in-process propagation resolves opentracing/specification#23

opentracing-api/src/main/java/io/opentracing/Span.java

@@ -1,5 +1,5 @@
 /**
- * Copyright 2016 The OpenTracing Authors
+ * Copyright 2016-2017 The OpenTracing Authors
  *
  * 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
@@ -22,6 +22,9 @@
  * <p>Spans are created by the {@link Tracer#buildSpan} interface.
  */
 public interface Span extends Closeable {
+
+    SpanManager.Visibility visibility();
+
     /**
      * Retrieve the associated SpanContext.
      *
@@ -42,6 +45,8 @@ public interface Span extends Closeable {
     void finish();
 
     /**
+     * Deactivates spans from spanManager.
+     *
      * Sets an explicit end timestamp and records the span.
      *
      * <p>With the exception of calls to Span.context(), this should be the last call made to the span instance, and to

opentracing-api/src/main/java/io/opentracing/SpanManager.java

@@ -0,0 +1,70 @@
+/**
+ * Copyright 2016-2017 The OpenTracing Authors
+ *
+ * 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 io.opentracing;
+
+/**
+ * @author Pavol Loffay
+ */
+public interface SpanManager {
+
+    /**
+     * @param span span to bundle into visibility, there is always only one visibility per span
+     * @return visibility
+     */
+    Visibility bundle(Span span);
+
+    /**
+     * @return not finished active span or null
+     */
+    VisibilityContext active();
+
+    interface Visibility {
+        /**
+         * @return visibility context which is used to activate/deactivate span
+         */
+        VisibilityContext capture();
+
+        /**
+         * @return associated span or null if visibility is marked as finished.
+         */
+        Span span();
+        /**
+         * @return always spanContext
+         */
+        SpanContext context();
+
+        /**
+         * Mark associated span as finished.
+         *
+         * Should be called by {@link Span#finish()} or directly if one does not want to expose span.
+         * This method should be idempotent.
+         *
+         * review note: reverse operation should not be allowed.
+         */
+        void hideSpan();
+    }
+
+    interface VisibilityContext {
+        /**
+         * on/activate - {@link SpanManager#active()} will return this object.
+         */
+        VisibilityContext on();
+        /**
+         * off/deactivate - {@link SpanManager#active()} will not return this object.
+         */
+        VisibilityContext off();
+
+        Visibility visibility();
+    }
+}

opentracing-api/src/main/java/io/opentracing/ThreadLocalSpanManager.java

@@ -0,0 +1,95 @@
+/**
+ * Copyright 2016-2017 The OpenTracing Authors
+ *
+ * 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 io.opentracing;
+
+import java.util.concurrent.atomic.AtomicBoolean;
+
+/**
+ * @author Pavol Loffay
+ */
+public class ThreadLocalSpanManager implements SpanManager {
+
+    private final ThreadLocal<SimpleLinkedVisibilityContext> activeContext = new ThreadLocal<SimpleLinkedVisibilityContext>();
+
+    @Override
+    public Visibility bundle(Span span) {
+        return span.visibility() == null ? new SimpleVisibility(span) : span.visibility();
+    }
+
+    @Override
+    public SimpleLinkedVisibilityContext active() {
+        return activeContext.get();
+    }
+
+    class SimpleVisibility implements Visibility {
+        private final Span span;
+        private AtomicBoolean hideSpan = new AtomicBoolean(false);
+
+        public SimpleVisibility(Span span) {
+            this.span = span;
+        }
+
+        @Override
+        public Span span() {
+            return hideSpan.get() ? null : span;
+        }
+
+        @Override
+        public SpanContext context() {
+            return span.context();
+        }
+
+        @Override
+        public SimpleLinkedVisibilityContext capture() {
+            return new SimpleLinkedVisibilityContext(this);
+        }
+
+        @Override
+        public void hideSpan() {
+            hideSpan.set(true);
+        }
+    }
+
+    class SimpleLinkedVisibilityContext implements SpanManager.VisibilityContext {
+
+        private final SimpleVisibility visibility;
+        private SimpleLinkedVisibilityContext previous;
+
+        public SimpleLinkedVisibilityContext(SimpleVisibility visibility) {
+            this.visibility = visibility;
+        }
+
+        @Override
+        public SimpleLinkedVisibilityContext on() {
+            previous = activeContext.get();
+            activeContext.set(this);
+            return this;
+        }
+
+        @Override
+        public SimpleLinkedVisibilityContext off() {
+            if (this == activeContext.get()) {
+                activeContext.set(previous);
+            }
+            // else should not happen
+
+            return this;
+        }
+
+        @Override
+        public Visibility visibility() {
+            return visibility;
+        }
+    }
+}

opentracing-api/src/main/java/io/opentracing/Tracer.java

@@ -20,6 +20,9 @@
  */
 public interface Tracer {
 
+    // span could be directly returned
+    SpanManager spanManager();
+
     /**
      * Return a new SpanBuilder for a Span with the given `operationName`.
      *
@@ -113,6 +116,8 @@ interface SpanBuilder extends SpanContext {
          */
         SpanBuilder addReference(String referenceType, SpanContext referencedContext);
 
+        SpanBuilder asRoot();
+
         /** Same as {@link Span#setTag(String, String)}, but for the span being built. */
         SpanBuilder withTag(String key, String value);
 
