Bug#316337: Proof

[Goswin von Brederlow <brederlo@informatik.uni-tuebingen.de>]

Roan Kattouw <roan.kattouw@home.nl> writes:

> Goswin von Brederlow wrote:
>> I think 0 size files are just a case of partial files that isn't
>> handled special. With other partial files you want to keep them and
>> resume downloading. With 0 bytes there is 0 gain in resuming but
>> removing them would haven been extra code.
>>
>> I think the bigger question is where those files come from in the
>> first place. Where does it start fetching them and quits after 0
>> bytes? Maybe that apt method should not create the files unless it
>> actualy has data to write to them in the first place.
> I uploaded my strace reports to a public location:
> http://members.lycos.nl/kattouw/traces/ contains reports of an apt-get
> update spewing errors, while
> http://members.lycos.nl/kattouw/traces/traces2 contains reports of
> apt-get update running on an empty partial dir.
>
> According to the second series, the methods/ftp helper program is
> responsible for creating those files. After negotiating a lot with the
> remote FTP server (strace cuts strings at 32 chars, so I didn't see
> those negotiations. The uploaded reports do show them, but I didn't
> really feel like reading them at 1 AM) and stat(2)ing a non-existent
> partial file, it creates one by open(2)ing it with the O_CREAT flag
> set (i.e. opening it in destructive write mode). These reports may
> clarify things a little about why those empty partial files are
> created.
>
> The most logical scheme would be to create a partial file only when
> we're sure we're actually going to receive data to put in it, backup
> all the data we receive into it, and remove it as soon as we know
> we've got everything. An alternative would be to remove all empty
> partial files at cleanup, but that's ugly and still causes trouble
> when apt-get dies unexpectedly.
>
>
> NB: If you're really curious, the command line used to generate the
> strace reports was
> strace -o trace -ff -s 300 apt-get update

I don't get why you get a bzip2 error at all.

The strace shows that apt fails to download Packages.bz2 files (which
don't exist) and then it fetches Packages.gz instead. So why is it
even trying to bunzip2 the file? It should fork the gunzip method
instead.

MfG
        Goswin