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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.55 by root, Fri Aug 14 23:17:17 2009 UTC vs.
Revision 1.101 by root, Tue Oct 6 01:31:22 2009 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; # -OR-	15	configure;
17	initialise_node "localhost:4040"; # -OR-
18	initialise_node "slave/", "localhost:4040"
19		16
20	# ports are message endpoints	17	# ports are message destinations
21		18
22	# sending messages	19	# sending messages
23	snd $port, type => data...;	20	snd $port, type => data...;
24	snd $port, @msg;	21	snd $port, @msg;
25	snd @msg_with_first_element_being_a_port;	22	snd @msg_with_first_element_being_a_port;
26		23
27	# creating/using ports, the simple way	24	# creating/using ports, the simple way
28	my $simple_port = port { my @msg = @_; 0 };	25	my $simple_port = port { my @msg = @_ };
29		26
30	# creating/using ports, tagged message matching	27	# creating/using ports, tagged message matching
31	my $port = port;	28	my $port = port;
32	rcv $port, ping => sub { snd $_[0], "pong"; 0 };	29	rcv $port, ping => sub { snd $_[0], "pong" };
33	rcv $port, pong => sub { warn "pong received\n"; 0 };	30	rcv $port, pong => sub { warn "pong received\n" };
34		31
35	# create a port on another node	32	# create a port on another node
36	my $port = spawn $node, $initfunc, @initdata;	33	my $port = spawn $node, $initfunc, @initdata;
37		34
		35	# destroy a prot again
		36	kil $port; # "normal" kill
		37	kil $port, my_error => "everything is broken"; # error kill
		38
38	# monitoring	39	# monitoring
39	mon $port, $cb->(@msg) # callback is invoked on death	40	mon $localport, $cb->(@msg) # callback is invoked on death
40	mon $port, $otherport # kill otherport on abnormal death	41	mon $localport, $otherport # kill otherport on abnormal death
41	mon $port, $otherport, @msg # send message on death	42	mon $localport, $otherport, @msg # send message on death
		43
		44	# temporarily execute code in port context
		45	peval $port, sub { die "kill the port!" };
		46
		47	# execute callbacks in $SELF port context
		48	my $timer = AE::timer 1, 0, psub {
		49	die "kill the port, delayed";
		50	};
42		51
43	=head1 CURRENT STATUS	52	=head1 CURRENT STATUS
44		53
		54	bin/aemp - stable.
45	AnyEvent::MP - stable API, should work	55	AnyEvent::MP - stable API, should work.
46	AnyEvent::MP::Intro - outdated	56	AnyEvent::MP::Intro - explains most concepts.
47	AnyEvent::MP::Kernel - WIP
48	AnyEvent::MP::Transport - mostly stable	57	AnyEvent::MP::Kernel - mostly stable API.
49		58	AnyEvent::MP::Global - stable API.
50	stay tuned.
51		59
52	=head1 DESCRIPTION	60	=head1 DESCRIPTION
53		61
54	This module (-family) implements a simple message passing framework.	62	This module (-family) implements a simple message passing framework.
55		63
56	Despite its simplicity, you can securely message other processes running	64	Despite its simplicity, you can securely message other processes running
57	on the same or other hosts.	65	on the same or other hosts, and you can supervise entities remotely.
58		66
59	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	67	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
60	manual page.	68	manual page and the examples under F<eg/>.
61
62	At the moment, this module family is severly broken and underdocumented,
63	so do not use. This was uploaded mainly to reserve the CPAN namespace -
64	stay tuned!
65		69
66	=head1 CONCEPTS	70	=head1 CONCEPTS
67		71
68	=over 4	72	=over 4
69		73
70	=item port	74	=item port
71		75
72	A port is something you can send messages to (with the C<snd> function).	76	Not to be confused with a TCP port, a "port" is something you can send
		77	messages to (with the C<snd> function).
73		78
74	Ports allow you to register C<rcv> handlers that can match all or just	79	Ports allow you to register C<rcv> handlers that can match all or just
75	some messages. Messages will not be queued.	80	some messages. Messages send to ports will not be queued, regardless of
		81	anything was listening for them or not.
76		82
77	=item port id - C<noderef#portname>	83	=item port ID - C<nodeid#portname>
78		84
79	A port ID is the concatenation of a noderef, a hash-mark (C<#>) as	85	A port ID is the concatenation of a node ID, a hash-mark (C<#>) as
80	separator, and a port name (a printable string of unspecified format). An	86	separator, and a port name (a printable string of unspecified format).
81	exception is the the node port, whose ID is identical to its node
82	reference.
83		87
84	=item node	88	=item node
85		89
86	A node is a single process containing at least one port - the node port,	90	A node is a single process containing at least one port - the node port,
87	which provides nodes to manage each other remotely, and to create new	91	which enables nodes to manage each other remotely, and to create new
88	ports.	92	ports.
89		93
90	Nodes are either private (single-process only), slaves (connected to a	94	Nodes are either public (have one or more listening ports) or private
91	master node only) or public nodes (connectable from unrelated nodes).	95	(no listening ports). Private nodes cannot talk to other private nodes
		96	currently.
92		97
93	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	98	=item node ID - C<[A-Z_][a-zA-Z0-9_\-.:]*>
94		99
95	A node reference is a string that either simply identifies the node (for	100	A node ID is a string that uniquely identifies the node within a
96	private and slave nodes), or contains a recipe on how to reach a given	101	network. Depending on the configuration used, node IDs can look like a
97	node (for public nodes).	102	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		103	doesn't interpret node IDs in any way.
