AnyEvent-MP/MP.pm

=head1 NAME

AnyEvent::MP - multi-processing/message-passing framework

=head1 SYNOPSIS

   use AnyEvent::MP;

   $NODE      # contains this node's noderef
   NODE       # returns this node's noderef
   NODE $port # returns the noderef of the port

   snd $port, type => data...;

   $SELF      # receiving/own port id in rcv callbacks

   rcv $port, smartmatch => $cb->($port, @msg);

   # examples:
   rcv $port2, ping => sub { snd $_[0], "pong"; 0 };
   rcv $port1, pong => sub { warn "pong received\n" };
   snd $port2, ping => $port1;

   # more, smarter, matches (_any_ is exported by this module)
   rcv $port, [child_died => $pid] => sub { ...
   rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3

=head1 DESCRIPTION

This module (-family) implements a simple message passing framework.

Despite its simplicity, you can securely message other processes running
on the same or other hosts.

For an introduction to this module family, see the L<AnyEvent::MP::Intro>
manual page.

At the moment, this module family is severly broken and underdocumented,
so do not use. This was uploaded mainly to reserve the CPAN namespace -
stay tuned! The basic API should be finished, however.

=head1 CONCEPTS

=over 4

=item port

A port is something you can send messages to (with the C<snd> function).

Some ports allow you to register C<rcv> handlers that can match specific
messages. All C<rcv> handlers will receive messages they match, messages
will not be queued.

=item port id - C<noderef#portname>

A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as
separator, and a port name (a printable string of unspecified format). An
exception is the the node port, whose ID is identical to it's node
reference.

=item node

A node is a single process containing at least one port - the node
port. You can send messages to node ports to find existing ports or to
create new ports, among other things.

Nodes are either private (single-process only), slaves (connected to a
master node only) or public nodes (connectable from unrelated nodes).

=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>

A node reference is a string that either simply identifies the node (for
private and slave nodes), or contains a recipe on how to reach a given
node (for public nodes).

This recipe is simply a comma-separated list of C<address:port> pairs (for
TCP/IP, other protocols might look different).

Node references come in two flavours: resolved (containing only numerical
addresses) or unresolved (where hostnames are used instead of addresses).

Before using an unresolved node reference in a message you first have to
resolve it.

=back

=head1 VARIABLES/FUNCTIONS

=over 4

=cut

package AnyEvent::MP;

use AnyEvent::MP::Base;

use common::sense;

use Carp ();

use AE ();

use base "Exporter";

our $VERSION = '0.1';
our @EXPORT = qw(
   NODE $NODE *SELF node_of _any_
   resolve_node
   become_slave become_public
   snd rcv mon kil reg psub
   port
);

our $SELF;

sub _self_die() {
   my $msg = $@;
   $msg =~ s/\n+$// unless ref $msg;
   kil $SELF, die => $msg;
}

=item $thisnode = NODE / $NODE

The C<NODE> function returns, and the C<$NODE> variable contains
the noderef of the local node. The value is initialised by a call
to C<become_public> or C<become_slave>, after which all local port
identifiers become invalid.

=item $noderef = node_of $portid

Extracts and returns the noderef from a portid or a noderef.

=item $cv = resolve_node $noderef

Takes an unresolved node reference that may contain hostnames and
abbreviated IDs, resolves all of them and returns a resolved node
reference.

In addition to C<address:port> pairs allowed in resolved noderefs, the
following forms are supported:

=over 4

=item the empty string

An empty-string component gets resolved as if the default port (4040) was
specified.

=item naked port numbers (e.g. C<1234>)

These are resolved by prepending the local nodename and a colon, to be
further resolved.

=item hostnames (e.g. C<localhost:1234>, C<localhost>)

These are resolved by using AnyEvent::DNS to resolve them, optionally
looking up SRV records for the C<aemp=4040> port, if no port was
specified.

=back

=item $SELF

Contains the current port id while executing C<rcv> callbacks or C<psub>
blocks.

=item SELF, %SELF, @SELF...

Due to some quirks in how perl exports variables, it is impossible to
just export C<$SELF>, all the symbols called C<SELF> are exported by this
module, but only C<$SELF> is currently used.

=item snd $portid, type => @data

=item snd $portid, @msg

Send the given message to the given port ID, which can identify either
a local or a remote port, and can be either a string or soemthignt hat
stringifies a sa port ID (such as a port object :).

While the message can be about anything, it is highly recommended to use a
string as first element (a portid, or some word that indicates a request
type etc.).

The message data effectively becomes read-only after a call to this
function: modifying any argument is not allowed and can cause many
problems.

