c3p0存在严重bug
开发的系统使用了Spring JdbcTemplate + c3p0组合，在做性能测试的时候出现了严重的性能问题。40的并发访问，开始的时候系统正常，等过了几分钟后，应用程序不能访问了。停止40并发的压力后，过1分钟左右又可以正常访问应用程序了，很迷茫。后台log文件有警告信息：
[com.mchange.v2.async.ThreadPoolAsynchronousRunner:435]-[WARN] com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector@4ec5571b -- APPARENT DEADLOCK!!! Complete Status: [num_managed_threads: 10, num_active: 10; activeTasks: com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@7dd9d603 (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#6), com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@68719f81 (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#9), com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@7b9f03b8 (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#7), com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@4ad6470 (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#4), com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@139cf776 (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#0), com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@263a6e09 (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#2), com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@460e247a (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#3), com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@4a7ce984 (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#1), com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@4ec6ff50 (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#5), com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@6aa40597 (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#8); pendingTasks: com.mchange.v2.resourcepool.BasicResourcePool$6@366b3333, com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@37ee752e, com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@84f3bb2, com.mchange.v2.resourcepool.BasicResourcePool$6@9d82761, com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@4e015653, com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@39ca8b27, com.mchange.v2.resourcepool.BasicResourcePool$6@2075cb15, com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@1567e059, com.mchange.v2.resourcepool.BasicResourcePool$6@56b9fe09,
?可以看到AcquireTask占用了内部线程池的所有线程，没有线程可以来执行BasicResourcePool$6对应的任务，而这个任务的作用就是把池外使用完的连接放回池内的，c3p0被挂起了。
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我的解决方法是用单独的线程来处理“归还”连接的任务，因为这个任务的优先级最高，而且耗费的时间很短。
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上传我修改后的 c3p0 jar包，只改了一个文件：BasicResourcePool
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1 楼 qiankun 2012-01-29 很需要的，谢谢，这个真让人头痛