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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.65 by root, Fri Aug 28 01:00:34 2009 UTC vs.
Revision 1.141 by root, Fri Mar 23 03:24:41 2012 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent::MP - multi-processing/message-passing framework	3	AnyEvent::MP - erlang-style multi-processing/message-passing framework
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use AnyEvent::MP;	7	use AnyEvent::MP;
8		8
9	$NODE # contains this node's noderef	9	$NODE # contains this node's node ID
10	NODE # returns this node's noderef	10	NODE # returns this node's node ID
11	NODE $port # returns the noderef of the port
12		11
13	$SELF # receiving/own port id in rcv callbacks	12	$SELF # receiving/own port id in rcv callbacks
14		13
15	# initialise the node so it can send/receive messages	14	# initialise the node so it can send/receive messages
16	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 - WIP	49	die "kill the port, delayed";
46	AnyEvent::MP::Transport - mostly stable	50	};
47
48	stay tuned.
49		51
50	=head1 DESCRIPTION	52	=head1 DESCRIPTION
51		53
52	This module (-family) implements a simple message passing framework.	54	This module (-family) implements a simple message passing framework.
53		55
54	Despite its simplicity, you can securely message other processes running	56	Despite its simplicity, you can securely message other processes running
55	on the same or other hosts.	57	on the same or other hosts, and you can supervise entities remotely.
56		58
57	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	59	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
58	manual page.	60	manual page and the examples under F<eg/>.
59
60	At the moment, this module family is severly broken and underdocumented,
61	so do not use. This was uploaded mainly to reserve the CPAN namespace -
62	stay tuned!
63		61
64	=head1 CONCEPTS	62	=head1 CONCEPTS
65		63
66	=over 4	64	=over 4
67		65
68	=item port	66	=item port
69		67
70	A port is something you can send messages to (with the C<snd> function).	68	Not to be confused with a TCP port, a "port" is something you can send
		69	messages to (with the C<snd> function).
71		70
72	Ports allow you to register C<rcv> handlers that can match all or just	71	Ports allow you to register C<rcv> handlers that can match all or just
73	some messages. Messages send to ports will not be queued, regardless of	72	some messages. Messages send to ports will not be queued, regardless of
74	anything was listening for them or not.	73	anything was listening for them or not.
75		74
		75	Ports are represented by (printable) strings called "port IDs".
		76
76	=item port ID - C<noderef#portname>	77	=item port ID - C<nodeid#portname>
77		78
78	A port ID is the concatenation of a noderef, a hash-mark (C<#>) as	79	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). An	80	as separator, and a port name (a printable string of unspecified
80	exception is the the node port, whose ID is identical to its node	81	format created by AnyEvent::MP).
81	reference.
82		82
83	=item node	83	=item node
84		84
85	A node is a single process containing at least one port - the node port,	85	A node is a single process containing at least one port - the node port,
86	which provides nodes to manage each other remotely, and to create new	86	which enables nodes to manage each other remotely, and to create new
87	ports.	87	ports.
88		88
89	Nodes are either private (single-process only), slaves (can only talk to	89	Nodes are either public (have one or more listening ports) or private
90	public nodes, but do not need an open port) or public nodes (connectable	90	(no listening ports). Private nodes cannot talk to other private nodes
91	from any other node).	91	currently, but all nodes can talk to public nodes.
92		92
		93	Nodes is represented by (printable) strings called "node IDs".
		94
93	=item node ID - C<[a-za-Z0-9_\-.:]+>	95	=item node ID - C<[A-Za-z0-9_\-.:]*>
94		96
95	A node ID is a string that uniquely identifies the node within a	97	A node ID is a string that uniquely identifies the node within a
96	network. Depending on the configuration used, node IDs can look like a	98	network. Depending on the configuration used, node IDs can look like a
97	hostname, a hostname and a port, or a random string. AnyEvent::MP itself	99	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
98	doesn't interpret node IDs in any way.	100	doesn't interpret node IDs in any way except to uniquely identify a node.
99		101
100	=item binds - C<ip:port>	102	=item binds - C<ip:port>
101		103
102	Nodes can only talk to each other by creating some kind of connection to	104	Nodes can only talk to each other by creating some kind of connection to
103	each other. To do this, nodes should listen on one or more local transport	105	each other. To do this, nodes should listen on one or more local transport
		106	endpoints - binds.
		107
104	endpoints - binds. Currently, only standard C<ip:port> specifications can	108	Currently, only standard C<ip:port> specifications can be used, which
105	be used, which specify TCP ports to listen on.	109	specify TCP ports to listen on. So a bind is basically just a tcp socket
		110	in listening mode thta accepts conenctions form other nodes.
106		111
		112	=item seed nodes
		113
		114	When a node starts, it knows nothing about the network it is in - it
		115	needs to connect to at least one other node that is already in the
		116	network. These other nodes are called "seed nodes".
		117
		118	Seed nodes themselves are not special - they are seed nodes only because
		119	some other node I<uses> them as such, but any node can be used as seed
		120	node for other nodes, and eahc node cna use a different set of seed nodes.
		121
		122	In addition to discovering the network, seed nodes are also used to
		123	maintain the network - all nodes using the same seed node form are part of
		124	the same network. If a network is split into multiple subnets because e.g.
		125	the network link between the parts goes down, then using the same seed
		126	nodes for all nodes ensures that eventually the subnets get merged again.
		127
		128	Seed nodes are expected to be long-running, and at least one seed node
		129	should always be available. They should also be relatively responsive - a
		130	seed node that blocks for long periods will slow down everybody else.
		131
		132	For small networks, it's best if every node uses the same set of seed
		133	nodes. For large networks, it can be useful to specify "regional" seed
		134	nodes for most nodes in an area, and use all seed nodes as seed nodes for
		135	each other. What's important is that all seed nodes connections form a
		136	complete graph, so that the network cannot split into separate subnets
		137	forever.
		138
		139	Seed nodes are represented by seed IDs.
		140
107	=item seeds - C<host:port>	141	=item seed IDs - C<host:port>
108		142
109	When a node starts, it knows nothing about the network. To teach the node	143	Seed IDs are transport endpoint(s) (usually a hostname/IP address and a
110	about the network it first has to contact some other node within the	144	TCP port) of nodes that should be used as seed nodes.
111	network. This node is called a seed.
112		145
113	Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes	146	=item global nodes
114	are expected to be long-running, and at least one of those should always	147
115	be available. When nodes run out of connections (e.g. due to a network	148	An AEMP network needs a discovery service - nodes need to know how to
116	error), they try to re-establish connections to some seednodes again to	149	connect to other nodes they only know by name. In addition, AEMP offers a
117	join the network.	150	distributed "group database", which maps group names to a list of strings
		151	- for example, to register worker ports.
		152
		153	A network needs at least one global node to work, and allows every node to
		154	be a global node.
		155
		156	Any node that loads the L<AnyEvent::MP::Global> module becomes a global
		157	node and tries to keep connections to all other nodes. So while it can
		158	make sense to make every node "global" in small networks, it usually makes
		159	sense to only make seed nodes into global nodes in large networks (nodes
		160	keep connections to seed nodes and global nodes, so makign them the same
		161	reduces overhead).
