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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.30 by root, Tue Aug 4 23:35:51 2009 UTC vs.
Revision 1.79 by root, Fri Sep 4 21:52:09 2009 UTC

…		…
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
		12	$SELF # receiving/own port id in rcv callbacks
		13
		14	# initialise the node so it can send/receive messages
		15	configure;
		16
		17	# ports are message destinations
		18
		19	# sending messages
13	snd $port, type => data...;	20	snd $port, type => data...;
		21	snd $port, @msg;
		22	snd @msg_with_first_element_being_a_port;
14		23
15	$SELF # receiving/own port id in rcv callbacks	24	# creating/using ports, the simple way
		25	my $simple_port = port { my @msg = @_ };
16		26
17	rcv $port, smartmatch => $cb->($port, @msg);	27	# creating/using ports, tagged message matching
18		28	my $port = port;
19	# examples:
20	rcv $port2, ping => sub { snd $_[0], "pong"; 0 };	29	rcv $port, ping => sub { snd $_[0], "pong" };
21	rcv $port1, pong => sub { warn "pong received\n" };	30	rcv $port, pong => sub { warn "pong received\n" };
22	snd $port2, ping => $port1;
23		31
24	# more, smarter, matches (_any_ is exported by this module)	32	# create a port on another node
25	rcv $port, [child_died => $pid] => sub { ...	33	my $port = spawn $node, $initfunc, @initdata;
26	rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3	34
		35	# monitoring
		36	mon $port, $cb->(@msg) # callback is invoked on death
		37	mon $port, $otherport # kill otherport on abnormal death
		38	mon $port, $otherport, @msg # send message on death
		39
		40	=head1 CURRENT STATUS
		41
		42	bin/aemp - stable.
		43	AnyEvent::MP - stable API, should work.
		44	AnyEvent::MP::Intro - explains most concepts.
		45	AnyEvent::MP::Kernel - mostly stable.
		46	AnyEvent::MP::Global - stable but incomplete, protocol not yet final.
		47
		48	stay tuned.
27		49
28	=head1 DESCRIPTION	50	=head1 DESCRIPTION
29		51
30	This module (-family) implements a simple message passing framework.	52	This module (-family) implements a simple message passing framework.
31		53
32	Despite its simplicity, you can securely message other processes running	54	Despite its simplicity, you can securely message other processes running
33	on the same or other hosts.	55	on the same or other hosts, and you can supervise entities remotely.
34		56
35	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	57	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
36	manual page.	58	manual page and the examples under F<eg/>.
37
38	At the moment, this module family is severly broken and underdocumented,
39	so do not use. This was uploaded mainly to reserve the CPAN namespace -
40	stay tuned! The basic API should be finished, however.
41		59
42	=head1 CONCEPTS	60	=head1 CONCEPTS
43		61
44	=over 4	62	=over 4
45		63
46	=item port	64	=item port
47		65
48	A port is something you can send messages to (with the C<snd> function).	66	Not to be confused with a TCP port, a "port" is something you can send
		67	messages to (with the C<snd> function).
49		68
50	Some ports allow you to register C<rcv> handlers that can match specific	69	Ports allow you to register C<rcv> handlers that can match all or just
51	messages. All C<rcv> handlers will receive messages they match, messages	70	some messages. Messages send to ports will not be queued, regardless of
52	will not be queued.	71	anything was listening for them or not.
53		72
54	=item port id - C<noderef#portname>	73	=item port ID - C<nodeid#portname>
55		74
56	A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as	75	A port ID is the concatenation of a node ID, a hash-mark (C<#>) as
57	separator, and a port name (a printable string of unspecified format). An	76	separator, and a port name (a printable string of unspecified format).
58	exception is the the node port, whose ID is identical to its node
59	reference.
60		77
61	=item node	78	=item node
62		79
63	A node is a single process containing at least one port - the node	80	A node is a single process containing at least one port - the node port,
64	port. You can send messages to node ports to find existing ports or to	81	which enables nodes to manage each other remotely, and to create new
65	create new ports, among other things.	82	ports.
66		83
67	Nodes are either private (single-process only), slaves (connected to a	84	Nodes are either public (have one or more listening ports) or private
68	master node only) or public nodes (connectable from unrelated nodes).	85	(no listening ports). Private nodes cannot talk to other private nodes
		86	currently.
69		87
70	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	88	=item node ID - C<[a-za-Z0-9_\-.:]+>
71		89
72	A node reference is a string that either simply identifies the node (for	90	A node ID is a string that uniquely identifies the node within a
73	private and slave nodes), or contains a recipe on how to reach a given	91	network. Depending on the configuration used, node IDs can look like a
74	node (for public nodes).	92	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		93	doesn't interpret node IDs in any way.
75		94
76	This recipe is simply a comma-separated list of C<address:port> pairs (for	95	=item binds - C<ip:port>
77	TCP/IP, other protocols might look different).
78		96
79	Node references come in two flavours: resolved (containing only numerical	97	Nodes can only talk to each other by creating some kind of connection to
80	addresses) or unresolved (where hostnames are used instead of addresses).	98	each other. To do this, nodes should listen on one or more local transport
		99	endpoints - binds. Currently, only standard C<ip:port> specifications can
		100	be used, which specify TCP ports to listen on.
81		101
82	Before using an unresolved node reference in a message you first have to	102	=item seeds - C<host:port>
83	resolve it.	103
		104	When a node starts, it knows nothing about the network. To teach the node
		105	about the network it first has to contact some other node within the
		106	network. This node is called a seed.
