Merge pull request #199 from wu-sheng/feature/198

 Support leaf span

apm-commons/apm-trace/src/main/java/org/skywalking/apm/trace/Span.java

@@ -83,7 +83,7 @@ public class Span {
      *                      means no parent span if this {@link TraceSegment}.
      * @param operationName {@link #operationName}
      */
-    private Span(int spanId, int parentSpanId, String operationName) {
+    protected Span(int spanId, int parentSpanId, String operationName) {
         this(spanId, parentSpanId, operationName, System.currentTimeMillis());
     }
 
@@ -97,7 +97,7 @@ public class Span {
      * @param operationName {@link #operationName}
      * @param startTime     given start timestamp.
      */
-    private Span(int spanId, int parentSpanId, String operationName, long startTime) {
+    protected Span(int spanId, int parentSpanId, String operationName, long startTime) {
         this();
         this.spanId = spanId;
         this.parentSpanId = parentSpanId;
@@ -200,17 +200,17 @@ public class Span {
      *
      * @return this Span instance, for chaining
      */
-    public final Span setTag(String key, String value) {
+    public Span setTag(String key, String value) {
         tagsWithStr.put(key, value);
         return this;
     }
 
-    public final Span setTag(String key, boolean value) {
+    public Span setTag(String key, boolean value) {
         tagsWithBool.put(key, value);
         return this;
     }
 
-    public final Span setTag(String key, Integer value) {
+    public Span setTag(String key, Integer value) {
         tagsWithInt.put(key, value);
         return this;
     }
@@ -359,6 +359,10 @@ public class Span {
         return Collections.unmodifiableList(logs);
     }
 
+    public boolean isLeaf() {
+        return false;
+    }
+
     @Override
     public String toString() {
         return "Span{" +

apm-sniffer/apm-agent-core/src/main/java/org/skywalking/apm/agent/core/context/ContextManager.java

@@ -55,11 +55,19 @@ public class ContextManager implements TracerContextListener, BootService {
     }
 
     public static Span createSpan(String operationName) {
-        return get().createSpan(operationName);
+        return get().createSpan(operationName, false);
     }
 
     public static Span createSpan(String operationName, long startTime) {
-        return get().createSpan(operationName, startTime);
+        return get().createSpan(operationName, startTime, false);
+    }
+
+    public static Span createLeafSpan(String operationName) {
+        return get().createSpan(operationName, true);
+    }
+
+    public static Span createLeafSpan(String operationName, long startTime) {
+        return get().createSpan(operationName, startTime, true);
     }
 
     public static Span activeSpan() {

apm-sniffer/apm-agent-core/src/main/java/org/skywalking/apm/agent/core/context/LeafSpan.java

