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Connection pooling in multithreaded Java application

I am working on an application that has about 15 threads running the entire time.We recently started using HikariCP for connection pooling.
These threads are restarted every 24 hours. When the threads are restarted, we explicitly close the Hikari datasource by calling dataSource.close() Until before we started to use Connection pooling, One connection object was passed around in the thread to all functions. Now, when the dataSource is closed and if the old connection object was already passed to a method, that returned an error that said dataSource has already been closed which makes sense.
To get around this issue, instead of passing around same connection object in a thread, we started creating them in methods in DBUtils class(Basically functions with queries)
This is how run method of a thread in our application looks like:
#Override
public void run() {
consumer.subscribe(this.topics);
while (!isStopped.get()) {
try {
for (ConsumerRecord<Integer, String> record : records) {
try{
/*some code*/
}catch(JsonProcessingException ex){
ex.printStackTrace();
}
}
DBUtils.Messages(LOGGER.getName(),entryExitList);
} catch (IOException exception) {
this.interrupt();
}
consumer.close();
}
Now, after starting to use HikariCP, instead of passing connection object to DBUtils.Messages, we get a connection from the pool in the method itself
i.e
public static final void Messages(String threadName, List<EntryExit> entryExitMessages) throws SQLException {
Connection connection = DBUtils.getConnection(threadName);
/*code*/
try{
connection.close();
}catch(SQLException se){}
}
This is what getConnection method of DBUtils looks like
public static synchronized Connection getConnection(String threadName) {
Connection connection = null;
try {
if (ds == null || ds.isClosed()) {
config.setJdbcUrl(getProperty("postgres.url"));
config.setUsername(getProperty("postgres.username"));
config.setPassword(getProperty("postgres.password"));
config.setDriverClassName(getProperty("postgres.driver"));
config.setMaximumPoolSize(getProperty("postgres.max-pool-size"));
config.setMetricRegistry(ApplicationUtils.getMetricRegistry());
config.setConnectionTimeout(getProperty("postgres.connection-timeout"));
config.setLeakDetectionThreshold(getProperty("postgres.leak-detection-threshold"));
config.setIdleTimeout(getProperty("postgres.idle-timeout"));
config.setMaxLifetime(getProperty("postgres.max-lifetime"));
config.setValidationTimeout(getProperty("postgres.validation-timeout"));
config.setMinimumIdle(getProperty("postgres.minimum-idle"));
config.setPoolName("PostgresConnectionPool");
ds = new HikariDataSource(config);
}
connection = ds.getConnection();
return connection;
} catch (Exception exception) {
exception.printStackTrace();
}
}
But since call to this method is inside while loop in the thread, PostgresConnectionPool.pool.Wait keeps increasing.
.What's the best way to deal with this?
Edit: PostgresConnection is the pool name . PoolPostgresConnectionPool.pool.Wait is coming from Dropwizard metrics :
https://github.com/brettwooldridge/HikariCP/wiki/Dropwizard-Metrics

JMS transaction exception thrown in nontransaction session

Hello I have problem with my jms code when I try to send over 1000 messages to MDB. Following code:
#Stateless(mappedName = "RequestProcessingQueue")
public class RequestProcessingQueue {
private static final Logger logger = Logger.getLogger(RequestProcessingQueue.class);
#Resource(mappedName = "jmsRequestsFactory")
private ConnectionFactory connectionFactory;
#Resource(mappedName = "jmsRequestsDestination")
private Queue queue;
public void add(String participant, String password, List<Long> documents) throws JmsAppException {
try {
logger.debug("requests to process " + documents);
Connection connecton = connectionFactory.createConnection();
connecton.start();
Session session = connecton.createSession(false, Session.AUTO_ACKNOWLEDGE);
QueueSender sender = (QueueSender) session.createProducer(queue);
Message msg = msg = session.createMessage();
msg.setStringProperty("participant", participant);
msg.setStringProperty("password", password);
for (Long id : documents) {
msg.setLongProperty("request", id);
sender.send(msg);
}
sender.close();
session.close();
connecton.close();
} catch (JMSException e) {
throw new JmsAppException(e);
} catch (Throwable e) {
throw new JmsAppException("Fatal error occured while sending request to be processed", e);
}
}
}
throws
MQJMSRA_DS4001: JMSServiceException on send message:sendMessage: Sending message failed. Connection ID: 2979509408914231552 com.sun.messaging.jms.ra.DirectSession._sendMessage(DirectSession.java:1844) / sendMessage: Sending message failed. Connection ID: 2979509408914231552 com.sun.messaging.jmq.jmsserver.service.imq.IMQDirectService.sendMessage(IMQDirectService.java:1955) / transaction failed: [B4303]: The maximum number of messages [1 000] that the producer can process in a single transaction (TID=2979509408914244096) has been exceeded. Please either limit the # of messages per transaction or increase the imq.transaction.producer.maxNumMsgs property. com.sun.messaging.jmq.jmsserver.data.handlers.DataHandler.routeMessage(DataHandler.java:467)'}
at jms.example.RequestProcessingQueue.add(RequestProcessingQueue.java:48)
I do not understand why cus when I create session I pass false as first param indicating that session is non transactional mode.

