Module metrics 

Per-instance metrics wrapper.

Wraps a base Producer / Consumer pair behind try_push / try_pop and records:

• enqueue_success, enqueue_fail (ring full)
• dequeue_success, dequeue_fail (ring empty)
• max_depth_observed (gauge; high-water mark of in-flight items)
• cas_retries (only set by the mpmc-disruptor path; SPSC never CAS-retries)

Counter overhead is one fetch_add per op - measurable on a hot loop, so reach for this when you’re explicitly capturing operational stats, not when you need the absolute lowest latency.

Structs

InstrumentedConsumer

InstrumentedProducer

InstrumentedSpsc

Helper that constructs a metrics-wrapped (producer, consumer, metrics) triple from a base SPSC pair.

RingMetrics

Shared counter set. Hold an Arc<RingMetrics> across producer + consumer so the snapshot reflects both sides.

RingMetricsSnapshot

Snapshot value-type returned by RingMetrics::snapshot. Clone + Copy so callers can stash + compare across calls.