rotatable_logger.rb

require 'logger'

# This logger will notice the log has been rotated and reopen it.
# The logrotate options must include 'nocreate'.
class RotatableLogger < Logger
  def add(*args)
    reopen if @logdev.filename && !File.exist?(@logdev.filename)
    super
  end
end

logger = RotatableLogger.new('sample.log')
loop do
  logger.info Time.now
  sleep 0.5
end