--- AnyEvent-MP/MP.pm 2009/08/04 20:00:00 1.24 +++ AnyEvent-MP/MP.pm 2010/04/03 15:32:18 1.113 @@ -1,43 +1,71 @@ =head1 NAME -AnyEvent::MP - multi-processing/message-passing framework +AnyEvent::MP - erlang-style multi-processing/message-passing framework =head1 SYNOPSIS use AnyEvent::MP; - $NODE # contains this node's noderef - NODE # returns this node's noderef - NODE $port # returns the noderef of the port + $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; - $SELF # receiving/own port id in rcv callbacks + # 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 prot again + kil $port; # "normal" kill + kil $port, my_error => "everything is broken"; # error kill + + # monitoring + mon $localport, $cb->(@msg) # callback is invoked on death + mon $localport, $otherport # kill otherport on abnormal death + mon $localport, $otherport, @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"; + }; - rcv $port, smartmatch => $cb->($port, @msg); +=head1 CURRENT STATUS - # examples: - rcv $port2, ping => sub { snd $_[0], "pong"; 0 }; - rcv $port1, pong => sub { warn "pong received\n" }; - snd $port2, ping => $port1; - - # more, smarter, matches (_any_ is exported by this module) - rcv $port, [child_died => $pid] => sub { ... - rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3 + bin/aemp - stable. + AnyEvent::MP - stable API, should work. + AnyEvent::MP::Intro - explains most concepts. + AnyEvent::MP::Kernel - mostly stable API. + AnyEvent::MP::Global - stable API. =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. +on the same or other hosts, and you can supervise entities remotely. For an introduction to this module family, see the L -manual page. - -At the moment, this module family is severly broken and underdocumented, -so do not use. This was uploaded mainly to reserve the CPAN namespace - -stay tuned! The basic API should be finished, however. +manual page and the examples under F. =head1 CONCEPTS @@ -45,30 +73,69 @@ =item port -A port is something you can send messages to with the C function, and -you can register C handlers with. All C handlers will receive -messages they match, messages will not be queued. +Not to be confused with a TCP port, a "port" is something you can send +messages to (with the C function). -=item port id - C +Ports allow you to register C 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. -A port id is always the noderef, a hash-mark (C<#>) as separator, followed -by a port name (a printable string of unspecified format). +=item port ID - C + +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). =item node -A node is a single process containing at least one port - the node -port. You can send messages to node ports to let them create new ports, -among other things. - -Initially, nodes are either private (single-process only) or hidden -(connected to a master node only). Only when they epxlicitly "become -public" can you send them messages from unrelated other nodes. - -=item noderef - C, C, C - -A noderef is a string that either uniquely identifies a given node (for -private and hidden nodes), or contains a recipe on how to reach a given -node (for public nodes). +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. + +=item node ID - C<[A-Z_][a-zA-Z0-9_\-.:]*> + +A node ID is a string that uniquely identifies the node within a +network. Depending on the configuration used, node IDs can look like a +hostname, a hostname and a port, or a random string. AnyEvent::MP itself +doesn't interpret node IDs in any way. + +=item binds - C + +Nodes can only talk to each other by creating some kind of connection to +each other. To do this, nodes should listen on one or more local transport +endpoints - binds. Currently, only standard C specifications can +be used, which specify TCP ports to listen on. + +=item seed nodes + +When a node starts, it knows nothing about the network. To teach the node +about the network it first has to contact some other node within the +network. This node is called a seed. + +Apart from the fact that other nodes know them as seed nodes and they have +to have fixed listening addresses, seed nodes are perfectly normal nodes - +any node can function as a seed node for others. + +In addition to discovering the network, seed nodes are also used to +maintain the network and to connect nodes that otherwise would have +trouble connecting. They form the backbone of an AnyEvent::MP network. + +Seed nodes are expected to be long-running, and at least one seed node +should always be available. They should also be relatively responsive - a +seed node that blocks for long periods will slow down everybody else. + +=item seeds - C + +Seeds are transport endpoint(s) (usually a hostname/IP address and a +TCP port) of nodes that should be used as seed nodes. + +The nodes listening on those endpoints are expected to be long-running, +and at least one of those should always be available. When nodes run out +of connections (e.g. due to a network error), they try to re-establish +connections to some seednodes again to join the network. =back @@ -80,7 +147,7 @@ package AnyEvent::MP; -use