From 407d74e89acdd4dff5a887c1ae5793d63e9e7a2e Mon Sep 17 00:00:00 2001
From: Ivan Topolnjak <ivantopo@gmail.com>
Date: Mon, 14 Aug 2017 23:08:14 +0200
Subject: expose the identity provider through the Tracer

---
 .../src/main/scala/kamon/trace/SpanCodec.scala     | 99 ++++++++++++++++++++++
 1 file changed, 99 insertions(+)
 create mode 100644 kamon-core/src/main/scala/kamon/trace/SpanCodec.scala

(limited to 'kamon-core/src/main/scala/kamon/trace/SpanCodec.scala')

diff --git a/kamon-core/src/main/scala/kamon/trace/SpanCodec.scala b/kamon-core/src/main/scala/kamon/trace/SpanCodec.scala
new file mode 100644
index 00000000..e04ceb03
--- /dev/null
+++ b/kamon-core/src/main/scala/kamon/trace/SpanCodec.scala
@@ -0,0 +1,99 @@
+/* =========================================================================================
+ * Copyright © 2013-2017 the kamon project <http://kamon.io/>
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file
+ * except in compliance with the License. You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the
+ * License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
+ * either express or implied. See the License for the specific language governing permissions
+ * and limitations under the License.
+ * =========================================================================================
+ */
+
+package kamon.trace
+
+import java.net.{URLDecoder, URLEncoder}
+
+import kamon.Kamon
+import kamon.context.{Codec, Context, TextMap}
+import kamon.trace.SpanContext.SamplingDecision
+
+
+object SpanCodec {
+
+  class B3 extends Codec.ForEntry[TextMap] {
+    import B3.Headers
+
+    override def encode(context: Context): TextMap = {
+      val span = context.get(Span.ContextKey)
+      val carrier = TextMap.Default()
+
+      if(span.nonEmpty()) {
+        val spanContext = span.context
+        carrier.put(Headers.TraceIdentifier, urlEncode(spanContext.traceID.string))
+        carrier.put(Headers.SpanIdentifier, urlEncode(spanContext.spanID.string))
+        carrier.put(Headers.ParentSpanIdentifier, urlEncode(spanContext.parentID.string))
+
+        encodeSamplingDecision(spanContext.samplingDecision).foreach { samplingDecision =>
+          carrier.put(Headers.Sampled, samplingDecision)
+        }
+      }
+
+      carrier
+    }
+
+    override def decode(carrier: TextMap, context: Context): Context = {
+      val identityProvider = Kamon.tracer.identityProvider
+      val traceID = carrier.get(Headers.TraceIdentifier)
+        .map(id => identityProvider.traceIdGenerator().from(urlDecode(id)))
+        .getOrElse(IdentityProvider.NoIdentifier)
+
+      val spanID = carrier.get(Headers.SpanIdentifier)
+        .map(id => identityProvider.spanIdGenerator().from(urlDecode(id)))
+        .getOrElse(IdentityProvider.NoIdentifier)
+
+      if(traceID != IdentityProvider.NoIdentifier && spanID != IdentityProvider.NoIdentifier) {
+        val parentID = carrier.get(Headers.ParentSpanIdentifier)
+          .map(id => identityProvider.spanIdGenerator().from(urlDecode(id)))
+          .getOrElse(IdentityProvider.NoIdentifier)
+
+        val flags = carrier.get(Headers.Flags)
+
+        val samplingDecision = flags.orElse(carrier.get(Headers.Sampled)) match {
+          case Some(sampled) if sampled == "1" => SamplingDecision.Sample
+          case Some(sampled) if sampled == "0" => SamplingDecision.DoNotSample
+          case _ => SamplingDecision.Unknown
+        }
+
+        context.withKey(Span.ContextKey, Span.Remote(SpanContext(traceID, spanID, parentID, samplingDecision)))
+
+      } else context
+    }
+
+    private def encodeSamplingDecision(samplingDecision: SamplingDecision): Option[String] = samplingDecision match {
+      case SamplingDecision.Sample      => Some("1")
+      case SamplingDecision.DoNotSample => Some("0")
+      case SamplingDecision.Unknown     => None
+    }
+
+    private def urlEncode(s: String): String = URLEncoder.encode(s, "UTF-8")
+    private def urlDecode(s: String): String = URLDecoder.decode(s, "UTF-8")
+  }
+
+  object B3 {
+
+    def apply(): B3 =
+      new B3()
+
+    object Headers {
+      val TraceIdentifier = "X-B3-TraceId"
+      val ParentSpanIdentifier = "X-B3-ParentSpanId"
+      val SpanIdentifier = "X-B3-SpanId"
+      val Sampled = "X-B3-Sampled"
+      val Flags = "X-B3-Flags"
+    }
+  }
+}
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