optional internal metrics (#1106)

adding a configuration option OTEL_PHP_INTERNAL_METRICS_ENABLED which
controls whether the SDK will emit its own metrics (eg batch processor
state).

examples/enabling_internal_metrics.php

@@ -0,0 +1,24 @@
+<?php
+
+declare(strict_types=1);
+
+namespace OpenTelemetry\Example;
+
+use OpenTelemetry\API\Globals;
+
+/**
+ * The OpenTelemetry SDK is able to emit some metrics about its internal state. For example,
+ * batch span and log processor state.
+ * This feature can be enabled via the OTEL_PHP_INTERNAL_METRICS_ENABLED setting.
+ */
+
+putenv('OTEL_PHP_INTERNAL_METRICS_ENABLED=true');
+putenv('OTEL_PHP_AUTOLOAD_ENABLED=true');
+putenv('OTEL_TRACES_EXPORTER=console');
+putenv('OTEL_METRICS_EXPORTER=console');
+putenv('OTEL_LOGS_EXPORTER=console');
+
+require __DIR__ . '/../vendor/autoload.php';
+
+$tracerProvider = Globals::tracerProvider();
+$tracerProvider->getTracer('demo')->spanBuilder('root')->startSpan()->end();

rector.php

@@ -27,7 +27,6 @@ return static function (RectorConfig $rectorConfig): void {
         FlipTypeControlToUseExclusiveTypeRector::class,
         \Rector\Strict\Rector\Empty_\DisallowedEmptyRuleFixerRector::class,
         \Rector\CodeQuality\Rector\If_\ExplicitBoolCompareRector::class,
-        \Rector\RemovingStatic\Rector\ClassMethod\LocallyCalledStaticMethodToNonStaticRector::class,
         \Rector\CodeQuality\Rector\ClassMethod\LocallyCalledStaticMethodToNonStaticRector::class,
     ]);
 };

src/SDK/Common/Configuration/Defaults.php

@@ -113,6 +113,7 @@ interface Defaults
     public const OTEL_PHP_TRACES_PROCESSOR = 'batch';
     public const OTEL_PHP_DETECTORS = 'all';
     public const OTEL_PHP_AUTOLOAD_ENABLED = 'false';
+    public const OTEL_PHP_INTERNAL_METRICS_ENABLED = 'false';
     public const OTEL_PHP_DISABLED_INSTRUMENTATIONS = [];
     public const OTEL_PHP_LOGS_PROCESSOR = 'batch';
 }

src/SDK/Common/Configuration/ValueTypes.php

@@ -119,5 +119,6 @@ interface ValueTypes
     public const OTEL_PHP_TRACES_PROCESSOR = VariableTypes::ENUM;
     public const OTEL_PHP_DETECTORS = VariableTypes::LIST;
     public const OTEL_PHP_AUTOLOAD_ENABLED = VariableTypes::BOOL;
+    public const OTEL_PHP_INTERNAL_METRICS_ENABLED = VariableTypes::BOOL;
     public const OTEL_PHP_DISABLED_INSTRUMENTATIONS = VariableTypes::LIST;
 }

src/SDK/Common/Configuration/Variables.php

@@ -135,5 +135,6 @@ interface Variables
     public const OTEL_PHP_LOGS_PROCESSOR = 'OTEL_PHP_LOGS_PROCESSOR';
     public const OTEL_PHP_DETECTORS = 'OTEL_PHP_DETECTORS';
     public const OTEL_PHP_AUTOLOAD_ENABLED = 'OTEL_PHP_AUTOLOAD_ENABLED';
+    public const OTEL_PHP_INTERNAL_METRICS_ENABLED = 'OTEL_PHP_INTERNAL_METRICS_ENABLED'; //whether the SDK should emit its own metrics
     public const OTEL_PHP_DISABLED_INSTRUMENTATIONS = 'OTEL_PHP_DISABLED_INSTRUMENTATIONS';
 }

src/SDK/SdkAutoloader.php

@@ -40,16 +40,17 @@ class SdkAutoloader
                 //@see https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/sdk-environment-variables.md#general-sdk-configuration
                 return $configurator->withPropagator($propagator);
             }
+            $emitMetrics = Configuration::getBoolean(Variables::OTEL_PHP_INTERNAL_METRICS_ENABLED);
 
             $exporter = (new ExporterFactory())->create();
             $meterProvider = (new MeterProviderFactory())->create();
-            $spanProcessor = (new SpanProcessorFactory())->create($exporter, $meterProvider);
+            $spanProcessor = (new SpanProcessorFactory())->create($exporter, $emitMetrics ? $meterProvider : null);
             $tracerProvider = (new TracerProviderBuilder())
                 ->addSpanProcessor($spanProcessor)
                 ->setSampler((new SamplerFactory())->create())
                 ->build();
 
-            $loggerProvider = (new LoggerProviderFactory())->create($meterProvider);
+            $loggerProvider = (new LoggerProviderFactory())->create($emitMetrics ? $meterProvider : null);
 
             ShutdownHandler::register([$tracerProvider, 'shutdown']);
             ShutdownHandler::register([$meterProvider, 'shutdown']);

tests/Unit/Context/ScopeTest.php

@@ -116,7 +116,7 @@ class ScopeTest extends TestCase
         $scope['key'] = 'value';
         $scope = $storage->scope();
         $this->assertNotNull($scope);
-        $this->assertArrayHasKey('key', $scope); /** @phpstan-ignore-line */
+        $this->assertArrayHasKey('key', $scope);
         $this->assertSame('value', $scope['key']);
 
         unset($scope['key']);