From 1c0ebc2bc04aed67cbbd8fe04dc53bf7b7d08643 Mon Sep 17 00:00:00 2001
From: Ahmad Bamieh <ahmadbamieh@gmail.com>
Date: Mon, 28 Jun 2021 15:32:06 +0300
Subject: [PATCH] track event loop utilization

---
 .../event_loop_utilization/constants.ts       | 17 ++++
 .../event_loop_utilization.ts                 | 79 +++++++++++++++++++
 2 files changed, 96 insertions(+)
 create mode 100644 src/plugins/kibana_usage_collection/server/collectors/event_loop_utilization/constants.ts
 create mode 100644 src/plugins/kibana_usage_collection/server/collectors/event_loop_utilization/event_loop_utilization.ts

diff --git a/src/plugins/kibana_usage_collection/server/collectors/event_loop_utilization/constants.ts b/src/plugins/kibana_usage_collection/server/collectors/event_loop_utilization/constants.ts
new file mode 100644
index 0000000000000..552aac3d1babe
--- /dev/null
+++ b/src/plugins/kibana_usage_collection/server/collectors/event_loop_utilization/constants.ts
@@ -0,0 +1,17 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0 and the Server Side Public License, v 1; you may not use this file except
+ * in compliance with, at your election, the Elastic License 2.0 or the Server
+ * Side Public License, v 1.
+ */
+
+/**
+ * Start monitoring the event loop utilization after 1 minute
+ */
+export const MONITOR_EVENT_LOOP_UTILIZATION_START = 1 * 60 * 1000;
+
+/**
+ * Check the event loop utilization every 5 seconds
+ */
+export const MONITOR_EVENT_LOOP_UTILIZATION_INTERVAL = 5 * 1000;
diff --git a/src/plugins/kibana_usage_collection/server/collectors/event_loop_utilization/event_loop_utilization.ts b/src/plugins/kibana_usage_collection/server/collectors/event_loop_utilization/event_loop_utilization.ts
new file mode 100644
index 0000000000000..8e96a72d9372a
--- /dev/null
+++ b/src/plugins/kibana_usage_collection/server/collectors/event_loop_utilization/event_loop_utilization.ts
@@ -0,0 +1,79 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0 and the Server Side Public License, v 1; you may not use this file except
+ * in compliance with, at your election, the Elastic License 2.0 or the Server
+ * Side Public License, v 1.
+ */
+
+import type { EventLoopUtilization } from 'perf_hooks';
+import { performance } from 'perf_hooks';
+import { takeUntil } from 'rxjs/operators';
+import { Observable, timer } from 'rxjs';
+import type { Logger } from 'kibana/server';
+
+import { UsageCollectionSetup } from '../../../../usage_collection/server';
+
+import {
+  MONITOR_EVENT_LOOP_UTILIZATION_START,
+  MONITOR_EVENT_LOOP_UTILIZATION_INTERVAL,
+} from './constants';
+
+export class EventLoopUtlizationCollector {
+  private elu: EventLoopUtilization;
+
+  constructor() {
+    this.elu = performance.eventLoopUtilization();
+  }
+
+  public collect() {
+    const { active, idle, utilization } = performance.eventLoopUtilization(this.elu);
+
+    return {
+      active,
+      idle,
+      utilization,
+    };
+  }
+
+  public reset() {
+    this.elu = performance.eventLoopUtilization();
+  }
+}
+
+/**
+ * The monitoring of the event loop utilization starts immediately.
+ * The first collection happens after 1 minute.
+ * The utilization is collected and reset every 5 seconds.
+ * logs a warning when threshold is exceeded and increments usage counter.
+ */
+export function startTrackingEventLoopDelaysUsage(
+  usageCollection: UsageCollectionSetup,
+  logger: Logger,
+  utilizationThreshold = 0.75,
+  stopMonitoringEventLoop$: Observable<void>,
+  collectionStartDelay = MONITOR_EVENT_LOOP_UTILIZATION_START,
+  collectionInterval = MONITOR_EVENT_LOOP_UTILIZATION_INTERVAL
+) {
+  const eventLoopUtilizationCollector = new EventLoopUtlizationCollector();
+  const eventLoopUtilizationCounter = usageCollection.getUsageCounterByType('eventLoopUtilization');
+
+  timer(collectionStartDelay, collectionInterval)
+    .pipe(takeUntil(stopMonitoringEventLoop$))
+    .subscribe(async () => {
+      const { active, utilization, idle } = eventLoopUtilizationCollector.collect();
+
+      if (utilization > utilizationThreshold) {
+        logger.warn(
+          `Eventloop delay threshold exceeded. Utilization: ${
+            utilization * 100
+          }%. Idle: ${idle}ms. Active: ${active}ms.`
+        );
+        eventLoopUtilizationCounter?.incrementCounter({
+          counterName: 'utilization_threshold_exceeded',
+        });
+      }
+
+      eventLoopUtilizationCollector.reset();
+    });
+}