Do not count shard changes tasks against REST tests (#33738)

When executing CCR REST tests it is going to be expected after global
checkpoint polling goes in that shard changes tasks can still be pending
at the end of the test. One way to deal with this is to set a low
timeout on these polls, but then that means we are not executing our
REST tests with our default production settings and instead would be
using an unrealistic low timeout. Alternatively, since we expect these
tasks to be there, we can not count them against the test. That is what
this commit does.

x-pack/plugin/ccr/qa/rest/src/test/java/org/elasticsearch/xpack/ccr/CcrRestIT.java

@@ -12,6 +12,7 @@
 import org.elasticsearch.common.util.concurrent.ThreadContext;
 import org.elasticsearch.test.rest.yaml.ClientYamlTestCandidate;
 import org.elasticsearch.test.rest.yaml.ESClientYamlSuiteTestCase;
+import org.elasticsearch.xpack.ccr.action.ShardChangesAction;
 import org.elasticsearch.xpack.test.rest.XPackRestTestHelper;
 import org.junit.After;
 
@@ -36,7 +37,7 @@ protected Settings restClientSettings() {
 
     @After
     public void cleanup() throws Exception {
-        XPackRestTestHelper.waitForPendingTasks(adminClient());
+        XPackRestTestHelper.waitForPendingTasks(adminClient(), taskName -> taskName.startsWith(ShardChangesAction.NAME));
     }
 
 }

x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/test/rest/XPackRestTestHelper.java

@@ -14,6 +14,7 @@
 import org.elasticsearch.client.Response;
 import org.elasticsearch.client.ResponseException;
 import org.elasticsearch.client.RestClient;
+import org.elasticsearch.common.CheckedRunnable;
 import org.elasticsearch.common.xcontent.XContentHelper;
 import org.elasticsearch.common.xcontent.json.JsonXContent;
 import org.elasticsearch.test.ESTestCase;
@@ -29,7 +30,9 @@
 import java.util.List;
 import java.util.Map;
 import java.util.concurrent.atomic.AtomicReference;
+import java.util.function.Predicate;
 
+import static org.elasticsearch.test.ESTestCase.assertBusy;
 import static org.junit.Assert.assertEquals;
 
 public final class XPackRestTestHelper {
@@ -84,34 +87,54 @@ public static void waitForMlTemplates(RestClient client) throws InterruptedExcep
     }
 
     /**
-     * Waits for pending tasks to complete
+     * Wait for outstanding tasks to complete. The specified admin client is used to check the outstanding tasks and this is done using
+     * {@link ESTestCase#assertBusy(CheckedRunnable)} to give a chance to any outstanding tasks to complete.
+     *
+     * @param adminClient the admin client
+     * @throws Exception if an exception is thrown while checking the outstanding tasks
      */
-    public static void waitForPendingTasks(RestClient adminClient) throws Exception {
-        ESTestCase.assertBusy(() -> {
+    public static void waitForPendingTasks(final RestClient adminClient) throws Exception {
+        waitForPendingTasks(adminClient, taskName -> false);
+    }
+
+    /**
+     * Wait for outstanding tasks to complete. The specified admin client is used to check the outstanding tasks and this is done using
+     * {@link ESTestCase#assertBusy(CheckedRunnable)} to give a chance to any outstanding tasks to complete. The specified filter is used
+     * to filter out outstanding tasks that are expected to be there.
+     *
+     * @param adminClient the admin client
+     * @param taskFilter  predicate used to filter tasks that are expected to be there
+     * @throws Exception if an exception is thrown while checking the outstanding tasks
+     */
+    public static void waitForPendingTasks(final RestClient adminClient, final Predicate<String> taskFilter) throws Exception {
+        assertBusy(() -> {
             try {
-                Request request = new Request("GET", "/_cat/tasks");
+                final Request request = new Request("GET", "/_cat/tasks");
                 request.addParameter("detailed", "true");
-                Response response = adminClient.performRequest(request);
-                // Check to see if there are tasks still active. We exclude the
-                // list tasks
-                // actions tasks form this otherwise we will always fail
+                final Response response = adminClient.performRequest(request);
+                /*
+                 * Check to see if there are outstanding tasks; we exclude the list task itself, and any expected outstanding tasks using
+                 * the specified task filter.
+                 */
                 if (response.getStatusLine().getStatusCode() == HttpStatus.SC_OK) {
                     try (BufferedReader responseReader = new BufferedReader(
                             new InputStreamReader(response.getEntity().getContent(), StandardCharsets.UTF_8))) {
                         int activeTasks = 0;
                         String line;
-                        StringBuilder tasksListString = new StringBuilder();
+                        final StringBuilder tasksListString = new StringBuilder();
                         while ((line = responseReader.readLine()) != null) {
-                            if (line.startsWith(ListTasksAction.NAME) == false) {
-                                activeTasks++;
-                                tasksListString.append(line);
-                                tasksListString.append('\n');
+                            final String taskName = line.split("\\s+")[0];
+                            if (taskName.startsWith(ListTasksAction.NAME) || taskFilter.test(taskName)) {
+                                continue;
                             }
+                            activeTasks++;
+                            tasksListString.append(line);
+                            tasksListString.append('\n');
                         }
                         assertEquals(activeTasks + " active tasks found:\n" + tasksListString, 0, activeTasks);
                     }
                 }
-            } catch (IOException e) {
+            } catch (final IOException e) {
                 throw new AssertionError("Error getting active tasks list", e);
             }
         });