AnyEvent-MP
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=head1 NAME
AnyEvent::MP - erlang-style multi-processing/message-passing framework
=head1 SYNOPSIS
use AnyEvent::MP;
$NODE # contains this node's node ID
NODE # returns this node's node ID
$SELF # receiving/own port id in rcv callbacks
# initialise the node so it can send/receive messages
configure;
# ports are message destinations
# sending messages
snd $port, type => data...;
snd $port, @msg;
snd @msg_with_first_element_being_a_port;
# creating/using ports, the simple way
my $simple_port = port { my @msg = @_ };
# creating/using ports, tagged message matching
my $port = port;
rcv $port, ping => sub { snd $_[0], "pong" };
rcv $port, pong => sub { warn "pong received\n" };
# create a port on another node
my $port = spawn $node, $initfunc, @initdata;
# destroy a port again
kil $port; # "normal" kill
kil $port, my_error => "everything is broken"; # error kill
# monitoring
mon $port, $cb->(@msg) # callback is invoked on death
mon $port, $localport # kill localport on abnormal death
mon $port, $localport, @msg # send message on death
# temporarily execute code in port context
peval $port, sub { die "kill the port!" };
# execute callbacks in $SELF port context
my $timer = AE::timer 1, 0, psub {
die "kill the port, delayed";
};
# distributed database - modification
db_set $family => $subkey [=> $value] # add a subkey
db_del $family => $subkey... # delete one or more subkeys
db_reg $family => $port [=> $value] # register a port
# distributed database - queries
db_family $family => $cb->(\%familyhash)
db_keys $family => $cb->(\@keys)
db_values $family => $cb->(\@values)
# distributed database - monitoring a family
db_mon $family => $cb->(\%familyhash, \@added, \@changed, \@deleted)
=head1 DESCRIPTION
This module (-family) implements a simple message passing framework.
Despite its simplicity, you can securely message other processes running
on the same or other hosts, and you can supervise entities remotely.
For an introduction to this module family, see the L<AnyEvent::MP::Intro>
manual page and the examples under F<eg/>.
=head1 CONCEPTS
=over 4
=item port
Not to be confused with a TCP port, a "port" is something you can send
messages to (with the C<snd> function).
Ports allow you to register C<rcv> handlers that can match all or just
some messages. Messages send to ports will not be queued, regardless of
anything was listening for them or not.
Ports are represented by (printable) strings called "port IDs".
=item port ID - C<nodeid#portname>
A port ID is the concatenation of a node ID, a hash-mark (C<#>)
as separator, and a port name (a printable string of unspecified
format created by AnyEvent::MP).
=item node
A node is a single process containing at least one port - the node port,
which enables nodes to manage each other remotely, and to create new
ports.
Nodes are either public (have one or more listening ports) or private
(no listening ports). Private nodes cannot talk to other private nodes
currently, but all nodes can talk to public nodes.
Nodes is represented by (printable) strings called "node IDs".
and can only be used to specify defaults.
If the profile specifies a node ID, then this will become the node ID of
this process. If not, then the profile name will be used as node ID, with
a unique randoms tring (C</%u>) appended.
The node ID can contain some C<%> sequences that are expanded: C<%n>
is expanded to the local nodename, C<%u> is replaced by a random
strign to make the node unique. For example, the F<aemp> commandline
utility uses C<aemp/%n/%u> as nodename, which might expand to
C<aemp/cerebro/ZQDGSIkRhEZQDGSIkRhE>.
=item step 2, bind listener sockets
The next step is to look up the binds in the profile, followed by binding
aemp protocol listeners on all binds specified (it is possible and valid
to have no binds, meaning that the node cannot be contacted from the
outside. This means the node cannot talk to other nodes that also have no
binds, but it can still talk to all "normal" nodes).
If the profile does not specify a binds list, then a default of C<*> is
used, meaning the node will bind on a dynamically-assigned port on every
local IP address it finds.
=item step 3, connect to seed nodes
As the last step, the seed ID list from the profile is passed to the
L<AnyEvent::MP::Global> module, which will then use it to keep
connectivity with at least one node at any point in time.
