使用C3P0时如何修复'com.mchange.v2.resourcepool.TimeoutException'

Question

我使用了c3p0-0.9.1.1.jar。数据库是Vertica。
最多有12个并发线程。所以我将minPoolSize设置为12，maxPoolSize设置为24，initialPoolSize设置为12。
我有连接问题。多数情况下，它运行良好，但有时却不行。这是错误：

    java.util.concurrent.ExecutionException: org.springframework.jdbc.CannotGetJdbcConnectionException: Could not get JDBC Connection; nested exception is java.sql.SQLException: An attempt by a client to checkout a Connection has timed out.
        at java.util.concurrent.FutureTask.report(FutureTask.java:122)
        at java.util.concurrent.FutureTask.get(FutureTask.java:206)
        ...
        at com.cmb.mr.mc.scheduler.ScheduledTasks.largePoolTask(ScheduledTasks.java:48)
        at sun.reflect.GeneratedMethodAccessor117.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:498)
        at org.springframework.scheduling.support.ScheduledMethodRunnable.run(ScheduledMethodRunnable.java:65)
        at org.springframework.scheduling.support.DelegatingErrorHandlingRunnable.run(DelegatingErrorHandlingRunnable.java:54)
        at org.springframework.scheduling.concurrent.ReschedulingRunnable.run(ReschedulingRunnable.java:81)
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
        at java.util.concurrent.FutureTask.run(FutureTask.java:266)
        at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:180)
        at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
        at java.lang.Thread.run(Thread.java:748)
    Caused by: org.springframework.jdbc.CannotGetJdbcConnectionException: Could not get JDBC Connection; nested exception is java.sql.SQLException: An attempt by a client to checkout a Connection has timed out.
        at org.springframework.jdbc.datasource.DataSourceUtils.getConnection(DataSourceUtils.java:80)
        at org.springframework.jdbc.core.JdbcTemplate.execute(JdbcTemplate.java:394)
        at org.springframework.jdbc.core.JdbcTemplate.query(JdbcTemplate.java:474)
        at org.springframework.jdbc.core.JdbcTemplate.queryForRowSet(JdbcTemplate.java:515)
        ...
    ... 3 more
    Caused by: java.sql.SQLException: An attempt by a client to checkout a Connection has timed out.
        at com.mchange.v2.sql.SqlUtils.toSQLException(SqlUtils.java:106)
        at com.mchange.v2.sql.SqlUtils.toSQLException(SqlUtils.java:65)
        at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:527)
        at com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource.getConnection(AbstractPoolBackedDataSource.java:128)
        at org.springframework.jdbc.datasource.DataSourceUtils.doGetConnection(DataSourceUtils.java:111)
        at org.springframework.jdbc.datasource.DataSourceUtils.getConnection(DataSourceUtils.java:77)
    ... 27 more
    Caused by: com.mchange.v2.resourcepool.TimeoutException: A client timed out while waiting to acquire a resource from com.mchange.v2.resourcepool.BasicResourcePool@3956dfb1 -- timeout at awaitAvailable()
        at com.mchange.v2.resourcepool.BasicResourcePool.awaitAvailable(BasicResourcePool.java:1317)
        at com.mchange.v2.resourcepool.BasicResourcePool.prelimCheckoutResource(BasicResourcePool.java:557)
        at com.mchange.v2.resourcepool.BasicResourcePool.checkoutResource(BasicResourcePool.java:477)
        at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:525)
    ... 30 more

---

配置：

    <bean id="dataSourceP" class="com.mchange.v2.c3p0.ComboPooledDataSource"
      destroy-method="close">
    <property name="driverClass" value="com.vertica.jdbc.Driver" />

    <property name="jdbcUrl" value="jdbc:vertica://${Url}/${Db}" />
    <property name="user" value="${User}" />
    <property name="password" value="${Password}" />
    <property name="idleConnectionTestPeriod" value="600"/>
    <property name="breakAfterAcquireFailure" value="false"/>
    <property name="acquireRetryAttempts" value="0"/>
    <property name="checkoutTimeout" value="5000"/>
    <property name="minPoolSize" value="12"/>
    <property name="maxPoolSize" value="24"/>
    <property name="initialPoolSize" value="12"/>
    <property name="maxIdleTime" value="60"/>
</bean>

<bean id="jdbcTemplate" class="org.springframework.jdbc.core.JdbcTemplate">
    <constructor-arg ref="dataSourceP"/>
</bean>

能否请您提供一些解决方法的提示？