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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 $port # returns the noderef of the port |
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|
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$SELF # receiving/own port id in rcv callbacks |
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# initialise the node so it can send/receive messages |
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initialise_node; |
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|
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# ports are message endpoints |
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# sending messages |
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snd $port, type => data...; |
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snd $port, @msg; |
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snd @msg_with_first_element_being_a_port; |
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|
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# creating/using ports, the simple way |
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my $simple_port = port { my @msg = @_; 0 }; |
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|
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# creating/using ports, tagged message matching |
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my $port = port; |
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rcv $port, ping => sub { snd $_[0], "pong"; 0 }; |
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rcv $port, pong => sub { warn "pong received\n"; 0 }; |
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|
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# create a port on another node |
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my $port = spawn $node, $initfunc, @initdata; |
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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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1.45 |
=head1 CURRENT STATUS |
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AnyEvent::MP - stable API, should work |
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AnyEvent::MP::Intro - outdated |
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AnyEvent::MP::Kernel - WIP |
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AnyEvent::MP::Transport - mostly stable |
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stay tuned. |
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1.1 |
=head1 DESCRIPTION |
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1.2 |
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! |
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1.2 |
=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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Ports allow you to register C<rcv> handlers that can match all or just |
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some messages. Messages will not be queued. |
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|
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=item port ID - C<noderef#portname> |
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|
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A port ID is 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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|
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=item node |
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A node is a single process containing at least one port - the node port, |
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which provides nodes to manage each other remotely, and to create new |
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ports. |
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|
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Nodes are either private (single-process only), slaves (can only talk to |
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public nodes, but do not need an open port) or public nodes (connectable |
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from any other node). |
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|
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=item node ID - C<[a-za-Z0-9_\-.:]+> |
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|
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A node ID 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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1.2 |
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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1.2 |
=back |
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1.3 |
=head1 VARIABLES/FUNCTIONS |
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1.2 |
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=over 4 |
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1.1 |
=cut |
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package AnyEvent::MP; |
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1.44 |
use AnyEvent::MP::Kernel; |
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1.2 |
|
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1.1 |
use common::sense; |
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1.2 |
use Carp (); |
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use AE (); |
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1.2 |
