DataDog · SammyK · Oct 16, 2019 · Oct 15, 2019 · brettlangdon · Oct 15, 2019
@@ -44,6 +44,13 @@ abstract class SpanContext implements SpanContextInterface
      */
     public $propagatedPrioritySampling;
 
+    /**
+     * The origin of the distributed trace.
+     *
+     * @var string|null
+     */
+    public $origin;
+
     /**
      * @var SpanContextInterface
      */

@@ -7,6 +7,7 @@
 use DDTrace\GlobalTracer;
 use DDTrace\Log\LoggingTrait;
 use DDTrace\Sampling\PrioritySampling;
+use DDTrace\Tag;
 
 final class SpanEncoder
 {
@@ -43,6 +44,12 @@ public static function encode(DataSpan $span)
         }
 
         $tags = $span->tags;
+        if (
+            !empty($span->context->origin)
+            && $span->context->isHostRoot()
+        ) {
+            $tags[Tag::ORIGIN] = $span->context->origin;
+        }
         if (!empty($tags)) {
             $arraySpan['meta'] = $tags;
         }

@@ -14,6 +14,7 @@ interface Propagator
     const DEFAULT_TRACE_ID_HEADER = 'x-datadog-trace-id';
     const DEFAULT_PARENT_ID_HEADER = 'x-datadog-parent-id';
     const DEFAULT_SAMPLING_PRIORITY_HEADER = 'x-datadog-sampling-priority';
+    const DEFAULT_ORIGIN_HEADER = 'x-datadog-origin';
 
     /**
      * Inject takes the SpanContext and injects it into the carrier using

@@ -33,23 +33,11 @@ public function inject(SpanContext $spanContext, &$carrier)
     {
         foreach ($carrier as $index => $value) {
             if (
-                substr($value, 0, strlen(Propagator::DEFAULT_TRACE_ID_HEADER))
-                === Propagator::DEFAULT_TRACE_ID_HEADER
-            ) {
-                unset($carrier[$index]);
-            } elseif (
-                substr($value, 0, strlen(Propagator::DEFAULT_PARENT_ID_HEADER))
-                === Propagator::DEFAULT_PARENT_ID_HEADER
-            ) {
-                unset($carrier[$index]);
-            } elseif (
-                substr($value, 0, strlen(Propagator::DEFAULT_BAGGAGE_HEADER_PREFIX))
-                === Propagator::DEFAULT_BAGGAGE_HEADER_PREFIX
-            ) {
-                unset($carrier[$index]);
-            } elseif (
-                substr($value, 0, strlen(Propagator::DEFAULT_SAMPLING_PRIORITY_HEADER))
-                === Propagator::DEFAULT_SAMPLING_PRIORITY_HEADER
+                strpos($value, Propagator::DEFAULT_TRACE_ID_HEADER) === 0
+                || strpos($value, Propagator::DEFAULT_PARENT_ID_HEADER) === 0
+                || strpos($value, Propagator::DEFAULT_BAGGAGE_HEADER_PREFIX) === 0
+                || strpos($value, Propagator::DEFAULT_SAMPLING_PRIORITY_HEADER) === 0
+                || strpos($value, Propagator::DEFAULT_ORIGIN_HEADER) === 0
             ) {
                 unset($carrier[$index]);
             }
@@ -66,6 +54,9 @@ public function inject(SpanContext $spanContext, &$carrier)
         if (PrioritySampling::UNKNOWN !== $prioritySampling) {
             $carrier[] = Propagator::DEFAULT_SAMPLING_PRIORITY_HEADER . ': ' . $prioritySampling;
         }
+        if (!empty($spanContext->origin)) {
+            $carrier[] = Propagator::DEFAULT_ORIGIN_HEADER . ': ' . $spanContext->origin;
+        }
     }
 
     /**

@@ -39,6 +39,9 @@ public function inject(SpanContextInterface $spanContext, &$carrier)
         if (PrioritySampling::UNKNOWN !== $prioritySampling) {
             $carrier[Propagator::DEFAULT_SAMPLING_PRIORITY_HEADER] = $prioritySampling;
         }
+        if (!empty($spanContext->origin)) {
+            $carrier[Propagator::DEFAULT_ORIGIN_HEADER] = $spanContext->origin;
+        }
     }
 
     /**
@@ -67,6 +70,7 @@ public function extract($carrier)
 
         $spanContext = new SpanContext($traceId, $spanId, null, $baggageItems, true);
         $this->extractPrioritySampling($spanContext, $carrier);
+        $this->extractOrigin($spanContext, $carrier);
         return $spanContext;
     }
 
