Adding async examples

dd-trace-examples/async-tracing/async-tracing.gradle

@@ -5,4 +5,7 @@ description = 'async-tracing'
 dependencies {
   compile project(':dd-trace')
   compile group: 'io.opentracing.contrib', name: 'opentracing-spanmanager', version: '0.0.5'
+  compile group: 'ch.qos.logback', name: 'logback-classic', version: '1.2.3'
+  compile group:'io.reactivex.rxjava2', name:'rxjava', version:'2.1.1'
+
 }

dd-trace-examples/async-tracing/src/main/java/com/datadoghq/trace/AsyncExample.java

@@ -0,0 +1,69 @@
+package com.datadoghq.trace;
+
+import com.datadoghq.trace.sampling.AllSampler;
+import com.datadoghq.trace.writer.DDAgentWriter;
+import com.datadoghq.trace.writer.DDApi;
+import io.opentracing.ActiveSpan;
+import io.opentracing.Tracer;
+import io.opentracing.util.GlobalTracer;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+
+public class AsyncExample {
+
+  private static ExecutorService ex = Executors.newFixedThreadPool(1);
+
+  public static Integer bar() throws Exception {
+
+    try (ActiveSpan __ = GlobalTracer.get()
+      .buildSpan("bar")
+      .startActive()) {
+      System.out.println("bar");
+      Thread.sleep(1000);
+    }
+
+    return 42;
+  }
+
+  public static Future<Integer> foo() throws Exception {
+
+    try (ActiveSpan span = GlobalTracer.get()
+      .buildSpan("foo")
+      .startActive()) {
+
+      System.out.println("foo");
+      Thread.sleep(500);
+
+      final ActiveSpan.Continuation cont = span.capture();
+
+      Future<Integer> future = ex.submit(() -> {
+        try (ActiveSpan __ = cont.activate()) {
+
+          return bar();
+        }
+      });
+
+
+
+      return future;
+
+
+    }
+  }
+
+  public static void main(String[] args) throws Exception {
+
+    DDAgentWriter writer = new DDAgentWriter(new DDApi("localhost", 8126));
+    Tracer tracer = new DDTracer("dd-trace-test-app", writer, new AllSampler());
+//		Tracer tracer = new DDTracer(new LoggingWriter(), new AllSampler());
+    GlobalTracer.register(tracer);
+
+    System.out.printf("%d%n", foo().get());
+
+    writer.close();
+    ex.shutdownNow();
+
+  }
+
+}

dd-trace-examples/async-tracing/src/main/java/com/datadoghq/trace/AsyncExampleReactive.java

@@ -0,0 +1,54 @@
+package com.datadoghq.trace;
+
+import com.datadoghq.trace.sampling.AllSampler;
+import com.datadoghq.trace.writer.DDAgentWriter;
+import com.datadoghq.trace.writer.DDApi;
+import io.opentracing.ActiveSpan;
+import io.opentracing.Tracer;
+import io.opentracing.util.GlobalTracer;
+import io.reactivex.Observable;
+
+
+public class AsyncExampleReactive {
+
+
+  public static Integer bar() throws Exception {
+    try (ActiveSpan __ = GlobalTracer.get()
+      .buildSpan("bar")
+      .startActive()) {
+      System.out.println("bar");
+      Thread.sleep(1000);
+    }
+
+    return 42;
+  }
+
+  public static Observable<Integer> foo() throws Exception {
+    try (ActiveSpan span = GlobalTracer.get()
+      .buildSpan("foo")
+      .startActive()) {
+
+      System.out.println("foo");
+      Thread.sleep(500);
+
+      final ActiveSpan.Continuation cont = span.capture();
+      return Observable.fromCallable(() -> {
+        try (ActiveSpan __ = cont.activate()) {
+          return bar();
+        }
+      });
+    }
+  }
+
+  public static void main(String[] args) throws Exception {
+    DDAgentWriter writer = new DDAgentWriter(new DDApi("localhost", 8126));
+    Tracer tracer = new DDTracer("dd-trace-test-app", writer, new AllSampler());
+    GlobalTracer.register(tracer);
+
+    foo().subscribe(System.out::println);
+
+    writer.close();
+  }
+
+}
+

dd-trace-examples/async-tracing/src/main/resources/logback.xml

@@ -0,0 +1,16 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<configuration>
+
+    <appender name="console" class="ch.qos.logback.core.ConsoleAppender">
+        <layout class="ch.qos.logback.classic.PatternLayout">
+            <Pattern>
+                %d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n
+            </Pattern>
+        </layout>
+    </appender>
+
+    <root level="debug">
+        <appender-ref ref="console"/>
+    </root>
+
+</configuration>

dd-trace/src/main/java/com/datadoghq/trace/DDBaseSpan.java

@@ -304,6 +304,10 @@ public abstract class DDBaseSpan<S extends BaseSpan> implements BaseSpan<S> {
 
   @Override
   public String toString() {
-    return context.toString();
+    return new StringBuilder()
+      .append(context.toString())
+      .append(", duration_ns=")
+      .append(durationNano)
+      .toString();
   }
 }

dd-trace/src/main/java/com/datadoghq/trace/DDSpanContext.java

@@ -200,19 +200,20 @@ public class DDSpanContext implements io.opentracing.SpanContext {
 
   @Override
   public String toString() {
-    return "Span [ "
-        + traceId
-        + " ] [ "
-        + spanId
-        + " | "
-        + parentId
-        + " ] [ "
-        + getServiceName()
-        + " | "
-        + getOperationName()
-        + " | "
-        + getResourceName()
-        + " ]";
+    return new StringBuilder()
+      .append("Span [ t_id=")
+      .append(traceId)
+      .append(", s_id=")
+      .append(spanId)
+      .append(", p_id=")
+      .append(parentId)
+      .append("] trace=")
+      .append(getServiceName())
+      .append("/")
+      .append(getOperationName())
+      .append("/")
+      .append(getResourceName())
+      .toString();
   }
 
   public void setOperationName(String operationName) {