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

Comparing cvsroot/AnyEvent-MP/MP.pm (file contents):
Revision 1.69 by root, Sun Aug 30 18:51:49 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	AnyEvent::MP - stable API, should work	47	# execute callbacks in $SELF port context
44	AnyEvent::MP::Intro - outdated	48	my $timer = AE::timer 1, 0, psub {
45	AnyEvent::MP::Kernel - mostly stable	49	die "kill the port, delayed";
46	AnyEvent::MP::Global - mostly stable	50	};
47	AnyEvent::MP::Node - mostly stable, but internal anyways
48	AnyEvent::MP::Transport - mostly stable, but internal anyways
49		51
50	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)
51		64
52	=head1 DESCRIPTION	65	=head1 DESCRIPTION
53		66
54	This module (-family) implements a simple message passing framework.	67	This module (-family) implements a simple message passing framework.
55		68
57	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.
58		71
59	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>
60	manual page and the examples under F<eg/>.	73	manual page and the examples under F<eg/>.
61		74
62	At the moment, this module family is a bit underdocumented.
63
64	=head1 CONCEPTS	75	=head1 CONCEPTS
65		76
66	=over 4	77	=over 4
67		78
68	=item port	79	=item port
69		80
70	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).
71		83
72	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
73	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
74	anything was listening for them or not.	86	anything was listening for them or not.
75		87
		88	Ports are represented by (printable) strings called "port IDs".
		89
76	=item port ID - C<nodeid#portname>	90	=item port ID - C<nodeid#portname>
77		91
78	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<#>)
79	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).
80		95
81	=item node	96	=item node
82		97
83	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,
84	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
85	ports.	100	ports.
86		101
87	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
88	(no listening ports). Private nodes cannot talk to other private nodes	103	(no listening ports). Private nodes cannot talk to other private nodes
89	currently.	104	currently, but all nodes can talk to public nodes.
90		105
		106	Nodes is represented by (printable) strings called "node IDs".
		107
91	=item node ID - C<[a-za-Z0-9_\-.:]+>	108	=item node ID - C<[A-Za-z0-9_\-.:]*>
92		109
93	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
94	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
95	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
96	doesn't interpret node IDs in any way.	113	doesn't interpret node IDs in any way except to uniquely identify a node.
97		114
98	=item binds - C<ip:port>	115	=item binds - C<ip:port>
99		116
100	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
101	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
102	endpoints - binds. Currently, only standard C<ip:port> specifications can	121	Currently, only standard C<ip:port> specifications can be used, which
103	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.
104		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
105	=item seeds - C<host:port>	154	=item seed IDs - C<host:port>
106		155
107	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
108	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.
109	network. This node is called a seed.
110		158
111	Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes	159	=item global nodes
112	are expected to be long-running, and at least one of those should always
113	be available. When nodes run out of connections (e.g. due to a network
114	error), they try to re-establish connections to some seednodes again to
115	join the network.
116		160
117	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
118	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).
119		175
120	=back	176	=back
121		177
122	=head1 VARIABLES/FUNCTIONS	178	=head1 VARIABLES/FUNCTIONS
123		179
…		…
125		181
126	=cut	182	=cut
127		183
128	package AnyEvent::MP;	184	package AnyEvent::MP;
129		185
		186	use AnyEvent::MP::Config ();
130	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	);
131		199
132	use common::sense;	200	use common::sense;
133		201
134	use Carp ();	202	use Carp ();
135		203
136	use AE ();	204	use AnyEvent ();
		205	use Guard ();
137		206
138	use base "Exporter";	207	use base "Exporter";
139		208
140	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	209	our $VERSION = '2.02'; # also in MP/Config.pm
141		210
142	our @EXPORT = qw(	211	our @EXPORT = qw(
143	NODE $NODE *SELF node_of after	212	configure
144	initialise_node	213
145	snd rcv mon mon_guard kil reg psub spawn	214	NODE $NODE
146	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
147	);	225	);
148		226
149	our $SELF;	227	our $SELF;
150		228
151	sub _self_die() {	229	sub _self_die() {
…		…
156		234
157	=item $thisnode = NODE / $NODE	235	=item $thisnode = NODE / $NODE
158		236
159	The C<NODE> function returns, and the C<$NODE> variable contains, the node	237	The C<NODE> function returns, and the C<$NODE> variable contains, the node
160	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
161	a call to C<initialise_node>.	239	a call to C<configure>.
