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1.1 |
=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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1.22 |
$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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1.2 |
|
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1.38 |
$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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1.63 |
initialise_node; |
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|
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1.38 |
# ports are message endpoints |
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# sending messages |
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1.2 |
snd $port, type => data...; |
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1.38 |
snd $port, @msg; |
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snd @msg_with_first_element_being_a_port; |
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1.2 |
|
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1.50 |
# creating/using ports, the simple way |
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1.53 |
my $simple_port = port { my @msg = @_; 0 }; |
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1.22 |
|
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1.52 |
# creating/using ports, tagged message matching |
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1.38 |
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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1.2 |
|
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1.48 |
# create a port on another node |
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my $port = spawn $node, $initfunc, @initdata; |
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1.35 |
# 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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1.23 |
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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1.21 |
so do not use. This was uploaded mainly to reserve the CPAN namespace - |
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1.45 |
stay tuned! |
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1.6 |
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1.2 |
=head1 CONCEPTS |
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=over 4 |
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=item port |
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1.29 |
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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1.64 |
some messages. Messages send to ports will not be queued, regardless of |
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anything was listening for them or not. |
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1.2 |
|
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=item port ID - C<noderef#portname> |
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1.2 |
|
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1.53 |
A port ID is the concatenation of a noderef, a hash-mark (C<#>) as |
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1.29 |
separator, and a port name (a printable string of unspecified format). An |
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1.30 |
exception is the the node port, whose ID is identical to its node |
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1.29 |
reference. |
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1.2 |
|
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=item node |
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1.53 |
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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1.2 |
|
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1.62 |
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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1.2 |
|
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=item node ID - C<[a-za-Z0-9_\-.:]+> |
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1.2 |
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1.64 |
A node ID is a string that uniquely identifies the node within a |
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network. Depending on the configuration used, node IDs can look like a |
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hostname, a hostname and a port, or a random string. AnyEvent::MP itself |
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doesn't interpret node IDs in any way. |
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=item binds - C<ip:port> |
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Nodes can only talk to each other by creating some kind of connection to |
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each other. To do this, nodes should listen on one or more local transport |
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endpoints - binds. Currently, only standard C<ip:port> specifications can |
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be used, which specify TCP ports to listen on. |
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=item seeds - C<host:port> |
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When a node starts, it knows nothing about the network. To teach the node |
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about the network it first has to contact some other node within the |
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network. This node is called a seed. |
