Re: [Caml-list] Create a deployable application unit from OPAM?

[David Scott <scott.dj@gmail.com>]

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Hi,

I had a quick go at creating something with Docker: (and alpine since I was
more familiar with it, but I suspect a similar technique would work with
ubuntu)

https://github.com/djs55/experiments/pull/1

It uses `opam` to build a simple OCaml example (taken from cryptokit) which
needs `libgmp` at runtime. The `Dockerfile` has a slightly hacky attempt to
detect the runtime dependency:

opam depext -n cryptokit | grep -v '#' | grep '\-dev' | while read in; do
basename "$in" -dev; done > needed-packages.txt

It assumes that

- all external C libraries have an alpine depext called foo-dev
- foo-dev has a corresponding runtime package called foo

and installs these `foo` in an output minimal alpine image (i.e. one
without the development tools or other unnecessary stuff)

Another approach would be to use `ldd` or `objdump` recursively to find
libraries and copy only those binaries into the output (possibly using
`FROM scratch`?)

I don't know if this will help -- I realise my test case is a bit minimal
:-)

Cheers,
Dave


On Thu, Mar 29, 2018 at 5:31 PM, Hans Ole Rafaelsen <hrafaelsen@gmail.com>
wrote:

> Hi,
>
> I have small application written using Ocsigen. Ocaml and the rest of the
> development environment is installed using OPAM.
>
> Now I want to install this application on a few other nodes, without
> having to bring bring along the whole development process for deployment on
> each node. What I want to end up with, is a single unit, e.g a tar-file, a
> docker container or similar, that can be copied and deployed to the target
> nodes. This unit should only contain the binaries needed to run the
> application.
>
> I have tried to ask on the Ocsigen mailing-list how do do this for Ocsigen
> applications, but without success. But I guess the problem is more related
> to how to deploy applications built using OPAM. I did not find any way to
> do this with OPAM, but I might have missed something. I have tried to copy
> all the binary files (.so, .cmxa .cmxs, etc) from the OPAM directory and
> setting the environment variables to point the this new location, but
> without much success. When starting ocsigenserver it was not able to solve
> all symbols. Looking more into the problem, it looks like binaries such as
> ocsigenserver has hard coded the location of the OPAM development
> environment. Might be possible to override this using environment
> variables, but I'm not sure how. So I gave up on this track.
>
>
> Is there a way to generate such a deployable unit from OPAM development
> environment?
>
> Do anyone have some tips / best practice on how to deploy applications
> built using OPAM?
>
> (I'm developing and want to deploy on Ubuntu 16.04.)
>
> Regards,
>
> Hans Ole Rafaelsen
>



-- 
Dave Scott

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