[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 1.156 by root, Sat Oct 23 03:35:49 2021 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		51
48	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)
49		64
50	=head1 DESCRIPTION	65	=head1 DESCRIPTION
51		66
52	This module (-family) implements a simple message passing framework.	67	This module (-family) implements a simple message passing framework.
53		68
54	Despite its simplicity, you can securely message other processes running	69	Despite its simplicity, you can securely message other processes running
55	on the same or other hosts.	70	on the same or other hosts, and you can supervise entities remotely.
56		71
57	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>
58	manual page.	73	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		74
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 TCP ports, 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	whether 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<noderef#portname>	90	=item port ID - C<nodeid#portname>
77		91
78	A port ID is the concatenation of a noderef, 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). An	93	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	94	format created by AnyEvent::MP).
81	reference.
82		95
83	=item node	96	=item node
84		97
85	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,
86	which provides nodes to manage each other remotely, and to create new	99	which enables nodes to manage each other remotely, and to create new
87	ports.	100	ports.
88		101
89	Nodes are either private (single-process only), slaves (can only talk to	102	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	103	(no listening ports). Private nodes cannot talk to other private nodes
91	from any other node).	104	currently, but all nodes can talk to public nodes.
92		105
		106	Nodes is represented by (printable) strings called "node IDs".
		107
93	=item node ID - C<[a-za-Z0-9_\-.:]+>	108	=item node ID - C<[A-Za-z0-9_\-.:]*>
94		109
95	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
96	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
97	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
98	doesn't interpret node IDs in any way.	113	doesn't interpret node IDs in any way except to uniquely identify a node.
99		114
100	=item binds - C<ip:port>	115	=item binds - C<ip:port>
101		116
102	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
103	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
104	endpoints - binds. Currently, only standard C<ip:port> specifications can	121	Currently, only standard C<ip:port> specifications can be used, which
105	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.
106		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
107	=item seeds - C<host:port>	154	=item seed IDs - C<host:port>
108		155
109	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
110	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.
111	network. This node is called a seed.
112		158
113	Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes	159	=item global nodes
114	are expected to be long-running, and at least one of those should always	160
115	be available. When nodes run out of connections (e.g. due to a network	161	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	162	connect to other nodes they only know by name. In addition, AEMP offers a
117	join the network.	163	distributed "group database", which maps group names to a list of strings
		164	- for example, to register worker ports.
		165
		166	A network needs at least one global node to work, and allows every node to
		167	be a global node.
		168
		169	Any node that loads the L<AnyEvent::MP::Global> module becomes a global
		170	node and tries to keep connections to all other nodes. So while it can
		171	make sense to make every node "global" in small networks, it usually makes
		172	sense to only make seed nodes into global nodes in large networks (nodes
		173	keep connections to seed nodes and global nodes, so making them the same
		174	reduces overhead).
118		175
119	=back	176	=back
120		177
121	=head1 VARIABLES/FUNCTIONS	178	=head1 VARIABLES/FUNCTIONS
122		179
124		181
125	=cut	182	=cut
126		183
127	package AnyEvent::MP;	184	package AnyEvent::MP;
128		185
		186	use AnyEvent::MP::Config ();
129	use AnyEvent::MP::Kernel;	187	use AnyEvent::MP::Kernel;
		188	use AnyEvent::MP::Kernel qw(
		189	%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID
		190	add_node load_func
		191
		192	NODE $NODE
		193	configure
		194	node_of port_is_local
		195	snd kil
		196	db_set db_del
		197	db_mon db_family db_keys db_values
		198	);
130		199
131	use common::sense;	200	use common::sense;
132		201
133	use Carp ();	202	use Carp ();
134		203
135	use AE ();	204	use AnyEvent ();
		205	use Guard ();
136		206
137	use base "Exporter";	207	use base "Exporter";
138		208
139	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	209	our $VERSION = '2.02'; # also in MP/Config.pm
140		210
141	our @EXPORT = qw(	211	our @EXPORT = qw(
142	NODE $NODE *SELF node_of after	212	configure
143	resolve_node initialise_node	213
144	snd rcv mon mon_guard kil reg psub spawn	214	NODE $NODE
145	port	215	*SELF
		216
		217	node_of port_is_local
		218
		219	snd kil
		220	port rcv mon mon_guard psub peval spawn cal
		221	db_set db_del db_reg
		222	db_mon db_family db_keys db_values
		223
		224	after
146	);	225	);
147		226
148	our $SELF;	227	our $SELF;
149		228
150	sub _self_die() {	229	sub _self_die() {
…		…
153	kil $SELF, die => $msg;	232	kil $SELF, die => $msg;
154	}	233	}
155		234
156	=item $thisnode = NODE / $NODE	235	=item $thisnode = NODE / $NODE
157		236
158	The C<NODE> function returns, and the C<$NODE> variable contains the node	237	The C<NODE> function returns, and the C<$NODE> variable contains, the node
159	ID of the node running in the current process. This value is initialised by	238	ID of the node running in the current process. This value is initialised by
160	a call to C<initialise_node>.	239	a call to C<configure>.
161		240
162	=item $nodeid = node_of $port	241	=item $nodeid = node_of $port
163		242
164	Extracts and returns the node ID part from a port ID or a node ID.	243	Extracts and returns the node ID from a port ID or a node ID.
165		244
166	=item initialise_node $profile_name	245	=item $is_local = port_is_local $port
		246
		247	Returns true iff the port is a local port.
		248
		249	=item configure $profile, key => value...
		250
		251	=item configure key => value...
167		252
168	Before a node can talk to other nodes on the network (i.e. enter	253	Before a node can talk to other nodes on the network (i.e. enter
169	"distributed mode") it has to initialise itself - the minimum a node needs	254	"distributed mode") it has to configure itself - the minimum a node needs
170	to know is its own name, and optionally it should know the addresses of	255	to know is its own name, and optionally it should know the addresses of
171	some other nodes in the network to discover other nodes.	256	some other nodes in the network to discover other nodes.
