Conditional Get

rubyonrails-talk
1

Does anyone have any suggestions on how to create Conditional Get requests in rails? I understand the basic philosophy of the concept, I was just wondering if there was an easy way (a helper or plugin) to automatically generate the proper http headers when checking on whether a file has been updated on a server. Ideally, I would like to generate a conditional get in an if statement, followed by the caching algorithm if the conditional get returns the document.

Thanks!

2

Is RESTful Rails the answer?

3

Yep, there are built in functionality to support conditional requests (bot etags and last modified). Just use it in the controller action:

def some_action if stale?(:last_modified => @post.updated_at.utc, :etag => @post)    respond_to do |format|      # generate a full response    end end # otherwise cached will be used end

See: http://ryandaigle.com/articles/2008/10/25/what-s-new-in-edge-rails-even-better-conditional-get-support

Dmitry

4

Thanks for the conditional_get tip.

When looking at the api for stale? and fresh_when, I see that these methods are part of action controller. I would like to use this methodology to determine if an rss feed should be updated or not. The validation process all resides in the Feed model and a related module, so when I try to use the stale? method, I get an undefined method error. Would it be better to recreate the source code in my module, or is this the first indication that what I am trying to do is going about it the wrong way? I would very much like to keep the process in a module, as I am using a template pattern to define several different caching methods for experiments on speed and agility.

Any suggestions or advice you may have on this subject would be greatly appreciated!

Thanks!

Jay

5

In short — you're doing it in the wrong way. Caching should be handled on the controller layer, unless you really need something advanced (and I don't think you need it). So rethink the way your app is designed.

Dmitry

6

I agree, and appreciate your insight.

I want to be the RECIPIENT of either the "304 Not Modified" result, or the document if it has been modified. If I am reading the documentation properly, It is describing ways to handle a request and return the message, so I am looking for the other end of the stick.

I have been successful at generating my desired results using open- uri. Detailed information is available here:

around page 245.

Thanks for your help.

Jay