The type of data you can transfer depends on the transport protocol: when
JSON is used, then only strings, numbers and arrays and hashes consisting
of those are allowed (no objects). When Storable is used, then anything
that Storable can serialise and deserialise is allowed, and for the local
node, anything can be passed.

=item kil $portid[, @reason]

Kill the specified port with the given C<@reason>.

If no C<@reason> is specified, then the port is killed "normally" (linked
ports will not be kileld, or even notified).

Otherwise, linked ports get killed with the same reason (second form of
C<mon>, see below).

Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
will be reported as reason C<< die => $@ >>.

Transport/communication errors are reported as C<< transport_error =>
$message >>.

=item $guard = mon $portid, $cb->(@reason)

=item $guard = mon $portid, $otherport

=item $guard = mon $portid, $otherport, @msg

Monitor the given port and do something when the port is killed.

In the first form, the callback is simply called with any number
of C<@reason> elements (no @reason means that the port was deleted
"normally"). Note also that I<< the callback B<must> never die >>, so use
C<eval> if unsure.

In the second form, the other port will be C<kil>'ed with C<@reason>, iff
a @reason was specified, i.e. on "normal" kils nothing happens, while
under all other conditions, the other port is killed with the same reason.

In the last form, a message of the form C<@msg, @reason> will be C<snd>.

Example: call a given callback when C<$port> is killed.

   mon $port, sub { warn "port died because of <@_>\n" };

Example: kill ourselves when C<$port> is killed abnormally.

   mon $port, $self;

Example: send us a restart message another C<$port> is killed.

   mon $port, $self => "restart";

=cut

sub mon {
   my ($noderef, $port, $cb) = ((split /#/, shift, 2), shift);

   my $node = $NODE{$noderef} || add_node $noderef;

   #TODO: ports must not be references
   if (!ref $cb or "AnyEvent::MP::Port" eq ref $cb) {
      if (@_) {
         # send a kill info message
         my (@msg) = ($cb, @_);
         $cb = sub { snd @msg, @_ };
      } else {
         # simply kill other port
         my $port = $cb;
         $cb = sub { kil $port, @_ if @_ };
      }
   }

   $node->monitor ($port, $cb);

   defined wantarray
      and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }
}

=item $guard = mon_guard $port, $ref, $ref...

Monitors the given C<$port> and keeps the passed references. When the port
is killed, the references will be freed.

Optionally returns a guard that will stop the monitoring.

This function is useful when you create e.g. timers or other watchers and
want to free them when the port gets killed:

  $port->rcv (start => sub {
     my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {
        undef $timer if 0.9 < rand;
     });
  });

=cut

sub mon_guard {
   my ($port, @refs) = @_;

   mon $port, sub { 0 && @refs }
}

=item lnk $port1, $port2

Link two ports. This is simply a shorthand for:

   mon $port1, $port2;
   mon $port2, $port1;

It means that if either one is killed abnormally, the other one gets
killed as well.

=item $local_port = port

Create a new local port object that supports message matching.

=item $portid = port { my @msg = @_; $finished }

Creates a "mini port", that is, a very lightweight port without any
pattern matching behind it, and returns its ID.

The block will be called for every message received on the port. When the
callback returns a true value its job is considered "done" and the port
will be destroyed. Otherwise it will stay alive.

The message will be passed as-is, no extra argument (i.e. no port id) will
be passed to the callback.

If you need the local port id in the callback, this works nicely:

   my $port; $port = miniport {
      snd $otherport, reply => $port;
   };

=cut

sub port(;&) {
   my $id = "$UNIQ." . $ID++;
   my $port = "$NODE#$id";

   if (@_) {
      my $cb = shift;
      $PORT{$id} = sub {
         local $SELF = $port;
         eval {
            &$cb
               and kil $id;
         };
         _self_die if $@;
      };
   } else {
      my $self = bless {
         id    => "$NODE#$id",
      }, "AnyEvent::MP::Port";

      $PORT_DATA{$id} = $self;
      $PORT{$id} = sub {
         local $SELF = $port;

         eval {
            for (@{ $self->{rc0}{$_[0]} }) {
               $_ && &{$_->[0]}
                  && undef $_;
            }

            for (@{ $self->{rcv}{$_[0]} }) {
               $_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
                  && &{$_->[0]}
                  && undef $_;
            }

            for (@{ $self->{any} }) {
               $_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
                  && &{$_->[0]}
                  && undef $_;
            }
         };
         _self_die if $@;
      };
   }

   $port
}

=item reg $portid, $name

Registers the given port under the name C<$name>. If the name already
exists it is replaced.

A port can only be registered under one well known name.

A port automatically becomes unregistered when it is killed.

=cut

sub reg(@) {
   my ($portid, $name) = @_;

   $REG{$name} = $portid;
}

=item rcv $portid, tagstring        => $callback->(@msg), ...