172		257
173	This function initialises a node - it must be called exactly once (or	258	This function configures a node - it must be called exactly once (or
174	never) before calling other AnyEvent::MP functions.	259	never) before calling other AnyEvent::MP functions.
175		260
176	The first argument is a profile name. If it is C<undef> or missing, then	261	The key/value pairs are basically the same ones as documented for the
177	the current nodename will be used instead (i.e. F<uname -n>).	262	F<aemp> command line utility (sans the set/del prefix), with these additions:
178		263
		264	=over 4
		265
		266	=item norc => $boolean (default false)
		267
		268	If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I<not>
		269	be consulted - all configuration options must be specified in the
		270	C<configure> call.
		271
		272	=item force => $boolean (default false)
		273
		274	IF true, then the values specified in the C<configure> will take
		275	precedence over any values configured via the rc file. The default is for
		276	the rc file to override any options specified in the program.
		277
		278	=back
		279
		280	=over 4
		281
		282	=item step 1, gathering configuration from profiles
		283
179	The function then looks up the profile in the aemp configuration (see the	284	The function first looks up a profile in the aemp configuration (see the
180	L<aemp> commandline utility).	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.
		288
		289	The profile data is then gathered as follows:
		290
		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
		297	That means that the values specified in the profile have highest priority
		298	and the values specified directly via C<configure> have lowest priority,
		299	and can only be used to specify defaults.
181		300
182	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
183	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
184	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	string 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
185		312
186	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
187	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
188	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
189	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
190	binds, but it can still talk to all "normal" nodes).	317	binds, but it can still talk to all "normal" nodes).
191		318
192	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
193	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
194	used as binds list.	321	local IP address it finds.
195		322
		323	=item step 3, connect to seed nodes
		324
196	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
197	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
198	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.
199		328
200	Example: become a distributed node listening on the guessed noderef, or	329	=back
201	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.
202	most common form of invocation for "daemon"-type nodes.	332	This should be the most common form of invocation for "daemon"-type nodes.
203		333
204	initialise_node;	334	configure
205		335
206	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
207	clients.	337	commandline clients.
208		338
209	initialise_node "anon/";	339	configure nodeid => "myscript/%n/%u";
210		340
211	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
212	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,
213	on the resulting addresses.	343	customary for aemp).
214		344
215	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)"
216		356
217	=item $SELF	357	=item $SELF
218		358
219	Contains the current port id while executing C<rcv> callbacks or C<psub>	359	Contains the current port id while executing C<rcv> callbacks or C<psub>
220	blocks.	360	blocks.
221		361
222	=item SELF, %SELF, @SELF...	362	=item *SELF, SELF, %SELF, @SELF...
223		363
224	Due to some quirks in how perl exports variables, it is impossible to	364	Due to some quirks in how perl exports variables, it is impossible to
225	just export C<$SELF>, all the symbols called C<SELF> are exported by this	365	just export C<$SELF>, all the symbols named C<SELF> are exported by this
226	module, but only C<$SELF> is currently used.	366	module, but only C<$SELF> is currently used.
227		367
228	=item snd $port, type => @data	368	=item snd $port, type => @data
229		369
230	=item snd $port, @msg	370	=item snd $port, @msg
231		371
232	Send the given message to the given port ID, which can identify either	372	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.	373	local or a remote port, and must be a port ID.
234		374
235	While the message can be about anything, it is highly recommended to use a	375	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	376	use a string as first element (a port ID, or some word that indicates a
237	type etc.).	377	request type etc.) and to consist if only simple perl values (scalars,
		378	arrays, hashes) - if you think you need to pass an object, think again.
238		379
239	The message data effectively becomes read-only after a call to this	380	The message data logically becomes read-only after a call to this
240	function: modifying any argument is not allowed and can cause many	381	function: modifying any argument (or values referenced by them) is
241	problems.	382	forbidden, as there can be considerable time between the call to C<snd>
		383	and the time the message is actually being serialised - in fact, it might
		384	never be copied as within the same process it is simply handed to the
		385	receiving port.
242		386
243	The type of data you can transfer depends on the transport protocol: when	387	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	388	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	389	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	390	that Storable can serialise and deserialise is allowed, and for the local
247	node, anything can be passed.	391	node, anything can be passed. Best rely only on the common denominator of
		392	these.
248		393
249	=item $local_port = port	394	=item $local_port = port
250		395
251	Create a new local port object and returns its port ID. Initially it has	396	Create a new local port object and returns its port ID. Initially it has
252	no callbacks set and will throw an error when it receives messages.	397	no callbacks set and will throw an error when it receives messages.
…		…
271		416
272	=cut	417	=cut
273		418
274	sub rcv($@);	419	sub rcv($@);
275		420
276	sub _kilme {	421	my $KILME = sub {
277	die "received message on port without callback";	422	(my $tag = substr $_[0], 0, 30) =~ s/([^\x20-\x7e])/./g;
278	}	423	kil $SELF, unhandled_message => "no callback found for message '$tag'";
		424	};
279		425
280	sub port(;&) {	426	sub port(;&) {
281	my $id = "$UNIQ." . $ID++;	427	my $id = $UNIQ . ++$ID;
282	my $port = "$NODE#$id";	428	my $port = "$NODE#$id";
283		429
284	rcv $port, shift \|\| \&_kilme;	430	rcv $port, shift \|\| $KILME;
285		431
286	$port	432	$port
287	}	433	}
288		434
289	=item rcv $local_port, $callback->(@msg)	435	=item rcv $local_port, $callback->(@msg)
…		…
294		440
295	The global C<$SELF> (exported by this module) contains C<$port> while	441	The global C<$SELF> (exported by this module) contains C<$port> while
296	executing the callback. Runtime errors during callback execution will	442	executing the callback. Runtime errors during callback execution will
297	result in the port being C<kil>ed.	443	result in the port being C<kil>ed.