Your code does not work because the basic JMS API was designed to work in any environment, not just from within an EJB container. Runtime environment programming restrictions and behaviour are described in the EJB specifications and JavaDoc, in particular javax.jms.Connection.createSession(boolean transacted, int acknowledgeMode).
Your code can be simplified (assuming you're using at least Java 7) to:
#TransactionAttribute(TransactionAttributeType.NOTSUPPORTED)
public void add(String participant, String password, List<Long> documents) throws OgnivoException {
try (Connection connection = connectionFactory.createConnection();
Session session = connection.createSession();
// session.start() not required
MessageProducer sender = session.createProducer(queue)) {
logger.debug("requests to process " + documents);
for (Long id : documents) {
Message msg = msg = session.createMessage();
msg.setStringProperty("participant", participant);
msg.setStringProperty("password", password);
msg.setLongProperty("request", id);
sender.send(msg);
}
} catch (JMSException e) {
throw new JmsAppException(e);
}
// Don't catch throwable because it hides bugs
}
Remember that EJB methods are automatically associated with a transaction unless you specify otherwise. Additionally, be sure to check the javadoc for javax.jms.Connection.createSession() and associated methods, particularly the sections describing behaviour in different runtime environments.

Timing out DriverManager.getConnection()?

I'm working with Java and mysql for database and I ran into a weird problem:
One of my clients have a very unstable connection and sometimes packet loss can be high. Ok that's not software's fault I know, but I went there to test and, when the program calls "DriverManager.getConnection()" and the network connection gets unstable, that line gets to lock the application (or the given thread) by several minutes. I have added some logics of course to use another datasource for caching data locally then saving to the network host when possible, but, I can't often let the program hang for longer than 10s (And this method doesn't seem to have any timeout specification).
So, I came out with a workaround like this:
public class CFGBanco implements Serializable {
public String driver = "com.mysql.jdbc.Driver";
public String host;
public String url = "";
public String proto = "jdbc:mysql://";
public String database;
public String user;
public String password;
}
private static java.sql.Connection Connect(HostConfig dataHost) throws java.sql.SQLException, ClassNotFoundException
{
dataHost.url = dataHost.proto+dataHost.host;
if(dataHost.database != null && !dataHost.database.equals("")) dataHost.url += "/"+dataHost.database;
java.lang.Class.forName(dataHost.driver);
ArrayList<Object> lh = new ArrayList<>();
lh.add(0, null);
Thread ConThread = new Thread(()-> {
try {
lh.add(0, java.sql.DriverManager.getConnection(
dataHost.url, dataHost.user, dataHost.password));
} catch(Exception x ) {
System.out.println(x.getMessage());
}
}, "ConnThread-"+SessId);
ConThread.start();
Thread TimeoutThread = new Thread(() -> {
int c = 0;
int delay = 100;
try {
try {
do {
try {
if(t.isAlive())
Thread.sleep(delay);
else
break;
} catch(Exception x) {}
} while((c+=delay) < 10000);
} catch(Exception x){}
} finally {
try {
t.stop();
} catch(Exception x){}
}
}, "ConTimeout-"+SessId);
TimeoutThread.start();
try {
ConThread.join();
} catch(Exception x) {}
if(lh.get(0) == null)
throw new SQLException();
return (Connection) lh.get(0);
}
I call getConnection from another thread, then make a secondary "timeout" thread to watch it and then Join the calling thread to the ConThread.
I have been getting results close to expected, indeed, but it got me wondering:
Is there a better way to do this? Does the creation of 2 threads eat up much on system resources, enough to make this approach unpractical?

You need connection pooling. Pool in the connection and reuse it rather than recreating everytime. One such library for DB connection pooling is DBCP by Apache
It will take care of when connection gets dropped off and so on. You could have validation Query and it would query DB say before borrowing connection from the pool and once it validates successfully, it will fire your actual query.

