--- AnyEvent-MP/MP.pm 2009/08/05 19:58:46 1.32 +++ AnyEvent-MP/MP.pm 2012/03/23 21:16:25 1.144 @@ -1,43 +1,76 @@ =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 = @_ }; - rcv $port, smartmatch => $cb->($port, @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) - # 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 + # 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. +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 @@ -45,42 +78,100 @@ =item port -A port is something you can send messages to (with the C function). +Not to be confused with a TCP port, a "port" is something you can send +messages to (with the C function). + +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. -Some ports allow you to register C handlers that can match specific -messages. All C handlers will receive messages they match, messages -will not be queued. - -=item port id - C - -A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as -separator, and a port name (a printable string of unspecified format). An -exception is the the node port, whose ID is identical to its node -reference. +Ports are represented by (printable) strings called "port IDs". + +=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 created by AnyEvent::MP). =item node -A node is a single process containing at least one port - the node -port. You can send messages to node ports to find existing ports or to -create new ports, among other things. +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". + +=item node ID - C<[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 except to uniquely identify a node. + +=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. -Nodes are either private (single-process only), slaves (connected to a -master node only) or public nodes (connectable from unrelated nodes). +Currently, only standard C specifications can be used, which +specify TCP ports to listen on. So a bind is basically just a tcp socket +in listening mode thta accepts conenctions form other nodes. -=item noderef - C, C, C +=item seed nodes -A node reference is a string that either simply identifies the node (for -private and slave nodes), or contains a recipe on how to reach a given -node (for public nodes). +When a node starts, it knows nothing about the network it is in - it +needs to connect to at least one other node that is already in the +network. These other nodes are called "seed nodes". -This recipe is simply a comma-separated list of C pairs (for -TCP/IP, other protocols might look different). +Seed nodes themselves are not special - they are seed nodes only because +some other node I them as such, but any node can be used as seed +node for other nodes, and eahc node cna use a different set of seed nodes. -Node references come in two flavours: resolved (containing only numerical -addresses) or unresolved (where hostnames are used instead of addresses). +In addition to discovering the network, seed nodes are also used to +maintain the network - all nodes using the same seed node form are part of +the same network. If a network is split into multiple subnets because e.g. +the network link between the parts goes down, then using the same seed +nodes for all nodes ensures that eventually the subnets get merged again. -Before using an unresolved node reference in a message you first have to -resolve it. +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. + +For small networks, it's best if every node uses the same set of seed +nodes. For large networks, it can be useful to specify "regional" seed +nodes for most nodes in an area, and use all seed nodes as seed nodes for +each other. What's important is that all seed nodes connections form a +complete graph, so that the network cannot split into separate subnets +forever. + +Seed nodes are represented by seed IDs. + +=item seed IDs - C + +Seed IDs are transport endpoint(s) (usually a hostname/IP address and a +TCP port) of nodes that should be used as seed nodes. + +=item global nodes + +An AEMP network needs a discovery service - nodes need to know how to +connect to other nodes they only know by name. In addition, AEMP offers a +distributed "group database", which maps group names to a list of strings +- for example, to register worker ports. + +A network needs at least one global node to work, and allows every node to +be a global node. + +Any node that loads the L module becomes a global +node and tries to keep connections to all other nodes. So while it can +make sense to make every node "global" in small networks, it usually makes +sense to only make seed nodes into global nodes in large networks (nodes +keep connections to seed nodes and global nodes, so makign them the same +reduces overhead). =back @@ -92,22 +183,46 @@ package AnyEvent::MP; -use AnyEvent::MP::Base; +use AnyEvent::MP::Config (); +use AnyEvent::MP::Kernel; +use