298		444
299	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
300	C<tag> match.	446	C<tag> match.
301		447
302	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...	448	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
303		449
304	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
…		…
325	msg1 => sub { ... },	471	msg1 => sub { ... },
326	...	472	...
327	;	473	;
328		474
329	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
330	(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.
331		477
332	rcv $port, $otherport => sub {	478	rcv $port, $otherport => sub {
333	my @reply = @_;	479	my @reply = @_;
334		480
335	rcv $SELF, $otherport;	481	rcv $SELF, $otherport;
…		…
337		483
338	=cut	484	=cut
339		485
340	sub rcv($@) {	486	sub rcv($@) {
341	my $port = shift;	487	my $port = shift;
342	my ($noderef, $portid) = split /#/, $port, 2;	488	my ($nodeid, $portid) = split /#/, $port, 2;
343		489
344	$NODE{$noderef} == $NODE{""}	490	$nodeid eq $NODE
345	or Carp::croak "$port: rcv can only be called on local ports, caught";	491	or Carp::croak "$port: rcv can only be called on local ports, caught";
346		492
347	while (@_) {	493	while (@_) {
348	if (ref $_[0]) {	494	if (ref $_[0]) {
349	if (my $self = $PORT_DATA{$portid}) {	495	if (my $self = $PORT_DATA{$portid}) {
350	"AnyEvent::MP::Port" eq ref $self	496	"AnyEvent::MP::Port" eq ref $self
351	or Carp::croak "$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";
352		498
353	$self->[2] = shift;	499	$self->[0] = shift;
354	} else {	500	} else {
355	my $cb = shift;	501	my $cb = shift;
356	$PORT{$portid} = sub {	502	$PORT{$portid} = sub {
357	local $SELF = $port;	503	local $SELF = $port;
358	eval { &$cb }; _self_die if $@;	504	eval { &$cb }; _self_die if $@;
359	};	505	};
360	}	506	}
361	} elsif (defined $_[0]) {	507	} elsif (defined $_[0]) {
362	my $self = $PORT_DATA{$portid} \|\|= do {	508	my $self = $PORT_DATA{$portid} \|\|= do {
363	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	509	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
364		510
365	$PORT{$portid} = sub {	511	$PORT{$portid} = sub {
366	local $SELF = $port;	512	local $SELF = $port;
367		513
368	if (my $cb = $self->[1]{$_[0]}) {	514	if (my $cb = $self->[1]{$_[0]}) {
…		…
390	}	536	}
391		537
392	$port	538	$port
393	}	539	}
394		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
395	=item $closure = psub { BLOCK }	578	=item $closure = psub { BLOCK }
396		579
397	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
398	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>
399	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 }, @_ } >>.
400		586
401	This is useful when you register callbacks from C<rcv> callbacks:	587	This is useful when you register callbacks from C<rcv> callbacks:
402		588
403	rcv delayed_reply => sub {	589	rcv delayed_reply => sub {
404	my ($delay, @reply) = @_;	590	my ($delay, @reply) = @_;
…		…
428	$res	614	$res
429	}	615	}
430	}	616	}
431	}	617	}
432		618
433	=item $guard = mon $port, $cb->(@reason)	619	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
434		620
435	=item $guard = mon $port, $rcvport	621	=item $guard = mon $port # kill $SELF when $port dies
436		622
437	=item $guard = mon $port	623	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
438		624
439	=item $guard = mon $port, $rcvport, @msg	625	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
440		626
441	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
442	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
443	to stop monitoring again.	629	to stop monitoring again.
444		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 (but monitoring actions added after
		656	that will again trigger).
		657
		658	As a rule of thumb, monitoring requests should always monitor a remote
		659	port locally (using a local C<$rcvport> or a callback). The reason is that
		660	kill messages might get lost, just like any other message. Another less
		661	obvious reason is that even monitoring requests can get lost (for example,
		662	when the connection to the other node goes down permanently). When
		663	monitoring a port locally these problems do not exist.
		664
445	C<mon> effectively guarantees that, in the absence of hardware failures,	665	C<mon> effectively guarantees that, in the absence of hardware failures,
446	that after starting the monitor, either all messages sent to the port	666	after starting the monitor, either all messages sent to the port will
447	will arrive, or the monitoring action will be invoked after possible	667	arrive, or the monitoring action will be invoked after possible message
448	message loss has been detected. No messages will be lost "in between"	668	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	669	the first lost message no further messages will be received by the
450	port). After the monitoring action was invoked, further messages might get	670	port). After the monitoring action was invoked, further messages might get
451	delivered again.	671	delivered again.
452		672
453	Note that monitoring-actions are one-shot: once released, they are removed	673	Inter-host-connection timeouts and monitoring depend on the transport
454	and will not trigger again.	674	used. The only transport currently implemented is TCP, and AnyEvent::MP
		675	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		676	non-idle connection, and usually around two hours for idle connections).
455		677
456	In the first form (callback), the callback is simply called with any	678	This means that monitoring is good for program errors and cleaning up
457	number of C<@reason> elements (no @reason means that the port was deleted	679	stuff eventually, but they are no replacement for a timeout when you need
458	"normally"). Note also that I<< the callback B<must> never die >>, so use	680	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		681
479	Example: call a given callback when C<$port> is killed.	682	Example: call a given callback when C<$port> is killed.
480		683
481	mon $port, sub { warn "port died because of <@_>\n" };	684	mon $port, sub { warn "port died because of <@_>\n" };
482		685
…		…
489	mon $port, $self => "restart";	692	mon $port, $self => "restart";
490		693
491	=cut	694	=cut
492		695
493	sub mon {	696	sub mon {
494	my ($noderef, $port) = split /#/, shift, 2;	697	my ($nodeid, $port) = split /#/, shift, 2;
495		698
496	my $node = $NODE{$noderef} \|\| add_node $noderef;	699	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
497		700
498	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	701	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
499		702
500	unless (ref $cb) {	703	unless (ref $cb) {
501	if (@_) {	704	if (@_) {
…		…
510	}	713	}
511		714
512	$node->monitor ($port, $cb);	715	$node->monitor ($port, $cb);
513		716
514	defined wantarray	717	defined wantarray
515	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	718	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
516	}	719	}
517		720
518	=item $guard = mon_guard $port, $ref, $ref...	721	=item $guard = mon_guard $port, $ref, $ref...
