CODEWITHSUNDEEP
jmsmulevirtual-machineesbmule-studio
FutureI.T.
FutureI.T.

Reputation: 23

How to maintain order of messages being processed in a mule flow from VM to JMS using one-way message exchange pattern?

I am using mulesoft ESB with Anypoint studio for a project. In one of my flows I am using one-way message exchange pattern to dispatch from VM (persistence file store VM connector) to JMS, both xa transaction enabled to avoid losing messages.

Consider a scenario where we send a message every time user updates his/her last name to ESB. For example, let's say user changes last name to 'A', but quickly changes to 'B', so final result is expected to be 'B'.

1) Is it likely that message 'B' gets processed before message 'A' in my case? and thus last name being set to 'A' instead of 'B'?

2) How do I avoid that apart from using 'request-response' MEP?

3) Is there a way to write unit tests for making sure order of messages being processed is maintained from VM (one-way, xa enabled) to JMS (one-way, xa enabled)?

4) How do I go about testing that manually?

Thank you in advance. Any pointers/help will be appreciated.

Upvotes: 2

Views: 1845

Answers (1)

Petter Nordlander
Petter Nordlander

Reputation: 22279

It's not likely, since your system would normally react way quicker than a user can submit requests. However, that may be the case during a load peak.

To really ensure message order, you really need a single bottleneck (a single instance/thread) in your solution to handle all requests. That is, you need to make sure your processing strategy in Mule is synchronous and that you only have a single consumer on the VM queue. If you have a HA setup with multiple Mule servers, you may have potential to get messages out of order. In that case, and if the user initially is connected using HTTP, you can get around most of the problem using a load balancer with a sticky session strategy.

A perhaps more robust and scalable solution is to make sure the user submits it's local timestamp on each request with high resolution. Then you can make sure to discard any "obsolete" updates when storing the information into a database. However, that is not in the mule VM/JMS layer, but rather in the database.

For testability - no, I don't think there is a truly satisfying way to be 100% sure messages won't come out of order during any condition by just writing integration tests or performing manual tests. You need to verify the message path theoretically to make sure there is no part where one message can bypass another.

Upvotes: 1

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