Ensure proper cleanup of dangling resources in case of failure

drivers/amazonec2/amazonec2.go

@@ -109,6 +109,8 @@ type Driver struct {
 	Endpoint                string
 	DisableSSL              bool
 	UserDataFile            string
+
+	spotInstanceRequestId string
 }
 
 type clientFactory interface {
@@ -573,6 +575,16 @@ func (d *Driver) Create() error {
 		return err
 	}
 
+	if err := d.innerCreate(); err != nil {
+		// cleanup partially created resources
+		d.Remove()
+		return err
+	}
+
+	return nil
+}
+
+func (d *Driver) innerCreate() error {
 	log.Infof("Launching instance...")
 
 	if err := d.createKeyPair(); err != nil {
@@ -639,12 +651,13 @@ func (d *Driver) Create() error {
 		if err != nil {
 			return fmt.Errorf("Error request spot instance: %s", err)
 		}
+		d.spotInstanceRequestId = *spotInstanceRequest.SpotInstanceRequests[0].SpotInstanceRequestId
 
 		log.Info("Waiting for spot instance...")
 		for i := 0; i < 3; i++ {
 			// AWS eventual consistency means we could not have SpotInstanceRequest ready yet
 			err = d.getClient().WaitUntilSpotInstanceRequestFulfilled(&ec2.DescribeSpotInstanceRequestsInput{
-				SpotInstanceRequestIds: []*string{spotInstanceRequest.SpotInstanceRequests[0].SpotInstanceRequestId},
+				SpotInstanceRequestIds: []*string{&d.spotInstanceRequestId},
 			})
 			if err != nil {
 				if awsErr, ok := err.(awserr.Error); ok {
@@ -657,15 +670,15 @@ func (d *Driver) Create() error {
 			}
 			break
 		}
-		log.Info("Created spot instance request %v", *spotInstanceRequest.SpotInstanceRequests[0].SpotInstanceRequestId)
+		log.Infof("Created spot instance request %v", d.spotInstanceRequestId)
 		// resolve instance id
 		for i := 0; i < 3; i++ {
 			// Even though the waiter succeeded, eventual consistency means we could
 			// get a describe output that does not include this information. Try a
 			// few times just in case
 			var resolvedSpotInstance *ec2.DescribeSpotInstanceRequestsOutput
 			resolvedSpotInstance, err = d.getClient().DescribeSpotInstanceRequests(&ec2.DescribeSpotInstanceRequestsInput{
-				SpotInstanceRequestIds: []*string{spotInstanceRequest.SpotInstanceRequests[0].SpotInstanceRequestId},
+				SpotInstanceRequestIds: []*string{&d.spotInstanceRequestId},
 			})
 			if err != nil {
 				// Unexpected; no need to retry
@@ -868,6 +881,14 @@ func (d *Driver) Remove() error {
 		multierr.Errs = append(multierr.Errs, err)
 	}
 
+	// In case of failure waiting for a SpotInstance, we must cancel the unfulfilled request, otherwise an instance may be created later.
+	// If the instance was created, terminating it will be enough for canceling the SpotInstanceRequest
+	if d.RequestSpotInstance && d.spotInstanceRequestId != "" {
+		if err := d.cancelSpotInstanceRequest(); err != nil {
+			multierr.Errs = append(multierr.Errs, err)
+		}
+	}
+
 	if !d.ExistingKey {
 		if err := d.deleteKeyPair(); err != nil {
 			multierr.Errs = append(multierr.Errs, err)
@@ -881,6 +902,15 @@ func (d *Driver) Remove() error {
 	return multierr
 }
 
+func (d *Driver) cancelSpotInstanceRequest() error {
+	// NB: Canceling a Spot instance request does not terminate running Spot instances associated with the request
+	_, err := d.getClient().CancelSpotInstanceRequests(&ec2.CancelSpotInstanceRequestsInput{
+		SpotInstanceRequestIds: []*string{&d.spotInstanceRequestId},
+	})
+
+	return err
+}
+
 func (d *Driver) getInstance() (*ec2.Instance, error) {
 	instances, err := d.getClient().DescribeInstances(&ec2.DescribeInstancesInput{
 		InstanceIds: []*string{&d.InstanceId},
@@ -955,7 +985,8 @@ func (d *Driver) createKeyPair() error {
 
 func (d *Driver) terminate() error {
 	if d.InstanceId == "" {
-		return fmt.Errorf("unknown instance")
+		log.Warn("Missing instance ID, this is likely due to a failure during machine creation")
+		return nil
 	}
 
 	log.Debugf("terminating instance: %s", d.InstanceId)
@@ -1168,6 +1199,11 @@ func (d *Driver) configureSecurityGroupPermissions(group *ec2.SecurityGroup) ([]
 }
 
 func (d *Driver) deleteKeyPair() error {
+	if d.KeyName == "" {
+		log.Warn("Missing key pair name, this is likely due to a failure during machine creation")
+		return nil
+	}
+
 	log.Debugf("deleting key pair: %s", d.KeyName)
 
 	_, err := d.getClient().DeleteKeyPair(&ec2.DeleteKeyPairInput{

drivers/amazonec2/ec2client.go

@@ -48,4 +48,5 @@ type Ec2Client interface {
 	DescribeSpotInstanceRequests(input *ec2.DescribeSpotInstanceRequestsInput) (*ec2.DescribeSpotInstanceRequestsOutput, error)
 
 	WaitUntilSpotInstanceRequestFulfilled(input *ec2.DescribeSpotInstanceRequestsInput) error
+	CancelSpotInstanceRequests(input *ec2.CancelSpotInstanceRequestsInput) (*ec2.CancelSpotInstanceRequestsOutput, error)
 }