check at bootstrap which cluster is reachable, fix current cluster

pkg/cfg/config.go

@@ -17,6 +17,7 @@ along with this program. If not, see <http://www.gnu.org/licenses/>.
 package cfg
 
 import (
+	"context"
 	"crypto/tls"
 	"errors"
 	"fmt"
@@ -76,6 +77,8 @@ func (conf *Config) Init() error {
 		}
 	}
 
+	conf.SetupES()
+
 	if conf.CurrentCluster != "" {
 		current, exists := conf.Clusters[conf.CurrentCluster]
 		if !exists {
@@ -83,14 +86,29 @@ func (conf *Config) Init() error {
 		} else {
 			conf.DefaultCluster = current
 		}
+	} else {
+		if len(conf.Clusters) == 1 {
+			for _, cluster := range conf.Clusters {
+				conf.DefaultCluster = cluster
+			}
+		} else {
+			for _, cluster := range conf.Clusters {
+				_, err := cluster.ES.Cluster.Health().
+					Header("content-type", "application/json").
+					Header("accept", "application/json").
+					Do(context.Background())
+
+				if err == nil {
+					conf.DefaultCluster = cluster
+				}
+			}
+		}
 	}
 
 	if conf.Debug {
 		repr.Println(conf)
 	}
 
-	conf.SetupES()
-
 	return nil
 }