Live reloading when MinimumLevel changes

Author: Sergey Komisarchik

sample/Sample/Program.cs

@@ -1,4 +1,6 @@
-using Microsoft.Extensions.Configuration;
+using System;
+
+using Microsoft.Extensions.Configuration;
 using Serilog;
 using System.IO;
 
@@ -10,14 +12,18 @@ public static void Main(string[] args)
         {
             var configuration = new ConfigurationBuilder()
                 .SetBasePath(Directory.GetCurrentDirectory())
-                .AddJsonFile("appsettings.json")
+                .AddJsonFile(path: "appsettings.json", optional: false, reloadOnChange: true)
                 .Build();
 
             var logger = new LoggerConfiguration()
                 .ReadFrom.Configuration(configuration)
                 .CreateLogger();
 
-            logger.Information("Hello, world!");
+            do
+            {
+                logger.Information("Hello, world!");
+            }
+            while (Console.ReadKey().KeyChar != 'q');
         }
     }
 }

src/Serilog.Settings.Configuration/Settings/Configuration/ConfigurationReader.cs

@@ -5,7 +5,11 @@
 using System.Runtime.CompilerServices;
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyModel;
+using Microsoft.Extensions.Primitives;
+
 using Serilog.Configuration;
+using Serilog.Core;
+using Serilog.Debugging;
 using Serilog.Events;
 
 namespace Serilog.Settings.Configuration
@@ -103,7 +107,23 @@ void ApplyMinimumLevel(LoggerConfiguration loggerConfiguration)
                 if (!Enum.TryParse(minimumLevelDirective.Value, out minimumLevel))
                     throw new InvalidOperationException($"The value {minimumLevelDirective.Value} is not a valid Serilog level.");
 
-                loggerConfiguration.MinimumLevel.Is(minimumLevel);
+                var levelSwitch = new LoggingLevelSwitch(minimumLevel);
+                
+                ChangeToken.OnChange(
+                    () => minimumLevelDirective.GetReloadToken(),
+                    () =>
+                    {
+                        if (Enum.TryParse(minimumLevelDirective.Value, out minimumLevel))
+                        {
+                            levelSwitch.MinimumLevel = minimumLevel;
+                        }
+                        else
+                        {
+                            SelfLog.WriteLine($"The value {minimumLevelDirective.Value} is not a valid Serilog level.");
+                        }
+                    });
+
+                loggerConfiguration.MinimumLevel.ControlledBy(levelSwitch);
             }
         }