AnyEvent::MP::Kernel qw( + %NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID + add_node load_func + + NODE $NODE + configure + node_of port_is_local + snd kil + db_set db_del + db_mon db_family db_keys db_values +); use common::sense; use Carp (); -use AE (); +use AnyEvent (); +use Guard (); use base "Exporter"; -our $VERSION = '0.1'; +our $VERSION = $AnyEvent::MP::Config::VERSION; + our @EXPORT = qw( - NODE $NODE *SELF node_of _any_ - resolve_node initialise_node - snd rcv mon kil reg psub - port + NODE $NODE + configure + node_of port_is_local + snd kil + db_set db_del + db_mon db_family db_keys db_values + + *SELF + + port rcv mon mon_guard psub peval spawn cal + db_set db_del db_reg + db_mon db_family db_keys db_values + + after ); our $SELF; @@ -120,234 +235,345 @@ =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 -=item $noderef = node_of $portid +Extracts and returns the node ID from a port ID or a node ID. -Extracts and returns the noderef from a portid or a noderef. +=item $is_local = port_is_local $port -=item $cv = resolve_node $noderef +Returns true iff the port is a local port. -Takes an unresolved node reference that may contain hostnames and -abbreviated IDs, resolves all of them and returns a resolved node -reference. +=item configure $profile, key => value... -In addition to C pairs allowed in resolved noderefs, the -following forms are supported: +=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. + +This function configures a node - it must be called exactly once (or +never) before calling other AnyEvent::MP functions. + +The key/value pairs are basically the same ones as documented for the +F command line utility (sans the set/del prefix), with these additions: =over 4 -=item the empty string +=item norc => $boolean (default false) + +If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I +be consulted - all configuraiton options must be specified in the +C call. -An empty-string component gets resolved as if the default port (4040) was -specified. +=item force => $boolean (default false) -=item naked port numbers (e.g. C<1234>) +IF true, then the values specified in the C will take +precedence over any values configured via the rc file. The default is for +the rc file to override any options specified in the program. -These are resolved by prepending the local nodename and a colon, to be -further resolved. +=back + +=over 4 -=item hostnames (e.g. C, C) +=item step 1, gathering configuration from profiles -These are resolved by using AnyEvent::DNS to resolve them, optionally -looking up SRV records for the C port, if no port was -specified. +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, with +a unique randoms tring (C) 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 commandline +utility uses C as nodename, which might expand to +C. + +=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 seed ID 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 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 $SELF Contains the current port id while executing C callbacks or C blocks. -=item SELF, %SELF, @SELF... +=item *SELF, SELF, %SELF, @SELF... Due to some quirks in how perl exports variables, it is impossible to -just export C<$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 $local_port = port -Create a new local port object that can be used either as a pattern -matching port ("full port") or a single-callback port ("miniport"), -depending on how C callbacks are bound to the object. +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 $portid = port { my @msg = @_; $finished } +=item $local_port = port { my @msg = @_ } -Creates a "mini port", that is, a very lightweight port without any -pattern matching behind it, and returns its ID. +Creates a new local port, and returns its ID. Semantically the same as +creating a port and calling C on it. -The block will be called for every message received on the port. When the -callback returns a true value its job is considered "done" and the port -will be destroyed. Otherwise it will stay alive. +The block will be called for every message received on the port, with the +global variable C<$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. -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 it: -If you need the local port id in the callback, this works nicely: - - my $port; $port = port { - snd $otherport, reply => $port; + 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 $id = $UNIQ . ++$ID; my $port = "$NODE#$id"; - 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 $@; - }; - } + rcv $port, shift || $KILME; $port } -=item reg $portid, $name +=item rcv $local_port, $callback->(@msg) -Registers the given port under the name C<$name>. If the name already -exists it is replaced. +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. -A