c# - 如何在 C# 中进行并发 API 调用？

问题描述

我需要从抵押 API 中提取自定义字段。问题是总共有 11000 条记录，每个 API 请求需要 1 秒。我想找到一种异步并行发送请求的方法，以提高效率。

我尝试遍历所有请求，然后Task.WaitAll()等待响应返回。我只收到两个响应，然后应用程序无限期地等待。

我首先为HttpClient

 public static class ApiHelper
    {
        public static HttpClient ApiClient { get; set; }

        public static void InitializeClient()
        {
            ApiClient = new HttpClient();
            ApiClient.DefaultRequestHeaders.Add("ContentType", "application/json");
        }
    }

我收集我的抵押 ID 列表并循环通过 API Post Calls

        static public DataTable GetCustomFields(DataTable dt, List<string> cf, string auth)
        {

                //set auth header
                ApiHelper.ApiClient.DefaultRequestHeaders.Authorization = new System.Net.Http.Headers.AuthenticationHeaderValue("Bearer", auth);

                //format body
                string jsonBody = JArray.FromObject(cf).ToString();
                var content = new StringContent(jsonBody, Encoding.UTF8, "application/json");



                var responses = new List<Task<string>>();


                foreach (DataRow dr in dt.Rows)
                {

                    string guid = dr["GUID"].ToString().Replace("{", "").Replace("}", ""); //remove {} from string

                    responses.Add(GetData(guid, content));

                }

                Task.WaitAll(responses.ToArray());
                //some code here to process through the responses and return a datatable

                return updatedDT;

        }

每个 API 调用都需要 URL 中的抵押 ID (GUID)

  async static Task<string> GetData(string guid, StringContent json)
        {

            string url = "https://api.elliemae.com/encompass/v1/loans/" + guid + "/fieldReader";
            Console.WriteLine("{0} has started .....", guid);
            using (HttpResponseMessage response = await ApiHelper.ApiClient.PostAsync(url, json))
            {
                if (response.IsSuccessStatusCode)
                {
                    Console.WriteLine("{0} has returned response....", guid);
                    return await response.Content.ReadAsStringAsync();
                }
                else
                {
                    Console.WriteLine(response.ReasonPhrase);
                    throw new Exception(response.ReasonPhrase);
                }

            }

        }

我现在只测试 10 条记录并发送所有 10 个请求。但我只收到两回。

结果就在这里。

你能告诉我发送并发 API 调用的正确方法吗？

标签： c#apihttpclient

解决方案

所有人GetData Task都使用相同的HttpClient单例实例。HttpClient 不能同时服务多个调用。最佳实践是使用PoolHttpClient 来确保没有 Task 同时访问同一个 HttpClient。

另外，小心抛出exception任务，它会停止第WaitAll()一次抛出的异常

解决方案我在这里发布了整个项目：https ://github.com/jonathanlarouche/stackoverflow_58137212 这个解决方案使用[3] 池
发送 25 个请求；max sized

基本上，ApiHelper包含一个HttpClient pool，使用 Generic 类ArrayPool<T>。您可以使用任何其他池化库，我只是想发布一个独立的解决方案。

建议 ApiHelper Bellow，这个类现在包含一个池和一个Use接收的方法，池中的Action一个 Item 将在 Action 期间“租用”，然后通过该ArrayPool.Use函数返回到池中。Use函数还接收 apiToken 以更改请求身份验证标头。

public static class ApiHelper
{
    public static int PoolSize { get => apiClientPool.Size; }

    private static ArrayPool<HttpClient> apiClientPool = new ArrayPool<HttpClient>(() => {
        var apiClient = new HttpClient();
        apiClient.DefaultRequestHeaders.Add("ContentType", "application/json");
        return apiClient;
    });

    public static Task Use(string apiToken, Func<HttpClient, Task> action)
    {
        return apiClientPool.Use(client => {
            client.DefaultRequestHeaders.Authorization = new System.Net.Http.Headers.AuthenticationHeaderValue("Bearer", apiToken);
            return action(client);
        });
    }
}

获取数据函数。Get Data 将收到 apiToken 并等待该ApiHelper.Use函数。对象的新实例StringContent()需要在此函数中完成，因为它不能在不同的 Http Post 调用中重复使用。

async static Task<string> GetData(string apiToken, Guid guid, string jsonBody)
{

    string url = "https://api.elliemae.com/encompass/v1/loans/" + guid + "/fieldReader";
    Console.WriteLine("{0} has started .....", guid);
    string output = null;
    await ApiHelper.Use(apiToken, (client) => 
    {
        var json = new StringContent(jsonBody, Encoding.UTF8, "application/json");
        return client.PostAsync(url, json).ContinueWith(postTaskResult =>
        {

            return postTaskResult.Result.Content.ReadAsStringAsync().ContinueWith(s => {

                output = s.Result;
                return s;
            });
        });
    });
    Console.WriteLine("{0} has finished .....", guid);
    return output;
}

数组池

public class ArrayPool<T>
{
    public int Size { get => pool.Count(); }
    public int maxSize = 3;
    public int circulingObjectCount = 0;
    private Queue<T> pool = new Queue<T>();
    private Func<T> constructorFunc;

    public ArrayPool(Func<T> constructorFunc) {
        this.constructorFunc = constructorFunc;
    }

    public Task Use(Func<T, Task> action)
    {
        T item = GetNextItem(); //DeQueue the item
        var t = action(item);
        t.ContinueWith(task => pool.Enqueue(item)); //Requeue the item
        return t;
    }

    private T GetNextItem()
    {
        //Create new object if pool is empty and not reached maxSize
        if (pool.Count == 0 && circulingObjectCount < maxSize)
        {
            T item = constructorFunc();
            circulingObjectCount++;
            Console.WriteLine("Pool empty, adding new item");
            return item;
        }
        //Wait for Queue to have at least 1 item
        WaitForReturns();

        return pool.Dequeue();
    }

    private void WaitForReturns()
    {
        long timeouts = 60000;
        while (pool.Count == 0 && timeouts > 0) { timeouts--; System.Threading.Thread.Sleep(1); }
        if(timeouts == 0)
        {
            throw new Exception("Wait timed-out");
        }
    }
}

c# - 如何在 C# 中进行并发 API 调用？

问题描述

解决方案

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