Add client side long polling support and server side mock impl

apollo-client/src/main/java/com/ctrip/apollo/internals/ConfigServiceLocator.java

@@ -30,7 +30,7 @@ public class ConfigServiceLocator {
   private Type m_responseType;
 
   /**
-   * Create a config service locator
+   * Create a config service locator.
    */
   public ConfigServiceLocator() {
     List<ServiceDTO> initial = Lists.newArrayList();
@@ -88,8 +88,8 @@ public class ConfigServiceLocator {
     throw new RuntimeException("Get config services failed", exception);
   }
 
-  private void logConfigServicesToCat(List<ServiceDTO> serviceDTOs) {
-    for (ServiceDTO serviceDTO : serviceDTOs) {
+  private void logConfigServicesToCat(List<ServiceDTO> serviceDtos) {
+    for (ServiceDTO serviceDTO : serviceDtos) {
       Cat.logEvent("Apollo.Config.Services", serviceDTO.getHomepageUrl());
     }
   }

apollo-client/src/main/java/com/ctrip/apollo/internals/DefaultConfig.java

@@ -95,7 +95,14 @@ public class DefaultConfig extends AbstractConfig implements RepositoryChangeLis
 
     Map<String, ConfigChange> actualChanges = updateAndCalcConfigChanges(newConfigProperties);
 
+    //check double checked result
+    if (actualChanges.isEmpty()) {
+      return;
+    }
+
     this.fireConfigChange(new ConfigChangeEvent(m_namespace, actualChanges));
+
+    Cat.logEvent("Apollo.Client.ConfigChanges", m_namespace);
   }
 
   private Map<String, ConfigChange> updateAndCalcConfigChanges(Properties newConfigProperties) {

apollo-client/src/main/java/com/ctrip/apollo/internals/LocalFileConfigRepository.java

@@ -120,7 +120,9 @@ public class LocalFileConfigRepository extends AbstractConfigRepository
       updateFileProperties(properties);
     } catch (Throwable ex) {
       Cat.logError(ex);
-      logger.warn("Sync config from fallback repository {} failed, reason: {}", m_fallback.getClass(), ex);
+      logger
+          .warn("Sync config from fallback repository {} failed, reason: {}", m_fallback.getClass(),
+              ex);
     }
   }
 

apollo-client/src/main/java/com/ctrip/apollo/internals/RemoteConfigRepository.java

 package com.ctrip.apollo.internals;
 
+import com.google.common.base.Joiner;
 import com.google.common.base.Strings;
 import com.google.common.collect.Lists;
+import com.google.common.collect.Maps;
+import com.google.common.escape.Escaper;
+import com.google.common.net.UrlEscapers;
 
 import com.ctrip.apollo.core.dto.ApolloConfig;
+import com.ctrip.apollo.core.dto.ApolloConfigNotification;
 import com.ctrip.apollo.core.dto.ServiceDTO;
 import com.ctrip.apollo.core.utils.ApolloThreadFactory;
 import com.ctrip.apollo.util.ConfigUtil;
@@ -22,10 +27,14 @@ import org.unidal.lookup.ContainerLoader;
 
 import java.util.Collections;
 import java.util.List;
+import java.util.Map;
 import java.util.Properties;
+import java.util.Random;
+import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
 import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicReference;
 
 /**
@@ -40,6 +49,7 @@ public class RemoteConfigRepository extends AbstractConfigRepository {
   private volatile AtomicReference<ApolloConfig> m_configCache;
   private final String m_namespace;
   private final ScheduledExecutorService m_executorService;
+  private final AtomicBoolean m_longPollingStopped;
 
   /**
    * Constructor.
@@ -58,10 +68,12 @@ public class RemoteConfigRepository extends AbstractConfigRepository {
       Cat.logError(ex);
       throw new IllegalStateException("Unable to load component!", ex);
     }
+    this.m_longPollingStopped = new AtomicBoolean(false);
     this.m_executorService = Executors.newScheduledThreadPool(1,
         ApolloThreadFactory.create("RemoteConfigRepository", true));
     this.trySync();
     this.schedulePeriodicRefresh();
+    this.scheduleLongPollingRefresh();
   }
 