+package org.skywalking.apm.agent.core.context;
+
+import org.skywalking.apm.trace.Span;
+import org.skywalking.apm.trace.TraceSegment;
+
+/**
+ * LeafSpan is a special type of {@link Span}
+ *
+ * In rpc-client tracing scenario, one component could constitute by many other rpc-client.
+ * e.g Feign constitutes by okhttp, apache httpclient, etc.
+ *
+ * By having leaf concept, no need so many spans for single rpc call.
+ *
+ * @author wusheng
+ */
+public class LeafSpan extends Span {
+    private int stackDepth = 0;
+
+    /**
+     * Create a new span, by given span id and give startTime but no parent span id,
+     * No parent span id means that, this Span is the first span of the {@link TraceSegment}
+     *
+     * @param spanId given by the creator, and must be unique id in the {@link TraceSegment}
+     * @param operationName {@link #operationName}
+     * @param startTime given start time of span
+     */
+    public LeafSpan(int spanId, String operationName, long startTime) {
+        super(spanId, -1, operationName, startTime);
+    }
+
+    /**
+     * Create a new span, by given span id, parent span, operationName and startTime.
+     * This span must belong a {@link TraceSegment}, also is a part of Distributed Trace.
+     *
+     * @param spanId given by the creator, and must be unique id in the {@link TraceSegment}
+     * @param parentSpan {@link Span}
+     * @param operationName {@link #operationName}
+     * @param startTime given start timestamp
+     */
+    public LeafSpan(int spanId, Span parentSpan, String operationName, long startTime) {
+        super(spanId, parentSpan.getSpanId(), operationName, startTime);
+    }
+
+    void push() {
+        stackDepth++;
+    }
+
+    void pop() {
+        stackDepth--;
+    }
+
+    boolean isFinished() {
+        return stackDepth == 0;
+    }
+
+    @Override
+    public boolean isLeaf() {
+        return true;
+    }
+
+    private boolean isInOwnerContext() {
+        return stackDepth == 1;
+    }
+
+    /**
+     * Sets the string name for the logical operation this span represents,
+     * only when this is in context of the leaf span owner.
+     *
+     * @return this Span instance, for chaining
+     */
+    @Override
+    public Span setOperationName(String operationName) {
+        if (isInOwnerContext()) {
+            super.setOperationName(operationName);
+        }
+        return this;
+    }
+
+    /**
+     * Set a key:value tag on the Span,
+     * only when this is in context of the leaf span owner.
+     *
+     * @return this Span instance, for chaining
+     */
+    @Override
+    public final Span setTag(String key, String value) {
+        if (isInOwnerContext()) {
+            super.setTag(key, value);
+        }
+        return this;
+    }
+
+    @Override
+    public final Span setTag(String key, boolean value) {
+        if (isInOwnerContext()) {
+            super.setTag(key, value);
+        }
+        return this;
+    }
+
+    @Override
+    public final Span setTag(String key, Integer value) {
+        if (isInOwnerContext()) {
+            super.setTag(key, value);
+        }
+        return this;
+    }
+}

apm-sniffer/apm-agent-core/src/main/java/org/skywalking/apm/agent/core/context/TracerContext.java

@@ -46,26 +46,40 @@ public final class TracerContext {
      * @param operationName {@link Span#operationName}
      * @return the new active span.
      */
-    public Span createSpan(String operationName) {
-        return this.createSpan(operationName, System.currentTimeMillis());
+    public Span createSpan(String operationName, boolean isLeaf) {
+        return this.createSpan(operationName, System.currentTimeMillis(), isLeaf);
     }
 
     /**
      * Create a new span, as an active span, by the given operationName and startTime;
      *
      * @param operationName {@link Span#operationName}
-     * @param startTime     {@link Span#startTime}
+     * @param startTime {@link Span#startTime}
+     * @param isLeaf is true, if the span is a leaf in trace tree.
      * @return
      */
-    public Span createSpan(String operationName, long startTime) {
+    public Span createSpan(String operationName, long startTime, boolean isLeaf) {
         Span parentSpan = peek();
         Span span;
         if (parentSpan == null) {
-            span = new Span(spanIdGenerator++, operationName, startTime);
+            if (isLeaf) {
+                span = new LeafSpan(spanIdGenerator++, operationName, startTime);
+            } else {
+                span = new Span(spanIdGenerator++, operationName, startTime);
+            }
+            push(span);
+        } else if (parentSpan.isLeaf()) {
+            span = parentSpan;
+            LeafSpan leafSpan = (LeafSpan)span;
+            leafSpan.push();
         } else {
-            span = new Span(spanIdGenerator++, parentSpan, operationName, startTime);
+            if (isLeaf) {
+                span = new LeafSpan(spanIdGenerator++, parentSpan, operationName, startTime);
+            } else {
+                span = new Span(spanIdGenerator++, parentSpan, operationName, startTime);
+            }
+            push(span);
         }
-        push(span);
         return span;
     }
 
