正在尝试连接到tomcat6上的mysql服务器: java.net.UnknownHostException

Question

我在从java/scala worker连接到mysql服务器时遇到了一些问题。

下面是我得到的堆栈跟踪：

The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
    at sun.reflect.GeneratedConstructorAccessor25.newInstance(Unknown Source) ~[na:na]
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[na:1.6.0_27]
    at java.lang.reflect.Constructor.newInstance(Constructor.java:532) ~[na:1.6.0_27]
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:411) ~[indexer-worker-1.0-SNAPSHOT-jar-with-dependencies.jar:na]
    at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1121) ~[indexer-worker-1.0-SNAPSHOT-jar-with-dependencies.jar:na]
    at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:355) ~[indexer-worker-1.0-SNAPSHOT-jar-with-dependencies.jar:na]
    at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2479) ~[indexer-worker-1.0-SNAPSHOT-jar-with-dependencies.jar:na]
    at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2516) ~[indexer-worker-1.0-SNAPSHOT-jar-with-dependencies.jar:na]
    at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2301) ~[indexer-worker-1.0-SNAPSHOT-jar-with-dependencies.jar:na]
    at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:834) ~[indexer-worker-1.0-SNAPSHOT-jar-with-dependencies.jar:na]
    at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47) ~[indexer-worker-1.0-SNAPSHOT-jar-with-dependencies.jar:na]
    at sun.reflect.GeneratedConstructorAccessor10.newInstance(Unknown Source) ~[na:na]
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[na:1.6.0_27]
    at java.lang.reflect.Constructor.newInstance(Constructor.java:532) ~[na:1.6.0_27]
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:411) ~[indexer-worker-1.0-SNAPSHOT-jar-with-dependencies.jar:na]
    at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:416) ~[indexer-worker-1.0-SNAPSHOT-jar-with-dependencies.jar:na]
    at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:317) ~[indexer-worker-1.0-SNAPSHOT-jar-with-dependencies.jar:na]
    at java.sql.DriverManager.getConnection(DriverManager.java:620) ~[na:1.6.0_27]
    at java.sql.DriverManager.getConnection(DriverManager.java:200) ~[na:1.6.0_27]
    at listen$IndexTransactionWorkerImpl.run(listen.scala:38) [indexer-worker-1.0-SNAPSHOT-jar-with-dependencies.jar:na]
    at net.greghaines.jesque.worker.WorkerImpl.execute(WorkerImpl.java:630) [indexer-worker-1.0-SNAPSHOT-jar-with-dependencies.jar:na]
    at net.greghaines.jesque.worker.WorkerImpl.process(WorkerImpl.java:600) [indexer-worker-1.0-SNAPSHOT-jar-with-dependencies.jar:na]
    at net.greghaines.jesque.worker.WorkerImpl.poll(WorkerImpl.java:491) [indexer-worker-1.0-SNAPSHOT-jar-with-dependencies.jar:na]
    at net.greghaines.jesque.worker.WorkerImpl.run(WorkerImpl.java:230) [indexer-worker-1.0-SNAPSHOT-jar-with-dependencies.jar:na]
    at java.lang.Thread.run(Thread.java:679) [na:1.6.0_27]
Caused by: java.net.UnknownHostException: mysql-vip
    at java.net.InetAddress.getAllByName0(InetAddress.java:1229) ~[na:1.6.0_27]
    at java.net.InetAddress.getAllByName(InetAddress.java:1156) ~[na:1.6.0_27]
    at java.net.InetAddress.getAllByName(InetAddress.java:1092) ~[na:1.6.0_27]
    at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:249) ~[indexer-worker-1.0-SNAPSHOT-jar-with-dependencies.jar:na]
    at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:305) ~[indexer-worker-1.0-SNAPSHOT-jar-with-dependencies.jar:na]
    ... 29 common frames omitted

它工作得很好，直到某个点，工作程序无法解析主机。如果我重新启动worker，它将再次工作。

重要的是:我能够从机器上ping到主机！

我尝试在Djava.net.preferIPv4Stack=true中使用ipv4，但我在ipv4堆栈中遇到了同样的错误。

到目前为止我还没有任何线索！谢谢你们的帮助！

Answer 1

这可能有多种原因，如果你没有正确地管理你的连接池，它可能会发生。从某种意义上说，如果你自己维护一个连接池(或者说使用apache dhcp之类的东西)，那么要么你有太多的连接被打开，导致所有东西都被阻塞，要么你没有很好地管理资源。

另一个原因可能是：(它发生在我们一个多月前)。当一次执行过多的长查询时。我们在过程端做了一些优化，事情开始工作了(通过禁用读锁定)。