CODEWITHSUNDEEP
ruby-on-railseventsruby-on-rails-3.1
NordishBen
NordishBen

Reputation: 77

Rails 3.1 - Firing an specific event with the EventMachine

I would like to use the plugin em-eventsource ( https://github.com/AF83/em-eventsource ) for server-sent events in a Rails 3.1-project. My problem is, that there is only explained how to listen on events and receive messages, but not how to fire a specific event up and send the message. I would like to produce the event in an Active Record-Observer. Am I right when I think that I have to defer a operation with EventMachine to produce this event, or how can I solve this?

And yes, it has to be Ruby on Rails. If I don't get this to work with EventMachine, I would try to bypass the whole ruby-part with node.js.

Upvotes: 0

Views: 737

Answers (2)

chikamichi
chikamichi

Reputation: 2220

Actually I worked on this library a little with the maintainer. I think you mixed the client part with the server one. em-eventsource is a client library which you can use to consume a ServerSentEvent API, it's not meant to fire SSE.

On the server side, it quite doesn't matter whether you are using Rails or any other stack (nodejs, php…) as long as the server you are running on supports streaming. The default web server shipped with Rails does not (Webrick) but there are many others which do: Thin, Puma, Goliath…

In order to fire SSE in Rails, you would have to use both a streaming-capable server among those cited, and abide by the SSE specification. It mostly falls down to, first, responding with the proper Content-type header ("text/event-stream") so that the client (browser) knows it should hang-on, and then start streaming on the socket. That latter part is the one not easily possible as of today in Rails 3 (yet not impossible!); Rails 4 actually now supports streaming in an easy way, with a clean and simple internal API, so it's definitely coming.

In the mean time, you'd either:

  • mess with Rack's API in Rails (using EventMachine I guess, there are some examples in the wild)
  • or have it smart and make use of the streaming feature provided by Sinatra, built on top of Rack (see https://gist.github.com/1476463 for an example of Sinatra app which can be mounted in a Rails one!)
  • or you could use an external service such as Pusher
  • or leverage a entirely different stack…

A good overview: http://blog.phusion.nl/2012/08/03/why-rails-4-live-streaming-is-a-big-deal/

Upvotes: 1

MBO
MBO

Reputation: 30995

Maybe I'm wrong, but if IIRC Rails can't support long pooling. Rails block whole server (or thread if you have more than one running inside server) for each request and can't reuse them unless whole response was send. That's why you should setup reverse proxy (like nginx) in front of Rails application if you suspect there could be many concurrent connections - to proxy slow client requests and send them to Rails when whole request is received. It's just how Rack works, there's not much you can do about this probably.

Upvotes: 0

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