instructure/canvas-lms · error · Canvas::Migration::Error

$!.message

Error message

$!.message

What it means

Canvas::Migration::Worker#download_attachment rescues Attachment::OverQuotaError and re-raises it as Canvas::Migration::Error with the original message. It means the migration could not attach the file because the context (course/user) exceeded its storage quota.

Solutions

1. Increase the course/account storage quota (course advanced settings or account quota settings)
2. Remove unused files from the target course to free space, then retry the migration
3. Handle the raised message in the UI to show users the quota problem
4. For account-level imports, raise default quota via account settings

Example fix

// before
# import fails silently with generic error
// after
begin
  Canvas::Migration::Worker.download_attachment(cm, url)
rescue Canvas::Migration::Error => e
  if e.message =~ /quota/i
    show_quota_error_dialog
  end
end

quota = cm.context.storage_quota
used = cm.context.storage_quota_used
raise 'over quota' if used + expected_size > quota

begin
  att = Canvas::Migration::Worker.download_attachment(cm, url)
rescue Canvas::Migration::Error => e
  raise if e.message !~ /quota/i
  notify_quota_exceeded(cm.context)
end

When it happens

Trigger: download_attachment (clone_url path) raising Attachment::OverQuotaError when importing course files into a context already at or above its storage quota.

Common situations: Importing a large course export into a course with a small quota, user files quota exceeded during course copy, quota lowered after content was created.

Understand the failure class

Background: "File too large" / "file size exceeds limit" errors: why libraries cap file sizes and how to fix them — this error's family across 46 libraries.

Related errors

• att.upload_error_message
• No exported data to import
• # : #
• e.message
• Error identifying package type

AI-assisted analysis of instructure/canvas-lms@1c9f0bb801 (2026-09-15). Data as JSON: /api/errors/5b7d66d4ebde06bd. Report an issue: GitHub.

Appendix: source

Thrown at lib/canvas/migration/worker.rb:102

    Rails.logger.warn "Couldn't clear export data for content_migration #{content_migration.id}"
  end

  def self.download_attachment(cm, url)
    att = Attachment.new
    att.context = cm
    att.file_state = "deleted"
    att.workflow_state = "unattached"
    att.clone_url(url, false, true, quota_context: cm.context)

    if att.file_state == "errored"
      raise Canvas::Migration::Error, att.upload_error_message
    end

    cm.attachment = att
    cm.save!
    att
  rescue Attachment::OverQuotaError
    raise Canvas::Migration::Error, $!.message
  end
end

View on GitHub (pinned to 1c9f0bb801)