NAME

Mojo::Pg::PubSub - Publish/Subscribe

SYNOPSIS

  use Mojo::Pg::PubSub;
  my $pubsub = Mojo::Pg::PubSub->new(pg => $pg);
  my $cb = $pubsub->listen(foo => sub ($pubsub, $payload) {
    say "Received: $payload";
  });
  $pubsub->notify(foo => 'I ♥ Mojolicious!');
  $pubsub->unlisten(foo => $cb);

DESCRIPTION

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

EVENTS

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

disconnect

  $pubsub->on(disconnect => sub ($pubsub, $db) {
    ...
  });

Emitted after the current database connection is lost.

reconnect

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

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

ATTRIBUTES

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

pg

  my $pg  = $pubsub->pg;
  $pubsub = $pubsub->pg(Mojo::Pg->new);

Mojo::Pg object this publish/subscribe container belongs to. Note that this attribute is weakened.

reconnect_interval

  my $interval = $pubsub->reconnect_interval;
  $pubsub      = $pubsub->reconnect_interval(0.1);

Amount of time in seconds to wait to reconnect after disconnecting, defaults to 1.

METHODS

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

db

  my $db = $pubsub->db;

Build and cache or get cached Mojo::Pg::Database connection from "pg". Used to reconnect if disconnected.

  # Reconnect immediately
  $pubsub->unsubscribe('disconnect')->on(disconnect => sub ($pubsub, $db) { pubsub->db });

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
  $pubsub->json('foo')->listen(foo => sub ($pubsub, $payload) {
    say $payload->{bar};
  });
  $pubsub->notify(foo => {bar => 'I ♥ Mojolicious!'});

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
  $pubsub->listen(foo => sub ($pubsub, $payload) {
    say "One: $payload";
  });
  $pubsub->listen(foo => sub ($pubsub, $payload) {
    say "Two: $payload";
  });

new

  my $pubsub = Mojo::Pg::PubSub->new;
  my $pubsub = Mojo::Pg::PubSub->new(pg => Mojo::Pg->new);
  my $pubsub = Mojo::Pg::PubSub->new({pg => Mojo::Pg->new});

Construct a new Mojo::Pg::PubSub object and subscribe to the "disconnect" event with default reconnect logic.

notify

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

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

reset

  $pubsub->reset;

Reset all subscriptions and the database connection. This is usually done after a new process has been forked, to prevent the child process from stealing notifications meant for the parent process.

unlisten

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

Unsubscribe from a channel.