通信链路故障；使用ClearDB附加组件在Heroku上进行spray.io

Question

我无法维护到ClearDB实例的连接。当我的应用程序第一次运行时，我可以向它发出访问数据库的请求。一两分钟后，如果我提出同样的请求，我会得到一个通信链接失败。以下是我申请的详细信息：

• 使用spray.io的Scala
• 用于DB交互的滑头
• cleardb:在测试这个新应用程序时点火
• 数据源类:com.mchange.v2.c3p0.compopooledDataSource

我联系了ClearDB支持部门，他们告诉我他们不能帮助我，因为他们不直接支持Spray.io，我应该尝试直接从Heroku那里获得帮助。我已经向Heroku发送了一个帮助请求，但并不期待太多，因为我认为那里也不直接支持Spray.io或Slick。我一直在搜索Stackoverflow，也没有运气，所以我现在发布这个。

下面是我在本地复制时得到的完整堆栈跟踪。

java.lang.x:com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

The last packet successfully received from the server was 185,507 milliseconds ago.  The last packet sent successfully to the server was 1 milliseconds ago.
com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

The last packet successfully received from the server was 185,507 milliseconds ago.  The last packet sent successfully to the server was 1 milliseconds ago.
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)[WARN] [01/26/2014 20:48:42.906] [LottoREST-akka.actor.default-dispatcher-4] [akka://LottoREST/user/lotto-service] Request HttpRequest(GET,http://localhost:8080/drawing,List(Cookie: JSESSIONID=4EFAE21258F8AF891C010DD14F9BC3F1, Accept-Language: en-US, en, Accept-Encoding: gzip, deflate, sdch, User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/32.0.1700.77 Safari/537.36, Cache-Control: max-age=0, Connection: keep-alive, Host: localhost:8080),Empty,HTTP/1.1) could not be handled normally

    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
    at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1121)
    at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:3720)
    at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:3609)
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4160)
    at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2617)
    at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2778)
    at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2825)
    at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:2156)
    at com.mysql.jdbc.PreparedStatement.execute(PreparedStatement.java:1379)
    at com.mchange.v2.c3p0.impl.NewProxyPreparedStatement.execute(NewProxyPreparedStatement.java:989)
    at scala.slick.jdbc.StatementInvoker.results(StatementInvoker.scala:34)
    at scala.slick.jdbc.StatementInvoker.elementsTo(StatementInvoker.scala:17)
    at scala.slick.jdbc.Invoker$class.foreach(Invoker.scala:90)
    at scala.slick.jdbc.StatementInvoker.foreach(StatementInvoker.scala:10)
    at scala.slick.jdbc.Invoker$class.build(Invoker.scala:66)
    at scala.slick.jdbc.StatementInvoker.build(StatementInvoker.scala:10)
    at scala.slick.jdbc.Invoker$class.list(Invoker.scala:56)
    at scala.slick.jdbc.StatementInvoker.list(StatementInvoker.scala:10)
    at scala.slick.jdbc.UnitInvoker$class.list(Invoker.scala:150)
    at scala.slick.driver.BasicInvokerComponent$QueryInvoker.list(BasicInvokerComponent.scala:19)
    at com.megalottopools.model.DrawingComponent$Drawings$.findAllDrawings(Drawing.scala:28)
    at com.megalottopools.model.Model.getDrawings(Model.scala:20)
    at com.megalottopools.api.DrawingService$$anonfun$1.apply(DrawingService.scala:27)
    at com.megalottopools.api.DrawingService$$anonfun$1.apply(DrawingService.scala:25)
    at spray.routing.directives.BasicDirectives$$anonfun$mapRequestContext$1$$anonfun$apply$1.apply(BasicDirectives.scala:30)
    at spray.routing.directives.BasicDirectives$$anonfun$mapRequestContext$1$$anonfun$apply$1.apply(BasicDirectives.scala:30)
    at spray.routing.directives.BasicDirectives$$anon$3$$anonfun$happly$1.apply(BasicDirectives.scala:92)
    at spray.routing.directives.BasicDirectives$$anon$3$$anonfun$happly$1.apply(BasicDirectives.scala:92)
    at spray.routing.RouteConcatenation$RouteConcatenation$$anonfun$$tilde$1.apply(RouteConcatenation.scala:30)
    at spray.routing.RouteConcatenation$RouteConcatenation$$anonfun$$tilde$1.apply(RouteConcatenation.scala:29)
    at spray.routing.directives.BasicDirectives$$anonfun$mapRequestContext$1$$anonfun$apply$1.apply(BasicDirectives.scala:30)
    at spray.routing.directives.BasicDirectives$$anonfun$mapRequestContext$1$$anonfun$apply$1.apply(BasicDirectives.scala:30)
    at spray.routing.directives.BasicDirectives$$anon$3$$anonfun$happly$1.apply(BasicDirectives.scala:92)
    at spray.routing.directives.BasicDirectives$$anon$3$$anonfun$happly$1.apply(BasicDirectives.scala:92)
    at spray.routing.RouteConcatenation$RouteConcatenation$$anonfun$$tilde$1.apply(RouteConcatenation.scala:30)
    at spray.routing.RouteConcatenation$RouteConcatenation$$anonfun$$tilde$1.apply(RouteConcatenation.scala:29)
    at spray.routing.RouteConcatenation$RouteConcatenation$$anonfun$$tilde$1.apply(RouteConcatenation.scala:30)
    at spray.routing.RouteConcatenation$RouteConcatenation$$anonfun$$tilde$1.apply(RouteConcatenation.scala:29)
    at spray.routing.directives.BasicDirectives$$anonfun$mapRequestContext$1$$anonfun$apply$1.apply(BasicDirectives.scala:30)
    at spray.routing.directives.BasicDirectives$$anonfun$mapRequestContext$1$$anonfun$apply$1.apply(BasicDirectives.scala:30)
    at spray.routing.directives.ExecutionDirectives$$anonfun$handleExceptions$1$$anonfun$apply$4.apply(ExecutionDirectives.scala:35)
    at spray.routing.directives.ExecutionDirectives$$anonfun$handleExceptions$1$$anonfun$apply$4.apply(ExecutionDirectives.scala:33)
    at spray.routing.HttpServiceBase$class.runSealedRoute$1(HttpService.scala:36)
    at spray.routing.HttpServiceBase$$anonfun$runRoute$1.applyOrElse(HttpService.scala:46)
    at akka.actor.ActorCell.receiveMessage(ActorCell.scala:425)
    at akka.actor.ActorCell.invoke(ActorCell.scala:386)
    at akka.dispatch.Mailbox.processMailbox(Mailbox.scala:230)
    at akka.dispatch.Mailbox.run(Mailbox.scala:212)
    at akka.dispatch.ForkJoinExecutorConfigurator$MailboxExecutionTask.exec(AbstractDispatcher.scala:506)
    at scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260)
    at scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1339)
    at scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979)
    at scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107)
Caused by: java.io.EOFException: Can not read response from server. Expected to read 4 bytes, read 0 bytes before connection was unexpectedly lost.
    at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:3166)
    at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:3620)
    ... 51 more

Answer 1

听起来像是连接超时问题。检查c3p0是否能正确地保持到ClearDB的连接活动。一些DB连接池使用网络ping或运行简单的select语句，如select1来保持连接活动。您可以检查数据库可用的配置选项。为了验证这是一个问题，每隔几秒钟运行一些虚拟的db操作，看看是否在一段时间后得到相同的错误（保持池大小==1)。