Refactor InMemory exporters to use shared storage manager (#1559)

Introduced `InMemoryStorageManager` to centralize storage management for spans, metrics, and logs. Updated InMemory exporters and their factory classes to utilize this shared storage.

* Add integration test for InMemoryExporter

- add integration test that shows that storage contains metrics
- because of src/SDK/Metrics/MetricReader/ExportingReader.php:148 I had to add `PushMetricExporterInterface` to InMemoryExporter class

* Add integration test for InMemoryExporter

Author: GrzegorzDrozd

Common/Export/InMemoryStorageManager.php

@@ -0,0 +1,32 @@
+<?php
+
+declare(strict_types=1);
+
+namespace OpenTelemetry\SDK\Common\Export;
+
+use ArrayObject;
+
+class InMemoryStorageManager
+{
+    private static ArrayObject $spans;
+    private static ArrayObject $metrics;
+    private static ArrayObject $logs;
+
+    public static function metrics(): ArrayObject
+    {
+        /** @psalm-suppress RedundantPropertyInitializationCheck */
+        return self::$metrics ??= new ArrayObject();
+    }
+
+    public static function logs(): ArrayObject
+    {
+        /** @psalm-suppress RedundantPropertyInitializationCheck */
+        return self::$logs ??= new ArrayObject();
+    }
+
+    public static function spans(): ArrayObject
+    {
+        /** @psalm-suppress RedundantPropertyInitializationCheck */
+        return self::$spans ??= new ArrayObject();
+    }
+}

Logs/Exporter/InMemoryExporterFactory.php

@@ -4,13 +4,14 @@
 
 namespace OpenTelemetry\SDK\Logs\Exporter;
 
+use OpenTelemetry\SDK\Common\Export\InMemoryStorageManager;
 use OpenTelemetry\SDK\Logs\LogRecordExporterFactoryInterface;
 use OpenTelemetry\SDK\Logs\LogRecordExporterInterface;
 
 class InMemoryExporterFactory implements LogRecordExporterFactoryInterface
 {
     public function create(): LogRecordExporterInterface
     {
-        return new InMemoryExporter();
+        return new InMemoryExporter(InMemoryStorageManager::logs());
     }
 }

Metrics/MetricExporter/InMemoryExporter.php

@@ -4,27 +4,30 @@
 
 namespace OpenTelemetry\SDK\Metrics\MetricExporter;
 
-use function array_push;
+use ArrayObject;
 use OpenTelemetry\SDK\Metrics\AggregationTemporalitySelectorInterface;
 use OpenTelemetry\SDK\Metrics\Data\Metric;
 use OpenTelemetry\SDK\Metrics\Data\Temporality;
 use OpenTelemetry\SDK\Metrics\MetricExporterInterface;
 use OpenTelemetry\SDK\Metrics\MetricMetadataInterface;
+use OpenTelemetry\SDK\Metrics\PushMetricExporterInterface;
 
 /**
  * @see https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/sdk_exporters/in-memory.md
  */
-final class InMemoryExporter implements MetricExporterInterface, AggregationTemporalitySelectorInterface
+final class InMemoryExporter implements MetricExporterInterface, AggregationTemporalitySelectorInterface, PushMetricExporterInterface
 {
-    /**
-     * @var list<Metric>
-     */
-    private array $metrics = [];
-
     private bool $closed = false;
 
-    public function __construct(private readonly string|Temporality|null $temporality = null)
-    {
+    /**
+     * @template-implements ArrayObject<Metric> $storage
+     * @param ArrayObject $storage
+     * @param string|Temporality|null $temporality
+     */
+    public function __construct(
+        private ArrayObject $storage = new ArrayObject(),
+        private readonly string|Temporality|null $temporality = null,
+    ) {
     }
 
     public function temporality(MetricMetadataInterface $metric): string|Temporality|null
@@ -33,13 +36,13 @@ public function temporality(MetricMetadataInterface $metric): string|Temporality
     }
 
     /**
-     * @return list<Metric>
+     * @return Metric[]
      */
     public function collect(bool $reset = false): array
     {
-        $metrics = $this->metrics;
+        $metrics = $this->storage->getArrayCopy();
         if ($reset) {
-            $this->metrics = [];
+            $this->storage = new ArrayObject();
         }
 
         return $metrics;
@@ -51,8 +54,9 @@ public function export(iterable $batch): bool
             return false;
         }
 
-        /** @psalm-suppress InvalidPropertyAssignmentValue */
-        array_push($this->metrics, ...$batch);
+        foreach ($batch as $metric) {
+            $this->storage->append($metric);
+        }
 
         return true;
     }
@@ -67,4 +71,9 @@ public function shutdown(): bool
 
         return true;
     }
+
+    public function forceFlush(): bool
+    {
+        return true;
+    }
 }

Metrics/MetricExporter/InMemoryExporterFactory.php

@@ -4,13 +4,14 @@
 
 namespace OpenTelemetry\SDK\Metrics\MetricExporter;
 
+use OpenTelemetry\SDK\Common\Export\InMemoryStorageManager;
 use OpenTelemetry\SDK\Metrics\MetricExporterFactoryInterface;
 use OpenTelemetry\SDK\Metrics\MetricExporterInterface;
 
 class InMemoryExporterFactory implements MetricExporterFactoryInterface
 {
     public function create(): MetricExporterInterface
     {
-        return new InMemoryExporter();
+        return new InMemoryExporter(InMemoryStorageManager::metrics());
     }
 }

Trace/SpanExporter/InMemorySpanExporterFactory.php

@@ -4,12 +4,13 @@
 
 namespace OpenTelemetry\SDK\Trace\SpanExporter;
 
+use OpenTelemetry\SDK\Common\Export\InMemoryStorageManager;
 use OpenTelemetry\SDK\Trace\SpanExporterInterface;
 
 class InMemorySpanExporterFactory implements SpanExporterFactoryInterface
 {
     public function create(): SpanExporterInterface
     {
-        return new InMemoryExporter();
+        return new InMemoryExporter(InMemoryStorageManager::spans());
     }
 }