Introduce SecretsManagerPollingWatcher

README.md

@@ -132,7 +132,7 @@ builder.Configuration.AddSecretsManager(
     "my-secret-secrets",
     c => 
     {
-        c.ConfigurationWatcher = new PeriodicConfigurationWatcher(TimeSpan.FromMinutes(5)); // implements `IConfigurationWatcher`
+        c.ConfigurationWatcher = new SecretsManagerPollingWatcher(TimeSpan.FromMinutes(5)); // implements `IConfigurationWatcher`
     });
 ```
 

W4k.Extensions.Configuration.Aws.SecretsManager/Activity.cs

@@ -0,0 +1,8 @@
+using System.Diagnostics;
+
+namespace W4k.Extensions.Configuration.Aws.SecretsManager;
+
+internal static class Activity
+{
+    public static ActivitySource Source { get; } = new("W4k.Extensions.Configuration.Aws.SecretsManager");
+}

W4k.Extensions.Configuration.Aws.SecretsManager/SecretsManagerPollingWatcher.cs

@@ -0,0 +1,87 @@
+using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
+
+namespace W4k.Extensions.Configuration.Aws.SecretsManager;
+
+/// <summary>
+/// AWS Secrets Manager configuration watcher that polls for changes.
+/// </summary>
+public sealed class SecretsManagerPollingWatcher : IConfigurationWatcher, IDisposable, IAsyncDisposable
+{
+    private readonly TimeSpan _interval;
+    private Timer? _timer;
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="SecretsManagerPollingWatcher"/> class.
+    /// </summary>
+    /// <param name="interval">Polling interval.</param>
+    /// <exception cref="ArgumentOutOfRangeException">Thrown when <paramref name="interval"/> is less or equal to <see cref="TimeSpan.Zero"/>.</exception>
+    public SecretsManagerPollingWatcher(TimeSpan interval)
+    {
+#if NET8_0_OR_GREATER
+        ArgumentOutOfRangeException.ThrowIfLessThanOrEqual(interval, TimeSpan.Zero);
+#else
+        if (interval <= TimeSpan.Zero)
+        {
+            throw new ArgumentOutOfRangeException(nameof(interval));
+        }
+#endif
+        _interval = interval;
+    }
+
+    /// <inheritdoc />
+    public void Dispose() => _timer?.Dispose();
+
+    /// <inheritdoc />
+    public async ValueTask DisposeAsync()
+    {
+        if (_timer != null)
+        {
+            await _timer.DisposeAsync();
+        }
+    }
+
+    /// <inheritdoc />
+    /// <exception cref="InvalidOperationException">Thrown when watcher is already started.</exception>
+    /// <exception cref="ArgumentNullException">Thrown when <paramref name="refresher"/> is <see langword="null"/>.</exception>
+    public void Start(IConfigurationRefresher refresher)
+    {
+        ThrowIfStarted(_timer);
+        ArgumentNullException.ThrowIfNull(refresher);
+
+        _timer = new Timer(ExecuteRefresh, refresher, _interval, _interval);
+    }
+
+    [SuppressMessage("ReSharper", "ExplicitCallerInfoArgument", Justification = "Explicitly passing activity name")]
+    private static void ExecuteRefresh(object? state)
+    {
+        using var activity = Activity.Source.StartActivity("Refresh");
+
+        var refresher = (IConfigurationRefresher)state!;
+        try
+        {
+            refresher.RefreshAsync(CancellationToken.None).ConfigureAwait(false).GetAwaiter().GetResult();
+
+            activity?.AddEvent(new ActivityEvent("Refresh completed"));
+            activity?.SetStatus(ActivityStatusCode.Ok);
+        }
+        catch(Exception e)
+        {
+            activity?.AddEvent(new ActivityEvent("Refresh failed"));
+            activity?.SetTag("Error", e.Message);
+            activity?.SetStatus(ActivityStatusCode.Error);
+        }
+    }
+
+    private static void ThrowIfStarted(Timer? timer)
+    {
+        if (timer is not null)
+        {
+            ThrowInvalidOperationNotStarted();
+        }
+    }
+
+    [DoesNotReturn]
+    private static void ThrowInvalidOperationNotStarted() =>
+        throw new InvalidOperationException("Watcher is already started, have you re-used watcher instance?");
+}