// Start sending traffic.
	Start() Generator

	// Stop sending traffic and wait for any in-flight requests to complete.
	// Returns the Result
	Stop() Result
}

// NewGenerator returns a new Generator with the given configuration.
func NewGenerator(t test.Failer, cfg Config) Generator {
	fillInDefaults(&cfg)
	return &generator{
		Config:  cfg,
		t:       t,
		stop:    make(chan struct{}),
		stopped: make(chan struct{}),

	generators["grpc/"+v3.ListenerType] = generators["grpc"]
	generators["grpc/"+v3.RouteType] = generators["grpc"]
	generators["grpc/"+v3.ClusterType] = generators["grpc"]

	generators["api"] = apigen.NewGenerator(env.ConfigStore)
	generators["api/"+v3.EndpointType] = edsGen

	generators["event"] = xds.NewStatusGen(s)
	generators[v3.DebugType] = xds.NewDebugGen(s, systemNameSpace, internalDebugMux)
	s.Generators = generators

			{
				Name:         "http",
				Protocol:     protocol.HTTP,
				WorkloadPort: 8080,
			},
		},
	})
	builder.BuildOrFail(t)

	// Create a traffic generator between A and B.
	g := traffic.NewGenerator(t, traffic.Config{
		Source: apps.A[0],
		Options: echo.CallOptions{
			To:    apps.B,
			Count: 1,
			Port: echo.Port{
				Name: "http",
			},
		},
		Interval: callInterval,
	}).Start()

//
// TODO: we can also add a special marker in the header)
type APIGenerator struct {
	// ConfigStore interface for listing istio api resources.
	store model.ConfigStore
}

func NewGenerator(store model.ConfigStore) *APIGenerator {
	return &APIGenerator{
		store: store,
	}
}

// TODO: take 'updates' into account, don't send pushes for resources that haven't changed