Tomcat, Hibernate and the java.io.EOFException

Question

Hi,

My Java application, which uses Hibernate and it's hosted by Tomcat 6.0, gets the following exception after a long time of inactivity when it tries to access the DB:

com.mysql.jdbc.CommunicationsException: Communications link failure due to underlying exception: 

** BEGIN NESTED EXCEPTION ** 

java.io.EOFException

STACKTRACE:

java.io.EOFException
    at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:1963)
    at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2375)
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:2874)
    at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1623)
    at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:1715)
    at com.mysql.jdbc.Connection.execSQL(Connection.java:3249)
    at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:1268)
    at com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:1403)
    at org.hibernate.jdbc.AbstractBatcher.getResultSet(AbstractBatcher.java:208)
    at org.hibernate.loader.Loader.getResultSet(Loader.java:1812)
    at org.hibernate.loader.Loader.doQuery(Loader.java:697)
    at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:259)
    at org.hibernate.loader.Loader.doList(Loader.java:2232)
    at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2129)
    at org.hibernate.loader.Loader.list(Loader.java:2124)
    at org.hibernate.loader.hql.QueryLoader.list(QueryLoader.java:401)
    at org.hibernate.hql.ast.QueryTranslatorImpl.list(QueryTranslatorImpl.java:363)
    at org.hibernate.engine.query.HQLQueryPlan.performList(HQLQueryPlan.java:196)
    at org.hibernate.impl.SessionImpl.list(SessionImpl.java:1149)
    at org.hibernate.impl.QueryImpl.list(QueryImpl.java:102)

Any tips?

Thanks

Answer 1

MySQL will close idle connections after 8 hours by default (the wait_timeout). This is a "famous problem" and you'll find many references of it on the internet, for example this one. So either:

• configure tomcat to test connections on borrow using a validationQuery in the datasource configuration:

  <parameter>
    <name>validationQuery</name>
    <value>select 1</value>
  </parameter>
  

• increase MySQL's wait_timeout via my.cnf/my.ini, or by connecting with a command-line SQL client and entering SET GLOBAL wait_timeout=86400, or some other suitable number of seconds.

Note that I'm not aware of all consequences of the second option. If you decide to go the second option way, I'd suggest posting another question to get feedback from MySQL experts.