Using ServiceTransportType.Persistent in Management SDK breaks enum serialization

[arek-avanade]

I'm using Management SDK in Azure Function to send messages back to our SignalR clients. Recently we switched to ServiceTransportType.Persistent (websocket) in the SDK to improve performance, but then messages arriving on the client side had Enums serialized as integers rather than strings, despite our Newtonsoft.Json settings. When using ServiceTransportType.Transient transport everything was working fine and our JSON settings were properly respected.

Please note since there is no way to configure Newtonsoft.Json in ServiceManagerBuilder currently, we are configuring it globally in function Startup class in the following manner:

JsonConvert.DefaultSettings = () => new JsonSerializerSettings
{
   ContractResolver = new CamelCasePropertyNamesContractResolver(),
   Converters = { new StringEnumConverter() }
};

This has worked perfectly find with 'transient' transport, so for example the below enum:

public enum Error
{
   SignalLost
}

was serialized as "SignalLost", but after switching to 'persistent' transport it's serialized as 0.

[wanlwanl]

Could you provide the version of Management SDK and the function app project?
The .csproj file is better.

[arek-avanade]

I cannot share the entire project file but here's an excerpt. We're running on .NET Core 3.1.

    <PackageReference Include="Microsoft.Azure.Functions.Extensions" Version="1.1.0" />
    <PackageReference Include="Microsoft.Azure.SignalR.Management" Version="1.7.1" />
    <PackageReference Include="Microsoft.Azure.WebJobs.Extensions.EventHubs" Version="4.0.1" />
    <PackageReference Include="Microsoft.Extensions.Http" Version="3.1.12" />
    <PackageReference Include="Microsoft.Extensions.Logging.ApplicationInsights" Version="2.16.0" />
    <PackageReference Include="Microsoft.NET.Sdk.Functions" Version="3.0.11" />
    <PackageReference Include="Newtonsoft.Json" Version="12.0.3" />
    <PackageReference Include="StyleCop.Analyzers" Version="1.1.118">
      <PrivateAssets>all</PrivateAssets>
      <IncludeAssets>runtime; build; native; contentfiles; analyzers</IncludeAssets>
    </PackageReference>

[wanlwanl]

the json serializer is changed to System.Text.Json in function v3 and .Net Core 3.1, please use:
using System.Text.Json.Serialization;
and then add JsonStringEnumConverter like this:

    [JsonConverter(typeof(JsonStringEnumConverter))]
    public enum Error
    {
        SignalLost
    }

[arek-avanade]

I'm not using output binding but Microsoft.Azure.SignalR.Management nuget. The reason is actually that I don't want to use System.Text.Json.Serialization, but rather Newtonsoft.Json. I can see in the code below that in the Transient transport mode the nuget is actually using Newtonsoft.Json through RestHubLifetimeManager and RestClientclasses:

azure-signalr/src/Microsoft.Azure.SignalR.Common/Utilities/RestClient.cs

Line 139 in 9e90627

request.Content = new StringContent(JsonConvert.SerializeObject(payload, JsonSerializerSettings), Encoding.UTF8, "application/json");

But for the Persistent transport there is some more low-level SignalR stuff happening in the SDK so it's not clear how to control serialization for this case, because I don't see any JSON serialization there.

[wanlwanl]

Persistent transport reuse Microsoft.Azure.SignalR package, it uses System.Text.Json by default.
Plan to expose the configuration of JSON serialization in the future, then you can configure the System.Text.Json or Newtonsoft.Json.
For now, Management SDK doesn't support it. How about keep using Transient mode for now? I will update here when the JSON configuration is exposed.

[arek-avanade]

Yeah, for now we switched back to Transient mode. It'd be great to get JSON configuration exposed moving forward. Looking forward to it!

[SebastianBienert]

Hi @wanlwanl any updates on progress of message serialization settings?

[Y-Sindo]

@SebastianBienert We have added a method to customize the message serialization for both two modes. But the method is not public now. Will make it public for the next release.
https://github.com/Azure/azure-signalr/blob/dev/src/Microsoft.Azure.SignalR.Management/ServiceManagerBuilder.cs#L55