View source for Extending the software stack on Hunter with Spack

'''''This page is work in progress!!!'''''

'''''In its current form, this page is meant for HLRS staff. Expect thing to change and break at any time.'''''

== Introduction ==

Most of the software stack on Hunter is build on top of Spack. Once released, a software stack is immutable. Also, during development of a new software stack, working directly on the files and directories is strongly discouraged. The normal workflow is to use Spack's capabilities to "chain" a private Spack instance to an upstream instance (i.e. the HLRS release). This allows to do modifications, tests, and adjustments to your private Spack instance without interfering with the upstream instance. Once you are satisfied with your modifications, it is possible to incorporate them and thus extend the upstream instance without mutating existing state. 

== Pre-requisites ==

# working access to internet from Hunter, e.g. ssh reverse tunnel with proxy setup


== Spack Module ==

Spack is available after loading the module <code>spack-user</code>. The module however, can only be loaded if the environment variables <code>TMPDIR</code> and <code>SPACK_USER_PREFIX</code> are exported and point to existing directories. Spack will be configured to expect and place most of its data in the directory <code>$SPACK_USER_PREFIX</code>. 

{{Command 
| command = $ export TMPDIR=/localscratch/${UID} <br/>
$ export SPACK_USER_PREFIX=${HOME}/my-spack <br/>
$ mkdir -p $TMPDIR; mkdir -p $SPACK_USER_PREFIX <br/>
$ module use /sw/hunter-rh9/hlrs/testing/release/main/modulefiles <br/>
$ module load spack-user
}}

Essentially, the module does two things: 
# set the environment variable <code>SPACK_ROOT</code> pointing to the base of HLRS' Spack instance, and 
# provide the command alias <code>spack</code> which wraps the original Spack command and adds some additional parameters to pick up relevant configuration files.

{{Command 
| command = $ alias spack </br>
 alias spack='spack -C $SPACK_ROOT/../config-hlrs -C $SPACK_ROOT/../config-user'
}}

The first time you use Spack it is recommended to bootstrap it. This may take up to several minutes
{{Command 
| command = $ spack bootstrap now
}}

== Your private Spack environment ==
All your private configuration and customization needs to be done in a so-called Spack environment. These are essentially directories below <code>$SPACK_USER_PREFIX/environments</code>. You may create multiple environments, but only one can be active at any given time. Creating an environment takes a somewhat lengthy command:

{{Command 
| command =
spack -C $SPACK_ROOT/../config-user env create --include-concrete $SPACK_ROOT/../environments/hlrs  --without-view my-tools </br>
==> Created environment my-tools in: .../my-spack/environments/my-tools </br>                                                                                                    
==> Activate with: spack env activate my-tools
}}
This will create the environment labeled ''my-tool'' in the indicated directory.

The option <code>--include-concrete</code> is what ties your environment to the HLRS software stack and must therefore not be omitted.