What causes "invalid file name %s" in derailed/k9s?

Rename the file to include at least one underscore: 'nginx_run1.txt' style, i.e. _ [_ ]

invalid file name %s

Error message

invalid file name %s

What it means

Benchmark.initRow splits the bench file base name on '_' and requires at least 2 tokens: token 0 becomes the container column, token 1 the command column. A file with no underscore cannot populate the row schema and is rejected.

Source

Thrown at internal/render/benchmark.go:117

	return nil
}

// ----------------------------------------------------------------------------
// Helpers...

func (Benchmark) readFile(file string) (string, error) {
	data, err := os.ReadFile(file)
	if err != nil {
		return "", err
	}
	return string(data), nil
}

func (Benchmark) initRow(row model1.Fields, f os.FileInfo) error {
	tokens := strings.Split(f.Name(), "_")
	if len(tokens) < 2 {
		return fmt.Errorf("invalid file name %s", f.Name())
	}
	row[0] = tokens[0]
	row[1] = tokens[1]
	row[7] = f.Name()
	row[9] = ToAge(metav1.Time{Time: f.ModTime()})

	return nil
}

func (b Benchmark) augmentRow(fields model1.Fields, data string) {
	if data == "" {
		return
	}

	col := 2
	fields[col] = "pass"
	mf := toastRx.FindAllStringSubmatch(data, 1)
	if len(mf) > 0 {

View on GitHub (pinned to 2d3ccc6ba2)

Solutions

Rename the file to include at least one underscore: 'nginx_run1.txt' style, i.e. <container>_<label>[_<timestamp>]
Only let k9s create bench files via the bench command so naming stays canonical
Remove foreign files from the bench directory

Example fix

# before
mv bench1.txt nginx_run1.txt
# after: file 'nginx_run1.txt' -> container=nginx, command=run1

Defensive patterns

Strategy: validation

Validate before calling

func validBenchFileName(name string) bool {
	return strings.Count(name, "_") >= 1
}

Try / catch

On 'invalid file name' from initRow, skip the file and log it as foreign to the bench directory rather than aborting the row batch.

Prevention

Let k9s create bench files so naming stays '<container>_<command>[_<ts>]'
Keep foreign files out of the bench directory
If scripting bench results, encode container and label as underscore-separated tokens

When it happens

Trigger: A bench file manually created or renamed without '_', e.g. 'bench1.txt' or 'run.log'; k9s-generated names like '<container>_<command>_<ts>.txt' always pass.

Common situations: Users dropping custom files into the bench directory; scripts writing results with their own naming scheme; renames that strip the underscore.

Related errors

AI-assisted analysis of derailed/k9s@2d3ccc6ba2 (2026-08-15). Data as JSON: /api/errors/a039f05e07902eba. Report an issue: GitHub.