rails json response with gzip compression - ruby-on-rails

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

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.

Answer 4

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 5

Consider not putting Rack middlewares in config.ru when using Rails
Rails has it's own middleware stack manager since Rails 2.
The correct way is:
# config/application.rb or config/environment.rb depends on your Rails version
config.middleware.use Rack::Deflater
Don't use #djcp's solution when using Rack::ETag
Short answer:
module MyApp
class Application < Rails::Application
config.middleware.insert_before Rack::ETag, Rack::Deflater
end
end
The order of Rack::Deflater and Rack::ETag matters because Rack::Deflater uses Zlib::GzipWriter to compress the response body and it would compress with a timestamp by default, which means the compressed response body would change every second even if the original response body is the same.
To reproduce this problem, run the following script:
require 'rack/etag'
require 'rack/deflater'
require 'rack/content_length'
#app = Rack::Builder.new do
use Rack::ETag
use Rack::Deflater
use Rack::ContentLength
run ->(*) { [200, {}, ['hello world']] }
end
def puts_etag
puts #app.call({ 'HTTP_ACCEPT_ENCODING' => 'gzip' })[1]['ETag']
end
puts_etag
sleep 1
puts_etag
One can simply swap the lines of Rack::ETag and Rack::Deflater and get the expected output.
Rails uses Rack::ETag by default and config.middleware.use is just appending. To insert Rack::Deflater before Rack::Etag, use config.middleware.insert_before instead.
🍻