1 | =head1 NAME |
1 | =head1 NAME |
2 | |
2 | |
3 | AnyEvent::MP - multi-processing/message-passing framework |
3 | AnyEvent::MP - erlang-style multi-processing/message-passing framework |
4 | |
4 | |
5 | =head1 SYNOPSIS |
5 | =head1 SYNOPSIS |
6 | |
6 | |
7 | use AnyEvent::MP; |
7 | use AnyEvent::MP; |
8 | |
8 | |
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31 | |
31 | |
32 | # create a port on another node |
32 | # create a port on another node |
33 | my $port = spawn $node, $initfunc, @initdata; |
33 | my $port = spawn $node, $initfunc, @initdata; |
34 | |
34 | |
35 | # monitoring |
35 | # monitoring |
36 | mon $port, $cb->(@msg) # callback is invoked on death |
36 | mon $localport, $cb->(@msg) # callback is invoked on death |
37 | mon $port, $otherport # kill otherport on abnormal death |
37 | mon $localport, $otherport # kill otherport on abnormal death |
38 | mon $port, $otherport, @msg # send message on death |
38 | mon $localport, $otherport, @msg # send message on death |
39 | |
39 | |
40 | =head1 CURRENT STATUS |
40 | =head1 CURRENT STATUS |
41 | |
41 | |
42 | bin/aemp - stable. |
42 | bin/aemp - stable. |
43 | AnyEvent::MP - stable API, should work. |
43 | AnyEvent::MP - stable API, should work. |
44 | AnyEvent::MP::Intro - explains most concepts. |
44 | AnyEvent::MP::Intro - explains most concepts. |
45 | AnyEvent::MP::Kernel - mostly stable. |
45 | AnyEvent::MP::Kernel - mostly stable API. |
46 | AnyEvent::MP::Global - stable but incomplete, protocol not yet final. |
46 | AnyEvent::MP::Global - stable API. |
47 | |
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48 | stay tuned. |
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49 | |
47 | |
50 | =head1 DESCRIPTION |
48 | =head1 DESCRIPTION |
51 | |
49 | |
52 | This module (-family) implements a simple message passing framework. |
50 | This module (-family) implements a simple message passing framework. |
53 | |
51 | |
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83 | |
81 | |
84 | Nodes are either public (have one or more listening ports) or private |
82 | Nodes are either public (have one or more listening ports) or private |
85 | (no listening ports). Private nodes cannot talk to other private nodes |
83 | (no listening ports). Private nodes cannot talk to other private nodes |
86 | currently. |
84 | currently. |
87 | |
85 | |
88 | =item node ID - C<[a-za-Z0-9_\-.:]+> |
86 | =item node ID - C<[A-Z_][a-zA-Z0-9_\-.:]*> |
89 | |
87 | |
90 | A node ID is a string that uniquely identifies the node within a |
88 | A node ID is a string that uniquely identifies the node within a |
91 | network. Depending on the configuration used, node IDs can look like a |
89 | network. Depending on the configuration used, node IDs can look like a |
92 | hostname, a hostname and a port, or a random string. AnyEvent::MP itself |
90 | hostname, a hostname and a port, or a random string. AnyEvent::MP itself |
93 | doesn't interpret node IDs in any way. |
91 | doesn't interpret node IDs in any way. |
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97 | Nodes can only talk to each other by creating some kind of connection to |
95 | Nodes can only talk to each other by creating some kind of connection to |
98 | each other. To do this, nodes should listen on one or more local transport |
96 | each other. To do this, nodes should listen on one or more local transport |
99 | endpoints - binds. Currently, only standard C<ip:port> specifications can |
97 | endpoints - binds. Currently, only standard C<ip:port> specifications can |
100 | be used, which specify TCP ports to listen on. |
98 | be used, which specify TCP ports to listen on. |
101 | |
99 | |
102 | =item seeds - C<host:port> |
100 | =item seed nodes |
103 | |
101 | |
104 | When a node starts, it knows nothing about the network. To teach the node |
102 | When a node starts, it knows nothing about the network. To teach the node |
105 | about the network it first has to contact some other node within the |
103 | about the network it first has to contact some other node within the |
106 | network. This node is called a seed. |
104 | network. This node is called a seed. |
107 | |
105 | |
108 | Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes |
106 | Apart from the fact that other nodes know them as seed nodes and they have |
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107 | to have fixed listening addresses, seed nodes are perfectly normal nodes - |
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108 | any node can function as a seed node for others. |
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109 | |
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110 | In addition to discovering the network, seed nodes are also used to |
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111 | maintain the network and to connect nodes that otherwise would have |
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112 | trouble connecting. They form the backbone of an AnyEvent::MP network. |
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113 | |
109 | are expected to be long-running, and at least one of those should always |
114 | Seed nodes are expected to be long-running, and at least one seed node |
