leif 02/02/22 01:26:21
Modified: src/scratchpad/org/apache/avalon/excalibur/datasource
ResourceLimitingJdbcDataSource.java
Log:
Make it possible to set the max-strict flag on the pool.
Based on changes by Mark Woon.
Revision Changes Path
1.6 +85 -42
jakarta-avalon-excalibur/src/scratchpad/org/apache/avalon/excalibur/datasource/ResourceLimitingJdbcDataSource.java
Index: ResourceLimitingJdbcDataSource.java
===================================================================
RCS file:
/home/cvs/jakarta-avalon-excalibur/src/scratchpad/org/apache/avalon/excalibur/datasource/ResourceLimitingJdbcDataSource.java,v
retrieving revision 1.5
retrieving revision 1.6
diff -u -r1.5 -r1.6
--- ResourceLimitingJdbcDataSource.java 8 Feb 2002 12:03:52 -0000
1.5
+++ ResourceLimitingJdbcDataSource.java 22 Feb 2002 09:26:21 -0000
1.6
@@ -19,15 +19,29 @@
import org.apache.avalon.framework.logger.AbstractLogEnabled;
/**
- * The ResourceLimiting implementation for DataSources in Avalon. This uses
the
- * normal <code>java.sql.Connection</code> object and
+ * The ResourceLimiting implementation for DataSources in Avalon.
+ * This uses the normal <code>java.sql.Connection</code> object and
* <code>java.sql.DriverManager</code>.
* <p>
+ * This datasource pool implementation is designed to make as many
+ * database connections as are needed available without placing
+ * undo load on the database server.
+ * <p>
+ * If an application under normal load needs 3 database connections
+ * for example, then the <code>max</code> pool size should be set
+ * to a value like 10. This will allow the pool to grow to accomodate
+ * a sudden spike in load without allowing the pool to grow to such
+ * a large size as to place undo load on the database server. The
+ * pool's trimming features will keep track of how many connections
+ * are actually needed and close those connections which are no longer
+ * required.
+ * <p>
* Configuration Example:
* <pre>
* <jdbc>
- * <pool-controller max="<i>10</i>" blocking="<i>true</i>"
- * timeout="<i>-1</i>" trim-interval="<i>60000</i>"
+ * <pool-controller max="<i>10</i>" maxStrict="<i>true</i>"
+ * blocking="<i>true</i>" timeout="<i>-1</i>"
+ * trim-interval="<i>60000</i>" auto-commit="true"
* connection-class="<i>my.overrided.ConnectionClass</i>">
* <keep-alive disable="false">select 1</keep-alive>
* </pool-controller>
@@ -50,48 +64,74 @@
* <p>
* Configuration Attributes:
* <ul>
- * <li>The <code>max</code> attribute is used to set the maximum number of
connections which
- * will be opened. See the <code>blocking</code> attribute. (Defaults to
"3")</li>
+ * <li>The <code>max</code> attribute is used to set the maximum
+ * number of connections which will be opened. See the
+ * <code>blocking</code> attribute. (Defaults to "3")</li>
+ *
+ * <li>The <code>max-strict</code> attribute is used to determine whether
+ * or not the maximum number of connections can be exceeded. If true,
+ * then an exception will be thrown if more than max connections are
+ * requested and blocking is false. (Defaults to "true")<br>
+ * <i>WARNING: In most cases, this value
+ * should always be set to true. Setting it to false means that under
+ * heavy load, your application may open a very large number of
+ * connections to the database. Some database servers behave very poorly
+ * under large connection loads and can even crash.</i></li>
+ *
+ * <li>The <code>blocking</code> attributes is used to specify the
+ * behavior of the DataSource pool when an attempt is made to allocate
+ * more than <code>max</code> concurrent connections. If true, the
+ * request will block until a connection is released, otherwise, a
+ * NoAvailableConnectionException will be thrown. Ignored if
+ * <code>max-strict</code> is false. (Defaults to "true")</li>
+ *
+ * <li>The <code>timeout</code> attribute is used to specify the
+ * maximum amount of time in milliseconds that a request for a
+ * connection will be allowed to block before a
+ * NoAvailableConnectionException is thrown. A value of "0" specifies
+ * that the block will never timeout. (Defaults to "0")</li>
+ *
+ * <li>The <code>trim-interval</code> attribute is used to specify how
+ * long idle connections will be maintained in the pool before being
+ * closed. For a complete explanation on how this works, see [EMAIL
PROTECTED]
+ * org.apache.avalon.excalibur.pool.ResourceLimitingPool#trim()}
+ * (Defaults to "60000", 1 minute)</li>
+ *
+ * <li>The <code>auto-commit</code> attribute is used to determine the
+ * default auto-commit mode for the <code>Connection</code>s returned
+ * by this <code>DataSource</code>.
+ *
+ * <li>The <code>connection-class</code> attribute is used to override
+ * the Connection class returned by the DataSource from calls to
+ * getConnection(). Set this to
+ * "org.apache.avalon.excalibur.datasource.Jdbc3Connection" to gain
+ * access to JDBC3 features. Jdbc3Connection does not exist if your
+ * JVM does not support JDBC3. (Defaults to
+ * "org.apache.avalon.excalibur.datasource.JdbcConnection")</li>
*
- * <li>The <code>blocking</code> attributes is used to specify the behavior
of the DataSource
- * pool when an attempt is made to allocate more than <code>max</code>
concurrent connections.