162		240
163	=item $nodeid = node_of $port	241	=item $nodeid = node_of $port
164		242
165	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.
166		244
167	=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...
168		252
169	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
170	"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
171	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
172	some other nodes in the network to discover other nodes.	256	some other nodes in the network to discover other nodes.
173		257
174	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
175	never) before calling other AnyEvent::MP functions.	259	never) before calling other AnyEvent::MP functions.
176		260
177	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
178	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:
179		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
180	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
181	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.
182		288
183	First, all remaining key => value pairs will be used. Then they will be	289	The profile data is then gathered as follows:
184	overwritten by any values specified in the global default configuration	290
185	(see the F<aemp> utility), then the chain of profiles selected, if	291	First, all remaining key => value pairs (all of which are conveniently
		292	undocumented at the moment) will be interpreted as configuration
		293	data. Then they will be overwritten by any values specified in the global
		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	any. That means that the values specified in the profile have highest	297	That means that the values specified in the profile have highest priority
187	priority and the values specified via C<initialise_node> have lowest	298	and the values specified directly via C<configure> have lowest priority,
188	priority.	299	and can only be used to specify defaults.
189		300
190	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
191	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
192	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
193		312
194	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
195	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
196	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
197	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
198	binds, but it can still talk to all "normal" nodes).	317	binds, but it can still talk to all "normal" nodes).
199		318
200	If the profile does not specify a binds list, then the node ID will be	319	If the profile does not specify a binds list, then a default of C<*> is
201	treated as if it were of the form C<host:port>, which will be resolved and	320	used, meaning the node will bind on a dynamically-assigned port on every
202	used as binds list.	321	local IP address it finds.
203		322
		323	=item step 3, connect to seed nodes
		324
204	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
205	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
206	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.
207		328
208	Example: become a distributed node listening on the guessed noderef, or	329	=back
209	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.
210	most common form of invocation for "daemon"-type nodes.	332	This should be the most common form of invocation for "daemon"-type nodes.
211		333
212	initialise_node;	334	configure
213		335
214	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
215	clients.	337	commandline clients.
216		338
217	initialise_node "anon/";	339	configure nodeid => "myscript/%n/%u";
218		340
219	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
220	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,
221	on the resulting addresses.	343	customary for aemp).
222		344
223	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)"
224		356
225	=item $SELF	357	=item $SELF
226		358
227	Contains the current port id while executing C<rcv> callbacks or C<psub>	359	Contains the current port id while executing C<rcv> callbacks or C<psub>
228	blocks.	360	blocks.
…		…
284		416
285	=cut	417	=cut
286		418
287	sub rcv($@);	419	sub rcv($@);
288		420
289	sub _kilme {	421	my $KILME = sub {
290	die "received message on port without callback";	422	(my $tag = substr $_[0], 0, 30) =~ s/([^\x20-\x7e])/./g;
291	}	423	kil $SELF, unhandled_message => "no callback found for message '$tag'";
		424	};
292		425
293	sub port(;&) {	426	sub port(;&) {
294	my $id = "$UNIQ." . $ID++;	427	my $id = $UNIQ . ++$ID;
295	my $port = "$NODE#$id";	428	my $port = "$NODE#$id";
296		429
297	rcv $port, shift \|\| \&_kilme;	430	rcv $port, shift \|\| $KILME;
298		431
299	$port	432	$port
300	}	433	}
301		434
302	=item rcv $local_port, $callback->(@msg)	435	=item rcv $local_port, $callback->(@msg)
…		…
307		440
308	The global C<$SELF> (exported by this module) contains C<$port> while	441	The global C<$SELF> (exported by this module) contains C<$port> while
309	executing the callback. Runtime errors during callback execution will	442	executing the callback. Runtime errors during callback execution will
310	result in the port being C<kil>ed.	443	result in the port being C<kil>ed.
