherwise discover other nodes (and their IDs) itself.
690		1136
691	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	1137	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
692	uses "local ports are like remote ports".	1138	uses "local ports are like remote ports".
693		1139
694	The failure modes for local ports are quite different (runtime errors	1140	The failure modes for local ports are quite different (runtime errors
…		…
703	ports being the special case/exception, where transport errors cannot	1149	ports being the special case/exception, where transport errors cannot
704	occur.	1150	occur.
705		1151
706	=item * Erlang uses processes and a mailbox, AEMP does not queue.	1152	=item * Erlang uses processes and a mailbox, AEMP does not queue.
707		1153
708	Erlang uses processes that selectively receive messages, and therefore	1154	Erlang uses processes that selectively receive messages out of order, and
709	needs a queue. AEMP is event based, queuing messages would serve no	1155	therefore needs a queue. AEMP is event based, queuing messages would serve
710	useful purpose. For the same reason the pattern-matching abilities of	1156	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	1157	of AnyEvent::MP are more limited, as there is little need to be able to
712	filter messages without dequeing them.	1158	filter messages without dequeuing them.
713		1159
714	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	1160	This is not a philosophical difference, but simply stems from AnyEvent::MP
		1161	being event-based, while Erlang is process-based.
		1162
		1163	You can have a look at L<Coro::MP> for a more Erlang-like process model on
		1164	top of AEMP and Coro threads.
715		1165
716	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	1166	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
717		1167
718	Sending messages in Erlang is synchronous and blocks the process (and	1168	Sending messages in Erlang is synchronous and blocks the process until
		1169	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,	1170	need a queue that can overflow). AEMP sends return immediately, connection
720	connection establishment is handled in the background.	1171	establishment is handled in the background.
721		1172
722	=item * Erlang suffers from silent message loss, AEMP does not.	1173	=item * Erlang suffers from silent message loss, AEMP does not.
723		1174
724	Erlang makes few guarantees on messages delivery - messages can get lost	1175	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,	1176	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).	1177	b, and c, and the other side only receives messages a and c).
727		1178
728	AEMP guarantees correct ordering, and the guarantee that after one message	1179	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	1180	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	1181	same port are lost as well, until monitoring raises an error, so there are
731	sequence.	1182	no silent "holes" in the message sequence.
		1183
		1184	If you want your software to be very reliable, you have to cope with
		1185	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
		1186	simply tries to work better in common error cases, such as when a network
		1187	link goes down.
732		1188
733	=item * Erlang can send messages to the wrong port, AEMP does not.	1189	=item * Erlang can send messages to the wrong port, AEMP does not.
734		1190
735	In Erlang it is quite likely that a node that restarts reuses a process ID	1191	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	1192	process ID known to other nodes for a completely different process,
737	destined for that process to end up in an unrelated process.	1193	causing messages destined for that process to end up in an unrelated
		1194	process.
738		1195
739	AEMP never reuses port IDs, so old messages or old port IDs floating	1196	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.	1197	around in the network will not be sent to an unrelated port.
741		1198
742	=item * Erlang uses unprotected connections, AEMP uses secure	1199	=item * Erlang uses unprotected connections, AEMP uses secure
743	authentication and can use TLS.	1200	authentication and can use TLS.
744		1201
…		…
747		1204
748	=item * The AEMP protocol is optimised for both text-based and binary	1205	=item * The AEMP protocol is optimised for both text-based and binary
749	communications.	1206	communications.
750		1207
751	The AEMP protocol, unlike the Erlang protocol, supports both programming	1208	The AEMP protocol, unlike the Erlang protocol, supports both programming
752	language independent text-only protocols (good for debugging) and binary,	1209	language independent text-only protocols (good for debugging), and binary,
753	language-specific serialisers (e.g. Storable). By default, unless TLS is	1210	language-specific serialisers (e.g. Storable). By default, unless TLS is
754	used, the protocol is actually completely text-based.	1211	used, the protocol is actually completely text-based.
755		1212
756	It has also been carefully designed to be implementable in other languages	1213	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	1214	with a minimum of work while gracefully degrading functionality to make the
758	protocol simple.	1215	protocol simple.
759		1216
760	=item * AEMP has more flexible monitoring options than Erlang.	1217	=item * AEMP has more flexible monitoring options than Erlang.
761		1218
762	In Erlang, you can chose to receive I<all> exit signals as messages	1219	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	1220	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	1221	difficult to implement.
765	Erlang, as one can choose between automatic kill, exit message or callback	1222
766	on a per-process basis.	1223	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		1224	between automatic kill, exit message or callback on a per-port basis.
767		1225
768	=item * Erlang tries to hide remote/local connections, AEMP does not.	1226	=item * Erlang tries to hide remote/local connections, AEMP does not.
769		1227
770	Monitoring in Erlang is not an indicator of process death/crashes, in the	1228	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).	1229	same way as linking is (except linking is unreliable in Erlang).
…		…
793	overhead, as well as having to keep a proxy object everywhere.	1251	overhead, as well as having to keep a proxy object everywhere.
794		1252
795	Strings can easily be printed, easily serialised etc. and need no special	1253	Strings can easily be printed, easily serialised etc. and need no special
796	procedures to be "valid".	1254	procedures to be "valid".
797		1255
798	And as a result, a miniport consists of a single closure stored in a	1256	And as a result, a port with just a default receiver consists of a single
799	global hash - it can't become much cheaper.	1257	code reference stored in a global hash - it can't become much cheaper.
800		1258
801	=item Why favour JSON, why not a real serialising format such as Storable?	1259	=item Why favour JSON, why not a real serialising format such as Storable?
