feat(metrics): add registerMetric and getMetrics

packages/opentelemetry-metrics/src/Meter.ts

@@ -143,6 +143,10 @@ export class Meter implements types.Meter {
     metric: Metric<T>
   ): void {
     if (this._metrics.has(name)) {
+      // @todo: decide how to handle already registered metric
+      // 1: Replace the old registered metric by the new
+      // 2. Throw error
+      // 3. skip duplicate metric (current approach)
       this._logger.error(
         `A metric with the name ${name} has already been registered.`
       );

packages/opentelemetry-metrics/test/Meter.test.ts

@@ -143,6 +143,30 @@ describe('Meter', () => {
       });
     });
 
+    describe('.registerMetric()', () => {
+      it('skip already registered Metric', () => {
+        const counter1 = meter.createCounter('name1') as CounterMetric;
+        counter1.getHandle(labelValues).add(10);
+
+        // should skip below metric
+        const counter2 = meter.createCounter('name1', {
+          valueType: types.ValueType.INT,
+        }) as CounterMetric;
+        counter2.getHandle(labelValues).add(500);
+
+        assert.strictEqual(meter.getMetrics().length, 1);
+        const [{ descriptor, timeseries }] = meter.getMetrics();
+        assert.deepStrictEqual(descriptor.name, 'name1');
+        assert.deepStrictEqual(
+          descriptor.type,
+          MetricDescriptorType.COUNTER_DOUBLE
+        );
+        assert.strictEqual(timeseries.length, 1);
+        assert.strictEqual(timeseries[0].points.length, 1);
+        assert.strictEqual(timeseries[0].points[0].value, 10);
+      });
+    });
+
     describe('names', () => {
       it('should create counter with valid names', () => {
         const counter1 = meter.createCounter('name1');