基於華為雲官方 .NET SDK 調用 CDN API 刷新緩存

准備將園子的部分圖片站切換到華為雲 CDN，切換前需要解決 CDN 緩存刷新問題。

華為雲 CDN 幫助文檔列出的 SDK 中沒有 .NET 版，原以為華為雲沒有提供官方 .NET SDK，於是在博問上提問看有沒有非官方的 .NET SDK —— 求華為雲CDN非官方.NET/C#版SDK。

在園友的回答中驚喜地知道，原來華為雲已經提供官方 .NET SDK —— Huawei Cloud .Net SDK，驚喜之余讓人失望的是沒有 CDN 部分的實現，慶幸的是認證鑒權部分已經在 HuaweiCloud.SDK.Core 中實現，自己寫代碼調用 CDN api 的工作量小了很多。

分享一下初步的實現代碼。

首先，創建 .NET 6 控制台程序並安裝 nuget 包 HuaweiCloud.SDK.Core

dotnet new console
dotnet add package HuaweiCloud.SDK.Core

接下來，創建 CdnClient 類並實現刷新緩存的異步方法 RefreshAsync

public class CdnClient : Client
{
    public async Task<bool> RefreshAsync(params string[] urls)
    {         
        SdkRequest request = HttpUtils.InitSdkRequest(
            "v1.0/cdn/content/refresh-tasks", 
            "application/json;charset=UTF-8");

        var data = new { 
            refresh_task = new 
            { 
                type = "file", 
                urls = urls
            } 
        };

        request.Body = JsonSerializer.Serialize(data);

        var response = await DoHttpRequestAsync("POST", request);

        if (response.IsSuccessStatusCode)
        {
            var resultType = new { refresh_task = "" }.GetType();
            dynamic? result = await response.Content.ReadFromJsonAsync(resultType);
            return int.TryParse(result?.refresh_task, out int taskId) && taskId > 0;
        }

        return false;
    }
}

最后，Program 中調用 CdnClient 刷新緩存

using huawei_cloud_cdn;
using HuaweiCloud.SDK.Core;
using HuaweiCloud.SDK.Core.Auth;
using Microsoft.Extensions.Logging;
using static HuaweiCloud.SDK.Core.Client;

const string ak = "我的憑證 -> 訪問密鑰 -> Access Key Id";
const string sk = "我的憑證 -> 訪問密鑰 -> Secret Access Key";
const string endpoint = "https://cdn.myhuaweicloud.com/";
const string projectId = "我的憑證 -> API憑證 -> 項目ID";

var auth = new BasicCredentials(ak, sk, projectId);
var config = HttpConfig.GetDefaultConfig();
config.IgnoreSslVerification = true;

var cdnClient = new ClientBuilder<CdnClient>()
    .WithCredential(auth)
    .WithEndPoint(endpoint)
    .WithHttpConfig(config)
    .WithLogging(LogLevel.Information)
    .Build();

var url = "https://common.cnblogs.com/logo.png";
var success = await cdnClient.RefreshAsync(url);
Console.WriteLine($"{(success ? "succeed": "fail")} to refresh {url}");

運行后成功刷新緩存。

$ dotnet run
info: System.Net.Http.HttpClient.SdkHttpClient.LogicalHandler[100]
      Start processing HTTP request POST https://cdn.myhuaweicloud.com/v1.0/cdn/content/refresh-tasks
info: System.Net.Http.HttpClient.SdkHttpClient.ClientHandler[100]
      Sending HTTP request POST https://cdn.myhuaweicloud.com/v1.0/cdn/content/refresh-tasks
info: System.Net.Http.HttpClient.SdkHttpClient.ClientHandler[101]
      Received HTTP response after 2271.4836ms - OK
info: System.Net.Http.HttpClient.SdkHttpClient.LogicalHandler[101]
      End processing HTTP request after 2301.9488ms - OK
succeed to refresh https://common.cnblogs.com/logo.png

實現過程中走了一個彎路，開始用下面的代碼反序列化響應的 json 內容

var result = await response.Content.ReadFromJsonAsync<dynamic>();
return int.TryParse(result?.refresh_task, out int taskId) && taskId > 0;

運行時報錯

'System.Text.Json.JsonElement' does not contain a definition for 'refresh_task'

原來是 System.Text.Json 不支持這樣反序列化匿名類型，反序列化的結果還是原來的 json 字符串。

后來改為下面的代碼解決了。

var resultType = new { refresh_task = "" }.GetType();
dynamic? result = await response.Content.ReadFromJsonAsync(resultType);
return int.TryParse(result?.refresh_task, out int taskId) && taskId > 0;