The last packet sent successfully to the server was > 70,400,003 milliseconds ago. is longer than the server configured

Question

I have below exception

javax.persistence.PersistenceException: Exception [EclipseLink-4002] (Eclipse Persistence Services - 2.5.2.v20140319-9ad6abd): org.eclipse.persistence.exceptions.DatabaseException Internal Exception: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: The last packet successfully received from the server was 70,400,002 milliseconds ago. The last packet sent successfully to the server was 70,400,003 milliseconds ago. is longer than the server configured value of 'wait_timeout'. You should consider either expiring and/or testing connection validity before use in your application, increasing the server configured values for client timeouts, or using the Connector/J connection property 'autoReconnect=true' to avoid this problem.

I did some research and change persistance.xml to this

Latest

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.1" xmlns="http://xmlns.jcp.org/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd">
  <persistence-unit name="unicorn" transaction-type="RESOURCE_LOCAL">
    <provider>org.hibernate.ejb.HibernatePersistence</provider>
    <class>com.rh.xxx</class>
    <properties>
      <property name="hibernate.connection.driver_class" value="com.mysql.jdbc.Driver"/>
      <property name="hibernate.dialect" value="org.hibernate.dialect.MySQLDialect"/>
      <property name="hibernate.connection.url" value="jdbc:mysql://xxx:3306/unicorndb?zeroDateTimeBehavior=convertToNull"/>
      <property name="hibernate.connection.password" value="xxx"/>
      <property name="hibernate.connection.username" value="student"/>
      <property name="hibernate.c3p0.max_size" value="100" />  <!--max number of JDBC connections -->
      <property name="hibernate.c3p0.min_size" value="10" />   <!--minimum number of JDBC connections-->
      <property name="hibernate.c3p0.idle_test_period" value="500" />
      <property name="hibernate.c3p0.acquire_increment" value="1" />
    </properties>
  </persistence-unit>
</persistence>

Did the latest code looked correct?

Any help would be appreciated

Answer 1

To start, keep your testing simple, just use

<property name="hibernate.c3p0.testConnectionOnCheckout" value="true" />

instead of the idle Connection check. See c3p0 docs on Connection testing

If the problem, um, persists then the issue isn't likely to be Connections held by the pool, but some Connection or Connections that your application is checking out and holding open for an indefinite period. Ideally, Connections should be checked out, used, then checked in immediately (and robustly, using try-with-resources or a careful finally block).