<flow name="untilFlow">
<until-successful>
<processor-chain>
<logger message="#[1]"/>
<logger message="#[2]"/>
</processor-chain>
</until-successful>
</flow>
Migrating the Until Successful
The Until Successful component for Mule 4 handles some processes differently than the Mule 3 version. Some elements and attributes associated with these changes are no longer present in Mule 4. In Mule 4, you can either achieve the same functionality through different attributes or components, or you no longer need to configure the functionality in Mule 4.
A manual migration of the Until Successful component involves these modifications:
-
Removal of any
<processor-chain/>
elements. -
Replacement of the
secondsBetweenRetries
attribute withmillisBetweenRetries
. -
Removal of the
failureExpression
and use of a Validation processor for Mule 4, instead. -
Replacement of the
deadLetterQueue-ref
attribute with an Error Handler for Mule 4. -
Removal of any
<threading-profile/>
elements. -
Removal of the
ackExpression
attribute and use of a Set Payload component, instead. -
Removal of any
synchronous
attributes.
These changes are detailed in the next sections.
Processor Chains Not Used in Mule 4
In Mule 3, executing more than one processor inside the Until Successful scope
requires you to wrap the processors inside a processor chain
(<processor-chain/>
). In Mule 4, Until Successful supports multiple processors
without the need for a processor chain.
Notice that in the Mule 4 example, the <processor-chain/>
element is not
present.
<flow name="untilFlow">
<until-successful>
<logger message="#[1]"/>
<logger message="#[2]"/>
</until-successful>
</flow>
Retry Attributes Revised in Mule 4
The Mule 3 secondsBetweenRetries
attribute has been removed from Mule 4. You
can use the millisBetweenRetries
attribute in Mule 4.
<flow name="untilFlow">
<until-successful secondsBetweenRetries="10">
<logger message="#[1]"/>
</until-successful>
</flow>
The Mule 4 example replaces secondsBetweenRetries="10"
with
millisBetweenRetries="10000"
.
<flow name="untilFlow">
<until-successful millisBetweenRetries="10000">
<logger message="#[1]"/>
<logger message="#[2]"/>
</until-successful>
</flow>
Failure Expressions Require Modifications
The failureExpression
attribute has been removed. You can replace it with
a Validation processor that sets your verification expression.
<flow name="untilFlow">
<until-successful failureExpression="#[regex:(?i).*error]">
<logger message="#[1]"/>
</until-successful>
</flow>
The failureExpression
setting in the Mule 3 example is replaced by a
<validation:is-false/>
configuration in Mule 4.
<flow name="untilFlow">
<until-successful>
<logger message="#[1]"/>
<validation:is-false expression="#[regex:(?i).*error]"/>
</until-successful>
</flow>
Dead Letter Queue Reference through Mule 4 Error Handler
The Mule 3 deadLetterQueue-ref
attribute enables you to send undeliverable
messages to an endpoint or processor once all retries result in failure. In
Mule 4, you can instead use an error handler to catch all the RETRY_EXHAUSTED
exceptions and send the message to that endpoint or processor.
<vm:endpoint name="dlqChannel" path="dlq" />
<flow name="untilFlow">
<until-successful deadLetterQueue-ref="dlqChannel">
<logger message="#[1]"/>
</until-successful>
</flow>
The Mule 4 example references the dlqChannel
through the On Error Propagate
<on-error-propagate/>
element within an Error Handler <error-handler/>
.
Mule 4:
<vm:endpoint name="dlqChannel" path="dlq" />
<flow name="untilFlow">
<until-successful>
<logger message="#[1]"/>
</until-successful>
<error-handler>
<on-error-propagate type="RETRY_EXHAUSTED">
<outbound-endpoint ref="dlqChannel"/>
</on-error-propagate>
</error-handler>
</flow>
Threading Profile Removed, Not Needed in Mule 4
In Mule 3, you can tune execution threads using the <threading-profile/>
child element. Mule 4 introduces several changes to the execution engine.
Because of the associated non-blocking architecture in Mule 4, you no longer
need to tune threads manually.
<flow name="untilFlow">
<until-successful>
<threading-profile maxThreadsActive="45" maxThreadsIdle="5" threadTTL="52" threadWaitTimeout="60"/>
<logger message="#[1]"/>
</until-successful>
</flow>
The Mule 4 example removes the <threading-profile/>
element.
<flow name="untilFlow">
<until-successful>
<logger message="#[1]"/>
</until-successful>
</flow>
ackExpression Attribute Removed, Use Set Payload
The Mule 3 ackExpression
attribute configures synchronous production of a response payload. This attribute no longer exists in Mule 4. To achieve this behavior in your app, you can configure a Set Payload component after Until Successful.
<flow name="untilFlow">
<until-successful ackExpression="#[message:correlationId]">
<logger message="#[1]"/>
</until-successful>
</flow>
The Mule 4 example sets the #[message:correlationId]
value through the
Set Payload <set-payload/>
component.
<flow name="untilFlow">
<until-successful>
<logger message="#[1]"/>
</until-successful>
<set-payload value="#[message:correlationId]"/>
</flow>