IE9: Cache-Busting with Grape Middleware

Ran into a series of weird bugs with IE9. Turned out that a lot of our API requests were cached on the client. I am not sure whether this is some clever plot to make things work faster, but it was rather puzzling. Nothing in our API headers indicated that the data can be cached for any duration, but nothing indicated otherwise either. Generally I’d like IE to work more like other browsers these days, not the other way around.

It was pretty easy to add a set of no-cache headers with Grape Middleware.

class ApiCacheBuster < Grape::Middleware::Base
  def after
    @app_response[1]["Cache-Control"] = "no-cache, no-store, max-age=0, must-revalidate"
    @app_response[1]["Pragma"] = "no-cache"
    @app_response[1]["Expires"] = "Fri, 01 Jan 1990 00:00:00 GMT"
    @app_response
  end
end

class Api < Grape::API
  use ApiCacheBuster
  ...
end

And, trying to get muscle memory for good habits, a test.

require 'spec_helper'

describe ApiCacheBuster do
  it "sets cache headers" do
    get "/api/v1/ping"
    response.body.should == "pong".to_json
    response.headers["Cache-Control"].should == "no-cache, no-store, max-age=0, must-revalidate"
    response.headers["Pragma"].should == "no-cache"
    response.headers["Expires"].should == "Fri, 01 Jan 1990 00:00:00 GMT"
  end
end

The headers are inspired from this StackOverflow article, which shows how to do it with plain Rails controllers.

Daniel Doubrovkine

IE9: Cache-Busting with Grape Middleware grape | rails | ruby

IE9: Cache-Busting with Grape Middleware