If-Modified-Since

Anders Berg andersb at vgnett.no
Tue Aug 15 10:53:01 CEST 2006


> In message <ujrodum4fvv.fsf at cat.linpro.no>, Dag-Erling
> =?iso-8859-1?Q?Sm=F8rgra
> v?= writes:
>>Arne managed to get a trace of an HTTP session where Varnish
>>incorrectly sent a 304 reply to an If-Modified-Since request.

Great. Good work.

> Well, without the varnish log we can't tell if it was really
> incorrect, but we can pressume that it was.

I guess this is an example of the "old-page" problem?

If it is, we now know that it can be triggered with:

Last page served by Varnish, new page served by Varnish.

Anders Berg

>>
>>> HTTP/1.1 304 Not Modified
>>> Via: 1.1 varnish
>>> X-Varnish: 44998848
>>> Last-Modified: Mon, 14 Aug 2006 13:30:03 GMT
>
> Inspecting the code I can see that we print the wrong thing
> in Last-Modified: header, we print what the user asked us about.
>
>>(note that the reply lacks a Date: header, we should fix that as well)
>>
>>unfortunately, I don't have the corresponding Varnish log.
>
> Which is the trouble because I can't possibly see how this test
> can fail:
>
> 	if (ims > sp->obj->last_modified) {
> 		VSL(SLT_Debug, sp->fd,
> 		    "Cond: %d > %d ", sp->obj->last_modified, ims);
> 		return (0);
> 	}
>
> unless we have no last_modified field on the object.
>
>
> --
> Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
> phk at FreeBSD.ORG         | TCP/IP since RFC 956
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> Never attribute to malice what can adequately be explained by
> incompetence.
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