les/vflux/server: fix priority cornercase causing fuzzer timeout (#22650)

* les/vflux/server: fix estimatePriority corner case

* les/vflux/server: simplify inactiveAllowance == 0 case

les/vflux/server/balance.go

@@ -358,11 +358,15 @@ func (n *nodeBalance) estimatePriority(capacity uint64, addBalance int64, future
 	if bias > 0 {
 		b = n.reducedBalance(b, now+mclock.AbsTime(future), bias, capacity, 0)
 	}
-	// Note: we subtract one from the estimated priority in order to ensure that biased
+	pri := n.balanceToPriority(now, b, capacity)
-	// estimates are always lower than actual priorities, even if the bias is very small.
+	// Ensure that biased estimates are always lower than actual priorities, even if
+	// the bias is very small.
 	// This ensures that two nodes will not ping-pong update signals forever if both of
 	// them have zero estimated priority drop in the projected future.
-	pri := n.balanceToPriority(now, b, capacity) - 1
+	current := n.balanceToPriority(now, n.balance, capacity)
+	if pri >= current {
+		pri = current - 1
+	}
 	if update {
 		n.addCallback(balanceCallbackUpdate, pri, n.signalPriorityUpdate)
 	}

les/vflux/server/balance_test.go

@@ -283,7 +283,7 @@ func TestEstimatedPriority(t *testing.T) {
 		{time.Second, 3 * time.Second, 1000000000, 48},
 
 		// All positive balance is used up
-		{time.Second * 55, 0, 0, 0},
+		{time.Second * 55, 0, 0, -1},
 
 		// 1 minute estimated time cost, 4/58 * 10^9 estimated request cost per sec.
 		{0, time.Minute, 0, -int64(time.Minute) - int64(time.Second)*120/29},
@@ -292,8 +292,8 @@ func TestEstimatedPriority(t *testing.T) {
 		b.clock.Run(i.runTime)
 		node.RequestServed(i.reqCost)
 		priority := node.estimatePriority(1000000000, 0, i.futureTime, 0, false)
-		if priority != i.priority-1 {
+		if priority != i.priority {
-			t.Fatalf("Estimated priority mismatch, want %v, got %v", i.priority-1, priority)
+			t.Fatalf("Estimated priority mismatch, want %v, got %v", i.priority, priority)
 		}
 	}
 }

les/vflux/server/clientpool.go

@@ -103,14 +103,7 @@ func NewClientPool(balanceDb ethdb.KeyValueStore, minCap uint64, connectedBias t
 			if c, ok := ns.GetField(node, setup.clientField).(clientPeer); ok {
 				timeout = c.InactiveAllowance()
 			}
-			if timeout > 0 {
 			ns.AddTimeout(node, setup.inactiveFlag, timeout)
-			} else {
-				// Note: if capacity is immediately available then priorityPool will set the active
-				// flag simultaneously with removing the inactive flag and therefore this will not
-				// initiate disconnection
-				ns.SetStateSub(node, nodestate.Flags{}, setup.inactiveFlag, 0)
-			}
 		}
 		if oldState.Equals(setup.inactiveFlag) && newState.Equals(setup.inactiveFlag.Or(setup.priorityFlag)) {
 			ns.SetStateSub(node, setup.inactiveFlag, nodestate.Flags{}, 0) // priority gained; remove timeout

les/vflux/server/clientpool_test.go

@@ -326,12 +326,13 @@ func TestPaidClientKickedOut(t *testing.T) {
 	if cap := connect(pool, newPoolTestPeer(11, kickedCh)); cap == 0 {
 		t.Fatalf("Free client should be accepted")
 	}
+	clock.Run(0)
 	select {
 	case id := <-kickedCh:
 		if id != 0 {
 			t.Fatalf("Kicked client mismatch, want %v, got %v", 0, id)
 		}
-	case <-time.NewTimer(time.Second).C:
+	default:
 		t.Fatalf("timeout")
 	}
 }
@@ -399,23 +400,27 @@ func TestFreeClientKickedOut(t *testing.T) {
 	if cap := connect(pool, newPoolTestPeer(10, kicked)); cap != 0 {
 		t.Fatalf("New free client should be rejected")
 	}
+	clock.Run(0)
 	select {
 	case <-kicked:
-	case <-time.NewTimer(time.Second).C:
+	default:
 		t.Fatalf("timeout")
 	}
 	disconnect(pool, newPoolTestPeer(10, kicked))
 	clock.Run(5 * time.Minute)
 	for i := 0; i < 10; i++ {
 		connect(pool, newPoolTestPeer(i+10, kicked))
+
 	}
+	clock.Run(0)
+
 	for i := 0; i < 10; i++ {
 		select {
 		case id := <-kicked:
 			if id >= 10 {
 				t.Fatalf("Old client should be kicked, now got: %d", id)
 			}
-		case <-time.NewTimer(time.Second).C:
+		default:
 			t.Fatalf("timeout")
 		}
 	}