   @Override
@@ -84,7 +96,10 @@ public class RemoteConfigRepository extends AbstractConfigRepository {
         new Runnable() {
           @Override
           public void run() {
+            Transaction transaction = Cat.newTransaction("Apollo.ConfigService", "periodicRefresh");
             trySync();
+            transaction.setStatus(Message.SUCCESS);
+            transaction.complete();
           }
         }, m_configUtil.getRefreshInterval(), m_configUtil.getRefreshInterval(),
         m_configUtil.getRefreshTimeUnit());
@@ -113,11 +128,11 @@ public class RemoteConfigRepository extends AbstractConfigRepository {
     return result;
   }
 
-
   private ApolloConfig loadApolloConfig() {
     String appId = m_configUtil.getAppId();
     String cluster = m_configUtil.getCluster();
-    Cat.logEvent("Apollo.Client.Config", String.format("%s-%s-%s", appId, cluster, m_namespace));
+    Cat.logEvent("Apollo.Client.ConfigInfo",
+        String.format("%s-%s-%s", appId, cluster, m_namespace));
     int maxRetries = 2;
     Throwable exception = null;
 
@@ -128,7 +143,7 @@ public class RemoteConfigRepository extends AbstractConfigRepository {
 
       for (ServiceDTO configService : randomConfigServices) {
         String url =
-            assembleUrl(configService.getHomepageUrl(), appId, cluster, m_namespace,
+            assembleQueryConfigUrl(configService.getHomepageUrl(), appId, cluster, m_namespace,
                 m_configCache.get());
 
         logger.debug("Loading config from {}", url);
@@ -172,18 +187,19 @@ public class RemoteConfigRepository extends AbstractConfigRepository {
     throw new RuntimeException(message, exception);
   }
 
-  private String assembleUrl(String uri, String appId, String cluster, String namespace,
-                             ApolloConfig previousConfig) {
+  private String assembleQueryConfigUrl(String uri, String appId, String cluster, String namespace,
+                                        ApolloConfig previousConfig) {
+    Escaper escaper = UrlEscapers.urlPathSegmentEscaper();
     String path = "configs/%s/%s";
-    List<String> params = Lists.newArrayList(appId, cluster);
+    List<String> params = Lists.newArrayList(escaper.escape(appId), escaper.escape(cluster));
 
     if (!Strings.isNullOrEmpty(namespace)) {
       path = path + "/%s";
-      params.add(namespace);
+      params.add(escaper.escape(namespace));
     }
     if (previousConfig != null) {
       path = path + "?releaseId=%s";
-      params.add(String.valueOf(previousConfig.getReleaseId()));
+      params.add(escaper.escape(String.valueOf(previousConfig.getReleaseId())));
     }
 
     String pathExpanded = String.format(path, params.toArray());
@@ -193,6 +209,106 @@ public class RemoteConfigRepository extends AbstractConfigRepository {
     return uri + pathExpanded;
   }
 
