Metrics

mercury-metrics provides latency histograms, PnL tracking, and a Prometheus export endpoint.

LatencyTracker

Uses HDR histograms (via hdrhistogram) to record latency with microsecond precision across several orders of magnitude.

Key measurements:

• Feed-to-strategy: time from BookUpdate publish to on_book return
• Signal-to-submit: time from Signal publish to submit_order call
• Submit-to-fill: exchange round-trip time

Access percentiles:

#![allow(unused)]
fn main() {
let p99 = tracker.percentile(99.0); // nanoseconds
let p999 = tracker.percentile(99.9);
}

PnlTracker

Tracks realized and unrealized PnL per symbol:

#![allow(unused)]
fn main() {
tracker.on_fill(&fill);
let pnl = tracker.unrealized_pnl(&symbol, current_mid_price);
}

Prometheus

Metrics are exported on 0.0.0.0:9090/metrics when --metrics is passed. Compatible with any Prometheus scrape target.

Available metrics:

• mercury_fill_latency_ns — histogram
• mercury_pnl_realized_usd — gauge per symbol
• mercury_orders_submitted_total — counter
• mercury_orders_cancelled_total — counter
• mercury_risk_rejections_total — counter