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=head1 NAME |
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AnyEvent::MP - multi-processing/message-passing framework |
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=head1 SYNOPSIS |
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use AnyEvent::MP; |
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$NODE # contains this node's noderef |
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NODE # returns this node's noderef |
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NODE $port # returns the noderef of the port |
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snd $port, type => data...; |
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$SELF # receiving/own port id in rcv callbacks |
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rcv $port, smartmatch => $cb->($port, @msg); |
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# examples: |
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rcv $port2, ping => sub { snd $_[0], "pong"; 0 }; |
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rcv $port1, pong => sub { warn "pong received\n" }; |
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snd $port2, ping => $port1; |
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# more, smarter, matches (_any_ is exported by this module) |
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rcv $port, [child_died => $pid] => sub { ... |
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rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3 |
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# monitoring |
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mon $port, $cb->(@msg) # callback is invoked on death |
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mon $port, $otherport # kill otherport on abnormal death |
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mon $port, $otherport, @msg # send message on death |
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1.1 |
=head1 DESCRIPTION |
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This module (-family) implements a simple message passing framework. |
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Despite its simplicity, you can securely message other processes running |
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on the same or other hosts. |
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For an introduction to this module family, see the L<AnyEvent::MP::Intro> |
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manual page. |
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At the moment, this module family is severly broken and underdocumented, |
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so do not use. This was uploaded mainly to reserve the CPAN namespace - |
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stay tuned! The basic API should be finished, however. |
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=head1 CONCEPTS |
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=over 4 |
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=item port |
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A port is something you can send messages to (with the C<snd> function). |
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Some ports allow you to register C<rcv> handlers that can match specific |
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messages. All C<rcv> handlers will receive messages they match, messages |
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will not be queued. |
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|
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=item port id - C<noderef#portname> |
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A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as |
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separator, and a port name (a printable string of unspecified format). An |
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exception is the the node port, whose ID is identical to its node |
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reference. |
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=item node |
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A node is a single process containing at least one port - the node |
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port. You can send messages to node ports to find existing ports or to |
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create new ports, among other things. |
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Nodes are either private (single-process only), slaves (connected to a |
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master node only) or public nodes (connectable from unrelated nodes). |
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=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id> |
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A node reference is a string that either simply identifies the node (for |
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private and slave nodes), or contains a recipe on how to reach a given |
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node (for public nodes). |
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This recipe is simply a comma-separated list of C<address:port> pairs (for |
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TCP/IP, other protocols might look different). |
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Node references come in two flavours: resolved (containing only numerical |
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addresses) or unresolved (where hostnames are used instead of addresses). |
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Before using an unresolved node reference in a message you first have to |
