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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.24 by root, Tue Aug 4 20:00:00 2009 UTC vs.
Revision 1.81 by root, Mon Sep 7 18:33:44 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, and	66	Not to be confused with a TCP port, a "port" is something you can send
49	you can register C<rcv> handlers with. All C<rcv> handlers will receive	67	messages to (with the C<snd> function).
50	messages they match, messages will not be queued.
51		68
		69	Ports allow you to register C<rcv> handlers that can match all or just
		70	some messages. Messages send to ports will not be queued, regardless of
		71	anything was listening for them or not.
		72
52	=item port id - C<noderef#portname>	73	=item port ID - C<nodeid#portname>
53		74
54	A port id is always the noderef, a hash-mark (C<#>) as separator, followed	75	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).	76	separator, and a port name (a printable string of unspecified format).
56		77
57	=item node	78	=item node
58		79
59	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,
60	port. You can send messages to node ports to let them create new ports,	81	which enables nodes to manage each other remotely, and to create new
61	among other things.	82	ports.
62		83
63	Initially, nodes are either private (single-process only) or hidden	84	Nodes are either public (have one or more listening ports) or private
64	(connected to a master node only). Only when they epxlicitly "become	85	(no listening ports). Private nodes cannot talk to other private nodes
65	public" can you send them messages from unrelated other nodes.	86	currently.
66		87
67	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	88	=item node ID - C<[a-za-Z0-9_\-.:]+>
68		89
69	A noderef is a string that either uniquely identifies a given node (for	90	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	91	network. Depending on the configuration used, node IDs can look like a
71	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.
		94
		95	=item binds - C<ip:port>
		96
		97	Nodes can only talk to each other by creating some kind of connection to
		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.
		101
		102	=item seeds - C<host:port>
		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.
72		116
73	=back	117	=back
74		118
75	=head1 VARIABLES/FUNCTIONS	119	=head1 VARIABLES/FUNCTIONS
76		120
…		…
78		122
79	=cut	123	=cut
80		124
81	package AnyEvent::MP;	125	package AnyEvent::MP;
82		126
83	use AnyEvent::MP::Base;	127	use AnyEvent::MP::Kernel;
84		128
85	use common::sense;	129	use common::sense;
86		130
87	use Carp ();	131	use Carp ();
88		132
89	use AE ();	133	use AE ();
90		134
91	use base "Exporter";	135	use base "Exporter";
92		136
93	our $VERSION = '0.02';	137	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
		138
94	our @EXPORT = qw(	139	our @EXPORT = qw(
95	NODE $NODE *SELF node_of _any_	140	NODE $NODE *SELF node_of after
96	become_slave become_public	141	configure
97	snd rcv mon kil reg psub	142	snd rcv mon mon_guard kil reg psub spawn
98	port	143	port
99	);	144	);
100		145
101	our $SELF;	146	our $SELF;
102		147
…		…
106	kil $SELF, die => $msg;	151	kil $SELF, die => $msg;
107	}	152	}
108		153
109	=item $thisnode = NODE / $NODE	154	=item $thisnode = NODE / $NODE
110		155
111	The C<NODE> function returns, and the C<$NODE> variable contains	156	The C<NODE> function returns, and the C<$NODE> variable contains, the node
112	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
113	to C<become_public> or C<become_slave>, after which all local port	158	a call to C<configure>.
114	identifiers become invalid.
115		159
116	=item $noderef = node_of $portid	160	=item $nodeid = node_of $port
117		161
118	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.
		163
		164	=item configure $profile, key => value...
		165
		166	=item configure key => value...
		167
		168	Before a node can talk to other nodes on the network (i.e. enter
		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.
		175
		176	=over 4
		177
		178	=item step 1, gathering configuration from profiles
		179
		180	The function first looks up a profile in the aemp configuration (see the
		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.
		184
		185	The profile data is then gathered as follows:
		186
		187	First, all remaining key => value pairs (all of which are conveniently
		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).
		192
		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.
		196
		197	If the profile specifies a node ID, then this will become the node ID of
		198	this process. If not, then the profile name will be used as node ID. The
		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.