110 | be available. When nodes run out of connections (e.g. due to a network |
115 | should always be available. They should also be relatively responsive - a |
111 | error), they try to re-establish connections to some seednodes again to |
116 | seed node that blocks for long periods will slow down everybody else. |
112 | join the network. |
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113 | |
117 | |
114 | Apart from being sued for seeding, seednodes are not special in any way - |
118 | =item seeds - C<host:port> |
115 | every public node can be a seednode. |
119 | |
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120 | Seeds are transport endpoint(s) (usually a hostname/IP address and a |
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121 | TCP port) of nodes that should be used as seed nodes. |
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122 | |
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123 | The nodes listening on those endpoints are expected to be long-running, |
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124 | and at least one of those should always be available. When nodes run out |
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125 | of connections (e.g. due to a network error), they try to re-establish |
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126 | connections to some seednodes again to join the network. |
116 | |
127 | |
117 | =back |
128 | =back |
118 | |
129 | |
119 | =head1 VARIABLES/FUNCTIONS |
130 | =head1 VARIABLES/FUNCTIONS |
120 | |
131 | |
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132 | |
143 | |
133 | use AE (); |
144 | use AE (); |
134 | |
145 | |
135 | use base "Exporter"; |
146 | use base "Exporter"; |
136 | |
147 | |
137 | our $VERSION = $AnyEvent::MP::Kernel::VERSION; |
148 | our $VERSION = 1.21; |
138 | |
149 | |
139 | our @EXPORT = qw( |
150 | our @EXPORT = qw( |
140 | NODE $NODE *SELF node_of after |
151 | NODE $NODE *SELF node_of after |
141 | configure |
152 | configure |
142 | snd rcv mon mon_guard kil reg psub spawn |
153 | snd rcv mon mon_guard kil psub spawn cal |
143 | port |
154 | port |
144 | ); |
155 | ); |
145 | |
156 | |
146 | our $SELF; |
157 | our $SELF; |
147 | |
158 | |
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216 | L<AnyEvent::MP::Global> module, which will then use it to keep |
227 | L<AnyEvent::MP::Global> module, which will then use it to keep |
217 | connectivity with at least one node at any point in time. |
228 | connectivity with at least one node at any point in time. |
218 | |
229 | |
219 | =back |
230 | =back |
220 | |
231 | |
221 | Example: become a distributed node using the locla node name as profile. |
232 | Example: become a distributed node using the local node name as profile. |
222 | This should be the most common form of invocation for "daemon"-type nodes. |
233 | This should be the most common form of invocation for "daemon"-type nodes. |
223 | |
234 | |
224 | configure |
235 | configure |
225 | |
236 | |
226 | Example: become an anonymous node. This form is often used for commandline |
237 | Example: become an anonymous node. This form is often used for commandline |
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512 | delivered again. |
523 | delivered again. |
513 | |
524 | |
514 | Inter-host-connection timeouts and monitoring depend on the transport |
525 | Inter-host-connection timeouts and monitoring depend on the transport |
515 | used. The only transport currently implemented is TCP, and AnyEvent::MP |
526 | used. The only transport currently implemented is TCP, and AnyEvent::MP |
516 | relies on TCP to detect node-downs (this can take 10-15 minutes on a |
527 | relies on TCP to detect node-downs (this can take 10-15 minutes on a |
517 | non-idle connection, and usually around two hours for idle conenctions). |
528 | non-idle connection, and usually around two hours for idle connections). |
518 | |
529 | |
519 | This means that monitoring is good for program errors and cleaning up |
530 | This means that monitoring is good for program errors and cleaning up |
520 | stuff eventually, but they are no replacement for a timeout when you need |
531 | stuff eventually, but they are no replacement for a timeout when you need |
521 | to ensure some maximum latency. |
532 | to ensure some maximum latency. |
522 | |
533 | |
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554 | } |
565 | } |
555 | |
566 | |
556 | $node->monitor ($port, $cb); |
567 | $node->monitor ($port, $cb); |
557 | |
568 | |
558 | defined wantarray |
569 | defined wantarray |
559 | and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) } |
570 | and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }) |
560 | } |
571 | } |
561 | |
572 | |
562 | =item $guard = mon_guard $port, $ref, $ref... |
573 | =item $guard = mon_guard $port, $ref, $ref... |
563 | |
574 | |
564 | Monitors the given C<$port> and keeps the passed references. When the port |
575 | Monitors the given C<$port> and keeps the passed references. When the port |
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621 | the package, then the package above the package and so on (e.g. |
632 | the package, then the package above the package and so on (e.g. |
622 | C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function |
