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

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

6 files changed, 43 insertions, 3 deletions

diff --git a/collector/filesystem_bsd.go b/collector/filesystem_bsd.go
index 9f20ec0..b9aa1cc 100644
--- a/collector/filesystem_bsd.go
+++ b/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),
diff --git a/collector/filesystem_freebsd.go b/collector/filesystem_freebsd.go
index 4df17d7..47c4833 100644
--- a/collector/filesystem_freebsd.go
+++ b/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),
diff --git a/collector/filesystem_linux.go b/collector/filesystem_linux.go
index f76aeaa..5ba4fe1 100644
--- a/collector/filesystem_linux.go
+++ b/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],
                 })
diff --git a/collector/filesystem_linux_test.go b/collector/filesystem_linux_test.go
index ebc6659..267ad06 100644
--- a/collector/filesystem_linux_test.go
+++ b/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)
+                }
+        }
+}
diff --git a/collector/fixtures_bindmount/proc/mounts b/collector/fixtures_bindmount/proc/mounts
new file mode 100644
index 0000000..2ef6401
--- /dev/null
+++ b/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
diff --git a/collector/paths.go b/collector/paths.go
index 5057f75..6150600 100644
--- a/collector/paths.go
+++ b/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)
+}