311		444
312	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
313	C<tag> match.	446	C<tag> match.
314		447
315	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...	448	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
316		449
317	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
…		…
338	msg1 => sub { ... },	471	msg1 => sub { ... },
339	...	472	...
340	;	473	;
341		474
342	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
343	(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.
344		477
345	rcv $port, $otherport => sub {	478	rcv $port, $otherport => sub {
346	my @reply = @_;	479	my @reply = @_;
347		480
348	rcv $SELF, $otherport;	481	rcv $SELF, $otherport;
…		…
350		483
351	=cut	484	=cut
352		485
353	sub rcv($@) {	486	sub rcv($@) {
354	my $port = shift;	487	my $port = shift;
355	my ($noderef, $portid) = split /#/, $port, 2;	488	my ($nodeid, $portid) = split /#/, $port, 2;
356		489
357	$NODE{$noderef} == $NODE{""}	490	$nodeid eq $NODE
358	or Carp::croak "$port: rcv can only be called on local ports, caught";	491	or Carp::croak "$port: rcv can only be called on local ports, caught";
359		492
360	while (@_) {	493	while (@_) {
361	if (ref $_[0]) {	494	if (ref $_[0]) {
362	if (my $self = $PORT_DATA{$portid}) {	495	if (my $self = $PORT_DATA{$portid}) {
363	"AnyEvent::MP::Port" eq ref $self	496	"AnyEvent::MP::Port" eq ref $self
364	or Carp::croak "$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";
365		498
366	$self->[2] = shift;	499	$self->[0] = shift;
367	} else {	500	} else {
368	my $cb = shift;	501	my $cb = shift;
369	$PORT{$portid} = sub {	502	$PORT{$portid} = sub {
370	local $SELF = $port;	503	local $SELF = $port;
371	eval { &$cb }; _self_die if $@;	504	eval { &$cb }; _self_die if $@;
372	};	505	};
373	}	506	}
374	} elsif (defined $_[0]) {	507	} elsif (defined $_[0]) {
375	my $self = $PORT_DATA{$portid} \|\|= do {	508	my $self = $PORT_DATA{$portid} \|\|= do {
376	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	509	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
377		510
378	$PORT{$portid} = sub {	511	$PORT{$portid} = sub {
379	local $SELF = $port;	512	local $SELF = $port;
380		513
381	if (my $cb = $self->[1]{$_[0]}) {	514	if (my $cb = $self->[1]{$_[0]}) {
…		…
403	}	536	}
404		537
405	$port	538	$port
406	}	539	}
407		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
408	=item $closure = psub { BLOCK }	578	=item $closure = psub { BLOCK }
409		579
410	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
411	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>
412	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 }, @_ } >>.
413		586
414	This is useful when you register callbacks from C<rcv> callbacks:	587	This is useful when you register callbacks from C<rcv> callbacks:
415		588
416	rcv delayed_reply => sub {	589	rcv delayed_reply => sub {
417	my ($delay, @reply) = @_;	590	my ($delay, @reply) = @_;
…		…
441	$res	614	$res
442	}	615	}
443	}	616	}
444	}	617	}
445		618
		619	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
		620
		621	=item $guard = mon $port # kill $SELF when $port dies
		622
446	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies	623	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
447
448	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
449
450	=item $guard = mon $port # kill $SELF when $port dies
451		624
452	=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
453		626
454	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
455	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
456	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.
