DamDownloadServlet doesn't handle exceptions thrown within the doGet method:

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        try {
            process(request, response);
        } catch (Exception e) {
            log.error("error during download", e);
        }
    }

If anything wrong happens when processing of the dam download, the exception thrown is only logged. The servlet should handle the error either throwing a new exception or taking care of the response manually.

This affects cases like using a database for the repository (with a file system datastore) and deleting (or loosing connection in case of NFS) the datastore folder.

When accessing an image through the dam servlet:
http://localhost:8080/magnoliaAuthor/dam/jcr:5b9ee0d9-9ee2-4943-ba91-ff8240065fda/youtube.png
It will return HTTP 200 with an empty image. Screenshot attached.