C3p0 APPARENT DEADLOCK异常

Question

我在Tomcat日志中不断收到此异常：

com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector run
WARNING: com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector@76b28200 -- APPARENT DEADLOCK!!! Creating emergency threads for unassigned pending tasks!
com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector run
WARNING: com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector@76b28200 -- APPARENT DEADLOCK!!! Complete Status: 
    Managed Threads: 3
    Active Threads: 3
    Active Tasks: 
        com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@1201fd18 (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#1)
        com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@408f3be4 (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#0)
        com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@7ba516d8 (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#2)
    Pending Tasks: 
        com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@137efe53
        com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@766b0524
Pool thread stack traces:
    Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#1,5,main]
        java.lang.Thread.sleep(Native Method)
        com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask.run(BasicResourcePool.java:1805)
        com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:547)
    Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#0,5,main]
        java.lang.Thread.sleep(Native Method)
        com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask.run(BasicResourcePool.java:1805)
        com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:547)
    Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#2,5,main]
        java.lang.Thread.sleep(Native Method)
        com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask.run(BasicResourcePool.java:1805)
        com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:547)

我正在将Hibernate 3.6.2和C3P0 0.9.1.2与MySQL一起使用。在搜索Google几个小时之后，此APPARENT
DEADLOCK异常似乎通常与准备好的语句缓存相关联。这是我的hibernate.cfg.xml中的C3P0配置：

<propertyname="connection.provider_class">org.hibernate.connection.C3P0ConnectionProvider</property>
<property name="hibernate.c3p0.acquire_increment">5</property>
<property name="hibernate.c3p0.min_size">5</property>
<property name="hibernate.c3p0.max_size">60</property>
<property name="hibernate.c3p0.idle_test_period">120</property>
<property name="hibernate.c3p0.timeout">180</property>              
<property name="hibernate.c3p0.max_statements">0</property>

我不做任何缓存语句。任何关于这里出什么问题的暗示将不胜感激。

Answer 1

脱钩的任务是连接获取任务。也就是说，c3p0尝试从数据库中获取新的连接，而这些连接获取尝试花费了很长时间。

我要做的第一件事是升级到0.9.2.1，这在获取尝试有时会失败的情况下，可以大大改善执行一轮Connection获取的方式。

如果那不能解决您的问题，那么您需要弄清楚为什么c3p0尝试获取连接的尝试长时间挂起了：成功与失败都不会出现异常。