519		722
520	Monitors the given C<$port> and keeps the passed references. When the port	723	Monitors the given C<$port> and keeps the passed references. When the port
521	is killed, the references will be freed.	724	is killed, the references will be freed.
522		725
523	Optionally returns a guard that will stop the monitoring.	726	Optionally returns a guard that will stop the monitoring.
524		727
525	This function is useful when you create e.g. timers or other watchers and	728	This function is useful when you create e.g. timers or other watchers and
526	want to free them when the port gets killed:	729	want to free them when the port gets killed (note the use of C<psub>):
527		730
528	$port->rcv (start => sub {	731	$port->rcv (start => sub {
529	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	732	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
530	undef $timer if 0.9 < rand;	733	undef $timer if 0.9 < rand;
531	});	734	});
532	});	735	});
533		736
534	=cut	737	=cut
…		…
543		746
544	=item kil $port[, @reason]	747	=item kil $port[, @reason]
545		748
546	Kill the specified port with the given C<@reason>.	749	Kill the specified port with the given C<@reason>.
547		750
548	If no C<@reason> is specified, then the port is killed "normally" (linked	751	If no C<@reason> is specified, then the port is killed "normally" -
549	ports will not be kileld, or even notified).	752	monitor callback will be invoked, but the kil will not cause linked ports
		753	(C<mon $mport, $lport> form) to get killed.
550		754
551	Otherwise, linked ports get killed with the same reason (second form of	755	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
552	C<mon>, see below).	756	form) get killed with the same reason.
553		757
554	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	758	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
555	will be reported as reason C<< die => $@ >>.	759	will be reported as reason C<< die => $@ >>.
556		760
557	Transport/communication errors are reported as C<< transport_error =>	761	Transport/communication errors are reported as C<< transport_error =>
558	$message >>.	762	$message >>.
559		763
560	=cut	764	Common idioms:
		765
		766	# silently remove yourself, do not kill linked ports
		767	kil $SELF;
		768
		769	# report a failure in some detail
		770	kil $SELF, failure_mode_1 => "it failed with too high temperature";
		771
		772	# do not waste much time with killing, just die when something goes wrong
		773	open my $fh, "<file"
		774	or die "file: $!";
561		775
562	=item $port = spawn $node, $initfunc[, @initdata]	776	=item $port = spawn $node, $initfunc[, @initdata]
563		777
564	Creates a port on the node C<$node> (which can also be a port ID, in which	778	Creates a port on the node C<$node> (which can also be a port ID, in which
565	case it's the node where that port resides).	779	case it's the node where that port resides).
566		780
567	The port ID of the newly created port is return immediately, and it is	781	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.	782	possible to immediately start sending messages or to monitor the port.
569		783
570	After the port has been created, the init function is	784	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	785	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	786	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
573	program, use C<::name>.	787	specify a function in the main program, use C<::name>.
574		788
575	If the function doesn't exist, then the node tries to C<require>	789	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.	790	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	791	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
578	exists or it runs out of package names.	792	exists or it runs out of package names.
579		793
580	The init function is then called with the newly-created port as context	794	The init function is then called with the newly-created port as context
581	object (C<$SELF>) and the C<@initdata> values as arguments.	795	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		796	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		797	the port might not get created.
582		798
583	A common idiom is to pass your own port, monitor the spawned port, and	799	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	800	port, and in the remote init function, immediately monitor the passed
585	ensures that both ports get cleaned up when there is a problem.	801	local port. This two-way monitoring ensures that both ports get cleaned up
		802	when there is a problem.
		803
		804	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		805	caller before C<spawn> returns (by delaying invocation when spawn is
		806	called for the local node).
586		807
587	Example: spawn a chat server port on C<$othernode>.	808	Example: spawn a chat server port on C<$othernode>.
588		809
589	# this node, executed from within a port context:	810	# this node, executed from within a port context:
590	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	811	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
605		826
606	sub _spawn {	827	sub _spawn {
607	my $port = shift;	828	my $port = shift;
608	my $init = shift;	829	my $init = shift;
609		830
		831	# rcv will create the actual port
610	local $SELF = "$NODE#$port";	832	local $SELF = "$NODE#$port";
611	eval {	833	eval {
612	&{ load_func $init }	834	&{ load_func $init }
613	};	835	};
614	_self_die if $@;	836	_self_die if $@;
615	}	837	}
616		838
617	sub spawn(@) {	839	sub spawn(@) {
618	my ($noderef, undef) = split /#/, shift, 2;	840	my ($nodeid, undef) = split /#/, shift, 2;
619		841
620	my $id = "$RUNIQ." . $ID++;	842	my $id = $RUNIQ . ++$ID;
621		843
622	$_[0] =~ /::/	844	$_[0] =~ /::/
623	or Carp::croak "spawn init function must be a fully-qualified name, caught";	845	or Carp::croak "spawn init function must be a fully-qualified name, caught";
624		846
625	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;	847	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
626		848
627	"$noderef#$id"	849	"$nodeid#$id"
628	}	850	}
		851
629		852
630	=item after $timeout, @msg	853	=item after $timeout, @msg
631		854
632	=item after $timeout, $callback	855	=item after $timeout, $callback
633		856
634	Either sends the given message, or call the given callback, after the	857	Either sends the given message, or call the given callback, after the
635	specified number of seconds.	858	specified number of seconds.
636		859
637	This is simply a utility function that come sin handy at times.	860	This is simply a utility function that comes in handy at times - the
		861	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		862	so it may go away in the future.
