Durable DDNS update queue (Persistence Manager for D2)

Problem

The DDNS update queue in the D2 process is not durable and queued requests may be lost if the process is stopped or crashes. The retry mechanism is non configurable, making two more attempts 100ms apart if the target DNS server cannot be reached.

Desired Solution

• A durable queue persists pending updates between restarts and crashes.
• A new configuration parameter is used to set the number of seconds that the D2 process waits for a response before retrying the DNS update.
• An additional configuration parameter is used to limit the number of times that D2 process tries to send the DNS update.

This may be covered in the design of a Persistence Manager in this wiki document.