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From John Allspaw <>
Subject Re: Precedent for single-use URLs?
Date Wed, 31 Oct 2012 22:30:22 GMT
Ah thanks. This helps and thanks for jogging my senile memory about the
eviction scenario for objects on disk. :)

I'll look into this approach, thanks!

On Wednesday, October 31, 2012, Leif Hedstrom wrote:

> On 10/31/12 9:45 AM, John Allspaw wrote:
>> Hey all -
>> Is there anyone doing logic in ATS to support single-use URLs?
>> Example: I have an mp3. I want exactly one person (i.e. client download)
>> to get at it, and no more. If the download doesn't complete, I'm willing to
>> risk that, no more than one download.
>> Has anyone approached this problem within ATS, or always just handled the
>> logic in the origin server? Presumably the object in cache has a reference
>> count associated with it that we can check if >1 than deny?
> But this would always be a cache miss then ? Or is the idea that the same
> user can fetch it multiple times ? If it's the former, why not always go to
> origin, and make it non cacheable? If the object is the same, but unique
> URLs for each user, I'd take a slightly different approach:
> 1) Generate cryptographically signed URLs, personalized, such that it's
> only valid from one client IP (or user cookie or whatever).
> 2) Validate the URL, if not valid for this particular user + URL combo,
> deny the request
> 3) Extract the "content" portion of the URL, and use that as the cache key.
> The cache doesn't keep any "ref count" on disk (you knew that ;), it does
> have an LRU for the in memory cache. An object that only gets one hit, but
> is cacheable, would get written to disk, but would not be in RAM cache.
> Cheers,
> -- Leif

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