use base "Exporter"; |
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our $VERSION = $AnyEvent::MP::Kernel::VERSION; |
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|
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our @EXPORT = qw( |
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1.59 |
NODE $NODE *SELF node_of after |
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1.31 |
resolve_node initialise_node |
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1.61 |
snd rcv mon mon_guard kil reg psub spawn |
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1.22 |
port |
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1.8 |
); |
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1.2 |
|
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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 the |
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node id of the local node. The value is initialised by a call to |
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C<initialise_node>. |
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1.22 |
|
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=item $nodeid = node_of $port |
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|
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Extracts and returns the noderef from a port ID or a node ID. |
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1.34 |
|
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=item initialise_node $profile_name |
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1.34 |
|
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Before a node can talk to other nodes on the network it has to initialise |
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itself - the minimum a node needs to know is it's own name, and optionally |
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it should know the noderefs of some other nodes in the network. |
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This function initialises a node - it must be called exactly once (or |
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never) before calling other AnyEvent::MP functions. |
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All arguments (optionally except for the first) are noderefs, which can be |
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either resolved or unresolved. |
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The first argument will be looked up in the configuration database first |
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(if it is C<undef> then the current nodename will be used instead) to find |
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the relevant configuration profile (see L<aemp>). If none is found then |
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the default configuration is used. The configuration supplies additional |
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seed/master nodes and can override the actual noderef. |
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1.34 |
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There are two types of networked nodes, public nodes and slave nodes: |
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=over 4 |
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=item public nodes |
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For public nodes, C<$noderef> (supplied either directly to |
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C<initialise_node> or indirectly via a profile or the nodename) must be a |
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noderef (possibly unresolved, in which case it will be resolved). |
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After resolving, the node will bind itself on all endpoints. |
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1.34 |
|
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=item slave nodes |
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When the C<$noderef> (either as given or overriden by the config file) |
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is the special string C<slave/>, then the node will become a slave |
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1.62 |
node. Slave nodes cannot be contacted from outside, and cannot talk to |
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each other (at least in this version of AnyEvent::MP). |
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1.49 |
|
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1.62 |
Slave nodes work by creating connections to all public nodes, using the |
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L<AnyEvent::MP::Global> service. |
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1.56 |
|
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1.34 |
=back |
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1.62 |
After initialising itself, the node will connect to all additional |
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C<$seednodes> that are specified diretcly or via a profile. Seednodes are |
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optional and can be used to quickly bootstrap the node into an existing |
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network. |
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1.34 |
|
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1.56 |
