嘗試連接到tomcat6上的mysql服務器：java.net.UnknownHostException

Question

我在從Java / scala worker連接到mysql服務器時遇到了一些麻煩。

這是我得到的堆棧跟蹤：

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

它可以正常工作，直到某一點，工作者無法解析主機。 如果我重新啟動工作程序，則它又可以工作了。

重要事項：我能夠從計算機ping主機！

我嘗試使用ipv4代替Djava.net.preferIPv4Stack=true但是ipv4堆棧出現相同的錯誤。

到目前為止我還沒有任何線索！ 感謝您的幫助！

Answer 1

造成此錯誤的原因可能有多種，如果您沒有正確管理連接池，則可能會發生這種情況。 從某種意義上說，如果您自己維護連接池（或說使用apache dhcp之類的東西），則說明您打開的連接太多，導致一切阻塞或無法很好地管理資源。

另一個原因可能是：（這發生在我們一個多月前）。 一次執行太多長查詢時。 我們在過程方面做了一些優化，事情開始起作用（通過禁用讀取鎖）。