TestGrokPatternAction is local-only

Misc tidy-up following elastic#104394:

- This action only runs on the coordinating node, no need to define wire
  serialization for its request/response types.

- No need to subclass `ActionType`, nor to define how to receive
  responses from remote clusters.

- Moves to executing an `AbstractRunnable` to be sure to handle all
  failures (including threadpool rejections) properly.

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/textstructure/action/TestGrokPatternAction.java

@@ -11,8 +11,8 @@
 import org.elasticsearch.action.ActionRequestValidationException;
 import org.elasticsearch.action.ActionResponse;
 import org.elasticsearch.action.ActionType;
+import org.elasticsearch.action.support.TransportAction;
 import org.elasticsearch.common.Strings;
-import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
 import org.elasticsearch.common.io.stream.Writeable;
 import org.elasticsearch.grok.GrokCaptureExtracter;
@@ -28,14 +28,11 @@
 import java.util.Map;
 import java.util.Objects;
 
-public class TestGrokPatternAction extends ActionType<TestGrokPatternAction.Response> {
+public class TestGrokPatternAction {
 
-    public static final TestGrokPatternAction INSTANCE = new TestGrokPatternAction();
-    public static final String NAME = "cluster:monitor/text_structure/test_grok_pattern";
-
-    private TestGrokPatternAction() {
-        super(NAME, Response::new);
-    }
+    public static final ActionType<TestGrokPatternAction.Response> INSTANCE = ActionType.localOnly(
+        "cluster:monitor/text_structure/test_grok_pattern"
+    );
 
     public static class Request extends ActionRequest {
 
@@ -87,23 +84,13 @@ private Request(String grokPattern, List<String> text, String ecsCompatibility)
             this.ecsCompatibility = ecsCompatibility;
         }
 
-        public Request(StreamInput in) throws IOException {
-            super(in);
-            grokPattern = in.readString();
-            text = in.readStringCollectionAsList();
-            ecsCompatibility = in.readOptionalString();
-        }
-
         public static Request parseRequest(String ecsCompatibility, XContentParser parser) throws IOException {
             return PARSER.parse(parser, null).ecsCompatibility(ecsCompatibility).build();
         }
 
         @Override
         public void writeTo(StreamOutput out) throws IOException {
-            super.writeTo(out);
-            out.writeString(grokPattern);
-            out.writeStringCollection(text);
-            out.writeOptionalString(ecsCompatibility);
+            TransportAction.localOnly();
         }
 
         public String getGrokPattern() {
@@ -150,11 +137,6 @@ public Response(List<Map<String, Object>> ranges) {
             this.ranges = ranges;
         }
 
-        public Response(StreamInput in) throws IOException {
-            super(in);
-            ranges = in.readCollectionAsList(StreamInput::readGenericMap);
-        }
-
         @Override
         public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
             builder.startObject();
@@ -193,7 +175,7 @@ public XContentBuilder toXContent(XContentBuilder builder, Params params) throws
 
         @Override
         public void writeTo(StreamOutput out) throws IOException {
-            out.writeGenericList(ranges, StreamOutput::writeGenericMap);
+            TransportAction.localOnly();
         }
     }
 }

x-pack/plugin/text-structure/src/main/java/org/elasticsearch/xpack/textstructure/transport/TransportTestGrokPatternAction.java

@@ -10,15 +10,16 @@
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 import org.elasticsearch.action.ActionListener;
+import org.elasticsearch.action.ActionRunnable;
 import org.elasticsearch.action.support.ActionFilters;
-import org.elasticsearch.action.support.HandledTransportAction;
+import org.elasticsearch.action.support.TransportAction;
 import org.elasticsearch.common.inject.Inject;
-import org.elasticsearch.common.util.concurrent.EsExecutors;
 import org.elasticsearch.grok.Grok;
 import org.elasticsearch.grok.GrokBuiltinPatterns;
 import org.elasticsearch.tasks.Task;
 import org.elasticsearch.threadpool.ThreadPool;
 import org.elasticsearch.transport.TransportService;
+import org.elasticsearch.transport.Transports;
 import org.elasticsearch.xpack.core.textstructure.action.TestGrokPatternAction;
 
 import java.util.ArrayList;
@@ -27,38 +28,26 @@
 
 import static org.elasticsearch.grok.GrokBuiltinPatterns.ECS_COMPATIBILITY_V1;
 
-public class TransportTestGrokPatternAction extends HandledTransportAction<TestGrokPatternAction.Request, TestGrokPatternAction.Response> {
+public class TransportTestGrokPatternAction extends TransportAction<TestGrokPatternAction.Request, TestGrokPatternAction.Response> {
 
     private static final Logger logger = LogManager.getLogger(TransportTestGrokPatternAction.class);
 
     private final ThreadPool threadPool;
 
     @Inject
     public TransportTestGrokPatternAction(TransportService transportService, ActionFilters actionFilters, ThreadPool threadPool) {
-        super(
-            TestGrokPatternAction.NAME,
-            transportService,
-            actionFilters,
-            TestGrokPatternAction.Request::new,
-            EsExecutors.DIRECT_EXECUTOR_SERVICE
-        );
+        super(TestGrokPatternAction.INSTANCE.name(), actionFilters, transportService.getTaskManager());
         this.threadPool = threadPool;
     }
 
     @Override
     protected void doExecute(Task task, TestGrokPatternAction.Request request, ActionListener<TestGrokPatternAction.Response> listener) {
-        // As matching a regular expression might take a while, we run
-        // in a different thread to avoid blocking the network thread.
-        threadPool.generic().execute(() -> {
-            try {
-                listener.onResponse(getResponse(request));
-            } catch (Exception e) {
-                listener.onFailure(e);
-            }
-        });
+        // As matching a regular expression might take a while, we run in a different thread to avoid blocking the network thread.
+        threadPool.generic().execute(ActionRunnable.supply(listener, () -> getResponse(request)));
     }
 
     private TestGrokPatternAction.Response getResponse(TestGrokPatternAction.Request request) {
+        assert Transports.assertNotTransportThread("matching regexes is too expensive for a network thread");
         boolean ecsCompatibility = ECS_COMPATIBILITY_V1.equals(request.getEcsCompatibility());
         Grok grok = new Grok(GrokBuiltinPatterns.get(ecsCompatibility), request.getGrokPattern(), logger::debug);
         List<Map<String, Object>> ranges = new ArrayList<>();