Configure a Redelivery Policy

A redelivery policy is a filter that helps you conserve resources by limiting the number of times the Mule runtime engine (Mule) executes messages that generate errors. You can add a redelivery policy to any source in a flow.

When you add a redelivery policy to a flow’s source, Mule evaluates the received data before it executes the flow’s components. If a message delivery fails a specified number of times, the redelivery policy prevents the flow from processing the received data and raises a REDELIVERY_EXHAUSTED error.

Redelivery Policy Configuration Parameters

Field Type Default Value Description

Field	Type	Default Value	Description
Max Redelivery Count	Number	5	Maximum number of times that a message can be redelivered to the flow and processed unsuccessfully before raising a MULE:REDELIVERY_EXHAUSTED error.
Use Secure Hash	Boolean	True	Indicates whether to use a secure hash algorithm to identify a redelivered message.
Message Digest Algorithm	String	SHA-256	Secure hashing algorithm to use for the message. If the payload of the message is a Java object, Mule ignores the Message Digest Algorithm value and returns the value that the payload’s `hashCode()` returned.
ID Expression	Expression	-	Defines one or more expressions that determine when a message has been redelivered. This property can be set only if the value of Use Secure Hash is False.
Object Store	String	Object Store created by Mule’s default `ObjectStoreManager`. Nonpersistent, with an `entryTtl` of 300 seconds and an `expirationInterval` of 6 seconds.	Object Store in which the redelivery counter for each message is stored. You can configure the Object Store as a reference or an inner element. For information, see the Object Store connector documentation.

Max Redelivery Count

Number

Maximum number of times that a message can be redelivered to the flow and processed unsuccessfully before raising a MULE:REDELIVERY_EXHAUSTED error.

Use Secure Hash

Boolean

True

Indicates whether to use a secure hash algorithm to identify a redelivered message.

Message Digest Algorithm

String

SHA-256

Secure hashing algorithm to use for the message. If the payload of the message is a Java object, Mule ignores the Message Digest Algorithm value and returns the value that the payload’s hashCode() returned.

ID Expression

Expression

Defines one or more expressions that determine when a message has been redelivered. This property can be set only if the value of Use Secure Hash is False.

Object Store

String

Object Store created by Mule’s default ObjectStoreManager. Nonpersistent, with an entryTtl of 300 seconds and an expirationInterval of 6 seconds.

Object Store in which the redelivery counter for each message is stored. You can configure the Object Store as a reference or an inner element.

For information, see the Object Store connector documentation.

How the Redelivery Policy Works

Each time the source receives a new message, Mule identifies the message by generating its key.

If the processing flow causes an exception, Mule increments the counter associated with the message key. When the counter reaches a value greater than the configured maxRedeliveryCount value, Mule throws a MULE:REDELIVERY_EXHAUSTED error.
If the processing flow does not cause an exception, its counter is reset.

Errors

MULE:REDELIVERY_EXHAUSTED

Thrown when the number of executions that raise an error is greater than the configured maxRedeliveryCount value.

Example

In this example, Mule logs an error with a Redelivery exhausted in http listener message when the maxRedeliveryCount of 2 is exceeded:

<flow name="logOnRedeliveryExhausted">
    <http:listener path="test" config-ref="listenerConfig">
        <redelivery-policy maxRedeliveryCount="2" useSecureHash="true"/>
    </http:listener>
    <flow-ref name="processData"/>
    <error-handler>
        <on-error-continue type="MULE:REDELIVERY_EXHAUSTED">
            <logger message="Redelivery exhausted in http listener" level="ERROR"/>
        </on-error-continue>
    </error-handler>
</flow>