ListenableFuture should preserve ThreadContext (#34394)

ListenableFuture may run a listener on the same thread that called the
addListener method or it may execute on another thread after the future
has completed. Whenever the ListenableFuture stores the listener for
execution later, it should preserve the thread context which is what
this change does.

Author: jaymode

server/src/main/java/org/elasticsearch/common/util/concurrent/ListenableFuture.java

@@ -20,6 +20,7 @@
 package org.elasticsearch.common.util.concurrent;
 
 import org.elasticsearch.action.ActionListener;
+import org.elasticsearch.action.support.ContextPreservingActionListener;
 import org.elasticsearch.common.collect.Tuple;
 
 import java.util.ArrayList;
@@ -47,7 +48,7 @@ public final class ListenableFuture<V> extends BaseFuture<V> implements ActionLi
      * If the future has completed, the listener will be notified immediately without forking to
      * a different thread.
      */
-    public void addListener(ActionListener<V> listener, ExecutorService executor) {
+    public void addListener(ActionListener<V> listener, ExecutorService executor, ThreadContext threadContext) {
         if (done) {
             // run the callback directly, we don't hold the lock and don't need to fork!
             notifyListener(listener, EsExecutors.newDirectExecutorService());
@@ -59,7 +60,7 @@ public void addListener(ActionListener<V> listener, ExecutorService executor) {
                 if (done) {
                     run = true;
                 } else {
-                    listeners.add(new Tuple<>(listener, executor));
+                    listeners.add(new Tuple<>(ContextPreservingActionListener.wrapPreservingContext(listener, threadContext), executor));
                     run = false;
                 }
             }

server/src/test/java/org/elasticsearch/common/util/concurrent/ListenableFutureTests.java

@@ -19,6 +19,7 @@
 
 package org.elasticsearch.common.util.concurrent;
 
+import org.apache.logging.log4j.message.ParameterizedMessage;
 import org.elasticsearch.action.ActionListener;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.test.ESTestCase;
@@ -30,9 +31,12 @@
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.atomic.AtomicInteger;
 
+import static org.hamcrest.Matchers.is;
+
 public class ListenableFutureTests extends ESTestCase {
 
     private ExecutorService executorService;
+    private ThreadContext threadContext = new ThreadContext(Settings.EMPTY);
 
     @After
     public void stopExecutorService() throws InterruptedException {
@@ -46,7 +50,7 @@ public void testListenableFutureNotifiesListeners() {
         AtomicInteger notifications = new AtomicInteger(0);
         final int numberOfListeners = scaledRandomIntBetween(1, 12);
         for (int i = 0; i < numberOfListeners; i++) {
-            future.addListener(ActionListener.wrap(notifications::incrementAndGet), EsExecutors.newDirectExecutorService());
+            future.addListener(ActionListener.wrap(notifications::incrementAndGet), EsExecutors.newDirectExecutorService(), threadContext);
         }
 
         future.onResponse("");
@@ -63,7 +67,7 @@ public void testListenableFutureNotifiesListenersOnException() {
             future.addListener(ActionListener.wrap(s -> fail("this should never be called"), e -> {
                 assertEquals(exception, e);
                 notifications.incrementAndGet();
-            }), EsExecutors.newDirectExecutorService());
+            }), EsExecutors.newDirectExecutorService(), threadContext);
         }
 