port can only be registered under one well known name. +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. -A port automatically becomes unregistered when it is killed. +The default callback receives all messages not matched by a more specific +C match. -=cut +=item rcv $local_port, tag => $callback->(@msg_without_tag), ... -sub reg(@) { - my ($portid, $name) = @_; +Register (or replace) callbacks to be called on messages starting with the +given tag on the given port (and return the port), or unregister it (when +C<$callback> is C<$undef> or missing). There can only be one callback +registered for each tag. - $REG{$name} = $portid; -} +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). -=item rcv $portid, $callback->(@msg) +Example: create a port and bind receivers on it in one go. -Replaces the callback on the specified miniport (or newly created port -object, see C). Full ports are configured with the following calls: + my $port = rcv port, + msg1 => sub { ... }, + msg2 => sub { ... }, + ; -=item rcv $portid, tagstring => $callback->(@msg), ... +Example: create a port, bind receivers and send it in a message elsewhere +in one go: -=item rcv $portid, $smartmatch => $callback->(@msg), ... + snd $otherport, reply => + rcv port, + msg1 => sub { ... }, + ... + ; -=item rcv $portid, [$smartmatch...] => $callback->(@msg), ... +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. -Register callbacks to be called on matching messages on the given full -port (or newly created port). + rcv $port, $otherport => sub { + my @reply = @_; -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. + rcv $SELF, $otherport; + }; -The global C<$SELF> (exported by this module) contains C<$portid> while -executing the callback. +=cut -Runtime errors wdurign callback execution will result in the port being -Ced. +sub rcv($@) { + my $port = shift; + my ($nodeid, $portid) = split /#/, $port, 2; -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. + $nodeid eq $NODE + or Carp::croak "$port: rcv can only be called on local ports, caught"; -Any element in the match that is specified as C<_any_> (a function -exported by this module) matches any single element of the message. + 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] }; + } + }; -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). + $self + }; -=cut + "AnyEvent::MP::Port" eq ref $self + or Carp::croak "$port: rcv can only be called on message matching ports, caught"; -sub rcv($@) { - my $portid = shift; - my ($noderef, $port) = split /#/, $port, 2; + my ($tag, $cb) = splice @_, 0, 2; - ($NODE{$noderef} || add_node $noderef) == $NODE{""} - or Carp::croak "$noderef#$port: rcv can only be called on local ports, caught"; + if (defined $cb) { + $self->[1]{$tag} = $cb; + } else { + delete $self->[1]{$tag}; + } + } + } - my $self = $PORT_DATA{$port} - or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught"; + $port +} - "AnyEvent::MP::Port" eq ref $self - or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught"; +=item peval $port, $coderef[, @args] - while (@_) { - my ($match, $cb) = splice @_, 0, 2; +Evaluates the given C<$codref> within the contetx of C<$port>, that is, +when the code throews an exception the C<$port> will be killed. - 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]; - } - } +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; - $portid + if (wantarray) { + my @res = eval { &$cb }; + _self_die if $@; + @res + } else { + my $res = eval { &$cb }; + _self_die if $@; + $res + } } =item $closure = psub { BLOCK } @@ -356,6 +582,9 @@ 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 { @@ -388,24 +617,67 @@ } } -=item $guard = mon $portid, $cb->(@reason) +=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: -=item $guard = mon $portid, $otherport +In the first form (another port given), if the C<$port> is C'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. -=item $guard = mon $portid, $otherport, @msg +The second form (kill self) is the same as the first form, except that +C<$rvport> defaults to C<$SELF>. -Monitor the given port and do something when the port is killed. +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 first form, the callback is simply called with any number -of C<@reason> elements (no @reason means that the port was deleted +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 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 (message), a message of the form C<$rcvport, @msg, +@reason> will be C. -In the last form, 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, 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. + +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. @@ -413,20 +685,20 @@ 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) = split /#/, shift, 2; + my ($nodeid, $port) = split /#/, shift, 2; - my $node = $NODE{$noderef} || add_node $noderef; + my $node = $NODE{$nodeid} || add_node $nodeid; - my $cb = shift; + my $cb = @_ ? shift : $SELF || Carp::croak 'mon: called with one argument only, but $SELF not set,'; unless (ref $cb) { if (@_) { @@ -443,7 +715,7 @@ $node->monitor ($port, $cb); defined wantarray - and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) } + and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) }) } =item $guard = mon_guard $port, $ref, $ref... @@ -454,10 +726,10 @@ 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; }); }); @@ -467,28 +739,21 @@ sub mon_guard { my ($port, @refs) = @_; + #TODO: mon-less form? + mon $port, sub { 0 && @refs } } -=item lnk $port1, $port2 - -Link two ports. This is simply a shorthand for: - - mon $port1, $port2; - mon $port2, $port1; - -It means that if either one is killed abnormally, the other one gets -killed as well. - -=item kil $portid[, @reason] +=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" (linked -ports will not be kileld, or even notified). +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. -Otherwise, linked ports get killed with the same reason (second form of -C, see below). +If a C<@reason> is specified, then linked ports (C +form) get killed with the same reason. Runtime errors while evaluating C callbacks or inside C blocks will be reported as reason C<< die => $@ >>. @@ -496,78 +761,362 @@ Transport/communication errors are reported as C<< transport_error => $message >>. -=back +Common idioms: -=head1 FUNCTIONS FOR NODES + # silently remove yourself, do not kill linked ports + kil $SELF; -=over 4 + # report a failure in some detail + kil $SELF, failure_mode_1 => "it failed with too high temperature"; -=item become_public $noderef + # do not waste much time with killing, just die when something goes wrong + open my $fh, " (which can also be a port ID, in which +case it's the node where that port resides). -It is quite common to not specify anything, in which case the local node -tries to listen on the default port, or to only specify a port number, in -which case AnyEvent::MP tries to guess the local addresses. +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 callback. This function must be a +fully-qualified function name (e.g. C). To +specify a function in the main program, use C<::name>. + +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. + +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. + +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 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). + +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 + +Either sends the given message, or call the given callback, after the +specified number of seconds. + +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 after($@) { + my ($timeout, @action) = @_; + + my $t; $t = AE::timer $timeout, 0, sub { + undef $t; + ref $action[0] + ? $action[0]() + : snd @action; + }; +} + +#=item $cb2 = timeout $seconds, $cb[, @args] + +=item cal $port, @msg, $callback[, $timeout] + +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. + +The reply port is created temporarily just for the purpose of receiving +the reply, and will be Ced when no longer needed. + +A reply message sent to the port is passed to the C<$callback> as-is. + +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. + +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. + +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 cal(@) { + my $timeout = ref $_[-1] ? undef : pop; + my $cb = pop; + + my $port = port { + undef $timeout; + kil $SELF; + &$cb; + }; + + if (defined $timeout) { + $timeout = AE::timer $timeout, 0, sub { + undef $timeout; + kil $port; + $cb->(); + }; + } else { + mon $_[0], sub { + kil $port; + $cb->(); + }; + } + + push @_, $port; + &snd; + + $port +} + =back -=head1 NODE MESSAGES +=head1 DISTRIBUTED DATABASE -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. +AnyEvent::MP comes with a simple distributed database. The database will +be mirrored asynchronously on all global nodes. Other nodes bind to one +of the global nodes for their needs. Every node has a "local database" +which contains all the values that are set locally. All local databases +are merged together to form the global database, which can be queried. -While other messages exist, they are not public and subject to change. +The database structure is that of a two-level hash - the database hash +contains hashes which contain values, similarly to a perl hash of hashes, +i.e.: -=over 4 + $DATABASE{$family}{$subkey} = $value + +The top level hash key is called "family", and the second-level hash key +is called "subkey" or simply "key". + +The family must be alphanumeric, i.e. start with a letter and consist +of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>, +pretty much like Perl module names. + +As the family namespace is global, it is recommended to prefix family names +with the name of the application or module using it. + +The subkeys must be non-empty strings, with no further restrictions. + +The values should preferably be strings, but other perl scalars should +work as well (such as C, arrays and hashes). + +Every database entry is owned by one node - adding the same family/subkey +combination on multiple nodes will not cause discomfort for AnyEvent::MP, +but the result might be nondeterministic, i.e. the key might have +different values on different nodes. + +Different subkeys in the same family can be owned by different nodes +without problems, and in fact, this is the common method to create worker +pools. For example, a worker port for image scaling might do this: + + db_set my_image_scalers => $port; + +And clients looking for an image scaler will want to get the +C keys from time to time: + + db_keys my_image_scalers => sub { + @ports = @{ $_[0] }; + }; + +Or better yet, they want to monitor the database family, so they always +have a reasonable up-to-date copy: + + db_mon my_image_scalers => sub { + @ports = keys %{ $_[0] }; + }; + +In general, you can set or delete single subkeys, but query and monitor +whole families only. + +If you feel the need to monitor or query a single subkey, try giving it +it's own family. + +=over + +=item $guard = db_set $family => $subkey [=> $value] + +Sets (or replaces) a key to the database - if C<$value> is omitted, +C is used instead. + +When called in non-void context, C returns a guard that +automatically calls C when it is destroyed. + +=item db_del $family => $subkey... + +Deletes one or more subkeys from the database family. + +=item $guard = db_reg $family => $port => $value + +=item $guard = db_reg $family => $port + +=item $guard = db_reg $family + +Registers a port in the given family and optionally returns a guard to +remove it. + +This function basically does the same as: + + db_set $family => $port => $value + +Except that the port is monitored and automatically removed from the +database family when it is kil'ed. + +If C<$value> is missing, C is used. If C<$port> is missing, then +C<$SELF> is used. + +This function is most useful to register a port in some port group (which +is just another name for a database family), and have it removed when the +port is gone. This works best when the port is a local port. =cut -=item lookup => $name, @reply +sub db_reg($$;$) { + my $family = shift; + my $port = @_ ? shift : $SELF; + + my $clr = sub { db_del $family => $port }; + mon $port, $clr; + + db_set $family => $port => $_[0]; + + defined wantarray + and &Guard::guard ($clr) +} + +=item db_family $family => $cb->(\%familyhash) -Replies with the port ID of the specified well-known port, or C. +Queries the named database C<$family> and call the callback with the +family represented as a hash. You can keep and freely modify the hash. -=item devnull => ... +=item db_keys $family => $cb->(\@keys) -Generic data sink/CPU heat conversion. +Same as C, except it only queries the family I and passes +them as array reference to the callback. -=item relay => $port, @msg +=item db_values $family => $cb->(\@values) -Simply forwards the message to the given port. +Same as C, except it only queries the family I and passes them +as array reference to the callback. -=item eval => $string[ @reply] +=item $guard = db_mon $family => $cb->(\%familyhash, \@added, \@changed, \@deleted) -Evaluates the given string. If C<@reply> is given, then a message of the -form C<@reply, $@, @evalres> is sent. +Creates a monitor on the given database family. Each time a key is set +or or is deleted the callback is called with a hash containing the +database family and three lists of added, changed and deleted subkeys, +respectively. If no keys have changed then the array reference might be +C or even missing. -Example: crash another node. +If not called in void context, a guard object is returned that, when +destroyed, stops the monitor. - snd $othernode, eval => "exit"; +The family hash reference and the key arrays belong to AnyEvent::MP and +B by the callback. When in doubt, make a +copy. -=item time => @reply +As soon as possible after the monitoring starts, the callback will be +called with the intiial contents of the family, even if it is empty, +i.e. there will always be a timely call to the callback with the current +contents. -Replies the the current node time to C<@reply>. +It is possible that the callback is called with a change event even though +the subkey is already present and the value has not changed. -Example: tell the current node to send the current time to C<$myport> in a -C message. +The monitoring stops when the guard object is destroyed. - snd $NODE, time => $myport, timereply => 1, 2; - # => snd $myport, timereply => 1, 2,