How to load Spack modules on AWS
================================

Follow the instructions below to load Spack modules on AWS. Spack is used for managing software
dependencies on AWS without needing to install them manually.

Related
-------

- :doc:`How to start an interactive compute node on AWS <aws-interactive-compute-node>`
- `Accessing the clusters (Confluence)
  <https://confluence.skatelescope.org/display/SE/Accessing+the+clusters>`_

Prerequisites
-------------

- An account on AWS and access to the headnode.

Steps
-----

.. note::

    If you are loading modules interactively you can run the commands in steps 2-3 on the CLI. If
    you are writing a SLURM script, add them to your script before loading any modules.

1. Log into the headnode on AWS and (optionally) start an interactive compute node if heavy
   computation is required.
2. Ensure that the environment is clean by unloading all modules.

   .. code-block:: bash

       module purge

3. Load the latest Spack environment:

   .. code-block:: bash

       module load ska-sdp-spack

   .. note::

       If you want to load an older Spack environment you can specify the tag (e.g. to load
       ``2025.12.1`` you would run ``module load ska-sdp-spack/2025.12.1``). You can check which
       Spack environments are available by running ``module avail ska-sdp-spack``.

4. You can now load your desired Spack module (e.g. ``carta``):

   .. code-block:: bash

       module load carta

Verification
------------

You can verify that the Spack module has been loaded successfully by checking the module list:

.. code-block:: bash

    module list

This should display the loaded Spack module along with any other modules that are currently loaded.

You can also check the version of the loaded module (e.g. carta) to ensure it matches the expected
version:

.. code-block:: bash

    carta --version

FAQ
---

**Q: How do I know which Spack modules are available?**

A: After loading the ``ska-sdp-spack`` module, you can list all available Spack modules by running:

.. code-block:: bash

    module avail

**Q: How can I check that the module I want to load is available?**

A: After loading the ``ska-sdp-spack`` module, you can check for a specific module by running:

.. code-block:: bash

    module avail <module_name>

**Q: Can I load multiple Spack modules at once?**

A: Yes, you can load multiple Spack modules by running the ``module load`` command with a list of
module names separated by spaces.

Troubleshooting
---------------

If you encounter issues loading Spack modules, consider the following troubleshooting steps:

- Ensure that ``/shared/fsx1/shared/metamodules`` is in your ``MODULEPATH``. You can verify this by
  running ``echo $MODULEPATH``. It should be there by default on all AWS nodes.
- Verify that the Spack environment you are trying to load exists by running ``module avail
  ska-sdp-spack``.
- Check for any typos in the module load commands.