118		162
119	=back	163	=back
120		164
121	=head1 VARIABLES/FUNCTIONS	165	=head1 VARIABLES/FUNCTIONS
122		166
124		168
125	=cut	169	=cut
126		170
127	package AnyEvent::MP;	171	package AnyEvent::MP;
128		172
		173	use AnyEvent::MP::Config ();
129	use AnyEvent::MP::Kernel;	174	use AnyEvent::MP::Kernel;
		175	use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID);
130		176
131	use common::sense;	177	use common::sense;
132		178
133	use Carp ();	179	use Carp ();
134		180
135	use AE ();	181	use AnyEvent ();
		182	use Guard ();
136		183
137	use base "Exporter";	184	use base "Exporter";
138		185
139	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	186	our $VERSION = $AnyEvent::MP::Config::VERSION;
140		187
141	our @EXPORT = qw(	188	our @EXPORT = qw(
142	NODE $NODE *SELF node_of after	189	NODE $NODE *SELF node_of after
143	resolve_node initialise_node	190	configure
144	snd rcv mon mon_guard kil reg psub spawn	191	snd rcv mon mon_guard kil psub peval spawn cal
145	port	192	port
		193	db_set db_del db_reg
		194	db_mon db_family db_keys db_values
146	);	195	);
147		196
148	our $SELF;	197	our $SELF;
149		198
150	sub _self_die() {	199	sub _self_die() {
…		…
153	kil $SELF, die => $msg;	202	kil $SELF, die => $msg;
154	}	203	}
155		204
156	=item $thisnode = NODE / $NODE	205	=item $thisnode = NODE / $NODE
157		206
158	The C<NODE> function returns, and the C<$NODE> variable contains the node	207	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	208	ID of the node running in the current process. This value is initialised by
160	a call to C<initialise_node>.	209	a call to C<configure>.
161		210
162	=item $nodeid = node_of $port	211	=item $nodeid = node_of $port
163		212
164	Extracts and returns the node ID part from a port ID or a node ID.	213	Extracts and returns the node ID from a port ID or a node ID.
165		214
166	=item initialise_node $profile_name	215	=item configure $profile, key => value...
		216
		217	=item configure key => value...
167		218
168	Before a node can talk to other nodes on the network (i.e. enter	219	Before a node can talk to other nodes on the network (i.e. enter
169	"distributed mode") it has to initialise itself - the minimum a node needs	220	"distributed mode") it has to configure itself - the minimum a node needs
170	to know is its own name, and optionally it should know the addresses of	221	to know is its own name, and optionally it should know the addresses of
171	some other nodes in the network to discover other nodes.	222	some other nodes in the network to discover other nodes.
172		223
173	This function initialises a node - it must be called exactly once (or	224	This function configures a node - it must be called exactly once (or
174	never) before calling other AnyEvent::MP functions.	225	never) before calling other AnyEvent::MP functions.
175		226
176	The first argument is a profile name. If it is C<undef> or missing, then	227	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>).	228	F<aemp> command line utility (sans the set/del prefix), with these additions:
178		229
		230	=over 4
		231
		232	=item norc => $boolean (default false)
		233
		234	If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I<not>
		235	be consulted - all configuraiton options must be specified in the
		236	C<configure> call.
		237
		238	=item force => $boolean (default false)
		239
		240	IF true, then the values specified in the C<configure> will take
		241	precedence over any values configured via the rc file. The default is for
		242	the rc file to override any options specified in the program.
		243
		244	=item secure => $pass->(@msg)
		245
		246	In addition to specifying a boolean, you can specify a code reference that
		247	is called for every code execution attempt - the execution request is
		248	granted iff the callback returns a true value.
		249
		250	Most of the time the callback should look only at
		251	C<$AnyEvent::MP::Kernel::SRCNODE> to make a decision, and not at the
		252	actual message (which can be about anything, and is mostly provided for
		253	diagnostic purposes).
		254
		255	See F<semp setsecure> for more info.
		256
		257	=back
		258
		259	=over 4
		260
		261	=item step 1, gathering configuration from profiles
		262
179	The function then looks up the profile in the aemp configuration (see the	263	The function first looks up a profile in the aemp configuration (see the
180	L<aemp> commandline utility).	264	L<aemp> commandline utility). The profile name can be specified via the
		265	named C<profile> parameter or can simply be the first parameter). If it is
		266	missing, then the nodename (F<uname -n>) will be used as profile name.
		267
		268	The profile data is then gathered as follows:
		269
		270	First, all remaining key => value pairs (all of which are conveniently
		271	undocumented at the moment) will be interpreted as configuration
		272	data. Then they will be overwritten by any values specified in the global
		273	default configuration (see the F<aemp> utility), then the chain of
		274	profiles chosen by the profile name (and any C<parent> attributes).
		275
		276	That means that the values specified in the profile have highest priority
		277	and the values specified directly via C<configure> have lowest priority,
		278	and can only be used to specify defaults.
181		279
182	If the profile specifies a node ID, then this will become the node ID of	280	If the profile specifies a node ID, then this will become the node ID of
183	this process. If not, then the profile name will be used as node ID. The	281	this process. If not, then the profile name will be used as node ID, with
184	special node ID of C<anon/> will be replaced by a random node ID.	282	a unique randoms tring (C</%u>) appended.
		283
		284	The node ID can contain some C<%> sequences that are expanded: C<%n>
		285	is expanded to the local nodename, C<%u> is replaced by a random
		286	strign to make the node unique. For example, the F<aemp> commandline
		287	utility uses C<aemp/%n/%u> as nodename, which might expand to
		288	C<aemp/cerebro/ZQDGSIkRhEZQDGSIkRhE>.
		289
		290	=item step 2, bind listener sockets
185		291
186	The next step is to look up the binds in the profile, followed by binding	292	The next step is to look up the binds in the profile, followed by binding
187	aemp protocol listeners on all binds specified (it is possible and valid	293	aemp protocol listeners on all binds specified (it is possible and valid
188	to have no binds, meaning that the node cannot be contacted form the	294	to have no binds, meaning that the node cannot be contacted form the
189	outside. This means the node cannot talk to other nodes that also have no	295	outside. This means the node cannot talk to other nodes that also have no
190	binds, but it can still talk to all "normal" nodes).	296	binds, but it can still talk to all "normal" nodes).
191		297
192	If the profile does not specify a binds list, then the node ID will be	298	If the profile does not specify a binds list, then a default of C<*> is
193	treated as if it were of the form C<host:port>, which will be resolved and	299	used, meaning the node will bind on a dynamically-assigned port on every
194	used as binds list.	300	local IP address it finds.
195		301
		302	=item step 3, connect to seed nodes
		303
196	Lastly, the seeds list from the profile is passed to the	304	As the last step, the seed ID list from the profile is passed to the
197	L<AnyEvent::MP::Global> module, which will then use it to keep	305	L<AnyEvent::MP::Global> module, which will then use it to keep
198	connectivity with at least on of those seed nodes at any point in time.	306	connectivity with at least one node at any point in time.
199		307
200	Example: become a distributed node listening on the guessed noderef, or	308	=back
201	the one specified via C<aemp> for the current node. This should be the	309
		310	Example: become a distributed node using the local node name as profile.
202	most common form of invocation for "daemon"-type nodes.	311	This should be the most common form of invocation for "daemon"-type nodes.
203		312
204	initialise_node;	313	configure
205		314
206	Example: become an anonymous node. This form is often used for commandline	315	Example: become a semi-anonymous node. This form is often used for
207	clients.	316	commandline clients.
208		317
209	initialise_node "anon/";	318	configure nodeid => "myscript/%n/%u";
210		319
211	Example: become a distributed node. If there is no profile of the given	320	Example: configure a node using a profile called seed, which is suitable
212	name, or no binds list was specified, resolve C<localhost:4044> and bind	321	for a seed node as it binds on all local addresses on a fixed port (4040,
213	on the resulting addresses.	322	customary for aemp).
