Azure durable functions sample says sync functions are not allowed

Question

I'm stepping through Azure training. I'm currently looking at https://docs.microsoft.com/en-us/learn/modules/create-long-running-serverless-workflow-with-durable-functions/4-exercise-create-a-workflow-using-durable-functions .

When I got to "Verify that the durable functions workflow starts" I noticed something was wrong. Instead of the json response that it predicted, I got a blank screen. Then, I checked the log of the HttpStart function, and I saw this:

Synchronous operations are disallowed. Call ReadAsync or set AllowSynchronousIO to true instead.

I'm not sure where I would do that, but at this point I went through all of the previous instructions looking for variances. The only thing I noticed was that in the instructions, where it showed what the "function.json" for HttpStart should look like, I noticed it had this:

"authLevel": "anonymous",

But I had this:

"authLevel": "function",

What I have seems more correct, in any case, so I think what was shown in the instructions was incorrect.

I also noticed that the instructions described installing the "Azure DurableTask extension", but I didn't see any prompt to install this.

I didn't see any other variances from the instructions.

I then googled the error message. The following seems relevant, but I don't know how or whether this really applies: https://github.com/dotnet/aspnetcore/issues/7644 .

Answer 1

forget the last sentence of my comment above regarding reverting to version 2.

I have changed my runtime version to version 2 and this time the HTTP Trigger was successful in running. To change the runtime version, I clicked on the "Function App settings" link underneath the Configured features heading on the Overview tab of the durable function I created

In the Function app settings tab, I selected the ~2 button to change the runtime version to 2.0.xxxx

Also, just to make sure the durable functions package was installed, I ran

npm view durable-functions

Answer 2

Another workaround without changing the azure SDK version is to add a compatibility app setting and setting it to true.

Go to:

• Platform Features
• Configurations
• Function Runtime Settings and
• add FUNCTIONS_V2_COMPATIBILITY_MODE and set it to true

This seems to do the trick while the azure-functions-durable package gets this fixed to deal with synchronous calls within the library, see the issue on GitHub