thanos-io/thanos · error

execute template

Error message

execute template

What it means

The `thanos tools bucket web` / inspect command parses the user-supplied Go template (via --format) and executes it against each block's *metadata.Meta. This error wraps any failure returned by tmpl.Execute, e.g. the template references a field that does not exist on metadata.Meta or a template function misuse. It indicates the template text is syntactically valid but cannot be evaluated against the data.

Solutions

1. Check every field reference in --format against the metadata.Meta struct (github.com/thanos-io/thanos/pkg/block/metadata) and fix names.
2. Guard possibly-nil pointer fields in the template, e.g. {{if .Thana}}...{{end}}, since m is passed as *metadata.Meta.
3. Verify with `template.New("").Parse` + Execute in a small Go snippet to see the precise field/function error.
4. If a field was removed in a Thanos upgrade, update the template to the new field name.

Example fix

// before
thanos tools bucket ls bkt --format '{{.Thanos.Version}}'
// after
thanos tools bucket ls bkt --format '{{.Thana.Version}}'

_, err := template.New("").Parse(format)
if err != nil {
    return fmt.Errorf("--format template is invalid: %w", err)
}

if err := printBlock(meta); err != nil {
    if strings.Contains(err.Error(), "execute template") {
        // fall back to default format
        format = "{{.ULID}}"
    }
}

When it happens

Trigger: Running `thanos tools bucket inspect/web/ls` (the printBlock path at cmd/thanos/tools_bucket.go:509) with a --format template like '{{.Thana.Oops}}' that accesses a nonexistent field of metadata.Meta, calls a method that errors, or uses an undefined template function.

Common situations: Copy-pasted templates from older Thanos versions where metadata.Meta fields were renamed/removed (e.g. downsampling or source fields), typos in field names (Go templates fail on nil-pointer field access), or templates written for Prometheus meta JSON instead of Thanos metadata.Meta.

Understand the failure class

Background: "Must be a positive integer", "Invalid value", "Unsupported": the invalid-argument-value error family, when a library rejects the value you pass — this error's family across 35 libraries.

Related errors

• iter
• level is bigger then default set of
• unknown sync strategy
• get compaction levels
• penalty based deduplication needs at least one replica…

AI-assisted analysis of thanos-io/thanos@35b8b99117 (2026-09-07). Data as JSON: /api/errors/3963cf6b9bd87337. Report an issue: GitHub.

Appendix: source

Thrown at cmd/thanos/tools_bucket.go:509

					return err
				}
				return nil
			}
		case "json":
			enc := json.NewEncoder(os.Stdout)
			enc.SetIndent("", "\t")

			printBlock = func(m *metadata.Meta) error {
				return enc.Encode(&m)
			}
		default:
			tmpl, err := template.New("").Parse(format)
			if err != nil {
				return errors.Wrap(err, "invalid template")
			}
			printBlock = func(m *metadata.Meta) error {
				if err := tmpl.Execute(os.Stdout, &m); err != nil {
					return errors.Wrap(err, "execute template")
				}
				fmt.Fprintln(os.Stdout, "")
				return nil
			}
		}

		metas, _, err := fetcher.Fetch(ctx)
		if err != nil {
			return err
		}

		for _, meta := range metas {
			objects++
			if err := printBlock(meta); err != nil {
				return errors.Wrap(err, "iter")
			}
		}
		level.Info(logger).Log("msg", "ls done", "objects", objects)

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