Asynchronous HTTP Response from a Flow | Power Automate

By default, whenever yo submit an HTTP Request to a Flow, your application will wait till the request is completed. Meaning, the HTTP Response by default in a Cloud Flow is Synchronous.

So, let’s see how you can make it Asynchronous and how you can later retrieve the status of the HTTP Request itself from the Flow. If you make a HTTP Response as Asynchronous, the calling HTTP Request application will receive a 202 Accepted in response.

HTTP Request by Default

Let us see how the HTTP Request and Response is structured by default.

Here’ s the HTTP Request which will receive the request and process the data further.
And let’s assume you some lengthy process involved in your Flow which is making an average execution time span to a significant time. To mimic that, I’ve simply introduced a delay of 3 minutes to demonstrate the Async example.

In case you want to review how to pause a Workflow using Delay and Delay Until, you can check this post – Pause a Flow using Delay and Delay Until | Power Automate
And finally, assuming my execution of the Flow has completed and I’m supposed to send the Response back to the HTTP Request calling application, I’ll use the Response Action from the Request connector
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And my Response will look something like this letting the caller application know that the processing has been successfully completed.

Now let’s see how this calling application will behave in this case. Assuming, we haven’t manipulated any settings as yet.

The Flow looks like this just to give you a visual perspective of the implementation.
Now, Once I send a Request from Postman, the Postman itself will be waiting for a response till the execution of the Flow is completed.
This is because the Flow itself is waiting to be processed and yet to reach the Response block in the Flow.

Asynchronous Response

We will now turn on the Asynchronous Response of the HTTP Response Action –

Go to Settings on the Response action step.
In Settings, turn on Asynchronous Response On and save it.
As mentioned in the description of the Asynchronous Response setting, the caller Application will immediately get a 202 Accepted code upon sending the HTTP Request.
Notice the Headers, you’ll see a Location header item
Capture this URL in your calling application as you can use it to check the status of the Request later on once the operation is completed on the Flow.

Checking Request Status

Since we have the Location information which was passed on from to the Response Header previously, we can use the URL to check the Response Status separately by making another call to the URL itself.

If the Status is still Running, you’ll get this response. It will imply that the Flow is still Running and the Response is not available yet.
Else, you’ll get the actual Response which was supposed to be received had the Flow’s HTTP Response was set to Synchronous by default (Asynchronous Response = OFF)