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resolve it. |
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=back |
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1.3 |
=head1 VARIABLES/FUNCTIONS |
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=over 4 |
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=cut |
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package AnyEvent::MP; |
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use AnyEvent::MP::Base; |
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use common::sense; |
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use Carp (); |
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use AE (); |
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use base "Exporter"; |
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our $VERSION = '0.1'; |
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our @EXPORT = qw( |
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1.22 |
NODE $NODE *SELF node_of _any_ |
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resolve_node initialise_node |
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1.22 |
snd rcv mon kil reg psub |
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port |
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1.8 |
); |
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our $SELF; |
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sub _self_die() { |
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my $msg = $@; |
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$msg =~ s/\n+$// unless ref $msg; |
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kil $SELF, die => $msg; |
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} |
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=item $thisnode = NODE / $NODE |
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The C<NODE> function returns, and the C<$NODE> variable contains |
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the noderef of the local node. The value is initialised by a call |
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to C<become_public> or C<become_slave>, after which all local port |
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identifiers become invalid. |
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=item $noderef = node_of $port |
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Extracts and returns the noderef from a portid or a noderef. |
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=item initialise_node $noderef, $seednode, $seednode... |
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=item initialise_node "slave/", $master, $master... |
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Before a node can talk to other nodes on the network it has to initialise |
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itself - the minimum a node needs to know is it's own name, and optionally |
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it should know the noderefs of some other nodes in the network. |
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This function initialises a node - it must be called exactly once (or |
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never) before calling other AnyEvent::MP functions. |
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All arguments are noderefs, which can be either resolved or unresolved. |
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There are two types of networked nodes, public nodes and slave nodes: |
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=over 4 |
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=item public nodes |
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For public nodes, C<$noderef> must either be a (possibly unresolved) |
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noderef, in which case it will be resolved, or C<undef> (or missing), in |
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which case the noderef will be guessed. |
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Afterwards, the node will bind itself on all endpoints and try to connect |
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to all additional C<$seednodes> that are specified. Seednodes are optional |
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and can be used to quickly bootstrap the node into an existing network. |
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=item slave nodes |
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When the C<$noderef> is the special string C<slave/>, then the node will |
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become a slave node. Slave nodes cannot be contacted from outside and will |
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route most of their traffic to the master node that they attach to. |
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At least one additional noderef is required: The node will try to connect |
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to all of them and will become a slave attached to the first node it can |
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successfully connect to. |
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=back |
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This function will block until all nodes have been resolved and, for slave |
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nodes, until it has successfully established a connection to a master |
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server. |
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Example: become a public node listening on the default node. |
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initialise_node; |
