refactor: session peer manager ordering

sessionpeermanager/sessionpeermanager.go

@@ -280,6 +280,8 @@ type getPeersMessage struct {
 // Get all optimized peers in order followed by randomly ordered unoptimized
 // peers, with a limit of maxOptimizedPeers
 func (prm *getPeersMessage) handle(spm *SessionPeerManager) {
+	randomOrder := rand.Perm(len(spm.unoptimizedPeersArr))
+
 	// Number of peers to get in total: unoptimized + optimized
 	// limited by maxOptimizedPeers
 	maxPeers := len(spm.unoptimizedPeersArr) + len(spm.optimizedPeersArr)
@@ -287,8 +289,8 @@ func (prm *getPeersMessage) handle(spm *SessionPeerManager) {
 		maxPeers = maxOptimizedPeers
 	}
 
-	// The best peer latency is 1 if we have recorded at least one peer's
-	// latency, 0 otherwise
+	// The best peer latency is the first optimized peer's latency.
+	// If we haven't recorded any peer's latency, use 0.
 	var bestPeerLatency float64
 	if len(spm.optimizedPeersArr) > 0 {
 		bestPeerLatency = float64(spm.activePeers[spm.optimizedPeersArr[0]].latency)
@@ -297,23 +299,20 @@ func (prm *getPeersMessage) handle(spm *SessionPeerManager) {
 	}
 
 	optimizedPeers := make([]bssd.OptimizedPeer, 0, maxPeers)
-
-	// Add optimized peers in order
-	for i := 0; i < maxPeers && i < len(spm.optimizedPeersArr); i++ {
+	for i := 0; i < maxPeers; i++ {
+		// First add optimized peers in order
+		if i < len(spm.optimizedPeersArr) {
 			p := spm.optimizedPeersArr[i]
 			optimizedPeers = append(optimizedPeers, bssd.OptimizedPeer{
 				Peer:               p,
 				OptimizationRating: bestPeerLatency / float64(spm.activePeers[p].latency),
 			})
-	}
-
-	// Add unoptimized peers in random order
-	randomOrder := rand.Perm(len(spm.unoptimizedPeersArr))
-	remaining := maxPeers - len(optimizedPeers)
-	for i := 0; i < remaining; i++ {
-		p := spm.unoptimizedPeersArr[randomOrder[i]]
+		} else {
+			// Then add unoptimized peers in random order
+			p := spm.unoptimizedPeersArr[randomOrder[i-len(spm.optimizedPeersArr)]]
 			optimizedPeers = append(optimizedPeers, bssd.OptimizedPeer{Peer: p, OptimizationRating: 0.0})
 		}
+	}
 	prm.resp <- optimizedPeers
 }
 

sessionpeermanager/sessionpeermanager_test.go

@@ -167,7 +167,7 @@ func TestOrderingPeers(t *testing.T) {
 	case <-ctx.Done():
 		t.Fatal("Did not finish finding providers")
 	}
-	time.Sleep(20 * time.Millisecond)
+	time.Sleep(5 * time.Millisecond)
 
 	// record broadcast
 	sessionPeerManager.RecordPeerRequests(nil, c)