+  private void scheduleLongPollingRefresh() {
+    final String appId = m_configUtil.getAppId();
+    final String cluster = m_configUtil.getCluster();
+    final ExecutorService longPollingService =
+        Executors.newFixedThreadPool(2,
+            ApolloThreadFactory.create("RemoteConfigRepository-LongPolling", true));
+    longPollingService.submit(new Runnable() {
+      @Override
+      public void run() {
+        doLongPollingRefresh(appId, cluster, longPollingService);
+      }
+    });
+  }
+
+  private void doLongPollingRefresh(String appId, String cluster,
+                                    ExecutorService longPollingService) {
+    final Random random = new Random();
+    ServiceDTO lastServiceDto = null;
+    Transaction transaction = null;
+    while (!m_longPollingStopped.get() && !Thread.currentThread().isInterrupted()) {
+      try {
+        if (lastServiceDto == null) {
+          List<ServiceDTO> configServices = getConfigServices();
+          lastServiceDto = configServices.get(random.nextInt(configServices.size()));
+        }
+
+        String url =
+            assembleLongPollRefreshUrl(lastServiceDto.getHomepageUrl(), appId, cluster,
+                m_namespace, m_configCache.get());
+
+        logger.debug("Long polling from {}", url);
+        HttpRequest request = new HttpRequest(url);
+        //no timeout for read
+        request.setReadTimeout(0);
+
+        transaction = Cat.newTransaction("Apollo.ConfigService", "pollNotification");
+        transaction.addData("Url", url);
+
+        HttpResponse<ApolloConfigNotification> response =
+            m_httpUtil.doGet(request, ApolloConfigNotification.class);
+
+        logger.debug("Long polling response: {}, url: {}", response.getStatusCode(), url);
+        if (response.getStatusCode() == 200) {
+          longPollingService.submit(new Runnable() {
+            @Override
+            public void run() {
+              trySync();
+            }
+          });
+        }
+        transaction.addData("StatusCode", response.getStatusCode());
+        transaction.setStatus(Message.SUCCESS);
+      } catch (Throwable ex) {
+        logger.warn("Long polling failed for appId: {}, cluster: {}, namespace: {}, reason: {}",
+            appId, cluster, m_namespace, ex);
+        lastServiceDto = null;
+        Cat.logError(ex);
+        if (transaction != null) {
+          transaction.setStatus(ex);
+        }
+        try {
+          TimeUnit.SECONDS.sleep(10);
+        } catch (InterruptedException ie) {
+          //ignore
+        }
+      } finally {
+        if (transaction != null) {
+          transaction.complete();
+        }
+      }
+    }
+  }
+
+  private String assembleLongPollRefreshUrl(String uri, String appId, String cluster,
+                                            String namespace,
+                                            ApolloConfig previousConfig) {
+    Escaper escaper = UrlEscapers.urlPathSegmentEscaper();
+    Map<String, String> queryParams = Maps.newHashMap();
+    queryParams.put("appId", escaper.escape(appId));
+    queryParams.put("cluster", escaper.escape(cluster));
+
+    if (!Strings.isNullOrEmpty(namespace)) {
+      queryParams.put("namespace", escaper.escape(namespace));
+    }
+    if (previousConfig != null) {
+      queryParams.put("releaseId", escaper.escape(previousConfig.getReleaseId()));
+    }
+
+    String params = Joiner.on("&").withKeyValueSeparator("=").join(queryParams);
+    if (!uri.endsWith("/")) {
+      uri += "/";
+    }
+
+    return uri + "notifications?" + params;
+  }
+
+  void stopLongPollingRefresh() {
+    this.m_longPollingStopped.compareAndSet(false, true);
+  }
+
   private List<ServiceDTO> getConfigServices() {
     List<ServiceDTO> services = m_serviceLocator.getConfigServices();
     if (services.size() == 0) {

apollo-client/src/main/java/com/ctrip/apollo/internals/SimpleConfig.java

@@ -74,5 +74,7 @@ public class SimpleConfig extends AbstractConfig implements RepositoryChangeList
     m_configProperties = newConfigProperties;
 
     this.fireConfigChange(new ConfigChangeEvent(m_namespace, changeMap));
+
+    Cat.logEvent("Apollo.Client.ConfigChanges", m_namespace);
   }
 }

apollo-client/src/main/java/com/ctrip/apollo/model/ConfigChangeEvent.java

@@ -40,7 +40,8 @@ public class ConfigChangeEvent {
   }
 
   /**
-   * Get the changes. Please note that the returned Map is immutable.
+   * Get the changes as <Key, Change> map.
+   * Please note that the returned Map is immutable.
    * @return changes
    */
   public Map<String, ConfigChange> getChanges() {

