Preserve the misspelled metric name for backwards compatibility

Author: brianaydemir

metrics/xrootd_metrics.go

@@ -460,13 +460,20 @@ var (
 		Help: "The total number of monitoring UDP packets received",
 	})
 
-	// TODO: Remove this metric (the line directly below)
-	// The renamed metric was added in v7.16
+	// TODO: Remove this metric when we can break backwards compatibility.
+	// The renamed metric ("count" -> "toal") was added in v7.16.
 	TransferReadvSegs = promauto.NewCounterVec(prometheus.CounterOpts{
 		Name: "xrootd_transfer_readv_segments_count",
 		Help: "Number of segments in readv operations",
 	}, []string{"path", "ap", "dn", "role", "org", "proj", "network"})
 
+	// TODO: Remove this metric when we can break backwards compatibility.
+	// The renamed metric ("toal" -> "total") was added in v7.25.
+	TransferReadvSegsTotalDeprecated = promauto.NewCounterVec(prometheus.CounterOpts{
+		Name: "xrootd_transfer_readv_segments_toal",
+		Help: "Number of segments in readv operations",
+	}, []string{"path", "ap", "dn", "role", "org", "proj", "network"})
+
 	TransferReadvSegsTotal = promauto.NewCounterVec(prometheus.CounterOpts{
 		Name: "xrootd_transfer_readv_segments_total",
 		Help: "Number of segments in readv operations",
@@ -1367,6 +1374,10 @@ func handlePacket(packet []byte) error {
 					// TODO: Remove this metric (the 2 lines directly below)
 					// The renamed metric was added in v7.16
 					counter := TransferReadvSegs.With(labels)
+					counter.Add(float64(int64(binary.BigEndian.Uint64(
+						packet[offset+opsOffset+16:offset+opsOffset+24]) -
+						oldReadvSegs)))
+					counter = TransferReadvSegsTotalDeprecated.With(labels)
 					counter.Add(float64(int64(binary.BigEndian.Uint64(
 						packet[offset+opsOffset+16:offset+opsOffset+24]) -
 						oldReadvSegs)))