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Mojo::Pg::PubSub

Section: User Contributed Perl Documentation (3)
Updated: 2019-01-21
Index

NAME

Mojo::Pg::PubSub - Publish/Subscribe

SYNOPSIS

  use Mojo::Pg::PubSub;  my $pubsub = Mojo::Pg::PubSub->new(pg => $pg);  my $cb = $pubsub->listen(foo => sub {    my ($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/subscribepattern used by Mojo::Pg. It is based on PostgreSQL notifications and allowsmany consumers to share the same database connection, to avoid many commonscalability problems.

EVENTS

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

disconnect

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

Emitted after the current database connection is lost.

reconnect

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

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

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 thisattribute 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 to1.

METHODS

Mojo::Pg::PubSub inherits all methods from Mojo::EventEmitter andimplements 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 { shift->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  $pubsub->json('foo')->listen(foo => sub {    my ($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 canhave. 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";  });

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 beactivated with ``json''.

reset

  $pubsub->reset;

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

unlisten

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

Unsubscribe from a channel.

ATTRIBUTES

pg
reconnect_interval

METHODS

db
json
listen
new
notify
reset
unlisten

SEE ALSO

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