Added WatchCancellationTokenSource (#135)

Author: muratyuceer

src/Winton.Extensions.Configuration.Consul/ConsulConfigurationProvider.cs

@@ -41,6 +41,16 @@ public ConsulConfigurationProvider(
             _source = source;
             _consulClientFactory = consulClientFactory;
             _cancellationTokenSource = new CancellationTokenSource();
+            if (_source.WatchCancellationTokenSource != null)
+            {
+                _source.WatchCancellationTokenSource.Token.Register(() =>
+                {
+                    if (!_disposed && !_cancellationTokenSource.IsCancellationRequested)
+                    {
+                        _cancellationTokenSource.Cancel();
+                    }
+                });
+            }
         }
 
         public void Dispose()
@@ -143,7 +153,7 @@ private async Task PollingLoop(CancellationToken cancellationToken)
                     SetLastIndex(result);
                     consecutiveFailureCount = 0;
                 }
-                catch (Exception exception)
+                catch (Exception exception) when (!cancellationToken.IsCancellationRequested)
                 {
                     var wait =
                         _source.OnWatchException?.Invoke(

src/Winton.Extensions.Configuration.Consul/ConsulConfigurationSource.cs

@@ -4,6 +4,7 @@
 using System;
 using System.Collections.Generic;
 using System.Net.Http;
+using System.Threading;
 using Consul;
 using Microsoft.Extensions.Configuration;
 using Winton.Extensions.Configuration.Consul.Extensions;
@@ -47,6 +48,8 @@ public string KeyToRemove
 
         public Func<ConsulWatchExceptionContext, TimeSpan>? OnWatchException { get; set; }
 
+        public CancellationTokenSource? WatchCancellationTokenSource { get; set; }
+
         public bool Optional { get; set; } = false;
 
         public IConfigurationParser Parser { get; set; }

src/Winton.Extensions.Configuration.Consul/IConsulConfigurationSource.cs

@@ -81,6 +81,16 @@ public interface IConsulConfigurationSource : IConfigurationSource
         /// </remarks>
         Func<ConsulWatchExceptionContext, TimeSpan>? OnWatchException { get; set; }
 
+        /// <summary>
+        ///     Gets or sets a <see cref="CancellationTokenSource" /> which can be used to cancel the background task that watches Consul for changes to this config.
+        /// </summary>
+        /// <remarks>
+        ///    Cancelling the watch task by calling <c>Cancel()</c> on this <c>CancellationTokenSource</c> will completely terminate the watching process and it is not possible to restart it after this.
+        ///    By default this configuration provider will terminate the watch task itself when the <c>ConsulConfigurationProvider</c> is disposed.
+        ///    This functionality is only useful if you need to terminate the watch task early in response to some other event or want explicit control over when it is cancelled for some other reasons.
+        /// </remarks>
+        CancellationTokenSource? WatchCancellationTokenSource { get; set; }
+
         /// <summary>
         ///     Gets or sets a value indicating whether the config is optional.
         /// </summary>