qlog changes of the PTO count

internal/ackhandler/sent_packet_handler.go

@@ -160,6 +160,9 @@ func (h *sentPacketHandler) dropPackets(encLevel protocol.EncryptionLevel) {
 	}
 	h.setLossDetectionTimer()
 	h.ptoCount = 0
+	if h.qlogger != nil {
+		h.qlogger.UpdatedPTOCount(time.Now(), 0)
+	}
 	h.ptoMode = SendNone
 }
 
@@ -286,6 +289,9 @@ func (h *sentPacketHandler) ReceivedAck(ack *wire.AckFrame, encLevel protocol.En
 	}
 
 	h.ptoCount = 0
+	if h.qlogger != nil {
+		h.qlogger.UpdatedPTOCount(rcvTime, 0)
+	}
 	h.numProbesToSend = 0
 
 	h.setLossDetectionTimer()
@@ -531,6 +537,9 @@ func (h *sentPacketHandler) onVerifiedLossDetectionTimeout() error {
 		h.logger.Debugf("Loss detection alarm for %s fired in PTO mode. PTO count: %d", encLevel, h.ptoCount)
 	}
 	h.ptoCount++
+	if h.qlogger != nil {
+		h.qlogger.UpdatedPTOCount(time.Now(), h.ptoCount)
+	}
 	h.numProbesToSend += 2
 	switch encLevel {
 	case protocol.EncryptionInitial:

qlog/event.go

@@ -181,6 +181,18 @@ func (e eventMetricsUpdated) MarshalJSONObject(enc *gojay.Encoder) {
 	enc.Uint64KeyOmitEmpty("packets_in_flight", uint64(e.PacketsInFlight))
 }
 
+type eventUpdatedPTO struct {
+	Value uint32
+}
+
+func (e eventUpdatedPTO) Category() category { return categoryRecovery }
+func (e eventUpdatedPTO) Name() string       { return "metrics_updated" }
+func (e eventUpdatedPTO) IsNil() bool        { return false }
+
+func (e eventUpdatedPTO) MarshalJSONObject(enc *gojay.Encoder) {
+	enc.Uint32Key("pto_count", e.Value)
+}
+
 type eventPacketLost struct {
 	PacketType   packetType
 	PacketNumber protocol.PacketNumber

qlog/qlog.go

@@ -21,6 +21,7 @@ type Tracer interface {
 	ReceivedPacket(t time.Time, hdr *wire.ExtendedHeader, packetSize protocol.ByteCount, frames []wire.Frame)
 	UpdatedMetrics(t time.Time, rttStats *congestion.RTTStats, cwnd protocol.ByteCount, bytesInFLight protocol.ByteCount, packetsInFlight int)
 	LostPacket(time.Time, protocol.EncryptionLevel, protocol.PacketNumber, PacketLossReason)
+	UpdatedPTOCount(time.Time, uint32)
 	UpdatedKeyFromTLS(time.Time, protocol.EncryptionLevel, protocol.Perspective)
 }
 
@@ -170,3 +171,10 @@ func (t *tracer) UpdatedKeyFromTLS(time time.Time, encLevel protocol.EncryptionL
 		},
 	})
 }
+
+func (t *tracer) UpdatedPTOCount(time time.Time, value uint32) {
+	t.events = append(t.events, event{
+		Time:         time,
+		eventDetails: eventUpdatedPTO{Value: value},
+	})
+}

qlog/qlog_test.go

@@ -277,5 +277,15 @@ var _ = Describe("Tracer", func() {
 			Expect(ev).ToNot(HaveKey("old"))
 			Expect(ev).ToNot(HaveKey("new"))
 		})
+
+		It("records PTO changes", func() {
+			now := time.Now()
+			tracer.UpdatedPTOCount(now, 42)
+			t, category, eventName, ev := exportAndParse()
+			Expect(t).To(BeTemporally("~", now, time.Millisecond))
+			Expect(category).To(Equal("recovery"))
+			Expect(eventName).To(Equal("metrics_updated"))
+			Expect(ev).To(HaveKeyWithValue("pto_count", float64(42)))
+		})
 	})
 })