Reload Routes and Clusters onChange in Config File

[AppDayme]

Hello @community,
I am using a custom ProxyConfigProvider (by implementing the IProxyConfigProvider). However, I am trying to reload the config file whenever it changes so that the ProxyConfig will be reloaded to reflect the new route values. I implemented a FileWatcher class that detects the change and calls the _proxyConfigProvider. GetConfig(). The method is called but the value of the _proxyConfig doesn't change.

The ProxyConfigProvider Class

using System;
using System.Collections.Generic;
using Microsoft.Extensions.Options;
using Yarp.ReverseProxy.Configuration;

namespace YarpExample
{
    public static class GlobalConfig
    {
        public static bool ConfigChanged { get; set; }
    }
    public class ProxyConfigProvider : IProxyConfigProvider
    {
        private readonly IOptionsMonitor<ProxyConfig> _proxyConfigMonitor;
        private ProxyConfig _config;
        public ProxyConfigProvider(IOptionsMonitor<ProxyConfig> proxyConfigMonitor)
        {
            _proxyConfigMonitor = proxyConfigMonitor ?? throw new ArgumentNullException(nameof(proxyConfigMonitor));
            _config = _proxyConfigMonitor.CurrentValue;
            _config.ChangeToken.RegisterChangeCallback(state => UpdateConfig(), _config);
        }
   

        public ProxyConfig ReloadConfig()
        {
            _proxyConfigMonitor.Get("Reload");

            return _config;
        }




        public IProxyConfig GetConfig()
        {
            if (GlobalConfig.ConfigChanged)
            {
                _config.SignalChange();
                _config = new ProxyConfig(ConfigureRoute(), ConfigureCluster());
                
            }
            return _config;
        }





        private void UpdateConfig()
        {
            var newConfig = new ProxyConfig(ConfigureRoute(), ConfigureCluster());

            _config = newConfig;

            _config.SignalChange();
        }




        public IReadOnlyList<RouteConfig> ConfigureRoute()
        {
            return new[]
            {
                new RouteConfig
                {
                    RouteId = "route1",
                    ClusterId = "cluster1",
                    Match = new RouteMatch
                    {
                        Path = "/en-US/{**remainder}"
                    }
                }
            };
        }

        public static IReadOnlyList<ClusterConfig> ConfigureCluster()
        {
            var address = ServiceConfiguration.GetXmlValue("url");

            return new[]
            {
                new ClusterConfig
                {
                    ClusterId = "cluster1",
                    Destinations = new Dictionary<string, DestinationConfig>
                    {
                        { "destination1", new DestinationConfig { Address = address } }
                    }
                }
            };
        }
    }



    

}

ProxyConfig Class

using Microsoft.Extensions.Primitives;
using System.Collections.Generic;
using System.Threading;
using Yarp.ReverseProxy.Configuration;

namespace YarpExample
{
    public class ProxyConfig : IProxyConfig
    {
        private CancellationTokenSource _cts;

        public ProxyConfig(IReadOnlyList<RouteConfig> routes, IReadOnlyList<ClusterConfig> clusters)
        {
            Routes = routes;
            Clusters = clusters;
            ResetChangeToken();
        }

        public ProxyConfig()
        {
            ResetChangeToken();
        }

        public IReadOnlyList<RouteConfig> Routes { get; }

        public IReadOnlyList<ClusterConfig> Clusters { get; }

        public IChangeToken ChangeToken => new CancellationChangeToken(_cts.Token);

        public void SignalChange()
        {
            // Dispose the old CancellationTokenSource and create a new one
           // _cts.Cancel();
            ResetChangeToken();
        }
        private void ResetChangeToken()
        {
            _cts = new CancellationTokenSource();
        }
        public void Dispose()
        {

            _cts.Dispose();
        }
    }
}

ServiceConfiguration class

using System;
using System.IO;
using System.Xml;

namespace YarpExample
{
    public static class ServiceConfiguration
    {
        private static readonly XmlDocument doc = new();
        private static readonly object lockObject = new();
     //   private static readonly FileWatcher fileWatcher;
        private static string configFile;

        public static void LoadXmlConfiguration()
        {
            configFile = Path.Combine(AppContext.BaseDirectory, "config.xml");

         
            var yarpConfiguration = new ConfigurationBuilder()
                            .SetBasePath(Directory.GetCurrentDirectory())
                            .AddXmlFile("config.xml", optional: false, reloadOnChange: true)
                            .Build();

           
            doc.LoadXml(yarpConfiguration.GetSection("AppConfiguration").Value!);
  
        }

        public static void ReloadConfiguration()
        {
            lock (lockObject)
            {
                var yarpConfiguration = new ConfigurationBuilder()
                          .SetBasePath(Directory.GetCurrentDirectory())
                          .AddXmlFile("config.xml", optional: false, reloadOnChange: true)
                          .Build();

                doc.LoadXml(yarpConfiguration.GetSection("AppConfiguration").Value!);

            }
        }

        public static string GetXmlValue(string name)
        {

            var yarpConfiguration = new ConfigurationBuilder()
                          .SetBasePath(Directory.GetCurrentDirectory())
                          .AddXmlFile("config.xml", optional: false, reloadOnChange: true)
                          .Build();
            yarpConfiguration.Reload();
            var configurationSection = yarpConfiguration.GetSection("destination");
            // Get the value of the 'url' element within the 'destination' section
            var url = configurationSection[name];
            return url;

        }

        private static bool IsFileLocked(FileInfo file)
        {
            try
            {
                using (file.Open(FileMode.Open, FileAccess.Read, FileShare.None))
                {
                    return false;
                }
            }
            catch (IOException)
            {
                return true;
            }
        }

    }
}

Config.xml

<?xml version="1.0" encoding="utf-8" ?>
<AppConfiguration>
    <destination>
            <url>https://www.mozilla.org/e-us/blog</url>
    </destination>
</AppConfiguration>

[samsp-msft]

YARP is going to listen to the cancellation token on the Config Provider to tell it when the config has changed. You seem to have that line commented out.

        public void SignalChange()
        {
            // Dispose the old CancellationTokenSource and create a new one
           // _cts.Cancel();
            ResetChangeToken();

Returning a new change token isn't going to do anything as the property that hands it to YARP doesn't have any notification semantics. Its the cancellation of the token that YARP is already holding on to that will have any effect.

[AppDayme]

GlobalConfig.ConfigChanged is set to false at the point of instantiating the file watcher. when the onChanged() method is called I set its value to true and call the get config method. see the code here

        private void OnFileChanged(object sender, FileSystemEventArgs e)
        {  
            GlobalConfig.ConfigChanged = true;
            proxyConfigProvider.GetConfig();
            GlobalConfig.ConfigChanged = false; 
                ConfigFileChanged?.Invoke();
        }

I've removed the IOptionsMonitor, but it seem like the routes are been cached somewhere and I am unable to get the _config to replace the current instance.

[Tratcher]

There's not enough context here for us to help you. Please put the code in a github repository so we can see the whole context and the most current version.

[AppDayme]

@Tratcher
here's the link to the repo

https://github.com/AppDayme/Yarp-Sample

[benjaminpetit]

I had a quick look to your repo, there is too many things that are commented out to really see what's wrong. I suggest you look at using directly the InMemoryConfigProvider, it might be simpler.