633 | C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function |
623 | exists or it runs out of package names. |
634 | exists or it runs out of package names. |
624 | |
635 | |
625 | The init function is then called with the newly-created port as context |
636 | The init function is then called with the newly-created port as context |
626 | object (C<$SELF>) and the C<@initdata> values as arguments. |
637 | object (C<$SELF>) and the C<@initdata> values as arguments. It I<must> |
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638 | call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise |
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639 | the port might not get created. |
627 | |
640 | |
628 | A common idiom is to pass a local port, immediately monitor the spawned |
641 | A common idiom is to pass a local port, immediately monitor the spawned |
629 | port, and in the remote init function, immediately monitor the passed |
642 | port, and in the remote init function, immediately monitor the passed |
630 | local port. This two-way monitoring ensures that both ports get cleaned up |
643 | local port. This two-way monitoring ensures that both ports get cleaned up |
631 | when there is a problem. |
644 | when there is a problem. |
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655 | |
668 | |
656 | sub _spawn { |
669 | sub _spawn { |
657 | my $port = shift; |
670 | my $port = shift; |
658 | my $init = shift; |
671 | my $init = shift; |
659 | |
672 | |
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673 | # rcv will create the actual port |
660 | local $SELF = "$NODE#$port"; |
674 | local $SELF = "$NODE#$port"; |
661 | eval { |
675 | eval { |
662 | &{ load_func $init } |
676 | &{ load_func $init } |
663 | }; |
677 | }; |
664 | _self_die if $@; |
678 | _self_die if $@; |
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699 | ? $action[0]() |
713 | ? $action[0]() |
700 | : snd @action; |
714 | : snd @action; |
701 | }; |
715 | }; |
702 | } |
716 | } |
703 | |
717 | |
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718 | =item cal $port, @msg, $callback[, $timeout] |
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719 | |
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720 | A simple form of RPC - sends a message to the given C<$port> with the |
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721 | given contents (C<@msg>), but adds a reply port to the message. |
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722 | |
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723 | The reply port is created temporarily just for the purpose of receiving |
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724 | the reply, and will be C<kil>ed when no longer needed. |
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725 | |
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726 | A reply message sent to the port is passed to the C<$callback> as-is. |
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727 | |
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728 | If an optional time-out (in seconds) is given and it is not C<undef>, |
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729 | then the callback will be called without any arguments after the time-out |
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730 | elapsed and the port is C<kil>ed. |
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731 | |
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732 | If no time-out is given (or it is C<undef>), then the local port will |
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733 | monitor the remote port instead, so it eventually gets cleaned-up. |
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734 | |
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735 | Currently this function returns the temporary port, but this "feature" |
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736 | might go in future versions unless you can make a convincing case that |
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737 | this is indeed useful for something. |
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738 | |
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739 | =cut |
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740 | |
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741 | sub cal(@) { |
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742 | my $timeout = ref $_[-1] ? undef : pop; |
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743 | my $cb = pop; |
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744 | |
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745 | my $port = port { |
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746 | undef $timeout; |
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747 | kil $SELF; |
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748 | &$cb; |
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749 | }; |
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750 | |
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751 | if (defined $timeout) { |
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752 | $timeout = AE::timer $timeout, 0, sub { |
