Reworked Asynchronous tasks

src/main/java/fr/altarik/toolbox/asynctasks/AsyncTasks.java

@@ -1,23 +1,43 @@
 package fr.altarik.toolbox.asynctasks;
 
-/**
- * A non-blocking small sized time-consuming tasks to executed asynchronously, this was developed mainly to be used to avoid to block main threads with mysql requests in mind
- */
-public class AsyncTasks {
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
 
-    private static final TasksThread worker = new TasksThread();
+/**
+ * A non-blocking small sized time-consuming tasks to executed asynchronously.
+ */
+public class AsyncTasks implements AutoCloseable {
+
+    private final ExecutorService worker;
+
+    private AsyncTasks(int numberOfWorker) {
+        if(numberOfWorker == 1) {
+            worker = Executors.newSingleThreadExecutor();
+        } else if (numberOfWorker <= 0) {
+            worker = Executors.newCachedThreadPool();
+        } else {
+            worker = Executors.newFixedThreadPool(numberOfWorker);
+        }
+    }
 
     /**
      * Call this method at startup or before first use of {@link AsyncTasks#addTask(Runnable)}, cause without it, nothing will work
      * This method declare worker thread and start it, without call it, by calling addTask(Runnable), it'll add your task to Queue, but tasks will never be consumed.
+     *
+     * @return an instance of AsyncTasks
      */
-    public static void initialize() {
-        worker.run();
+    public static AsyncTasks initialize(int numberOfWorker) {
+        return new AsyncTasks(numberOfWorker);
+    }
+
+    public static AsyncTasks initialize() {
+        return initialize(Runtime.getRuntime().availableProcessors());
     }
 
     /**
-     * <p>Method used to add your task to a list of task, task are stored in a FIFO(First-In First-Out) implementation ({@link java.util.concurrent.BlockingQueue}).
-     * As BlockingQueue is a synchronized class, all operations to add or remove elements inside cannot have collisions issues</p>
+     * <p>Method used to add your task to a list of task, task are stored in a FIFO(First-In First-Out) implementation ({@link java.util.concurrent.LinkedBlockingQueue}).
+     * As LinkedBlockingQueue is a synchronized class, all operations to add or remove elements inside cannot have collisions issues</p>
      * <p>Example: </p>
      * <pre>
      *      for(int i = 0; i &lt; 4; i++) {
@@ -40,28 +60,37 @@ public class AsyncTasks {
      *     task 3
      *     3
      * </pre>
-     * The worker thread is sleeping if it doesn't have task to execute and wake up if necessary when you add a task
+     * The worker thread is sleeping if it doesn't have task to execute and wake up if necessary when you add a task.
+     * A worker which crash due to exception in the code of your task will automatically be recreated (see {@link java.util.concurrent.ThreadPoolExecutor} for more informations).
      * @param function task to be executed
      * @throws InterruptedException when worker thread or BlockQueue has been interrupted while waiting (which is anormal)
      */
-    public static void addTask(Runnable function) throws InterruptedException {
-        if(worker.workerThread.isInterrupted())
-            throw new InterruptedException("Async task thread has been interrupted while waiting for another task, which is anormal, please report this issue to developers");
-        worker.tasks.put(function);
-        // this condition is non-atomic, but we want to avoid unwanted and useless interruption in the main thread(s) while waiting for the worker thread to be released
-        if(worker.isWaiting) {
-            worker.lock.lock();
-            worker.lockSignal.signalAll();
-            worker.lock.unlock();
+    public void addTask(Runnable function) throws InterruptedException {
+        if(worker.isTerminated() || worker.isShutdown()) {
+            throw new InterruptedException("Worker has been terminated or shutdown, it's impossible to add new task");
         }
+        worker.submit(function);
     }
 
     /**
-     *  Return the numbers of produced tasks which hasn't been consumed yet
-     * @return numbers of produced tasks which hasn't been consumed yet
+     * This method is call when you want to close workers and wait for waiting tasks to finish
+     *
      */
-    public static int numberOfWaitingTask() {
-        return worker.tasks.size();
+    @Override
+    public void close() throws Exception {
+        worker.shutdown();
+        boolean result = worker.awaitTermination(10, TimeUnit.SECONDS);
+        if(!result) {
+            worker.shutdownNow();
+            throw new UnfinishedTasksException("Tasks take too many time to finish, shutdown has been enforce");
+        }
     }
 
+    public static class UnfinishedTasksException extends Exception {
+
+        public UnfinishedTasksException(String message) {
+            super(message);
+        }
+
+    }
 }

src/main/java/fr/altarik/toolbox/asynctasks/TasksThread.java

@@ -1,44 +0,0 @@
-package fr.altarik.toolbox.asynctasks;
-
-import java.util.concurrent.BlockingQueue;
-import java.util.concurrent.LinkedBlockingQueue;
-import java.util.concurrent.locks.Condition;
-import java.util.concurrent.locks.ReentrantLock;
-
-/**
- * Package private class, AsyncTasks is the interface user need to interact with it and users should never directly call this class
- */
-class TasksThread {
-
-    boolean isWaiting = false;
-    final ReentrantLock lock = new ReentrantLock();
-    final Condition lockSignal = lock.newCondition();
-    Thread workerThread;
-
-    final BlockingQueue<Runnable> tasks = new LinkedBlockingQueue<>();
-
-    void run() {
-        workerThread = new Thread(() -> {
-
-            try {
-                for(;;) {
-                    while(tasks.isEmpty()) {
-                        lock.lock();
-                        isWaiting = true;
-                        lockSignal.await();
-                        isWaiting = false;
-                        lock.unlock();
-                    }
-                    while(!tasks.isEmpty()) {
-                        tasks.take().run();
-                    }
-                }
-            } catch (InterruptedException e) {
-                Thread.currentThread().interrupt();
-            }
-        });
-        workerThread.start();
-
-    }
-
-}

src/test/java/fr/altarik/toolbox/AsyncTaskTest.java

@@ -9,31 +9,27 @@ import java.util.concurrent.atomic.AtomicInteger;
 
 import static org.junit.jupiter.api.Assertions.assertArrayEquals;
 
-public class AsyncTaskTest {
+class AsyncTaskTest {
 
 
     private String log(String message) {
         return "[" + new Date() + "]" + message;
     }
     @Test
-    public void testAsyncOp() throws InterruptedException {
+    void testAsyncOp() throws Exception {
         int numberOfTasks = 10000;
         System.out.println("Initializing async tasks worker");
-        AsyncTasks.initialize();
+        AsyncTasks worker = AsyncTasks.initialize(1); // only testing on a single worker, otherwise result have a high chance to not be in the order we want
         Stack<Integer> results = new Stack<>();
         for(int i = 0; i < numberOfTasks; i++) {
             System.out.println(log("sending task " + i));
             AtomicInteger atomicInteger = new AtomicInteger(i);
-            AsyncTasks.addTask(() -> {
+            worker.addTask(() -> {
                 System.out.println(log(" task " + atomicInteger.get()));
                 results.push(atomicInteger.get());
             });
         }
-        while(AsyncTasks.numberOfWaitingTask() != 0) {
-            synchronized (this) {
-                wait(20); // wait till last task finish
-            }
-        }
+        worker.close(); // wait until all worker terminated
         Integer[] expected = new Integer[numberOfTasks];
         for(int i = 0; i < numberOfTasks; i++) {
             expected[i] = i;