etcdmain: fix the check in fallback-to-proxy case

advertise-client-urls has to be set if listen-client-urls is set when
fallbacking to proxy, which breaks the behavior. Loosen the check to fix
it.

etcdmain/config.go

@@ -260,7 +260,10 @@ func (cfg *config) Parse(arguments []string) error {
 	}
 
 	// when etcd runs in member mode user needs to set -advertise-client-urls if -listen-client-urls is set.
-	if cfg.proxy.String() != proxyFlagOn {
+	// TODO(yichengq): check this for joining through discovery service case
+	mayFallbackToProxy := flags.IsSet(cfg.FlagSet, "discovery") && cfg.fallback.String() == fallbackFlagProxy
+	mayBeProxy := cfg.proxy.String() != proxyFlagOff || mayFallbackToProxy
+	if !mayBeProxy {
 		if flags.IsSet(cfg.FlagSet, "listen-client-urls") && !flags.IsSet(cfg.FlagSet, "advertise-client-urls") {
 			return errUnsetAdvertiseClientURLsFlag
 		}

etcdmain/config_test.go

@@ -212,6 +212,71 @@ func TestConfigParsingConflictClusteringFlags(t *testing.T) {
 	}
 }
 
+func TestConfigParsingMissedAdvertiseClientURLsFlag(t *testing.T) {
+	tests := []struct {
+		args []string
+		werr error
+	}{
+		{
+			[]string{
+				"-initial-cluster=infra1=http://127.0.0.1:2380",
+				"-listen-client-urls=http://127.0.0.1:2379",
+			},
+			errUnsetAdvertiseClientURLsFlag,
+		},
+		{
+			[]string{
+				"-discovery-srv=example.com",
+				"-listen-client-urls=http://127.0.0.1:2379",
+			},
+			errUnsetAdvertiseClientURLsFlag,
+		},
+		{
+			[]string{
+				"-discovery=http://example.com/abc",
+				"-discovery-fallback=exit",
+				"-listen-client-urls=http://127.0.0.1:2379",
+			},
+			errUnsetAdvertiseClientURLsFlag,
+		},
+		{
+			[]string{
+				"-listen-client-urls=http://127.0.0.1:2379",
+			},
+			errUnsetAdvertiseClientURLsFlag,
+		},
+		{
+			[]string{
+				"-discovery=http://example.com/abc",
+				"-listen-client-urls=http://127.0.0.1:2379",
+			},
+			nil,
+		},
+		{
+			[]string{
+				"-proxy=on",
+				"-listen-client-urls=http://127.0.0.1:2379",
+			},
+			nil,
+		},
+		{
+			[]string{
+				"-proxy=readonly",
+				"-listen-client-urls=http://127.0.0.1:2379",
+			},
+			nil,
+		},
+	}
+
+	for i, tt := range tests {
+		cfg := NewConfig()
+		err := cfg.Parse(tt.args)
+		if err != tt.werr {
+			t.Errorf("%d: err = %v, want %v", i, err, tt.werr)
+		}
+	}
+}
+
 func TestConfigIsNewCluster(t *testing.T) {
 	tests := []struct {
 		state  string