与 App Engine 兼容的 JDBC 连接池

Question

注意：我知道 this 线程，但它已经很老了，而且该解决方案对我不起作用。

我正在使用 App Engine 和 Cloud SQL，我想在应用程序的所有当前用户之间共享一个开放连接池。我尝试了几种连接池实现，它们都可以与本地开发服务器完美配合，但是，当部署到云时，它们会失败。我想原因是 App Engine 受限的“沙盒”环境。有人知道在 App Engine 上工作的 JDBC 连接池吗？

Apache Commons DBCP

...
Caused by: java.lang.NoClassDefFoundError: Could not initialize class org.apache.commons.dbcp2.PoolableConnection
at com.google.appengine.runtime.Request.process-a49d46300800d0ca(Request.java)
at org.apache.commons.dbcp2.PoolableConnectionFactory.makeObject(PoolableConnectionFactory.java:254)
at org.apache.commons.dbcp2.BasicDataSource.validateConnectionFactory(BasicDataSource.java:2162)
at org.apache.commons.dbcp2.BasicDataSource.createPoolableConnectionFactory(BasicDataSource.java:2148)
at org.apache.commons.dbcp2.BasicDataSource.createDataSource(BasicDataSource.java:1903)
at org.apache.commons.dbcp2.BasicDataSource$PaGetConnection.run(BasicDataSource.java:2267)
at org.apache.commons.dbcp2.BasicDataSource$PaGetConnection.run(BasicDataSource.java:2263)
at java.security.AccessController.doPrivileged(AccessController.java:63)
at org.apache.commons.dbcp2.BasicDataSource.getConnection(BasicDataSource.java:1404)
...

Tomcat JDBC 连接池

...
Caused by: java.lang.SecurityException: Unable to get members for class org.apache.tomcat.jdbc.pool.DataSource

...

Caused by: java.lang.reflect.InvocationTargetException
at sun.reflect.GeneratedMethodAccessor9.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
... 45 more
Caused by: java.lang.NoClassDefFoundError: javax/management/MalformedObjectNameException
at java.lang.Class.getDeclaredMethods0(Native Method)
at java.lang.Class.privateGetDeclaredMethods(Class.java:2517)
... 45 more
Caused by: java.lang.ClassNotFoundException: javax.management.MalformedObjectNameException
... 45 more

HikariCP

...
java.security.AccessControlException: access denied ("java.lang.RuntimePermission" "modifyThreadGroup")
at java.security.AccessControlContext.checkPermission(AccessControlContext.java:375)
at java.security.AccessController.checkPermission(AccessController.java:565)
at java.lang.SecurityManager.checkPermission(SecurityManager.java:549)
at java.lang.ThreadGroup.checkAccess(ThreadGroup.java:315)
at java.lang.Thread.init(Thread.java:378)
at java.lang.Thread.<init>(Thread.java:527)
at com.zaxxer.hikari.util.DefaultThreadFactory.newThread(DefaultThreadFactory.java:32)
at java.util.concurrent.ThreadPoolExecutor$Worker.<init>(ThreadPoolExecutor.java:591)
at java.util.concurrent.ThreadPoolExecutor.addWorker(ThreadPoolExecutor.java:922)
at java.util.concurrent.ThreadPoolExecutor.ensurePrestart(ThreadPoolExecutor.java:1591)
at java.util.concurrent.ScheduledThreadPoolExecutor.delayedExecute(ScheduledThreadPoolExecutor.java:305)
at java.util.concurrent.ScheduledThreadPoolExecutor.scheduleAtFixedRate(ScheduledThreadPoolExecutor.java:542)
at com.zaxxer.hikari.pool.HikariPool.<init>(HikariPool.java:161)
at com.zaxxer.hikari.pool.HikariPool.<init>(HikariPool.java:114)
at com.zaxxer.hikari.HikariDataSource.getConnection(HikariDataSource.java:102)
...

Vibur DBCP

...
Caused by: java.security.AccessControlException: access denied ("java.lang.RuntimePermission" "modifyThreadGroup")
at java.security.AccessControlContext.checkPermission(AccessControlContext.java:375)
at java.security.AccessController.checkPermission(AccessController.java:565)
at java.lang.SecurityManager.checkPermission(SecurityManager.java:549)
at java.lang.ThreadGroup.checkAccess(ThreadGroup.java:315)
at java.lang.Thread.init(Thread.java:378)
at java.lang.Thread.<init>(Thread.java:448)
at org.vibur.objectpool.reducer.SamplingPoolReducer.<init>(SamplingPoolReducer.java:78)
at org.vibur.dbcp.pool.PoolOperations$PoolReducer.<init>(PoolOperations.java:88)
at org.vibur.dbcp.pool.PoolOperations$PoolReducer.<init>(PoolOperations.java:86)
at org.vibur.dbcp.pool.PoolOperations.<init>(PoolOperations.java:79)
at org.vibur.dbcp.ViburDBCPDataSource.start(ViburDBCPDataSource.java:197)
....

c3p0

...
Caused by: java.security.AccessControlException: access denied ("java.lang.RuntimePermission" "modifyThreadGroup")
at java.security.AccessControlContext.checkPermission(AccessControlContext.java:375)
at java.security.AccessController.checkPermission(AccessController.java:565)
at java.lang.SecurityManager.checkPermission(SecurityManager.java:549)
at java.lang.ThreadGroup.checkAccess(ThreadGroup.java:315)
at java.lang.Thread.init(Thread.java:378)
at java.lang.Thread.<init>(Thread.java:487)
...

Answer 1

您可能会收到 AccessControlException，因为您的应用程序设置为“自动缩放”。

过去，GAE 应用程序可以是“后端”或“前端”，并且只有后端可以使用后台线程。现在不推荐使用后端并替换为模块，后台线程的使用与应用程序的缩放类型相关。

https://cloud.google.com/appengine/docs/java/modules/#Java_Background_threads

Answer 2

我不得不使用 Tomcat DBCP 1.4（旧版本），因为 GAE 前端不允许线程存在于请求范围之外。这是一个示例项目： https://github.com/kennberg/appengine-java-connection-pool

请注意，一旦您有太多请求，连接池是必需的，因为每个实例的挂起连接数是有限制的。重复使用连接有助于保持在限制范围内。

Answer 3

您可能根本不需要连接池：

https://cloud.google.com/sql/faq#connections

...如果创建新连接的时间与测试 if 的时间大致相同 现有连接处于活动状态并重用它，那么我们建议 您创建一个新连接来服务每个 HTTP 请求，并重用它 在请求期间。特别是，后一种情况可能 当您从 Google App Engine 连接到 Google Cloud SQL 时应用。