chore: block concurrent requests in decorators

alsami · Oct 23, 2020 · a9aaa12 · a9aaa12
1 parent 267c2d5
commit a9aaa12
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Showing 7 changed files with 76 additions and 23 deletions.
diff --git a/src/Covid19Api.Services.Abstractions/Loader/ICountryMetaDataLoader.cs b/src/Covid19Api.Services.Abstractions/Loader/ICountryMetaDataLoader.cs
@@ -5,6 +5,6 @@ namespace Covid19Api.Services.Abstractions.Loader
 {
     public interface ICountryMetaDataLoader
     {
-        Task<CountryMetaData[]> LoadCountryMetaDataByCountryAsync();
+        Task<CountryMetaData[]> LoadCountryMetaDataAsync();
     }
 }
diff --git a/src/Covid19Api.Services.Abstractions/Models/CountryMetaData.cs b/src/Covid19Api.Services.Abstractions/Models/CountryMetaData.cs
@@ -1,8 +1,3 @@
-// ReSharper disable MemberCanBePrivate.Global
-// ReSharper disable AutoPropertyCanBeMadeGetOnly.Global
-// ReSharper disable UnusedMember.Local
-// ReSharper disable ClassNeverInstantiated.Global
-
 namespace Covid19Api.Services.Abstractions.Models
 {
     public class CountryMetaData
@@ -14,14 +9,10 @@ public CountryMetaData(string name, string alpha2Code, string[] altSpellings)
             this.AltSpellings = altSpellings;
         }
 
-        private CountryMetaData()
-        {
-        }
-
-        public string Name { get; set; } = null!;
+        public string Name { get; }
 
-        public string Alpha2Code { get; set; } = null!;
+        public string Alpha2Code { get; }
 
-        public string[] AltSpellings { get; set; } = null!;
+        public string[] AltSpellings { get; }
     }
 }
diff --git a/src/Covid19Api.Services/Covid19Api.Services.csproj b/src/Covid19Api.Services/Covid19Api.Services.csproj
@@ -2,14 +2,15 @@
 
     <PropertyGroup>
         <TargetFramework>net5.0</TargetFramework>
+        <NoWarn>S3881</NoWarn>
     </PropertyGroup>
 
     <ItemGroup>
-      <PackageReference Include="Microsoft.AspNet.WebApi.Client" Version="5.2.7" />
       <PackageReference Include="Microsoft.Extensions.Caching.Abstractions" Version="5.0.0-rc.2.20475.5" />
       <PackageReference Include="Microsoft.Extensions.Hosting.Abstractions" Version="5.0.0-rc.2.20475.5" />
       <PackageReference Include="Microsoft.Extensions.Http" Version="5.0.0-rc.2.20475.5" />
       <PackageReference Include="Newtonsoft.Json" Version="12.0.3" />
+      <PackageReference Include="System.Text.Json" Version="5.0.0-rc.2.20475.5" />
     </ItemGroup>
 
     <ItemGroup>

diff --git a/src/Covid19Api.Services/Decorator/CountryMetaDataLoaderDecorator.cs b/src/Covid19Api.Services/Decorator/CountryMetaDataLoaderDecorator.cs
@@ -2,6 +2,7 @@
 using System.Linq;
 using System.Text;
 using System.Text.Json;
+using System.Threading;
 using System.Threading.Tasks;
 using Covid19Api.Services.Abstractions.Compression;
 using Covid19Api.Services.Abstractions.Loader;
@@ -10,10 +11,12 @@
 
 namespace Covid19Api.Services.Decorator
 {
-    public class CountryMetaDataLoaderDecorator : ICountryMetaDataLoader
+    public class CountryMetaDataLoaderDecorator : ICountryMetaDataLoader, IDisposable
     {
         private const string CacheKey = "CountryMetaData";
 
+        private static readonly SemaphoreSlim Mutex = new SemaphoreSlim(1);
+
         private readonly IDistributedCache distributedCache;
         private readonly ICountryMetaDataLoader countryMetaDataLoader;
         private readonly ICompressionService compressionService;
@@ -25,8 +28,28 @@ public CountryMetaDataLoaderDecorator(IDistributedCache distributedCache,
             this.countryMetaDataLoader = countryMetaDataLoader;
             this.compressionService = compressionService;
         }
+
+
+        public void Dispose()
+        {
+            Mutex.Dispose();
+            GC.SuppressFinalize(this);
+        }
+
+        public async Task<CountryMetaData[]> LoadCountryMetaDataAsync()
+        {
+            try
+            {
+                await Mutex.WaitAsync();
+                return await this.LoadCountryMetaDataInternalAsync();
+            }
+            finally
+            {
+                Mutex.Release(1);
+            }
+        }
 
-        public async Task<CountryMetaData[]> LoadCountryMetaDataByCountryAsync()
+        private async Task<CountryMetaData[]> LoadCountryMetaDataInternalAsync()
         {
             var cached = await this.distributedCache.GetAsync(CacheKey);
 
@@ -36,17 +59,21 @@ public async Task<CountryMetaData[]> LoadCountryMetaDataByCountryAsync()
                 return JsonSerializer.Deserialize<CountryMetaData[]>(decompressed) ?? Array.Empty<CountryMetaData>();
             }
 
