Created listener for worker state change

https://github.com/awslabs/amazon-kinesis-client/issues/275

Update WorkerTest.java

src/main/java/com/amazonaws/services/kinesis/clientlibrary/lib/worker/NoOpWorkerStateChangeListener.java

@@ -0,0 +1,18 @@
+package com.amazonaws.services.kinesis.clientlibrary.lib.worker;
+
+import com.amazonaws.services.kinesis.clientlibrary.lib.worker.Worker.WorkerStateChangeListener;
+
+public class NoOpWorkerStateChangeListener implements WorkerStateChangeListener {
+
+	/**
+	 * Empty constructor for NoOp Worker State Change Listener
+	 */
+	public NoOpWorkerStateChangeListener() {
+
+	}
+
+	@Override
+	public void onWorkerStateChange(WorkerState newState) {
+
+	}
+}

src/main/java/com/amazonaws/services/kinesis/clientlibrary/lib/worker/Worker.java

@@ -93,7 +93,6 @@ public class Worker implements Runnable {
     private final Optional<Integer> retryGetRecordsInSeconds;
     private final Optional<Integer> maxGetRecordsThreadPool;
 
-    // private final KinesisClientLeaseManager leaseManager;
     private final KinesisClientLibLeaseCoordinator leaseCoordinator;
     private final ShardSyncTaskManager controlServer;
 
@@ -119,6 +118,8 @@ public class Worker implements Runnable {
     @VisibleForTesting
     protected GracefulShutdownCoordinator gracefulShutdownCoordinator = new GracefulShutdownCoordinator();
 
+    private WorkerStateChangeListener workerStateChangeListener;
+
     /**
      * Constructor.
      *
@@ -276,7 +277,8 @@ public class Worker implements Runnable {
                 config.getSkipShardSyncAtWorkerInitializationIfLeasesExist(),
                 config.getShardPrioritizationStrategy(),
                 config.getRetryGetRecordsInSeconds(),
-                config.getMaxGetRecordsThreadPool());
+                config.getMaxGetRecordsThreadPool(),
+                new NoOpWorkerStateChangeListener());
 
         // If a region name was explicitly specified, use it as the region for Amazon Kinesis and Amazon DynamoDB.
         if (config.getRegionName() != null) {
@@ -348,7 +350,7 @@ public class Worker implements Runnable {
         this(applicationName, recordProcessorFactory, config, streamConfig, initialPositionInStream, parentShardPollIntervalMillis,
                 shardSyncIdleTimeMillis, cleanupLeasesUponShardCompletion, checkpoint, leaseCoordinator, execService,
                 metricsFactory, taskBackoffTimeMillis, failoverTimeMillis, skipShardSyncAtWorkerInitializationIfLeasesExist,
-                shardPrioritization, Optional.empty(), Optional.empty());
+                shardPrioritization, Optional.empty(), Optional.empty(), new NoOpWorkerStateChangeListener());
     }
 
     /**
@@ -395,7 +397,7 @@ public class Worker implements Runnable {
            KinesisClientLibLeaseCoordinator leaseCoordinator, ExecutorService execService,
            IMetricsFactory metricsFactory, long taskBackoffTimeMillis, long failoverTimeMillis,
            boolean skipShardSyncAtWorkerInitializationIfLeasesExist, ShardPrioritization shardPrioritization,
-           Optional<Integer> retryGetRecordsInSeconds, Optional<Integer> maxGetRecordsThreadPool) {
+           Optional<Integer> retryGetRecordsInSeconds, Optional<Integer> maxGetRecordsThreadPool, WorkerStateChangeListener workerStateChangeListener) {
         this.applicationName = applicationName;
         this.recordProcessorFactory = recordProcessorFactory;
         this.config = config;
@@ -417,6 +419,8 @@ public class Worker implements Runnable {
         this.shardPrioritization = shardPrioritization;
         this.retryGetRecordsInSeconds = retryGetRecordsInSeconds;
         this.maxGetRecordsThreadPool = maxGetRecordsThreadPool;
+        this.workerStateChangeListener = workerStateChangeListener;
+        workerStateChangeListener.onWorkerStateChange(WorkerStateChangeListener.WorkerState.CREATED);
     }
 
     /**
@@ -440,6 +444,7 @@ public class Worker implements Runnable {
         if (shutdown) {
             return;
         }
+        workerStateChangeListener.onWorkerStateChange(WorkerStateChangeListener.WorkerState.INITIALIZING);
 
         try {
             initialize();
@@ -449,6 +454,7 @@ public class Worker implements Runnable {
             shutdown();
         }
 