=item rcv $portid, $smartmatch      => $callback->(@msg), ...

=item rcv $portid, [$smartmatch...] => $callback->(@msg), ...

Register callbacks to be called on matching messages on the given port.

The callback has to return a true value when its work is done, after
which is will be removed, or a false value in which case it will stay
registered.

The global C<$SELF> (exported by this module) contains C<$portid> while
executing the callback.

Runtime errors wdurign callback execution will result in the port being
C<kil>ed.

If the match is an array reference, then it will be matched against the
first elements of the message, otherwise only the first element is being
matched.

Any element in the match that is specified as C<_any_> (a function
exported by this module) matches any single element of the message.

While not required, it is highly recommended that the first matching
element is a string identifying the message. The one-string-only match is
also the most efficient match (by far).

=cut

sub rcv($@) {
   my ($noderef, $port) = split /#/, shift, 2;

   ($NODE{$noderef} || add_node $noderef) == $NODE{""}
      or Carp::croak "$noderef#$port: rcv can only be called on local ports, caught";

   my $self = $PORT_DATA{$port}
      or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught";

   "AnyEvent::MP::Port" eq ref $self
      or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught";

   while (@_) {
      my ($match, $cb) = splice @_, 0, 2;

      if (!ref $match) {
         push @{ $self->{rc0}{$match}      }, [$cb];
      } elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
         my ($type, @match) = @$match;
         @match
            ? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
            : push @{ $self->{rc0}{$match->[0]} }, [$cb];
      } else {
         push @{ $self->{any}              }, [$cb, $match];
      }
   }
}

=item $closure = psub { BLOCK }

Remembers C<$SELF> and creates a closure out of the BLOCK. When the
closure is executed, sets up the environment in the same way as in C<rcv>
callbacks, i.e. runtime errors will cause the port to get C<kil>ed.

This is useful when you register callbacks from C<rcv> callbacks:

   rcv delayed_reply => sub {
      my ($delay, @reply) = @_;
      my $timer = AE::timer $delay, 0, psub {
         snd @reply, $SELF;
      };
   };

=cut

sub psub(&) {
   my $cb = shift;

   my $port = $SELF
      or Carp::croak "psub can only be called from within rcv or psub callbacks, not";

   sub {
      local $SELF = $port;

      if (wantarray) {
         my @res = eval { &$cb };
         _self_die if $@;
         @res
      } else {
         my $res = eval { &$cb };
         _self_die if $@;
         $res
      }
   }
}

=back

=head1 FUNCTIONS FOR NODES

=over 4

=item become_public $noderef

Tells the node to become a public node, i.e. reachable from other nodes.

The first argument is the (unresolved) node reference of the local node
(if missing then the empty string is used).

It is quite common to not specify anything, in which case the local node
tries to listen on the default port, or to only specify a port number, in
which case AnyEvent::MP tries to guess the local addresses.

=cut

=back

=head1 NODE MESSAGES

Nodes understand the following messages sent to them. Many of them take
arguments called C<@reply>, which will simply be used to compose a reply
message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
the remaining arguments are simply the message data.

While other messages exist, they are not public and subject to change.

=over 4

=cut

=item lookup => $name, @reply

Replies with the port ID of the specified well-known port, or C<undef>.

=item devnull => ...

Generic data sink/CPU heat conversion.

=item relay => $port, @msg

Simply forwards the message to the given port.

=item eval => $string[ @reply]

Evaluates the given string. If C<@reply> is given, then a message of the
form C<@reply, $@, @evalres> is sent.

Example: crash another node.

   snd $othernode, eval => "exit";

=item time => @reply

Replies the the current node time to C<@reply>.

Example: tell the current node to send the current time to C<$myport> in a
C<timereply> message.

   snd $NODE, time => $myport, timereply => 1, 2;
   # => snd $myport, timereply => 1, 2, <time>

=back

=head1 AnyEvent::MP vs. Distributed Erlang

AnyEvent::MP got lots of its ideas from distributed erlang (erlang node
== aemp node, erlang process == aemp port), so many of the documents and
programming techniques employed by erlang apply to AnyEvent::MP. Here is a
sample:

   http://www.erlang.se/doc/programming_rules.shtml
   http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
   http://erlang.org/download/erlang-book-part1.pdf      # chapters 5 and 6
   http://erlang.org/download/armstrong_thesis_2003.pdf  # chapters 4 and 5

Despite the similarities, there are also some important differences:

=over 4

=item * Node references contain the recipe on how to contact them.

Erlang relies on special naming and DNS to work everywhere in the
same way. AEMP relies on each node knowing it's own address(es), with
convenience functionality.

