Merge pull request #79 from nobodyiam/client-refresh-merge

Add client side auto refresh capability

apollo-biz/src/main/java/com/ctrip/apollo/biz/repository/ReleaseRepository.java

@@ -13,8 +13,7 @@ import com.ctrip.apollo.biz.entity.Release;
  */
 public interface ReleaseRepository extends PagingAndSortingRepository<Release, Long> {
 
-  @Query("SELECT r FROM Release r WHERE r.appId = :appId AND r.clusterName = :clusterName AND r.namespaceName = :namespaceName order by r.id desc")
-  Release findLatest(@Param("appId") String appId, @Param("clusterName") String clusterName,
+  Release findFirstByAppIdAndClusterNameAndNamespaceNameOrderByIdDesc(@Param("appId") String appId, @Param("clusterName") String clusterName,
       @Param("namespaceName") String namespaceName);
 
   List<Release> findByAppIdAndClusterNameAndNamespaceName(String appId, String clusterName,

apollo-biz/src/main/java/com/ctrip/apollo/biz/service/ConfigService.java

@@ -30,7 +30,7 @@ public class ConfigService {
   private Type configurationTypeReference = new TypeToken<Map<String, String>>(){}.getType();
 
   public Release findRelease(String appId, String clusterName, String namespaceName) {
-    Release release = releaseRepository.findLatest(appId, clusterName, namespaceName);
+    Release release = releaseRepository.findFirstByAppIdAndClusterNameAndNamespaceNameOrderByIdDesc(appId, clusterName, namespaceName);
     return release;
   }
 

apollo-client/src/main/java/com/ctrip/apollo/Config.java

@@ -12,4 +12,6 @@ public interface Config {
    * @return the property value
    */
   public String getProperty(String key, String defaultValue);
+
+  public void addChangeListener(ConfigChangeListener listener);
 }

apollo-client/src/main/java/com/ctrip/apollo/ConfigChangeListener.java

+package com.ctrip.apollo;
+
+import com.ctrip.apollo.model.ConfigChangeEvent;
+
+/**
+ * @author Jason Song(song_s@ctrip.com)
+ */
+public interface ConfigChangeListener {
+  public void onChange(ConfigChangeEvent changeEvent);
+}

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

+package com.ctrip.apollo.internals;
+
+import com.google.common.base.Objects;
+import com.google.common.collect.Lists;
+import com.google.common.collect.Sets;
+
+import com.ctrip.apollo.Config;
+import com.ctrip.apollo.ConfigChangeListener;
+import com.ctrip.apollo.enums.PropertyChangeType;
+import com.ctrip.apollo.model.ConfigChange;
+import com.ctrip.apollo.model.ConfigChangeEvent;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.List;
+import java.util.Properties;
+import java.util.Set;
+
+/**
+ * @author Jason Song(song_s@ctrip.com)
+ */
+public abstract class AbstractConfig implements Config {
+  private static final Logger logger = LoggerFactory.getLogger(AbstractConfig.class);
+  private List<ConfigChangeListener> m_listeners = Lists.newCopyOnWriteArrayList();
+
+  @Override
+  public void addChangeListener(ConfigChangeListener listener) {
+    if (!m_listeners.contains(listener)) {
+      m_listeners.add(listener);
+    }
+  }
+
+  protected void fireConfigChange(ConfigChangeEvent changeEvent) {
+    for (ConfigChangeListener listener : m_listeners) {
+      try {
+        listener.onChange(changeEvent);
+      } catch (Throwable t) {
+        logger.error("Failed to invoke config change listener {}", listener.getClass(), t);
+      }
+    }
+  }
+
+  List<ConfigChange> calcPropertyChanges(Properties previous,
+                                         Properties current) {
+    if (previous == null) {
+      previous = new Properties();
+    }
+
+    if (current == null) {
+      current = new Properties();
+    }
+
+    Set<String> previousKeys = previous.stringPropertyNames();
+    Set<String> currentKeys = current.stringPropertyNames();
+
+    Set<String> commonKeys = Sets.intersection(previousKeys, currentKeys);
+    Set<String> newKeys = Sets.difference(currentKeys, commonKeys);
+    Set<String> removedKeys = Sets.difference(previousKeys, commonKeys);
+
+    List<ConfigChange> changes = Lists.newArrayList();
+
+    for (String newKey : newKeys) {
+      changes.add(new ConfigChange(newKey, null, current.getProperty(newKey), PropertyChangeType.NEW));
+    }
+
+    for (String removedKey : removedKeys) {
+      changes.add(new ConfigChange(removedKey, previous.getProperty(removedKey), null,
+          PropertyChangeType.DELETED));
+    }
+
+    for (String commonKey : commonKeys) {
+      String previousValue = previous.getProperty(commonKey);
+      String currentValue = current.getProperty(commonKey);
+      if (Objects.equal(previousValue, currentValue)) {
+        continue;
+      }
+      changes.add(new ConfigChange(commonKey, previousValue,
+          currentValue, PropertyChangeType.MODIFIED));
+    }
+
+    return changes;
+  }
+}

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

+package com.ctrip.apollo.internals;
+
+import com.google.common.collect.Lists;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.List;
+import java.util.Properties;
+
+/**
+ * @author Jason Song(song_s@ctrip.com)
+ */
+public abstract class AbstractConfigRepository implements ConfigRepository {
+  private static final Logger logger = LoggerFactory.getLogger(AbstractConfigRepository.class);
+  private List<RepositoryChangeListener> m_listeners = Lists.newCopyOnWriteArrayList();
+
+  @Override
+  public void addChangeListener(RepositoryChangeListener listener) {
+    if (!m_listeners.contains(listener)) {
+      m_listeners.add(listener);
+    }
+  }
+
+  @Override
+  public void removeChangeListener(RepositoryChangeListener listener) {
+    m_listeners.remove(listener);
+  }
+
+  protected void fireRepositoryChange(String namespace, Properties newProperties) {
+    for (RepositoryChangeListener listener : m_listeners) {
+      try {
+        listener.onRepositoryChange(namespace, newProperties);
+      } catch (Throwable t) {
+        logger.error("Failed to invoke repository change listener {}", listener.getClass(), t);
+      }
+    }
+  }
+}

