domain: set etcdClient loglevel to error (pingcap#15645) (pingcap#15683)

domain/domain.go

@@ -607,7 +607,12 @@ func (do *Domain) Init(ddlLease time.Duration, sysFactory func(*Domain) (pools.R
 	if ebd, ok := do.store.(tikv.EtcdBackend); ok {
 		if addrs := ebd.EtcdAddrs(); addrs != nil {
 			cfg := config.GetGlobalConfig()
+			// silence etcd warn log, when domain closed, it won't randomly print warn log
+			// see details at the issue https://github.com/pingcap/tidb/issues/15479
+			etcdLogCfg := zap.NewProductionConfig()
+			etcdLogCfg.Level = zap.NewAtomicLevelAt(zap.ErrorLevel)
 			cli, err := clientv3.New(clientv3.Config{
+				LogConfig:        &etcdLogCfg,
 				Endpoints:        addrs,
 				AutoSyncInterval: 30 * time.Second,
 				DialTimeout:      5 * time.Second,