Added unit tests for NettyMessaging

Change-Id: I9f57b04488f53af9e773078409970f0fa0d958f9

+package org.onlab.netty;
+
+import java.util.Arrays;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicReference;
+import java.util.function.BiFunction;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+import org.onlab.packet.IpAddress;
+import org.onosproject.store.cluster.messaging.Endpoint;
+
+import com.google.common.util.concurrent.MoreExecutors;
+import com.google.common.util.concurrent.Uninterruptibles;
+
+import static org.junit.Assert.*;
+
+/**
+ * Unit tests for NettyMessaging.
+ */
+public class NettyMessagingTest {
+
+    NettyMessaging netty1;
+    NettyMessaging netty2;
+
+    Endpoint ep1 = new Endpoint(IpAddress.valueOf("127.0.0.1"), 5001);
+    Endpoint ep2 = new Endpoint(IpAddress.valueOf("127.0.0.1"), 5002);
+    Endpoint invalidEndPoint = new Endpoint(IpAddress.valueOf("127.0.0.1"), 5003);
+
+    @Before
+    public void setUp() throws Exception {
+        netty1 = new NettyMessaging();
+        netty2 = new NettyMessaging();
+
+        netty1.start(12, ep1);
+        netty2.start(12, ep2);
+    }
+
+    @After
+    public void tearDown() throws Exception {
+        if (netty1 != null) {
+            netty1.stop();
+        }
+
+        if (netty2 != null) {
+            netty2.stop();
+        }
+    }
+
+    @Test
+    public void testSendAsync() {
+        CountDownLatch latch1 = new CountDownLatch(1);
+        CompletableFuture<Void> response = netty1.sendAsync(ep2, "test-subject", "hello world".getBytes());
+        response.whenComplete((r, e) -> {
+            assertNull(e);
+            latch1.countDown();
+        });
+        Uninterruptibles.awaitUninterruptibly(latch1);
+
+        CountDownLatch latch2 = new CountDownLatch(1);
+        response = netty1.sendAsync(invalidEndPoint, "test-subject", "hello world".getBytes());
+        response.whenComplete((r, e) -> {
+            assertNotNull(e);
+            latch2.countDown();
+        });
+        Uninterruptibles.awaitUninterruptibly(latch2);
+    }
+
+    @Test
+    public void testSendAndReceive() {
+        AtomicBoolean handlerInvoked = new AtomicBoolean(false);
+        AtomicReference<byte[]> request = new AtomicReference<>();
+        AtomicReference<Endpoint> sender = new AtomicReference<>();
+
+        BiFunction<Endpoint, byte[], byte[]> handler = (ep, data) -> {
+            handlerInvoked.set(true);
+            sender.set(ep);
+            request.set(data);
+            return "hello there".getBytes();
+        };
+        netty2.registerHandler("test-subject", handler, MoreExecutors.directExecutor());
+
+        CompletableFuture<byte[]> response = netty1.sendAndReceive(ep2, "test-subject", "hello world".getBytes());
+        assertTrue(Arrays.equals("hello there".getBytes(), response.join()));
+        assertTrue(handlerInvoked.get());
+        assertTrue(Arrays.equals(request.get(), "hello world".getBytes()));
+        assertEquals(ep1, sender.get());
+    }
+
+    /*
+     * Supplies executors when registering a handler and calling sendAndReceive and verifies the request handling
+     * and response completion occurs on the expected thread.
+     */
+    @Test
+    public void testSendAndReceiveWithExecutor() {
+        ExecutorService completionExecutor = Executors.newSingleThreadExecutor(r -> new Thread(r, "completion-thread"));
+        ExecutorService handlerExecutor = Executors.newSingleThreadExecutor(r -> new Thread(r, "handler-thread"));
+        AtomicReference<String> handlerThreadName = new AtomicReference<>();
+        AtomicReference<String> completionThreadName = new AtomicReference<>();
+
+        BiFunction<Endpoint, byte[], byte[]> handler = (ep, data) -> {
+            handlerThreadName.set(Thread.currentThread().getName());
+            return "hello there".getBytes();
+        };
+        netty2.registerHandler("test-subject", handler, handlerExecutor);
+
+        CompletableFuture<byte[]> response = netty1.sendAndReceive(ep2,
+                "test-subject",
+                "hello world".getBytes(),
+                completionExecutor);
+        response.whenComplete((r, e) -> {
+            completionThreadName.set(Thread.currentThread().getName());
+        });
+
+        // Verify that the message was request handling and response completion happens on the correct thread.
+        assertTrue(Arrays.equals("hello there".getBytes(), response.join()));
+        assertEquals("completion-thread", completionThreadName.get());
+        assertEquals("handler-thread", handlerThreadName.get());
+    }
+}