98		104
99	This recipe is simply a comma-separated list of C<address:port> pairs (for	105	=item binds - C<ip:port>
100	TCP/IP, other protocols might look different).
101		106
102	Node references come in two flavours: resolved (containing only numerical	107	Nodes can only talk to each other by creating some kind of connection to
103	addresses) or unresolved (where hostnames are used instead of addresses).	108	each other. To do this, nodes should listen on one or more local transport
		109	endpoints - binds. Currently, only standard C<ip:port> specifications can
		110	be used, which specify TCP ports to listen on.
104		111
105	Before using an unresolved node reference in a message you first have to	112	=item seed nodes
106	resolve it.	113
		114	When a node starts, it knows nothing about the network. To teach the node
		115	about the network it first has to contact some other node within the
		116	network. This node is called a seed.
		117
		118	Apart from the fact that other nodes know them as seed nodes and they have
		119	to have fixed listening addresses, seed nodes are perfectly normal nodes -
		120	any node can function as a seed node for others.
		121
		122	In addition to discovering the network, seed nodes are also used to
		123	maintain the network and to connect nodes that otherwise would have
		124	trouble connecting. They form the backbone of an AnyEvent::MP network.
		125
		126	Seed nodes are expected to be long-running, and at least one seed node
		127	should always be available. They should also be relatively responsive - a
		128	seed node that blocks for long periods will slow down everybody else.
		129
		130	=item seeds - C<host:port>
		131
		132	Seeds are transport endpoint(s) (usually a hostname/IP address and a
		133	TCP port) of nodes that should be used as seed nodes.
		134
		135	The nodes listening on those endpoints are expected to be long-running,
		136	and at least one of those should always be available. When nodes run out
		137	of connections (e.g. due to a network error), they try to re-establish
		138	connections to some seednodes again to join the network.
107		139
108	=back	140	=back
109		141
110	=head1 VARIABLES/FUNCTIONS	142	=head1 VARIABLES/FUNCTIONS
111		143
123		155
124	use AE ();	156	use AE ();
125		157
126	use base "Exporter";	158	use base "Exporter";
127		159
128	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	160	our $VERSION = 1.21;
129		161
130	our @EXPORT = qw(	162	our @EXPORT = qw(
131	NODE $NODE *SELF node_of _any_	163	NODE $NODE *SELF node_of after
132	resolve_node initialise_node	164	configure
133	snd rcv mon kil reg psub spawn	165	snd rcv mon mon_guard kil psub peval spawn cal
134	port	166	port
135	);	167	);
136		168
137	our $SELF;	169	our $SELF;
138		170
…		…
142	kil $SELF, die => $msg;	174	kil $SELF, die => $msg;
143	}	175	}
144		176
145	=item $thisnode = NODE / $NODE	177	=item $thisnode = NODE / $NODE
146		178
147	The C<NODE> function returns, and the C<$NODE> variable contains the	179	The C<NODE> function returns, and the C<$NODE> variable contains, the node
148	noderef of the local node. The value is initialised by a call to	180	ID of the node running in the current process. This value is initialised by
149	C<initialise_node>.	181	a call to C<configure>.
150		182
151	=item $noderef = node_of $port	183	=item $nodeid = node_of $port
152		184
153	Extracts and returns the noderef from a port ID or a noderef.	185	Extracts and returns the node ID from a port ID or a node ID.
154		186
155	=item initialise_node $noderef, $seednode, $seednode...	187	=item configure $profile, key => value...
156		188
157	=item initialise_node "slave/", $master, $master...	189	=item configure key => value...
158		190
159	Before a node can talk to other nodes on the network it has to initialise	191	Before a node can talk to other nodes on the network (i.e. enter
160	itself - the minimum a node needs to know is it's own name, and optionally	192	"distributed mode") it has to configure itself - the minimum a node needs
161	it should know the noderefs of some other nodes in the network.	193	to know is its own name, and optionally it should know the addresses of
		194	some other nodes in the network to discover other nodes.
162		195
163	This function initialises a node - it must be called exactly once (or	196	This function configures a node - it must be called exactly once (or
164	never) before calling other AnyEvent::MP functions.	197	never) before calling other AnyEvent::MP functions.
165		198
166	All arguments (optionally except for the first) are noderefs, which can be
167	either resolved or unresolved.
168
169	The first argument will be looked up in the configuration database first
170	(if it is C<undef> then the current nodename will be used instead) to find
171	the relevant configuration profile (see L<aemp>). If none is found then
172	the default configuration is used. The configuration supplies additional
173	seed/master nodes and can override the actual noderef.
174
175	There are two types of networked nodes, public nodes and slave nodes:
176
177	=over 4	199	=over 4
178		200
179	=item public nodes	201	=item step 1, gathering configuration from profiles
180		202
181	For public nodes, C<$noderef> (supplied either directly to	203	The function first looks up a profile in the aemp configuration (see the
182	C<initialise_node> or indirectly via a profile or the nodename) must be a	204	L<aemp> commandline utility). The profile name can be specified via the
183	noderef (possibly unresolved, in which case it will be resolved).	205	named C<profile> parameter or can simply be the first parameter). If it is
		206	missing, then the nodename (F<uname -n>) will be used as profile name.
184		207
185	After resolving, the node will bind itself on all endpoints and try to	208	The profile data is then gathered as follows:
186	connect to all additional C<$seednodes> that are specified. Seednodes are
187	optional and can be used to quickly bootstrap the node into an existing
188	network.
189		209
190	=item slave nodes	210	First, all remaining key => value pairs (all of which are conveniently
		211	undocumented at the moment) will be interpreted as configuration
		212	data. Then they will be overwritten by any values specified in the global
		213	default configuration (see the F<aemp> utility), then the chain of
		214	profiles chosen by the profile name (and any C<parent> attributes).
