In a production environment, some jobs with higher SLAs need to be restarted quickly if failover occurs. Checkpoint restore is an important part of task start. When the Flink task starts slowly, the related Log and Metric should be added to facilitate troubleshooting.
For example: ByteDance shared in FFA 2020: They made OperatorState parallelized restore. Without these metrics, there will be two problems:
1. It is not easy to find the problem. If the task starts slowly, it is not known whether the root cause is the slow Checkpoint restore.
2. If optimized, how much speed has been improved for restore? Need to be quantified.
I believe that many companies have made relevant metrics in their internal Flink versions.