		218
		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)"
119		246
120	=item $SELF	247	=item $SELF
121		248
122	Contains the current port id while executing C<rcv> callbacks or C<psub>	249	Contains the current port id while executing C<rcv> callbacks or C<psub>
123	blocks.	250	blocks.
124		251
125	=item SELF, %SELF, @SELF...	252	=item *SELF, SELF, %SELF, @SELF...
126		253
127	Due to some quirks in how perl exports variables, it is impossible to	254	Due to some quirks in how perl exports variables, it is impossible to
128	just export C<$SELF>, all the symbols called C<SELF> are exported by this	255	just export C<$SELF>, all the symbols named C<SELF> are exported by this
129	module, but only C<$SELF> is currently used.	256	module, but only C<$SELF> is currently used.
130		257
131	=item snd $portid, type => @data	258	=item snd $port, type => @data
132		259
133	=item snd $portid, @msg	260	=item snd $port, @msg
134		261
135	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
136	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.
137	stringifies a sa port ID (such as a port object :).
138		264
139	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
140	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
141	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.
142		269
143	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
144	function: modifying any argument is not allowed and can cause many	271	function: modifying any argument (or values referenced by them) is
145	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.
146		276
147	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
148	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
149	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
150	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
151	node, anything can be passed.	281	node, anything can be passed. Best rely only on the common denominator of
		282	these.
152		283
153	=item kil $portid[, @reason]	284	=item $local_port = port
154		285
155	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.
156		288
157	If no C<@reason> is specified, then the port is killed "normally" (linked	289	=item $local_port = port { my @msg = @_ }
158	ports will not be kileld, or even notified).
159		290
160	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
161	C<mon>, see below).	292	creating a port and calling C<rcv $port, $callback> on it.
162		293
163	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
164	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.
165		298
166	Transport/communication errors are reported as C<< transport_error =>	299	If you want to stop/destroy the port, simply C<kil> it:
167	$message >>.
168		300
169	=item $guard = mon $portid, $cb->(@reason)	301	my $port = port {
		302	my @msg = @_;
		303	...
		304	kil $SELF;
		305	};
170		306
171	=item $guard = mon $portid, $otherport	307	=cut
172		308
173	=item $guard = mon $portid, $otherport, @msg	309	sub rcv($@);
174		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 $port dies
		475
175	Monitor the given port and do something when the port is killed.	476	Monitor the given port and do something when the port is killed or
		477	messages to it were lost, and optionally return a guard that can be used
		478	to stop monitoring again.
176		479
177	In the first form, the callback is simply called with any number	480	In the first form (callback), the callback is simply called with any
178	of C<@reason> elements (no @reason means that the port was deleted	481	number of C<@reason> elements (no @reason means that the port was deleted
179	"normally"). Note also that I<< the callback B<must> never die >>, so use	482	"normally"). Note also that I<< the callback B<must> never die >>, so use
180	C<eval> if unsure.	483	C<eval> if unsure.
181		484
182	In the second form, the other port will be C<kil>'ed with C<@reason>, iff	485	In the second form (another port given), the other port (C<$rcvport>)
183	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
184	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.
185		489
		490	The third form (kill self) is the same as the second form, except that
		491	C<$rvport> defaults to C<$SELF>.
		492
186	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.
187		522
188	Example: call a given callback when C<$port> is killed.	523	Example: call a given callback when C<$port> is killed.
189		524
190	mon $port, sub { warn "port died because of <@_>\n" };	525	mon $port, sub { warn "port died because of <@_>\n" };
191		526
192	Example: kill ourselves when C<$port> is killed abnormally.	527	Example: kill ourselves when C<$port> is killed abnormally.
193		528
194	mon $port, $self;	529	mon $port;
195		530
196	Example: send us a restart message another C<$port> is killed.	531	Example: send us a restart message when another C<$port> is killed.