191		215
192	When the C<$noderef> (either as given or overriden by the config file)	216	That means that the values specified in the profile have highest priority
193	is the special string C<slave/>, then the node will become a slave	217	and the values specified directly via C<configure> have lowest priority,
194	node. Slave nodes cannot be contacted from outside and will route most of	218	and can only be used to specify defaults.
195	their traffic to the master node that they attach to.
196		219
197	At least one additional noderef is required (either by specifying it	220	If the profile specifies a node ID, then this will become the node ID of
198	directly or because it is part of the configuration profile): The node	221	this process. If not, then the profile name will be used as node ID. The
199	will try to connect to all of them and will become a slave attached to the	222	special node ID of C<anon/> will be replaced by a random node ID.
200	first node it can successfully connect to.	223
		224	=item step 2, bind listener sockets
		225
		226	The next step is to look up the binds in the profile, followed by binding
		227	aemp protocol listeners on all binds specified (it is possible and valid
		228	to have no binds, meaning that the node cannot be contacted form the
		229	outside. This means the node cannot talk to other nodes that also have no
		230	binds, but it can still talk to all "normal" nodes).
		231
		232	If the profile does not specify a binds list, then a default of C<*> is
		233	used, meaning the node will bind on a dynamically-assigned port on every
		234	local IP address it finds.
		235
		236	=item step 3, connect to seed nodes
		237
		238	As the last step, the seeds list from the profile is passed to the
		239	L<AnyEvent::MP::Global> module, which will then use it to keep
		240	connectivity with at least one node at any point in time.
201		241
202	=back	242	=back
203		243
204	This function will block until all nodes have been resolved and, for slave	244	Example: become a distributed node using the local node name as profile.
205	nodes, until it has successfully established a connection to a master	245	This should be the most common form of invocation for "daemon"-type nodes.
206	server.
207		246
208	Example: become a public node listening on the guessed noderef, or the one	247	configure
209	specified via C<aemp> for the current node. This should be the most common
210	form of invocation for "daemon"-type nodes.
211		248
212	initialise_node;	249	Example: become an anonymous node. This form is often used for commandline
		250	clients.
213		251
214	Example: become a slave node to any of the the seednodes specified via	252	configure nodeid => "anon/";
215	C<aemp>. This form is often used for commandline clients.
216		253
217	initialise_node "slave/";	254	Example: configure a node using a profile called seed, which si suitable
		255	for a seed node as it binds on all local addresses on a fixed port (4040,
		256	customary for aemp).
218		257
219	Example: become a slave node to any of the specified master servers. This	258	# use the aemp commandline utility
220	form is also often used for commandline clients.	259	# aemp profile seed nodeid anon/ binds '*:4040'
221		260
222	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";	261	# then use it
		262	configure profile => "seed";
223		263
224	Example: become a public node, and try to contact some well-known master	264	# or simply use aemp from the shell again:
225	servers to become part of the network.	265	# aemp run profile seed
226		266
227	initialise_node undef, "master1", "master2";	267	# or provide a nicer-to-remember nodeid
228		268	# aemp run profile seed nodeid "$(hostname)"
229	Example: become a public node listening on port C<4041>.
230
231	initialise_node 4041;
232
233	Example: become a public node, only visible on localhost port 4044.
234
235	initialise_node "localhost:4044";
236
237	=item $cv = resolve_node $noderef
238
239	Takes an unresolved node reference that may contain hostnames and
240	abbreviated IDs, resolves all of them and returns a resolved node
241	reference.
242
243	In addition to C<address:port> pairs allowed in resolved noderefs, the
244	following forms are supported:
245
246	=over 4
247
248	=item the empty string
249
250	An empty-string component gets resolved as if the default port (4040) was
251	specified.
252
253	=item naked port numbers (e.g. C<1234>)
254
255	These are resolved by prepending the local nodename and a colon, to be
256	further resolved.
257
258	=item hostnames (e.g. C<localhost:1234>, C<localhost>)
259
260	These are resolved by using AnyEvent::DNS to resolve them, optionally
261	looking up SRV records for the C<aemp=4040> port, if no port was
262	specified.
263
264	=back
265		269
266	=item $SELF	270	=item $SELF
267		271
268	Contains the current port id while executing C<rcv> callbacks or C<psub>	272	Contains the current port id while executing C<rcv> callbacks or C<psub>
269	blocks.	273	blocks.
270		274
271	=item SELF, %SELF, @SELF...	275	=item *SELF, SELF, %SELF, @SELF...
272		276
273	Due to some quirks in how perl exports variables, it is impossible to	277	Due to some quirks in how perl exports variables, it is impossible to
274	just export C<$SELF>, all the symbols called C<SELF> are exported by this	278	just export C<$SELF>, all the symbols named C<SELF> are exported by this
275	module, but only C<$SELF> is currently used.	279	module, but only C<$SELF> is currently used.
276		280
277	=item snd $port, type => @data	281	=item snd $port, type => @data
278		282
279	=item snd $port, @msg	283	=item snd $port, @msg
280		284
281	Send the given message to the given port ID, which can identify either	285	Send the given message to the given port, which can identify either a
282	a local or a remote port, and must be a port ID.	286	local or a remote port, and must be a port ID.
283		287
284	While the message can be about anything, it is highly recommended to use a	288	While the message can be almost anything, it is highly recommended to
285	string as first element (a port ID, or some word that indicates a request	289	use a string as first element (a port ID, or some word that indicates a
286	type etc.).	290	request type etc.) and to consist if only simple perl values (scalars,
		291	arrays, hashes) - if you think you need to pass an object, think again.
