From 79e28759f053a730ff2091403e50dd130e3edb55 Mon Sep 17 00:00:00 2001
From: Michele Azzolari <michele@azzolari.it>
Date: Tue, 10 Dec 2024 16:52:18 +0100
Subject: [PATCH] feat(sdk-metrics): PeriodicExportingMetricReader now flushes
 pending tasks at shutdown (#5242)

---
 CHANGELOG.md                                                 | 2 ++
 .../test/node/OTLPMetricExporter.test.ts                     | 5 +++--
 packages/sdk-metrics/src/MeterProvider.ts                    | 2 +-
 .../sdk-metrics/src/export/PeriodicExportingMetricReader.ts  | 2 +-
 packages/sdk-metrics/test/MeterProvider.test.ts              | 4 ++--
 .../test/export/PeriodicExportingMetricReader.test.ts        | 2 --
 6 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2f378c59c1..81905d18fb 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -13,6 +13,8 @@ For semantic convention package changes, see the [semconv CHANGELOG](packages/se
 
 ### :rocket: (Enhancement)
 
+* feat(sdk-metrics): PeriodicExportingMetricReader now flushes pending tasks at shutdown [#5242](https://github.com/open-telemetry/opentelemetry-js/pull/5242)
+
 ### :bug: (Bug Fix)
 
 * fix(sdk-trace-base): do not load OTEL_ env vars on module load, but when needed [#5224](https://github.com/open-telemetry/opentelemetry-js/pull/5224)
diff --git a/experimental/packages/opentelemetry-exporter-metrics-otlp-http/test/node/OTLPMetricExporter.test.ts b/experimental/packages/opentelemetry-exporter-metrics-otlp-http/test/node/OTLPMetricExporter.test.ts
index 87569f327a..04d3228dee 100644
--- a/experimental/packages/opentelemetry-exporter-metrics-otlp-http/test/node/OTLPMetricExporter.test.ts
+++ b/experimental/packages/opentelemetry-exporter-metrics-otlp-http/test/node/OTLPMetricExporter.test.ts
@@ -214,8 +214,9 @@ describe('OTLPMetricExporter', () => {
       meterProvider.getMeter('test-meter').createCounter('test-counter').add(1);
 
       // act
-      meterProvider.forceFlush();
-      meterProvider.shutdown();
+      meterProvider.forceFlush().then(() => {
+        return meterProvider.shutdown();
+      });
     });
   });
 });
diff --git a/packages/sdk-metrics/src/MeterProvider.ts b/packages/sdk-metrics/src/MeterProvider.ts
index 962d59b429..6d5cd56fd0 100644
--- a/packages/sdk-metrics/src/MeterProvider.ts
+++ b/packages/sdk-metrics/src/MeterProvider.ts
@@ -122,7 +122,7 @@ export class MeterProvider implements IMeterProvider {
   }
 
   /**
-   * Flush all buffered data and shut down the MeterProvider and all registered
+   * Shut down the MeterProvider and all registered
    * MetricReaders.
    *
    * Returns a promise which is resolved when all flushes are complete.
diff --git a/packages/sdk-metrics/src/export/PeriodicExportingMetricReader.ts b/packages/sdk-metrics/src/export/PeriodicExportingMetricReader.ts
index 646c832aa4..6a9096652d 100644
--- a/packages/sdk-metrics/src/export/PeriodicExportingMetricReader.ts
+++ b/packages/sdk-metrics/src/export/PeriodicExportingMetricReader.ts
@@ -161,7 +161,7 @@ export class PeriodicExportingMetricReader extends MetricReader {
     if (this._interval) {
       clearInterval(this._interval);
     }
-
+    await this.onForceFlush();
     await this._exporter.shutdown();
   }
 }
diff --git a/packages/sdk-metrics/test/MeterProvider.test.ts b/packages/sdk-metrics/test/MeterProvider.test.ts
index cc534adcb1..453945200d 100644
--- a/packages/sdk-metrics/test/MeterProvider.test.ts
+++ b/packages/sdk-metrics/test/MeterProvider.test.ts
@@ -126,9 +126,9 @@ describe('MeterProvider', () => {
       assert.strictEqual(meter1, meter2);
     });
 
-    it('get a noop meter on shutdown', () => {
+    it('get a noop meter on shutdown', async () => {
       const meterProvider = new MeterProvider();
-      meterProvider.shutdown();
+      await meterProvider.shutdown();
       const meter = meterProvider.getMeter('meter1', '1.0.0');
       // returned tracer should be no-op, not instance of Meter (from SDK)
       assert.ok(!(meter instanceof Meter));
diff --git a/packages/sdk-metrics/test/export/PeriodicExportingMetricReader.test.ts b/packages/sdk-metrics/test/export/PeriodicExportingMetricReader.test.ts
index 9210f4622f..1fe248cab8 100644
--- a/packages/sdk-metrics/test/export/PeriodicExportingMetricReader.test.ts
+++ b/packages/sdk-metrics/test/export/PeriodicExportingMetricReader.test.ts
@@ -77,9 +77,7 @@ class TestMetricExporter implements PushMetricExporter {
 
   async shutdown(): Promise<void> {
     if (this._shutdown) return;
-    const flushPromise = this.forceFlush();
     this._shutdown = true;
-    await flushPromise;
   }
 
   async forceFlush(): Promise<void> {