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Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes |
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are expected to be long-running, and at least one of those should always |
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be available. When nodes run out of connections (e.g. due to a network |
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error), they try to re-establish connections to some seednodes again to |
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join the network. |
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1.29 |
|
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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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1.1 |
use AE (); |
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1.2 |
use base "Exporter"; |
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1.44 |
our $VERSION = $AnyEvent::MP::Kernel::VERSION; |
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1.43 |
|
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1.8 |
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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1.22 |
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 / $NODE |
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1.64 |
The C<NODE> function returns, and the C<$NODE> variable contains the node |
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ID of the node running in the current process. This value is initialised by |
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a call to C<initialise_node>. |
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1.22 |
|
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1.63 |
=item $nodeid = node_of $port |
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1.22 |
|
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1.64 |
Extracts and returns the node ID part from a port ID or a node ID. |
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1.34 |
|
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1.63 |
=item initialise_node $profile_name |
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1.34 |
|
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1.64 |
Before a node can talk to other nodes on the network (i.e. enter |
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"distributed mode") it has to initialise itself - the minimum a node needs |
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to know is its own name, and optionally it should know the addresses of |
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some other nodes in the network to discover other nodes. |
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1.34 |
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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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1.64 |
The first argument is a profile name. If it is C<undef> or missing, then |
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the current nodename will be used instead (i.e. F<uname -n>). |
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1.34 |
|
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1.64 |
The function then looks up the profile in the aemp configuration (see the |
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L<aemp> commandline utility). |
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1.49 |
|
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1.64 |
If the profile specifies a node ID, then this will become the node ID of |
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this process. If not, then the profile name will be used as node ID. The |
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special node ID of C<anon/> will be replaced by a random node ID. |
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The next step is to look up the binds in the profile, followed by binding |
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aemp protocol listeners on all binds specified (it is possible and valid |
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to have no binds, meaning that the node cannot be contacted form the |
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outside. This means the node cannot talk to other nodes that also have no |
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binds, but it can still talk to all "normal" nodes). |
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If the profile does not specify a binds list, then the node ID will be |
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treated as if it were of the form C<host:port>, which will be resolved and |
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used as binds list. |
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Lastly, the seeds list from the profile is passed to the |
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L<AnyEvent::MP::Global> module, which will then use it to keep |
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connectivity with at least on of those seed nodes at any point in time. |
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Example: become a distributed node listening on the guessed noderef, or |
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the one specified via C<aemp> for the current node. This should be the |
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most common form of invocation for "daemon"-type nodes. |
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1.34 |
|
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initialise_node; |
