sse.rb

require 'net/http'
require 'set'
require 'uri'

uri = URI.parse 'https://example.com/events'

class ImageSet

  def initialize
    @set = Set.new
    @mutex = Mutex.new
  end

  def << image_url
    @mutex.synchronize { @set << image_url }
  end

  def fetch
    @mutex.synchronize { @set.dup }
  end

end

is = ImageSet.new

sse_thread = Thread.new do
  Net::HTTP.start(uri.host, uri.port, use_ssl: true) do |http|
    req = Net::HTTP::Get.new(uri)
    req['accept'] = 'text/event-stream'
    http.request(req) do |res|
      res.read_body do |event|
        event.split("\n").each do |l|

          if l.start_with? 'data: '
            image_url = l[6..-1]
            is << image_url
          end

        end
      end
    end

  end
end

loop do
  sleep 5
  p is.fetch.to_a
end