并行 HttpClient 调用引发 500 内部服务器错误

Question

I need to implement parallel calls to API.

It's weird because If I have 3 requests, 2 passed to external api and third failed (Error 500). If I leave 2 requests, first time I get success message 200 OK for a both requests.If I go to another link or refresh my browser and result with two calls throw exception error 500.

Sometimes with two call first running works OK and next time throw exception. If I have 3 requests, first and second return 200 OK and third throw exception message.

I was trying with two paraellel approach but I feel the HttpClient has some limit. How can I fix this ? Resolving for the get array results in one call won't do because I can not change external api methods.

These are methods:

    private async Task<IEnumerable<PaymentDetailsResponseDto>> GetPaymentDetails(CancellationToken cancellationToken)
    {
            try
            {
                    var paymentDetailsResponse = new List<PaymentDetailsResponseDto>();
                    var cardInfo = new List<CardResponseDto>();                                  
                    long[] paymentIds = { 2, 3};

                   //  // PARALLEL REQUESTS WITH BACTHES //
                    var batchSize = 100;
                    int numberOfBatches = (int)Math.Ceiling((double)paymentIds.Count() / batchSize);

                    for (int i = 0; i < numberOfBatches; i++)
                    {
                        var currentIds = paymentIds.Skip(i * batchSize).Take(batchSize);
                        var tasks = paymentIds.Select(id => _paymentsService.GetCardInfo(id, cancellationToken));
                        cardInfo.AddRange(await Task.WhenAll(tasks));
                    }

                     // PARALLEL REQUESTS //
                    //var tasks = paymentIds.Select(id => _paymentsService.GetCardInfo(id, cancellationToken));
                    //var results = await Task.WhenAll(tasks);

                    paymentDetailsResponse = cardInfo.Select(x => new PaymentDetailsResponseDto
                    {
                        CardNumber = x.CardNumber,
                        ExpirationDate = x.ExpirationDate,
                        CardSecurityCode = x.CardSecurityCode,
                        Amount = x.Amount,
                        Address = BILLING_ADDRESS,
                        City = BILLING_CITY,
                        State = BILLING_STATE,
                        Zip = BILLING_ZIP
                    }).ToList();

                return paymentDetailsResponse;             
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, $"Error duriduring getting card info.");
                throw;
            }
    } 

    public async Task<VirtualCardResponseDto> GetCardInfo(long? paymentId, string virtualCardId, CancellationToken cancellationToken)
    {                    
                try
                {
                    var response = await _client.GetAsync(string.Format(/api/payments/card-info/?paymentId={0}, paymentId, cancellationToken));

                    response.EnsureSuccessStatusCode();

                    var result = await response.Content.ReadAsStringAsync();
                    if (!string.IsNullOrEmpty(result))
                    {
                        return JsonSerializer.Deserialize<CardResponseDto>(result, new JsonSerializerOptions { PropertyNamingPolicy = JsonNamingPolicy.CamelCase });
                    }

                    throw new Exception($"An error occurred while getting data in Payment Service, Status Code {response.StatusCode.ToString()}");
                }
                catch (Exception ex)
                {
                    _logger.LogError(ex, "Error occurred in Payment Service client during getting card info.");
                    throw;
                }
    }

    [HttpGet("card-info")]
    public async Task<ActionResult<CardResponseDto>> GetCardInfo(long paymentId,  CancellationToken cancellationToken)
    {
        return Ok(await _paymentManager.GetCardInfoAsync(paymentId, cancellationToken));
    }

Thanks in advance.

Answer 1

It is not a problem with HttpClient . According to the documentation GetAsync is thread safe.

You have to debug the code on the server or obtain the full error message from the server because it's a problem with the API you are calling.