client: do not timeout when wait is true

Current V2 watch waits by encoding URL with wait=true.
When a client sets 'no-sync', it requests directly to
proxy and the proxy redirects it by cloning the request
object, which leads to cancel the original request when
it times out and the cloned request gets closed prematurely.

This fixes etcd-io#3894 by querying
the original client request in order to not use context timeout
when 'wait=true'.

client/client.go

@@ -24,6 +24,7 @@ import (
 	"net/url"
 	"reflect"
 	"sort"
+	"strconv"
 	"sync"
 	"time"
 
@@ -442,9 +443,11 @@ func (c *simpleHTTPClient) Do(ctx context.Context, act httpAction) (*http.Respon
 		return nil, nil, err
 	}
 
+	isWait, _ := strconv.ParseBool(req.URL.Query().Get("wait"))
+
 	var hctx context.Context
 	var hcancel context.CancelFunc
-	if c.headerTimeout > 0 {
+	if !isWait && c.headerTimeout > 0 {
 		hctx, hcancel = context.WithTimeout(ctx, c.headerTimeout)
 	} else {
 		hctx, hcancel = context.WithCancel(ctx)