logging: add a Debug function to the Tracer (#4297)

logging/multiplex_test.go

@@ -64,6 +64,12 @@ var _ = Describe("Tracing", func() {
 				tr2.EXPECT().DroppedPacket(remote, PacketTypeRetry, ByteCount(1024), PacketDropDuplicate)
 				tracer.DroppedPacket(remote, PacketTypeRetry, 1024, PacketDropDuplicate)
 			})
+
+			It("traces the Debug event", func() {
+				tr1.EXPECT().Debug("foo", "bar")
+				tr2.EXPECT().Debug("foo", "bar")
+				tracer.Debug("foo", "bar")
+			})
 		})
 	})
 

logging/tracer.go

@@ -7,6 +7,7 @@ type Tracer struct {
 	SentPacket                   func(net.Addr, *Header, ByteCount, []Frame)
 	SentVersionNegotiationPacket func(_ net.Addr, dest, src ArbitraryLenConnectionID, _ []VersionNumber)
 	DroppedPacket                func(net.Addr, PacketType, ByteCount, PacketDropReason)
+	Debug                        func(name, msg string)
 }
 
 // NewMultiplexedTracer creates a new tracer that multiplexes events to multiple tracers.
@@ -39,5 +40,12 @@ func NewMultiplexedTracer(tracers ...*Tracer) *Tracer {
 				}
 			}
 		},
+		Debug: func(name, msg string) {
+			for _, t := range tracers {
+				if t.Debug != nil {
+					t.Debug(name, msg)
+				}
+			}
+		},
 	}
 }