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https://issues.apache.org/jira/browse/DBCP-595?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17816463#comment-17816463
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Phil Steitz commented on DBCP-595:
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I am still working through the repro code, but the symptoms don't make sense to
me yet. The stack trace is indicating pool exhaustion, which would mean
clients are holding or abandoning connections. If connections go bad, since
all validation is turned off in the repro code, clients will keep getting bad
connections and their operations will fail; but that does not explain the pool
exhaustion, unless clients are not returning (closing) connections when they
hit the exceptions. Have you tried turning on say testOnReturn? That will
cause bad connections to be closed when they are returned to the pool.
> 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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