Add a rumor mill to throttle dht maintenance traffic

src/yggdrasil/dht.go

@@ -62,6 +62,11 @@ type dhtRes struct {
 	infos  []*dhtInfo // response
 }
 
+type dht_rumor struct {
+	info   *dhtInfo
+	target *NodeID
+}
+
 type dht struct {
 	core           *Core
 	nodeID         NodeID
@@ -69,6 +74,7 @@ type dht struct {
 	peers          chan *dhtInfo             // other goroutines put incoming dht updates here
 	reqs           map[boxPubKey]map[NodeID]time.Time
 	offset         int
+	rumorMill      []dht_rumor
 }
 
 func (t *dht) init(c *Core) {
@@ -143,7 +149,7 @@ func (t *dht) handleRes(res *dhtRes) {
 		if b.contains(info) {
 			continue
 		} // wait for maintenance cycle to get them
-		t.ping(info, info.getNodeID())
+		t.addToMill(info, info.getNodeID())
 	}
 }
 
@@ -379,6 +385,14 @@ func (t *dht) ping(info *dhtInfo, target *NodeID) {
 	t.sendReq(&req, info)
 }
 
+func (t *dht) addToMill(info *dhtInfo, target *NodeID) {
+	rumor := dht_rumor{
+		info:   info,
+		target: target,
+	}
+	t.rumorMill = append(t.rumorMill, rumor)
+}
+
 func (t *dht) doMaintenance() {
 	// First clean up reqs
 	for key, reqs := range t.reqs {
@@ -391,36 +405,43 @@ func (t *dht) doMaintenance() {
 			delete(t.reqs, key)
 		}
 	}
-	// Ping the least recently contacted node
-	//  This is to make sure we eventually notice when someone times out
-	var oldest *dhtInfo
-	last := 0
-	for bidx := 0; bidx < t.nBuckets(); bidx++ {
-		b := t.getBucket(bidx)
-		if !b.isEmpty() {
-			last = bidx
-			toPing := b.nextToPing()
-			if toPing == nil {
-				continue
-			} // We've recently pinged everyone in b
-			if oldest == nil || toPing.recv.Before(oldest.recv) {
-				oldest = toPing
+	if len(t.rumorMill) == 0 {
+		// Ping the least recently contacted node
+		//  This is to make sure we eventually notice when someone times out
+		var oldest *dhtInfo
+		last := 0
+		for bidx := 0; bidx < t.nBuckets(); bidx++ {
+			b := t.getBucket(bidx)
+			if !b.isEmpty() {
+				last = bidx
+				toPing := b.nextToPing()
+				if toPing == nil {
+					continue
+				} // We've recently pinged everyone in b
+				if oldest == nil || toPing.recv.Before(oldest.recv) {
+					oldest = toPing
+				}
 			}
 		}
+		if oldest != nil {
+			t.addToMill(oldest, nil)
+		} // if the DHT isn't empty
+		// Refresh buckets
+		if t.offset > last {
+			t.offset = 0
+		}
+		target := t.getTarget(t.offset)
+		for _, info := range t.lookup(target) {
+			t.addToMill(info, target)
+			break
+		}
+		t.offset++
 	}
-	if oldest != nil {
-		t.ping(oldest, nil)
-	} // if the DHT isn't empty
-	// Refresh buckets
-	if t.offset > last {
-		t.offset = 0
+	if len(t.rumorMill) > 0 {
+		var rumor dht_rumor
+		rumor, t.rumorMill = t.rumorMill[0], t.rumorMill[1:]
+		t.ping(rumor.info, rumor.target)
 	}
-	target := t.getTarget(t.offset)
-	for _, info := range t.lookup(target) {
-		t.ping(info, target)
-		break
-	}
-	t.offset++
 }
 
 func dht_firstCloserThanThird(first *NodeID,