214		323
215	initialise_node "localhost:4044";	324	# use the aemp commandline utility
		325	# aemp profile seed binds '*:4040'
		326
		327	# then use it
		328	configure profile => "seed";
		329
		330	# or simply use aemp from the shell again:
		331	# aemp run profile seed
		332
		333	# or provide a nicer-to-remember nodeid
		334	# aemp run profile seed nodeid "$(hostname)"
216		335
217	=item $SELF	336	=item $SELF
218		337
219	Contains the current port id while executing C<rcv> callbacks or C<psub>	338	Contains the current port id while executing C<rcv> callbacks or C<psub>
220	blocks.	339	blocks.
221		340
222	=item SELF, %SELF, @SELF...	341	=item *SELF, SELF, %SELF, @SELF...
223		342
224	Due to some quirks in how perl exports variables, it is impossible to	343	Due to some quirks in how perl exports variables, it is impossible to
225	just export C<$SELF>, all the symbols called C<SELF> are exported by this	344	just export C<$SELF>, all the symbols named C<SELF> are exported by this
226	module, but only C<$SELF> is currently used.	345	module, but only C<$SELF> is currently used.
227		346
228	=item snd $port, type => @data	347	=item snd $port, type => @data
229		348
230	=item snd $port, @msg	349	=item snd $port, @msg
231		350
232	Send the given message to the given port ID, which can identify either	351	Send the given message to the given port, which can identify either a
233	a local or a remote port, and must be a port ID.	352	local or a remote port, and must be a port ID.
234		353
235	While the message can be about anything, it is highly recommended to use a	354	While the message can be almost anything, it is highly recommended to
236	string as first element (a port ID, or some word that indicates a request	355	use a string as first element (a port ID, or some word that indicates a
237	type etc.).	356	request type etc.) and to consist if only simple perl values (scalars,
		357	arrays, hashes) - if you think you need to pass an object, think again.
238		358
239	The message data effectively becomes read-only after a call to this	359	The message data logically becomes read-only after a call to this
240	function: modifying any argument is not allowed and can cause many	360	function: modifying any argument (or values referenced by them) is
241	problems.	361	forbidden, as there can be considerable time between the call to C<snd>
		362	and the time the message is actually being serialised - in fact, it might
		363	never be copied as within the same process it is simply handed to the
		364	receiving port.
242		365
243	The type of data you can transfer depends on the transport protocol: when	366	The type of data you can transfer depends on the transport protocol: when
244	JSON is used, then only strings, numbers and arrays and hashes consisting	367	JSON is used, then only strings, numbers and arrays and hashes consisting
245	of those are allowed (no objects). When Storable is used, then anything	368	of those are allowed (no objects). When Storable is used, then anything
246	that Storable can serialise and deserialise is allowed, and for the local	369	that Storable can serialise and deserialise is allowed, and for the local
247	node, anything can be passed.	370	node, anything can be passed. Best rely only on the common denominator of
		371	these.
248		372
249	=item $local_port = port	373	=item $local_port = port
250		374
251	Create a new local port object and returns its port ID. Initially it has	375	Create a new local port object and returns its port ID. Initially it has
252	no callbacks set and will throw an error when it receives messages.	376	no callbacks set and will throw an error when it receives messages.
…		…
271		395
272	=cut	396	=cut
273		397
274	sub rcv($@);	398	sub rcv($@);
275		399
276	sub _kilme {	400	my $KILME = sub {
277	die "received message on port without callback";	401	(my $tag = substr $_[0], 0, 30) =~ s/([\x20-\x7e])/./g;
278	}	402	kil $SELF, unhandled_message => "no callback found for message '$tag'";
		403	};
279		404
280	sub port(;&) {	405	sub port(;&) {
281	my $id = "$UNIQ." . $ID++;	406	my $id = $UNIQ . ++$ID;
282	my $port = "$NODE#$id";	407	my $port = "$NODE#$id";
283		408
284	rcv $port, shift \|\| \&_kilme;	409	rcv $port, shift \|\| $KILME;
285		410
286	$port	411	$port
287	}	412	}
288		413
289	=item rcv $local_port, $callback->(@msg)	414	=item rcv $local_port, $callback->(@msg)
…		…
294		419
295	The global C<$SELF> (exported by this module) contains C<$port> while	420	The global C<$SELF> (exported by this module) contains C<$port> while
296	executing the callback. Runtime errors during callback execution will	421	executing the callback. Runtime errors during callback execution will
297	result in the port being C<kil>ed.	422	result in the port being C<kil>ed.
298		423
299	The default callback received all messages not matched by a more specific	424	The default callback receives all messages not matched by a more specific
300	C<tag> match.	425	C<tag> match.
301		426
302	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...	427	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
303		428
304	Register (or replace) callbacks to be called on messages starting with the	429	Register (or replace) callbacks to be called on messages starting with the
…		…
325	msg1 => sub { ... },	450	msg1 => sub { ... },
326	...	451	...
327	;	452	;
328		453
329	Example: temporarily register a rcv callback for a tag matching some port	454	Example: temporarily register a rcv callback for a tag matching some port
330	(e.g. for a rpc reply) and unregister it after a message was received.	455	(e.g. for an rpc reply) and unregister it after a message was received.
331		456
332	rcv $port, $otherport => sub {	457	rcv $port, $otherport => sub {
333	my @reply = @_;	458	my @reply = @_;
334		459
335	rcv $SELF, $otherport;	460	rcv $SELF, $otherport;
…		…
337		462
338	=cut	463	=cut
339		464
340	sub rcv($@) {	465	sub rcv($@) {
341	my $port = shift;	466	my $port = shift;
342	my ($noderef, $portid) = split /#/, $port, 2;	467	my ($nodeid, $portid) = split /#/, $port, 2;
343		468
344	$NODE{$noderef} == $NODE{""}	469	$NODE{$nodeid} == $NODE{""}
345	or Carp::croak "$port: rcv can only be called on local ports, caught";	470	or Carp::croak "$port: rcv can only be called on local ports, caught";
346		471
347	while (@_) {	472	while (@_) {
348	if (ref $_[0]) {	473	if (ref $_[0]) {
349	if (my $self = $PORT_DATA{$portid}) {	474	if (my $self = $PORT_DATA{$portid}) {
350	"AnyEvent::MP::Port" eq ref $self	475	"AnyEvent::MP::Port" eq ref $self
351	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	476	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
352		477
353	$self->[2] = shift;	478	$self->[0] = shift;
354	} else {	479	} else {
355	my $cb = shift;	480	my $cb = shift;
356	$PORT{$portid} = sub {	481	$PORT{$portid} = sub {
357	local $SELF = $port;	482	local $SELF = $port;
358	eval { &$cb }; _self_die if $@;	483	eval { &$cb }; _self_die if $@;
359	};	484	};
360	}	485	}
361	} elsif (defined $_[0]) {	486	} elsif (defined $_[0]) {
362	my $self = $PORT_DATA{$portid} \|\|= do {	487	my $self = $PORT_DATA{$portid} \|\|= do {
363	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	488	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
364		489
365	$PORT{$portid} = sub {	490	$PORT{$portid} = sub {
366	local $SELF = $port;	491	local $SELF = $port;
367		492
368	if (my $cb = $self->[1]{$_[0]}) {	493	if (my $cb = $self->[1]{$_[0]}) {
…		…
390	}	515	}
391		516
392	$port	517	$port
393	}	518	}
394		519
		520	=item peval $port, $coderef[, @args]
		521
		522	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		523	when the code throews an exception the C<$port> will be killed.
		524
		525	Any remaining args will be passed to the callback. Any return values will
		526	be returned to the caller.
