It's possible that it strips the GA cookies (which is cool, I had no idea), but Varnish doesn't strip cookie information from the browser. If it did you wouldn't get any Rails sessions or anything.
You can set cookies on uncached pages in ruby and read them without issue in JS on Varnish cached pages. The page will still be cached even if the user has a session cookie.
Basically: don't set or get cookies in ruby on cached pages and you'll be fine.
You can set cookies on uncached pages in ruby and read them without issue in JS on Varnish cached pages. The page will still be cached even if the user has a session cookie.
Basically: don't set or get cookies in ruby on cached pages and you'll be fine.