All the seednodes will also be specially marked to automatically retry |
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1.62 |
connecting to them indefinitely, so make sure that seednodes are really |
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reliable and up (this might also change in the future). |
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|
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1.49 |
Example: become a public node listening on the guessed noderef, or the one |
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specified via C<aemp> for the current node. This should be the most common |
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form of invocation for "daemon"-type nodes. |
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1.34 |
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initialise_node; |
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Example: become a slave node to any of the the seednodes specified via |
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C<aemp>. This form is often used for commandline clients. |
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initialise_node "slave/"; |
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1.34 |
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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1.49 |
initialise_node "localhost:4044"; |
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1.34 |
|
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1.29 |
=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 |
248 |
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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 |
253 |
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looking up SRV records for the C<aemp=4040> port, if no port was |
254 |
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specified. |
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=back |
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1.22 |
=item $SELF |
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260 |
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Contains the current port id while executing C<rcv> callbacks or C<psub> |
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blocks. |
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1.3 |
|
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1.22 |
=item SELF, %SELF, @SELF... |
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Due to some quirks in how perl exports variables, it is impossible to |
266 |
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just export C<$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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1.52 |
a local or a remote port, and must be a port ID. |
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1.8 |
|
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While the message can be about anything, it is highly recommended to use a |
277 |
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1.52 |
string as first element (a port ID, or some word that indicates a request |
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1.8 |
type etc.). |
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1.3 |
|
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The message data effectively becomes read-only after a call to this |
281 |
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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 |
286 |
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of those are allowed (no objects). When Storable is used, then anything |
287 |
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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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=item $local_port = port |
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1.2 |
|
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Create a new local port object and returns its port ID. Initially it has |
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no callbacks set and will throw an error when it receives messages. |
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1.10 |
|
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=item $local_port = port { my @msg = @_ } |
296 |
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1.15 |
|
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Creates a new local port, and returns its ID. Semantically the same as |
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creating a port and calling C<rcv $port, $callback> on it. |
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1.15 |
|
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The block will be called for every message received on the port, with the |
301 |
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global variable C<$SELF> set to the port ID. Runtime errors will cause the |
302 |
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port to be C<kil>ed. The message will be passed as-is, no extra argument |
303 |
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(i.e. no port ID) will be passed to the callback. |
304 |
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1.15 |
|
305 |
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1.50 |
If you want to stop/destroy the port, simply C<kil> it: |
306 |
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1.15 |
