*: drain http.Response.Body before closing

Draining the body prevents the TCP/TLS connection from closing
and makes the connection available for reuse.

etcdserver/cluster_util.go

@@ -17,6 +17,7 @@ package etcdserver
 import (
 	"encoding/json"
 	"fmt"
+	"io"
 	"io/ioutil"
 	"net/http"
 	"sort"
@@ -231,6 +232,7 @@ func getVersion(m *Member, rt http.RoundTripper) (*version.Versions, error) {
 		}
 		// etcd 2.0 does not have version endpoint on peer url.
 		if resp.StatusCode == http.StatusNotFound {
+			io.Copy(ioutil.Discard, resp.Body)
 			resp.Body.Close()
 			return &version.Versions{
 				Server:  "2.0.0",

rafthttp/snapshot_sender.go

@@ -124,7 +124,12 @@ func (s *snapshotSender) post(req *http.Request) (err error) {
 		// close the response body when timeouts.
 		// prevents from reading the body forever when the other side dies right after
 		// successfully receives the request body.
-		time.AfterFunc(snapResponseReadTimeout, func() { resp.Body.Close() })
+		time.AfterFunc(snapResponseReadTimeout, func() {
+			// Draining the body prevents the TCP/TLS connection from closing
+			// and makes the connection available for reuse
+			io.Copy(ioutil.Discard, resp.Body)
+			resp.Body.Close()
+		})
 		body, err := ioutil.ReadAll(resp.Body)
 		result <- responseAndError{resp, body, err}
 	}()

rafthttp/stream.go

@@ -417,13 +417,15 @@ func (cr *streamReader) dial(t streamType) (io.ReadCloser, error) {
 	rv := serverVersion(resp.Header)
 	lv := semver.Must(semver.NewVersion(version.Version))
 	if compareMajorMinorVersion(rv, lv) == -1 && !checkStreamSupport(rv, t) {
+		io.Copy(ioutil.Discard, resp.Body)
 		resp.Body.Close()
 		cr.picker.unreachable(u)
 		return nil, errUnsupportedStreamType
 	}
 
 	switch resp.StatusCode {
 	case http.StatusGone:
+		io.Copy(ioutil.Discard, resp.Body)
 		resp.Body.Close()
 		cr.picker.unreachable(u)
 		err := fmt.Errorf("the member has been permanently removed from the cluster")
@@ -435,6 +437,7 @@ func (cr *streamReader) dial(t streamType) (io.ReadCloser, error) {
 	case http.StatusOK:
 		return resp.Body, nil
 	case http.StatusNotFound:
+		io.Copy(ioutil.Discard, resp.Body)
 		resp.Body.Close()
 		cr.picker.unreachable(u)
 		return nil, fmt.Errorf("remote member %s could not recognize local member", cr.remote)
@@ -444,6 +447,7 @@ func (cr *streamReader) dial(t streamType) (io.ReadCloser, error) {
 			cr.picker.unreachable(u)
 			return nil, err
 		}
+		io.Copy(ioutil.Discard, resp.Body)
 		resp.Body.Close()
 		cr.picker.unreachable(u)
 
@@ -459,6 +463,7 @@ func (cr *streamReader) dial(t streamType) (io.ReadCloser, error) {
 			return nil, fmt.Errorf("unhandled error %q when precondition failed", string(b))
 		}
 	default:
+		io.Copy(ioutil.Discard, resp.Body)
 		resp.Body.Close()
 		cr.picker.unreachable(u)
 		return nil, fmt.Errorf("unhandled http status %d", resp.StatusCode)