This means that AEMP requires a less tightly controlled environment at the
cost of longer node references and a slightly higher management overhead.

=item * Erlang uses processes and a mailbox, AEMP does not queue.

Erlang uses processes that selctively receive messages, and therefore
needs a queue. AEMP is event based, queuing messages would serve no useful
purpose.

(But see L<Coro::MP> for a more erlang-like process model on top of AEMP).

=item * Erlang sends are synchronous, AEMP sends are asynchronous.

Sending messages in erlang is synchronous and blocks the process. AEMP
sends are immediate, connection establishment is handled in the
background.

=item * Erlang can silently lose messages, AEMP cannot.

Erlang makes few guarantees on messages delivery - messages can get lost
without any of the processes realising it (i.e. you send messages a, b,
and c, and the other side only receives messages a and c).

AEMP guarantees correct ordering, and the guarantee that there are no
holes in the message sequence.

=item * In erlang, processes can be declared dead and later be found to be
alive.

In erlang it can happen that a monitored process is declared dead and
linked processes get killed, but later it turns out that the process is
still alive - and can receive messages.

In AEMP, when port monitoring detects a port as dead, then that port will
eventually be killed - it cannot happen that a node detects a port as dead
and then later sends messages to it, finding it is still alive.

=item * Erlang can send messages to the wrong port, AEMP does not.

In erlang it is quite possible that a node that restarts reuses a process
ID known to other nodes for a completely different process, causing
messages destined for that process to end up in an unrelated process.

AEMP never reuses port IDs, so old messages or old port IDs floating
around in the network will not be sent to an unrelated port.

=item * Erlang uses unprotected connections, AEMP uses secure
authentication and can use TLS.

AEMP can use a proven protocol - SSL/TLS - to protect connections and
securely authenticate nodes.

=item * The AEMP protocol is optimised for both text-based and binary
communications.

The AEMP protocol, unlike the erlang protocol, supports both
language-independent text-only protocols (good for debugging) and binary,
language-specific serialisers (e.g. Storable).

It has also been carefully designed to be implementable in other languages
with a minimum of work while gracefully degrading fucntionality to make the
protocol simple.

=back

=head1 SEE ALSO

L<AnyEvent>.

