Implement a util class to manage push queues using Cloud Tasks API (#1290)

* Implement a util class to manage push queues using Cloud Tasks API

Push queues were part of App Engine when they debuted. As a result the
Task Queue API were part of the App Engine SDK and can only be used in
App Engine classic runtime. The new Cloud Tasks API can be used in any
runtime but it only supports push queues. In this PR we implement a util
class (CloudTasksUtils) like TaskQueueUtils to handle enqueuing tasks to
push queues using Cloud Tasks. One action (TldFanoutAction) was
converted to use the new API as a demo. Mass migration of other call sites of
the old API will follow in a separate PR.

TESTED=deployed to alpha and verified that tasks are corrected enqueued
and executed.

util/src/test/java/google/registry/util/CloudTasksUtilsTest.java

@@ -0,0 +1,117 @@
+// Copyright 2021 The Nomulus Authors. All Rights Reserved.
+//
+// Licensed 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 google.registry.util;
+
+import static com.google.common.truth.Truth.assertThat;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+import com.google.cloud.tasks.v2.CloudTasksClient;
+import com.google.cloud.tasks.v2.HttpMethod;
+import com.google.cloud.tasks.v2.QueueName;
+import com.google.cloud.tasks.v2.Task;
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.LinkedListMultimap;
+import google.registry.testing.FakeClock;
+import google.registry.testing.FakeSleeper;
+import java.nio.charset.StandardCharsets;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+/** Unit tests for {@link CloudTasksUtils}. */
+public class CloudTasksUtilsTest {
+  // Use a LinkedListMultimap to preserve order of the inserted entries for assertion.
+  private final LinkedListMultimap<String, String> params = LinkedListMultimap.create();
+  private final CloudTasksClient mockClient = mock(CloudTasksClient.class);
+  private final CloudTasksUtils cloudTasksUtils =
+      new CloudTasksUtils(
+          new Retrier(new FakeSleeper(new FakeClock()), 1),
+          "project",
+          "location",
+          () -> mockClient);
+
+  @BeforeEach
+  void beforeEach() {
+    params.put("key1", "val1");
+    params.put("key2", "val2");
+    params.put("key1", "val3");
+    when(mockClient.createTask(any(QueueName.class), any(Task.class)))
+        .thenAnswer(invocation -> invocation.getArgument(1));
+  }
+
+  @Test
+  void testSuccess_createGetTasks() {
+    Task task = CloudTasksUtils.createGetTask("/the/path", "myservice", params);
+    assertThat(task.getAppEngineHttpRequest().getHttpMethod()).isEqualTo(HttpMethod.GET);
+    assertThat(task.getAppEngineHttpRequest().getRelativeUri())
+        .isEqualTo("/the/path?key1=val1&key2=val2&key1=val3");
+    assertThat(task.getAppEngineHttpRequest().getAppEngineRouting().getService())
+        .isEqualTo("myservice");
+  }
+
+  @Test
+  void testSuccess_createPostTasks() {
+    Task task = CloudTasksUtils.createPostTask("/the/path", "myservice", params);
+    assertThat(task.getAppEngineHttpRequest().getHttpMethod()).isEqualTo(HttpMethod.POST);
+    assertThat(task.getAppEngineHttpRequest().getRelativeUri()).isEqualTo("/the/path");
+    assertThat(task.getAppEngineHttpRequest().getAppEngineRouting().getService())
+        .isEqualTo("myservice");
+    assertThat(task.getAppEngineHttpRequest().getHeadersMap().get("Content-Type"))
+        .isEqualTo("application/x-www-form-urlencoded");
+    assertThat(task.getAppEngineHttpRequest().getBody().toString(StandardCharsets.UTF_8))
+        .isEqualTo("key1=val1&key2=val2&key1=val3");
+  }
+
+  @Test
+  void testFailure_illegalPath() {
+    assertThrows(
+        IllegalArgumentException.class,
+        () -> CloudTasksUtils.createPostTask("the/path", "myservice", params));
+    assertThrows(
+        IllegalArgumentException.class,
+        () -> CloudTasksUtils.createPostTask(null, "myservice", params));
+    assertThrows(
+        IllegalArgumentException.class,
+        () -> CloudTasksUtils.createPostTask("", "myservice", params));
+  }
+
+  @Test
+  void testSuccess_enqueueTask() {
+    Task task = CloudTasksUtils.createGetTask("/the/path", "myservice", params);
+    cloudTasksUtils.enqueue("test-queue", task);
+    verify(mockClient).createTask(QueueName.of("project", "location", "test-queue"), task);
+  }
+
+  @Test
+  void testSuccess_enqueueTasks_varargs() {
+    Task task1 = CloudTasksUtils.createGetTask("/the/path", "myservice", params);
+    Task task2 = CloudTasksUtils.createGetTask("/other/path", "yourservice", params);
+    cloudTasksUtils.enqueue("test-queue", task1, task2);
+    verify(mockClient).createTask(QueueName.of("project", "location", "test-queue"), task1);
+    verify(mockClient).createTask(QueueName.of("project", "location", "test-queue"), task2);
+  }
+
+  @Test
+  void testSuccess_enqueueTasks_iterable() {
+    Task task1 = CloudTasksUtils.createGetTask("/the/path", "myservice", params);
+    Task task2 = CloudTasksUtils.createGetTask("/other/path", "yourservice", params);
+    cloudTasksUtils.enqueue("test-queue", ImmutableList.of(task1, task2));
+    verify(mockClient).createTask(QueueName.of("project", "location", "test-queue"), task1);
+    verify(mockClient).createTask(QueueName.of("project", "location", "test-queue"), task2);
+  }
+}