Fixes #207 - notify listeners even if key doesn't exists in consul

src/main/java/com/orbitz/consul/cache/ConsulCache.java

@@ -47,7 +47,7 @@ enum State {latent, starting, started, stopped }
     private static final long BACKOFF_DELAY_QTY_IN_MS = getBackOffDelayInMs(System.getProperties());
 
     private final AtomicReference<BigInteger> latestIndex = new AtomicReference<BigInteger>(null);
-    private final AtomicReference<ImmutableMap<K, V>> lastResponse = new AtomicReference<ImmutableMap<K, V>>(ImmutableMap.<K, V>of());
+    private final AtomicReference<ImmutableMap<K, V>> lastResponse = new AtomicReference<ImmutableMap<K, V>>(null);
     private final AtomicReference<State> state = new AtomicReference<State>(State.latent);
     private final CountDownLatch initLatch = new CountDownLatch(1);
     private final ScheduledExecutorService executorService = Executors.newSingleThreadScheduledExecutor(

src/test/java/com/orbitz/consul/cache/ConsulCacheTest.java

@@ -25,6 +25,7 @@
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.fail;
 
 public class ConsulCacheTest extends BaseIntegrationTest {
@@ -188,11 +189,11 @@ public void notify(Map<String, Value> newValues) {
             Thread.sleep(100);
         }
 
-        assertEquals(5, events.size());
+        assertEquals(6, events.size());
 
-        for (int i = 0; i < 5; i++) {
+        for (int i = -1; i < 5; i++) {
 
-            Map<String, Value> map = events.get(i);
+            Map<String, Value> map = events.get(i+1);
             assertEquals(i + 1, map.size());
             for (int j = 0; j < i; j++) {
                 String keyStr = "" + j;
@@ -244,6 +245,36 @@ public void notify(Map<String, Value> newValues) {
         kvClient.deleteKeys(root);
     }
 
+    @Test
+    public void testListenersNonExistingKeys() throws Exception {
+        KeyValueClient kvClient = client.keyValueClient();
+        String root = UUID.randomUUID().toString();
+
+        KVCache nc = KVCache.newCache(
+                kvClient, root, 10
+        );
+
+        final List<Map<String, Value>> events = new ArrayList<Map<String, Value>>();
+        nc.addListener(new ConsulCache.Listener<String, Value>() {
+            @Override
+            public void notify(Map<String, Value> newValues) {
+                events.add(newValues);
+            }
+        });
+
+        nc.start();
+
+        if (!nc.awaitInitialized(1, TimeUnit.SECONDS)) {
+            fail("cache initialization failed");
+        }
+
+        Thread.sleep(100);
+
+        assertEquals(1, events.size());
+        Map<String, Value> map = events.get(0);
+        assertEquals(0, map.size());
+    }
+
     @Test(expected = IllegalStateException.class)
     public void testLifeCycleDoubleStart() throws Exception {
         KeyValueClient kvClient = client.keyValueClient();