Detecting Repeatedly Redelivered Messages¶
In JMS 2.0, it is mandatory for JMS providers to set the JMSXDeliveryCount property, which allows an application that receive a message to determine how many times the message is redelivered.
If a message is being redelivered, it means that a previous attempt to deliver the message failed due to some reason. If a message is being redelivered multiple times, it can be because the message is bad in some way. When such a message is being redelivered over and over again, it wastes resources and prevents subsequent good messages from being processed.
When you work with ESB Micro Integrator, you can detect such repeatedly redelivered messages using the JMSXDeliveryCount property that is set in messages. The ability to detect repeatedly redelivered messages is particularly useful because you can take the necessary steps to handle such messages in a proper manner. For example, you can consume such a message and send it to a separate queue.
To demonstrate this scenario, let's configure the JMS inbound endpoint in ESB Micro Integrator using HornetQ as the message broker.
Synapse configuration¶
Given below are the synapse configurations that are required for mediating the above use case.
See the instructions on how to build and run this example.
<inboundEndpoint name="jms_inbound" onError="fault" protocol="jms" sequence="request" suspend="false">
<parameters>
<parameter name="interval">1000</parameter>
<parameter name="transport.jms.Destination">queue/mySampleQueue</parameter>
<parameter name="transport.jms.CacheLevel">1</parameter>
<parameter name="transport.jms.ConnectionFactoryJNDIName">QueueConnectionFactory</parameter>
<parameter name="sequential">true</parameter>
<parameter name="java.naming.factory.initial">org.jnp.interfaces.NamingContextFactory</parameter>
<parameter name="java.naming.provider.url">jnp://localhost:1099</parameter>
<parameter name="transport.jms.SessionAcknowledgement">AUTO_ACKNOWLEDGE</parameter>
<parameter name="transport.jms.SessionTransacted">false</parameter>
</parameters>
</inboundEndpoint><sequence name="request" onError="fault">
<log level="full"/>
<filter regex="1" source="get-property('default','jms.message.delivery.count')" xmlns:ns="http://org.apache.synapse/xsd">
<then>
<log>
<property name="DeliveryCounter" value="1"/>
</log>
</then>
<else>
<store messageStore="JMS-Redelivered-Store"/>
<log>
<property name="DeliveryCounter" value="more than 1"/>
</log>
</else>
</filter>
<drop/>
</sequence><registry provider="org.wso2.micro.integrator.registry.MicroIntegratorRegistry">
<parameter name="cachableDuration">15000</parameter>
</registry><taskManager provider="org.wso2.micro.integrator.mediation.ntask.NTaskTaskManager">
<parameter name="cachableDuration">15000</parameter>
</taskManager><sequence name="main">
<log level="full"/>
<drop/>
</sequence><sequence name="fault">
<log level="full">
<property name="MESSAGE" value="Executing default "fault" sequence"/>
<property expression="get-property('ERROR_CODE')" name="ERROR_CODE"/>
<property expression="get-property('ERROR_MESSAGE')" name="ERROR_MESSAGE"/>
</log>
<drop/>
</sequence><messageStore name="JMS-Redelivered-Store"/>See the descriptions of the above configurations:
| Artifact | Description |
|---|---|
| Inbound Endpoint | This configuration creates an inbound endpoint to the JMS broker and has a simple sequence that logs the message status using the `JMSXDeliveryCount` value. |
Build and run¶
Create the artifacts:
- Set up ESB Integration Studio.
- Create an integration project with an ESB Configs module and an Composite Exporter.
- Create the inbound endpoint, registry artifact, scheduled task, and sequences with the configurations given above.
- Deploy the artifacts in your Micro Integrator.
Set up the broker:
- Configure a broker with your Micro Integrator instance. Let's use HornetQ for this example.
