Review comments

Author: Liang Mei

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

@@ -5,13 +5,8 @@
 import com.uber.cadence.client.WorkflowOptions;
 import com.uber.cadence.worker.Worker;
 import com.uber.cadence.workflow.*;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
 
 import java.time.Duration;
-import java.util.ArrayList;
-import java.util.List;
-import java.util.concurrent.atomic.AtomicInteger;
 
 import static com.uber.cadence.samples.common.SampleConstants.DOMAIN;
 
@@ -20,19 +15,17 @@
  */
 public class HelloSaga {
   static final String TASK_LIST = "HelloSaga";
-  static final List<String> transactions = new ArrayList<>();
 
   public interface ChildWorkflowOperation {
     @WorkflowMethod
     void execute(int amount);
   }
 
   public static class ChildWorkflowOperationImpl implements ChildWorkflowOperation {
-    Logger log = Workflow.getLogger(ChildWorkflowOperationImpl.class);
+    ActivityOperation activity = Workflow.newActivityStub(ActivityOperation.class);
 
     public void execute(int amount) {
-      log.info("ChildWorkflowOperationImpl.execute() is called.");
-      transactions.add("child workflow execution: " + amount);
+      activity.execute(amount);
     }
   }
 
@@ -42,39 +35,29 @@ public interface ChildWorkflowCompensation {
   }
 
   public static class ChildWorkflowCompensationImpl implements ChildWorkflowCompensation {
-    Logger log = Workflow.getLogger(ChildWorkflowCompensationImpl.class);
+    ActivityOperation activity = Workflow.newActivityStub(ActivityOperation.class);
 
     public void compensate(int amount) {
-      log.info("ChildWorkflowCompensationImpl.compensate() is called.");
-      transactions.add("child workflow compensation: " + amount);
+      activity.compensate(amount);
     }
   }
 
   public interface ActivityOperation {
     @ActivityMethod(scheduleToCloseTimeoutSeconds = 2)
     void execute(int amount);
+
+    @ActivityMethod(scheduleToCloseTimeoutSeconds = 2)
+    void compensate(int amount);
   }
 
   public static class ActivityOperationImpl implements ActivityOperation {
-    Logger log = LoggerFactory.getLogger(ActivityOperationImpl.class);
 
     public void execute(int amount) {
-      log.info("ActivityOperationImpl.execute() is called.");
-      transactions.add("activity execution: " + amount);
+      System.out.println("ActivityOperationImpl.execute() is called with amount " + amount);
     }
-  }
-
-  public interface ActivityCompensation {
-    @ActivityMethod(scheduleToCloseTimeoutSeconds = 2)
-    void compensate(int amount);
-  }
-
-  public static class ActivityCompensationImpl implements ActivityCompensation {
-    Logger log = LoggerFactory.getLogger(ActivityCompensationImpl.class);
 
     public void compensate(int amount) {
-      log.info("ActivityCompensationImpl.execute() is called.");
-      transactions.add("activity compensation: " + amount);
+      System.out.println("ActivityCompensationImpl.compensate() is called with amount " + amount);
     }
   }
 
@@ -83,39 +66,37 @@ public interface SagaWorkflow {
      * Main saga workflow.
      */
     @WorkflowMethod
-    List<String> execute();
+    void execute();
   }
 
   public static class SagaWorkflowImpl implements SagaWorkflow {
+    ActivityOperation activity = Workflow.newActivityStub(ActivityOperation.class);
+
     @Override
-    public List<String> execute() {
+    public void execute() {
       Saga saga = new Saga(new Saga.Options.Builder().setParallelCompensation(false).build());
       try {
         ChildWorkflowOperation op1 = Workflow.newChildWorkflowStub(ChildWorkflowOperation.class);
         op1.execute(10);
         ChildWorkflowCompensation c1 = Workflow.newChildWorkflowStub(ChildWorkflowCompensation.class);
         saga.addCompensation(c1::compensate, -10);
 
-        ActivityOperation op2 = Workflow.newActivityStub(ActivityOperation.class);
-        Promise<Void> result = Async.procedure(op2::execute, 20);
+        Promise<Void> result = Async.procedure(activity::execute, 20);
         result.get();
-        ActivityCompensation c2 = Workflow.newActivityStub(ActivityCompensation.class);
-        saga.addCompensation(c2::compensate, -20);
-
-        transactions.add("main workflow: " + 30);
-        saga.addCompensation(()->transactions.add("main workflow compensation: " + -30));
+        saga.addCompensation(activity::compensate, -20);
 
+        // The following is just to demonstrate the ability of supplying arbitrary lambda as a
+        // saga compensation function. In production code please always use Workflow.getLogger
+        // to log messages in workflow code.
+        saga.addCompensation(() -> System.out.println("Other compensation logic in main workflow."));
         throw new RuntimeException("some error");
 
       } catch (Exception e) {
         saga.compensate();
       }
-
-      return transactions;
     }
   }
 
-
   public static void main(String[] args) {
     // Start a worker that hosts the workflow implementation.
     Worker.Factory factory = new Worker.Factory(DOMAIN);
@@ -124,7 +105,7 @@ public static void main(String[] args) {
         HelloSaga.SagaWorkflowImpl.class,
         HelloSaga.ChildWorkflowOperationImpl.class,
         HelloSaga.ChildWorkflowCompensationImpl.class);
-    worker.registerActivitiesImplementations(new ActivityOperationImpl(), new ActivityCompensationImpl());
+    worker.registerActivitiesImplementations(new ActivityOperationImpl());
     factory.start();
 
     // Start a workflow execution. Usually this is done from another program.
@@ -137,7 +118,7 @@ public static void main(String[] args) {
             .build();
     HelloSaga.SagaWorkflow workflow =
         workflowClient.newWorkflowStub(HelloSaga.SagaWorkflow.class, workflowOptions);
-    System.out.println(workflow.execute());
+    workflow.execute();
     System.exit(0);
   }
 }