在.net Core C＃中并行校准API调用的最佳方法是什么？

debugcn 发表于 Dev

学习AspNet

我想并行调用我的API次数，以便可以快速完成处理。我下面有三种方法必须并行调用API。我试图了解哪种是执行此操作的最佳方法。

基本代码

var client = new System.Net.Http.HttpClient();
client.DefaultRequestHeaders.Add("Accept", "application/json");

client.BaseAddress = new Uri("https://jsonplaceholder.typicode.com");
var list = new List<int>();

var listResults = new List<string>();
for (int i = 1; i < 5; i++)
{
    list.Add(i);
}

使用Parallel.ForEach的第一种方法

Parallel.ForEach(list,new ParallelOptions() { MaxDegreeOfParallelism = 3 }, index =>
{
    var response = client.GetAsync("posts/" + index).Result;

    var contents =  response.Content.ReadAsStringAsync().Result;
    listResults.Add(contents);
    Console.WriteLine(contents);
});

Console.WriteLine("After all parallel tasks are done with Parallel for each");

带有任务的第二种方法。我不确定这是否并行。让我知道是否可以

var loadPosts = new List<Task<string>>();
foreach(var post in list)
{
    var response = await client.GetAsync("posts/" + post);

    var contents = response.Content.ReadAsStringAsync();
    loadPosts.Add(contents);
    Console.WriteLine(contents.Result);
}

await Task.WhenAll(loadPosts);

Console.WriteLine("After all parallel tasks are done with Task When All");

使用动作阻止的第三种方法-这是我应该一直做的事情，但我希望听到社区的意见

var responses = new List<string>();

var block = new ActionBlock<int>(
    async x => {
        var response = await client.GetAsync("posts/" + x);
        var contents = await response.Content.ReadAsStringAsync();
        Console.WriteLine(contents);
        responses.Add(contents);                
    },
    new ExecutionDataflowBlockOptions
    {
        MaxDegreeOfParallelism = 6, // Parallelize on all cores
    });

for (int i = 1; i < 5; i++)
{
    block.Post(i);
}

block.Complete();
await block.Completion;

Console.WriteLine("After all parallel tasks are done with Action block");

尤利·邦纳（Yuli Bonner）

方法2接近。这是一条经验法则：I / O绑定操作=>使用Tasks / WhenAll（异步），计算绑定操作=>使用并行性。Http请求是网络I / O。

            foreach (var post in list)
            {
                async Task<string> func()
                {
                    var response = await client.GetAsync("posts/" + post);
                    return await response.Content.ReadAsStringAsync();
                }

                tasks.Add(func());
            }

            await Task.WhenAll(tasks);

            var postResponses = new List<string>();

            foreach (var t in tasks) {
                var postResponse = await t; //t.Result would be okay too.
                postResponses.Add(postResponse);
                Console.WriteLine(postResponse);
            }

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