Example of how to do a live streaming Rails 4 model and controller using postgresql pubsub. + event module for formatting SSE.

evacuation.rb

class Evacuation < ActiveRecord::Base

  def self.notify_person_found

    connection.execute "NOTIFY evac, #{connection.quote 'found person'}"

  end
  
  def self.on_person_found

    begin
      connection.execute "LISTEN evac"
      loop do
        connection.raw_connection.wait_for_notify do |event, pid, message|
          yield message
        end
      end
    ensure
      connection.execute "UNLISTEN evac"
    end

  end

end

sse.rb

require 'json'

module Eventer

  class SSE

    def initialize io

      @io = io

    end

    def write object, options = {}

      options.each do |k,v|
        @io.write "#{k}: #{v}\n"
      end

      @io.write "data: #{JSON.dump(object)}\n\n"

    end

    def close

      @io.close
      
    end

  end

end

tracking_controller.rb

require 'eventer/sse'

class TrackingController < ApplicationController
  include ActionController::Live
  
  def listen

    response.headers['Content-Type'] = 'text/event-stream'

    sse = Eventer::SSE.new(response.stream)

    begin
      Evacuation.on_person_found do
        sse.write({ :time => Time.now }, {event: 'found'})
        sleep 1
      end
    rescue IOError
      # Client disconnect
    ensure
      sse.close
    end

  end

end