Add kubernetes probe helpers

components/common-go/kubernetes/probes.go

@@ -0,0 +1,69 @@
+// Copyright (c) 2022 Gitpod GmbH. All rights reserved.
+// Licensed under the GNU Affero General Public License (AGPL).
+// See License-AGPL.txt in the project root for license information.
+
+package kubernetes
+
+import (
+	"context"
+	"crypto/tls"
+	"fmt"
+	"net"
+	"net/http"
+	"time"
+
+	"github.com/gitpod-io/gitpod/common-go/log"
+)
+
+func NetworkIsReachableProbe(url string) func() error {
+	log.Infof("creating network check using URL %v", url)
+	return func() error {
+		tr := &http.Transport{
+			TLSClientConfig: &tls.Config{InsecureSkipVerify: true},
+		}
+		client := &http.Client{
+			Transport: tr,
+			Timeout:   1 * time.Second,
+			// never follow redirects
+			CheckRedirect: func(*http.Request, []*http.Request) error {
+				return http.ErrUseLastResponse
+			},
+		}
+
+		resp, err := client.Get(url)
+		if err != nil {
+			log.Errorf("unexpected error checking URL %v: %v", url, err)
+			return err
+		}
+		resp.Body.Close()
+
+		if resp.StatusCode > 399 {
+			log.WithField("url", url).WithField("statusCode", resp.StatusCode).Error("NetworkIsReachableProbe: unexpected status code checking URL")
+			return fmt.Errorf("returned status %d", resp.StatusCode)
+		}
+
+		return nil
+	}
+}
+
+func DNSCanResolveProbe(host string, timeout time.Duration) func() error {
+	log.Infof("creating DNS check for host %v", host)
+
+	resolver := net.Resolver{}
+	return func() error {
+		ctx, cancel := context.WithTimeout(context.Background(), timeout)
+		defer cancel()
+
+		addrs, err := resolver.LookupHost(ctx, host)
+		if err != nil {
+			log.WithField("host", host).Error("NetworkIsReachableProbe: unexpected error resolving host")
+			return err
+		}
+
+		if len(addrs) < 1 {
+			return fmt.Errorf("could not resolve host")
+		}
+
+		return nil
+	}
+}