ipfs/kubo · error

creating output file %q: %w

Error message

creating output file %q: %w

What it means

runProfile consumes collected profile results and adds each one to the output archive via p.archive.Create(res.fName). This error means the archive writer refused to create the named entry for a profile. It is wrapped with the entry name so the developer knows which profile entry failed; the root cause is on the archive/underlying writer side, not profile collection.

Source

Thrown at profile/profile.go:190

			}
			select {
			case results <- profileResult{buf: &b, fName: fName}:
			case <-ctx.Done():
			}
		}(c)
	}
	go func() {
		wg.Wait()
		close(results)
	}()

	for res := range results {
		if res.err != nil {
			return res.err
		}
		out, err := p.archive.Create(res.fName)
		if err != nil {
			return fmt.Errorf("creating output file %q: %w", res.fName, err)
		}
		_, err = io.Copy(out, res.buf)
		if err != nil {
			return fmt.Errorf("compressing result %q: %w", res.fName, err)
		}
	}

	return nil
}

func goroutineStacksText(ctx context.Context, _ Options, w io.Writer) error {
	return WriteAllGoroutineStacks(w)
}

func goroutineStacksProto(ctx context.Context, _ Options, w io.Writer) error {
	return pprof.Lookup("goroutine").WriteTo(w, 0)
}

View on GitHub (pinned to 329838acdf)

Solutions

1. Inspect the wrapped error from archive.Create — it names the underlying cause (closed writer, path, permission)
2. Keep the archive open until runProfile has fully drained the results channel (do not close it concurrently or early)
3. Verify the output destination (file/mount) is writable and has free space
4. Check fName for characters the archive format disallows

Example fix

// before
archive, _ := archiveBuilder(p.outputFile)
archive.Close() // closed too early
err := WriteProfiles(ctx, p) // Create fails: writer closed
// after
archive, _ := archiveBuilder(p.outputFile)
err := WriteProfiles(ctx, p)
archive.Close() // close only after profiles are written

f, err := os.OpenFile(dest, os.O_CREATE|os.O_WRONLY, 0o644)
if err != nil {
    return fmt.Errorf("archive destination unwritable: %w", err)
}
f.Close()

err := WriteProfiles(ctx, p)
if err != nil {
    if strings.HasPrefix(err.Error(), "creating output file") {
        log.Printf("archive entry creation failed, check archive lifetime/disk: %v", errors.Unwrap(err))
    }
    return err
}

When it happens

Trigger: p.archive.Create(fName) returns an error: the underlying archive writer was already closed or corrupted, the backing output file became unwritable mid-run, the archive implementation rejects the fName (invalid/duplicate entry name), or the underlying io.Writer to disk failed.

Common situations: Writing a diagnostics archive to a full disk or read-only mount; closing the archive writer before runProfile finishes draining the results channel; custom archive implementations that reject entry names.

Related errors

• compressing result %q: %w
• opening binary %q: %w
• copying binary %q: %w
• e (stream error trailer header value)
• cannot read migration: %w

AI-assisted analysis of ipfs/kubo@329838acdf (2026-09-03). Data as JSON: /api/errors/80f5fb482b8033ad. Report an issue: GitHub.