+        workerStateChangeListener.onWorkerStateChange(WorkerStateChangeListener.WorkerState.STARTED);
         while (!shouldShutdown()) {
             runProcessLoop();
         }
@@ -755,6 +761,10 @@ public class Worker implements Runnable {
         return shardInfoShardConsumerMap;
     }
 
+    WorkerStateChangeListener getWorkerStateChangeListener() {
+        return workerStateChangeListener;
+    }
+
     /**
      * Signals worker to shutdown. Worker will try initiating shutdown of all record processors. Note that if executor
      * services were passed to the worker by the user, worker will not attempt to shutdown those resources.
@@ -775,6 +785,7 @@ public class Worker implements Runnable {
             LOG.warn("Shutdown requested a second time.");
             return;
         }
+        workerStateChangeListener.onWorkerStateChange(WorkerStateChangeListener.WorkerState.SHUTTING_DOWN);
         LOG.info("Worker shutdown requested.");
 
         // Set shutdown flag, so Worker.run can start shutdown process.
@@ -801,6 +812,7 @@ public class Worker implements Runnable {
         if (metricsFactory instanceof WorkerCWMetricsFactory) {
             ((CWMetricsFactory) metricsFactory).shutdown();
         }
+        workerStateChangeListener.onWorkerStateChange(WorkerStateChangeListener.WorkerState.SHUT_DOWN);
         shutdownComplete = true;
     }
 
@@ -874,6 +886,22 @@ public class Worker implements Runnable {
 
     }
 
+    /**
+     * A listener for callbacks on changes worker state
+     */
+    @FunctionalInterface
+    public interface WorkerStateChangeListener {
+        enum WorkerState {
+            CREATED,
+            INITIALIZING,
+            STARTED,
+            SHUTTING_DOWN,
+            SHUT_DOWN
+        }
+
+        void onWorkerStateChange(WorkerState newState);
+    }
+
     /**
      * Logger for suppressing too much INFO logging. To avoid too much logging information Worker will output logging at
      * INFO level for a single pass through the main loop every minute. At DEBUG level it will output all INFO logs on
@@ -1089,6 +1117,7 @@ public class Worker implements Runnable {
         private ExecutorService execService;
         private ShardPrioritization shardPrioritization;
         private IKinesisProxy kinesisProxy;
+        private WorkerStateChangeListener workerStateChangeListener;
 
         /**
          * Default constructor.
@@ -1233,6 +1262,17 @@ public class Worker implements Runnable {
             return this;
         }
 
+        /**
+         * Set WorkerStateChangeListener for the worker
+         * @param workerStateChangeListener
+         *             Sets the WorkerStateChangeListener
+         * @return A reference to this updated object so that method calls can be chained together.
+         */
+        public Builder workerStateChangeListener(WorkerStateChangeListener workerStateChangeListener) {
+            this.workerStateChangeListener = workerStateChangeListener;
+            return this;
+        }
+
         /**
          * Build the Worker instance.
          *
@@ -1305,6 +1345,10 @@ public class Worker implements Runnable {
                 kinesisProxy = new KinesisProxy(config, kinesisClient);
             }
 
+            if (workerStateChangeListener == null){
+                workerStateChangeListener = new NoOpWorkerStateChangeListener();
+            }
+
             return new Worker(config.getApplicationName(),
                     recordProcessorFactory,
                     config,
@@ -1336,9 +1380,8 @@ public class Worker implements Runnable {
                     config.getSkipShardSyncAtWorkerInitializationIfLeasesExist(),
                     shardPrioritization,
                     config.getRetryGetRecordsInSeconds(),
-                    config.getMaxGetRecordsThreadPool());
-
-        }
-
+                    config.getMaxGetRecordsThreadPool(),
+                    workerStateChangeListener);
+        }
     }
 }

src/test/java/com/amazonaws/services/kinesis/clientlibrary/lib/worker/WorkerTest.java

@@ -1500,6 +1500,16 @@ public class WorkerTest {
         Assert.assertTrue(worker.getStreamConfig().getStreamProxy() instanceof KinesisLocalFileProxy);
     }
 
+    @Test
+    public void testBuilderForWorkerStateListener() {
+        IRecordProcessorFactory recordProcessorFactory = mock(IRecordProcessorFactory.class);
+        Worker worker = new Worker.Builder()
+                .recordProcessorFactory(recordProcessorFactory)
+                .config(config)
+                .build();
+        Assert.assertTrue(worker.getWorkerStateChangeListener() instanceof NoOpWorkerStateChangeListener);
+    }
+
     @Test
     public void testBuilderWithDefaultLeaseManager()  {
         IRecordProcessorFactory recordProcessorFactory = mock(IRecordProcessorFactory.class);