         future.onFailure(exception);
@@ -76,7 +80,7 @@ public void testConcurrentListenerRegistrationAndCompletion() throws BrokenBarri
         final int completingThread = randomIntBetween(0, numberOfThreads - 1);
         final ListenableFuture<String> future = new ListenableFuture<>();
         executorService = EsExecutors.newFixed("testConcurrentListenerRegistrationAndCompletion", numberOfThreads, 1000,
-            EsExecutors.daemonThreadFactory("listener"), new ThreadContext(Settings.EMPTY));
+            EsExecutors.daemonThreadFactory("listener"), threadContext);
         final CyclicBarrier barrier = new CyclicBarrier(1 + numberOfThreads);
         final CountDownLatch listenersLatch = new CountDownLatch(numberOfThreads - 1);
         final AtomicInteger numResponses = new AtomicInteger(0);
@@ -85,20 +89,31 @@ public void testConcurrentListenerRegistrationAndCompletion() throws BrokenBarri
         for (int i = 0; i < numberOfThreads; i++) {
             final int threadNum = i;
             Thread thread = new Thread(() -> {
+                threadContext.putTransient("key", threadNum);
                 try {
                     barrier.await();
                     if (threadNum == completingThread) {
+                        // we need to do more than just call onResponse as this often results in synchronous
+                        // execution of the listeners instead of actually going async
+                        final int waitTime = randomIntBetween(0, 50);
+                        Thread.sleep(waitTime);
+                        logger.info("completing the future after sleeping {}ms", waitTime);
                         future.onResponse("");
+                        logger.info("future received response");
                     } else {
+                        logger.info("adding listener {}", threadNum);
                         future.addListener(ActionListener.wrap(s -> {
+                            logger.info("listener {} received value {}", threadNum, s);
                             assertEquals("", s);
+                            assertThat(threadContext.getTransient("key"), is(threadNum));
                             numResponses.incrementAndGet();
                             listenersLatch.countDown();
                         }, e -> {
-                            logger.error("caught unexpected exception", e);
+                            logger.error(new ParameterizedMessage("listener {} caught unexpected exception", threadNum), e);
                             numExceptions.incrementAndGet();
                             listenersLatch.countDown();
-                        }), executorService);
+                        }), executorService, threadContext);
+                        logger.info("listener {} added", threadNum);
                     }
                     barrier.await();
                 } catch (InterruptedException | BrokenBarrierException e) {

x-pack/plugin/security/src/main/java/org/elasticsearch/xpack/security/authc/support/CachingUsernamePasswordRealm.java

@@ -122,7 +122,7 @@ private void authenticateWithCache(UsernamePasswordToken token, ActionListener<A
                         listener);
                 }
             }, e -> handleFailure(future, createdAndStartedFuture.get(), token, e, listener)),
-                threadPool.executor(ThreadPool.Names.GENERIC));
+                threadPool.executor(ThreadPool.Names.GENERIC), threadPool.getThreadContext());
         } catch (ExecutionException e) {
             listener.onResponse(AuthenticationResult.unsuccessful("", e));
         }
@@ -220,7 +220,7 @@ public final void lookupUser(String username, ActionListener<User> listener) {
                     } else {
                         listener.onResponse(null);
                     }
-                }, listener::onFailure), threadPool.executor(ThreadPool.Names.GENERIC));
+                }, listener::onFailure), threadPool.executor(ThreadPool.Names.GENERIC), threadPool.getThreadContext());
             } catch (ExecutionException e) {
                 listener.onFailure(e);
             }

x-pack/plugin/security/src/test/java/org/elasticsearch/xpack/security/authc/support/CachingUsernamePasswordRealmTests.java

@@ -439,14 +439,17 @@ protected void doLookupUser(String username, ActionListener<User> listener) {
         List<Thread> threads = new ArrayList<>(numberOfThreads);
         for (int i = 0; i < numberOfThreads; i++) {
             final boolean invalidPassword = randomBoolean();
+            final int threadNum = i;
             threads.add(new Thread(() -> {
+                threadPool.getThreadContext().putTransient("key", threadNum);
                 try {
                     latch.countDown();
                     latch.await();
                     for (int i1 = 0; i1 < numberOfIterations; i1++) {
                         UsernamePasswordToken token = new UsernamePasswordToken(username, invalidPassword ? randomPassword : password);
 
                         realm.authenticate(token, ActionListener.wrap((result) -> {
+                            assertThat(threadPool.getThreadContext().getTransient("key"), is(threadNum));
                             if (invalidPassword && result.isAuthenticated()) {
                                 throw new RuntimeException("invalid password led to an authenticated user: " + result);
                             } else if (invalidPassword == false && result.isAuthenticated() == false) {
@@ -499,12 +502,15 @@ protected void doLookupUser(String username, ActionListener<User> listener) {
         final CountDownLatch latch = new CountDownLatch(1 + numberOfThreads);
         List<Thread> threads = new ArrayList<>(numberOfThreads);
         for (int i = 0; i < numberOfThreads; i++) {
+            final int threadNum = i;
             threads.add(new Thread(() -> {
                 try {
+                    threadPool.getThreadContext().putTransient("key", threadNum);
                     latch.countDown();
                     latch.await();
                     for (int i1 = 0; i1 < numberOfIterations; i1++) {
                         realm.lookupUser(username, ActionListener.wrap((user) -> {
+                            assertThat(threadPool.getThreadContext().getTransient("key"), is(threadNum));
                             if (user == null) {
                                 throw new RuntimeException("failed to lookup user");
                             }