apollo-client/src/main/java/com/ctrip/apollo/util/http/HttpUtil.java

@@ -27,20 +27,23 @@ public class HttpUtil {
   private ConfigUtil m_configUtil;
   private Gson gson;
   private String basicAuth;
-  
+
+  /**
+   * Constructor.
+   */
   public HttpUtil() {
     gson = new Gson();
     try {
-      basicAuth =  "Basic " + BaseEncoding.base64().encode("user:".getBytes("UTF-8"));
-    } catch (UnsupportedEncodingException e) {
-      e.printStackTrace();
+      basicAuth = "Basic " + BaseEncoding.base64().encode("user:".getBytes("UTF-8"));
+    } catch (UnsupportedEncodingException ex) {
+      ex.printStackTrace();
     }
   }
 
   /**
    * Do get operation for the http request.
    *
-   * @param httpRequest the request
+   * @param httpRequest  the request
    * @param responseType the response type
    * @return the response
    * @throws RuntimeException if any error happened or response code is neither 200 nor 304
@@ -59,7 +62,7 @@ public class HttpUtil {
   /**
    * Do get operation for the http request.
    *
-   * @param httpRequest the request
+   * @param httpRequest  the request
    * @param responseType the response type
    * @return the response
    * @throws RuntimeException if any error happened or response code is neither 200 nor 304
@@ -76,14 +79,14 @@ public class HttpUtil {
   }
 
   private <T> HttpResponse<T> doGetWithSerializeFunction(HttpRequest httpRequest,
-      Function<String, T> serializeFunction) {
+                                                         Function<String, T> serializeFunction) {
     InputStream is = null;
     try {
       HttpURLConnection conn = (HttpURLConnection) new URL(httpRequest.getUrl()).openConnection();
 
       conn.setRequestMethod("GET");
-      conn.setRequestProperty ("Authorization", basicAuth);
-      
+      conn.setRequestProperty("Authorization", basicAuth);
+
       int connectTimeout = httpRequest.getConnectTimeout();
       if (connectTimeout < 0) {
         connectTimeout = m_configUtil.getConnectTimeout();

apollo-client/src/test/java/com/ctrip/apollo/integration/ConfigIntegrationTest.java

@@ -9,6 +9,7 @@ import com.ctrip.apollo.ConfigChangeListener;
 import com.ctrip.apollo.ConfigService;
 import com.ctrip.apollo.core.ConfigConsts;
 import com.ctrip.apollo.core.dto.ApolloConfig;
+import com.ctrip.apollo.core.dto.ApolloConfigNotification;
 import com.ctrip.apollo.core.utils.ClassLoaderUtil;
 import com.ctrip.apollo.model.ConfigChangeEvent;
 
@@ -196,6 +197,7 @@ public class ConfigIntegrationTest extends BaseIntegrationTest {
 
     config.addChangeListener(new ConfigChangeListener() {
       AtomicInteger counter = new AtomicInteger(0);
+
       @Override
       public void onChange(ConfigChangeEvent changeEvent) {
         //only need to assert once
@@ -220,6 +222,66 @@ public class ConfigIntegrationTest extends BaseIntegrationTest {
     assertEquals(anotherValue, config.getProperty(someKey, null));
   }
 
