Ask for confirmation before destroy (#1178)

Closes #1165

README.md

@@ -77,7 +77,7 @@ $ kube-aws update --s3-uri s3://<your-bucket>/<optional-prefix>
 Destroy:
 
 ```
-# Destroy all the cfn stacks including the one for control-plane and the ones for worker node pools
+# Destroy all the cfn stacks including the one for control-plane and the ones for worker node pools. Use `--force` for skip confirmation. 
 $ kube-aws destroy
 ```
 

cmd/destroy.go

@@ -1,7 +1,10 @@
 package cmd
 
 import (
+	"bufio"
 	"fmt"
+	"os"
+	"strings"
 
 	"github.com/spf13/cobra"
 
@@ -22,9 +25,15 @@ var (
 func init() {
 	RootCmd.AddCommand(cmdDestroy)
 	cmdDestroy.Flags().BoolVar(&destroyOpts.AwsDebug, "aws-debug", false, "Log debug information from aws-sdk-go library")
+	cmdDestroy.Flags().BoolVar(&destroyOpts.Force, "force", false, "Don't ask for confirmation")
 }
 
 func runCmdDestroy(cmd *cobra.Command, args []string) error {
+	if !destroyOpts.Force && !destroyConfirmation() {
+		fmt.Printf("Operation Cancelled")
+		return nil
+	}
+
 	c, err := root.ClusterDestroyerFromFile(configPath, destroyOpts)
 	if err != nil {
 		return fmt.Errorf("Error parsing config: %v", err)
@@ -37,3 +46,12 @@ func runCmdDestroy(cmd *cobra.Command, args []string) error {
 	fmt.Println("CloudFormation stack is being destroyed. This will take several minutes")
 	return nil
 }
+
+func destroyConfirmation() bool {
+	reader := bufio.NewReader(os.Stdin)
+	fmt.Print("This operation will destroy the cluster. Are you sure? [y,n]: ")
+	text, _ := reader.ReadString('\n')
+	text = strings.TrimSuffix(strings.ToLower(text), "\n")
+
+	return text == "y" || text == "yes"
+}

core/root/destroyer.go

@@ -2,6 +2,7 @@ package root
 
 import (
 	"fmt"
+
 	"github.com/aws/aws-sdk-go/aws"
 	"github.com/aws/aws-sdk-go/aws/session"
 	"github.com/kubernetes-incubator/kube-aws/cfnstack"
@@ -10,6 +11,7 @@ import (
 
 type DestroyOptions struct {
 	AwsDebug bool
+	Force    bool
 }
 
 type ClusterDestroyer interface {

docs/getting-started/step-7-destroy.md

@@ -1,5 +1,5 @@
 ## Destroy the cluster
 
-When you are done with your cluster `kube-aws destroy` to destroy all the cluster components.
+When you are done with your cluster `kube-aws destroy` to destroy all the cluster components. It will as for confirmation. Use `--force` to skip confirmation step.
 
 If you created any Kubernetes Services of type `LoadBalancer`, you must delete these first, as the CloudFormation cannot be fully destroyed if any externally-managed resources still exist.