Overview:

Adds per-worker and cumulative estimated kv cache hit metrics (ISL blocks / Overlapping blocks) in Grafana.

Details:

Changes:

• Adds EventSubscriber trait and implements it for Namespace
• Publishes ISL blocks and Overlap blocks as events from the KV Router when selecting a worker for a given request
• Subscribes to those events from metric aggregator (count)
• Adds corresponding prometheus metrics and grafana dashboard panels

Future Work:

• Add event pub/sub to more granular level like Component/Endpoint instead of Namespace
• Improve mock_worker.rs to publish mock kv cache hit events for lighter debug/testing

Example Grafana Dashboard with new timeseries panels and gauge for Per-worker and Cumulative KV Cache Hit Rate estimation: