kubernetes/kops · error

reading data: %w

Error message

reading data: %w

What it means

In kOps' VFS layer, AzureBlobPath.RenderTerraform writes a blob resource into generated Terraform output. Before doing so it slurps the blob contents from the io.Reader passed in; if that read fails (e.g. an underlying reader error), the read error is wrapped as "reading data: %w" so the original cause is preserved for the caller.

Source

Thrown at util/pkg/vfs/azureblob_terraform.go:37

import (
	"fmt"
	"io"

	"k8s.io/kops/upup/pkg/fi/cloudup/terraformWriter"
)

type terraformAzureBlobFile struct {
	Name               string                   `cty:"name"`
	StorageContainerID string                   `cty:"storage_container_id"`
	Type               string                   `cty:"type"`
	Source             *terraformWriter.Literal `cty:"source"`
	Provider           *terraformWriter.Literal `cty:"provider"`
}

func (p *AzureBlobPath) RenderTerraform(w *terraformWriter.TerraformWriter, name string, data io.Reader, acl ACL) error {
	bytes, err := io.ReadAll(data)
	if err != nil {
		return fmt.Errorf("reading data: %w", err)
	}

	w.EnsureTerraformProvider("azurerm", map[string]string{})

	if p.account == "" {
		return fmt.Errorf("Azure storage account is not set on path %q", p.Path())
	}
	if w.AzureStorageAccountID == "" {
		return fmt.Errorf("Azure storage account ID is not set; it is required to render blob %q", p.Path())
	}

	source, err := w.AddFilePath("azurerm_storage_blob", name, "source", bytes, false)
	if err != nil {
		return fmt.Errorf("rendering Azure Blob file: %w", err)
	}

	tf := &terraformAzureBlobFile{
		Name:               p.key,

View on GitHub (pinned to 4c8573c808)

Solutions

1. Inspect the wrapped cause (%w) in the error chain with errors.Unwrap/ %v to see why the read failed
2. Verify the source data exists and is readable before calling RenderTerraform
3. Ensure the io.Reader is freshly opened and not already exhausted (check for io.EOF consumed earlier)
4. Re-run the kops update command after fixing the input file

Example fix

// before
f, _ := os.Open(path)
defer f.Close()
p.RenderTerraform(w, name, f, acl)

// after
f, err := os.Open(path)
if err != nil {
	return fmt.Errorf("opening blob source %q: %w", path, err)
}
defer f.Close()
if _, err := f.Stat(); err != nil {
	return fmt.Errorf("blob source %q unreadable: %w", path, err)
}
return p.RenderTerraform(w, name, f, acl)

if f, ok := data.(*os.File); ok {
	if _, err := f.Stat(); err != nil {
		return fmt.Errorf("blob source unreadable: %w", err)
	}
}

err := p.RenderTerraform(w, name, data, acl)
if err != nil && strings.Contains(err.Error(), "reading data:") {
	cause := errors.Unwrap(err)
	log.Printf("blob data read failed: %v", cause)
	// fix or re-open the source reader, then retry
}

When it happens

Trigger: Calling RenderTerraform on an *AzureBlobPath where the `data io.Reader` argument returns a non-nil error from io.ReadAll — e.g. a reader backed by a file that cannot be opened/read, a network-backed reader, or a reader already consumed/closed.

Common situations: The local file backing the VFS path was deleted or permission-denied before rendering; a bytes.Reader wrapped around a failed asset load; a custom io.Reader implementation erroring mid-read during `kops update cluster --target=terraform`.

Related errors

• Azure storage account is not set on path %q
• Azure storage account ID is not set; it is required to rende
• rendering Azure Blob file: %w
• reading data: %v
• rendering Azure Blob file: %w

AI-assisted analysis of kubernetes/kops@4c8573c808 (2026-09-05). Data as JSON: /api/errors/44cc7b0a7624cfb7. Report an issue: GitHub.