AnyEvent::MP::Base; +use AnyEvent::MP::Kernel; use common::sense; @@ -90,11 +157,12 @@ use base "Exporter"; -our $VERSION = '0.02'; +our $VERSION = 1.28; + our @EXPORT = qw( - NODE $NODE *SELF node_of _any_ - become_slave become_public - snd rcv mon kil reg psub + NODE $NODE *SELF node_of after + configure + snd rcv mon mon_guard kil psub peval spawn cal port ); @@ -108,82 +176,415 @@ =item $thisnode = NODE / $NODE -The C function returns, and the C<$NODE> variable contains -the noderef of the local node. The value is initialised by a call -to C or C, after which all local port -identifiers become invalid. +The C function returns, and the C<$NODE> variable contains, the node +ID of the node running in the current process. This value is initialised by +a call to C. + +=item $nodeid = node_of $port + +Extracts and returns the node ID from a port ID or a node ID. + +=item configure $profile, key => value... + +=item configure key => value... + +Before a node can talk to other nodes on the network (i.e. enter +"distributed mode") it has to configure itself - the minimum a node needs +to know is its own name, and optionally it should know the addresses of +some other nodes in the network to discover other nodes. + +The key/value pairs are basically the same ones as documented for the +F command line utility (sans the set/del prefix). + +This function configures a node - it must be called exactly once (or +never) before calling other AnyEvent::MP functions. + +=over 4 -=item $noderef = node_of $portid +=item step 1, gathering configuration from profiles -Extracts and returns the noderef from a portid or a noderef. +The function first looks up a profile in the aemp configuration (see the +L commandline utility). The profile name can be specified via the +named C parameter or can simply be the first parameter). If it is +missing, then the nodename (F) will be used as profile name. + +The profile data is then gathered as follows: + +First, all remaining key => value pairs (all of which are conveniently +undocumented at the moment) will be interpreted as configuration +data. Then they will be overwritten by any values specified in the global +default configuration (see the F utility), then the chain of +profiles chosen by the profile name (and any C attributes). + +That means that the values specified in the profile have highest priority +and the values specified directly via C have lowest priority, +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. The +special node ID of C will be replaced by a random node ID. + +=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 form 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 seeds list from the profile is passed to the +L 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 an anonymous node. This form is often used for commandline +clients. + + configure nodeid => "anon/"; + +Example: configure a node using a profile called seed, which si 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 nodeid anon/ 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 $SELF Contains the current port id while executing C callbacks or C blocks. -=item SELF, %SELF, @SELF... +=item *SELF, SELF, %SELF, @SELF... Due to some quirks in how perl exports variables, it is impossible to -just export C<$SELF>, all the symbols called C are exported by this +just export C<$SELF>, all the symbols named C are exported by this module, but only C<$SELF> is currently used. -=item snd $portid, type => @data - -=item snd $portid, @msg +=item snd $port, type => @data -Send the given message to the given port ID, which can identify either -a local or a remote port, and can be either a string or soemthignt hat -stringifies a sa port ID (such as a port object :). +=item snd $port, @msg -While the message can be about anything, it is highly recommended to use a -string as first element (a portid, or some word that indicates a request -type etc.). +Send the given message to the given port, which can identify either a +local or a remote port, and must be a port ID. -The message data effectively becomes read-only after a call to this -function: modifying any argument is not allowed and can cause many -problems. +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 +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. +node, anything can be passed. Best rely only on the common denominator of +these. -=item kil $portid[, @reason] +=item $local_port = port -Kill the specified port with the given C<@reason>. +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. -If no C<@reason> is specified, then the port is killed "normally" (linked -ports will not be kileld, or even notified). +=item $local_port = port { my @msg = @_ } -Otherwise, linked ports get killed with the same reason (second form of -C, see below). +Creates a new local port, and returns its ID. Semantically the same as +creating a port and calling C on it. -Runtime errors while evaluating C callbacks or inside C blocks -will be reported as reason C<< die => $@ >>. +The block will be called for every message received on the port, with the +global variable C<$SELF> set to the