		107
		108	Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes
		109	are expected to be long-running, and at least one of those should always
		110	be available. When nodes run out of connections (e.g. due to a network
		111	error), they try to re-establish connections to some seednodes again to
		112	join the network.
		113
		114	Apart from being sued for seeding, seednodes are not special in any way -
		115	every public node can be a seednode.
84		116
85	=back	117	=back
86		118
87	=head1 VARIABLES/FUNCTIONS	119	=head1 VARIABLES/FUNCTIONS
88		120
…		…
90		122
91	=cut	123	=cut
92		124
93	package AnyEvent::MP;	125	package AnyEvent::MP;
94		126
95	use AnyEvent::MP::Base;	127	use AnyEvent::MP::Kernel;
96		128
97	use common::sense;	129	use common::sense;
98		130
99	use Carp ();	131	use Carp ();
100		132
101	use AE ();	133	use AE ();
102		134
103	use base "Exporter";	135	use base "Exporter";
104		136
105	our $VERSION = '0.1';	137	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
		138
106	our @EXPORT = qw(	139	our @EXPORT = qw(
107	NODE $NODE *SELF node_of _any_	140	NODE $NODE *SELF node_of after
108	resolve_node	141	configure
109	become_slave become_public
110	snd rcv mon kil reg psub	142	snd rcv mon mon_guard kil reg psub spawn
111	port	143	port
112	);	144	);
113		145
114	our $SELF;	146	our $SELF;
115		147
…		…
119	kil $SELF, die => $msg;	151	kil $SELF, die => $msg;
120	}	152	}
121		153
122	=item $thisnode = NODE / $NODE	154	=item $thisnode = NODE / $NODE
123		155
124	The C<NODE> function returns, and the C<$NODE> variable contains	156	The C<NODE> function returns, and the C<$NODE> variable contains, the node
125	the noderef of the local node. The value is initialised by a call	157	ID of the node running in the current process. This value is initialised by
126	to C<become_public> or C<become_slave>, after which all local port	158	a call to C<configure>.
127	identifiers become invalid.
128		159
129	=item $noderef = node_of $portid	160	=item $nodeid = node_of $port
130		161
131	Extracts and returns the noderef from a portid or a noderef.	162	Extracts and returns the node ID from a port ID or a node ID.
132		163
133	=item $cv = resolve_node $noderef	164	=item configure $profile, key => value...
134		165
135	Takes an unresolved node reference that may contain hostnames and	166	=item configure key => value...
136	abbreviated IDs, resolves all of them and returns a resolved node
137	reference.
138		167
139	In addition to C<address:port> pairs allowed in resolved noderefs, the	168	Before a node can talk to other nodes on the network (i.e. enter
140	following forms are supported:	169	"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
		171	some other nodes in the network to discover other nodes.
		172
		173	This function configures a node - it must be called exactly once (or
		174	never) before calling other AnyEvent::MP functions.
141		175
142	=over 4	176	=over 4
143		177
144	=item the empty string	178	=item step 1, gathering configuration from profiles
145		179
146	An empty-string component gets resolved as if the default port (4040) was	180	The function first looks up a profile in the aemp configuration (see the
147	specified.	181	L<aemp> commandline utility). The profile name can be specified via the
		182	named C<profile> parameter or can simply be the first parameter). If it is
		183	missing, then the nodename (F<uname -n>) will be used as profile name.
148		184
149	=item naked port numbers (e.g. C<1234>)	185	The profile data is then gathered as follows:
150		186
151	These are resolved by prepending the local nodename and a colon, to be	187	First, all remaining key => value pairs (all of which are conveniently
152	further resolved.	188	undocumented at the moment) will be interpreted as configuration
		189	data. Then they will be overwritten by any values specified in the global
		190	default configuration (see the F<aemp> utility), then the chain of
		191	profiles chosen by the profile name (and any C<parent> attributes).
153		192
154	=item hostnames (e.g. C<localhost:1234>, C<localhost>)	193	That means that the values specified in the profile have highest priority
		194	and the values specified directly via C<configure> have lowest priority,
		195	and can only be used to specify defaults.
155		196
156	These are resolved by using AnyEvent::DNS to resolve them, optionally	197	If the profile specifies a node ID, then this will become the node ID of
157	looking up SRV records for the C<aemp=4040> port, if no port was	198	this process. If not, then the profile name will be used as node ID. The
158	specified.	199	special node ID of C<anon/> will be replaced by a random node ID.
		200
		201	=item step 2, bind listener sockets
		202
		203	The next step is to look up the binds in the profile, followed by binding
		204	aemp protocol listeners on all binds specified (it is possible and valid
		205	to have no binds, meaning that the node cannot be contacted form the
		206	outside. This means the node cannot talk to other nodes that also have no
		207	binds, but it can still talk to all "normal" nodes).
		208
		209	If the profile does not specify a binds list, then a default of C<*> is
		210	used, meaning the node will bind on a dynamically-assigned port on every
		211	local IP address it finds.
		212
		213	=item step 3, connect to seed nodes
		214
		215	As the last step, the seeds list from the profile is passed to the
		216	L<AnyEvent::MP::Global> module, which will then use it to keep
		217	connectivity with at least one node at any point in time.
159		218
160	=back	219	=back
		220
		221	Example: become a distributed node using the locla node name as profile.
		222	This should be the most common form of invocation for "daemon"-type nodes.
		223
		224	configure
		225
		226	Example: become an anonymous node. This form is often used for commandline
		227	clients.
		228
		229	configure nodeid => "anon/";
		230
		231	Example: configure a node using a profile called seed, which si suitable
		232	for a seed node as it binds on all local addresses on a fixed port (4040,
		233	customary for aemp).