@@ -98,6 +112,13 @@ public final class TracerContext {
 
     public void stopSpan(Span span, Long endTime) {
         Span lastSpan = peek();
+        if (lastSpan.isLeaf()) {
+            LeafSpan leafSpan = (LeafSpan)lastSpan;
+            leafSpan.pop();
+            if (!leafSpan.isFinished()) {
+                return;
+            }
+        }
         if (lastSpan == span) {
             pop().finish(segment, endTime);
         } else {
@@ -142,7 +163,7 @@ public final class TracerContext {
      * Ref this {@link ContextCarrier} to this {@link TraceSegment}
      *
      * @param carrier holds the snapshot, if get this {@link ContextCarrier} from remote, make sure {@link
-     *                ContextCarrier#deserialize(String)} called.
+     * ContextCarrier#deserialize(String)} called.
      */
     public void extract(ContextCarrier carrier) {
         if (carrier.isValid()) {

apm-sniffer/apm-agent-core/src/test/java/org/skywalking/apm/agent/core/context/LeafSpanTestCase.java

+package org.skywalking.apm.agent.core.context;
+
+import java.util.Map;
+import org.junit.Assert;
+import org.junit.Test;
+
+/**
+ * @author wusheng
+ */
+public class LeafSpanTestCase {
+    @Test
+    public void testLeaf() {
+        LeafSpan span = new LeafSpan(0, "serviceA", System.currentTimeMillis());
+        span.push();
+        span.setOperationName("serviceA2");
+        span.setTag("key", "value-text");
+        span.setTag("key2", false);
+        span.setTag("key3", 1);
+
+        //start 2nd span
+        span.push();
+
+        Assert.assertFalse(span.isFinished());
+        Assert.assertTrue(span.isLeaf());
+        span.setOperationName("service123");
+        span.setTag("key", "value-text2");
+        span.setTag("key2", true);
+        span.setTag("key3", 2);
+        Assert.assertEquals("serviceA2", span.getOperationName());
+        Assert.assertEquals("value-text", span.getStrTag("key"));
+        Assert.assertFalse(span.getBoolTag("key2"));
+        Assert.assertEquals(1, span.getIntTag("key3").intValue());
+
+        //end 2nd span
+        span.pop();
+
+        span.pop();
+        Assert.assertTrue(span.isFinished());
+    }
+}

apm-sniffer/apm-agent-core/src/test/java/org/skywalking/apm/agent/core/context/TracerContextTestCase.java

@@ -19,7 +19,7 @@ public class TracerContextTestCase {
     @Test
     public void testSpanLifeCycle() {
         TracerContext context = new TracerContext();
-        Span span = context.createSpan("/serviceA");
+        Span span = context.createSpan("/serviceA", false);
 
         Assert.assertEquals(span, context.activeSpan());
 
@@ -35,8 +35,8 @@ public class TracerContextTestCase {
     @Test
     public void testChildOfSpan() {
         TracerContext context = new TracerContext();
-        Span serviceSpan = context.createSpan("/serviceA");
-        Span dbSpan = context.createSpan("db/preparedStatement/execute");
+        Span serviceSpan = context.createSpan("/serviceA", false);
+        Span dbSpan = context.createSpan("db/preparedStatement/execute", false);
 
         Assert.assertEquals(dbSpan, context.activeSpan());
 
@@ -60,8 +60,8 @@ public class TracerContextTestCase {
     @Test
     public void testInject() {
         TracerContext context = new TracerContext();
-        Span serviceSpan = context.createSpan("/serviceA");
-        Span dbSpan = context.createSpan("db/preparedStatement/execute");
+        Span serviceSpan = context.createSpan("/serviceA", false);
+        Span dbSpan = context.createSpan("db/preparedStatement/execute", false);
         Tags.PEER_HOST.set(dbSpan, "127.0.0.1");
         Tags.PEER_PORT.set(dbSpan, 8080);
 
@@ -87,7 +87,7 @@ public class TracerContextTestCase {
 
         TracerContext context = new TracerContext();
         context.extract(carrier);
-        Span span = context.createSpan("/serviceC");
+        Span span = context.createSpan("/serviceC", false);
 
         TracerContext.ListenerManager.add(TestTracerContextListener.INSTANCE);
         final TraceSegment[] finishedSegmentCarrier = TestTracerContextListener.INSTANCE.finishedSegmentCarrier;