planner: add a NodeSelector function to the planner

This planner function will select and/or combine the possible sources
for our default node selector value(s). If there's no default node
selector value in the config or if it is not valid JSON, fall back to
the hard-coded default. If available, use the admin specified value.

Signed-off-by: John Mulligan <[email protected]>

Author: phlogistonjohn

internal/planner/selector.go

@@ -0,0 +1,29 @@
+// SPDX-License-Identifier: Apache-2.0
+
+package planner
+
+import (
+	"encoding/json"
+)
+
+// builtinDefaultNodeSelector defines our defaults if no administrative
+// overrides are supplied. Samba containers run only on linux. Currently
+// they're only built for x86_64 (amd64).
+var builtinDefaultNodeSelector = map[string]string{
+	"kubernetes.io/os":   "linux",
+	"kubernetes.io/arch": "amd64",
+}
+
+// NodeSelector returns a mapping of k8s label names to values that are
+// used to select what nodes resources are scheduled to run on.
+func (pl *Planner) NodeSelector() (map[string]string, error) {
+	if pl.GlobalConfig.DefaultNodeSelector == "" {
+		return builtinDefaultNodeSelector, nil
+	}
+	var nsel map[string]string
+	err := json.Unmarshal([]byte(pl.GlobalConfig.DefaultNodeSelector), &nsel)
+	if err != nil {
+		return builtinDefaultNodeSelector, err
+	}
+	return nsel, nil
+}