		234
		235	# use the aemp commandline utility
		236	# aemp profile seed nodeid anon/ binds '*:4040'
		237
		238	# then use it
		239	configure profile => "seed";
		240
		241	# or simply use aemp from the shell again:
		242	# aemp run profile seed
		243
		244	# or provide a nicer-to-remember nodeid
		245	# aemp run profile seed nodeid "$(hostname)"
161		246
162	=item $SELF	247	=item $SELF
163		248
164	Contains the current port id while executing C<rcv> callbacks or C<psub>	249	Contains the current port id while executing C<rcv> callbacks or C<psub>
165	blocks.	250	blocks.
166		251
167	=item SELF, %SELF, @SELF...	252	=item *SELF, SELF, %SELF, @SELF...
168		253
169	Due to some quirks in how perl exports variables, it is impossible to	254	Due to some quirks in how perl exports variables, it is impossible to
170	just export C<$SELF>, all the symbols called C<SELF> are exported by this	255	just export C<$SELF>, all the symbols named C<SELF> are exported by this
171	module, but only C<$SELF> is currently used.	256	module, but only C<$SELF> is currently used.
172		257
173	=item snd $portid, type => @data	258	=item snd $port, type => @data
174		259
175	=item snd $portid, @msg	260	=item snd $port, @msg
176		261
177	Send the given message to the given port ID, which can identify either	262	Send the given message to the given port, which can identify either a
178	a local or a remote port, and can be either a string or soemthignt hat	263	local or a remote port, and must be a port ID.
179	stringifies a sa port ID (such as a port object :).
180		264
181	While the message can be about anything, it is highly recommended to use a	265	While the message can be almost anything, it is highly recommended to
182	string as first element (a portid, or some word that indicates a request	266	use a string as first element (a port ID, or some word that indicates a
183	type etc.).	267	request type etc.) and to consist if only simple perl values (scalars,
		268	arrays, hashes) - if you think you need to pass an object, think again.
184		269
185	The message data effectively becomes read-only after a call to this	270	The message data logically becomes read-only after a call to this
186	function: modifying any argument is not allowed and can cause many	271	function: modifying any argument (or values referenced by them) is
187	problems.	272	forbidden, as there can be considerable time between the call to C<snd>
		273	and the time the message is actually being serialised - in fact, it might
		274	never be copied as within the same process it is simply handed to the
		275	receiving port.
188		276
189	The type of data you can transfer depends on the transport protocol: when	277	The type of data you can transfer depends on the transport protocol: when
190	JSON is used, then only strings, numbers and arrays and hashes consisting	278	JSON is used, then only strings, numbers and arrays and hashes consisting
191	of those are allowed (no objects). When Storable is used, then anything	279	of those are allowed (no objects). When Storable is used, then anything
192	that Storable can serialise and deserialise is allowed, and for the local	280	that Storable can serialise and deserialise is allowed, and for the local
193	node, anything can be passed.	281	node, anything can be passed. Best rely only on the common denominator of
		282	these.
194		283
195	=item kil $portid[, @reason]	284	=item $local_port = port
196		285
197	Kill the specified port with the given C<@reason>.	286	Create a new local port object and returns its port ID. Initially it has
		287	no callbacks set and will throw an error when it receives messages.
198		288
199	If no C<@reason> is specified, then the port is killed "normally" (linked	289	=item $local_port = port { my @msg = @_ }
200	ports will not be kileld, or even notified).
201		290
202	Otherwise, linked ports get killed with the same reason (second form of	291	Creates a new local port, and returns its ID. Semantically the same as
203	C<mon>, see below).	292	creating a port and calling C<rcv $port, $callback> on it.
204		293
205	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	294	The block will be called for every message received on the port, with the
206	will be reported as reason C<< die => $@ >>.	295	global variable C<$SELF> set to the port ID. Runtime errors will cause the
		296	port to be C<kil>ed. The message will be passed as-is, no extra argument
		297	(i.e. no port ID) will be passed to the callback.
207		298
208	Transport/communication errors are reported as C<< transport_error =>	299	If you want to stop/destroy the port, simply C<kil> it:
209	$message >>.
210		300
211	=item $guard = mon $portid, $cb->(@reason)	301	my $port = port {
		302	my @msg = @_;
		303	...
		304	kil $SELF;
		305	};
212		306
213	=item $guard = mon $portid, $otherport	307	=cut
214		308
215	=item $guard = mon $portid, $otherport, @msg	309	sub rcv($@);
216		310
		311	sub _kilme {
		312	die "received message on port without callback";
		313	}
		314
		315	sub port(;&) {
		316	my $id = "$UNIQ." . $ID++;
		317	my $port = "$NODE#$id";
		318
		319	rcv $port, shift \|\| \&_kilme;
		320
		321	$port
		322	}
		323
		324	=item rcv $local_port, $callback->(@msg)
		325
		326	Replaces the default callback on the specified port. There is no way to
		327	remove the default callback: use C<sub { }> to disable it, or better
		328	C<kil> the port when it is no longer needed.
		329
		330	The global C<$SELF> (exported by this module) contains C<$port> while
		331	executing the callback. Runtime errors during callback execution will
		332	result in the port being C<kil>ed.
		333
		334	The default callback received all messages not matched by a more specific
		335	C<tag> match.
		336
		337	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
		338
		339	Register (or replace) callbacks to be called on messages starting with the
		340	given tag on the given port (and return the port), or unregister it (when
		341	C<$callback> is C<$undef> or missing). There can only be one callback
		342	registered for each tag.
