NAME
Mojolicious::Plugin::Multiplex - A websocket multiplexing layer for
Mojolicious applications
SYNOPSIS
use Mojolicious::Lite;
plugin 'Multiplex';
get '/' => 'index';
websocket '/multiplex' => sub {
my $c = shift;
my $multiplex = $c->multiplex;
$multiplex->on(subscribe => sub { ... });
$multiplex->on(message => sub { ... });
$multiplex->on(unsubscribe => sub { ... });
};
__DATA__
@@ index.html.ep
%= javascript 'websocket_multiplex';
CAUTION
This module is in its infancy and things can and will change in
incompatible ways until this warning is removed. That said, the author
is using it for real work so hopefully incompatible changes will be
minimal (for his own sanity).
DESCRIPTION
Mojolicious::Plugin::Multiplex implements a mechanism proposed by
SockJS for the
multiplexing of data on a single websocket. Rather than proposing both
a protocol and a programmatic api to use it, they propose
a very simple protocol and reusing the api of the existing Javascript
WebSocket api. This has the immediate advantage (beyond having to dream
up a client api) that existing front-end code that is written for a
WebSocket can immediately use the multiplexer with no changes
necessary.
Their proposal only includes a partially implemented reference
implementation. This module extends the protocol slightly in order to
enough of the "WebSocket API"
to be
useful. More extensions may be necessary if the API is to be completely
implemented, however those last few details are rarely used and will
likely not be missed.
On the server-side the logic is entirely up to the application author.
The module simply parses the multiplexed messages and emits events in
accordance with them. A typical use case may be to relay message to a
bus, subscribing and unsubscribing from topics that it presents.
Another might be to stream updates to multiple types of data (perhaps
in multiple parts of a single page application). (Indeed those might
not be distinct cases from each other).
For reference, the distribution comes with an example which uses
Mojo::Pg as a message broker for a multi-channel chat application. The
example may also be seen on GitHub
.
HELPERS
multiplex
my $multiplex = $c->multiplex;
Establishes the WebSocket connection (if it hasn't been already) and
returns an instance of Mojolicious::Plugin::Multiplex::Multiplexer. The
multiplexer is attached to the websocket stream and begins listening
for messages. The multiplexer emits events for incoming messages and
has methods to send outgoing messages; more details about those are
contained in its own documentation.
Note that for each websocket connection the same instance of the
multiplexer will be returned on any subsequent call. Though not
prevented, the user is highly discouraged from sending other traffic
over any websocket connection that is managed by a multiplexer.
BUNDLED FILES
websocket_multiplex.js
# in your template
%= javascript 'websocket_multiplex.js';
var ws = new WebSocket(url);
var multiplex = new WebSocketMultiplex(ws);
var channel = multiplex.channel(topic);
Bundled with this plugin is a javascript file which provides the
front-end code to create a multiplexer entitled websocket_multiplex.js.
It provides the new class WebSocketMultiplex whose constructor takes as
its only argument an existing WebSocket object. This then is used to
open new channel objects via the channel method which takes a topic
string as an arugment. Topics can be almost any string, however they
must not contain a comma (a limitation of the protocol). The resulting
channel objects implement the same API as a WebSocket (though they do
not inherit from it).
The client-side multiplexer will also attempt to reconnect to closed
sockets and when successful will automatically resubscribe to the
channels that were subscribed.
N.B. This library is the least stable of the entire project. Use with
caution.
SOURCE REPOSITORY
http://github.com/jberger/Mojolicious-Plugin-Multiplex
AUTHOR
Joel Berger,
COPYRIGHT AND LICENSE
Copyright (C) 2016 by Joel Berger
This library is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
The multiplexer protocol and javascript code (both extended by this
project) are copyright their original authors and by their nature are
assumed to be in the public domain.