OpenShift Container Platform 4 CSRs were not approved automatically during over 100 nodes certificate renewal in UPI environment

Issue

• In UPI environment, there are over 100+ nodes has been added to the cluster, the cluster nodes certificate renewal requests will be received at the same time.
• Check whether the pending CSRs have been created over 100+ requests in oc get csr results during the nodes certificate renewal every month(CSRs may be approved once they have reached 80% +/-10% of their expiry period - Understanding the certificate rotation configuration), the machine-approver log will be printing the following errors if the CSRs cannot be approved automatically.

E1125 14:20:25.439889       1 main.go:161] Pending CSRs: 110; Max pending allowed: 100. Difference between pending CSRs and machines > 100. Ignoring all CSRs as too many recent pending CSRs seen