		343
		344	The original message will be passed to the callback, after the first
		345	element (the tag) has been removed. The callback will use the same
		346	environment as the default callback (see above).
		347
		348	Example: create a port and bind receivers on it in one go.
		349
		350	my $port = rcv port,
		351	msg1 => sub { ... },
		352	msg2 => sub { ... },
		353	;
		354
		355	Example: create a port, bind receivers and send it in a message elsewhere
		356	in one go:
		357
		358	snd $otherport, reply =>
		359	rcv port,
		360	msg1 => sub { ... },
		361	...
		362	;
		363
		364	Example: temporarily register a rcv callback for a tag matching some port
		365	(e.g. for a rpc reply) and unregister it after a message was received.
		366
		367	rcv $port, $otherport => sub {
		368	my @reply = @_;
		369
		370	rcv $SELF, $otherport;
		371	};
		372
		373	=cut
		374
		375	sub rcv($@) {
		376	my $port = shift;
		377	my ($nodeid, $portid) = split /#/, $port, 2;
		378
		379	$NODE{$nodeid} == $NODE{""}
		380	or Carp::croak "$port: rcv can only be called on local ports, caught";
		381
		382	while (@_) {
		383	if (ref $_[0]) {
		384	if (my $self = $PORT_DATA{$portid}) {
		385	"AnyEvent::MP::Port" eq ref $self
		386	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		387
		388	$self->[2] = shift;
		389	} else {
		390	my $cb = shift;
		391	$PORT{$portid} = sub {
		392	local $SELF = $port;
		393	eval { &$cb }; _self_die if $@;
		394	};
		395	}
		396	} elsif (defined $_[0]) {
		397	my $self = $PORT_DATA{$portid} \|\|= do {
		398	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
		399
		400	$PORT{$portid} = sub {
		401	local $SELF = $port;
		402
		403	if (my $cb = $self->[1]{$_[0]}) {
		404	shift;
		405	eval { &$cb }; _self_die if $@;
		406	} else {
		407	&{ $self->[0] };
		408	}
		409	};
		410
		411	$self
		412	};
		413
		414	"AnyEvent::MP::Port" eq ref $self
		415	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		416
		417	my ($tag, $cb) = splice @_, 0, 2;
		418
		419	if (defined $cb) {
		420	$self->[1]{$tag} = $cb;
		421	} else {
		422	delete $self->[1]{$tag};
		423	}
		424	}
		425	}
		426
		427	$port
		428	}
		429
		430	=item $closure = psub { BLOCK }
		431
		432	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
		433	closure is executed, sets up the environment in the same way as in C<rcv>
		434	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		435
		436	This is useful when you register callbacks from C<rcv> callbacks:
		437
		438	rcv delayed_reply => sub {
		439	my ($delay, @reply) = @_;
		440	my $timer = AE::timer $delay, 0, psub {
		441	snd @reply, $SELF;
		442	};
		443	};
		444
		445	=cut
		446
		447	sub psub(&) {
		448	my $cb = shift;
		449
		450	my $port = $SELF
		451	or Carp::croak "psub can only be called from within rcv or psub callbacks, not";
		452
		453	sub {
		454	local $SELF = $port;
		455
		456	if (wantarray) {
		457	my @res = eval { &$cb };
		458	_self_die if $@;
		459	@res
		460	} else {
		461	my $res = eval { &$cb };
		462	_self_die if $@;
		463	$res
		464	}
		465	}
		466	}
		467
		468	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
		469
		470	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
		471
		472	=item $guard = mon $port # kill $SELF when $port dies
		473
		474	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
		475
217	Monitor the given port and do something when the port is killed.	476	Monitor the given port and do something when the port is killed or
		477	messages to it were lost, and optionally return a guard that can be used
		478	to stop monitoring again.
218		479
219	In the first form, the callback is simply called with any number	480	In the first form (callback), the callback is simply called with any
220	of C<@reason> elements (no @reason means that the port was deleted	481	number of C<@reason> elements (no @reason means that the port was deleted
221	"normally"). Note also that I<< the callback B<must> never die >>, so use	482	"normally"). Note also that I<< the callback B<must> never die >>, so use
222	C<eval> if unsure.	483	C<eval> if unsure.
223		484
224	In the second form, the other port will be C<kil>'ed with C<@reason>, iff	485	In the second form (another port given), the other port (C<$rcvport>)
225	a @reason was specified, i.e. on "normal" kils nothing happens, while	486	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
226	under all other conditions, the other port is killed with the same reason.	487	"normal" kils nothing happens, while under all other conditions, the other
		488	port is killed with the same reason.
227		489
		490	The third form (kill self) is the same as the second form, except that
		491	C<$rvport> defaults to C<$SELF>.
		492
228	In the last form, a message of the form C<@msg, @reason> will be C<snd>.	493	In the last form (message), a message of the form C<@msg, @reason> will be
		494	C<snd>.
		495
		496	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		497	alert was raised), they are removed and will not trigger again.
		498
		499	As a rule of thumb, monitoring requests should always monitor a port from
		500	a local port (or callback). The reason is that kill messages might get
		501	lost, just like any other message. Another less obvious reason is that
		502	even monitoring requests can get lost (for example, when the connection
		503	to the other node goes down permanently). When monitoring a port locally
		504	these problems do not exist.
		505
		506	C<mon> effectively guarantees that, in the absence of hardware failures,
		507	after starting the monitor, either all messages sent to the port will
		508	arrive, or the monitoring action will be invoked after possible message
		509	loss has been detected. No messages will be lost "in between" (after
		510	the first lost message no further messages will be received by the
		511	port). After the monitoring action was invoked, further messages might get
		512	delivered again.
