Manually close the entity manager for async requests.

apollo-biz/src/main/java/com/ctrip/apollo/biz/utils/EntityManagerUtil.java

+package com.ctrip.apollo.biz.utils;
+
+import org.springframework.orm.jpa.EntityManagerFactoryAccessor;
+import org.springframework.orm.jpa.EntityManagerFactoryUtils;
+import org.springframework.orm.jpa.EntityManagerHolder;
+import org.springframework.stereotype.Component;
+import org.springframework.transaction.support.TransactionSynchronizationManager;
+
+/**
+ * @author Jason Song(song_s@ctrip.com)
+ */
+@Component
+public class EntityManagerUtil extends EntityManagerFactoryAccessor {
+  /**
+   * close the entity manager.
+   * Use it with caution! This is only intended for use with async request, which Spring won't
+   * close the entity manager until the async request is finished.
+   */
+  public void closeEntityManager() {
+    EntityManagerHolder emHolder = (EntityManagerHolder)
+        TransactionSynchronizationManager.getResource(getEntityManagerFactory());
+    logger.debug("Closing JPA EntityManager in EntityManagerUtil");
+    EntityManagerFactoryUtils.closeEntityManager(emHolder.getEntityManager());
+  }
+}

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

@@ -12,6 +12,7 @@ import com.ctrip.apollo.biz.entity.AppNamespace;
 import com.ctrip.apollo.biz.message.MessageListener;
 import com.ctrip.apollo.biz.message.Topics;
 import com.ctrip.apollo.biz.service.AppNamespaceService;
+import com.ctrip.apollo.biz.utils.EntityManagerUtil;
 import com.ctrip.apollo.core.ConfigConsts;
 import com.ctrip.apollo.core.dto.ApolloConfigNotification;
 import com.dianping.cat.Cat;
@@ -49,6 +50,9 @@ public class NotificationController implements MessageListener {
   @Autowired
   private AppNamespaceService appNamespaceService;
 
+  @Autowired
+  private EntityManagerUtil entityManagerUtil;
+
   @RequestMapping(method = RequestMethod.GET)
   public DeferredResult<ResponseEntity<ApolloConfigNotification>> pollNotification(
       @RequestParam(value = "appId") String appId,
@@ -94,6 +98,13 @@ public class NotificationController implements MessageListener {
                                                 String dataCenter) {
     List<String> publicWatchedKeys = Lists.newArrayList();
     AppNamespace appNamespace = appNamespaceService.findByNamespaceName(namespace);
+    /**
+     * Manually close the entity manager.
+     * Since for async request, Spring won't do so until the request is finished,
+     * which is unacceptable since we are doing long polling - means the db connection would be hold
+     * for a very long time
+     */
+    entityManagerUtil.closeEntityManager();
 
     //check whether the namespace's appId equals to current one
     if (Objects.isNull(appNamespace) || Objects.equals(applicationId, appNamespace.getAppId())) {

apollo-configservice/src/test/java/com/ctrip/apollo/configservice/controller/NotificationControllerTest.java

@@ -7,6 +7,7 @@ import com.google.common.collect.Multimap;
 import com.ctrip.apollo.biz.entity.AppNamespace;
 import com.ctrip.apollo.biz.message.Topics;
 import com.ctrip.apollo.biz.service.AppNamespaceService;
+import com.ctrip.apollo.biz.utils.EntityManagerUtil;
 import com.ctrip.apollo.core.ConfigConsts;
 import com.ctrip.apollo.core.dto.ApolloConfigNotification;
 
@@ -15,6 +16,7 @@ import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.mockito.Mock;
 import org.mockito.runners.MockitoJUnitRunner;
+import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.ResponseEntity;
 import org.springframework.test.util.ReflectionTestUtils;
@@ -39,6 +41,8 @@ public class NotificationControllerTest {
   private String someDataCenter;
   @Mock
   private AppNamespaceService appNamespaceService;
+  @Mock
+  private EntityManagerUtil entityManagerUtil;
   private Multimap<String, DeferredResult<ResponseEntity<ApolloConfigNotification>>>
       deferredResults;
 
@@ -46,6 +50,7 @@ public class NotificationControllerTest {
   public void setUp() throws Exception {
     controller = new NotificationController();
     ReflectionTestUtils.setField(controller, "appNamespaceService", appNamespaceService);
+    ReflectionTestUtils.setField(controller, "entityManagerUtil", entityManagerUtil);
 
     someAppId = "someAppId";
     someCluster = "someCluster";