utils: let http client can reuse connections (#6914) (#6916)

close #6913

utils: let HTTP client can reuse connections

Signed-off-by: ti-chi-bot <ti-community-prow-bot@tidb.io>
Signed-off-by: nolouch <nolouch@gmail.com>

Co-authored-by: ShuNing <nolouch@gmail.com>
Co-authored-by: nolouch <nolouch@gmail.com>

server/server.go

@@ -368,12 +368,16 @@ func (s *Server) startEtcd(ctx context.Context) error {
 		}
 	}
 	s.client = client
-	s.httpClient = &http.Client{
-		Transport: &http.Transport{
-			DisableKeepAlives: true,
-			TLSClientConfig:   tlsConfig,
-		},
-	}
+	// FIXME: Currently, there is no timeout set for certain requests, such as GetRegions,
+	// which may take a significant amount of time. However, it might be necessary to
+	// define an appropriate timeout in the future.
+	httpCli := &http.Client{}
+	if tlsConfig != nil {
+		transport := http.DefaultTransport.(*http.Transport).Clone()
+		transport.TLSClientConfig = tlsConfig
+		httpCli.Transport = transport
+	}
+	s.httpClient = httpCli
 
 	failpoint.Inject("memberNil", func() {
 		time.Sleep(1500 * time.Millisecond)