+  @Test
+  public void testLongPollRefresh() throws Exception {
+    final String someKey = "someKey";
+    final String someValue = "someValue";
+    final String anotherValue = "anotherValue";
+
+    Map<String, String> configurations = Maps.newHashMap();
+    configurations.put(someKey, someValue);
+    ApolloConfig apolloConfig = assembleApolloConfig(configurations);
+    ContextHandler configHandler = mockConfigServerHandler(HttpServletResponse.SC_OK, apolloConfig);
+    ContextHandler pollHandler =
+        mockPollNotificationHandler(50, HttpServletResponse.SC_OK,
+            new ApolloConfigNotification(apolloConfig.getAppId(), apolloConfig.getCluster(),
+                apolloConfig.getNamespace()), false);
+
+    startServerWithHandlers(configHandler, pollHandler);
+
+    Config config = ConfigService.getConfig();
+    assertEquals(someValue, config.getProperty(someKey, null));
+
+    apolloConfig.getConfigurations().put(someKey, anotherValue);
+
+    TimeUnit.MILLISECONDS.sleep(60);
+
+    assertEquals(anotherValue, config.getProperty(someKey, null));
+
+  }
+
+  private ContextHandler mockPollNotificationHandler(final long pollResultTimeOutInMS,
+                                                     final int statusCode,
+                                                     final ApolloConfigNotification result,
+                                                     final boolean failedAtFirstTime) {
+    ContextHandler context = new ContextHandler("/notifications");
+    context.setHandler(new AbstractHandler() {
+      AtomicInteger counter = new AtomicInteger(0);
+
+      @Override
+      public void handle(String target, Request baseRequest, HttpServletRequest request,
+                         HttpServletResponse response) throws IOException, ServletException {
+        if (failedAtFirstTime && counter.incrementAndGet() == 1) {
+          response.setStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
+          baseRequest.setHandled(true);
+          return;
+        }
+
+        try {
+          TimeUnit.MILLISECONDS.sleep(pollResultTimeOutInMS);
+        } catch (InterruptedException e) {
+        }
+
+        response.setContentType("application/json;charset=UTF-8");
+        response.setStatus(statusCode);
+        response.getWriter().println(gson.toJson(result));
+        baseRequest.setHandled(true);
+      }
+    });
+
+    return context;
+  }
+
   private ContextHandler mockConfigServerHandler(final int statusCode, final ApolloConfig result,
                                                  final boolean failedAtFirstTime) {
     ContextHandler context = new ContextHandler("/configs/*");
@@ -237,15 +299,11 @@ public class ConfigIntegrationTest extends BaseIntegrationTest {
 
         response.setContentType("application/json;charset=UTF-8");
         response.setStatus(statusCode);
-
         response.getWriter().println(gson.toJson(result));
-
         baseRequest.setHandled(true);
       }
     });
-
     return context;
-
   }
 
 

apollo-client/src/test/java/com/ctrip/apollo/internals/RemoteConfigRepositoryTest.java

@@ -5,6 +5,7 @@ import com.google.common.collect.Lists;
 import com.google.common.collect.Maps;
 
 import com.ctrip.apollo.core.dto.ApolloConfig;
+import com.ctrip.apollo.core.dto.ApolloConfigNotification;
 import com.ctrip.apollo.core.dto.ServiceDTO;
 import com.ctrip.apollo.util.ConfigUtil;
 import com.ctrip.apollo.util.http.HttpRequest;
@@ -22,6 +23,9 @@ import org.unidal.lookup.ComponentTestCase;
 import java.util.List;
 import java.util.Map;
 import java.util.Properties;
+import java.util.concurrent.TimeUnit;
+
+import javax.servlet.http.HttpServletResponse;
 
 import static org.junit.Assert.assertEquals;
 import static org.mockito.Matchers.eq;
@@ -41,6 +45,8 @@ public class RemoteConfigRepositoryTest extends ComponentTestCase {
   @Mock
   private static HttpResponse<ApolloConfig> someResponse;
   @Mock
+  private static HttpResponse<ApolloConfigNotification> pollResponse;
+  @Mock
   private ConfigUtil someConfigUtil;
 
   @Before
@@ -48,6 +54,8 @@ public class RemoteConfigRepositoryTest extends ComponentTestCase {
     super.setUp();
     someNamespace = "someName";
 
+    when(pollResponse.getStatusCode()).thenReturn(HttpServletResponse.SC_NOT_MODIFIED);
+
     defineComponent(ConfigUtil.class, MockConfigUtil.class);
     defineComponent(ConfigServiceLocator.class, MockConfigServiceLocator.class);
     defineComponent(HttpUtil.class, MockHttpUtil.class);
@@ -65,9 +73,11 @@ public class RemoteConfigRepositoryTest extends ComponentTestCase {
     when(someResponse.getBody()).thenReturn(someApolloConfig);
 
