test(instr-runtime-node): add tests for gcDurationBuckets config

Add tests verifying that the GC duration histogram is created correctly
with both default and custom bucket boundaries.

Author: lukeramsden

packages/instrumentation-runtime-node/test/gc.test.ts

@@ -0,0 +1,128 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import * as assert from 'assert';
+import { MeterProvider, DataPointType } from '@opentelemetry/sdk-metrics';
+import { RuntimeNodeInstrumentation } from '../src';
+import { TestMetricReader } from './testMetricsReader';
+import { METRIC_V8JS_GC_DURATION } from '../src/semconv';
+
+const MEASUREMENT_INTERVAL = 10;
+
+// Helper to trigger GC by allocating memory
+function triggerGC() {
+  const arrays = [];
+  for (let i = 0; i < 100; i++) {
+    arrays.push(new Array(10000).fill(i));
+  }
+  // Allow garbage collection by clearing references
+  arrays.length = 0;
+  if (global.gc) {
+    global.gc();
+  }
+}
+
+describe('v8js.gc.duration', function () {
+  let metricReader: TestMetricReader;
+  let meterProvider: MeterProvider;
+  let instrumentation: RuntimeNodeInstrumentation;
+
+  beforeEach(() => {
+    metricReader = new TestMetricReader();
+    meterProvider = new MeterProvider({
+      readers: [metricReader],
+    });
+  });
+
+  afterEach(() => {
+    instrumentation.disable();
+  });
+
+  it('should create histogram with default gcDurationBuckets', async function () {
+    // arrange
+    instrumentation = new RuntimeNodeInstrumentation({
+      monitoringPrecision: MEASUREMENT_INTERVAL,
+    });
+    instrumentation.setMeterProvider(meterProvider);
+
+    // act - trigger GC
+    triggerGC();
+    await new Promise(resolve => setTimeout(resolve, MEASUREMENT_INTERVAL * 10));
+    triggerGC();
+    await new Promise(resolve => setTimeout(resolve, MEASUREMENT_INTERVAL * 5));
+
+    const { resourceMetrics, errors } = await metricReader.collect();
+
+    // assert
+    assert.deepEqual(
+      errors,
+      [],
+      'expected no errors from the callback during collection'
+    );
+    const scopeMetrics = resourceMetrics.scopeMetrics;
+    const metric = scopeMetrics[0]?.metrics.find(
+      x => x.descriptor.name === METRIC_V8JS_GC_DURATION
+    );
+
+    assert.notEqual(metric, undefined, `${METRIC_V8JS_GC_DURATION} not found`);
+    assert.strictEqual(
+      metric!.dataPointType,
+      DataPointType.HISTOGRAM,
+      'expected histogram'
+    );
+    assert.strictEqual(
+      metric!.descriptor.unit,
+      's',
+      'expected unit to be seconds'
+    );
+  });
+
+  it('should allow custom gcDurationBuckets configuration', async function () {
+    // arrange
+    const customBuckets = [0.001, 0.005, 0.01, 0.05, 0.1, 0.5, 1];
+    instrumentation = new RuntimeNodeInstrumentation({
+      monitoringPrecision: MEASUREMENT_INTERVAL,
+      gcDurationBuckets: customBuckets,
+    });
+    instrumentation.setMeterProvider(meterProvider);
+
+    // act - trigger GC
+    triggerGC();
+    await new Promise(resolve => setTimeout(resolve, MEASUREMENT_INTERVAL * 10));
+    triggerGC();
+    await new Promise(resolve => setTimeout(resolve, MEASUREMENT_INTERVAL * 5));
+
+    const { resourceMetrics, errors } = await metricReader.collect();
+
+    // assert
+    assert.deepEqual(
+      errors,
+      [],
+      'expected no errors from the callback during collection'
+    );
+    const scopeMetrics = resourceMetrics.scopeMetrics;
+    const metric = scopeMetrics[0]?.metrics.find(
+      x => x.descriptor.name === METRIC_V8JS_GC_DURATION
+    );
+
+    assert.notEqual(metric, undefined, `${METRIC_V8JS_GC_DURATION} not found`);
+    assert.strictEqual(
+      metric!.dataPointType,
+      DataPointType.HISTOGRAM,
+      'expected histogram'
+    );
+  });
+});