port ID. Runtime errors will cause the +port to be Ced. The message will be passed as-is, no extra argument +(i.e. no port ID) will be passed to the callback. -Transport/communication errors are reported as C<< transport_error => -$message >>. +If you want to stop/destroy the port, simply C it: + + my $port = port { + my @msg = @_; + ... + kil $SELF; + }; + +=cut + +sub rcv($@); + +sub _kilme { + die "received message on port without callback"; +} + +sub port(;&) { + my $id = "$UNIQ." . $ID++; + my $port = "$NODE#$id"; + + rcv $port, shift || \&_kilme; + + $port +} + +=item rcv $local_port, $callback->(@msg) + +Replaces the default callback on the specified port. There is no way to +remove the default callback: use C to disable it, or better +C the port when it is no longer needed. + +The global C<$SELF> (exported by this module) contains C<$port> while +executing the callback. Runtime errors during callback execution will +result in the port being Ced. + +The default callback received all messages not matched by a more specific +C 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; + + $NODE{$nodeid} == $NODE{""} + or Carp::croak "$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"; + + $PORT{$portid} = sub { + local $SELF = $port; + + if (my $cb = $self->[1]{$_[0]}) { + shift; + eval { &$cb }; _self_die if $@; + } else { + &{ $self->[0] }; + } + }; + + $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 contetx of C<$port>, that is, +when the code throews an exception the C<$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 +callbacks, i.e. runtime errors will cause the port to get Ced. + +The effect is basically as if it returned C<< sub { peval $SELF, sub { +BLOCK } } >>. + +This is useful when you register callbacks from C callbacks: + + rcv delayed_reply => sub { + my ($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, $cb->(@reason) # call $cb when $port dies -=item $guard = mon $portid, $cb->(@reason) +=item $guard = mon $port, $rcvport # kill $rcvport when $port dies -=item $guard = mon $portid, $otherport +=item $guard = mon $port # kill $SELF when $port dies -=item $guard = mon $portid, $otherport, @msg +=item $guard = mon $port, $rcvport, @msg # send a message when $port dies -Monitor the given port and do something when the port is killed. +Monitor the given port and do something when the port is killed or +messages to it were lost, and optionally return a guard that can be used +to stop monitoring again. -In the first form, the callback is simply called with any number -of C<@reason> elements (no @reason means that the port was deleted +In the first form (callback), the callback is simply called with any +number of C<@reason> elements (no @reason means that the port was deleted "normally"). Note also that I<< the callback B never die >>, so use C if unsure. -In the second form, the other port will be C'ed with C<@reason>, iff -a @reason was specified, i.e. on "normal" kils nothing happens, while -under all other conditions, the other port is killed with the same reason. - -In the last form, a message of the form C<@msg, @reason> will be C. +In the second form (another port given), the other port (C<$rcvport>) +will be C'ed with C<@reason>, if a @reason was specified, i.e. on +"normal" kils nothing happens, while under all other conditions, the other +port is killed with the same reason. + +The third form (kill self) is the same as the second form, except that +C<$rvport> defaults to C<$SELF>. + +In the last form (message), a message of the form C<@msg, @reason> will be +C. + +Monitoring-actions are one-shot: once messages are lost (and a monitoring +alert was raised), they are removed and will not trigger again. + +As a rule of thumb, monitoring requests should always monitor a port from +a local port (or 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. + +C effectively guarantees that, in the absence of hardware failures, +after starting the monitor, either all messages sent to the port will +arrive, or the monitoring action will be invoked after possible message +loss has been detected. No messages will be lost "in between" (after +the first lost message no further messages will be received by the +port). After the monitoring action was invoked, further messages might get +delivered again. + +Inter-host-connection timeouts and monitoring depend on the transport +used. The only transport currently implemented is TCP, and AnyEvent::MP +relies on TCP to detect node-downs (this can take 10-15 minutes on a +non-idle connection, and usually around two hours for idle connections). + +This means that monitoring is good for program errors and cleaning up +stuff eventually, but they are no replacement for a timeout when you need +to ensure some maximum latency. Example: call a given callback when C<$port> is killed. @@ -191,21 +592,22 @@ Example: kill ourselves when C<$port> is killed abnormally. - mon $port, $self; + mon $port; -Example: send us a restart message another C<$port> is killed. +Example: send us a restart message when another C<$port> is killed. mon $port, $self => "restart"; =cut sub mon { - my ($noderef, $port, $cb) = ((split /#/, shift, 2), shift); + my ($nodeid, $port) = split /#/, shift, 2; + + my $node = $NODE{$nodeid} || add_node $nodeid; - my $node = $NODE{$noderef} || add_node $noderef; + my $cb = @_ ? shift : $SELF || Carp::croak 'mon: called with one argument only, but $SELF not set,'; - #TODO: ports must not be references - if (!ref $cb or "AnyEvent::MP::Port" eq ref $cb) { + unless (ref $cb) { if (@_) { # send a kill info message my (@msg) = ($cb, @_); @@ -220,7 +622,7 @@ $node->monitor ($port, $cb); defined wantarray - and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) } + and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }) } =item $guard = mon_guard $port, $ref, $ref... @@ -231,10 +633,10 @@ 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: +want to free them when the port gets killed (note the use of C): $port->rcv (start => sub { - my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub { + my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub { undef $timer if 0.9 < rand; }); }); @@ -244,274 +646,349 @@ sub mon_guard { my ($port, @refs) = @_; + #TODO: mon-less form? + mon $port, sub { 0 && @refs } } -=item lnk $port1, $port2 +=item kil $port[, @reason] -Link two ports. This is simply a shorthand for: +Kill the specified port with the given C<@reason>. - mon $port1, $port2; - mon $port2, $port1; +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 form) to get killed. -It means that if either one is killed abnormally, the other one gets -killed as well. +If a C<@reason> is specified, then linked ports (C +form) get killed with the same reason. -=item $local_port = port +Runtime errors while evaluating C callbacks or inside C blocks +will be reported as reason C<< die => $@ >>. -Create a new local port object that supports message matching. +Transport/communication errors are reported as C<< transport_error => +$message >>. -=item $portid = port { my @msg = @_; $finished } +=cut -Creates a "mini port", that is, a very lightweight port without any -pattern matching behind it, and returns its ID. +=item $port = spawn $node, $initfunc[, @initdata] -The block will be called for every message received on the port. When the -callback returns a true value its job is considered "done" and the port -will be destroyed. Otherwise it will stay alive. +Creates a port on the node C<$node> (which can also be a port ID, in which +case it's the node where that port resides). -The message will be passed as-is, no extra argument (i.e. no port id) will -be passed to the callback. +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. -If you need the local port id in the callback, this works nicely: +After the port has been created, the init function is called on the remote +node, in the same context as a C callback. This function must be a +fully-qualified function name (e.g. C). To +specify a function in the main program, use C<::name>. - my $port; $port = miniport { - snd $otherport, reply => $port; - }; +If the function doesn't exist, then the node tries to C +the package, then the package above the package and so on (e.g. +C, C, C) until the function +exists or it runs out of package names. -=cut +The init function is then called with the newly-created port as context +object (C<$SELF>) and the C<@initdata> values as arguments. It I +call one of the C functions to set callbacks on C<$SELF>, otherwise +the port might not get created. -sub port(;&) { - my $id = "$UNIQ." . $ID++; - my $port = "$NODE#$id"; +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. - if (@_) { - my $cb = shift; - $PORT{$id} = sub { - local $SELF = $port; - eval { - &$cb - and kil $id; - }; - _self_die if $@; - }; - } else { - my $self = bless { - id => "$NODE#$id", - }, "AnyEvent::MP::Port"; - - $PORT_DATA{$id} = $self; - $PORT{$id} = sub { - local $SELF = $port; - - eval { - for (@{ $self->{rc0}{$_[0]} }) { - $_ && &{$_->[0]} - && undef $_; - } - - for (@{ $self->{rcv}{$_[0]} }) { - $_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1] - && &{$_->[0]} - && undef $_; - } - - for (@{ $self->{any} }) { - $_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1] - && &{$_->[0]} - && undef $_; - } - }; - _self_die if $@; - }; - } +C guarantees that the C<$initfunc> has no visible effects on the +caller before C returns (by delaying invocation when spawn is +called for the local node). - $port -} +Example: spawn a chat server port on C<$othernode>. -=item reg $portid, $name + # this node, executed from within a port context: + my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF; + mon $server; -Registers the given port under the name C<$name>. If the name already -exists it is replaced. + # init function on C<$othernode> + sub connect { + my ($srcport) = @_; -A port can only be registered under one well known name. + mon $srcport; -A port automatically becomes unregistered when it is killed. + rcv $SELF, sub { + ... + }; + } =cut -sub reg(@) { - my ($portid, $name) = @_; - - $REG{$name} = $portid; +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 $@; } -=item rcv $portid, tagstring => $callback->(@msg), ... - -=item