287		292
288	The message data effectively becomes read-only after a call to this	293	The message data logically becomes read-only after a call to this
289	function: modifying any argument is not allowed and can cause many	294	function: modifying any argument (or values referenced by them) is
290	problems.	295	forbidden, as there can be considerable time between the call to C<snd>
		296	and the time the message is actually being serialised - in fact, it might
		297	never be copied as within the same process it is simply handed to the
		298	receiving port.
291		299
292	The type of data you can transfer depends on the transport protocol: when	300	The type of data you can transfer depends on the transport protocol: when
293	JSON is used, then only strings, numbers and arrays and hashes consisting	301	JSON is used, then only strings, numbers and arrays and hashes consisting
294	of those are allowed (no objects). When Storable is used, then anything	302	of those are allowed (no objects). When Storable is used, then anything
295	that Storable can serialise and deserialise is allowed, and for the local	303	that Storable can serialise and deserialise is allowed, and for the local
296	node, anything can be passed.	304	node, anything can be passed. Best rely only on the common denominator of
		305	these.
297		306
298	=item $local_port = port	307	=item $local_port = port
299		308
300	Create a new local port object and returns its port ID. Initially it has	309	Create a new local port object and returns its port ID. Initially it has
301	no callbacks set and will throw an error when it receives messages.	310	no callbacks set and will throw an error when it receives messages.
…		…
386		395
387	=cut	396	=cut
388		397
389	sub rcv($@) {	398	sub rcv($@) {
390	my $port = shift;	399	my $port = shift;
391	my ($noderef, $portid) = split /#/, $port, 2;	400	my ($nodeid, $portid) = split /#/, $port, 2;
392		401
393	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	402	$NODE{$nodeid} == $NODE{""}
394	or Carp::croak "$port: rcv can only be called on local ports, caught";	403	or Carp::croak "$port: rcv can only be called on local ports, caught";
395		404
396	while (@_) {	405	while (@_) {
397	if (ref $_[0]) {	406	if (ref $_[0]) {
398	if (my $self = $PORT_DATA{$portid}) {	407	if (my $self = $PORT_DATA{$portid}) {
…		…
439	}	448	}
440		449
441	$port	450	$port
442	}	451	}
443		452
		453	=item peval $port, $coderef[, @args]
		454
		455	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		456	when the code throews an exception the C<$port> will be killed.
		457
		458	Any remaining args will be passed to the callback. Any return values will
		459	be returned to the caller.
		460
		461	This is useful when you temporarily want to execute code in the context of
		462	a port.
		463
		464	Example: create a port and run some initialisation code in it's context.
		465
		466	my $port = port { ... };
		467
		468	peval $port, sub {
		469	init
		470	or die "unable to init";
		471	};
		472
		473	=cut
		474
		475	sub peval($$) {
		476	local $SELF = shift;
		477	my $cb = shift;
		478
		479	if (wantarray) {
		480	my @res = eval { &$cb };
		481	_self_die if $@;
		482	@res
		483	} else {
		484	my $res = eval { &$cb };
		485	_self_die if $@;
		486	$res
		487	}
		488	}
		489
444	=item $closure = psub { BLOCK }	490	=item $closure = psub { BLOCK }
445		491
446	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	492	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
447	closure is executed, sets up the environment in the same way as in C<rcv>	493	closure is executed, sets up the environment in the same way as in C<rcv>
448	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.	494	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		495
		496	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		497	BLOCK } } >>.
449		498
450	This is useful when you register callbacks from C<rcv> callbacks:	499	This is useful when you register callbacks from C<rcv> callbacks:
451		500
452	rcv delayed_reply => sub {	501	rcv delayed_reply => sub {
453	my ($delay, @reply) = @_;	502	my ($delay, @reply) = @_;
…		…
477	$res	526	$res
478	}	527	}
479	}	528	}
480	}	529	}
481		530
482	=item $guard = mon $port, $cb->(@reason)	531	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
483		532
484	=item $guard = mon $port, $rcvport	533	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
485		534
486	=item $guard = mon $port	535	=item $guard = mon $port # kill $SELF when $port dies
487		536
488	=item $guard = mon $port, $rcvport, @msg	537	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
489		538
490	Monitor the given port and do something when the port is killed or	539	Monitor the given port and do something when the port is killed or
491	messages to it were lost, and optionally return a guard that can be used	540	messages to it were lost, and optionally return a guard that can be used
492	to stop monitoring again.	541	to stop monitoring again.
493
494	C<mon> effectively guarantees that, in the absence of hardware failures,
495	that after starting the monitor, either all messages sent to the port
496	will arrive, or the monitoring action will be invoked after possible
497	message loss has been detected. No messages will be lost "in between"
498	(after the first lost message no further messages will be received by the
499	port). After the monitoring action was invoked, further messages might get
500	delivered again.
501		542
502	In the first form (callback), the callback is simply called with any	543	In the first form (callback), the callback is simply called with any
503	number of C<@reason> elements (no @reason means that the port was deleted	544	number of C<@reason> elements (no @reason means that the port was deleted
504	"normally"). Note also that I<< the callback B<must> never die >>, so use	545	"normally"). Note also that I<< the callback B<must> never die >>, so use
505	C<eval> if unsure.	546	C<eval> if unsure.
506		547
507	In the second form (another port given), the other port (C<$rcvport>)	548	In the second form (another port given), the other port (C<$rcvport>)
508	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	549	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
509	"normal" kils nothing happens, while under all other conditions, the other	550	"normal" kils nothing happens, while under all other conditions, the other
510	port is killed with the same reason.	551	port is killed with the same reason.
