diskstats: add fallback to ID_SERIAL for virtio devices (#3398)

Virtio devices don't have ID_SERIAL_SHORT but do have ID_SERIAL.
This change adds a fallback to use ID_SERIAL when ID_SERIAL_SHORT
is not available, allowing serial numbers to be properly exposed
for virtio block devices.

Also updates test expectations to reflect that devices with only
ID_SERIAL (like mmcblk devices in fixtures) now report their serial
numbers instead of empty strings.

Signed-off-by: illustris <[email protected]>

Author: illustris

collector/diskstats_linux.go

@@ -60,6 +60,7 @@ const (
 	udevIDModel                 = "ID_MODEL"
 	udevIDPath                  = "ID_PATH"
 	udevIDRevision              = "ID_REVISION"
+	udevIDSerial                = "ID_SERIAL"
 	udevIDSerialShort           = "ID_SERIAL_SHORT"
 	udevIDWWN                   = "ID_WWN"
 	udevSCSIIdentSerial         = "SCSI_IDENT_SERIAL"
@@ -294,6 +295,11 @@ func (c *diskstatsCollector) Update(ch chan<- prometheus.Metric) error {
 			serial = info[udevIDSerialShort]
 		}
 
+		// If still undefined, fallback to ID_SERIAL (used by virtio devices).
+		if serial == "" {
+			serial = info[udevIDSerial]
+		}
+
 		queueStats, err := c.fs.SysBlockDeviceQueueStats(dev)
 		// Block Device Queue stats may not exist for all devices.
 		if err != nil && !os.IsNotExist(err) {

collector/diskstats_linux_test.go

@@ -119,9 +119,9 @@ node_disk_info{device="dm-2",major="252",minor="2",model="",path="",revision="",
 node_disk_info{device="dm-3",major="252",minor="3",model="",path="",revision="",rotational="0",serial="",wwn=""} 1
 node_disk_info{device="dm-4",major="252",minor="4",model="",path="",revision="",rotational="0",serial="",wwn=""} 1
 node_disk_info{device="dm-5",major="252",minor="5",model="",path="",revision="",rotational="0",serial="",wwn=""} 1
-node_disk_info{device="mmcblk0",major="179",minor="0",model="",path="platform-df2969f3.mmc",revision="",rotational="0",serial="",wwn=""} 1
-node_disk_info{device="mmcblk0p1",major="179",minor="1",model="",path="platform-df2969f3.mmc",revision="",rotational="0",serial="",wwn=""} 1
-node_disk_info{device="mmcblk0p2",major="179",minor="2",model="",path="platform-df2969f3.mmc",revision="",rotational="0",serial="",wwn=""} 1
+node_disk_info{device="mmcblk0",major="179",minor="0",model="",path="platform-df2969f3.mmc",revision="",rotational="0",serial="0x83e36d93",wwn=""} 1
+node_disk_info{device="mmcblk0p1",major="179",minor="1",model="",path="platform-df2969f3.mmc",revision="",rotational="0",serial="0x83e36d93",wwn=""} 1
+node_disk_info{device="mmcblk0p2",major="179",minor="2",model="",path="platform-df2969f3.mmc",revision="",rotational="0",serial="0x83e36d93",wwn=""} 1
 node_disk_info{device="nvme0n1",major="259",minor="0",model="SAMSUNG EHFTF55LURSY-000Y9",path="pci-0000:02:00.0-nvme-1",revision="4NBTUY95",rotational="0",serial="S252B6CU1HG3M1",wwn="eui.p3vbbiejx5aae2r3"} 1
 node_disk_info{device="sda",major="8",minor="0",model="TOSHIBA_KSDB4U86",path="pci-0000:3b:00.0-sas-phy7-lun-0",revision="0102",rotational="1",serial="2160A0D5FVGG",wwn="0x7c72382b8de36a64"} 1
 node_disk_info{device="sdb",major="8",minor="16",model="SuperMicro_SSD",path="pci-0000:00:1f.2-ata-1",revision="0R",rotational="0",serial="SMC0E1B87ABBB16BD84E",wwn="0xe1b87abbb16bd84e"} 1

