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From "Mark Stevens" <mark.steven...@googlemail.com>
Subject Re: [users@httpd] Re: mod_cache intermittently corrupting PDF's or storing incomplete version of file.
Date Tue, 17 Jul 2007 09:22:39 GMT
Hi Jacqui,

Thanks for the response,

Initially I suspected the issue could have been related to client
type, however I was able to create a broken item in the cache by
running the following command from a remote server.

  - wget -S --no-cache http://sitename/mypdf.pdf?<random number>'

and then kept changing the random number until I received HTTP 416
(Requested range not satisfiable)

On getting the 416 response, the item would remain in the cache
smaller than expected size when attempting to view via browser,
response is 'the file is damaged and could not be repaired'.

Being I was testing against the live site, it is possible someone had
send a bytes range request during my testing with wget, and then Maybe
Apache stored the bytes range as the entire item.

I'll continue testing and let you know how I get on, if I don't get a
resolve soon, I will try rolling back to Apache 1.3 to rule out
mod_cache as being the culprit.

Thanks again,

Mark.













On 17/07/07, Jacqui caren <jacqui.caren@ntlworld.com> wrote:
> Mark Stevens wrote:
> > Anyone?
>
> It is likely that PDF viewers will ask for byteranges.
>
> If the cache is storing what is requested rather that the entire
> file, then this make sense. IIRC mod_proxy does the correct thing
> (requests the byterange it does not have and put chunks together then
> serves the requested range).
>
> PDFs were designed so that the TOC is at the head of the document.
> If you find that you are only storing the first NNNN bytes
> and then only sporadic contiguous chunks I would assume
> byterange requests are the problem and hand code a number
> of test requests to confirm it.
>
> HTH
>
> > On 16/07/07, Mark Stevens <mark.stevens99@googlemail.com> wrote:
> >
> >> Has anyone had problems in the past with Apache mod_cache storing
> >> incomplete versions of files such as PDF's, and if so did you manage
> >> to resolve it?
> >>
> >> The problem is intermittent, and I can confirm PDF's from the origin
> >> source are OK.
> >>
> >> I would be interested in any combination of setup and version of
> >> Apache you may have seen this with.
> >>
> >> I posted something related to this issue regarding removal of
> >> individual files from cache, sorry if this is seen as double posting,
> >> but felt I ought to have been more direct.
> >>
> >>
> >> Many thanks in advance.
> >>
> >> Mark.
> >>
>
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