foo.rb

def get_data(n)
    fn = 'g8/%s' % n
    if File.exist? fn
        File.read fn
    else
        link = 'http://gynvael.coldwind.pl/misja008_drone_io/scans/%s' % n
        begin
            b = Time.now
            Thread.current[:c] = HTTPClient.new unless Thread.current[:c]
            body = Thread.current[:c].get_content link
            a = Time.now
            if a - b > 0.1
                puts 'Downloading %s took %.03fs' % [link, a-b]
            end
        rescue => e
            puts 'Download failed: %s' % e
            retry
        end
        File.write fn, body
        body
    end
end