[#301] rpc: Make client stream initialization get cancelled by dial timeout

* `c.conn` may be already invalidated but the rpc client can't detect this.
  `NewStream` may hang trying to open a stream with invalidated connection.
   Using timer with `dialTimeout` for `NewStream` fixes this problem.

Signed-off-by: Airat Arifullin <a.arifullin@yadro.com>

rpc/client/init.go

@@ -3,6 +3,7 @@ package client
 import (
 	"context"
 	"io"
+	"time"
 
 	"git.frostfs.info/TrueCloudLab/frostfs-api-go/v2/rpc/common"
 	"git.frostfs.info/TrueCloudLab/frostfs-api-go/v2/rpc/message"
@@ -51,18 +52,56 @@ func (c *Client) Init(info common.CallMethodInfo, opts ...CallOption) (MessageRe
 	}
 
 	ctx, cancel := context.WithCancel(prm.ctx)
-	stream, err := c.conn.NewStream(ctx, &grpc.StreamDesc{
-		StreamName:    info.Name,
-		ServerStreams: info.ServerStream(),
-		ClientStreams: info.ClientStream(),
-	}, toMethodName(info))
-	if err != nil {
+
+	// `conn.NewStream` doesn't check if `conn` may turn up invalidated right before this invocation.
+	// In such cases, the operation can hang indefinitely, with the context timeout being the only
+	// mechanism to cancel it.
+	//
+	// We use a separate timer instead of context timeout because the latter
+	// would propagate to all subsequent read/write operations on the opened stream,
+	// which is not desired for the stream's lifecycle management.
+	dialTimeoutTimer := time.NewTimer(c.dialTimeout)
+	defer dialTimeoutTimer.Stop()
+
+	type newStreamRes struct {
+		stream grpc.ClientStream
+		err    error
+	}
+	newStreamCh := make(chan newStreamRes)
+
+	go func() {
+		stream, err := c.conn.NewStream(ctx, &grpc.StreamDesc{
+			StreamName:    info.Name,
+			ServerStreams: info.ServerStream(),
+			ClientStreams: info.ClientStream(),
+		}, toMethodName(info))
+
+		newStreamCh <- newStreamRes{
+			stream: stream,
+			err:    err,
+		}
+	}()
+
+	var res newStreamRes
+
+	select {
+	case <-dialTimeoutTimer.C:
 		cancel()
-		return nil, err
+		res = <-newStreamCh
+		if res.stream != nil && res.err == nil {
+			_ = res.stream.CloseSend()
+		}
+		return nil, context.Canceled
+	case res = <-newStreamCh:
+	}
+
+	if res.err != nil {
+		cancel()
+		return nil, res.err
 	}
 
 	return &streamWrapper{
-		ClientStream: stream,
+		ClientStream: res.stream,
 		cancel:       cancel,
 		timeout:      c.rwTimeout,
 	}, nil