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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.27 by root, Tue Aug 4 22:13:45 2009 UTC vs.
Revision 1.67 by root, Fri Aug 28 22:21:53 2009 UTC

…		…
8		8
9	$NODE # contains this node's noderef	9	$NODE # contains this node's noderef
10	NODE # returns this node's noderef	10	NODE # returns this node's noderef
11	NODE $port # returns the noderef of the port	11	NODE $port # returns the noderef of the port
12		12
		13	$SELF # receiving/own port id in rcv callbacks
		14
		15	# initialise the node so it can send/receive messages
		16	initialise_node;
		17
		18	# ports are message endpoints
		19
		20	# sending messages
13	snd $port, type => data...;	21	snd $port, type => data...;
		22	snd $port, @msg;
		23	snd @msg_with_first_element_being_a_port;
14		24
15	$SELF # receiving/own port id in rcv callbacks	25	# creating/using ports, the simple way
		26	my $simple_port = port { my @msg = @_; 0 };
16		27
17	rcv $port, smartmatch => $cb->($port, @msg);	28	# creating/using ports, tagged message matching
18		29	my $port = port;
19	# examples:
20	rcv $port2, ping => sub { snd $_[0], "pong"; 0 };	30	rcv $port, ping => sub { snd $_[0], "pong"; 0 };
21	rcv $port1, pong => sub { warn "pong received\n" };	31	rcv $port, pong => sub { warn "pong received\n"; 0 };
22	snd $port2, ping => $port1;
23		32
24	# more, smarter, matches (_any_ is exported by this module)	33	# create a port on another node
25	rcv $port, [child_died => $pid] => sub { ...	34	my $port = spawn $node, $initfunc, @initdata;
26	rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3	35
		36	# monitoring
		37	mon $port, $cb->(@msg) # callback is invoked on death
		38	mon $port, $otherport # kill otherport on abnormal death
		39	mon $port, $otherport, @msg # send message on death
		40
		41	=head1 CURRENT STATUS
		42
		43	AnyEvent::MP - stable API, should work
		44	AnyEvent::MP::Intro - outdated
		45	AnyEvent::MP::Kernel - mostly stable
		46	AnyEvent::MP::Global - mostly stable
		47	AnyEvent::MP::Node - mostly stable, but internal anyways
		48	AnyEvent::MP::Transport - mostly stable, but internal anyways
		49
		50	stay tuned.
27		51
28	=head1 DESCRIPTION	52	=head1 DESCRIPTION
29		53
30	This module (-family) implements a simple message passing framework.	54	This module (-family) implements a simple message passing framework.
31		55
32	Despite its simplicity, you can securely message other processes running	56	Despite its simplicity, you can securely message other processes running
33	on the same or other hosts.	57	on the same or other hosts, and you can supervise entities remotely.
34		58
35	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	59	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
36	manual page.	60	manual page and the examples under F<eg/>.
37		61
38	At the moment, this module family is severly broken and underdocumented,	62	At the moment, this module family is a bit 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		63
42	=head1 CONCEPTS	64	=head1 CONCEPTS
43		65
44	=over 4	66	=over 4
45		67
46	=item port	68	=item port
47		69
48	A port is something you can send messages to with the C<snd> function, and	70	A port is something you can send messages to (with the C<snd> function).
49	you can register C<rcv> handlers with. All C<rcv> handlers will receive
50	messages they match, messages will not be queued.
51		71
		72	Ports allow you to register C<rcv> handlers that can match all or just
		73	some messages. Messages send to ports will not be queued, regardless of
		74	anything was listening for them or not.
		75
52	=item port id - C<noderef#portname>	76	=item port ID - C<nodeid#portname>
53		77
54	A port id is always the noderef, a hash-mark (C<#>) as separator, followed	78	A port ID is the concatenation of a node ID, a hash-mark (C<#>) as
55	by a port name (a printable string of unspecified format).	79	separator, and a port name (a printable string of unspecified format).
56		80
57	=item node	81	=item node
58		82
59	A node is a single process containing at least one port - the node	83	A node is a single process containing at least one port - the node port,
60	port. You can send messages to node ports to let them create new ports,	84	which enables nodes to manage each other remotely, and to create new
61	among other things.	85	ports.
62		86
63	Initially, nodes are either private (single-process only) or hidden	87	Nodes are either public (have one or more listening ports) or private
64	(connected to a master node only). Only when they epxlicitly "become	88	(no listening ports). Private nodes cannot talk to other private nodes
65	public" can you send them messages from unrelated other nodes.	89	currently.
66		90
67	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	91	=item node ID - C<[a-za-Z0-9_\-.:]+>
68		92
69	A noderef is a string that either uniquely identifies a given node (for	93	A node ID is a string that uniquely identifies the node within a
70	private and hidden nodes), or contains a recipe on how to reach a given	94	network. Depending on the configuration used, node IDs can look like a
71	node (for public nodes).	95	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		96	doesn't interpret node IDs in any way.
		97
		98	=item binds - C<ip:port>
		99
		100	Nodes can only talk to each other by creating some kind of connection to
		101	each other. To do this, nodes should listen on one or more local transport
		102	endpoints - binds. Currently, only standard C<ip:port> specifications can
		103	be used, which specify TCP ports to listen on.
