Add MDCScopeManager for correlating logs with trace context

jaeger-core/src/main/java/io/jaegertracing/internal/JaegerTracer.java

@@ -611,6 +611,11 @@ public Builder withScopeManager(ScopeManager scopeManager) {
       return this;
     }
 
+    public Builder withMDcScopeManager() {
+      this.scopeManager = new MDcScopeManager();
+      return this;
+    }
+
     public Builder withClock(Clock clock) {
       this.clock = clock;
       return this;

jaeger-core/src/main/java/io/jaegertracing/internal/MDcScope.java

@@ -0,0 +1,69 @@
+/*
+ * Copyright (c) 2018, The Jaeger 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.jaegertracing.internal;
+
+import io.opentracing.Scope;
+import io.opentracing.Span;
+import org.slf4j.MDC;
+
+public class MDcScope implements Scope {
+  private static final String TRACE_ID = "traceId";
+  private static final String SPAN_ID = "spanId";
+  private static final String SAMPLED = "sampled";
+
+  private final Scope wrapped;
+  private final String originalTraceId;
+  private final String originalSpanId;
+  private final String originalSampled;
+
+  /**
+   * mdcScope.
+   */
+  public MDcScope(Scope scope, Span span) {
+    this.wrapped = scope;
+    this.originalTraceId = MDC.get(TRACE_ID);
+    this.originalSpanId = MDC.get(SPAN_ID);
+    this.originalSampled = MDC.get(SAMPLED);
+
+    if (span.context() instanceof JaegerSpanContext) {
+      putContext((JaegerSpanContext) span.context());
+    }
+  }
+
+  @Override
+  public void close() {
+    wrapped.close();
+
+    MDC.remove(TRACE_ID);
+    MDC.remove(SPAN_ID);
+    MDC.remove(SAMPLED);
+
+    if (originalTraceId != null) {
+      MDC.put(TRACE_ID, originalTraceId);
+    }
+    if (originalSpanId != null) {
+      MDC.put(SPAN_ID, originalSpanId);
+    }
+    if (originalSampled != null) {
+      MDC.put(SAMPLED, originalSampled);
+    }
+  }
+
+  protected void putContext(JaegerSpanContext spanContext) {
+    MDC.put(TRACE_ID, spanContext.getTraceId());
+    MDC.put(SPAN_ID, String.format("%16x", spanContext.getSpanId()));
+    MDC.put(SAMPLED, Boolean.toString(spanContext.isSampled()));
+  }
+}

jaeger-core/src/main/java/io/jaegertracing/internal/MDcScopeManager.java

@@ -0,0 +1,34 @@
+/*
+ * Copyright (c) 2018, The Jaeger 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.jaegertracing.internal;
+
+import io.opentracing.Scope;
+import io.opentracing.ScopeManager;
+import io.opentracing.Span;
+import io.opentracing.util.ThreadLocalScopeManager;
+
+public class MDcScopeManager implements ScopeManager {
+  private final ScopeManager wrapped = new ThreadLocalScopeManager();
+
+  @Override
+  public Scope activate(Span span) {
+    return new MDcScope(wrapped.activate(span), span);
+  }
+
+  @Override
+  public Span activeSpan() {
+    return wrapped.activeSpan();
+  }
+}