457		663
458	C<mon> effectively guarantees that, in the absence of hardware failures,	664	C<mon> effectively guarantees that, in the absence of hardware failures,
459	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
460	arrive, or the monitoring action will be invoked after possible message	666	arrive, or the monitoring action will be invoked after possible message
461	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
462	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
463	port). After the monitoring action was invoked, further messages might get	669	port). After the monitoring action was invoked, further messages might get
464	delivered again.	670	delivered again.
465		671
466	Note that monitoring-actions are one-shot: once messages are lost (and a	672	Inter-host-connection timeouts and monitoring depend on the transport
467	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).
468		676
469	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
470	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
471	"normally"). Note also that I<< the callback B<must> never die >>, so use	679	to ensure some maximum latency.
472	C<eval> if unsure.
473
474	In the second form (another port given), the other port (C<$rcvport>)
475	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
476	"normal" kils nothing happens, while under all other conditions, the other
477	port is killed with the same reason.
478
479	The third form (kill self) is the same as the second form, except that
480	C<$rvport> defaults to C<$SELF>.
481
482	In the last form (message), a message of the form C<@msg, @reason> will be
483	C<snd>.
484
485	As a rule of thumb, monitoring requests should always monitor a port from
486	a local port (or callback). The reason is that kill messages might get
487	lost, just like any other message. Another less obvious reason is that
488	even monitoring requests can get lost (for exmaple, when the connection
489	to the other node goes down permanently). When monitoring a port locally
490	these problems do not exist.
491		680
492	Example: call a given callback when C<$port> is killed.	681	Example: call a given callback when C<$port> is killed.
493		682
494	mon $port, sub { warn "port died because of <@_>\n" };	683	mon $port, sub { warn "port died because of <@_>\n" };
495		684
…		…
502	mon $port, $self => "restart";	691	mon $port, $self => "restart";
503		692
504	=cut	693	=cut
505		694
506	sub mon {	695	sub mon {
507	my ($noderef, $port) = split /#/, shift, 2;	696	my ($nodeid, $port) = split /#/, shift, 2;
508		697
509	my $node = $NODE{$noderef} \|\| add_node $noderef;	698	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
510		699
511	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,';
512		701
513	unless (ref $cb) {	702	unless (ref $cb) {
514	if (@_) {	703	if (@_) {
…		…
523	}	712	}
524		713
525	$node->monitor ($port, $cb);	714	$node->monitor ($port, $cb);
526		715
527	defined wantarray	716	defined wantarray
528	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	717	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
529	}	718	}
530		719
531	=item $guard = mon_guard $port, $ref, $ref...	720	=item $guard = mon_guard $port, $ref, $ref...
532		721
533	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
…		…
556		745
557	=item kil $port[, @reason]	746	=item kil $port[, @reason]
558		747
559	Kill the specified port with the given C<@reason>.	748	Kill the specified port with the given C<@reason>.
560		749
561	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" -
562	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
563	"normally").	752	(C<mon $mport, $lport> form) to get killed.
564		753
565	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>
566	C<mon>, see above).	755	form) get killed with the same reason.
567		756
568	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
569	will be reported as reason C<< die => $@ >>.	758	will be reported as reason C<< die => $@ >>.
570		759
571	Transport/communication errors are reported as C<< transport_error =>	760	Transport/communication errors are reported as C<< transport_error =>
572	$message >>.	761	$message >>.
573		762
574	=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: $!";
575		774
576	=item $port = spawn $node, $initfunc[, @initdata]	775	=item $port = spawn $node, $initfunc[, @initdata]
577		776
578	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
579	case it's the node where that port resides).	778	case it's the node where that port resides).
…		…
590	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.
591	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
592	exists or it runs out of package names.	791	exists or it runs out of package names.
593		792
594	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
595	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.
596		797
597	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
598	port, and in the remote init function, immediately monitor the passed	799	port, and in the remote init function, immediately monitor the passed
599	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
600	when there is a problem.	801	when there is a problem.
