Question

I am working on a project which involves uploading flash video files to a S3 bucket from a number of geographically distributed nodes.

The video files are about 2-3mb each, and we are only sending one file (per node) every ten minutes, however the bandwidth we consume needs to be rate limited to ~20k/s, as these nodes are delivering streaming media to a CDN, and due to the locations we are only able to get 512k max upload.

I have been looking into the ASW-S3 gem and while it doesn’t offer any kind of rate limiting I am aware that you can pass in a IO Stream. Given this I am wondering if it might be possible to create a rate-limited stream which overrides the read method, adds in the rate limiting logic (e.g. in its simplest form a call to sleep between reads) and then call out to the super of the overridden method.

Another option I considered is hacking the code for Net::HTTP and putting the rate limiting into the send_request_with_body_stream method which is using a while loop, but I’m not entirely sure which would be the best option.

I have attempted at extending the IO class, however that didn’t work at all, simply inheriting from the class with class ThrottledIO < IO didn’t do anything.

Any suggestions will be greatly appreciated.

Answer 1

You need to use Delegate if you want to “augment” an IO. This puts a “facade” around your IO object that will be used by all “external” readers of the object but will have no effect on the operation of the object itself.

I’ve extracted that into a gem since it proved to be generally useful

Here’s an example for an IO that gets read from

http://rubygems.org/gems/progressive_io

Here there is an aspect added to all reading methods. I think you might be able to extend that to do basic throttling. After you are done you will be able to wrap your, say, File, into it:

 throttled_file = ProgressiveIO.new(some_file) do | offset, size |
    # compute rate and if needed sleep()
 end