feat: add InMemoryMetricExporter

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

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

@@ -0,0 +1,78 @@
+/*
+ * 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"
+
+/**
+ * TODO
+ */
+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) {
+      process.nextTick(() => resultCallback({ code: ExportResultCode.FAILED }));
+      return
+    }
+
+    this._metrics.push(metrics)
+    process.nextTick(() => resultCallback({ code: ExportResultCode.SUCCESS }));
+  }
+
+  /**
+   * Returns all the collected scope metrics
+   * @returns ScopeMetric[]
+   */
+  public getMetrics(): ResourceMetrics[] {
+    return this._metrics
+  }
+
+  /**
+   * Clear the collected metrics
+   */
+  public clear(): void {
+    this._metrics = []
+  }
+
+  async forceFlush() {
+    this._metrics = []
+    return Promise.resolve()
+  }
+
+  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 +1,25 @@
+/*
+ * 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 { AggregationTemporality } from "../../src/export/AggregationTemporality"
+import { InMemoryMetricExporter } from "../../src/export/InMemoryMetricExporter"
+
+describe('InMemoryMetricExporter', () => {
+  describe('clear metrics on request', () => {
+    const exporter = new InMemoryMetricExporter(AggregationTemporality.CUMULATIVE)
+    assert.ok(exporter, 'exporter exists')
+  })
+})