couchdb_attachments.rb

module CouchDBAttachments
  def attachment(*args)
    lambda do |env|
      request = ActionDispatch::Request.new(env)
      doc = DocWithAttachments.get(request.params[:doc])
      serve_attachment(doc, request.params[:path])
    end
  end

  private

    # TODO: Add whatever you want
    def serve_attachment(doc, filename)
      if doc && attachment = doc["_attachments"][filename]
        headers = {}
        headers["Content-Type"] = attachment["content_type"]
        headers["Content-Disposition"] = "inline; filename=#{filename}"
        headers["X-Accel-Redirect"] = "/couch/#{doc.database.name}/#{doc["_id"]}/#{filename}"
        [200, headers, []]
      else
        [404, { "Content-Type", "text/html" }, []]
      end
   end
end

nginx.conf

http {
    include       mime.types;
    default_type  application/octet-stream;

    upstream couchdb {
        server 127.0.0.1:5984;
    }

    upstream unicorn {
        server 127.0.0.1:3000;
    }

    server {
        listen       7000;
        server_name  proxy.caprica.local;

        location / {
            proxy_set_header  X-Real-IP  $remote_addr;
            proxy_set_header  X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header  Host $http_host;
            proxy_redirect    off;
            proxy_pass http://unicorn/;
        }

        location /couch/ {
            internal;
            proxy_set_header  X-Real-IP  $remote_addr;
            proxy_set_header  X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_pass http://couchdb/;
        }
    }
}

routes.rb

Example::Application.routes.draw do |map|
  extend CouchDBAttachments

  match "/assets/:doc/*path", :to => attachment()
end