Support copying logging context to background threads

The logging context (contains logging tags) is stored in ThreadLocal
variables. When we execute work in background threads we must propagate
the logging context from the current thread to the background threads.
Add a LoggingContextAwareThreadFactory that does this and use it in all
places where we create new threads.

Change-Id: I349f0a8b667266df1684ae5f5d8fb0bcae9aceaa
Signed-off-by: Edwin Kempin <ekempin@google.com>

java/com/google/gerrit/server/config/SysExecutorModule.java

@@ -19,6 +19,7 @@ import com.google.common.util.concurrent.MoreExecutors;
 import com.google.common.util.concurrent.ThreadFactoryBuilder;
 import com.google.gerrit.server.FanOutExecutor;
 import com.google.gerrit.server.git.WorkQueue;
+import com.google.gerrit.server.logging.LoggingContextAwareThreadFactory;
 import com.google.inject.AbstractModule;
 import com.google.inject.Provides;
 import com.google.inject.Singleton;
@@ -89,7 +90,11 @@ public class SysExecutorModule extends AbstractModule {
                 10,
                 TimeUnit.MINUTES,
                 new ArrayBlockingQueue<Runnable>(poolSize),
-                new ThreadFactoryBuilder().setNameFormat("ChangeUpdate-%d").setDaemon(true).build(),
+                new ThreadFactoryBuilder()
+                    .setThreadFactory(new LoggingContextAwareThreadFactory())
+                    .setNameFormat("ChangeUpdate-%d")
+                    .setDaemon(true)
+                    .build(),
                 new ThreadPoolExecutor.CallerRunsPolicy())));
   }
 }