     RemoteConfigRepository remoteConfigRepository = new RemoteConfigRepository(someNamespace);
+
     Properties config = remoteConfigRepository.getConfig();
 
     assertEquals(configurations, config);
+    remoteConfigRepository.stopLongPollingRefresh();
   }
 
   @Test(expected = RuntimeException.class)
@@ -76,6 +86,10 @@ public class RemoteConfigRepositoryTest extends ComponentTestCase {
     when(someResponse.getStatusCode()).thenReturn(500);
 
     RemoteConfigRepository remoteConfigRepository = new RemoteConfigRepository(someNamespace);
+
+    //must stop the long polling before exception occurred
+    remoteConfigRepository.stopLongPollingRefresh();
+
     remoteConfigRepository.getConfig();
   }
 
@@ -102,6 +116,35 @@ public class RemoteConfigRepositoryTest extends ComponentTestCase {
     verify(someListener, times(1)).onRepositoryChange(eq(someNamespace), captor.capture());
 
     assertEquals(newConfigurations, captor.getValue());
+
+    remoteConfigRepository.stopLongPollingRefresh();
+  }
+
+  @Test
+  public void testLongPollingRefresh() throws Exception {
+    Map<String, String> configurations = ImmutableMap.of("someKey", "someValue");
+    ApolloConfig someApolloConfig = assembleApolloConfig(configurations);
+
+    when(someResponse.getStatusCode()).thenReturn(200);
+    when(someResponse.getBody()).thenReturn(someApolloConfig);
+
+    RepositoryChangeListener someListener = mock(RepositoryChangeListener.class);
+    RemoteConfigRepository remoteConfigRepository = new RemoteConfigRepository(someNamespace);
+    remoteConfigRepository.addChangeListener(someListener);
+    final ArgumentCaptor<Properties> captor = ArgumentCaptor.forClass(Properties.class);
+
+    Map<String, String> newConfigurations = ImmutableMap.of("someKey", "anotherValue");
+    ApolloConfig newApolloConfig = assembleApolloConfig(newConfigurations);
+
+    when(pollResponse.getStatusCode()).thenReturn(HttpServletResponse.SC_OK);
+    when(someResponse.getBody()).thenReturn(newApolloConfig);
+
+    TimeUnit.MILLISECONDS.sleep(60);
+
+    remoteConfigRepository.stopLongPollingRefresh();
+
+    verify(someListener, times(1)).onRepositoryChange(eq(someNamespace), captor.capture());
+    assertEquals(newConfigurations, captor.getValue());
   }
 
   private ApolloConfig assembleApolloConfig(Map<String, String> configurations) {
@@ -109,7 +152,7 @@ public class RemoteConfigRepositoryTest extends ComponentTestCase {
     String someClusterName = "cluster";
     String someReleaseId = "1";
     ApolloConfig apolloConfig =
-            new ApolloConfig(someAppId, someClusterName, someNamespace, someReleaseId);
+        new ApolloConfig(someAppId, someClusterName, someNamespace, someReleaseId);
 
     apolloConfig.setConfigurations(configurations);
 
@@ -143,6 +186,13 @@ public class RemoteConfigRepositoryTest extends ComponentTestCase {
   public static class MockHttpUtil extends HttpUtil {
     @Override
     public <T> HttpResponse<T> doGet(HttpRequest httpRequest, Class<T> responseType) {
+      if (httpRequest.getUrl().contains("notifications?")) {
+        try {
+          TimeUnit.MILLISECONDS.sleep(50);
+        } catch (InterruptedException e) {
+        }
+        return (HttpResponse<T>) pollResponse;
+      }
       return (HttpResponse<T>) someResponse;
     }
   }

apollo-configservice/src/main/java/com/ctrip/apollo/configservice/controller/ConfigController.java

