Log if availability zone does not exist

Improve user experience by logging availability zone
does not exist instead of logging subnet not found if
availability zone does not exist.

pkg/actuators/machine/actuator_test.go

@@ -679,7 +679,7 @@ func TestAvailabiltyZone(t *testing.T) {
 
 			mockAWSClient.EXPECT().TerminateInstances(gomock.Any()).Return(&ec2.TerminateInstancesOutput{}, nil)
 			mockAWSClient.EXPECT().RegisterInstancesWithLoadBalancer(gomock.Any()).AnyTimes()
-
+			mockAWSClient.EXPECT().DescribeAvailabilityZones(gomock.Any()).Return(nil, nil).AnyTimes()
 			mockAWSClient.EXPECT().DescribeSubnets(gomock.Any()).Return(&ec2.DescribeSubnetsOutput{}, nil)
 
 			actuator.Create(context.TODO(), cluster, machine)

pkg/actuators/machine/instaces_test.go

@@ -263,6 +263,7 @@ func TestLaunchInstance(t *testing.T) {
 		securityGroupErr    error
 		subnetOutput        *ec2.DescribeSubnetsOutput
 		subnetErr           error
+		azErr               error
 		imageOutput         *ec2.DescribeImagesOutput
 		imageErr            error
 	}{
@@ -327,6 +328,13 @@ func TestLaunchInstance(t *testing.T) {
 			}),
 			subnetErr: fmt.Errorf("error"),
 		},
+		{
+			name: "Subnet with availability zone with error",
+			providerConfig: stubPCSubnet(providerconfigv1.AWSResourceReference{
+				Filters: []providerconfigv1.Filter{},
+			}),
+			azErr: fmt.Errorf("error"),
+		},
 		{
 			name: "AMI with filters",
 			providerConfig: stubPCAMI(providerconfigv1.AWSResourceReference{
@@ -396,6 +404,7 @@ func TestLaunchInstance(t *testing.T) {
 			mockAWSClient := mockaws.NewMockClient(mockCtrl)
 
 			mockAWSClient.EXPECT().DescribeSecurityGroups(gomock.Any()).Return(tc.securityGroupOutput, tc.securityGroupErr).AnyTimes()
+			mockAWSClient.EXPECT().DescribeAvailabilityZones(gomock.Any()).Return(nil, tc.azErr).AnyTimes()
 			mockAWSClient.EXPECT().DescribeSubnets(gomock.Any()).Return(tc.subnetOutput, tc.subnetErr).AnyTimes()
 			mockAWSClient.EXPECT().DescribeImages(gomock.Any()).Return(tc.imageOutput, tc.imageErr).AnyTimes()
 			mockAWSClient.EXPECT().RunInstances(gomock.Any())

pkg/actuators/machine/instances.go

@@ -102,6 +102,16 @@ func getSubnetIDs(subnet providerconfigv1.AWSResourceReference, availabilityZone
 	} else {
 		var filters []providerconfigv1.Filter
 		if availabilityZone != "" {
+			// Improve error logging for better user experience.
+			// Otherwise, during the process of minimizing API calls, this is a good
+			// candidate for removal.
+			_, err := client.DescribeAvailabilityZones(&ec2.DescribeAvailabilityZonesInput{
+				ZoneNames: []*string{aws.String(availabilityZone)},
+			})
+			if err != nil {
+				glog.Errorf("error describing availability zones: %v", err)
+				return nil, fmt.Errorf("error describing availability zones: %v", err)
+			}
 			filters = append(filters, providerconfigv1.Filter{Name: "availabilityZone", Values: []string{availabilityZone}})
 		}
 		filters = append(filters, subnet.Filters...)

pkg/client/client.go

@@ -51,6 +51,7 @@ type Client interface {
 	DescribeImages(*ec2.DescribeImagesInput) (*ec2.DescribeImagesOutput, error)
 	DescribeVpcs(*ec2.DescribeVpcsInput) (*ec2.DescribeVpcsOutput, error)
 	DescribeSubnets(*ec2.DescribeSubnetsInput) (*ec2.DescribeSubnetsOutput, error)
+	DescribeAvailabilityZones(*ec2.DescribeAvailabilityZonesInput) (*ec2.DescribeAvailabilityZonesOutput, error)
 	DescribeSecurityGroups(*ec2.DescribeSecurityGroupsInput) (*ec2.DescribeSecurityGroupsOutput, error)
 	RunInstances(*ec2.RunInstancesInput) (*ec2.Reservation, error)
 	DescribeInstances(*ec2.DescribeInstancesInput) (*ec2.DescribeInstancesOutput, error)
@@ -80,6 +81,10 @@ func (c *awsClient) DescribeSubnets(input *ec2.DescribeSubnetsInput) (*ec2.Descr
 	return c.ec2Client.DescribeSubnets(input)
 }
 
+func (c *awsClient) DescribeAvailabilityZones(input *ec2.DescribeAvailabilityZonesInput) (*ec2.DescribeAvailabilityZonesOutput, error) {
+	return c.ec2Client.DescribeAvailabilityZones(input)
+}
+
 func (c *awsClient) DescribeSecurityGroups(input *ec2.DescribeSecurityGroupsInput) (*ec2.DescribeSecurityGroupsOutput, error) {
 	return c.ec2Client.DescribeSecurityGroups(input)
 }

pkg/client/fake/fake.go

@@ -44,6 +44,10 @@ func (c *awsClient) DescribeSubnets(input *ec2.DescribeSubnetsInput) (*ec2.Descr
 	}, nil
 }
 
+func (c *awsClient) DescribeAvailabilityZones(*ec2.DescribeAvailabilityZonesInput) (*ec2.DescribeAvailabilityZonesOutput, error) {
+	return &ec2.DescribeAvailabilityZonesOutput{}, nil
+}
+
 func (c *awsClient) DescribeSecurityGroups(input *ec2.DescribeSecurityGroupsInput) (*ec2.DescribeSecurityGroupsOutput, error) {
 	return &ec2.DescribeSecurityGroupsOutput{
 		SecurityGroups: []*ec2.SecurityGroup{