|
307 |
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1.50 |
my $port = port { |
308 |
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my @msg = @_; |
309 |
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... |
310 |
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kil $SELF; |
311 |
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1.15 |
}; |
312 |
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1.10 |
|
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=cut |
314 |
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315 |
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1.33 |
sub rcv($@); |
316 |
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317 |
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1.50 |
sub _kilme { |
318 |
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die "received message on port without callback"; |
319 |
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} |
320 |
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1.22 |
sub port(;&) { |
322 |
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my $id = "$UNIQ." . $ID++; |
323 |
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my $port = "$NODE#$id"; |
324 |
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1.50 |
rcv $port, shift || \&_kilme; |
326 |
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1.10 |
|
327 |
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1.22 |
$port |
328 |
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1.10 |
} |
329 |
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330 |
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1.50 |
=item rcv $local_port, $callback->(@msg) |
331 |
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1.31 |
|
332 |
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1.50 |
Replaces the default callback on the specified port. There is no way to |
333 |
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remove the default callback: use C<sub { }> to disable it, or better |
334 |
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C<kil> the port when it is no longer needed. |
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1.3 |
|
336 |
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1.33 |
The global C<$SELF> (exported by this module) contains C<$port> while |
337 |
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1.50 |
executing the callback. Runtime errors during callback execution will |
338 |
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result in the port being C<kil>ed. |
339 |
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1.22 |
|
340 |
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1.50 |
The default callback received all messages not matched by a more specific |
341 |
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C<tag> match. |
342 |
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1.22 |
|
343 |
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1.50 |
=item rcv $local_port, tag => $callback->(@msg_without_tag), ... |
344 |
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1.3 |
|
345 |
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1.54 |
Register (or replace) callbacks to be called on messages starting with the |
346 |
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given tag on the given port (and return the port), or unregister it (when |
347 |
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C<$callback> is C<$undef> or missing). There can only be one callback |
348 |
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registered for each tag. |
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1.3 |
|
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1.50 |
The original message will be passed to the callback, after the first |
351 |
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element (the tag) has been removed. The callback will use the same |
352 |
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environment as the default callback (see above). |
353 |
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1.3 |
|
354 |
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1.36 |
Example: create a port and bind receivers on it in one go. |
355 |
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|
356 |
|
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my $port = rcv port, |
357 |
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1.50 |
msg1 => sub { ... }, |
358 |
|
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msg2 => sub { ... }, |
359 |
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1.36 |
; |
360 |
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|
361 |
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Example: create a port, bind receivers and send it in a message elsewhere |
362 |
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in one go: |
363 |
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|
364 |
|
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snd $otherport, reply => |
365 |
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rcv port, |
366 |
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1.50 |
msg1 => sub { ... }, |
367 |
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1.36 |
... |
368 |
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; |
369 |
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|
370 |
