试图连接到tomcat6上的mysql服务器：java.net.UnknownHostException答案

【问题标题】：trying to connect to the mysql server on tomcat6: java.net.UnknownHostException试图连接到tomcat6上的mysql服务器：java.net.UnknownHostException
【发布时间】：2013-09-02 07:40:41
【问题描述】：

我在从我的 java/scala worker 连接到我的 mysql 服务器时遇到了一些麻烦。

这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

它工作正常，直到某个点，工作人员无法解析主机。如果我重新启动工作器，它会再次工作。

重要的是：我可以从机器上 ping 主机！

我尝试将 ipv4 与 Djava.net.preferIPv4Stack=true 一起使用，但在使用 ipv4 堆栈时遇到了同样的错误。

到目前为止我还没有任何线索！谢谢你们的帮助！

【问题讨论】：

您是否已经尝试使用主机名而不是 IP 地址？
@Ankit ip 地址是动态的，我只能使用 mysql-vip 的主机名（可以从机器上ping）
您是否尝试过使用完全限定的主机名而不仅仅是“mysql-vip”？域搜索路径可能有问题。
好的，只是为了确认你使用这个模式对吗??jdbc:mysql://[host][,failoverhost...][:port]/[database]
我正要请您检查解析器 conf 文件中的主机条目。可惜！！！这确实是一个有趣的问题。

标签： java mysql exception tomcat6

【解决方案1】：

这可能有多种原因如果您没有正确管理连接池，可能会发生这种情况。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 或其他东西），那么要么你打开了太多的连接，所以一切都被阻塞了，要么没有很好地管理资源。

另一个原因可能是：（一个多月前发生在我们身上）。当一次执行太多长查询时。我们在程序方面做了一些优化，事情开始起作用了（通过禁用读锁）。

【讨论】：