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1.64 |
Example: become an anonymous node. This form is often used for commandline |
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clients. |
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1.34 |
|
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1.64 |
initialise_node "anon/"; |
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1.34 |
|
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1.64 |
Example: become a distributed node. If there is no profile of the given |
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name, or no binds list was specified, resolve C<localhost:4044> and bind |
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on the resulting addresses. |
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1.34 |
|
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1.49 |
initialise_node "localhost:4044"; |
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1.34 |
|
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1.22 |
=item $SELF |
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Contains the current port id while executing C<rcv> callbacks or C<psub> |
220 |
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blocks. |
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1.3 |
|
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1.22 |
=item SELF, %SELF, @SELF... |
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Due to some quirks in how perl exports variables, it is impossible to |
225 |
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just export C<$SELF>, all the symbols called C<SELF> are exported by this |
226 |
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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 |
229 |
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1.3 |
|
230 |
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1.33 |
=item snd $port, @msg |
231 |
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1.3 |
|
232 |
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1.8 |
Send the given message to the given port ID, which can identify either |
233 |
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1.52 |
a local or a remote port, and must be a port ID. |
234 |
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1.8 |
|
235 |
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While the message can be about anything, it is highly recommended to use a |
236 |
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1.52 |
string as first element (a port ID, or some word that indicates a request |
237 |
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1.8 |
type etc.). |
238 |
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1.3 |
|
239 |
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The message data effectively becomes read-only after a call to this |
240 |
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function: modifying any argument is not allowed and can cause many |
241 |
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problems. |
242 |
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|
243 |
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The type of data you can transfer depends on the transport protocol: when |
244 |
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JSON is used, then only strings, numbers and arrays and hashes consisting |
245 |
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of those are allowed (no objects). When Storable is used, then anything |
246 |
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that Storable can serialise and deserialise is allowed, and for the local |
247 |
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node, anything can be passed. |
248 |
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|
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1.22 |
=item $local_port = port |
250 |
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1.2 |
|
251 |
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1.50 |
Create a new local port object and returns its port ID. Initially it has |
252 |
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no callbacks set and will throw an error when it receives messages. |
253 |
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1.10 |
|
254 |
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1.50 |
=item $local_port = port { my @msg = @_ } |
255 |
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1.15 |
|
256 |
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1.50 |
Creates a new local port, and returns its ID. Semantically the same as |
257 |
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creating a port and calling C<rcv $port, $callback> on it. |
258 |
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1.15 |
|
259 |
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1.50 |
The block will be called for every message received on the port, with the |
260 |
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global variable C<$SELF> set to the port ID. Runtime errors will cause the |
261 |
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port to be C<kil>ed. The message will be passed as-is, no extra argument |
262 |
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(i.e. no port ID) will be passed to the callback. |
263 |
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1.15 |
|
264 |
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1.50 |
If you want to stop/destroy the port, simply C<kil> it: |
265 |
root |
1.15 |
|
266 |
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1.50 |
my $port = port { |
