Add non-dispatching listenable action future (#24412)

Currently the only implementation of `ListenableActionFuture` requires
dispatching listener execution to a thread pool. This commit renames
that variant to `DispatchingListenableActionFuture` and converts
`AbstractListenableActionFuture` to be a variant that does not require
dispatching. That class is now named `PlainListenableActionFuture`.

2 files changed, 9 insertions, 2 deletions

diff --git a/core/src/test/java/org/elasticsearch/action/support/ListenableActionFutureTests.java b/core/src/test/java/org/elasticsearch/action/support/ListenableActionFutureTests.java
index 8169a674be..0dbf460345 100644
--- a/core/src/test/java/org/elasticsearch/action/support/ListenableActionFutureTests.java
+++ b/core/src/test/java/org/elasticsearch/action/support/ListenableActionFutureTests.java
@@ -34,7 +34,12 @@ public class ListenableActionFutureTests extends ESTestCase {
     public void testListenerIsCallableFromNetworkThreads() throws Throwable {
         ThreadPool threadPool = new TestThreadPool("testListenerIsCallableFromNetworkThreads");
         try {
-            final PlainListenableActionFuture<Object> future = new PlainListenableActionFuture<>(threadPool);
+            final PlainListenableActionFuture<Object> future;
+            if (randomBoolean()) {
+                future = PlainListenableActionFuture.newDispatchingListenableFuture(threadPool);
+            } else {
+                future = PlainListenableActionFuture.newListenableFuture();
+            }
             final CountDownLatch listenerCalled = new CountDownLatch(1);
             final AtomicReference<Throwable> error = new AtomicReference<>();
             final Object response = new Object();
diff --git a/core/src/test/java/org/elasticsearch/action/support/TransportActionFilterChainTests.java b/core/src/test/java/org/elasticsearch/action/support/TransportActionFilterChainTests.java
index d5aab07f24..3eb1616348 100644
--- a/core/src/test/java/org/elasticsearch/action/support/TransportActionFilterChainTests.java
+++ b/core/src/test/java/org/elasticsearch/action/support/TransportActionFilterChainTests.java
@@ -91,7 +91,8 @@ public class TransportActionFilterChainTests extends ESTestCase {
             }
         }
 
-        PlainActionFuture<TestResponse> future = new PlainActionFuture<>();
+        PlainActionFuture<TestResponse> future = PlainActionFuture.newFuture();
+
         transportAction.execute(new TestRequest(), future);
         try {
             assertThat(future.get(), notNullValue());
@@ -104,6 +105,7 @@ public class TransportActionFilterChainTests extends ESTestCase {
         for (ActionFilter actionFilter : actionFilters.filters()) {
             testFiltersByLastExecution.add((RequestTestFilter) actionFilter);
         }
+
         testFiltersByLastExecution.sort(Comparator.comparingInt(o -> o.executionToken));
 
         ArrayList<RequestTestFilter> finalTestFilters = new ArrayList<>();