high level REST api: cancel task (#30745)

* Initial commit of rest high level exposure of cancel task

* fix javadocs

* address some code review comments

* update branch to use tasks namespace instead of cluster

* High-level client: list tasks failure to not lose nodeId

This commit reworks testing for `ListTasksResponse` so that random
fields insertion can be tested and xcontent equivalence can be checked
too. Proper exclusions need to be configured, and failures need to be
tested separately. This helped finding a little problem, whenever there
is a node failure returned, the nodeId was lost as it was never printed
out as part of the exception toXContent.

* added comment

* merge from master

* re-work CancelTasksResponseTests to separate XContent failure cases from non-failure cases

* remove duplication of logic in parser creation

* code review changes

* refactor TasksClient to support RequestOptions

* add tests for parent task id

* address final PR review comments, mostly formatting and such

client/rest-high-level/src/main/java/org/elasticsearch/client/RequestConverters.java

@@ -29,6 +29,7 @@ import org.apache.http.entity.ByteArrayEntity;
 import org.apache.http.entity.ContentType;
 import org.apache.lucene.util.BytesRef;
 import org.elasticsearch.action.DocWriteRequest;
+import org.elasticsearch.action.admin.cluster.node.tasks.cancel.CancelTasksRequest;
 import org.elasticsearch.action.admin.cluster.node.tasks.list.ListTasksRequest;
 import org.elasticsearch.action.admin.cluster.repositories.delete.DeleteRepositoryRequest;
 import org.elasticsearch.action.admin.cluster.repositories.get.GetRepositoriesRequest;
@@ -108,6 +109,17 @@ final class RequestConverters {
         // Contains only status utility methods
     }
 
+    static Request cancelTasks(CancelTasksRequest cancelTasksRequest) {
+        Request request = new Request(HttpPost.METHOD_NAME, "/_tasks/_cancel");
+        Params params = new Params(request);
+        params.withTimeout(cancelTasksRequest.getTimeout())
+            .withTaskId(cancelTasksRequest.getTaskId())
+            .withNodes(cancelTasksRequest.getNodes())
+            .withParentTaskId(cancelTasksRequest.getParentTaskId())
+            .withActions(cancelTasksRequest.getActions());
+        return request;
+    }
+
     static Request delete(DeleteRequest deleteRequest) {
         String endpoint = endpoint(deleteRequest.index(), deleteRequest.type(), deleteRequest.id());
         Request request = new Request(HttpDelete.METHOD_NAME, endpoint);
@@ -1070,6 +1082,13 @@ final class RequestConverters {
             return this;
         }
 
+        Params withTaskId(TaskId taskId) {
+            if (taskId != null && taskId.isSet()) {
+                return putParam("task_id", taskId.toString());
+            }
+            return this;
+        }
+
         Params withParentTaskId(TaskId parentTaskId) {
             if (parentTaskId != null && parentTaskId.isSet()) {
                 return putParam("parent_task_id", parentTaskId.toString());

client/rest-high-level/src/main/java/org/elasticsearch/client/TasksClient.java

@@ -20,6 +20,8 @@
 package org.elasticsearch.client;
 
 import org.elasticsearch.action.ActionListener;
+import org.elasticsearch.action.admin.cluster.node.tasks.cancel.CancelTasksRequest;
+import org.elasticsearch.action.admin.cluster.node.tasks.cancel.CancelTasksResponse;
 import org.elasticsearch.action.admin.cluster.node.tasks.list.ListTasksRequest;
 import org.elasticsearch.action.admin.cluster.node.tasks.list.ListTasksResponse;
 
