… | |
… | |
11 | NODE $port # returns the noderef of the port |
11 | NODE $port # returns the noderef of the port |
12 | |
12 | |
13 | $SELF # receiving/own port id in rcv callbacks |
13 | $SELF # receiving/own port id in rcv callbacks |
14 | |
14 | |
15 | # initialise the node so it can send/receive messages |
15 | # initialise the node so it can send/receive messages |
16 | initialise_node; # -OR- |
16 | initialise_node; |
17 | initialise_node "localhost:4040"; # -OR- |
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18 | initialise_node "slave/", "localhost:4040" |
|
|
19 | |
17 | |
20 | # ports are message endpoints |
18 | # ports are message endpoints |
21 | |
19 | |
22 | # sending messages |
20 | # sending messages |
23 | snd $port, type => data...; |
21 | snd $port, type => data...; |
… | |
… | |
70 | =item port |
68 | =item port |
71 | |
69 | |
72 | A port is something you can send messages to (with the C<snd> function). |
70 | A port is something you can send messages to (with the C<snd> function). |
73 | |
71 | |
74 | Ports allow you to register C<rcv> handlers that can match all or just |
72 | Ports allow you to register C<rcv> handlers that can match all or just |
75 | some messages. Messages will not be queued. |
73 | some messages. Messages send to ports will not be queued, regardless of |
|
|
74 | anything was listening for them or not. |
76 | |
75 | |
77 | =item port id - C<noderef#portname> |
76 | =item port ID - C<noderef#portname> |
78 | |
77 | |
79 | A port ID is the concatenation of a noderef, a hash-mark (C<#>) as |
78 | A port ID is the concatenation of a noderef, a hash-mark (C<#>) as |
80 | separator, and a port name (a printable string of unspecified format). An |
79 | separator, and a port name (a printable string of unspecified format). An |
81 | exception is the the node port, whose ID is identical to its node |
80 | exception is the the node port, whose ID is identical to its node |
82 | reference. |
81 | reference. |
… | |
… | |
85 | |
84 | |
86 | A node is a single process containing at least one port - the node port, |
85 | A node is a single process containing at least one port - the node port, |
87 | which provides nodes to manage each other remotely, and to create new |
86 | which provides nodes to manage each other remotely, and to create new |
88 | ports. |
87 | ports. |
89 | |
88 | |
90 | Nodes are either private (single-process only), slaves (connected to a |
89 | Nodes are either private (single-process only), slaves (can only talk to |
91 | master node only) or public nodes (connectable from unrelated nodes). |
90 | public nodes, but do not need an open port) or public nodes (connectable |
|
|
91 | from any other node). |
92 | |
92 | |
93 | =item noderef - C<host:port,host:port...>, C<id@noderef>, C<id> |
93 | =item node ID - C<[a-za-Z0-9_\-.:]+> |
94 | |
94 | |
95 | A node reference is a string that either simply identifies the node (for |
95 | A node ID is a string that uniquely identifies the node within a |
96 | private and slave nodes), or contains a recipe on how to reach a given |
96 | network. Depending on the configuration used, node IDs can look like a |
97 | node (for public nodes). |
97 | hostname, a hostname and a port, or a random string. AnyEvent::MP itself |
|
|
98 | doesn't interpret node IDs in any way. |
98 | |
99 | |
99 | This recipe is simply a comma-separated list of C<address:port> pairs (for |
100 | =item binds - C<ip:port> |
100 | TCP/IP, other protocols might look different). |
|
|
101 | |
101 | |
102 | Node references come in two flavours: resolved (containing only numerical |
102 | Nodes can only talk to each other by creating some kind of connection to |
103 | addresses) or unresolved (where hostnames are used instead of addresses). |
103 | each other. To do this, nodes should listen on one or more local transport |
|
|
104 | endpoints - binds. Currently, only standard C<ip:port> specifications can |
