do not export empty metrics (#907)

If no metrics have been generated, do not send an empty export request (except via forceFlush()) Closes 905
open-telemetry · Jan 9, 2023 · 2bd6bc5 · 2bd6bc5
1 parent 558e7ce
commit 2bd6bc5
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Showing 3 changed files with 37 additions and 3 deletions.
diff --git a/src/SDK/Metrics/MetricReader/ExportingReader.php b/src/SDK/Metrics/MetricReader/ExportingReader.php
@@ -70,6 +70,10 @@ private function doCollect(): bool
             $metrics[] = $source->collect($timestamp);
         }
 
+        if ($metrics === []) {
+            return true;
+        }
+
         return $this->exporter->export($metrics);
     }
 

diff --git a/tests/Unit/SDK/Metrics/MeterProviderTest.php b/tests/Unit/SDK/Metrics/MeterProviderTest.php
@@ -94,7 +94,6 @@ public function test_shutdown_calls_metric_reader_shutdown(): void
             ClockFactory::getDefault(),
             Attributes::factory(),
             new InstrumentationScopeFactory(Attributes::factory()),
-            /** @phpstan-ignore-next-line */
             [$metricReader->reveal()],
             new CriteriaViewRegistry(),
             null,
@@ -123,7 +122,6 @@ public function test_force_flush_calls_metric_reader_force_flush(): void
             ClockFactory::getDefault(),
             Attributes::factory(),
             new InstrumentationScopeFactory(Attributes::factory()),
-            /** @phpstan-ignore-next-line */
             [$metricReader->reveal()],
             new CriteriaViewRegistry(),
             null,

diff --git a/tests/Unit/SDK/Metrics/MetricReader/ExportingReaderTest.php b/tests/Unit/SDK/Metrics/MetricReader/ExportingReaderTest.php
@@ -157,18 +157,50 @@ public function test_collect_collects_sources_with_current_timestamp(): void
     public function test_shutdown_calls_exporter_shutdown(): void
     {
         $exporter = $this->createMock(MetricExporterInterface::class);
+        $exporter->expects($this->once())->method('shutdown')->willReturn(true);
+        $clock = new TestClock();
+        $reader = new ExportingReader($exporter, $clock);
+
+        $this->assertTrue($reader->shutdown());
+    }
+
+    public function test_shutdown_does_not_export_empty_metrics(): void
+    {
+        $exporter = $this->createMock(MetricExporterInterface::class);
+        $exporter->expects($this->never())->method('export');
+        $exporter->expects($this->once())->method('shutdown')->willReturn(true);
+
+        $clock = new TestClock();
+        $reader = new ExportingReader($exporter, $clock);
+
+        $reader->shutdown();
+    }
+
+    public function test_shutdown_exports_metrics(): void
+    {
+        $exporter = $this->createMock(MetricExporterInterface::class);
+        $provider = $this->createMock(MetricSourceProviderInterface::class);
+        $source = $this->createMock(MetricSourceInterface::class);
+        $source->method('collect')->willReturn($this->createMock(Metric::class));
+        $provider->method('create')->willReturn($source);
+        $exporter->method('temporality')->willReturn('foo');
         $exporter->expects($this->once())->method('export')->willReturn(true);
         $exporter->expects($this->once())->method('shutdown')->willReturn(true);
+
         $clock = new TestClock();
         $reader = new ExportingReader($exporter, $clock);
+        $reader->add(
+            $provider,
+            $this->createMock(MetricMetadataInterface::class),
+            $this->createMock(StalenessHandlerInterface::class)
+        );
 
         $this->assertTrue($reader->shutdown());
     }
 
     public function test_force_flush_calls_exporter_force_flush(): void
     {
         $exporter = $this->createMock(MetricExporterInterface::class);
-        $exporter->expects($this->once())->method('export')->willReturn(true);
         $exporter->expects($this->once())->method('forceFlush')->willReturn(true);
         $clock = new TestClock();
         $reader = new ExportingReader($exporter, $clock);