docs: DYN-1967 update metrics docs after kvstats removal

[keivenchang]

Overview:

Update Dynamo docs after the kvstats Prometheus names removal (DYN-1967).

Details:

• Update docs

Where should the reviewer start?

docs/observability/metrics.md
docs/kubernetes/autoscaling.md

Related Issues: (use Closes / Fixes / Resolves / Relates to)

Relates to DYN-1967

/coderabbit profile chill

Summary by CodeRabbit

• Documentation

  • Updated autoscaling guidance with new SGLang KV cache hit rate metric for Decode service recommendations.
  • Renamed KV Router metrics section and introduced new kv_cache_events_applied counter metric with event tracking labels.

• Chores

  • Updated code generation documentation and examples to reflect new metric naming conventions.

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[coderabbitai]

Walkthrough

The pull request updates KV cache and router metrics throughout documentation and code examples. The changes replace kvstats_gpu_cache_usage_percent with sglang:cache_hit_rate in autoscaling guidance, rename the KV Router section from "kvstats" to "kvrouter", and introduce the new dynamo_component_kv_cache_events_applied metric with associated labels in observability documentation.

Changes

Cohort / File(s)	Summary
Metrics Documentation docs/kubernetes/autoscaling.md, docs/observability/metrics.md, fern/pages/kubernetes/autoscaling.md, fern/pages/observability/metrics.md	Replaced KV cache usage metric from kvstats_gpu_cache_usage_percent to sglang:cache_hit_rate in autoscaling context. Renamed KV Router section from "kvstats" to "kvrouter" and replaced old GPU cache metrics with new dynamo_component_kv_cache_events_applied counter metric featuring event_type and status labels.
Python Codegen Documentation lib/bindings/python/codegen/README.md, lib/bindings/python/codegen/src/gen_python_prometheus_names.rs	Updated code examples and generated output text to reflect metric naming changes from kvstats to kvrouter (e.g., kvstats_active_blocks → kv_cache_events_applied). Removed reference to macro-expansion documentation.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~12 minutes

Poem

🐰 Hops through metrics with delight,
Old kvstats fading from sight,
Cache hit rates and routers anew,
Dynamo components shining through!
Documentation refreshed and bright! ✨

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The PR title clearly and concisely summarizes the main change: updating metrics documentation after kvstats removal with the issue reference DYN-1967.
Description check	✅ Passed	The description follows the required template with all key sections completed: Overview explains the kvstats removal context, Details outlines documentation updates, and specific files are called out for review with related issue reference.

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[coderabbitai]

Actionable comments posted: 1

🤖 Fix all issues with AI agents

In `@fern/pages/observability/metrics.md`:
- Around line 125-131: The metric name documented as
`dynamo_component_kv_cache_events_applied` is missing the required `_total`
Prometheus suffix; update the documentation to
`dynamo_component_kv_cache_events_applied_total` wherever it appears
(referencing the KV Router metric entry and the `kv_cache_events_applied` metric
mention) to match team conventions (see `prometheus_names.rs` and PR 3035) while
leaving the existing label set (`event_type`, `status`) unchanged.

[biswapanda]

lgtm from k8s perspective

[jh-nv]

👍