6.7. Advanced Handlers
Handlers have a "notifications" feature that has been in Mongrel since 0.3.13.3, but which will receive a major change in a version to come after 0.3.13.4. Rather than explain how to use the featuresince it will most likely changewe'll instead refer you to the mongrel_upload_progress plugin that is available as a stock Mongrel gem.
The mongrel_upload_progress plugin utilizes the notification callbacks to update a visual progress feedback for users uploading files. The example includes Mongrel code and a small Rails example.