=head1 AUTHOR

 Marc Lehmann <schmorp@schmorp.de>
 http://home.schmorp.de/

=cut

1

Revision:	1.29
Committed:	Tue Aug 4 23:16:57 2009 UTC (14 years, 9 months ago) by root
Branch:	MAIN
Changes since 1.28:	+63 -21 lines
Log Message:	* empty log message *
#	User	Rev	Content
1	root	1.1	=head1 NAME
2
3			AnyEvent::MP - multi-processing/message-passing framework
4
5			=head1 SYNOPSIS
6
7			use AnyEvent::MP;
8
9	root	1.22	$NODE # contains this node's noderef
10			NODE # returns this node's noderef
11			NODE $port # returns the noderef of the port
12	root	1.2
13			snd $port, type => data...;
14
15	root	1.22	$SELF # receiving/own port id in rcv callbacks
16
17	root	1.2	rcv $port, smartmatch => $cb->($port, @msg);
18
19			# examples:
20			rcv $port2, ping => sub { snd $_[0], "pong"; 0 };
21			rcv $port1, pong => sub { warn "pong received\n" };
22			snd $port2, ping => $port1;
23
24			# more, smarter, matches (_any_ is exported by this module)
25			rcv $port, [child_died => $pid] => sub { ...
26			rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3
27
28	root	1.1	=head1 DESCRIPTION
29
30	root	1.2	This module (-family) implements a simple message passing framework.
31
32			Despite its simplicity, you can securely message other processes running
33			on the same or other hosts.
34
35	root	1.23	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
36			manual page.
37
38			At the moment, this module family is severly broken and underdocumented,
39	root	1.21	so do not use. This was uploaded mainly to reserve the CPAN namespace -
40	root	1.23	stay tuned! The basic API should be finished, however.
41	root	1.6
42	root	1.2	=head1 CONCEPTS
43
44			=over 4
45
46			=item port
47
48	root	1.29	A port is something you can send messages to (with the C<snd> function).
49
50			Some ports allow you to register C<rcv> handlers that can match specific
51			messages. All C<rcv> handlers will receive messages they match, messages
52			will not be queued.
53	root	1.2
54	root	1.3	=item port id - C<noderef#portname>
55	root	1.2
56	root	1.29	A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as
57			separator, and a port name (a printable string of unspecified format). An
58			exception is the the node port, whose ID is identical to it's node
59			reference.
60	root	1.2
61			=item node
62
63			A node is a single process containing at least one port - the node
64	root	1.29	port. You can send messages to node ports to find existing ports or to
65			create new ports, among other things.
66	root	1.2
67	root	1.29	Nodes are either private (single-process only), slaves (connected to a
68			master node only) or public nodes (connectable from unrelated nodes).
69	root	1.2
70	root	1.5	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>
71	root	1.2
72	root	1.29	A node reference is a string that either simply identifies the node (for
73			private and slave nodes), or contains a recipe on how to reach a given
74	root	1.2	node (for public nodes).
75
76	root	1.29	This recipe is simply a comma-separated list of C<address:port> pairs (for
77			TCP/IP, other protocols might look different).
78
79			Node references come in two flavours: resolved (containing only numerical
80			addresses) or unresolved (where hostnames are used instead of addresses).
81
82			Before using an unresolved node reference in a message you first have to
83			resolve it.
84
85	root	1.2	=back
86
87	root	1.3	=head1 VARIABLES/FUNCTIONS
88	root	1.2
89			=over 4
90
91	root	1.1	=cut
92
93			package AnyEvent::MP;
94
95	root	1.8	use AnyEvent::MP::Base;
96	root	1.2
97	root	1.1	use common::sense;
98
99	root	1.2	use Carp ();
100
101	root	1.1	use AE ();
102
103	root	1.2	use base "Exporter";
104
105	root	1.25	our $VERSION = '0.1';
106	root	1.8	our @EXPORT = qw(
107	root	1.22	NODE $NODE *SELF node_of _any_
108	root	1.29	resolve_node
109	root	1.8	become_slave become_public
110	root	1.22	snd rcv mon kil reg psub
111			port
112	root	1.8	);
113	root	1.2
114	root	1.22	our $SELF;
115
116			sub _self_die() {
117			my $msg = $@;
118			$msg =~ s/\n+$// unless ref $msg;
119			kil $SELF, die => $msg;
120			}
121
122			=item $thisnode = NODE / $NODE
123
124			The C<NODE> function returns, and the C<$NODE> variable contains
125			the noderef of the local node. The value is initialised by a call
126			to C<become_public> or C<become_slave>, after which all local port
127			identifiers become invalid.
128
129			=item $noderef = node_of $portid
130
131			Extracts and returns the noderef from a portid or a noderef.
132
133	root	1.29	=item $cv = resolve_node $noderef
134
135			Takes an unresolved node reference that may contain hostnames and
136			abbreviated IDs, resolves all of them and returns a resolved node
137			reference.
138
139			In addition to C<address:port> pairs allowed in resolved noderefs, the
140			following forms are supported:
141
142			=over 4
143
144			=item the empty string
145
146			An empty-string component gets resolved as if the default port (4040) was
147			specified.
148
149			=item naked port numbers (e.g. C<1234>)
150
151			These are resolved by prepending the local nodename and a colon, to be
152			further resolved.
153
154			=item hostnames (e.g. C<localhost:1234>, C<localhost>)
155
156			These are resolved by using AnyEvent::DNS to resolve them, optionally
157			looking up SRV records for the C<aemp=4040> port, if no port was
158			specified.
159
160			=back
161
162	root	1.22	=item $SELF
163