802		1260
803	In fact, any AnyEvent::MP node will happily accept Storable as framing	1261	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	1262	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	1272	Keeping your messages simple, concentrating on data structures rather than
815	objects, will keep your messages clean, tidy and efficient.	1273	objects, will keep your messages clean, tidy and efficient.
816		1274
817	=back	1275	=back
818		1276
		1277	=head1 PORTING FROM AnyEvent::MP VERSION 1.X
		1278
		1279	AEMP version 2 has a few major incompatible changes compared to version 1:
		1280
		1281	=over 4
		1282
		1283	=item AnyEvent::MP::Global no longer has group management functions.
		1284
		1285	At least not officially - the grp_* functions are still exported and might
		1286	work, but they will be removed in some later release.
		1287
		1288	AnyEvent::MP now comes with a distributed database that is more
		1289	powerful. Its database families map closely to port groups, but the API
		1290	has changed (the functions are also now exported by AnyEvent::MP). Here is
		1291	a rough porting guide:
		1292
		1293	grp_reg $group, $port # old
		1294	db_reg $group, $port # new
		1295
		1296	$list = grp_get $group # old
		1297	db_keys $group, sub { my $list = shift } # new
		1298
		1299	grp_mon $group, $cb->(\@ports, $add, $del) # old
		1300	db_mon $group, $cb->(\%ports, $add, $change, $del) # new
		1301
		1302	C<grp_reg> is a no-brainer (just replace by C<db_reg>), but C<grp_get> is
		1303	no longer instant, because the local node might not have a copy of the
		1304	group. You can either modify your code to allow for a callback, or use
		1305	C<db_mon> to keep an updated copy of the group:
		1306
		1307	my $local_group_copy;
		1308	db_mon $group => sub { $local_group_copy = $_[0] };
		1309
		1310	# now "keys %$local_group_copy" always returns the most up-to-date
		1311	# list of ports in the group.
		1312
		1313	C<grp_mon> can be replaced by C<db_mon> with minor changes - C<db_mon>
		1314	passes a hash as first argument, and an extra C<$chg> argument that can be
		1315	ignored:
		1316
		1317	db_mon $group => sub {
		1318	my ($ports, $add, $chg, $del) = @_;
		1319	$ports = [keys %$ports];
		1320
		1321	# now $ports, $add and $del are the same as
		1322	# were originally passed by grp_mon.
		1323	...
		1324	};
		1325
		1326	=item Nodes not longer connect to all other nodes.
		1327
		1328	In AEMP 1.x, every node automatically loads the L<AnyEvent::MP::Global>
		1329	module, which in turn would create connections to all other nodes in the
		1330	network (helped by the seed nodes).
		1331
		1332	In version 2.x, global nodes still connect to all other global nodes, but
		1333	other nodes don't - now every node either is a global node itself, or
		1334	attaches itself to another global node.
		1335
		1336	If a node isn't a global node itself, then it attaches itself to one
		1337	of its seed nodes. If that seed node isn't a global node yet, it will
		1338	automatically be upgraded to a global node.
		1339
		1340	So in many cases, nothing needs to be changed - one just has to make sure
		1341	that all seed nodes are meshed together with the other seed nodes (as with
		1342	AEMP 1.x), and other nodes specify them as seed nodes. This is most easily
		1343	achieved by specifying the same set of seed nodes for all nodes in the
		1344	network.
		1345
		1346	Not opening a connection to every other node is usually an advantage,
		1347	except when you need the lower latency of an already established
		1348	connection. To ensure a node establishes a connection to another node,
		1349	you can monitor the node port (C<mon $node, ...>), which will attempt to
		1350	create the connection (and notify you when the connection fails).
		1351
		1352	=item Listener-less nodes (nodes without binds) are gone.
		1353
		1354	And are not coming back, at least not in their old form. If no C<binds>
		1355	are specified for a node, AnyEvent::MP assumes a default of C<:>.
		1356
		1357	There are vague plans to implement some form of routing domains, which
		1358	might or might not bring back listener-less nodes, but don't count on it.
		1359
		1360	The fact that most connections are now optional somewhat mitigates this,
		1361	as a node can be effectively unreachable from the outside without any
		1362	problems, as long as it isn't a global node and only reaches out to other
		1363	nodes (as opposed to being contacted from other nodes).
		1364
		1365	=item $AnyEvent::MP::Kernel::WARN has gone.
		1366
		1367	AnyEvent has acquired a logging framework (L<AnyEvent::Log>), and AEMP now
		1368	uses this, and so should your programs.
		1369
		1370	Every module now documents what kinds of messages it generates, with
		1371	AnyEvent::MP acting as a catch all.
		1372
		1373	On the positive side, this means that instead of setting
		1374	C<PERL_ANYEVENT_MP_WARNLEVEL>, you can get away by setting C<AE_VERBOSE> -
		1375	much less to type.
		1376
		1377	=back
		1378
		1379	=head1 LOGGING
		1380
		1381	AnyEvent::MP does not normally log anything by itself, but since it is the
		1382	root of the context hierarchy for AnyEvent::MP modules, it will receive
		1383	all log messages by submodules.
		1384
819	=head1 SEE ALSO	1385	=head1 SEE ALSO
820		1386
821	L<AnyEvent::MP::Intro> - a gentle introduction.	1387	L<AnyEvent::MP::Intro> - a gentle introduction.
822		1388
823	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.	1389	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
824		1390
825	L<AnyEvent::MP::Global> - network maintainance and port groups, to find	1391	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
826	your applications.	1392	your applications.
		1393
		1394	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		1395
		1396	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		1397	all nodes.
827		1398
828	L<AnyEvent>.	1399	L<AnyEvent>.
829		1400
830	=head1 AUTHOR	1401	=head1 AUTHOR
831		1402

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Revision 1.153 by root, Sat Nov 2 01:30:49 2019 UTC