		104
		105	=item seeds - C<host:port>
		106
		107	When a node starts, it knows nothing about the network. To teach the node
		108	about the network it first has to contact some other node within the
		109	network. This node is called a seed.
		110
		111	Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes
		112	are expected to be long-running, and at least one of those should always
		113	be available. When nodes run out of connections (e.g. due to a network
		114	error), they try to re-establish connections to some seednodes again to
		115	join the network.
		116
		117	Apart from being sued for seeding, seednodes are not special in any way -
		118	every public node can be a seednode.
72		119
73	=back	120	=back
74		121
75	=head1 VARIABLES/FUNCTIONS	122	=head1 VARIABLES/FUNCTIONS
76		123
…		…
78		125
79	=cut	126	=cut
80		127
81	package AnyEvent::MP;	128	package AnyEvent::MP;
82		129
83	use AnyEvent::MP::Base;	130	use AnyEvent::MP::Kernel;
84		131
85	use common::sense;	132	use common::sense;
86		133
87	use Carp ();	134	use Carp ();
88		135
89	use AE ();	136	use AE ();
90		137
91	use base "Exporter";	138	use base "Exporter";
92		139
93	our $VERSION = '0.1';	140	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
		141
94	our @EXPORT = qw(	142	our @EXPORT = qw(
95	NODE $NODE *SELF node_of _any_	143	NODE $NODE *SELF node_of after
96	become_slave become_public	144	initialise_node
97	snd rcv mon kil reg psub	145	snd rcv mon mon_guard kil reg psub spawn
98	port	146	port
99	);	147	);
100		148
101	our $SELF;	149	our $SELF;
102		150
…		…
106	kil $SELF, die => $msg;	154	kil $SELF, die => $msg;
107	}	155	}
108		156
109	=item $thisnode = NODE / $NODE	157	=item $thisnode = NODE / $NODE
110		158
111	The C<NODE> function returns, and the C<$NODE> variable contains	159	The C<NODE> function returns, and the C<$NODE> variable contains, the node
112	the noderef of the local node. The value is initialised by a call	160	ID of the node running in the current process. This value is initialised by
113	to C<become_public> or C<become_slave>, after which all local port	161	a call to C<initialise_node>.
114	identifiers become invalid.
115		162
116	=item $noderef = node_of $portid	163	=item $nodeid = node_of $port
117		164
118	Extracts and returns the noderef from a portid or a noderef.	165	Extracts and returns the node ID from a port ID or a node ID.
		166
		167	=item initialise_node $profile_name
		168
		169	Before a node can talk to other nodes on the network (i.e. enter
		170	"distributed mode") it has to initialise itself - the minimum a node needs
		171	to know is its own name, and optionally it should know the addresses of
		172	some other nodes in the network to discover other nodes.
		173
		174	This function initialises a node - it must be called exactly once (or
		175	never) before calling other AnyEvent::MP functions.
		176
		177	The first argument is a profile name. If it is C<undef> or missing, then
		178	the current nodename will be used instead (i.e. F<uname -n>).
		179
		180	The function then looks up the profile in the aemp configuration (see the
		181	L<aemp> commandline utility).
		182
		183	If the profile specifies a node ID, then this will become the node ID of
		184	this process. If not, then the profile name will be used as node ID. The
		185	special node ID of C<anon/> will be replaced by a random node ID.
		186
		187	The next step is to look up the binds in the profile, followed by binding
		188	aemp protocol listeners on all binds specified (it is possible and valid
		189	to have no binds, meaning that the node cannot be contacted form the
		190	outside. This means the node cannot talk to other nodes that also have no
		191	binds, but it can still talk to all "normal" nodes).
		192
		193	If the profile does not specify a binds list, then the node ID will be
		194	treated as if it were of the form C<host:port>, which will be resolved and
		195	used as binds list.
		196
		197	Lastly, the seeds list from the profile is passed to the
		198	L<AnyEvent::MP::Global> module, which will then use it to keep
		199	connectivity with at least on of those seed nodes at any point in time.
		200
		201	Example: become a distributed node listening on the guessed noderef, or
		202	the one specified via C<aemp> for the current node. This should be the
		203	most common form of invocation for "daemon"-type nodes.
		204
		205	initialise_node;
		206
		207	Example: become an anonymous node. This form is often used for commandline
		208	clients.
		209
		210	initialise_node "anon/";
		211
		212	Example: become a distributed node. If there is no profile of the given
		213	name, or no binds list was specified, resolve C<localhost:4044> and bind
		214	on the resulting addresses.
		215
		216	initialise_node "localhost:4044";
119		217
120	=item $SELF	218	=item $SELF
121		219
122	Contains the current port id while executing C<rcv> callbacks or C<psub>	220	Contains the current port id while executing C<rcv> callbacks or C<psub>
123	blocks.	221	blocks.
124		222
125	=item SELF, %SELF, @SELF...	223	=item *SELF, SELF, %SELF, @SELF...
126		224
127	Due to some quirks in how perl exports variables, it is impossible to	225	Due to some quirks in how perl exports variables, it is impossible to
128	just export C<$SELF>, all the symbols called C<SELF> are exported by this	226	just export C<$SELF>, all the symbols named C<SELF> are exported by this
129	module, but only C<$SELF> is currently used.	227	module, but only C<$SELF> is currently used.
