[FLINK-34558] Add RocksDB key/value size metrics

• Type: Improvement
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 1.19.0
• Component/s: Runtime / State Backends
• Assignee: Unassigned
• Reporter: Jufang He
• Created: 01/Mar/24 08:10
• Updated: 08/Mar/24 01:46

Description

In some scenarios, the poor performance of RocksDB may be caused by too large key/value size, but now there is a lack of metrics for key/value size. By adding these metrics, we can conveniently calculate the distribution of key/value size, such as the average size and p99 size.  To reduce the negative impact of adding metric on RocksDB performance, we could reduce the impact by supporting sampling.

The possible implementation is as follows: After the RocksDB key/value serialization, we could obtain the byte array and report the size of the array through histogram metrics.