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Example: become a public node, and try to contact some well-known master |
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servers to become part of the network. |
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initialise_node undef, "master1", "master2"; |
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Example: become a public node listening on port C<4041>. |
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initialise_node 4041; |
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Example: become a public node, only visible on localhost port 4044. |
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initialise_node "locahost:4044"; |
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Example: become a slave node to any of the specified master servers. |
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initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net"; |
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=item $cv = resolve_node $noderef |
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Takes an unresolved node reference that may contain hostnames and |
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abbreviated IDs, resolves all of them and returns a resolved node |
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reference. |
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In addition to C<address:port> pairs allowed in resolved noderefs, the |
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following forms are supported: |
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=over 4 |
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=item the empty string |
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An empty-string component gets resolved as if the default port (4040) was |
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specified. |
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=item naked port numbers (e.g. C<1234>) |
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These are resolved by prepending the local nodename and a colon, to be |
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further resolved. |
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=item hostnames (e.g. C<localhost:1234>, C<localhost>) |
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These are resolved by using AnyEvent::DNS to resolve them, optionally |
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looking up SRV records for the C<aemp=4040> port, if no port was |
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specified. |
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=back |
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1.22 |
=item $SELF |
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Contains the current port id while executing C<rcv> callbacks or C<psub> |
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blocks. |
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1.3 |
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=item SELF, %SELF, @SELF... |
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Due to some quirks in how perl exports variables, it is impossible to |
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just export C<$SELF>, all the symbols called C<SELF> are exported by this |
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module, but only C<$SELF> is currently used. |
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1.3 |
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1.33 |
=item snd $port, type => @data |
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1.3 |
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1.33 |
=item snd $port, @msg |
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1.3 |
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1.8 |
Send the given message to the given port ID, which can identify either |
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a local or a remote port, and can be either a string or soemthignt hat |
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stringifies a sa port ID (such as a port object :). |
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While the message can be about anything, it is highly recommended to use a |
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string as first element (a portid, or some word that indicates a request |
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type etc.). |
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1.3 |
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The message data effectively becomes read-only after a call to this |
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function: modifying any argument is not allowed and can cause many |
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problems. |
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The type of data you can transfer depends on the transport protocol: when |
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JSON is used, then only strings, numbers and arrays and hashes consisting |
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of those are allowed (no objects). When Storable is used, then anything |
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that Storable can serialise and deserialise is allowed, and for the local |
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node, anything can be passed. |
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1.22 |
=item $local_port = port |
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1.2 |
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Create a new local port object that can be used either as a pattern |
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matching port ("full port") or a single-callback port ("miniport"), |
