Include more information when multiple security groups are tagged

pkg/cloudprovider/providers/aws/aws.go

@@ -3653,7 +3653,11 @@ func findSecurityGroupForInstance(instance *ec2.Instance, taggedSecurityGroups m
 		// We create instances with one SG
 		// If users create multiple SGs, they must tag one of them as being k8s owned
 		if len(tagged) != 1 {
-			return nil, fmt.Errorf("Multiple tagged security groups found for instance %s; ensure only the k8s security group is tagged", instanceID)
+			taggedGroups := ""
+			for _, v := range tagged {
+				taggedGroups += fmt.Sprintf("%s(%s) ", *v.GroupId, *v.GroupName)
+			}
+			return nil, fmt.Errorf("Multiple tagged security groups found for instance %s; ensure only the k8s security group is tagged; the tagged groups were %v", instanceID, taggedGroups)
 		}
 		return tagged[0], nil
 	}

pkg/cloudprovider/providers/aws/aws_test.go

@@ -1302,6 +1302,29 @@ func TestEnsureLoadBalancerHealthCheck(t *testing.T) {
 	})
 }
 
+func TestFindSecurityGroupForInstance(t *testing.T) {
+	groups := map[string]*ec2.SecurityGroup{"sg123": {GroupId: aws.String("sg123")}}
+	id, err := findSecurityGroupForInstance(&ec2.Instance{SecurityGroups: []*ec2.GroupIdentifier{{GroupId: aws.String("sg123"), GroupName: aws.String("my_group")}}}, groups)
+	if err != nil {
+		t.Error()
+	}
+	assert.Equal(t, *id.GroupId, "sg123")
+	assert.Equal(t, *id.GroupName, "my_group")
+}
+
+func TestFindSecurityGroupForInstanceMultipleTagged(t *testing.T) {
+	groups := map[string]*ec2.SecurityGroup{"sg123": {GroupId: aws.String("sg123")}}
+	_, err := findSecurityGroupForInstance(&ec2.Instance{
+		SecurityGroups: []*ec2.GroupIdentifier{
+			{GroupId: aws.String("sg123"), GroupName: aws.String("my_group")},
+			{GroupId: aws.String("sg123"), GroupName: aws.String("another_group")},
+		},
+	}, groups)
+	require.Error(t, err)
+	assert.Contains(t, err.Error(), "sg123(my_group)")
+	assert.Contains(t, err.Error(), "sg123(another_group)")
+}
+
 func newMockedFakeAWSServices(id string) *FakeAWSServices {
 	s := NewFakeAWSServices(id)
 	s.ec2 = &MockedFakeEC2{FakeEC2Impl: s.ec2.(*FakeEC2Impl)}