clustermesh status: improve error reporting when not ready

Let's leverage the additional status flags introduced in
cilium/cilium#26788 to provide more detailed information
concerning why a node cannot connect to a remote cluster,
and simplify troubleshooting. In particular, it might be
due to an etcd connection problem, to the cluster config
being required but not found, or to the synchronization
process being still in progress.

Signed-off-by: Marco Iorio <marco.iorio@isovalent.com>

clustermesh/clustermesh.go

@@ -1220,6 +1220,36 @@ func (c *ConnectivityStatus) addError(pod, cluster string, err error) {
 	m[cluster].Errors = append(m[cluster].Errors, err)
 }
 
+func remoteClusterStatusToError(status *models.RemoteCluster) error {
+	switch {
+	case status == nil:
+		return errors.New("unknown status")
+	case !status.Connected:
+		return errors.New(status.Status)
+	case status.Config == nil:
+		return errors.New("remote cluster configuration retrieval status unknown")
+	case status.Config.Required && !status.Config.Retrieved:
+		return errors.New("remote cluster configuration required but not found")
+	case status.Synced == nil:
+		return errors.New("synchronization status unknown")
+	case !(status.Synced.Nodes && status.Synced.Endpoints && status.Synced.Identities && status.Synced.Services):
+		var toSync []string
+		appendNotSynced := func(name string, synced bool) {
+			if !synced {
+				toSync = append(toSync, name)
+			}
+		}
+		appendNotSynced("endpoints", status.Synced.Endpoints)
+		appendNotSynced("identities", status.Synced.Identities)
+		appendNotSynced("nodes", status.Synced.Nodes)
+		appendNotSynced("services", status.Synced.Services)
+
+		return fmt.Errorf("synchronization in progress for %s", strings.Join(toSync, ", "))
+	default:
+		return errors.New("not ready")
+	}
+}
+
 func (c *ConnectivityStatus) parseAgentStatus(name string, expected []string, s *status.ClusterMeshAgentConnectivityStatus) {
 	if c.GlobalServices.Min < 0 || c.GlobalServices.Min > s.GlobalServices {
 		c.GlobalServices.Min = s.GlobalServices
@@ -1246,7 +1276,7 @@ func (c *ConnectivityStatus) parseAgentStatus(name string, expected []string, s
 			ready++
 			stats.Connected++
 		} else {
-			c.addError(name, cluster.Name, fmt.Errorf("cluster is not ready: %s", cluster.Status))
+			c.addError(name, cluster.Name, remoteClusterStatusToError(cluster))
 		}
 	}
 

clustermesh/clustermesh_test.go

@@ -4,6 +4,7 @@ import (
 	"errors"
 	"testing"
 
+	"github.com/cilium/cilium/api/v1/models"
 	"github.com/stretchr/testify/assert"
 	"helm.sh/helm/v3/pkg/chart"
 	"helm.sh/helm/v3/pkg/release"
@@ -206,6 +207,74 @@ func TestRemoveFromClustermeshConfig(t *testing.T) {
 	}
 }
 
+func TestRemoteClusterStatusToError(t *testing.T) {
+	tests := []struct {
+		name     string
+		status   *models.RemoteCluster
+		expected string
+	}{
+		{
+			name:     "nil status",
+			expected: "unknown status",
+		},
+		{
+			name:     "not connected",
+			status:   &models.RemoteCluster{Status: "foo"},
+			expected: "foo",
+		},
+		{
+			name:     "connected, unknown config",
+			status:   &models.RemoteCluster{Connected: true},
+			expected: "remote cluster configuration retrieval status unknown",
+		},
+		{
+			name: "connected, config not found",
+			status: &models.RemoteCluster{
+				Connected: true, Config: &models.RemoteClusterConfig{Required: true}},
+			expected: "remote cluster configuration required but not found",
+		},
+		{
+			name: "connected, config not required, sync status unknown",
+			status: &models.RemoteCluster{
+				Connected: true, Config: &models.RemoteClusterConfig{}},
+			expected: "synchronization status unknown",
+		},
+		{
+			name: "connected, config found, no resource type synced",
+			status: &models.RemoteCluster{
+				Connected: true,
+				Config:    &models.RemoteClusterConfig{Required: true, Retrieved: true},
+				Synced:    &models.RemoteClusterSynced{},
+			},
+			expected: "synchronization in progress for endpoints, identities, nodes, services",
+		},
+		{
+			name: "connected, config found, some resource type not synced",
+			status: &models.RemoteCluster{
+				Connected: true,
+				Config:    &models.RemoteClusterConfig{Required: true, Retrieved: true},
+				Synced:    &models.RemoteClusterSynced{Endpoints: true, Nodes: true, Services: true},
+			},
+			expected: "synchronization in progress for identities",
+		},
+		{
+			name: "none of the above",
+			status: &models.RemoteCluster{
+				Connected: true,
+				Config:    &models.RemoteClusterConfig{Required: true, Retrieved: true},
+				Synced:    &models.RemoteClusterSynced{Endpoints: true, Identities: true, Nodes: true, Services: true},
+			},
+			expected: "not ready",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			assert.Equal(t, tt.expected, remoteClusterStatusToError(tt.status).Error())
+		})
+	}
+}
+
 // Helpers
 
 type noOptWriter struct{}