Friday, April 13, 2012

JSON caching with Rails

So the other day, I needed to cache an action which was basically a proxy action to return JSON.

Basically, 3rd party company X has an XML API for it's deals. Ideally we would use JavaScript to pull the feed, but unfortunately, the feed is using XML which means we need to use the server to pull this "deal" and then reformat it in JSON for our site to use.

To render the JSON we were using a render call


render offer.to_json


It can get expensive to pull this deal over the wire every time, so we looked into using caches action and set it to expire in 5 minutes (because that is how often the deal feed updates).


caches_action :index, :expires_in => 5.minutes


(Oh, also we need to turn caching on in dev to see this happening)


config.action_controller.perform_caching = true


While this worked fine for the first call, I noticed that in the subsequent calls, the application type was being set to 'text/html' instead of 'application/json'. This was causing the AJAX call to fail. I then noticed that the AJAX call was calling the action directly instead of using the .json suffix.

i.e.
/offers/1234

instead of

/offers.json/1234

So it appeared that because I was not using the suffix, the cache was forcing the application/type header to text/html.

In any case, after a quick update to the JavaScript call, the caching worked fine.

4 comments:

unsymbol said...

How did you change the js to fix this? I'm having a similar issue but with serving js for ajax requests.

Anonymous said...

Where the url used to point to "/offers" I updated it to point to "/offers.json" instead.

Anonymous said...

Hey thanks for the great info... i was looking for same...

Anonymous said...

Hey thanks for great info..