How to process message just before it send to DLQ

Question

I am using the following server side re-delivery configurations

 <plugins>
    <redeliveryPlugin fallbackToDeadLetter="true" sendToDlqIfMaxRetriesExceeded="true">
        <redeliveryPolicyMap>
            <redeliveryPolicyMap>
                <redeliveryPolicyEntries>
                    <redeliveryPolicy 
                        queue = "com.api.RequestQueue.v1"
                        maximumRedeliveries="20"                        
                        initialRedeliveryDelay="60000" 
                        redeliveryDelay="60000" />

                    <redeliveryPolicy 
                        queue = "com.api.RequestQueue.v2"
                        maximumRedeliveries="10"                        
                        initialRedeliveryDelay="30000" 
                        redeliveryDelay="30000" />
                    <redeliveryPolicy 
                        queue = "com.api.ResponseQueue.v1"
                        maximumRedeliveries="3"                         
                        initialRedeliveryDelay="34000" 
                        redeliveryDelay="34000" />                          
                </redeliveryPolicyEntries>
            </redeliveryPolicyMap>
        </redeliveryPolicyMap>
    </redeliveryPlugin>
</plugins>

How to set a custom end point to process the failed message after retries and just before it send to the DLQ? I did refer the following links but couldn't find anything mentioned about server side or redeliveryPlugin configurations

1.dead-letter-channel

2.logging-camel-exceptions-and-sending-to-the-dead-letter-channel

score 2 · Answer 1 · answered Feb 15 '17 at 15:28

If you are using blueprint or spring then it can be easily done as such:

<!-- Redelivery Policy -->
<bean class="org.apache.camel.processor.RedeliveryPolicy" id="redeliveryPolicyConfig">
    <property name="5" />
    <property name="redeliveryDelay" value="5000" />
    <property name="logRetryAttempted" value="true" />
</bean>

<!-- Error Handler -->
<bean class="org.apache.camel.builder.DeadLetterChannelBuilder" id="errorHandler">
    <property name="deadLetterUri" value="direct:error" />
    <property name="useOriginalMessage" value="true" />
    <property name="redeliveryPolicy" ref="redeliveryPolicyConfig" />
</bean>

And then you add your route to which the error handler is pointing in the "deadLetterUri" property as such:

<!-- Perform custom logic and send to DLQ -->
<route id="myDLQ-route">
    <from uri="direct:error" />
    <!-- Maybe some logic here, logging perhaps? -->
    <to uri="activemq:queue:myDLQ" />
</route>

Nandan · Accepted Answer · 2017-05-30T10:58:18.610

I am using spring but the re-delivery configurations are in a separate broker container, which can't change at present.

But the following configuration works.

Route:

     public class MyMessageRoute extends RouteBuilder {
       public void configure() throws Exception {
           onException(Exception.class)
            .handled(true)
            .bean(PreDLQLogWriter.class) ;

           from(fromQueueName).id("RouteId")
            .transacted()
            //process message 

            ;
       }}

public class PreDLQLogWriter {
private static final org.slf4j.Logger LOG = 
                 org.slf4j.LoggerFactory.getLogger( PreDLQLogWriter.class ); 

int configuredDeliveryCount = maximumRedeliveries+1;
public void logMessageDetails(Exchange exchange) throws Exception {

  int actualDeliveryCount = exchange.getIn().getHeader("JMSXDeliveryCount") 
                   != null ? exchange.getIn().getHeader("JMSXDeliveryCount", 
                    Integer.class) : 0 ;
  if(actualDeliveryCount = configuredDeliveryCount) {
             LOG.info(" Pre-DLQ Log: Log the message with message id ");
   }}

How to process message just before it send to DLQ

2 Answers2