return service unavailable from k0s api when etcd is unhealthy

cmd/api/api.go

@@ -135,6 +135,12 @@ func (c *command) etcdHandler() http.Handler {
 			return
 		}
 
+		err = etcdClient.Health(ctx)
+		if err != nil {
+			sendError(err, resp, http.StatusServiceUnavailable)
+			return
+		}
+
 		memberList, err := etcdClient.AddMember(ctx, etcdReq.Node, etcdReq.PeerAddress)
 		if err != nil {
 			sendError(err, resp)

pkg/token/joinclient.go

@@ -20,17 +20,23 @@ import (
 	"bytes"
 	"context"
 	"encoding/json"
+	"errors"
 	"fmt"
 
 	"github.com/k0sproject/k0s/pkg/apis/k0s/v1beta1"
 	"github.com/k0sproject/k0s/pkg/kubernetes"
 
+	apierrors "k8s.io/apimachinery/pkg/api/errors"
 	"k8s.io/client-go/dynamic"
 	"k8s.io/client-go/rest"
 	"k8s.io/client-go/tools/clientcmd"
 	"k8s.io/client-go/tools/clientcmd/api"
 )
 
+var (
+	ErrEtcdUnhealthy = errors.New("etcd is unhealthy")
+)
+
 // JoinClient is the client we can use to call k0s join APIs
 type JoinClient struct {
 	joinTokenType string
@@ -101,6 +107,9 @@ func (j *JoinClient) JoinEtcd(ctx context.Context, etcdRequest v1beta1.EtcdReque
 	if err == nil {
 		err = json.Unmarshal(b, &etcdResponse)
 	}
+	if apierrors.IsServiceUnavailable(err) {
+		return etcdResponse, ErrEtcdUnhealthy
+	}
 
 	return etcdResponse, err
 }

pkg/token/joinclient_test.go

@@ -106,10 +106,6 @@ func TestJoinClient_Cancellation(t *testing.T) {
 		name          string
 		funcUnderTest func(context.Context, *token.JoinClient) error
 	}{
-		{"GetCA", func(ctx context.Context, c *token.JoinClient) error {
-			_, err := c.GetCA(ctx)
-			return err
-		}},
 		{"JoinEtcd", func(ctx context.Context, c *token.JoinClient) error {
 			_, err := c.JoinEtcd(ctx, k0sv1beta1.EtcdRequest{})
 			return err
@@ -140,6 +136,30 @@ func TestJoinClient_Cancellation(t *testing.T) {
 	}
 }
 
+func TestJoinClient_EtcdUnhealthy(t *testing.T) {
+	t.Parallel()
+
+	joinURL, certData := startFakeJoinServer(t, func(res http.ResponseWriter, req *http.Request) {
+		res.WriteHeader(http.StatusServiceUnavailable)
+	})
+
+	joinURL.Path = "/some/sub/path"
+	kubeconfig, err := token.GenerateKubeconfig(joinURL.String(), certData, t.Name(), "the-token")
+	require.NoError(t, err)
+	tok, err := token.JoinEncode(bytes.NewReader(kubeconfig))
+	require.NoError(t, err)
+
+	underTest, err := token.JoinClientFromToken(tok)
+	require.NoError(t, err)
+
+	response, err := underTest.JoinEtcd(context.TODO(), k0sv1beta1.EtcdRequest{
+		Node:        "the-node",
+		PeerAddress: "the-peer-address",
+	})
+	assert.ErrorIs(t, err, token.ErrEtcdUnhealthy)
+	assert.Zero(t, response)
+}
+
 func startFakeJoinServer(t *testing.T, handler func(http.ResponseWriter, *http.Request)) (*url.URL, []byte) {
 	requestCtx, cancelRequests := context.WithCancel(context.Background())
 	var ok bool