feat: pad nodebalancer backend names

Nodebalancers must have a name that is 3-32 characters in length.
This adds support to pad the node name if it's too short,
since in Kubernetes it's valid to have node names of only
1 or 2 characters.

Author: wbh1

cloud/linode/loadbalancers.go

@@ -644,9 +644,14 @@ func (l *loadbalancers) buildLoadBalancerRequest(ctx context.Context, clusterNam
 	return l.createNodeBalancer(ctx, clusterName, service, configs)
 }
 
-func trimString(s string, maxLen int) string {
+func coerceString(s string, minLen, maxLen int, padding string) string {
+	if len(padding) == 0 {
+		padding = "x"
+	}
 	if len(s) > maxLen {
 		return s[:maxLen]
+	} else if len(s) < minLen {
+		return coerceString(fmt.Sprintf("%s%s", padding, s), minLen, maxLen, padding)
 	}
 	return s
 }
@@ -655,7 +660,8 @@ func (l *loadbalancers) buildNodeBalancerNodeCreateOptions(node *v1.Node, nodePo
 	return linodego.NodeBalancerNodeCreateOptions{
 		Address: fmt.Sprintf("%v:%v", getNodePrivateIP(node), nodePort),
 		// NodeBalancer backends must be 3-32 chars in length
-		Label:  trimString(node.Name, 32),
+		// If < 3 chars, pad node name with "node-" prefix
+		Label:  coerceString(node.Name, 3, 32, "node-"),
 		Mode:   "accept",
 		Weight: 100,
 	}

cloud/linode/loadbalancers_test.go

@@ -2114,3 +2114,45 @@ func addTLSSecret(t *testing.T, kubeClient kubernetes.Interface) {
 		t.Fatalf("failed to add TLS secret: %s\n", err)
 	}
 }
+
+func Test_LoadbalNodeNameCoercion(t *testing.T) {
+	type testCase struct {
+		nodeName       string
+		padding        string
+		expectedOutput string
+	}
+	testCases := []testCase{
+		{
+			nodeName:       "n",
+			padding:        "z",
+			expectedOutput: "zzn",
+		},
+		{
+			nodeName:       "n",
+			padding:        "node-",
+			expectedOutput: "node-n",
+		},
+		{
+			nodeName:       "n",
+			padding:        "",
+			expectedOutput: "xxn",
+		},
+		{
+			nodeName:       "infra-logging-controlplane-3-atl1-us-prod",
+			padding:        "node-",
+			expectedOutput: "infra-logging-controlplane-3-atl",
+		},
+		{
+			nodeName:       "node1",
+			padding:        "node-",
+			expectedOutput: "node1",
+		},
+	}
+
+	for _, tc := range testCases {
+		if out := coerceString(tc.nodeName, 3, 32, tc.padding); out != tc.expectedOutput {
+			t.Fatalf("Expected loadbal backend name to be %s (got: %s)", tc.expectedOutput, out)
+		}
+	}
+
+}