(#2) Start work on refreshable values

Author: colinangusmackay

src/Example/TheHostedService.cs

@@ -17,19 +17,23 @@ public class TheHostedService : IHostedService, IDisposable
 {
     private readonly ILogger<TheHostedService> _logger;
     private readonly IConfigurationRoot _configRoot;
-    private readonly IOptions<MyFeatureConfiguration> _featureValues;
+    private readonly IOptionsMonitor<MyFeatureConfiguration> _featureValues;
     private readonly Timer _timer;
 
     public TheHostedService(
         ILogger<TheHostedService> logger,
         IConfigurationRoot configRoot,
-        IOptions<MyFeatureConfiguration> featureValues)
+        IOptionsMonitor<MyFeatureConfiguration> featureValues)
     {
         _logger = logger;
         _configRoot = configRoot;
         _featureValues = featureValues;
         _timer = new Timer(10000);
         _timer.Elapsed += TimerOnElapsed;
+        featureValues.OnChange((v, s) =>
+        {
+            Console.WriteLine($"Change detected. {s}");
+        });
     }
 
     private void TimerOnElapsed(object? sender, ElapsedEventArgs e)
@@ -38,7 +42,7 @@ private void TimerOnElapsed(object? sender, ElapsedEventArgs e)
         {
             WriteIndented = true,
         };
-        string json = JsonSerializer.Serialize(_featureValues.Value, jsonOptions);
+        string json = JsonSerializer.Serialize(_featureValues.CurrentValue, jsonOptions);
         Console.Clear();
         _logger.LogInformation(
             "At {Time} the object looks like:\n{Json}",

src/Example/appsettings.json

@@ -3,6 +3,7 @@
         "AppConfiguration": {
             "SchemaName": "Stravaig",
             "TableName": "AppConfiguration",
+            "RefreshSeconds": 15,
             "ConnectionString": "*** Found in User Secrets ***"
         }
     },

src/Stravaig.Configuration.SqlServer/ISqlServerConfigurationWatcher.cs

@@ -0,0 +1,6 @@
+namespace Stravaig.Configuration.SqlServer;
+
+public interface ISqlServerConfigurationWatcher
+{
+    void EnsureStarted();
+}

src/Stravaig.Configuration.SqlServer/NullSqlServerConfigurationWatcher.cs

@@ -0,0 +1,8 @@
+namespace Stravaig.Configuration.SqlServer;
+
+public class NullSqlServerConfigurationWatcher : ISqlServerConfigurationWatcher
+{
+    public void EnsureStarted()
+    {
+    }
+}

src/Stravaig.Configuration.SqlServer/SqlServerConfigurationBuilderExtensions.cs

@@ -15,6 +15,7 @@ public static IConfigurationBuilder AddSqlServer(this IConfigurationBuilder buil
 
         return builder.Add(new SqlServerConfigurationSource(
             options.ConnectionString ?? throw new InvalidOperationException("Cannot build a SQL Server Configuration Provider with a null connection string."),
+            TimeSpan.FromSeconds(options.RefreshSeconds),
             options.SchemaName,
             options.TableName));
     }

src/Stravaig.Configuration.SqlServer/SqlServerConfigurationOptions.cs

@@ -8,6 +8,8 @@ public class SqlServerConfigurationOptions
     public string? ConfigurationSection { get; set; }
     public string SchemaName { get; set; } = DefaultValues.SchemaName;
     public string TableName { get; set; } = DefaultValues.TableName;
+
+    public int RefreshSeconds { get; set; } = 0;
 
     public SqlServerConfigurationOptions FromExistingConfiguration(string configurationSection = DefaultValues.ConfigurationSection)
     {

src/Stravaig.Configuration.SqlServer/SqlServerConfigurationProvider.cs

@@ -7,9 +7,10 @@ namespace Stravaig.Configuration.SqlServer;
 
 public class SqlServerConfigurationProvider : ConfigurationProvider
 {
-    private Lazy<string> _toStringValue;
+    private readonly Lazy<string> _toStringValue;
     private readonly SqlServerConfigurationSource _source;
     private readonly IDataLoader _dataLoader;
+    private readonly ISqlServerConfigurationWatcher _watcher;
 
     public SqlServerConfigurationProvider(SqlServerConfigurationSource source)
         : this (source, new DataLoader())
@@ -21,12 +22,16 @@ internal SqlServerConfigurationProvider(SqlServerConfigurationSource source, IDa
         _source = source;
         _dataLoader = dataLoader;
         _toStringValue = new Lazy<string>(BuildToStringValue);
+        _watcher = source.RefreshInterval == TimeSpan.Zero
+            ? new NullSqlServerConfigurationWatcher()
+            : new SqlServerConfigurationWatcher(source.RefreshInterval, this);
     }
 
     public override void Load()
     {
         var data = _dataLoader.RetrieveData(_source);
         Data = new Dictionary<string, string>(data, StringComparer.OrdinalIgnoreCase);
+        _watcher.EnsureStarted();
     }
 
     public override string ToString()

src/Stravaig.Configuration.SqlServer/SqlServerConfigurationSource.cs

@@ -11,15 +11,17 @@ public class SqlServerConfigurationSource : IConfigurationSource
     public string ConnectionString { get; private set; }
     public string SchemaName { get; private set; }
     public string TableName { get; private set; }
+    public TimeSpan RefreshInterval { get; private set; }
 
-    public SqlServerConfigurationSource(string connectionString, string schemaName = "Stravaig", string tableName = "AppConfiguration")
+    public SqlServerConfigurationSource(string connectionString, TimeSpan? refreshInterval = null, string schemaName = "Stravaig", string tableName = "AppConfiguration")
     {
         ValidateConnectionString(connectionString);
         ValidateSchemaName(schemaName);
         ValidateTableName(tableName);
         ConnectionString = connectionString;
         SchemaName = schemaName;
         TableName = tableName;
+        RefreshInterval = refreshInterval ?? TimeSpan.Zero;
     }
 
     private void ValidateTableName(string tableName)

src/Stravaig.Configuration.SqlServer/SqlServerConfigurationWatcher.cs

@@ -0,0 +1,38 @@
+using System;
+using System.Timers;
+
+namespace Stravaig.Configuration.SqlServer;
+
+public class SqlServerConfigurationWatcher : ISqlServerConfigurationWatcher
+{
+    private readonly SqlServerConfigurationProvider _provider;
+    private readonly Timer _timer;
+    
+    public SqlServerConfigurationWatcher(TimeSpan interval, SqlServerConfigurationProvider provider)
+    {
+        _provider = provider;
+        _timer = new Timer(interval.TotalMilliseconds);
+        _timer.Elapsed += TimerOnElapsed;
+    }
+
+    private void TimerOnElapsed(object? sender, ElapsedEventArgs e)
+    {
+        try
+        {
+            Console.WriteLine("Timer elapsed");
+            _provider.Load();
+        }
+        catch (Exception ex)
+        {
+            Console.WriteLine(ex.ToString());
+            // How do we log this? How do we get the logger in here?
+        }
+    }
+
+    public void EnsureStarted()
+    {
+        if (!_timer.Enabled)
+            _timer.Start();
+    }
+    
+}