feat: added ELU metrics

packages/beacon-node/src/metrics/nodeJsMetrics.ts

@@ -1,6 +1,51 @@
-import {collectDefaultMetrics, Registry} from "prom-client";
+import {EventLoopUtilization, performance} from "node:perf_hooks";
+import {collectDefaultMetrics, Histogram, Registry} from "prom-client";
 import {gcStats} from "@chainsafe/prometheus-gc-stats";
 
+/**
+ * Collects event loop utilization metrics compared to the last call
+ */
+function collectEventLoopUtilization(register: Registry, prefix?: string, intervalMs: number = 5000): () => void {
+  const key = `${prefix}_` ?? "";
+
+  const metricUtilization = new Histogram({
+    name: `${key}nodejs_eventloop_utilization`,
+    help: "Histogram of Event Loop utilization between two successive calls.",
+    registers: [register],
+    buckets: [0.001, 0.01, 0.1, 0.5, 1],
+  });
+
+  const metricIdle = new Histogram({
+    name: `${key}nodejs_eventloop_idle`,
+    help: "Histogram of Event Loop idle time between two successive calls.",
+    registers: [register],
+    buckets: [1, intervalMs / 10, intervalMs / 2, intervalMs],
+  });
+
+  const metricActive = new Histogram({
+    name: `${key}nodejs_eventloop_active`,
+    help: "Histogram of Event Loop active time between two successive calls.",
+    registers: [register],
+    buckets: [1, intervalMs / 10, intervalMs / 2, intervalMs],
+  });
+
+  const previousEventLoopUtilizations = new Map<string, EventLoopUtilization>();
+  const interval = setInterval(() => {
+    const previousElu = previousEventLoopUtilizations.get(key);
+    const currentElu = performance.eventLoopUtilization();
+    const {utilization, idle, active} = performance.eventLoopUtilization(currentElu, previousElu);
+    metricUtilization.observe(utilization); /* between 0-1 */
+    metricIdle.observe(idle); /* in ms, max `intervalMs` */
+    metricActive.observe(active); /* in ms, max `intervalMs` */
+    previousEventLoopUtilizations.set(key, currentElu);
+  }, intervalMs);
+
+  return () => {
+    clearInterval(interval);
+    previousEventLoopUtilizations.clear();
+  };
+}
+
 export function collectNodeJSMetrics(register: Registry, prefix?: string): () => void {
   collectDefaultMetrics({
     register,
@@ -9,11 +54,17 @@ export function collectNodeJSMetrics(register: Registry, prefix?: string): () =>
     eventLoopMonitoringPrecision: 10,
   });
 
+  const terminateEluCollection = collectEventLoopUtilization(register, prefix);
+
   // Collects GC metrics using a native binding module
   // - nodejs_gc_runs_total: Counts the number of time GC is invoked
   // - nodejs_gc_pause_seconds_total: Time spent in GC in seconds
   // - nodejs_gc_reclaimed_bytes_total: The number of bytes GC has freed
   // `close` must be called to stop the gc collection process from continuing
-  const close = gcStats(register, {collectionInterval: 6000, prefix});
-  return close;
+  const terminateGCCollection = gcStats(register, {collectionInterval: 6000, prefix});
+
+  return () => {
+    terminateGCCollection();
+    terminateEluCollection();
+  };
 }