130		228
131	=item snd $portid, type => @data	229	=item snd $port, type => @data
132		230
133	=item snd $portid, @msg	231	=item snd $port, @msg
134		232
135	Send the given message to the given port ID, which can identify either	233	Send the given message to the given port, which can identify either a
136	a local or a remote port, and can be either a string or soemthignt hat	234	local or a remote port, and must be a port ID.
137	stringifies a sa port ID (such as a port object :).
138		235
139	While the message can be about anything, it is highly recommended to use a	236	While the message can be almost anything, it is highly recommended to
140	string as first element (a portid, or some word that indicates a request	237	use a string as first element (a port ID, or some word that indicates a
141	type etc.).	238	request type etc.) and to consist if only simple perl values (scalars,
		239	arrays, hashes) - if you think you need to pass an object, think again.
142		240
143	The message data effectively becomes read-only after a call to this	241	The message data logically becomes read-only after a call to this
144	function: modifying any argument is not allowed and can cause many	242	function: modifying any argument (or values referenced by them) is
145	problems.	243	forbidden, as there can be considerable time between the call to C<snd>
		244	and the time the message is actually being serialised - in fact, it might
		245	never be copied as within the same process it is simply handed to the
		246	receiving port.
146		247
147	The type of data you can transfer depends on the transport protocol: when	248	The type of data you can transfer depends on the transport protocol: when
148	JSON is used, then only strings, numbers and arrays and hashes consisting	249	JSON is used, then only strings, numbers and arrays and hashes consisting
149	of those are allowed (no objects). When Storable is used, then anything	250	of those are allowed (no objects). When Storable is used, then anything
150	that Storable can serialise and deserialise is allowed, and for the local	251	that Storable can serialise and deserialise is allowed, and for the local
151	node, anything can be passed.	252	node, anything can be passed. Best rely only on the common denominator of
		253	these.
152		254
153	=item kil $portid[, @reason]	255	=item $local_port = port
154		256
155	Kill the specified port with the given C<@reason>.	257	Create a new local port object and returns its port ID. Initially it has
		258	no callbacks set and will throw an error when it receives messages.
156		259
157	If no C<@reason> is specified, then the port is killed "normally" (linked	260	=item $local_port = port { my @msg = @_ }
158	ports will not be kileld, or even notified).
159		261
160	Otherwise, linked ports get killed with the same reason (second form of	262	Creates a new local port, and returns its ID. Semantically the same as
161	C<mon>, see below).	263	creating a port and calling C<rcv $port, $callback> on it.
162		264
163	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	265	The block will be called for every message received on the port, with the
164	will be reported as reason C<< die => $@ >>.	266	global variable C<$SELF> set to the port ID. Runtime errors will cause the
		267	port to be C<kil>ed. The message will be passed as-is, no extra argument
		268	(i.e. no port ID) will be passed to the callback.
165		269
166	Transport/communication errors are reported as C<< transport_error =>	270	If you want to stop/destroy the port, simply C<kil> it:
167	$message >>.
168		271
169	=item $guard = mon $portid, $cb->(@reason)	272	my $port = port {
		273	my @msg = @_;
		274	...
		275	kil $SELF;
		276	};
170		277
171	=item $guard = mon $portid, $otherport	278	=cut
172		279
173	=item $guard = mon $portid, $otherport, @msg	280	sub rcv($@);
174		281
		282	sub _kilme {
		283	die "received message on port without callback";
		284	}
		285
		286	sub port(;&) {
		287	my $id = "$UNIQ." . $ID++;
		288	my $port = "$NODE#$id";
		289
		290	rcv $port, shift \|\| \&_kilme;
		291
		292	$port
		293	}
		294
		295	=item rcv $local_port, $callback->(@msg)
		296
		297	Replaces the default callback on the specified port. There is no way to
		298	remove the default callback: use C<sub { }> to disable it, or better
		299	C<kil> the port when it is no longer needed.
		300
		301	The global C<$SELF> (exported by this module) contains C<$port> while
		302	executing the callback. Runtime errors during callback execution will
		303	result in the port being C<kil>ed.
		304
		305	The default callback received all messages not matched by a more specific
		306	C<tag> match.
		307
		308	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
		309
		310	Register (or replace) callbacks to be called on messages starting with the
		311	given tag on the given port (and return the port), or unregister it (when
		312	C<$callback> is C<$undef> or missing). There can only be one callback
		313	registered for each tag.
		314
		315	The original message will be passed to the callback, after the first
		316	element (the tag) has been removed. The callback will use the same
		317	environment as the default callback (see above).
		318
		319	Example: create a port and bind receivers on it in one go.
		320
		321	my $port = rcv port,
		322	msg1 => sub { ... },
		323	msg2 => sub { ... },
		324	;
		325
		326	Example: create a port, bind receivers and send it in a message elsewhere
		327	in one go:
		328
		329	snd $otherport, reply =>
		330	rcv port,
		331	msg1 => sub { ... },
		332	...
		333	;
		334
		335	Example: temporarily register a rcv callback for a tag matching some port
		336	(e.g. for a rpc reply) and unregister it after a message was received.
