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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.38 by root, Fri Aug 7 22:55:18 2009 UTC vs.
Revision 1.49 by root, Thu Aug 13 15:29:58 2009 UTC

    $NODE      # contains this node's noderef
    NODE       # returns this node's noderef
    NODE $port # returns the noderef of the port
    $SELF      # receiving/own port id in rcv callbacks
+   # initialise the node so it can send/receive messages
+   initialise_node;                  # -OR-
+   initialise_node "localhost:4040"; # -OR-
+   initialise_node "slave/", "localhost:4040"
    # ports are message endpoints
    # sending messages
    snd $port, type => data...;
    snd $port, @msg;
    snd @msg_with_first_element_being_a_port;
-   # miniports
+   # creating/using miniports
    my $miniport = port { my @msg = @_; 0 };
-   # full ports
+   # creating/using full ports
    my $port = port;
    rcv $port, smartmatch => $cb->(@msg);
    rcv $port, ping => sub { snd $_[0], "pong"; 0 };
    rcv $port, pong => sub { warn "pong received\n"; 0 };
-   # remote ports
-   my $port = spawn $node, $initfunc, @initdata;
    # more, smarter, matches (_any_ is exported by this module)
    rcv $port, [child_died => $pid] => sub { ...
    rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3
+   # create a port on another node
+   my $port = spawn $node, $initfunc, @initdata;
    # monitoring
    mon $port, $cb->(@msg)      # callback is invoked on death
    mon $port, $otherport       # kill otherport on abnormal death
    mon $port, $otherport, @msg # send message on death
+=head1 CURRENT STATUS
+   AnyEvent::MP            - stable API, should work
+   AnyEvent::MP::Intro     - outdated
+   AnyEvent::MP::Kernel    - WIP
+   AnyEvent::MP::Transport - mostly stable
+   stay tuned.
 =head1 DESCRIPTION
 This module (-family) implements a simple message passing framework.
 Despite its simplicity, you can securely message other processes running
 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.
+stay tuned!
 =head1 CONCEPTS
 =over 4
 =cut
 package AnyEvent::MP;
-use AnyEvent::MP::Base;
+use AnyEvent::MP::Kernel;
 use common::sense;
 use Carp ();
 use AE ();
 use base "Exporter";
-our $VERSION = '0.1';
+our $VERSION = $AnyEvent::MP::Kernel::VERSION;
 our @EXPORT = qw(
    NODE $NODE *SELF node_of _any_
    resolve_node initialise_node
    snd rcv mon kil reg psub spawn
    port
 it should know the noderefs of some other nodes in the network.
 This function initialises a node - it must be called exactly once (or
 never) before calling other AnyEvent::MP functions.
-All arguments are noderefs, which can be either resolved or unresolved.
+All arguments (optionally except for the first) are noderefs, which can be
+either resolved or unresolved.
+The first argument will be looked up in the configuration database first
+(if it is C<undef> then the current nodename will be used instead) to find
+the relevant configuration profile (see L<aemp>). If none is found then
+the default configuration is used. The configuration supplies additional
+seed/master nodes and can override the actual noderef.
 There are two types of networked nodes, public nodes and slave nodes:
 =over 4
 =item public nodes
-For public nodes, C<$noderef> must either be a (possibly unresolved)
+For public nodes, C<$noderef> (supplied either directly to
-noderef, in which case it will be resolved, or C<undef> (or missing), in
+C<initialise_node> or indirectly via a profile or the nodename) must be a
-which case the noderef will be guessed.
+noderef (possibly unresolved, in which case it will be resolved).
-Afterwards, the node will bind itself on all endpoints and try to connect
+After resolving, the node will bind itself on all endpoints and try to
-to all additional C<$seednodes> that are specified. Seednodes are optional
+connect to all additional C<$seednodes> that are specified. Seednodes are
-and can be used to quickly bootstrap the node into an existing network.
+optional and can be used to quickly bootstrap the node into an existing
+network.
 =item slave nodes
-When the C<$noderef> is the special string C<slave/>, then the node will
+When the C<$noderef> (either as given or overriden by the config file)
+is the special string C<slave/>, then the node will become a slave
-become a slave node. Slave nodes cannot be contacted from outside and will
+node. Slave nodes cannot be contacted from outside and will route most of
-route most of their traffic to the master node that they attach to.
+their traffic to the master node that they attach to.
-At least one additional noderef is required: The node will try to connect
+At least one additional noderef is required (either by specifying it
-to all of them and will become a slave attached to the first node it can
+directly or because it is part of the configuration profile): The node
-successfully connect to.
+will try to connect to all of them and will become a slave attached to the
+first node it can successfully connect to.
 =back
 This function will block until all nodes have been resolved and, for slave
 nodes, until it has successfully established a connection to a master
 server.
-Example: become a public node listening on the default node.
+Example: become a public node listening on the guessed noderef, or the one
+specified via C<aemp> for the current node. This should be the most common
+form of invocation for "daemon"-type nodes.
    initialise_node;
+Example: become a slave node to any of the the seednodes specified via
+C<aemp>.  This form is often used for commandline clients.
+   initialise_node "slave/";