197		532
198	mon $port, $self => "restart";	533	mon $port, $self => "restart";
199		534
200	=cut	535	=cut
201		536
202	sub mon {	537	sub mon {
203	my ($noderef, $port, $cb) = ((split /#/, shift, 2), shift);	538	my ($nodeid, $port) = split /#/, shift, 2;
204		539
205	my $node = $NODE{$noderef} \|\| add_node $noderef;	540	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
206		541
207	#TODO: ports must not be references	542	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) {	543
		544	unless (ref $cb) {
209	if (@_) {	545	if (@_) {
210	# send a kill info message	546	# send a kill info message
211	my (@msg) = ($cb, @_);	547	my (@msg) = ($cb, @_);
212	$cb = sub { snd @msg, @_ };	548	$cb = sub { snd @msg, @_ };
213	} else {	549	} else {
…		…
229	is killed, the references will be freed.	565	is killed, the references will be freed.
230		566
231	Optionally returns a guard that will stop the monitoring.	567	Optionally returns a guard that will stop the monitoring.
232		568
233	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
234	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>):
235		571
236	$port->rcv (start => sub {	572	$port->rcv (start => sub {
237	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	573	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
238	undef $timer if 0.9 < rand;	574	undef $timer if 0.9 < rand;
239	});	575	});
240	});	576	});
241		577
242	=cut	578	=cut
243		579
244	sub mon_guard {	580	sub mon_guard {
245	my ($port, @refs) = @_;	581	my ($port, @refs) = @_;
246		582
		583	#TODO: mon-less form?
		584
247	mon $port, sub { 0 && @refs }	585	mon $port, sub { 0 && @refs }
248	}	586	}
249		587
250	=item lnk $port1, $port2	588	=item kil $port[, @reason]
251		589
252	Link two ports. This is simply a shorthand for:	590	Kill the specified port with the given C<@reason>.
253		591
254	mon $port1, $port2;	592	If no C<@reason> is specified, then the port is killed "normally" (ports
255	mon $port2, $port1;	593	monitoring other ports will not necessarily die because a port dies
		594	"normally").
256		595
257	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
258	killed as well.	597	C<mon>, see above).
259		598
260	=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 => $@ >>.
261		601
262	Create a new local port object that supports message matching.	602	Transport/communication errors are reported as C<< transport_error =>
		603	$message >>.
263		604
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	605	=cut
283		606
284	sub port(;&) {	607	=item $port = spawn $node, $initfunc[, @initdata]
285	my $id = "$UNIQ." . $ID++;
286	my $port = "$NODE#$id";
287		608
288	if (@_) {	609	Creates a port on the node C<$node> (which can also be a port ID, in which
289	my $cb = shift;	610	case it's the node where that port resides).
290	$PORT{$id} = sub {	611
291	local $SELF = $port;	612	The port ID of the newly created port is returned immediately, and it is
292	eval {	613	possible to immediately start sending messages or to monitor the port.
293	&$cb	614
294	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	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		634	caller before C<spawn> returns (by delaying invocation when spawn is
		635	called for the local node).
		636
		637	Example: spawn a chat server port on C<$othernode>.
		638
		639	# this node, executed from within a port context:
		640	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
		641	mon $server;
		642
		643	# init function on C<$othernode>
		644	sub connect {
		645	my ($srcport) = @_;
		646
		647	mon $srcport;
		648
		649	rcv $SELF, sub {
295	};	650	...
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	};	651	};
327	}	652	}
328		653
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	654	=cut
342		655
343	sub reg(@) {	656	sub _spawn {
344	my ($portid, $name) = @_;	657	my $port = shift;
		658	my $init = shift;
345		659
346	$REG{$name} = $portid;	660	local $SELF = "$NODE#$port";
347	}	661	eval {
348		662	&{ 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	};	663	};
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 $@;	664	_self_die if $@;
437	@res	665	}
438	} else {	666
439	my $res = eval { &$cb };	667	sub spawn(@) {
440	_self_die if $@;	668	my ($nodeid, undef) = split /#/, shift, 2;
441	$res	669
442	}	670	my $id = "$RUNIQ." . $ID++;
		671
		672	$_[0] =~ /::/
		673	or Carp::croak "spawn init function must be a fully-qualified name, caught";
		674
		675	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
		676
		677	"$nodeid#$id"
		678	}
		679
		680	=item after $timeout, @msg
		681
		682	=item after $timeout, $callback
		683
		684	Either sends the given message, or call the given callback, after the
		685	specified number of seconds.
