Add a Tracer.close() method (#78)

- shuts down the reporter and sampler used by the tracer

jaeger-core/src/main/java/com/uber/jaeger/Tracer.java

@@ -142,6 +142,14 @@ public <T> io.opentracing.SpanContext extract(Format<T> format, T carrier) {
     return extractor.extract(carrier);
   }
 
+  /**
+   * Shuts down the {@link Reporter} and {@link Sampler}
+   */
+  public void close(){
+    reporter.close();
+    sampler.close();
+  }
+
   private class SpanBuilder implements io.opentracing.Tracer.SpanBuilder {
 
     private String operationName = null;

jaeger-core/src/test/java/com/uber/jaeger/TracerTest.java

@@ -21,10 +21,17 @@
  */
 package com.uber.jaeger;
 
+import static org.junit.Assert.assertEquals;
+import static org.mockito.Matchers.any;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+
 import com.uber.jaeger.metrics.InMemoryStatsReporter;
 import com.uber.jaeger.propagation.Injector;
 import com.uber.jaeger.reporters.InMemoryReporter;
+import com.uber.jaeger.reporters.Reporter;
 import com.uber.jaeger.samplers.ConstSampler;
+import com.uber.jaeger.samplers.Sampler;
 import io.opentracing.propagation.Format;
 import io.opentracing.propagation.TextMap;
 import io.opentracing.propagation.TextMapExtractAdapter;
@@ -36,11 +43,6 @@
 import java.util.HashMap;
 import java.util.Map;
 
-import static org.junit.Assert.assertEquals;
-import static org.mockito.Matchers.any;
-import static org.mockito.Mockito.mock;
-import static org.mockito.Mockito.verify;
-
 public class TracerTest {
 
   Tracer tracer;
@@ -132,4 +134,14 @@ public void testServiceNameNotNull() {
   public void testServiceNameNotEmptyNull() {
     new Tracer.Builder("  ", new InMemoryReporter(), new ConstSampler(true));
   }
+
+  @Test
+  public void testClose(){
+    Reporter reporter = mock(Reporter.class);
+    Sampler sampler = mock(Sampler.class);
+    tracer = new Tracer.Builder("bonda", reporter, sampler).build();
+    tracer.close();
+    verify(reporter).close();
+    verify(sampler).close();
+  }
 }