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

@@ -6,7 +6,19 @@ import java.util.Properties;
  * @author Jason Song(song_s@ctrip.com)
  */
 public interface ConfigRepository {
-  public Properties loadConfig();
+  /**
+   * Get the config from this repository
+   * @return
+   */
+  public Properties getConfig();
 
+  /**
+   * Set the fallback repo for this repository
+   * @param fallbackConfigRepository
+   */
   public void setFallback(ConfigRepository fallbackConfigRepository);
+
+  public void addChangeListener(RepositoryChangeListener listener);
+
+  public void removeChangeListener(RepositoryChangeListener listener);
 }

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

 package com.ctrip.apollo.internals;
 
-import com.ctrip.apollo.Config;
+import com.google.common.collect.ImmutableMap;
+
 import com.ctrip.apollo.core.utils.ClassLoaderUtil;
+import com.ctrip.apollo.enums.PropertyChangeType;
+import com.ctrip.apollo.model.ConfigChange;
+import com.ctrip.apollo.model.ConfigChangeEvent;
 import com.dianping.cat.Cat;
 
 import org.slf4j.Logger;
@@ -9,12 +13,15 @@ import org.slf4j.LoggerFactory;
 
 import java.io.IOException;
 import java.io.InputStream;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
 import java.util.Properties;
 
 /**
  * @author Jason Song(song_s@ctrip.com)
  */
-public class DefaultConfig implements Config {
+public class DefaultConfig extends AbstractConfig implements RepositoryChangeListener {
   private static final Logger logger = LoggerFactory.getLogger(DefaultConfig.class);
   private final String m_namespace;
   private Properties m_resourceProperties;
@@ -30,7 +37,8 @@ public class DefaultConfig implements Config {
 
   private void initialize() {
     try {
-      m_configProperties = m_configRepository.loadConfig();
+      m_configProperties = m_configRepository.getConfig();
+      m_configRepository.addChangeListener(this);
     } catch (Throwable ex) {
       String message = String.format("Init Apollo Local Config failed - namespace: %s",
           m_namespace);
@@ -68,6 +76,69 @@ public class DefaultConfig implements Config {
     return value == null ? defaultValue : value;
   }
 
+  @Override
+  public synchronized void onRepositoryChange(String namespace, Properties newProperties) {
+    if (newProperties.equals(m_configProperties)) {
+      return;
+    }
+    Properties newConfigProperties = new Properties();
+    newConfigProperties.putAll(newProperties);
+
+    Map<String, ConfigChange> actualChanges = updateAndCalcConfigChanges(newConfigProperties);
+
+    this.fireConfigChange(new ConfigChangeEvent(m_namespace, actualChanges));
+  }
+
+  private Map<String, ConfigChange> updateAndCalcConfigChanges(Properties newConfigProperties) {
+    List<ConfigChange> configChanges =
+        calcPropertyChanges(m_configProperties, newConfigProperties);
+//    List<ConfigChange> actualChanges = Lists.newArrayListWithCapacity(configChanges.size());
+
+    ImmutableMap.Builder<String, ConfigChange> actualChanges =
+        new ImmutableMap.Builder<>();
+
+    /** === Double check since DefaultConfig has multiple config sources ==== **/
+
+    //1. use getProperty to update configChanges's old value
+    for (ConfigChange change : configChanges) {
+      change.setOldValue(this.getProperty(change.getPropertyName(), change.getOldValue()));
+    }
+
+    //2. update m_configProperties
+    m_configProperties = newConfigProperties;
+
+    //3. use getProperty to update configChange's new value and calc the final changes
+    for (ConfigChange change : configChanges) {
+      change.setNewValue(this.getProperty(change.getPropertyName(), change.getNewValue()));
+      switch (change.getChangeType()) {
+        case NEW:
+          if (Objects.equals(change.getOldValue(), change.getNewValue())) {
+            break;
+          }
+          if (!Objects.isNull(change.getOldValue())) {
+            change.setChangeType(PropertyChangeType.MODIFIED);
+          }
+          actualChanges.put(change.getPropertyName(), change);
+          break;
+        case MODIFIED:
+          if (!Objects.equals(change.getOldValue(), change.getNewValue())) {
+            actualChanges.put(change.getPropertyName(), change);
+          }
+          break;
+        case DELETED:
+          if (Objects.equals(change.getOldValue(), change.getNewValue())) {
+            break;
+          }
+          if (!Objects.isNull(change.getNewValue())) {
+            change.setChangeType(PropertyChangeType.MODIFIED);
+          }
+          actualChanges.put(change.getPropertyName(), change);
+          break;
+      }
+    }
+    return actualChanges.build();
+  }
+
   private Properties loadFromResource(String namespace) {
     String name = String.format("META-INF/config/%s.properties", namespace);
     InputStream in = ClassLoaderUtil.getLoader().getResourceAsStream(name);
@@ -92,6 +163,4 @@ public class DefaultConfig implements Config {
 
     return properties;
   }
-
-
 }

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

@@ -19,7 +19,7 @@ public class DefaultConfigManager implements ConfigManager {
   @Inject
   private ConfigFactoryManager m_factoryManager;
 
-  private Map<String, Config> m_configs = Maps.newHashMap();
+  private Map<String, Config> m_configs = Maps.newConcurrentMap();
 
