Get VPC configuration from stack outputs

This allows us to also obtain public and private subnets separately,
so that we have complete set of identifiers that would be of use
to create build the nodegroup stack.

pkg/cfn/manager/cluster.go

@@ -1,7 +1,11 @@
 package manager
 
 import (
+	"strings"
+
+	cfn "github.com/aws/aws-sdk-go/service/cloudformation"
 	"github.com/kris-nova/logger"
+	api "github.com/weaveworks/eksctl/pkg/apis/eksctl.io/v1alpha3"
 	"github.com/weaveworks/eksctl/pkg/cfn/builder"
 )
 
@@ -22,6 +26,24 @@ func (c *StackCollection) CreateCluster(errs chan error, _ interface{}) error {
 	return c.CreateStack(name, stack, nil, nil, errs)
 }
 
+// DescribeClusterStack calls DescribeStacks and filters out cluster stack
+func (c *StackCollection) DescribeClusterStack() (*Stack, error) {
+	stacks, err := c.DescribeStacks()
+	if err != nil {
+		return nil, err
+	}
+
+	for _, s := range stacks {
+		if *s.StackStatus == cfn.StackStatusDeleteComplete {
+			continue
+		}
+		if getClusterName(s) != "" {
+			return s, nil
+		}
+	}
+	return nil, nil
+}
+
 // DeleteCluster deletes the cluster
 func (c *StackCollection) DeleteCluster() error {
 	_, err := c.DeleteStack(c.makeClusterStackName())
@@ -32,3 +54,18 @@ func (c *StackCollection) DeleteCluster() error {
 func (c *StackCollection) WaitDeleteCluster() error {
 	return c.BlockingWaitDeleteStack(c.makeClusterStackName())
 }
+
+func getClusterName(s *Stack) string {
+	for _, tag := range s.Tags {
+		if *tag.Key == api.ClusterNameTag {
+			if strings.HasSuffix(*s.StackName, "-cluster") {
+				return *tag.Value
+			}
+		}
+	}
+
+	if strings.HasPrefix(*s.StackName, "EKS-") && strings.HasSuffix(*s.StackName, "-ControlPlane") {
+		return strings.TrimPrefix("EKS-", strings.TrimSuffix(*s.StackName, "-ControlPlane"))
+	}
+	return ""
+}

pkg/cfn/manager/nodegroup.go

@@ -249,12 +249,3 @@ func getNodeGroupName(s *Stack) string {
 	}
 	return ""
 }
-
-func getClusterName(s *Stack) string {
-	for _, tag := range s.Tags {
-		if *tag.Key == api.ClusterNameTag {
-			return *tag.Value
-		}
-	}
-	return ""
-}

pkg/eks/eks.go

@@ -7,12 +7,14 @@ import (
 	"strings"
 	"time"
 
+	"github.com/weaveworks/eksctl/pkg/cfn/builder"
+	"github.com/weaveworks/eksctl/pkg/vpc"
+
 	awseks "github.com/aws/aws-sdk-go/service/eks"
 	"github.com/kris-nova/logger"
 	"github.com/pkg/errors"
 	api "github.com/weaveworks/eksctl/pkg/apis/eksctl.io/v1alpha3"
 	"github.com/weaveworks/eksctl/pkg/printers"
-	"github.com/weaveworks/eksctl/pkg/vpc"
 	"k8s.io/apimachinery/pkg/util/sets"
 	"k8s.io/client-go/kubernetes"
 )
@@ -86,25 +88,42 @@ func (c *ClusterProvider) GetCredentials(spec *api.ClusterConfig) error {
 
 // GetClusterVPC retrieves the VPC configuration
 func (c *ClusterProvider) GetClusterVPC(spec *api.ClusterConfig) error {
-	// Check the cluster exists and is active
-	cluster, err := c.DescribeControlPlaneMustBeActive(spec.Metadata)
+	cluster, err := c.NewStackManager(spec).DescribeClusterStack()
 	if err != nil {
 		return err
 	}
-	logger.Debug("cluster = %#v", cluster)
+
+	outputs := map[string]string{}
+	for _, x := range cluster.Outputs {
+		outputs[*x.OutputKey] = *x.OutputValue
+	}
 
 	if spec.VPC == nil {
 		spec.VPC = &api.ClusterVPC{}
 	}
 
-	if err := vpc.ImportVPC(c.Provider, spec, *cluster.ResourcesVpcConfig.VpcId); err != nil {
-		return err
+	requiredKeyErrFmt := "cluster stack has no output key %q"
+
+	if vpc, ok := outputs[builder.CfnOutputClusterVPC]; ok {
+		spec.VPC.ID = vpc
+	} else {
+		return fmt.Errorf(requiredKeyErrFmt, builder.CfnOutputClusterVPC)
 	}
 
-	if numSGs := len(cluster.ResourcesVpcConfig.SecurityGroupIds); numSGs == 1 {
-		spec.VPC.SecurityGroup = *cluster.ResourcesVpcConfig.SecurityGroupIds[0]
+	if securityGroup, ok := outputs[builder.CfnOutputClusterSecurityGroup]; ok {
+		spec.VPC.SecurityGroup = securityGroup
 	} else {
-		return fmt.Errorf("cluster %q has %d security groups, expected 1", spec.Metadata.Name, numSGs)
+		return fmt.Errorf(requiredKeyErrFmt, builder.CfnOutputClusterSecurityGroup)
+	}
+
+	for _, topology := range api.SubnetTopologies() {
+		// either of subnet topologies are optional
+		if subnets, ok := outputs[builder.CfnOutputClusterSubnets+string(topology)]; ok {
+			subnets := strings.Split(subnets, ",")
+			if err := vpc.UseSubnets(c.Provider, spec, topology, subnets); err != nil {
+				return err
+			}
+		}
 	}
 
 	return nil