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.