- * If true, the request will block until a connection is released,
otherwise, a
- * NoAvailableConnectionException will be thrown. (Defaults to "true")</li>
- *
- * <li>The <code>timeout</code> attribute is used to specify the maximum
amount of time in
- * milliseconds that a request for a connection will be allowed to block
before a
- * NoAvailableConnectionException is thrown. A value of "0" specifies that
the block will never
- * timeout. (Defaults to "0")</li>
- *
- * <li>The <code>trim-interval</code> attribute is used to specify how long
idle connections will
- * be maintained in the pool before being closed. For a complete
explanation on how this works,
- * see [EMAIL PROTECTED]
org.apache.avalon.excalibur.pool.ResourceLimitingPool#trim()}
- * (Defaults to "60000", 1 minute)</li>
- *
- * <li>The <code>connection-class</code> attribute is used to override the
Connection class returned
- * by the DataSource from calls to getConnection(). Set this to
- * "org.apache.avalon.excalibur.datasource.Jdbc3Connection" to gain access
to JDBC3 features.
- * Jdbc3Connection does not exist if your JVM does not support JDBC3.
- * (Defaults to
"org.apache.avalon.excalibur.datasource.JdbcConnection")</li>
- *
- * <li>The <code>keep-alive</code> element is used to override the query
used to monitor the health
- * of connections. If a connection has not been used for 5 seconds then
before returning the
- * connection from a call to getConnection(), the connection is first used
to ping the database
- * to make sure that it is still alive. Setting the <code>disable</code>
attribute to true will
- * disable this feature. (Defaults to a query of "SELECT 1" and being
enabled)</li>
+ * <li>The <code>keep-alive</code> element is used to override the
+ * query used to monitor the health of connections. If a connection
+ * has not been used for 5 seconds then before returning the
+ * connection from a call to getConnection(), the connection is first
+ * used to ping the database to make sure that it is still alive.
+ * Setting the <code>disable</code> attribute to true will disable
+ * this feature. (Defaults to a query of "SELECT 1" and being
+ * enabled)</li>
*
- * <li>The <code>driver</code> element is used to specify the driver to use
when connecting to the
- * database. The specified class must be in the classpath. (Required)</li>
+ * <li>The <code>driver</code> element is used to specify the driver
+ * to use when connecting to the database. The specified class must
+ * be in the classpath. (Required)</li>
*
- * <li>The <code>dburl</code> element is the JDBC connection string which
will be used to connect to
- * the database. (Required)</li>
+ * <li>The <code>dburl</code> element is the JDBC connection string
+ * which will be used to connect to the database. (Required)</li>
*
- * <li>The <code>user</code> and <code>password</code> attributes are used
to specify the user and
- * password for connections to the database. (Required)</li>
+ * <li>The <code>user</code> and <code>password</code> attributes are
+ * used to specify the user and password for connections to the
+ * database. (Required)</li>
* </ul>
*
* @author <a href="mailto:[EMAIL PROTECTED]">Leif Mortenson</a>
- * @version CVS $Revision: 1.5 $ $Date: 2002/02/08 12:03:52 $
+ * @version CVS $Revision: 1.6 $ $Date: 2002/02/22 09:26:21 $
* @since 4.1
*/
public class ResourceLimitingJdbcDataSource
@@ -172,9 +212,11 @@
final Configuration controller = configuration.getChild(
"pool-controller" );
String keepAlive = controller.getChild( "keep-alive" ).getValue(
"SELECT 1" );
- final boolean disableKeepAlive = controller.getChild( "keep-alive"
).getAttributeAsBoolean( "disable", false );
+ final boolean disableKeepAlive =
+ controller.getChild( "keep-alive" ).getAttributeAsBoolean(
"disable", false );
final int max = controller.getAttributeAsInteger(
"max", 3 );
+ final boolean maxStrict = controller.getAttributeAsBoolean(
"max-strict", true );
final boolean blocking = controller.getAttributeAsBoolean(
"blocking", true );
final long timeout = controller.getAttributeAsLong (
"timeout", 0 );
final long trimInterval = controller.getAttributeAsLong (
"trim-interval", 60000 );
@@ -222,7 +264,8 @@
l_max = max;
}
- // If the keepAlive disable attribute was set, then set the
keepAlive query to null, disabling it.
+ // If the keepAlive disable attribute was set, then set the
keepAlive query to null,
+ // disabling it.
if (disableKeepAlive)
{
keepAlive = null;
@@ -251,7 +294,7 @@
try
{
m_pool = new ResourceLimitingJdbcConnectionPool
- (factory, l_max, true, blocking, timeout, trimInterval,
autoCommit );
+ (factory, l_max, maxStrict, blocking, timeout, trimInterval,
autoCommit );
m_pool.enableLogging( getLogger() );
}
catch (Exception e)
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