@@ -102,4 +106,20 @@ private function extractPrioritySampling(SpanContextInterface $spanContext, $car
             $spanContext->setPropagatedPrioritySampling(PrioritySampling::parse($rawValue));
         }
     }
+
+    /**
+     * Extract the origin from the carrier.
+     *
+     * @param SpanContextInterface $spanContext
+     * @param array $carrier
+     */
+    private function extractOrigin(SpanContextInterface $spanContext, $carrier)
+    {
+        if (
+            property_exists($spanContext, 'origin')
+            && isset($carrier[Propagator::DEFAULT_ORIGIN_HEADER])
+        ) {
+            $spanContext->origin = $this->extractStringOrFirstArrayElement($carrier[Propagator::DEFAULT_ORIGIN_HEADER]);
+        }
+    }
 }
@@ -40,6 +40,12 @@ public static function createAsChild(SpanContextInterface $parentContext)
         );
         $instance->parentContext = $parentContext;
         $instance->setPropagatedPrioritySampling($parentContext->getPropagatedPrioritySampling());
+        if (
+            property_exists($instance, 'origin')
+            && !empty($parentContext->origin)
+        ) {
+            $instance->origin = $parentContext->origin;
+        }
         return $instance;
     }
 

@@ -31,6 +31,7 @@ class Tag
     const BYTES_OUT = 'net.out.bytes';
     const ANALYTICS_KEY = '_dd1.sr.eausr';
     const HOSTNAME = '_dd.hostname';
+    const ORIGIN = '_dd.origin';
 
     // Elasticsearch
     const ELASTICSEARCH_BODY = 'elasticsearch.body';

@@ -250,6 +250,26 @@ public function testDistributedTracingIsPropagated()
         $this->assertSame('preserved_value', $found['headers']['Honored']);
     }
 
+    public function testOriginIsPropagatedAndSetsRootSpanTag()
+    {
+        $found = [];
+        $traces = $this->isolateTracer(function () use (&$found) {
+            /** @var Tracer $tracer */
+            $tracer = GlobalTracer::get();
+            $span = $tracer->startActiveSpan('custom')->getSpan();
+            $span->getContext()->origin = 'foo_origin';
+
+            $ch = curl_init(self::URL . '/headers');
+            curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
+            $found = json_decode(curl_exec($ch), 1);
+
+            $span->finish();
+        });
+
+        $this->assertSame('foo_origin', $found['headers']['X-Datadog-Origin']);
+        $this->assertSame('foo_origin', $traces[0][0]['meta']['_dd.origin']);
+    }
+
     public function testDistributedTracingIsPropagatedOnCopiedHandle()
     {
         $found = [];

@@ -87,4 +87,16 @@ public function testExistingDistributedTracingHeadersAreReplaced()
             'ot-baggage-' . self::BAGGAGE_ITEM_KEY . ': ' . self::BAGGAGE_ITEM_VALUE,
         ], array_values($carrier));
     }
+
+    public function testOriginIsPropagated()
+    {
+        $rootContext = SpanContext::createAsRoot();
+        $rootContext->origin = 'foo_origin';
+        $context = SpanContext::createAsChild($rootContext);
+
+        $carrier = [];
+        (new CurlHeadersMap($this->tracer))->inject($context, $carrier);
+
+        $this->assertContains('x-datadog-origin: foo_origin', $carrier);
+    }
 }
@@ -104,4 +104,30 @@ public function testExtractPrioritySamplingWhenNotProvided()
         $context = $textMapPropagator->extract($carrier);
         $this->assertSame(null, $context->getPropagatedPrioritySampling());
     }
+
+    public function testOriginIsPropagated()
+    {
+        $rootContext = SpanContext::createAsRoot();
+        $rootContext->origin = 'foo_origin';
+        $context = SpanContext::createAsChild($rootContext);
+
+        $carrier = [];
+        $textMapPropagator = new TextMap($this->tracer);
+        $textMapPropagator->inject($context, $carrier);
+
+        $this->assertSame('foo_origin', $carrier['x-datadog-origin']);
+    }
+
+    public function testOriginIsExtracted()
+    {
+        $carrier = [
+            'x-datadog-trace-id' => self::TRACE_ID,
+            'x-datadog-parent-id' => self::SPAN_ID,
+            'x-datadog-origin' => 'foo_origin',
+        ];
+        $textMapPropagator = new TextMap($this->tracer);
+        $context = $textMapPropagator->extract($carrier);
+
+        $this->assertSame('foo_origin', $context->origin);
+    }
 }