How to add vnfs to VNFMonitor when Tacker restarts

Hi,

VNFMonitor module holds a dict called "_hosting_vnfs" that defines the vnfs to be monitored. When Tacker starts, "_hosting_vnfs" is supposed to be empty at first. When Tacker creates/deletes vnfs, "_hosting_vnfs" will add/delete vnfs accordingly and dynamically. Given following scenario as an example:
1. Tacker is hosting 5 vnfs and VNFMonitor is monitoring these 5 vnfs.
2. Tacker is down, but 5 vnfs are still working fine. And the database is also working fine.
3. Restart Tacker. Tacker reads information from database and gets these 5 vnfs.
4. However, VNFMonitor does not monitor these 5 vnfs, since "_hosting_vnfs" is empty now.

How to re-add these 5 vnfs into VNFMonitor? I find "add_vnf_to_monitor" from vnfm/plugin.py. I would like to know the correct process to do this. Could anyone help?

Best Regards,
Yimeng