Added HelloActivityRetry (#3)

* Added HelloActivityRetry

* Updated comments

Author: mfateev

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

@@ -52,7 +52,7 @@ public interface GreetingActivities {
     }
 
     /**
-     * GreetingWorkflow implementation that calls GreetingsActivities#printIt.
+     * GreetingWorkflow implementation that calls GreetingsActivities#composeGreeting.
      */
     public static class GreetingWorkflowImpl implements GreetingWorkflow {
 

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

@@ -0,0 +1,124 @@
+/*
+ *  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 com.uber.cadence.client.WorkflowClient;
+import com.uber.cadence.client.WorkflowOptions;
+import com.uber.cadence.worker.Worker;
+import com.uber.cadence.workflow.ActivityOptions;
+import com.uber.cadence.workflow.Functions;
+import com.uber.cadence.workflow.RetryOptions;
+import com.uber.cadence.workflow.Workflow;
+import com.uber.cadence.workflow.WorkflowMethod;
+
+import java.time.Duration;
+
+import static com.uber.cadence.samples.common.SampleConstants.DOMAIN;
+
+/**
+ * Demonstrates activity retries using exponential backoff algorithm.
+ * Requires a local instance of Cadence server running.
+ */
+public class HelloActivityRetry {
+
+    private static final String TASK_LIST = "HelloActivity";
+
+    public interface GreetingWorkflow {
+        /**
+         * @return greeting string
+         */
+        @WorkflowMethod
+        String getGreeting(String name);
+    }
+
+    public interface GreetingActivities {
+        String composeGreeting(String greeting, String name);
+    }
+
+    /**
+     * GreetingWorkflow implementation that demonstrates activity stub configured with
+     * {@link RetryOptions}.
+     */
+    public static class GreetingWorkflowImpl implements GreetingWorkflow {
+
+        /**
+         * To enable activity retry set {@link RetryOptions} on {@link ActivityOptions}.
+         * It also works for activities invoked through
+         * {@link com.uber.cadence.workflow.Async#invoke(Functions.Proc)} and for child workflows.
+         */
+        private final GreetingActivities activities = Workflow.newActivityStub(
+                GreetingActivities.class,
+                new ActivityOptions.Builder()
+                        .setScheduleToCloseTimeoutSeconds(10)
+                        .setRetryOptions(new RetryOptions.Builder()
+                                .setInitialInterval(Duration.ofSeconds(1))
+                                .setExpiration(Duration.ofMinutes(1))
+                                .build())
+                        .build());
+
+        @Override
+        public String getGreeting(String name) {
+            // This is blocking call that returns only after activity is completed.
+            return activities.composeGreeting("Hello", name);
+        }
+    }
+
+    private static class GreetingActivitiesImpl implements GreetingActivities {
+        private int callCount;
+        private long lastInvocationTime;
+
+        @Override
+        public synchronized String composeGreeting(String greeting, String name) {
+            if (lastInvocationTime != 0) {
+                long timeSinceLastInvocation = System.currentTimeMillis() - lastInvocationTime;
+                System.out.print(timeSinceLastInvocation + " milliseconds since last invocation. ");
+            }
+            lastInvocationTime = System.currentTimeMillis();
+            if (++callCount < 4) {
+                System.out.println("composeGreeting activity is going to fail");
+                throw new IllegalStateException("not yet");
+            }
+            System.out.println("composeGreeting activity is going to complete");
+            return greeting + " " + name + "!";
+        }
+    }
+
+    public static void main(String[] args) {
+        // Start a worker that hosts both workflow and activity implementation
+        Worker worker = new Worker(DOMAIN, TASK_LIST);
+        // Workflows are stateful. So need a type to create instances.
+        worker.registerWorkflowImplementationTypes(GreetingWorkflowImpl.class);
+        // Activities are stateless and thread safe. So a shared instance is used.
+        worker.registerActivitiesImplementations(new GreetingActivitiesImpl());
+        // Start listening to the workflow and activity task lists.
+        worker.start();
+
+        // Start a workflow execution. Usually it is done from another program.
+        WorkflowClient workflowClient = WorkflowClient.newInstance(DOMAIN);
+        // Get a workflow stub using the same task list the worker uses.
+        WorkflowOptions workflowOptions = new WorkflowOptions.Builder()
+                .setTaskList(TASK_LIST)
+                .setExecutionStartToCloseTimeoutSeconds(30)
+                .build();
+        GreetingWorkflow workflow = workflowClient.newWorkflowStub(GreetingWorkflow.class,
+                workflowOptions);
+        // Execute a workflow waiting for it complete.
+        String greeting = workflow.getGreeting("World");
+        System.out.println(greeting);
+        System.exit(0);
+    }
+}