		527
		528	This is useful when you temporarily want to execute code in the context of
		529	a port.
		530
		531	Example: create a port and run some initialisation code in it's context.
		532
		533	my $port = port { ... };
		534
		535	peval $port, sub {
		536	init
		537	or die "unable to init";
		538	};
		539
		540	=cut
		541
		542	sub peval($$) {
		543	local $SELF = shift;
		544	my $cb = shift;
		545
		546	if (wantarray) {
		547	my @res = eval { &$cb };
		548	_self_die if $@;
		549	@res
		550	} else {
		551	my $res = eval { &$cb };
		552	_self_die if $@;
		553	$res
		554	}
		555	}
		556
395	=item $closure = psub { BLOCK }	557	=item $closure = psub { BLOCK }
396		558
397	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	559	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
398	closure is executed, sets up the environment in the same way as in C<rcv>	560	closure is executed, sets up the environment in the same way as in C<rcv>
399	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.	561	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		562
		563	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		564	BLOCK }, @_ } >>.
400		565
401	This is useful when you register callbacks from C<rcv> callbacks:	566	This is useful when you register callbacks from C<rcv> callbacks:
402		567
403	rcv delayed_reply => sub {	568	rcv delayed_reply => sub {
404	my ($delay, @reply) = @_;	569	my ($delay, @reply) = @_;
…		…
428	$res	593	$res
429	}	594	}
430	}	595	}
431	}	596	}
432		597
433	=item $guard = mon $port, $cb->(@reason)	598	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
434		599
435	=item $guard = mon $port, $rcvport	600	=item $guard = mon $port # kill $SELF when $port dies
436		601
437	=item $guard = mon $port	602	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
438		603
439	=item $guard = mon $port, $rcvport, @msg	604	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
440		605
441	Monitor the given port and do something when the port is killed or	606	Monitor the given port and do something when the port is killed or
442	messages to it were lost, and optionally return a guard that can be used	607	messages to it were lost, and optionally return a guard that can be used
443	to stop monitoring again.	608	to stop monitoring again.
444		609
		610	The first two forms distinguish between "normal" and "abnormal" kil's:
		611
		612	In the first form (another port given), if the C<$port> is C<kil>'ed with
		613	a non-empty reason, the other port (C<$rcvport>) will be kil'ed with the
		614	same reason. That is, on "normal" kil's nothing happens, while under all
		615	other conditions, the other port is killed with the same reason.
		616
		617	The second form (kill self) is the same as the first form, except that
		618	C<$rvport> defaults to C<$SELF>.
		619
		620	The remaining forms don't distinguish between "normal" and "abnormal" kil's
		621	- it's up to the callback or receiver to check whether the C<@reason> is
		622	empty and act accordingly.
		623
		624	In the third form (callback), the callback is simply called with any
		625	number of C<@reason> elements (empty @reason means that the port was deleted
		626	"normally"). Note also that I<< the callback B<must> never die >>, so use
		627	C<eval> if unsure.
		628
		629	In the last form (message), a message of the form C<$rcvport, @msg,
		630	@reason> will be C<snd>.
		631
		632	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		633	alert was raised), they are removed and will not trigger again, even if it
		634	turns out that the port is still alive.
		635
		636	As a rule of thumb, monitoring requests should always monitor a remote
		637	port locally (using a local C<$rcvport> or a callback). The reason is that
		638	kill messages might get lost, just like any other message. Another less
		639	obvious reason is that even monitoring requests can get lost (for example,
		640	when the connection to the other node goes down permanently). When
		641	monitoring a port locally these problems do not exist.
		642
445	C<mon> effectively guarantees that, in the absence of hardware failures,	643	C<mon> effectively guarantees that, in the absence of hardware failures,
446	that after starting the monitor, either all messages sent to the port	644	after starting the monitor, either all messages sent to the port will
447	will arrive, or the monitoring action will be invoked after possible	645	arrive, or the monitoring action will be invoked after possible message
448	message loss has been detected. No messages will be lost "in between"	646	loss has been detected. No messages will be lost "in between" (after
449	(after the first lost message no further messages will be received by the	647	the first lost message no further messages will be received by the
450	port). After the monitoring action was invoked, further messages might get	648	port). After the monitoring action was invoked, further messages might get
451	delivered again.	649	delivered again.
452		650
453	Note that monitoring-actions are one-shot: once released, they are removed	651	Inter-host-connection timeouts and monitoring depend on the transport
454	and will not trigger again.	652	used. The only transport currently implemented is TCP, and AnyEvent::MP
		653	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		654	non-idle connection, and usually around two hours for idle connections).
455		655
456	In the first form (callback), the callback is simply called with any	656	This means that monitoring is good for program errors and cleaning up
457	number of C<@reason> elements (no @reason means that the port was deleted	657	stuff eventually, but they are no replacement for a timeout when you need
458	"normally"). Note also that I<< the callback B<must> never die >>, so use	658	to ensure some maximum latency.
459	C<eval> if unsure.
460
461	In the second form (another port given), the other port (C<$rcvport>)
462	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
463	"normal" kils nothing happens, while under all other conditions, the other
464	port is killed with the same reason.
465
466	The third form (kill self) is the same as the second form, except that
467	C<$rvport> defaults to C<$SELF>.
468
469	In the last form (message), a message of the form C<@msg, @reason> will be
470	C<snd>.
471
472	As a rule of thumb, monitoring requests should always monitor a port from
473	a local port (or callback). The reason is that kill messages might get
474	lost, just like any other message. Another less obvious reason is that
475	even monitoring requests can get lost (for exmaple, when the connection
476	to the other node goes down permanently). When monitoring a port locally
477	these problems do not exist.
478		659
479	Example: call a given callback when C<$port> is killed.	660	Example: call a given callback when C<$port> is killed.
480		661
481	mon $port, sub { warn "port died because of <@_>\n" };	662	mon $port, sub { warn "port died because of <@_>\n" };
482		663
…		…
489	mon $port, $self => "restart";	670	mon $port, $self => "restart";
490		671
491	=cut	672	=cut
492		673
493	sub mon {	674	sub mon {
494	my ($noderef, $port) = split /#/, shift, 2;	675	my ($nodeid, $port) = split /#/, shift, 2;
495		676
496	my $node = $NODE{$noderef} \|\| add_node $noderef;	677	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
497		678
498	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	679	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
499		680
500	unless (ref $cb) {	681	unless (ref $cb) {
501	if (@_) {	682	if (@_) {
…		…
510	}	691	}
511		692
512	$node->monitor ($port, $cb);	693	$node->monitor ($port, $cb);
513		694
514	defined wantarray	695	defined wantarray
515	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	696	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
516	}	697	}
517		698
518	=item $guard = mon_guard $port, $ref, $ref...	699	=item $guard = mon_guard $port, $ref, $ref...
519		700
520	Monitors the given C<$port> and keeps the passed references. When the port	701	Monitors the given C<$port> and keeps the passed references. When the port
521	is killed, the references will be freed.	702	is killed, the references will be freed.
522		703
523	Optionally returns a guard that will stop the monitoring.	704	Optionally returns a guard that will stop the monitoring.
