Function registerBlockingBalancer

stats/opentelemetry/e2e_test.go:1448–1468

registerBlockingBalancer registers a stub balancer that delegates to pick_first. It wraps the ClientConn to intercept state updates and wraps the picker to detect calls to Pick. This guarantees the "Delayed LB pick complete" event is emitted reliably.

(t *testing.T, balancerName string)

// the picker to detect calls to Pick. This guarantees the "Delayed LB pick
// complete" event is emitted reliably.
func registerBlockingBalancer(t *testing.T, balancerName string) {
	t.Helper()
	stub.Register(balancerName, stub.BalancerFuncs{
		Init: func(bd *stub.BalancerData) {
			cc := &testCCWrapper{
				ClientConn:  bd.ClientConn,
				pickInvoked: grpcsync.NewEvent(),
			}
			bd.ChildBalancer = balancer.Get(pickfirst.Name).Build(cc, bd.BuildOptions)
		},
		Close: func(bd *stub.BalancerData) {
			bd.ChildBalancer.Close()
		},
		UpdateClientConnState: func(bd *stub.BalancerData, ccs balancer.ClientConnState) error {
			return bd.ChildBalancer.UpdateClientConnState(ccs)
		},
		ExitIdle: func(bd *stub.BalancerData) {
			bd.ChildBalancer.ExitIdle()
		},
	})
}

// TestTraceSpan_WithRetriesAndNameResolutionDelay verifies that
// "Delayed name resolution complete" event is recorded in the call trace span