		686
		687	This is simply a utility function that comes in handy at times - the
		688	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		689	so it may go away in the future.
		690
		691	=cut
		692
		693	sub after($@) {
		694	my ($timeout, @action) = @_;
		695
		696	my $t; $t = AE::timer $timeout, 0, sub {
		697	undef $t;
		698	ref $action[0]
		699	? $action[0]()
		700	: snd @action;
443	}	701	};
444	}	702	}
445		703
446	=back	704	=back
447		705
448	=head1 FUNCTIONS FOR NODES	706	=head1 AnyEvent::MP vs. Distributed Erlang
		707
		708	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
		709	== aemp node, Erlang process == aemp port), so many of the documents and
		710	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
		711	sample:
		712
		713	http://www.Erlang.se/doc/programming_rules.shtml
		714	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
		715	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6
		716	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
		717
		718	Despite the similarities, there are also some important differences:
449		719
450	=over 4	720	=over 4
451		721
452	=item become_public endpoint...	722	=item * Node IDs are arbitrary strings in AEMP.
453		723
454	Tells the node to become a public node, i.e. reachable from other nodes.	724	Erlang relies on special naming and DNS to work everywhere in the same
		725	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
		726	configuration or DNS), but will otherwise discover other odes itself.
455		727
456	If no arguments are given, or the first argument is C<undef>, then	728	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
457	AnyEvent::MP tries to bind on port C<4040> on all IP addresses that the	729	uses "local ports are like remote ports".
458	local nodename resolves to.
459		730
460	Otherwise the first argument must be an array-reference with transport	731	The failure modes for local ports are quite different (runtime errors
461	endpoints ("ip:port", "hostname:port") or port numbers (in which case the	732	only) then for remote ports - when a local port dies, you I<know> it dies,
462	local nodename is used as hostname). The endpoints are all resolved and	733	when a connection to another node dies, you know nothing about the other
463	will become the node reference.	734	port.
464		735
465	=cut	736	Erlang pretends remote ports are as reliable as local ports, even when
		737	they are not.
		738
		739	AEMP encourages a "treat remote ports differently" philosophy, with local
		740	ports being the special case/exception, where transport errors cannot
		741	occur.
		742
		743	=item * Erlang uses processes and a mailbox, AEMP does not queue.
		744
		745	Erlang uses processes that selectively receive messages, and therefore
		746	needs a queue. AEMP is event based, queuing messages would serve no
		747	useful purpose. For the same reason the pattern-matching abilities of
		748	AnyEvent::MP are more limited, as there is little need to be able to
		749	filter messages without dequeuing them.
		750
		751	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
		752
		753	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
		754
		755	Sending messages in Erlang is synchronous and blocks the process (and
		756	so does not need a queue that can overflow). AEMP sends are immediate,
		757	connection establishment is handled in the background.
		758
		759	=item * Erlang suffers from silent message loss, AEMP does not.
		760
		761	Erlang makes few guarantees on messages delivery - messages can get lost
		762	without any of the processes realising it (i.e. you send messages a, b,
		763	and c, and the other side only receives messages a and c).
		764
		765	AEMP guarantees correct ordering, and the guarantee that after one message
		766	is lost, all following ones sent to the same port are lost as well, until
		767	monitoring raises an error, so there are no silent "holes" in the message
		768	sequence.
		769
		770	=item * Erlang can send messages to the wrong port, AEMP does not.
		771
		772	In Erlang it is quite likely that a node that restarts reuses a process ID
		773	known to other nodes for a completely different process, causing messages
		774	destined for that process to end up in an unrelated process.
		775
		776	AEMP never reuses port IDs, so old messages or old port IDs floating
		777	around in the network will not be sent to an unrelated port.
		778
		779	=item * Erlang uses unprotected connections, AEMP uses secure
		780	authentication and can use TLS.
		781
		782	AEMP can use a proven protocol - TLS - to protect connections and
		783	securely authenticate nodes.
		784
		785	=item * The AEMP protocol is optimised for both text-based and binary
		786	communications.
