Is it possible to rename a file name before user right-click's + save as with Carrierwave + S3 + Heroku + Content-Disposition? - heroku

Question

Is it possible to rename a file name before user right-click's + save as with Carrierwave + S3 + Heroku + Content-Disposition? I'm thinking of sanitizing file names (e.g. 193712391231.flv) before the file is saved on the S3 server and saving the original file name in a column in the db.
When a user decides to download the file (right-click and save as). I can't serve / send it as 193712391231.flv. Instead, I would like to send the file with its original file name.
How can this be implemented?
Using Carrierwave. I've come across this:
uploaded = Video.first.attachment
uploader.retrieve_from_store!(File.basename(Video.first.attachment.url))
uploader.cache_stored_file!
send_file uploader.file.path
This wont be served by S3, because it first caches the file in the local filesystem and then sends it to the browser. Which takes up a whole web process (Dyno in Heroku).
If anyone has any ideas, please suggest.

Answer 1

Akshully, you can:
# minimal example,
# here using mongoid, but it doesn't really matter
class Media
field :filename, type: String # i.e. "cute-puppy"
field :extension, type: String # i.e. "mp4"
mount_uploader :media, MediaUploader
end
class MediaUploader < CarrierWave::Uploader::Base
# Files on S3 are only accessible via signed URLS:
#fog_public = false
# Signed URLS expire after ...:
#fog_authenticated_url_expiration = 2.hours # in seconds from now, (default is 10.minutes)
# MIME-Type and filename that the user will see:
def fog_attributes
{
"Content-Disposition" => "attachment; filename*=UTF-8''#{model.filename}",
"Content-Type" => MIME::Types.type_for(model.extension).first.content_type
}
end
# ...
end
The url that model.media.url yields will then return the following headers:
Accept-Ranges:bytes
Content-Disposition:attachment; filename*=UTF-8''yourfilename.mp4
Content-Length:3926746
Content-Type:video/mpeg
Date:Thu, 28 Feb 2013 10:09:14 GMT
Last-Modified:Thu, 28 Feb 2013 09:53:50 GMT
Server:AmazonS3
...
The browser will then force a download (instead of opening in browser) and use the filename you set, regardless of the file name use used to store stuff in the bucket. The only drawback of this is that the Content-Disposition header is set when Carrierwave creates the file, so you couldn't for example use different filenames on the same file for different users.
In that case you could use RightAWS to generate the signed URL:
class Media
def to_url
s3_key = "" # the 'path' to the file in the S3 bucket
request_header = {}
response_header = {
"response-content-disposition" => "attachment; filename*=UTF-8''#{filename_with_extension}",
"response-content-type" => MIME::Types.type_for(extension).first.content_type
}
RightAws::S3Generator.new(
Settings.aws.key,
Settings.aws.secret,
:port => 80,
:protocol => 'http').
bucket(Settings.aws.bucket).
get(s3_key, 2.hours, request_header, response_header)
end
end
EDIT: It is not necessary to use RightAWS, uploader#url supports overriding response headers, the syntax is just a bit confusing (as is everything with CarrierWave, imho, but it's still awesome):
Media.last.media.url(query: {"response-content-disposition" => "attachment; filename*=UTF-8''huhuhuhuhu"})
# results in:
# => https://yourbucket.s3.amazonaws.com/media/512f292be75ab5a46f000001/yourfile.mp4?response-content-disposition=attachment%3B%20filename%2A%3DUTF-8%27%27huhuhuhuhu&AWSAccessKeyId=key&Signature=signature%3D&Expires=1362055338

Answer 2

If you're sending the file to the user direct from S3 you've no option. If you route the file through a dyno you can call it what you want, but you're using a dyno for the entire duration of the download.
I would store the files in a user friendly manner where possible and use folders to organise them.