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1.54 |
Example: temporarily register a rcv callback for a tag matching some port |
371 |
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(e.g. for a rpc reply) and unregister it after a message was received. |
372 |
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373 |
|
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rcv $port, $otherport => sub { |
374 |
|
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my @reply = @_; |
375 |
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376 |
|
|
rcv $SELF, $otherport; |
377 |
|
|
}; |
378 |
|
|
|
379 |
root |
1.3 |
=cut |
380 |
|
|
|
381 |
|
|
sub rcv($@) { |
382 |
root |
1.33 |
my $port = shift; |
383 |
|
|
my ($noderef, $portid) = split /#/, $port, 2; |
384 |
root |
1.3 |
|
385 |
root |
1.58 |
$NODE{$noderef} == $NODE{""} |
386 |
root |
1.33 |
or Carp::croak "$port: rcv can only be called on local ports, caught"; |
387 |
root |
1.22 |
|
388 |
root |
1.50 |
while (@_) { |
389 |
|
|
if (ref $_[0]) { |
390 |
|
|
if (my $self = $PORT_DATA{$portid}) { |
391 |
|
|
"AnyEvent::MP::Port" eq ref $self |
392 |
|
|
or Carp::croak "$port: rcv can only be called on message matching ports, caught"; |
393 |
root |
1.33 |
|
394 |
root |
1.50 |
$self->[2] = shift; |
395 |
|
|
} else { |
396 |
|
|
my $cb = shift; |
397 |
|
|
$PORT{$portid} = sub { |
398 |
|
|
local $SELF = $port; |
399 |
|
|
eval { &$cb }; _self_die if $@; |
400 |
|
|
}; |
401 |
|
|
} |
402 |
|
|
} elsif (defined $_[0]) { |
403 |
|
|
my $self = $PORT_DATA{$portid} ||= do { |
404 |
|
|
my $self = bless [$PORT{$port} || sub { }, { }, $port], "AnyEvent::MP::Port"; |
405 |
|
|
|
406 |
|
|
$PORT{$portid} = sub { |
407 |
|
|
local $SELF = $port; |
408 |
|
|
|
409 |
|
|
if (my $cb = $self->[1]{$_[0]}) { |
410 |
|
|
shift; |
411 |
|
|
eval { &$cb }; _self_die if $@; |
412 |
|
|
} else { |
413 |
|
|
&{ $self->[0] }; |
414 |
root |
1.33 |
} |
415 |
|
|
}; |
416 |
root |
1.50 |
|
417 |
|
|
$self |
418 |
root |
1.33 |
}; |
419 |
|
|
|
420 |
root |
1.50 |
"AnyEvent::MP::Port" eq ref $self |
421 |
|
|
or Carp::croak "$port: rcv can only be called on message matching ports, caught"; |
422 |
root |
1.22 |
|
423 |
root |
1.50 |
my ($tag, $cb) = splice @_, 0, 2; |
424 |
root |
1.33 |
|
425 |
root |
1.50 |
if (defined $cb) { |
426 |
|
|
$self->[1]{$tag} = $cb; |
427 |
root |
1.33 |
} else { |
428 |
root |
1.50 |
delete $self->[1]{$tag}; |
429 |
root |
1.33 |
} |
430 |
root |
1.22 |
} |
431 |
root |
1.3 |
} |
432 |
root |
1.31 |
|
433 |
root |
1.33 |
$port |
434 |
root |
1.2 |
} |
435 |
|
|
|
436 |
root |
1.22 |
=item $closure = psub { BLOCK } |
437 |
root |
1.2 |
|
438 |
root |
1.22 |
Remembers C<$SELF> and creates a closure out of the BLOCK. When the |
439 |
|
|
closure is executed, sets up the environment in the same way as in C<rcv> |
440 |
|
|
callbacks, i.e. runtime errors will cause the port to get C<kil>ed. |
441 |
|
|
|
442 |
|
|
This is useful when you register callbacks from C<rcv> callbacks: |
443 |
|
|
|
444 |
|
|
rcv delayed_reply => sub { |
445 |
|
|
my ($delay, @reply) = @_; |
446 |
|
|
my $timer = AE::timer $delay, 0, psub { |
447 |
|
|
snd @reply, $SELF; |
448 |
|
|
}; |
449 |
|
|
}; |
450 |
root |
1.3 |
|
451 |
root |
1.8 |
=cut |
452 |
root |
1.3 |
|
453 |
root |
1.22 |
sub psub(&) { |
454 |
|
|
my $cb = shift; |
455 |
root |
1.3 |
|
456 |
root |
1.22 |
my $port = $SELF |
457 |
|
|
or Carp::croak "psub can only be called from within rcv or psub callbacks, not"; |
458 |
root |
1.1 |
|
459 |
root |
1.22 |
sub { |
460 |
|
|
local $SELF = $port; |
461 |
root |
1.2 |
|
462 |
root |
1.22 |
if (wantarray) { |
463 |
|
|
my @res = eval { &$cb }; |
464 |
|
|
_self_die if $@; |
465 |
|
|
@res |
466 |
|
|
} else { |
467 |
|
|
my $res = eval { &$cb }; |
468 |
|
|
_self_die if $@; |
469 |
|
|
$res |
470 |
|
|
} |
471 |
|
|
} |
472 |
root |
1.2 |
} |
473 |
|
|
|
474 |
root |
1.33 |
=item $guard = mon $port, $cb->(@reason) |
475 |
root |
1.32 |
|
476 |
root |
1.36 |
=item $guard = mon $port, $rcvport |
477 |
|
|
|
478 |
|
|
=item $guard = mon $port |
479 |
root |
1.32 |
|
480 |
root |
1.36 |
=item $guard = mon $port, $rcvport, @msg |
481 |
root |
1.32 |
|
482 |
root |
1.42 |
Monitor the given port and do something when the port is killed or |
483 |
|
|
messages to it were lost, and optionally return a guard that can be used |
484 |
|
|
to stop monitoring again. |
485 |
|
|
|
486 |
|
|
C<mon> effectively guarantees that, in the absence of hardware failures, |
487 |
|
|
that after starting the monitor, either all messages sent to the port |
488 |
|
|
will arrive, or the monitoring action will be invoked after possible |
489 |
|
|
message loss has been detected. No messages will be lost "in between" |
490 |
|
|
(after the first lost message no further messages will be received by the |
491 |
|
|
port). After the monitoring action was invoked, further messages might get |
492 |
|
|
delivered again. |
493 |
root |
1.32 |
|
494 |
root |
1.58 |
Note that monitoring-actions are one-shot: once released, they are removed |
495 |
|
|
and will not trigger again. |
496 |
|
|
|
497 |
root |
1.36 |
In the first form (callback), the callback is simply called with any |
498 |
|
|
number of C<@reason> elements (no @reason means that the port was deleted |
499 |
root |
1.32 |
"normally"). Note also that I<< the callback B<must> never die >>, so use |
500 |
|
|
C<eval> if unsure. |
501 |
|
|
|
502 |
root |
1.43 |
