Achieving Fail-safe behaviour in flow

Question

I am trying to create a fail-safe scenario in my flow.

My flow looks like below. It involves some sub-flows which intern have call to web-services. In any scenario if one of the web-service is not available the connection-refused exception is thrown and the whole processing stops.

Instead I want a fail-safe scenario where the flow should continue with the next sub-flows even if the current out-bound call fails.

Is there any message processor or flow-control processor that could help acheive this behaviour in Mule.

Given below is my abstract flow

<flow name="main_flow" >
    ....
    ....
    <flow-ref  name="subflow_1" />
    ....
    ....
    <flow-ref  name="subflow_2" />
    ....
    ....
    <flow-ref  name="subflow_3" />
    ....
    ....

</flow>

<sub-flow name="subflow_1">
    ....
    ....
    <out-bound call to web-service />
    ....
    ....
</sub-flow>

<sub-flow name="subflow_2">
    ....
    ....
    <out-bound call to web-service />
    ....
    ....
</sub-flow>

<sub-flow name="subflow_3">
    ....
    ....
    <out-bound call to web-service />
    ....
    ....
</sub-flow>

Answer 1

You can achive the fail-safe behaviour with the flows.

<flow name="main_flow" >
    ....
    ....
    <flow-ref  name="flow_1" />
    ....
    ....
    <flow-ref  name="flow_2" />
    ....
    ....
    <flow-ref  name="flow_3" />
    ....
    ....

</flow>

<flow name="flow_1" processingStrategy="synchronous" >
    ....
    ....
    <out-bound call to web-service />
    ....
    <catch-exception-strategy >
      .... Your FailSafe code to recover. Also you will have the exception here.
     </catch-exception-strategy>
</flow>

This way you can schieve the fail safe behaviour using the flows.

Happy Coding :)

Answer 2

One hack could be to store the payload in a variable, have a <catch-exception-strategy> block which will catch your web-service invoke exception, use <set-payload> to overwrite the current payload and then call sub-flow2 manually from catch-exception flow of sub-flow1

Answer 3

For each web-service call, use a first-successful router, having your web-service call as the first child and the fall-back mechanism as the second one.