524		705
525	This function is useful when you create e.g. timers or other watchers and	706	This function is useful when you create e.g. timers or other watchers and
526	want to free them when the port gets killed:	707	want to free them when the port gets killed (note the use of C<psub>):
527		708
528	$port->rcv (start => sub {	709	$port->rcv (start => sub {
529	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	710	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
530	undef $timer if 0.9 < rand;	711	undef $timer if 0.9 < rand;
531	});	712	});
532	});	713	});
533		714
534	=cut	715	=cut
…		…
543		724
544	=item kil $port[, @reason]	725	=item kil $port[, @reason]
545		726
546	Kill the specified port with the given C<@reason>.	727	Kill the specified port with the given C<@reason>.
547		728
548	If no C<@reason> is specified, then the port is killed "normally" (linked	729	If no C<@reason> is specified, then the port is killed "normally" -
549	ports will not be kileld, or even notified).	730	monitor callback will be invoked, but the kil will not cause linked ports
		731	(C<mon $mport, $lport> form) to get killed.
550		732
551	Otherwise, linked ports get killed with the same reason (second form of	733	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
552	C<mon>, see below).	734	form) get killed with the same reason.
553		735
554	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	736	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
555	will be reported as reason C<< die => $@ >>.	737	will be reported as reason C<< die => $@ >>.
556		738
557	Transport/communication errors are reported as C<< transport_error =>	739	Transport/communication errors are reported as C<< transport_error =>
558	$message >>.	740	$message >>.
559		741
560	=cut	742	Common idioms:
		743
		744	# silently remove yourself, do not kill linked ports
		745	kil $SELF;
		746
		747	# report a failure in some detail
		748	kil $SELF, failure_mode_1 => "it failed with too high temperature";
		749
		750	# do not waste much time with killing, just die when something goes wrong
		751	open my $fh, "<file"
		752	or die "file: $!";
561		753
562	=item $port = spawn $node, $initfunc[, @initdata]	754	=item $port = spawn $node, $initfunc[, @initdata]
563		755
564	Creates a port on the node C<$node> (which can also be a port ID, in which	756	Creates a port on the node C<$node> (which can also be a port ID, in which
565	case it's the node where that port resides).	757	case it's the node where that port resides).
566		758
567	The port ID of the newly created port is return immediately, and it is	759	The port ID of the newly created port is returned immediately, and it is
568	permissible to immediately start sending messages or monitor the port.	760	possible to immediately start sending messages or to monitor the port.
569		761
570	After the port has been created, the init function is	762	After the port has been created, the init function is called on the remote
571	called. This function must be a fully-qualified function name	763	node, in the same context as a C<rcv> callback. This function must be a
572	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	764	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
573	program, use C<::name>.	765	specify a function in the main program, use C<::name>.
574		766
575	If the function doesn't exist, then the node tries to C<require>	767	If the function doesn't exist, then the node tries to C<require>
576	the package, then the package above the package and so on (e.g.	768	the package, then the package above the package and so on (e.g.
577	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	769	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
578	exists or it runs out of package names.	770	exists or it runs out of package names.
579		771
580	The init function is then called with the newly-created port as context	772	The init function is then called with the newly-created port as context
581	object (C<$SELF>) and the C<@initdata> values as arguments.	773	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		774	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		775	the port might not get created.
582		776
583	A common idiom is to pass your own port, monitor the spawned port, and	777	A common idiom is to pass a local port, immediately monitor the spawned
584	in the init function, monitor the original port. This two-way monitoring	778	port, and in the remote init function, immediately monitor the passed
585	ensures that both ports get cleaned up when there is a problem.	779	local port. This two-way monitoring ensures that both ports get cleaned up
		780	when there is a problem.
		781
		782	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		783	caller before C<spawn> returns (by delaying invocation when spawn is
		784	called for the local node).
586		785
587	Example: spawn a chat server port on C<$othernode>.	786	Example: spawn a chat server port on C<$othernode>.
588		787
589	# this node, executed from within a port context:	788	# this node, executed from within a port context:
590	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	789	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
605		804
606	sub _spawn {	805	sub _spawn {
607	my $port = shift;	806	my $port = shift;
608	my $init = shift;	807	my $init = shift;
609		808
		809	# rcv will create the actual port
610	local $SELF = "$NODE#$port";	810	local $SELF = "$NODE#$port";
611	eval {	811	eval {
612	&{ load_func $init }	812	&{ load_func $init }
613	};	813	};
614	_self_die if $@;	814	_self_die if $@;
615	}	815	}
616		816
617	sub spawn(@) {	817	sub spawn(@) {
618	my ($noderef, undef) = split /#/, shift, 2;	818	my ($nodeid, undef) = split /#/, shift, 2;
619		819
620	my $id = "$RUNIQ." . $ID++;	820	my $id = $RUNIQ . ++$ID;
621		821
622	$_[0] =~ /::/	822	$_[0] =~ /::/
623	or Carp::croak "spawn init function must be a fully-qualified name, caught";	823	or Carp::croak "spawn init function must be a fully-qualified name, caught";
624		824
625	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;	825	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
626		826
627	"$noderef#$id"	827	"$nodeid#$id"
628	}	828	}
		829
629		830
630	=item after $timeout, @msg	831	=item after $timeout, @msg
631		832
632	=item after $timeout, $callback	833	=item after $timeout, $callback
633		834
634	Either sends the given message, or call the given callback, after the	835	Either sends the given message, or call the given callback, after the
635	specified number of seconds.	836	specified number of seconds.
636		837
637	This is simply a utility function that come sin handy at times.	838	This is simply a utility function that comes in handy at times - the
		839	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		840	so it may go away in the future.
638		841
639	=cut	842	=cut
640		843
641	sub after($@) {	844	sub after($@) {
642	my ($timeout, @action) = @_;	845	my ($timeout, @action) = @_;
…		…
647	? $action[0]()	850	? $action[0]()
648	: snd @action;	851	: snd @action;
649	};	852	};
650	}	853	}
651		854
		855	#=item $cb2 = timeout $seconds, $cb[, @args]
		856
		857	=item cal $port, @msg, $callback[, $timeout]
		858
		859	A simple form of RPC - sends a message to the given C<$port> with the
		860	given contents (C<@msg>), but adds a reply port to the message.
		861
		862	The reply port is created temporarily just for the purpose of receiving
		863	the reply, and will be C<kil>ed when no longer needed.
		864
		865	A reply message sent to the port is passed to the C<$callback> as-is.
		866
		867	If an optional time-out (in seconds) is given and it is not C<undef>,
		868	then the callback will be called without any arguments after the time-out
		869	elapsed and the port is C<kil>ed.
		870
		871	If no time-out is given (or it is C<undef>), then the local port will
		872	monitor the remote port instead, so it eventually gets cleaned-up.
		873
		874	Currently this function returns the temporary port, but this "feature"
		875	might go in future versions unless you can make a convincing case that
		876	this is indeed useful for something.
		877
		878	=cut
		879
		880	sub cal(@) {
		881	my $timeout = ref $_[-1] ? undef : pop;
		882	my $cb = pop;
		883
		884	my $port = port {
		885	undef $timeout;
		886	kil $SELF;
		887	&$cb;
		888	};
		889
		890	if (defined $timeout) {
		891	$timeout = AE::timer $timeout, 0, sub {
		892	undef $timeout;
		893	kil $port;
		894	$cb->();
		895	};
		896	} else {
		897	mon $_[0], sub {
		898	kil $port;
		899	$cb->();
		900	};
		901	}
		902
		903	push @_, $port;
		904	&snd;
		905
		906	$port
		907	}
		908
		909	=back
		910
		911	=head1 DISTRIBUTED DATABASE
		912
		913	AnyEvent::MP comes with a simple distributed database. The database will
		914	be mirrored asynchronously on all global nodes. Other nodes bind to one
		915	of the global nodes for their needs. Every node has a "local database"
		916	which contains all the values that are set locally. All local databases
		917	are merged together to form the global database, which can be queried.
