Kelaparan ThreadPool HttpClient GetAsync

Kami memiliki tumpukan backend berorientasi layanan mikro. Semua layanan mikro dibangun di atas Nancy dan terdaftar sebagai layanan windows dengan topshelf.

Salah satu layanan, yang menangani sebagian besar lalu lintas (~5000 req/s), mulai mengalami masalah kelaparan threadpool di 3 dari 8 server.

Ini adalah pengecualian yang kami dapatkan ketika mencapai titik akhir tertentu:

System.InvalidOperationException: There were not enough free threads in the ThreadPool to complete the operation.
   at System.Net.HttpWebRequest.BeginGetResponse(AsyncCallback callback, Object state)
   at System.Net.Http.HttpClientHandler.StartGettingResponse(RequestState state)
   at System.Net.Http.HttpClientHandler.StartRequest(Object obj)
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at RandomNamedClient.<GetProductBySkuAsync>d__20.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at ProductService.<GetBySkuAsync>d__3.MoveNext() in ...\ProductService.cs:line 34
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at ProductModule.<>c__DisplayClass15.<<.ctor>b__b>d__1d.MoveNext() in ...\ProductModule.cs:line 32

Titik akhir ini memanggil layanan lain -yang berada di luar domain tim saya- untuk mendapatkan data produk. Implementasinya sebagai berikut:

Get["/product/sku/{sku}", true] = async (parameters, ctx) =>
{
    string sku = parameters.sku;
    var product = await productService.GetBySkuAsync(sku);
    return Response.AsJson(new ProductRepresentation(product));
};

ProductService.GetBySkuAsync(string sku) implementasi:

public async Task<Product> GetBySkuAsync(string sku)
{
    var productDto = await randomNamedClient.GetProductBySkuAsync(sku);
    if (productDto == null)
    {
        throw new ProductDtoNotFoundException("sku", sku);
    }

    var variantDto = productDto.VariantList.FirstOrDefault(v => v.Sku == sku);

    if (variantDto == null)
    {
        throw new ProductVariantDtoNotFoundException("sku", sku);
    }

    return MapVariantDtoToProduct(variantDto, productDto);
}

RandomNamedClient.GetProductBySkuAsync(string sku) implementasi (dari paket internal):

public async Task<ProductDto> GetProductBySkuAsync(string sku)
{
  HttpResponseMessage result = await this._serviceClient.GetAsync("Product?Sku=" + sku);
  return result == null || result.StatusCode != HttpStatusCode.OK ? (ProductDto) null : this.Decompress<ProductDto>(result);
}

RandomNamedClient.Decompress<T>(HttpResponseMessage response) implementasi:

private T Decompress<T>(HttpResponseMessage response)
{
  if (!response.Content.Headers.ContentEncoding.Contains("gzip"))
    return HttpContentExtensions.ReadAsAsync<T>(response.Content).Result;
  using (GZipStream gzipStream = new GZipStream((Stream) new MemoryStream(response.Content.ReadAsByteArrayAsync().Result), CompressionMode.Decompress))
  {
    byte[] buffer = new byte[8192];
    using (MemoryStream memoryStream = new MemoryStream())
    {
      int count;
      do
      {
        count = gzipStream.Read(buffer, 0, 8192);
        if (count > 0)
          memoryStream.Write(buffer, 0, count);
      }
      while (count > 0);
      return JsonConvert.DeserializeObject<T>(Encoding.UTF8.GetString(memoryStream.ToArray()));
    }
  }
}

Semua layanan kami dibuat sebagai Rilis/32-bit. Kami tidak mengubah apa pun tentang penggunaan threadpool.