Reload on change works only once

[victorhurdugaci]

From scenario: https://github.com/aspnet/Release/issues/66

1. Create the default web app in VS
2. Set all the log levels to None in appsettings.json
3. Run and notice no logs in console (expected)
4. Change Microsoft log level to Debug and notice logs in console (expected)
5. Change Microsoft log level back to None

Expected: logs stop showing up
Actual: Debug logs still show up

It seems that the reload on change only works on the first change and it stops afterwards

[divega]

@victorhurdugaci thanks for the details on this. Have you tried or are you planning to try reload on non-logging scenarios? Just wondering about the scope of the issue.

[victorhurdugaci]

It's not logging specific. You can repro with this simple console app:

ConfigurationBuilder builder = new ConfigurationBuilder();
builder.AddJsonFile(s =>
{
    s.Path = "appsettings.json";
    s.ReloadOnChange = true;
});
var config = builder.Build();
var token = config.GetReloadToken();
token.RegisterChangeCallback(_ =>
{
    Console.WriteLine("Changed");
}, null);

while(true)
{
    Thread.Sleep(1000);
}

The token only fires once

[divega]

The token only fires once

That is by actually by design. We supposedly have code in the callbacks in components that are listening to a change token (e.g. Logging and reloadable options) that takes care of rewiring the callback to a new token, but apparently that isn't working correctly.

[victorhurdugaci]

Okay, then this is a logging issue

[victorhurdugaci]

cc @CesarBS because he tests logging

[divega]

Okay, then this is a logging issue.

Yep, though this is probably the right repo for the bug anyway. Thanks.

[HaoK]

I can't repro this issue for logging, here's the test I tried, which changes the configuration

        [Fact]
        public void ConsoleLogger_ReloadSettings_CanReloadMultipleTimesFromConfiguration()
        {
            var file = Path.GetTempFileName();
            File.WriteAllText(file, @"{""LogLevel"": {""Test"":""Information""} }");
            var config = new ConfigurationBuilder().SetBasePath(Path.GetTempPath()).AddJsonFile(Path.GetFileName(file), optional: false, reloadOnChange: true).Build();

            // Arrange
            var settings = new ConfigurationConsoleLoggerSettings(config);

            var loggerFactory = new LoggerFactory();
            loggerFactory.AddConsole(settings);

            var logger = loggerFactory.CreateLogger("Test");
            Assert.False(logger.IsEnabled(LogLevel.Trace));

            // Act & Assert
            for (var i = 0; i < 10; i++)
            {
                if (i % 2 == 0)
                {
                    File.WriteAllText(file, @"{""LogLevel"": {""Test"":""Information""} }");
                }
                else
                {
                    File.WriteAllText(file, @"{""LogLevel"": {""Test"":""Trace""} }");
                }

                Thread.Sleep(100);

                Assert.Equal(i % 2 == 1, logger.IsEnabled(LogLevel.Trace));
            }
        }

[HaoK]

@CesarBS can you actually repro this behavior?

[HaoK]

I tried manually on an app as well, toggling Microsoft to None/Information a few times and things worked as far as I could tell with the logs showing up and then not showing up each time

[conniey]

I am currently experiencing this issue as well using rc2-final... The event only gets fired once for my appsettings.json file.

Repro Steps

1. Copy Program.cs below.
2. Add appsettings.json to project
3. Change properties for appsettings.json to copy to output directory.
4. Compile and run the code.
5. Edit the appsettings.json in the bin\Debug folder (ie. changing options2 to another value)
6. Notice how it updates
7. Update the appsettings.json again.

Expected

The callback in RegisterChangeCallback gets fired again.

Actual

Nothing happens. (But I can see that the values in IConfigurationRoot have changed with each update... just that the event isn't firing.)

Program.cs

using Microsoft.Extensions.Configuration;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;

namespace configuration_demo
{
    class Program
    {
        static void Main(string[] args)
        {
            var autoReset = new AutoResetEvent(false);
            var builder = new ConfigurationBuilder();
            builder.AddJsonFile(s =>
            {
                s.Path = "appsettings.json";
                s.ReloadOnChange = true;
            });

            var root = builder.Build();
            var reloadToken = root.GetReloadToken();
            reloadToken.RegisterChangeCallback(callback =>
            {
                autoReset.Set();
            }, null);

            Print(root);

            Console.WriteLine();

            for (int i = 0; i < 10; i++)
            {
                Console.WriteLine("Waiting for a change in values...");

                autoReset.WaitOne(TimeSpan.FromMinutes(1));

                Console.WriteLine("Values changed!");
                Console.WriteLine("------------------------------------");
                Print(root);
                Console.WriteLine("------------------------------------");
            }
        }

        private static void Print(IConfigurationRoot root)
        {
            foreach (var child in root.GetChildren())
            {
                Print(new Stack<string>(), child);
            }
        }

        private static void Print(Stack<string> keys, IConfigurationSection section)
        {
            var children = section.GetChildren();

            if (!children.Any())
            {
                var key = ConfigurationPath.Combine(keys.Reverse());
                var fullKey = string.IsNullOrEmpty(key) ? section.Key : ConfigurationPath.Combine(key, section.Key);
                Console.WriteLine($"[{fullKey}] : {section.Value}");
                return;
            }

            keys.Push(section.Key);

            foreach (var child in children)
            {
                Print(keys, child);
            }

            keys.Pop();
        }
    }
}

[HaoK]

RegisterChangeCallback is only going to fire once, you need to reregister it for it be fired again.

There's a helper in Primitives which takes care of making the callback persistent

  ChangeToken.OnChange(() => root.GetReloadToken(), () => autoReset.Set());

[conniey]

@HaoK Thanks for clarifying this behaviour! Is there going to be any documentation explaining this? There weren't any docs to go off of, so I assumed that it would be persistent.

[HaoK]

I hope so :)

[divega]

I created an issue in the docs repo: dotnet/AspNetCore.Docs#1291

[RoboBurned]

I have the same issue so I used code by @conniey except I use ChangeToken.OnChange as suggested.
Also I added SetBasePath because VS starts program in bin\Debug\netcoreapp1.0\ but working dir is project's root dir, where I have settings file.
My Main looks like this. I open the appsettings.json file in editor (Notepad++)

{
  "key": "value"
}

Then I just add line break to the file and save. 4 times it worked, but then any changes in file no longer trigger event. I am on Windows 7 x64 SP1 Enterprise.

static void Main(string[] args)
{
    var autoReset = new AutoResetEvent(false);
    var builder = new ConfigurationBuilder();
    builder
        .SetBasePath(Directory.GetCurrentDirectory())
        .AddJsonFile("appsettings.json", optional: false, reloadOnChange: true);

    var root = builder.Build();
    ChangeToken.OnChange(() => root.GetReloadToken(), () => autoReset.Set());

    Print(root);

    Console.WriteLine();

    for (int i = 0; i < 10; i++)
    {
        Console.WriteLine("Waiting for a change in values...");

        autoReset.WaitOne(TimeSpan.FromMinutes(1));

        Console.WriteLine("Values changed!");
        Console.WriteLine("------------------------------------");
        Print(root);
        Console.WriteLine("------------------------------------");
    }
}