@@ -65,4 +67,45 @@ public final class TasksClient {
         restHighLevelClient.performRequestAsyncAndParseEntity(request, RequestConverters::listTasks, options,
                 ListTasksResponse::fromXContent, listener, emptySet());
     }
+
+    /**
+     * Cancel one or more cluster tasks using the Task Management API.
+     *
+     * See
+     * <a href="https://www.elastic.co/guide/en/elasticsearch/reference/current/tasks.html"> Task Management API on elastic.co</a>
+     * @param cancelTasksRequest the request
+     * @param options the request options (e.g. headers), use {@link RequestOptions#DEFAULT} if nothing needs to be customized
+     * @return the response
+     * @throws IOException in case there is a problem sending the request or parsing back the response
+     *
+     */
+    public CancelTasksResponse cancel(CancelTasksRequest cancelTasksRequest, RequestOptions options ) throws IOException {
+        return restHighLevelClient.performRequestAndParseEntity(
+            cancelTasksRequest,
+            RequestConverters::cancelTasks,
+            options,
+            parser -> CancelTasksResponse.fromXContent(parser),
+            emptySet()
+        );
+    }
+
+    /**
+     * Asynchronously cancel one or more cluster tasks using the Task Management API.
+     *
+     * See
+     * <a href="https://www.elastic.co/guide/en/elasticsearch/reference/current/tasks.html"> Task Management API on elastic.co</a>
+     * @param cancelTasksRequest the request
+     * @param options the request options (e.g. headers), use {@link RequestOptions#DEFAULT} if nothing needs to be customized
+     * @param listener the listener to be notified upon request completion
+     */
+    public void cancelAsync(CancelTasksRequest cancelTasksRequest, RequestOptions options, ActionListener<CancelTasksResponse> listener) {
+        restHighLevelClient.performRequestAsyncAndParseEntity(
+            cancelTasksRequest,
+            RequestConverters::cancelTasks,
+            options,
+            parser -> CancelTasksResponse.fromXContent(parser),
+            listener,
+            emptySet()
+        );
+    }
 }

client/rest-high-level/src/test/java/org/elasticsearch/client/RequestConvertersTests.java

@@ -29,6 +29,8 @@ import org.apache.http.entity.ByteArrayEntity;
 import org.apache.http.util.EntityUtils;
 import org.elasticsearch.action.ActionRequestValidationException;
 import org.elasticsearch.action.DocWriteRequest;
+import org.elasticsearch.action.admin.cluster.node.tasks.cancel.CancelTasksRequest;
+import org.elasticsearch.action.admin.cluster.node.tasks.cancel.CancelTasksResponse;
 import org.elasticsearch.action.admin.cluster.node.tasks.list.ListTasksRequest;
 import org.elasticsearch.action.admin.cluster.repositories.delete.DeleteRepositoryRequest;
 import org.elasticsearch.action.admin.cluster.repositories.get.GetRepositoriesRequest;
@@ -1587,6 +1589,23 @@ public class RequestConvertersTests extends ESTestCase {
         assertEquals(expectedParams, request.getParameters());
     }
 
+    public void testCancelTasks() {
+        CancelTasksRequest request = new CancelTasksRequest();
+        Map<String, String> expectedParams = new HashMap<>();
+        TaskId taskId = new TaskId(randomAlphaOfLength(5), randomNonNegativeLong());
+        TaskId parentTaskId = new TaskId(randomAlphaOfLength(5), randomNonNegativeLong());
+        request.setTaskId(taskId);
+        request.setParentTaskId(parentTaskId);
+        expectedParams.put("task_id", taskId.toString());
+        expectedParams.put("parent_task_id", parentTaskId.toString());
+        Request httpRequest = RequestConverters.cancelTasks(request);
+        assertThat(httpRequest, notNullValue());
+        assertThat(httpRequest.getMethod(), equalTo(HttpPost.METHOD_NAME));
+        assertThat(httpRequest.getEntity(), nullValue());
+        assertThat(httpRequest.getEndpoint(), equalTo("/_tasks/_cancel"));
+        assertThat(httpRequest.getParameters(), equalTo(expectedParams));
+    }
+
     public void testListTasks() {
         {
             ListTasksRequest request = new ListTasksRequest();

client/rest-high-level/src/test/java/org/elasticsearch/client/TasksIT.java

@@ -19,9 +19,12 @@
 
 package org.elasticsearch.client;
 
