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From "Phil Steitz (JIRA)" <j...@apache.org>
Subject [jira] Reopened: (DBCP-291) setting maxWait does not work as expected
Date Wed, 23 Dec 2009 23:41:29 GMT

     [ https://issues.apache.org/jira/browse/DBCP-291?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Phil Steitz reopened DBCP-291:
------------------------------


We need to protect the userkeys map.  The uderlying LRUMap impl is not threadsafe.  I just
got this:

 org.apache.commons.dbcp.SQLNestedException: Could not retrieve connection info from pool
    [junit] 	at org.apache.commons.dbcp.datasources.SharedPoolDataSource.getPooledConnectionAndInfo(SharedPoolDataSource.java:183)
    [junit] 	at org.apache.commons.dbcp.datasources.InstanceKeyDataSource.getConnection(InstanceKeyDataSource.java:680)
    [junit] 	at org.apache.commons.dbcp.datasources.TestSharedPoolDataSource.getConnection(TestSharedPoolDataSource.java:49)
    [junit] 	at org.apache.commons.dbcp.TestConnectionPool.newConnection(TestConnectionPool.java:84)
    [junit] 	at org.apache.commons.dbcp.TestConnectionPool$TestThread.run(TestConnectionPool.java:595)
    [junit] 	at java.lang.Thread.run(Thread.java:613)
    [junit] Caused by: java.lang.NullPointerException
    [junit] 	at org.apache.commons.dbcp.datasources.SequencedHashMap.removeEntry(SequencedHashMap.java:217)
    [junit] 	at org.apache.commons.dbcp.datasources.SequencedHashMap.removeImpl(SequencedHashMap.java:471)
    [junit] 	at org.apache.commons.dbcp.datasources.SequencedHashMap.remove(SequencedHashMap.java:459)
    [junit] 	at org.apache.commons.dbcp.datasources.LRUMap.get(LRUMap.java:97)
    [junit] 	at org.apache.commons.dbcp.datasources.SharedPoolDataSource.getUserPassKey(SharedPoolDataSource.java:203)
    [junit] 	at org.apache.commons.dbcp.datasources.SharedPoolDataSource.getPooledConnectionAndInfo(SharedPoolDataSource.java:172)

The problem is (I think) caused by concurrent modification to the LRUMap.  The get method
modifies the map.



> setting maxWait does not work as expected
> -----------------------------------------
>
>                 Key: DBCP-291
>                 URL: https://issues.apache.org/jira/browse/DBCP-291
>             Project: Commons Dbcp
>          Issue Type: Bug
>            Reporter: Arie
>             Fix For: 1.3
>
>
> My expectation was that if maxWait is set to X seconds and there are N requests waiting
to get a connection (in a case where the pool is bounded and 
> all the connection are used) if none of the used connection gets free than all N requests
will time-out at the same time.
> In reality it seems that 1 request will be timed-out after X seconds the second one after
2 * X and the last one after N * X.
> The problem is that getPooledConnectionAndInfo is synchronized (and therefore will look
all N requests) and only one request will be processed at the time.
> This process includes waiting until freed connection or timed-out (done by commons.pool
GenericKeyedObjectPool).
> I am not sure why the getPooledConnectionAndInfo has to be synchronized and not only
the pool creation part.

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