[Pkg-leofs-devel] Bug#748343: erlang-cowboy installs to /usr/lib/erlang/lib

[Balint Reczey]

Hi Simon,

On Wed, 25 Jun 2014 11:55:33 +0100 Simon MacMullen <simon at rabbitmq.com>
wrote:
> On 25/06/14 10:21, Sergei Golovan wrote:
> > I think that installing erlang-cowboy into the system-wide Erlang
> > directory is fine.
> > If an application needs cowboy then it can either
> >
> > 1) ensure it works wit a system-wide version and depend on erlang-cowboy, or
> 
> This would be tremendously painful since the API of cowboy undergoes 
> frequent incompatible changes.
This is true for many C libraries as well. The process of upgrading
libraries involves coordination with reverse dependencies and if any
Debian package depended on on erlang-cowboy, their maintainers had been
notified for API bumps.

$ apt-cache rdepends erlang-cowboy
erlang-cowboy
Reverse Depends:
  erlang-cowboy-examples

> 
> > 2) include its own version and make sure that it's the one which is used
> > (add -pa option to erl or otherwise).
> 
> We load the code dynamically, so -pa won't work. We may be able to 
> change our code loading strategy though.
There is also ErlSvc, which may or may not help in maintaining the
version of Erlang applications used:
https://packages.qa.debian.org/e/erlsvc.html

> 
> > I'd prefer that this local cowboy wasn't
> > easily accessible by other Erlang applications (god knows which local changes
> > it has).
> 
> Believe me, we do not add it to a path that any other application could 
> pick up.
> 
> > Anyway, placing applications from regular Debian packages into /usr/lib/erlang
> > shouldn't be considered a bug.
> 
> Well, if that's the decision then fair enough. For most other languages 
> though it seems to be policy that the language's standard library goes 
> in a different place from any other random packages; I assumed that was 
> the default.
I will happily adapt to any scheme for Debian's Erlang packages, but I
think erlang-cowboy is packaged properly according to the current scheme.
Note that erlang-cowboy does not change in stable and you can always
stick to one particular package version on your production system if
you don't want changes in testing/unstable:

echo "package hold" | sudo dpkg --set-selections

Cheers,
Balint