Deployed against real llama.cpp, every scrape failed. The mapping named
llamacpp:kv_cache_usage_ratio; build b10991 serves fifteen metric families
and none is a cache ratio. Because KV usage was mandatory, that one absent
name threw away the two metrics the engine does publish, and the router
scheduled to all three replicas blind while the cluster looked healthy.
A mapping that leaves a metric unnamed now means the engine does not publish
it, and the field stays zero. Naming one the engine does not serve is still a
violation, so this does not become a way to tolerate a typo. Running and
waiting can never be omitted: an engine that reports neither what it is doing
nor what is queued cannot be scheduled against at all. For llama.cpp this
costs the KV half of the saturation signal, which is a real loss softened by
its fixed slot count — queue depth already says when it is full.
The second half is why it took a deployment to notice. A contract violation
was logged per scrape at debug level, so at the default level nothing said
anything. It is now a warning, once, with a matching line when it clears.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