|
|
105 | be used, which specify TCP ports to listen on. |
104 | |
106 | |
105 | Before using an unresolved node reference in a message you first have to |
107 | =item seeds - C<host:port> |
106 | resolve it. |
108 | |
|
|
109 | When a node starts, it knows nothing about the network. To teach the node |
|
|
110 | about the network it first has to contact some other node within the |
|
|
111 | network. This node is called a seed. |
|
|
112 | |
|
|
113 | Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes |
|
|
114 | are expected to be long-running, and at least one of those should always |
|
|
115 | be available. When nodes run out of connections (e.g. due to a network |
|
|
116 | error), they try to re-establish connections to some seednodes again to |
|
|
117 | join the network. |
107 | |
118 | |
108 | =back |
119 | =back |
109 | |
120 | |
110 | =head1 VARIABLES/FUNCTIONS |
121 | =head1 VARIABLES/FUNCTIONS |
111 | |
122 | |
… | |
… | |
126 | use base "Exporter"; |
137 | use base "Exporter"; |
127 | |
138 | |
128 | our $VERSION = $AnyEvent::MP::Kernel::VERSION; |
139 | our $VERSION = $AnyEvent::MP::Kernel::VERSION; |
129 | |
140 | |
130 | our @EXPORT = qw( |
141 | our @EXPORT = qw( |
131 | NODE $NODE *SELF node_of _any_ |
142 | NODE $NODE *SELF node_of after |
132 | resolve_node initialise_node |
143 | resolve_node initialise_node |
133 | snd rcv mon kil reg psub spawn |
144 | snd rcv mon mon_guard kil reg psub spawn |
134 | port |
145 | port |
135 | ); |
146 | ); |
136 | |
147 | |
137 | our $SELF; |
148 | our $SELF; |
138 | |
149 | |
… | |
… | |
142 | kil $SELF, die => $msg; |
153 | kil $SELF, die => $msg; |
143 | } |
154 | } |
144 | |
155 | |
145 | =item $thisnode = NODE / $NODE |
156 | =item $thisnode = NODE / $NODE |
146 | |
157 | |
147 | The C<NODE> function returns, and the C<$NODE> variable contains the |
158 | The C<NODE> function returns, and the C<$NODE> variable contains the node |
148 | noderef of the local node. The value is initialised by a call to |
159 | ID of the node running in the current process. This value is initialised by |
149 | C<initialise_node>. |
160 | a call to C<initialise_node>. |
150 | |
161 | |
151 | =item $noderef = node_of $port |
162 | =item $nodeid = node_of $port |
152 | |
163 | |
153 | Extracts and returns the noderef from a port ID or a noderef. |
164 | Extracts and returns the node ID part from a port ID or a node ID. |
154 | |
165 | |
155 | =item initialise_node $noderef, $seednode, $seednode... |
166 | =item initialise_node $profile_name |
156 | |
167 | |
157 | =item initialise_node "slave/", $master, $master... |
|
|
158 | |
|
|
159 | Before a node can talk to other nodes on the network it has to initialise |
168 | Before a node can talk to other nodes on the network (i.e. enter |
160 | itself - the minimum a node needs to know is it's own name, and optionally |
169 | "distributed mode") it has to initialise itself - the minimum a node needs |
161 | it should know the noderefs of some other nodes in the network. |
170 | to know is its own name, and optionally it should know the addresses of |
|
|
171 | some other nodes in the network to discover other nodes. |
162 | |
172 | |
163 | This function initialises a node - it must be called exactly once (or |
173 | This function initialises a node - it must be called exactly once (or |
164 | never) before calling other AnyEvent::MP functions. |
174 | never) before calling other AnyEvent::MP functions. |
165 | |
175 | |
166 | All arguments (optionally except for the first) are noderefs, which can be |
176 | The first argument is a profile name. If it is C<undef> or missing, then |
167 | either resolved or unresolved. |
177 | the current nodename will be used instead (i.e. F<uname -n>). |
168 | |
178 | |
169 | The first argument will be looked up in the configuration database first |
