Communicating with Functions across Function Apps using Durable Functions

Question

Just double checking my approach here...

Consider that you're using Azure Functions as a microservices platform -- you're drawing a boundary between separate concerns and making each one its own Function app.

Consider that you have a primary workflow modeled with Durable functions in one of the Apps that need to query data from multiple services (on the backend, not frontend). Can we use Durable functions CallHttpAsync to achieve this, or is this a better-preferred solution to cross communicate with Functions apps?

For example.

App1:
Durable Functions Orchestrator:
CallActivityAsync("some local function")
CallHttpAsync(some function from App2)
CallHttpAsync(some function from App3)
CallActivityAsync("some local function")
CallActivityAsync("some local function")

Answer 1

Hi @Nick2035 ,

Thanks for reaching out to Q&A forum.

Durable functions would be a good solution to your requirement. Durable functions are stateful and long running. As you are aware of, you can use orchestrators, sub orchestrators and activity functions.

Looking at the example you have provided, it can be achieved using durable function.

Orchestrator would call the activity functions. The activity functions can call the other functions or do I/O operations. Starting with Durable Functions 2.0, orchestrations can natively consume HTTP APIs by using the orchestration trigger binding.

Consume Http Api : https://learn.microsoft.com/en-us/azure/azure-functions/durable/durable-functions-http-features?tabs=csharp#consuming-http-apis

Before starting the development, I would suggest you to look into the orchestrator code constraints

I hope this helps!

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