[Feature]: [P/D] Expose kv_transfer metrics (print to console, and to promethus)

[lk-chen]

🚀 The feature, motivation and pitch

Now P/D is supported in latest release, it would be great to expose metrics like kv_xfer_time, kv_xfer_bytes, kv_xfer_num_blocks etc. to both console and prometheus, for performance monitoring.

I think we can break the work into several parts

1. pipe the metrics from nixl_connector all the way to model_runner , this can be further broken into
   a. change interface of get_finished to return not only ids, ideally a new class to aggregate all the infomation
   b. add metrics to the new class, it's worth discussion wether we want aggregated stats (avg, sum) or raw stats
2. consume the metrics from logger, in vllm/v1/metrics/loggers.py
3. consume the metrics from promethus logger, to be done in vllm/v1/metrics/loggers.py

Alternatives

No response

Additional context

No response

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[lk-chen]

#22188

[github-actions]

This issue has been automatically marked as stale because it has not had any activity within 90 days. It will be automatically closed if no further activity occurs within 30 days. Leave a comment if you feel this issue should remain open. Thank you!

[NickLucche]

This is now done, see

• [NIXL][Misc] Expose metrics from NIXL for logging to CLI #25388
• [KVConnector] Add metrics to Prometheus-Grafana dashboard #26811