638		863
639	=cut	864	=cut
640		865
641	sub after($@) {	866	sub after($@) {
642	my ($timeout, @action) = @_;	867	my ($timeout, @action) = @_;
…		…
647	? $action[0]()	872	? $action[0]()
648	: snd @action;	873	: snd @action;
649	};	874	};
650	}	875	}
651		876
		877	#=item $cb2 = timeout $seconds, $cb[, @args]
		878
		879	=item cal $port, @msg, $callback[, $timeout]
		880
		881	A simple form of RPC - sends a message to the given C<$port> with the
		882	given contents (C<@msg>), but appends a reply port to the message.
		883
		884	The reply port is created temporarily just for the purpose of receiving
		885	the reply, and will be C<kil>ed when no longer needed.
		886
		887	A reply message sent to the port is passed to the C<$callback> as-is.
		888
		889	If an optional time-out (in seconds) is given and it is not C<undef>,
		890	then the callback will be called without any arguments after the time-out
		891	elapsed and the port is C<kil>ed.
		892
		893	If no time-out is given (or it is C<undef>), then the local port will
		894	monitor the remote port instead, so it eventually gets cleaned-up.
		895
		896	Currently this function returns the temporary port, but this "feature"
		897	might go in future versions unless you can make a convincing case that
		898	this is indeed useful for something.
		899
		900	=cut
		901
		902	sub cal(@) {
		903	my $timeout = ref $_[-1] ? undef : pop;
		904	my $cb = pop;
		905
		906	my $port = port {
		907	undef $timeout;
		908	kil $SELF;
		909	&$cb;
		910	};
		911
		912	if (defined $timeout) {
		913	$timeout = AE::timer $timeout, 0, sub {
		914	undef $timeout;
		915	kil $port;
		916	$cb->();
		917	};
		918	} else {
		919	mon $_[0], sub {
		920	kil $port;
		921	$cb->();
		922	};
		923	}
		924
		925	push @_, $port;
		926	&snd;
		927
		928	$port
		929	}
		930
		931	=back
		932
		933	=head1 DISTRIBUTED DATABASE
		934
		935	AnyEvent::MP comes with a simple distributed database. The database will
		936	be mirrored asynchronously on all global nodes. Other nodes bind to one
		937	of the global nodes for their needs. Every node has a "local database"
		938	which contains all the values that are set locally. All local databases
		939	are merged together to form the global database, which can be queried.
		940
		941	The database structure is that of a two-level hash - the database hash
		942	contains hashes which contain values, similarly to a perl hash of hashes,
		943	i.e.:
		944
		945	$DATABASE{$family}{$subkey} = $value
		946
		947	The top level hash key is called "family", and the second-level hash key
		948	is called "subkey" or simply "key".
		949
		950	The family must be alphanumeric, i.e. start with a letter and consist
		951	of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
		952	pretty much like Perl module names.
		953
		954	As the family namespace is global, it is recommended to prefix family names
		955	with the name of the application or module using it.
		956
		957	The subkeys must be non-empty strings, with no further restrictions.
		958
		959	The values should preferably be strings, but other perl scalars should
		960	work as well (such as C<undef>, arrays and hashes).
		961
		962	Every database entry is owned by one node - adding the same family/subkey
		963	combination on multiple nodes will not cause discomfort for AnyEvent::MP,
		964	but the result might be nondeterministic, i.e. the key might have
		965	different values on different nodes.
		966
		967	Different subkeys in the same family can be owned by different nodes
		968	without problems, and in fact, this is the common method to create worker
		969	pools. For example, a worker port for image scaling might do this:
		970
		971	db_set my_image_scalers => $port; # value not used
		972
		973	And clients looking for an image scaler will want to get the
		974	C<my_image_scalers> keys from time to time:
		975
		976	db_keys my_image_scalers => sub {
		977	@ports = @{ $_[0] };
		978	};
		979
		980	Or better yet, they want to monitor the database family, so they always
		981	have a reasonable up-to-date copy:
		982
		983	db_mon my_image_scalers => sub {
		984	@ports = keys %{ $_[0] };
		985	};
		986
		987	In general, you can set or delete single subkeys, but query and monitor
		988	whole families only.
		989
		990	If you feel the need to monitor or query a single subkey, try giving it
		991	it's own family.
		992
		993	=over
		994
		995	=item $guard = db_set $family => $subkey [=> $value]
		996
		997	Sets (or replaces) a key to the database - if C<$value> is omitted,
		998	C<undef> is used instead.
		999
		1000	When called in non-void context, C<db_set> returns a guard that
		1001	automatically calls C<db_del> when it is destroyed.
		1002
		1003	=item db_del $family => $subkey...
		1004
		1005	Deletes one or more subkeys from the database family.
		1006
		1007	=item $guard = db_reg $family => $port => $value
		1008
		1009	=item $guard = db_reg $family => $port
		1010
		1011	=item $guard = db_reg $family
		1012
		1013	Registers a port in the given family and optionally returns a guard to
		1014	remove it.
		1015
		1016	This function basically does the same as:
		1017
		1018	db_set $family => $port => $value
		1019
		1020	Except that the port is monitored and automatically removed from the
		1021	database family when it is kil'ed.
		1022
		1023	If C<$value> is missing, C<undef> is used. If C<$port> is missing, then
		1024	C<$SELF> is used.
		1025
		1026	This function is most useful to register a port in some port group (which
		1027	is just another name for a database family), and have it removed when the
		1028	port is gone. This works best when the port is a local port.
		1029
		1030	=cut
		1031
		1032	sub db_reg($$;$) {
		1033	my $family = shift;
		1034	my $port = @_ ? shift : $SELF;
		1035
		1036	my $clr = sub { db_del $family => $port };
		1037	mon $port, $clr;
		1038
		1039	db_set $family => $port => $_[0];
		1040
		1041	defined wantarray
		1042	and &Guard::guard ($clr)
		1043	}
		1044
		1045	=item db_family $family => $cb->(\%familyhash)
		1046
		1047	Queries the named database C<$family> and call the callback with the
		1048	family represented as a hash. You can keep and freely modify the hash.
		1049
		1050	=item db_keys $family => $cb->(\@keys)
		1051
		1052	Same as C<db_family>, except it only queries the family I<subkeys> and passes
		1053	them as array reference to the callback.