   @Override
   public Config getConfig(String namespace) {

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

@@ -22,14 +22,15 @@ import java.util.Properties;
 /**
  * @author Jason Song(song_s@ctrip.com)
  */
-public class LocalFileConfigRepository implements ConfigRepository {
+public class LocalFileConfigRepository extends AbstractConfigRepository
+    implements RepositoryChangeListener {
   private static final Logger logger = LoggerFactory.getLogger(LocalFileConfigRepository.class);
-  private PlexusContainer m_container;
+  private final PlexusContainer m_container;
   private final String m_namespace;
   private final File m_baseDir;
   private final ConfigUtil m_configUtil;
-  private Properties m_fileProperties;
-  private ConfigRepository m_fallback;
+  private volatile Properties m_fileProperties;
+  private volatile ConfigRepository m_fallback;
 
   public LocalFileConfigRepository(File baseDir, String namespace) {
     m_baseDir = baseDir;
@@ -43,7 +44,7 @@ public class LocalFileConfigRepository implements ConfigRepository {
   }
 
   @Override
-  public Properties loadConfig() {
+  public Properties getConfig() {
     if (m_fileProperties == null) {
       initLocalConfig();
     }
@@ -54,26 +55,51 @@ public class LocalFileConfigRepository implements ConfigRepository {
 
   @Override
   public void setFallback(ConfigRepository fallbackConfigRepository) {
+    //clear previous listener
+    if (m_fallback != null) {
+      m_fallback.removeChangeListener(this);
+    }
     m_fallback = fallbackConfigRepository;
+    fallbackConfigRepository.addChangeListener(this);
+  }
+
+  @Override
+  public synchronized void onRepositoryChange(String namespace, Properties newProperties) {
+    if (newProperties.equals(m_fileProperties)) {
+      return;
+    }
+    Properties newFileProperties = new Properties();
+    newFileProperties.putAll(newProperties);
+    this.m_fileProperties = newFileProperties;
+    persistLocalCacheFile(m_baseDir, m_namespace);
+    this.fireRepositoryChange(namespace, newProperties);
   }
 
   void initLocalConfig() {
-    if (m_fallback != null) {
     try {
-        m_fileProperties = m_fallback.loadConfig();
-        //TODO register change listener
-        persistLocalCacheFile(m_baseDir, m_namespace);
-        return;
+      m_fileProperties = this.loadFromLocalCacheFile(m_baseDir, m_namespace);
     } catch (Throwable ex) {
-        logger.error("Load config from fallback loader failed", ex);
-        Cat.logError(ex);
+      logger.error("Load config from local config cache file failed", ex);
+    }
+
+    //TODO check whether properties is expired or should we return after it's synced with fallback?
+    if (m_fileProperties != null) {
+      return;
     }
+
+    if (m_fallback == null) {
+      throw new RuntimeException(
+          "Load config from local config cache failed and there is no fallback repository!");
     }
 
     try {
-      m_fileProperties = this.loadFromLocalCacheFile(m_baseDir, m_namespace);
-    } catch (IOException ex) {
-      throw new RuntimeException("Loading config from local cache file failed", ex);
+      m_fileProperties = m_fallback.getConfig();
+      persistLocalCacheFile(m_baseDir, m_namespace);
+    } catch (Throwable ex) {
+      String message =
+          String.format("Load config from fallback repository %s failed", m_fallback.getClass());
+      logger.error(message, ex);
+      throw new RuntimeException(message, ex);
     }
   }
 

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

@@ -5,6 +5,7 @@ import com.google.common.collect.Lists;
 
 import com.ctrip.apollo.core.dto.ApolloConfig;
 import com.ctrip.apollo.core.dto.ServiceDTO;
+import com.ctrip.apollo.core.utils.ApolloThreadFactory;
 import com.ctrip.apollo.util.ConfigUtil;
 import com.ctrip.apollo.util.http.HttpRequest;
 import com.ctrip.apollo.util.http.HttpResponse;
@@ -18,19 +19,22 @@ import org.unidal.lookup.ContainerLoader;
 
 import java.util.List;
 import java.util.Properties;
+import java.util.concurrent.Executors;
+import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.atomic.AtomicReference;
 
 /**
  * @author Jason Song(song_s@ctrip.com)
  */
-public class RemoteConfigRepository implements ConfigRepository {
+public class RemoteConfigRepository extends AbstractConfigRepository{
   private static final Logger logger = LoggerFactory.getLogger(RemoteConfigRepository.class);
   private PlexusContainer m_container;
-  private ConfigServiceLocator m_serviceLocator;
-  private HttpUtil m_httpUtil;
-  private ConfigUtil m_configUtil;
-  private AtomicReference<ApolloConfig> m_configCache;
-  private String m_namespace;
+  private final ConfigServiceLocator m_serviceLocator;
+  private final HttpUtil m_httpUtil;
+  private final ConfigUtil m_configUtil;
+  private volatile AtomicReference<ApolloConfig> m_configCache;
+  private final String m_namespace;
+  private final ScheduledExecutorService m_executorService;
 
   public RemoteConfigRepository(String namespace) {
     m_namespace = namespace;
@@ -43,12 +47,15 @@ public class RemoteConfigRepository implements ConfigRepository {
     } catch (ComponentLookupException e) {
       throw new IllegalStateException("Unable to load component!", e);
     }
+    this.m_executorService = Executors.newScheduledThreadPool(1,
+            ApolloThreadFactory.create("RemoteConfigRepository", true));
+    this.schedulePeriodicRefresh();
   }
 
   @Override
-  public Properties loadConfig() {
+  public Properties getConfig() {
     if (m_configCache.get() == null) {
-      initRemoteConfig();
+      this.loadRemoteConfig();
     }
     return transformApolloConfigToProperties(m_configCache.get());
   }
@@ -58,8 +65,37 @@ public class RemoteConfigRepository implements ConfigRepository {
     //remote config doesn't need fallback
   }
 
