adding a quick concurrency feature

[tomharvey]

tomharvey wants to merge 1 commit

... well that's overstating things a bit. This is a draft PR for a reason and for the discussion of #30

I can well imagine some philosophical objection to adding the concurrency gem, and if we want to go down this path there is some work on exception handling, testing and making the thread pool size configurable.

But, my deploy went from > 10min (got bored waiting) to < 1min.

If you're interested in seeing the performance change with your own use case, adding this to your Gemfile will do:

gem 's3_asset_deploy', :git => 'https://github.com/tomharvey/s3_asset_deploy.git', branch: 'concurrency'

Currently, logging is broken - it logs when we start, but not complete the upload.

[tomharvey]

rails/sprokets is using the concurrency library (so it'll be in any rails user's Gems already. But, it's using promises instead of a low level TPE https://github.com/rails/sprockets/search?q=export_concurrent might be some good inspiration for how this might work "properly"

[summera]

@tomharvey sorry for the delay on this! It's a great idea. I'll take a look as soon as I can.