		787
		788	The AEMP protocol, unlike the Erlang protocol, supports both programming
		789	language independent text-only protocols (good for debugging) and binary,
		790	language-specific serialisers (e.g. Storable). By default, unless TLS is
		791	used, the protocol is actually completely text-based.
		792
		793	It has also been carefully designed to be implementable in other languages
		794	with a minimum of work while gracefully degrading functionality to make the
		795	protocol simple.
		796
		797	=item * AEMP has more flexible monitoring options than Erlang.
		798
		799	In Erlang, you can chose to receive I<all> exit signals as messages
		800	or I<none>, there is no in-between, so monitoring single processes is
		801	difficult to implement. Monitoring in AEMP is more flexible than in
		802	Erlang, as one can choose between automatic kill, exit message or callback
		803	on a per-process basis.
		804
		805	=item * Erlang tries to hide remote/local connections, AEMP does not.
		806
		807	Monitoring in Erlang is not an indicator of process death/crashes, in the
		808	same way as linking is (except linking is unreliable in Erlang).
		809
		810	In AEMP, you don't "look up" registered port names or send to named ports
		811	that might or might not be persistent. Instead, you normally spawn a port
		812	on the remote node. The init function monitors you, and you monitor the
		813	remote port. Since both monitors are local to the node, they are much more
		814	reliable (no need for C<spawn_link>).
		815
		816	This also saves round-trips and avoids sending messages to the wrong port
		817	(hard to do in Erlang).
466		818
467	=back	819	=back
468		820
469	=head1 NODE MESSAGES	821	=head1 RATIONALE
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		822
476	=over 4	823	=over 4
477		824
478	=cut	825	=item Why strings for port and node IDs, why not objects?
479		826
480	=item lookup => $name, @reply	827	We considered "objects", but found that the actual number of methods
		828	that can be called are quite low. Since port and node IDs travel over
		829	the network frequently, the serialising/deserialising would add lots of
		830	overhead, as well as having to keep a proxy object everywhere.
481		831
482	Replies with the port ID of the specified well-known port, or C<undef>.	832	Strings can easily be printed, easily serialised etc. and need no special
		833	procedures to be "valid".
483		834
484	=item devnull => ...	835	And as a result, a miniport consists of a single closure stored in a
		836	global hash - it can't become much cheaper.
485		837
486	Generic data sink/CPU heat conversion.	838	=item Why favour JSON, why not a real serialising format such as Storable?
487		839
488	=item relay => $port, @msg	840	In fact, any AnyEvent::MP node will happily accept Storable as framing
		841	format, but currently there is no way to make a node use Storable by
		842	default (although all nodes will accept it).
489		843
490	Simply forwards the message to the given port.	844	The default framing protocol is JSON because a) JSON::XS is many times
		845	faster for small messages and b) most importantly, after years of
		846	experience we found that object serialisation is causing more problems
		847	than it solves: Just like function calls, objects simply do not travel
		848	easily over the network, mostly because they will always be a copy, so you
		849	always have to re-think your design.
491		850
492	=item eval => $string[ @reply]	851	Keeping your messages simple, concentrating on data structures rather than
493		852	objects, will keep your messages clean, tidy and efficient.
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		853
511	=back	854	=back
512		855
513	=head1 SEE ALSO	856	=head1 SEE ALSO
		857
		858	L<AnyEvent::MP::Intro> - a gentle introduction.
		859
		860	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		861
		862	L<AnyEvent::MP::Global> - network maintainance and port groups, to find
		863	your applications.
		864
		865	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		866	all nodes.
514		867
515	L<AnyEvent>.	868	L<AnyEvent>.
516		869
517	=head1 AUTHOR	870	=head1 AUTHOR
518		871

Diff Legend

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

Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.24 by root, Tue Aug 4 20:00:00 2009 UTC vs. Revision 1.81 by root, Mon Sep 7 18:33:44 2009 UTC

Diff Legend

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.24 by root, Tue Aug 4 20:00:00 2009 UTC vs.
Revision 1.81 by root, Mon Sep 7 18:33:44 2009 UTC