Question
REST Services - Transaction Rollback
Hi
I have a scenario where my pega flow makes three REST calls (C1, C2 and C3) sequentially to three different external systems to complete a business transaction. All these are POST operations and makes some changes in their respective systems. If C3 fails, I want changes occurred within C1 and C2 should be rolled back. Is there a standard design approach for this? Please advise.
Thanks mrwolf for the response. It appears C1Validate can validate the request structure and available of C1's end point but still C1 can fail due to other points of failures like it can call other external services. Currently we are doing like DELETE kind of option.
What you described here is called 2-phase commit protocol.
That's a standard practice for distributed databases, but could be applied in your situation as well.
Please, read more about it on, for example, wikipedia. The only requirement is that you should have access to external services to change it (add new operations)
Two phase commit can be applied for internal DB using obj-methods or when the app server is connected to external DB with java XA support.
I dont think there is a standard way to maintain transactional integrity with REST services.
You can design custom architecture like the one mrwolf suggested
Since REST is stateless by design, there is no way to roll back a transaction. A possible way is to create certain endpoints/methods designated to validating a request. Let's say that you want to call UploadDocument -- there could be a ValidateUploadDocument. If the latter returns anything else than 200, you just won't call the former.
In your case:
Naturally, this could require changing your services in the first place. Another potentially less elegant way is to use DELETE for C1 and C2 if C3 fails (if DELETE methods are available).