511		552
512	The third form (kill self) is the same as the second form, except that	553	The third form (kill self) is the same as the second form, except that
513	C<$rvport> defaults to C<$SELF>.	554	C<$rvport> defaults to C<$SELF>.
514		555
515	In the last form (message), a message of the form C<@msg, @reason> will be	556	In the last form (message), a message of the form C<@msg, @reason> will be
516	C<snd>.	557	C<snd>.
		558
		559	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		560	alert was raised), they are removed and will not trigger again.
517		561
518	As a rule of thumb, monitoring requests should always monitor a port from	562	As a rule of thumb, monitoring requests should always monitor a port from
519	a local port (or callback). The reason is that kill messages might get	563	a local port (or callback). The reason is that kill messages might get
520	lost, just like any other message. Another less obvious reason is that	564	lost, just like any other message. Another less obvious reason is that
521	even monitoring requests can get lost (for exmaple, when the connection	565	even monitoring requests can get lost (for example, when the connection
522	to the other node goes down permanently). When monitoring a port locally	566	to the other node goes down permanently). When monitoring a port locally
523	these problems do not exist.	567	these problems do not exist.
524		568
		569	C<mon> effectively guarantees that, in the absence of hardware failures,
		570	after starting the monitor, either all messages sent to the port will
		571	arrive, or the monitoring action will be invoked after possible message
		572	loss has been detected. No messages will be lost "in between" (after
		573	the first lost message no further messages will be received by the
		574	port). After the monitoring action was invoked, further messages might get
		575	delivered again.
		576
		577	Inter-host-connection timeouts and monitoring depend on the transport
		578	used. The only transport currently implemented is TCP, and AnyEvent::MP
		579	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		580	non-idle connection, and usually around two hours for idle connections).
		581
		582	This means that monitoring is good for program errors and cleaning up
		583	stuff eventually, but they are no replacement for a timeout when you need
		584	to ensure some maximum latency.
		585
525	Example: call a given callback when C<$port> is killed.	586	Example: call a given callback when C<$port> is killed.
526		587
527	mon $port, sub { warn "port died because of <@_>\n" };	588	mon $port, sub { warn "port died because of <@_>\n" };
528		589
529	Example: kill ourselves when C<$port> is killed abnormally.	590	Example: kill ourselves when C<$port> is killed abnormally.
…		…
535	mon $port, $self => "restart";	596	mon $port, $self => "restart";
536		597
537	=cut	598	=cut
538		599
539	sub mon {	600	sub mon {
540	my ($noderef, $port) = split /#/, shift, 2;	601	my ($nodeid, $port) = split /#/, shift, 2;
541		602
542	my $node = $NODE{$noderef} \|\| add_node $noderef;	603	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
543		604
544	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	605	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
545		606
546	unless (ref $cb) {	607	unless (ref $cb) {
547	if (@_) {	608	if (@_) {
…		…
556	}	617	}
557		618
558	$node->monitor ($port, $cb);	619	$node->monitor ($port, $cb);
559		620
560	defined wantarray	621	defined wantarray
561	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	622	and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) })
562	}	623	}
563		624
564	=item $guard = mon_guard $port, $ref, $ref...	625	=item $guard = mon_guard $port, $ref, $ref...
565		626
566	Monitors the given C<$port> and keeps the passed references. When the port	627	Monitors the given C<$port> and keeps the passed references. When the port
567	is killed, the references will be freed.	628	is killed, the references will be freed.
568		629
569	Optionally returns a guard that will stop the monitoring.	630	Optionally returns a guard that will stop the monitoring.
570		631
571	This function is useful when you create e.g. timers or other watchers and	632	This function is useful when you create e.g. timers or other watchers and
572	want to free them when the port gets killed:	633	want to free them when the port gets killed (note the use of C<psub>):
573		634
574	$port->rcv (start => sub {	635	$port->rcv (start => sub {
575	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	636	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
576	undef $timer if 0.9 < rand;	637	undef $timer if 0.9 < rand;
577	});	638	});
578	});	639	});
579		640
580	=cut	641	=cut
…		…
589		650
590	=item kil $port[, @reason]	651	=item kil $port[, @reason]
591		652
592	Kill the specified port with the given C<@reason>.	653	Kill the specified port with the given C<@reason>.
593		654
594	If no C<@reason> is specified, then the port is killed "normally" (linked	655	If no C<@reason> is specified, then the port is killed "normally" (ports
595	ports will not be kileld, or even notified).	656	monitoring other ports will not necessarily die because a port dies
		657	"normally").
596		658
597	Otherwise, linked ports get killed with the same reason (second form of	659	Otherwise, linked ports get killed with the same reason (second form of
598	C<mon>, see below).	660	C<mon>, see above).
599		661
600	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	662	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
601	will be reported as reason C<< die => $@ >>.	663	will be reported as reason C<< die => $@ >>.
602		664
603	Transport/communication errors are reported as C<< transport_error =>	665	Transport/communication errors are reported as C<< transport_error =>
…		…
608	=item $port = spawn $node, $initfunc[, @initdata]	670	=item $port = spawn $node, $initfunc[, @initdata]
609		671
610	Creates a port on the node C<$node> (which can also be a port ID, in which	672	Creates a port on the node C<$node> (which can also be a port ID, in which
611	case it's the node where that port resides).	673	case it's the node where that port resides).