267 |
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my @msg = @_; |
268 |
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... |
269 |
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kil $SELF; |
270 |
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1.15 |
}; |
271 |
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1.10 |
|
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=cut |
273 |
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274 |
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1.33 |
sub rcv($@); |
275 |
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276 |
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1.50 |
sub _kilme { |
277 |
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die "received message on port without callback"; |
278 |
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} |
279 |
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1.22 |
sub port(;&) { |
281 |
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my $id = "$UNIQ." . $ID++; |
282 |
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my $port = "$NODE#$id"; |
283 |
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1.50 |
rcv $port, shift || \&_kilme; |
285 |
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1.10 |
|
286 |
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1.22 |
$port |
287 |
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1.10 |
} |
288 |
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|
289 |
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1.50 |
=item rcv $local_port, $callback->(@msg) |
290 |
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1.31 |
|
291 |
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1.50 |
Replaces the default callback on the specified port. There is no way to |
292 |
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remove the default callback: use C<sub { }> to disable it, or better |
293 |
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C<kil> the port when it is no longer needed. |
294 |
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1.3 |
|
295 |
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1.33 |
The global C<$SELF> (exported by this module) contains C<$port> while |
296 |
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1.50 |
executing the callback. Runtime errors during callback execution will |
297 |
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result in the port being C<kil>ed. |
298 |
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1.22 |
|
299 |
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1.50 |
The default callback received all messages not matched by a more specific |
300 |
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C<tag> match. |
301 |
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1.22 |
|
302 |
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1.50 |
=item rcv $local_port, tag => $callback->(@msg_without_tag), ... |
303 |
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1.3 |
|
304 |
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1.54 |
Register (or replace) callbacks to be called on messages starting with the |
305 |
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given tag on the given port (and return the port), or unregister it (when |
306 |
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C<$callback> is C<$undef> or missing). There can only be one callback |
307 |
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registered for each tag. |
308 |
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1.3 |
|
309 |
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1.50 |
The original message will be passed to the callback, after the first |
310 |
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element (the tag) has been removed. The callback will use the same |
311 |
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environment as the default callback (see above). |
312 |
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1.3 |
|
313 |
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1.36 |
Example: create a port and bind receivers on it in one go. |
314 |
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|
315 |
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my $port = rcv port, |
316 |
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1.50 |
msg1 => sub { ... }, |
317 |
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msg2 => sub { ... }, |
318 |
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1.36 |
; |
319 |
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|
320 |
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Example: create a port, bind receivers and send it in a message elsewhere |
321 |
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in one go: |
322 |
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|
323 |
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snd $otherport, reply => |
324 |
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rcv port, |
325 |
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1.50 |
msg1 => sub { ... }, |
326 |
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1.36 |
... |
327 |
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; |
328 |
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|
329 |
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1.54 |
Example: temporarily register a rcv callback for a tag matching some port |
330 |
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(e.g. for a rpc reply) and unregister it after a message was received. |
331 |
