ec2: check subnet exists in vpc

drivers/amazonec2/amazonec2.go

@@ -210,6 +210,42 @@ func (d *Driver) checkPrereqs() error {
 	if key != nil {
 		return fmt.Errorf("There is already a keypair with the name %s.  Please either remove that keypair or use a different machine name.", d.MachineName)
 	}
+
+	regionZone := d.Region + d.Zone
+	if d.SubnetId == "" {
+		filters := []amz.Filter{
+			{
+				Name:  "availabilityZone",
+				Value: regionZone,
+			},
+			{
+				Name:  "vpc-id",
+				Value: d.VpcId,
+			},
+		}
+
+		subnets, err := d.getClient().GetSubnets(filters)
+		if err != nil {
+			return err
+		}
+
+		if len(subnets) == 0 {
+			return fmt.Errorf("unable to find a subnet in the zone: %s", regionZone)
+		}
+
+		d.SubnetId = subnets[0].SubnetId
+
+		// try to find default
+		if len(subnets) > 1 {
+			for _, subnet := range subnets {
+				if subnet.DefaultForAz {
+					d.SubnetId = subnet.SubnetId
+					break
+				}
+			}
+		}
+	}
+
 	return nil
 }
 
@@ -239,39 +275,28 @@ func (d *Driver) Create() error {
 		VolumeType:          "gp2",
 	}
 
-	// get the subnet id
-	regionZone := d.Region + d.Zone
-	subnetId := d.SubnetId
+	log.Debugf("launching instance in subnet %s", d.SubnetId)
+	instance, err := d.getClient().RunInstance(d.AMI, d.InstanceType, d.Zone, 1, 1, d.SecurityGroupId, d.KeyName, d.SubnetId, bdm)
 
-	if d.SubnetId == "" {
-		subnets, err := d.getClient().GetSubnets()
+	if err != nil {
+		return fmt.Errorf("Error launching instance: %s", err)
+	}
+
+	d.InstanceId = instance.InstanceId
+	log.Debug("waiting for ip address to become available")
+	for {
+		ip, err := d.GetIP()
 		if err != nil {
 			return err
 		}
+		if ip != "" {
 
-		for _, s := range subnets {
-			if s.AvailabilityZone == regionZone {
-				subnetId = s.SubnetId
-				break
-			}
+			d.IPAddress = instance.IpAddress
+			break
 		}
-
+		time.Sleep(5 * time.Second)
 	}
 
-	if subnetId == "" {
-		return fmt.Errorf("unable to find a subnet in the zone: %s", regionZone)
-	}
-
-	log.Debugf("launching instance in subnet %s", subnetId)
-	instance, err := d.getClient().RunInstance(d.AMI, d.InstanceType, d.Zone, 1, 1, d.SecurityGroupId, d.KeyName, subnetId, bdm)
-
-	if err != nil {
-		return fmt.Errorf("Error launching instance: %s", err)
-	}
-
-	d.InstanceId = instance.InstanceId
-	d.IPAddress = instance.IpAddress
-
 	if len(instance.NetworkInterfaceSet) > 0 {
 		d.PrivateIPAddress = instance.NetworkInterfaceSet[0].PrivateIpAddress
 	}
@@ -320,7 +345,6 @@ func (d *Driver) Create() error {
 }
 
 func (d *Driver) GetURL() (string, error) {
-
 	if d.IPAddress == "" {
 		return "", nil
 	}

drivers/amazonec2/amz/describe_subnets.go

@@ -11,4 +11,5 @@ type Subnet struct {
 	VpcId            string `xml:"vpcId"`
 	CidrBlock        string `xml:"cidrBlock"`
 	AvailabilityZone string `xml:"availabilityZone"`
+	DefaultForAz     bool   `xml:"defaultForAz"`
 }

drivers/amazonec2/amz/ec2.go

@@ -417,13 +417,20 @@ func (e *EC2) GetSecurityGroupById(id string) (*SecurityGroup, error) {
 	return nil, nil
 }
 
-func (e *EC2) GetSubnets() ([]Subnet, error) {
+func (e *EC2) GetSubnets(filters []Filter) ([]Subnet, error) {
 	subnets := []Subnet{}
-	resp, err := e.performStandardAction("DescribeSubnets")
-	if err != nil {
-		return subnets, err
+	v := url.Values{}
+	v.Set("Action", "DescribeSubnets")
+
+	for idx, filter := range filters {
+		n := idx + 1 // amazon starts counting from 1 not 0
+		v.Set(fmt.Sprintf("Filter.%d.Name", n), filter.Name)
+		v.Set(fmt.Sprintf("Filter.%d.Value", n), filter.Value)
 	}
+
+	resp, err := e.awsApiCall(v)
 	defer resp.Body.Close()
+
 	contents, err := ioutil.ReadAll(resp.Body)
 	if err != nil {
 		return subnets, fmt.Errorf("Error reading AWS response body: %s", err)

drivers/amazonec2/amz/filter.go

@@ -0,0 +1,6 @@
+package amz
+
+type Filter struct {
+	Name  string
+	Value string
+}