-  private void initRemoteConfig() {
-    m_configCache.set(this.loadApolloConfig());
+  private void schedulePeriodicRefresh() {
+    logger.info("Schedule periodic refresh with interval: {} {}",
+        m_configUtil.getRefreshInterval(), m_configUtil.getRefreshTimeUnit());
+    this.m_executorService.scheduleAtFixedRate(
+        new Runnable() {
+          @Override
+          public void run() {
+            try {
+              loadRemoteConfig();
+            } catch (Throwable ex) {
+              logger.error("Refreshing config failed", ex);
+            }
+          }
+        }, m_configUtil.getRefreshInterval(), m_configUtil.getRefreshInterval(),
+        m_configUtil.getRefreshTimeUnit());
+  }
+
+  synchronized void loadRemoteConfig() {
+    ApolloConfig previous = m_configCache.get();
+    ApolloConfig current = loadApolloConfig();
+
+    //HTTP 304, nothing changed
+    if (previous == current) {
+      return;
+    }
+
+    logger.info("Remote Config changes!");
+
+    m_configCache.set(current);
+
+    this.fireRepositoryChange(m_namespace, this.getConfig());
   }
 
   private Properties transformApolloConfigToProperties(ApolloConfig apolloConfig) {
@@ -72,16 +108,15 @@ public class RemoteConfigRepository implements ConfigRepository {
   private ApolloConfig loadApolloConfig() {
     String appId = m_configUtil.getAppId();
     String cluster = m_configUtil.getCluster();
-    String uri = getConfigServiceUrl();
+    String url = assembleUrl(getConfigServiceUrl(), appId, cluster, m_namespace, m_configCache.get());
 
-    logger.info("Loading config from {}, appId={}, cluster={}, namespace={}", uri, appId, cluster,
-        m_namespace);
-    HttpRequest request =
-        new HttpRequest(assembleUrl(uri, appId, cluster, m_namespace, m_configCache.get()));
+    logger.info("Loading config from {}", url);
+    HttpRequest request = new HttpRequest(url);
 
     try {
       HttpResponse<ApolloConfig> response = m_httpUtil.doGet(request, ApolloConfig.class);
       if (response.getStatusCode() == 304) {
+        logger.info("Config server responds with 304 HTTP status code.");
         return m_configCache.get();
       }
 

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

+package com.ctrip.apollo.internals;
+
+import java.util.Properties;
+
+/**
+ * @author Jason Song(song_s@ctrip.com)
+ */
+public interface RepositoryChangeListener {
+  public void onRepositoryChange(String namespace, Properties newProperties);
+}

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

 package com.ctrip.apollo.internals;
 
-import com.ctrip.apollo.Config;
+import com.google.common.base.Function;
+import com.google.common.collect.Maps;
+
+import com.ctrip.apollo.model.ConfigChange;
+import com.ctrip.apollo.model.ConfigChangeEvent;
 
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import java.util.List;
+import java.util.Map;
 import java.util.Properties;
 
 /**
  * @author Jason Song(song_s@ctrip.com)
  */
-public class SimpleConfig implements Config {
+public class SimpleConfig extends AbstractConfig implements RepositoryChangeListener {
   private static final Logger logger = LoggerFactory.getLogger(SimpleConfig.class);
-  private String m_namespace;
-  private ConfigRepository m_configRepository;
-  private Properties m_configProperties;
+  private final String m_namespace;
+  private final ConfigRepository m_configRepository;
+  private volatile Properties m_configProperties;
 
   public SimpleConfig(String namespace, ConfigRepository configRepository) {
     m_namespace = namespace;
@@ -24,9 +30,10 @@ public class SimpleConfig implements Config {
 
   private void initialize() {
     try {
-      m_configProperties = m_configRepository.loadConfig();
+      m_configProperties = m_configRepository.getConfig();
+      m_configRepository.addChangeListener(this);
     } catch (Throwable ex) {
-      String message = String.format("Init Apollo Remote Config failed - namespace: %s",
+      String message = String.format("Init Apollo Simple Config failed - namespace: %s",
           m_namespace);
       logger.error(message, ex);
       throw new RuntimeException(message, ex);
@@ -38,4 +45,25 @@ public class SimpleConfig implements Config {
     return this.m_configProperties.getProperty(key, defaultValue);
   }
 
+  @Override
+  public synchronized void onRepositoryChange(String namespace, Properties newProperties) {
+    if (newProperties.equals(m_configProperties)) {
+      return;
+    }
+    Properties newConfigProperties = new Properties();
+    newConfigProperties.putAll(newProperties);
+
+    List<ConfigChange> changes = calcPropertyChanges(m_configProperties, newConfigProperties);
+    Map<String, ConfigChange> changeMap = Maps.uniqueIndex(changes,
+        new Function<ConfigChange, String>() {
+          @Override
+          public String apply(ConfigChange input) {
+            return input.getPropertyName();
+          }
+        });
+
+    m_configProperties = newConfigProperties;
+
+    this.fireConfigChange(new ConfigChangeEvent(m_namespace, changeMap));
+  }
 }

apollo-client/src/main/java/com/ctrip/apollo/model/PropertyChange.java → apollo-client/src/main/java/com/ctrip/apollo/model/ConfigChange.java

 package com.ctrip.apollo.model;
 
 
+import com.google.common.base.MoreObjects;
+
 import com.ctrip.apollo.enums.PropertyChangeType;
 
 /**
  * @author Jason Song(song_s@ctrip.com)
  */
-public class PropertyChange {
-  private String propertyName;
-  private Object oldValue;
-  private Object newValue;
+public class ConfigChange {
+  private final String propertyName;
+  private String oldValue;
+  private String newValue;
   private PropertyChangeType changeType;
 
-  public PropertyChange(String propertyName, Object oldValue, Object newValue,
+  public ConfigChange(String propertyName, String oldValue, String newValue,
                       PropertyChangeType changeType) {
     this.propertyName = propertyName;
     this.oldValue = oldValue;
@@ -24,31 +26,38 @@ public class PropertyChange {
     return propertyName;
   }
 
-  public void setPropertyName(String propertyName) {
-    this.propertyName = propertyName;
-  }
-
-  public Object getOldValue() {
+  public String getOldValue() {
     return oldValue;
   }
 