In the second form (another port given), the other port (C<$rcvport>) |
503 |
root |
1.36 |
will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on |
504 |
|
|
"normal" kils nothing happens, while under all other conditions, the other |
505 |
|
|
port is killed with the same reason. |
506 |
root |
1.32 |
|
507 |
root |
1.36 |
The third form (kill self) is the same as the second form, except that |
508 |
|
|
C<$rvport> defaults to C<$SELF>. |
509 |
|
|
|
510 |
|
|
In the last form (message), a message of the form C<@msg, @reason> will be |
511 |
|
|
C<snd>. |
512 |
root |
1.32 |
|
513 |
root |
1.37 |
As a rule of thumb, monitoring requests should always monitor a port from |
514 |
|
|
a local port (or callback). The reason is that kill messages might get |
515 |
|
|
lost, just like any other message. Another less obvious reason is that |
516 |
|
|
even monitoring requests can get lost (for exmaple, when the connection |
517 |
|
|
to the other node goes down permanently). When monitoring a port locally |
518 |
|
|
these problems do not exist. |
519 |
|
|
|
520 |
root |
1.32 |
Example: call a given callback when C<$port> is killed. |
521 |
|
|
|
522 |
|
|
mon $port, sub { warn "port died because of <@_>\n" }; |
523 |
|
|
|
524 |
|
|
Example: kill ourselves when C<$port> is killed abnormally. |
525 |
|
|
|
526 |
root |
1.36 |
mon $port; |
527 |
root |
1.32 |
|
528 |
root |
1.36 |
Example: send us a restart message when another C<$port> is killed. |
529 |
root |
1.32 |
|
530 |
|
|
mon $port, $self => "restart"; |
531 |
|
|
|
532 |
|
|
=cut |
533 |
|
|
|
534 |
|
|
sub mon { |
535 |
|
|
my ($noderef, $port) = split /#/, shift, 2; |
536 |
|
|
|
537 |
|
|
my $node = $NODE{$noderef} || add_node $noderef; |
538 |
|
|
|
539 |
root |
1.41 |
my $cb = @_ ? shift : $SELF || Carp::croak 'mon: called with one argument only, but $SELF not set,'; |
540 |
root |
1.32 |
|
541 |
|
|
unless (ref $cb) { |
542 |
|
|
if (@_) { |
543 |
|
|
# send a kill info message |
544 |
root |
1.41 |
my (@msg) = ($cb, @_); |
545 |
root |
1.32 |
$cb = sub { snd @msg, @_ }; |
546 |
|
|
} else { |
547 |
|
|
# simply kill other port |
548 |
|
|
my $port = $cb; |
549 |
|
|
$cb = sub { kil $port, @_ if @_ }; |
550 |
|
|
} |
551 |
|
|
} |
552 |
|
|
|
553 |
|
|
$node->monitor ($port, $cb); |
554 |
|
|
|
555 |
|
|
defined wantarray |
556 |
|
|
and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) } |
557 |
|
|
} |
558 |
|
|
|
559 |
|
|
=item $guard = mon_guard $port, $ref, $ref... |
560 |
|
|
|
561 |
|
|
Monitors the given C<$port> and keeps the passed references. When the port |
562 |
|
|
is killed, the references will be freed. |
563 |
|
|
|
564 |
|
|
Optionally returns a guard that will stop the monitoring. |
565 |
|
|
|
566 |
|
|
This function is useful when you create e.g. timers or other watchers and |
567 |
|
|
want to free them when the port gets killed: |
568 |
|
|
|
569 |
|
|
$port->rcv (start => sub { |
570 |
|
|
my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub { |
571 |
|
|
undef $timer if 0.9 < rand; |
572 |
|
|
}); |
573 |
|
|
}); |
574 |
|
|
|
575 |
|
|
=cut |
576 |
|
|
|
577 |
|
|
sub mon_guard { |
578 |
|
|
my ($port, @refs) = @_; |
579 |
|
|
|
580 |
root |
1.36 |
#TODO: mon-less form? |
581 |
|
|
|
582 |
root |
1.32 |
mon $port, sub { 0 && @refs } |
583 |
|
|
} |
584 |
|
|
|
585 |
root |
1.33 |
=item kil $port[, @reason] |
586 |
root |
1.32 |
|
587 |
|
|
Kill the specified port with the given C<@reason>. |
588 |
|
|
|
589 |
|
|
If no C<@reason> is specified, then the port is killed "normally" (linked |
590 |
|
|
ports will not be kileld, or even notified). |
591 |
|
|
|
592 |
|
|
Otherwise, linked ports get killed with the same reason (second form of |
593 |
|
|
C<mon>, see below). |
594 |
|
|
|
595 |
|
|
Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks |
596 |
|
|
will be reported as reason C<< die => $@ >>. |
597 |
|
|
|
598 |
|
|
Transport/communication errors are reported as C<< transport_error => |
599 |
|
|
$message >>. |
600 |
|
|
|
601 |
root |
1.38 |
=cut |
602 |
|
|
|
603 |
|
|
=item $port = spawn $node, $initfunc[, @initdata] |
604 |
|
|
|
605 |
|
|
Creates a port on the node C<$node> (which can also be a port ID, in which |
606 |
|
|
case it's the node where that port resides). |
607 |
|
|
|
608 |
|
|
The port ID of the newly created port is return immediately, and it is |
609 |
|
|
permissible to immediately start sending messages or monitor the port. |
610 |
|
|
|
611 |
|
|
After the port has been created, the init function is |
612 |
root |
1.39 |
called. This function must be a fully-qualified function name |
613 |
root |
1.40 |
(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main |
614 |
|
|
program, use C<::name>. |
615 |
root |
1.38 |
|
616 |
|
|
If the function doesn't exist, then the node tries to C<require> |
617 |
|
|
the package, then the package above the package and so on (e.g. |
618 |
|
|
C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function |
619 |
|
|
exists or it runs out of package names. |
620 |
|
|
|
621 |
|
|
The init function is then called with the newly-created port as context |
622 |
|
|
object (C<$SELF>) and the C<@initdata> values as arguments. |
623 |
|
|
|
624 |
|
|
A common idiom is to pass your own port, monitor the spawned port, and |
625 |
|
|
in the init function, monitor the original port. This two-way monitoring |
626 |
|
|
ensures that both ports get cleaned up when there is a problem. |