		1054
		1055	=item db_values $family => $cb->(\@values)
		1056
		1057	Same as C<db_family>, except it only queries the family I<values> and passes them
		1058	as array reference to the callback.
		1059
		1060	=item $guard = db_mon $family => $cb->(\%familyhash, \@added, \@changed, \@deleted)
		1061
		1062	Creates a monitor on the given database family. Each time a key is
		1063	set or is deleted the callback is called with a hash containing the
		1064	database family and three lists of added, changed and deleted subkeys,
		1065	respectively. If no keys have changed then the array reference might be
		1066	C<undef> or even missing.
		1067
		1068	If not called in void context, a guard object is returned that, when
		1069	destroyed, stops the monitor.
		1070
		1071	The family hash reference and the key arrays belong to AnyEvent::MP and
		1072	B<must not be modified or stored> by the callback. When in doubt, make a
		1073	copy.
		1074
		1075	As soon as possible after the monitoring starts, the callback will be
		1076	called with the intiial contents of the family, even if it is empty,
		1077	i.e. there will always be a timely call to the callback with the current
		1078	contents.
		1079
		1080	It is possible that the callback is called with a change event even though
		1081	the subkey is already present and the value has not changed.
		1082
		1083	The monitoring stops when the guard object is destroyed.
		1084
		1085	Example: on every change to the family "mygroup", print out all keys.
		1086
		1087	my $guard = db_mon mygroup => sub {
		1088	my ($family, $a, $c, $d) = @_;
		1089	print "mygroup members: ", (join " ", keys %$family), "\n";
		1090	};
		1091
		1092	Exmaple: wait until the family "My::Module::workers" is non-empty.
		1093
		1094	my $guard; $guard = db_mon My::Module::workers => sub {
		1095	my ($family, $a, $c, $d) = @_;
		1096	return unless %$family;
		1097	undef $guard;
		1098	print "My::Module::workers now nonempty\n";
		1099	};
		1100
		1101	Example: print all changes to the family "AnyEvent::Fantasy::Module".
		1102
		1103	my $guard = db_mon AnyEvent::Fantasy::Module => sub {
		1104	my ($family, $a, $c, $d) = @_;
		1105
		1106	print "+$_=$family->{$_}\n" for @$a;
		1107	print "*$_=$family->{$_}\n" for @$c;
		1108	print "-$_=$family->{$_}\n" for @$d;
		1109	};
		1110
		1111	=cut
		1112
652	=back	1113	=back
653		1114
654	=head1 AnyEvent::MP vs. Distributed Erlang	1115	=head1 AnyEvent::MP vs. Distributed Erlang
655		1116
656	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	1117	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
657	== aemp node, Erlang process == aemp port), so many of the documents and	1118	== aemp node, Erlang process == aemp port), so many of the documents and
658	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	1119	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
659	sample:	1120	sample:
660		1121
661	http://www.Erlang.se/doc/programming_rules.shtml	1122	http://www.erlang.se/doc/programming_rules.shtml
662	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	1123	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
663	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	1124	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
664	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	1125	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
665		1126
666	Despite the similarities, there are also some important differences:	1127	Despite the similarities, there are also some important differences:
667		1128
668	=over 4	1129	=over 4
669		1130
670	=item * Node IDs are arbitrary strings in AEMP.	1131	=item * Node IDs are arbitrary strings in AEMP.
671		1132
672	Erlang relies on special naming and DNS to work everywhere in the same	1133	Erlang relies on special naming and DNS to work everywhere in the same
673	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by	1134	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
674	configuraiton or DNS), but will otherwise discover other odes itself.	1135	configuration or DNS), and possibly the addresses of some seed nodes, but
		1136	will otherwise discover other nodes (and their IDs) itself.
675		1137
676	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	1138	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
677	uses "local ports are like remote ports".	1139	uses "local ports are like remote ports".
678		1140
679	The failure modes for local ports are quite different (runtime errors	1141	The failure modes for local ports are quite different (runtime errors
…		…
688	ports being the special case/exception, where transport errors cannot	1150	ports being the special case/exception, where transport errors cannot
689	occur.	1151	occur.
690		1152
691	=item * Erlang uses processes and a mailbox, AEMP does not queue.	1153	=item * Erlang uses processes and a mailbox, AEMP does not queue.
692		1154
693	Erlang uses processes that selectively receive messages, and therefore	1155	Erlang uses processes that selectively receive messages out of order, and
694	needs a queue. AEMP is event based, queuing messages would serve no	1156	therefore needs a queue. AEMP is event based, queuing messages would serve
695	useful purpose. For the same reason the pattern-matching abilities of	1157	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	1158	of AnyEvent::MP are more limited, as there is little need to be able to
697	filter messages without dequeing them.	1159	filter messages without dequeuing them.
698		1160
699	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	1161	This is not a philosophical difference, but simply stems from AnyEvent::MP
		1162	being event-based, while Erlang is process-based.
		1163
		1164	You can have a look at L<Coro::MP> for a more Erlang-like process model on
		1165	top of AEMP and Coro threads.
700		1166
701	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	1167	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
702		1168
703	Sending messages in Erlang is synchronous and blocks the process (and	1169	Sending messages in Erlang is synchronous and blocks the process until
		1170	a connection has been established and the message sent (and so does not
704	so does not need a queue that can overflow). AEMP sends are immediate,	1171	need a queue that can overflow). AEMP sends return immediately, connection
705	connection establishment is handled in the background.	1172	establishment is handled in the background.
706		1173
707	=item * Erlang suffers from silent message loss, AEMP does not.	1174	=item * Erlang suffers from silent message loss, AEMP does not.
708		1175
709	Erlang makes few guarantees on messages delivery - messages can get lost	1176	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,	1177	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).	1178	b, and c, and the other side only receives messages a and c).
