Provide custom BackgroundExecutorWrapper to pass thread locals

ebean-api/src/main/java/io/ebean/config/BackgroundExecutorWrapper.java

@@ -0,0 +1,23 @@
+package io.ebean.config;
+
+import java.util.concurrent.Callable;
+
+/**
+ * BackgroundExecutorWrapper that can be used to wrap tasks that are sent to background (i.e. an other thread).
+ * It should copy all neccessary thread-local variables. See {@link MdcBackgroundExecutorWrapper} for implementation details.
+ * 
+ * @author Roland Praml, FOCONIS AG
+ */
+public interface BackgroundExecutorWrapper {
+
+  /**
+   * Wrap the task with MDC context if defined.
+   */
+  <T> Callable<T> wrap(Callable<T> task);
+
+  /**
+   * Wrap the task with MDC context if defined.
+   */
+  Runnable wrap(Runnable task);
+
+}

ebean-api/src/main/java/io/ebean/config/DatabaseConfig.java

@@ -454,6 +454,7 @@ public class DatabaseConfig {
 
   private int backgroundExecutorSchedulePoolSize = 1;
   private int backgroundExecutorShutdownSecs = 30;
+  private BackgroundExecutorWrapper backgroundExecutorWrapper = new MdcBackgroundExecutorWrapper();
 
   // defaults for the L2 bean caching
 
@@ -1480,6 +1481,20 @@ public class DatabaseConfig {
     this.backgroundExecutorShutdownSecs = backgroundExecutorShutdownSecs;
   }
 
+  /**
+   * Return the background executor wrapper.
+   */
+  public BackgroundExecutorWrapper getBackgroundExecutorWrapper() {
+    return backgroundExecutorWrapper;
+  }
+
+  /**
+   * Sets the background executor wrapper. The wrapper is used when a task is sent to background and should copy the thread-locals.
+   */
+  public void setBackgroundExecutorWrapper(BackgroundExecutorWrapper backgroundExecutorWrapper) {
+    this.backgroundExecutorWrapper = backgroundExecutorWrapper;
+  }
+
   /**
    * Return the L2 cache default max size.
    */
@@ -2926,6 +2941,7 @@ public class DatabaseConfig {
 
     backgroundExecutorSchedulePoolSize = p.getInt("backgroundExecutorSchedulePoolSize", backgroundExecutorSchedulePoolSize);
     backgroundExecutorShutdownSecs = p.getInt("backgroundExecutorShutdownSecs", backgroundExecutorShutdownSecs);
+    backgroundExecutorWrapper = p.createInstance(BackgroundExecutorWrapper.class, "backgroundExecutorWrapper", backgroundExecutorWrapper);
     disableClasspathSearch = p.getBoolean("disableClasspathSearch", disableClasspathSearch);
     currentUserProvider = p.createInstance(CurrentUserProvider.class, "currentUserProvider", currentUserProvider);
     databasePlatform = p.createInstance(DatabasePlatform.class, "databasePlatform", databasePlatform);

ebean-api/src/main/java/io/ebean/config/MdcBackgroundExecutorWrapper.java

@@ -0,0 +1,50 @@
+package io.ebean.config;
+
+import java.util.Map;
+import java.util.concurrent.Callable;
+
+import org.slf4j.MDC;
+
+public class MdcBackgroundExecutorWrapper implements BackgroundExecutorWrapper {
+
+  
+  /**
+   * Wrap the task with MDC context if defined.
+   */
+  @Override
+  public <T> Callable<T> wrap(Callable<T> task) {
+    final Map<String, String> map = MDC.getCopyOfContextMap();
+    if (map == null) {
+      return task;
+    } else {
+      return () -> {
+        MDC.setContextMap(map);
+        try {
+          return task.call();
+        } finally {
+          MDC.clear();
+        }
+      };
+    }
+  }
+
+  /**
+   * Wrap the task with MDC context if defined.
+   */
+  @Override
+  public Runnable wrap(Runnable task) {
+    final Map<String, String> map = MDC.getCopyOfContextMap();
+    if (map == null) {
+      return task;
+    } else {
+      return () -> {
+        MDC.setContextMap(map);
+        try {
+          task.run();
+        } finally {
+          MDC.clear();
+        }
+      };
+    }
+  }
+}