Add root span/scope tracking

CHANGELOG.md

@@ -5,6 +5,7 @@ All notable changes to this project will be documented in this file - [read more
 
 ### Added
 - Request init hook configuration allowing running arbitrary code before actual request execution #175
+- `Tracer::startRootSpan()` to track the root `Scope` instance which can be accessed with `Tracer::getRootScope()` #241
 
 ### Changed
 

src/DDTrace/Contracts/Tracer.php

@@ -127,4 +127,19 @@ public function flush();
      * @return mixed
      */
     public function getPrioritySampling();
+
+    /**
+     * This behaves just like Tracer::startActiveSpan(), but it saves the Scope instance
+     * on the tracer to be accessed later by Tracer::getRootScope().
+     *
+     * @param string $operationName
+     * @param array $options
+     * @return Scope
+     */
+    public function startRootSpan($operationName, $options = []);
+
+    /**
+     * @return Scope|null
+     */
+    public function getRootScope();
 }

src/DDTrace/NoopTracer.php

@@ -46,7 +46,6 @@ public function startSpan($operationName, $options = [])
      */
     public function startActiveSpan($operationName, $finishSpanOnClose = true, $options = [])
     {
-
         return NoopScope::create();
     }
 
@@ -79,4 +78,20 @@ public function getPrioritySampling()
     {
         return null;
     }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function startRootSpan($operationName, $options = [])
+    {
+        return NoopScope::create();
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function getRootScope()
+    {
+        return NoopScope::create();
+    }
 }

src/DDTrace/Tracer.php

@@ -11,6 +11,7 @@
 use DDTrace\Transport\Http;
 use DDTrace\Transport\Noop as NoopTransport;
 use DDTrace\Exceptions\UnsupportedFormat;
+use DDTrace\Contracts\Scope as ScopeInterface;
 use DDTrace\Contracts\SpanContext as SpanContextInterface;
 use DDTrace\Contracts\Tracer as TracerInterface;
 
@@ -63,6 +64,11 @@ final class Tracer implements TracerInterface
      */
     private $scopeManager;
 
+    /**
+     * @var ScopeInterface|null
+     */
+    private $rootScope;
+
     /**
      * @var Configuration
      */
@@ -151,6 +157,22 @@ public function startSpan($operationName, $options = [])
         return $span;
     }
 
+    /**
+     * {@inheritdoc}
+     */
+    public function startRootSpan($operationName, $options = [])
+    {
+        return $this->rootScope = $this->startActiveSpan($operationName, $options);
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function getRootScope()
+    {
+        return $this->rootScope;
+    }
+
     /**
      * {@inheritdoc}
      */

tests/Unit/TracerTest.php

@@ -195,4 +195,17 @@ public function testUnfinishedSpansCanBeFinishedOnFlush()
         $this->assertSame('root', $sent[0][0]->getOperationName());
         $this->assertSame('child', $sent[0][1]->getOperationName());
     }
+
+    public function testSpanStartedAtRootCanBeAccessedLater()
+    {
+        $tracer = new Tracer(new NoopTransport());
+        $scope = $tracer->startRootSpan(self::OPERATION_NAME);
+        $this->assertSame($scope, $tracer->getRootScope());
+    }
+
+    public function testIfNoRootScopeExistsItWillBeNull()
+    {
+        $tracer = new Tracer(new NoopTransport());
+        $this->assertNull($tracer->getRootScope());
+    }
 }