The document discusses how Mule's Request Reply scope enables asynchronous flows to receive responses. It explains that Request Reply converts one-way flows like VM or JMS to request-response by setting the MULE_REPLYTO property with the inbound endpoint path. When exceptions occur in the one-way flow, the Request Reply scope inbound endpoint needs to be explicitly called to handle the response instead of waiting infinitely.

1. Mule Request Reply
By Ram Bavireddi

2. • Sometimes we want response from an asynchronous Mule
flow .
• For example, we want response from a one-way VM or JMS
flow .
• How is it possible?
• Mule’s Request Reply scope makes is possible

3. Mule Request Reply
• The Request Reply enables us to receive a response from an
asynchronous flow without hard coding the destination of the
response
• We can convert a one-way VM or JMS flow to a request-
response flow without having to change it’s configuration

4. Let us get response from this one-way VM flow

5. Using Request Reply

6. Testing
• Test the flow by hitting this url http://localhost:8081/test
• We can see below logger on the console
org.mule.api.processor.LoggerMessageProcessor: one -
way VM payload
• So the Request Reply waits for the response from the one-
way VM flow
• How it works?

7. How it works?
• When Mule asynchronously sends a request via the VM
outbound-endpoint in the Request-Reply scope, it implicitly
sets the message’s outbound property – MULE_REPLYTO
• The value of this MULE_REPLYTO property would refer to path
of inbound-endpoint in the Request-Reply scope

8. When an Exception occurs in the one-way VM flow
• When an Exception occurs in the one-way VM flow, Mule is
unable to call the inbound-endpoint in the Request-Reply
scope.
• In such a case we need to explicitly call the inbound-endpoint
by handling the exception. Otherwise the caller flow where
Request-Reply is configured waits infinitely for the response
from the one-way VM flow

9. When an Exception occurs in the one-way VM flow
Let us suppose the component org.ram.BusinessComponent
throws an exception