Caching dragonfly in sinatra

[Michał Bajur]

Hello everyone!

it's not strictly dragonfly question but a question about dragonfly and sinatra working together. I have a following endpoit in my sinatra app, which basically downloads an image from the URL and applies a "play" png button on top of it. Here is the code:

require 'sinatra'
require 'dragonfly'
require 'rmagick'
require 'rack-cache'

app = Dragonfly[:images].configure_with(:imagemagick)

app.processor.add :play_button do |temp_object, *args|
  canvas = Magick::Image.read(temp_object.path).first
  append_image = Magick::Image.read('play.png').first
  canvas.composite!(append_image, Magick::CenterGravity, Magick::OverCompositeOp)
  canvas.to_blob
end

get "/thumb/:url" do |url|
  app.fetch_url(url)
     .process(:play_button)
     .to_response(env)
end

and basically it works prety well. The thing is - it's not using server caching at all, image is being regenerated on each request - which obviously sucks. I'm looking for any solutions on how can i use some third-party (or built-in) mechanism to cache images produced by that endpoint. I know there is a whole section in dragonfly docs dedicated to cacheing but it's not helpfull when it comes down to using it with sinatra. 

Maybe that's something obvious - i've just never done such thing before.

Thanks in advance!

[Mark Evans]

Hi - you’ve required rack-cache but you don’t appear to be using it.

you need to have a “use Rack::Cache” somewhere like in the sinatra example https://github.com/rtomayko/rack-cache/blob/master/example/sinatra/app.rb

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[Michał Bajur]

Yeah, that's actually some legacy code left for something else i was working on. Anyway - is that a good idea to use it? Will it work out of the box or it will need some extra config to cover given code/scenario?

Thanks in advance

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[Mark Evans]

It should just work.
All Dragonfly does is set the appropriate caching headers. to_response makes sure the headers are set appropriately
Rack-Cache (or whatever other cache) use those headers to do their magic.

[Michał Bajur]

I probably should mentioned it - i don't want to cache it on user side (well, actally i can do this as well but that's not so important). What i want to do is to cache it on server side and serve generated images from cache instead of generating it on each request for each user.

[Walter Lee Davis]

Unless the url for one image is different per user, then you will get the same content when you request that url a second time. The cache is server-side

Walter

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