		337
		338	rcv $port, $otherport => sub {
		339	my @reply = @_;
		340
		341	rcv $SELF, $otherport;
		342	};
		343
		344	=cut
		345
		346	sub rcv($@) {
		347	my $port = shift;
		348	my ($noderef, $portid) = split /#/, $port, 2;
		349
		350	$NODE{$noderef} == $NODE{""}
		351	or Carp::croak "$port: rcv can only be called on local ports, caught";
		352
		353	while (@_) {
		354	if (ref $_[0]) {
		355	if (my $self = $PORT_DATA{$portid}) {
		356	"AnyEvent::MP::Port" eq ref $self
		357	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		358
		359	$self->[2] = shift;
		360	} else {
		361	my $cb = shift;
		362	$PORT{$portid} = sub {
		363	local $SELF = $port;
		364	eval { &$cb }; _self_die if $@;
		365	};
		366	}
		367	} elsif (defined $_[0]) {
		368	my $self = $PORT_DATA{$portid} \|\|= do {
		369	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
		370
		371	$PORT{$portid} = sub {
		372	local $SELF = $port;
		373
		374	if (my $cb = $self->[1]{$_[0]}) {
		375	shift;
		376	eval { &$cb }; _self_die if $@;
		377	} else {
		378	&{ $self->[0] };
		379	}
		380	};
		381
		382	$self
		383	};
		384
		385	"AnyEvent::MP::Port" eq ref $self
		386	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		387
		388	my ($tag, $cb) = splice @_, 0, 2;
		389
		390	if (defined $cb) {
		391	$self->[1]{$tag} = $cb;
		392	} else {
		393	delete $self->[1]{$tag};
		394	}
		395	}
		396	}
		397
		398	$port
		399	}
		400
		401	=item $closure = psub { BLOCK }
		402
		403	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
		404	closure is executed, sets up the environment in the same way as in C<rcv>
		405	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		406
		407	This is useful when you register callbacks from C<rcv> callbacks:
		408
		409	rcv delayed_reply => sub {
		410	my ($delay, @reply) = @_;
		411	my $timer = AE::timer $delay, 0, psub {
		412	snd @reply, $SELF;
		413	};
		414	};
		415
		416	=cut
		417
		418	sub psub(&) {
		419	my $cb = shift;
		420
		421	my $port = $SELF
		422	or Carp::croak "psub can only be called from within rcv or psub callbacks, not";
		423
		424	sub {
		425	local $SELF = $port;
		426
		427	if (wantarray) {
		428	my @res = eval { &$cb };
		429	_self_die if $@;
		430	@res
		431	} else {
		432	my $res = eval { &$cb };
		433	_self_die if $@;
		434	$res
		435	}
		436	}
		437	}
		438
		439	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
		440
		441	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
		442
		443	=item $guard = mon $port # kill $SELF when $port dies
		444
		445	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
		446
175	Monitor the given port and do something when the port is killed.	447	Monitor the given port and do something when the port is killed or
		448	messages to it were lost, and optionally return a guard that can be used
		449	to stop monitoring again.
176		450
		451	C<mon> effectively guarantees that, in the absence of hardware failures,
		452	after starting the monitor, either all messages sent to the port will
		453	arrive, or the monitoring action will be invoked after possible message
		454	loss has been detected. No messages will be lost "in between" (after
		455	the first lost message no further messages will be received by the
		456	port). After the monitoring action was invoked, further messages might get
		457	delivered again.
		458
		459	Note that monitoring-actions are one-shot: once messages are lost (and a
		460	monitoring alert was raised), they are removed and will not trigger again.
		461
177	In the first form, the callback is simply called with any number	462	In the first form (callback), the callback is simply called with any
178	of C<@reason> elements (no @reason means that the port was deleted	463	number of C<@reason> elements (no @reason means that the port was deleted
179	"normally"). Note also that I<< the callback B<must> never die >>, so use	464	"normally"). Note also that I<< the callback B<must> never die >>, so use
180	C<eval> if unsure.	465	C<eval> if unsure.
181		466
182	In the second form, the other port will be C<kil>'ed with C<@reason>, iff	467	In the second form (another port given), the other port (C<$rcvport>)
183	a @reason was specified, i.e. on "normal" kils nothing happens, while	468	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
184	under all other conditions, the other port is killed with the same reason.	469	"normal" kils nothing happens, while under all other conditions, the other
		470	port is killed with the same reason.
185		471
		472	The third form (kill self) is the same as the second form, except that
		473	C<$rvport> defaults to C<$SELF>.
		474
186	In the last form, a message of the form C<@msg, @reason> will be C<snd>.	475	In the last form (message), a message of the form C<@msg, @reason> will be
		476	C<snd>.
		477
		478	As a rule of thumb, monitoring requests should always monitor a port from
		479	a local port (or callback). The reason is that kill messages might get
		480	lost, just like any other message. Another less obvious reason is that
		481	even monitoring requests can get lost (for exmaple, when the connection
		482	to the other node goes down permanently). When monitoring a port locally
		483	these problems do not exist.
187		484
188	Example: call a given callback when C<$port> is killed.	485	Example: call a given callback when C<$port> is killed.
189		486
190	mon $port, sub { warn "port died because of <@_>\n" };	487	mon $port, sub { warn "port died because of <@_>\n" };
191		488
192	Example: kill ourselves when C<$port> is killed abnormally.	489	Example: kill ourselves when C<$port> is killed abnormally.
