Force execution of finish shard bulk request (#51957)

Currently the shard bulk request can be rejected by the write threadpool
after a mapping update. This introduces a scenario where the mapping
listener thread will attempt to finish the request and fsync. This
thread can potentially be a transport thread. This commit fixes this
issue by forcing the finish action to happen on the write threadpool.

Fixes #51904.

server/src/main/java/org/elasticsearch/action/bulk/TransportShardBulkAction.java

@@ -170,16 +170,29 @@ protected void doRun() throws Exception {
 
             @Override
             public void onRejection(Exception e) {
-                // Fail all operations after a bulk rejection hit an action that waited for a mapping update and finish the request
-                while (context.hasMoreOperationsToExecute()) {
-                    context.setRequestToExecute(context.getCurrent());
-                    final DocWriteRequest<?> docWriteRequest = context.getRequestToExecute();
-                    onComplete(
-                        exceptionToResult(
-                            e, primary, docWriteRequest.opType() == DocWriteRequest.OpType.DELETE, docWriteRequest.version()),
-                        context, null);
-                }
-                finishRequest();
+                // We must finish the outstanding request. Finishing the outstanding request can include
+                //refreshing and fsyncing. Therefore, we must force execution on the WRITE thread.
+                executor.execute(new ActionRunnable<>(listener) {
+
+                    @Override
+                    protected void doRun() {
+                        // Fail all operations after a bulk rejection hit an action that waited for a mapping update and finish the request
+                        while (context.hasMoreOperationsToExecute()) {
+                            context.setRequestToExecute(context.getCurrent());
+                            final DocWriteRequest<?> docWriteRequest = context.getRequestToExecute();
+                            onComplete(
+                                exceptionToResult(
+                                    e, primary, docWriteRequest.opType() == DocWriteRequest.OpType.DELETE, docWriteRequest.version()),
+                                context, null);
+                        }
+                        finishRequest();
+                    }
+
+                    @Override
+                    public boolean isForceExecution() {
+                        return true;
+                    }
+                });
             }
 
             private void finishRequest() {

server/src/test/java/org/elasticsearch/action/bulk/TransportShardBulkActionTests.java

@@ -40,6 +40,7 @@
 import org.elasticsearch.cluster.metadata.IndexMetaData;
 import org.elasticsearch.common.lucene.uid.Versions;
 import org.elasticsearch.common.settings.Settings;
+import org.elasticsearch.common.util.concurrent.EsRejectedExecutionException;
 import org.elasticsearch.index.IndexSettings;
 import org.elasticsearch.index.VersionType;
 import org.elasticsearch.index.engine.Engine;
@@ -53,13 +54,18 @@
 import org.elasticsearch.index.shard.ShardId;
 import org.elasticsearch.index.translog.Translog;
 import org.elasticsearch.rest.RestStatus;
+import org.elasticsearch.threadpool.TestThreadPool;
+import org.elasticsearch.threadpool.ThreadPool;
 
 import java.io.IOException;
 import java.util.Collections;
+import java.util.concurrent.BrokenBarrierException;
 import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.CyclicBarrier;
 import java.util.concurrent.atomic.AtomicInteger;
 
 import static org.hamcrest.CoreMatchers.equalTo;
+import static org.hamcrest.CoreMatchers.instanceOf;
 import static org.hamcrest.CoreMatchers.not;
 import static org.hamcrest.CoreMatchers.notNullValue;
 import static org.hamcrest.Matchers.arrayWithSize;
@@ -809,6 +815,105 @@ public void testRetries() throws Exception {
         latch.await();
     }
 
