Dynamo frontend inter-token-latency histogram

Buckets are GENERATED, not literal: generate_log_buckets(0.001, 80.0, 20) produces log-spaced bounds rounded to 2 significant figures, always with a leading 0.0. This exact 20-bound ladder is asserted as a shipped contract by the test itl_default_buckets_reach_80_seconds, whose comment explains why it is pinned: the ceiling used to be 2.0 s, so any ITL above it fell into +Inf and histogram_quantile reported p99 as exactly 2.0 - indistinguishable from a genuine 2 s measurement. The same comment notes the 0.0018 bottom edge is deliberate: vLLM's ITL ladder starts at 0.01 and cannot resolve anything faster than 10 ms per token, so raising the ceiling here must not cost the low-end resolution. That is the whole reason to prefer Dynamo's ITL over vLLM's for slow-token-count workloads. Overridable via DYN_METRICS_ITL_{MIN,MAX,COUNT} (a deprecated DYN_HISTOGRAM_-prefixed form is still honoured with a deprecation warning), so treat the ladder as deployment-specific and read the le labels rather than assuming. NVIDIA Dynamo main (ai-dynamo/dynamo), read 2026-10-05. IMPORTANT CONTEXT that changes how every record in this set reads: Dynamo is a serving framework that BRIDGES vendor engine registries rather than reimplementing them. components/src/dynamo/common/backend/metrics.py has engines call register_global_registry (default prometheus_client.REGISTRY) or register_engine_registry (a custom CollectorRegistry, e.g. SGLang's multiprocess one), and their vendor-prefixed series - vllm:, sglang:, trtllm_, lmcache: - appear on the SAME /metrics endpoint alongside Dynamo's own dynamo_* names. So on a Dynamo deployment you will find vLLM and SGLang metrics that are recorded in this repo against THOSE engines, and the dynamo_component / dynamo_namespace / dynamo_endpoint labels plus model and model_name are injected at scrape time by Dynamo. The names below are Dynamo's OWN, from the auto-generated prometheus_names.py (generated from lib/runtime/src/metrics/prometheus_names.rs - do not hand-edit). Prefix is dynamo_frontend.