On 21 Nov 2011, at 09:28, "app...@dsl.pipex.com" <app...@dsl.pipex.com> wrote:
> Hello
>
> I don't think this is a Tomcat issue but I thought I would post here just in
> case.
>
> I have a Java, JSP and MySQL application running under Apache Tomcat 6.0.26
> which I've been testing with JMeter.
> What I find is that for a simple test having 10 users logging in and
> displaying a JSP which is populated from
> several database reads, everything is fine.
>
> But when I increase the number of users in JMeter to 20+, logging in starts
> to fail with HTTP request 500. Checking
> the logs I find that I am getting large numbers of
> MySQLNonTransientConnectionExceptions as follows:
> com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Could
> not create connection to database
> server. Attempted reconnect 3 times. Giving up.
>
> So this indicates that there's an issue either with the connection pooling
> through Apache Tomcat 6.0.26 or MySQL
> Community Server 5.X.
>
> The relevant part of the application's context.xml file in the project reads
> as follows:
> <Resource auth="Container" driverClassName="com.mysql.jdbc.Driver"
> logAbandoned="true" maxActive="-1" maxIdle="30"
> maxWait="10000" minEvictableIdleTimeMillis="30000"
> name="jdbc/myApp" numTestsPerEvictionRun="5"
> password="XXXXXXXXXX" removeAbandoned="true"
> removeAbandonedTimeout="120" testOnBorrow="true"
> testOnReturn="false" testWhileIdle="true"
> timeBetweenEvictionRunsMillis="-1"
> type="javax.sql.DataSource"
> url="jdbc:mysql://localhost:3306/myApp?autoReconnect=true"
> username="XXXXXXXXXX" validationQuery="select 1"/>
>
> I've set maxActive above to -1 on the understanding that this is unlimited. I
> think that the MySQL error is because
> MySQL is refusing the connections.
>
> Am I correct here? Can anyone suggest a workaround or advise?
>
> Typically, my database operations are as follows:
>
> // Gets an ArrayList of Datasets.
> public static ArrayList<Dataset> getDatasets() {
> ConnectionPool_DB pool = ConnectionPool_DB.getInstance();
> Connection connection = pool.getConnection();
Usually the connection is initialised as null and then assigned inside
the try block. What happens if the method above throws an error after
a connection is removed from the pool?
p
> PreparedStatement ps = null;
> ResultSet rs = null;
>
> String query = ("SELECT * " +
> "FROM Dataset " +
> "WHERE Active = '" + Valid.TRUE + "';");
>
> try {
> ps = connection.prepareStatement(query);
> rs = ps.executeQuery();
> ArrayList<Dataset> datasets = new ArrayList<Dataset>();
> while (rs.next()) {
> datasets.add(mapDataset(rs));
> }
> return datasets;
> }
> catch(Exception ex) {
> logger.error("Error getting list of Datasets\n", ex);
> return null;
> }
> finally {
> Database_Utils.closeResultSet(rs);
> Database_Utils.closeStatement(ps);
> pool.freeConnection(connection);
> }
> }
>
> And there can be quite a few of these per page.
>
> Thanks
>
> Martin O'Shea
>
>
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