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

[Hans Ole Rafaelsen <hrafaelsen@gmail.com>]

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Hi David,

It helps a bit. But my biggest problem is that the Ocaml application
(main.exe in your example) has dependencies to other Ocaml libraries built
using OPAM. I need to find a way to find those dependencies and make sure
that the paths are resolved correctly once libraries have have been copied
to the image.

-- 
Hans Ole

On Thu, Mar 29, 2018 at 8:13 PM, David Scott <scott.dj@gmail.com> wrote:

> 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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