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|
332 |
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rcv $port, $otherport => sub { |
333 |
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my @reply = @_; |
334 |
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335 |
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rcv $SELF, $otherport; |
336 |
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}; |
337 |
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|
338 |
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1.3 |
=cut |
339 |
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|
340 |
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sub rcv($@) { |
341 |
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1.33 |
my $port = shift; |
342 |
|
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my ($noderef, $portid) = split /#/, $port, 2; |
343 |
root |
1.3 |
|
344 |
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1.58 |
$NODE{$noderef} == $NODE{""} |
345 |
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1.33 |
or Carp::croak "$port: rcv can only be called on local ports, caught"; |
346 |
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1.22 |
|
347 |
root |
1.50 |
while (@_) { |
348 |
|
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if (ref $_[0]) { |
349 |
|
|
if (my $self = $PORT_DATA{$portid}) { |
350 |
|
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"AnyEvent::MP::Port" eq ref $self |
351 |
|
|
or Carp::croak "$port: rcv can only be called on message matching ports, caught"; |
352 |
root |
1.33 |
|
353 |
root |
1.50 |
$self->[2] = shift; |
354 |
|
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} else { |
355 |
|
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my $cb = shift; |
356 |
|
|
$PORT{$portid} = sub { |
357 |
|
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local $SELF = $port; |
358 |
|
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eval { &$cb }; _self_die if $@; |
359 |
|
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}; |
360 |
|
|
} |
361 |
|
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} elsif (defined $_[0]) { |
362 |
|
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my $self = $PORT_DATA{$portid} ||= do { |
363 |
|
|
my $self = bless [$PORT{$port} || sub { }, { }, $port], "AnyEvent::MP::Port"; |
364 |
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|
365 |
|
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$PORT{$portid} = sub { |
366 |
|
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local $SELF = $port; |
367 |
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|
368 |
|
|
if (my $cb = $self->[1]{$_[0]}) { |
369 |
|
|
shift; |
370 |
|
|
eval { &$cb }; _self_die if $@; |
371 |
|
|
} else { |
372 |
|
|
&{ $self->[0] }; |
373 |
root |
1.33 |
} |
374 |
|
|
}; |
375 |
root |
1.50 |
|
376 |
|
|
$self |
377 |
root |
1.33 |
}; |
378 |
|
|
|
379 |
root |
1.50 |
"AnyEvent::MP::Port" eq ref $self |
380 |
|
|
or Carp::croak "$port: rcv can only be called on message matching ports, caught"; |
381 |
root |
1.22 |
|
382 |
root |
1.50 |
my ($tag, $cb) = splice @_, 0, 2; |
383 |
root |
1.33 |
|
384 |
root |
1.50 |
if (defined $cb) { |
385 |
|
|
$self->[1]{$tag} = $cb; |
386 |
root |
1.33 |
} else { |
387 |
root |
1.50 |
delete $self->[1]{$tag}; |
388 |
root |
1.33 |
} |
389 |
root |
1.22 |
} |
390 |
root |
1.3 |
} |
391 |
root |
1.31 |
|
392 |
root |
1.33 |
$port |
393 |
root |
1.2 |
} |
394 |
|
|
|
395 |
root |
1.22 |
=item $closure = psub { BLOCK } |
396 |
root |
1.2 |
|
397 |
root |
1.22 |
Remembers C<$SELF> and creates a closure out of the BLOCK. When the |
398 |
|
|
closure is executed, sets up the environment in the same way as in C<rcv> |
399 |
|
|
callbacks, i.e. runtime errors will cause the port to get C<kil>ed. |
400 |
|
|
|
401 |
|
|
This is useful when you register callbacks from C<rcv> callbacks: |
402 |
|
|
|
403 |
|
|
rcv delayed_reply => sub { |
404 |
|
|
my ($delay, @reply) = @_; |
405 |
|
|
my $timer = AE::timer $delay, 0, psub { |
406 |
|
|
snd @reply, $SELF; |
407 |
|
|
}; |
408 |
|
|
}; |
409 |
root |
1.3 |
|
410 |
root |
1.8 |
=cut |
411 |
root |
1.3 |
|
412 |
root |
1.22 |
sub psub(&) { |
413 |
|
|
my $cb = shift; |
414 |
root |
1.3 |
|
415 |
root |
1.22 |
my $port = $SELF |
416 |
|
|
or Carp::croak "psub can only be called from within rcv or psub callbacks, not"; |
417 |
root |
1.1 |
|
418 |
root |
1.22 |
sub { |
419 |
|
|
local $SELF = $port; |
420 |
root |
1.2 |
|
421 |
root |
1.22 |
if (wantarray) { |
422 |
|
|
my @res = eval { &$cb }; |
423 |
|
|
_self_die if $@; |
424 |
|
|
@res |
425 |
|
|
} else { |
426 |
|
|
my $res = eval { &$cb }; |
427 |
|
|
_self_die if $@; |
428 |
|
|
$res |
429 |
|
|
} |
430 |
|
|
} |
431 |
root |
1.2 |
} |
432 |
|
|
|
433 |
root |
1.33 |
=item $guard = mon $port, $cb->(@reason) |
434 |
root |
1.32 |
|
435 |
root |
1.36 |
=item $guard = mon $port, $rcvport |
436 |
|
|
|
437 |
|
|
=item $guard = mon $port |
438 |
root |
1.32 |
|
439 |
root |
1.36 |
=item $guard = mon $port, $rcvport, @msg |
440 |
root |
1.32 |
|
441 |
root |
1.42 |
Monitor the given port and do something when the port is killed or |
442 |
|
|
messages to it were lost, and optionally return a guard that can be used |
443 |
|
|
to stop monitoring again. |
444 |
|
|
|
445 |
|
|
C<mon> effectively guarantees that, in the absence of hardware failures, |
446 |
|
|
that after starting the monitor, either all messages sent to the port |
447 |
|
|
will arrive, or the monitoring action will be invoked after possible |
448 |
|
|
message loss has been detected. No messages will be lost "in between" |