179 | The function then looks up the profile in the aemp configuration (see the |
170 | (if it is C<undef> then the current nodename will be used instead) to find |
180 | L<aemp> commandline utility). |
171 | the relevant configuration profile (see L<aemp>). If none is found then |
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172 | the default configuration is used. The configuration supplies additional |
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|
173 | seed/master nodes and can override the actual noderef. |
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174 | |
181 | |
175 | There are two types of networked nodes, public nodes and slave nodes: |
182 | If the profile specifies a node ID, then this will become the node ID of |
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|
183 | this process. If not, then the profile name will be used as node ID. The |
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|
184 | special node ID of C<anon/> will be replaced by a random node ID. |
176 | |
185 | |
177 | =over 4 |
186 | The next step is to look up the binds in the profile, followed by binding |
|
|
187 | aemp protocol listeners on all binds specified (it is possible and valid |
|
|
188 | to have no binds, meaning that the node cannot be contacted form the |
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|
189 | outside. This means the node cannot talk to other nodes that also have no |
|
|
190 | binds, but it can still talk to all "normal" nodes). |
178 | |
191 | |
179 | =item public nodes |
192 | If the profile does not specify a binds list, then the node ID will be |
|
|
193 | treated as if it were of the form C<host:port>, which will be resolved and |
|
|
194 | used as binds list. |
180 | |
195 | |
181 | For public nodes, C<$noderef> (supplied either directly to |
196 | Lastly, the seeds list from the profile is passed to the |
182 | C<initialise_node> or indirectly via a profile or the nodename) must be a |
197 | L<AnyEvent::MP::Global> module, which will then use it to keep |
183 | noderef (possibly unresolved, in which case it will be resolved). |
198 | connectivity with at least on of those seed nodes at any point in time. |
184 | |
199 | |
185 | After resolving, the node will bind itself on all endpoints and try to |
|
|
186 | connect to all additional C<$seednodes> that are specified. Seednodes are |
|
|
187 | optional and can be used to quickly bootstrap the node into an existing |
|
|
188 | network. |
|
|
189 | |
|
|
190 | =item slave nodes |
|
|
191 | |
|
|
192 | When the C<$noderef> (either as given or overriden by the config file) |
|
|
193 | is the special string C<slave/>, then the node will become a slave |
|
|
194 | node. Slave nodes cannot be contacted from outside and will route most of |
|
|
195 | their traffic to the master node that they attach to. |
|
|
196 | |
|
|
197 | At least one additional noderef is required (either by specifying it |
|
|
198 | directly or because it is part of the configuration profile): The node |
|
|
199 | will try to connect to all of them and will become a slave attached to the |
|
|
200 | first node it can successfully connect to. |
|
|
201 | |
|
|
202 | Note that slave nodes cannot change their name, and consequently, their |
|
|
203 | master, so if the master goes down, the slave node will not function well |
|
|
204 | anymore until it can re-establish conenciton to its master. This makes |
|
|
205 | slave nodes unsuitable for long-term nodes or fault-tolerant networks. |
|
|
206 | |
|
|
207 | =back |
|
|
208 | |
|
|
209 | This function will block until all nodes have been resolved and, for slave |
|
|
210 | nodes, until it has successfully established a connection to a master |
|
|
211 | server. |
|
|
212 | |
|
|
213 | All the seednodes will also be specially marked to automatically retry |
|
|
214 | connecting to them infinitely. |
|
|
215 | |
|
|