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depending on how C<rcv> callbacks are bound to the object. |
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1.3 |
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=item $port = port { my @msg = @_; $finished } |
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1.10 |
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1.33 |
Creates a "miniport", that is, a very lightweight port without any pattern |
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matching behind it, and returns its ID. Semantically the same as creating |
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a port and calling C<rcv $port, $callback> on it. |
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1.15 |
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The block will be called for every message received on the port. When the |
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callback returns a true value its job is considered "done" and the port |
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will be destroyed. Otherwise it will stay alive. |
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1.17 |
The message will be passed as-is, no extra argument (i.e. no port id) will |
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1.15 |
be passed to the callback. |
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If you need the local port id in the callback, this works nicely: |
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1.31 |
my $port; $port = port { |
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1.15 |
snd $otherport, reply => $port; |
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}; |
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1.10 |
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=cut |
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1.33 |
sub rcv($@); |
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1.22 |
sub port(;&) { |
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my $id = "$UNIQ." . $ID++; |
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my $port = "$NODE#$id"; |
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if (@_) { |
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1.33 |
rcv $port, shift; |
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1.22 |
} else { |
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1.33 |
$PORT{$id} = sub { }; # nop |
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1.22 |
} |
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1.10 |
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1.22 |
$port |
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1.10 |
} |
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1.33 |
=item reg $port, $name |
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1.8 |
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1.36 |
=item reg $name |
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Registers the given port (or C<$SELF><<< if missing) under the name |
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C<$name>. If the name already exists it is replaced. |
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1.8 |
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1.22 |
A port can only be registered under one well known name. |
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1.8 |
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1.22 |
A port automatically becomes unregistered when it is killed. |
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1.8 |
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=cut |
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1.22 |
sub reg(@) { |
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1.36 |
my $port = @_ > 1 ? shift : $SELF || Carp::croak 'reg: called with one argument only, but $SELF not set,'; |
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1.8 |
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1.36 |
$REG{$_[0]} = $port; |
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1.22 |
} |
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1.18 |
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1.33 |
=item rcv $port, $callback->(@msg) |
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1.31 |
|
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1.33 |
Replaces the callback on the specified miniport (after converting it to |
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one if required). |
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1.31 |
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1.33 |
=item rcv $port, tagstring => $callback->(@msg), ... |
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1.3 |
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1.33 |
=item rcv $port, $smartmatch => $callback->(@msg), ... |
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1.3 |
|
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1.33 |
=item rcv $port, [$smartmatch...] => $callback->(@msg), ... |
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1.3 |
|
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1.32 |
Register callbacks to be called on matching messages on the given full |
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1.36 |
port (after converting it to one if required) and return the port. |
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1.3 |
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The callback has to return a true value when its work is done, after |
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which is will be removed, or a false value in which case it will stay |
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registered. |
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1.33 |
The global C<$SELF> (exported by this module) contains C<$port> while |
