Question

I want to write in simple logger for my that puts messages in memory and, in background, every X seconds write it to a database.

Here is the buffered logger code:

module BufferedLogger
  def buffer
    @buffer ||= []
  end

  def log( message )
    buffer << message
  end

  def write_buffer  
    while message = buffer.shift do 
      # save the message in nosql
    end
  end

  def repeat_every( interval )
    Thread.new do
      loop do
        start_time = Time.now
        yield
        elapsed = Time.now - start_time
        sleep([interval - elapsed, 0].max)
      end
    end
  end

  extend self

  thread = repeat_every(10) do
    write_buffer
  end 

end

In development, this works fine, buffer() access to the same @buffer var in both log and write_buffer method. But as soon as I go to production or staging env, i.e. as soon as I’m behind passenger, this @buffer don’t seem to be shared anymore.

Any pointer?

Answer 1

Since passenger create separate process, and how these process will persists depends on passenger’s algorithm, I guess it will not work well as you expect. (btw, I had bad experience in this regard using global variables/class variables.)

My suggestion to buffer the log is, use logger like fluentd as intermediate processor. Fluentd can monitor and gather the log. You can write a plugin to write the collected log to DB. I think this will suit your needs.