-  public void setOldValue(Object oldValue) {
-    this.oldValue = oldValue;
+  public String getNewValue() {
+    return newValue;
   }
 
-  public Object getNewValue() {
-    return newValue;
+  public PropertyChangeType getChangeType() {
+    return changeType;
   }
 
-  public void setNewValue(Object newValue) {
-    this.newValue = newValue;
+  public void setOldValue(String oldValue) {
+    this.oldValue = oldValue;
   }
 
-  public PropertyChangeType getChangeType() {
-    return changeType;
+  public void setNewValue(String newValue) {
+    this.newValue = newValue;
   }
 
   public void setChangeType(PropertyChangeType changeType) {
     this.changeType = changeType;
   }
+
+  @Override
+  public String toString() {
+    return MoreObjects.toStringHelper(this)
+        .omitNullValues()
+        .add("propertyName", propertyName)
+        .add("oldValue", oldValue)
+        .add("newValue", newValue)
+        .add("changeType", changeType)
+        .toString();
+  }
 }

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

+package com.ctrip.apollo.model;
+
+import java.util.Map;
+import java.util.Set;
+
+/**
+ * @author Jason Song(song_s@ctrip.com)
+ */
+public class ConfigChangeEvent {
+  private final String m_namespace;
+  private final Map<String, ConfigChange> changes;
+
+  public ConfigChangeEvent(String m_namespace,
+                           Map<String, ConfigChange> changes) {
+    this.m_namespace = m_namespace;
+    this.changes = changes;
+  }
+
+  public Set<String> changedKeys() {
+    return changes.keySet();
+  }
+
+  public ConfigChange getChange(String key) {
+    return changes.get(key);
+  }
+
+  /**
+   * Please note that the returned Map is immutable
+   * @return changes
+   */
+  public Map<String, ConfigChange> getChanges() {
+    return changes;
+  }
+
+  public String getNamespace() {
+    return m_namespace;
+  }
+}

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

-package com.ctrip.apollo.model;
-
-import com.google.common.collect.Lists;
-
-import java.util.List;
-import java.util.Properties;
-
-/**
- * @author Jason Song(song_s@ctrip.com)
- */
-public class ConfigRefreshResult {
-  private String m_namespace;
-  private Properties m_properties;
-  private List<PropertyChange> m_changes;
-
-  public ConfigRefreshResult(String namespace, Properties properties) {
-    this.m_namespace = namespace;
-    this.m_properties = properties;
-    m_changes = Lists.newArrayList();
-  }
-
-  public Properties getProperties() {
-    return m_properties;
-  }
-
-  public String getNamespace() {
-    return m_namespace;
-  }
-
-  public List<PropertyChange> getChanges() {
-    return m_changes;
-  }
-
-  public void setChanges(List<PropertyChange> changes) {
-    this.m_changes = changes;
-  }
-
-  public boolean hasChanges() {
-    return !m_changes.isEmpty();
-  }
-}

apollo-client/src/main/java/com/ctrip/apollo/spi/DefaultConfigFactory.java

@@ -33,8 +33,7 @@ public class DefaultConfigFactory implements ConfigFactory {
   }
 
   LocalFileConfigRepository createLocalConfigRepository(String namespace) {
-    LocalFileConfigRepository
-        localFileConfigLoader =
+    LocalFileConfigRepository localFileConfigLoader =
         new LocalFileConfigRepository(m_baseDir, namespace);
     localFileConfigLoader.setFallback(createRemoteConfigRepository(namespace));
     return localFileConfigLoader;

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

@@ -39,18 +39,19 @@ public class HttpUtil {
 
       conn.setRequestMethod("GET");
 
-      if (httpRequest.getConnectTimeout() < 0) {
-        conn.setConnectTimeout(m_configUtil.getConnectTimeout());
-      } else {
-        conn.setConnectTimeout(httpRequest.getConnectTimeout());
+      int connectTimeout = httpRequest.getConnectTimeout();
+      if (connectTimeout < 0) {
+        connectTimeout = m_configUtil.getConnectTimeout();
       }
 
-      if (httpRequest.getReadTimeout() < 0) {
-        conn.setReadTimeout(m_configUtil.getReadTimeout());
-      } else {
-        conn.setReadTimeout(httpRequest.getReadTimeout());
+      int readTimeout = httpRequest.getReadTimeout();
+      if (readTimeout < 0) {
+        readTimeout = m_configUtil.getReadTimeout();
       }
 
+      conn.setConnectTimeout(connectTimeout);
+      conn.setReadTimeout(readTimeout);
+
       conn.connect();
 
       int statusCode = conn.getResponseCode();
@@ -66,7 +67,7 @@ public class HttpUtil {
       }
 
       throw new RuntimeException(
-          String.format("Get operation failed, status code - %d", statusCode));
+          String.format("Get operation failed for %s, status code - %d", httpRequest.getUrl(), statusCode));
 
     } catch (Throwable ex) {
       throw new RuntimeException("Could not complete get operation", ex);

apollo-client/src/test/java/com/ctrip/apollo/ConfigServiceTest.java

@@ -71,6 +71,11 @@ public class ConfigServiceTest extends ComponentTestCase {
 
       return m_namespace + ":" + key;
     }
+
+    @Override
+    public void addChangeListener(ConfigChangeListener listener) {
+
+    }
   }
 
   public static class MockConfigFactory implements ConfigFactory {

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

 package com.ctrip.apollo.internals;
 
 import com.ctrip.apollo.Config;
+import com.ctrip.apollo.ConfigChangeListener;
 import com.ctrip.apollo.spi.ConfigFactory;
 import com.ctrip.apollo.spi.ConfigFactoryManager;
 
@@ -60,6 +61,12 @@ public class DefaultConfigManagerTest extends ComponentTestCase {
             public String getProperty(String key, String defaultValue) {
               return namespace + ":" + key;
             }
+
+            @Override
+            public void addChangeListener(ConfigChangeListener listener) {
+
+            }
+
           };
         }
       };