612		674
613	The port ID of the newly created port is return immediately, and it is	675	The port ID of the newly created port is returned immediately, and it is
614	permissible to immediately start sending messages or monitor the port.	676	possible to immediately start sending messages or to monitor the port.
615		677
616	After the port has been created, the init function is	678	After the port has been created, the init function is called on the remote
617	called. This function must be a fully-qualified function name	679	node, in the same context as a C<rcv> callback. This function must be a
618	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	680	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
619	program, use C<::name>.	681	specify a function in the main program, use C<::name>.
620		682
621	If the function doesn't exist, then the node tries to C<require>	683	If the function doesn't exist, then the node tries to C<require>
622	the package, then the package above the package and so on (e.g.	684	the package, then the package above the package and so on (e.g.
623	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	685	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
624	exists or it runs out of package names.	686	exists or it runs out of package names.
625		687
626	The init function is then called with the newly-created port as context	688	The init function is then called with the newly-created port as context
627	object (C<$SELF>) and the C<@initdata> values as arguments.	689	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		690	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		691	the port might not get created.
628		692
629	A common idiom is to pass your own port, monitor the spawned port, and	693	A common idiom is to pass a local port, immediately monitor the spawned
630	in the init function, monitor the original port. This two-way monitoring	694	port, and in the remote init function, immediately monitor the passed
631	ensures that both ports get cleaned up when there is a problem.	695	local port. This two-way monitoring ensures that both ports get cleaned up
		696	when there is a problem.
		697
		698	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		699	caller before C<spawn> returns (by delaying invocation when spawn is
		700	called for the local node).
632		701
633	Example: spawn a chat server port on C<$othernode>.	702	Example: spawn a chat server port on C<$othernode>.
634		703
635	# this node, executed from within a port context:	704	# this node, executed from within a port context:
636	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	705	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
651		720
652	sub _spawn {	721	sub _spawn {
653	my $port = shift;	722	my $port = shift;
654	my $init = shift;	723	my $init = shift;
655		724
		725	# rcv will create the actual port
656	local $SELF = "$NODE#$port";	726	local $SELF = "$NODE#$port";
657	eval {	727	eval {
658	&{ load_func $init }	728	&{ load_func $init }
659	};	729	};
660	_self_die if $@;	730	_self_die if $@;
661	}	731	}
662		732
663	sub spawn(@) {	733	sub spawn(@) {
664	my ($noderef, undef) = split /#/, shift, 2;	734	my ($nodeid, undef) = split /#/, shift, 2;
665		735
666	my $id = "$RUNIQ." . $ID++;	736	my $id = "$RUNIQ." . $ID++;
667		737
668	$_[0] =~ /::/	738	$_[0] =~ /::/
669	or Carp::croak "spawn init function must be a fully-qualified name, caught";	739	or Carp::croak "spawn init function must be a fully-qualified name, caught";
670		740
671	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;	741	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
672		742
673	"$noderef#$id"	743	"$nodeid#$id"
674	}	744	}
675		745
676	=back	746	=item after $timeout, @msg
677		747
678	=head1 NODE MESSAGES	748	=item after $timeout, $callback
679		749
680	Nodes understand the following messages sent to them. Many of them take	750	Either sends the given message, or call the given callback, after the
681	arguments called C<@reply>, which will simply be used to compose a reply	751	specified number of seconds.
682	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
683	the remaining arguments are simply the message data.
684		752
685	While other messages exist, they are not public and subject to change.	753	This is simply a utility function that comes in handy at times - the
		754	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		755	so it may go away in the future.
686		756
687	=over 4
688
689	=cut	757	=cut
690		758
691	=item lookup => $name, @reply	759	sub after($@) {
		760	my ($timeout, @action) = @_;
692		761
693	Replies with the port ID of the specified well-known port, or C<undef>.	762	my $t; $t = AE::timer $timeout, 0, sub {
		763	undef $t;
		764	ref $action[0]
		765	? $action[0]()
		766	: snd @action;
		767	};
		768	}
694		769
695	=item devnull => ...	770	=item cal $port, @msg, $callback[, $timeout]
696		771
697	Generic data sink/CPU heat conversion.	772	A simple form of RPC - sends a message to the given C<$port> with the
		773	given contents (C<@msg>), but adds a reply port to the message.
698		774
699	=item relay => $port, @msg	775	The reply port is created temporarily just for the purpose of receiving
		776	the reply, and will be C<kil>ed when no longer needed.
700		777
701	Simply forwards the message to the given port.	778	A reply message sent to the port is passed to the C<$callback> as-is.
702		779
703	=item eval => $string[ @reply]	780	If an optional time-out (in seconds) is given and it is not C<undef>,
		781	then the callback will be called without any arguments after the time-out
		782	elapsed and the port is C<kil>ed.
704		783
705	Evaluates the given string. If C<@reply> is given, then a message of the	784	If no time-out is given (or it is C<undef>), then the local port will
706	form C<@reply, $@, @evalres> is sent.	785	monitor the remote port instead, so it eventually gets cleaned-up.
707		786
708	Example: crash another node.	787	Currently this function returns the temporary port, but this "feature"
		788	might go in future versions unless you can make a convincing case that
		789	this is indeed useful for something.
