调用 API 20 次以生成列表，最佳实践？

Question

案例是我调用一次 API 来获取租户列表，然后对于每个租户，我必须再次调用以获取租户的使用列表。 不幸的是，没有办法在一次通话中获得所有租户的使用情况。

现在我希望通过同时进行这些调用来节省时间。 然后在最后一个到达后将它们放在一起。 到目前为止，这是我的尝试：

public async Task<List<Usage>> GetUsagesAsync2(Task<List<Tenant>> tenants)
{
    List<Usage> usages = new List<Usage>();

    foreach (var tenant in await tenants)
    {
        //Generate request
        RestRequest request = new RestRequest("tenants/{tenantID}/usages", Method.Get);
        request.AddParameter("tenantID", tenant.id, ParameterType.UrlSegment);
        request.AddHeader("Authorization", $"Bearer {Token.access_token}");

        //Get response
        RestResponse response = await _client.ExecuteAsync(request)
            .ConfigureAwait(false);

        //Validate response
        if (response.StatusCode != HttpStatusCode.OK)
            throw new Exception("Failed at Getting usages for a tenant: ");

        //Add to list
        var t_usage = JsonConvert.DeserializeObject<Wrapper<Usage>>(response.Content);
        usages.AddRange(t_usage.items);
    }
    return usages;
}

代码运行并执行它应该做的事情，但我不确定它实际上是异步运行的。 运行大约需要 7-8 秒，我发现在网页上等待的时间有点长。

Answer 1

这是并行实现：

.NET 6

public async Task<ConcurrentBag<Usage>> GetUsagesAsync2(Task<List<Tenant>> tenants)
{
    ConcurrentBag<Usage> usages = new ConcurrentBag<Usage>();

    await Parallel.ForEachAsync(await tenants, async (tenant) =>
    {
        //Generate request
        RestRequest request = new RestRequest("tenants/{tenantID}/usages", Method.Get);
        request.AddParameter("tenantID", tenant.id, ParameterType.UrlSegment);
        request.AddHeader("Authorization", $"Bearer {Token.access_token}");

        //Get response
        RestResponse response = await _client.ExecuteAsync(request).ConfigureAwait(false);

        //Validate response
        if (response.StatusCode != HttpStatusCode.OK)
            throw new Exception("Failed at Getting usages for a tenant: ");

        //Add to list
        var t_usage = JsonConvert.DeserializeObject<Wrapper<Usage>>(response.Content);
        usages.AddRange(t_usage.items);
    });

    return usages;
}

预网 6

public async Task<ConcurrentBag<Usage>> GetUsagesAsync2(Task<List<Tenant>> tenants)
{
    ConcurrentBag<Usage> usages = new ConcurrentBag<Usage>();
    var tasks = new List<Task>();

    foreach (var tenant in await tenants)
    {
        tasks.Add(Task.Run(async () =>
        {
            //Generate request
            RestRequest request = new RestRequest("tenants/{tenantID}/usages", Method.Get);
            request.AddParameter("tenantID", tenant.id, ParameterType.UrlSegment);
            request.AddHeader("Authorization", $"Bearer {Token.access_token}");

            //Get response
            RestResponse response = await _client.ExecuteAsync(request)
                .ConfigureAwait(false);

            //Validate response
            if (response.StatusCode != HttpStatusCode.OK)
                throw new Exception("Failed at Getting usages for a tenant: ");

            //Add to list
            var t_usage = JsonConvert.DeserializeObject<Wrapper<Usage>>(response.Content);
            usages.AddRange(t_usage.items);
        }));
    }

    await Task.WhenAll(tasks);

    return usages;
}

注意List改为ConcurrentBag因为它不是线程安全的

Answer 2

你基本上可以做的是：

IEnumerable<Task<List<Usage>> loadTasks = tenants.Select(LoadUsages);
List<Usage>[] usages = await Task.WhenAll(loadTasks);

async Task<List<Usage>> LoadUsages(Tenant t) {
    // your web call goes here
    return t_usage.items;
}

但是，正如评论中所指出的，这不会受到限制，并且可能一次发出太多请求。 如果您确定租户数量将保持在 20 左右，那应该没问题。 否则，您将不得不实施更复杂的批处理解决方案。