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1.22 |
executing the callback. |
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Runtime errors wdurign callback execution will result in the port being |
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C<kil>ed. |
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1.3 |
If the match is an array reference, then it will be matched against the |
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first elements of the message, otherwise only the first element is being |
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matched. |
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Any element in the match that is specified as C<_any_> (a function |
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exported by this module) matches any single element of the message. |
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While not required, it is highly recommended that the first matching |
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element is a string identifying the message. The one-string-only match is |
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also the most efficient match (by far). |
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1.36 |
Example: create a port and bind receivers on it in one go. |
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my $port = rcv port, |
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msg1 => sub { ...; 0 }, |
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msg2 => sub { ...; 0 }, |
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; |
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Example: create a port, bind receivers and send it in a message elsewhere |
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in one go: |
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snd $otherport, reply => |
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rcv port, |
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msg1 => sub { ...; 0 }, |
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... |
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; |
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1.3 |
=cut |
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sub rcv($@) { |
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1.33 |
my $port = shift; |
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my ($noderef, $portid) = split /#/, $port, 2; |
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1.3 |
|
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1.22 |
($NODE{$noderef} || add_node $noderef) == $NODE{""} |
382 |
root |
1.33 |
or Carp::croak "$port: rcv can only be called on local ports, caught"; |
383 |
root |
1.22 |
|
384 |
root |
1.33 |
if (@_ == 1) { |
385 |
|
|
my $cb = shift; |
386 |
|
|
delete $PORT_DATA{$portid}; |
387 |
|
|
$PORT{$portid} = sub { |
388 |
|
|
local $SELF = $port; |
389 |
|
|
eval { |
390 |
|
|
&$cb |
391 |
|
|
and kil $port; |
392 |
|
|
}; |
393 |
|
|
_self_die if $@; |
394 |
|
|
}; |
395 |
|
|
} else { |
396 |
|
|
my $self = $PORT_DATA{$portid} ||= do { |
397 |
|
|
my $self = bless { |
398 |
|
|
id => $port, |
399 |
|
|
}, "AnyEvent::MP::Port"; |
400 |
|
|
|
401 |
|
|
$PORT{$portid} = sub { |
402 |
|
|
local $SELF = $port; |
403 |
|
|
|
404 |
|
|
eval { |
405 |
|
|
for (@{ $self->{rc0}{$_[0]} }) { |
406 |
|
|
$_ && &{$_->[0]} |
407 |
|
|
&& undef $_; |
408 |
|
|
} |
409 |
|
|
|
410 |
|
|
for (@{ $self->{rcv}{$_[0]} }) { |
411 |
|
|
$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1] |
412 |
|
|
&& &{$_->[0]} |
413 |
|
|
&& undef $_; |
414 |
|
|
} |
415 |
|
|
|
416 |
|
|
for (@{ $self->{any} }) { |
417 |
|
|
$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1] |
418 |
|
|
&& &{$_->[0]} |
419 |
|
|
&& undef $_; |
420 |
|
|
} |
421 |
|
|
}; |
422 |
|
|
_self_die if $@; |
423 |
|
|
}; |
424 |
|
|
|
425 |
|
|
$self |
426 |
|
|
}; |
427 |
root |
1.22 |
|
428 |
root |
1.33 |
"AnyEvent::MP::Port" eq ref $self |
429 |
|
|
or Carp::croak "$port: rcv can only be called on message matching ports, caught"; |
430 |
root |
1.22 |
|
431 |
root |
1.33 |
while (@_) { |
432 |
|
|
my ($match, $cb) = splice @_, 0, 2; |
433 |
|
|
|
434 |
|
|
if (!ref $match) { |
435 |
|
|
push @{ $self->{rc0}{$match} }, [$cb]; |
436 |
|
|
} elsif (("ARRAY" eq ref $match && !ref $match->[0])) { |
437 |
|
|
my ($type, @match) = @$match; |
438 |
|
|
@match |
439 |
|
|
? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match] |
440 |
|
|
: push @{ $self->{rc0}{$match->[0]} }, [$cb]; |
441 |
|
|
} else { |
442 |
|
|
push @{ $self->{any} }, [$cb, $match]; |
443 |
|
|
} |
444 |
root |
1.22 |
} |
445 |
root |
1.3 |
} |
446 |
root |
1.31 |
|
447 |
root |
1.33 |
$port |
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 |
1.33 |
=item $guard = mon $port, $cb->(@reason) |
489 |
root |
1.32 |
|
490 |
root |
1.36 |
=item $guard = mon $port, $rcvport |
491 |
|
|
|
492 |
|
|
=item $guard = mon $port |
493 |
root |
1.32 |
|
494 |
root |
1.36 |
=item $guard = mon $port, $rcvport, @msg |
495 |
root |
1.32 |
|
496 |
root |
1.36 |
Monitor the given port and do something when the port is killed, and |
497 |
|
|
optionally return a guard that can be used to stop monitoring again. |
498 |
root |
1.32 |
|
499 |
root |
1.36 |
In the first form (callback), the callback is simply called with any |
500 |
|
|
number of C<@reason> elements (no @reason means that the port was deleted |
501 |
root |
1.32 |
"normally"). Note also that I<< the callback B<must> never die >>, so use |
502 |
|
|
C<eval> if unsure. |
503 |
|
|
|
504 |
root |
1.36 |
In the second form (another port given), the other port (C<$rcvport) |
505 |
|
|
will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on |
506 |
|
|
"normal" kils nothing happens, while under all other conditions, the other |