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

 package com.ctrip.apollo.internals;
 
 import com.google.common.base.Charsets;
+import com.google.common.collect.ImmutableMap;
 import com.google.common.io.Files;
 
+import com.ctrip.apollo.ConfigChangeListener;
 import com.ctrip.apollo.core.utils.ClassLoaderUtil;
+import com.ctrip.apollo.enums.PropertyChangeType;
+import com.ctrip.apollo.model.ConfigChange;
+import com.ctrip.apollo.model.ConfigChangeEvent;
 
 import org.junit.After;
 import org.junit.Before;
 import org.junit.Test;
+import org.mockito.ArgumentCaptor;
 
 import java.io.File;
 import java.util.Properties;
 
 import static org.junit.Assert.assertEquals;
 import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
 
 /**
@@ -69,7 +77,7 @@ public class DefaultConfigTest {
     someProperties = new Properties();
     someProperties.setProperty(someKey, someLocalFileValue);
     someProperties.setProperty(anotherKey, someLocalFileValue);
-    when(configRepository.loadConfig()).thenReturn(someProperties);
+    when(configRepository.getConfig()).thenReturn(someProperties);
 
     //set up resource file
     File resourceFile = new File(someResourceDir, someNamespace + ".properties");
@@ -79,8 +87,7 @@ public class DefaultConfigTest {
     Files.append(System.getProperty("line.separator"), resourceFile, Charsets.UTF_8);
     Files.append(lastKey + "=" + someResourceValue, resourceFile, Charsets.UTF_8);
 
-    DefaultConfig
-            defaultConfig =
+    DefaultConfig defaultConfig =
         new DefaultConfig(someNamespace, configRepository);
 
     String someKeyValue = defaultConfig.getProperty(someKey, null);
@@ -95,4 +102,80 @@ public class DefaultConfigTest {
     assertEquals(someResourceValue, lastKeyValue);
 
   }
+
+  @Test
+  public void testOnRepositoryChange() throws Exception {
+    String someKey = "someKey";
+    String someSystemPropertyValue = "system-property-value";
+
+    String anotherKey = "anotherKey";
+    String someLocalFileValue = "local-file-value";
+
+    String keyToBeDeleted = "keyToBeDeleted";
+    String keyToBeDeletedValue = "keyToBeDeletedValue";
+
+    String yetAnotherKey = "yetAnotherKey";
+    String yetAnotherValue = "yetAnotherValue";
+
+    String yetAnotherResourceValue = "yetAnotherResourceValue";
+    //set up system property
+    System.setProperty(someKey, someSystemPropertyValue);
+
+    //set up config repo
+    someProperties = new Properties();
+    someProperties.putAll(ImmutableMap
+        .of(someKey, someLocalFileValue, anotherKey, someLocalFileValue, keyToBeDeleted,
+            keyToBeDeletedValue, yetAnotherKey, yetAnotherValue));
+    when(configRepository.getConfig()).thenReturn(someProperties);
+
+    //set up resource file
+    File resourceFile = new File(someResourceDir, someNamespace + ".properties");
+    Files.append(yetAnotherKey + "=" + yetAnotherResourceValue, resourceFile, Charsets.UTF_8);
+
+    DefaultConfig defaultConfig =
+        new DefaultConfig(someNamespace, configRepository);
+
+    ConfigChangeListener someListener = mock(ConfigChangeListener.class);
+    defaultConfig.addChangeListener(someListener);
+
+    Properties newProperties = new Properties();
+    String someKeyNewValue = "new-some-value";
+    String anotherKeyNewValue = "another-new-value";
+    String newKey = "newKey";
+    String newValue = "newValue";
+    newProperties.putAll(ImmutableMap
+        .of(someKey, someKeyNewValue, anotherKey, anotherKeyNewValue, newKey, newValue));
+
+    final ArgumentCaptor<ConfigChangeEvent> captor =
+        ArgumentCaptor.forClass(ConfigChangeEvent.class);
+
+    defaultConfig.onRepositoryChange(someNamespace, newProperties);
+
+    verify(someListener, times(1)).onChange(captor.capture());
+
+    ConfigChangeEvent changeEvent = captor.getValue();
+
+    assertEquals(someNamespace, changeEvent.getNamespace());
+    assertEquals(4, changeEvent.getChanges().size());
+
+    ConfigChange anotherKeyChange = changeEvent.getChange(anotherKey);
+    assertEquals(someLocalFileValue, anotherKeyChange.getOldValue());
+    assertEquals(anotherKeyNewValue, anotherKeyChange.getNewValue());
+    assertEquals(PropertyChangeType.MODIFIED, anotherKeyChange.getChangeType());
+
+    ConfigChange yetAnotherKeyChange = changeEvent.getChange(yetAnotherKey);
+    assertEquals(yetAnotherValue, yetAnotherKeyChange.getOldValue());
+    assertEquals(yetAnotherResourceValue, yetAnotherKeyChange.getNewValue());
+    assertEquals(PropertyChangeType.MODIFIED, yetAnotherKeyChange.getChangeType());
+
+    ConfigChange keyToBeDeletedChange = changeEvent.getChange(keyToBeDeleted);
+    assertEquals(keyToBeDeletedValue, keyToBeDeletedChange.getOldValue());
+    assertEquals(null, keyToBeDeletedChange.getNewValue());
+    assertEquals(PropertyChangeType.DELETED, keyToBeDeletedChange.getChangeType());
+
+    ConfigChange newKeyChange = changeEvent.getChange(newKey);
+    assertEquals(null, newKeyChange.getOldValue());
+    assertEquals(newValue, newKeyChange.getNewValue());
+    assertEquals(PropertyChangeType.NEW, newKeyChange.getChangeType());
+  }
 }