712		1179
713	AEMP guarantees correct ordering, and the guarantee that there are no	1180	AEMP guarantees (modulo hardware errors) correct ordering, and the
		1181	guarantee that after one message is lost, all following ones sent to the
		1182	same port are lost as well, until monitoring raises an error, so there are
714	holes in the message sequence.	1183	no silent "holes" in the message sequence.
715		1184
716	=item * In Erlang, processes can be declared dead and later be found to be	1185	If you want your software to be very reliable, you have to cope with
717	alive.	1186	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
718		1187	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	1188	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		1189
727	=item * Erlang can send messages to the wrong port, AEMP does not.	1190	=item * Erlang can send messages to the wrong port, AEMP does not.
728		1191
729	In Erlang it is quite likely that a node that restarts reuses a process ID	1192	In Erlang it is quite likely that a node that restarts reuses an Erlang
730	known to other nodes for a completely different process, causing messages	1193	process ID known to other nodes for a completely different process,
731	destined for that process to end up in an unrelated process.	1194	causing messages destined for that process to end up in an unrelated
		1195	process.
732		1196
733	AEMP never reuses port IDs, so old messages or old port IDs floating	1197	AEMP does not reuse port IDs, so old messages or old port IDs floating
734	around in the network will not be sent to an unrelated port.	1198	around in the network will not be sent to an unrelated port.
735		1199
736	=item * Erlang uses unprotected connections, AEMP uses secure	1200	=item * Erlang uses unprotected connections, AEMP uses secure
737	authentication and can use TLS.	1201	authentication and can use TLS.
738		1202
739	AEMP can use a proven protocol - SSL/TLS - to protect connections and	1203	AEMP can use a proven protocol - TLS - to protect connections and
740	securely authenticate nodes.	1204	securely authenticate nodes.
741		1205
742	=item * The AEMP protocol is optimised for both text-based and binary	1206	=item * The AEMP protocol is optimised for both text-based and binary
743	communications.	1207	communications.
744		1208
745	The AEMP protocol, unlike the Erlang protocol, supports both	1209	The AEMP protocol, unlike the Erlang protocol, supports both programming
746	language-independent text-only protocols (good for debugging) and binary,	1210	language independent text-only protocols (good for debugging), and binary,
747	language-specific serialisers (e.g. Storable).	1211	language-specific serialisers (e.g. Storable). By default, unless TLS is
		1212	used, the protocol is actually completely text-based.
748		1213
749	It has also been carefully designed to be implementable in other languages	1214	It has also been carefully designed to be implementable in other languages
750	with a minimum of work while gracefully degrading fucntionality to make the	1215	with a minimum of work while gracefully degrading functionality to make the
751	protocol simple.	1216	protocol simple.
752		1217
753	=item * AEMP has more flexible monitoring options than Erlang.	1218	=item * AEMP has more flexible monitoring options than Erlang.
754		1219
755	In Erlang, you can chose to receive I<all> exit signals as messages	1220	In Erlang, you can chose to receive I<all> exit signals as messages or
756	or I<none>, there is no in-between, so monitoring single processes is	1221	I<none>, there is no in-between, so monitoring single Erlang processes is
757	difficult to implement. Monitoring in AEMP is more flexible than in	1222	difficult to implement.
758	Erlang, as one can choose between automatic kill, exit message or callback	1223
759	on a per-process basis.	1224	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		1225	between automatic kill, exit message or callback on a per-port basis.
760		1226
761	=item * Erlang tries to hide remote/local connections, AEMP does not.	1227	=item * Erlang tries to hide remote/local connections, AEMP does not.
762		1228
763	Monitoring in Erlang is not an indicator of process death/crashes,	1229	Monitoring in Erlang is not an indicator of process death/crashes, in the
764	as linking is (except linking is unreliable in Erlang).	1230	same way as linking is (except linking is unreliable in Erlang).
765		1231
766	In AEMP, you don't "look up" registered port names or send to named ports	1232	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	1233	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	1234	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	1235	remote port. Since both monitors are local to the node, they are much more
770	more reliable.	1236	reliable (no need for C<spawn_link>).
771		1237
772	This also saves round-trips and avoids sending messages to the wrong port	1238	This also saves round-trips and avoids sending messages to the wrong port
773	(hard to do in Erlang).	1239	(hard to do in Erlang).
774		1240
775	=back	1241	=back
776		1242
777	=head1 RATIONALE	1243	=head1 RATIONALE
778		1244
779	=over 4	1245	=over 4
780		1246
781	=item Why strings for ports and noderefs, why not objects?	1247	=item Why strings for port and node IDs, why not objects?
782		1248
783	We considered "objects", but found that the actual number of methods	1249	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	1250	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	1251	the network frequently, the serialising/deserialising would add lots of
786	overhead, as well as having to keep a proxy object.	1252	overhead, as well as having to keep a proxy object everywhere.
787		1253
788	Strings can easily be printed, easily serialised etc. and need no special	1254	Strings can easily be printed, easily serialised etc. and need no special
789	procedures to be "valid".	1255	procedures to be "valid".
790		1256
791	And a a miniport consists of a single closure stored in a global hash - it	1257	And as a result, a port with just a default receiver consists of a single
792	can't become much cheaper.	1258	code reference stored in a global hash - it can't become much cheaper.
793		1259
794	=item Why favour JSON, why not real serialising format such as Storable?	1260	=item Why favour JSON, why not a real serialising format such as Storable?
795		1261
796	In fact, any AnyEvent::MP node will happily accept Storable as framing	1262	In fact, any AnyEvent::MP node will happily accept Storable as framing
797	format, but currently there is no way to make a node use Storable by	1263	format, but currently there is no way to make a node use Storable by
798	default.	1264	default (although all nodes will accept it).
799		1265
800	The default framing protocol is JSON because a) JSON::XS is many times	1266	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	1267	faster for small messages and b) most importantly, after years of
802	experience we found that object serialisation is causing more problems	1268	experience we found that object serialisation is causing more problems
803	than it gains: Just like function calls, objects simply do not travel	1269	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	1270	easily over the network, mostly because they will always be a copy, so you
805	always have to re-think your design.	1271	always have to re-think your design.
