apiserver_client_certificate_expiration_second证书定义的位置：kubernetes/staging/src/k8s.io/apiserver/pkg/authentication/request/x509/x509.go at 244fbf94fd736e94071a77a8b7c91d81163249d4 · kubernetes/kubernetes (github.com)
apiserver_client_certificate_expiration_seconds表示的含义：src/k8s.io/apiserver: Increase cert expiration histogram resolution · kubernetes/kubernetes@f90bbc3 (github.com)