449 |
|
|
(after the first lost message no further messages will be received by the |
450 |
|
|
port). After the monitoring action was invoked, further messages might get |
451 |
|
|
delivered again. |
452 |
root |
1.32 |
|
453 |
root |
1.58 |
Note that monitoring-actions are one-shot: once released, they are removed |
454 |
|
|
and will not trigger again. |
455 |
|
|
|
456 |
root |
1.36 |
In the first form (callback), the callback is simply called with any |
457 |
|
|
number of C<@reason> elements (no @reason means that the port was deleted |
458 |
root |
1.32 |
"normally"). Note also that I<< the callback B<must> never die >>, so use |
459 |
|
|
C<eval> if unsure. |
460 |
|
|
|
461 |
root |
1.43 |
In the second form (another port given), the other port (C<$rcvport>) |
462 |
root |
1.36 |
will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on |
463 |
|
|
"normal" kils nothing happens, while under all other conditions, the other |
464 |
|
|
port is killed with the same reason. |
465 |
root |
1.32 |
|
466 |
root |
1.36 |
The third form (kill self) is the same as the second form, except that |
467 |
|
|
C<$rvport> defaults to C<$SELF>. |
468 |
|
|
|
469 |
|
|
In the last form (message), a message of the form C<@msg, @reason> will be |
470 |
|
|
C<snd>. |
471 |
root |
1.32 |
|
472 |
root |
1.37 |
As a rule of thumb, monitoring requests should always monitor a port from |
473 |
|
|
a local port (or callback). The reason is that kill messages might get |
474 |
|
|
lost, just like any other message. Another less obvious reason is that |
475 |
|
|
even monitoring requests can get lost (for exmaple, when the connection |
476 |
|
|
to the other node goes down permanently). When monitoring a port locally |
477 |
|
|
these problems do not exist. |
478 |
|
|
|
479 |
root |
1.32 |
Example: call a given callback when C<$port> is killed. |
480 |
|
|
|
481 |
|
|
mon $port, sub { warn "port died because of <@_>\n" }; |
482 |
|
|
|
483 |
|
|
Example: kill ourselves when C<$port> is killed abnormally. |
484 |
|
|
|
485 |
root |
1.36 |
mon $port; |
486 |
root |
1.32 |
|
487 |
root |
1.36 |
Example: send us a restart message when another C<$port> is killed. |
488 |
root |
1.32 |
|
489 |
|
|
mon $port, $self => "restart"; |
490 |
|
|
|
491 |
|
|
=cut |
492 |
|
|
|
493 |
|
|
sub mon { |
494 |
|
|
my ($noderef, $port) = split /#/, shift, 2; |
495 |
|
|
|
496 |
|
|
my $node = $NODE{$noderef} || add_node $noderef; |
497 |
|
|
|
498 |
root |
1.41 |
my $cb = @_ ? shift : $SELF || Carp::croak 'mon: called with one argument only, but $SELF not set,'; |
499 |
root |
1.32 |
|
500 |
|
|
unless (ref $cb) { |
501 |
|
|
if (@_) { |
502 |
|
|
# send a kill info message |
503 |
root |
1.41 |
my (@msg) = ($cb, @_); |
504 |
root |
1.32 |
$cb = sub { snd @msg, @_ }; |
505 |
|
|
} else { |
506 |
|
|
# simply kill other port |
507 |
|
|
my $port = $cb; |
508 |
|
|
$cb = sub { kil $port, @_ if @_ }; |
509 |
|
|
} |
510 |
|
|
} |
511 |
|
|
|
512 |
|
|
$node->monitor ($port, $cb); |
513 |
|
|
|
514 |
|
|
defined wantarray |
515 |
|
|
and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) } |
516 |
|
|
} |
517 |
|
|
|
518 |
|
|
=item $guard = mon_guard $port, $ref, $ref... |
519 |
|
|
|
520 |
|
|
Monitors the given C<$port> and keeps the passed references. When the port |
521 |
|
|
is killed, the references will be freed. |
522 |
|
|
|
523 |
|
|
Optionally returns a guard that will stop the monitoring. |
524 |
|
|
|
525 |
|
|
This function is useful when you create e.g. timers or other watchers and |
526 |
|
|
want to free them when the port gets killed: |
527 |
|
|
|
528 |
|
|
$port->rcv (start => sub { |
529 |
|
|
my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub { |
530 |
|
|
undef $timer if 0.9 < rand; |
531 |
|
|
}); |
532 |
|
|
}); |
533 |
|
|
|
534 |
|
|
=cut |
535 |
|
|
|
536 |
|
|
sub mon_guard { |
537 |
|
|
my ($port, @refs) = @_; |
538 |
|
|
|
539 |
root |
1.36 |
#TODO: mon-less form? |
540 |
|
|
|
541 |
root |
1.32 |
mon $port, sub { 0 && @refs } |
542 |
|
|
} |
543 |
|
|
|
544 |
root |
1.33 |
=item kil $port[, @reason] |
545 |
root |
1.32 |
|
546 |
|
|
Kill the specified port with the given C<@reason>. |
547 |
|
|
|
548 |
|
|
If no C<@reason> is specified, then the port is killed "normally" (linked |
549 |
|
|
ports will not be kileld, or even notified). |
550 |
|
|
|
551 |
|
|
Otherwise, linked ports get killed with the same reason (second form of |
552 |
|
|
C<mon>, see below). |
553 |
|
|
|
554 |
|
|
Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks |
555 |
|
|
will be reported as reason C<< die => $@ >>. |
556 |
|
|
|
557 |
|
|
Transport/communication errors are reported as C<< transport_error => |
558 |
|
|
$message >>. |
559 |
|
|
|
560 |
root |
1.38 |
=cut |
561 |
|
|
|
562 |
|
|
=item $port = spawn $node, $initfunc[, @initdata] |
563 |
|
|
|
564 |
|
|
Creates a port on the node C<$node> (which can also be a port ID, in which |
565 |
|
|
case it's the node where that port resides). |
566 |
|
|
|
567 |
|
|
The port ID of the newly created port is return immediately, and it is |
568 |
|
|
permissible to immediately start sending messages or monitor the port. |
569 |
|
|
|
570 |
|
|
After the port has been created, the init function is |
571 |
root |
1.39 |
called. This function must be a fully-qualified function name |
572 |
root |
1.40 |
(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main |
573 |
|
|
program, use C<::name>. |
574 |
root |
1.38 |
|
575 |
|
|
If the function doesn't exist, then the node tries to C<require> |
576 |
|
|
the package, then the package above the package and so on (e.g. |
577 |
|
|