@@ -40,7 +40,7 @@ public class ConfigController {
                                   @RequestParam(value = "releaseId", defaultValue = "-1") String clientSideReleaseId,
                                   HttpServletResponse response) throws IOException {
     Release release = configService.findRelease(appId, clusterName, namespace);
-    //TODO if namespace != application, should also query config by namespace and DC?
+    //TODO if namespace != application, should also query config by namespace and DC(default if DC not found)?
     //And if found, should merge config, as well as releaseId -> make releaseId a string?
     if (release == null) {
       response.sendError(HttpServletResponse.SC_NOT_FOUND,

apollo-configservice/src/main/java/com/ctrip/apollo/configservice/controller/NotificationController.java

+package com.ctrip.apollo.configservice.controller;
+
+import com.google.common.collect.HashMultimap;
+import com.google.common.collect.Multimap;
+import com.google.common.collect.Multimaps;
+
+import com.ctrip.apollo.core.ConfigConsts;
+import com.ctrip.apollo.core.dto.ApolloConfigNotification;
+import com.ctrip.apollo.core.utils.ApolloThreadFactory;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RequestMethod;
+import org.springframework.web.bind.annotation.RequestParam;
+import org.springframework.web.bind.annotation.RestController;
+import org.springframework.web.context.request.async.DeferredResult;
+
+import java.util.Random;
+import java.util.concurrent.Executors;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.TimeUnit;
+
+import javax.servlet.http.HttpServletResponse;
+
+/**
+ * @author Jason Song(song_s@ctrip.com)
+ */
+@RestController
+@RequestMapping("/notifications")
+public class NotificationController {
+  private static final Logger logger = LoggerFactory.getLogger(NotificationController.class);
+  private final static long TIMEOUT = 60 * 60 * 1000;//60 MINUTES
+  private final Multimap<String, DeferredResult<ApolloConfigNotification>> deferredResults =
+      Multimaps.synchronizedSetMultimap(HashMultimap.create());
+
+  {
+    startRandomChange();
+  }
+
+  @RequestMapping(method = RequestMethod.GET)
+  public DeferredResult<ApolloConfigNotification> pollNotification(
+      @RequestParam(value = "appId") String appId,
+      @RequestParam(value = "cluster") String cluster,
+      @RequestParam(value = "namespace", defaultValue = ConfigConsts.NAMESPACE_APPLICATION) String namespace,
+      @RequestParam(value = "releaseId", defaultValue = "-1") String clientSideReleaseId,
+      HttpServletResponse response) {
+    DeferredResult<ApolloConfigNotification> deferredResult =
+        new DeferredResult<>(TIMEOUT);
+    String key = assembleKey(appId, cluster, namespace);
+    this.deferredResults.put(key, deferredResult);
+
+    deferredResult.onCompletion(() -> {
+      logger.info("deferred result for {} {} {} completed", appId, cluster, namespace);
+      deferredResults.remove(key, deferredResult);
+    });
+
+    deferredResult.onTimeout(() -> {
+      logger.info("deferred result for {} {} {} timeout", appId, cluster, namespace);
+      response.setStatus(HttpServletResponse.SC_NOT_MODIFIED);
+    });
+
+    logger.info("deferred result for {} {} {} returned", appId, cluster, namespace);
+    return deferredResult;
+  }
+
+  private void startRandomChange() {
+    Random random = new Random();
+    ScheduledExecutorService testService = Executors.newScheduledThreadPool(1,
+        ApolloThreadFactory.create("NotificationController", true));
+    testService.scheduleAtFixedRate((Runnable) () -> deferredResults
+        .entries().stream().filter(entry -> random.nextBoolean()).forEach(entry -> {
+          String[] keys = entry.getKey().split("-");
+          entry.getValue().setResult(new ApolloConfigNotification(keys[0], keys[1], keys[2]));
+        }), 30, 30, TimeUnit.SECONDS);
+  }
+
+  private String assembleKey(String appId, String cluster, String namespace) {
+    return String.format("%s-%s-%s", appId, cluster, namespace);
+  }
+}
+