+import org.elasticsearch.action.admin.cluster.node.tasks.cancel.CancelTasksRequest;
+import org.elasticsearch.action.admin.cluster.node.tasks.cancel.CancelTasksResponse;
 import org.elasticsearch.action.admin.cluster.node.tasks.list.ListTasksRequest;
 import org.elasticsearch.action.admin.cluster.node.tasks.list.ListTasksResponse;
 import org.elasticsearch.action.admin.cluster.node.tasks.list.TaskGroup;
+import org.elasticsearch.tasks.TaskId;
 import org.elasticsearch.tasks.TaskInfo;
 
 import java.io.IOException;
@@ -58,4 +61,26 @@ public class TasksIT extends ESRestHighLevelClientTestCase {
         assertTrue("List tasks were not found", listTasksFound);
     }
 
+    public void testCancelTasks() throws IOException {
+        ListTasksRequest listRequest = new ListTasksRequest();
+        ListTasksResponse listResponse = execute(
+            listRequest,
+            highLevelClient().tasks()::list,
+            highLevelClient().tasks()::listAsync
+        );
+        // in this case, probably no task will actually be cancelled.
+        // this is ok, that case is covered in TasksIT.testTasksCancellation
+        TaskInfo firstTask = listResponse.getTasks().get(0);
+        String node = listResponse.getPerNodeTasks().keySet().iterator().next();
+
+        CancelTasksRequest cancelTasksRequest = new CancelTasksRequest();
+        cancelTasksRequest.setTaskId(new TaskId(node, firstTask.getId()));
+        cancelTasksRequest.setReason("testreason");
+        CancelTasksResponse response = execute(cancelTasksRequest,
+            highLevelClient().tasks()::cancel,
+            highLevelClient().tasks()::cancelAsync);
+        // Since the task may or may not have been cancelled, assert that we received a response only
+        // The actual testing of task cancellation is covered by TasksIT.testTasksCancellation
+        assertThat(response, notNullValue());
+    }
 }

client/rest-high-level/src/test/java/org/elasticsearch/client/documentation/ClusterClientDocumentationIT.java

@@ -178,4 +178,5 @@ public class ClusterClientDocumentationIT extends ESRestHighLevelClientTestCase
             assertTrue(latch.await(30L, TimeUnit.SECONDS));
         }
     }
+
 }

client/rest-high-level/src/test/java/org/elasticsearch/client/documentation/TasksClientDocumentationIT.java

