Hello,
I am using commons-pool2-2.5.0 for a MySQL connection pooler. The reason
for not using out-of-the-box is that the existing code relies on
changing catalogs at runtime reusing an existing connection. The
original design was to use multiple databases using the same connection
and this cannot be changed.
I recently replaced a lot of hand crafted code with the commons-pool2
implementation.
The issue I have is that one server I manage went into a state where
there are plenty of connections, but none are being returned to the
pool. They are all stuck on a lock inside of
GenericKeyedObjectPool.returnObject.
The config is basically
GenericKeyedObjectPoolConfig config = new
GenericKeyedObjectPoolConfig();
config.setBlockWhenExhausted(true);
config.setMaxTotal(120);
config.setMaxTotalPerKey(60);
config.setTestOnBorrow(true);
config.setTimeBetweenEvictionRunsMillis(60000);
config.setMinEvictableIdleTimeMillis(0); // don't starve
connections because of catalog switches.
/**
* For database connections, use FIFO so that we get rid of
older connections first before newer ones.
*/
config.setLifo(false);
return new GenericKeyedObjectPool<String, PooledConnection>(new
PooledConnectionFactory(), config);
There are 150 of these threads waiting on a lock to release connections
java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for <0x00000006471cd7d8> (a
java.util.concurrent.locks.ReentrantLock$NonfairSync)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
at
java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:836)
at
java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(AbstractQueuedSynchronizer.java:870)
at
java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(AbstractQueuedSynchronizer.java:1199)
at
java.util.concurrent.locks.ReentrantLock$NonfairSync.lock(ReentrantLock.java:209)
at
java.util.concurrent.locks.ReentrantLock.lock(ReentrantLock.java:285)
at
org.apache.commons.pool2.impl.LinkedBlockingDeque.hasTakeWaiters(LinkedBlockingDeque.java:1389)
at
org.apache.commons.pool2.impl.GenericKeyedObjectPool.hasBorrowWaiters(GenericKeyedObjectPool.java:849)
at
org.apache.commons.pool2.impl.GenericKeyedObjectPool.returnObject(GenericKeyedObjectPool.java:551)
at
com.ilrn.util.sql.connectionpooler.ConnectionPooler.releaseConnection(ConnectionPooler.java:358)
at
com.ilrn.util.sql.connectionpooler.PooledConnection.close(PooledConnection.java:141)
at
com.ilrn.util.sql.connectionpooler.ConnectionPooler.safeClose(ConnectionPooler.java:480)
and 158 of these threads waiting to open connections.
java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for <0x00000006471cd7d8> (a
java.util.concurrent.locks.ReentrantLock$NonfairSync)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
at
java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:836)
at
java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(AbstractQueuedSynchronizer.java:870)
at
java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(AbstractQueuedSynchronizer.java:1199)
at
java.util.concurrent.locks.ReentrantLock$NonfairSync.lock(ReentrantLock.java:209)
at
java.util.concurrent.locks.ReentrantLock.lock(ReentrantLock.java:285)
at
org.apache.commons.pool2.impl.LinkedBlockingDeque.pollFirst(LinkedBlockingDeque.java:560)
at
org.apache.commons.pool2.impl.GenericKeyedObjectPool.borrowObject(GenericKeyedObjectPool.java:356)
at
org.apache.commons.pool2.impl.GenericKeyedObjectPool.borrowObject(GenericKeyedObjectPool.java:281)
at
com.ilrn.util.sql.connectionpooler.ConnectionPooler.getConnection(ConnectionPooler.java:197)
at com.ilrn.util.sql.Database.getConnection(Database.java:1273)
For the "- parking to wait for <0x00000006471cd7d8> (a
java.util.concurrent.locks.ReentrantLock$NonfairSync)" there are 155.
Though I see no other messages with that object in the thread dump.
Has anyone run into this? It seems like some sort of deadlock.
--
Bruce Milner
Senior Software Developer (Emberex)
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