Live / Streaming API?

[activestylus]

Not an issue as much as an inquiry. I am THIS close to selling my team on Roda, but we do need a bit of async action, mostly in the form of SSE, though there could be room for a full on pub/sub solution down the line.

Curious if you have ever dealt with these specs or how plausible it even is within the scope of a plugin. My own research shows people reaching a dead end in terms of mixing synchronous with asynchronous code, like the ill-fated Rack Stream library.

I am personally considering Rack AMQP to fill this void, but the jury is still out until I can really kick the tires on this badboy.

Thoughts?

[jeremyevans]

The streaming plugin handles streaming, and I use it for SSE in one of my apps. I'm using LISTEN in PostgreSQL for updates and a Queue for synchronization. See http://roda.jeremyevans.net/rdoc/classes/Roda/RodaPlugins/Streaming.html for details on the streaming support. Here's a basic idea of what I'm doing:

# outside your Roda.route block
Thread.new do
  DB.listen('channel_name', :loop=>proc{QUEUES.each{|q| q.push('')}}, :timeout=>60) do |_, _, msg|
    QUEUES.each{|q| q.push(msg)}
  end
end

# inside your Roda.route block
r.get "streaming" do
  response['Content-Type'] = 'text/event-stream;charset=UTF-8'
  response['X-Accel-Buffering'] = 'no' # for nginx
  q = Queue.new
  QUEUES.each{|q| q.push('')}
  QUEUES << q
  stream(:loop=>true, :callback=>proc{QUEUES.delete(q)}) do |out|
    out << "data: #{q.pop}\n\n"
  end
end

Note that as this isn't a bug in Roda, per the contribution guidelines, you should probably be asking about it on the ruby-roda Google Group or the IRC channel.

[activestylus]

Thanks for the quick response and duly noted - I wiIl post further queries of this nature in the group.

I continue to be impressed by how many batteries come included in this tiny framework. Bravo!

[tobymao]

This guide helped me, but I couldn't get messages streamed in until i set

response['Transfer-Encoding'] = 'identity'

[makevoid]

thanks @tobymao for pointing this out, I had some code that wasn't working anymore on latest Chrome and adding response['Transfer-Encoding'] = 'identity' made it work again! many thanks!

I think someone should probably update Roda's streaming plugin documentation with your note https://github.com/jeremyevans/roda/blob/master/lib/roda/plugins/streaming.rb#L6

The alternative I guess is to provide an example implementation of chunked (default) encoding where apparently you need to pass the size of the chunk in hex and /r/n as separators.