@@ -23,6 +23,8 @@ import org.elasticsearch.ElasticsearchException;
 import org.elasticsearch.action.ActionListener;
 import org.elasticsearch.action.LatchedActionListener;
 import org.elasticsearch.action.TaskOperationFailure;
+import org.elasticsearch.action.admin.cluster.node.tasks.cancel.CancelTasksRequest;
+import org.elasticsearch.action.admin.cluster.node.tasks.cancel.CancelTasksResponse;
 import org.elasticsearch.action.admin.cluster.node.tasks.list.ListTasksRequest;
 import org.elasticsearch.action.admin.cluster.node.tasks.list.ListTasksResponse;
 import org.elasticsearch.action.admin.cluster.node.tasks.list.TaskGroup;
@@ -146,4 +148,74 @@ public class TasksClientDocumentationIT extends ESRestHighLevelClientTestCase {
             assertTrue(latch.await(30L, TimeUnit.SECONDS));
         }
     }
+
+    public void testCancelTasks() throws IOException {
+        RestHighLevelClient client = highLevelClient();
+        {
+            // tag::cancel-tasks-request
+            CancelTasksRequest request = new CancelTasksRequest();
+            // end::cancel-tasks-request
+
+            // tag::cancel-tasks-request-filter
+            request.setTaskId(new TaskId("nodeId1", 42)); //<1>
+            request.setActions("cluster:*"); // <2>
+            request.setNodes("nodeId1", "nodeId2"); // <3>
+            // end::cancel-tasks-request-filter
+
+        }
+
+        CancelTasksRequest request = new CancelTasksRequest();
+        request.setTaskId(TaskId.EMPTY_TASK_ID);
+
+        // tag::cancel-tasks-execute
+        CancelTasksResponse response = client.tasks().cancel(request, RequestOptions.DEFAULT);
+        // end::cancel-tasks-execute
+
+        assertThat(response, notNullValue());
+
+        // tag::cancel-tasks-response-tasks
+        List<TaskInfo> tasks = response.getTasks(); // <1>
+        // end::cancel-tasks-response-tasks
+
+
+        // tag::cancel-tasks-response-failures
+        List<ElasticsearchException> nodeFailures = response.getNodeFailures(); // <1>
+        List<TaskOperationFailure> taskFailures = response.getTaskFailures(); // <2>
+        // end::-tasks-response-failures
+
+        assertThat(response.getNodeFailures(), equalTo(emptyList()));
+        assertThat(response.getTaskFailures(), equalTo(emptyList()));
+    }
+
+    public void testAsyncCancelTasks() throws InterruptedException {
+
+        RestHighLevelClient client = highLevelClient();
+        {
+            CancelTasksRequest request = new CancelTasksRequest();
+
+            // tag::cancel-tasks-execute-listener
+            ActionListener<CancelTasksResponse> listener =
+                new ActionListener<CancelTasksResponse>() {
+                    @Override
+                    public void onResponse(CancelTasksResponse response) {
+                        // <1>
+                    }
+                    @Override
+                    public void onFailure(Exception e) {
+                        // <2>
+                    }
+                };
+            // end::cancel-tasks-execute-listener
+
+            // Replace the empty listener by a blocking listener in test
+            final CountDownLatch latch = new CountDownLatch(1);
+            listener = new LatchedActionListener<>(listener, latch);
+
+            // tag::cancel-tasks-execute-async
+            client.tasks().cancelAsync(request, RequestOptions.DEFAULT, listener); // <1>
+            // end::cancel-tasks-execute-async
+
+            assertTrue(latch.await(30L, TimeUnit.SECONDS));
+        }
+    }
 }

docs/java-rest/high-level/supported-apis.asciidoc

@@ -140,5 +140,7 @@ include::snapshot/verify_repository.asciidoc[]
 The Java High Level REST Client supports the following Tasks APIs:
 
 * <<java-rest-high-tasks-list>>
+* <<java-rest-high-cluster-cancel-tasks>>
 
 include::tasks/list_tasks.asciidoc[]
+include::tasks/cancel_tasks.asciidoc[]