216 | Example: become a public node listening on the guessed noderef, or the one |
200 | Example: become a distributed node listening on the guessed noderef, or |
217 | specified via C<aemp> for the current node. This should be the most common |
201 | the one specified via C<aemp> for the current node. This should be the |
218 | form of invocation for "daemon"-type nodes. |
202 | most common form of invocation for "daemon"-type nodes. |
219 | |
203 | |
220 | initialise_node; |
204 | initialise_node; |
221 | |
205 | |
222 | Example: become a slave node to any of the the seednodes specified via |
206 | Example: become an anonymous node. This form is often used for commandline |
223 | C<aemp>. This form is often used for commandline clients. |
207 | clients. |
224 | |
208 | |
225 | initialise_node "slave/"; |
209 | initialise_node "anon/"; |
226 | |
210 | |
227 | Example: become a slave node to any of the specified master servers. This |
211 | Example: become a distributed node. If there is no profile of the given |
228 | form is also often used for commandline clients. |
212 | name, or no binds list was specified, resolve C<localhost:4044> and bind |
229 | |
213 | on the resulting addresses. |
230 | initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net"; |
|
|
231 | |
|
|
232 | Example: become a public node, and try to contact some well-known master |
|
|
233 | servers to become part of the network. |
|
|
234 | |
|
|
235 | initialise_node undef, "master1", "master2"; |
|
|
236 | |
|
|
237 | Example: become a public node listening on port C<4041>. |
|
|
238 | |
|
|
239 | initialise_node 4041; |
|
|
240 | |
|
|
241 | Example: become a public node, only visible on localhost port 4044. |
|
|
242 | |
214 | |
243 | initialise_node "localhost:4044"; |
215 | initialise_node "localhost:4044"; |
244 | |
|
|
245 | =item $cv = resolve_node $noderef |
|
|
246 | |
|
|
247 | Takes an unresolved node reference that may contain hostnames and |
|
|
248 | abbreviated IDs, resolves all of them and returns a resolved node |
|
|
249 | reference. |
|
|
250 | |
|
|
251 | In addition to C<address:port> pairs allowed in resolved noderefs, the |
|
|
252 | following forms are supported: |
|
|
253 | |
|
|
254 | =over 4 |
|
|
255 | |
|
|
256 | =item the empty string |
|
|
257 | |
|
|
258 | An empty-string component gets resolved as if the default port (4040) was |
|
|
259 | specified. |
|
|
260 | |
|
|
261 | =item naked port numbers (e.g. C<1234>) |
|
|
262 | |
|
|
263 | These are resolved by prepending the local nodename and a colon, to be |
|
|
264 | further resolved. |
|
|
265 | |
|
|
266 | =item hostnames (e.g. C<localhost:1234>, C<localhost>) |
|
|
267 | |
|
|
268 | These are resolved by using AnyEvent::DNS to resolve them, optionally |
|
|
269 | looking up SRV records for the C<aemp=4040> port, if no port was |
|
|
270 | specified. |
|
|
271 | |
|
|
272 | =back |
|
|
273 | |
216 | |
274 | =item $SELF |
217 | =item $SELF |
275 | |
218 | |
276 | Contains the current port id while executing C<rcv> callbacks or C<psub> |
219 | Contains the current port id while executing C<rcv> callbacks or C<psub> |
277 | blocks. |
220 | blocks. |
… | |
… | |
396 | |
339 | |
397 | sub rcv($@) { |
340 | sub rcv($@) { |
398 | my $port = shift; |
341 | my $port = shift; |
399 | my ($noderef, $portid) = split /#/, $port, 2; |
342 | my ($noderef, $portid) = split /#/, $port, 2; |
400 | |
343 | |
401 | ($NODE{$noderef} || add_node $noderef) == $NODE{""} |
344 | $NODE{$noderef} == $NODE{""} |
402 | or Carp::croak "$port: rcv can only be called on local ports, caught"; |
345 | or Carp::croak "$port: rcv can only be called on local ports, caught"; |
403 | |
346 | |
404 | while (@_) { |
347 | while (@_) { |
405 | if (ref $_[0]) { |
348 | if (ref $_[0]) { |
406 | if (my $self = $PORT_DATA{$portid}) { |
349 | if (my $self = $PORT_DATA{$portid}) { |
… | |
… | |
505 | message loss has been detected. No messages will be lost "in between" |