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

@@ -8,6 +8,7 @@ import com.ctrip.apollo.util.ConfigUtil;
 import org.junit.After;
 import org.junit.Before;
 import org.junit.Test;
+import org.mockito.ArgumentCaptor;
 import org.unidal.lookup.ComponentTestCase;
 
 import java.io.File;
@@ -16,7 +17,11 @@ import java.util.Properties;
 import static org.hamcrest.core.IsEqual.equalTo;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertThat;
+import static org.mockito.Matchers.eq;
 import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.only;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
 
 /**
@@ -40,7 +45,7 @@ public class LocalFileConfigRepositoryTest extends ComponentTestCase {
     someProperties = new Properties();
     someProperties.setProperty("defaultKey", "defaultValue");
     fallbackRepo = mock(ConfigRepository.class);
-    when(fallbackRepo.loadConfig()).thenReturn(someProperties);
+    when(fallbackRepo.getConfig()).thenReturn(someProperties);
 
     defineComponent(ConfigUtil.class, MockConfigUtil.class);
   }
@@ -83,7 +88,7 @@ public class LocalFileConfigRepositoryTest extends ComponentTestCase {
     Files.write(someKey + "=" + someValue, file, Charsets.UTF_8);
 
     LocalFileConfigRepository localRepo = new LocalFileConfigRepository(someBaseDir, someNamespace);
-    Properties properties = localRepo.loadConfig();
+    Properties properties = localRepo.getConfig();
 
     assertEquals(someValue, properties.getProperty(someKey));
 
@@ -97,7 +102,7 @@ public class LocalFileConfigRepositoryTest extends ComponentTestCase {
 
     localFileConfigRepository.setFallback(fallbackRepo);
 
-    Properties result = localFileConfigRepository.loadConfig();
+    Properties result = localFileConfigRepository.getConfig();
 
     assertThat(
         "LocalFileConfigRepository's properties should be the same as fallback repo's when there is no local cache",
@@ -111,13 +116,13 @@ public class LocalFileConfigRepositoryTest extends ComponentTestCase {
 
     localRepo.setFallback(fallbackRepo);
 
-    Properties someProperties = localRepo.loadConfig();
+    Properties someProperties = localRepo.getConfig();
 
     LocalFileConfigRepository
         anotherLocalRepoWithNoFallback =
         new LocalFileConfigRepository(someBaseDir, someNamespace);
 
-    Properties anotherProperties = anotherLocalRepoWithNoFallback.loadConfig();
+    Properties anotherProperties = anotherLocalRepoWithNoFallback.getConfig();
 
     assertThat(
         "LocalFileConfigRepository should persist local cache files and return that afterwards",
@@ -125,6 +130,30 @@ public class LocalFileConfigRepositoryTest extends ComponentTestCase {
 
   }
 
+  @Test
+  public void testOnRepositoryChange() throws Exception {
+    RepositoryChangeListener someListener = mock(RepositoryChangeListener.class);
+
+    LocalFileConfigRepository localFileConfigRepository =
+        new LocalFileConfigRepository(someBaseDir, someNamespace);
+    localFileConfigRepository.setFallback(fallbackRepo);
+    localFileConfigRepository.addChangeListener(someListener);
+
+    localFileConfigRepository.getConfig();
+
+    Properties anotherProperties = new Properties();
+    anotherProperties.put("anotherKey", "anotherValue");
+
+    localFileConfigRepository.onRepositoryChange(someNamespace, anotherProperties);
+
+    final ArgumentCaptor<Properties> captor = ArgumentCaptor.forClass(Properties.class);
+
+    verify(someListener, times(1)).onRepositoryChange(eq(someNamespace), captor.capture());
+
+    assertEquals(anotherProperties, captor.getValue());
+
+  }
+
   public static class MockConfigUtil extends ConfigUtil {
     @Override
     public String getAppId() {

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

 package com.ctrip.apollo.internals;
 
+import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.Lists;
 import com.google.common.collect.Maps;
 
@@ -13,6 +14,7 @@ import com.ctrip.apollo.util.http.HttpUtil;
 import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;
+import org.mockito.ArgumentCaptor;
 import org.mockito.Mock;
 import org.mockito.runners.MockitoJUnitRunner;
 import org.unidal.lookup.ComponentTestCase;
@@ -22,7 +24,10 @@ import java.util.Map;
 import java.util.Properties;
 
 import static org.junit.Assert.assertEquals;
+import static org.mockito.Matchers.eq;
 import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
 
 /**
@@ -60,7 +65,7 @@ public class RemoteConfigRepositoryTest extends ComponentTestCase {
     when(someResponse.getBody()).thenReturn(someApolloConfig);
 
     RemoteConfigRepository remoteConfigRepository = new RemoteConfigRepository(someNamespace);
-    Properties config = remoteConfigRepository.loadConfig();
+    Properties config = remoteConfigRepository.getConfig();
 
     assertEquals(configurations, config);
   }
@@ -71,7 +76,27 @@ public class RemoteConfigRepositoryTest extends ComponentTestCase {
     when(someResponse.getStatusCode()).thenReturn(500);
 
     RemoteConfigRepository remoteConfigRepository = new RemoteConfigRepository(someNamespace);
-    remoteConfigRepository.loadConfig();
+    remoteConfigRepository.getConfig();
+  }
+
+  @Test
+  public void testRepositoryChangeListener() 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);
+
+    remoteConfigRepository.loadRemoteConfig();
+
+    verify(someListener, times(1)).onRepositoryChange(eq(someNamespace), captor.capture());
+
+    assertEquals(configurations, captor.getValue());
   }
 
   private ApolloConfig assembleApolloConfig(Map<String, String> configurations) {

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

 package com.ctrip.apollo.internals;
 