collector/fixtures/e2e-64k-page-output.txt

@@ -494,9 +494,9 @@ node_disk_info{device="dm-2",major="252",minor="2",model="",path="",revision="",
 node_disk_info{device="dm-3",major="252",minor="3",model="",path="",revision="",rotational="0",serial="",wwn=""} 1
 node_disk_info{device="dm-4",major="252",minor="4",model="",path="",revision="",rotational="0",serial="",wwn=""} 1
 node_disk_info{device="dm-5",major="252",minor="5",model="",path="",revision="",rotational="0",serial="",wwn=""} 1
-node_disk_info{device="mmcblk0",major="179",minor="0",model="",path="platform-df2969f3.mmc",revision="",rotational="0",serial="",wwn=""} 1
-node_disk_info{device="mmcblk0p1",major="179",minor="1",model="",path="platform-df2969f3.mmc",revision="",rotational="0",serial="",wwn=""} 1
-node_disk_info{device="mmcblk0p2",major="179",minor="2",model="",path="platform-df2969f3.mmc",revision="",rotational="0",serial="",wwn=""} 1
+node_disk_info{device="mmcblk0",major="179",minor="0",model="",path="platform-df2969f3.mmc",revision="",rotational="0",serial="0x83e36d93",wwn=""} 1
+node_disk_info{device="mmcblk0p1",major="179",minor="1",model="",path="platform-df2969f3.mmc",revision="",rotational="0",serial="0x83e36d93",wwn=""} 1
+node_disk_info{device="mmcblk0p2",major="179",minor="2",model="",path="platform-df2969f3.mmc",revision="",rotational="0",serial="0x83e36d93",wwn=""} 1
 node_disk_info{device="nvme0n1",major="259",minor="0",model="SAMSUNG EHFTF55LURSY-000Y9",path="pci-0000:02:00.0-nvme-1",revision="4NBTUY95",rotational="0",serial="S252B6CU1HG3M1",wwn="eui.p3vbbiejx5aae2r3"} 1
 node_disk_info{device="sda",major="8",minor="0",model="TOSHIBA_KSDB4U86",path="pci-0000:3b:00.0-sas-phy7-lun-0",revision="0102",rotational="1",serial="2160A0D5FVGG",wwn="0x7c72382b8de36a64"} 1
 node_disk_info{device="sdb",major="8",minor="16",model="SuperMicro_SSD",path="pci-0000:00:1f.2-ata-1",revision="0R",rotational="0",serial="SMC0E1B87ABBB16BD84E",wwn="0xe1b87abbb16bd84e"} 1

collector/fixtures/e2e-output.txt

@@ -526,9 +526,9 @@ node_disk_info{device="dm-2",major="252",minor="2",model="",path="",revision="",
 node_disk_info{device="dm-3",major="252",minor="3",model="",path="",revision="",rotational="0",serial="",wwn=""} 1
 node_disk_info{device="dm-4",major="252",minor="4",model="",path="",revision="",rotational="0",serial="",wwn=""} 1
 node_disk_info{device="dm-5",major="252",minor="5",model="",path="",revision="",rotational="0",serial="",wwn=""} 1
-node_disk_info{device="mmcblk0",major="179",minor="0",model="",path="platform-df2969f3.mmc",revision="",rotational="0",serial="",wwn=""} 1
-node_disk_info{device="mmcblk0p1",major="179",minor="1",model="",path="platform-df2969f3.mmc",revision="",rotational="0",serial="",wwn=""} 1
-node_disk_info{device="mmcblk0p2",major="179",minor="2",model="",path="platform-df2969f3.mmc",revision="",rotational="0",serial="",wwn=""} 1
+node_disk_info{device="mmcblk0",major="179",minor="0",model="",path="platform-df2969f3.mmc",revision="",rotational="0",serial="0x83e36d93",wwn=""} 1
+node_disk_info{device="mmcblk0p1",major="179",minor="1",model="",path="platform-df2969f3.mmc",revision="",rotational="0",serial="0x83e36d93",wwn=""} 1
+node_disk_info{device="mmcblk0p2",major="179",minor="2",model="",path="platform-df2969f3.mmc",revision="",rotational="0",serial="0x83e36d93",wwn=""} 1
 node_disk_info{device="nvme0n1",major="259",minor="0",model="SAMSUNG EHFTF55LURSY-000Y9",path="pci-0000:02:00.0-nvme-1",revision="4NBTUY95",rotational="0",serial="S252B6CU1HG3M1",wwn="eui.p3vbbiejx5aae2r3"} 1
 node_disk_info{device="sda",major="8",minor="0",model="TOSHIBA_KSDB4U86",path="pci-0000:3b:00.0-sas-phy7-lun-0",revision="0102",rotational="1",serial="2160A0D5FVGG",wwn="0x7c72382b8de36a64"} 1
 node_disk_info{device="sdb",major="8",minor="16",model="SuperMicro_SSD",path="pci-0000:00:1f.2-ata-1",revision="0R",rotational="0",serial="SMC0E1B87ABBB16BD84E",wwn="0xe1b87abbb16bd84e"} 1