propagate mdc to child thread

Author: yifeih

launcher/pom.xml

@@ -54,7 +54,6 @@
     <dependency>
       <groupId>org.slf4j</groupId>
       <artifactId>slf4j-api</artifactId>
-      <scope>test</scope>
     </dependency>
     <dependency>
       <groupId>org.slf4j</groupId>

launcher/src/main/java/org/apache/spark/launcher/InProcessAppHandle.java

@@ -17,7 +17,10 @@
 
 package org.apache.spark.launcher;
 
+import org.slf4j.MDC;
+
 import java.lang.reflect.Method;
+import java.util.Map;
 import java.util.concurrent.atomic.AtomicLong;
 import java.util.logging.Level;
 import java.util.logging.Logger;
@@ -58,7 +61,9 @@ synchronized void start(String appName, Method main, String[] args) {
       appName = "..." + appName.substring(appName.length() - MAX_APP_NAME_LEN);
     }
 
+    Map<String, String> mdcContextMap = MDC.getCopyOfContextMap();
     app = new Thread(() -> {
+      MDC.setContextMap(mdcContextMap);
       try {
         main.invoke(null, (Object) args);
       } catch (Throwable t) {