feat: Warn if bootstrap_expect is even number (#12961)

command/agent/command.go

@@ -436,6 +436,9 @@ func (c *Command) IsValidConfig(config, cmdConfig *Config) bool {
 		if config.Server.Enabled && config.Server.BootstrapExpect == 1 {
 			c.Ui.Error("WARNING: Bootstrap mode enabled! Potentially unsafe operation.")
 		}
+		if config.Server.Enabled && config.Server.BootstrapExpect%2 == 0 {
+			c.Ui.Error("WARNING: Number of bootstrap servers should ideally be set to an odd number.")
+		}
 	}
 
 	// ProtocolVersion has never been used. Warn if it is set as someone

command/agent/command_test.go

@@ -44,6 +44,10 @@ func TestCommand_Args(t *testing.T) {
 			[]string{"-data-dir=" + tmpDir, "-server", "-bootstrap-expect=1"},
 			"WARNING: Bootstrap mode enabled!",
 		},
+		{
+			[]string{"-data-dir=" + tmpDir, "-server", "-bootstrap-expect=2"},
+			"Number of bootstrap servers should ideally be set to an odd number",
+		},
 		{
 			[]string{"-server"},
 			"Must specify \"data_dir\" config option or \"data-dir\" CLI flag",