To configure the Fog S3 endpoint:
If you use Heroku:
heroku config:add FOG_REGION=eu-west-1
If you use a custom Rails initializer (config/initializers/asset_sync.rb):
AssetSync.configure do |config|
config.fog_region = 'eu-west-1'
For additional details see:
https://github.com/rumblelabs/asset_sync#built-in-initializer-environment-variables
As for the asset_host
configuration, I think your current setup should work but the assets_sync readme has the following note:
On non default S3 bucket region: If your bucket is set to a region that is not the default US Standard (us-east-1) you must use the first style of url //#{ENV['FOG_DIRECTORY']}.s3.amazonaws.com or amazon will return a 301 permanently moved when assets are requested. Note the caveat above about bucket names and periods.
So if you do see any 301 redirects when requesting the assets, try:
config.action_controller.asset_host = "//BUCKETNAME.s3.amazonaws.com"