193		490
194	mon $port, $self;	491	mon $port;
195		492
196	Example: send us a restart message another C<$port> is killed.	493	Example: send us a restart message when another C<$port> is killed.
197		494
198	mon $port, $self => "restart";	495	mon $port, $self => "restart";
199		496
200	=cut	497	=cut
201		498
202	sub mon {	499	sub mon {
203	my ($noderef, $port, $cb) = ((split /#/, shift, 2), shift);	500	my ($noderef, $port) = split /#/, shift, 2;
204		501
205	my $node = $NODE{$noderef} \|\| add_node $noderef;	502	my $node = $NODE{$noderef} \|\| add_node $noderef;
206		503
207	#TODO: ports must not be references	504	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
208	if (!ref $cb or "AnyEvent::MP::Port" eq ref $cb) {	505
		506	unless (ref $cb) {
209	if (@_) {	507	if (@_) {
210	# send a kill info message	508	# send a kill info message
211	my (@msg) = ($cb, @_);	509	my (@msg) = ($cb, @_);
212	$cb = sub { snd @msg, @_ };	510	$cb = sub { snd @msg, @_ };
213	} else {	511	} else {
…		…
229	is killed, the references will be freed.	527	is killed, the references will be freed.
230		528
231	Optionally returns a guard that will stop the monitoring.	529	Optionally returns a guard that will stop the monitoring.
232		530
233	This function is useful when you create e.g. timers or other watchers and	531	This function is useful when you create e.g. timers or other watchers and
234	want to free them when the port gets killed:	532	want to free them when the port gets killed (note the use of C<psub>):
235		533
236	$port->rcv (start => sub {	534	$port->rcv (start => sub {
237	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	535	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
238	undef $timer if 0.9 < rand;	536	undef $timer if 0.9 < rand;
239	});	537	});
240	});	538	});
241		539
242	=cut	540	=cut
243		541
244	sub mon_guard {	542	sub mon_guard {
245	my ($port, @refs) = @_;	543	my ($port, @refs) = @_;
246		544
		545	#TODO: mon-less form?
		546
247	mon $port, sub { 0 && @refs }	547	mon $port, sub { 0 && @refs }
248	}	548	}
249		549
250	=item lnk $port1, $port2	550	=item kil $port[, @reason]
251		551
252	Link two ports. This is simply a shorthand for:	552	Kill the specified port with the given C<@reason>.
253		553
254	mon $port1, $port2;	554	If no C<@reason> is specified, then the port is killed "normally" (ports
255	mon $port2, $port1;	555	monitoring other ports will not necessarily die because a port dies
		556	"normally").
256		557
257	It means that if either one is killed abnormally, the other one gets	558	Otherwise, linked ports get killed with the same reason (second form of
258	killed as well.	559	C<mon>, see above).
259		560
260	=item $local_port = port	561	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
		562	will be reported as reason C<< die => $@ >>.
261		563
262	Create a new local port object that supports message matching.	564	Transport/communication errors are reported as C<< transport_error =>
		565	$message >>.
263		566
264	=item $portid = port { my @msg = @_; $finished }
265
266	Creates a "mini port", that is, a very lightweight port without any
267	pattern matching behind it, and returns its ID.
268
269	The block will be called for every message received on the port. When the
270	callback returns a true value its job is considered "done" and the port
271	will be destroyed. Otherwise it will stay alive.
272
273	The message will be passed as-is, no extra argument (i.e. no port id) will
274	be passed to the callback.
275
276	If you need the local port id in the callback, this works nicely:
277
278	my $port; $port = miniport {
279	snd $otherport, reply => $port;
280	};
281
282	=cut	567	=cut
283		568
284	sub port(;&) {	569	=item $port = spawn $node, $initfunc[, @initdata]
285	my $id = "$UNIQ." . $ID++;
286	my $port = "$NODE#$id";
287		570
288	if (@_) {	571	Creates a port on the node C<$node> (which can also be a port ID, in which
289	my $cb = shift;	572	case it's the node where that port resides).
290	$PORT{$id} = sub {	573
291	local $SELF = $port;	574	The port ID of the newly created port is returned immediately, and it is
292	eval {	575	possible to immediately start sending messages or to monitor the port.
293	&$cb	576
294	and kil $id;	577	After the port has been created, the init function is called on the remote
		578	node, in the same context as a C<rcv> callback. This function must be a
		579	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
		580	specify a function in the main program, use C<::name>.
		581
		582	If the function doesn't exist, then the node tries to C<require>
		583	the package, then the package above the package and so on (e.g.
		584	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
		585	exists or it runs out of package names.
		586
		587	The init function is then called with the newly-created port as context
		588	object (C<$SELF>) and the C<@initdata> values as arguments.
		589
		590	A common idiom is to pass a local port, immediately monitor the spawned
		591	port, and in the remote init function, immediately monitor the passed
		592	local port. This two-way monitoring ensures that both ports get cleaned up
		593	when there is a problem.
		594
		595	Example: spawn a chat server port on C<$othernode>.
		596
		597	# this node, executed from within a port context:
		598	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
		599	mon $server;
		600
		601	# init function on C<$othernode>
		602	sub connect {
		603	my ($srcport) = @_;
		604
		605	mon $srcport;
		606
		607	rcv $SELF, sub {
295	};	608	...
