gRPC WatchEvent method with WatchEventRequest_Table_Filter_BEST returns `best: false` on all paths

[roman901]

Minimal example code using latest GoBGP and gRPC API:

stream, err := client.WatchEvent(ctx, &pb.WatchEventRequest{
	Table: &pb.WatchEventRequest_Table{
		Filters: []*pb.WatchEventRequest_Table_Filter{
			{
				Type: pb.WatchEventRequest_Table_Filter_BEST,
				Init: true,
			},
		},
	},
})

for {
	r, err := stream.Recv()
	if err == io.EOF {
		break
	} else if err != nil {
		return err
	}

	t := r.GetTable()
	if t == nil {
		continue
	}

	destinations := apiutil.NewDestination(&pb.Destination{Paths: t.Paths})
	for _, path := range destinations.Paths {
		...
	}
}

I expect that path.Best will be true or false, but it is always false.
At the same time ListPath method returns correct values.
Is this bug or planned behavior?

[liuzhenjieabc]

Is the issue you’re describing the same as the one I encountered? Here are the details of the problem I faced:
I intended to use this interface to capture EVPN Type2 route updates, but after a route update occurs, it triggers two messages:

A WITHDRAW message (Message A) flagged by isWithdraw, which I could filter out.
However, a subsequent UPDATE message (Message B) is generated almost simultaneously. The only difference between Message B and A is the isWithdraw field.
This dual-message behavior causes ambiguity, making it impossible to accurately identify true route update events. The conflict arises because both messages represent the same routing change but with opposite operational flags.

[fujita]

Isn't it impossible for the Watch API to determine the best path, since which path is best depends on the advertising peer?

[liuzhenjieabc]

Isn't it impossible for the Watch API to determine the best path, since which path is best depends on the advertising peer?

This scenario is: a peer sent a route withdrawal message, but after GoBGP received this message, it not only triggered a WITHDRAW message (Message A) but also simultaneously generated an UPDATE message (Message B). My question is: since the peer only sent Message A, why does GoBGP additionally produce a Message B?