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753 | undef $timeout; |
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754 | kil $port; |
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755 | $cb->(); |
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756 | }; |
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757 | } else { |
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758 | mon $_[0], sub { |
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759 | kil $port; |
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760 | $cb->(); |
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761 | }; |
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762 | } |
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763 | |
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764 | push @_, $port; |
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765 | &snd; |
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766 | |
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767 | $port |
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768 | } |
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769 | |
704 | =back |
770 | =back |
705 | |
771 | |
706 | =head1 AnyEvent::MP vs. Distributed Erlang |
772 | =head1 AnyEvent::MP vs. Distributed Erlang |
707 | |
773 | |
708 | AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node |
774 | AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node |
709 | == aemp node, Erlang process == aemp port), so many of the documents and |
775 | == aemp node, Erlang process == aemp port), so many of the documents and |
710 | programming techniques employed by Erlang apply to AnyEvent::MP. Here is a |
776 | programming techniques employed by Erlang apply to AnyEvent::MP. Here is a |
711 | sample: |
777 | sample: |
712 | |
778 | |
713 | http://www.Erlang.se/doc/programming_rules.shtml |
779 | http://www.erlang.se/doc/programming_rules.shtml |
714 | http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4 |
780 | http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4 |
715 | http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6 |
781 | http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6 |
716 | http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5 |
782 | http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5 |
717 | |
783 | |
718 | Despite the similarities, there are also some important differences: |
784 | Despite the similarities, there are also some important differences: |
719 | |
785 | |
720 | =over 4 |
786 | =over 4 |
721 | |
787 | |
722 | =item * Node IDs are arbitrary strings in AEMP. |
788 | =item * Node IDs are arbitrary strings in AEMP. |
723 | |
789 | |
724 | Erlang relies on special naming and DNS to work everywhere in the same |
790 | Erlang relies on special naming and DNS to work everywhere in the same |
725 | way. AEMP relies on each node somehow knowing its own address(es) (e.g. by |
791 | way. AEMP relies on each node somehow knowing its own address(es) (e.g. by |
726 | configuration or DNS), but will otherwise discover other odes itself. |
792 | configuration or DNS), and possibly the addresses of some seed nodes, but |
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793 | will otherwise discover other nodes (and their IDs) itself. |
727 | |
794 | |
728 | =item * Erlang has a "remote ports are like local ports" philosophy, AEMP |
795 | =item * Erlang has a "remote ports are like local ports" philosophy, AEMP |
729 | uses "local ports are like remote ports". |
796 | uses "local ports are like remote ports". |
730 | |
797 | |
731 | The failure modes for local ports are quite different (runtime errors |
798 | The failure modes for local ports are quite different (runtime errors |
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756 | so does not need a queue that can overflow). AEMP sends are immediate, |
823 | so does not need a queue that can overflow). AEMP sends are immediate, |
757 | connection establishment is handled in the background. |
824 | connection establishment is handled in the background. |
758 | |
825 | |
759 | =item * Erlang suffers from silent message loss, AEMP does not. |
826 | =item * Erlang suffers from silent message loss, AEMP does not. |
760 | |
827 | |
761 | Erlang makes few guarantees on messages delivery - messages can get lost |
828 | Erlang implements few guarantees on messages delivery - messages can get |
762 | without any of the processes realising it (i.e. you send messages a, b, |
829 | lost without any of the processes realising it (i.e. you send messages a, |
763 | and c, and the other side only receives messages a and c). |
830 | b, and c, and the other side only receives messages a and c). |
764 | |
831 | |
765 | AEMP guarantees correct ordering, and the guarantee that after one message |
832 | AEMP guarantees correct ordering, and the guarantee that after one message |
766 | is lost, all following ones sent to the same port are lost as well, until |
833 | is lost, all following ones sent to the same port are lost as well, until |
767 | monitoring raises an error, so there are no silent "holes" in the message |
834 | monitoring raises an error, so there are no silent "holes" in the message |
768 | sequence. |
835 | sequence. |