164			Contains the current port id while executing C<rcv> callbacks or C<psub>
165			blocks.
166	root	1.3
167	root	1.22	=item SELF, %SELF, @SELF...
168
169			Due to some quirks in how perl exports variables, it is impossible to
170			just export C<$SELF>, all the symbols called C<SELF> are exported by this
171			module, but only C<$SELF> is currently used.
172	root	1.3
173			=item snd $portid, type => @data
174
175			=item snd $portid, @msg
176
177	root	1.8	Send the given message to the given port ID, which can identify either
178			a local or a remote port, and can be either a string or soemthignt hat
179			stringifies a sa port ID (such as a port object :).
180
181			While the message can be about anything, it is highly recommended to use a
182			string as first element (a portid, or some word that indicates a request
183			type etc.).
184	root	1.3
185			The message data effectively becomes read-only after a call to this
186			function: modifying any argument is not allowed and can cause many
187			problems.
188
189			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
191			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
193			node, anything can be passed.
194
195	root	1.22	=item kil $portid[, @reason]
196
197			Kill the specified port with the given C<@reason>.
198
199			If no C<@reason> is specified, then the port is killed "normally" (linked
200			ports will not be kileld, or even notified).
201
202			Otherwise, linked ports get killed with the same reason (second form of
203			C<mon>, see below).
204
205			Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
206			will be reported as reason C<< die => $@ >>.
207
208			Transport/communication errors are reported as C<< transport_error =>
209			$message >>.
210
211			=item $guard = mon $portid, $cb->(@reason)
212	root	1.18
213	root	1.21	=item $guard = mon $portid, $otherport
214
215			=item $guard = mon $portid, $otherport, @msg
216
217	root	1.22	Monitor the given port and do something when the port is killed.
218
219			In the first form, the callback is simply called with any number
220			of C<@reason> elements (no @reason means that the port was deleted
221			"normally"). Note also that I<< the callback B<must> never die >>, so use
222			C<eval> if unsure.
223
224			In the second form, the other port will be C<kil>'ed with C<@reason>, iff
225			a @reason was specified, i.e. on "normal" kils nothing happens, while
226			under all other conditions, the other port is killed with the same reason.
227	root	1.20
228	root	1.22	In the last form, a message of the form C<@msg, @reason> will be C<snd>.
229
230			Example: call a given callback when C<$port> is killed.
231
232			mon $port, sub { warn "port died because of <@_>\n" };
233
234			Example: kill ourselves when C<$port> is killed abnormally.
235
236			mon $port, $self;
237
238			Example: send us a restart message another C<$port> is killed.
239
240			mon $port, $self => "restart";
241	root	1.18
242			=cut
243
244			sub mon {
245	root	1.21	my ($noderef, $port, $cb) = ((split /#/, shift, 2), shift);
246	root	1.18
247	root	1.22	my $node = $NODE{$noderef} \|\| add_node $noderef;
248	root	1.18
249	root	1.21	#TODO: ports must not be references
250			if (!ref $cb or "AnyEvent::MP::Port" eq ref $cb) {
251			if (@_) {
252			# send a kill info message
253			my (@msg) = ($cb, @_);
254			$cb = sub { snd @msg, @_ };
255			} else {
256			# simply kill other port
257			my $port = $cb;
258	root	1.22	$cb = sub { kil $port, @_ if @_ };
259	root	1.21	}
260			}
261	root	1.18
262			$node->monitor ($port, $cb);
263
264			defined wantarray
265			and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }
266			}
267
268	root	1.21	=item $guard = mon_guard $port, $ref, $ref...
269
270			Monitors the given C<$port> and keeps the passed references. When the port
271			is killed, the references will be freed.
272
273			Optionally returns a guard that will stop the monitoring.
274
275			This function is useful when you create e.g. timers or other watchers and
276			want to free them when the port gets killed:
277
278			$port->rcv (start => sub {
279			my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {
280			undef $timer if 0.9 < rand;
281			});
282			});
283
284			=cut
285
286			sub mon_guard {
287			my ($port, @refs) = @_;
288
289			mon $port, sub { 0 && @refs }
290			}
291
292	root	1.24	=item lnk $port1, $port2
293
294			Link two ports. This is simply a shorthand for:
295
296			mon $port1, $port2;
297			mon $port2, $port1;
298
299			It means that if either one is killed abnormally, the other one gets
300			killed as well.
301
302	root	1.22	=item $local_port = port
303	root	1.2
304	root	1.22	Create a new local port object that supports message matching.
305	root	1.3
306	root	1.22	=item $portid = port { my @msg = @_; $finished }
307	root	1.10
308	root	1.15	Creates a "mini port", that is, a very lightweight port without any
309			pattern matching behind it, and returns its ID.
310
311			The block will be called for every message received on the port. When the
312			callback returns a true value its job is considered "done" and the port
313			will be destroyed. Otherwise it will stay alive.
314
315	root	1.17	The message will be passed as-is, no extra argument (i.e. no port id) will
316	root	1.15	be passed to the callback.
317
318			If you need the local port id in the callback, this works nicely:
319
320			my $port; $port = miniport {
