#328 Add support to pass worker process loop exceptions back to the client to enable error handling if required.

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

@@ -19,6 +19,7 @@ import java.util.HashSet;
 import java.util.List;
 import java.util.Optional;
 import java.util.Set;
+import java.util.ArrayList;
 import java.util.concurrent.Callable;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentMap;
@@ -106,6 +107,8 @@ public class Worker implements Runnable {
 
     private WorkerLog wlog = new WorkerLog();
 
+    private List<WorkerProcessLoopExceptionListener> workerProcessLoopExceptionListeners = new ArrayList<>();
+
     private final String applicationName;
     private final IRecordProcessorFactory recordProcessorFactory;
     private final KinesisClientLibConfiguration config;
@@ -704,6 +707,12 @@ public class Worker implements Runnable {
         } catch (Exception e) {
             LOG.error(String.format("Worker.run caught exception, sleeping for %s milli seconds!",
                     String.valueOf(idleTimeInMilliseconds)), e);
+
+            // notify the listeners that an error has occurred and pass down the exception for the client to handle
+            for (WorkerProcessLoopExceptionListener workerProcessLoopExceptionListener : workerProcessLoopExceptionListeners) {
+                workerProcessLoopExceptionListener.exceptionOccured(e);
+            }
+
             try {
                 Thread.sleep(idleTimeInMilliseconds);
             } catch (InterruptedException ex) {
@@ -713,6 +722,14 @@ public class Worker implements Runnable {
         wlog.resetInfoLogging();
     }
 
+    public void addWorkerProcessLoopExceptionObserver(final WorkerProcessLoopExceptionListener workerProcessLoopExceptionListener) {
+        workerProcessLoopExceptionListeners.add(workerProcessLoopExceptionListener);
+    }
+
+    public void removeWorkerProcessLoopExceptionObserver(final WorkerProcessLoopExceptionListener workerProcessLoopExceptionListener) {
+        workerProcessLoopExceptionListeners.remove(workerProcessLoopExceptionListener);
+    }
+
     private void initialize() {
         workerStateChangeListener.onWorkerStateChange(WorkerStateChangeListener.WorkerState.INITIALIZING);
         boolean isDone = false;

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

@@ -0,0 +1,15 @@
+package com.amazonaws.services.kinesis.clientlibrary.lib.worker;
+
+/**
+ * A listener for when the worker processing loop encounters an unexpected exception
+ * so the client caller can inspect the error that occurred and take action.
+ */
+public interface WorkerProcessLoopExceptionListener {
+
+    /**
+     * Listeners implement this method and can read the exception to take the appropriate action.
+     *
+     * @param e the exception that occurred
+     */
+    void exceptionOccured(Exception e);
+}