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Sinatra Server Side Event streaming.
# Usage: redis-cli publish message hello
require 'sinatra'
require 'redis'
conns = []
get '/' do
erb :index
get '/subscribe' do
content_type 'text/event-stream'
stream(:keep_open) do |out|
conns << out
out.callback { conns.delete(out) }
end do
redis = Redis.connect
redis.psubscribe('message', 'message.*') do |on|
on.pmessage do |match, channel, message|
channel = channel.sub('message.', '')
conns.each do |out|
out << "event: #{channel}\n\n"
out << "data: #{message}\n\n"
@@ index
<article id="log"></article>
var source = new EventSource('/subscribe');
source.addEventListener('message', function (event) {
log.innerText += '\n' +;
}, false);

Don't you need to set your log variable, i.e. "var log = document.getElementById('log');".


maccman commented Jun 26, 2012

Nope, elements can be referenced from JavaScript by their ID.

jrom commented Jun 27, 2012

OMG I can't believe I just discovered this tip.

mind blown

That's what I said when replying on Twitter... 14 years of JavaScript and then I come across this. Made me feel at little daft :)

pahagon commented Aug 15, 2012

try do this without chrome/v8

You should use document.getElementById('log'). Accessing an element by its id in a globally-scoped variable is a relic of ancient versions of Internet Explorer which, for whatever reason; Google decided to implement in V8. It is non-standard and bad practice, though; and won't work in Firefox.

niklas commented Oct 5, 2014

Thank you for that inspiration, I almost used faye..

There is a typo (?) in line 27, there should be only one newline to keep both lines close together:

      conns.each do |out|
        out << "event: #{channel}\n"
        out << "data: #{message}\n\n"

Else the pushed message won't have the right type bound, and source.addEventListener('different'..) won't react at all.

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