=back
Example: become a distributed node using the local node name as profile.
This should be the most common form of invocation for "daemon"-type nodes.
configure
Example: become a semi-anonymous node. This form is often used for
commandline clients.
configure nodeid => "myscript/%n/%u";
Example: configure a node using a profile called seed, which is suitable
for a seed node as it binds on all local addresses on a fixed port (4040,
customary for aemp).
# use the aemp commandline utility
# aemp profile seed binds '*:4040'
# then use it
configure profile => "seed";
# or simply use aemp from the shell again:
# aemp run profile seed
# or provide a nicer-to-remember nodeid
# aemp run profile seed nodeid "$(hostname)"
=item $SELF
Contains the current port id while executing C<rcv> callbacks or C<psub>
blocks.
=item *SELF, SELF, %SELF, @SELF...
Due to some quirks in how perl exports variables, it is impossible to
just export C<$SELF>, all the symbols named C<SELF> are exported by this
module, but only C<$SELF> is currently used.
=item snd $port, type => @data
=item snd $port, @msg
Send the given message to the given port, which can identify either a
local or a remote port, and must be a port ID.
While the message can be almost anything, it is highly recommended to
use a string as first element (a port ID, or some word that indicates a
request type etc.) and to consist if only simple perl values (scalars,
arrays, hashes) - if you think you need to pass an object, think again.
The message data logically becomes read-only after a call to this
function: modifying any argument (or values referenced by them) is
forbidden, as there can be considerable time between the call to C<snd>
and the time the message is actually being serialised - in fact, it might
never be copied as within the same process it is simply handed to the
receiving port.
The type of data you can transfer depends on the transport protocol: when
JSON is used, then only strings, numbers and arrays and hashes consisting
of those are allowed (no objects). When Storable is used, then anything
that Storable can serialise and deserialise is allowed, and for the local
node, anything can be passed. Best rely only on the common denominator of
these.
=item $local_port = port
Create a new local port object and returns its port ID. Initially it has
no callbacks set and will throw an error when it receives messages.
=item $local_port = port { my @msg = @_ }
Creates a new local port, and returns its ID. Semantically the same as
creating a port and calling C<rcv $port, $callback> on it.
The block will be called for every message received on the port, with the
global variable C<$SELF> set to the port ID. Runtime errors will cause the
port to be C<kil>ed. The message will be passed as-is, no extra argument
(i.e. no port ID) will be passed to the callback.
If you want to stop/destroy the port, simply C<kil> it:
my $port = port {
my @msg = @_;
...
kil $SELF;
};
=cut
sub rcv($@);
my $KILME = sub {
(my $tag = substr $_[0], 0, 30) =~ s/([^\x20-\x7e])/./g;
kil $SELF, unhandled_message => "no callback found for message '$tag'";
};
sub port(;&) {
my $id = $UNIQ . ++$ID;
my $port = "$NODE#$id";
rcv $port, shift || $KILME;
$port
}
=item rcv $local_port, $callback->(@msg)
Replaces the default callback on the specified port. There is no way to
remove the default callback: use C<sub { }> to disable it, or better
C<kil> the port when it is no longer needed.
The global C<$SELF> (exported by this module) contains C<$port> while
executing the callback. Runtime errors during callback execution will
result in the port being C<kil>ed.
The default callback receives all messages not matched by a more specific
C<tag> match.
=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
Register (or replace) callbacks to be called on messages starting with the
given tag on the given port (and return the port), or unregister it (when
C<$callback> is C<$undef> or missing). There can only be one callback
registered for each tag.
The original message will be passed to the callback, after the first
element (the tag) has been removed. The callback will use the same
environment as the default callback (see above).
Example: create a port and bind receivers on it in one go.
my $port = rcv port,
msg1 => sub { ... },
msg2 => sub { ... },
;
Example: create a port, bind receivers and send it in a message elsewhere
in one go:
snd $otherport, reply =>
rcv port,
msg1 => sub { ... },
...
