Getting a callback when processing is done

[eduardm]

I am running a video processing engine with Paperclip and Delayed_paperclip gems.

Everything works fine, but I need to trigger some things when processing is done (sending emails, copy some files somewhere else, etc). Problem is that I do not know when is ready.

I know that there is a column in DB media_processing that gets updated when the processing is done, but to use that, I have to use another table and store there any video when processing is starting, then to keep pooling the db to see which one got processing status changed.

I tried after_processing in paperclip, after_update in video model, nothing works.

My question is: How to set a callback to execute some code when processing is done.

[rafaelmotta]

+1

[bdewater]

I have a similar use case to yours. Both callbacks provided by Paperclip (after_processing :enqueue_upload and after_foo_processing :enqueue_upload) work for me to enqueue another job. This makes sense because DelayedPaperclip::ProcessJob ultimately calls Paperclip's save method (via reprocess!).

The gotcha for me was that I am running my background processor (Que) in a separate process so I needed to stop en start it every time I made changes that I wanted to test. Afaik so far only Sidekiq has adopted the new code reloading mechanism in Rails 5 to hot reload job classes for every file change.

This is what works for me on Paperclip 5.1.0 and DelayedPaperclip 3.0.1:

# models/foo_request.rb
class FooRequest < ActiveRecord::Base
  ACCEPTED_CONTENT_TYPES = %w(application/pdf image/jpeg image/tiff)

  has_attached_file :foo,
                    styles: { export: { format: 'tiff' } },
                    processors: [:foo]
  validates_attachment_content_type :foo, content_type: ACCEPTED_CONTENT_TYPES
  validates_attachment_file_name :foo, matches: [/(pdf|jpe?g|tiff)\Z/i]
  process_in_background :foo, queue: ''

  # validations omitted

  after_post_process :queue_upload

  # other methods omitted

  def queue_upload
    FooUploadJob.perform_later(self)
  end
end