-            var fetchedCountryMetaData = await this.countryMetaDataLoader.LoadCountryMetaDataByCountryAsync();
+            var fetchedCountryMetaData = await this.countryMetaDataLoader.LoadCountryMetaDataAsync();
+            await this.CacheAsync(fetchedCountryMetaData);
+
+            return fetchedCountryMetaData;
+        }
 
+        private async ValueTask CacheAsync(CountryMetaData[] fetchedCountryMetaData)
+        {
             var serialized = JsonSerializer.Serialize(fetchedCountryMetaData);
             var compressed = await this.compressionService.CompressAsync(Encoding.UTF8.GetBytes(serialized));
 
             await this.distributedCache.SetAsync(CacheKey, compressed, new DistributedCacheEntryOptions
             {
                 AbsoluteExpiration = DateTime.UtcNow.AddDays(10)
             });
-
-            return fetchedCountryMetaData;
         }
     }
 }
diff --git a/src/Covid19Api.Services/Decorator/HtmlDocumentLoaderDecorator.cs b/src/Covid19Api.Services/Decorator/HtmlDocumentLoaderDecorator.cs
@@ -1,6 +1,7 @@
 using System;
 using System.Linq;
 using System.Text;
+using System.Threading;
 using System.Threading.Tasks;
 using Covid19Api.Services.Abstractions.Compression;
 using Covid19Api.Services.Abstractions.Loader;
@@ -9,10 +10,12 @@
 
 namespace Covid19Api.Services.Decorator
 {
-    public class HtmlDocumentLoaderDecorator : IHtmlDocumentLoader
+    public class HtmlDocumentLoaderDecorator : IHtmlDocumentLoader, IDisposable
     {
         private const string Key = "HTMLDOCCACHE";
 
+        private static readonly SemaphoreSlim Mutex = new SemaphoreSlim(1);
+
         private readonly IDistributedCache distributedCache;
         private readonly IHtmlDocumentLoader htmlDocumentLoader;
         private readonly ICompressionService compressionService;
@@ -25,7 +28,26 @@ public HtmlDocumentLoaderDecorator(IDistributedCache distributedCache, IHtmlDocu
             this.compressionService = compressionService;
         }
 
+        public void Dispose()
+        {
+            Mutex.Dispose();
+            GC.SuppressFinalize(this);
+        }
+
         public async Task<HtmlDocument> LoadAsync()
+        {
+            try
+            {
+                await Mutex.WaitAsync();
+                return await this.LoadInternalAsync();
+            }
+            finally
+            {
+                Mutex.Release(1);
+            }
+        }
+
+        private async Task<HtmlDocument> LoadInternalAsync()
         {
             HtmlDocument document;
             var compressed = await this.distributedCache.GetAsync(Key);

diff --git a/src/Covid19Api.Services/Loader/CountryMetaDataLoader.cs b/src/Covid19Api.Services/Loader/CountryMetaDataLoader.cs
@@ -1,5 +1,6 @@
 using System;
 using System.Net.Http;
+using System.Text.Json;
 using System.Threading.Tasks;
 using Covid19Api.Services.Abstractions.Loader;
 using Covid19Api.Services.Abstractions.Models;
@@ -13,6 +14,11 @@ public class CountryMetaDataLoader : ICountryMetaDataLoader
         private const string ApiUrl = "https://restcountries.eu/rest/v2/all";
 #pragma warning restore
 
+        private static readonly JsonSerializerOptions SerializerOptions = new JsonSerializerOptions
+        {
+            PropertyNamingPolicy = JsonNamingPolicy.CamelCase
+        };
+
         private readonly ILogger<CountryMetaDataLoader> logger;
         private readonly IHttpClientFactory httpClientFactory;
 
@@ -22,13 +28,19 @@ public CountryMetaDataLoader(ILogger<CountryMetaDataLoader> logger, IHttpClientF
             this.httpClientFactory = httpClientFactory;
         }
 
-        public async Task<CountryMetaData[]> LoadCountryMetaDataByCountryAsync()
+        public async Task<CountryMetaData[]> LoadCountryMetaDataAsync()
         {
             var client = this.httpClientFactory.CreateClient();
 
             var response = await client.GetAsync(ApiUrl);
 
-            if (response.IsSuccessStatusCode) return await response.Content.ReadAsAsync<CountryMetaData[]>();
+            if (response.IsSuccessStatusCode)
+            {
+                var deserialized = await JsonSerializer.DeserializeAsync<CountryMetaData[]>(
+                    await response.Content.ReadAsStreamAsync(), SerializerOptions);
+
+                return deserialized ?? Array.Empty<CountryMetaData>();
+            }
 
             var error = await response.Content.ReadAsStringAsync();
             this.logger.LogError("Failed load country meta-data from {url}! Status-Code: {statusCode} Error:\n{error}",

diff --git a/src/Covid19Api.Services/Loader/CountryStatisticsLoader.cs b/src/Covid19Api.Services/Loader/CountryStatisticsLoader.cs
@@ -29,7 +29,7 @@ public CountryStatisticsLoader(ICountryMetaDataLoader countryMetaDataLoader,
         {
             var document = await this.htmlDocumentLoader.LoadAsync();
 
-            var countryMetaData = await this.countryMetaDataLoader.LoadCountryMetaDataByCountryAsync();
+            var countryMetaData = await this.countryMetaDataLoader.LoadCountryMetaDataAsync();
 
             var countryStatistics = GetTableRows(document)
                 .Select(tableRow => Parse(countryMetaData, tableRow, fetchedAt))