		918
		919	The database structure is that of a two-level hash - the database hash
		920	contains hashes which contain values, similarly to a perl hash of hashes,
		921	i.e.:
		922
		923	$DATABASE{$family}{$subkey} = $value
		924
		925	The top level hash key is called "family", and the second-level hash key
		926	is called "subkey" or simply "key".
		927
		928	The family must be alphanumeric, i.e. start with a letter and consist
		929	of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
		930	pretty much like Perl module names.
		931
		932	As the family namespace is global, it is recommended to prefix family names
		933	with the name of the application or module using it.
		934
		935	The subkeys must be non-empty strings, with no further restrictions.
		936
		937	The values should preferably be strings, but other perl scalars should
		938	work as well (such as C<undef>, arrays and hashes).
		939
		940	Every database entry is owned by one node - adding the same family/subkey
		941	combination on multiple nodes will not cause discomfort for AnyEvent::MP,
		942	but the result might be nondeterministic, i.e. the key might have
		943	different values on different nodes.
		944
		945	Different subkeys in the same family can be owned by different nodes
		946	without problems, and in fact, this is the common method to create worker
		947	pools. For example, a worker port for image scaling might do this:
		948
		949	db_set my_image_scalers => $port;
		950
		951	And clients looking for an image scaler will want to get the
		952	C<my_image_scalers> keys from time to time:
		953
		954	db_keys my_image_scalers => sub {
		955	@ports = @{ $_[0] };
		956	};
		957
		958	Or better yet, they want to monitor the database family, so they always
		959	have a reasonable up-to-date copy:
		960
		961	db_mon my_image_scalers => sub {
		962	@ports = keys %{ $_[0] };
		963	};
		964
		965	In general, you can set or delete single subkeys, but query and monitor
		966	whole families only.
		967
		968	If you feel the need to monitor or query a single subkey, try giving it
		969	it's own family.
		970
		971	=over
		972
		973	=item $guard = db_set $family => $subkey [=> $value]
		974
		975	Sets (or replaces) a key to the database - if C<$value> is omitted,
		976	C<undef> is used instead.
		977
		978	When called in non-void context, C<db_set> returns a guard that
		979	automatically calls C<db_del> when it is destroyed.
		980
		981	=item db_del $family => $subkey...
		982
		983	Deletes one or more subkeys from the database family.
		984
		985	=item $guard = db_reg $family => $port => $value
		986
		987	=item $guard = db_reg $family => $port
		988
		989	=item $guard = db_reg $family
		990
		991	Registers a port in the given family and optionally returns a guard to
		992	remove it.
		993
		994	This function basically does the same as:
		995
		996	db_set $family => $port => $value
		997
		998	Except that the port is monitored and automatically removed from the
		999	database family when it is kil'ed.
		1000
		1001	If C<$value> is missing, C<undef> is used. If C<$port> is missing, then
		1002	C<$SELF> is used.
		1003
		1004	This function is most useful to register a port in some port group (which
		1005	is just another name for a database family), and have it removed when the
		1006	port is gone. This works best when the port is a local port.
		1007
		1008	=cut
		1009
		1010	sub db_reg($$;$) {
		1011	my $family = shift;
		1012	my $port = @_ ? shift : $SELF;
		1013
		1014	my $clr = sub { db_del $family => $port };
		1015	mon $port, $clr;
		1016
		1017	db_set $family => $port => $_[0];
		1018
		1019	defined wantarray
		1020	and &Guard::guard ($clr)
		1021	}
		1022
		1023	=item db_family $family => $cb->(\%familyhash)
		1024
		1025	Queries the named database C<$family> and call the callback with the
		1026	family represented as a hash. You can keep and freely modify the hash.
		1027
		1028	=item db_keys $family => $cb->(\@keys)
		1029
		1030	Same as C<db_family>, except it only queries the family I<subkeys> and passes
		1031	them as array reference to the callback.
		1032
		1033	=item db_values $family => $cb->(\@values)
		1034
		1035	Same as C<db_family>, except it only queries the family I<values> and passes them
		1036	as array reference to the callback.
		1037
		1038	=item $guard = db_mon $family => $cb->($familyhash, \@added, \@changed, \@deleted)
		1039
		1040	Creates a monitor on the given database family. Each time a key is set
		1041	or or is deleted the callback is called with a hash containing the
		1042	database family and three lists of added, changed and deleted subkeys,
		1043	respectively. If no keys have changed then the array reference might be
		1044	C<undef> or even missing.
		1045
		1046	If not called in void context, a guard object is returned that, when
		1047	destroyed, stops the monitor.
		1048
		1049	The family hash reference and the key arrays belong to AnyEvent::MP and
		1050	B<must not be modified or stored> by the callback. When in doubt, make a
		1051	copy.
		1052
		1053	As soon as possible after the monitoring starts, the callback will be
		1054	called with the intiial contents of the family, even if it is empty,
		1055	i.e. there will always be a timely call to the callback with the current
		1056	contents.
		1057
		1058	It is possible that the callback is called with a change event even though
		1059	the subkey is already present and the value has not changed.
		1060
		1061	The monitoring stops when the guard object is destroyed.
		1062
		1063	Example: on every change to the family "mygroup", print out all keys.
		1064
		1065	my $guard = db_mon mygroup => sub {
		1066	my ($family, $a, $c, $d) = @_;
		1067	print "mygroup members: ", (join " ", keys %$family), "\n";
		1068	};
		1069
		1070	Exmaple: wait until the family "My::Module::workers" is non-empty.
		1071
		1072	my $guard; $guard = db_mon My::Module::workers => sub {
		1073	my ($family, $a, $c, $d) = @_;
		1074	return unless %$family;
		1075	undef $guard;
		1076	print "My::Module::workers now nonempty\n";
		1077	};
		1078
		1079	Example: print all changes to the family "AnyRvent::Fantasy::Module".
		1080
		1081	my $guard = db_mon AnyRvent::Fantasy::Module => sub {
		1082	my ($family, $a, $c, $d) = @_;
		1083
		1084	print "+$_=$family->{$_}\n" for @$a;
		1085	print "*$_=$family->{$_}\n" for @$c;
		1086	print "-$_=$family->{$_}\n" for @$d;
		1087	};
		1088
		1089	=cut
		1090
652	=back	1091	=back
653		1092
654	=head1 AnyEvent::MP vs. Distributed Erlang	1093	=head1 AnyEvent::MP vs. Distributed Erlang
655		1094
656	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	1095	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
657	== aemp node, Erlang process == aemp port), so many of the documents and	1096	== aemp node, Erlang process == aemp port), so many of the documents and
658	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	1097	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
659	sample:	1098	sample:
660		1099
661	http://www.Erlang.se/doc/programming_rules.shtml	1100	http://www.erlang.se/doc/programming_rules.shtml
662	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	1101	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
663	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	1102	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
664	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	1103	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
665		1104
666	Despite the similarities, there are also some important differences:	1105	Despite the similarities, there are also some important differences:
667		1106
668	=over 4	1107	=over 4
669		1108
670	=item * Node IDs are arbitrary strings in AEMP.	1109	=item * Node IDs are arbitrary strings in AEMP.
671		1110
672	Erlang relies on special naming and DNS to work everywhere in the same	1111	Erlang relies on special naming and DNS to work everywhere in the same
673	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by	1112	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
674	configuraiton or DNS), but will otherwise discover other odes itself.	1113	configuration or DNS), and possibly the addresses of some seed nodes, but
		1114	will otherwise discover other nodes (and their IDs) itself.
675		1115
676	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	1116	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
677	uses "local ports are like remote ports".	1117	uses "local ports are like remote ports".