docs/java-rest/high-level/tasks/cancel_tasks.asciidoc

@@ -0,0 +1,82 @@
+[[java-rest-high-cluster-cancel-tasks]]
+=== Cancel Tasks API
+
+The Cancel Tasks API allows cancellation of a currently running task.
+
+==== Cancel Tasks Request
+
+A `CancelTasksRequest`:
+
+["source","java",subs="attributes,callouts,macros"]
+--------------------------------------------------
+include-tagged::{doc-tests}/TasksClientDocumentationIT.java[cancel-tasks-request]
+--------------------------------------------------
+There are no required parameters. The task cancellation command supports the same
+task selection parameters as the list tasks command.
+
+==== Parameters
+
+["source","java",subs="attributes,callouts,macros"]
+--------------------------------------------------
+include-tagged::{doc-tests}/TasksClientDocumentationIT.java[list-tasks-request-filter]
+--------------------------------------------------
+<1> Cancel a task
+<2> Cancel only cluster-related tasks
+<3> Cancel all tasks running on nodes nodeId1 and nodeId2
+
+==== Synchronous Execution
+
+["source","java",subs="attributes,callouts,macros"]
+--------------------------------------------------
+include-tagged::{doc-tests}/TasksClientDocumentationIT.java[list-tasks-execute]
+--------------------------------------------------
+
+==== Asynchronous Execution
+
+The asynchronous execution requires `CancelTasksRequest` instance and an
+`ActionListener` instance to be passed to the asynchronous method:
+
+["source","java",subs="attributes,callouts,macros"]
+--------------------------------------------------
+include-tagged::{doc-tests}/TasksClientDocumentationIT.java[cancel-tasks-execute-async]
+--------------------------------------------------
+<1> The `CancelTasksRequest` to execute and the `ActionListener` to use
+when the execution completes
+
+The asynchronous method does not block and returns immediately. Once it is
+completed the `ActionListener` is called back using the `onResponse` method
+if the execution successfully completed or using the `onFailure` method if
+it failed.
+
+A typical listener for `CancelTasksResponse` looks like:
+
+["source","java",subs="attributes,callouts,macros"]
+--------------------------------------------------
+include-tagged::{doc-tests}/TasksClientDocumentationIT.java[cancel-tasks-execute-listener]
+--------------------------------------------------
+<1> Called when the execution is successfully completed. The response is
+provided as an argument
+<2> Called in case of a failure. The raised exception is provided as an argument
+
+==== Cancel Tasks Response
+
+["source","java",subs="attributes,callouts,macros"]
+--------------------------------------------------
+include-tagged::{doc-tests}/TasksClientDocumentationIT.java[list-tasks-response-tasks]
+--------------------------------------------------
+<1> List of cancelled tasks
+
+["source","java",subs="attributes,callouts,macros"]
+--------------------------------------------------
+include-tagged::{doc-tests}/TasksClientDocumentationIT.java[list-tasks-response-calc]
+--------------------------------------------------
+<1> List of cancelled tasks grouped by a node
+<2> List of cancelled tasks grouped by a parent task
+
+["source","java",subs="attributes,callouts,macros"]
+--------------------------------------------------
+include-tagged::{doc-tests}/TasksClientDocumentationIT.java[list-tasks-response-failures]
+--------------------------------------------------
+<1> List of node failures
+<2> List of task cancellation failures
+

server/src/main/java/org/elasticsearch/action/admin/cluster/node/tasks/cancel/CancelTasksResponse.java

@@ -19,23 +19,48 @@
 
 package org.elasticsearch.action.admin.cluster.node.tasks.cancel;
 
-import org.elasticsearch.action.FailedNodeException;
+import org.elasticsearch.ElasticsearchException;
 import org.elasticsearch.action.TaskOperationFailure;
 import org.elasticsearch.action.admin.cluster.node.tasks.list.ListTasksResponse;
+import org.elasticsearch.common.ParseField;
+import org.elasticsearch.common.Strings;
+import org.elasticsearch.common.xcontent.ConstructingObjectParser;
+import org.elasticsearch.common.xcontent.XContentBuilder;
+import org.elasticsearch.common.xcontent.XContentParser;
 import org.elasticsearch.tasks.TaskInfo;
 
+import java.io.IOException;
 import java.util.List;
 
+import static org.elasticsearch.common.xcontent.ConstructingObjectParser.optionalConstructorArg;
+
 /**
  * Returns the list of tasks that were cancelled
  */
 public class CancelTasksResponse extends ListTasksResponse {
 
+    private static final ConstructingObjectParser<CancelTasksResponse, Void> PARSER =
+        setupParser("cancel_tasks_response", CancelTasksResponse::new);
+
     public CancelTasksResponse() {
     }
 
