tail_logs.rb

#!/usr/bin/env ruby

#usage: tail_logs.rb APP_NAME
#merely tails the log to STDOUT, exiting on errors. Intended to be run from some kind of loop.
#Auth: requires ENV['HEROKU_API_KEY'] to be set.

require 'bundler'
Bundler.require

app_name = ARGV[0]

class LogTailer
  def initialize(app_name)
    @app_name = app_name

    begin
      tail
    rescue Exception=>e
      STDERR.puts e
    end
  end

  private

  def tail
    buffer = ""
    request(get_log_url).stream do |chunk|
      buffer << chunk
      while line = buffer.slice!(/.+\n/)
        puts line
      end
    end
  end

  def request(url)
    EventMachine::HttpRequest.new(url, keepalive: true, connection_timeout: 15, inactivity_timeout: 0).get
  end

  def get_log_url
    api.get_logs(@app_name, {'tail' => 1, 'num' => 1500}).body
  end

  def api
    @api ||= Heroku::API.new
  end
end


EventMachine.run {
  LogTailer.new app_name
}