[#125] Adds support for zipkin span.kind tag. (#138)

* [#125] Adds support for zipkin span.kind tag.

* [#125] Fixes compatibility with 7.2

* [#125] Fixes lint

Author: jcchavezs

src/Trace/Exporter/ZipkinExporter.php

@@ -17,6 +17,7 @@
 
 namespace OpenCensus\Trace\Exporter;
 
+use OpenCensus\Trace\MessageEvent;
 use OpenCensus\Trace\Tracer\TracerInterface;
 use OpenCensus\Trace\Span;
 
@@ -35,6 +36,9 @@
  */
 class ZipkinExporter implements ExporterInterface
 {
+    const KIND_SERVER = 'SERVER';
+    const KIND_CLIENT = 'CLIENT';
+
     /**
      * @var string
      */
@@ -153,7 +157,7 @@ public function convertSpans(TracerInterface $tracer, $headers = null)
         $isDebug = array_key_exists('HTTP_X_B3_FLAGS', $headers) && $headers['HTTP_X_B3_FLAGS'] == '1';
 
         // True if we are contributing to a span started by another tracer (ex on a different host).
-        $isShared = !empty($spans) && $spans[0]->parentSpanId() != null;
+        $isShared = !empty($spans) && $spans[0]->parentSpanId() !== null;
 
         $zipkinSpans = [];
         foreach ($spans as $span) {
@@ -180,12 +184,46 @@ public function convertSpans(TracerInterface $tracer, $headers = null)
                 'debug' => $isDebug,
                 'shared' => $isShared,
                 'localEndpoint' => $this->localEndpoint,
-                'tags' => $attributes
+                'tags' => $attributes,
             ];
 
+            if (null !== ($kind = $this->spanKind($span))) {
+                $zipkinSpan['kind'] = $kind;
+            }
+
             $zipkinSpans[] = $zipkinSpan;
         }
 
         return $zipkinSpans;
     }
+
+    private function spanKind(Span $span)
+    {
+        if (strpos($span->name(), 'Sent.') === 0) {
+            return self::KIND_CLIENT;
+        }
+
+        if (strpos($span->name(), 'Recv.') === 0) {
+            return self::KIND_SERVER;
+        }
+
+        if ($span->timeEvents()) {
+            foreach ($span->timeEvents() as $event) {
+                if (!($event instanceof MessageEvent)) {
+                    continue;
+                }
+
+                switch ($event->type()) {
+                    case MessageEvent::TYPE_SENT:
+                        return self::KIND_CLIENT;
+                        break;
+                    case MessageEvent::TYPE_RECEIVED:
+                        return self::KIND_SERVER;
+                        break;
+                }
+            }
+        }
+
+        return null;
+    }
 }

tests/unit/Trace/Exporter/ZipkinExporterTest.php

@@ -19,6 +19,7 @@
 
 use OpenCensus\Core\Context;
 use OpenCensus\Trace\Exporter\ZipkinExporter;
+use OpenCensus\Trace\MessageEvent;
 use OpenCensus\Trace\SpanContext;
 use OpenCensus\Trace\Span;
 use OpenCensus\Trace\Tracer\TracerInterface;
@@ -79,25 +80,32 @@ public function testFormatsTrace()
         }
     }
 
-    public function testSpanKind()
+    /**
+     * @dataProvider spanOptionsForKind
+     */
+    public function testSpanKind($spanOpts, $kind)
     {
         $tracer = new ContextTracer(new SpanContext('testtraceid'));
-        $tracer->inSpan(['name' => 'main'], function () use ($tracer) {
-            $tracer->inSpan(['name' => 'span1'], 'usleep', [1]);
-            $tracer->inSpan(['name' => 'span2'], 'usleep', [1]);
-            $tracer->inSpan(['name' => 'span3'], 'usleep', [1]);
-            $tracer->inSpan(['name' => 'span4'], 'usleep', [1]);
+        $tracer->inSpan(['name' => 'main'], function () use ($tracer, $spanOpts) {
+            $tracer->inSpan($spanOpts, 'usleep', [1]);
         });
 
         $reporter = new ZipkinExporter('myapp', 'localhost', 9411);
         $spans = $reporter->convertSpans($tracer);
 
-        $annotationValue = function ($annotation) {
-            return $annotation['value'];
-        };
-
-        $this->assertCount(5, $spans);
+        $this->assertCount(2, $spans);
         $this->assertFalse(array_key_exists('kind', $spans[0]));
+        $this->assertEquals($kind, $spans[1]['kind']);
+    }
+
+    public function spanOptionsForKind()
+    {
+        return [
+            [['name' => 'Recv.Span1'], 'SERVER'],
+            [['name' => 'Sent.Span2'], 'CLIENT'],
+            [['name' => 'span3', 'timeEvents' => [new MessageEvent(MessageEvent::TYPE_RECEIVED, '')]], 'SERVER'],
+            [['name' => 'span4', 'timeEvents' => [new MessageEvent(MessageEvent::TYPE_SENT, '')]], 'CLIENT'],
+        ];
     }
 
     public function testSpanDebug()