properly strip path.rootfs from mountpoint labels (prometheus#1421)

Change-type: patch
Connects-to: prometheus#1418
Signed-off-by: dt-rush <nickp@balena.io>

Author: dt-rush

CHANGELOG.md

@@ -17,6 +17,7 @@
 * [ENHANCEMENT] Include additional XFS runtime statistics. #1423
 * [BUGFIX] Renamed label `state` to `name` on `node_systemd_service_restart_total`. #1393
 * [BUGFIX] Fix netdev nil reference on Darwin #1414
+* [BUGFIX] Strip path.rootfs from mountpoint labels #1421
 
 ## 0.18.1 / 2019-06-04
 

collector/filesystem_bsd.go

@@ -69,7 +69,7 @@ func (c *filesystemCollector) GetStats() (stats []filesystemStats, err error) {
 		stats = append(stats, filesystemStats{
 			labels: filesystemLabels{
 				device:     device,
-				mountPoint: mountpoint,
+				mountPoint: rootfsStripPrefix(mountpoint),
 				fsType:     fstype,
 			},
 			size:      float64(mnt[i].f_blocks) * float64(mnt[i].f_bsize),

collector/filesystem_freebsd.go

@@ -73,7 +73,7 @@ func (c *filesystemCollector) GetStats() ([]filesystemStats, error) {
 		stats = append(stats, filesystemStats{
 			labels: filesystemLabels{
 				device:     device,
-				mountPoint: mountpoint,
+				mountPoint: rootfsStripPrefix(mountpoint),
 				fsType:     fstype,
 			},
 			size:      float64(fs.Blocks) * float64(fs.Bsize),

collector/filesystem_linux.go

@@ -165,7 +165,7 @@ func parseFilesystemLabels(r io.Reader) ([]filesystemLabels, error) {
 
 		filesystems = append(filesystems, filesystemLabels{
 			device:     parts[0],
-			mountPoint: parts[1],
+			mountPoint: rootfsStripPrefix(parts[1]),
 			fsType:     parts[2],
 			options:    parts[3],
 		})

collector/filesystem_linux_test.go

@@ -112,3 +112,30 @@ func TestMountsFallback(t *testing.T) {
 		}
 	}
 }
+
+func TestPathRootfs(t *testing.T) {
+	if _, err := kingpin.CommandLine.Parse([]string{"--path.procfs", "./fixtures_bindmount/proc", "--path.rootfs", "/host"}); err != nil {
+		t.Fatal(err)
+	}
+
+	expected := map[string]string{
+		// should modify these mountpoints (removes /host, see fixture proc file)
+		"/media/volume1": "",
+		"/media/volume2": "",
+		// should not modify these mountpoints
+		"/dev/shm":       "",
+		"/run/lock":      "",
+		"/sys/fs/cgroup": "",
+	}
+
+	filesystems, err := mountPointDetails()
+	if err != nil {
+		t.Log(err)
+	}
+
+	for _, fs := range filesystems {
+		if _, ok := expected[fs.mountPoint]; !ok {
+			t.Errorf("Got unexpected %s", fs.mountPoint)
+		}
+	}
+}

collector/fixtures_bindmount/proc/mounts

@@ -0,0 +1,5 @@
+/dev/nvme1n1 /host/media/volume1 ext4 rw,seclabel,relatime,data=ordered 0 0
+/dev/nvme1n2 /host/media/volume2 ext4 rw,seclabel,relatime,data=ordered 0 0
+tmpfs /dev/shm tmpfs rw,nosuid,nodev 0 0
+tmpfs /run/lock tmpfs rw,nosuid,nodev,noexec,relatime,size=5120k 0 0
+tmpfs /sys/fs/cgroup tmpfs ro,nosuid,nodev,noexec,mode=755 0 0

collector/paths.go

@@ -15,6 +15,7 @@ package collector
 
 import (
 	"path/filepath"
+	"strings"
 
 	"github.com/prometheus/procfs"
 	kingpin "gopkg.in/alecthomas/kingpin.v2"
@@ -38,3 +39,10 @@ func sysFilePath(name string) string {
 func rootfsFilePath(name string) string {
 	return filepath.Join(*rootfsPath, name)
 }
+
+func rootfsStripPrefix(path string) string {
+	if *rootfsPath == "/" {
+		return path
+	}
+	return strings.TrimPrefix(path, *rootfsPath)
+}