fix(InMemoryMetricExporter) clear metrics after shutdown

CHANGELOG.md

@@ -12,6 +12,7 @@ For semantic convention package changes, see the [semconv CHANGELOG](packages/se
 ### :boom: Breaking Change
 
 * feat(sdk-metrics): Add support for aggregation cardinality limit with a default limit of 2000. This limit can be customized via views [#5182](https://github.com/open-telemetry/opentelemetry-js/pull/5128)
+* fix(InMemoryMetricExporter) clear metrics after shutdown to align with other exporters [#5131](https://github.com/open-telemetry/opentelemetry-js/issues/5131) @paper2
 
 ### :rocket: (Enhancement)
 

packages/sdk-metrics/src/export/InMemoryMetricExporter.ts

@@ -76,6 +76,7 @@ export class InMemoryMetricExporter implements PushMetricExporter {
 
   shutdown(): Promise<void> {
     this._shutdown = true;
+    this._metrics = [];
     return Promise.resolve();
   }
 }

packages/sdk-metrics/test/export/InMemoryMetricExporter.test.ts

@@ -113,6 +113,24 @@ describe('InMemoryMetricExporter', () => {
     await metricReader.shutdown();
   });
 
+  it('should get no metrics after shutdown', 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);
+
+    await exporter.shutdown();
+
+    const otherMetrics = exporter.getMetrics();
+    assert.ok(otherMetrics.length === 0);
+
+    await metricReader.shutdown();
+  });
+
   it('should be able to access metric', async () => {
     const counter = meter.createCounter('counter_total', {
       description: 'a test description',