feat: add InMemoryMetricExporter (#3039)

* feat: add InMemoryMetricExporter

Introduces the `InMemoryMetricExporter`-class which collects metrics and stores it in memory

* style: improve comments

* style: improve comments

* test: created test for the `InMemoryMetricExporter`-class

* fix: remove the `clear`-method from `InMemoryMetricExporter`-class

* fix: add missing `ResourceMetrics` import

* style: ran `lint:fix` command on the code base

* docs: add CHANGELOG.md entry for the new `InMemoryMetricExporter`-class

* test: drop the `describe.only`

* test: improve test coverage

* Split reset and forceFlush

* fix: remove meterprovider typo

* Remove calls to missing setup method

* Use api meter in test

* Browser support

* style: lint

Co-authored-by: Weyert de Boer <weyert.deboer@tapico.io>
Co-authored-by: Daniel Dyla <dyladan@users.noreply.github.com>

experimental/CHANGELOG.md

@@ -19,6 +19,7 @@ All notable changes to experimental packages in this project will be documented
 
 * feat(metrics-api): use common attributes definitions #3038 @legendecas
 * feat(otlp-proto): pre-compile proto files [#3098](https://github.com/open-telemetry/opentelemetry-js/pull/3098) @legendecas
+* feat(opentelemetry-sdk-metrics-base): added InMemoryMetricExporter [#3039](https://github.com/open-telemetry/opentelemetry-js/pull/3039) @weyert
 
 ### :bug: (Bug Fix)
 

experimental/packages/opentelemetry-sdk-metrics-base/src/export/InMemoryMetricExporter.ts

@@ -0,0 +1,76 @@
+/*
+ * 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 { ExportResultCode } from '@opentelemetry/core';
+import { ExportResult } from '@opentelemetry/core';
+import { InstrumentType } from '../InstrumentDescriptor';
+import { AggregationTemporality } from './AggregationTemporality';
+import { ResourceMetrics } from './MetricData';
+import { PushMetricExporter } from './MetricExporter';
+
+/**
+ * In-memory Metrics Exporter is a Push Metric Exporter
+ * which accumulates metrics data in the local memory and
+ * allows to inspect it (useful for e.g. unit tests).
+ */
+export class InMemoryMetricExporter implements PushMetricExporter {
+  protected _shutdown = false;
+  protected _aggregationTemporality: AggregationTemporality;
+  private _metrics: ResourceMetrics[] = [];
+
+  constructor(aggregationTemporality: AggregationTemporality) {
+    this._aggregationTemporality = aggregationTemporality;
+  }
+
+  /**
+   * @inheritedDoc
+   */
+  export(metrics: ResourceMetrics, resultCallback: (result: ExportResult) => void): void {
+    // Avoid storing metrics when exporter is shutdown
+    if (this. _shutdown) {
+      setTimeout(() => resultCallback({ code: ExportResultCode.FAILED }), 0);
+      return;
+    }
+
+    this._metrics.push(metrics);
+    setTimeout(() => resultCallback({ code: ExportResultCode.SUCCESS }), 0);
+  }
+
+  /**
+   * Returns all the collected resource metrics
+   * @returns ResourceMetrics[]
+   */
+  public getMetrics(): ResourceMetrics[] {
+    return this._metrics;
+  }
+
+  forceFlush(): Promise<void> {
+    return Promise.resolve();
+  }
+
+  reset() {
+    this._metrics = [];
+  }
+
+  selectAggregationTemporality(_instrumentType: InstrumentType): AggregationTemporality {
+    return this._aggregationTemporality;
+  }
+
+  shutdown(): Promise<void> {
+    this._shutdown = true;
+    return Promise.resolve();
+  }
+}

experimental/packages/opentelemetry-sdk-metrics-base/src/index.ts

@@ -21,6 +21,7 @@ export * from './export/MetricExporter';
 export * from './export/MetricProducer';
 export * from './export/MetricReader';
 export * from './export/PeriodicExportingMetricReader';
+export * from './export/InMemoryMetricExporter';
 export { InstrumentDescriptor, InstrumentType } from './InstrumentDescriptor';
 export * from './Meter';
 export * from './MeterProvider';

experimental/packages/opentelemetry-sdk-metrics-base/test/export/InMemoryMetricExporter.test.ts

