enhancement(slurmctld): enforce job level memory

These changes introduce default values for SelectTypeParameters
and MemSpecLimit.

`SelectTypeParameters=CR_CPU_Memory` to enable memory allocation
enforcement.

`MemSpecLimit=1024` to ensure systems always have 1G available
memory that jobs cannot consume.

charms/slurmctld/src/constants.py

@@ -18,6 +18,7 @@
     "PluginDir": ["/usr/lib/x86_64-linux-gnu/slurm-wlm"],
     "PlugStackConfig": "/etc/slurm/plugstack.conf.d/plugstack.conf",
     "SelectType": "select/cons_tres",
+    "SelectTypeParameters": "CR_CPU_Memory",
     "SlurmctldPort": "6817",
     "SlurmdPort": "6818",
     "StateSaveLocation": "/var/lib/slurm/checkpoint",

charms/slurmd/src/charm.py

@@ -7,6 +7,7 @@
 import logging
 from typing import Any, Dict, cast
 
+from constants import CHARM_MAINTAINED_NODE_PARAMETERS
 from interface_slurmctld import Slurmctld, SlurmctldAvailableEvent
 from ops import (
     ActionEvent,
@@ -326,6 +327,7 @@ def get_node(self) -> Dict[Any, Any]:
         node = {
             "node_parameters": {
                 **machine.get_slurmd_info(),
+                **CHARM_MAINTAINED_NODE_PARAMETERS,
                 **self._user_supplied_node_parameters,
             },
             "new_node": self._new_node,

charms/slurmd/src/constants.py

@@ -0,0 +1,6 @@
+# Copyright 2024 Omnivector, LLC.
+# See LICENSE file for licensing details.
+
+"""This module provides constants for the slurmd-operator charm."""
+
+CHARM_MAINTAINED_NODE_PARAMETERS = {"MemSpecLimit": "1024"}