296	_self_die if $@;
297	};
298	} else {
299	my $self = bless {
300	id => "$NODE#$id",
301	}, "AnyEvent::MP::Port";
302
303	$PORT_DATA{$id} = $self;
304	$PORT{$id} = sub {
305	local $SELF = $port;
306
307	eval {
308	for (@{ $self->{rc0}{$_[0]} }) {
309	$_ && &{$_->[0]}
310	&& undef $_;
311	}
312
313	for (@{ $self->{rcv}{$_[0]} }) {
314	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
315	&& &{$_->[0]}
316	&& undef $_;
317	}
318
319	for (@{ $self->{any} }) {
320	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
321	&& &{$_->[0]}
322	&& undef $_;
323	}
324	};
325	_self_die if $@;
326	};	609	};
327	}	610	}
328		611
329	$port
330	}
331
332	=item reg $portid, $name
333
334	Registers the given port under the name C<$name>. If the name already
335	exists it is replaced.
336
337	A port can only be registered under one well known name.
338
339	A port automatically becomes unregistered when it is killed.
340
341	=cut	612	=cut
342		613
343	sub reg(@) {	614	sub _spawn {
344	my ($portid, $name) = @_;	615	my $port = shift;
		616	my $init = shift;
345		617
346	$REG{$name} = $portid;	618	local $SELF = "$NODE#$port";
347	}	619	eval {
348		620	&{ load_func $init }
349	=item rcv $portid, tagstring => $callback->(@msg), ...
350
351	=item rcv $portid, $smartmatch => $callback->(@msg), ...
352
353	=item rcv $portid, [$smartmatch...] => $callback->(@msg), ...
354
355	Register callbacks to be called on matching messages on the given port.
356
357	The callback has to return a true value when its work is done, after
358	which is will be removed, or a false value in which case it will stay
359	registered.
360
361	The global C<$SELF> (exported by this module) contains C<$portid> while
362	executing the callback.
363
364	Runtime errors wdurign callback execution will result in the port being
365	C<kil>ed.
366
367	If the match is an array reference, then it will be matched against the
368	first elements of the message, otherwise only the first element is being
369	matched.
370
371	Any element in the match that is specified as C<_any_> (a function
372	exported by this module) matches any single element of the message.
373
374	While not required, it is highly recommended that the first matching
375	element is a string identifying the message. The one-string-only match is
376	also the most efficient match (by far).
377
378	=cut
379
380	sub rcv($@) {
381	my ($noderef, $port) = split /#/, shift, 2;
382
383	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}
384	or Carp::croak "$noderef#$port: rcv can only be called on local ports, caught";
385
386	my $self = $PORT_DATA{$port}
387	or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught";
388
389	"AnyEvent::MP::Port" eq ref $self
390	or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught";
391
392	while (@_) {
393	my ($match, $cb) = splice @_, 0, 2;
394
395	if (!ref $match) {
396	push @{ $self->{rc0}{$match} }, [$cb];
397	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
398	my ($type, @match) = @$match;
399	@match
400	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
401	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
402	} else {
403	push @{ $self->{any} }, [$cb, $match];
404	}
405	}
406	}
407
408	=item $closure = psub { BLOCK }
409
410	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
411	closure is executed, sets up the environment in the same way as in C<rcv>
412	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
413
414	This is useful when you register callbacks from C<rcv> callbacks:
415
416	rcv delayed_reply => sub {
417	my ($delay, @reply) = @_;
418	my $timer = AE::timer $delay, 0, psub {
419	snd @reply, $SELF;
420	};
421	};	621	};
422
423	=cut
424
425	sub psub(&) {
426	my $cb = shift;
427
428	my $port = $SELF
429	or Carp::croak "psub can only be called from within rcv or psub callbacks, not";
430
431	sub {
432	local $SELF = $port;
433
434	if (wantarray) {
435	my @res = eval { &$cb };
436	_self_die if $@;	622	_self_die if $@;
437	@res	623	}
438	} else {	624
439	my $res = eval { &$cb };	625	sub spawn(@) {
440	_self_die if $@;	626	my ($noderef, undef) = split /#/, shift, 2;
441	$res	627
442	}	628	my $id = "$RUNIQ." . $ID++;
		629
		630	$_[0] =~ /::/
		631	or Carp::croak "spawn init function must be a fully-qualified name, caught";
		632
		633	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;
		634
		635	"$noderef#$id"
		636	}
		637
		638	=item after $timeout, @msg
		639
		640	=item after $timeout, $callback
		641
		642	Either sends the given message, or call the given callback, after the
		643	specified number of seconds.
		644
		645	This is simply a utility function that comes in handy at times - the
		646	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		647	so it may go away in the future.