		513
		514	Inter-host-connection timeouts and monitoring depend on the transport
		515	used. The only transport currently implemented is TCP, and AnyEvent::MP
		516	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		517	non-idle connection, and usually around two hours for idle conenctions).
		518
		519	This means that monitoring is good for program errors and cleaning up
		520	stuff eventually, but they are no replacement for a timeout when you need
		521	to ensure some maximum latency.
229		522
230	Example: call a given callback when C<$port> is killed.	523	Example: call a given callback when C<$port> is killed.
231		524
232	mon $port, sub { warn "port died because of <@_>\n" };	525	mon $port, sub { warn "port died because of <@_>\n" };
233		526
234	Example: kill ourselves when C<$port> is killed abnormally.	527	Example: kill ourselves when C<$port> is killed abnormally.
235		528
236	mon $port, $self;	529	mon $port;
237		530
238	Example: send us a restart message another C<$port> is killed.	531	Example: send us a restart message when another C<$port> is killed.
239		532
240	mon $port, $self => "restart";	533	mon $port, $self => "restart";
241		534
242	=cut	535	=cut
243		536
244	sub mon {	537	sub mon {
245	my ($noderef, $port) = split /#/, shift, 2;	538	my ($nodeid, $port) = split /#/, shift, 2;
246		539
247	my $node = $NODE{$noderef} \|\| add_node $noderef;	540	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
248		541
249	my $cb = shift;	542	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
250		543
251	unless (ref $cb) {	544	unless (ref $cb) {
252	if (@_) {	545	if (@_) {
253	# send a kill info message	546	# send a kill info message
254	my (@msg) = ($cb, @_);	547	my (@msg) = ($cb, @_);
…		…
272	is killed, the references will be freed.	565	is killed, the references will be freed.
273		566
274	Optionally returns a guard that will stop the monitoring.	567	Optionally returns a guard that will stop the monitoring.
275		568
276	This function is useful when you create e.g. timers or other watchers and	569	This function is useful when you create e.g. timers or other watchers and
277	want to free them when the port gets killed:	570	want to free them when the port gets killed (note the use of C<psub>):
278		571
279	$port->rcv (start => sub {	572	$port->rcv (start => sub {
280	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	573	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
281	undef $timer if 0.9 < rand;	574	undef $timer if 0.9 < rand;
282	});	575	});
283	});	576	});
284		577
285	=cut	578	=cut
286		579
287	sub mon_guard {	580	sub mon_guard {
288	my ($port, @refs) = @_;	581	my ($port, @refs) = @_;
289		582
		583	#TODO: mon-less form?
		584
290	mon $port, sub { 0 && @refs }	585	mon $port, sub { 0 && @refs }
291	}	586	}
292		587
293	=item lnk $port1, $port2	588	=item kil $port[, @reason]
294		589
295	Link two ports. This is simply a shorthand for:	590	Kill the specified port with the given C<@reason>.
296		591
297	mon $port1, $port2;	592	If no C<@reason> is specified, then the port is killed "normally" (ports
298	mon $port2, $port1;	593	monitoring other ports will not necessarily die because a port dies
		594	"normally").
299		595
300	It means that if either one is killed abnormally, the other one gets	596	Otherwise, linked ports get killed with the same reason (second form of
301	killed as well.	597	C<mon>, see above).
302		598
303	=item $local_port = port	599	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
		600	will be reported as reason C<< die => $@ >>.
304		601
305	Create a new local port object that supports message matching.	602	Transport/communication errors are reported as C<< transport_error =>
		603	$message >>.
306		604
307	=item $portid = port { my @msg = @_; $finished }
308
309	Creates a "mini port", that is, a very lightweight port without any
310	pattern matching behind it, and returns its ID.
311
312	The block will be called for every message received on the port. When the
313	callback returns a true value its job is considered "done" and the port
314	will be destroyed. Otherwise it will stay alive.
315
316	The message will be passed as-is, no extra argument (i.e. no port id) will
317	be passed to the callback.
318
319	If you need the local port id in the callback, this works nicely:
320
321	my $port; $port = miniport {
322	snd $otherport, reply => $port;
323	};
324
325	=cut	605	=cut
326		606
327	sub port(;&) {	607	=item $port = spawn $node, $initfunc[, @initdata]
328	my $id = "$UNIQ." . $ID++;
329	my $port = "$NODE#$id";
330		608
331	if (@_) {	609	Creates a port on the node C<$node> (which can also be a port ID, in which
332	my $cb = shift;	610	case it's the node where that port resides).
333	$PORT{$id} = sub {	611
334	local $SELF = $port;	612	The port ID of the newly created port is returned immediately, and it is
335	eval {	613	possible to immediately start sending messages or to monitor the port.
336	&$cb	614
337	and kil $id;	615	After the port has been created, the init function is called on the remote
		616	node, in the same context as a C<rcv> callback. This function must be a
		617	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
		618	specify a function in the main program, use C<::name>.
		619
		620	If the function doesn't exist, then the node tries to C<require>
		621	the package, then the package above the package and so on (e.g.
		622	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
		623	exists or it runs out of package names.
		624
		625	The init function is then called with the newly-created port as context
		626	object (C<$SELF>) and the C<@initdata> values as arguments.
		627
		628	A common idiom is to pass a local port, immediately monitor the spawned
		629	port, and in the remote init function, immediately monitor the passed
		630	local port. This two-way monitoring ensures that both ports get cleaned up
		631	when there is a problem.