321			snd $otherport, reply => $port;
322			};
323	root	1.10
324			=cut
325
326	root	1.22	sub port(;&) {
327			my $id = "$UNIQ." . $ID++;
328			my $port = "$NODE#$id";
329
330			if (@_) {
331			my $cb = shift;
332			$PORT{$id} = sub {
333			local $SELF = $port;
334			eval {
335			&$cb
336			and kil $id;
337			};
338			_self_die if $@;
339			};
340			} else {
341			my $self = bless {
342			id => "$NODE#$id",
343			}, "AnyEvent::MP::Port";
344
345			$PORT_DATA{$id} = $self;
346			$PORT{$id} = sub {
347			local $SELF = $port;
348
349			eval {
350			for (@{ $self->{rc0}{$_[0]} }) {
351			$_ && &{$_->[0]}
352			&& undef $_;
353			}
354
355			for (@{ $self->{rcv}{$_[0]} }) {
356			$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
357			&& &{$_->[0]}
358			&& undef $_;
359			}
360
361			for (@{ $self->{any} }) {
362			$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
363			&& &{$_->[0]}
364			&& undef $_;
365			}
366			};
367			_self_die if $@;
368			};
369			}
370	root	1.10
371	root	1.22	$port
372	root	1.10	}
373
374	root	1.22	=item reg $portid, $name
375	root	1.8
376	root	1.22	Registers the given port under the name C<$name>. If the name already
377			exists it is replaced.
378	root	1.8
379	root	1.22	A port can only be registered under one well known name.
380	root	1.8
381	root	1.22	A port automatically becomes unregistered when it is killed.
382	root	1.8
383			=cut
384
385	root	1.22	sub reg(@) {
386			my ($portid, $name) = @_;
387	root	1.8
388	root	1.22	$REG{$name} = $portid;
389			}
390	root	1.18
391	root	1.22	=item rcv $portid, tagstring => $callback->(@msg), ...
392	root	1.3
393	root	1.22	=item rcv $portid, $smartmatch => $callback->(@msg), ...
394	root	1.3
395	root	1.22	=item rcv $portid, [$smartmatch...] => $callback->(@msg), ...
396	root	1.3
397	root	1.22	Register callbacks to be called on matching messages on the given port.
398	root	1.3
399			The callback has to return a true value when its work is done, after
400			which is will be removed, or a false value in which case it will stay
401			registered.
402
403	root	1.22	The global C<$SELF> (exported by this module) contains C<$portid> while
404			executing the callback.
405
406			Runtime errors wdurign callback execution will result in the port being
407			C<kil>ed.
408
409	root	1.3	If the match is an array reference, then it will be matched against the
410			first elements of the message, otherwise only the first element is being
411			matched.
412
413			Any element in the match that is specified as C<_any_> (a function
414			exported by this module) matches any single element of the message.
415
416			While not required, it is highly recommended that the first matching
417			element is a string identifying the message. The one-string-only match is
418			also the most efficient match (by far).
419
420			=cut
421
422			sub rcv($@) {
423	root	1.22	my ($noderef, $port) = split /#/, shift, 2;
424	root	1.3
425	root	1.22	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}
426			or Carp::croak "$noderef#$port: rcv can only be called on local ports, caught";
427
428			my $self = $PORT_DATA{$port}
429			or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught";
430
431			"AnyEvent::MP::Port" eq ref $self
432			or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught";
433
434			while (@_) {
435			my ($match, $cb) = splice @_, 0, 2;
436
437			if (!ref $match) {
438			push @{ $self->{rc0}{$match} }, [$cb];
439			} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
440			my ($type, @match) = @$match;
441			@match
442			? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
443			: push @{ $self->{rc0}{$match->[0]} }, [$cb];
444			} else {
445			push @{ $self->{any} }, [$cb, $match];
446			}
447	root	1.3	}
448	root	1.2	}
449
450	root	1.22	=item $closure = psub { BLOCK }
451	root	1.2
452	root	1.22	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
453			closure is executed, sets up the environment in the same way as in C<rcv>
454			callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
455
456			This is useful when you register callbacks from C<rcv> callbacks:
457
458			rcv delayed_reply => sub {
459			my ($delay, @reply) = @_;
460			my $timer = AE::timer $delay, 0, psub {
461			snd @reply, $SELF;
462			};
463			};
464	root	1.3
465	root	1.8	=cut
466	root	1.3
467	root	1.22	sub psub(&) {
468			my $cb = shift;
469	root	1.3
470	root	1.22	my $port = $SELF
471			or Carp::croak "psub can only be called from within rcv or psub callbacks, not";
472	root	1.1
473	root	1.22	sub {
474			local $SELF = $port;
475	root	1.2
476	root	1.22	if (wantarray) {
477			my @res = eval { &$cb };
478			_self_die if $@;
479			@res
480			} else {
481			my $res = eval { &$cb };
482			_self_die if $@;
483			$res
484			}
485			}
486	root	1.2	}
487
488	root	1.8	=back
489
490			=head1 FUNCTIONS FOR NODES
491
492			=over 4
493	root	1.2
494	root	1.29	=item become_public $noderef
495	root	1.8
496			Tells the node to become a public node, i.e. reachable from other nodes.
497
498	root	1.29	The first argument is the (unresolved) node reference of the local node
499			(if missing then the empty string is used).
500
501			It is quite common to not specify anything, in which case the local node
502			tries to listen on the default port, or to only specify a port number, in
503			which case AnyEvent::MP tries to guess the local addresses.
504	root	1.2
505	root	1.8	=cut
506	root	1.1
507	root	1.4	=back
508
509			=head1 NODE MESSAGES
