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From David Blevins <david.blev...@visi.com>
Subject Re: getConnection
Date Mon, 06 Aug 2007 17:51:54 GMT

On Jun 18, 2007, at 11:48 PM, David Blevins wrote:

>
> On Jun 15, 2007, at 9:52 AM, zeperdi wrote:
>
>> Currently, any attempt to open a connection, after the max pool  
>> size is
>> reached, fails immediately. What I wanted was that the  
>> getConnection wait --
>> a configurable number of seconds (connection timeout) -- for a  
>> connection to
>> become available. The getConnection should fail only after the  
>> connection
>> timeout is reached.
>> is that possible?
>
> At the moment we're using older connection management code that  
> doesn't support this, but we are working on getting the Geronimo  
> JCA connection manager in place for JDBC (it's already used for  
> JMS) which would allow you to set the pool size in OpenEJB to the  
> same pool size you DB allows.  Then you'd get the desired behavior  
> of waiting for the timeout you've preconfigured.

FYI, this feature is now in.  We switched to commons-dbcp and  
enhanced it to support transactions.

The following properties are now available on any JDBC <Resource>  
declaration in the openejb.xml:


     # The default auto-commit state of new connections

     DefaultAutoCommit true

     # The default read-only state of new connections
     # If not set then the setReadOnly method will not be called.
     # (Some drivers don't support read only mode, ex: Informix)

     # DefaultReadOnly


     # The default TransactionIsolation state of new connections
     # If not set then the setTransactionIsolation method will not
     # be called. The allowed values for this property are:
     #     NONE
     #     READ_COMMITTED
     #     READ_UNCOMMITTED
     #     REPEATABLE_READ
     #     SERIALIZABLE
     #
     # Note: Most JDBC drivers do not support all isolation levels

     # DefaultTransactionIsolation


     # The initial number of connections that are created when the
     # pool is started

     InitialSize	0

     # The maximum number of active connections that can be
     # allocated from this pool at the same time, or a negative
     # number for no limit.

     MaxActive	20

     # The maximum number of connections that can remain idle in
     # the pool, without extra ones being released, or a negative
     # number for no limit.

     MaxIdle	20

     # The minimum number of connections that can remain idle in
     # the pool, without extra ones being created, or zero to
     # create none.

     MinIdle	0

     # The maximum number of milliseconds that the pool will wait
     # (when there are no available connections) for a connection
     # to be returned before throwing an exception, or -1 to wait
     # indefinitely.

     MaxWait	-1

     # The SQL query that will be used to validate connections from
     # this pool before returning them to the caller. If specified,
     # this query MUST be an SQL SELECT statement that returns at
     # least one row.

     # ValidationQuery

     # If true connections will be validated before being returned
     # from the pool. If the validation fails, the connection is
     # destroyed, and a new conection will be retrieved from the
     # pool (and validated).
     #
     # NOTE - for a true value to have any effect, the
     # ValidationQuery parameter must be set.

     TestOnBorrow	true

     # If true connections will be validated before being returned
     # to the pool.  If the validation fails, the connection is
     # destroyed instead of being returned to the pool.
     #
     # NOTE - for a true value to have any effect, the
     # ValidationQuery parameter must be set.

     TestOnReturn	false

     # If true connections will be validated by the idle connection
     # evictor (if any). If the validation fails, the connection is
     # destroyed and removed from the pool
     #
     # NOTE - for a true value to have any effect, the
     # timeBetweenEvictionRunsMillis property must be a positive
     # number and the ValidationQuery parameter must be set.

     TestWhileIdle	false

     # The number of milliseconds to sleep between runs of the idle
     # connection evictor thread. When set to a negative number, no
     # idle connection evictor thread will be run.

     TimeBetweenEvictionRunsMillis	-1

     # The number of connectionss to examine during each run of the
     # idle connection evictor thread (if any).

     NumTestsPerEvictionRun	3

     # The minimum amount of time a connection may sit idle in the
     # pool before it is eligable for eviction by the idle
     # connection evictor (if any).

     MinEvictableIdleTimeMillis	1800000

     # If true, a statement pool is created for each Connection and
     # PreparedStatements created by one of the following methods are
     # pooled:
     #    public PreparedStatement prepareStatement(String sql);
     #    public PreparedStatement prepareStatement(String sql,
     #            int resultSetType,
     #            int resultSetConcurrency)

     PoolPreparedStatements false

     # The maximum number of open statements that can be allocated
     # from the statement pool at the same time, or zero for no
     # limit.
     #
     # NOTE - Some drivers have limits on the number of open
     # statements, so make sure there are some resources left
     # for the other (non-prepared) statements.

     MaxOpenPreparedStatements 0

     # If true the raw physical connection to the database can be
     # accessed using the following construct:
     #     Connection conn = ds.getConnection();
     #     Connection rawConn = ((DelegatingConnection)  
conn).getInnermostDelegate();
     #     ...
     #     conn.close()
     #
     # Default is false, because misbehaving programs can do harmfull
     # things to the raw connection shuch as closing the raw
     # connection or continuing to use the raw connection after it
     # has been assigned to another logical connection.  Be carefull
     # and only use when you need direct access to driver specific
     # extentions.
     #
     # NOTE: Do NOT close the underlying connection, only the
     # original logical connection wrapper.

     AccessToUnderlyingConnectionAllowed	false



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