;
Example: temporarily register a rcv callback for a tag matching some port
(e.g. for an rpc reply) and unregister it after a message was received.
rcv $port, $otherport => sub {
my @reply = @_;
rcv $SELF, $otherport;
};
=cut
sub rcv($@) {
my $port = shift;
my ($nodeid, $portid) = split /#/, $port, 2;
$nodeid eq $NODE
or Carp::croak "$port: rcv can only be called on local ports, caught";
while (@_) {
if (ref $_[0]) {
if (my $self = $PORT_DATA{$portid}) {
"AnyEvent::MP::Port" eq ref $self
or Carp::croak "$port: rcv can only be called on message matching ports, caught";
$self->[0] = shift;
} else {
my $cb = shift;
$PORT{$portid} = sub {
local $SELF = $port;
eval { &$cb }; _self_die if $@;
};
}
} elsif (defined $_[0]) {
my $self = $PORT_DATA{$portid} ||= do {
my $self = bless [$PORT{$portid} || sub { }, { }, $port], "AnyEvent::MP::Port";
$self
};
"AnyEvent::MP::Port" eq ref $self
or Carp::croak "$port: rcv can only be called on message matching ports, caught";
my ($tag, $cb) = splice @_, 0, 2;
if (defined $cb) {
$self->[1]{$tag} = $cb;
} else {
delete $self->[1]{$tag};
}
}
}
$port
}
=item peval $port, $coderef[, @args]
Evaluates the given C<$codref> within the context of C<$port>, that is,
when the code throws an exception the C<$port> will be killed.
Any remaining args will be passed to the callback. Any return values will
be returned to the caller.
This is useful when you temporarily want to execute code in the context of
a port.
Example: create a port and run some initialisation code in it's context.
my $port = port { ... };
peval $port, sub {
init
or die "unable to init";
};
=cut
sub peval($$) {
local $SELF = shift;
my $cb = shift;
if (wantarray) {
my @res = eval { &$cb };
_self_die if $@;
@res
} else {
my $res = eval { &$cb };
_self_die if $@;
$res
}
}
=item $closure = psub { BLOCK }
Remembers C<$SELF> and creates a closure out of the BLOCK. When the
closure is executed, sets up the environment in the same way as in C<rcv>
callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
The effect is basically as if it returned C<< sub { peval $SELF, sub {
BLOCK }, @_ } >>.
This is useful when you register callbacks from C<rcv> callbacks:
rcv delayed_reply => sub {
my ($delay, @reply) = @_;
my $timer = AE::timer $delay, 0, psub {
snd @reply, $SELF;
};
};
=cut
sub psub(&) {
my $cb = shift;
my $port = $SELF
or Carp::croak "psub can only be called from within rcv or psub callbacks, not";
sub {
local $SELF = $port;
if (wantarray) {
my @res = eval { &$cb };
_self_die if $@;
@res
} else {
my $res = eval { &$cb };
_self_die if $@;
$res
}
}
}
=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
=item $guard = mon $port # kill $SELF when $port dies
=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
Monitor the given port and do something when the port is killed or
messages to it were lost, and optionally return a guard that can be used
to stop monitoring again.
The first two forms distinguish between "normal" and "abnormal" kil's:
In the first form (another port given), if the C<$port> is C<kil>'ed with
a non-empty reason, the other port (C<$rcvport>) will be kil'ed with the
same reason. That is, on "normal" kil's nothing happens, while under all
other conditions, the other port is killed with the same reason.
The second form (kill self) is the same as the first form, except that
C<$rvport> defaults to C<$SELF>.
The remaining forms don't distinguish between "normal" and "abnormal" kil's
- it's up to the callback or receiver to check whether the C<@reason> is
empty and act accordingly.
In the third form (callback), the callback is simply called with any
number of C<@reason> elements (empty @reason means that the port was deleted
"normally"). Note also that I<< the callback B<must> never die >>, so use
C<eval> if unsure.
In the last form (message), a message of the form C<$rcvport, @msg,
@reason> will be C<snd>.