@@ -127,6 +132,5 @@ interface SpanBuilder extends SpanContext {
 
         /** Returns the started Span. */
         Span start();
-
     }
 }

opentracing-mock/pom.xml

@@ -36,6 +36,26 @@
             <groupId>${project.groupId}</groupId>
             <artifactId>opentracing-api</artifactId>
         </dependency>
+
+        <!-- for MDC demo will go away -->
+        <dependency>
+            <groupId>org.slf4j</groupId>
+            <artifactId>slf4j-api</artifactId>
+            <version>1.7.23</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>log4j</groupId>
+            <artifactId>log4j</artifactId>
+            <version>1.2.17</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.slf4j</groupId>
+            <artifactId>slf4j-log4j12</artifactId>
+            <version>1.7.23</version>
+            <scope>test</scope>
+        </dependency>
     </dependencies>
 
 </project>

opentracing-mock/src/main/java/io/opentracing/mock/MockSpan.java

@@ -18,6 +18,7 @@
 
 import io.opentracing.Span;
 import io.opentracing.SpanContext;
+import io.opentracing.SpanManager;
 
 /**
  * MockSpans are created via MockTracer.buildSpan(...), but they are also returned via calls to
@@ -29,6 +30,8 @@ public final class MockSpan implements Span {
     // A simple-as-possible (consecutive for repeatability) id generator.
     private static AtomicLong nextId = new AtomicLong(0);
 
+    private final SpanManager.Visibility visibility;
+
     private final MockTracer mockTracer;
     private MockContext context;
     private final long parentId; // 0 if there's no parent.
@@ -93,6 +96,11 @@ public List<RuntimeException> generatedErrors() {
         return new ArrayList<>(errors);
     }
 
+    @Override
+    public SpanManager.Visibility visibility() {
+        return visibility;
+    }
+
     @Override
     public synchronized MockContext context() {
         return this.context;
@@ -107,6 +115,7 @@ public void finish() {
     public synchronized void finish(long finishMicros) {
         finishedCheck("Finishing already finished span");
         this.finishMicros = finishMicros;
+        visibility.hideSpan();
         this.mockTracer.appendFinishedSpan(this);
         this.finished = true;
     }
@@ -248,10 +257,17 @@ public long timestampMicros() {
         }
     }
 
-    MockSpan(MockTracer tracer, String operationName, long startMicros, Map<String, Object> initialTags, MockContext parent) {
+    MockSpan(MockTracer tracer, String operationName, long startMicros, Map<String, Object> initialTags, MockContext
+            parent, boolean activate) {
         this.mockTracer = tracer;
         this.operationName = operationName;
         this.startMicros = startMicros;
+
+        this.visibility = tracer.spanManager().bundle(this);
+        if (activate) {
+            this.visibility.capture().on();
+        }
+
         if (initialTags == null) {
             this.tags = new HashMap<>();
         } else {

opentracing-mock/src/main/java/io/opentracing/mock/MockTracer.java

@@ -23,6 +23,8 @@
 import io.opentracing.References;
 import io.opentracing.Span;
 import io.opentracing.SpanContext;
+import io.opentracing.SpanManager;
+import io.opentracing.ThreadLocalSpanManager;
 import io.opentracing.Tracer;
 import io.opentracing.propagation.Format;
 import io.opentracing.propagation.TextMap;
@@ -38,16 +40,22 @@
 public class MockTracer implements Tracer {
     private List<MockSpan> finishedSpans = new ArrayList<>();
     private final Propagator propagator;
+    private final SpanManager spanManager;
 
     public MockTracer() {
-        this(Propagator.PRINTER);
+        this(Propagator.PRINTER, new ThreadLocalSpanManager());
     }
 
     /**
      * Create a new MockTracer that passes through any calls to inject() and/or extract().
      */
     public MockTracer(Propagator propagator) {
+        this(propagator, new ThreadLocalSpanManager());
+    }
+
+    public MockTracer(Propagator propagator, SpanManager spanManager) {
         this.propagator = propagator;
+        this.spanManager = spanManager;
     }
 
     /**
@@ -144,9 +152,14 @@ public <C> MockSpan.MockContext extract(Format<C> format, C carrier) {
         };
     }
 
+    @Override
+    public SpanManager spanManager() {
+        return spanManager;
+    }
+
     @Override
     public SpanBuilder buildSpan(String operationName) {
-        return new SpanBuilder(operationName);
+        return new SpanBuilder(operationName, spanManager);
     }
 
     @Override
@@ -170,8 +183,14 @@ public final class SpanBuilder implements Tracer.SpanBuilder {
         private MockSpan.MockContext firstParent;
         private Map<String, Object> initialTags = new HashMap<>();
 
-        SpanBuilder(String operationName) {
+        SpanBuilder(String operationName, SpanManager spanManager) {
             this.operationName = operationName;
+
+            SpanManager.VisibilityContext inferredParent = spanManager.active();
+            if (inferredParent != null) {
+                addReference(inferredParent.visibility().span() == null ? References.FOLLOWS_FROM : References.CHILD_OF,
+                        inferredParent.visibility().span().context());
+            }
         }
         @Override
         public SpanBuilder asChildOf(SpanContext parent) {
@@ -192,6 +211,12 @@ public SpanBuilder addReference(String referenceType, SpanContext referencedCont
             return this;
         }
 
+        @Override
+        public Tracer.SpanBuilder asRoot() {
+            firstParent = null;
+            return this;
+        }
+
         @Override
         public SpanBuilder withTag(String key, String value) {
             this.initialTags.put(key, value);
@@ -221,7 +246,8 @@ public MockSpan start() {
             if (this.startMicros == 0) {
                 this.startMicros = MockSpan.nowMicros();
             }
-            return new MockSpan(MockTracer.this, this.operationName, this.startMicros, initialTags, this.firstParent);
+            return new MockSpan(MockTracer.this, this.operationName, this.startMicros, initialTags,
+                    this.firstParent, false);
         }
 
         @Override