+import com.google.common.collect.ImmutableMap;
+
+import com.ctrip.apollo.ConfigChangeListener;
+import com.ctrip.apollo.enums.PropertyChangeType;
+import com.ctrip.apollo.model.ConfigChange;
+import com.ctrip.apollo.model.ConfigChangeEvent;
+
 import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;
+import org.mockito.ArgumentCaptor;
 import org.mockito.Mock;
 import org.mockito.runners.MockitoJUnitRunner;
 
 import java.util.Properties;
 
 import static org.junit.Assert.assertEquals;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
 
 /**
@@ -32,7 +43,7 @@ public class SimpleConfigTest {
     String someValue = "someValue";
     someProperties.setProperty(someKey, someValue);
 
-    when(configRepository.loadConfig()).thenReturn(someProperties);
+    when(configRepository.getConfig()).thenReturn(someProperties);
 
     SimpleConfig config = new SimpleConfig(someNamespace, configRepository);
 
@@ -41,8 +52,57 @@ public class SimpleConfigTest {
 
   @Test(expected = RuntimeException.class)
   public void testLoadConfigFromConfigRepositoryError() throws Exception {
-    when(configRepository.loadConfig()).thenThrow(Throwable.class);
+    when(configRepository.getConfig()).thenThrow(Throwable.class);
 
     new SimpleConfig(someNamespace, configRepository);
   }
+
+  @Test
+  public void testOnRepositoryChange() throws Exception {
+    Properties someProperties = new Properties();
+    String someKey = "someKey";
+    String someValue = "someValue";
+    String anotherKey = "anotherKey";
+    String anotherValue = "anotherValue";
+    someProperties.putAll(ImmutableMap.of(someKey, someValue, anotherKey, anotherValue));
+
+    Properties anotherProperties = new Properties();
+    String newKey = "newKey";
+    String newValue = "newValue";
+    String someValueNew = "someValueNew";
+    anotherProperties.putAll(ImmutableMap.of(someKey, someValueNew, newKey, newValue));
+
+    when(configRepository.getConfig()).thenReturn(someProperties);
+
+    ConfigChangeListener someListener = mock(ConfigChangeListener.class);
+
+    SimpleConfig config = new SimpleConfig(someNamespace, configRepository);
+    config.addChangeListener(someListener);
+
+    config.onRepositoryChange(someNamespace, anotherProperties);
+
+    ArgumentCaptor<ConfigChangeEvent> captor = ArgumentCaptor.forClass(ConfigChangeEvent.class);
+
+    verify(someListener, times(1)).onChange(captor.capture());
+
+    ConfigChangeEvent changeEvent = captor.getValue();
+
+    assertEquals(someNamespace, changeEvent.getNamespace());
+    assertEquals(3, changeEvent.getChanges().size());
+
+    ConfigChange someKeyChange = changeEvent.getChange(someKey);
+    assertEquals(someValue, someKeyChange.getOldValue());
+    assertEquals(someValueNew, someKeyChange.getNewValue());
+    assertEquals(PropertyChangeType.MODIFIED, someKeyChange.getChangeType());
+
+    ConfigChange anotherKeyChange = changeEvent.getChange(anotherKey);
+    assertEquals(anotherValue, anotherKeyChange.getOldValue());
+    assertEquals(null, anotherKeyChange.getNewValue());
+    assertEquals(PropertyChangeType.DELETED, anotherKeyChange.getChangeType());
+
+    ConfigChange newKeyChange = changeEvent.getChange(newKey);
+    assertEquals(null, newKeyChange.getOldValue());
+    assertEquals(newValue, newKeyChange.getNewValue());
+    assertEquals(PropertyChangeType.NEW, newKeyChange.getChangeType());
+  }
 }

apollo-client/src/test/java/com/ctrip/apollo/spi/DefaultConfigFactoryTest.java

@@ -40,7 +40,7 @@ public class DefaultConfigFactoryTest extends ComponentTestCase {
     someProperties.setProperty(someKey, someValue);
 
     LocalFileConfigRepository someLocalConfigRepo = mock(LocalFileConfigRepository.class);
-    when(someLocalConfigRepo.loadConfig()).thenReturn(someProperties);
+    when(someLocalConfigRepo.getConfig()).thenReturn(someProperties);
 
     doReturn(someLocalConfigRepo).when(defaultConfigFactory).createLocalConfigRepository(someNamespace);
 

apollo-demo/src/main/java/ApolloConfigDemo.java

 
 import com.ctrip.apollo.Config;
+import com.ctrip.apollo.ConfigChangeListener;
 import com.ctrip.apollo.ConfigService;
+import com.ctrip.apollo.model.ConfigChange;
+import com.ctrip.apollo.model.ConfigChangeEvent;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 import java.io.BufferedReader;
 import java.io.IOException;
@@ -9,16 +15,18 @@ import java.io.InputStreamReader;
 /**
  * @author Jason Song(song_s@ctrip.com)
  */
-public class ApolloConfigDemo {
+public class ApolloConfigDemo implements ConfigChangeListener {
+  private static final Logger logger = LoggerFactory.getLogger(ApolloConfigDemo.class);
   private Config config;
 
   public ApolloConfigDemo() {
     config = ConfigService.getConfig();
+    config.addChangeListener(this);
   }
 
   private String getConfig(String key) {
     String result = config.getProperty(key, "undefined");
-    System.out.println(String.format("Loading key: %s with value: %s", key, result));
+    logger.info(String.format("Loading key: %s with value: %s", key, result));
     return result;
   }
 
@@ -35,4 +43,14 @@ public class ApolloConfigDemo {
       apolloConfigDemo.getConfig(input);
     }
   }
+
+  @Override
+  public void onChange(ConfigChangeEvent changeEvent) {
+    logger.info("Changes for namespace {}", changeEvent.getNamespace());
+    for (ConfigChange change : changeEvent.getChanges().values()) {
+      logger.info("Change - key: {}, oldValue: {}, newValue: {}, changeType: {}",
+          change.getPropertyName(), change.getOldValue(), change.getNewValue(),
+          change.getChangeType());
+    }
+  }
 }