Re: Corrupt cache or what else could cause this?

On 13 March 2011 22:57, Hendrik Visage <[email protected]> wrote:
>   On Sun, Mar 13, 2011 at 9:31 PM, Roland Giesler
>   <[1][email protected]> wrote:
>
>>      This points to a corrupt cached copy somewhere, doesn't it?
>
>
>>       Doesn't the checksumming in a cache server prevent this kind of
>>       thing from happening?
>
>   What checksumming in the cache servers?
>   The hashing typically done inside cache servers, is on the URL to
>   "compress" it and make it more manageable in computer storage terms.

Of course, thinking just a little harder about it, what I asked
doesn't make much sense!

>
>>       Surely a cache server is clever enough to see that it's copy is
>>       not the same as the one requested?
>
>   How? By re-downloading the same file, thus not caching? The upstream
>   could touch/change the date on the file, that way the upstream could
>   "force" a refetch if the cache time have expired.

Ja-nee.

>
>   Yes, cache "corruption" can happen, especially when they've received a
>   bad copy from upstream (read: solar flares ;) but more so when a
>   download manager asks for several pieces at once, and the upstream
>   gives an error half way through a transfer. I've seen a case many
>   summers ago that cached a page with the error at the bottom of the
>   partial HTML.
>   What would be nice/interesting is to redo the wget, but with the needed
>   pragma=no-cache etc. to attempt a single threaded cache-bypass request.

Makes no discernible difference:

roland@gts-server:~/Downloads$ wget -S --no-cache
http://www.teamviewer.com/download/teamviewer_linux.deb
--2011-03-13 23:05:18--  http://www.teamviewer.com/download/teamviewer_linux.deb
Resolving www.teamviewer.com... 87.230.73.24
Connecting to www.teamviewer.com|87.230.73.24|:80... connected.
HTTP request sent, awaiting response...
  HTTP/1.1 200 OK
  Content-Length: 19093632
  Content-Type: application/x-deb
  Last-Modified: Tue, 30 Nov 2010 13:57:02 GMT
  Accept-Ranges: bytes
  ETag: "2eea30779690cb1:1d7f"
  Server: Microsoft-IIS/6.0
  X-Powered-By: ASP.NET
  Date: Sun, 13 Mar 2011 21:05:06 GMT
  Connection: keep-alive
Length: 19093632 (18M) [application/x-deb]
Saving to: `teamviewer_linux.deb.3'

100%[==============================================================================================================>]
19,093,632   405K/s   in 58s

2011-03-13 23:06:17 (319 KB/s) - `teamviewer_linux.deb.3' saved
[19093632/19093632]

roland@gts-server:~/Downloads$ md5sum teamviewer*
d81b99241ba7bb04058f87ed0db1af8b  teamviewer5_linux.deb
968f9c674ec2a6dca63682f7433bc59b  teamviewer_linux(2).deb
75be172866aa2d770a91db37e712beb0  teamviewer_linux.deb
75be172866aa2d770a91db37e712beb0  teamviewer_linux.deb.1
75be172866aa2d770a91db37e712beb0  teamviewer_linux.deb.3

I'll wait for jc to tell me if they've found anything on their side.
At least I've got the file with https.

Roland

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