@@ -0,0 +1,147 @@
+/*
+ * 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 { ExportResultCode } from '@opentelemetry/core';
+import { Resource } from '@opentelemetry/resources';
+import * as metrics from '@opentelemetry/api-metrics';
+import assert = require('assert');
+import { AggregationTemporality } from '../../src/export/AggregationTemporality';
+import { InMemoryMetricExporter } from '../../src/export/InMemoryMetricExporter';
+import { ResourceMetrics } from '../../src/export/MetricData';
+import { PeriodicExportingMetricReader } from '../../src/export/PeriodicExportingMetricReader';
+import { MeterProvider } from '../../src/MeterProvider';
+import { defaultResource } from '../util';
+
+async function waitForNumberOfExports(exporter: InMemoryMetricExporter , numberOfExports: number): Promise<ResourceMetrics[]> {
+  if (numberOfExports <= 0) {
+    throw new Error('numberOfExports must be greater than or equal to 0');
+  }
+
+  let totalExports = 0;
+  while (totalExports < numberOfExports) {
+    await new Promise(resolve => setTimeout(resolve, 20));
+    const exportedMetrics = exporter.getMetrics();
+    totalExports = exportedMetrics.length;
+  }
+
+  return exporter.getMetrics();
+}
+
+describe('InMemoryMetricExporter', () => {
+  let exporter: InMemoryMetricExporter;
+  let meterProvider: MeterProvider;
+  let meterReader: PeriodicExportingMetricReader;
+  let meter: metrics.Meter;
+
+  beforeEach(() => {
+    exporter = new InMemoryMetricExporter(AggregationTemporality.CUMULATIVE);
+    meterProvider = new MeterProvider({ resource: defaultResource });
+    meter = meterProvider.getMeter('InMemoryMetricExporter', '1.0.0');
+    meterReader = new PeriodicExportingMetricReader({
+      exporter: exporter,
+      exportIntervalMillis: 100,
+      exportTimeoutMillis: 100
+    });
+    meterProvider.addMetricReader(meterReader);
+  });
+
+  afterEach(async () => {
+    await exporter.shutdown();
+    await meterReader.shutdown();
+  });
+
+  it('should return failed result code', done => {
+    exporter.shutdown().then(() => {
+      const resource = new Resource({
+        'resource-attribute': 'resource attribute value',
+      });
+      const resourceMetrics: ResourceMetrics = {
+        resource: resource,
+        scopeMetrics:
+          [
+            {
+              scope: {
+                name: 'mylib',
+                version: '0.1.0',
+                schemaUrl: 'http://url.to.schema'
+              },
+              metrics: [],
+            }
+          ]
+      };
+      exporter.export(resourceMetrics, result => {
+        assert.ok(result.code === ExportResultCode.FAILED);
+        meterReader.shutdown().then(() => {
+          done();
+        });
+      });
+    });
+  });
+
+  it('should reset metrics when reset is called', async () => {
+    const counter = meter.createCounter('counter_total', {
+      description: 'a test description',
+    });
+    const counterAttribute = { key1: 'attributeValue1' };
+    counter.add(10, counterAttribute);
+
+    const exportedMetrics = await waitForNumberOfExports(exporter, 1);
+    assert.ok(exportedMetrics.length > 0);
+
+    exporter.reset();
+
+    const otherMetrics = exporter.getMetrics();
+    assert.ok(otherMetrics.length === 0);
+
+    await exporter.shutdown();
+    await meterReader.shutdown();
+  });
+
+  it('should be able to access metric', async () => {
+    const counter = meter.createCounter('counter_total', {
+      description: 'a test description',
+    });
+    const counterAttribute = { key1: 'attributeValue1' };
+    counter.add(10, counterAttribute);
+    counter.add(10, counterAttribute);
+
+    const histogram = meter.createHistogram('histogram', { description: 'a histogram' });
+    histogram.record(10);
+    histogram.record(100);
+    histogram.record(1000);
+
+    const exportedMetrics = await waitForNumberOfExports(exporter, 1);
+    assert.ok(exportedMetrics.length > 0);
+
+    const resourceMetrics = exportedMetrics.shift();
+    assert.ok(resourceMetrics);
+    const firstScopeMetric = resourceMetrics?.scopeMetrics.shift();
+    assert.ok(firstScopeMetric);
+    assert.ok(firstScopeMetric.metrics.length > 0);
+    const [counterMetric, histogramMetric] = firstScopeMetric.metrics;
+    assert.ok(counterMetric.descriptor.name, 'counter_total');
+    assert.ok(counterMetric.dataPoints.length > 0);
+    const counterDataPoint = counterMetric.dataPoints.shift();
+    assert.ok(counterDataPoint);
+    assert.strictEqual(counterDataPoint.attributes, counterAttribute);
+
+    assert.ok(histogramMetric.descriptor.name, 'histogram');
+    assert.ok(histogramMetric.dataPoints.length > 0);
+    const histogramDataPoint = histogramMetric.dataPoints.shift();
+    assert.ok(histogramDataPoint);
+
+    await meterReader.shutdown();
+  });
+});