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 coreos#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"
 
@@ -99,6 +100,8 @@ type Config struct {
 	// watch start. But if server is behind some kind of proxy, the response
 	// header may be cached at proxy, and Client cannot rely on this behavior.
 	//
+	// Especially, wait request will ignore this timeout.
+	//
 	// One API call may send multiple requests to different etcd servers until it
 	// succeeds. Use context of the API to specify the overall timeout.
 	//
@@ -383,9 +386,21 @@ func (c *simpleHTTPClient) Do(ctx context.Context, act httpAction) (*http.Respon
 		return nil, nil, err
 	}
 
+	isWait := false
+	if req != nil && req.URL != nil {
+		ws := req.URL.Query().Get("wait")
+		if len(ws) != 0 {
+			var err error
+			isWait, err = strconv.ParseBool(ws)
+			if err != nil {
+				return nil, nil, fmt.Errorf("wrong wait value %s (%v for %+v)", ws, err, req)
+			}
+		}
+	}
+
 	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)