[8.19] Do not run ES|QL planning and scheduling on transport thread

docs/changelog/133313.yaml

@@ -0,0 +1,5 @@
+pr: 133313
+summary: Do not run on transport thread
+area: ES|QL
+type: enhancement
+issues: []

x-pack/plugin/esql/qa/testFixtures/src/main/java/org/elasticsearch/xpack/esql/EsqlTestUtils.java

@@ -24,6 +24,7 @@
 import org.elasticsearch.common.regex.Regex;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.util.BigArrays;
+import org.elasticsearch.common.util.concurrent.EsExecutors;
 import org.elasticsearch.common.xcontent.XContentHelper;
 import org.elasticsearch.compute.data.AggregateMetricDoubleBlockBuilder;
 import org.elasticsearch.compute.data.BlockFactory;
@@ -42,6 +43,7 @@
 import org.elasticsearch.search.SearchService;
 import org.elasticsearch.tasks.TaskCancelledException;
 import org.elasticsearch.test.ESTestCase;
+import org.elasticsearch.threadpool.ThreadPool;
 import org.elasticsearch.transport.RemoteTransportException;
 import org.elasticsearch.transport.TransportService;
 import org.elasticsearch.xcontent.XContentType;
@@ -160,7 +162,9 @@
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertNull;
 import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.anyString;
 import static org.mockito.Mockito.doAnswer;
+import static org.mockito.Mockito.doReturn;
 import static org.mockito.Mockito.mock;
 
 public final class EsqlTestUtils {
@@ -392,7 +396,7 @@ public static LogicalOptimizerContext unboundLogicalOptimizerContext() {
     public static final Verifier TEST_VERIFIER = new Verifier(new Metrics(new EsqlFunctionRegistry()), new XPackLicenseState(() -> 0L));
 
     public static final TransportActionServices MOCK_TRANSPORT_ACTION_SERVICES = new TransportActionServices(
-        mock(TransportService.class),
+        createMockTransportService(),
         mock(SearchService.class),
         null,
         mock(ClusterService.class),
@@ -401,6 +405,18 @@ public static LogicalOptimizerContext unboundLogicalOptimizerContext() {
         mockInferenceRunner()
     );
 
+    private static TransportService createMockTransportService() {
+        var service = mock(TransportService.class);
+        doReturn(createMockThreadPool()).when(service).getThreadPool();
+        return service;
+    }
+
+    private static ThreadPool createMockThreadPool() {
+        var threadPool = mock(ThreadPool.class);
+        doReturn(EsExecutors.DIRECT_EXECUTOR_SERVICE).when(threadPool).executor(anyString());
+        return threadPool;
+    }
+
     @SuppressWarnings("unchecked")
     private static InferenceRunner mockInferenceRunner() {
         InferenceRunner inferenceRunner = mock(InferenceRunner.class);

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/planner/premapper/PreMapper.java

@@ -8,20 +8,26 @@
 package org.elasticsearch.xpack.esql.planner.premapper;
 
 import org.elasticsearch.action.ActionListener;
+import org.elasticsearch.action.support.SubscribableListener;
+import org.elasticsearch.threadpool.ThreadPool;
 import org.elasticsearch.xpack.esql.expression.function.fulltext.QueryBuilderResolver;
 import org.elasticsearch.xpack.esql.plan.logical.LogicalPlan;
 import org.elasticsearch.xpack.esql.plugin.TransportActionServices;
 
+import java.util.concurrent.Executor;
+
 /**
  * The class is responsible for invoking any premapping steps that need to be applied to the logical plan,
  * before this is being mapped to a physical one.
  */
 public class PreMapper {
 
     private final TransportActionServices services;
+    private final Executor searchExecutor;
 
     public PreMapper(TransportActionServices services) {
         this.services = services;
+        this.searchExecutor = services.transportService().getThreadPool().executor(ThreadPool.Names.SEARCH);
     }
 
     /**
@@ -35,6 +41,9 @@ public void preMapper(LogicalPlan plan, ActionListener<LogicalPlan> listener) {
     }
 
     private void queryRewrite(LogicalPlan plan, ActionListener<LogicalPlan> listener) {
-        QueryBuilderResolver.resolveQueryBuilders(plan, services, listener);
+        // see https://github.com/elastic/elasticsearch/issues/133312
+        // ThreadedActionListener might be removed if above issue is resolved
+        SubscribableListener.<LogicalPlan>newForked(l -> QueryBuilderResolver.resolveQueryBuilders(plan, services, l))
+            .addListener(listener, searchExecutor, null);
     }
 }

