amazon elastic transcode with shrine - ruby-on-rails

Question

I am working on an app that require to upload videos. I added Shrine and s3 storage.
Till here everything is working. Now I need to transcode the videos and I added the following code to the video_uploader file
class VideoUploader < Shrine
plugin :processing
plugin :versions
process(:store) do |io|
transcoder = Aws::ElasticTranscoder::Client.new(
access_key_id: ENV['AWS_ACCESS_KEY_ID'],
secret_access_key: ENV['AWS_SECRET_ACCESS_KEY'],
region: 'us-east-1',
)
pipeline = transcoder.create_pipeline(options = {
:name => "name",
:input_bucket => "bucket",
:output_bucket => "bucket",
:role => "arn:aws:iam::XXXXX:role/Elastic_Transcoder_Default_Role",
})
PIPELINE_ID = pipeline[:pipeline][:id]
transcode_hd = transcoder.create_job({
:pipeline_id=>PIPELINE_ID,
:input=> {
:key=> "cache/"+io.id,
:frame_rate=> "auto",
:resolution => "auto",
:aspect_ratio => "auto",
:container => 'auto'
},
:outputs=>[{
:key=>"store/"+io.id,
:preset_id=>"1351620000001-000010",
}]
})
end
end
The transcoding is working and basically is transcoding the new file uploaded to cache folder and put in the store folder with the same name.
The issue now is to attach this file to the record in the database. As of now the record is updated with a different name it creates a new file in the store folder of 0mb.
How can I attach the results of processing into Shrine's uploaded file for storage?

Answer 1

The process(:store) block expects you to return a file for Shrine to upload to permanent storage, so this flow won't work Amazon Elastic Transcoder, because Amazon Elastic Transcoder is now the one that will upload the cached file to permanent storage.
You can delay the transcoding request into a background job, poll the transcoding job every N seconds, and create a Shrine::UploadedFile from the results and update the record. Something like the following should work:
# superclass for all uploaders that use Amazon Elastic Transcoder
class TranscoderUploader < Shrine
plugin :backgrounding
Attacher.promote { |data| TranscodeJob.perform_async(data) }
end
class VideoUploader < TranscoderUploader
plugin :versions
end
class TranscodeJob
include Sidekiq::Worker
def perform(data)
attacher = TranscoderUploader::Attacher.load(data)
cached_file = attacher.get #=> #<Shrine::UploadedFile>
# create transcoding job, use `cached_file.id`
transcoder.wait_until(:job_complete, id: job.id)
response = transcoder.read_job(id: job.id)
output = response.output
versions = {
video: attacher.shrine_class::UploadedFile.new(
"id" => cached_file.id,
"storage" => "store",
"metadata" => {
"width" => output.width,
"height" => output.height,
# ...
}
),
...
}
attacher.swap(versions)
end
end
If you'll by any chance be interested in making a Shrine plugin for Amazon Elastic Transcoder, take a look at shrine-transloadit which provides integration for Transloadit, which uses practically the same flow as the Amazon Elastic Transcoder, and it works with webhooks rather than polling for the response.