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.\" ========================================================================
.\"
.IX Title "Mojo::Pg::PubSub 3pm"
.TH Mojo::Pg::PubSub 3pm "2022-03-19" "perl v5.34.0" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.nh
.SH "NAME"
Mojo::Pg::PubSub \- Publish/Subscribe
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\&  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 => \*(AqI ♥ Mojolicious!\*(Aq);
\&  $pubsub\->unlisten(foo => $cb);
.Ve
.SH "DESCRIPTION"
.IX Header "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.
.SH "EVENTS"
.IX Header "EVENTS"
Mojo::Pg::PubSub inherits all events from Mojo::EventEmitter and can emit the following new ones.
.SS "disconnect"
.IX Subsection "disconnect"
.Vb 3
\&  $pubsub\->on(disconnect => sub ($pubsub, $db) {
\&    ...
\&  });
.Ve
.PP
Emitted after the current database connection is lost.
.SS "reconnect"
.IX Subsection "reconnect"
.Vb 3
\&  $pubsub\->on(reconnect => sub ($pubsub, $db) {
\&    ...
\&  });
.Ve
.PP
Emitted after switching to a new database connection for sending and receiving notifications.
.SH "ATTRIBUTES"
.IX Header "ATTRIBUTES"
Mojo::Pg::PubSub implements the following attributes.
.SS "pg"
.IX Subsection "pg"
.Vb 2
\&  my $pg  = $pubsub\->pg;
\&  $pubsub = $pubsub\->pg(Mojo::Pg\->new);
.Ve
.PP
Mojo::Pg object this publish/subscribe container belongs to. Note that this attribute is weakened.
.SS "reconnect_interval"
.IX Subsection "reconnect_interval"
.Vb 2
\&  my $interval = $pubsub\->reconnect_interval;
\&  $pubsub      = $pubsub\->reconnect_interval(0.1);
.Ve
.PP
Amount of time in seconds to wait to reconnect after disconnecting, defaults to \f(CW1\fR.
.SH "METHODS"
.IX Header "METHODS"
Mojo::Pg::PubSub inherits all methods from Mojo::EventEmitter and implements the following new ones.
.SS "db"
.IX Subsection "db"
.Vb 1
\&  my $db = $pubsub\->db;
.Ve
.PP
Build and cache or get cached Mojo::Pg::Database connection from \*(L"pg\*(R". Used to reconnect if disconnected.
.PP
.Vb 2
\&  # Reconnect immediately
\&  $pubsub\->unsubscribe(\*(Aqdisconnect\*(Aq)\->on(disconnect => sub ($pubsub, $db) { pubsub\->db });
.Ve
.SS "json"
.IX Subsection "json"
.Vb 1
\&  $pubsub = $pubsub\->json(\*(Aqfoo\*(Aq);
.Ve
.PP
Activate automatic \s-1JSON\s0 encoding and decoding with \*(L"to_json\*(R" in Mojo::JSON and \*(L"from_json\*(R" in Mojo::JSON for a channel.
.PP
.Vb 5
\&  # Send and receive data structures
\&  $pubsub\->json(\*(Aqfoo\*(Aq)\->listen(foo => sub ($pubsub, $payload) {
\&    say $payload\->{bar};
\&  });
\&  $pubsub\->notify(foo => {bar => \*(AqI ♥ Mojolicious!\*(Aq});
.Ve
.SS "listen"
.IX Subsection "listen"
.Vb 1
\&  my $cb = $pubsub\->listen(foo => sub {...});
.Ve
.PP
Subscribe to a channel, there is no limit on how many subscribers a channel can have. Automatic decoding of \s-1JSON\s0 text
to Perl values can be activated with \*(L"json\*(R".
.PP
.Vb 7
\&  # Subscribe to the same channel twice
\&  $pubsub\->listen(foo => sub ($pubsub, $payload) {
\&    say "One: $payload";
\&  });
\&  $pubsub\->listen(foo => sub ($pubsub, $payload) {
\&    say "Two: $payload";
\&  });
.Ve
.SS "new"
.IX Subsection "new"
.Vb 3
\&  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});
.Ve
.PP
Construct a new Mojo::Pg::PubSub object and subscribe to the \*(L"disconnect\*(R" event with default reconnect logic.
.SS "notify"
.IX Subsection "notify"
.Vb 3
\&  $pubsub = $pubsub\->notify(\*(Aqfoo\*(Aq);
\&  $pubsub = $pubsub\->notify(foo => \*(AqI ♥ Mojolicious!\*(Aq);
\&  $pubsub = $pubsub\->notify(foo => {bar => \*(Aqbaz\*(Aq});
.Ve
.PP
Notify a channel. Automatic encoding of Perl values to \s-1JSON\s0 text can be activated with \*(L"json\*(R".
.SS "reset"
.IX Subsection "reset"
.Vb 1
\&  $pubsub\->reset;
.Ve
.PP
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.
.SS "unlisten"
.IX Subsection "unlisten"
.Vb 2
\&  $pubsub = $pubsub\->unlisten(\*(Aqfoo\*(Aq);
\&  $pubsub = $pubsub\->unlisten(foo => $cb);
.Ve
.PP
Unsubscribe from a channel.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
Mojo::Pg, Mojolicious::Guides, <https://mojolicious.org>.