What is the difference between using private flow
- 1. What is the difference between using private flow versus VM transport?
- 2. • In this post, I will show the differences between chaining flows with VM transport versus chaining flows with flow reference. When I need to divide my Mule flows into reusable units, I often break them into smaller flows and then chain them together in a main flow. • Flows can be chained together using flow-refs or using VM connectors; most recent examples use the flow-refs. However, flow- refs are a Mule 3 addition and in Mule 2 VM connectors were used to chain flows.
- 3. • Given this background and with flow-refs being more of the recommended approach, is there a scenario when we would want to use VM connectors? Yes, there is! But the majority of the time flow- refs are preferred over the VM transport and here is why. • * VM connector creates a transport barrier in the flow: In a transport barrier, your Mule message goes through an entire serialization and deserialization process which results in a new Mule message with the same payload. Read about the effect of transport barrier on a mule message here.
- 4. When one would prefer to use a VM transport over a flow reference • One case would be that VM endpoints enable message redelivery strategies to be configured in your exception handling blocks – this is not possible with flow-refs. VMs can do this because they internally use a queue to hold messages while flow-refs are similar to simple method calls.
- 5. • Look at the sample flow below; here the message will be redelivered five times and is enabled by the use of VM inbound
- 6. • Contrast that to a private flow and chaining with flow-refs, if an exception occurs in the called flow even though we have a rollback strategy configured it will NOT execute because there is no internal queue involved.
- 8. • To summarize, don’t hesitate to use VM transports if you need redelivery of messages. There are also differences in the use of thread pools between private flows and VMs, but I will leave that for another post. The sample source code for this post is available on Github. • If you want to learn more about Mule ESB, Mule ESB is a great platform for developers to connect applications together quickly and easily. Feel free to try Anypoint Platform for 30 days