678		1118
679	The failure modes for local ports are quite different (runtime errors	1119	The failure modes for local ports are quite different (runtime errors
…		…
688	ports being the special case/exception, where transport errors cannot	1128	ports being the special case/exception, where transport errors cannot
689	occur.	1129	occur.
690		1130
691	=item * Erlang uses processes and a mailbox, AEMP does not queue.	1131	=item * Erlang uses processes and a mailbox, AEMP does not queue.
692		1132
693	Erlang uses processes that selectively receive messages, and therefore	1133	Erlang uses processes that selectively receive messages out of order, and
694	needs a queue. AEMP is event based, queuing messages would serve no	1134	therefore needs a queue. AEMP is event based, queuing messages would serve
695	useful purpose. For the same reason the pattern-matching abilities of	1135	no useful purpose. For the same reason the pattern-matching abilities
696	AnyEvent::MP are more limited, as there is little need to be able to	1136	of AnyEvent::MP are more limited, as there is little need to be able to
697	filter messages without dequeing them.	1137	filter messages without dequeuing them.
698		1138
699	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	1139	This is not a philosophical difference, but simply stems from AnyEvent::MP
		1140	being event-based, while Erlang is process-based.
		1141
		1142	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		1143	top of AEMP and Coro threads.
700		1144
701	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	1145	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
702		1146
703	Sending messages in Erlang is synchronous and blocks the process (and	1147	Sending messages in Erlang is synchronous and blocks the process until
		1148	a conenction has been established and the message sent (and so does not
704	so does not need a queue that can overflow). AEMP sends are immediate,	1149	need a queue that can overflow). AEMP sends return immediately, connection
705	connection establishment is handled in the background.	1150	establishment is handled in the background.
706		1151
707	=item * Erlang suffers from silent message loss, AEMP does not.	1152	=item * Erlang suffers from silent message loss, AEMP does not.
708		1153
709	Erlang makes few guarantees on messages delivery - messages can get lost	1154	Erlang implements few guarantees on messages delivery - messages can get
710	without any of the processes realising it (i.e. you send messages a, b,	1155	lost without any of the processes realising it (i.e. you send messages a,
711	and c, and the other side only receives messages a and c).	1156	b, and c, and the other side only receives messages a and c).
712		1157
713	AEMP guarantees correct ordering, and the guarantee that there are no	1158	AEMP guarantees (modulo hardware errors) correct ordering, and the
		1159	guarantee that after one message is lost, all following ones sent to the
		1160	same port are lost as well, until monitoring raises an error, so there are
714	holes in the message sequence.	1161	no silent "holes" in the message sequence.
715		1162
716	=item * In Erlang, processes can be declared dead and later be found to be	1163	If you want your software to be very reliable, you have to cope with
717	alive.	1164	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
718		1165	simply tries to work better in common error cases, such as when a network
719	In Erlang it can happen that a monitored process is declared dead and	1166	link goes down.
720	linked processes get killed, but later it turns out that the process is
721	still alive - and can receive messages.
722
723	In AEMP, when port monitoring detects a port as dead, then that port will
724	eventually be killed - it cannot happen that a node detects a port as dead
725	and then later sends messages to it, finding it is still alive.
726		1167
727	=item * Erlang can send messages to the wrong port, AEMP does not.	1168	=item * Erlang can send messages to the wrong port, AEMP does not.
728		1169
729	In Erlang it is quite likely that a node that restarts reuses a process ID	1170	In Erlang it is quite likely that a node that restarts reuses an Erlang
730	known to other nodes for a completely different process, causing messages	1171	process ID known to other nodes for a completely different process,
731	destined for that process to end up in an unrelated process.	1172	causing messages destined for that process to end up in an unrelated
		1173	process.
732		1174
733	AEMP never reuses port IDs, so old messages or old port IDs floating	1175	AEMP does not reuse port IDs, so old messages or old port IDs floating
734	around in the network will not be sent to an unrelated port.	1176	around in the network will not be sent to an unrelated port.
735		1177
736	=item * Erlang uses unprotected connections, AEMP uses secure	1178	=item * Erlang uses unprotected connections, AEMP uses secure
737	authentication and can use TLS.	1179	authentication and can use TLS.
738		1180
739	AEMP can use a proven protocol - SSL/TLS - to protect connections and	1181	AEMP can use a proven protocol - TLS - to protect connections and
740	securely authenticate nodes.	1182	securely authenticate nodes.
741		1183
742	=item * The AEMP protocol is optimised for both text-based and binary	1184	=item * The AEMP protocol is optimised for both text-based and binary
743	communications.	1185	communications.
744		1186
745	The AEMP protocol, unlike the Erlang protocol, supports both	1187	The AEMP protocol, unlike the Erlang protocol, supports both programming
746	language-independent text-only protocols (good for debugging) and binary,	1188	language independent text-only protocols (good for debugging), and binary,
747	language-specific serialisers (e.g. Storable).	1189	language-specific serialisers (e.g. Storable). By default, unless TLS is
		1190	used, the protocol is actually completely text-based.
748		1191
749	It has also been carefully designed to be implementable in other languages	1192	It has also been carefully designed to be implementable in other languages
750	with a minimum of work while gracefully degrading fucntionality to make the	1193	with a minimum of work while gracefully degrading functionality to make the
751	protocol simple.	1194	protocol simple.
752		1195
753	=item * AEMP has more flexible monitoring options than Erlang.	1196	=item * AEMP has more flexible monitoring options than Erlang.
754		1197
755	In Erlang, you can chose to receive I<all> exit signals as messages	1198	In Erlang, you can chose to receive I<all> exit signals as messages or
756	or I<none>, there is no in-between, so monitoring single processes is	1199	I<none>, there is no in-between, so monitoring single Erlang processes is
757	difficult to implement. Monitoring in AEMP is more flexible than in	1200	difficult to implement.
758	Erlang, as one can choose between automatic kill, exit message or callback	1201
759	on a per-process basis.	1202	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		1203	between automatic kill, exit message or callback on a per-port basis.
760		1204
761	=item * Erlang tries to hide remote/local connections, AEMP does not.	1205	=item * Erlang tries to hide remote/local connections, AEMP does not.
762		1206
763	Monitoring in Erlang is not an indicator of process death/crashes,	1207	Monitoring in Erlang is not an indicator of process death/crashes, in the
764	as linking is (except linking is unreliable in Erlang).	1208	same way as linking is (except linking is unreliable in Erlang).
765		1209
766	In AEMP, you don't "look up" registered port names or send to named ports	1210	In AEMP, you don't "look up" registered port names or send to named ports
767	that might or might not be persistent. Instead, you normally spawn a port	1211	that might or might not be persistent. Instead, you normally spawn a port
768	on the remote node. The init function monitors the you, and you monitor	1212	on the remote node. The init function monitors you, and you monitor the
769	the remote port. Since both monitors are local to the node, they are much	1213	remote port. Since both monitors are local to the node, they are much more
770	more reliable.	1214	reliable (no need for C<spawn_link>).
771		1215
772	This also saves round-trips and avoids sending messages to the wrong port	1216	This also saves round-trips and avoids sending messages to the wrong port
773	(hard to do in Erlang).	1217	(hard to do in Erlang).
774		1218
775	=back	1219	=back
776		1220
777	=head1 RATIONALE	1221	=head1 RATIONALE
778		1222
779	=over 4	1223	=over 4
780		1224
781	=item Why strings for ports and noderefs, why not objects?	1225	=item Why strings for port and node IDs, why not objects?
