Check sampling mechanism.

skywalking-sniffer/skywalking-api/src/main/java/com/a/eye/skywalking/api/sampling/SamplingService.java

@@ -40,6 +40,7 @@ public class SamplingService implements BootService {
         if (on) {
             if (rollingSeed % Config.Agent.SAMPLING_CYCLE != 0) {
                 segment.setSampled(false);
+                this.rollingSeed = 1;
             }
             rollingSeed++;
         }

skywalking-sniffer/skywalking-api/src/test/java/com/a/eye/skywalking/api/context/TracerContextTestCase.java

@@ -5,6 +5,7 @@ import com.a.eye.skywalking.trace.TraceId.DistributedTraceId;
 import com.a.eye.skywalking.trace.TraceId.PropagatedTraceId;
 import com.a.eye.skywalking.trace.TraceSegment;
 import com.a.eye.skywalking.trace.tag.Tags;
+import java.awt.SystemTray;
 import java.util.LinkedList;
 import java.util.List;
 import org.junit.After;

skywalking-sniffer/skywalking-api/src/test/java/com/a/eye/skywalking/api/sampling/SamplingServiceTest.java

@@ -26,6 +26,10 @@ public class SamplingServiceTest {
         segment = new TraceSegment();
         service.trySampling(segment);
         Assert.assertTrue(segment.isSampled());
+
+        segment = new TraceSegment();
+        service.trySampling(segment);
+        Assert.assertFalse(segment.isSampled());
     }
 
     @AfterClass