		632
		633	Example: spawn a chat server port on C<$othernode>.
		634
		635	# this node, executed from within a port context:
		636	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
		637	mon $server;
		638
		639	# init function on C<$othernode>
		640	sub connect {
		641	my ($srcport) = @_;
		642
		643	mon $srcport;
		644
		645	rcv $SELF, sub {
338	};	646	...
339	_self_die if $@;
340	};
341	} else {
342	my $self = bless {
343	id => "$NODE#$id",
344	}, "AnyEvent::MP::Port";
345
346	$PORT_DATA{$id} = $self;
347	$PORT{$id} = sub {
348	local $SELF = $port;
349
350	eval {
351	for (@{ $self->{rc0}{$_[0]} }) {
352	$_ && &{$_->[0]}
353	&& undef $_;
354	}
355
356	for (@{ $self->{rcv}{$_[0]} }) {
357	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
358	&& &{$_->[0]}
359	&& undef $_;
360	}
361
362	for (@{ $self->{any} }) {
363	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
364	&& &{$_->[0]}
365	&& undef $_;
366	}
367	};
368	_self_die if $@;
369	};	647	};
370	}	648	}
371		649
372	$port
373	}
374
375	=item reg $portid, $name
376
377	Registers the given port under the name C<$name>. If the name already
378	exists it is replaced.
379
380	A port can only be registered under one well known name.
381
382	A port automatically becomes unregistered when it is killed.
383
384	=cut	650	=cut
385		651
386	sub reg(@) {	652	sub _spawn {
387	my ($portid, $name) = @_;	653	my $port = shift;
		654	my $init = shift;
388		655
389	$REG{$name} = $portid;	656	local $SELF = "$NODE#$port";
390	}	657	eval {
391		658	&{ load_func $init }
392	=item rcv $portid, tagstring => $callback->(@msg), ...
393
394	=item rcv $portid, $smartmatch => $callback->(@msg), ...
395
396	=item rcv $portid, [$smartmatch...] => $callback->(@msg), ...
397
398	Register callbacks to be called on matching messages on the given port.
399
400	The callback has to return a true value when its work is done, after
401	which is will be removed, or a false value in which case it will stay
402	registered.
403
404	The global C<$SELF> (exported by this module) contains C<$portid> while
405	executing the callback.
406
407	Runtime errors wdurign callback execution will result in the port being
408	C<kil>ed.
409
410	If the match is an array reference, then it will be matched against the
411	first elements of the message, otherwise only the first element is being
412	matched.
413
414	Any element in the match that is specified as C<_any_> (a function
415	exported by this module) matches any single element of the message.
416
417	While not required, it is highly recommended that the first matching
418	element is a string identifying the message. The one-string-only match is
419	also the most efficient match (by far).
420
421	=cut
422
423	sub rcv($@) {
424	my ($noderef, $port) = split /#/, shift, 2;
425
426	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}
427	or Carp::croak "$noderef#$port: rcv can only be called on local ports, caught";
428
429	my $self = $PORT_DATA{$port}
430	or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught";
431
432	"AnyEvent::MP::Port" eq ref $self
433	or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught";
434
435	while (@_) {
436	my ($match, $cb) = splice @_, 0, 2;
437
438	if (!ref $match) {
439	push @{ $self->{rc0}{$match} }, [$cb];
440	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
441	my ($type, @match) = @$match;
442	@match
443	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
444	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
445	} else {
446	push @{ $self->{any} }, [$cb, $match];
447	}
448	}
449	}
450
451	=item $closure = psub { BLOCK }
452
453	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
454	closure is executed, sets up the environment in the same way as in C<rcv>
455	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
456
457	This is useful when you register callbacks from C<rcv> callbacks:
458
459	rcv delayed_reply => sub {
460	my ($delay, @reply) = @_;
461	my $timer = AE::timer $delay, 0, psub {
462	snd @reply, $SELF;
463	};
464	};	659	};
465
466	=cut
467
468	sub psub(&) {
469	my $cb = shift;
470
471	my $port = $SELF
472	or Carp::croak "psub can only be called from within rcv or psub callbacks, not";
473
474	sub {
475	local $SELF = $port;
476
477	if (wantarray) {
478	my @res = eval { &$cb };
479	_self_die if $@;	660	_self_die if $@;
480	@res	661	}
481	} else {	662
482	my $res = eval { &$cb };	663	sub spawn(@) {
483	_self_die if $@;	664	my ($nodeid, undef) = split /#/, shift, 2;
484	$res	665
485	}	666	my $id = "$RUNIQ." . $ID++;
		667
		668	$_[0] =~ /::/
		669	or Carp::croak "spawn init function must be a fully-qualified name, caught";
		670
		671	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
		672
		673	"$nodeid#$id"
		674	}
		675
		676	=item after $timeout, @msg
		677
		678	=item after $timeout, $callback
		679
		680	Either sends the given message, or call the given callback, after the
		681	specified number of seconds.
		682
		683	This is simply a utility function that comes in handy at times - the
		684	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		685	so it may go away in the future.