709		790
710	snd $othernode, eval => "exit";	791	=cut
711		792
712	=item time => @reply	793	sub cal(@) {
		794	my $timeout = ref $_[-1] ? undef : pop;
		795	my $cb = pop;
713		796
714	Replies the the current node time to C<@reply>.	797	my $port = port {
		798	undef $timeout;
		799	kil $SELF;
		800	&$cb;
		801	};
715		802
716	Example: tell the current node to send the current time to C<$myport> in a	803	if (defined $timeout) {
717	C<timereply> message.	804	$timeout = AE::timer $timeout, 0, sub {
		805	undef $timeout;
		806	kil $port;
		807	$cb->();
		808	};
		809	} else {
		810	mon $_[0], sub {
		811	kil $port;
		812	$cb->();
		813	};
		814	}
718		815
719	snd $NODE, time => $myport, timereply => 1, 2;	816	push @_, $port;
720	# => snd $myport, timereply => 1, 2, <time>	817	&snd;
		818
		819	$port
		820	}
721		821
722	=back	822	=back
723		823
724	=head1 AnyEvent::MP vs. Distributed Erlang	824	=head1 AnyEvent::MP vs. Distributed Erlang
725		825
726	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	826	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
727	== aemp node, Erlang process == aemp port), so many of the documents and	827	== aemp node, Erlang process == aemp port), so many of the documents and
728	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	828	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
729	sample:	829	sample:
730		830
731	http://www.Erlang.se/doc/programming_rules.shtml	831	http://www.erlang.se/doc/programming_rules.shtml
732	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	832	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
733	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	833	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
734	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	834	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
735		835
736	Despite the similarities, there are also some important differences:	836	Despite the similarities, there are also some important differences:
737		837
738	=over 4	838	=over 4
739		839
740	=item * Node references contain the recipe on how to contact them.	840	=item * Node IDs are arbitrary strings in AEMP.
741		841
742	Erlang relies on special naming and DNS to work everywhere in the	842	Erlang relies on special naming and DNS to work everywhere in the same
743	same way. AEMP relies on each node knowing it's own address(es), with	843	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
744	convenience functionality.	844	configuration or DNS), and possibly the addresses of some seed nodes, but
745		845	will otherwise discover other nodes (and their IDs) itself.
746	This means that AEMP requires a less tightly controlled environment at the
747	cost of longer node references and a slightly higher management overhead.
748		846
749	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	847	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
750	uses "local ports are like remote ports".	848	uses "local ports are like remote ports".
751		849
752	The failure modes for local ports are quite different (runtime errors	850	The failure modes for local ports are quite different (runtime errors
…		…
765		863
766	Erlang uses processes that selectively receive messages, and therefore	864	Erlang uses processes that selectively receive messages, and therefore
767	needs a queue. AEMP is event based, queuing messages would serve no	865	needs a queue. AEMP is event based, queuing messages would serve no
768	useful purpose. For the same reason the pattern-matching abilities of	866	useful purpose. For the same reason the pattern-matching abilities of
769	AnyEvent::MP are more limited, as there is little need to be able to	867	AnyEvent::MP are more limited, as there is little need to be able to
770	filter messages without dequeing them.	868	filter messages without dequeuing them.
771		869
772	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	870	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
773		871
774	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	872	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
775		873
…		…
777	so does not need a queue that can overflow). AEMP sends are immediate,	875	so does not need a queue that can overflow). AEMP sends are immediate,
778	connection establishment is handled in the background.	876	connection establishment is handled in the background.
779		877
780	=item * Erlang suffers from silent message loss, AEMP does not.	878	=item * Erlang suffers from silent message loss, AEMP does not.
781		879
782	Erlang makes few guarantees on messages delivery - messages can get lost	880	Erlang implements few guarantees on messages delivery - messages can get
783	without any of the processes realising it (i.e. you send messages a, b,	881	lost without any of the processes realising it (i.e. you send messages a,
784	and c, and the other side only receives messages a and c).	882	b, and c, and the other side only receives messages a and c).
785		883
786	AEMP guarantees correct ordering, and the guarantee that there are no	884	AEMP guarantees correct ordering, and the guarantee that after one message
787	holes in the message sequence.	885	is lost, all following ones sent to the same port are lost as well, until
788		886	monitoring raises an error, so there are no silent "holes" in the message
789	=item * In Erlang, processes can be declared dead and later be found to be	887	sequence.
790	alive.
791
792	In Erlang it can happen that a monitored process is declared dead and
793	linked processes get killed, but later it turns out that the process is
794	still alive - and can receive messages.
795
796	In AEMP, when port monitoring detects a port as dead, then that port will
797	eventually be killed - it cannot happen that a node detects a port as dead
798	and then later sends messages to it, finding it is still alive.
799		888
800	=item * Erlang can send messages to the wrong port, AEMP does not.	889	=item * Erlang can send messages to the wrong port, AEMP does not.
801		890
802	In Erlang it is quite likely that a node that restarts reuses a process ID	891	In Erlang it is quite likely that a node that restarts reuses a process ID
803	known to other nodes for a completely different process, causing messages	892	known to other nodes for a completely different process, causing messages
…		…
807	around in the network will not be sent to an unrelated port.	896	around in the network will not be sent to an unrelated port.
808		897
809	=item * Erlang uses unprotected connections, AEMP uses secure	898	=item * Erlang uses unprotected connections, AEMP uses secure
810	authentication and can use TLS.	899	authentication and can use TLS.
811		900
812	AEMP can use a proven protocol - SSL/TLS - to protect connections and	901	AEMP can use a proven protocol - TLS - to protect connections and
813	securely authenticate nodes.	902	securely authenticate nodes.
814		903
815	=item * The AEMP protocol is optimised for both text-based and binary	904	=item * The AEMP protocol is optimised for both text-based and binary
816	communications.	905	communications.
817		906
818	The AEMP protocol, unlike the Erlang protocol, supports both	907	The AEMP protocol, unlike the Erlang protocol, supports both programming
819	language-independent text-only protocols (good for debugging) and binary,	908	language independent text-only protocols (good for debugging) and binary,
820	language-specific serialisers (e.g. Storable).	909	language-specific serialisers (e.g. Storable). By default, unless TLS is
		910	used, the protocol is actually completely text-based.