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

@@ -21,14 +21,15 @@
 import com.uber.cadence.worker.Worker;
 import com.uber.cadence.workflow.ActivityOptions;
 import com.uber.cadence.workflow.Async;
+import com.uber.cadence.workflow.Functions;
 import com.uber.cadence.workflow.Promise;
 import com.uber.cadence.workflow.Workflow;
 import com.uber.cadence.workflow.WorkflowMethod;
 
 import static com.uber.cadence.samples.common.SampleConstants.DOMAIN;
 
 /**
- * Hello World Cadence workflow that executes a couple activities in parallel.
+ * Demonstrates asynchronous activity invocation.
  * Requires a local instance of Cadence server running.
  */
 public class HelloAsync {
@@ -40,15 +41,13 @@ public interface GreetingWorkflow {
         String getGreeting(String name);
     }
 
-    /**
-     * Activity interface is just a POJI
-     */
     public interface GreetingActivities {
         String composeGreeting(String greeting, String name);
     }
 
     /**
-     * GreetingWorkflow implementation that calls GreetingsActivities#printIt.
+     * GreetingWorkflow implementation that calls GreetingsActivities#composeGreeting
+     * using {@link Async#invoke(Functions.Proc)}.
      */
     public static class GreetingWorkflowImpl implements GreetingWorkflow {
 

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

@@ -31,16 +31,13 @@
 import static com.uber.cadence.samples.common.SampleConstants.DOMAIN;
 
 /**
- * Hello World Cadence workflow that executes a single activity.
+ * Demonstrates an asynchronous activity implementation.
  * Requires a local instance of Cadence server running.
  */
 public class HelloAsyncActivityCompletion {
 
     private static final String TASK_LIST = "HelloActivity";
 
-    /**
-     * Workflow interface has to have at least one method annotated with @WorkflowMethod.
-     */
     public interface GreetingWorkflow {
         /**
          * @return greeting string

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

@@ -29,7 +29,7 @@
 import static com.uber.cadence.samples.common.SampleConstants.DOMAIN;
 
 /**
- * Hello World Cadence workflow that executes two sequences of activities in parallel.
+ * Demonstrates async invocation of an entire sequence of activities.
  * Requires a local instance of Cadence server running.
  */
 public class HelloAsyncLambda {

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

@@ -30,7 +30,7 @@
 import static com.uber.cadence.samples.common.SampleConstants.DOMAIN;
 
 /**
- * Hello World Cadence workflow that executes a single child workflow.
+ * Demonstrates child workflow.
  * Requires a local instance of Cadence server running.
  */
 public class HelloChild {

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

@@ -32,7 +32,7 @@
 import static com.uber.cadence.samples.common.SampleConstants.DOMAIN;
 
 /**
- * Hello World Cadence workflow that executes a single activity periodically.
+ * Demonstrates a "cron" workflow that executes activity periodically.
  * Requires a local instance of Cadence server running.
  */
 public class HelloPeriodic {

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

@@ -28,7 +28,7 @@
 import static com.uber.cadence.samples.common.SampleConstants.DOMAIN;
 
 /**
- * Hello World Cadence workflow that returns greeting when queried.
+ * Demonstrates query capability.
  * Requires a local instance of Cadence server running.
  */
 public class HelloQuery {

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

@@ -27,7 +27,7 @@
 import static com.uber.cadence.samples.common.SampleConstants.DOMAIN;
 
 /**
- * Hello World Cadence workflow that blocks until a signal is received.
+ * Demonstrates asynchronous signalling of a workflow.
  * Requires a local instance of Cadence server running.
  */
 @SuppressWarnings("ALL")