[Mondrian] [Olap4j-devel] connection issues with mondrianOlap4j

Paul Stoellberger p.stoellberger at gmail.com
Fri Jun 10 13:25:37 EDT 2011


Hi,

I was trying all afternoon to come up with a Testcase or even figure out how I could get more debug info from DBCP / Mondrian.
Unfortunately I was not successful at all.

There is no logging in DBCP or mondrian regarding the pool.
I think this issue is related to the internal Pool (RolapConnectionPool) since its happening to JDBC connection as well as JNDI.

Any input on how I could debug / test it would be appreciated.
Otherwise I need to file a bug without any more detailed info.

-Paul


On Jun 8, 2011, at 20:57 , Julian Hyde wrote:

> Sounds like JDBC connections are being taken from the connection pool but
> not returned. The pool is finite: there can be no more than N open
> connections at a time. When they ask for connection N+1 it will block and
> eventually time out.
> 
> The connection leak is likely to be in Mondrian's code, and not your fault.
> Likely there is an error and Mondrian is not returning the connection to the
> pool.
> 
> Keeping olap4j connections open shouldn't be the problem. Mondrian does not
> keep JDBC connections open for the duration of an olap4j connection -- it
> opens & closes them (more precisely borrows & returns them) for each access
> to the database.
> 
> Please log a bug with a testcase. Or maybe there's tracing in dbcp you can
> enable to show the callstack for each of the still-open connections.
> 
> Julian
> 
>> -----Original Message-----
>> From: mondrian-bounces at pentaho.org 
>> [mailto:mondrian-bounces at pentaho.org] On Behalf Of Paul Stoellberger
>> Sent: Wednesday, June 08, 2011 10:12 AM
>> To: olap4j-devel at lists.sourceforge.net; Mondrian developer 
>> mailing list
>> Subject: [Mondrian] connection issues with mondrianOlap4j
>> 
>> Hi,
>> 
>> since quite a while we are experiencing very strange 
>> behaviour on our demo.
>> At some point olap4j / mondrian cant execute any queries anymore.
>> We were initially using normal jdbc based connections for 
>> mondrian / olap4j. Which resulted in "freeze" behaviour 
>> without any info in any log file what went wrong whenever 
>> mondrian tried to execute something on the database
>> 
>> Now with JNDI i get the following exception:
>>        at 
>> mondrian.rolap.RolapConnection.execute(RolapConnection.java:582)
>>        ... 79 more
>> Caused by: org.apache.commons.dbcp.SQLNestedException: Cannot 
>> get a connection, pool error Timeout waiting for idle object
>>        at 
>> org.apache.commons.dbcp.PoolingDataSource.getConnection(Poolin
>> gDataSource.java:104)
>>        at 
>> org.apache.commons.dbcp.BasicDataSource.getConnection(BasicDat
>> aSource.java:880)
>>        at mondrian.rolap.SqlStatement.execute(SqlStatement.java:123)
>>        ... 90 more
>> Caused by: java.util.NoSuchElementException: Timeout waiting 
>> for idle object
>>        at 
>> org.apache.commons.pool.impl.GenericObjectPool.borrowObject(Ge
>> nericObjectPool.java:958)
>>        at 
>> org.apache.commons.dbcp.PoolingDataSource.getConnection(Poolin
>> gDataSource.java:96)
>>        ... 92 more
>> 
>> 
>> In our workflow we create one olap4j connection on server 
>> startup and use that to create new Query objects.
>> We never close any connections, nor remove query objects that 
>> are abandoned by users, we keep them indefinitely at the moment.
>> I was looking at the log files and saw that the error 
>> occurred suddenly, not after a timeout or something. There 
>> was something successfully executed 5 mins before on the database.
>> Mysql doesn't report anything on "SHOW PROCESSLIST", so i'm 
>> assuming the connection pool is not exhausted from the DB 
>> point of view, but rather because of mondrian.
>> 
>> Is there anything in our workflow that could  cause mondrian 
>> to behave like that?
>> Does it not close its jdbc connections?
>> 
>> This error occurs with both, mysql and hsqldb.
>> 
>> I'm running out of ideas what i could do to fix or even debug 
>> this issues.
>> 
>> If anyone has any idea on what I could try, please step forward ;-)
>> 
>> -Paul
>> 
>> _______________________________________________
>> Mondrian mailing list
>> Mondrian at pentaho.org
>> http://lists.pentaho.org/mailman/listinfo/mondrian
>> 
> 
> 
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