-    public CancelTasksResponse(List<TaskInfo> tasks, List<TaskOperationFailure> taskFailures, List<? extends FailedNodeException>
+    public CancelTasksResponse(List<TaskInfo> tasks, List<TaskOperationFailure> taskFailures, List<? extends ElasticsearchException>
         nodeFailures) {
         super(tasks, taskFailures, nodeFailures);
     }
+
+    @Override
+    public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
+        return super.toXContent(builder, params);
+    }
+
+    public static CancelTasksResponse fromXContent(XContentParser parser) {
+        return PARSER.apply(parser, null);
+    }
+
+    @Override
+    public String toString() {
+        return Strings.toString(this, true, true);
+    }
 }

server/src/main/java/org/elasticsearch/action/admin/cluster/node/tasks/list/ListTasksResponse.java

@@ -26,6 +26,7 @@ import org.elasticsearch.cluster.node.DiscoveryNode;
 import org.elasticsearch.cluster.node.DiscoveryNodes;
 import org.elasticsearch.common.ParseField;
 import org.elasticsearch.common.Strings;
+import org.elasticsearch.common.TriFunction;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
 import org.elasticsearch.common.xcontent.ConstructingObjectParser;
@@ -70,8 +71,14 @@ public class ListTasksResponse extends BaseTasksResponse implements ToXContentOb
         this.tasks = tasks == null ? Collections.emptyList() : Collections.unmodifiableList(new ArrayList<>(tasks));
     }
 
-    private static final ConstructingObjectParser<ListTasksResponse, Void> PARSER =
+
-        new ConstructingObjectParser<>("list_tasks_response", true,
+    protected static <T> ConstructingObjectParser<T, Void> setupParser(String name,
+                                                                       TriFunction<
+                                                                           List<TaskInfo>,
+                                                                           List<TaskOperationFailure>,
+                                                                           List<ElasticsearchException>,
+                                                                           T> ctor) {
+        ConstructingObjectParser<T, Void> parser = new ConstructingObjectParser<>(name, true,
             constructingObjects -> {
                 int i = 0;
                 @SuppressWarnings("unchecked")
@@ -80,16 +87,18 @@ public class ListTasksResponse extends BaseTasksResponse implements ToXContentOb
                 List<TaskOperationFailure> tasksFailures = (List<TaskOperationFailure>) constructingObjects[i++];
                 @SuppressWarnings("unchecked")
                 List<ElasticsearchException> nodeFailures = (List<ElasticsearchException>) constructingObjects[i];
-                return new ListTasksResponse(tasks, tasksFailures, nodeFailures);
+                return ctor.apply(tasks,tasksFailures, nodeFailures);
             });
-
+        parser.declareObjectArray(optionalConstructorArg(), TaskInfo.PARSER, new ParseField(TASKS));
-    static {
+        parser.declareObjectArray(optionalConstructorArg(), (p, c) -> TaskOperationFailure.fromXContent(p), new ParseField(TASK_FAILURES));
-        PARSER.declareObjectArray(constructorArg(), TaskInfo.PARSER, new ParseField(TASKS));
+        parser.declareObjectArray(optionalConstructorArg(),
-        PARSER.declareObjectArray(optionalConstructorArg(), (p, c) -> TaskOperationFailure.fromXContent(p), new ParseField(TASK_FAILURES));
+            (p, c) -> ElasticsearchException.fromXContent(p), new ParseField(NODE_FAILURES));
-        PARSER.declareObjectArray(optionalConstructorArg(),
+        return parser;
-            (parser, c) -> ElasticsearchException.fromXContent(parser), new ParseField(NODE_FAILURES));
     }
 
