feat: add ConsoleMetricExporter (#500)

* feat: add ConsoleMetricExporter

* fix: review comments

* fix: linting

packages/opentelemetry-metrics/package.json

@@ -41,11 +41,13 @@
   "devDependencies": {
     "@types/mocha": "^5.2.7",
     "@types/node": "^12.6.9",
+    "@types/sinon": "^7.0.13",
     "codecov": "^3.5.0",
     "gts": "^1.1.0",
     "mocha": "^6.2.0",
     "nyc": "^14.1.1",
     "rimraf": "^3.0.0",
+    "sinon": "^7.5.0",
     "ts-mocha": "^6.0.0",
     "ts-node": "^8.3.0",
     "tslint-consistent-codestyle": "^1.15.1",

packages/opentelemetry-metrics/src/export/ConsoleMetricExporter.ts

@@ -0,0 +1,58 @@
+/*!
+ * Copyright 2019, 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 { MetricExporter, ReadableMetric } from './types';
+import { ExportResult } from '@opentelemetry/base';
+
+/**
+ * This is implementation of {@link MetricExporter} that prints metrics data to
+ * the console. This class can be used for diagnostic purposes.
+ */
+export class ConsoleMetricExporter implements MetricExporter {
+  export(
+    metrics: ReadableMetric[],
+    resultCallback: (result: ExportResult) => void
+  ): void {
+    for (const metric of metrics) {
+      const descriptor = metric.descriptor;
+      const timeseries = metric.timeseries;
+      console.log({
+        name: descriptor.name,
+        description: descriptor.description,
+      });
+
+      for (const ts of timeseries) {
+        const labels = descriptor.labelKeys
+          .map((k, i) => [k, ts.labelValues[i]])
+          .reduce(
+            (p, c) => ({
+              ...p,
+              [c[0] as string]: typeof c[1] === 'string' ? c[1] : c[1].value,
+            }),
+            {}
+          );
+        for (const point of ts.points) {
+          console.log({ labels, value: point.value });
+        }
+      }
+    }
+    return resultCallback(ExportResult.SUCCESS);
+  }
+
+  shutdown(): void {
+    // By default does nothing
+  }
+}

packages/opentelemetry-metrics/src/index.ts

@@ -17,4 +17,5 @@
 export * from './Handle';
 export * from './Meter';
 export * from './Metric';
+export * from './export/ConsoleMetricExporter';
 export * from './export/types';

packages/opentelemetry-metrics/test/export/ConsoleMetricExporter.test.ts

@@ -0,0 +1,61 @@
+/*!
+ * Copyright 2019, 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 * as sinon from 'sinon';
+import { ConsoleMetricExporter, Meter, GaugeMetric } from '../../src';
+
+describe('ConsoleMetricExporter', () => {
+  let consoleExporter: ConsoleMetricExporter;
+  let previousConsoleLog: any;
+
+  beforeEach(() => {
+    previousConsoleLog = console.log;
+    console.log = () => {};
+    consoleExporter = new ConsoleMetricExporter();
+  });
+
+  afterEach(() => {
+    console.log = previousConsoleLog;
+  });
+
+  describe('.export()', () => {
+    it('should export information about metrics', () => {
+      const spyConsole = sinon.spy(console, 'log');
+
+      const meter = new Meter();
+      meter.addExporter(consoleExporter);
+      const gauge = meter.createGauge('gauge', {
+        description: 'a test description',
+        labelKeys: ['key1', 'key2'],
+      }) as GaugeMetric;
+      const handle = gauge.getHandle(
+        meter.labels({ key1: 'labelValue1', key2: 'labelValue2' })
+      );
+      handle.set(10);
+      const [descriptor, timeseries] = spyConsole.args;
+      assert.deepStrictEqual(descriptor, [
+        { description: 'a test description', name: 'gauge' },
+      ]);
+      assert.deepStrictEqual(timeseries, [
+        {
+          labels: { key1: 'labelValue1', key2: 'labelValue2' },
+          value: 10,
+        },
+      ]);
+    });
+  });
+});