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< title > HornetQ JMS Scale Down Example< / title >
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< h1 > JMS Colocated Failover Shared Store Example< / h1 >
< p > This example demonstrates how you can configure a live server to scale down messages to another live server on shutdown.
< p > This example starts 2 live servers each one with a connector configured for the other live server.< / p >
< p > The second live server is killed and its messages are scaled down to the first server on shutdown.< / p >
< p > The following shows how to configure the live servers to scale down to one another.< / p >
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< ha-policy>
< live-only>
< scale-down>
< connectors>
< connector-ref>server0-connector< /connector-ref>
< /connectors>
< /scale-down>
< /live-only>
< /ha-policy>
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< h2 > Example step-by-step< / h2 >
< p > < i > To run the example, simply type < code > mvn verify< / code > from this directory< / i > < / p >
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< li > Get an initial context for looking up JNDI for both servers< / li >
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initialContext1 = getContext(1);
initialContext = getContext(0);
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< li > Look up the JMS resources from JNDI< / li >
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Queue queue = (Queue)initialContext.lookup("/queue/exampleQueue");
ConnectionFactory connectionFactory = (ConnectionFactory)initialContext.lookup("/ConnectionFactory");
ConnectionFactory connectionFactory1 = (ConnectionFactory)initialContext1.lookup("/ConnectionFactory");
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< li > Create a JMS Connections< / li >
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connection = connectionFactory.createConnection();
connection1 = connectionFactory1.createConnection();
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< li > Create a *non-transacted* JMS Session with client acknowledgement< / li >
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Session session = connection.createSession(false, Session.CLIENT_ACKNOWLEDGE);
Session session1 = connection1.createSession(false, Session.CLIENT_ACKNOWLEDGE);
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< li > Create a JMS MessageProducer< / li >
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MessageProducer producer = session.createProducer(queue);
MessageProducer producer1 = session1.createProducer(queue);
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< li > Send some messages to both servers< / li >
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for (int i = 0; i < numMessages ; i + + )
{
TextMessage message = session.createTextMessage("This is text message " + i);
producer.send(message);
System.out.println("Sent message: " + message.getText());
message = session1.createTextMessage("This is another text message " + i);
producer1.send(message);
System.out.println("Sent message: " + message.getText());
}
< / code >
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< li > Crash server #0, the live server< / li >
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killServer(0);
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< li > start the connection ready to receive messages< / li >
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connection.start();
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< li > create a consumer< / li >
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< code >
MessageConsumer consumer = session.createConsumer(queue);
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< li > Receive and acknowledge all of the sent messages, you will notice that messages from both servers are received< / li >
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TextMessage message0 = null;
for (int i = 0; i < numMessages ; i + + )
{
message0 = (TextMessage)consumer.receive(5000);
System.out.println("Got message: " + message0.getText());
}
message0.acknowledge();
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< li > And finally (no pun intended), < b > always< / b > remember to close your JMS resources after use, in a < code > finally< / code > block. Closing a JMS connection will automatically close all of its sessions, consumers, producer and browser objects< / li >
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finally
{
if (connection != null)
{
connection.close();
}
if (initialContext != null)
{
initialContext.close();
}
if (connection1 != null)
{
connection1.close();
}
if (initialContext1 != null)
{
initialContext1.close();
}
}
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