806		1272
807	Keeping your messages simple, concentrating on data structures rather than	1273	Keeping your messages simple, concentrating on data structures rather than
808	objects, will keep your messages clean, tidy and efficient.	1274	objects, will keep your messages clean, tidy and efficient.
809		1275
810	=back	1276	=back
811		1277
		1278	=head1 PORTING FROM AnyEvent::MP VERSION 1.X
		1279
		1280	AEMP version 2 has a few major incompatible changes compared to version 1:
		1281
		1282	=over 4
		1283
		1284	=item AnyEvent::MP::Global no longer has group management functions.
		1285
		1286	At least not officially - the grp_* functions are still exported and might
		1287	work, but they will be removed in some later release.
		1288
		1289	AnyEvent::MP now comes with a distributed database that is more
		1290	powerful. Its database families map closely to port groups, but the API
		1291	has changed (the functions are also now exported by AnyEvent::MP). Here is
		1292	a rough porting guide:
		1293
		1294	grp_reg $group, $port # old
		1295	db_reg $group, $port # new
		1296
		1297	$list = grp_get $group # old
		1298	db_keys $group, sub { my $list = shift } # new
		1299
		1300	grp_mon $group, $cb->(\@ports, $add, $del) # old
		1301	db_mon $group, $cb->(\%ports, $add, $change, $del) # new
		1302
		1303	C<grp_reg> is a no-brainer (just replace by C<db_reg>), but C<grp_get> is
		1304	no longer instant, because the local node might not have a copy of the
		1305	group. You can either modify your code to allow for a callback, or use
		1306	C<db_mon> to keep an updated copy of the group:
		1307
		1308	my $local_group_copy;
		1309	db_mon $group => sub { $local_group_copy = $_[0] };
		1310
		1311	# now "keys %$local_group_copy" always returns the most up-to-date
		1312	# list of ports in the group.
		1313
		1314	C<grp_mon> can be replaced by C<db_mon> with minor changes - C<db_mon>
		1315	passes a hash as first argument, and an extra C<$chg> argument that can be
		1316	ignored:
		1317
		1318	db_mon $group => sub {
		1319	my ($ports, $add, $chg, $del) = @_;
		1320	$ports = [keys %$ports];
		1321
		1322	# now $ports, $add and $del are the same as
		1323	# were originally passed by grp_mon.
		1324	...
		1325	};
		1326
		1327	=item Nodes not longer connect to all other nodes.
		1328
		1329	In AEMP 1.x, every node automatically loads the L<AnyEvent::MP::Global>
		1330	module, which in turn would create connections to all other nodes in the
		1331	network (helped by the seed nodes).
		1332
		1333	In version 2.x, global nodes still connect to all other global nodes, but
		1334	other nodes don't - now every node either is a global node itself, or
		1335	attaches itself to another global node.
		1336
		1337	If a node isn't a global node itself, then it attaches itself to one
		1338	of its seed nodes. If that seed node isn't a global node yet, it will
		1339	automatically be upgraded to a global node.
		1340
		1341	So in many cases, nothing needs to be changed - one just has to make sure
		1342	that all seed nodes are meshed together with the other seed nodes (as with
		1343	AEMP 1.x), and other nodes specify them as seed nodes. This is most easily
		1344	achieved by specifying the same set of seed nodes for all nodes in the
		1345	network.
		1346
		1347	Not opening a connection to every other node is usually an advantage,
		1348	except when you need the lower latency of an already established
		1349	connection. To ensure a node establishes a connection to another node,
		1350	you can monitor the node port (C<mon $node, ...>), which will attempt to
		1351	create the connection (and notify you when the connection fails).
		1352
		1353	=item Listener-less nodes (nodes without binds) are gone.
		1354
		1355	And are not coming back, at least not in their old form. If no C<binds>
		1356	are specified for a node, AnyEvent::MP assumes a default of C<:>.
		1357
		1358	There are vague plans to implement some form of routing domains, which
		1359	might or might not bring back listener-less nodes, but don't count on it.
		1360
		1361	The fact that most connections are now optional somewhat mitigates this,
		1362	as a node can be effectively unreachable from the outside without any
		1363	problems, as long as it isn't a global node and only reaches out to other
		1364	nodes (as opposed to being contacted from other nodes).
		1365
		1366	=item $AnyEvent::MP::Kernel::WARN has gone.
		1367
		1368	AnyEvent has acquired a logging framework (L<AnyEvent::Log>), and AEMP now
		1369	uses this, and so should your programs.
		1370
		1371	Every module now documents what kinds of messages it generates, with
		1372	AnyEvent::MP acting as a catch all.
		1373
		1374	On the positive side, this means that instead of setting
		1375	C<PERL_ANYEVENT_MP_WARNLEVEL>, you can get away by setting C<AE_VERBOSE> -
		1376	much less to type.
		1377
		1378	=back
		1379
		1380	=head1 LOGGING
		1381
		1382	AnyEvent::MP does not normally log anything by itself, but since it is the
		1383	root of the context hierarchy for AnyEvent::MP modules, it will receive
		1384	all log messages by submodules.
		1385
812	=head1 SEE ALSO	1386	=head1 SEE ALSO
		1387
		1388	L<AnyEvent::MP::Intro> - a gentle introduction.
		1389
		1390	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		1391
		1392	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
		1393	your applications.
		1394
		1395	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		1396
		1397	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		1398	all nodes.
813		1399
814	L<AnyEvent>.	1400	L<AnyEvent>.
815		1401
816	=head1 AUTHOR	1402	=head1 AUTHOR
817		1403

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Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.65 by root, Fri Aug 28 01:00:34 2009 UTC vs. Revision 1.156 by root, Sat Oct 23 03:35:49 2021 UTC

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Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.65 by root, Fri Aug 28 01:00:34 2009 UTC vs.
Revision 1.156 by root, Sat Oct 23 03:35:49 2021 UTC