		648
		649	=cut
		650
		651	sub after($@) {
		652	my ($timeout, @action) = @_;
		653
		654	my $t; $t = AE::timer $timeout, 0, sub {
		655	undef $t;
		656	ref $action[0]
		657	? $action[0]()
		658	: snd @action;
443	}	659	};
444	}	660	}
445		661
446	=back	662	=back
447		663
448	=head1 FUNCTIONS FOR NODES	664	=head1 AnyEvent::MP vs. Distributed Erlang
		665
		666	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
		667	== aemp node, Erlang process == aemp port), so many of the documents and
		668	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
		669	sample:
		670
		671	http://www.Erlang.se/doc/programming_rules.shtml
		672	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
		673	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6
		674	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
		675
		676	Despite the similarities, there are also some important differences:
449		677
450	=over 4	678	=over 4
451		679
452	=item become_public endpoint...	680	=item * Node IDs are arbitrary strings in AEMP.
453		681
454	Tells the node to become a public node, i.e. reachable from other nodes.
455
456	If no arguments are given, or the first argument is C<undef>, then
457	AnyEvent::MP tries to bind on port C<4040> on all IP addresses that the
458	local nodename resolves to.
459
460	Otherwise the first argument must be an array-reference with transport
461	endpoints ("ip:port", "hostname:port") or port numbers (in which case the
462	local nodename is used as hostname). The endpoints are all resolved and
463	will become the node reference.
464
465	=cut
466
467	=back
468
469	=head1 NODE MESSAGES
470
471	Nodes understand the following messages sent to them. Many of them take
472	arguments called C<@reply>, which will simply be used to compose a reply
473	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
474	the remaining arguments are simply the message data.
475
476	=over 4
477
478	=cut
479
480	=item lookup => $name, @reply
481
482	Replies with the port ID of the specified well-known port, or C<undef>.
483
484	=item devnull => ...
485
486	Generic data sink/CPU heat conversion.
487
488	=item relay => $port, @msg
489
490	Simply forwards the message to the given port.
491
492	=item eval => $string[ @reply]
493
494	Evaluates the given string. If C<@reply> is given, then a message of the
495	form C<@reply, $@, @evalres> is sent.
496
497	Example: crash another node.
498
499	snd $othernode, eval => "exit";
500
501	=item time => @reply
502
503	Replies the the current node time to C<@reply>.
504
505	Example: tell the current node to send the current time to C<$myport> in a
506	C<timereply> message.
507
508	snd $NODE, time => $myport, timereply => 1, 2;
509	# => snd $myport, timereply => 1, 2, <time>
510
511	=back
512
513	=head1 AnyEvent::MP vs. Distributed Erlang
514
515	AnyEvent::MP got lots of its ideas from distributed erlang (erlang node
516	== aemp node, erlang process == aemp port), so many of the documents and
517	programming techniques employed by erlang apply to AnyEvent::MP. Here is a
518	sample:
519
520	http://www.erlang.se/doc/programming_rules.shtml
521	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
522	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
523	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
524
525	Despite the similarities, there are also some important differences:
526
527	=over 4
528
529	=item * Node references contain the recipe on how to contact them.
530
531	Erlang relies on special naming and DNS to work everywhere in the	682	Erlang relies on special naming and DNS to work everywhere in the same
532	same way. AEMP relies on each node knowing it's own address(es), with	683	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
533	convenience functionality.	684	configuraiton or DNS), but will otherwise discover other odes itself.
534		685
535	This means that AEMP requires a less tightly controlled environment at the	686	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
536	cost of longer node references and a slightly higher management overhead.	687	uses "local ports are like remote ports".
		688
		689	The failure modes for local ports are quite different (runtime errors
		690	only) then for remote ports - when a local port dies, you I<know> it dies,
		691	when a connection to another node dies, you know nothing about the other
		692	port.
		693
		694	Erlang pretends remote ports are as reliable as local ports, even when
		695	they are not.
		696
		697	AEMP encourages a "treat remote ports differently" philosophy, with local
		698	ports being the special case/exception, where transport errors cannot
		699	occur.
537		700
538	=item * Erlang uses processes and a mailbox, AEMP does not queue.	701	=item * Erlang uses processes and a mailbox, AEMP does not queue.
539		702
540	Erlang uses processes that selctively receive messages, and therefore	703	Erlang uses processes that selectively receive messages, and therefore
541	needs a queue. AEMP is event based, queuing messages would serve no useful	704	needs a queue. AEMP is event based, queuing messages would serve no
542	purpose.	705	useful purpose. For the same reason the pattern-matching abilities of
		706	AnyEvent::MP are more limited, as there is little need to be able to
		707	filter messages without dequeing them.
543		708
544	(But see L<Coro::MP> for a more erlang-like process model on top of AEMP).	709	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
545		710
546	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	711	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
547		712
548	Sending messages in erlang is synchronous and blocks the process. AEMP	713	Sending messages in Erlang is synchronous and blocks the process (and
549	sends are immediate, connection establishment is handled in the	714	so does not need a queue that can overflow). AEMP sends are immediate,
550	background.	715	connection establishment is handled in the background.
551		716
552	=item * Erlang can silently lose messages, AEMP cannot.	717	=item * Erlang suffers from silent message loss, AEMP does not.
553		718
554	Erlang makes few guarantees on messages delivery - messages can get lost	719	Erlang makes few guarantees on messages delivery - messages can get lost
555	without any of the processes realising it (i.e. you send messages a, b,	720	without any of the processes realising it (i.e. you send messages a, b,
556	and c, and the other side only receives messages a and c).	721	and c, and the other side only receives messages a and c).