448 | message loss has been detected. No messages will be lost "in between" |
506 | (after the first lost message no further messages will be received by the |
449 | (after the first lost message no further messages will be received by the |
507 | port). After the monitoring action was invoked, further messages might get |
450 | port). After the monitoring action was invoked, further messages might get |
508 | delivered again. |
451 | delivered again. |
509 | |
452 | |
|
|
453 | Note that monitoring-actions are one-shot: once released, they are removed |
|
|
454 | and will not trigger again. |
|
|
455 | |
510 | In the first form (callback), the callback is simply called with any |
456 | In the first form (callback), the callback is simply called with any |
511 | number of C<@reason> elements (no @reason means that the port was deleted |
457 | number of C<@reason> elements (no @reason means that the port was deleted |
512 | "normally"). Note also that I<< the callback B<must> never die >>, so use |
458 | "normally"). Note also that I<< the callback B<must> never die >>, so use |
513 | C<eval> if unsure. |
459 | C<eval> if unsure. |
514 | |
460 | |
… | |
… | |
679 | snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_; |
625 | snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_; |
680 | |
626 | |
681 | "$noderef#$id" |
627 | "$noderef#$id" |
682 | } |
628 | } |
683 | |
629 | |
|
|
630 | =item after $timeout, @msg |
|
|
631 | |
|
|
632 | =item after $timeout, $callback |
|
|
633 | |
|
|
634 | Either sends the given message, or call the given callback, after the |
|
|
635 | specified number of seconds. |
|
|
636 | |
|
|
637 | This is simply a utility function that come sin handy at times. |
|
|
638 | |
|
|
639 | =cut |
|
|
640 | |
|
|
641 | sub after($@) { |
|
|
642 | my ($timeout, @action) = @_; |
|
|
643 | |
|
|
644 | my $t; $t = AE::timer $timeout, 0, sub { |
|
|
645 | undef $t; |
|
|
646 | ref $action[0] |
|
|
647 | ? $action[0]() |
|
|
648 | : snd @action; |
|
|
649 | }; |
|
|
650 | } |
|
|
651 | |
684 | =back |
652 | =back |
685 | |
653 | |
686 | =head1 AnyEvent::MP vs. Distributed Erlang |
654 | =head1 AnyEvent::MP vs. Distributed Erlang |
687 | |
655 | |
688 | AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node |
656 | AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node |
… | |
… | |
697 | |
665 | |
698 | Despite the similarities, there are also some important differences: |
666 | Despite the similarities, there are also some important differences: |
699 | |
667 | |
700 | =over 4 |
668 | =over 4 |
701 | |
669 | |
702 | =item * Node references contain the recipe on how to contact them. |
670 | =item * Node IDs are arbitrary strings in AEMP. |
703 | |
671 | |
704 | Erlang relies on special naming and DNS to work everywhere in the |
672 | Erlang relies on special naming and DNS to work everywhere in the same |
705 | same way. AEMP relies on each node knowing it's own address(es), with |
673 | way. AEMP relies on each node somehow knowing its own address(es) (e.g. by |
706 | convenience functionality. |
674 | configuraiton or DNS), but will otherwise discover other odes itself. |
707 | |
|
|
708 | This means that AEMP requires a less tightly controlled environment at the |
|
|
709 | cost of longer node references and a slightly higher management overhead. |
|
|
710 | |
675 | |
711 | =item * Erlang has a "remote ports are like local ports" philosophy, AEMP |
676 | =item * Erlang has a "remote ports are like local ports" philosophy, AEMP |
712 | uses "local ports are like remote ports". |
677 | uses "local ports are like remote ports". |
713 | |
678 | |
714 | The failure modes for local ports are quite different (runtime errors |
679 | The failure modes for local ports are quite different (runtime errors |
… | |
… | |
743 | |
708 | |
744 | Erlang makes few guarantees on messages delivery - messages can get lost |
