WebApi HttpClient per request per new connection in pool - asp.net-web-api

Question

In my case, I make web request to server side by HttpClient. But every time, there will be a new connection in the connection pool. The program only used one connection string. The new connection goes up too quickly, and then exceeds the max pool size 100. I have to inverstigate the issue about the database connection pool and IIS.
sqlserver database connection string:
<connectionStrings>
<add name="WERP2ConnectionString" connectionString="Data Source=localhost;Initial Catalog=WERP2-1108;User ID=sa;Password=sasa;Connect Timeout=15;Encrypt=False;"/>
</connectionStrings>
client program:
static void Main(string[] args)
{
for (int i = 0; i < 5; i++)
{
Console.WriteLine("api test: {0}", i);
ApiTest(); //to mimic the 5 different users make the api request.
}
Console.ReadLine();
}
private static void ApiTest()
{
using (HttpClient client = new HttpClient())
{
client.BaseAddress = new Uri("http://localhost/StressApi/");
client.DefaultRequestHeaders.Accept.Add(
new System.Net.Http.Headers.MediaTypeWithQualityHeaderValue("application/json"));
var response = client.GetAsync("api/order/GetOrder").Result;
if (response.IsSuccessStatusCode)
{
var message = response.Content.ReadAsStringAsync().Result;
if (!string.IsNullOrEmpty(message))
{
Console.WriteLine(message);
}
}
else
{
Console.WriteLine("Error Code" +
response.StatusCode + " : Message - " + response.ReasonPhrase);
}
//Console.ReadLine();
}
}
WebApi controller:
public class OrderController : ApiController
{
[HttpGet]
public HttpResponseMessage GetOrder()
{
OrderModel model = new OrderModel();
var entity = model.GetByID();
HttpResponseMessage response = Request.CreateResponse<OrderEntity>(HttpStatusCode.OK, entity);
return response;
}
}
public class OrderEntity
{
public int ID { get; set; }
public string OrderCode { get; set; }
public int OrderType { get; set; }
}
public class OrderModel
{
public OrderEntity GetByID()
{
OrderEntity entity = new OrderEntity();
string sql = #"select * from salorder where id=97";
using (SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["WERP2ConnectionString"].ToString()))
using (SqlCommand cmd = new SqlCommand(sql, conn))
{
// don't forget to actually open the connection before using it
conn.Open();
try
{
using (SqlDataReader dataReader = cmd.ExecuteReader(CommandBehavior.CloseConnection))
{
while (dataReader.Read())
{
// do something
Console.WriteLine(dataReader.GetValue(0) + " - " + dataReader.GetValue(1) + " - " + dataReader.GetValue(2));
entity.ID = int.Parse(dataReader.GetValue(0).ToString());
entity.OrderCode = dataReader.GetValue(1).ToString();
entity.OrderType = int.Parse(dataReader.GetValue(2).ToString());
//dataReader
}
}
}
finally
{
//SqlConnection.ClearPool(conn);
}
}
return entity;
}
}
Every sql query will make a process in sqlserver, we can find them in SQL SERVER Activity Monitor, and there are 5 records, becuase I repeat 5 times of the query.
If we use SP_WHO command, we also can verify the 5 process records, and they are in sleeping and AWAITTING COMMAND state.
I am confused that how I can avoid this connection leak issue. Although I make the same sql query every time, there are still new connection regenerated. And I have tested that these connection will be recycled about 6min20s. Of course I could reset IIS or make application pool recycled to free them. But this definitely cannot be accepted in the on line system. please someone can make any suggestoins? Thanks.
By the way, the programming is run with .NET Framework 4.0, IIS7 and SQLSERVER2008 R2.

Answer 1

HttpClient will open a new socket with each request. So it is recommended to use a single instance of this .
For more information go to below link
https://www.codeproject.com/Articles/1194406/Using-HttpClient-As-It-Was-Intended-Because-You-re