1 files changed, 37 insertions, 20 deletions

diff --git a/dedupe/dedupe.go b/dedupe/dedupe.go
index c8ff5e9..a78df98 100644
--- a/dedupe/dedupe.go
+++ b/dedupe/dedupe.go
@@ -2,6 +2,7 @@ package dedup
 
 import (
 	"hash/maphash"
+	"math/rand"
 	"sync"
 	"time"
 )
@@ -11,42 +12,34 @@ import (
 type PacketDeduplicator struct {
 	expiresAfter time.Duration // expiresAfter defines the duration after which a seen packet record expires.
 	seed         maphash.Seed
-	sync.Mutex                 // protects the seen map from concurrent access.
+	sync.Mutex                        // protects the seen map from concurrent access.
 	seen         map[uint64]time.Time // seen maps a packet identifier to the last time it was seen.
 }
 
 // NewDeduplicator creates a new PacketDeduplicator with a given hasher and expiration duration for packet records.
 // It starts a background goroutine to periodically clean up expired packet records.
 func NewDeduplicator(expiresAfter time.Duration) *PacketDeduplicator {
-	pd := &PacketDeduplicator{
+	return &PacketDeduplicator{
 		seen:         map[uint64]time.Time{},
 		seed:         maphash.MakeSeed(),
 		expiresAfter: expiresAfter,
 	}
-	go func() {
-		for range time.NewTicker(time.Second * 10).C {
-			pd.Lock()
-			for packet, timestamp := range pd.seen {
-				if time.Since(timestamp) > pd.expiresAfter {
-					delete(pd.seen, packet)
-				}
-			}
-			pd.Unlock()
-		}
-	}()
-
-	return pd
 }
 
-func (p *PacketDeduplicator) isSeen(k uint64) bool {
+func (p *PacketDeduplicator) isSeen(now time.Time, k uint64) bool {
+	// Checking for dedup purges ~5% of the time
+	if rand.Intn(100) < 5 {
+		p.deleteUntil(now.Add(-p.expiresAfter))
+	}
+
 	p.Lock()
 	defer p.Unlock()
 	d, exists := p.seen[k]
 	if !exists {
-		p.seen[k] = time.Now()
+		p.seen[k] = now
 		return false
 	}
-	if time.Since(d) > p.expiresAfter {
+	if now.Sub(d) > p.expiresAfter {
 		delete(p.seen, k)
 		return false
 	}
@@ -56,11 +49,35 @@ func (p *PacketDeduplicator) isSeen(k uint64) bool {
 // Seen checks whether a packet with the given sender and packetID has been seen before.
 // If not, it records the packet as seen and returns false. Otherwise, it returns true.
 func (p *PacketDeduplicator) Seen(sender, packetID uint32) bool {
-	return p.isSeen((uint64(sender) << 32) | uint64(packetID))
+	return p.seenAt(time.Now(), sender, packetID)
 }
 
 // SeenData checks whether the data has been seen before based on its hashed value.
 // If not, it records the data as seen and returns false. Otherwise, it returns true.
 func (p *PacketDeduplicator) SeenData(data []byte) bool {
-	return p.isSeen(maphash.Bytes(p.seed, data))
+	return p.seenDataAt(time.Now(), data)
+}
+
+//
+// These are used internally and are test hooks allowing us to avoid the clock.
+//
+
+func (p *PacketDeduplicator) deleteUntil(t time.Time) {
+	p.Lock()
+	defer p.Unlock()
+	for packet, timestamp := range p.seen {
+		if timestamp.Before(t) {
+			delete(p.seen, packet)
+		}
+	}
+}
+
+// Seendata with an explicit time
+func (p *PacketDeduplicator) seenDataAt(now time.Time, data []byte) bool {
+	return p.isSeen(now, maphash.Bytes(p.seed, data))
+}
+
+// Seen with an explicit time
+func (p *PacketDeduplicator) seenAt(now time.Time, sender uint32, packetID uint32) bool {
+	return p.isSeen(now, (uint64(sender)<<32)|uint64(packetID))
 }