Alerts in Alertmanger cannot be cleared

[Vu Tuan Dat]

Hello,

I got an issue with Alertmanager and Prometheus synchronization.

My system has a cluster of two Alertmanager nodes for multiple Prometheus clusters. 

Yesterday, I updated Prometheus config (targets) using `/-/reload` endpoints then I got several unresolved alerts which were NOT (for sure) in Prometheus.

At first, I thought it was Alertmanager kind of bug, I tried:

- Restart AM container

- Delete nflog

- Delete nflog and recreate AM container

However, neither of those worked for me.

Does anyone have the same situation or solution for deleting those annoying alerts?

Best Regards,

Dat