discovery: restrict stickiness to eligible active quota and test with active URLs

Author: gg582

portal/discovery/mols.go

@@ -422,21 +422,27 @@ func applyActiveStickiness(ranked []string, activeRelayURLs []string, states []R
 		}
 	}
 
+	// Active quota boundary: only candidates ranked within the eligible active quota
+	// (top maxActive in the ranked pool) can exercise stickiness. Candidates demoted
+	// outside the active quota (e.g. by P2C pressure demotion or saturation tiering)
+	// cannot be promoted back over healthier candidates.
+	quotaLen := min(len(ranked), maxActive)
+	eligibleQuota := ranked[:quotaLen]
+
 	selected := make([]string, 0, len(ranked))
-	// Layer 1: Retain currently active sticky relays that remain healthy (capped at maxActive)
-	for _, u := range ranked {
+	// Layer 1: Retain currently active sticky relays among the eligible quota candidates
+	for _, u := range eligibleQuota {
 		if _, isActive := activeSet[u]; isActive {
 			selected = append(selected, u)
-			if len(selected) == maxActive {
-				break
-			}
 		}
 	}
-	// Layer 2 & Trailing: Append remaining candidates preserving their relative MOLS ranking
-	for _, u := range ranked {
+	// Layer 2: Fill remaining quota slots with top-ranked candidates from eligible quota
+	for _, u := range eligibleQuota {
 		if !slices.Contains(selected, u) {
 			selected = append(selected, u)
 		}
 	}
+	// Trailing: Preserve remaining reserve candidates in their ranked order
+	selected = append(selected, ranked[quotaLen:]...)
 	return selected
 }

portal/discovery/mols_test.go

@@ -416,8 +416,10 @@ func TestMOLSP2CActiveSetMembershipChangeDefaultQuota(t *testing.T) {
 		}
 	}
 
-	// Under default MaxActiveRelays = 3, overloaded top candidate MUST be evicted from active set
+	// Under default MaxActiveRelays = 3 with ActiveRelayURLs POPULATED (production path),
+	// overloaded top candidate MUST be evicted from active set despite active stickiness.
 	newPicks := SelectPriority(loadedRelays, RouteState{
+		ActiveRelayURLs: basePicks,              // Simulates active connections in Exposure.reconcileRelayListeners
 		MaxActiveRelays: defaultMaxActiveRelays, // 3
 		LocalAddress:    clientAddr,
 	})