507 |
|
|
port is killed with the same reason. |
508 |
root |
1.32 |
|
509 |
root |
1.36 |
The third form (kill self) is the same as the second form, except that |
510 |
|
|
C<$rvport> defaults to C<$SELF>. |
511 |
|
|
|
512 |
|
|
In the last form (message), a message of the form C<@msg, @reason> will be |
513 |
|
|
C<snd>. |
514 |
root |
1.32 |
|
515 |
root |
1.37 |
As a rule of thumb, monitoring requests should always monitor a port from |
516 |
|
|
a local port (or callback). The reason is that kill messages might get |
517 |
|
|
lost, just like any other message. Another less obvious reason is that |
518 |
|
|
even monitoring requests can get lost (for exmaple, when the connection |
519 |
|
|
to the other node goes down permanently). When monitoring a port locally |
520 |
|
|
these problems do not exist. |
521 |
|
|
|
522 |
root |
1.32 |
Example: call a given callback when C<$port> is killed. |
523 |
|
|
|
524 |
|
|
mon $port, sub { warn "port died because of <@_>\n" }; |
525 |
|
|
|
526 |
|
|
Example: kill ourselves when C<$port> is killed abnormally. |
527 |
|
|
|
528 |
root |
1.36 |
mon $port; |
529 |
root |
1.32 |
|
530 |
root |
1.36 |
Example: send us a restart message when another C<$port> is killed. |
531 |
root |
1.32 |
|
532 |
|
|
mon $port, $self => "restart"; |
533 |
|
|
|
534 |
|
|
=cut |
535 |
|
|
|
536 |
|
|
sub mon { |
537 |
|
|
my ($noderef, $port) = split /#/, shift, 2; |
538 |
|
|
|
539 |
|
|
my $node = $NODE{$noderef} || add_node $noderef; |
540 |
|
|
|
541 |
root |
1.36 |
my $cb = @_ ? $_[0] : $SELF || Carp::croak 'mon: called with one argument only, but $SELF not set,'; |
542 |
root |
1.32 |
|
543 |
|
|
unless (ref $cb) { |
544 |
|
|
if (@_) { |
545 |
|
|
# send a kill info message |
546 |
root |
1.36 |
my (@msg) = @_; |
547 |
root |
1.32 |
$cb = sub { snd @msg, @_ }; |
548 |
|
|
} else { |
549 |
|
|
# simply kill other port |
550 |
|
|
my $port = $cb; |
551 |
|
|
$cb = sub { kil $port, @_ if @_ }; |
552 |
|
|
} |
553 |
|
|
} |
554 |
|
|
|
555 |
|
|
$node->monitor ($port, $cb); |
556 |
|
|
|
557 |
|
|
defined wantarray |
558 |
|
|
and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) } |
559 |
|
|
} |
560 |
|
|
|
561 |
|
|
=item $guard = mon_guard $port, $ref, $ref... |
562 |
|
|
|
563 |
|
|
Monitors the given C<$port> and keeps the passed references. When the port |
564 |
|
|
is killed, the references will be freed. |
565 |
|
|
|
566 |
|
|
Optionally returns a guard that will stop the monitoring. |
567 |
|
|
|
568 |
|
|
This function is useful when you create e.g. timers or other watchers and |
569 |
|
|
want to free them when the port gets killed: |
570 |
|
|
|
571 |
|
|
$port->rcv (start => sub { |
572 |
|
|
my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub { |
573 |
|
|
undef $timer if 0.9 < rand; |
574 |
|
|
}); |
575 |
|
|
}); |
576 |
|
|
|
577 |
|
|
=cut |
578 |
|
|
|
579 |
|
|
sub mon_guard { |
580 |
|
|
my ($port, @refs) = @_; |
581 |
|
|
|
582 |
root |
1.36 |
#TODO: mon-less form? |
583 |
|
|
|
584 |
root |
1.32 |
mon $port, sub { 0 && @refs } |
585 |
|
|
} |
586 |
|
|
|
587 |
root |
1.33 |
=item kil $port[, @reason] |
588 |
root |
1.32 |
|
589 |
|
|
Kill the specified port with the given C<@reason>. |
590 |
|
|
|
591 |
|
|
If no C<@reason> is specified, then the port is killed "normally" (linked |
592 |
|
|
ports will not be kileld, or even notified). |
593 |
|
|
|
594 |
|
|
Otherwise, linked ports get killed with the same reason (second form of |
595 |
|
|
C<mon>, see below). |
596 |
|
|
|
597 |
|
|
Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks |
598 |
|
|
will be reported as reason C<< die => $@ >>. |
599 |
|
|
|
600 |
|
|
Transport/communication errors are reported as C<< transport_error => |
601 |
|
|
$message >>. |
602 |
|
|
|
603 |
root |
1.8 |
=back |
604 |
|
|
|
605 |
root |
1.4 |
=head1 NODE MESSAGES |
606 |
|
|
|
607 |
root |
1.5 |
Nodes understand the following messages sent to them. Many of them take |
608 |
|
|
arguments called C<@reply>, which will simply be used to compose a reply |
609 |
|
|
message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and |
610 |
|
|
the remaining arguments are simply the message data. |
611 |
root |
1.4 |
|
612 |
root |
1.29 |
While other messages exist, they are not public and subject to change. |
613 |
|
|
|
614 |
root |
1.4 |
=over 4 |
615 |
|
|
|
616 |
|
|
=cut |
617 |
|
|
|
618 |
root |
1.22 |
=item lookup => $name, @reply |
619 |
root |
1.3 |
|
620 |
root |
1.8 |
Replies with the port ID of the specified well-known port, or C<undef>. |
621 |
root |
1.3 |
|
622 |
root |
1.7 |
=item devnull => ... |
623 |
|
|
|
624 |
|
|
Generic data sink/CPU heat conversion. |
625 |
|
|
|
626 |
root |
1.4 |
=item relay => $port, @msg |
627 |
|
|
|
628 |
|
|
Simply forwards the message to the given port. |
629 |
|
|
|
630 |
|
|
=item eval => $string[ @reply] |
631 |
|
|
|
632 |
|
|
Evaluates the given string. If C<@reply> is given, then a message of the |
633 |
root |
1.5 |
form C<@reply, $@, @evalres> is sent. |
634 |
|
|
|
635 |
|
|
Example: crash another node. |
636 |
|
|
|
637 |
|
|
snd $othernode, eval => "exit"; |
638 |
root |
1.4 |
|
639 |
|
|
=item time => @reply |
640 |
|
|
|
641 |
|
|
Replies the the current node time to C<@reply>. |
642 |
|
|
|
643 |
root |
1.5 |
Example: tell the current node to send the current time to C<$myport> in a |
644 |
|
|
C<timereply> message. |
645 |
|
|
|
646 |
|
|
snd $NODE, time => $myport, timereply => 1, 2; |
647 |
|
|
# => snd $myport, timereply => 1, 2, <time> |
648 |
|
|
|
649 |
root |
1.2 |
=back |
650 |
|
|
|
651 |
root |
1.26 |
=head1 AnyEvent::MP vs. Distributed Erlang |
652 |
|
|
|
653 |
root |
1.35 |
AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node |
654 |
|
|
== aemp node, Erlang process == aemp port), so many of the documents and |
655 |
|
|
