On Fri, 6 Jun 2003 12:41 am, Timothy Bennett wrote:
I recently added the DataSourceSelector block to my Phoenix application,
and now my Phoenix no longer shuts down cleanly.
The problem is that DataSourceComponent objects are hanging. Unfortunately it is difficult to determine where exactly it is but I am willing to bet it is a deadlock in the pooling layer. I would recomend you move to a better tested and supported db pool such as
http://jakarta.apache.org/commons/dbcp/
The only thing that I am aware of that would cause DataSourceComponent to lock is not closing connections you get from it.
JdbcDataSourceComponent uses a hard limiting pool, as our users wanted. That means that the pool will wait for a Connection object to be released back to the pool. Connection objects are released when you call the close() method. If all the connection objects are in use, and none are ever released, then you will experience hanging.
The proper way to do ANY JDBC work (whether you are using it directly, or using a pooling code like DataSourceComponent or DBCP) is to ensure a close in the finally block. Otherwise if an exception is thrown your connection is never closed.
For instance:
Connection conn = null; Statement stmt = null; ResultSet result = null;
try
{
conn = dataSource.getConnection();
stmt = conn.createStatement();
result = stmt.executeQuery("SELECT * FROM foo"); while (result.next())
{
// do stuff
}
}
finally
{
if (null != result) try {result.close();} catch(Exception e){}
if (null != stmt) try {stmt.close();} catch(Exception e){}
if (null != conn) try {conn.close();} catch(Exception e){}
}
This protects you from ideosynchrasies in different vendor's JDBC drivers. For instance, with Oracle you will run out of cursors if you do not ensure your result sets and statements are closed, and with pooling code your connection will never be returned to the pool if that is not closed.
You will continue to see the blocking with DBCP if you have it configured to have a hard limit on the number of connections. That is a requirement if you only have so many connections allowed to you (such as with Oracle, Informix, DB2, etc.).
As to DBCP vs. Excalibur DataSource, they both work and are well tested and used. Cocoon developers have been using Excalibur for a couple years now. It is being actively supported, and if you find a problem we will have a fix for you.
BTW, another source of hanging might be the ThreadPool code used in the Cornerstone ThreadManager which is used by Cornerstone Scheduler.
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