etcd: Warn about invalid configuration, clarify --no-server

etcd/etcd.go

@@ -223,6 +223,10 @@ func NewEmbdEtcd(hostname string, seeds, clientURLs, serverURLs, advertiseClient
 	if hostname == seedSentinel { // safety
 		return nil
 	}
+	if noServer && len(seeds) == 0 {
+		log.Printf("Etcd: need at least one seed if running with --no-server!")
+		return nil
+	}
 	if len(seeds) > 0 {
 		endpoints[seedSentinel] = seeds
 		idealClusterSize = 0 // unset, get from running cluster

etcd/etcd_test.go

@@ -0,0 +1,49 @@
+// Mgmt
+// Copyright (C) 2013-2018+ James Shubin and the project contributors
+// Written by James Shubin <james@shubin.ca> and the project contributors
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package etcd
+
+import (
+	"testing"
+
+	etcdtypes "github.com/coreos/etcd/pkg/types"
+)
+
+func TestNewEmbdEtcd(t *testing.T) {
+	// should return a new etcd object
+
+	noServer := false
+	var flags Flags
+
+	obj := NewEmbdEtcd("", nil, nil, nil, nil, nil, noServer, 0, flags, "", nil)
+	if obj == nil {
+		t.Fatal("failed to create server object")
+	}
+}
+
+func TestNewEmbdEtcdConfigValidation(t *testing.T) {
+	// running --no-server with no --seeds specified should fail early
+
+	seeds := make(etcdtypes.URLs, 0)
+	noServer := true
+	var flags Flags
+
+	obj := NewEmbdEtcd("", seeds, nil, nil, nil, nil, noServer, 0, flags, "", nil)
+	if obj != nil {
+		t.Fatal("server initialization should fail on invalid configuration")
+	}
+}

lib/cli.go

@@ -296,7 +296,7 @@ func CLI(program, version string, flags Flags) error {
 		},
 		cli.BoolFlag{
 			Name:  "no-server",
-			Usage: "do not let other servers peer with me",
+			Usage: "do not start embedded etcd server (do not promote from client to peer)",
 		},
 
 		cli.IntFlag{