C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function |
578 |
|
|
exists or it runs out of package names. |
579 |
|
|
|
580 |
|
|
The init function is then called with the newly-created port as context |
581 |
|
|
object (C<$SELF>) and the C<@initdata> values as arguments. |
582 |
|
|
|
583 |
|
|
A common idiom is to pass your own port, monitor the spawned port, and |
584 |
|
|
in the init function, monitor the original port. This two-way monitoring |
585 |
|
|
ensures that both ports get cleaned up when there is a problem. |
586 |
|
|
|
587 |
|
|
Example: spawn a chat server port on C<$othernode>. |
588 |
|
|
|
589 |
|
|
# this node, executed from within a port context: |
590 |
|
|
my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF; |
591 |
|
|
mon $server; |
592 |
|
|
|
593 |
|
|
# init function on C<$othernode> |
594 |
|
|
sub connect { |
595 |
|
|
my ($srcport) = @_; |
596 |
|
|
|
597 |
|
|
mon $srcport; |
598 |
|
|
|
599 |
|
|
rcv $SELF, sub { |
600 |
|
|
... |
601 |
|
|
}; |
602 |
|
|
} |
603 |
|
|
|
604 |
|
|
=cut |
605 |
|
|
|
606 |
|
|
sub _spawn { |
607 |
|
|
my $port = shift; |
608 |
|
|
my $init = shift; |
609 |
|
|
|
610 |
|
|
local $SELF = "$NODE#$port"; |
611 |
|
|
eval { |
612 |
|
|
&{ load_func $init } |
613 |
|
|
}; |
614 |
|
|
_self_die if $@; |
615 |
|
|
} |
616 |
|
|
|
617 |
|
|
sub spawn(@) { |
618 |
|
|
my ($noderef, undef) = split /#/, shift, 2; |
619 |
|
|
|
620 |
|
|
my $id = "$RUNIQ." . $ID++; |
621 |
|
|
|
622 |
root |
1.39 |
$_[0] =~ /::/ |
623 |
|
|
or Carp::croak "spawn init function must be a fully-qualified name, caught"; |
624 |
|
|
|
625 |
root |
1.55 |
snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_; |
626 |
root |
1.38 |
|
627 |
|
|
"$noderef#$id" |
628 |
|
|
} |
629 |
|
|
|
630 |
root |
1.59 |
=item after $timeout, @msg |
631 |
|
|
|
632 |
|
|
=item after $timeout, $callback |
633 |
|
|
|
634 |
|
|
Either sends the given message, or call the given callback, after the |
635 |
|
|
specified number of seconds. |
636 |
|
|
|
637 |
|
|
This is simply a utility function that come sin handy at times. |
638 |
|
|
|
639 |
|
|
=cut |
640 |
|
|
|
641 |
|
|
sub after($@) { |
642 |
|
|
my ($timeout, @action) = @_; |
643 |
|
|
|
644 |
|
|
my $t; $t = AE::timer $timeout, 0, sub { |
645 |
|
|
undef $t; |
646 |
|
|
ref $action[0] |
647 |
|
|
? $action[0]() |
648 |
|
|
: snd @action; |
649 |
|
|
}; |
650 |
|
|
} |
651 |
|
|
|
652 |
root |
1.8 |
=back |
653 |
|
|
|
654 |
root |
1.26 |
=head1 AnyEvent::MP vs. Distributed Erlang |
655 |
|
|
|
656 |
root |
1.35 |
AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node |
657 |
|
|
== aemp node, Erlang process == aemp port), so many of the documents and |
658 |
|
|
programming techniques employed by Erlang apply to AnyEvent::MP. Here is a |
659 |
root |
1.27 |
sample: |
660 |
|
|
|
661 |
root |
1.35 |
http://www.Erlang.se/doc/programming_rules.shtml |
662 |
|
|
http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4 |
663 |
|
|
http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6 |
664 |
|
|
http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5 |
665 |
root |
1.27 |
|
666 |
|
|
Despite the similarities, there are also some important differences: |
667 |
root |
1.26 |
|
668 |
|
|
=over 4 |
669 |
|
|
|
670 |
root |
1.65 |
=item * Node IDs are arbitrary strings in AEMP. |
671 |
root |
1.26 |
|
672 |
root |
1.65 |
Erlang relies on special naming and DNS to work everywhere in the same |
673 |
|
|
way. AEMP relies on each node somehow knowing its own address(es) (e.g. by |
674 |
|
|
configuraiton or DNS), but will otherwise discover other odes itself. |
675 |
root |
1.27 |
|
676 |
root |
1.54 |
=item * Erlang has a "remote ports are like local ports" philosophy, AEMP |
677 |
root |
1.51 |
uses "local ports are like remote ports". |
678 |
|
|
|
679 |
|
|
The failure modes for local ports are quite different (runtime errors |
680 |
|
|
only) then for remote ports - when a local port dies, you I<know> it dies, |
681 |
|
|
when a connection to another node dies, you know nothing about the other |
682 |
|
|
port. |
683 |
|
|
|
684 |
|
|
Erlang pretends remote ports are as reliable as local ports, even when |
685 |
|
|
they are not. |
686 |
|
|
|
687 |
|
|
AEMP encourages a "treat remote ports differently" philosophy, with local |
688 |
|
|
ports being the special case/exception, where transport errors cannot |
689 |
|
|
occur. |
690 |
|
|
|
691 |
root |
1.26 |
=item * Erlang uses processes and a mailbox, AEMP does not queue. |
692 |
|
|
|
693 |
root |
1.51 |
Erlang uses processes that selectively receive messages, and therefore |
694 |
|
|
needs a queue. AEMP is event based, queuing messages would serve no |
695 |
|
|
useful purpose. For the same reason the pattern-matching abilities of |
696 |
|
|
AnyEvent::MP are more limited, as there is little need to be able to |
697 |
|
|
filter messages without dequeing them. |
698 |
root |
1.26 |
|
699 |
root |
1.35 |
(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP). |
700 |
root |
1.26 |
|
701 |
|
|
=item * Erlang sends are synchronous, AEMP sends are asynchronous. |
702 |
|
|
|
703 |
root |
1.51 |
Sending messages in Erlang is synchronous and blocks the process (and |
704 |
|
|
so does not need a queue that can overflow). AEMP sends are immediate, |
705 |
|
|
connection establishment is handled in the background. |
706 |
root |
1.26 |
|
707 |
root |
1.51 |
=item * Erlang suffers from silent message loss, AEMP does not. |
708 |
root |
1.26 |
|
709 |
|
|
Erlang makes few guarantees on messages delivery - messages can get lost |
710 |
|
|
without any of the processes realising it (i.e. you send messages a, b, |
