Replace HashSet with ConcurrentDictionary in WorkflowLoggingService

This should help with issue #1273 - intermittent exceptions from
WorkflowLoggingService.

There is no concurrent HashSet in .NET, so we use ConcurrentDictionary
with a byte as the value to simulate a set. For this use-case we do not
care if the Key already exists, so we can use TryAdd to add items
without considering the return value.

Signed-off-by: Tomas Ekeli <tomas.ekeli@gmail.com>

Author: TomasEkeli

src/Dapr.Workflow/WorkflowLoggingService.cs

@@ -13,21 +13,20 @@
 
 namespace Dapr.Workflow
 {
-    using System.Collections.Generic;
     using System.Threading;
     using System.Threading.Tasks;
     using Microsoft.Extensions.Hosting;
     using Microsoft.Extensions.Logging;
-    using Microsoft.Extensions.Configuration;
+    using System.Collections.Concurrent;
 
     /// <summary>
     /// Defines runtime options for workflows.
     /// </summary>
     internal sealed class WorkflowLoggingService : IHostedService
     {
         private readonly ILogger<WorkflowLoggingService> logger;
-        private static readonly HashSet<string> registeredWorkflows = new();
-        private static readonly HashSet<string> registeredActivities = new();
+        private static readonly ConcurrentDictionary<string, byte> registeredWorkflows = new();
+        private static readonly ConcurrentDictionary<string, byte> registeredActivities = new();
 
         public WorkflowLoggingService(ILogger<WorkflowLoggingService> logger)
         {
@@ -38,13 +37,13 @@ public Task StartAsync(CancellationToken cancellationToken)
             this.logger.Log(LogLevel.Information, "WorkflowLoggingService started");
 
             this.logger.Log(LogLevel.Information, "List of registered workflows");
-            foreach (string item in registeredWorkflows)
+            foreach (string item in registeredWorkflows.Keys)
             {
                 this.logger.Log(LogLevel.Information, item);
             }
 
             this.logger.Log(LogLevel.Information, "List of registered activities:");
-            foreach (string item in registeredActivities)
+            foreach (string item in registeredActivities.Keys)
             {
                 this.logger.Log(LogLevel.Information, item);
             }
@@ -55,18 +54,18 @@ public Task StartAsync(CancellationToken cancellationToken)
         public Task StopAsync(CancellationToken cancellationToken)
         {
             this.logger.Log(LogLevel.Information, "WorkflowLoggingService stopped");
-    
+
             return Task.CompletedTask;
         }
 
         public static void LogWorkflowName(string workflowName)
         {
-            registeredWorkflows.Add(workflowName);
+            registeredWorkflows.TryAdd(workflowName, 0);
         }
 
         public static void LogActivityName(string activityName)
         {
-            registeredActivities.Add(activityName);
+            registeredActivities.TryAdd(activityName, 0);
         }
 
     }