601		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
602	Example: spawn a chat server port on C<$othernode>.	807	Example: spawn a chat server port on C<$othernode>.
603		808
604	# this node, executed from within a port context:	809	# this node, executed from within a port context:
605	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	810	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
606	mon $server;	811	mon $server;
…		…
620		825
621	sub _spawn {	826	sub _spawn {
622	my $port = shift;	827	my $port = shift;
623	my $init = shift;	828	my $init = shift;
624		829
		830	# rcv will create the actual port
625	local $SELF = "$NODE#$port";	831	local $SELF = "$NODE#$port";
626	eval {	832	eval {
627	&{ load_func $init }	833	&{ load_func $init }
628	};	834	};
629	_self_die if $@;	835	_self_die if $@;
630	}	836	}
631		837
632	sub spawn(@) {	838	sub spawn(@) {
633	my ($noderef, undef) = split /#/, shift, 2;	839	my ($nodeid, undef) = split /#/, shift, 2;
634		840
635	my $id = "$RUNIQ." . $ID++;	841	my $id = $RUNIQ . ++$ID;
636		842
637	$_[0] =~ /::/	843	$_[0] =~ /::/
638	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";
639		845
640	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;	846	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
641		847
642	"$noderef#$id"	848	"$nodeid#$id"
643	}	849	}
		850
644		851
645	=item after $timeout, @msg	852	=item after $timeout, @msg
646		853
647	=item after $timeout, $callback	854	=item after $timeout, $callback
648		855
…		…
664	? $action[0]()	871	? $action[0]()
665	: snd @action;	872	: snd @action;
666	};	873	};
667	}	874	}
668		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
669	=back	1112	=back
670		1113
671	=head1 AnyEvent::MP vs. Distributed Erlang	1114	=head1 AnyEvent::MP vs. Distributed Erlang
672		1115
673	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
674	== 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
675	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
676	sample:	1119	sample:
677		1120
678	http://www.Erlang.se/doc/programming_rules.shtml	1121	http://www.erlang.se/doc/programming_rules.shtml
679	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
680	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
681	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
682		1125
683	Despite the similarities, there are also some important differences:	1126	Despite the similarities, there are also some important differences:
684		1127
685	=over 4	1128	=over 4
686		1129
687	=item * Node IDs are arbitrary strings in AEMP.	1130	=item * Node IDs are arbitrary strings in AEMP.
688		1131
689	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
690	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
691	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.
692		1136
693	=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
694	uses "local ports are like remote ports".	1138	uses "local ports are like remote ports".
695		1139
696	The failure modes for local ports are quite different (runtime errors	1140	The failure modes for local ports are quite different (runtime errors
…		…
705	ports being the special case/exception, where transport errors cannot	1149	ports being the special case/exception, where transport errors cannot
706	occur.	1150	occur.
707		1151
708	=item * Erlang uses processes and a mailbox, AEMP does not queue.	1152	=item * Erlang uses processes and a mailbox, AEMP does not queue.
709		1153
710	Erlang uses processes that selectively receive messages, and therefore	1154	Erlang uses processes that selectively receive messages out of order, and
711	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
712	useful purpose. For the same reason the pattern-matching abilities of	1156	no useful purpose. For the same reason the pattern-matching abilities
713	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
714	filter messages without dequeing them.	1158	filter messages without dequeuing them.
715		1159
716	(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.
717		1165
718	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	1166	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
719		1167
720	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
721	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
722	connection establishment is handled in the background.	1171	establishment is handled in the background.
723		1172
724	=item * Erlang suffers from silent message loss, AEMP does not.	1173	=item * Erlang suffers from silent message loss, AEMP does not.
725		1174
726	Erlang makes few guarantees on messages delivery - messages can get lost	1175	Erlang implements few guarantees on messages delivery - messages can get
727	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,
728	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).
