added test case for the impossibility of thread pool depletion by tasks throwing exceptions

Change-Id: I529d230299abc3a97bccc194611e182bb7ad744f

java/com.sap.sse.test/src/com/sap/sse/test/ThreadPoolWithExceptionsTest.java

@@ -0,0 +1,64 @@
+package com.sap.sse.test;
+
+import static org.junit.Assert.assertEquals;
+
+import java.util.concurrent.LinkedBlockingQueue;
+import java.util.concurrent.ThreadPoolExecutor;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.logging.Logger;
+
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.Timeout;
+
+import com.sap.sse.util.impl.ThreadFactoryWithPriority;
+
+/**
+ * Tests that deal with the question whether a thread pool may be "depleted" by threads throwing exceptions and hence leading
+ * to abnormal worker thread termination.
+ * 
+ * @author Axel Uhl (D043530)
+ *
+ */
+public class ThreadPoolWithExceptionsTest {
+    @Rule public Timeout threadPoolWithExceptionsTestTimeout = new Timeout(10 * 1000); // 10s timeout
+    
+    private static final Logger logger = Logger.getLogger(ThreadPoolWithExceptionsTest.class.getName());
+    
+    final int THREAD_POOL_SIZE = 100;
+    
+    private ThreadPoolExecutor executor;
+    
+    @Before
+    public void setUp() {
+        executor = new ThreadPoolExecutor(/* corePoolSize */ THREAD_POOL_SIZE,
+                /* maximumPoolSize */ THREAD_POOL_SIZE,
+                /* keepAliveTime */ 60, TimeUnit.SECONDS,
+                /* workQueue */ new LinkedBlockingQueue<Runnable>(),
+                /* thread factory */ new ThreadFactoryWithPriority(Thread.NORM_PRIORITY, /* daemon */ true));
+    }
+    
+    @Test
+    public void tryToDepletePoolByTasksThatThrowExceptions() throws InterruptedException {
+        final AtomicInteger counter = new AtomicInteger(0);
+        for (int i=0; i<2*THREAD_POOL_SIZE; i++) {
+            final Runnable r = () -> {
+                final int count = counter.incrementAndGet();
+                logger.info("Worked thread executing job #"+count+": "+Thread.currentThread());
+                synchronized (ThreadPoolWithExceptionsTest.this) {
+                    ThreadPoolWithExceptionsTest.this.notifyAll();
+                }
+                throw new NullPointerException();
+            };
+            executor.execute(r);
+        }
+        synchronized (this) {
+            while (counter.get() < 2*THREAD_POOL_SIZE) {
+                this.wait();
+            }
+        }
+        assertEquals(2*THREAD_POOL_SIZE, counter.get());
+    }
+}