Adds support for configuration hot reload. Closes #247

[waldekmastykarz]

Adds support for configuration hot reload. Closes #247

[Copilot]

Pull request overview

This pull request adds configuration hot reload support to Dev Proxy, allowing the application to automatically restart when the configuration file changes. The implementation introduces a ConfigFileWatcher service that monitors the config file using FileSystemWatcher, coordinates graceful proxy shutdown, and triggers application restart through a loop in the main program. Additionally, the PR implements proper disposal patterns across all plugins by making BasePlugin implement IDisposable and updating derived plugins to dispose their resources correctly.

Key changes:

• Adds ConfigFileWatcher hosted service to monitor configuration file changes with debouncing
• Implements restart loop in Program.cs that waits for complete proxy shutdown before restarting
• Updates BasePlugin to implement IDisposable and adds disposal overrides to 15+ plugin classes

Reviewed changes

Copilot reviewed 22 out of 22 changed files in this pull request and generated 8 comments.

Show a summary per file

File	Description
DevProxy/Proxy/ConfigFileWatcher.cs	New hosted service that watches config file and coordinates restart via static properties
DevProxy/Program.cs	Restructured to support restart loop with proper cleanup between restarts
DevProxy/Proxy/ProxyEngine.cs	Enhanced cleanup to remove endpoints and signal when proxy fully stopped
DevProxy/Extensions/IServiceCollectionExtensions.cs	Registered ConfigFileWatcher as hosted service
DevProxy.Abstractions/Plugins/BasePlugin.cs	Implemented IDisposable with virtual Dispose pattern and updated Configuration property to use field keyword
DevProxy.Abstractions/Plugins/BaseLoader.cs	Improved thread safety by marking _isDisposed as volatile and checking it before processing changes
DevProxy.Plugins/Reporting/MinimalCsomPermissionsPlugin.cs	Added Dispose override to clean up _loader
DevProxy.Plugins/Reporting/GraphMinimalPermissionsPlugin.cs	Added pragma to suppress false positive CA2213 warning for DI-injected HttpClient
DevProxy.Plugins/Reporting/GraphMinimalPermissionsGuidancePlugin.cs	Added pragma to suppress false positive CA2213 warning for DI-injected HttpClient
DevProxy.Plugins/Reporting/ApiCenterProductionVersionPlugin.cs	Added Dispose override to clean up _apiCenterClient
DevProxy.Plugins/Reporting/ApiCenterMinimalPermissionsPlugin.cs	Added Dispose override to clean up _apiCenterClient
DevProxy.Plugins/Mocking/MockResponsePlugin.cs	Added Dispose override to clean up _loader
DevProxy.Plugins/Mocking/MockRequestPlugin.cs	Refactored to use base class Dispose pattern instead of custom IDisposable implementation
DevProxy.Plugins/Mocking/CrudApiPlugin.cs	Added Dispose override to clean up _loader
DevProxy.Plugins/Manipulation/RewritePlugin.cs	Added Dispose override to clean up _loader
DevProxy.Plugins/Inspection/OpenAITelemetryPlugin.cs	Refactored to use base class Dispose pattern and clean up multiple resources
DevProxy.Plugins/Inspection/DevToolsPlugin.cs	Refactored to use base class Dispose pattern for _webSocket cleanup
DevProxy.Plugins/Guidance/GraphSelectGuidancePlugin.cs	Added Dispose override to clean up _msGraphDb
DevProxy.Plugins/Generation/ApiCenterOnboardingPlugin.cs	Added Dispose override to clean up _apiCenterClient
DevProxy.Plugins/Behavior/RateLimitingPlugin.cs	Added Dispose override to clean up _loader
DevProxy.Plugins/Behavior/LanguageModelRateLimitingPlugin.cs	Added Dispose override to clean up _loader
DevProxy.Plugins/Behavior/GenericRandomErrorPlugin.cs	Added Dispose override to clean up _loader

Comments suppressed due to low confidence (1)

DevProxy/Proxy/ProxyEngine.cs:331

• The call to ConfigFileWatcher.SignalProxyStopped() is inside a try-catch block that logs but swallows all exceptions. If an exception occurs before this line (e.g., during proxy cleanup), the signal will never be sent, causing the restart loop in Program.cs to hang indefinitely. Move the SignalProxyStopped() call to a finally block or ensure it's called in the catch block as well to guarantee it always executes.

    private void StopProxy()
    {
        // Unsubscribe & Quit
        try
        {
            _explicitEndPoint?.BeforeTunnelConnectRequest -= OnBeforeTunnelConnectRequestAsync;

            if (ProxyServer is not null)
            {
                ProxyServer.BeforeRequest -= OnRequestAsync;
                ProxyServer.BeforeResponse -= OnBeforeResponseAsync;
                ProxyServer.AfterResponse -= OnAfterResponseAsync;
                ProxyServer.ServerCertificateValidationCallback -= OnCertificateValidationAsync;
                ProxyServer.ClientCertificateSelectionCallback -= OnCertificateSelectionAsync;

                if (ProxyServer.ProxyRunning)
                {
                    ProxyServer.Stop();
                }

                if (_explicitEndPoint != null && ProxyServer.ProxyEndPoints.Contains(_explicitEndPoint))
                {
                    ProxyServer.RemoveEndPoint(_explicitEndPoint);
                }
            }

            _inactivityTimer?.Stop();

            if (RunTime.IsMac && _config.AsSystemProxy)
            {
                ToggleSystemProxy(ToggleSystemProxyAction.Off);
            }

            // Signal that proxy has fully stopped (including system proxy deregistration)
            ConfigFileWatcher.SignalProxyStopped();
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "An error occurred while stopping the proxy");
        }

[garrytrinder]

Tested with default config, issued first request, then changed showTimestamps to false, Dev Proxy automatically reloaded configuration, second request does not display timestamp in the output confirming that the new configuration has been applied.