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Re: Change of APT interface

Dnia 2014-07-09, śro o godzinie 21:36 +0200, Anders Ingemann pisze:
> On 9 July 2014 21:30, Jimmy Kaplowitz <jkaplowitz@google.com> wrote:
[ cut ]

>         Switching to python-apt seems right in general, but is it
>         worth the disruption? Maybe yes, but it's tough to be sure.
[ cut ]

> I definitely think that python-apt is the way to go. You list quite a
> few changes that are required for this to work and some affect the
> manifest - I am not against that in any way and as long as 1.0 isn't
> out I am fine with changing the API (i.e. the structure of the
> manifest). However: besides the (albeit cool) feature of being able to
> hold the apt-cache in memory I don't see a whole lot of advantages of
> using python-apt right now - so: is it worth it?

I assume that calling of apt-get and family is left-over from
the times when build-debian-cloud was written as set of shell
scripts. It was natural approach then, and was translated
to bootstrap-vz. I did the same when moving GCE provider to Python.

It looks like there is consensus that going to python-apt is
The Good Thing, but you have worries about cost of doing it.

First some disadvantages.
1. It seems that only I know some of python-apt, although my
knowledge of it is limited. For example I still do not
know what is the best way of passing equivalent of "--assume-yes"
and I am not always sure whether to use apt, or more low-level
2. It'll require change in manifest.
3. Everyone knows apt-get so everyone working on bootstrap-vz
knows what commands in particular plugins are doing.

1. IMO it is the correct way of interacting with apt. Now
we are trying to steer apt and family through CLI which limits
us. Besides - now we use apt-get, while it seems that apt
is preferred way of managing packages.
2. It'll reduce number of called processes. It is not the biggest
cost in building images, and it might be premature optimization,
but I like this.
3. We are still before 1.0 so now it'd be right time to do it.
After 1.0, and after more people will use bootstrap-vz, it might
be harder to perform this change.
4. We will be able to delete some code from base.pkg.

I do not see one obvious killer feature which would speak for
python-apt. It's more sum of small things - like the ability to
get list of available versions of packages and decide which
of them to install, read package metadata and see what it depends
on or what are its conflicts.
IMO it could allow us in long term to have some plugins or code
which would interact more deeply with package subsystem. But
for now I do not know python-apt deeply enough so I cannot
see what are far-away advantages of this move.

Best regards.

Tomasz Rybak  GPG/PGP key ID: 2AD5 9860
Fingerprint A481 824E 7DD3 9C0E C40A  488E C654 FB33 2AD5 9860

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