+    public void testForceExecutionOnRejectionAfterMappingUpdate() throws Exception {
+        TestThreadPool rejectingThreadPool = new TestThreadPool(
+            "TransportShardBulkActionTests#testForceExecutionOnRejectionAfterMappingUpdate",
+            Settings.builder()
+                .put("thread_pool." + ThreadPool.Names.WRITE + ".size", 1)
+                .put("thread_pool." + ThreadPool.Names.WRITE + ".queue_size", 1)
+                .build());
+        CyclicBarrier cyclicBarrier = new CyclicBarrier(2);
+        rejectingThreadPool.executor(ThreadPool.Names.WRITE).execute(() -> {
+            try {
+                cyclicBarrier.await();
+                logger.info("blocking the write executor");
+                cyclicBarrier.await();
+                logger.info("unblocked the write executor");
+            } catch (Exception e) {
+                throw new RuntimeException(e);
+            }
+        });
+        try {
+            cyclicBarrier.await();
+            // Place a task in the queue to block next enqueue
+            rejectingThreadPool.executor(ThreadPool.Names.WRITE).execute(() -> {});
+
+            BulkItemRequest[] items = new BulkItemRequest[2];
+            DocWriteRequest<IndexRequest> writeRequest1 = new IndexRequest("index").id("id")
+                .source(Requests.INDEX_CONTENT_TYPE, "foo", 1);
+            DocWriteRequest<IndexRequest> writeRequest2 = new IndexRequest("index").id("id")
+                .source(Requests.INDEX_CONTENT_TYPE, "foo", "bar");
+            items[0] = new BulkItemRequest(0, writeRequest1);
+            items[1] = new BulkItemRequest(1, writeRequest2);
+            BulkShardRequest bulkShardRequest = new BulkShardRequest(shardId, RefreshPolicy.NONE, items);
+
+            Engine.IndexResult mappingUpdate =
+                new Engine.IndexResult(new Mapping(null, mock(RootObjectMapper.class), new MetadataFieldMapper[0], Collections.emptyMap()));
+            Translog.Location resultLocation1 = new Translog.Location(42, 36, 36);
+            Translog.Location resultLocation2 = new Translog.Location(42, 42, 42);
+            Engine.IndexResult success1 = new FakeIndexResult(1, 1, 10, true, resultLocation1);
+            Engine.IndexResult success2 = new FakeIndexResult(1, 1, 13, true, resultLocation2);
+
+            IndexShard shard = mock(IndexShard.class);
+            when(shard.shardId()).thenReturn(shardId);
+            when(shard.applyIndexOperationOnPrimary(anyLong(), any(), any(), anyLong(), anyLong(), anyLong(), anyBoolean()))
+                .thenReturn(success1, mappingUpdate, success2);
+            when(shard.getFailedIndexResult(any(EsRejectedExecutionException.class), anyLong())).thenCallRealMethod();
+            when(shard.mapperService()).thenReturn(mock(MapperService.class));
+
+            randomlySetIgnoredPrimaryResponse(items[0]);
+
+            AtomicInteger updateCalled = new AtomicInteger();
+
+            final CountDownLatch latch = new CountDownLatch(1);
+            TransportShardBulkAction.performOnPrimary(
+                bulkShardRequest, shard, null, rejectingThreadPool::absoluteTimeInMillis, (update, shardId, listener) -> {
+                    // There should indeed be a mapping update
+                    assertNotNull(update);
+                    updateCalled.incrementAndGet();
+                    listener.onResponse(null);
+                    try {
+                        // Release blocking task now that the continue write execution has been rejected and
+                        // the finishRequest execution has been force enqueued
+                        cyclicBarrier.await();
+                    } catch (InterruptedException | BrokenBarrierException e) {
+                        throw new IllegalStateException(e);
+                    }
+                }, listener -> listener.onResponse(null), new LatchedActionListener<>(
+                    ActionTestUtils.assertNoFailureListener(result ->
+                        // Assert that we still need to fsync the location that was successfully written
+                        assertThat(((WritePrimaryResult<BulkShardRequest, BulkShardResponse>) result).location,
+                            equalTo(resultLocation1))), latch),
+                rejectingThreadPool);
+            latch.await();
+
+            assertThat("mappings were \"updated\" once", updateCalled.get(), equalTo(1));
+
+            verify(shard, times(2)).applyIndexOperationOnPrimary(anyLong(), any(), any(), anyLong(), anyLong(), anyLong(), anyBoolean());
+
+            BulkItemResponse primaryResponse1 = bulkShardRequest.items()[0].getPrimaryResponse();
+            assertThat(primaryResponse1.getItemId(), equalTo(0));
+            assertThat(primaryResponse1.getId(), equalTo("id"));
+            assertThat(primaryResponse1.getOpType(), equalTo(DocWriteRequest.OpType.INDEX));
+            assertFalse(primaryResponse1.isFailed());
+            assertThat(primaryResponse1.getResponse().status(), equalTo(RestStatus.CREATED));
+            assertThat(primaryResponse1.getResponse().getSeqNo(), equalTo(10L));
+
+            BulkItemResponse primaryResponse2 = bulkShardRequest.items()[1].getPrimaryResponse();
+            assertThat(primaryResponse2.getItemId(), equalTo(1));
+            assertThat(primaryResponse2.getId(), equalTo("id"));
+            assertThat(primaryResponse2.getOpType(), equalTo(DocWriteRequest.OpType.INDEX));
+            assertTrue(primaryResponse2.isFailed());
+            assertNull(primaryResponse2.getResponse());
+            assertEquals(primaryResponse2.status(), RestStatus.TOO_MANY_REQUESTS);
+            assertThat(primaryResponse2.getFailure().getCause(), instanceOf(EsRejectedExecutionException.class));
+
+            closeShards(shard);
+        } finally {
+            rejectingThreadPool.shutdownNow();
+        }
+    }
+
     private void randomlySetIgnoredPrimaryResponse(BulkItemRequest primaryRequest) {
         if (randomBoolean()) {
             // add a response to the request and thereby check that it is ignored for the primary.