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/plugin/ComputeService.java

@@ -145,7 +145,12 @@ public void execute(
         EsqlExecutionInfo execInfo,
         ActionListener<Result> listener
     ) {
-
+        assert ThreadPool.assertCurrentThreadPool(
+            EsqlPlugin.ESQL_WORKER_THREAD_POOL_NAME,
+            ThreadPool.Names.SYSTEM_READ,
+            ThreadPool.Names.SEARCH,
+            ThreadPool.Names.SEARCH_COORDINATION
+        );
         Tuple<PhysicalPlan, PhysicalPlan> coordinatorAndDataNodePlan = PlannerUtils.breakPlanBetweenCoordinatorAndDataNode(
             physicalPlan,
             configuration

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/plugin/DataNodeRequestSender.java

@@ -32,6 +32,7 @@
 import org.elasticsearch.search.internal.AliasFilter;
 import org.elasticsearch.tasks.CancellableTask;
 import org.elasticsearch.tasks.TaskCancelledException;
+import org.elasticsearch.threadpool.ThreadPool;
 import org.elasticsearch.transport.TransportException;
 import org.elasticsearch.transport.TransportRequestOptions;
 import org.elasticsearch.transport.TransportService;
@@ -123,6 +124,12 @@ abstract class DataNodeRequestSender {
     }
 
     final void startComputeOnDataNodes(Set<String> concreteIndices, Runnable runOnTaskFailure, ActionListener<ComputeResponse> listener) {
+        assert ThreadPool.assertCurrentThreadPool(
+            EsqlPlugin.ESQL_WORKER_THREAD_POOL_NAME,
+            ThreadPool.Names.SYSTEM_READ,
+            ThreadPool.Names.SEARCH,
+            ThreadPool.Names.SEARCH_COORDINATION
+        );
         final long startTimeInNanos = System.nanoTime();
         searchShards(concreteIndices, ActionListener.wrap(targetShards -> {
             try (

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/session/EsqlSession.java

@@ -32,6 +32,7 @@
 import org.elasticsearch.logging.LogManager;
 import org.elasticsearch.logging.Logger;
 import org.elasticsearch.search.SearchShardTarget;
+import org.elasticsearch.threadpool.ThreadPool;
 import org.elasticsearch.xpack.esql.VerificationException;
 import org.elasticsearch.xpack.esql.action.EsqlExecutionInfo;
 import org.elasticsearch.xpack.esql.action.EsqlQueryRequest;
@@ -186,6 +187,11 @@ public void execute(EsqlQueryRequest request, EsqlExecutionInfo executionInfo, P
             new EsqlCCSUtils.CssPartialErrorsActionListener(executionInfo, listener) {
                 @Override
                 public void onResponse(LogicalPlan analyzedPlan) {
+                    assert ThreadPool.assertCurrentThreadPool(
+                        ThreadPool.Names.SEARCH,
+                        ThreadPool.Names.SEARCH_COORDINATION,
+                        ThreadPool.Names.SYSTEM_READ
+                    );
                     preMapper.preMapper(
                         analyzedPlan,
                         listener.delegateFailureAndWrap(
@@ -208,6 +214,11 @@ public void executeOptimizedPlan(
         LogicalPlan optimizedPlan,
         ActionListener<Result> listener
     ) {
+        assert ThreadPool.assertCurrentThreadPool(
+            ThreadPool.Names.SEARCH,
+            ThreadPool.Names.SEARCH_COORDINATION,
+            ThreadPool.Names.SYSTEM_READ
+        );
         PhysicalPlan physicalPlan = logicalPlanToPhysicalPlan(optimizedPlan, request);
         // TODO: this could be snuck into the underlying listener
         EsqlCCSUtils.updateExecutionInfoAtEndOfPlanning(executionInfo);
@@ -360,6 +371,7 @@ public void analyzedPlan(
         QueryBuilder requestFilter,
         ActionListener<LogicalPlan> logicalPlanListener
     ) {
+        assert ThreadPool.assertCurrentThreadPool(ThreadPool.Names.SEARCH);
         if (parsed.analyzed()) {
             logicalPlanListener.onResponse(parsed);
             return;