711 |
|
|
and c, and the other side only receives messages a and c). |
712 |
|
|
|
713 |
|
|
AEMP guarantees correct ordering, and the guarantee that there are no |
714 |
|
|
holes in the message sequence. |
715 |
|
|
|
716 |
root |
1.35 |
=item * In Erlang, processes can be declared dead and later be found to be |
717 |
root |
1.26 |
alive. |
718 |
|
|
|
719 |
root |
1.35 |
In Erlang it can happen that a monitored process is declared dead and |
720 |
root |
1.26 |
linked processes get killed, but later it turns out that the process is |
721 |
|
|
still alive - and can receive messages. |
722 |
|
|
|
723 |
|
|
In AEMP, when port monitoring detects a port as dead, then that port will |
724 |
|
|
eventually be killed - it cannot happen that a node detects a port as dead |
725 |
|
|
and then later sends messages to it, finding it is still alive. |
726 |
|
|
|
727 |
|
|
=item * Erlang can send messages to the wrong port, AEMP does not. |
728 |
|
|
|
729 |
root |
1.51 |
In Erlang it is quite likely that a node that restarts reuses a process ID |
730 |
|
|
known to other nodes for a completely different process, causing messages |
731 |
|
|
destined for that process to end up in an unrelated process. |
732 |
root |
1.26 |
|
733 |
|
|
AEMP never reuses port IDs, so old messages or old port IDs floating |
734 |
|
|
around in the network will not be sent to an unrelated port. |
735 |
|
|
|
736 |
|
|
=item * Erlang uses unprotected connections, AEMP uses secure |
737 |
|
|
authentication and can use TLS. |
738 |
|
|
|
739 |
|
|
AEMP can use a proven protocol - SSL/TLS - to protect connections and |
740 |
|
|
securely authenticate nodes. |
741 |
|
|
|
742 |
root |
1.28 |
=item * The AEMP protocol is optimised for both text-based and binary |
743 |
|
|
communications. |
744 |
|
|
|
745 |
root |
1.35 |
The AEMP protocol, unlike the Erlang protocol, supports both |
746 |
root |
1.28 |
language-independent text-only protocols (good for debugging) and binary, |
747 |
|
|
language-specific serialisers (e.g. Storable). |
748 |
|
|
|
749 |
|
|
It has also been carefully designed to be implementable in other languages |
750 |
|
|
with a minimum of work while gracefully degrading fucntionality to make the |
751 |
|
|
protocol simple. |
752 |
|
|
|
753 |
root |
1.35 |
=item * AEMP has more flexible monitoring options than Erlang. |
754 |
|
|
|
755 |
|
|
In Erlang, you can chose to receive I<all> exit signals as messages |
756 |
|
|
or I<none>, there is no in-between, so monitoring single processes is |
757 |
|
|
difficult to implement. Monitoring in AEMP is more flexible than in |
758 |
|
|
Erlang, as one can choose between automatic kill, exit message or callback |
759 |
|
|
on a per-process basis. |
760 |
|
|
|
761 |
root |
1.37 |
=item * Erlang tries to hide remote/local connections, AEMP does not. |
762 |
root |
1.35 |
|
763 |
|
|
Monitoring in Erlang is not an indicator of process death/crashes, |
764 |
root |
1.37 |
as linking is (except linking is unreliable in Erlang). |
765 |
|
|
|
766 |
|
|
In AEMP, you don't "look up" registered port names or send to named ports |
767 |
|
|
that might or might not be persistent. Instead, you normally spawn a port |
768 |
|
|
on the remote node. The init function monitors the you, and you monitor |
769 |
|
|
the remote port. Since both monitors are local to the node, they are much |
770 |
|
|
more reliable. |
771 |
|
|
|
772 |
|
|
This also saves round-trips and avoids sending messages to the wrong port |
773 |
|
|
(hard to do in Erlang). |
774 |
root |
1.35 |
|
775 |
root |
1.26 |
=back |
776 |
|
|
|
777 |
root |
1.46 |
=head1 RATIONALE |
778 |
|
|
|
779 |
|
|
=over 4 |
780 |
|
|
|
781 |
|
|
=item Why strings for ports and noderefs, why not objects? |
782 |
|
|
|
783 |
|
|
We considered "objects", but found that the actual number of methods |
784 |
|
|
thatc an be called are very low. Since port IDs and noderefs travel over |
785 |
|
|
the network frequently, the serialising/deserialising would add lots of |
786 |
|
|
overhead, as well as having to keep a proxy object. |
787 |
|
|
|
788 |
|
|
Strings can easily be printed, easily serialised etc. and need no special |
789 |
|
|
procedures to be "valid". |
790 |
|
|
|
791 |
root |
1.47 |
And a a miniport consists of a single closure stored in a global hash - it |
792 |
|
|
can't become much cheaper. |
793 |
|
|
|
794 |
root |
1.46 |
=item Why favour JSON, why not real serialising format such as Storable? |
795 |
|
|
|
796 |
|
|
In fact, any AnyEvent::MP node will happily accept Storable as framing |
797 |
|
|
format, but currently there is no way to make a node use Storable by |
798 |
|
|
default. |
799 |
|
|
|
800 |
|
|
The default framing protocol is JSON because a) JSON::XS is many times |
801 |
|
|
faster for small messages and b) most importantly, after years of |
802 |
|
|
experience we found that object serialisation is causing more problems |
803 |
|
|
than it gains: Just like function calls, objects simply do not travel |
804 |
|
|
easily over the network, mostly because they will always be a copy, so you |
805 |
|
|
always have to re-think your design. |
806 |
|
|
|
807 |
|
|
Keeping your messages simple, concentrating on data structures rather than |
808 |
|
|
objects, will keep your messages clean, tidy and efficient. |
809 |
|
|
|
810 |
|
|
=back |
811 |
|
|
|
812 |
root |
1.1 |
=head1 SEE ALSO |
813 |
|
|
|
814 |
|
|
L<AnyEvent>. |
815 |
|
|
|
816 |
|
|
=head1 AUTHOR |
817 |
|
|
|
818 |
|
|
Marc Lehmann <schmorp@schmorp.de> |
819 |
|
|
http://home.schmorp.de/ |
820 |
|
|
|
821 |
|
|
=cut |
822 |
|
|
|
823 |
|
|
1 |
824 |
|
|
|