510
511	root	1.5	Nodes understand the following messages sent to them. Many of them take
512			arguments called C<@reply>, which will simply be used to compose a reply
513			message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
514			the remaining arguments are simply the message data.
515	root	1.4
516	root	1.29	While other messages exist, they are not public and subject to change.
517
518	root	1.4	=over 4
519
520			=cut
521
522	root	1.22	=item lookup => $name, @reply
523	root	1.3
524	root	1.8	Replies with the port ID of the specified well-known port, or C<undef>.
525	root	1.3
526	root	1.7	=item devnull => ...
527
528			Generic data sink/CPU heat conversion.
529
530	root	1.4	=item relay => $port, @msg
531
532			Simply forwards the message to the given port.
533
534			=item eval => $string[ @reply]
535
536			Evaluates the given string. If C<@reply> is given, then a message of the
537	root	1.5	form C<@reply, $@, @evalres> is sent.
538
539			Example: crash another node.
540
541			snd $othernode, eval => "exit";
542	root	1.4
543			=item time => @reply
544
545			Replies the the current node time to C<@reply>.
546
547	root	1.5	Example: tell the current node to send the current time to C<$myport> in a
548			C<timereply> message.
549
550			snd $NODE, time => $myport, timereply => 1, 2;
551			# => snd $myport, timereply => 1, 2, <time>
552
553	root	1.2	=back
554
555	root	1.26	=head1 AnyEvent::MP vs. Distributed Erlang
556
557	root	1.27	AnyEvent::MP got lots of its ideas from distributed erlang (erlang node
558			== aemp node, erlang process == aemp port), so many of the documents and
559			programming techniques employed by erlang apply to AnyEvent::MP. Here is a
560			sample:
561
562			http://www.erlang.se/doc/programming_rules.shtml
563			http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
564			http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
565			http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
566
567			Despite the similarities, there are also some important differences:
568	root	1.26
569			=over 4
570
571			=item * Node references contain the recipe on how to contact them.
572
573			Erlang relies on special naming and DNS to work everywhere in the
574			same way. AEMP relies on each node knowing it's own address(es), with
575			convenience functionality.
576
577	root	1.27	This means that AEMP requires a less tightly controlled environment at the
578			cost of longer node references and a slightly higher management overhead.
579
580	root	1.26	=item * Erlang uses processes and a mailbox, AEMP does not queue.
581
582			Erlang uses processes that selctively receive messages, and therefore
583			needs a queue. AEMP is event based, queuing messages would serve no useful
584			purpose.
585
586			(But see L<Coro::MP> for a more erlang-like process model on top of AEMP).
587
588			=item * Erlang sends are synchronous, AEMP sends are asynchronous.
589
590			Sending messages in erlang is synchronous and blocks the process. AEMP
591			sends are immediate, connection establishment is handled in the
592			background.
593
594			=item * Erlang can silently lose messages, AEMP cannot.
595
596			Erlang makes few guarantees on messages delivery - messages can get lost
597			without any of the processes realising it (i.e. you send messages a, b,
598			and c, and the other side only receives messages a and c).
599
600			AEMP guarantees correct ordering, and the guarantee that there are no
601			holes in the message sequence.
602
603			=item * In erlang, processes can be declared dead and later be found to be
604			alive.
605
606			In erlang it can happen that a monitored process is declared dead and
607			linked processes get killed, but later it turns out that the process is
608			still alive - and can receive messages.
609
610			In AEMP, when port monitoring detects a port as dead, then that port will
611			eventually be killed - it cannot happen that a node detects a port as dead
612			and then later sends messages to it, finding it is still alive.
613
614			=item * Erlang can send messages to the wrong port, AEMP does not.
615
616			In erlang it is quite possible that a node that restarts reuses a process
617			ID known to other nodes for a completely different process, causing
618			messages destined for that process to end up in an unrelated process.
619
620			AEMP never reuses port IDs, so old messages or old port IDs floating
621			around in the network will not be sent to an unrelated port.
622
623			=item * Erlang uses unprotected connections, AEMP uses secure
624			authentication and can use TLS.
625
626			AEMP can use a proven protocol - SSL/TLS - to protect connections and
627			securely authenticate nodes.
628
629	root	1.28	=item * The AEMP protocol is optimised for both text-based and binary
630			communications.
631
632			The AEMP protocol, unlike the erlang protocol, supports both
633			language-independent text-only protocols (good for debugging) and binary,
634			language-specific serialisers (e.g. Storable).
635
636			It has also been carefully designed to be implementable in other languages
637			with a minimum of work while gracefully degrading fucntionality to make the
638			protocol simple.
639
640	root	1.26	=back
641
642	root	1.1	=head1 SEE ALSO
643
644			L<AnyEvent>.
645
646			=head1 AUTHOR
647
648			Marc Lehmann <schmorp@schmorp.de>
649			http://home.schmorp.de/
650
651			=cut
652
653			1
654