Hacker News Reader

Comment by thrill | Hacker News Reader

SHOULD is not MUST

Why is he being downvoted?

As per RFC2119 (http://www.ietf.org/rfc/rfc2119.txt):

    3. SHOULD   This word, or the adjective "RECOMMENDED", mean that there
    may exist valid reasons in particular circumstances to ignore a
    particular item, but the full implications must be understood and
    carefully weighed before choosing a different course.

Because the problem goes beyond failing to invalidate the existing cache for the resource (which is a SHOULD), Chrome does not even make the request, which most definitely isn't acceptable under any circumstance, even after careful considerations. The spec even emphatically says that responses to a DELETE are not cacheable, how could you use an existing cached response as valid for a DELETE if you are not allowed to cache a delete in the first place?

Then there is a PERIOD, and it says "Responses to this method are not cacheable."

So caching DELETE is against the spec.

But returning already cached GET response to DELETE request is not.

I, however, agree that this behaviour shouldn't happen.

I believe the spec is saying that if you are a proxy, and you have a cached value for X, then you see a delete for X, you are allowed to immediately expire your entry for X. In other words, the proxy is permitted to assume that a delete request is so likely to result in a change on that resource that it may simply assume the cache is bad. It isn't required to, though.

It does not mean that if you receive a DELETE request you can just substitute the value of what is a completely different request (the GET request). I believe eloisius is not correct about the spec banning this behavior with that line. It's "banned" because it's just broken, nonsensical. It's not the same request in the first place, any more than you can just substitute POST results for GET.

But returning already cached GET response to DELETE request is not.

Yes, you're right.. the spec doesn't mention what should happen when the developer does something completely irrational, like returning a cached GET response to a DELETE request.

Yes, but mailing a bicycle to a random US address as a response to the DELETE request is also not explicitly forbidden in the spec. This doesn't mean that the spec provides for commercial suicide through bicycle mail.

Reply on news.ycombinator.com