NullPointerException when creating connection from connection factory

I am trying to create a connection using connectionFactory.createConnection() method but it returns a null.
Below is my code :
#Stateless
public class test
{
#Resource(mappedName = "java:comp/DefaultJMSConnectionFactory")
private static ConnectionFactory connectionFactory;
#Resource(mappedName = "jdbc/JurassicParkCon")
private static Queue queue;
public static void main(String args[])
{
Connection connection = null;
Session session = null;
MessageProducer messageProducer = null;
TextMessage message = null;
final int NUM_MSGS = 3;
try {
connection = connectionFactory.createConnection();
}
catch(Exception e){System.out.println("It is:"+e.getMessage());}
In the above code am only trying to create a connection but it returns NullPointerException. I have added a JMS resource through the admin console in GlassFish (name is jdbc/JurassicParkCon).
Recently only I started working with EJB's so I am not very familiar with errors. I have added the #Stateless annotation because there was a similar problem which was posted on StackOverflow and for that user adding the annotation worked but not for me.
What might be the problem here ?
Thank you for your time.

It won't work as a standalone application. You need to run it in a container.

Java - Code Coverage

I have a method in one of the classes in my code base that for the life of me, I cannot get into with my junit tests.
Basically this class is called when I request a database connection, if a stale connection is returned, a new connection is established
Here is the snippet of the mthod in my class (trimmed down for this purpose)
public class TCSOracleDataSourceWrapper extends OracleDataSource {
private static final int STALE_CONNECTION_EX_CODE = 17143;
private OracleConnectionCacheManager cacheManager;
private String cacheName;
/** Local log variable **/
private final Log logger = LogFactory.getLog(getClass());
/**
* Class constructor
* #throws SQLException
*/
public TCSOracleDataSourceWrapper() throws SQLException {
super();
}
private static final long serialVersionUID = 1L;
#Override
/**
* Get a connection but if the connection is stale then refresh all DB connections
*
*/
public final Connection getConnection() throws SQLException {
logger.debug("Retrieving a database connection from the pool");
Connection connection = null;
try{
connection = super.getConnection();
}
catch(SQLException e)
{
if(e.getErrorCode() == STALE_CONNECTION_EX_CODE)
{
logger.error("Stale Oracle connection found in the Connection Pool. Refreshing invalid DB connections.");
//refresh invalid connections
cacheManager.refreshCache(cacheName, OracleConnectionCacheManager.REFRESH_INVALID_CONNECTIONS);
//now try to get the connection again
connection = super.getConnection();
}
else
{
throw e;
}
}
return connection;
}}
Any idea how I can ensure my junit tests execute the if statement?
I am currently using EasyMock and Powermock but I cannot find a way to get into this if statment using these tools
All help is greatly appreciated
Thank you
Damien

You should refactor your class to become a proxy for another data source, rather than inherit from one. This way you can easily inject into it a mock data source instead of the real one.
import javax.sql.DataSource;
public class TCSOracleDataSourceWrapper implements DataSource {
...
private DataSource wrappedDataSource;
...
public TCSOracleDataSourceWrapper(DataSource ds) {
wrappedDataSource = ds;
}
...
public final Connection getConnection() throws SQLException {
...
Connection connection = null;
try{
connection = ds.getConnection();
}
catch(SQLException e)
{
...
}
return connection;
}
}

One idea springs to mind: use aggregation rather than inheritance. This problem and others like it would go away because you can then mock the aggregated object to have whatever behavior you want. I don't see another way of getting in there right off hand. In fact, the name TCSOracleDataSourceWrapper already indicates that it's wrapping a data source (aggregation), when it actually isn't.

One quick workaround is to factor out the super.getConnection() call to a new private / protected method. Once you make that change it would be easy to mock the getBaseConnection method using power mock. This is short term fix, like the other answers suggest it is better to use delegation instead of inheritance for the wrapper implementation.
Connection getBaseConnection() throws SQLException {
return super.getConnection();
}
public final Connection getConnection() throws SQLException {
logger.debug("Retrieving a database connection from the pool");
Connection connection = null;
try{
connection = getBaseConnection();
}
catch(SQLException e)
{
if(e.getErrorCode() == STALE_CONNECTION_EX_CODE)
{
logger.error("Stale Oracle connection found in the Connection Pool. Refreshing invalid DB connections.");
//refresh invalid connections
cacheManager.refreshCache(cacheName, OracleConnectionCacheManager.REFRESH_INVALID_CONNECTIONS);
//now try to get the connection again
connection = getBaseConnection();
}
else
{
throw e;
}
}
return connection;
}