+    private static final ConstructingObjectParser<ListTasksResponse, Void> PARSER =
+        setupParser("list_tasks_response", ListTasksResponse::new);
+
     @Override
     public void readFrom(StreamInput in) throws IOException {
         super.readFrom(in);

server/src/test/java/org/elasticsearch/tasks/CancelTasksResponseTests.java

@@ -0,0 +1,116 @@
+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.elasticsearch.tasks;
+
+import org.elasticsearch.action.FailedNodeException;
+import org.elasticsearch.action.TaskOperationFailure;
+import org.elasticsearch.action.admin.cluster.node.tasks.cancel.CancelTasksResponse;
+import org.elasticsearch.action.admin.cluster.node.tasks.list.ListTasksResponse;
+import org.elasticsearch.common.Strings;
+import org.elasticsearch.common.xcontent.XContentParser;
+import org.elasticsearch.test.AbstractXContentTestCase;
+
+import java.io.IOException;
+import java.net.ConnectException;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.function.Predicate;
+import java.util.function.Supplier;
+
+import static org.hamcrest.Matchers.equalTo;
+
+public class CancelTasksResponseTests extends AbstractXContentTestCase<CancelTasksResponse> {
+
+    @Override
+    protected CancelTasksResponse createTestInstance() {
+        List<TaskInfo> randomTasks = randomTasks();
+        return new CancelTasksResponse(randomTasks, Collections.emptyList(), Collections.emptyList());
+    }
+
+    private static List<TaskInfo> randomTasks() {
+        List<TaskInfo> randomTasks = new ArrayList<>();
+        for (int i = 0; i < randomInt(10); i++) {
+            randomTasks.add(TaskInfoTests.randomTaskInfo());
+        }
+        return randomTasks;
+    }
+
+    @Override
+    protected Predicate<String> getRandomFieldsExcludeFilter() {
+        //status and headers hold arbitrary content, we can't inject random fields in them
+        return field -> field.endsWith("status") || field.endsWith("headers");
+    }
+
+    @Override
+    protected void assertEqualInstances(CancelTasksResponse expectedInstance, CancelTasksResponse newInstance) {
+        assertNotSame(expectedInstance, newInstance);
+        assertThat(newInstance.getTasks(), equalTo(expectedInstance.getTasks()));
+        ListTasksResponseTests.assertOnNodeFailures(newInstance.getNodeFailures(), expectedInstance.getNodeFailures());
+        ListTasksResponseTests.assertOnTaskFailures(newInstance.getTaskFailures(), expectedInstance.getTaskFailures());
+    }
+
+    @Override
+    protected CancelTasksResponse doParseInstance(XContentParser parser) {
+        return CancelTasksResponse.fromXContent(parser);
+    }
+
+    @Override
+    protected boolean supportsUnknownFields() {
+        return true;
+    }
+
+    @Override
+    protected boolean assertToXContentEquivalence() {
+        return true;
+    }
+
+    /**
+     * Test parsing {@link ListTasksResponse} with inner failures as they don't support asserting on xcontent equivalence, given that
+     * exceptions are not parsed back as the same original class. We run the usual {@link AbstractXContentTestCase#testFromXContent()}
+     * without failures, and this other test with failures where we disable asserting on xcontent equivalence at the end.
+     */
+    public void testFromXContentWithFailures() throws IOException {
+        Supplier<CancelTasksResponse> instanceSupplier = CancelTasksResponseTests::createTestInstanceWithFailures;
+        //with random fields insertion in the inner exceptions, some random stuff may be parsed back as metadata,
+        //but that does not bother our assertions, as we only want to test that we don't break.
+        boolean supportsUnknownFields = true;
+        //exceptions are not of the same type whenever parsed back
+        boolean assertToXContentEquivalence = false;
+        AbstractXContentTestCase.testFromXContent(NUMBER_OF_TEST_RUNS, instanceSupplier, supportsUnknownFields, Strings.EMPTY_ARRAY,
+            getRandomFieldsExcludeFilter(), this::createParser, this::doParseInstance,
+            this::assertEqualInstances, assertToXContentEquivalence);
+    }
+
+    private static CancelTasksResponse createTestInstanceWithFailures() {
+        int numNodeFailures = randomIntBetween(0, 3);
+        List<FailedNodeException> nodeFailures = new ArrayList<>(numNodeFailures);
+        for (int i = 0; i < numNodeFailures; i++) {
+            nodeFailures.add(new FailedNodeException(randomAlphaOfLength(5), "error message", new ConnectException()));
+        }
+        int numTaskFailures = randomIntBetween(0, 3);
+        List<TaskOperationFailure> taskFailures = new ArrayList<>(numTaskFailures);
+        for (int i = 0; i < numTaskFailures; i++) {
+            taskFailures.add(new TaskOperationFailure(randomAlphaOfLength(5), randomLong(), new IllegalStateException()));
+        }
+        return new CancelTasksResponse(randomTasks(), taskFailures, nodeFailures);
+    }
+
+}

