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It is common for a temporary outage or database deadlock to cause a message to fail to process; but the chances are if its tried a few more times with some time delay then it will complete fine. So we typically wish to use some kind of redelivery policy to decide how many times to try redeliver a message and how long to wait before redelivery attempts.

The RedeliveryPolicy defines how the message is to be redelivered. You can customize things like

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Camel will log delivery failures at the ERROR logging level by default. You can change this by specifying retriesExhaustedLogLevel and/or retryAttemptedLogLevel. See ExceptionBuilderWithRetryLoggingLevelSetTest for an example.

Redelivery header

When a message is redelivered the DeadLetterChannel will append a customizable header to the message to indicate how many times its been redelivered. The default value is org.apache.camel.redeliveryCount.
The header org.apache.camel.Redelivered contains a boolean if the message is redelivered or not.

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{snippet:id=e3|lang=java|url=activemq/camel/trunk/camel-core/src/test/java/org/apache/camel/builder/ErrorHandlerTest.java}

You can also configure the RedeliveryPolicy as this example shows

{snippet:id=e4|lang=java|url=activemq/camel/trunk/camel-core/src/test/java/org/apache/camel/builder/ErrorHandlerTest.java}

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{snippet:id=e1|lang=java|url=activemq/camel/trunk/camel-core/src/test/java/org/apache/camel/processor/interceptor/InterceptAlterMessageBeforeRedeliveryTest.java}

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{snippet:id=e1|lang=java|url=activemq/camel/trunk/camel-core/src/test/java/org/apache/camel/processor/DeadLetterChannelOnRedeliveryTest.java}

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{snippet:id=e2|lang=java|url=activemq/camel/trunk/camel-core/src/test/java/org/apache/camel/processor/DeadLetterChannelOnRedeliveryTest.java}

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