Fix race condition when IoT message arrives immediately after subscribe (#2794)

Author: schuenadel

aws-android-sdk-iot/src/main/java/com/amazonaws/mobileconnectors/iot/AWSIotMqttManager.java

@@ -1477,6 +1477,9 @@ public void subscribeToTopic(final String topic, final AWSIotMqttQos qos,
 
         if (null != mqttClient) {
             try {
+                final AWSIotMqttTopic topicModel = new AWSIotMqttTopic(topic, qos, callback);
+                topicListeners.put(topic, topicModel);
+
                 if (subscriptionStatusCallback != null) {
                     mqttClient.subscribe(topic, qos.asInt(), null, new IMqttActionListener() {
                         @Override
@@ -1495,14 +1498,14 @@ public void onFailure(IMqttToken asyncActionToken, Throwable exception) {
                     mqttClient.subscribe(topic, qos.asInt());
                 }
             } catch (final MqttException e) {
-                if(subscriptionStatusCallback != null) {
+                topicListeners.remove(topic);
+
+                if (subscriptionStatusCallback != null) {
                     subscriptionStatusCallback.onFailure(e);
                 } else {
                     throw new AmazonClientException("Client error when subscribing.", e);
                 }
             }
-            final AWSIotMqttTopic topicModel = new AWSIotMqttTopic(topic, qos, callback);
-            topicListeners.put(topic, topicModel);
         }
     }
 
@@ -2051,4 +2054,4 @@ enum AuthenticationMode {
     public boolean getSessionPresent() {
         return sessionPresent;
     }
-}
+}

aws-android-sdk-iot/src/test/java/com/amazonaws/mobileconnectors/iot/AWSIotMqttManagerTest.java

@@ -1131,6 +1131,48 @@ public void testSubscribeToTopic() throws Exception {
         assertEquals("unit/test/topic" + "test payload", mcb.receivedMessages.get(0));
     }
 
+    @Test
+    public void testSubscribeToTopicWithImmediateMessageArriving() throws Exception {
+        final MockMqttClient mockClient = new MockMqttClient();
+
+        AWSIotMqttManager testClient = new AWSIotMqttManager("test-client",
+                Region.getRegion(Regions.US_EAST_1), TEST_ENDPOINT_PREFIX);
+        testClient.setMqttClient(mockClient);
+
+        KeyStore testKeystore = AWSIotKeystoreHelper.getIotKeystore(CERT_ID, KEYSTORE_PATH,
+                KEYSTORE_NAME, KEYSTORE_PASSWORD);
+        testClient.connect(testKeystore, null);
+
+        TestNewMessageCallback mcb = new TestNewMessageCallback();
+
+        AWSIotMqttSubscriptionStatusCallback subscriptionStatusCallback = new AWSIotMqttSubscriptionStatusCallback() {
+            @Override
+            public void onSuccess() {
+                MqttMessage msg = new MqttMessage();
+                msg.setPayload("test payload".getBytes(StringUtils.UTF8));
+                try {
+                    mockClient.mockCallback.messageArrived("unit/test/topic", msg);
+                } catch (Exception e) {
+                    fail("Could not simulate arriving message: " + e);
+                }
+            }
+
+            @Override
+            public void onFailure(Throwable exception) {
+                fail("Subscribing failed while simulate arriving message: " + exception);
+            }
+        };
+
+        testClient.subscribeToTopic("unit/test/topic", AWSIotMqttQos.QOS0, subscriptionStatusCallback, mcb);
+
+        assertEquals(1, mockClient.subscribeCalls);
+        assertTrue(mockClient.mockSubscriptions.containsKey("unit/test/topic"));
+        assertEquals((Integer) 0, mockClient.mockSubscriptions.get("unit/test/topic"));
+
+        assertEquals(1, mcb.receivedMessages.size());
+        assertEquals("unit/test/topic" + "test payload", mcb.receivedMessages.get(0));
+    }
+
     @Test(expected = IllegalArgumentException.class)
     public void testSubscribeToTopicNullTopic() throws Exception {
         MockMqttClient mockClient = new MockMqttClient();