557		722
558	AEMP guarantees correct ordering, and the guarantee that there are no	723	AEMP guarantees correct ordering, and the guarantee that after one message
559	holes in the message sequence.	724	is lost, all following ones sent to the same port are lost as well, until
560		725	monitoring raises an error, so there are no silent "holes" in the message
561	=item * In erlang, processes can be declared dead and later be found to be	726	sequence.
562	alive.
563
564	In erlang it can happen that a monitored process is declared dead and
565	linked processes get killed, but later it turns out that the process is
566	still alive - and can receive messages.
567
568	In AEMP, when port monitoring detects a port as dead, then that port will
569	eventually be killed - it cannot happen that a node detects a port as dead
570	and then later sends messages to it, finding it is still alive.
571		727
572	=item * Erlang can send messages to the wrong port, AEMP does not.	728	=item * Erlang can send messages to the wrong port, AEMP does not.
573		729
574	In erlang it is quite possible that a node that restarts reuses a process	730	In Erlang it is quite likely that a node that restarts reuses a process ID
575	ID known to other nodes for a completely different process, causing	731	known to other nodes for a completely different process, causing messages
576	messages destined for that process to end up in an unrelated process.	732	destined for that process to end up in an unrelated process.
577		733
578	AEMP never reuses port IDs, so old messages or old port IDs floating	734	AEMP never reuses port IDs, so old messages or old port IDs floating
579	around in the network will not be sent to an unrelated port.	735	around in the network will not be sent to an unrelated port.
580		736
581	=item * Erlang uses unprotected connections, AEMP uses secure	737	=item * Erlang uses unprotected connections, AEMP uses secure
582	authentication and can use TLS.	738	authentication and can use TLS.
583		739
584	AEMP can use a proven protocol - SSL/TLS - to protect connections and	740	AEMP can use a proven protocol - TLS - to protect connections and
585	securely authenticate nodes.	741	securely authenticate nodes.
		742
		743	=item * The AEMP protocol is optimised for both text-based and binary
		744	communications.
		745
		746	The AEMP protocol, unlike the Erlang protocol, supports both programming
		747	language independent text-only protocols (good for debugging) and binary,
		748	language-specific serialisers (e.g. Storable). By default, unless TLS is
		749	used, the protocol is actually completely text-based.
		750
		751	It has also been carefully designed to be implementable in other languages
		752	with a minimum of work while gracefully degrading functionality to make the
		753	protocol simple.
		754
		755	=item * AEMP has more flexible monitoring options than Erlang.
		756
		757	In Erlang, you can chose to receive I<all> exit signals as messages
		758	or I<none>, there is no in-between, so monitoring single processes is
		759	difficult to implement. Monitoring in AEMP is more flexible than in
		760	Erlang, as one can choose between automatic kill, exit message or callback
		761	on a per-process basis.
		762
		763	=item * Erlang tries to hide remote/local connections, AEMP does not.
		764
		765	Monitoring in Erlang is not an indicator of process death/crashes, in the
		766	same way as linking is (except linking is unreliable in Erlang).
		767
		768	In AEMP, you don't "look up" registered port names or send to named ports
		769	that might or might not be persistent. Instead, you normally spawn a port
		770	on the remote node. The init function monitors you, and you monitor the
		771	remote port. Since both monitors are local to the node, they are much more
		772	reliable (no need for C<spawn_link>).
		773
		774	This also saves round-trips and avoids sending messages to the wrong port
		775	(hard to do in Erlang).
		776
		777	=back
		778
		779	=head1 RATIONALE
		780
		781	=over 4
		782
		783	=item Why strings for port and node IDs, why not objects?
		784
		785	We considered "objects", but found that the actual number of methods
		786	that can be called are quite low. Since port and node IDs travel over
		787	the network frequently, the serialising/deserialising would add lots of
		788	overhead, as well as having to keep a proxy object everywhere.
		789
		790	Strings can easily be printed, easily serialised etc. and need no special
		791	procedures to be "valid".
		792
		793	And as a result, a miniport consists of a single closure stored in a
		794	global hash - it can't become much cheaper.
		795
		796	=item Why favour JSON, why not a real serialising format such as Storable?
		797
		798	In fact, any AnyEvent::MP node will happily accept Storable as framing
		799	format, but currently there is no way to make a node use Storable by
		800	default (although all nodes will accept it).
		801
		802	The default framing protocol is JSON because a) JSON::XS is many times
		803	faster for small messages and b) most importantly, after years of
		804	experience we found that object serialisation is causing more problems
		805	than it solves: Just like function calls, objects simply do not travel
		806	easily over the network, mostly because they will always be a copy, so you
		807	always have to re-think your design.
		808
		809	Keeping your messages simple, concentrating on data structures rather than
		810	objects, will keep your messages clean, tidy and efficient.
586		811
587	=back	812	=back
588		813
589	=head1 SEE ALSO	814	=head1 SEE ALSO
590		815

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Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.27 by root, Tue Aug 4 22:13:45 2009 UTC vs. Revision 1.67 by root, Fri Aug 28 22:21:53 2009 UTC

Diff Legend

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.27 by root, Tue Aug 4 22:13:45 2009 UTC vs.
Revision 1.67 by root, Fri Aug 28 22:21:53 2009 UTC