Output of custom Activity sent to HTTP Response asynchronously

[fulganta]

Hi,
The goal of my workflow is to perform an asynchronous activity.
We receive input from a http post which includes a callback url. We reply an correlation id of the current treatment, continue and post the result on the callback url provided by the user.

Here is the following activity I have:

1- HttpEndpoint - POST

2- SetVariable that store the post into a variable named quoteRequestInput. (Your example show to use "input.Body", but it can work just with "input" I think)

3- Custom Activity named GetCorrelationId that generate a unique ID and send it back to the caller that did the POST.
I tried to name the activity to be able to use it's output in the next activity as I have issue to catch it just writing "input". I seem to get the original post 1 activity input.

The code include something simple here:

[ActivityOutput(Hint = "Correaltion ID", DefaultWorkflowStorageProvider = TransientWorkflowStorageProvider.ProviderName,
DisableWorkflowProviderSelection = true)]
public string CorrelationIdOuput { get; set; } = default!;

protected override async ValueTask<IActivityExecutionResult> OnExecuteAsync(ActivityExecutionContext context)
		{
			CorrelationIdOuput = "1234abcd";
			return Done();
		}

4- WriteHttpResponse that send back the Correl ID "1234abcd".
I tried both JV and Liquid, but both seem to fail.

5- Last activity that take the httpPost input and do something and post it to a callback URL
I seem to be able to get the correct data from quoteRequestInput, so all good here.

So 2 questions:

1- How can I catch the output of my GetCorrelationId activity named CorrelationIdOuput (step 3) in my WriteHttpResponse (step 4) ? I don't seem to be able to do it even if follow your tutorial.

2- It seems that the output WriteHttpResponse is sent after execution of activity 5, so it's not really asynchronous here... which is the goal. How can I reply to the original post before the all workflow is executed?

[sfmskywalker]

Hi @cfrelet ,

1. All looks good, so I'm surprised that the output doesn't render the expected correlation ID. By the way, if you rename your CorrelationIdOuput property to Output, it will become available via the input JS and Input Liquid variables. However, even with your current code you should definitely be able to do Activities.GenCorrActivity.CorrelationIdOuput and get the generated value printed to the response, so something else must be going on.
2. The Write HTTP Response doesn't terminate the current request, it will simply do Response.WriteAsync internally and the workflow engine will continue executing subsequent activities until it either encounters a blocking activity or reaches the end of the workflow. This will be configurable with Flushing and closing connection with HTTP Response acitivity #1144. Until that's done, one thing you can do to continue the workflow asynchronously is to add a blocking activity right after the Write HTTP Response activity. For example, you could add a Timer activity (make sure to enter a non-zero timeout, like 1 second or less, but greater than 0). This will cause the workflow to get suspended and then resumed immediately from a background process.

Regarding the input issue, feel free to send me a (simplified) project that demonstrates the issue.

[fulganta]

HI @sfmskywalker ,
Thanks a lot for your quick feedback as usual.
1- Replacing CorrelationIdOuput by Output fix the issue indeed. I didn't know we have to stick out that name to use it in JS and Liquid.
2- This trick work indeed with a Timer thank you. I'm looking forward to be able to do it natively with HTTP answer.

[sfmskywalker]

Replacing CorrelationIdOuput by Output fix the issue indeed. I didn't know we have to stick out that name to use it in JS and Liquid.

Technically you can use any name you want, including CorrelationIdOuput. But any output property that is named Output will be automatically passed as input into the next activity, made available via the global input JS variable or Input Liquid variable.

But if you name it CorrelationIdOuput for example, you can still access it from other activities, just using a different syntax, e.g.: activities.GenCorrActivity.CorrelationIdOuput().

It's strange that Input works for you, while Activities.GenCorrActivity.CorrelationIdOuput does not.

If you want to send me a repro I'd be happy to investigate.

[fulganta]

Maybe i messed up somewhere….
One more question, can I take multiple input in an activity? In my case I want to take the correlationID generated + the quoterequestInput I get from the original user Post. I guess it’s possible, maybe just need separate by coma the parameters?

[fulganta]

Ok I found a way to have 2 input in a activity.
I just have to double the activity tag:

[ActivityInput(Label = "Quote Request",
			Hint = "Quote Request details",
			SupportedSyntaxes = new[] { SyntaxNames.JavaScript, SyntaxNames.Liquid })]
public Dictionary<string, string> quoteRequestInput { get; set; } = default!;

[ActivityInput(Label = "Correlation ID",
			Hint = "input correl id generated",
			SupportedSyntaxes = new[] { SyntaxNames.JavaScript, SyntaxNames.Liquid })]
public string corridVal { get; set; } = default!;

The input comes from a first post I get that I save in SetVariable activity as quoteRequestInput

The second input comes from the output from another activity that I catch also with a SetVariable activity as corridVal

Note that at the input activity level I add quoteRequestInput as a Javascript as it's a dictionary and I didn't succeed to make it with Liquid.
But for the other input corridVal I use Liquid expression.

Let me know if there was a simpler way to do it.

[sfmskywalker]

I can't think of a better way. An alternative solution might be the use of the RunJavaScript activity to set both variables from a single script, reducing the two SetVariable activities to a single RunJavaScript that sets two variables (using the setVariable function).