729		1178
730	AEMP guarantees correct ordering, and the guarantee that after one message	1179	AEMP guarantees (modulo hardware errors) correct ordering, and the
731	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
732	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
733	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.
734		1188
735	=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.
736		1190
737	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
738	known to other nodes for a completely different process, causing messages	1192	process ID known to other nodes for a completely different process,
739	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.
740		1195
741	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
742	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.
743		1198
744	=item * Erlang uses unprotected connections, AEMP uses secure	1199	=item * Erlang uses unprotected connections, AEMP uses secure
745	authentication and can use TLS.	1200	authentication and can use TLS.
746		1201
…		…
749		1204
750	=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
751	communications.	1206	communications.
752		1207
753	The AEMP protocol, unlike the Erlang protocol, supports both programming	1208	The AEMP protocol, unlike the Erlang protocol, supports both programming
754	language independent text-only protocols (good for debugging) and binary,	1209	language independent text-only protocols (good for debugging), and binary,
755	language-specific serialisers (e.g. Storable). By default, unless TLS is	1210	language-specific serialisers (e.g. Storable). By default, unless TLS is
756	used, the protocol is actually completely text-based.	1211	used, the protocol is actually completely text-based.
757		1212
758	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
759	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
760	protocol simple.	1215	protocol simple.
761		1216
762	=item * AEMP has more flexible monitoring options than Erlang.	1217	=item * AEMP has more flexible monitoring options than Erlang.
763		1218
764	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
765	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
766	difficult to implement. Monitoring in AEMP is more flexible than in	1221	difficult to implement.
767	Erlang, as one can choose between automatic kill, exit message or callback	1222
768	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.
769		1225
770	=item * Erlang tries to hide remote/local connections, AEMP does not.	1226	=item * Erlang tries to hide remote/local connections, AEMP does not.
771		1227
772	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
773	same way as linking is (except linking is unreliable in Erlang).	1229	same way as linking is (except linking is unreliable in Erlang).
…		…
795	overhead, as well as having to keep a proxy object everywhere.	1251	overhead, as well as having to keep a proxy object everywhere.
796		1252
797	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
798	procedures to be "valid".	1254	procedures to be "valid".
799		1255
800	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
801	global hash - it can't become much cheaper.	1257	code reference stored in a global hash - it can't become much cheaper.
802		1258
803	=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?
804		1260
805	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
806	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
…		…
816	Keeping your messages simple, concentrating on data structures rather than	1272	Keeping your messages simple, concentrating on data structures rather than
817	objects, will keep your messages clean, tidy and efficient.	1273	objects, will keep your messages clean, tidy and efficient.
818		1274
819	=back	1275	=back
820		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
821	=head1 SEE ALSO	1385	=head1 SEE ALSO
822		1386
823	L<AnyEvent::MP::Intro> - a gentle introduction.	1387	L<AnyEvent::MP::Intro> - a gentle introduction.
824		1388
825	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.	1389	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
826		1390
827	L<AnyEvent::MP::Global> - network maintainance and port groups, to find	1391	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
828	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.
829		1398
830	L<AnyEvent>.	1399	L<AnyEvent>.
831		1400
832	=head1 AUTHOR	1401	=head1 AUTHOR
833		1402

Diff Legend

-–
+Removed lines
-+
+Added lines
-<
+Changed lines
->
+Changed lines

Comparing cvsroot/AnyEvent-MP/MP.pm (file contents): Revision 1.69 by root, Sun Aug 30 18:51:49 2009 UTC vs. Revision 1.153 by root, Sat Nov 2 01:30:49 2019 UTC

Diff Legend

Comparing cvsroot/AnyEvent-MP/MP.pm (file contents):
Revision 1.69 by root, Sun Aug 30 18:51:49 2009 UTC vs.
Revision 1.153 by root, Sat Nov 2 01:30:49 2019 UTC