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https://issues.apache.org/jira/browse/DBCP-595?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17817059#comment-17817059
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Dénes Bodó commented on DBCP-595:
---------------------------------
Thank you Phil for your inputs.
I'll go back testing your suggestions and will provide answers for your
questions in one-two days.
> Connection pool can be exhausted when connections are killed on the DB side
> ---------------------------------------------------------------------------
>
> Key: DBCP-595
> URL: https://issues.apache.org/jira/browse/DBCP-595
> Project: Commons DBCP
> Issue Type: Bug
> Affects Versions: 2.11.0
> Reporter: Dénes Bodó
> Priority: Critical
> Labels: deadlock, robustness
>
> Apache Oozie 5.2.1 uses OpenJPA 2.4.2 and commons-dbcp 1.4 and commons-pool
> 1.5.4. These are ancient versions, I know.
> h1. Description
> The issue is that when due to some network issues or "maintenance work" on
> the DB side (especially PostgreSQL) which causes the DB connection to be
> closed, it results exhausted Pool on the client side. Many threads are
> waiting at this point:
> {noformat}
> "pool-2-thread-4" #20 prio=5 os_prio=31 tid=0x00007faf7903b800 nid=0x8603
> waiting on condition [0x000000030f3e7000]
> java.lang.Thread.State: WAITING (parking)
> at sun.misc.Unsafe.park(Native Method)
> - parking to wait for <0x000000066aca8e70> (a
> java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
> at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
> at
> java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)
> at
> org.apache.commons.pool2.impl.LinkedBlockingDeque.takeFirst(LinkedBlockingDeque.java:1324)
> {noformat}
> According to my observation this is because the JDBC driver does not get
> closed on the client side, nor the abstract DBCP connection
> _org.apache.commons.dbcp2.PoolableConnection_ .
> h1. Repro
> (Un)Fortunately I can reproduce the issue using the latest and greatest
> commons-dbcp 2.11.0 and commons-pool 2.12.0 along with OpenJPA 3.2.2.
> I've just created a Java application to reproduce the issue:
> [https://github.com/dionusos/pool_exhausted_repro] . See README.md for
> detailed repro steps.
> h1. Kind of solution?
> To be honest I am not really familiar with DBCP but with this change I
> managed to make my application more robust:
> {code:java}
> diff --git a/src/main/java/org/apache/commons/dbcp2/PoolableConnection.java
> b/src/main/java/org/apache/commons/dbcp2/PoolableConnection.java
> index 440cb756..678550bf 100644
> --- a/src/main/java/org/apache/commons/dbcp2/PoolableConnection.java
> +++ b/src/main/java/org/apache/commons/dbcp2/PoolableConnection.java
> @@ -214,6 +214,10 @@ public class PoolableConnection extends
> DelegatingConnection<Connection> impleme
> @Override
> protected void handleException(final SQLException e) throws SQLException
> {
> fatalSqlExceptionThrown |= isFatalException(e);
> + if (fatalSqlExceptionThrown && getDelegate() != null) {
> + getDelegate().close();
> + this.close();
> + }
> super.handleException(e);
> }{code}
> What do you think about this approach?
> Is it a completely dead-end or we can start working on it in this direction?
> Do you agree that the reported and reproduced issue is a real one and nut
> just some kind of misconfiguration?
>
> I am lost at this point and I need to move forward so I am asking for
> guidance here.
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