programming techniques employed by Erlang apply to AnyEvent::MP. Here is a |
656 |
root |
1.27 |
sample: |
657 |
|
|
|
658 |
root |
1.35 |
http://www.Erlang.se/doc/programming_rules.shtml |
659 |
|
|
http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4 |
660 |
|
|
http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6 |
661 |
|
|
http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5 |
662 |
root |
1.27 |
|
663 |
|
|
Despite the similarities, there are also some important differences: |
664 |
root |
1.26 |
|
665 |
|
|
=over 4 |
666 |
|
|
|
667 |
|
|
=item * Node references contain the recipe on how to contact them. |
668 |
|
|
|
669 |
|
|
Erlang relies on special naming and DNS to work everywhere in the |
670 |
|
|
same way. AEMP relies on each node knowing it's own address(es), with |
671 |
|
|
convenience functionality. |
672 |
|
|
|
673 |
root |
1.27 |
This means that AEMP requires a less tightly controlled environment at the |
674 |
|
|
cost of longer node references and a slightly higher management overhead. |
675 |
|
|
|
676 |
root |
1.26 |
=item * Erlang uses processes and a mailbox, AEMP does not queue. |
677 |
|
|
|
678 |
|
|
Erlang uses processes that selctively receive messages, and therefore |
679 |
|
|
needs a queue. AEMP is event based, queuing messages would serve no useful |
680 |
|
|
purpose. |
681 |
|
|
|
682 |
root |
1.35 |
(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP). |
683 |
root |
1.26 |
|
684 |
|
|
=item * Erlang sends are synchronous, AEMP sends are asynchronous. |
685 |
|
|
|
686 |
root |
1.35 |
Sending messages in Erlang is synchronous and blocks the process. AEMP |
687 |
root |
1.26 |
sends are immediate, connection establishment is handled in the |
688 |
|
|
background. |
689 |
|
|
|
690 |
|
|
=item * Erlang can silently lose messages, AEMP cannot. |
691 |
|
|
|
692 |
|
|
Erlang makes few guarantees on messages delivery - messages can get lost |
693 |
|
|
without any of the processes realising it (i.e. you send messages a, b, |
694 |
|
|
and c, and the other side only receives messages a and c). |
695 |
|
|
|
696 |
|
|
AEMP guarantees correct ordering, and the guarantee that there are no |
697 |
|
|
holes in the message sequence. |
698 |
|
|
|
699 |
root |
1.35 |
=item * In Erlang, processes can be declared dead and later be found to be |
700 |
root |
1.26 |
alive. |
701 |
|
|
|
702 |
root |
1.35 |
In Erlang it can happen that a monitored process is declared dead and |
703 |
root |
1.26 |
linked processes get killed, but later it turns out that the process is |
704 |
|
|
still alive - and can receive messages. |
705 |
|
|
|
706 |
|
|
In AEMP, when port monitoring detects a port as dead, then that port will |
707 |
|
|
eventually be killed - it cannot happen that a node detects a port as dead |
708 |
|
|
and then later sends messages to it, finding it is still alive. |
709 |
|
|
|
710 |
|
|
=item * Erlang can send messages to the wrong port, AEMP does not. |
711 |
|
|
|
712 |
root |
1.35 |
In Erlang it is quite possible that a node that restarts reuses a process |
713 |
root |
1.26 |
ID known to other nodes for a completely different process, causing |
714 |
|
|
messages destined for that process to end up in an unrelated process. |
715 |
|
|
|
716 |
|
|
AEMP never reuses port IDs, so old messages or old port IDs floating |
717 |
|
|
around in the network will not be sent to an unrelated port. |
718 |
|
|
|
719 |
|
|
=item * Erlang uses unprotected connections, AEMP uses secure |
720 |
|
|
authentication and can use TLS. |
721 |
|
|
|
722 |
|
|
AEMP can use a proven protocol - SSL/TLS - to protect connections and |
723 |
|
|
securely authenticate nodes. |
724 |
|
|
|
725 |
root |
1.28 |
=item * The AEMP protocol is optimised for both text-based and binary |
726 |
|
|
communications. |
727 |
|
|
|
728 |
root |
1.35 |
The AEMP protocol, unlike the Erlang protocol, supports both |
729 |
root |
1.28 |
language-independent text-only protocols (good for debugging) and binary, |
730 |
|
|
language-specific serialisers (e.g. Storable). |
731 |
|
|
|
732 |
|
|
It has also been carefully designed to be implementable in other languages |
733 |
|
|
with a minimum of work while gracefully degrading fucntionality to make the |
734 |
|
|
protocol simple. |
735 |
|
|
|
736 |
root |
1.35 |
=item * AEMP has more flexible monitoring options than Erlang. |
737 |
|
|
|
738 |
|
|
In Erlang, you can chose to receive I<all> exit signals as messages |
739 |
|
|
or I<none>, there is no in-between, so monitoring single processes is |
740 |
|
|
difficult to implement. Monitoring in AEMP is more flexible than in |
741 |
|
|
Erlang, as one can choose between automatic kill, exit message or callback |
742 |
|
|
on a per-process basis. |
743 |
|
|
|
744 |
root |
1.37 |
=item * Erlang tries to hide remote/local connections, AEMP does not. |
745 |
root |
1.35 |
|
746 |
|
|
Monitoring in Erlang is not an indicator of process death/crashes, |
747 |
root |
1.37 |
as linking is (except linking is unreliable in Erlang). |
748 |
|
|
|
749 |
|
|
In AEMP, you don't "look up" registered port names or send to named ports |
750 |
|
|
that might or might not be persistent. Instead, you normally spawn a port |
751 |
|
|
on the remote node. The init function monitors the you, and you monitor |
752 |
|
|
the remote port. Since both monitors are local to the node, they are much |
753 |
|
|
more reliable. |
754 |
|
|
|
755 |
|
|
This also saves round-trips and avoids sending messages to the wrong port |
756 |
|
|
(hard to do in Erlang). |
757 |
root |
1.35 |
|
758 |
root |
1.26 |
=back |
759 |
|
|
|
760 |
root |
1.1 |
=head1 SEE ALSO |
761 |
|
|
|
762 |
|
|
L<AnyEvent>. |
763 |
|
|
|
764 |
|
|
=head1 AUTHOR |
765 |
|
|
|
766 |
|
|
Marc Lehmann <schmorp@schmorp.de> |
767 |
|
|
http://home.schmorp.de/ |
768 |
|
|
|
769 |
|
|
=cut |
770 |
|
|
|
771 |
|
|
1 |
772 |
|
|
|