-
Start HornetQ with the following command:
- On Windows: HORNETQ_HOME\bin\run.bat --run
- On MacOS/Linux/Solaris: sh HORNETQ_HOME/bin/run.sh
-
Start the Micro Integrator (after starting the broker).
Run the following java file (SOAPPublisher.java) to publish a message to the JMS queue:
package JMSXDeliveryCount;
import java.util.Properties;
import java.util.logging.Logger;
import javax.jms.ConnectionFactory;
import javax.jms.Destination;
import javax.jms.JMSContext;
import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NamingException;
public class SOAPPublisher {
private static final Logger log = Logger.getLogger(SOAPPublisher.class.getName());
// Set up all the default values
private static final String param = "IBM";
// with header for inbounds
private static final String MESSAGE_WITH_HEADER =
"<soapenv:Envelope xmlns:soapenv=\"http://schemas.xmlsoap.org/soap/envelope/\">\n" +
" <soapenv:Header/>\n" +
"<soapenv:Body>\n" +
"<m:placeOrder xmlns:m=\"http://services.samples\">\n" +
" <m:order>\n" +
" <m:price>" +
getRandom(100, 0.9, true) +
"</m:price>\n" +
" <m:quantity>" +
(int) getRandom(10000, 1.0, true) +
"</m:quantity>\n" +
" <m:symbol>" +
param +
"</m:symbol>\n" +
" </m:order>\n" +
"</m:placeOrder>" +
" </soapenv:Body>\n" +
"</soapenv:Envelope>";
private static final String DEFAULT_CONNECTION_FACTORY = "QueueConnectionFactory";
private static final String DEFAULT_DESTINATION = "queue/mySampleQueue";
private static final String INITIAL_CONTEXT_FACTORY = "org.jnp.interfaces.NamingContextFactory";
private static final String PROVIDER_URL = "jnp://localhost:1099";
public static void main(String[] args) {
Context namingContext = null;
try {
// Set up the namingContext for the JNDI lookup
final Properties env = new Properties();
env.put(Context.INITIAL_CONTEXT_FACTORY, INITIAL_CONTEXT_FACTORY);
env.put(Context.PROVIDER_URL, System.getProperty(Context.PROVIDER_URL, PROVIDER_URL));
namingContext = new InitialContext(env);
// Perform the JNDI lookups
String connectionFactoryString =
System.getProperty("connection.factory",
DEFAULT_CONNECTION_FACTORY);
log.info("Attempting to acquire connection factory \"" + connectionFactoryString + "\"");
ConnectionFactory connectionFactory =
(ConnectionFactory) namingContext.lookup(connectionFactoryString);
log.info("Found connection factory \"" + connectionFactoryString + "\" in JNDI");
String destinationString = System.getProperty("destination", DEFAULT_DESTINATION);
log.info("Attempting to acquire destination \"" + destinationString + "\"");
Destination destination = (Destination) namingContext.lookup(destinationString);
log.info("Found destination \"" + destinationString + "\" in JNDI");
// String content = System.getProperty("message.content",
// DEFAULT_MESSAGE);
String content = System.getProperty("message.content", MESSAGE_WITH_HEADER);
try (JMSContext context = connectionFactory.createContext()) {
log.info("Sending message");
// Send the message
context.createProducer().send(destination, content);
}
} catch (NamingException e) {
log.severe(e.getMessage());
} finally {
if (namingContext != null) {
try {
namingContext.close();
} catch (NamingException e) {
log.severe(e.getMessage());
}
}
}
}
private static double getRandom(double base, double varience, boolean onlypositive) {
double rand = Math.random();
return (base + (rand > 0.5 ? 1 : -1) * varience * base * rand) *
(onlypositive ? 1 : rand > 0.5 ? 1 : -1);
}
}When you analyze the output on the MI server console, you will see an entry similar to the following:
INFO - LogMediator To: , MessageID: ID:419a4153-01e8-11ea-b4f3-7f52bbde3597, Direction: request, DeliveryCounter = 1