1Mojo::Pg::PubSub(3)   User Contributed Perl Documentation  Mojo::Pg::PubSub(3)
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NAME

6       Mojo::Pg::PubSub - Publish/Subscribe
7

SYNOPSIS

9         use Mojo::Pg::PubSub;
10
11         my $pubsub = Mojo::Pg::PubSub->new(pg => $pg);
12         my $cb = $pubsub->listen(foo => sub ($pubsub, $payload) {
13           say "Received: $payload";
14         });
15         $pubsub->notify(foo => 'I ♥ Mojolicious!');
16         $pubsub->unlisten(foo => $cb);
17

DESCRIPTION

19       Mojo::Pg::PubSub is a scalable implementation of the publish/subscribe
20       pattern used by Mojo::Pg. It is based on PostgreSQL notifications and
21       allows many consumers to share the same database connection, to avoid
22       many common scalability problems.
23

EVENTS

25       Mojo::Pg::PubSub inherits all events from Mojo::EventEmitter and can
26       emit the following new ones.
27
28   disconnect
29         $pubsub->on(disconnect => sub ($pubsub, $db) {
30           ...
31         });
32
33       Emitted after the current database connection is lost.
34
35   reconnect
36         $pubsub->on(reconnect => sub ($pubsub, $db) {
37           ...
38         });
39
40       Emitted after switching to a new database connection for sending and
41       receiving notifications.
42

ATTRIBUTES

44       Mojo::Pg::PubSub implements the following attributes.
45
46   pg
47         my $pg  = $pubsub->pg;
48         $pubsub = $pubsub->pg(Mojo::Pg->new);
49
50       Mojo::Pg object this publish/subscribe container belongs to. Note that
51       this attribute is weakened.
52
53   reconnect_interval
54         my $interval = $pubsub->reconnect_interval;
55         $pubsub      = $pubsub->reconnect_interval(0.1);
56
57       Amount of time in seconds to wait to reconnect after disconnecting,
58       defaults to 1.
59

METHODS

61       Mojo::Pg::PubSub inherits all methods from Mojo::EventEmitter and
62       implements the following new ones.
63
64   db
65         my $db = $pubsub->db;
66
67       Build and cache or get cached Mojo::Pg::Database connection from "pg".
68       Used to reconnect if disconnected.
69
70         # Reconnect immediately
71         $pubsub->unsubscribe('disconnect')->on(disconnect => sub ($pubsub, $db) { pubsub->db });
72
73   json
74         $pubsub = $pubsub->json('foo');
75
76       Activate automatic JSON encoding and decoding with "to_json" in
77       Mojo::JSON and "from_json" in Mojo::JSON for a channel.
78
79         # Send and receive data structures
80         $pubsub->json('foo')->listen(foo => sub ($pubsub, $payload) {
81           say $payload->{bar};
82         });
83         $pubsub->notify(foo => {bar => 'I ♥ Mojolicious!'});
84
85   listen
86         my $cb = $pubsub->listen(foo => sub {...});
87
88       Subscribe to a channel, there is no limit on how many subscribers a
89       channel can have. Automatic decoding of JSON text to Perl values can be
90       activated with "json".
91
92         # Subscribe to the same channel twice
93         $pubsub->listen(foo => sub ($pubsub, $payload) {
94           say "One: $payload";
95         });
96         $pubsub->listen(foo => sub ($pubsub, $payload) {
97           say "Two: $payload";
98         });
99
100   new
101         my $pubsub = Mojo::Pg::PubSub->new;
102         my $pubsub = Mojo::Pg::PubSub->new(pg => Mojo::Pg->new);
103         my $pubsub = Mojo::Pg::PubSub->new({pg => Mojo::Pg->new});
104
105       Construct a new Mojo::Pg::PubSub object and subscribe to the
106       "disconnect" event with default reconnect logic.
107
108   notify
109         $pubsub = $pubsub->notify('foo');
110         $pubsub = $pubsub->notify(foo => 'I ♥ Mojolicious!');
111         $pubsub = $pubsub->notify(foo => {bar => 'baz'});
112
113       Notify a channel. Automatic encoding of Perl values to JSON text can be
114       activated with "json".
115
116   reset
117         $pubsub->reset;
118
119       Reset all subscriptions and the database connection. This is usually
120       done after a new process has been forked, to prevent the child process
121       from stealing notifications meant for the parent process.
122
123   unlisten
124         $pubsub = $pubsub->unlisten('foo');
125         $pubsub = $pubsub->unlisten(foo => $cb);
126
127       Unsubscribe from a channel.
128

SEE ALSO

130       Mojo::Pg, Mojolicious::Guides, <https://mojolicious.org>.
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134perl v5.34.0                      2022-01-21               Mojo::Pg::PubSub(3)
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