Unicorn configuration for Rails 3.2 application to log to a different file per worker (to stop logs interleaving with one another).

unicorn.conf.rb

after_fork do |server, worker|

  # Override the default logger to use a separate log for each Unicorn worker.
  # https://github.com/rails/rails/blob/3-2-stable/railties/lib/rails/application/bootstrap.rb#L23-L49
  Rails.logger = ActiveRecord::Base.logger = ActionController::Base.logger = begin
    path = Rails.configuration.paths["log"].first
    f = File.open(path.sub(".log", "-#{worker.nr}.log"), "a")
    f.binmode
    f.sync = true
    logger = ActiveSupport::TaggedLogging.new(ActiveSupport::BufferedLogger.new(f))
    logger.level = ActiveSupport::BufferedLogger.const_get(Rails.configuration.log_level.to_s.upcase)

    logger
  end
end