		686
		687	=cut
		688
		689	sub after($@) {
		690	my ($timeout, @action) = @_;
		691
		692	my $t; $t = AE::timer $timeout, 0, sub {
		693	undef $t;
		694	ref $action[0]
		695	? $action[0]()
		696	: snd @action;
486	}	697	};
487	}	698	}
488		699
489	=back	700	=back
490		701
491	=head1 FUNCTIONS FOR NODES	702	=head1 AnyEvent::MP vs. Distributed Erlang
		703
		704	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
		705	== aemp node, Erlang process == aemp port), so many of the documents and
		706	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
		707	sample:
		708
		709	http://www.Erlang.se/doc/programming_rules.shtml
		710	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
		711	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6
		712	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
		713
		714	Despite the similarities, there are also some important differences:
492		715
493	=over 4	716	=over 4
494		717
495	=item become_public $noderef	718	=item * Node IDs are arbitrary strings in AEMP.
496		719
497	Tells the node to become a public node, i.e. reachable from other nodes.
498
499	The first argument is the (unresolved) node reference of the local node
500	(if missing then the empty string is used).
501
502	It is quite common to not specify anything, in which case the local node
503	tries to listen on the default port, or to only specify a port number, in
504	which case AnyEvent::MP tries to guess the local addresses.
505
506	=cut
507
508	=back
509
510	=head1 NODE MESSAGES
511
512	Nodes understand the following messages sent to them. Many of them take
513	arguments called C<@reply>, which will simply be used to compose a reply
514	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
515	the remaining arguments are simply the message data.
516
517	While other messages exist, they are not public and subject to change.
518
519	=over 4
520
521	=cut
522
523	=item lookup => $name, @reply
524
525	Replies with the port ID of the specified well-known port, or C<undef>.
526
527	=item devnull => ...
528
529	Generic data sink/CPU heat conversion.
530
531	=item relay => $port, @msg
532
533	Simply forwards the message to the given port.
534
535	=item eval => $string[ @reply]
536
537	Evaluates the given string. If C<@reply> is given, then a message of the
538	form C<@reply, $@, @evalres> is sent.
539
540	Example: crash another node.
541
542	snd $othernode, eval => "exit";
543
544	=item time => @reply
545
546	Replies the the current node time to C<@reply>.
547
548	Example: tell the current node to send the current time to C<$myport> in a
549	C<timereply> message.
550
551	snd $NODE, time => $myport, timereply => 1, 2;
552	# => snd $myport, timereply => 1, 2, <time>
553
554	=back
555
556	=head1 AnyEvent::MP vs. Distributed Erlang
557
558	AnyEvent::MP got lots of its ideas from distributed erlang (erlang node
559	== aemp node, erlang process == aemp port), so many of the documents and
560	programming techniques employed by erlang apply to AnyEvent::MP. Here is a
561	sample:
562
563	http://www.erlang.se/doc/programming_rules.shtml
564	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
565	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
566	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
567
568	Despite the similarities, there are also some important differences:
569
570	=over 4
571
572	=item * Node references contain the recipe on how to contact them.
573
574	Erlang relies on special naming and DNS to work everywhere in the	720	Erlang relies on special naming and DNS to work everywhere in the same
575	same way. AEMP relies on each node knowing it's own address(es), with	721	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
576	convenience functionality.	722	configuration or DNS), but will otherwise discover other odes itself.
577		723
578	This means that AEMP requires a less tightly controlled environment at the	724	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
579	cost of longer node references and a slightly higher management overhead.	725	uses "local ports are like remote ports".
		726
		727	The failure modes for local ports are quite different (runtime errors
		728	only) then for remote ports - when a local port dies, you I<know> it dies,
		729	when a connection to another node dies, you know nothing about the other
		730	port.
		731
		732	Erlang pretends remote ports are as reliable as local ports, even when
		733	they are not.
		734
		735	AEMP encourages a "treat remote ports differently" philosophy, with local
		736	ports being the special case/exception, where transport errors cannot
		737	occur.
580		738
581	=item * Erlang uses processes and a mailbox, AEMP does not queue.	739	=item * Erlang uses processes and a mailbox, AEMP does not queue.
582		740
583	Erlang uses processes that selctively receive messages, and therefore	741	Erlang uses processes that selectively receive messages, and therefore
584	needs a queue. AEMP is event based, queuing messages would serve no useful	742	needs a queue. AEMP is event based, queuing messages would serve no
585	purpose.	743	useful purpose. For the same reason the pattern-matching abilities of
		744	AnyEvent::MP are more limited, as there is little need to be able to
		745	filter messages without dequeuing them.
586		746
587	(But see L<Coro::MP> for a more erlang-like process model on top of AEMP).	747	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
588		748
589	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	749	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
590		750
591	Sending messages in erlang is synchronous and blocks the process. AEMP	751	Sending messages in Erlang is synchronous and blocks the process (and
592	sends are immediate, connection establishment is handled in the	752	so does not need a queue that can overflow). AEMP sends are immediate,
593	background.	753	connection establishment is handled in the background.
594		754
595	=item * Erlang can silently lose messages, AEMP cannot.	755	=item * Erlang suffers from silent message loss, AEMP does not.
596		756
597	Erlang makes few guarantees on messages delivery - messages can get lost	757	Erlang makes few guarantees on messages delivery - messages can get lost
598	without any of the processes realising it (i.e. you send messages a, b,	758	without any of the processes realising it (i.e. you send messages a, b,
599	and c, and the other side only receives messages a and c).	759	and c, and the other side only receives messages a and c).
600		760
601	AEMP guarantees correct ordering, and the guarantee that there are no	761	AEMP guarantees correct ordering, and the guarantee that after one message
602	holes in the message sequence.	762	is lost, all following ones sent to the same port are lost as well, until
603		763	monitoring raises an error, so there are no silent "holes" in the message
604	=item * In erlang, processes can be declared dead and later be found to be	764	sequence.
605	alive.
