rails json response with gzip compression

Question

I have an api written in rails which on each request responds with a JSON response.

The response could be huge, so i need to compress the JSON response using gzip.

Wondering how to do this in rails controller?

I have added the line

use Rack::Deflater

in config.ru

Should I also be changing something in the line which renders JSON?

render :json => response.to_json()

Also, how do i check if the response is in gzip format or not..??

I did a curl request from terminal, I see only the normal plain JSON.

Answer 1

My post Content Compression with Rack::Deflater describes a couple of ways to integrate Rack::Deflater. The easiest would be to just update config/application.rb with:

module YourApp
  class Application < Rails::Application
    config.middleware.use Rack::Deflater
  end
end

and you'll automatically compress all controller responses with deflate / gzip if the client explicitly says they can handle it.

Answer 2

For the response to be in gzip format we don't have to change the render method call.
If the request has the header Accept-Encoding: gzip, Rails will automatically compress the JSON response using gzip.

If you don't want the user to send a request with preset header., you can add the header to the request manually in the controller before rendering the response:

request.env['HTTP_ACCEPT_ENCODING'] = 'gzip'
render :json => response.to_json()

Answer 3

In some cases you can consider to write huge response into a file and gzip it:

res = {} # huge data hash
json = res.to_json

Zlib::GzipWriter.open('public/api/huge_data.json.gz') { |gz| gz.write json }

and update this file regularly

Answer 4

You can query Curl by setting a custom header to get gzipped response

$ curl -H "Accept-Encoding: gzip, deflate" localhost:3000/posts.json > posts_json.gz

then, then decompress it to view the actual response json

 $ gzip -d posts_json.gz
 $ cat posts_json

If it doesn't work. post back with output of rake middlewares to help us troubleshoot further.