627 |
|
|
|
628 |
|
|
Example: spawn a chat server port on C<$othernode>. |
629 |
|
|
|
630 |
|
|
# this node, executed from within a port context: |
631 |
|
|
my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF; |
632 |
|
|
mon $server; |
633 |
|
|
|
634 |
|
|
# init function on C<$othernode> |
635 |
|
|
sub connect { |
636 |
|
|
my ($srcport) = @_; |
637 |
|
|
|
638 |
|
|
mon $srcport; |
639 |
|
|
|
640 |
|
|
rcv $SELF, sub { |
641 |
|
|
... |
642 |
|
|
}; |
643 |
|
|
} |
644 |
|
|
|
645 |
|
|
=cut |
646 |
|
|
|
647 |
|
|
sub _spawn { |
648 |
|
|
my $port = shift; |
649 |
|
|
my $init = shift; |
650 |
|
|
|
651 |
|
|
local $SELF = "$NODE#$port"; |
652 |
|
|
eval { |
653 |
|
|
&{ load_func $init } |
654 |
|
|
}; |
655 |
|
|
_self_die if $@; |
656 |
|
|
} |
657 |
|
|
|
658 |
|
|
sub spawn(@) { |
659 |
|
|
my ($noderef, undef) = split /#/, shift, 2; |
660 |
|
|
|
661 |
|
|
my $id = "$RUNIQ." . $ID++; |
662 |
|
|
|
663 |
root |
1.39 |
$_[0] =~ /::/ |
664 |
|
|
or Carp::croak "spawn init function must be a fully-qualified name, caught"; |
665 |
|
|
|
666 |
root |
1.55 |
snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_; |
667 |
root |
1.38 |
|
668 |
|
|
"$noderef#$id" |
669 |
|
|
} |
670 |
|
|
|
671 |
root |
1.59 |
=item after $timeout, @msg |
672 |
|
|
|
673 |
|
|
=item after $timeout, $callback |
674 |
|
|
|
675 |
|
|
Either sends the given message, or call the given callback, after the |
676 |
|
|
specified number of seconds. |
677 |
|
|
|
678 |
|
|
This is simply a utility function that come sin handy at times. |
679 |
|
|
|
680 |
|
|
=cut |
681 |
|
|
|
682 |
|
|
sub after($@) { |
683 |
|
|
my ($timeout, @action) = @_; |
684 |
|
|
|
685 |
|
|
my $t; $t = AE::timer $timeout, 0, sub { |
686 |
|
|
undef $t; |
687 |
|
|
ref $action[0] |
688 |
|
|
? $action[0]() |
689 |
|
|
: snd @action; |
690 |
|
|
}; |
691 |
|
|
} |
692 |
|
|
|
693 |
root |
1.8 |
=back |
694 |
|
|
|
695 |
root |
1.26 |
=head1 AnyEvent::MP vs. Distributed Erlang |
696 |
|
|
|
697 |
root |
1.35 |
AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node |
698 |
|
|
== aemp node, Erlang process == aemp port), so many of the documents and |
699 |
|
|
programming techniques employed by Erlang apply to AnyEvent::MP. Here is a |
700 |
root |
1.27 |
sample: |
701 |
|
|
|
702 |
root |
1.35 |
http://www.Erlang.se/doc/programming_rules.shtml |
703 |
|
|
http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4 |
704 |
|
|
http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6 |
705 |
|
|
http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5 |
706 |
root |
1.27 |
|
707 |
|
|
Despite the similarities, there are also some important differences: |
708 |
root |
1.26 |
|
709 |
|
|
=over 4 |
710 |
|
|
|
711 |
|
|
=item * Node references contain the recipe on how to contact them. |
712 |
|
|
|
713 |
|
|
Erlang relies on special naming and DNS to work everywhere in the |
714 |
|
|
same way. AEMP relies on each node knowing it's own address(es), with |
715 |
|
|
convenience functionality. |
716 |
|
|
|
717 |
root |
1.27 |
This means that AEMP requires a less tightly controlled environment at the |
718 |
|
|
cost of longer node references and a slightly higher management overhead. |
719 |
|
|
|
720 |
root |
1.54 |
=item * Erlang has a "remote ports are like local ports" philosophy, AEMP |
721 |
root |
1.51 |
uses "local ports are like remote ports". |
722 |
|
|
|
723 |
|
|
The failure modes for local ports are quite different (runtime errors |
724 |
|
|
only) then for remote ports - when a local port dies, you I<know> it dies, |
725 |
|
|
when a connection to another node dies, you know nothing about the other |
726 |
|
|
port. |
727 |
|
|
|
728 |
|
|
Erlang pretends remote ports are as reliable as local ports, even when |
729 |
|
|
they are not. |
730 |
|
|
|
731 |
|
|
AEMP encourages a "treat remote ports differently" philosophy, with local |
732 |
|
|
ports being the special case/exception, where transport errors cannot |
733 |
|
|
occur. |
734 |
|
|
|
735 |
root |
1.26 |
=item * Erlang uses processes and a mailbox, AEMP does not queue. |
736 |
|
|
|
737 |
root |
1.51 |
Erlang uses processes that selectively receive messages, and therefore |
738 |
|
|
needs a queue. AEMP is event based, queuing messages would serve no |
739 |
|
|
useful purpose. For the same reason the pattern-matching abilities of |
740 |
|
|
AnyEvent::MP are more limited, as there is little need to be able to |
741 |
|
|
filter messages without dequeing them. |
742 |
root |
1.26 |
|
743 |
root |
1.35 |
(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP). |
744 |
root |
1.26 |
|
745 |
|
|
=item * Erlang sends are synchronous, AEMP sends are asynchronous. |
746 |
|
|
|
747 |
root |
1.51 |
Sending messages in Erlang is synchronous and blocks the process (and |
748 |
|
|
so does not need a queue that can overflow). AEMP sends are immediate, |
749 |
|
|
connection establishment is handled in the background. |
750 |
root |
1.26 |
|
751 |
root |
1.51 |
=item * Erlang suffers from silent message loss, AEMP does not. |
752 |
root |
1.26 |
|
753 |
|
|
Erlang makes few guarantees on messages delivery - messages can get lost |
754 |
|
|
without any of the processes realising it (i.e. you send messages a, b, |
755 |
|
|
and c, and the other side only receives messages a and c). |
756 |
|
|
|
757 |
|
|
AEMP guarantees correct ordering, and the guarantee that there are no |
758 |
|
|