606
607	In erlang it can happen that a monitored process is declared dead and
608	linked processes get killed, but later it turns out that the process is
609	still alive - and can receive messages.
610
611	In AEMP, when port monitoring detects a port as dead, then that port will
612	eventually be killed - it cannot happen that a node detects a port as dead
613	and then later sends messages to it, finding it is still alive.
614		765
615	=item * Erlang can send messages to the wrong port, AEMP does not.	766	=item * Erlang can send messages to the wrong port, AEMP does not.
616		767
617	In erlang it is quite possible that a node that restarts reuses a process	768	In Erlang it is quite likely that a node that restarts reuses a process ID
618	ID known to other nodes for a completely different process, causing	769	known to other nodes for a completely different process, causing messages
619	messages destined for that process to end up in an unrelated process.	770	destined for that process to end up in an unrelated process.
620		771
621	AEMP never reuses port IDs, so old messages or old port IDs floating	772	AEMP never reuses port IDs, so old messages or old port IDs floating
622	around in the network will not be sent to an unrelated port.	773	around in the network will not be sent to an unrelated port.
623		774
624	=item * Erlang uses unprotected connections, AEMP uses secure	775	=item * Erlang uses unprotected connections, AEMP uses secure
625	authentication and can use TLS.	776	authentication and can use TLS.
626		777
627	AEMP can use a proven protocol - SSL/TLS - to protect connections and	778	AEMP can use a proven protocol - TLS - to protect connections and
628	securely authenticate nodes.	779	securely authenticate nodes.
629		780
630	=item * The AEMP protocol is optimised for both text-based and binary	781	=item * The AEMP protocol is optimised for both text-based and binary
631	communications.	782	communications.
632		783
633	The AEMP protocol, unlike the erlang protocol, supports both	784	The AEMP protocol, unlike the Erlang protocol, supports both programming
634	language-independent text-only protocols (good for debugging) and binary,	785	language independent text-only protocols (good for debugging) and binary,
635	language-specific serialisers (e.g. Storable).	786	language-specific serialisers (e.g. Storable). By default, unless TLS is
		787	used, the protocol is actually completely text-based.
636		788
637	It has also been carefully designed to be implementable in other languages	789	It has also been carefully designed to be implementable in other languages
638	with a minimum of work while gracefully degrading fucntionality to make the	790	with a minimum of work while gracefully degrading functionality to make the
639	protocol simple.	791	protocol simple.
640		792
		793	=item * AEMP has more flexible monitoring options than Erlang.
		794
		795	In Erlang, you can chose to receive I<all> exit signals as messages
		796	or I<none>, there is no in-between, so monitoring single processes is
		797	difficult to implement. Monitoring in AEMP is more flexible than in
		798	Erlang, as one can choose between automatic kill, exit message or callback
		799	on a per-process basis.
		800
		801	=item * Erlang tries to hide remote/local connections, AEMP does not.
		802
		803	Monitoring in Erlang is not an indicator of process death/crashes, in the
		804	same way as linking is (except linking is unreliable in Erlang).
		805
		806	In AEMP, you don't "look up" registered port names or send to named ports
		807	that might or might not be persistent. Instead, you normally spawn a port
		808	on the remote node. The init function monitors you, and you monitor the
		809	remote port. Since both monitors are local to the node, they are much more
		810	reliable (no need for C<spawn_link>).
		811
		812	This also saves round-trips and avoids sending messages to the wrong port
		813	(hard to do in Erlang).
		814
641	=back	815	=back
642		816
		817	=head1 RATIONALE
		818
		819	=over 4
		820
		821	=item Why strings for port and node IDs, why not objects?
		822
		823	We considered "objects", but found that the actual number of methods
		824	that can be called are quite low. Since port and node IDs travel over
		825	the network frequently, the serialising/deserialising would add lots of
		826	overhead, as well as having to keep a proxy object everywhere.
		827
		828	Strings can easily be printed, easily serialised etc. and need no special
		829	procedures to be "valid".
		830
		831	And as a result, a miniport consists of a single closure stored in a
		832	global hash - it can't become much cheaper.
		833
		834	=item Why favour JSON, why not a real serialising format such as Storable?
		835
		836	In fact, any AnyEvent::MP node will happily accept Storable as framing
		837	format, but currently there is no way to make a node use Storable by
		838	default (although all nodes will accept it).
		839
		840	The default framing protocol is JSON because a) JSON::XS is many times
		841	faster for small messages and b) most importantly, after years of
		842	experience we found that object serialisation is causing more problems
		843	than it solves: Just like function calls, objects simply do not travel
		844	easily over the network, mostly because they will always be a copy, so you
		845	always have to re-think your design.
		846
		847	Keeping your messages simple, concentrating on data structures rather than
		848	objects, will keep your messages clean, tidy and efficient.
		849
		850	=back
		851
643	=head1 SEE ALSO	852	=head1 SEE ALSO
		853
		854	L<AnyEvent::MP::Intro> - a gentle introduction.
		855
		856	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		857
		858	L<AnyEvent::MP::Global> - network maintainance and port groups, to find
		859	your applications.
644		860
645	L<AnyEvent>.	861	L<AnyEvent>.
646		862
647	=head1 AUTHOR	863	=head1 AUTHOR
648		864

Diff Legend

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

Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.30 by root, Tue Aug 4 23:35:51 2009 UTC vs. Revision 1.79 by root, Fri Sep 4 21:52:09 2009 UTC

Diff Legend

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.30 by root, Tue Aug 4 23:35:51 2009 UTC vs.
Revision 1.79 by root, Fri Sep 4 21:52:09 2009 UTC