fix: Coalesce file system watcher reloads.

Author: kinyoklion

pkgs/sdk/server/src/Internal/DataSources/FileDataSource.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.IO;
@@ -23,6 +23,7 @@ internal sealed class FileDataSource : IDataSource
         private readonly FileDataTypes.IFileReader _fileReader;
         private readonly bool _skipMissingPaths;
         private readonly Logger _logger;
+        private readonly object _loadLock = new object();
         private volatile bool _started;
         private volatile bool _loadedValidData;
         private volatile int _lastVersion;
@@ -88,35 +89,38 @@ private void Dispose(bool disposing)
 
         private void LoadAll()
         {
-            var version = Interlocked.Increment(ref _lastVersion);
-            var flags = new Dictionary<string, ItemDescriptor>();
-            var segments = new Dictionary<string, ItemDescriptor>();
-            foreach (var path in _paths)
+            lock (_loadLock)
             {
-                try
-                {
-                    var content = _fileReader.ReadAllText(path);
-                    _logger.Debug("file data: {0}", content);
-                    var data = _parser.Parse(content, version);
-                    _dataMerger.AddToData(data, flags, segments);
-                }
-                catch (FileNotFoundException) when (_skipMissingPaths)
+                var version = Interlocked.Increment(ref _lastVersion);
+                var flags = new Dictionary<string, ItemDescriptor>();
+                var segments = new Dictionary<string, ItemDescriptor>();
+                foreach (var path in _paths)
                 {
-                    _logger.Debug("{0}: {1}", path, "File not found");
-                }
-                catch (Exception e)
-                {
-                    LogHelpers.LogException(_logger, "Failed to load " + path, e);
-                    return;
+                    try
+                    {
+                        var content = _fileReader.ReadAllText(path);
+                        _logger.Debug("file data: {0}", content);
+                        var data = _parser.Parse(content, version);
+                        _dataMerger.AddToData(data, flags, segments);
+                    }
+                    catch (FileNotFoundException) when (_skipMissingPaths)
+                    {
+                        _logger.Debug("{0}: {1}", path, "File not found");
+                    }
+                    catch (Exception e)
+                    {
+                        LogHelpers.LogException(_logger, "Failed to load " + path, e);
+                        return;
+                    }
                 }
+                var allData = new FullDataSet<ItemDescriptor>(
+                    ImmutableDictionary.Create<DataKind, KeyedItems<ItemDescriptor>>()
+                        .SetItem(DataModel.Features, new KeyedItems<ItemDescriptor>(flags))
+                        .SetItem(DataModel.Segments, new KeyedItems<ItemDescriptor>(segments))
+                );
+                _dataSourceUpdates.Init(allData);
+                _loadedValidData = true;
             }
-            var allData = new FullDataSet<ItemDescriptor>(
-                ImmutableDictionary.Create<DataKind, KeyedItems<ItemDescriptor>>()
-                    .SetItem(DataModel.Features, new KeyedItems<ItemDescriptor>(flags))
-                    .SetItem(DataModel.Segments, new KeyedItems<ItemDescriptor>(segments))
-            );
-            _dataSourceUpdates.Init(allData);
-            _loadedValidData = true;
         }
 
         private void TriggerReload()
@@ -183,10 +187,15 @@ internal sealed class FileWatchingReloader : IDisposable
         private readonly ISet<string> _filePaths;
         private readonly Action _reload;
         private readonly List<FileSystemWatcher> _watchers;
+        private readonly Timer _debounceTimer;
+        private readonly int _debounceMillis;
+        private readonly object _timerLock = new object();
 
-        public FileWatchingReloader(List<string> paths, Action reload)
+        public FileWatchingReloader(List<string> paths, Action reload, int debounceMillis = 100)
         {
             _reload = reload;
+            _debounceMillis = debounceMillis;
+            _debounceTimer = new Timer(OnDebounceTimerElapsed, null, Timeout.Infinite, Timeout.Infinite);
 
             _filePaths = new HashSet<string>();
             var dirPaths = new HashSet<string>();
@@ -216,10 +225,19 @@ private void ChangedPath(string path)
         {
             if (_filePaths.Contains(path))
             {
-                _reload();
+                lock (_timerLock)
+                {
+                    // Reset the timer to debounce multiple rapid file changes
+                    _debounceTimer.Change(_debounceMillis, Timeout.Infinite);
+                }
             }
         }
 
+        private void OnDebounceTimerElapsed(object state)
+        {
+            _reload();
+        }
+
         public void Dispose()
         {
             Dispose(true);
@@ -229,6 +247,7 @@ private void Dispose(bool disposing)
         {
             if (disposing)
             {
+                _debounceTimer?.Dispose();
                 foreach (var w in _watchers)
                 {
                     w.Dispose();