Where can I find the description documents of these metrics? example:
alertmanager_cluster_pings_seconds_sum
apiserver_request_total
certificate_depth
Are there metrics documents to explain? I'don't know where to get it.
As @weibeld said in a comment you should find metrics' description in the target that you fetch them from. By now, please find description of metrics that you are looking for:
I hope it will helps you.