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From "Karl Wright (JIRA)" <j...@apache.org>
Subject [jira] [Reopened] (CONNECTORS-1202) JDBC connection handling doesn't always recover if connections can go stale
Date Tue, 23 Jun 2015 16:50:00 GMT

     [ https://issues.apache.org/jira/browse/CONNECTORS-1202?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Karl Wright reopened CONNECTORS-1202:
-------------------------------------

User reports the following problem:

"i tested CONNECTORS-1202 (stale connection check) and i encounter a dead lock in the connection
pool when i simulate a database outage. 

I use ManifoldCF 1.7.1 with CONNECOTRS-1202 patch applied an MySQL as Database.

Steps for reproduction :

1. Start ManifoldCF with a limited ConnectionPool Max size of 5
2. When everything is running stop the database
3. Wait for connection exeptions to occur
4. Click around in the ui to start more threads that want to aquire a connection
5. Everything freezes 
6. Start the database
7. Still everything is freezed. no recovery is happening.

As far as i understand the ConnectionPool implementation, the problem is that the activeConnections
counter is not decremented when the DriverManager fails to get a Connection. On every failed
DriverManager.getConnection call the pool gets more and more 'exhausted'. When activeConnections
hits the size limit, threads go to Object.wait(). But notifyAll will never be called because
there is no outstanding connection to return."

> JDBC connection handling doesn't always recover if connections can go stale
> ---------------------------------------------------------------------------
>
>                 Key: CONNECTORS-1202
>                 URL: https://issues.apache.org/jira/browse/CONNECTORS-1202
>             Project: ManifoldCF
>          Issue Type: Bug
>          Components: Framework core
>    Affects Versions: ManifoldCF 1.9, ManifoldCF 2.1
>            Reporter: Karl Wright
>            Assignee: Karl Wright
>             Fix For: ManifoldCF 1.10, ManifoldCF 2.2
>
>         Attachments: CONNECTORS-1202.patch
>
>
> Our connection pool doesn't deal well with JDBC connection handles that go stale because
the database server was shut down.
> This isn't a problem for most databases, but MySQL seems to not have good recovery in
their JDBC driver.



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