From 91799f778b9b544575837b85f3eba27728218e1f Mon Sep 17 00:00:00 2001
From: Vaughan Knight <vaughan@vaughanknight.com>
Date: Wed, 19 Jun 2024 11:10:05 +1000
Subject: [PATCH] Fixed a bug where location sources were loading twice

Fixed a bug where location sources were loading twice.  Added a semaphore to stop any threading issues, and also stopped it loading twice in the service configuration.
---
 .../src/LocationSource.cs                     | 43 ++++++++++++++-----
 .../ServiceCollectionExtensions.cs            | 22 ++++++++--
 2 files changed, 51 insertions(+), 14 deletions(-)

diff --git a/src/CarbonAware.LocationSources/src/LocationSource.cs b/src/CarbonAware.LocationSources/src/LocationSource.cs
index 793b09dd8..96eb5e5a7 100644
--- a/src/CarbonAware.LocationSources/src/LocationSource.cs
+++ b/src/CarbonAware.LocationSources/src/LocationSource.cs
@@ -6,6 +6,7 @@
 using Microsoft.Extensions.Options;
 using System.Reflection;
 using System.Text.Json;
+using System.Threading;
 
 namespace CarbonAware.LocationSources;
 
@@ -22,7 +23,6 @@ internal class LocationSource : ILocationSource
 
     private LocationDataSourcesConfiguration _configuration => _configurationMonitor.CurrentValue;
 
-
     /// <summary>
     /// Creates a new instance of the <see cref="LocationSource"/> class.
     /// </summary>
@@ -61,14 +61,21 @@ private async Task LoadLocationJsonFileAsync()
         var sourceFiles = !_configuration.LocationSourceFiles.Any() ? DiscoverFiles() : _configuration.LocationSourceFiles;
         foreach (var source in sourceFiles)
         {
-            using Stream stream = GetStreamFromFileLocation(source);
-            var namedGeoMap = await JsonSerializer.DeserializeAsync<Dictionary<string, NamedGeoposition>>(stream, options);
-            foreach (var locationKey in namedGeoMap!.Keys) 
+            if (File.Exists(source.DataFileLocation!))
+            {
+                using Stream stream = GetStreamFromFileLocation(source);
+                var namedGeoMap = await JsonSerializer.DeserializeAsync<Dictionary<string, NamedGeoposition>>(stream, options);
+                foreach (var locationKey in namedGeoMap!.Keys)
+                {
+                    var geoInstance = namedGeoMap[locationKey];
+                    geoInstance.AssertValid();
+                    var key = BuildKey(source, locationKey);
+                    AddToLocationMap(key, geoInstance, source.DataFileLocation, keyCounter);
+                }
+            }
+            else
             {
-                var geoInstance = namedGeoMap[locationKey];
-                geoInstance.AssertValid();
-                var key = BuildKey(source, locationKey);
-                AddToLocationMap(key, geoInstance, source.DataFileLocation, keyCounter);
+                _logger.LogError($"Configured data source not found at '{source.DataFileLocation}'");
             }
         }
     }
@@ -78,11 +85,27 @@ private String BuildKey(LocationSourceFile locationData, string locationName)
         return $"{locationData.Prefix}{locationData.Delimiter}{locationName}";
     }
 
+    /// <summary>
+    /// Semaphore is to stop any concurrent loading of the file, which 
+    /// could in turn update the list twice and result in duplicate entries, 
+    /// in turn resulting in suffixed keys to avoid clashes when not 
+    /// required.
+    /// </summary>
+    private readonly SemaphoreSlim _semaphore = new SemaphoreSlim(1, 1);
     private async Task LoadLocationFromFileIfNotPresentAsync()
     {
-        if (!_allLocations.Any())
+        await _semaphore.WaitAsync();
+
+        try
+        {
+            if (!_allLocations.Any())
+            {
+                await LoadLocationJsonFileAsync();
+            }
+        }
+        finally
         {
-            await LoadLocationJsonFileAsync();
+            _semaphore.Release();
         }
     }
 
diff --git a/src/GSF.CarbonAware/src/Configuration/ServiceCollectionExtensions.cs b/src/GSF.CarbonAware/src/Configuration/ServiceCollectionExtensions.cs
index 440e657b4..ee38dddad 100644
--- a/src/GSF.CarbonAware/src/Configuration/ServiceCollectionExtensions.cs
+++ b/src/GSF.CarbonAware/src/Configuration/ServiceCollectionExtensions.cs
@@ -6,6 +6,7 @@
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.DependencyInjection.Extensions;
+using System.Linq;
 
 namespace GSF.CarbonAware.Configuration;
 
@@ -26,21 +27,34 @@ private  static IServiceCollection ConfigureLocationDataSourcesConfiguration(thi
     /// </summary>
     public static IServiceCollection AddEmissionsServices(this IServiceCollection services, IConfiguration configuration)
     {
-        services.ConfigureLocationDataSourcesConfiguration(configuration);
-        services.TryAddSingleton<ILocationSource, LocationSource>();
+        AddLocationServices(services, configuration);
         services.AddDataSourceService(configuration);
         services.TryAddSingleton<IEmissionsHandler, EmissionsHandler>();
         services.TryAddSingleton<ILocationHandler, LocationHandler>();
         return services;
     }
 
+    /// <summary>
+    /// This stops the location configuration being loaded twice if needed for 
+    /// historical emissions and forecasted emissions services.  
+    /// </summary>
+    /// <param name="services"></param>
+    /// <param name="configuration"></param>
+    private static void AddLocationServices(IServiceCollection services, IConfiguration configuration)
+    {
+        if (!services.Any(x => x.ServiceType == typeof(ILocationSource)))
+        {
+            services.ConfigureLocationDataSourcesConfiguration(configuration);
+            services.TryAddSingleton<ILocationSource, LocationSource>();
+        }
+    }
+
     /// <summary>
     /// Add services needed in order to use an Forecast service.
     /// </summary>
     public static IServiceCollection AddForecastServices(this IServiceCollection services, IConfiguration configuration)
     {
-        services.ConfigureLocationDataSourcesConfiguration(configuration);
-        services.TryAddSingleton<ILocationSource, LocationSource>();
+        AddLocationServices(services, configuration);
         services.AddDataSourceService(configuration);
         services.TryAddSingleton<IForecastHandler, ForecastHandler>();
         services.TryAddSingleton<ILocationHandler, LocationHandler>();