[Feature]: Propagate served-model-name to LMCache metrics

[mustafayildirim]

Feature Request: Propagate served-model-name to LMCache metrics

Summary

When running vLLM using the OpenAI-compatible API, the --served-model-name parameter is not propagated to LMCache-related Prometheus metrics. Instead, the internal model_name label reflects the underlying model path (e.g. /huggingface/cache/.../DeepSeek-V3-0324).

This makes it difficult to correlate metrics with the externally-exposed model name, especially when multiple served aliases point to the same model or when deployments rely on logical model names rather than filesystem paths.

Current Behavior

Running vLLM with:

--served-model-name deepseek-v3-0324-longrunning
--kv-transfer-config='{"kv_connector":"LMCacheConnectorV1","kv_role":"kv_both"}'

Yields metrics such as:

lmcache_local_cache_usage{
  model_name="/huggingface/cache/hub/deepseek-ai/DeepSeek-V3-0324",
  ...
}

The model_name label is always the internal model path, not the served alias.

Requested Behavior

Expose served-model-name in LMCache-related metrics, such as:

• Replace model_name with the served name or
• Add a second label, e.g. served_model_name, while preserving the internal model path

Example desired metric:

lmcache_local_cache_usage{
  model_name="/huggingface/cache/hub/deepseek-ai/DeepSeek-V3-0324",
  served_model_name="deepseek-v3-0324-longrunning",
  ...
}

Motivation

• Easier multi-model monitoring when models are served under logical aliases.
• Prometheus/Grafana dashboards become simpler; no need for external relabeling.
• Avoids confusion when multiple deployments load the same underlying model path but serve it under different names.
• Aligns with user expectations: model name shown to API clients should match model name appearing in server metrics.

Use Case Example

Running:

python3 -m vllm.entrypoints.openai.api_server \
  --model /huggingface/cache/hub/deepseek-ai/DeepSeek-V3-0324 \
  --served-model-name deepseek-v3-0324-longrunning \
  --kv-transfer-config='{"kv_connector":"LMCacheConnectorV1","kv_role":"kv_both"}'

Metrics show:

model_name="/huggingface/cache/hub/deepseek-ai/DeepSeek-V3-0324"

Expected:

served_model_name="deepseek-v3-0324-longrunning"

Proposed Implementation

• Inject served-model-name into the worker model metadata.
• When generating LMCache metrics, add it as an additional Prometheus label.
• Backward-compatible: existing label values unchanged.

Alternatives

No response

Additional context

No response

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