709 | Erlang makes few guarantees on messages delivery - messages can get lost |
745 | without any of the processes realising it (i.e. you send messages a, b, |
710 | without any of the processes realising it (i.e. you send messages a, b, |
746 | and c, and the other side only receives messages a and c). |
711 | and c, and the other side only receives messages a and c). |
747 | |
712 | |
748 | AEMP guarantees correct ordering, and the guarantee that there are no |
713 | AEMP guarantees correct ordering, and the guarantee that after one message |
749 | holes in the message sequence. |
714 | is lost, all following ones sent to the same port are lost as well, until |
750 | |
715 | monitoring raises an error, so there are no silent "holes" in the message |
751 | =item * In Erlang, processes can be declared dead and later be found to be |
716 | sequence. |
752 | alive. |
|
|
753 | |
|
|
754 | In Erlang it can happen that a monitored process is declared dead and |
|
|
755 | linked processes get killed, but later it turns out that the process is |
|
|
756 | still alive - and can receive messages. |
|
|
757 | |
|
|
758 | In AEMP, when port monitoring detects a port as dead, then that port will |
|
|
759 | eventually be killed - it cannot happen that a node detects a port as dead |
|
|
760 | and then later sends messages to it, finding it is still alive. |
|
|
761 | |
717 | |
762 | =item * Erlang can send messages to the wrong port, AEMP does not. |
718 | =item * Erlang can send messages to the wrong port, AEMP does not. |
763 | |
719 | |
764 | In Erlang it is quite likely that a node that restarts reuses a process ID |
720 | In Erlang it is quite likely that a node that restarts reuses a process ID |
765 | known to other nodes for a completely different process, causing messages |
721 | known to other nodes for a completely different process, causing messages |
… | |
… | |
769 | around in the network will not be sent to an unrelated port. |
725 | around in the network will not be sent to an unrelated port. |
770 | |
726 | |
771 | =item * Erlang uses unprotected connections, AEMP uses secure |
727 | =item * Erlang uses unprotected connections, AEMP uses secure |
772 | authentication and can use TLS. |
728 | authentication and can use TLS. |
773 | |
729 | |
774 | AEMP can use a proven protocol - SSL/TLS - to protect connections and |
730 | AEMP can use a proven protocol - TLS - to protect connections and |
775 | securely authenticate nodes. |
731 | securely authenticate nodes. |
776 | |
732 | |
777 | =item * The AEMP protocol is optimised for both text-based and binary |
733 | =item * The AEMP protocol is optimised for both text-based and binary |
778 | communications. |
734 | communications. |
779 | |
735 | |
780 | The AEMP protocol, unlike the Erlang protocol, supports both |
736 | The AEMP protocol, unlike the Erlang protocol, supports both programming |
781 | language-independent text-only protocols (good for debugging) and binary, |
737 | language independent text-only protocols (good for debugging) and binary, |
782 | language-specific serialisers (e.g. Storable). |
738 | language-specific serialisers (e.g. Storable). |
783 | |
739 | |
784 | It has also been carefully designed to be implementable in other languages |
740 | It has also been carefully designed to be implementable in other languages |
785 | with a minimum of work while gracefully degrading fucntionality to make the |
741 | with a minimum of work while gracefully degrading functionality to make the |
786 | protocol simple. |
742 | protocol simple. |
787 | |
743 | |
788 | =item * AEMP has more flexible monitoring options than Erlang. |
744 | =item * AEMP has more flexible monitoring options than Erlang. |
789 | |
745 | |
790 | In Erlang, you can chose to receive I<all> exit signals as messages |
746 | In Erlang, you can chose to receive I<all> exit signals as messages |