rcv $portid, $smartmatch => $callback->(@msg), ... +sub spawn(@) { + my ($nodeid, undef) = split /#/, shift, 2; -=item rcv $portid, [$smartmatch...] => $callback->(@msg), ... + my $id = "$RUNIQ." . $ID++; -Register callbacks to be called on matching messages on the given port. + $_[0] =~ /::/ + or Carp::croak "spawn init function must be a fully-qualified name, caught"; -The callback has to return a true value when its work is done, after -which is will be removed, or a false value in which case it will stay -registered. + snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_; -The global C<$SELF> (exported by this module) contains C<$portid> while -executing the callback. + "$nodeid#$id" +} -Runtime errors wdurign callback execution will result in the port being -Ced. +=item after $timeout, @msg -If the match is an array reference, then it will be matched against the -first elements of the message, otherwise only the first element is being -matched. +=item after $timeout, $callback -Any element in the match that is specified as C<_any_> (a function -exported by this module) matches any single element of the message. +Either sends the given message, or call the given callback, after the +specified number of seconds. -While not required, it is highly recommended that the first matching -element is a string identifying the message. The one-string-only match is -also the most efficient match (by far). +This is simply a utility function that comes in handy at times - the +AnyEvent::MP author is not convinced of the wisdom of having it, though, +so it may go away in the future. =cut -sub rcv($@) { - my ($noderef, $port) = split /#/, shift, 2; +sub after($@) { + my ($timeout, @action) = @_; - ($NODE{$noderef} || add_node $noderef) == $NODE{""} - or Carp::croak "$noderef#$port: rcv can only be called on local ports, caught"; + my $t; $t = AE::timer $timeout, 0, sub { + undef $t; + ref $action[0] + ? $action[0]() + : snd @action; + }; +} - my $self = $PORT_DATA{$port} - or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught"; +=item cal $port, @msg, $callback[, $timeout] - "AnyEvent::MP::Port" eq ref $self - or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught"; +A simple form of RPC - sends a message to the given C<$port> with the +given contents (C<@msg>), but adds a reply port to the message. - while (@_) { - my ($match, $cb) = splice @_, 0, 2; +The reply port is created temporarily just for the purpose of receiving +the reply, and will be Ced when no longer needed. - if (!ref $match) { - push @{ $self->{rc0}{$match} }, [$cb]; - } elsif (("ARRAY" eq ref $match && !ref $match->[0])) { - my ($type, @match) = @$match; - @match - ? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match] - : push @{ $self->{rc0}{$match->[0]} }, [$cb]; - } else { - push @{ $self->{any} }, [$cb, $match]; - } - } -} +A reply message sent to the port is passed to the C<$callback> as-is. -=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 -callbacks, i.e. runtime errors will cause the port to get Ced. +If an optional time-out (in seconds) is given and it is not C, +then the callback will be called without any arguments after the time-out +elapsed and the port is Ced. -This is useful when you register callbacks from C callbacks: +If no time-out is given (or it is C), then the local port will +monitor the remote port instead, so it eventually gets cleaned-up. - rcv delayed_reply => sub { - my ($delay, @reply) = @_; - my $timer = AE::timer $delay, 0, psub { - snd @reply, $SELF; - }; - }; +Currently this function returns the temporary port, but this "feature" +might go in future versions unless you can make a convincing case that +this is indeed useful for something. =cut -sub psub(&) { - my $cb = shift; +sub cal(@) { + my $timeout = ref $_[-1] ? undef : pop; + my $cb = pop; + + my $port = port { + undef $timeout; + kil $SELF; + &$cb; + }; - my $port = $SELF - or Carp::croak "psub can only be called from within rcv or psub callbacks, not"; + if (defined $timeout) { + $timeout = AE::timer $timeout, 0, sub { + undef $timeout; + kil $port; + $cb->(); + }; + } else { + mon $_[0], sub { + kil $port; + $cb->(); + }; + } - sub { - local $SELF = $port; + push @_, $port; + &snd; - if (wantarray) { - my @res = eval { &$cb }; - _self_die if $@; - @res - } else { - my $res = eval { &$cb }; - _self_die if $@; - $res - } - } + $port } =back -=head1 FUNCTIONS FOR NODES +=head1 AnyEvent::MP vs. Distributed Erlang + +AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node +== aemp node, Erlang process == aemp port), so many of the documents and +programming techniques employed by Erlang apply to AnyEvent::MP. Here is a +sample: + + http://www.erlang.se/doc/programming_rules.shtml + http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4 + http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6 + http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5 + +Despite the similarities, there are also some important differences: =over 4 -=item become_public endpoint... +=item * Node IDs are arbitrary strings in AEMP. -Tells the node to become a public node, i.e. reachable