[kv] Implement KvTablet RocksDB Lazy Open #2913
Description
Search before asking
- I searched in the issues and found nothing similar.
Motivation
When a tablet server hosts thousands of KV buckets, all RocksDB instances are opened eagerly at startup, consuming significant memory. In practice, many buckets may receive no traffic for hours or even days — especially in multi-tenant or high-partition-count deployments. These idle RocksDB instances waste memory without serving any requests.
Solution
Defer RocksDB open to first access. Each KV tablet starts as a lightweight sentinel (no RocksDB). When the first read/write arrives, RocksDB is opened on demand. After a configurable idle timeout, the tablet is automatically released back to the lightweight state, preserving local SST files for fast reopen.
Anything else?
No response
Willingness to contribute
- I'm willing to submit a PR!