I have a ASP.NET Core backend (with Azure Service Bus) and a Blazor Server frontend.
The purpose of the backend and the frontend is to trigger manual and automatic pushing of single data points (hereafter called the “data pushing process”) to 2 different external systems (two different, unrelated APIs, that I don’t control) via the backend making HTTP requests to these external systems. One HTTP request to each external system is required to push the data. The requests will carry a slightly different payload, since each system has its own contracts.
The data pushing process can be triggered by:
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The user clicking a button (called the “push” button in the frontend, which results in a HTTP PUT request to the backend.
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The backend receives data itself from an external service (via a different protocol). The received data can either by “ready for export” or not. If it is not ready for export, a user needs to fill out a text field on the frontend, and click the “push” button.
When a user clicks a button in the frontend, it sends a HTTP PUT request to the backend. I wish this to result in the backend sending it’s own HTTP requests to 2 external systems, ie. pushing data to the two systems, when triggered by the user.
Question
- What type of coordination would be good for this scenario?
It does not seem optimal to do this with two synchronous HTTP requests in a controller method. What would be a good design (pattern) for managing the work of making the HTTP requests to the external systems?
I have considered the Saga pattern.
Notes
- It’s the backend that makes the HTTP requests to the external systems.
- I need to keep track of if the data point is pushed to the external systems yet or not.
- EDIT: The order of the HTTP requests does not matter.
- EDIT: The external endpoints can return HTTP 200 and 400 codes, if upserting data succeeeds, or if the user is trying to update a data point they are not allowed to update.
- EDIT: If the request(s) fail, I would like to show an error in the frontend.
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Since
- There is no compensation action to take in case one of the external HTTP calls fails (no system is changed as a result of either of these calls alone)
- It’s a simple [ call 1 OK && call 2 OK ] check,
I don’t see a Saga being necessary here.
Just do the 2 calls in a sequence and don’t continue if one of them fails. There are several ways to disrupt the flow of execution, whether it be via an exception, simple if‘s, etc. The Retry pattern could also be useful based on your description of the problem.
Whether to put it in a controller method or elsewhere depends on your architecture and layering style.
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