from other nodes. +Erlang relies on special naming and DNS to work everywhere in the same +way. AEMP relies on each node somehow knowing its own address(es) (e.g. by +configuration or DNS), and possibly the addresses of some seed nodes, but +will otherwise discover other nodes (and their IDs) itself. -If no arguments are given, or the first argument is C, then -AnyEvent::MP tries to bind on port C<4040> on all IP addresses that the -local nodename resolves to. - -Otherwise the first argument must be an array-reference with transport -endpoints ("ip:port", "hostname:port") or port numbers (in which case the -local nodename is used as hostname). The endpoints are all resolved and -will become the node reference. +=item * Erlang has a "remote ports are like local ports" philosophy, AEMP +uses "local ports are like remote ports". -=cut +The failure modes for local ports are quite different (runtime errors +only) then for remote ports - when a local port dies, you I it dies, +when a connection to another node dies, you know nothing about the other +port. -=back +Erlang pretends remote ports are as reliable as local ports, even when +they are not. -=head1 NODE MESSAGES +AEMP encourages a "treat remote ports differently" philosophy, with local +ports being the special case/exception, where transport errors cannot +occur. -Nodes understand the following messages sent to them. Many of them take -arguments called C<@reply>, which will simply be used to compose a reply -message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and -the remaining arguments are simply the message data. +=item * Erlang uses processes and a mailbox, AEMP does not queue. -=over 4 +Erlang uses processes that selectively receive messages, and therefore +needs a queue. AEMP is event based, queuing messages would serve no +useful purpose. For the same reason the pattern-matching abilities of +AnyEvent::MP are more limited, as there is little need to be able to +filter messages without dequeuing them. -=cut +(But see L for a more Erlang-like process model on top of AEMP). + +=item * Erlang sends are synchronous, AEMP sends are asynchronous. + +Sending messages in Erlang is synchronous and blocks the process (and +so does not need a queue that can overflow). AEMP sends are immediate, +connection establishment is handled in the background. + +=item * Erlang suffers from silent message loss, AEMP does not. -=item lookup => $name, @reply +Erlang implements few guarantees on messages delivery - messages can get +lost without any of the processes realising it (i.e. you send messages a, +b, and c, and the other side only receives messages a and c). -Replies with the port ID of the specified well-known port, or C. +AEMP guarantees correct ordering, and the guarantee that after one message +is lost, all following ones sent to the same port are lost as well, until +monitoring raises an error, so there are no silent "holes" in the message +sequence. -=item devnull => ... +=item * Erlang can send messages to the wrong port, AEMP does not. -Generic data sink/CPU heat conversion. +In Erlang it is quite likely that a node that restarts reuses a process ID +known to other nodes for a completely different process, causing messages +destined for that process to end up in an unrelated process. -=item relay => $port, @msg +AEMP never reuses port IDs, so old messages or old port IDs floating +around in the network will not be sent to an unrelated port. -Simply forwards the message to the given port. +=item * Erlang uses unprotected connections, AEMP uses secure +authentication and can use TLS. -=item eval => $string[ @reply] +AEMP can use a proven protocol - TLS - to protect connections and +securely authenticate nodes. -Evaluates the given string. If C<@reply> is given, then a message of the -form C<@reply, $@, @evalres> is sent. +=item * The AEMP protocol is optimised for both text-based and binary +communications. -Example: crash another node. +The AEMP protocol, unlike the Erlang protocol, supports both programming +language independent text-only protocols (good for debugging) and binary, +language-specific serialisers (e.g. Storable). By default, unless TLS is +used, the protocol is actually completely text-based. - snd $othernode, eval => "exit"; +It has also been carefully designed to be implementable in other languages +with a minimum of work while gracefully degrading functionality to make the +protocol simple. -=item time => @reply +=item * AEMP has more flexible monitoring options than Erlang. -Replies the the current node time to C<@reply>. +In Erlang, you can chose to receive I exit signals as messages +or I, there is no in-between, so monitoring single processes is +difficult to implement. Monitoring in AEMP is more flexible than in +Erlang, as one can choose between automatic kill, exit message or callback +on a per-process basis. -Example: tell the current node to send the current time to C<$myport> in a -C message. +=item * Erlang tries to hide remote/local connections, AEMP does not. - snd $NODE, time => $myport, timereply => 1, 2; - # => snd $myport, timereply => 1, 2,