azure-functions-durable-extension: Synchronous deserialization of request content in HandleStartOrchestratorRequestAsync results in InvalidOperationException.

Description

Calling the Durable Functions HTTP API to start an orchestration when running in a 3.0-preview (3.0.1740) Azure Functions Host results in an InvalidOperationException from Kestrel due to changes in .NET Core 3.0 regarding synchronous operations:

{
    "Message": "Something went wrong while processing your request",
    "ExceptionMessage": "Synchronous operations are disallowed. Call ReadAsync or set AllowSynchronousIO to true instead.",
    "ExceptionType": "System.InvalidOperationException",
    "StackTrace": "   at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.HttpRequestStream.Read(Byte[] buffer, Int32 offset, Int32 count)\n   at System.Net.Http.DelegatingStream.Read(Byte[] buffer, Int32 offset, Int32 count)\n   at System.IO.StreamReader.ReadBuffer(Span`1 userBuffer, Boolean& readToUserBuffer)\n   at System.IO.StreamReader.ReadSpan(Span`1 buffer)\n   at System.IO.StreamReader.Read(Char[] buffer, Int32 index, Int32 count)\n   at Newtonsoft.Json.JsonTextReader.ReadData(Boolean append, Int32 charsRequired)\n   at Newtonsoft.Json.JsonTextReader.ParseValue()\n   at Newtonsoft.Json.JsonReader.ReadAndMoveToContent()\n   at Newtonsoft.Json.JsonReader.ReadForType(JsonContract contract, Boolean hasConverter)\n   at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.Deserialize(JsonReader reader, Type objectType, Boolean checkAdditionalContent)\n   at Newtonsoft.Json.JsonSerializer.DeserializeInternal(JsonReader reader, Type objectType)\n   at Newtonsoft.Json.JsonSerializer.Deserialize(JsonReader reader, Type objectType)\n   at Newtonsoft.Json.JsonSerializer.Deserialize[T](JsonReader reader)\n   at Microsoft.Azure.WebJobs.Extensions.DurableTask.HttpApiHandler.HandleStartOrchestratorRequestAsync(HttpRequestMessage request, String functionName, String instanceId) in d:\\a\\r1\\a\\azure-functions-durable-extension\\src\\WebJobs.Extensions.DurableTask\\HttpApiHandler.cs:line 590\n   at Microsoft.Azure.WebJobs.Extensions.DurableTask.HttpApiHandler.HandleRequestAsync(HttpRequestMessage request) in d:\\a\\r1\\a\\azure-functions-durable-extension\\src\\WebJobs.Extensions.DurableTask\\HttpApiHandler.cs:line 200"
}

The synchronous read appears to be here.

See the Azure Functions Host issue regarding this breaking change in .NET Core 3.0.

Expected behavior

The read of the JSON request body should be async so that Kestrel’s happy.

Actual behavior

The unhandled exception results in a 500 being returned from the HTTP API, as described above.

Known workarounds

Presumably setting AllowSynchronousIO to true in appsettings.json should work around the issue (at the cost to throughput), but I haven’t been able to get that to work in the context of Azure Functions.

App Details

• Durable Functions extension version (e.g. v1.8.3): 2.0.0
• Azure Functions runtime version (1.0 or 2.0): 3.0.1740
• Programming language used: Rust 😄