821		911
822	It has also been carefully designed to be implementable in other languages	912	It has also been carefully designed to be implementable in other languages
823	with a minimum of work while gracefully degrading fucntionality to make the	913	with a minimum of work while gracefully degrading functionality to make the
824	protocol simple.	914	protocol simple.
825		915
826	=item * AEMP has more flexible monitoring options than Erlang.	916	=item * AEMP has more flexible monitoring options than Erlang.
827		917
828	In Erlang, you can chose to receive I<all> exit signals as messages	918	In Erlang, you can chose to receive I<all> exit signals as messages
…		…
831	Erlang, as one can choose between automatic kill, exit message or callback	921	Erlang, as one can choose between automatic kill, exit message or callback
832	on a per-process basis.	922	on a per-process basis.
833		923
834	=item * Erlang tries to hide remote/local connections, AEMP does not.	924	=item * Erlang tries to hide remote/local connections, AEMP does not.
835		925
836	Monitoring in Erlang is not an indicator of process death/crashes,	926	Monitoring in Erlang is not an indicator of process death/crashes, in the
837	as linking is (except linking is unreliable in Erlang).	927	same way as linking is (except linking is unreliable in Erlang).
838		928
839	In AEMP, you don't "look up" registered port names or send to named ports	929	In AEMP, you don't "look up" registered port names or send to named ports
840	that might or might not be persistent. Instead, you normally spawn a port	930	that might or might not be persistent. Instead, you normally spawn a port
841	on the remote node. The init function monitors the you, and you monitor	931	on the remote node. The init function monitors you, and you monitor the
842	the remote port. Since both monitors are local to the node, they are much	932	remote port. Since both monitors are local to the node, they are much more
843	more reliable.	933	reliable (no need for C<spawn_link>).
844		934
845	This also saves round-trips and avoids sending messages to the wrong port	935	This also saves round-trips and avoids sending messages to the wrong port
846	(hard to do in Erlang).	936	(hard to do in Erlang).
847		937
848	=back	938	=back
849		939
850	=head1 RATIONALE	940	=head1 RATIONALE
851		941
852	=over 4	942	=over 4
853		943
854	=item Why strings for ports and noderefs, why not objects?	944	=item Why strings for port and node IDs, why not objects?
855		945
856	We considered "objects", but found that the actual number of methods	946	We considered "objects", but found that the actual number of methods
857	thatc an be called are very low. Since port IDs and noderefs travel over	947	that can be called are quite low. Since port and node IDs travel over
858	the network frequently, the serialising/deserialising would add lots of	948	the network frequently, the serialising/deserialising would add lots of
859	overhead, as well as having to keep a proxy object.	949	overhead, as well as having to keep a proxy object everywhere.
860		950
861	Strings can easily be printed, easily serialised etc. and need no special	951	Strings can easily be printed, easily serialised etc. and need no special
862	procedures to be "valid".	952	procedures to be "valid".
863		953
864	And a a miniport consists of a single closure stored in a global hash - it	954	And as a result, a miniport consists of a single closure stored in a
865	can't become much cheaper.	955	global hash - it can't become much cheaper.
866		956
867	=item Why favour JSON, why not real serialising format such as Storable?	957	=item Why favour JSON, why not a real serialising format such as Storable?
868		958
869	In fact, any AnyEvent::MP node will happily accept Storable as framing	959	In fact, any AnyEvent::MP node will happily accept Storable as framing
870	format, but currently there is no way to make a node use Storable by	960	format, but currently there is no way to make a node use Storable by
871	default.	961	default (although all nodes will accept it).
872		962
873	The default framing protocol is JSON because a) JSON::XS is many times	963	The default framing protocol is JSON because a) JSON::XS is many times
874	faster for small messages and b) most importantly, after years of	964	faster for small messages and b) most importantly, after years of
875	experience we found that object serialisation is causing more problems	965	experience we found that object serialisation is causing more problems
876	than it gains: Just like function calls, objects simply do not travel	966	than it solves: Just like function calls, objects simply do not travel
877	easily over the network, mostly because they will always be a copy, so you	967	easily over the network, mostly because they will always be a copy, so you
878	always have to re-think your design.	968	always have to re-think your design.
879		969
880	Keeping your messages simple, concentrating on data structures rather than	970	Keeping your messages simple, concentrating on data structures rather than
881	objects, will keep your messages clean, tidy and efficient.	971	objects, will keep your messages clean, tidy and efficient.
882		972
883	=back	973	=back
884		974
885	=head1 SEE ALSO	975	=head1 SEE ALSO
886		976
		977	L<AnyEvent::MP::Intro> - a gentle introduction.
		978
		979	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		980
		981	L<AnyEvent::MP::Global> - network maintainance and port groups, to find
		982	your applications.
		983
		984	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		985	all nodes.
		986
887	L<AnyEvent>.	987	L<AnyEvent>.
888		988
889	=head1 AUTHOR	989	=head1 AUTHOR
890		990
891	Marc Lehmann <schmorp@schmorp.de>	991	Marc Lehmann <schmorp@schmorp.de>

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Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.55 by root, Fri Aug 14 23:17:17 2009 UTC vs. Revision 1.101 by root, Tue Oct 6 01:31:22 2009 UTC

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Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.55 by root, Fri Aug 14 23:17:17 2009 UTC vs.
Revision 1.101 by root, Tue Oct 6 01:31:22 2009 UTC