server/src/test/java/org/elasticsearch/tasks/ListTasksResponseTests.java

@@ -109,20 +109,30 @@ public class ListTasksResponseTests extends AbstractXContentTestCase<ListTasksRe
     protected void assertEqualInstances(ListTasksResponse expectedInstance, ListTasksResponse newInstance) {
         assertNotSame(expectedInstance, newInstance);
         assertThat(newInstance.getTasks(), equalTo(expectedInstance.getTasks()));
-        assertThat(newInstance.getNodeFailures().size(), equalTo(expectedInstance.getNodeFailures().size()));
+        assertOnNodeFailures(newInstance.getNodeFailures(), expectedInstance.getNodeFailures());
-        for (int i = 0; i < newInstance.getNodeFailures().size(); i++) {
+        assertOnTaskFailures(newInstance.getTaskFailures(), expectedInstance.getTaskFailures());
-            ElasticsearchException newException = newInstance.getNodeFailures().get(i);
+    }
-            ElasticsearchException expectedException = expectedInstance.getNodeFailures().get(i);
+
+    protected static void assertOnNodeFailures(List<ElasticsearchException> nodeFailures,
+                                               List<ElasticsearchException> expectedFailures) {
+        assertThat(nodeFailures.size(), equalTo(expectedFailures.size()));
+        for (int i = 0; i < nodeFailures.size(); i++) {
+            ElasticsearchException newException = nodeFailures.get(i);
+            ElasticsearchException expectedException = expectedFailures.get(i);
             assertThat(newException.getMetadata("es.node_id").get(0), equalTo(((FailedNodeException)expectedException).nodeId()));
             assertThat(newException.getMessage(), equalTo("Elasticsearch exception [type=failed_node_exception, reason=error message]"));
             assertThat(newException.getCause(), instanceOf(ElasticsearchException.class));
             ElasticsearchException cause = (ElasticsearchException) newException.getCause();
             assertThat(cause.getMessage(), equalTo("Elasticsearch exception [type=connect_exception, reason=null]"));
         }
-        assertThat(newInstance.getTaskFailures().size(), equalTo(expectedInstance.getTaskFailures().size()));
+    }
-        for (int i = 0; i < newInstance.getTaskFailures().size(); i++) {
+
-            TaskOperationFailure newFailure = newInstance.getTaskFailures().get(i);
+    protected static void assertOnTaskFailures(List<TaskOperationFailure> taskFailures,
-            TaskOperationFailure expectedFailure = expectedInstance.getTaskFailures().get(i);
+                                               List<TaskOperationFailure> expectedFailures) {
+        assertThat(taskFailures.size(), equalTo(expectedFailures.size()));
+        for (int i = 0; i < taskFailures.size(); i++) {
+            TaskOperationFailure newFailure = taskFailures.get(i);
+            TaskOperationFailure expectedFailure = expectedFailures.get(i);
             assertThat(newFailure.getNodeId(), equalTo(expectedFailure.getNodeId()));
             assertThat(newFailure.getTaskId(), equalTo(expectedFailure.getTaskId()));
             assertThat(newFailure.getStatus(), equalTo(expectedFailure.getStatus()));