Addition of waits and retries to have the instance vnc URL ready

cmd/instance/instance_vnc.go

@@ -1,14 +1,21 @@
 package instance
 
 import (
+	"fmt"
+	"net/http"
+	"os"
+	"time"
+
 	"github.com/civo/cli/common"
 	"github.com/civo/cli/config"
 	"github.com/civo/cli/pkg/browser"
 	"github.com/civo/cli/utility"
 	"github.com/spf13/cobra"
-	"os"
 )
 
+// maxAttempts represents the max number of attempts (each one every 7s) to connect to the vnc URL
+const maxAttempts = 5
+
 var instanceVncCmd = &cobra.Command{
 	Use:     "vnc",
 	Example: "civo instance vnc INSTANCE-ID/NAME",
@@ -46,7 +53,16 @@ var instanceVncCmd = &cobra.Command{
 		// Display VNC details
 		utility.Info("VNC has been successfully enabled for instance: %s", instance.Hostname)
 		utility.Info("VNC URL: %s", vnc.URI)
+		utility.Info("We're preparing the VNC Console Access. This may take a while...")
+
+		err = waitEndpointReady(vnc.URI)
+		if err != nil {
+			utility.Error("VNC Console URL is not reachable: %s", err)
+			os.Exit(1)
+		}
+
 		utility.Info("Opening VNC in your default browser...")
+		time.Sleep(3 * time.Second)
 
 		// Open VNC in the browser
 		err = browser.OpenInBrowser(vnc.URI)
@@ -57,3 +73,32 @@ var instanceVncCmd = &cobra.Command{
 		}
 	},
 }
+
+// endpointReady checks if the given URL endpoint is ready by sending a GET request
+// and returning true if the HTTP status code is not 503 or 40x
+func endpointReady(url string) bool {
+	utility.Info("New attempt to reach the VNC Console URI...")
+	resp, err := http.Get(url)
+	if err != nil {
+		return false
+	}
+	defer resp.Body.Close()
+
+	return resp.StatusCode != http.StatusServiceUnavailable
+}
+
+// waitEndpointReady continuously checks the given URL endpoint every 5 seconds
+// until it becomes ready (i.e., it does not return an HTTP 503 status).
+func waitEndpointReady(url string) error {
+	var attempt int
+	for {
+		attempt++
+		if endpointReady(url) {
+			return nil
+		}
+		if attempt == maxAttempts {
+			return fmt.Errorf("max num of attempts reached: VNC endpoint not ready - please contact the support")
+		}
+		time.Sleep(7 * time.Second) // Wait for 7 seconds before the next attempt
+	}
+}