+Example: become a slave node to any of the specified master servers. This
+form is also often used for commandline clients.
+   initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
 Example: become a public node, and try to contact some well-known master
 servers to become part of the network.
    initialise_node undef, "master1", "master2";
    initialise_node 4041;
 Example: become a public node, only visible on localhost port 4044.
-   initialise_node "locahost:4044";
+   initialise_node "localhost:4044";
-Example: become a slave node to any of the specified master servers.
-   initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
 =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
 =item $guard = mon $port
 =item $guard = mon $port, $rcvport, @msg
-Monitor the given port and do something when the port is killed, and
+Monitor the given port and do something when the port is killed or
-optionally return a guard that can be used to stop monitoring again.
+messages to it were lost, and optionally return a guard that can be used
+to stop monitoring again.
+C<mon> effectively guarantees that, in the absence of hardware failures,
+that after starting the monitor, either all messages sent to the port
+will arrive, or the monitoring action will be invoked after possible
+message loss has been detected. No messages will be lost "in between"
+(after the first lost message no further messages will be received by the
+port). After the monitoring action was invoked, further messages might get
+delivered again.
 In the first form (callback), the callback is simply called with any
 number of C<@reason> elements (no @reason means that the port was deleted
 "normally"). Note also that I<< the callback B<must> never die >>, so use
 C<eval> if unsure.
-In the second form (another port given), the other port (C<$rcvport)
+In the second form (another port given), the other port (C<$rcvport>)
 will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
 "normal" kils nothing happens, while under all other conditions, the other
 port is killed with the same reason.
 The third form (kill self) is the same as the second form, except that
 sub mon {
    my ($noderef, $port) = split /#/, shift, 2;
    my $node = $NODE{$noderef} || add_node $noderef;
-   my $cb = @_ ? $_[0] : $SELF || Carp::croak 'mon: called with one argument only, but $SELF not set,';
+   my $cb = @_ ? shift : $SELF || Carp::croak 'mon: called with one argument only, but $SELF not set,';
    unless (ref $cb) {
       if (@_) {
          # send a kill info message
-         my (@msg) = @_;
+         my (@msg) = ($cb, @_);
          $cb = sub { snd @msg, @_ };
       } else {
          # simply kill other port
          my $port = $cb;
          $cb = sub { kil $port, @_ if @_ };
 The port ID of the newly created port is return immediately, and it is
 permissible to immediately start sending messages or monitor the port.
 After the port has been created, the init function is
-called. This fucntion must be a fully-qualified function name
+called. This function must be a fully-qualified function name
-(e.g. C<MyApp::Chat::Server::init>).
+(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main
+program, use C<::name>.
 If the function doesn't exist, then the node tries to C<require>
 the package, then the package above the package and so on (e.g.
 C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
 exists or it runs out of package names.
 sub spawn(@) {
    my ($noderef, undef) = split /#/, shift, 2;
    my $id = "$RUNIQ." . $ID++;
+   $_[0] =~ /::/
+      or Carp::croak "spawn init function must be a fully-qualified name, caught";
    ($NODE{$noderef} || add_node $noderef)
       ->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
    "$noderef#$id"
 }
 This also saves round-trips and avoids sending messages to the wrong port
 (hard to do in Erlang).
 =back
+=head1 RATIONALE
+=over 4
+=item Why strings for ports and noderefs, why not objects?
+We considered "objects", but found that the actual number of methods
+thatc an be called are very low. Since port IDs and noderefs travel over
+the network frequently, the serialising/deserialising would add lots of
+overhead, as well as having to keep a proxy object.
+Strings can easily be printed, easily serialised etc. and need no special
+procedures to be "valid".
+And a a miniport consists of a single closure stored in a global hash - it
+can't become much cheaper.
+=item Why favour JSON, why not real serialising format such as Storable?
+In fact, any AnyEvent::MP node will happily accept Storable as framing
+format, but currently there is no way to make a node use Storable by
+default.
+The default framing protocol is JSON because a) JSON::XS is many times
+faster for small messages and b) most importantly, after years of
+experience we found that object serialisation is causing more problems
+than it gains: Just like function calls, objects simply do not travel
+easily over the network, mostly because they will always be a copy, so you
+always have to re-think your design.
+Keeping your messages simple, concentrating on data structures rather than
+objects, will keep your messages clean, tidy and efficient.
+=back
 =head1 SEE ALSO
 L<AnyEvent>.
 =head1 AUTHOR

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Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.38 by root, Fri Aug 7 22:55:18 2009 UTC vs. Revision 1.49 by root, Thu Aug 13 15:29:58 2009 UTC

Diff Legend

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.38 by root, Fri Aug 7 22:55:18 2009 UTC vs.
Revision 1.49 by root, Thu Aug 13 15:29:58 2009 UTC