Re: best practices on setting HTTP headers and status codes

On Thu, Sep 11, 2014 at 2:55 PM, Héctor Velarde
<[email protected]> wrote:

> what I want is to return a 304 status code if the view has not changed since
> the last time the client got it. as I want to be a good citizen, I want to
> handle this with and without proxies (Varnish).
>
> to solve this problem I'm handling the "If-Modified-Since" request header
> and, while working on that, I found some code in different parts of the
> Plone core code that handles similar situations; an example, for images, can
> be found here:

I am sure I have not thought this through entirely, but could you set
the Vary header in the response for the If-Modified-Since request
header?  OTOH, that may have the practical effect of making cache hits
pretty unlikely.

One alternative: leverage traversal semantics by making your view
provide IPublishTraverse, where you have a URL path like this:

/path/to/liveblog-post/@@since/2014-09-12T15:20

Making YourView.publishTraverse() do the fun work of parsing the
ISO8601 stamp, and setting internal datetime.datetime attribute on the
view object, then having the YourView.__call__() method calculate and
return the result.

Then you have a URL you don't have to worry too much about headers for
re: caching?  If you do this on a one-minute granularity, high traffic
ought to leverage Varnish HITs (but even then, maybe you can make the
caching interval configurable to more or less granular).

Sean

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