gohugoio/hugo · error

failed to start trace: %w

Error message

failed to start trace: %w

What it means

Returned by initTraceProfile when runtime/trace.Start(f) fails after the trace file was created. trace.Start errors when tracing is already enabled for the process; Hugo wraps and returns it. Note the file is not closed on this path.

Source

Thrown at commands/hugobuilder.go:304

		if stopMemTicker != nil {
			stopMemTicker()
		}
	}, nil
}

func (c *hugoBuilder) initTraceProfile() (func(), error) {
	if c.r.traceprofile == "" {
		return nil, nil
	}

	f, err := os.Create(c.r.traceprofile)
	if err != nil {
		return nil, fmt.Errorf("failed to create trace file: %w", err)
	}

	if err := trace.Start(f); err != nil {
		return nil, fmt.Errorf("failed to start trace: %w", err)
	}

	return func() {
		trace.Stop()
		f.Close()
	}, nil
}

// newWatcher creates a new watcher to watch filesystem events.
func (c *hugoBuilder) newWatcher(pollIntervalStr string, dirList ...string) (*watcher.Batcher, error) {
	staticSyncer := &staticSyncer{c: c}

	var pollInterval time.Duration
	poll := pollIntervalStr != ""
	if poll {
		pollInterval, err := types.ToDurationE(pollIntervalStr)
		if err != nil {
			return nil, fmt.Errorf("invalid value for flag poll: %s", err)

View on GitHub ↗ (pinned to 8a468df065)

Solutions

1. Ensure runtime tracing is started only once per process; remove any competing trace.Start call in an embedding program.
2. Rerun without --profile-trace to continue the build while investigating.

// runtime/trace allows only one active trace per process;
// ensure your host program isn't already tracing

if err := b.build(); err != nil {
    if strings.Contains(err.Error(), "start trace") {
        trace.Stop() // stop any host-owned trace, then rerun without the flag
    }
    return err
}

When it happens

Trigger: trace.Start returning non-nil, i.e. a runtime execution trace is already active in the process (double start), since file creation already succeeded.

Common situations: Essentially only when embedding Hugo in a program that already started runtime tracing, or invoking the profiling init path twice.

Related errors

• errConfigNotSet
• failed to start CPU profile: %w
• failed to create trace file: %w
• failed to compile cache buster target %q: %w
• failed to compile whitelist pattern %q: %w

AI-assisted analysis of gohugoio/hugo@8a468df065 (2026-07-31). Data as JSON: /data/errors/13d84285d9d7b975.json. Report an issue: GitHub ↗.