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PMM-14832 Make mount path configurable #212

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PMM-14832 Make mount path configurable #212

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36a0824
PMM-14832 make mount path configurable
nmarukovich Feb 26, 2026
e3877c1
chore: update the test
ademidoff Mar 27, 2026
8b08bd6
PMM-14832 Rename the parameter
ademidoff Mar 27, 2026
c6bae39
PMM-14832 Update the param description
ademidoff Mar 27, 2026
af143c1
Merge branch 'main' into PMM-14832
ademidoff Mar 27, 2026
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13 changes: 10 additions & 3 deletions collector/filesystem_linux.go
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Original file line number Diff line number Diff line change
Expand Up @@ -18,7 +18,6 @@ package collector

import (
"bufio"
"errors"
"fmt"
"io"
"os"
Expand All @@ -43,6 +42,9 @@ var mountTimeout = kingpin.Flag("collector.filesystem.mount-timeout",
var statWorkerCount = kingpin.Flag("collector.filesystem.stat-workers",
"how many stat calls to process simultaneously").
Hidden().Default("4").Int()
var procMountsPath = kingpin.Flag("collector.filesystem.proc-mounts-path",
"Override absolute path to mounts file. If set, disables the default /proc/1/mounts fallback logic.").
Default("").String()
var stuckMounts = make(map[string]struct{})
var stuckMountsMtx = &sync.Mutex{}

Expand Down Expand Up @@ -178,8 +180,13 @@ func stuckMountWatcher(mountPoint string, success chan struct{}, logger log.Logg
}

func mountPointDetails(logger log.Logger) ([]filesystemLabels, error) {
file, err := os.Open(procFilePath("1/mounts"))
if errors.Is(err, os.ErrNotExist) {
path := procFilePath("1/mounts")
if *procMountsPath != "" {
path = *procMountsPath
}
Comment on lines +183 to +186
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@maxkondr maxkondr Mar 30, 2026

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Suggested change
path := procFilePath("1/mounts")
if *procMountsPath != "" {
path = *procMountsPath
}
path := *procMountsPath
if path == "" {
path = procFilePath("1/mounts")
}
  1. Isn't it better to prepare a list of paths to try to open like:
    paths := []string{'/proc/1/mounts', '/proc/mounts'}
    if *procMountsPath != "" {
        slices.Insert(paths, 0, *procMountsPath)
    }
    <iterate over paths and try to os.Open()>

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@ademidoff ademidoff Mar 30, 2026

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For 1: will consider, neet to test
For 2: that was my initial reaction, but it wasn't the intention of the request, the path, according to @nmarukovich, has to be defined by the user.


file, err := os.Open(path)
if err != nil && *procMountsPath == "" {
// Fallback to `/proc/mounts` if `/proc/1/mounts` is missing due hidepid.
level.Debug(logger).Log("msg", "Reading root mounts failed, falling back to system mounts", "err", err)
file, err = os.Open(procFilePath("mounts"))
Expand Down
40 changes: 40 additions & 0 deletions collector/filesystem_linux_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -142,3 +142,43 @@ func TestPathRootfs(t *testing.T) {
}
}
}

func TestProcMountsPathOverride(t *testing.T) {
// Save and restore flag values so changes don't leak into other tests.
priorProcMountsPath := *procMountsPath
priorProcPath := *procPath
t.Cleanup(func() {
_, _ = kingpin.CommandLine.Parse([]string{
"--path.procfs", priorProcPath,
"--collector.filesystem.proc-mounts-path", priorProcMountsPath,
})
})

// --path.procfs points to fixtures with 25+ mount points,
// but --collector.filesystem.proc-mounts-path overrides to a file with only 1 mount.
_, err := kingpin.CommandLine.Parse([]string{
"--path.procfs", "./fixtures/proc",
"--collector.filesystem.proc-mounts-path", "./fixtures_hidepid/proc/mounts",
})
if err != nil {
t.Fatal(err)
}

expected := map[string]string{
"/": "",
}

filesystems, err := mountPointDetails(log.NewNopLogger())
if err != nil {
t.Fatal(err)
}

if len(filesystems) != len(expected) {
t.Errorf("expected %d mounts, got %d", len(expected), len(filesystems))
}
for _, fs := range filesystems {
if _, ok := expected[fs.mountPoint]; !ok {
t.Errorf("Got unexpected %s", fs.mountPoint)
}
}
}
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