OpenNHP/opennhp · error

could not create form file

Error message

could not create form file: %v

What it means

The multipart writer wraps the file as a form part named 'file' using CreateFormFile. The error 'could not create form file: %v' wraps that failure. In Go, CreateFormFile only fails when writing the part header to the backing buffer errors — for a bytes.Buffer backing this is effectively a non-recoverable internal failure and is extremely rare in practice.

Solutions

1. Check host memory availability; an OOM-condition allocation failure is the realistic cause
2. Retry the upload after freeing memory
3. Keep the code as-is otherwise — this branch is defensive and rarely hit
4. If recurring, profile memory usage of the nhp-db process

// no meaningful pre-call validation; CreateFormFile on a bytes.Buffer
// only fails on allocation error. Ensure host memory headroom:
var m runtime.MemStats
runtime.ReadMemStats(&m)
if m.Sys > 3<<30 { // example threshold: 3GB in use
    log.Warn("high memory usage before upload")
}

url, err := dev.UploadFileToNHPServer(filePath)
if err != nil {
    if strings.Contains(err.Error(), "could not create form file") {
        return fmt.Errorf("multipart setup failed (likely OOM): %w", err)
    }
    return err
}

When it happens

Trigger: Calling writer.CreateFormFile when the underlying bytes.Buffer write fails — essentially only on memory allocation failure (out of memory) since multipart.WithBufferSize/backing writers are fixed here.

Common situations: Running nhp-db in a severely memory-constrained environment where even the tiny part-header allocation fails; corrupting the multipart.Writer via misuse (not applicable in normal use).

Understand the failure class

Background: "failed to write file", "Could not save figure", "Error saving remote file" — file write failed: causes and fixes across languages and libraries — this error's family across 38 libraries.

Related errors

• could not copy file to server
• could not close writer
• could not get file info
• unknown remote provider
• unknown remote provider

AI-assisted analysis of OpenNHP/opennhp@6e04ca5ff0 (2026-09-07). Data as JSON: /api/errors/5842c9aeece8bdf3. Report an issue: GitHub.

Appendix: source

Thrown at endpoints/db/utils.go:227

	fileInfo, err := file.Stat()
	if err != nil {
		return "", fmt.Errorf("could not get file info: %v", err)
	}

	// create upload progress
	progress := &UploadProgress{
		TotalSize: fileInfo.Size(),
	}

	startTime := time.Now()

	body := &bytes.Buffer{}
	writer := multipart.NewWriter(body)

	part, err := writer.CreateFormFile("file", filepath.Base(filePath))
	if err != nil {
		return "", fmt.Errorf("could not create form file: %v", err)
	}

	progressReader := &ProgressReader{
		Reader:   file,
		Progress: progress,
	}

	_, err = io.Copy(part, progressReader)
	if err != nil {
		return "", fmt.Errorf("could not copy file to server: %v", err)
	}

	err = writer.Close()
	if err != nil {
		return "", fmt.Errorf("could not close writer: %v", err)
	}

	uploadUrl := httpHost + "storage/upload"

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