Add sample of cancellation populated from parent to child workflow

src/main/java/com/uber/cadence/samples/hello/HelloCancelChild.java

@@ -0,0 +1,155 @@
+/*
+ *  Copyright 2012-2016 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ *  Modifications copyright (C) 2017 Uber Technologies, Inc.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License"). You may not
+ *  use this file except in compliance with the License. A copy of the License is
+ *  located at
+ *
+ *  http://aws.amazon.com/apache2.0
+ *
+ *  or in the "license" file accompanying this file. This file 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 com.uber.cadence.samples.hello;
+
+import static com.uber.cadence.samples.common.SampleConstants.DOMAIN;
+
+import com.google.common.base.Throwables;
+import com.uber.cadence.activity.ActivityOptions;
+import com.uber.cadence.client.WorkflowClient;
+import com.uber.cadence.client.WorkflowClientOptions;
+import com.uber.cadence.client.WorkflowException;
+import com.uber.cadence.client.WorkflowOptions;
+import com.uber.cadence.client.WorkflowStub;
+import com.uber.cadence.serviceclient.ClientOptions;
+import com.uber.cadence.serviceclient.WorkflowServiceTChannel;
+import com.uber.cadence.worker.Worker;
+import com.uber.cadence.worker.WorkerFactory;
+import com.uber.cadence.workflow.CancellationScope;
+import com.uber.cadence.workflow.Workflow;
+import com.uber.cadence.workflow.WorkflowMethod;
+import java.time.Duration;
+import java.util.concurrent.CancellationException;
+
+/** Demonstrates how cancellation populated from parent to child workflow */
+public class HelloCancelChild {
+
+  static final String TASK_LIST = "HelloCancelChild";
+
+  public interface GreetingWorkflow {
+    @WorkflowMethod
+    String getGreeting(String name);
+  }
+
+  public interface GreetingChild {
+    @WorkflowMethod
+    String composeGreeting(String greeting, String name);
+  }
+
+  public interface GreetingActivities {
+    String sayGoodbye(String name);
+  }
+
+  /** Parent implementation that calls GreetingChild#composeGreeting. */
+  public static class GreetingWorkflowImpl implements GreetingWorkflow {
+
+    @Override
+    public String getGreeting(String name) {
+      GreetingChild child = Workflow.newChildWorkflowStub(GreetingChild.class);
+      return child.composeGreeting("Hello", name);
+    }
+  }
+
+  /** Child workflow implementation. */
+  public static class GreetingChildImpl implements GreetingChild {
+
+    private final GreetingActivities activities =
+        Workflow.newActivityStub(
+            GreetingActivities.class,
+            new ActivityOptions.Builder()
+                .setScheduleToCloseTimeout(Duration.ofSeconds(20))
+                .build());
+
+    @Override
+    public String composeGreeting(String greeting, String name) {
+      try {
+        Workflow.sleep(Duration.ofDays(10));
+        return greeting + name;
+        // This exception is thrown when a cancellation is requested on the current workflow
+      } catch (CancellationException e) {
+        // clean up on cancellation
+        /**
+         * Any call to an activity or a child workflow after the workflow is cancelled is going to
+         * fail immediately with the CancellationException. the DetachedCancellationScope doesn't
+         * inherit its cancellation status from the enclosing scope. Thus it allows running a
+         * cleanup activity even if the workflow cancellation was requested.
+         */
+        CancellationScope scope =
+            Workflow.newDetachedCancellationScope(() -> activities.sayGoodbye(name));
+        scope.run();
+        throw e;
+      }
+    }
+  }
+
+  static class GreetingActivitiesImpl implements GreetingActivities {
+    @Override
+    public String sayGoodbye(String name) {
+      try {
+        Thread.sleep(1000 * 10);
+      } catch (InterruptedException e) {
+        e.printStackTrace();
+      }
+      return name;
+    }
+  }
+
+  public static void main(String[] args) {
+    // Get a new client
+    // NOTE: to set a different options, you can do like this:
+    // ClientOptions.newBuilder().setRpcTimeout(5 * 1000).build();
+    WorkflowClient workflowClient =
+        WorkflowClient.newInstance(
+            new WorkflowServiceTChannel(ClientOptions.defaultInstance()),
+            WorkflowClientOptions.newBuilder().setDomain(DOMAIN).build());
+    // Get worker to poll the task list.
+    WorkerFactory factory = WorkerFactory.newInstance(workflowClient);
+    Worker worker = factory.newWorker(TASK_LIST);
+    worker.registerWorkflowImplementationTypes(GreetingWorkflowImpl.class, GreetingChildImpl.class);
+    worker.registerActivitiesImplementations(new GreetingActivitiesImpl());
+    factory.start();
+
+    WorkflowOptions workflowOptions =
+        new WorkflowOptions.Builder()
+            .setTaskList(TASK_LIST)
+            .setExecutionStartToCloseTimeout(Duration.ofSeconds(30))
+            .build();
+    GreetingWorkflow workflow =
+        workflowClient.newWorkflowStub(GreetingWorkflow.class, workflowOptions);
+    try {
+      // NOTE: strongly typed workflow stub doesn't cancel method.
+      WorkflowStub stub =
+          workflowClient.newUntypedWorkflowStub("GreetingWorkflow::getGreeting", workflowOptions);
+
+      stub.start("World");
+      // wait for child workflow to start
+      Thread.sleep(1000);
+
+      // issue cancellation request. This will trigger a CancellationException on the workflow.
+      stub.cancel();
+
+      stub.getResult(String.class);
+    } catch (WorkflowException | InterruptedException e) {
+      Throwable cause = Throwables.getRootCause(e);
+      // prints "Hello World!"
+      System.out.println(cause.getMessage());
+      System.out.println("\nStack Trace:\n" + Throwables.getStackTraceAsString(e));
+    }
+    System.exit(0);
+  }
+}