/ 
Mojo-SQLite-1.000
River stage two • 14 direct dependents • 20 total dependents
/ Mojo::SQLite::PubSub

NAME

Mojo::SQLite::PubSub - Publish/Subscribe

SYNOPSIS

use Mojo::SQLite::PubSub;

my $pubsub = Mojo::SQLite::PubSub->new(sqlite => $sql);
my $cb = $pubsub->listen(foo => sub {
  my ($pubsub, $payload) = @_;
  say "Received: $payload";
});
$pubsub->notify(foo => 'I ♥ SQLite!');
$pubsub->unlisten(foo => $cb);

DESCRIPTION

Mojo::SQLite::PubSub is a scalable implementation of the publish/subscribe pattern used by Mojo::SQLite. It allows many consumers to share the same database connection, to avoid many common scalability problems. As SQLite has no notification system, it is implemented via event loop polling in Mojo::SQLite::Database, using automatically created tables prefixed with mojo_pubsub.

All subscriptions will be reset automatically and the database connection re-established if a new process has been forked, this allows multiple processes to share the same Mojo::SQLite::PubSub object safely.

EVENTS

Mojo::SQLite::PubSub inherits all events from Mojo::EventEmitter and can emit the following new ones.

reconnect

$pubsub->on(reconnect => sub {
  my ($pubsub, $db) = @_;
  ...
});

Emitted after switching to a new database connection for sending and receiving notifications.

ATTRIBUTES

Mojo::SQLite::PubSub implements the following attributes.

poll_interval

my $interval = $pubsub->poll_interval;
$pubsub      = $pubsub->poll_interval(0.25);

Interval in seconds to poll for notifications from "notify", passed along to "notification_poll_interval" in Mojo::SQLite::Database. Note that lower values will increase pubsub responsiveness as well as CPU utilization.

sqlite

my $sql = $pubsub->sqlite;
$pubsub = $pubsub->sqlite(Mojo::SQLite->new);

Mojo::SQLite object this publish/subscribe container belongs to.

METHODS

Mojo::SQLite::PubSub inherits all methods from Mojo::EventEmitter and implements the following new ones.

json

$pubsub = $pubsub->json('foo');

Activate automatic JSON encoding and decoding with "to_json" in Mojo::JSON and "from_json" in Mojo::JSON for a channel.

# Send and receive data structures
$pubsub->json('foo')->listen(foo => sub {
  my ($pubsub, $payload) = @_;
  say $payload->{bar};
});
$pubsub->notify(foo => {bar => 'I ♥ SQLite!'});

listen

my $cb = $pubsub->listen(foo => sub {...});

Subscribe to a channel, there is no limit on how many subscribers a channel can have. Automatic decoding of JSON text to Perl values can be activated with "json".

# Subscribe to the same channel twice
$pubsub->listen(foo => sub {
  my ($pubsub, $payload) = @_;
  say "One: $payload";
});
$pubsub->listen(foo => sub {
  my ($pubsub, $payload) = @_;
  say "Two: $payload";
});

notify

$pubsub = $pubsub->notify('foo');
$pubsub = $pubsub->notify(foo => 'I ♥ SQLite!');
$pubsub = $pubsub->notify(foo => {bar => 'baz'});

Notify a channel. Automatic encoding of Perl values to JSON text can be activated with "json".

unlisten

$pubsub = $pubsub->unlisten('foo');
$pubsub = $pubsub->unlisten(foo => $cb);

Unsubscribe from a channel.

SEE ALSO

Mojo::SQLite, Mojo::SQLite::Database