[PATCH consfigurator] APT properties: cache packages installed or removed this deployment

[Sean Whitton]

Hello,

On Sat 05 Nov 2022 at 11:58AM -04, David Bremner wrote:

> Sean Whitton <spwhitton at spwhitton.name> writes:
>
>> +
>> +- APT properties now cache what packages have been installed or removed for
>> +  the duration of the deployment.  This should significantly speed up some
>> +  deployments.  It could break some obscure consfigs.
>> +
>
> As mentioned on IRC, I currently have one use-case for calling apt-get
> directly, namely calling build-dep. I'm not sure if this is a problem or
> not. If you have a clear idea of what breaks if the cache(s) get out of
> sync, maybe it would be worth explaining.

The caching is only to avoid running commands that we don't have to run.
If it fails such that commands which we didn't have to run get run, then
no harm is done.  There'd only be a problem if we didn't run a command
that we in fact needed to run.

Your build-dep thing installs a series of packages.  Suppose one is foo.
Then if we have

    (apt:removed "foo")
    (bremner)
    (apt:removed "foo")

the second APT:REMOVED would do nothing, even though it was meant to.

Is there a sequence like this which could actually be a problem?

-- 
Sean Whitton