Monitoring-actions are one-shot: once messages are lost (and a monitoring
alert was raised), they are removed and will not trigger again, even if it
turns out that the port is still alive.
As a rule of thumb, monitoring requests should always monitor a remote
port locally (using a local C<$rcvport> or a callback). The reason is that
kill messages might get lost, just like any other message. Another less
obvious reason is that even monitoring requests can get lost (for example,
when the connection to the other node goes down permanently). When
monitoring a port locally these problems do not exist.
my $node = $NODE{$nodeid} || add_node $nodeid;
my $cb = @_ ? shift : $SELF || Carp::croak 'mon: called with one argument only, but $SELF not set,';
unless (ref $cb) {
if (@_) {
# send a kill info message
my (@msg) = ($cb, @_);
$cb = sub { snd @msg, @_ };
} else {
# simply kill other port
my $port = $cb;
$cb = sub { kil $port, @_ if @_ };
}
}
$node->monitor ($port, $cb);
defined wantarray
and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
}
=item $guard = mon_guard $port, $ref, $ref...
Monitors the given C<$port> and keeps the passed references. When the port
is killed, the references will be freed.
Optionally returns a guard that will stop the monitoring.
This function is useful when you create e.g. timers or other watchers and
want to free them when the port gets killed (note the use of C<psub>):
$port->rcv (start => sub {
my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
undef $timer if 0.9 < rand;
});
});
=cut
sub mon_guard {
my ($port, @refs) = @_;
#TODO: mon-less form?
mon $port, sub { 0 && @refs }
}
=item kil $port[, @reason]
Kill the specified port with the given C<@reason>.
If no C<@reason> is specified, then the port is killed "normally" -
monitor callback will be invoked, but the kil will not cause linked ports
(C<mon $mport, $lport> form) to get killed.
If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
form) get killed with the same reason.
Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
will be reported as reason C<< die => $@ >>.
Transport/communication errors are reported as C<< transport_error =>
$message >>.
Common idioms:
# silently remove yourself, do not kill linked ports
kil $SELF;
# report a failure in some detail
kil $SELF, failure_mode_1 => "it failed with too high temperature";
# do not waste much time with killing, just die when something goes wrong
open my $fh, "<file"
or die "file: $!";
=item $port = spawn $node, $initfunc[, @initdata]
Creates a port on the node C<$node> (which can also be a port ID, in which
case it's the node where that port resides).
The port ID of the newly created port is returned immediately, and it is
possible to immediately start sending messages or to monitor the port.
After the port has been created, the init function is called on the remote
node, in the same context as a C<rcv> callback. This function must be a
fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
specify a function in the main program, use C<::name>.
If the function doesn't exist, then the node tries to C<require>
the package, then the package above the package and so on (e.g.
C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
exists or it runs out of package names.
The init function is then called with the newly-created port as context
object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
the port might not get created.
A common idiom is to pass a local port, immediately monitor the spawned
port, and in the remote init function, immediately monitor the passed
local port. This two-way monitoring ensures that both ports get cleaned up
when there is a problem.
C<spawn> guarantees that the C<$initfunc> has no visible effects on the
caller before C<spawn> returns (by delaying invocation when spawn is
called for the local node).
Example: spawn a chat server port on C<$othernode>.
# this node, executed from within a port context:
my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
mon $server;
# init function on C<$othernode>
sub connect {
my ($srcport) = @_;
mon $srcport;
rcv $SELF, sub {
...
};
}
=cut
sub _spawn {
my $port = shift;
my $init = shift;
# rcv will create the actual port
local $SELF = "$NODE#$port";
eval {
&{ load_func $init }
};
_self_die if $@;
}
sub spawn(@) {
my ($nodeid, undef) = split /#/, shift, 2;
my $id = $RUNIQ . ++$ID;
$_[0] =~ /::/
or Carp::croak "spawn init function must be a fully-qualified name, caught";
snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
"$nodeid#$id"
}
=item after $timeout, @msg
=item after $timeout, $callback
( run in 1.962 second using v1.01-cache-2.11-cpan-cdf2f3d4e48 )