From a179cc0e92dbbd5b6b48a5fc1925c5af28370d0a Mon Sep 17 00:00:00 2001
From: Ray <zzll0603@126.com>
Date: Wed, 21 Dec 2016 16:33:02 +0800
Subject: [PATCH] NoopTracer as default

---
 .../filter-opentracing/pom.xml                | 10 +++++++--
 .../filter/opentracing/OpenTracingFilter.java |  9 ++++++--
 .../filter/opentracing/TracerFactory.java     | 21 ++++++++++++-------
 3 files changed, 29 insertions(+), 11 deletions(-)

diff --git a/motan-extension/filter-extension/filter-opentracing/pom.xml b/motan-extension/filter-extension/filter-opentracing/pom.xml
index d27b7efeb..1b5b102df 100644
--- a/motan-extension/filter-extension/filter-opentracing/pom.xml
+++ b/motan-extension/filter-extension/filter-opentracing/pom.xml
@@ -21,6 +21,7 @@
     <url>https://github.com/weibocom/motan</url>
     <properties>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+        <opentracing.version>0.20.2</opentracing.version>
     </properties>
     <dependencies>
         <dependency>
@@ -31,14 +32,19 @@
         <dependency>
             <groupId>io.opentracing</groupId>
             <artifactId>opentracing-api</artifactId>
-            <version>0.20.2</version>
+            <version>${opentracing.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>io.opentracing</groupId>
+            <artifactId>opentracing-impl</artifactId>
+            <version>${opentracing.version}</version>
         </dependency>
 
         <!-- for test -->
         <dependency>
             <groupId>io.opentracing</groupId>
             <artifactId>opentracing-mock</artifactId>
-            <version>0.20.2</version>
+            <version>${opentracing.version}</version>
             <scope>test</scope>
         </dependency>
         <dependency>
diff --git a/motan-extension/filter-extension/filter-opentracing/src/main/java/com/weibo/api/motan/filter/opentracing/OpenTracingFilter.java b/motan-extension/filter-extension/filter-opentracing/src/main/java/com/weibo/api/motan/filter/opentracing/OpenTracingFilter.java
index 25a20e04f..b8c334479 100644
--- a/motan-extension/filter-extension/filter-opentracing/src/main/java/com/weibo/api/motan/filter/opentracing/OpenTracingFilter.java
+++ b/motan-extension/filter-extension/filter-opentracing/src/main/java/com/weibo/api/motan/filter/opentracing/OpenTracingFilter.java
@@ -13,6 +13,7 @@
  */
 package com.weibo.api.motan.filter.opentracing;
 
+import io.opentracing.NoopTracer;
 import io.opentracing.Span;
 import io.opentracing.SpanContext;
 import io.opentracing.Tracer;
@@ -49,8 +50,8 @@ public class OpenTracingFilter implements Filter {
 
     @Override
     public Response filter(Caller<?> caller, Request request) {
-        Tracer tracer = OpenTracingContext.getTracer();
-        if (tracer == null) {
+        Tracer tracer = getTracer();
+        if (tracer == null || tracer instanceof NoopTracer) {
             return caller.call(request);
         }
         if (caller instanceof Provider) { // server end
@@ -59,6 +60,10 @@ public Response filter(Caller<?> caller, Request request) {
             return processRefererTrace(tracer, caller, request);
         }
     }
+    
+    protected Tracer getTracer(){
+        return OpenTracingContext.getTracer();
+    }
 
     /**
      * process trace in client end
diff --git a/motan-extension/filter-extension/filter-opentracing/src/main/java/com/weibo/api/motan/filter/opentracing/TracerFactory.java b/motan-extension/filter-extension/filter-opentracing/src/main/java/com/weibo/api/motan/filter/opentracing/TracerFactory.java
index 5b7c47bdb..d94654b27 100644
--- a/motan-extension/filter-extension/filter-opentracing/src/main/java/com/weibo/api/motan/filter/opentracing/TracerFactory.java
+++ b/motan-extension/filter-extension/filter-opentracing/src/main/java/com/weibo/api/motan/filter/opentracing/TracerFactory.java
@@ -15,12 +15,13 @@
  */
 package com.weibo.api.motan.filter.opentracing;
 
+import io.opentracing.NoopTracerFactory;
+import io.opentracing.Tracer;
+
 import java.util.Iterator;
 import java.util.ServiceLoader;
 
 import com.weibo.api.motan.util.LoggerUtil;
-
-import io.opentracing.Tracer;
 /**
  * 
  * @Description TracerFactory
@@ -40,23 +41,29 @@ public interface TracerFactory {
     Tracer getTracer();
 
     class DefaultTracerFactory implements TracerFactory {
-        private static Tracer tracer = null;
+        private static Tracer tracer =  NoopTracerFactory.create();
 
         static {
             loadDefaultTracer();
         }
 
         /**
-         * load SPI Tracer and set default. the first tracer was used if more than one tracer was
-         * found.
+         * load SPI Tracer and set default only if one tracer is found.
          */
         private static void loadDefaultTracer() {
             try {
                 Iterator<Tracer> implementations = ServiceLoader.load(Tracer.class, Tracer.class.getClassLoader()).iterator();
                 if (implementations.hasNext()) {
-                    tracer = implementations.next();
-                    LoggerUtil.info("io.opentracing.Tracer load in DefaultTracerFactory, " + tracer.getClass().getSimpleName()
+                    Tracer firstTracer = implementations.next();
+                    if(!implementations.hasNext()){
+                        // only one tracer is found.
+                        tracer = firstTracer;
+                        LoggerUtil.info("io.opentracing.Tracer load in DefaultTracerFactory, " + tracer.getClass().getSimpleName()
                             + " is used as default tracer.");
+                    } else {
+                        LoggerUtil.info("io.opentracing.Tracer load in DefaultTracerFactory, NoopTracer is used as default tracer since more than one tracer is found.");
+                    }
+                    
                 }
             } catch (Exception e) {
                 LoggerUtil.warn("DefaultTracerFactory load Tracer fail.", e);