782		1226
783	We considered "objects", but found that the actual number of methods	1227	We considered "objects", but found that the actual number of methods
784	thatc an be called are very low. Since port IDs and noderefs travel over	1228	that can be called are quite low. Since port and node IDs travel over
785	the network frequently, the serialising/deserialising would add lots of	1229	the network frequently, the serialising/deserialising would add lots of
786	overhead, as well as having to keep a proxy object.	1230	overhead, as well as having to keep a proxy object everywhere.
787		1231
788	Strings can easily be printed, easily serialised etc. and need no special	1232	Strings can easily be printed, easily serialised etc. and need no special
789	procedures to be "valid".	1233	procedures to be "valid".
790		1234
791	And a a miniport consists of a single closure stored in a global hash - it	1235	And as a result, a port with just a default receiver consists of a single
792	can't become much cheaper.	1236	code reference stored in a global hash - it can't become much cheaper.
793		1237
794	=item Why favour JSON, why not real serialising format such as Storable?	1238	=item Why favour JSON, why not a real serialising format such as Storable?
795		1239
796	In fact, any AnyEvent::MP node will happily accept Storable as framing	1240	In fact, any AnyEvent::MP node will happily accept Storable as framing
797	format, but currently there is no way to make a node use Storable by	1241	format, but currently there is no way to make a node use Storable by
798	default.	1242	default (although all nodes will accept it).
799		1243
800	The default framing protocol is JSON because a) JSON::XS is many times	1244	The default framing protocol is JSON because a) JSON::XS is many times
801	faster for small messages and b) most importantly, after years of	1245	faster for small messages and b) most importantly, after years of
802	experience we found that object serialisation is causing more problems	1246	experience we found that object serialisation is causing more problems
803	than it gains: Just like function calls, objects simply do not travel	1247	than it solves: Just like function calls, objects simply do not travel
804	easily over the network, mostly because they will always be a copy, so you	1248	easily over the network, mostly because they will always be a copy, so you
805	always have to re-think your design.	1249	always have to re-think your design.
806		1250
807	Keeping your messages simple, concentrating on data structures rather than	1251	Keeping your messages simple, concentrating on data structures rather than
808	objects, will keep your messages clean, tidy and efficient.	1252	objects, will keep your messages clean, tidy and efficient.
809		1253
810	=back	1254	=back
811		1255
		1256	=head1 PORTING FROM AnyEvent::MP VERSION 1.X
		1257
		1258	AEMP version 2 has a few major incompatible changes compared to version 1:
		1259
		1260	=over 4
		1261
		1262	=item AnyEvent::MP::Global no longer has group management functions.
		1263
		1264	At least not officially - the grp_* functions are still exported and might
		1265	work, but they will be removed in some later release.
		1266
		1267	AnyEvent::MP now comes with a distributed database that is more
		1268	powerful. Its database families map closely to port groups, but the API
		1269	has changed (the functions are also now exported by AnyEvent::MP). Here is
		1270	a rough porting guide:
		1271
		1272	grp_reg $group, $port # old
		1273	db_reg $group, $port # new
		1274
		1275	$list = grp_get $group # old
		1276	db_keys $group, sub { my $list = shift } # new
		1277
		1278	grp_mon $group, $cb->(\@ports, $add, $del) # old
		1279	db_mon $group, $cb->(\%ports, $add, $change, $del) # new
		1280
		1281	C<grp_reg> is a no-brainer (just replace by C<db_reg>), but C<grp_get> is
		1282	no longer instant, because the local node might not have a copy of the
		1283	group. You can either modify your code to allow for a callback, or use
		1284	C<db_mon> to keep an updated copy of the group:
		1285
		1286	my $local_group_copy;
		1287	db_mon $group => sub { $local_group_copy = $_[0] };
		1288
		1289	# now "keys %$local_group_copy" always returns the most up-to-date
		1290	# list of ports in the group.
		1291
		1292	C<grp_mon> can be replaced by C<db_mon> with minor changes - C<db_mon>
		1293	passes a hash as first argument, and an extra C<$chg> argument that can be
		1294	ignored:
		1295
		1296	db_mon $group => sub {
		1297	my ($ports, $add, $chg, $lde) = @_;
		1298	$ports = [keys %$ports];
		1299
		1300	# now $ports, $add and $del are the same as
		1301	# were originally passed by grp_mon.
		1302	...
		1303	};
		1304
		1305	=item Nodes not longer connect to all other nodes.
		1306
		1307	In AEMP 1.x, every node automatically loads the L<AnyEvent::MP::Global>
		1308	module, which in turn would create connections to all other nodes in the
		1309	network (helped by the seed nodes).
		1310
		1311	In version 2.x, global nodes still connect to all other global nodes, but
		1312	other nodes don't - now every node either is a global node itself, or
		1313	attaches itself to another global node.
		1314
		1315	If a node isn't a global node itself, then it attaches itself to one
		1316	of its seed nodes. If that seed node isn't a global node yet, it will
		1317	automatically be upgraded to a global node.
		1318
		1319	So in many cases, nothing needs to be changed - one just has to make sure
		1320	that all seed nodes are meshed together with the other seed nodes (as with
		1321	AEMP 1.x), and other nodes specify them as seed nodes. This is most easily
		1322	achieved by specifying the same set of seed nodes for all nodes in the
		1323	network.
		1324
		1325	Not opening a connection to every other node is usually an advantage,
		1326	except when you need the lower latency of an already established
		1327	connection. To ensure a node establishes a connection to another node,
		1328	you can monitor the node port (C<mon $node, ...>), which will attempt to
		1329	create the connection (and notify you when the connection fails).
		1330
		1331	=item Listener-less nodes (nodes without binds) are gone.
		1332
		1333	And are not coming back, at least not in their old form. If no C<binds>
		1334	are specified for a node, AnyEvent::MP assumes a default of C<:>.
		1335
		1336	There are vague plans to implement some form of routing domains, which
		1337	might or might not bring back listener-less nodes, but don't count on it.
		1338
		1339	The fact that most connections are now optional somewhat mitigates this,
		1340	as a node can be effectively unreachable from the outside without any
		1341	problems, as long as it isn't a global node and only reaches out to other
		1342	nodes (as opposed to being contacted from other nodes).
		1343
		1344	=item $AnyEvent::MP::Kernel::WARN has gone.
		1345
		1346	AnyEvent has acquired a logging framework (L<AnyEvent::Log>), and AEMP now
		1347	uses this, and so should your programs.
		1348
		1349	Every module now documents what kinds of messages it generates, with
		1350	AnyEvent::MP acting as a catch all.
		1351
		1352	On the positive side, this means that instead of setting
		1353	C<PERL_ANYEVENT_MP_WARNLEVEL>, you can get away by setting C<AE_VERBOSE> -
		1354	much less to type.
		1355
		1356	=back
		1357
		1358	=head1 LOGGING
		1359
		1360	AnyEvent::MP does not normally log anything by itself, but sinc eit is the
		1361	root of the contetx hierarchy for AnyEvent::MP modules, it will receive
		1362	all log messages by submodules.
		1363
812	=head1 SEE ALSO	1364	=head1 SEE ALSO
		1365
		1366	L<AnyEvent::MP::Intro> - a gentle introduction.
		1367
		1368	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		1369
		1370	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
		1371	your applications.
		1372
		1373	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		1374
		1375	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		1376	all nodes.
813		1377
814	L<AnyEvent>.	1378	L<AnyEvent>.
815		1379
816	=head1 AUTHOR	1380	=head1 AUTHOR
817		1381

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Revision 1.141 by root, Fri Mar 23 03:24:41 2012 UTC