In return, NC must periodically update the NS of its status because each host where the NC runs has a chance to be selected as backup DAPS candidate.
Besides collecting metric information from external services, NS is also responsible for notifying its corresponding NCs about its own status, status of the DAPS-hosting machine, and information of DAPS candidates as backups.
As an example, if it were discovered that the current DAPS is overloaded or failed, DMM of this host would instruct the MMM to activate the backup (DAPS candidate).
This static profile contains several properties of NC such as its URL, machine capacity of its host machine, and past DAPS hosting records (if any).
Upon receiving a NC registration request, NS replies by sending a brief heartbeat message with only the information of the current DAPS and NS.
These selected nodes are those that will be appointed as backup DAPS if the current DAPS failed or overloaded.
Heartbeat format: The heartbeat message consists of a list of URLs that is divided into two parts: the URL of DAPS and URL of NS.
Secondly, not every client is eligible to host DAPS.
The difference between VP and HP is that, the formal refers to the amount of voluntary periods that the client has offered since the first execution of its copy of CPFnode software, whereas the latter refers to the total time spent on hosting DAPS.
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