Getting "500 - InternalServerError" when using REST API for groups (POST)

Describe the bug

On our Hangfire Service we use the Azure SignalR RESTful API for broadcasting messages to groups: https://github.com/Azure/azure-signalr/blob/dev/docs/swagger/v1.md#post-broadcast-a-message-to-all-clients-within-the-target-group.

Since 10th or 11th of march last week this POST call does not work anymore, even in our production environment, where we didn’t change anything.

Sadly the Azure SignalR logs doesn’t show anything more then the “InternalServerError” message, with no additional information.

To Reproduce

I tried to expand all needed code into these 2 methods, not our actual code, but it also reproduces the error:

using System;

namespace Core.Application.Hangfire.SignalR
{
  using System.Collections.Generic;
  using System.IdentityModel.Tokens.Jwt;
  using System.Net;
  using System.Net.Http;
  using System.Net.Http.Headers;
  using System.Security.Claims;
  using System.Text;
  using System.Threading;
  using System.Threading.Tasks;

  using Microsoft.Extensions.Logging;
  using Microsoft.IdentityModel.Tokens;

  using JsonSerializer = System.Text.Json.JsonSerializer;

  public class SignalRNotificationService
  {
    private readonly ILogger<SignalRNotificationService> logger;

    public SignalRNotificationService(ILogger<SignalRNotificationService> logger)
    {
      this.logger = logger;
    }

    /// <inheritdoc />
    public async Task PublishMessageAsync(CancellationToken cancellationToken)
    {
      var signalRServiceName = "<AZURE-SIGNALR-SERVICE-NAME>";
      var accessKey = "<AZURE-SIGNALR-SERVICE-ACCESSKEY>";
      var hubName = "<AZURE-SIGNALR-HUB-NAME>"; // any string
      var groupName = "<AZURE-SIGNALR-GROUP-NAME>"; // any string
      var serverName = "<SIGNALR-SERVER-NAME>"; // any string
      
      var url = $"https://{signalRServiceName}.service.signalr.net/api/v1/hubs/{hubName}/groups/{WebUtility.UrlEncode(groupName)}";
      var jwtToken = GenerateAccessTokenExample(url, new[]
                                                  {
                                                    new Claim(ClaimTypes.NameIdentifier, serverName)
                                                  }, accessKey);
      
      var payload = new SignalRPayloadMessage();
      payload.Target = "TestTarget";
      payload.Arguments = new object[] { "{\"test\": \"value\"}" };
      
      var httpRequest = new HttpRequestMessage(HttpMethod.Post, new UriBuilder(url).Uri);
      httpRequest.Headers.Authorization =
        new AuthenticationHeaderValue("Bearer", jwtToken);
      httpRequest.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
      httpRequest.Content = new StringContent(JsonSerializer.Serialize(payload), Encoding.Unicode, "application/json");
      
      var httpClient = HttpClientFactory.Create();
      using var response = await httpClient.SendAsync(httpRequest, HttpCompletionOption.ResponseHeadersRead, cancellationToken);
      if (response.StatusCode != HttpStatusCode.Accepted)
      {
        var errorBody = await response.Content.ReadAsStringAsync();
        this.logger.LogError($"Error while sending signalR message to group {groupName}. Error response body: {errorBody}");
      }
      else
      {
        this.logger.LogInformation(
          $"Sending message to group '{groupName}'.");
      }
    }
    
    private string GenerateAccessTokenExample(string audience, IEnumerable<Claim> claims, string accessKey)
    {
      var jwtTokenHandler = new JwtSecurityTokenHandler();
      var lifetime = TimeSpan.FromHours(1);
      var expire = DateTime.UtcNow.Add(lifetime);
      var securityKey = new SymmetricSecurityKey(Encoding.UTF8.GetBytes(accessKey));
      var credentials = new SigningCredentials(securityKey, SecurityAlgorithms.HmacSha256);
      var token = jwtTokenHandler.CreateJwtSecurityToken(
        issuer: null,
        audience: audience,
        subject: claims == null ? null : new ClaimsIdentity(claims),
        expires: expire,
        signingCredentials: credentials);
      return jwtTokenHandler.WriteToken(token);
    }
  }

  public class SignalRPayloadMessage
  {
    public string Target { get; set; }

    public object[] Arguments { get; set; }
  }
}

Exceptions (if any)

“500 - InternalServerError” response from Azure SignalR service

Further technical details

• Server AspNetCore Version: 3.1

[DaGrisa]

Now he sent it to you

[vicancy]

Should be resolved now.