holes in the message sequence. |
759 |
|
|
|
760 |
root |
1.35 |
=item * In Erlang, processes can be declared dead and later be found to be |
761 |
root |
1.26 |
alive. |
762 |
|
|
|
763 |
root |
1.35 |
In Erlang it can happen that a monitored process is declared dead and |
764 |
root |
1.26 |
linked processes get killed, but later it turns out that the process is |
765 |
|
|
still alive - and can receive messages. |
766 |
|
|
|
767 |
|
|
In AEMP, when port monitoring detects a port as dead, then that port will |
768 |
|
|
eventually be killed - it cannot happen that a node detects a port as dead |
769 |
|
|
and then later sends messages to it, finding it is still alive. |
770 |
|
|
|
771 |
|
|
=item * Erlang can send messages to the wrong port, AEMP does not. |
772 |
|
|
|
773 |
root |
1.51 |
In Erlang it is quite likely that a node that restarts reuses a process ID |
774 |
|
|
known to other nodes for a completely different process, causing messages |
775 |
|
|
destined for that process to end up in an unrelated process. |
776 |
root |
1.26 |
|
777 |
|
|
AEMP never reuses port IDs, so old messages or old port IDs floating |
778 |
|
|
around in the network will not be sent to an unrelated port. |
779 |
|
|
|
780 |
|
|
=item * Erlang uses unprotected connections, AEMP uses secure |
781 |
|
|
authentication and can use TLS. |
782 |
|
|
|
783 |
|
|
AEMP can use a proven protocol - SSL/TLS - to protect connections and |
784 |
|
|
securely authenticate nodes. |
785 |
|
|
|
786 |
root |
1.28 |
=item * The AEMP protocol is optimised for both text-based and binary |
787 |
|
|
communications. |
788 |
|
|
|
789 |
root |
1.35 |
The AEMP protocol, unlike the Erlang protocol, supports both |
790 |
root |
1.28 |
language-independent text-only protocols (good for debugging) and binary, |
791 |
|
|
language-specific serialisers (e.g. Storable). |
792 |
|
|
|
793 |
|
|
It has also been carefully designed to be implementable in other languages |
794 |
|
|
with a minimum of work while gracefully degrading fucntionality to make the |
795 |
|
|
protocol simple. |
796 |
|
|
|
797 |
root |
1.35 |
=item * AEMP has more flexible monitoring options than Erlang. |
798 |
|
|
|
799 |
|
|
In Erlang, you can chose to receive I<all> exit signals as messages |
800 |
|
|
or I<none>, there is no in-between, so monitoring single processes is |
801 |
|
|
difficult to implement. Monitoring in AEMP is more flexible than in |
802 |
|
|
Erlang, as one can choose between automatic kill, exit message or callback |
803 |
|
|
on a per-process basis. |
804 |
|
|
|
805 |
root |
1.37 |
=item * Erlang tries to hide remote/local connections, AEMP does not. |
806 |
root |
1.35 |
|
807 |
|
|
Monitoring in Erlang is not an indicator of process death/crashes, |
808 |
root |
1.37 |
as linking is (except linking is unreliable in Erlang). |
809 |
|
|
|
810 |
|
|
In AEMP, you don't "look up" registered port names or send to named ports |
811 |
|
|
that might or might not be persistent. Instead, you normally spawn a port |
812 |
|
|
on the remote node. The init function monitors the you, and you monitor |
813 |
|
|
the remote port. Since both monitors are local to the node, they are much |
814 |
|
|
more reliable. |
815 |
|
|
|
816 |
|
|
This also saves round-trips and avoids sending messages to the wrong port |
817 |
|
|
(hard to do in Erlang). |
818 |
root |
1.35 |
|
819 |
root |
1.26 |
=back |
820 |
|
|
|
821 |
root |
1.46 |
=head1 RATIONALE |
822 |
|
|
|
823 |
|
|
=over 4 |
824 |
|
|
|
825 |
|
|
=item Why strings for ports and noderefs, why not objects? |
826 |
|
|
|
827 |
|
|
We considered "objects", but found that the actual number of methods |
828 |
|
|
thatc an be called are very low. Since port IDs and noderefs travel over |
829 |
|
|
the network frequently, the serialising/deserialising would add lots of |
830 |
|
|
overhead, as well as having to keep a proxy object. |
831 |
|
|
|
832 |
|
|
Strings can easily be printed, easily serialised etc. and need no special |
833 |
|
|
procedures to be "valid". |
834 |
|
|
|
835 |
root |
1.47 |
And a a miniport consists of a single closure stored in a global hash - it |
836 |
|
|
can't become much cheaper. |
837 |
|
|
|
838 |
root |
1.46 |
=item Why favour JSON, why not real serialising format such as Storable? |
839 |
|
|
|
840 |
|
|
In fact, any AnyEvent::MP node will happily accept Storable as framing |
841 |
|
|
format, but currently there is no way to make a node use Storable by |
842 |
|
|
default. |
843 |
|
|
|
844 |
|
|
The default framing protocol is JSON because a) JSON::XS is many times |
845 |
|
|
faster for small messages and b) most importantly, after years of |
846 |
|
|
experience we found that object serialisation is causing more problems |
847 |
|
|
than it gains: Just like function calls, objects simply do not travel |
848 |
|
|
easily over the network, mostly because they will always be a copy, so you |
849 |
|
|
always have to re-think your design. |
850 |
|
|
|
851 |
|
|
Keeping your messages simple, concentrating on data structures rather than |
852 |
|
|
objects, will keep your messages clean, tidy and efficient. |
853 |
|
|
|
854 |
|
|
=back |
855 |
|
|
|
856 |
root |
1.1 |
=head1 SEE ALSO |
857 |
|
|
|
858 |
|
|
L<AnyEvent>. |
859 |
|
|
|
860 |
|
|
=head1 AUTHOR |
861 |
|
|
|
862 |
|
|
Marc Lehmann <schmorp@schmorp.de> |
863 |
|
|
http://home.schmorp.de/ |
864 |
|
|
|
865 |
|
|
=cut |
866 |
|
|
|
867 |
|
|
1 |
868 |
|
|
|