增加并行API调用的延迟 [英] Add delay to parallel API call

问题描述

我正在使用Polly进行并行API调用.但是服务器每秒不能处理25个以上的呼叫，因此我想知道是否有办法在每25个呼叫之后添加1s的延迟?

I'm using Polly to make parallel API calls. The server however can't process more than 25 calls per second and so I'm wondering if there is a way to add a 1s delay after each batch of 25 calls?

var policy = Policy
    .Handle<HttpRequestException>()
    .RetryAsync(3);

foreach (var mediaItem in uploadedMedia)
{
    var mediaRequest = new HttpRequestMessage { *** }
    async Task<string> func()
    {
        var response = await client.SendAsync(mediaRequest);
        return await response.Content.ReadAsStringAsync();
    }
    tasks.Add(policy.ExecuteAsync(() => func()));
}
await Task.WhenAll(tasks);

我按照以下建议添加了一个计数，但似乎不起作用

I added a count as per the suggestion below but doesn't seem to work

foreach (var mediaItem in uploadedMedia.Items)
{
    var mediaRequest = new HttpRequestMessage
    {
        RequestUri = new Uri($"https://u48ydao1w4.execute-api.ap-southeast-2.amazonaws.com/test/downloads/thumbnails/{mediaItem.filename.S}"),
        Method = HttpMethod.Get,
        Headers = {
            { "id-token", id_Token },
            { "access-token", access_Token }
        }
    };

    async Task<string> func()
    {
        if (count == 24)
        {
            Thread.Sleep(1000);
            count = 0;
        }
        var response = await client.SendAsync(mediaRequest);
        count++;
        return await response.Content.ReadAsStringAsync();
    }
    tasks.Add(policy.ExecuteAsync(() => func()));
}

await Task.WhenAll(tasks);

foreach (var t in tasks)
{
    var postResponse = await t;
    urls.Add(postResponse);
}

推荐答案

您应该使用Microsoft的Reactive Framework(aka Rx)-NuGet System.Reactive ，并使用System.Reactive.Linq添加; -然后您可以执行以下操作:

You should use Microsoft's Reactive Framework (aka Rx) - NuGet System.Reactive and add using System.Reactive.Linq; - then you can do this:

HttpRequestMessage MakeMessage(MediaItem mi) => new HttpRequestMessage
{
    RequestUri = new Uri($"https://u48ydao1w4.execute-api.ap-southeast-2.amazonaws.com/test/downloads/thumbnails/{mi.filename}"),
    Method = HttpMethod.Get,
    Headers = {
        { "id-token", id_Token },
        { "access-token", access_Token }
    }
};

var urls = await
    uploadedMedia
        .Items
        .ToObservable()
        .Buffer(24)
        .Zip(Observable.Timer(TimeSpan.Zero, TimeSpan.FromSeconds(1.0)), (mrs, _) => mrs)
        .SelectMany(mrs => mrs.ToObservable().SelectMany(mr => Observable.FromAsync(() => client.SendAsync(MakeMessage(mr)))))
        .SelectMany(x => Observable.FromAsync(() => x.Content.ReadAsStringAsync()))
        .ToList();

我无法对其进行测试，但它应该相当接近.

I haven't been able to test it, but it should be fairly close.

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