adding new files for x-pack/migrate plugin

x-pack/plugin/migrate/build.gradle

@@ -0,0 +1,24 @@
+apply plugin: 'elasticsearch.internal-es-plugin'
+apply plugin: 'elasticsearch.internal-cluster-test'
+
+esplugin {
+  name 'x-pack-migrate'
+  description 'Elasticsearch Expanded Pack Plugin - Index and Data Stream Migration'
+  classname 'org.elasticsearch.xpack.migrate.MigratePlugin'
+  extendedPlugins = ['x-pack-core']
+  hasNativeController false
+  requiresKeystore true
+}
+base {
+  archivesName = 'x-pack-migrate'
+}
+
+dependencies {
+  compileOnly project(path: xpackModule('core'))
+  testImplementation(testArtifact(project(xpackModule('core'))))
+  testImplementation project(xpackModule('ccr'))
+  testImplementation project(':modules:data-streams')
+  testImplementation project(path: ':modules:reindex')
+}
+
+addQaCheckDependencies(project)

x-pack/plugin/migrate/src/main/java/org/elasticsearch/xpack/migrate/MigratePlugin.java

@@ -0,0 +1,90 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0; you may not use this file except in compliance with the Elastic License
+ * 2.0.
+ */
+
+package org.elasticsearch.xpack.migrate;
+
+import org.elasticsearch.action.ActionRequest;
+import org.elasticsearch.action.ActionResponse;
+import org.elasticsearch.client.internal.Client;
+import org.elasticsearch.cluster.metadata.IndexNameExpressionResolver;
+import org.elasticsearch.cluster.service.ClusterService;
+import org.elasticsearch.common.io.stream.NamedWriteableRegistry;
+import org.elasticsearch.common.settings.SettingsModule;
+import org.elasticsearch.persistent.PersistentTaskParams;
+import org.elasticsearch.persistent.PersistentTaskState;
+import org.elasticsearch.persistent.PersistentTasksExecutor;
+import org.elasticsearch.plugins.ActionPlugin;
+import org.elasticsearch.plugins.PersistentTaskPlugin;
+import org.elasticsearch.plugins.Plugin;
+import org.elasticsearch.tasks.Task;
+import org.elasticsearch.threadpool.ThreadPool;
+import org.elasticsearch.xcontent.NamedXContentRegistry;
+import org.elasticsearch.xcontent.ParseField;
+import org.elasticsearch.xpack.migrate.action.ReindexDataStreamAction;
+import org.elasticsearch.xpack.migrate.action.ReindexDataStreamTransportAction;
+import org.elasticsearch.xpack.migrate.task.ReindexDataStreamPersistentTaskExecutor;
+import org.elasticsearch.xpack.migrate.task.ReindexDataStreamPersistentTaskState;
+import org.elasticsearch.xpack.migrate.task.ReindexDataStreamStatus;
+import org.elasticsearch.xpack.migrate.task.ReindexDataStreamTask;
+import org.elasticsearch.xpack.migrate.task.ReindexDataStreamTaskParams;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class MigratePlugin extends Plugin implements ActionPlugin, PersistentTaskPlugin {
+
+    @Override
+    public List<ActionHandler<? extends ActionRequest, ? extends ActionResponse>> getActions() {
+        List<ActionHandler<? extends ActionRequest, ? extends ActionResponse>> actions = new ArrayList<>();
+        actions.add(new ActionHandler<>(ReindexDataStreamAction.INSTANCE, ReindexDataStreamTransportAction.class));
+        return actions;
+    }
+
+    @Override
+    public List<NamedXContentRegistry.Entry> getNamedXContent() {
+        return List.of(
+            new NamedXContentRegistry.Entry(
+                PersistentTaskState.class,
+                new ParseField(ReindexDataStreamPersistentTaskState.NAME),
+                ReindexDataStreamPersistentTaskState::fromXContent
+            ),
+            new NamedXContentRegistry.Entry(
+                PersistentTaskParams.class,
+                new ParseField(ReindexDataStreamTaskParams.NAME),
+                ReindexDataStreamTaskParams::fromXContent
+            )
+        );
+    }
+
+    @Override
+    public List<NamedWriteableRegistry.Entry> getNamedWriteables() {
+        return List.of(
+            new NamedWriteableRegistry.Entry(
+                PersistentTaskState.class,
+                ReindexDataStreamPersistentTaskState.NAME,
+                ReindexDataStreamPersistentTaskState::new
+            ),
+            new NamedWriteableRegistry.Entry(
+                PersistentTaskParams.class,
+                ReindexDataStreamTaskParams.NAME,
+                ReindexDataStreamTaskParams::new
+            ),
+            new NamedWriteableRegistry.Entry(Task.Status.class, ReindexDataStreamStatus.NAME, ReindexDataStreamStatus::new)
+        );
+    }
+
+    @Override
+    public List<PersistentTasksExecutor<?>> getPersistentTasksExecutor(
+        ClusterService clusterService,
+        ThreadPool threadPool,
+        Client client,
+        SettingsModule settingsModule,
+        IndexNameExpressionResolver expressionResolver
+    ) {
+        return List.of(new ReindexDataStreamPersistentTaskExecutor(client, clusterService, ReindexDataStreamTask.TASK_NAME, threadPool));
+    }
+}